The International Journal of Biochemistry & Cell Biology
ReviewMetalloproteinases and their inhibitors: Regulators of wound healing
Introduction
Metalloproteinases are endopeptidases that utilize a Zn2+ or Ca2+ ion in their active site. These include the metzincin family of enzymes that is comprised of the serralysins, astacins, adamalysins (a disintegrin and metalloproteinase domain or ADAMs), and matrixins (matrix metalloproteinases or MMPs; Huxley-Jones et al., 2007). The majority of research has focused on the matrixins and adamalysins, and thus, in this review, we will highlight the function of these two enzyme families and their inhibitors in wound healing.
There are 25 MMPs, 24 of which are found in mammals (Birkedal-Hansen et al., 1993; Parks, Wilson, & Lopez-Boado, 2004). Traditionally, the presumed role for MMPs was confined to catabolism of the extracellular matrix (ECM). In recent years, however, findings from several groups have established that MMPs cleave a wide range of extracellular, bioactive substrates, and regulating the activity of such proteins, typically in a gain-of-function manner, may indeed be the predominant function of MMPs in vivo (Mott & Werb, 2004; Parks et al., 2004). The established functions for MMPs include the release of growth factors from the cell membrane or ECM, cleavage of growth factor receptors from the cell surface, shedding of cell adhesion molecules, and activation of other MMPs, among other, non-catabolic functions (Egeblad & Werb, 2002; Mott & Werb, 2004; Parks et al., 2004).
As their name indicates, ADAMs contain a distintegrin or integrin-binding domain, and a metalloproteinase domain that is similar to the conserved Zn2+-binding catalytic domain in MMPs (Kheradmand & Werb, 2002). They are transmembrane proteases and their primary function is cleavage of extracellular domains of many membrane proteins from the cell surface, a process termed ectodomain shedding (Kheradmand & Werb, 2002; Moss & Bartsch, 2004; Seals & Courtneidge, 2003).
Among the endogenous inhibitors of MMPs are the tissue inhibitors of metalloproteinases (TIMPs), of which there are four family members, TIMP-1, -2, -3, and -4 (Baker, Edwards, & Murphy, 2002). TIMPs inhibit MMPs in a 1:1 inhibitor to enzyme ratio through interaction of the N-terminal domain of the TIMP molecule with the active site of the MMP (Brew, Dinakarpandian, & Nagase, 2000). TIMPs co-ordinate the catalytic site Zn2+ and bind to the active site in a similar fashion to an MMP substrate (Brew et al., 2000). Similar to MMPs, ADAMs are inhibited by TIMPs, although this inhibition is regulated primarily by TIMP3 (Amour et al., 2000, Amour et al., 1998; Kashiwagi, Tortorella, Nagase, & Brew, 2001; Loechel, Fox, Murphy, Albrechtsen, & Wewer, 2000). In addition, other proteins and mechanisms can inhibit metalloproteinase activity. These include α2-macroglobulin, a primary inhibitor of metalloproteinases in bodily fluid, such as synovial fluid, and reversion-inducing cysteine-rich protein with Kazal motifs (RECK), the only known membrane-bound MMP inhibitor (Baker et al., 2002; Egeblad & Werb, 2002). Further, modification by reactive oxygen species and internalization have been demonstrated to silence MMP activity (Fu, Parks, & Heinecke, 2008).
Wound healing provides a relevant model to illustrate the many functions – mostly beneficial, but some potentially deleterious – that metalloproteinases mediate via their ability to dramatically alter the activity of their protein substrates. In response to injury, essentially all cells within the tissue environment and circulation respond concurrently and quickly to stop blood loss, kill microorganisms, and close gaps to the environment. For the purpose of this review, we will focus on three processes of repair: re-epithelialization, which encompasses wound closure and re-differentiation; inflammation; and resolution of scar formation.
Re-epithelialization, which begins immediately after tissue injury (Martin, 1997; Singer & Clark, 1999), requires epithelial cells at the edge of the wounded tissue to loosen their cell–cell and cell–ECM contacts and assume a migratory phenotype. Once the cells at the wound edge begin to migrate, the epithelial cells behind the wound edge begin to proliferate and this continues until a new epithelium covers the damaged tissue (Singer & Clark, 1999; Werner et al., 1994). Although this conversion of epithelial cell behavior is called the epithelial-to-mesenchymal transition (EMT), which is mechanistically similar to early oncogenesis, the epithelial cells do not actually become mesenchymal, i.e., interstitial cells. They remain epithelial cells that are programmed to respond in manner that is highly conserved throughout the Animal Kingdom. Once wound closure is complete, the involved epithelial cells revert to their tissue-specific differentiated state.
The initiation of the inflammatory phase also occurs shortly after injury. The injured cells, which include epithelial and stromal cells as well as platelets from injured blood vessels, become activated and begin to produce chemotactic mediators that culminate in an inflammatory response (Martin & Leibovich, 2005; Singer & Clark, 1999). The primary role of inflammation in wound healing is to control infection, and this task is fulfilled by macrophages and neutrophils (Martin & Leibovich, 2005). It has also been suggested that inflammatory cells are required for other aspects of wound healing (i.e., to release cytokines and growth factors that stimulate cell proliferation and migration); however, this remains to be completely elucidated (Martin & Leibovich, 2005).
A few days after tissue damage occurs, new stromal tissue, called granulation tissue, is formed. This involves the proliferation of fibroblasts surrounding the wound and the subsequent migration of these fibroblasts into the damaged area. Fibroblasts produce ECM structural proteins and lay down a provisional, fibronectin-rich matrix (Clark, Lanigan, et al., 1982; Singer & Clark, 1999). Regulation of fibroblast proliferation and migration is thought to occur through the local release of growth factors and cytokines from macrophages as well as through cues from the provisional matrix (Singer & Clark, 1999; Xu & Clark, 1996). The provisional matrix is replaced by a collagen-rich scar, which is, ideally, a temporary scaffold to provide tissue strength. Formation of granulation tissue also requires the formation of new blood vessels to supply the newly formed tissue. Angiogenic signals are released from both macrophages and injured epithelial and endothelial cells (Brown et al., 1992). This process is also regulated by the provisional matrix, which provides a substrate for the sprouting endothelial cells to migrate across (Brooks, Clark, & Cheresh, 1994; Clark, Quinn, et al., 1982; Singer & Clark, 1999).
The final phase of wound healing is resolution, which involves ECM remodeling and contraction of the wound. Contraction of the wound occurs after formation of the granulation tissue and requires the fibroblasts to assume a myofibroblast phenotype (Welch, Odland, & Clark, 1990). Remodeling of the ECM, which leads to the conversion of granulation tissue to scar tissue, follows this, and is dependent on the continual synthesis and degradation of collagen fibrils (Parks, 1999; Singer & Clark, 1999).
Metalloproteinases participate in regulating mechanisms in all of these repair processes (Fig. 1). For example, inflammation is shaped by cytokines and chemokines, which arise largely from resident cells (epithelium, endothelium, fibroblasts, etc.). MMPs can activate these mediators, by cleaving them from the cell surface or processing them to increase their activity, or degrade them, thereby inhibiting inflammatory signals (Fig. 1). As well, MMPs are able to cleave components of cell–cell junctions and cell–matrix contacts within the epithelium to promote re-epithelialization (Fig. 1). Furthermore, MMPs are involved in remodeling the scar ECM either directly by proteolytic degradation of proteins, such as collagens, or indirectly via their ability to affect cell behavior. Alteration of the ECM is integral to the resolution of wound healing but also has implications in regulation of inflammation (Fig. 1). Thus, MMPs are key regulators of multiple aspects of tissue repair and further study of these enzymes and their interaction with their substrates will not only advance our basic knowledge of wound healing, but also provide insight into possible therapies.
Section snippets
Metalloproteinases in inflammation
Inflammation (i.e., the influx and activation of leukocytes) is influenced by antimicrobial peptides, lipid mediators, homing receptors, chemokines and cytokines, ECM fragments, and more. The production and activity of these factors is controlled by effector proteins, which include metalloproteinases. Findings from our lab and others demonstrate that epithelial-derived MMPs regulate numerous aspects of inflammation, such as the transepithelial migration of leukocytes and the activity and
Metalloproteinase inhibitors in inflammation
The inflammatory response is mediated by multiple cytokines and chemokines. One of the predominant cytokines involved in acute inflammation is TNFα, which is activated via cleavage from the cell membrane by TNFα converting enzyme (TACE) or ADAM17 (Black et al., 1997; Black & White, 1998). One effect that TNFα has on inflammatory cells, like monocytes, is that it stimulates expression of MMP9 through activation of the NFκB and p38 MAP kinase pathways (Nguyen, Gogusev, Knapnougel, & Bauvois, 2007
Summary
Wound healing is a complex process requiring the appropriate temporal and spatial expression of signaling molecules and their receptors, cellular adhesion molecules, and ECM proteins. Together, these molecules regulate the many processes involved in wound healing. Metalloproteinases and their inhibitors are capable of processing many of these signaling molecules, adhesion molecules, and ECM proteins and thus, are likely involved in the control of all aspects of wound healing (Fig. 1).
Acknowledgement
Salary support for S.E.G. was provided by the Canadian Institutes of Health Research.
References (96)
- et al.
The in vitro activity of ADAM-10 is inhibited by TIMP-1 and TIMP-3
FEBS Lett.
(2000) - et al.
TNF-alpha converting enzyme (TACE) is inhibited by TIMP-3
FEBS Lett.
(1998) - et al.
Gelatinase B is required for alveolar bronchiolization after intratracheal bleomycin
Am. J. Pathol.
(2000) - et al.
ADAMs: Focus on the protease domain
Curr. Opin. Cell. Biol.
(1998) - et al.
Tissue inhibitors of metalloproteinases: Evolution, structure and function
Biochim. Biophys. Acta
(2000) - et al.
Fibronectin and fibrin provide a provisional matrix for epidermal cell migration during wound re-epithelization
J. Invest. Dermatol.
(1982) - et al.
Cleavage of syndecan-1 by membrane type matrix metalloproteinase-1 stimulates cell migration
J. Biol. Chem.
(2003) - et al.
Activation and silencing of matrix metalloproteinases
Semin. Cell Dev. Biol.
(2008) - et al.
A null mutation for tissue inhibitor of metalloproteinases-3 (Timp-3) impairs murine bronchiole branching morphogenesis
Dev. Biol.
(2003) - et al.
Tissue inhibitor of metalloproteinases 3 regulates extracellular matrix–cell signaling during bronchiole branching morphogenesis
Dev. Biol.
(2006)
Collagenase expression is rapidly induced in wound-edge keratinocytes after acute injury in human skin, persists during healing, and stops at re-epithelialization
J. Invest. Dermatol.
TIMP-3 is a potent inhibitor of aggrecanase 1 (ADAM-TS4) and aggrecanase 2 (ADAM-TS5)
J. Biol. Chem.
Myofibroblast matrix metalloproteinases activate the neutrophil chemoattractant CXCL7 from intestinal epithelial cells
Gastroenterology
Matrilysin shedding of syndecan-1 regulates chemokine mobilization and transepithelial efflux of neutrophils in acute lung injury
Cell
ADAM 12-S cleaves IGFBP-3 and IGFBP-5 and is inhibited by TIMP-3
Biochem. Biophys. Res. Commun.
Inflammatory cells during wound repair: the good, the bad and the ugly
Trends Cell Biol.
Matrix metalloproteinases: they’re not just for matrix anymore!
Curr. Opin. Cell Biol.
Matrilysin (matrix metalloproteinase-7) mediates E-cadherin ectodomain shedding in injured lung epithelium
Am. J. Pathol.
Matrix metalloproteinase activity inactivates the CXC chemokine stromal cell-derived factor-1
J. Biol. Chem.
Matrix metalloproteinase processing of monocyte chemoattractant proteins generates CC chemokine receptor antagonists with anti-inflammatory properties in vivo
Blood
Matrix metalloproteinase inhibitor GM 6001 attenuates keratinocyte migration, contraction and myofibroblast formation in skin wounds
Exp. Cell Res.
Regulation of matrix biology by matrix metalloproteinases
Curr. Opin. Cell Biol.
MDC-L, a novel metalloprotease disintegrin cysteine-rich protein family member expressed by human lymphocytes
J. Biol. Chem.
Epilysin (MMP-28) expression is associated with cell proliferation during epithelial repair
J. Invest. Dermatol.
Matrix metalloproteinase matrilysin is constitutively expressed in adult human exocrine epithelium
J. Invest. Dermatol.
Interstitial collagenase is expressed by keratinocytes which are actively involved in re-epithelialization in blistering skin diseases
J. Invest. Dermatol.
Constitutive expression and regulated release of the transmembrane chemokine CXCL16 in human and murine skin
J. Invest. Dermatol.
Binding of ADAM28 to P-selectin glycoprotein ligand-1 enhances P-selectin-mediated leukocyte adhesion to endothelial cells
J. Biol. Chem.
Epsin 3 is a novel extracellular matrix-induced transcript specific to wounded epithelia
J. Biol. Chem.
Matrilysin (MMP-7) expression in renal tubular damage: Association with Wnt4
Kidney Int.
Neutrophil gelatinase B potentiates interleukin-8 tenfold by aminoterminal processing, whereas it degrades CTAP-III, PF-4, and GRO-alpha and leaves RANTES and MCP-2 intact
Blood
Matrix metalloproteinases in acute inflammation: induction of MMP-3 and MMP-9 in fibroblasts and epithelial cells following exposure to pro-inflammatory mediators in vitro
Exp. Mol. Pathol.
Interferon-gamma differentially regulates monocyte matrix metalloproteinase-1 and -9 through tumor necrosis factor-alpha and caspase 8
J. Biol. Chem.
Rescue of mammary epithelial cell apoptosis and entactin degradation by a tissue inhibitor of metalloproteinases-1 transgene
J. Cell Biol.
Extracellular matrix, junctional integrity and matrix metalloproteinase interactions in endothelial permeability regulation
J. Anat.
Membrane-type 1 matrix metalloproteinase is necessary for distal airway epithelial repair and keratinocyte growth factor receptor expression after acute injury
Am. J. Physiol. Lung Cell Mol. Physiol.
Metalloproteinase inhibitors: biological actions and therapeutic opportunities
J. Cell Sci.
Matrix metalloproteinases: A review
Crit. Rev. Oral Biol. Med.
A metalloproteinase disintegrin that releases tumour-necrosis factor-alpha from cells
Nature
Exogenous tissue inhibitor of metalloproteinase-1 promotes endothelial cell survival through activation of the phosphatidylinositol 3-kinase/Akt pathway
Ann. N. Y. Acad. Sci.
Nitric oxide promotes airway epithelial wound repair through enhanced activation of MMP-9
Am. J. Respir. Cell Mol. Biol.
Requirement of vascular integrin alpha v beta 3 for angiogenesis
Science
Expression of vascular permeability factor (vascular endothelial growth factor) by epidermal keratinocytes during wound healing
J. Exp. Med.
Impaired wound contraction in stromelysin-1-deficient mice
Ann. Surg.
Tissue inhibitor of metalloproteinase-1 deficiency abrogates obliterative airway disease after heterotopic tracheal transplantation
Am. J. Respir. Cell Mol. Biol.
Fibronectin is produced by blood vessels in response to injury
J. Exp. Med.
Structure–activity relationships of chemokines
J. Leukoc. Biol.
Differential expression of matrix metalloproteinases and interleukin-8 during regeneration of human airway epithelium in vivo
J. Pathol.
Cited by (572)
Comparative analysis of electrochemical and optical sensors for detection of chronic wounds biomarkers: A review
2024, Biosensors and BioelectronicsAnalysis of the permeable and retainable components of Cayratia japonica ointment through intact or broken skin after topical application by UPLC-Q-TOF-MS/MS combined with in vitro transdermal assay
2024, Journal of Pharmaceutical and Biomedical AnalysisElectrospun nanofiber composite mat based on ulvan for wound dressing applications
2023, International Journal of Biological Macromolecules