Chapter 10 MMPs and ADAMs in Inflammatory Bowel Disease Alicja Wiercinska-Drapalo, Jerzy Jaroszewicz, Anna Parfieniuk, Anna Moniuszko Department of Infectious Diseases, Medical University of Bialystok, Zurawia 14 Str., 15-540 Bialystok, Poland. 1. INTRODUCTION Idiopathic inflammatory bowel disease (IBD) is classified into two distinct disorders: ulcerative colitis (UC) and Crohn’s diseases (CD). IBD are chronic inflammatory bowel diseases characterized by repeated episodes of intestinal inflammation and damage following by relapses and intestine wound healing. Although classified together, UC and CD show a different localization and to some extent different pathogenesis. Ulcerative colitis affects colon and the intestine lesions are superficial while Crohn’s disease may involve any part of gastrointestinal tract and is characterized by transmural granulomatous infiltrations. The exact pathogenesis of UC and CD is still mysterious. A number of studies suggested that CD is T-cell mediated disorder with excessive Th-1 cell activity associated with pro-inflammatory cytokine overproduction. Less information on pathogenesis of UC is available. Many authors believe that in contrast to CD the predominant immune response type is Th2, however this hypothesis is not fully documented, for example IL-4, classical Th2-type cytokine seems not to increase in UC. The common feature of CD and UC is extracellular matrix (ECM) remodeling associated with ongoing inflammatory responses and intestinal lesions healing. The regulation of ECM turnover is a dynamic process essential for embryonic development, morphogenesis, reproduction, and tissue resorption and remodeling. The major regulators of collagen synthesis and degradation 235 U. Lendeckel and Nigel M. Hooper (eds.), Proteases in Gastrointestinal Tissue, 235-254. © 2006 Springer. Printed in the Netherlands 236 A. WIERCINSKA-DRAPALO, J. JAROSZEWICZ, ET AL. Chapter 10 are zinc-dependant enodpeptidases - matrix metalloproteinases (MMPs) and their inhibitors (tissue inhibitors of metalloproteinases - TIMPs). 2. MATRIX METALLOPROTEINASES 2.1 Expression, regulation and functions in the gut The variety of cells in the intestine are able to produce MMPs, among them fibroblasts (MMP-1, 2, 3, 14), macrophages (MMP-1, 3, 9, 12), epithelial cells (MMP-7, 8, 10), neutrophils (MMP-8) and eosinophils (MMP-9). It is believed that the major source of MMP-1 and MMP-3 are macrophages and T-cells-induced MMP production by those cells links mucosal inflammation and tissue destruction in chronic gut diseases (Goetzl et al 1996). However in-situ hybridization studies indicate that α-actin positive cells such as myofibroblasts are a main source of MMP mRNAs in the inflamed gut, which is not confirmed in immunochemistry (Pender et al 1998). According to hypothesis presented by von Lampe et al (2000) MMP produced by α-actin positive cells are not stored within these cells and are secreted and bound to ECM. In contrast with majority of other cells macrophages are able to store pro-MMP. In physiological condition MMPs are present at low levels and their expression and activation is regulated at the level of gene expression, their precursors activation, interaction with ECM components as well as inhibition by TIPMs (Pender et al 2004). The MMP expression “inductors” include (Nagase et al 1999) growth factors, cytokines (including TNF-alpha, IL-1β), chemical agents (among them phorbol esters) and oncogenes. On the contrary increased MMPs gene expression may be downregulated by suppressive factors including TGF-beta1, retinoids and glucocrticoids. Recently cell-to- cell and cell-to-ECM interactions were underlined as a important regulators of MMPs gene expression. For example expression of MT1-MMP by fibroblasts in cell-culture is mediated by α2β1 integrin (Seltzer et al 1994). Most of MMPs are secreted from the cell in inactive forms and anchored to the cell surface thus their activity is restrained to cell membrane or extracellular matrix. Secreted MMPs are activated in-vivo by tissue or plasma proteinases or bacterial proteinases, mainly on the cell surface. In 1994 Sato et al. (1994) cloned the first membrane-type MMP (MT1-MMP named MMP-14) and they demonstrated it to be an activator of pro-MMP2 (Sato et al 1994). The subsequent studies suggested that this process requires both active MT1-MMP and TIMP-2 bound MT1-MMP. 10. MMPs and ADAMs in Inflammatory Bowel Disease 237 Tissue activity of MMPs is controlled by their endogenous inhibitors (TIMPs) by forming 1:1 complexes with zinc in MMPs. In some disorders the production of MMP exceeds the inhibitory potential of TIMP which results in imbalance between ECM synthesis and breakdown. This process was proposed as a potential etiology of fistulae formation in Crhon’s disease (Kirkegaard et al 2004). The most extensively studied function of metalloproteinases, since the first MMP discovery in 1962 (Gross and Lapiere 1962) is degradation of all classes of ECM including collagens, non-collagenous glycoproteins and proteoglycans. In-vitro studies showed considerable overlap in MMP substrates (especially fibronectin, laminins, elastin, type IV collagen), (Sternlicht et al 2001). Substrates selectivity in-vivo is regulated by enzyme affinity and compartmentalization. Since MMPs are anchored on the cell membrane, bound to integrins, CD44 or surface proteoglycans they maintain high concentration locally and are able to target specific substrates in the pericellular space. In spite of the most widely discussed role of MMPs/TIMPs in ECM turnover, recent findings suggested their function in the inflammation and immunity, as a pro-inflammatory cytokines, chemokines and other immune and inflammation regulators (Parks et al 2004; McQuibban et al 2000 and 2001). Increased or misregulated levels of MMPs as well as TIMPs are observed in the majority immune-related or chronic inflammatory disorders including IBD. However the exact role of MMP family members, which comprises of more then 24 related but distinct proteins, in inflammatory conditions was not yet entirely revealed. Targeting of immune system by MMPs could be a result of chemokine as well as cytokine activity modulation and gradient formation (McQuibban et al 2002). It was shown that selected MMPs are able to convert initial forms of chemotactic factors into antagonistic molecules. For example CC-chemokine ligand 7 (CCL7) is a substrate for MMP-2, which after cleavage looses its chemotactic abilities and functions as chemokine antagonist. Similarly MMP- 1, 3 and 14 are capable of cleaving CCL2 which is also mechanism of angiogenesis regulation. (Galvez et al 2005). This MMP functions illustrates a possible anti-inflammatory activity of MMPs. Moreover several authors shown MMPs are able to directly or indirectly activate various cytokines engaged in inflammatory and wound healing processes. In in-vitro models it was suggested that MMP-3, 9 as well as 14 are able to activate TGF-β1. Since TGF-β1 is a cytokine of a known anti-inflammatory and immunou- pressive activity this could be another mechanism of MMP-mediated immune restrain. On the other hand several MMPs are engaged in pro-inflammatory cytokine activation. Despite the major activator of TNF-α is ADAM17, a number of MMPs (MMP-1, 2, 3, 9 and 17) are capable of processing pro- TNF into active form in-vitro (Mohan et al 2002, English et al 2000). 238 A. WIERCINSKA-DRAPALO, J. JAROSZEWICZ, ET AL. Chapter 10 Additionally MMP-7 and MMP-12 activate pro-TNF on macrophages. Schonbeck et al (1997) showed that at least three of MMP family members, namely MMP-2, 3, 9 can cleave and activated IL-β precursor. Interestingly after IL-1β activation MMP3 is able to degrade this cytokine into inactive form. In conclusions the regulation of immune and inflammation by MMPs is complex, probably bimodal and unrevealed even to the extent whether they act as a pro-inflammatory or anti-inflammatory factors. 2.2 Matrix metalloproteinases in IBD The hallmark of an IBD is tissue degradation and lesion development resulting from uncontrolled and chronic inflammatory responses. Among the modulators of an IBD activity the role cytokines, growth factors, chemokines, free radicals and recently metalloproteinases and their endogenous inhibitors – TIMPs is underlined. A number of up to date studies pointed to MMPs as the most important proteolytic enzymes engaged in extracellular matrix degradation in inflammatory bowel diseases. Although many authors showed overexpression of majority MMPs in IBD the MMP-1 (collagenase-1) and MMP-3 (stromelysin-1) are believed to be predominant in the IBD pathogenesis. von Lampe et al (2000) studied the expression of various MMPs (MMP-1, MMP-2, MMP-3, MMP-14) as well as TIMPs (TIMP-1 and TIMP-2) in IBD (UC and CD) patients as well as healthy controls at the protein and mRNA levels. They found the low expression of MMP-1 and MMP-3 in normal colonic mucosa. However in inflamed colon samples from IBD patients authors observed that mRNA expression of all studied MMPs was significantly increased in inflamed compared with non-inflamed colonic mucosa. Median expression of MMP-1 increased 20-fold in CD and 42-fold in UC subjects with analogous 15-fold and 43-fold (respectively) increase of MMP-3 expression. The increase in the expression of MMP-2 and MMP-14 mRNA was less pronounced. Analogous data indicating the increase in MMP- 1 and MMP-2 expression were obtained by Stallmach et al. (2000). Another major finding arising from the study of von Lampe et al (2000) was a strong, positive correlation between the histological degree of acute inflammation and MMP-1, MMP-2 and MMP-3 mRNA expression. The strongest correlation was noted between procollagen type III and MMP-2 mRNA expression. The most prominent expression of MMPs was noted in severely inflamed tissues characterized by ulcerations. In another study Heuschkel et al (2000) found the similar relationship between MMP-1 expression and loss of mucosal integrity in children with IBD, with MMP-1 normalization after introduction of eneteral nutrition.