Matrix metalloproteinases

In health and disease

1. Matrix metalloproteinases in health and disease

2. Overview Introduction Definition Anatomy Types Role in maintaining health Role in diseases and malignancy

3. Introduction Living tissues are not just accumulations of tightly packed cells . Much of a tissue's volume is made up of extracellular space .This void is filled with a complex meshwork called the  extracellular matrix . If cells were seeds then the extracellular matrix (ECM) would be the soil. In addition to providing structural support for the cells embedded within a tissue, the extracellular matrix guides their division, growth, and development . Hence ,the extracellular matrix largely determines how a tissue looks and functions .

4. CONTENTS OF ECM Collagen Elastin Fibronectin Laminin Growth factors and Metalloproteinases

5. Contents of ECm Collagen- M ain structural protein in the extracellular space. Type I: skin, tendon ,   bone Type II:  cartilage Type III: main component of reticular fibers, commonly found alongside type I . Type IV: basement membrane Type V: cell surfaces, hair and  placenta Elastin- H ighly elastic protein in connective tissue and allows many tissues in the body to resume their shape after stretching or contracting .

6. Contents of ECm Fibronectin- located within the basement membrane and key role in cell adhesion and wound healing response to injury . Laminins- are among the first proteins of the ECM to appear in embryos ,role in cell differentiation and migration Growth Factors- The ECM has been referred to as a ‘reservoir’ for GFs. VEGF, FGF and TGF are tied to the ECM through heparan sulphate . Matrix Metalloproteinases (MMPs)

7. Tale(tail) of matrix metalloproteinases MMPs were discovered, in 1962, by Jerome Gross while studying the degradation of triple-helical collagen during the metamorphosis of a tadpole tail. Tad pole tail Area of clearing Collagen gel

8. Metalloproteinases The timely breakdown of extracellular matrix (ECM ) is essential for embryonic development, morphogenesis, reproduction, and tissue resorption and remodeling. Metalloproteinases / Matrixins are a large group of zinc-dependent proteases responsible for cleaving and rebuilding connective tissue.

9. N-terminal propeptide domain-MMPs are initially synthesized as inactive zymogens with a pro-peptide domain that must be removed before the enzyme is active -Cysteine switch C-Terminal Domain- Structurally similar to proteins of the hemopexin family. The domain has a relatively large surface area for protein-protein interactions. Catalytic Domain- C ontains two zinc ions and two or three calcium ions. The first Zn ion present in the active site directly participates in catalytic processes. Calcium ions are necessary to stabilize the domain structure

10. Types Collagenases Gelatinases Stromelysins and M embrane-type metalloproteinases .

11. Collagenases Collagenases  are enzymes that break the peptide bonds in collagen .   MMP-1, MMP-8, and MMP-13 are the enzymes with the capacity to cleave the triple helix of fibrillar collagen . Interstitial collagenase(MMP-1) has preferential activity against type III collagen . MMP-1 is produced and secreted predominantly by cells prevalent in the post acute stages of wound healing (fibroblasts, endothelial cells)

12. Collagenases Polymorphonuclear collagenase (MMP-8) has an affinity for type I collagen . MMP-8 is stored in granules within the neutrophils and once activated can be released in seconds. MMP-13 appears to have the unique ability to cleave type I, type II, and type III collagen.

13. Gelatinases G elatinase  is a proteolytic enzyme that allows a living organism to hydrolyse gelatin into its sub-compounds  . The gelatinases (MMP-2 and MMP-9) cleave collagen types IV , V, VII, and X, elastin, basement membranes and denatured collagen . The gelatinases may also act synergistically with the collagenase family by further degrading types I, II, and III. MMP-2 is secreted by fibroblasts, MMP-9 is produced predominantly by leukocytes and keratinocytes .

14. Stromelysins Due to their broad base of substrate specificity , stromelysins (MMP-3, MMP-7, MMP-10 , MMP-11, and MMP-12) play a varied role in degradation of the extracellular matrix .   Degrades  collagen types II, III, IV, IX, an X , proteoglycans, fibronectin,  laminin , and elastin.

15. Membrane-Type Matrix Metalloproteinases M embers of this class of matrix metalloproteinases (MMP-14 , MMP-15, MMP-16, and MMP-17) have certain unique structural characteristics. T hey are not secreted into the extracellular matrix. Rather , they exist on cell membranes and appear to function by binding to other matrix metalloproteinases and activating them.

16. Activation and Deactivation 1)Gene level by transcriptional control 2)Molecular level by requiring factors to convert the proenzyme form to the active form. 3)Tissue level -Through Tissue Inhibitors of Metalloproteinases (TIMP)

17. Transcriptional control Two extensively studied factors which influence the MMP transcription are: IL-1β and TGF – β IL-1 β stimulates, whereas TGF- β inhibits MMP gene expression . Transcription of many MMPs is promoted by inflammatory cytokines, growth factors,  chemokines, oncogenes

18. Molecular control MMPs are synthesized as inactive zymogens and require activation . The cysteine in the propeptide interacts with a Zn2+ ion in the enzyme’s active site . This interaction, [Zn2+-cysteine], keeps the proMMP inactive Activation can occur by physical or chemical means by disturbing the cysteine –zinc interaction of the cysteine switch .

19. Deactivation of mmp Tissue inhibitors of matrix metalloproteinases ( TIMP) are major endogenous regulators of MMP The critical points in MMP inhibition by TIMPs are centred on the disulfidebonds at Cys and Cys . TIMPs catalysis of disulfide bond formation between cysteines prevents autocatalytic MMPs activation through the cysteine switch mechanism . In addition, TIMPs in complexes with other molecules involve in the inhibition of already active MMP

20. Physiological roles Apoptosis Ovulation Inflammation Angiogenesis Bone remodeling Mammary gland development Embryogenic remodeling Organ morphogenesis

21. Apoptosis MMP-3 has pro-apoptotic actions on neighboring epithelial cells by loss of β1-integrin engagement and epidermal  growth factor receptor expression. W hereas MMP-7 is able to release membrane bound Fas ligand and induces epithelial cell apoptosis.

22. Ovulation The preovulatory LH surge stimulates an increase in ovarian matrix metalloproteinases (MMPs) and their associated inhibitors, the TIMPs prior to follicular rupture .   Proteolytic enzymes are locally activated that digest a small part of the dominant follicle’s wall and extracellular matrix, releasing the oocyte .

23. Ovulation Pre Ovulatory phase-IHC-MMP2 Early ovulatory phase-TIMPs

24. Inflammation MMPs function as inflammatory cytokines during vascular formation or remodeling.  In matured and quiescent vessels, active MMPs are absent or expressed at low levels . But in tissues undergoing abnormal angiogenesis and vascular remodeling, MMPs are markedly expressed, secreted, and activated. M acrophages and neutrophils are an important resource of MMPs in vascular tissue .

25. MMP in inflammation TNF- α and ILs MMP   Stimulate Degrade ECM to facilitate migration and recruitment of cells. Cleave cell surface receptors and other non-ECM molecules to mediate adhesion, proliferation , and apoptosis of cells.

26. MMP in wound healing Healing of a skin wound requires several processes : C ell migration ECM degradation and T issue reorganization. MMP-1 : K eratinocyte migration MMP-3: Wound contraction

27. Vascular remodeling Hemodynamic forces such as shear stress and arterial pressure regulate MMP expression and participate in vascular remodeling . Elevated transmural pressure  E xtracellular signal–regulated kinases (ERKs ) NF- κ B ↑MMP 2 and 9 Remodeling due to hemodynamic adaptation of the vein to the arterial condition leads to saphenous vein graft bypass failure.

28. Bone remodelling During long bone development, an initial cartilaginous template is formed and replaced by bone in a coordinated and refined program. Chondrocyte proliferation and maturation, vascular invasion, recruitment of adult stem cells and intense remodeling of cartilage and bone matrix . Osteoclast express –MMP 9 and 13

29. Mammary gland development The epithelial ductal network of the mammary gland expands greatly during puberty in response to both local and systemic signals. This process requires degradation of the basement membrane and ECM, restructuring of the endogenous vascular network and large-scale epithelial morphogenesis 

30. Mammary gland development MMP 2-Primary invasion MMP 3-Secondary branching

31. Embrogenesis E mbryonic growth and tissue morphogenesis are fundamental events that require disruption of ECM barriers to allow cell migration and matrix microenvironment remodeling. Trophoblasts express high levels of MMP-9 MMP2 and 9 enable trophoblast cells to penetrate uterine vasculature during Implantation Development of the placenta starts with the invasion and migration of trophoblast cells into the maternal tissue to establish connection with the maternal circulation  .

32. MMPs in pathological conditions Diseases of CNS Cardiovascular diseases Lung fibroblastic disease Liver fibrosis Diseases of bone Tumor development and metastasis

33. MMP in Diseases of cns MMPs are largely absent from the normal CNS and their upregulation has been reported in several neurological disorders and after injury . Metalloproteinases in neuroinflammation and Multiple sclerosis: MS is an immune disorder characterized by demyelination and axonal loss. The presence of proteinases(MMP 9) in the cerebrospinal fluid (CSF ) of patients with MS has been known for over 20 years. MS patients show increased MMP9 messenger RNA in leukocytes and elevated MMP9 levels in serum.

34. MMP in Diseases of cns Leukocytes use MMPs to disrupt the basement membrane of the blood–brain barrier. MMPs can disrupt myelin and cause demyelination. MS patients treated with interferon-β show a decreased number of MMP9 expressing leukocytes.

35. MMP in Diseases of cns A role for metalloproteinases in stroke is indicated by the finding that MMP2 and -9 are rapidly upregulated after focal cerebral ischaemia . The elevated MMP expression might contribute to the tissue destruction in stroke . Viral infections of the CNS have been increasingly associated with the production of MMPs . Elevated expression of MMP9 has been detected in the CSF of HIV-infected patients.

36. MMP in Cardiovascular diseases Atherosclerosis : M MP 9- A dherence of circulating monocytes to the vascular endothelium, through which they gain entry to the sub intimal tissue . Plaque ruptures are associated with increased MMP-9 proteolytic activity. Increased activity of TIMPs- V ascular calcification

37. MMP in Cardiovascular diseases Aneurysm :Consists of destruction and functional loss of elastin in the aortic medium. MMP plays a significant role in weakening the ECM components (elastin, collagen, fibronectin and proteoglycans), thus harming the aortic wall . Varicose veins: Interstitial collagen III is important for the stretch resistance of the connective tissue of veins. MMP-3 may contribute to vein wall weakness and varicose vein formation via excessive degradation of collagen III.

38. MMPs in Acute myocardial infarction M yocardial collagens maintain the structural integrity of adjoining myocytes and cardiac pump function. Myocardialinfarction (MI) leads to complex architectural alterations involving both the infarcted and noninfarcted myocardium . Patients exhibiting extensive infarct expansion after MI are more likely to experience complications: Congestive heart failure Aneurysm formation and M yocardial rupture.

39. MMPs in Acute myocardial infarction One of the determinants of left ventricular remodeling is damage to and loss of the myocardial extracellular matrix (ECM) during the healing process after MI . R eduction in LV dilatation after MI that can be achieved with MMP inhibitor treatment .

40. MMPs in lung fibroblastic disease Lung fibrosis is the final result of a large and heterogeneous group of lung disorders, known as interstitial lung diseases. Scar formation, the accumulation of excess fibrous connective tissue leads to thickening of the walls, and causes reduced oxygen supply in the blood .   MMP1/Collagenase1 :Expressed primarily by epithelial cells –Cystic spaces (Honey comb pattern) MMP2-   Tissue migration of fibrocytes

41. MMPs in emphysema The lung is a sophisticated matrix scaffold on which lung epithelium and endothelium reside. When the wall of an alveolus is destroyed, the air sacs coalesce to form larger ones. These enlarged airspaces empty more slowly, resulting in airflow obstruction, the hallmark of COPD.

42. MMPs in emphysema Of all the MMPs, the evidence supporting a role for macrophage elastase (MMP12) in the pathogenesis of emphysema is the strongest.  Mmp12 expression is greatly increased in response to cigarette smoke exposure, due to a number of overlapping mechanisms.  Activation of the plasmin/thrombin–proteinase activated receptor (PAR-1) cascade leads to the expression of Mmp12. Inhibited by A1AT  and TGF- β  .

43. MMPs in liver fibrosis Liver fibrosis represents chronic wound repair following diverse insults. MMPs as bad role: In liver fibrogenesis hepatic stellate cells undergo dramatic morphological and functional changes –star shaped  HSC are converted to myofibroblastic cells  . P roteolytic degradation of the normal ECM helping inmobilization , migration and proliferation of cells during repair and regeneneration . MMPs as good role : The MMP-mediated resolution of tissue fibrosis may act through ECM degradation as well as by induction of HSC apoptosis .  

44. MMPs in Bone diseases The irreversible destruction of the cartilage, tendon, and bone that comprise synovial joints is the hallmark of both rheumatoid arthritis (RA) and osteoarthritis (OA ). C artilage is made up of proteoglycans and type II collagen T endon and bone are composed primarily of type I collagen RA is an autoimmune disease affecting numerous joints throughout the body OA develops in a small number of joints, usually resulting from chronic overuse or injury.

45. MMPs in Bone diseases In both RA and OA: Inflammatory cytokines:IL-1 β and TNF- α MMPs that can degrade all components of the extracellular matrix. MMP-1 synovial cells that line the joints MMP-13 is a product of the chondrocytes that reside in the cartilage In addition to collagen, MMP-13 also degrades the proteoglycan molecule, aggrecan , giving it a dual role in matrix destruction.  stimulate

46. MMPs in tumor growth MMPs can regulate the growth of tumour cells by the following mechanisms : R elease of cell membrane bound precursors of some growth factors M odulating the bioavailability of growth factors that are sequestrated by ECM proteins. I ndirectly regulating proliferative signals through integrins Because of the shedding of the E cadherin, β catenin translocates to the nucleus and leads to proliferation MMPs can inhibit growth by A ctivation of TGF-β G eneration of proapoptotic molecules. e.g. Fas ligand or TNF α

47. Regulation of Invasion and Metastasis Tumour invasion is a multistep process in which cell motility is coupled with proteolysis and involves interaction of cells with ECM . Cadherin are cell adhesion molecules that mediate cell-cell adhesion in normal mucosal cells and maintain epithelial integrity and its deregulation is associated with cancer progression .

48. Regulation of Invasion and Metastasis Decreased expression of E-cadherin causes loss of cell adhesion and contributes to cell dissociation, increased motility and invasion . E-cadherin is cleaved by MMP3 and 7 Detachment of cells by loss of intercellular junction Epithelial to mesenchymal transition(EMT) Migration Invasion

49. SUMMARY MMPs Physiological roles Pathological roles Collagenases Gelatinases Stromelysins and Membrane-type metalloproteinases . Apoptosis Ovulation Inflammation Angiogenesis Bone remodeling Mammary gland development Embryogenic remodeling Organ morphogenesis Diseases of CNS Cardiovascular diseases Lung fibroblastic disease Liver fibrosis Diseases of bone Tumor development and metastasis

50. REFERENCES Kumar, Vinay., Robbins and Cotran Pathologic Basis of Disease.9 th edition. Reed Elsevier India Private Limited, New Delhi.2015 Brinckerhoff CE, Matrisian LM. Matrix metalloproteinases : a tail of a frog that became a prince. Nature Rev Mol Cell Biol 2002;3:207–214. Birkedal-Hansen H, et al. Matrix metalloproteinases : a review. Crit Rev Oral Biol Med 1993;4:197–250. Stickens D, et al. Altered endochondral bone development in matrix metalloproteinase 13-deficient mice . Development 2004;131:5883–5895. Ducharme A, et al. Targeted deletion of matrix metalloproteinase-9 attenuates left ventricular enlargement and collagen accumulation after experimental myocardial infarction. J Clin Invest 2000;106:55–62 Yu Q, Stamenkovic I. Cell surface-localized matrix metalloproteinase-9 proteolytically activates TGF-β and promotes tumor invasion and angiogenesis. Genes Dev 2000;14:163–176.

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