1. Introduction

Matrix Metalloproteinases(MMP’s) MMP’s represent     calcium    -based     zinc-endopeptidases  that belong to the metzincin superfamily[1]. MMP possesses structurally a conserved Zn²⁺   -binding  motif within the catalytic –domain along with various conserved protein domains (figure1)[2,reviewed in 3].

MMP’s get expressed  in the form of inactive  zymogens  possessing a pro-peptide domain(pro- MMP’s),which need  removal  for the activation   of  MMP’s.This pro-peptide belongs to the portion of the ‘’cysteine switch’’.,that is an intra Molecular complex  among a single cysteine in the pro-peptide domain along with zinc in the active site.Via  cleavage  of the pro-peptide,  this cysteine separates  from the complex ,that activates  the MMP  enzymes  that    aids  binding  along with      cleavage  of MMP substrates . MMPs further possess amino terminal  signal  sequence  that guides the peptide towards the Endoplasmic reticulum(ER). Additionally, every MMP,but for MMP-7  along with    MMP-26   possess a haemopexin –like domain which is connected to the catalytic – domain ,besides having the role  in MMP’s Crosstalk    with substrates,endogenous inhibitors, In  addition to cell surface Molecules.

1.2 Discovery

Initial MMP(MMP1) got isolated by Gross  as  well as     Lapierre in 1962 in tadpole [4].The 1^st human MMP got discovered  in skin tissue [5]. Subsequently ,a huge family of MMP’s got detailed in different species[1]. MMP’s got demonstrated to get bio generated  in the form of bioactive precursors(zymogens) which needed  activation[6].The initial  inhibitors of Matrix Metalloproteinases, Tissue inhibitors of Matrix Metalloproteinases (TIMPs)  ,got isolated in 1975 along with till date ,4 TIMPs(TIMP1-4) have got detailed [7].In 1990,the ‘’cysteine switch’’ MMP activation   mode  got identified [8]. Following,   that our insight regarding  MMP  biology  has  escalated  considerably .On  finding of the MMP catalytic  cycle,   at present insight is there  regarding the method by which MMP’s  digest the extra cellular Matrix( ECM)   proteins along with further aiding in fine  tuning of the cellular events. Additionally,   newer  MMP’s  - MMP-20 ,  MMP-206  as  well as      MMP-28-got isolated  over the period of past 25 yrs[9].

1.3 Classification

Presently ,24 human MMP homologues have got detailed  getting divided into 6 families

i)collagenases(MMP’s  --1,-8 as  well as     -13) ii)gelatinases(MMP-2, as  well as     a-9iii)stromelysins (MMP-3,-10, as  well as    -11)iv)matrilysins (MMP -7 as  well as     -26)v) membrane    type Metalloproteinases()MT1-MMP’s),also known as  MMP-14,-15,-16,-17,-24, as  well as    -25) along with rest of MMP’s(MMP-12,18,-19,-20,-21,-22,-23,-27 as  well as    -28[10].

1.4 Actions of MMP’s

MMP’s possess a physiological part in tissue morphogenesis,cell  migration   along with angiogenesis.Besides that MMP’s are implicated in patho physiological events  like wound healing , inflammation, as  well as     cancer .Certain posits that MMP’s  cleave the extra cellular Matrix  (ECM )  proteins to aid in infiltration of leukocytes,metastatic   In  addition to transformed cells to be able to go through the ECM barriers [11]. Nevertheless, there is controversy  following the 1^st in vitro study  which correlated MMP’s  with cleavage   of the ECM   Molecules that were dependent  on experiments utilizing,enhanced levels of    MMP’s  in vivo[12].

Experiments      utilizing  mass spectrometry  point that extra cellular Matrix  (ECM)   Molecules are MMP substrates  as  well as     other studies demonstrated   that blocking MMP’s(MT1-MMP’s) avoid leukocytes crossing the artificial collagen along with ECM    layers[11,13].These studies illustrated that fibroblasts as  well as     tumor cells  tunnel via the dense barriers of cross linked type-1 collagen in vitro or  in vivo  through  a practically  undistinguishable proteolytic event  needing     MMP’s ,.Moreover Ota etal., demonstrated   that  cancer cells use   MT1 as  well as     MT2 based - MMP’s BM transmigration  event for intravasation into the vasculature in vivo  .

Separate work   utilizing   MMP knockout (KO) mice along with innovative mass spectrometry   methods which aided in better tissue evaluation illustrated a broad MMP substrates   spectrum like cell surface Molecules   ,besides soluble factors like cytokines,chemokines  as  well as     cytokine receptors [13]. Cleavage brought about  of substrates via    MMP,manipulated their activity along with being a significant mode for  fine  tuning of the cellular events like inflammation[13-15].Hence MMP s are key  for refashioning events in generation as  well as     regeneration of tissues[11,13].

1.5 Expression, control  as well as activation

Every MMP,other than MMP-28,are Expressed throught body in the mammalian organisms.Usually Expression, amounts remain while escalate only if and when required [16]other  than MMP-2  as  well as     MT1-MMP,(besides to a  lesser   amount for –MMP-9,that are constitutively expressed in the brain in both their pro along with  activated forms[17]. MMPs  get formed along with    liberated  into the  extra cellular  space in an active latent pro-peptide form( zymogens),that gets activated via the proteolysis  of the N-terminal pro- domain(figure1).This event  aids in fast control  of MMP activity ,hence regulates the cytokine as  well as        chemokine  availability. Subsequently, MMP’s remain key in regulating rapid cellular events ,like cell migration at the time of inflammation.

In normal physiological    situations,maximum MMP’s are  activated  by other MMP’s  or proteases in the extra cellular  spaces but certain MMP’s get activated  intracellularly  by the enzyme fibrin ,or via separate modes (like phosphorylation  . MMP inhibition conversely gets modulated via Tissue inhibitors of Matrix Metalloproteinases (TIMPs),that are copresent with   MMP’s[7,18]. TIMPs inactivate MMP action  by binding to them,that in physiological    situations avoid enhanced tissue breakdown along with     injury .In  pathophysiological events ,  activation of  reactive oxygen species(ROS)  along with  separate factors(like Nitric oxide(NO),hypoxia ,pH)via a mode  that probably implicates auto catalytic activation[19].

Regarding the transcriptional MMP control ,much knowledge does not exist ,just as for inflammatory signalling  .Tumor necrosis factor alpha(TNF-α)  along with     interleukin -17(IL-17) are believed to stimulate transcription of    via transcription factor activator  protein-1(AP-1 ) along with  nuclear factor kappa B    (NFκB)[20,21].This action is blocked  by interferon gamma via NFκB) inhibition[22].  Lipopolysaccharide(LPS)  ,an endotoxin  stimulates Reactive oxygen species(ROS ) generation along with     p38 kinase phosphorylation,that activates AP-1 besides stimulation of MMP-9 transcription[23] . Infigure2 the MMP-9 promoter along with    oneNuclear factor-κB immunoglobulin  κ chain enhancer of B-cell (NFκB) along with      2 AP-1 binding sites are illustrated.Conversely MMP-2 is controlled  by TNF-α  as  well as     p38- MAPK, working via NFκB,but not AP-1(fig2),besides a caspase-8 based pathway CNS [24].In toto MMP control is not clear fully as  well as     differs among cell kinds along with     context based manner[25].

Legend for Figure 2.

Courtesy ref no-3-MMP-2 and MMP-9 promoter region with putative transcription factor binding sites. The boxes represent binding sites for the corresponding transcription factors. TSS: transcription start site; AP-1: activator protein 1; AP-2: activator protein 2; GATA-1: GATA-binding factor 1, erythroid transcription factor, globin transcription factor 1; SP-1: specificity protein 1; NF-κB: nuclear factor-κB, CREB: cyclic AMP response-element binding protein; p53: tumor protein p53 (modified after Peters et al.³⁸ and Rosenberg³⁹).

1.6 MMP in brain along with     Blood Brain Barrier

MMPs take part in a lot of physiological along with    pathological events in the brain as  well as     Blood Brain Barrier (BBB).The BBB represents the capillary endothelium which partitions blood  frombrain[26].This physical  barrier function is present in 3 areas  which are key regards to  barrier integrity –i)the capillary endothelium of the Brain   ii)tight junctions in between endothelial cells iii)basement membrane(BM)(Figure3)[26].

Legend for Figure 3.

Courtesy ref no-3-Blood–brain barrier anatomy. The blood–brain barrier is formed by capillary endothelial cells that are linked by tight junctions, surrounded by a basement membrane, and astrocytic endfeet. Astrocytes provide the cellular link to neurons; pericytes are embedded in the basement membrane. In disease, MMP protein expression and activity levels are increased, which is thought to result in blood–brain barrier leakage, possibly through degradation of tight junction and basement membrane proteins.

i)the the capillary endothelium of the Brain becomes a barrier for small hydrophilic compounds.ii) tight junctions seals the openings  in between the endothelial cells next to it ,that avoids  the unregulated paracellular passing of solutes In  addition to converting the endothelium of brain,  a low permeability Barrier[27].The main tight junction  proteins in the endothelium of Brain being claudin -1, claudin -5,occludin  as  well as     zona occludens-1.iii)The (BM representing a specialized ECM,that bridges endothelial cells with the pericytes  along with    astrocytes  to generate the neurovascular unit as  well as     promoting  crosstalk among cells in this unit  via receptors  like integrins as  well as    dystroglycans[28].

Endothelial cells, tight junctions along with   BM are key for appropriate  Barrier function,subsequently for Brain homeostasis   as  well as     total health of brain.Hence pathological impeachment of the endothelium, tight junctions along with   BM,resulting in impairment of barrier integrity,that can cause marked problems for the Brain,resulting in disease propagation[29,30.It has been posited that  MMP’s  digest tight junctions along with   BM proteins,  hence being key in aiding towards brain disease along with     directly influencing Brain health[31,32]. Nevertheless, minimal data is there to validate  this in view of technical problems to show MMPactivity  in vivo.Like Gu etal.,[33] demonstrated  escalated MMPactivity as  well as    greater  permeability at the BBB  in stroke ,at the time of reperfusion in vivo. Escalated MMP2  as  well as     MMP-9mRNA along with    activity levels  following reperfusion in spontaneously hypertensive rats  with middle cerebral artery occlusion(MCAO).Rempe etal.[3]further saw BBB  leakage in the piriform cortex  along with impaired tight junctions proteins,  pointing that MMP’s interfere with barrier integrity by breaking down these tight junctions proteins[34].Inhibition of MMP’s avoided the tight junctions proteins getting lost [34].Hence although technical problems,present ,initial proof that MMP’s digest tight junctions along with    ECMproteins n vivo Is  getting demonstrated.

1.7 Studying MMP’s-Various methodologies

MMP’s-  have been maximum Evaluated at the mRNA, protein along with    activity levels  . Utilizing various  experimental studies implicating real time quantitative PCR’s  along with    microarray Evaluation MMP mRNA expression has been documented[35]. MMP protein expression   has usually been tested  by Western blotting  ELISA or by immunohistochemistry .For checking MMP activity in vitro,a commonly utilized  method is substrate zymography . Substrate zymography isolates MMP’s by the  breakdown  of their substrates along with     their molecular weight[[36].This technique aids in finding whether   MMP is active  or latent .Every kind of Substrate zymography started from gelatin zymography,that is utilized   to find gelatinases MMP-2 as  well as     MMP-9[37].For  checking the other MMP’s,  instead of gelatin collagen,carboxy methylated  transferring or casein is utilized  [35,38,39].Other technique utilized for MMP activity detection comprise of in vitro are fluorogenic MMP substrates.The artificial substrates are made up of a fluorescent dye  which communicates  through a peptide to the quencher leading to fluorescence ,that constitutes a direct measurement of the MMP activity[40].

At present it is not feasible to be able to pinpoint the MMP activity in tissues in view of absence of reagents that are appropriate reagents .Only exception is gelatin in situ  zymography,a  technique   which aids in checking MMP-2 as  well as    MMP-9. gelatin in situ  zymography is a manipulation of Substrate zymography in frozen tissue sections of an unfixed sample .In this particular technique   an  MMP substrates  gets shifted  to a frozen  sections of an unfixed sample.The substrate gets digested  by  active MMPs  in a time  along with     dose based method,which  gets visualized utilizing microscopy[41].More generation of this technique    is in vivo zymography[42] in which Substrates get utilized in a live animal  for finding the MMP activity in vivo[43].

Methods

Thus a systematic review was carried out using the pubmed  and Google Scholar Search  engine with the MeSH Terms;   Matrix Metalloproteinases (MMP’s) along with their inhibitors,namely the, Tissue inhibitors of Matrix Metalloproteinases(TIMP); MS; cerebral aneurysm,stroke ,epilepsy, Parkinson’s disease(PD) ,Alzheimers disease(AD); brain cancer;Newer MMP inhibitors ;other therapies related to thesefrom 1900 to date in January 2021.

Results

We found a total of 4500 articles out of which we selected 220 articles for this review.No meta-analysis was done .

2. MMPs in diseases of the Central Nervous System(CNS)

2.1 Neuroinflammation

By definition Neuroinflammation   represents  a nonspecific  inflammatory process  in the brain .Every Central Nervous System(  CNS) disease  like multiple sclerosis(MS),cerebral aneurysm,stroke ,epilepsy, Parkinson’s disease(PD) ,Alzheimers disease(AD), along with   brain cancer-possess a    Neuroinflammatory part which implicates MMPs

The modes by which MMPs result in Neuroinflammation are i) MMPs activate  Neuroinflammatory  pathways.This gets achieved by indirect activation   of enzymes which work on signalling molecules  like cytokines , cell surface receptors ,cell-cell adhesion Molecules,or clotting factors[44,45].  Alternate method  is MMPs directly  activate      Neuroinflammatory  pathways.Like MT4 – MMP  possesses a TNF-α convertase activity via which trans membrane TNF-α gets  proteolytically  changed into soluble active TNF-α[46].ii) MMPs by themselves work as Neuroinflammatory  signalling Molecules.On stimulation utilizing  lipopolysaccharides(LPS) , apoptotic signals ,or in PD, neurons liberate   active MMPs into the interstitium ,that stimulates  microglial  activation along with    generation as  well as     liberation of   pro inflammatory cytokines(figure4[2][47,48].

Legend for Figure 4.

Courtesy ref no-3-MMPs in neuroinflammation. MMPs contribute to neuroinflammation through four mechanisms. (1) MMPs activate neuroinflammatory pathways and/or neurosignaling components. (2) MMPs act as signaling molecules themselves. (3) MMPs contribute to neuroinflammation-mediated neurotoxicity. (4) MMPs compromise vascular integrity resulting in blood–brain barrier leakage.

Iii)  MMPs  aid in   Neuroinflammation   modulated neurotoxicity  via shedding death   Molecules like the Fas ligand ,by influencing gamma amino butyric acid(GABA)   as  well as     glycine  amounts ,that manipulate chloride  channel activity,  by stimulation  of glutamate receptor - modulated excitotoxicity,or by changing  cell-ECM  Crosstalk[49,50]. Nevertheless, the precise mode  via which   MMPs result neurotoxicity  are  not totally clear  in (figure4[3][51-53].iv) Neuroinflammation stimulated MMPs might proteolyze cerebrovascular BM as  well as     tight junctions proteins,that could reduce vascular integrity causing barrier leakage  as  well as     extravasation (figure4[4][54-56].

Legend for Figure 5.

Courtesy ref no-3-MMPs in multiple sclerosis. (a) Brain endothelial cells and leukocytes secrete MMPs, which are thought to degrade tight junction and extracellular matrix proteins leading to extravasation of immune cells. (b) Leukocytes, microglia, neurons, and reactive astrocytes secrete MMPs, which demyelinate neuronal axons

Overall, MMPs get stimulated by as  well as     aid  in Neuroinflammation via different modes .Further MMPs aid in inflammation stimulated  barrier impairment  with facilitation of propagation of different diseases of the CNS(MS,cerebral aneurysm,stroke ,epilepsy, Parkinson’s disease(PD) ,Alzheimers disease(AD),brain cancer).

2.2 Multiple Sclerosis (MS)

Multiple Sclerosis(MS), represents a Neuroinflammatory autoimmune disease which influences  roughly 1.3 million people worldwide[57,,reviewed by us58].The myelin sheaths which envelope Neuronal axons  as  well as     nerve fibers  in the brain along with     spinal cord  are injured,that interferes with the Crosstalk as  well as    results in a broad kind of disease symptoms[59].

In MS the part of MMPs have been markedly  Evaluated  both in animal models along with     human tissue[60--62].These studies demonstrated that MMPs digest myelin basic  proteins,that results in de myelination along with     promotes MS  propagation (fig5(a)[56,63]. Utilizing experimental  autoimmune encephalomyelitis (EAE) animal models of MS  various subgroups  evaluated MMPs in the brain, brain capillaries , endothelial   cells  ,spinal cord ,lymph nodes along with     spleen demonstrating that a lot of MMPs were enhanced  at the time of peak EAE stage [61,64-66]. Particularly  in EAE mouse as  well as     rat model , mRNA  as  well as     proteins amount got escalated for MMP-2,-3,-8,-9,-10,-11,-12,-13,-28 MT1 – MMP, as  well as     MT6 – MMP.Conversely     mRNA as  well as     proteins for MT2-5 – MMP as  well as     MT21 – MMP   were reduced in lumbar along with  sacral    spinal   cord tissue  of EAE mice[67].Whereas the result of reduced  MMP’s amount, Specifically, those for MT – MMP’s   were  not understood ,it is well known that enhanced MMPs  accelerate the disease severity  in EAE rodent  models[60,61,64,65,68].

One property of MS), is  leukocytes extravasation along with     trans migration via the Brain endothelium into the CNS. MMPs might promote  this event  via activation of adhesion Molecules along with    breakdown  of the BM which surrounds  blood  vessel    (figure4[1] as  well as    [5]. Nevertheless, this is conflicting  as no definitive proof  is existing.Agarwaletal. demonstrated that selective MMP-2 as  well as     MMP-9 modulated cleavage of dystroglycans,that is a correlator  among astrocytes endfeet  along with     parenchymal  BM Molecules .This event exists at post capillary venules ,where extravasation takes place[60]. Nevertheless, this  as  well as     other studies  like study of Buhler etal.[61], pointing that MMPs are implicated in  immune cell  extravasation into the brain at the time of EAE.

Studies utilizing Brain  tissue,serum cerebrospinal fluid(CSF) samples from  MS patients,repeatedly observed  escalated protein amounts  for MMP-2,-3,-7,-9,-12,-13 along with    MT1 – MMP[61,69-71].In these studies , leukocytes were isolated  as the main  liberator of MMPs,the one maximum evaluated in MS is MMP-9, MMP-9 mRNA  as  well as     proteins  along with    activity  amounts are escalated in mononuclear blood cells ,serum as  well as     CSF  along with    are linked with barrier impairment   along with    disease propagation[72-74].

Immune cells  from the blood  can cross the BBB through a trans cellular(possibly  no MMP’s implicated )or a paracellular(MMP’s implicated)pathway .Regards to para cellular pathway,it has got demonstrated   that T cells , monocytes, along with    dendritic  cells express as  well as      liberate  active MMP-2 as  well as     MMP-9 that open the Brain endothelial tight junctions to pass through the barrier  along with     shift to the brain[60,75-78]. Following passage  via the  tight junctions, MMP-2 as  well as     MMP-9 cleave the transmembrane receptor  β- dystroglycans,that fixes astrocytic endfeet to the BM[60]. Additionally,   in case of lesional  MS tissue,MMP-1,-2-3,-9 along with    - 19 got isolated in the microglial    nodules  as  well as     microglial    like cells  where they aid in inflammation as  well as     derail the BBB more[79,80].

The MMP that gets highlighted in the MS field is  MMP-12,that is known as  macrophages Metalloproteinase,is presumed to be necessary  in the etiopathogenesis of MS,most probably secondary to its primary myelin or oligodendrocyte –toxic potential along with     its part in macrophages extravasation[81]. Simultaneously, MMP-12 KO mice  with(EAE had a many  fold less  deteriorated  robust severity along with    disease  burden as   compared  to  EAE wild kind  mice , pointing that  escalated MMP-12, expression amounts  are protective in MS[65].An extra study  demonstrated  that wild kind along with   MMP-12, KO mice  with EAE were more robust along with    their remaining disability at remission  was greater.

Hence although clarification is there that MMP aids  in MS,it is less understood if this takes place  by breaking down  the endothelial    BM,  that might promote leukocytes getting extravasated along with     shifted to the brain(figure5(a]).In the brain leukocytes then liberate  greater MMPs which aid in the total MMP action on axonal  demyelination besides neuronal cell death.

2.3 Cerebral Aneurysms

Aneurysm by definition is a    blood filled –bulge appearing like a balloon  in the arterial wall.The etiology of brain aneurysms are multiple. Like aging,  atherosclerosis, hypertension ,robust head injury ,all of which are associated with  Neuroinflammation[82].Maximum cerebral aneurysms do not get  diagnosed  till rupture,that remains life-threatening [83].Thus it is key  to avoid rupture by utilizing invasive brain  surgical intervention[84].Lower  invasive  technique would be to  avoid generation of aneurysms,that needs insight of aneurysm pathology .As per one theory MMPs breakdown  the vascular    extra cellular Matrix   ,thus aiding  in limited area of  ballooning  of a blood  vessel    resulting in Aneurysm generation as  well as     growth[85,86].Like human brain samples , protein expression  amounts  of plasmin, MMP-2, MMP-9, along with    MT1 – MMPs  were  escalated  in the wall of the aneurysm as   compared  to normal   Cerebral   arteries  as  well as     in total MMP-2/ MMP-9 proteolytic  activation was greater in aneurysm  tissue as   compared  to  control arteries[85].

Current reports  point that MMPs are implicated  in vascular calcification [87,88],that could be an extra negative action of MMPs aiding in the pathological result  of cerebral aneurysms.The calcification presence as revealed in a retrospective study ,was the only  marker of poor result[89].It was observed that larger Aneurysms are more likely to be calcified,whereas size by itself  did not cause a poor  action on the  result.Moreover,  in surgically securing intracranial Aneurysms tend to be an important cause of morbidity[89].

 A way of minimizing aneurysms propagation as  well as       growth   is via MMPs inhibition ,that could probably decrease the requirement  for invasive  treatment[90,91].Pre clinical studies illustrate that MMPs inhibitors  block the aneurysms generation   as  well as     growth  [91-93].Xiong etal.,[93] documented in a mouse model of Marfan syndrome that inhibition of MMP-2, as  well as     MMP-9, expression  of protein utilizing doxycycline blocked   ECM  breakdown that significantly postponed the aneurysms rupture.Another study utilizing a  mouse model, in whom 70%  of animals  had  brain aneurysms generation    as by Nuki etal’.,[92], showed  that  doxycycline decreased the aneurysms incidence by 10%.They further documented a decreased incidence(40%) of intracranial aneurysms in MMP-9  KO mice,while greater than 60% of MMP-2  KO mice, still generated cerebral aneurysms   , pointing that MMP-9   is key for aneurysms generation, statins  got utilized   in rats by Aoki etal.,[94,95],in whom Cerebral Aneurysms, got induced  by unilaterally ligating the common carotid artery  as  well as     hypertension .Therapy with statins reduced aneurysm  size by 30-40% within one mth possibly via a mode  which reduced MMP amounts,that is believed  to postpone Aneurysms generation as  well as       growth[91].The mode by which statins achieve this  is related to their cholesterol-reducing, anti inflammatory, along with  NFκB actions ,that reduce   MMP action[91].Even in humans statins  got evaluated.A retrospective study was conducted by Yoshimura etal.,[96],where they Evaluated results  from 117 patients with  ruptured cerebral aneurysms  for Evaluating if statins avoid rupture.9% of patients in this study with  ruptured cerebral aneurysms utilized   statins ,whie 26% of patients with  unruptured   cerebral aneurysms   utilized   statins,that pointed  that statins  reduced the  risks of  rupture of  cerebral aneurysms .

Overall, MMPs aid  in generation ,  growth  along with   rupture of  cerebral aneurysms  by ECM  breakdown,  that results in ballooning of  blood  vessels.Thus MMPs inhibition , particularly MMP-9 might avoid cerebral aneurysms potentially .

2.4 Stroke

Stroke was responsible for 7 million deaths all  over the world in 2012,that is about12%of all deaths ,putting Stroke as the number 2 cause of mortality[97]. Additionally,   10 million people  survive following a Stroke/year,with greater than 30 million people   in total who got over  an earlier stroke[98].The properties of stroke  represent lost brain function due  to i)reduced Cerebral blood flow (ischaemic) secondary to  a blockade of a blood  vessel ,  or ii) secondary to   bleeding into the brain parenchyma  or subarachnoid space(haemorrhagic).

MMPs result in a harmful action in the acute phase ,while it proves to be advantageous  in the post stroke phase[99].The harmful action is brought about  by impairment in regulation of MMPs,constituting i) neurovascular interference along with  brain  parenchymal damage(figure6(a).Different studies Evaluating human as  well as     rat brains demonstrated that protein along with    activity amounts of MMP-2,-3 as  well as     -9 are escalated  following a stroke as  well as     MCAO as   compared  to  control  tissue[100,101].Such alterations in MMP-2,-3 as  well as     -9 protein along with    activity amounts cause abnormal  proteolysis  which aid in Blood Brain Barrier impairment,that partly  decides the degree of the infarct[100-102]. Additionally,    studies utilizing rat stroke model points that by breaking down the basal lamina, MMPs escalate the proneness of Brain capillaries to rupture along with    haemorrhagic conversions  following  a stroke[103,104].Other harmful actions of MMPs in stroke got demonstrated   in studies utilizing rodent models  of focal Cerebral ischaemia.In these studies, escalated  MMP-9 protein amounts  were observed in the  acute phase(12-24h) following  stroke which concurred with the opening of the Blood Brain Barrier. As   compared  to that  MMP-2  protein amounts  were  escalated  lot of days  following  stroke[105],at the time when barrier  leakage  probably gets reinstalled.

Whereas  maximum work on MMPs in stroke has concentrated on MMP-2   as  well as     MMP-9[106],other MMPs also possess harmful actions. Following treating mice  subsequent  to thrombotic MCAO utilizing  tissue-type   plasminogen activator (tPA),Suzuki etal.,[107]  demonstrated   an escalated incidence of intracranial bleeding  as   compared  to mice not receiving tPA  therapy.They demonstrated   an escalated MMP-3 mRNA along with  protein  amount in the capillary endothelium in the infarct area of tPA  treated  mice  as   compared  to  tPA  untreated control mice. Thus conclusions of  Suzuki etal.,[107,108] werethat  in case of   tPA receiving mice MMP-3 digested the neurovascular basal lamina,thus opening of the   endothelial  Barrier as  well as     aiding  in the intracranial bleeding. Such observations pointing that MMP-3 has harmful actions at the time of tPA  therapy or gets stimulated  by tPA  ,unfortunately as at present tPA is the only therapy   that received FDA approval for the ischaemic stroke.

Nevertheless, MMPs further had advantageous actions  at the time of  recovery phase following  stroke(figure6[b])[109].Studies pointed  that MMP-9, MMP-2, as  well as     MMP-7 , refashion the lesional ischaemia along with    infarcted tissue In  addition to take part in angiogenesis, vasculogenesis, along with    neurogenesis[110,111].Two modes got isolated  by which MMPs carry out these actions i)at the time of tissue refashioning in the post –stroke recovery along with     healing phase MMPs digest  old ECM,in view of new ECM   as  well as     tissue could get developed[3,109,112].ii) at the time of ECM  digestion, MMPs(major MMP-7 along with     MMP-9  but MMP-1,-2-3-10 as  well as     11) escalate the growth factors that could be attained(like nerve growth factors  , Brain-Derived neurotrophic  factor( BDNF),  neurotrophin3/4, along with   vascular endothelial growth factors( VEGF).This takes place  via  cleavage of the inactive  growth factor   precursor into their   active form  or via liberation of active  growth factor    by proteolysis  of ECM  [110]. Escalated  amounts of growth factors   aid in tissue remodeling by stimulation, of angiogenesis,  vasculogenesis, along with    neurogenesis,all of them that are key in stroke recovery.These observations  pointing that at the time of remodeling as  well as      healing  event , MMPs are implicated  in the migration   of neuronal precursor cells  to the areas injured by stroke[113].

Overall , MMPs are necessary  in stroke in the acute phase as  well as     post –stroke recovery phase(figure6).In the acute phase, MMPs interfere with the Barrier integrity In  addition to injure the parenchymal tissue,while in the post –stroke phase by refashioning lesional ischaemic as  well as     infarcted tissue along with   take part in angiogenesis, vasculogenesis, along with    neurogenesis.

2.5 Epilepsy  

As per the World Health Organization(WHO),a minimum of 65 million  people in the world are afflicted by  Epilepsy[114,115]. Epilepsy   encompasses  different diseases  along with     seizure syndromes , In  addition to get diagnosed with epilepsy following recurrent ,unprovoked seizures[116].

The part of MMPs in Epilepsy remains uncertain at present , nevertheless, studies point that  MMPs aid in  epilepgogenesis, epilepsy propagation   along with    brain remodeling following seizure.Like MMP-9 KO  mice possess lowersensitivity to chemically-stimulated   seizures as   compared  to  wild type mice,  whereas on the other hand  human  MMP-9 overexpressing  rats possess greater   sensitivity to chemically-stimulated   seizures  pointing that MMP-9 influences epilepgogenesis as  well as    /or seizures generation[117,118].

MMP  amounts are escalated  in the epileptic brain.  In case of chemically-stimulated   seizures models along with     temporal lobe epilepsy, MMP-9 protein as  well as     activity  amounts are escalated in neurons  of the parietal  along with   frontal cortex, in  addition to   the thalamus,  the areas where the seizures got initiated [51,118-120].Li etal.[121], observed escalated MMP-9 protein as  well as      activity  amounts in CSF in adult epilepsy  patients with generalized tonic –clonic  convulsions as   compared  to age matched controls  or non   epileptic   persons.   MMP-9 protein amounts were further observed to be  escalated in  serum from patients  following  convulsions.  Three  times greater MMP-9 protein amounts were  further observed by Suenaga etal[122],in serum from children  with encephalopathy subsequent to post febrile seizures, along with    children  with   convulsive status epilepticus,  in contrast to  healthy children[122].As per experimental work escalated MMP-9 protein as  well as     activity  amounts mainly possesses 2  functions  i) MMP-9 aids in  seizures stimulated   neuronal cell death  as  well as    ii) MMP-9  is key in refashioning   neuronal   networks  following seizures. Neuronal cell death   in regions, possessing escalated MMP-9 amounts was illustrated by Jourquin etal.[52], as  well as     Hoehna etal.[51], along with    documented  that inhibitors of MMP-9 decreased cell death  .Other studies revealed that MMP-9 is implicated in structural remodeling,  mossy fiber sprouting ,reduced   seizures stimulated   trimming of dendritic   spines along with    reduce abnormal synapses generation[118,120,123].

The part of MMP-2 in the epileptic brain is poorly known as   compared  to MMP-9. Jourquin etal. .[75], demonstrated that MMP-2 does not aid in neuronal cell death  in epilepsy. Nevertheless, it is feasible that MMP-2 aids in structural remodeling in epileptogenesis as MMP-2 mRNA, protein as  well as     activity  amounts are escalated following  convulsions[118,120,124]

Various sources revealed that Blood Brain Barrier impairment  exists in epilepsy along with    seizures stimulated    barrier leakage[125-128].Moreover, this barrier leakage by itself acts as a trigger for  seizures, pointing that  there  is a vicious feedback loop aiding in propagation   of epilepsy[128,129]. Possibly MMPs participate by breaking down of tight junctions  as  well as     ECM proteins,  that potentially aid  in barrier leakage following  convulsions[30-32].Li etal.[121], demonstrated that escalated MMP-9 protein as  well as     activity  amounts in serum CSF  of patients with generalized tonic –clonic  convulsions  were linked to barrier leakage. Moreover, this barrier leakage was correlated with  leukocytes extravasation  into the brain following  convulsions. leukocytes extravasation     implicates a complicated ,several steps  event needing MMPs Specifically, MMP-2 as  well as     MMP-9,both  coming from the endothelium  along with    activated T cells as  well as      macrophages[,78,110]. Li etal.[121], demonstrated that in patients with generalized tonic –clonic  convulsions   that escalated CSF  leukocytes  counts were associated with enhanced MMP-9 amounts, in     CSF In  addition to   the extent of barrier leakage[201].Hence MMP-2 as  well as     MMP-9 appeared to aid  in seizure as  well as    /or epilepgogenesis, neuronal   networks, remodeling, neuronal cell death   as  well as     barrier leakage following seizure.About the rest of MMPs not much insight exists in epilepsy.

2.6 Alzheimers disease (AD)

Alzheimers disease(AD ) represents a Neurodegenerative disease which implicates greater than 20million patients  worldwide[130,131].Further it has been anticipated  that about 100 million patients   of AD would be there by 2050[132].Inspite of all research work ,the etiopathogenesis along with    propagation   remains  ill understood ,besides the treatment  or avoidance is not present right now.The pathology of AD has the properties   of  brain collection of amyloid  beta(Aβ), generation  of amyloid  beta  plaques, generation  of neurofibrillary   tangles along with    Neuroinflammation,all of whom aid in Neurodegeneration [133,reviewed by us 134-139].

Various groups  demonstrated  that MMP amounts in rodent models  of AD  are enhanced  as   compared  to control   animals. Enhanced MMP-9 protein amounts were observed in brain slices from transgenic   amyloid precursor protein (APP)/PS1 mice , in contrast to  wild kind mice was revealed by Yan etal.[140]. Utilizing 5x  FAD mice ,Py etal.,[141]found escalated    MMP-2, MMP-9,MT1- MMP amounts   in the hippocampus in contrast to  control  mice.Primarily MMP-2, as  well as     MMP-9, were expressed  in astrocytes,while MT1- MMP were seen in  neurons, MT1- MMP as  well as     MMP-9, were also observed  in amyloid  beta  plaques.Validating these observations  various groups  found overexpression  of proteolytic activity MMP-2,-3 -9mRNA as  well as     protein  in post-mortem brains from patients   of AD[142,143] . Utilizing zymography , Horstmann etal[144], found MMP-2,-3 -9, as  well as     -10   activity  amounts in serum along with     CSF from patients   of AD as  well as     contrasted them  to gender  along with    age matched healthy control   persons from    patients   of AD.They detected  that MMP-3 activity was escalated by  40% in plasma   along with     60% in CSF patients   of AD as   compared  to control   persons was reduced by 32% in contrast to  CSF samples from healthy control   persons ,whereas   activity amounts were unaltered  in plasma  ,along with  MMP-9 as  well as     MMP-10  activity   were  not found in  CSF, MMP-9  activity  in plasma  was reduced by 41% as   compared  to healthy control   persons . Greater amounts  of pro- MMP-9    protein in   plasma   samples from  AD patients   as   compared  to control   persons.Lorenzi  etal.,[145]observed greater amounts of pro MMP-2  protein in plasma samples from patients   of AD in contrast to   control persons .

Certain work was conducted for getting insight into the correlation  of MMPs along with    Aβ.Deb as  well as     Gottschalk [146] revealed that in rat hippocampal  along with    astrocytes cultures that Aβ₄₀ stimulated protein expression  in  addition to  proteolytic activity of MMP-2,-3 -9.They documented that by exposure of segregated rat capillaries to Aβ₄₀  ex vivo enhanced MMP-2, as  well as     MMP -9  protein along with    activity amounts[147].Findings akin to these were made in a transgenic mouse AD  model(Tg 2567 hAPPmice),where    MMP-2, as  well as     MMP -9  amounts  in brain capillaries   were escalated in contrast to  capillaries   wild kind mice.Yin etal.[148], found in APP/PS1 mice that astrocytes that surrounded  amyloid  beta  plaques liberated greater MMP-2, as  well as    MMP -9 amounts.They further illustrated that on breeding  APP/PS1 mice with MMP-2 or  MMP -9  KO mice,or pharmacologically inhibited MMP-2 or  MMP -9  in APPsw mice amount,enhanced    Aβ  brain  amounts   by 1.5fold, in contrast to  controls along with    enhanced  Aβ half life  by approximately 50%[229].Further Yin etal.[149], revealed   in the phosphate buffer –insoluble fraction  of cortex as  well as     hippocampus  of MMP-2 KO mice   escalated murine Aβ₄₀       along with        Aβ₄₂  in contrast to    age matched wild kind mice,while Aβ₄₀       along with                 Aβ₄₂   continued to be unaltered  in the phosphate buffer –insoluble fraction  .In the cortex of MMP-9 KO mice,murine    Aβ₄₂ amounts were   escalated inthe  phosphate buffer –soluble fraction  of cortex as  well as     hippocampus   in contrast to    age matched wild kind mice,whereas they continued to be unaltered  in the phosphate buffer –insoluble fraction.These actions were secondary to reduced Aβ  proteolysis as  well as     were not  related to escalated Aβ generation.These   observations pointed  that  MMPs potentially aid in Aβ clearance .Concerning this MMP-2,-3 as  well as      MMP -9  proteolytically break down  Aβ[140,149,150].It was revealed by Ridnour etal.[151],that amounts of  Aβ_1-16,  that is a product of Aβ metabolism  by MMP -9   along with MMP -9  activity were reduced in brain lysates  of hAPPSwD1 mice where nitric oxide synthase(NOS) was absent in contrast to   their littermates  that expressed NOS .On the basis of these outcomes ,they concluded  that potentially nitric oxide (NO) is implicated  in clearing the plaques, via escalated MMP -9  activity.Yan etal[140], documented that  in brain slices of APP/PS1 mice in situ  that MMP -9   digests  the fibrillary  Aβ₄₂ along with    compact amyloid  plaques.The in vivo  association among  MMP -9  protein expression along with    Aβ plaques, was   Evaluated by Wang etal.,[152] by deletion of the MMP -9    gene  in APP/PS1 mice. Aβ plaques, were greater in size  along with     number ,in the  cortex as  well as      hippocampus  of these APP/PS1 MMP-9 KO mice, in contrast to    APP/PS1 mice possessing  functional MMP -9.Lastly Liao etal.[153] illustrated that MT1- MMP breaks  down   both soluble in  addition to    fibrillary  Aβ peptides  in a time –based way  in vitro along with     this action gets inhibited  by MMP inhibitors  GM 6001 along with  TIMP2.  Liaoetal.[153], further demonstrated   that  MT1- MMP breaks  down    brain fibrillary amyloid  plaques in another mouse AD  model(hAPPSwD1) in situ  .

These observations point  to an inverse association with    MMP-2/ MMP-9 along with    Aβ,where  one anticipates  lower MMP-9 amounts in the AD brain  possessing larger Aβ loads. Nevertheless,  MMP’s are upregulated   in the  AD brain  ,that is  separate from what one predicts  with the findings  observed earlier.1 reason for this  might be that  MMP-modulated Aβ breaking down is markedly less  to avoid Aβ collection in the brain.Whereas MMP’s might be  implicated in the Aβ processing  along with     clearing off the plaques they do not seem to be potentially  the main actors in this event [140,148].

Hence MMP’s are escalated  in the AD brain, Nevertheless,  the part played by them in AD remains unclear.The present literature available is not sure on if MMP’s aid in AD propagation or may possess an advantageous  role on this disease. Whereas probability exists  that MMP’s have no main role in  AD,studies  illustrated that MMP’s could probably be implicated in processing Aβ  along with    AD propagation.

2.7 Parkinson’s disease (PD)

Parkinson’s disease(PD)  represents a Neurodegenerative disease   implicating movement aberration  where over 6 million patients are afflicted  world over[154].In 1817 it was initially detailed by James Parkinson[155],although many  details of the disease remain unclear. Molecularly, PD has the properties  of collection of α-synuclein  in the dopaminergic neuron  leading to the generation of  Lewy bodies ,cell injury  along with neuronal death  of dopaminergic neurons .Further   PD is associated  with     Neuroinflammation that accelerates the   disease[156].

In the field involving PD, MMP’s have got evaluated. MMP- 1,2  as  well as      9 protein as  well as     activity  amounts were evaluated by Lorenzi etal.,[157] in postmortem  brain tissue from PD    patients  with age –matched control persons . Whereas  they did not  find any alteration  in MMP-1 as  well as       9,they observed a decrease  in 50% in MMP-2  activity  amounts in the substantia nigra [151].

Besides MMP-1,2  as well as 9,work on PD    has concentrated  basically on MMP-3.Three modes have been offered  regarding  how MMP-3 might be implicated in PD .i) Utilizing in vitro cell lines    along with   primary cultures of dopaminergic neurons from rat Choi etal.,[158] saw that active    MMP-3 gets liberated  from apoptotic  dopaminergic neurons In  addition to,that   MMP-3 protein amounts were greater in contrast to  healthy non apoptotic  dopaminergic neurons. Utilizing the  MPTP mouse PD model ,Chung etal.,[156] observed escalated MMP-3  protein  as  well as     activity  amounts  in contrast to control mice leading to  apoptosis    as  well as      cell death. MMP-3 is further implicated in caspase-3 activation, particularly in apoptotic  signalling upstream of  cJun N-terminal kinases [156,158].ii) MMP-3 might have potential role in α-synuclein  cleavage .Sung etal.,[159] illustrated that MMP-3  cleaves  purified α-synuclein   in vitro along with     that α-synuclein   accumulation  escalatedin  the existence of  MMP-3 cleaved   α-synuclein   fragments in contrast to   a solution  not possessing these fragments.Moreover ,collected α-synuclein   fragments possessed higher toxicity  in cell viability assays in contrast to  collections of nonfragmented α-synuclein.Further Sung etal.,[159] documented that MMP-1,2  as  well as    9 along with    MT1- MMP  cleaves  purified α-synuclein   also, Nevertheless,they possessed lesser efficacy  as   compared  to MMP-3.Further more Kim etal .,[160] demonstrated   in microglial cultures  along with    6OHDA mouse PD model that α-synuclein   -stimulated  cell migration of reactive microglia   into the pathological area ,that augmented PD pathogenesis.iii)Current work points that  neuroinflammatory   process is implicated  like microglial activation,T  leukocytes  infiltration  along with    Blood Brain Barrier impairment in PD[156,161].This validates ,Chung etal.,[156] results  who demonstrated    that infiltration   of peripheral  immune cells  along with    brain uptake of FITC –albumin (70kDa)in the MPTP mouse PD model, pointing thatneuroinflammation along with    barrier leakage .They  revealed in  MMP-3  KO mice   that  barrier leakage got ameliorated    Besides the  reduction of  immune cells   numbers  infiltrating the substantia nigra got reduced , illustrating MMP-3  implication in the MPTP mouse PD model.

Thus concluding ,that MMP-3    appears to be implicated   in dopaminergic  Neurodegeneration, neuroinflammation along with    barrier leakage.More work is required  for  clarification of the part  of MMPs  in PD along with     whether MMP inhibition  might turn out  to be a fruitful  treatment method.

2.8 Brain Cancer

Over 250,000 people got diagnosed with a newly  diagnosed Brain Cancer with about 190,000 patients dying world over  with the same in 2012[162]. Brain Cancer patients possess a very poor survival rates.Despite aggressive treatment,  the median survival of patients with glioblastoma multiforme ,that is amongst  the commonest  along with      a very aggressive  malignant  Brain Cancer, is only 12-17 mths [163,164].Thus  for efficacious therapy  of Brain Cancer,  newer novel strategies along with interventions arerequired. MMPs    serve as  those potential targets  in cancer  in view of their part in  Cancer biology .Thus , mRNA along with      protein overexpression  of   MMP-1,-2,-3,-7,-8,  9,-13, as well as     MT1- MMP  has been illustrated in a lot of malignant peripheral along with       CNS  tumors ,besides an association among MMP expression,  tumor  acceleration rate, staging of tumor along with      prognosis has been revealed[165].Actually liberated MMPs( MMP-1,-2,-3,-7,-8,  9, as well as    -13) along with   membrane  bound MT- MMPs are key  for the generation of   Cancer  metastases,their invasion   into the brain  along with   the generation of    secondary    tumors,with  MMPs taking part in maximum steps  of this metastatic event(figure7)[166,168].

i) Generation of metastatic cells at the initial tumor-In case of primary tumor,Li et al.,[165] demonstrated   that  MMP-7,transforms the transmembrane cell-cell adhesion protein   E-cadherin into a soluble protein leading to inefficacious binding among tumor cells ,that lets the  Cancer cells  to detach from the primary tumor along with    Generate    metastases having the capacity  of entering the blood   stream .

ii) metastatic cells intravasating  into the blood circulation-Junker Jenson [168],observed that MMP-1,- takes part in the metastatic cells intravasating   from a human Hep3 epidermoid carcinoma graft to chick embryos .They demonstrated    that MMP-1 controls endothelial permeability along with trans endothelial migration validated      tumor invasion     via  activation of the endothelial non tumor/non matrix receptor PAR1. Junker Jenson [168], further utilized    grafts with naturally  acquired or experimentally   stimulated  MMP-1 reduction ,observing that intravasation got reduced by greater than 80%[168].

iii) adhesion of metastatic cells with the brain capillary endothelium –it is not clear  if MMPs take part  in this particular step of the metastatic event ,   nevertheless,knowing the different functions MMPs possess this is feasible.It was illustrated by Hummel etal.,[169]that MMP-2,-3,  9, as well as    -12 are implicated in the shedding of cell  adhesion Molecules (like  vascular cell adhesion molecule[VCAM-1])from the plasma membrane of human brain endothelium cells      following   TNF-α stimulated  MMP  upregulation. MMPs might further aid in shedding CD44 in metastatic cells adhesion with the brain capillary endothelium[170].This is Specifically significant in view of CD44 being a cell surface glycoprotein  in endothelial cells, leukocytes along with a lot of  metastatic Cancer cells,where it  delivers selectins thus promoting adhesion of the host cell to the brain   capillary   endothelium[171].

iv) extravasation of metastatic Cancer cells- MMPs aid in extravasation of metastatic Cancer cells along with promote paracellular trans migration of  tumor  cells across brain capillary endothelial  cells   in vivo,besides the Blood Brain Barrier in vitro[172,173].That MMP-2      aids  the migration   of the breast Cancer cells  across the cell m       layer of an in vitro   human Blood Brain Barrier model  was demonstrated by Lee etal.[172]. Felding –HabermannB[173] revealed  in vivo how breast Cancer cells   injected into  the left carotid artery of BALB/cmice lead to    brain metastases.Regards to  paracellular extravasation, endothelial  cell – cell   contacts have to  be loosened so that   metastatic cells  can move across the endothelium.For this  junction proteins are needed to be breaking down.Actually MMPs proteolyse  tight junctions as well as     adherence  junctional proteins, thus opening  the paracellular  route[,30,31,165].Feng etal.,[30] ,illustrated in leukaemic BALB/c    nu/nu  mice that leukaemic cells liberate   MMP-2 as well as    MMP-9,that broke down  the tight junctions proteins zona occludens -1,claudin-5 and occludin.Hence   MMPs are key  for leukaemic as well as     other cells  to cross the  capillary endothelium as well as     get entry into brain .

v) metastatic cells adhesion to the ECM-various membrane type MMPs(MT1-,-2,-3,-5) MMPshed the cell   being a cell surface glycoprotein  CD44,that is key  in metastatic cells adhesion to the luminal  endothelial membrane along with the ECM on the basolateral  side of the endothelium[170,174]. CD44, is implicated in presenting cytokine, chemokine,  cells adhesion molecules, growth factors  along with other proteins likeMMP2 awa MMP9 to receptors on metastatic along with endothelial   cells   awa modulates signalling  which controls  metastatic cell migration along with  invasion  [174,175]. CD44, further crosstalks with ECM  proteins like fibronectin,,thus corroborating  metastatic cells adhesion to the ECM[176].

vi)Role of MMPs in ECM proteolysis-localized opening of the ECM(figure7)is essential for metastatic cells to  bypass it,with  MMP-2 as well as     MMP-9,appearing to assist this event  via ECM proteolysis. in contrast to  control samples Wang etal.,[271] checked the MMP-2 as well as     MMP-9 amounts  in human glioma samples  as well as     MMP-2 along with  MMP-9 , documented that MMP-2 as well as   MMP-9 amounts were escalated in human glioma,besides being associated with  the degree of    glioma malignancy . Wang etal.,[177] further illustrated that MMP-2 as well as    MMP-9 staining in gliomas was limited to  the cytoplasm of tumor cells , endothelial  cells along with their  ECM,Thus concluding that  by breaking down the ECM, MMP-2 as well as     MMP-9 are the factors that  decide how much invasiveness along with angiogenesis gliomas  possess[177].  Other studies in Cancer  cells  documented that CD44, captures MMP-2 as well as     MMP-9 at the tumor cell surface,  where MMPs then digest  locally the ECM that surrounds the tumor cell at the time of extravasation[178].

Other MMPs might further aid in ECM proteolysis.Despite conclusive   in vivo evidence  to validate this is lacking ,many observations  suggest these findings. Escalated  MT1- MMP  mRNA along with protein  amounts in resected Glioblastoma  tissue was documented by Shimada etal.,[180] as   compared  to non- tumor control tissue. MT1- MMP   amounts were associated  with pro- MMP-2 activation   along with     tumor malignancy  with Shiomi etal.,[180] offering a posit  that MMP-2 as well as     MT1- MMP    probably aid  in glioma invasion  via breaking down brain ECM proteoglycans besides glia limitans . Escalated  MT1- MMP   along with     MT2- MMP  mRNA along with protein  amounts were documented by Nakada etal.,[179] in astrocytomas in contrast to   control  brain  tissue.  Thus they concluded that both activate MMP-2,which then breaks down  the ECM.Other groups  revealed that MT3- MMP  directly cleaves   ECM  parts like type III collagen, proteoglycans as well as     interstitial  collagens[180].These observations are crucial for   Cancer  metastases as well as    as well as     invasion as they lead to digestion of ECM.

vii) utilizing  metastatic cells migration-for the generation of a secondarytumor, Cancer cells need space on settling in new tissues.This space is probably developed  by MMP-modulated ECM breaking down along with remodeling.In this regard Belien etal.,[181] illustrated MT1- MMP   digests axonal myelination  proteins which inhibits migration of cells  along with neurite outgrowth.With the knowledge that invasive glioma   cells  migrate  with preference  move along the white matter tracts  in  addition to  MT1- MMP     breaks  down  the cell membrane inhibiting proteins which are enmeshed  within white matter  fiber tracts ,with these findings pointing that MT1- MMP      promotes  cell migration ,hence escalatation of glioma malignancy.

viii) MMPs along with tumor microenvironment as well as     tumor  angiogenesis- escalatation of proof point that MMPs  develop along with sustain a microenvironment that  promotes tumor growth  as well as     survival . MMPs  promotes  Cancer cells proliferation  by control of cytokines , growth factors as well as      cell  adhesion Molecules which attract tumor cells along with aid in the tumor  spreading[167].Thus escalatation of MMPs amounts  are believed  to associate with  enhanced     malignancy,besides studies document that MMP mRNA, protein as  well as     activity  amounts are escalated in cancer[167]. Escalated MMP-1 as well as , protein amounts in glioma  in contrast to   amounts in the resected brain tissue in patients with epilepsy  were observed by Xu et al.[182]. Amounts of MMP-1,-2,-3,-7,-8,  9, as well as    -13,    MT1-,-2,-3,-5, as well as     -6 MMP were also enhanced in brain tumors in contrast to  non cancerous  brain tissue[177,178].Same MT MMPs activate pro MMP-2 as well as     pro MMP-13,besides protein as  well as     activity  amounts of those MT MMPs are associate with  pro MMP-2 activation in gliomas ,thus  with tumor  malignancy[183,185].MMPs further aid in angiogenesis,that is key  for the tumor microenvironment in view of blood  vessels   feeding the   tumors with  oxygen as well as     nutrients ,thus  aiding in   tumor survival, growth as well as     escalatation of  tumor malignancy[179,184]. Angiogenesis depends on endothelial cell  migration into the surrounding connective tissues as well as     MMPs are key  in this event [186]. MMPs break down the ECM, liberation of ECM concealed  pro- angiogenic   substances like VEGF,process growth factors  ,integrins   as well as      adhesion molecules thus maintaining a balance among pro  as well as     anti angiogenesis[179,184]. Tumor  stimulated   angiogenesis is significant in maintaining  growth of  solid tumors along with    the functional  part of  MMPs in  tumor angiogenesis has been well proven [187,188].Like MMPs  aid in recruitment of pericytes  ,that are present in tumor blood  vessels as well as     is key for the generation   of a      functional vascular network . MMPs take part in various steps of recruitment of pericytes. 1stly   MMPs break  down the ECM for aiding in pericytes invasion.Secondly ,  MMPs  induce  pericytes proliferation as well as     protection of pericytes from apoptosis.3^rd , MMPs aid  in recruitment of bone marrow obtained  stem cells ,that differentiateinto  pericytes[189].

Angiogenesis ,is necessary for  tumor growth,  hence blockade of angiogenesis is believed to be a good approach for regulation of malignant tumors.  Hence MMPs can prove to be  advantageous   in cancer in view of their anti angiogenic  action  which is dependent  on an processing growth factors ,integrins as well as      adhesion molecules.Like tumor angiogenesis is decreased in  integrin α1 null mice in contrast to   wild kind mice[87]. integrin α1 null mice overexpress  MMP-9 that cleaves angiostatin from plasminogen , as well as     angiostatin inhibits endothelial   cells    growth,  leading to tumor growth  inhibition[190].

MMPs further are implicated in tumor microenvironment by enhancing the permeability of the vascular endothelium    in  brain tumors,  which is then labelled as ‘’blood tumor barrier ‘’.Hence ’blood tumor barrier is leaky  in contrast to   healthy,  intact  ’blood brain barrier that aids in feeding the tumor with an enhanced needs of the nutrients[191].It was,  illustrated by Noell etal.,[192] that enhanced MMP2.-3 as well as     -9immunoreactivity  in brain slices of human papillary  glioblastomas    in contrast to    non  tumor brain tissue as well as     presumed  ’blood brain barrier  leakage in this region.Studies from different groups revealed  pro MMP-2 as well as     pro MMP-9  amounts in the CSF of dogs possessing intracranial tumors in contrast to     healthy dogs [193,194]. Escalated   CSF pro MMPs were described as secondary to  the  recruitment of leukocytes by the tumor was posited  by Turba et al.,[194] that MMPs probably promoted leukocytes bypassing the BBB  to be able to reach the  tumor, as well as     those leukocytes liberated - MMP 9  into the CSF.

Thus , MMP’s are key in many ways in brain cancer .Their major part  is in promotion of metastases along with angiogenesis  that makes them significant targets for brain cancer  therapy  along with     avoidance of   brain tumors.

3. Inhibition of MMP’s for Treatment of brain tumors

MMP  inhibitors like  batimastat, Marimastat   along with     doxycycline  could be utilized potentially [reviewed by us in gynae mmp 195].At present , Nevertheless,only MMP  inhibitors that got approval from FDA is the tetracycline analogue doxycycline(Periostat) for treating periodontal disease[196-197].The biggest hurdle  in generation of MMP  inhibitors as per clinical utilization  in patients  is the absence  of insight in the complicated   MMP biology,besides the part played by them in CNS disorders  like multiple sclerosis(MS),cerebral aneurysm,stroke ,epilepsy, Parkinson’s disease(PD) ,Alzheimers disease(AD).However , lot of preclinical results  which validate  MMP  inhibition  in the form of therapeutic approach in MS, stroke along with    brain cancer.

1^st ,a lot of MMP  inhibitors reduce the incidence as  well as      severity  of EAE in animal MS models [145,198,199]. MMP  inhibitor-Ro-31-9730 repressed EAE in rats[199], as well as      minocycline decreased MMP 9  protein along with   activity   in Tcells ,besides repressing  EAE in mice[198].2^nd, pre clinical results from mouse as well as     rat cancer models that included colon as  well as      breast cancer demonstrated that batimastat decreased tumor growth,  number along with   secondary  lung as  well as      lymphatic metastases taking place [200,201].3^rd, MMP  inhibition  utilizing  GM 6001 or BB94 in rodent  stroke models immediately(hours) following stroke  decreased edema, size of the infarct, as  well as      amount of haemorrhagic processes [107,202]. MMP Inhibition that was of longterm(days)  utilizing BB1101 for uptill 48hrs  following stroke in rats decreased barrier leakage , nevertheless,  their was no improvement in neurologic function as  well as     in behavioural tests[203]. Inhibition  of    MMPs  utilizing  FN-439 or BB94 in a rat stroke models for a week  even accelerated ischemic brain damage  besides appeared to stop functional improvement[112].

Despite MMP  inhibition    appears advantageous  in animal  models  ,it has not been, illustrated or only partially ,illustrated in clinical studies.In MS , 16 cases with relapsing –remitting MS got treated with doxycycline/interferon combination for 4 mths(NCT 00246324[204]).This doxycycline/interferon combination decreased  brain lesions which was associated  with    decreased   serum MMP 9  amounts  as  well as      improved post therapy EDDS values with just one patient relapsing.  In total doxycycline/interferon therapy was believed to be safe, efficacious ,well tolerated,with the conclusion that a trial with greater patient cohort  needs to be carried out. Nevertheless, a documentation on a follow up trial has not been published .

In a trial on stroke, minocycline was administered  with/without tPA  therapy to 60 patients within 6h following  stroke(NCT 00630396[205]).The mean baseline  NIH Stroke  Scale Score was 8.5±5.8(moderate stroke). Minocycline did not result in severe haemorrhages in patients receiving   tPA  therapy,was believed to be safe as  well as     well tolerated,upto  10mg/kg,iv alone or in with combination with tPA ,thus believed to be ideal for a combination tPA  therapy.Lampi et al.,[206], in another clinical study ,illustrated that  minocycline improved patient results significantly . Particularly, NIH     Stroke  Scale, as  well as     Rankin Scale Scores were lowered significantly  along with    the Barthel Index was significantly escalated  .Further more participants are still under recruitment  for a study Evaluating  the safety as  well as      effectiveness of Minocycline in acute cerebral haemorrhage(MACH Trial  NCT 01805895).

Finally ,various clinical studies  Evaluating  the MMP  inhibition     in brain cancer have been carried out.In 2 phase II  trials, a combination of Marimastat as  well as      temozolomide was  evaluated for recurrent GBM along with gliomas[[207,208]. These trials revealed  that  Marimastat as  well as      temozolomide seems to enhance propagation –free survival (PFS):at 6mths , PFS. 39% for GBM(target PFS40%) as   compared  to temozolomide alone.Other brain cancer trials with MMP  inhibitors demonstrated no improvement .Prinomastat as  well as      temozolomide  as   compared  to temozolomide alone    did not improve 1 yr survival or PFS (NCT 00042004147[209]Pfizer ).Akin to that phase I as  well as      II trial  with the MMP  inhibitor COL-3 in recurrent high grade gliomas  do not demand more studies(NCT   00042004147[308,9]). Additionally,   clinical trials Evaluating  greater than 50 MMP  inhibitors for cancer therapy have failed [210-214].Vandenbrouke and Libert[213] summarizing the causes for failure ,included complicated  MMP biology , as  well as      absence of insight into MMPs .Further suboptimal trial design ,inadequate clinical endpoints ,utilization of metabolically unstable MMP  inhibitors  ,poor oral bioavailability ,no action ,toxic side effects  as  well as      discrepancies in preclinical animal  model as  well as      human patients[213].Thus whereas lot of work has been done in MMP research over decades ,this field  is distant from a treatment    breakthrough .Hence greater work needs to be conducted to Evaluate if MMP  inhibition      can be a viable approach for treatment.

4. Conclusions

Thus we have summarized the insight  in the part played by MMPs  in health along with disease , Specifically, the BBB.Whereas  we have knowledge that take  part in significant  neuro physiological    functions  alomg with have basic insight of their part  like Neuroinflammation,MS,Stroke ,awa brain cancer ,little is clear regards to MMPs  in other conditions  like cerebral aneurysm,stroke ,epilepsy, Parkinson’s disease(PD) .

Lot of varied MMPs  possess  a wide range of separate function in different physiological   as  well as       pathological events leading to  both advantageous   along with     harmful actions within the same disease  based on their presence ,time point, as  well as       other factors.Hence MMP expression   along with  functional action differ  importantly ,besides being  context –base. Nevertheless there is one common denominator in all diseases  that is Neuroinflammation  which implicates MMPs.

From what we have learnt  is   MMP inhibition is an extra treatment choice  remains a problematic issue  with history of failure ,but still detailed in therapy of CNS conditions.Other than doxycycline nothing has therapeutic  significance .Knowing the gap in our understanding   greater insight needed for  preventing the earlier mistakes . Particularly  ,research just  concentrated on MMP-2 as  well as       MMP-9 requires to be broadened to include rest of MMPs  to get insight in their part in health  as  well as       disease  regards to MMP biology generally.Like  finding the mode of action  controlling the MMP s could give newer therapeutic options .Further   Particular as  well as       selective MMP  inhibitors  which can get safely utilized  with nil or just minor side actions  need to be isolated.

Our insight in getting MMP biology regards to health as  well as       disease is just seeping  in .Future MMP inhibitors like the one quoted earlier might aid in epilepsy therapy ,developing ECV related to NDEV in therapy of AD  as  well as       utilization of natural products like  from honey etc are getting explored besides for brain cancer newer methods getting designed.

Further Broekaart et al. observed in a rat model of temporal lobe epilepsyalong with status epilepticus patients  . Using quantitative PCR (qPCR) and immunohistochemistry, they   studied the expression of MMPs and their endogenous inhibitors tissue inhibitors of metalloproteinases (TIMPs) in patients with status epilepticus (SE) or temporal lobe epilepsy (TLE) and in a rat TLE model. Furthermore, we tested the MMP2/9 inhibitor IPR-179 in the rapid-kindling rat model and in the intrahippocampal kainic acid mouse model. In both human and experimental epilepsy, MMP and TIMP expression were persistently dysregulated in the hippocampus compared with in controls. IPR-179 treatment reduced seizure severity in the rapid-kindling model and reduced the number of spontaneous seizures in the kainic acid model (during and up to 7 weeks after delivery) without side effects while improving cognitive behavior. Moreover, our data suggest that IPR-179 prevented an MMP2/9-dependent switch-off normally restraining network excitability during the activity period. Since increased MMP expression is a prominent hallmark of the human epileptogenic brain and the MMP inhibitor IPR-179 exhibits antiseizure and antiepileptogenic effects in rodent epilepsy models and attenuates seizure-induced cognitive decline, it deserves further investigation in clinical trials[215]. Gu et al[216] studied thirty‐one patients with AD and 15 cognitively normal controls (NCs)for evaluation of plasma neuronally derived extracellular vesicle (NDEV) levels of core pathological markers [amyloid‐β (Aβ) and phosphorylated tau] and inflammatory biomarkers, including interleukin 6 (IL‐6) and matrix metalloproteinase‐9 (MMP‐9) in patients with Alzheimer’s disease (AD).

The diagnosis of AD was supported by fluorodeoxyglucose and Pittsburgh Compound‐B PET scans. Plasma extracellular vesicles were extracted, precipitated, and enriched for neuronal source by anti‐L1CAM antibody absorption. Levels of Aβ42, P‐T181‐tau, P‐S396‐tau, IL‐6, and MMP‐9 in plasma NDEVs were quantified by enzyme‐linked immunosorbent assay (ELISA).

They observed Aβ42, P‐T181‐tau, and MMP‐9 levels in plasma NDEVs were significantly greater er in patients with AD than NCs. However, P‐S396‐tau and IL‐6 levels in plasma NDEVs did not vary among AD patients and NCs. Moreover, there was no   association  among  any of these biomarker amounts and cognitive function as measured with Mini‐Mental State Examination in patients with AD.Thus concluding that levels of core pathological markers, including Aβ42 and P‐T181‐tau, are escalated in plasma NDEVs of patients with AD. Furthermore, MMP‐9 might play a significant part  in the pathogenesis of AD, and is a promising inflammatory biomarker for AD.[216]

Propolis is a common product of the beehive,which  has  a large number of therapeutic properties. Royal jelly (RJ) is a bee product that is fed to bee queens during their whole  life, and it aids in their great  physical fitness, fertility, and long lifespan. Evidence points that propolis and RJ can facilitate health by avoiding the occurrence of age-related debilitating diseases. Therefore, they have been used to treat different robust conditions  like  diabetes mellitus, cardiovascular diseases, and cancer. Some evolving studies used these bee products to treat PD in animal models. However, a clear insight of the collective effect of propolis and RJ as well as their mechanistic action in PD is absent . Thus Mohammad Ali and Kunugi evaluated  the available literature for the actions  of propolis and RJ on PD. They tried to explain how MMPs might be influenced through these bee products.[217].

Earlier Li etal.had Evaluated the differential   expression  of same miR-338-5p   of the sa miR-338-5p in gliomas and the role of miR-338-5p in glioma cell invasion via its potential target gene TSHZ3 encoding Teashirt zinc finger homobox 3, predicted by bioinformatics, and matrix metallopeptidase 2 (MMP2), the key pro-invasive protease overexpressed in gliomas. Quantitative real-time reverse transcription PCR (qRT-PCR) and Spearman correlation analysis were used to determine differential expressions of miR-338-5p and TSHZ3 in astrocytic gliomas of different grades (n = 35) and glioblastoma cell lines (U87 and U251) in comparison to non-neoplastic brain (NNB) tissues (n = 6). Western blotting was used to determine the protein levels of TSHZ3 and MMP2 in glioblastoma cell lines and Matrigel invasion assay to examine the role of miR-338-5p in cell invasiveness. The results   demonstrated that the expression of miR-338-5p, normalized to hsnRNA U6, was significantly higher in grade III and IV gliomas and glioblastoma cell lines in contrast to  that in NNB and grade II gliomas, whereas TSHZ3 expression, normalized to GAPDH, was inversely related to miR-338-5p (R = -0.636, P < 0.01). Luciferase assays showed TSHZ3 to be a target gene of miR-338-5p. In both U87 and U251 cells, miR-338-5p mimics increased MMP2 and invasiveness of the cells. Overexpression of ectopic TSHZ3 suppressed the cell invasiveness and attenuated the pro-invasive effect of miR-338-5p mimics. Overall, our results showed that miR-338-5p has a function in promoting glioma cell invasion by targeting TSHZ3 suppression on MMP2. In conclusion, miR-338-5p is a possible potential biomarker for the diagnosis and target for therapy of high-grade glioma[218].

This intricate insight has resulted in  not only treating tumours, utilizing ECV’s , but intricate knowledge of molecular modes like MMPs with micro RNA interaction might aid in developing therapies by delivering ECV’s from particular microRNA implicatedin the pathogenesis of diseasesin obstetrics  like preeclampsia ,IUGR,besides lot of malignancies like glioblastoma multiforme[[219]. Further Yohan et al showed how targeting the MMP-14/MMP-2/integrin α_vβ₃ axis with multispecific N-TIMP2–based antagonistsmight be utilized  for cancer therapythus utilizing the newer MMP-14or membrane type 1(MT-1-MMP)  axis [220]..