MMP2 activation by collagen I and concanavalin A in cultured human hepatic stellate cells

Abstract

Fibrosis occurs in most chronic liver injuries and results from changes in the balance between synthesis and degradation of extracellular matrix components. In fibrotic livers, there is a markedly increased activity of matrix metalloproteinase 2 (MMP2), a major enzyme involved in extracellular matrix remodeling. We have previously shown that hepatic stellate cells secrete latent MMP2 and that MMP2 activation occurs in coculture of hepatic stellate cells and hepatocytes concomitantly with matrix deposition. In the present work we investigated the effects of various extracellular matrix components and concanavalin A, an inducer of immunemediated liver injuries, on MMP2 activation in cultured human hepatic stellate cells. Collagen I induced a dosedependent MMP2 activation, which was not blocked by both actinomycin and cycloheximide. Collagen VI, laminin, and a reconstituted basement membrane (matrigel) were ineffective in inducing activation. Specific antibodies against the subunits of ␣2␤1 integrins, the major collagen I receptor, induced partial inhibition of MMP2 activation. Fibrosis is the common response of chronic liver injury from various origins, including metabolic diseases, viral infections, and alcohol consumption. 1 Fibrosis is often associated with inflammatory infiltrates and regulated through an immune-mediated response. Hepatic stellate cells (HSC) play a pivotal role in the cellular and molecular events that lead to fibrosis. 2 Following liver injury, these cells undergo changes toward a myofibroblast-like phenotype, they proliferate and secrete abundant extracellular matrix (ECM) components. In addition, activated HSC are involved in ECM degradation by providing matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). 3 MMPs form a family of proteases, which are collectively capable of degrading most if not all ECM components. 4 They can be divided into groups of intersticial collagenases, gelatinases, stromelysins, elastases, and membrane-type matrix metalloproteinases (MT-MMPs) according to their substrate specifities and structural features. The 5 currently characterized MT-MMPs differ from all other MMPs by having transmembrane domains and short cytoplasmic tails. 5 Gelatinase A, (i.e., MMP2) degrades gelatin, types IV, V, VII, and X collagens and elastin, fibronectin, and vitronectin, and its activity is associated with ECM remodeling in wound healing, development, inflammation, fibrosis, angiogenesis, and tumor invasion. 6 MMP2 is secreted as an inactive proenzyme, which is activated by a membrane-linked process that involves MT1-MMP 5 and tissue inhibitor of metalloproteinases-2 (TIMP2). 7 MT1-MMP complexed with TIMP2 has been found to serve as a cell surface receptor for MMP2. 8 The activation of bound MMP2 has been proposed to occur through an initial cleavage by other (free) MT1-MMP molecules to an intermediate form followed by autoproteolytic activation of MMP2 to a fully active enzyme. An excess of TIMP2 inhibits MMP2 activation by binding to all MT1-MMP m...

Loss of MMP 13 attenuates murine hepatic injury and fibrosis during cholestasis

“…This positive feedback loop has been implicated in previous studies and suggests a role for MMPs in HSC proliferation. 36,37 Such a mechanism could explain why HSC proliferation was suppressed in the BDL livers of the MMP-13Ϫ/Ϫ mice, as assessed by desmin immunostaining.…”

Increased extracellular matrix remodeling is associated with tumor progression in human hepatocellular carcinomas

“…First, we and others have shown that MMP2 activation depends on collagen I deposition in hepatic stellate cell cultures. 17,39 Second, the efficacy of 3-dimensional gels over coating of dishes with collagen I was reported, suggesting that fibrillar collagen organization is crucial in MMP2 activation. Interestingly, an enhanced expression of lysyl oxidase, the enzyme that initiates the first step of extracellular collagen cross-linking, was shown in early stages of liver fibrosis 40 and was suggested to play a role in the early host defense mechanisms in cancers.…”

“…We have recently shown that extracellular matrix deposition induces activation of the pro-MMP2, secreted by human activated hepatic stellate cell cultures, 15 this process being related to collagen I. 17 The role of collagen I in promoting MMP2 activation, as well as its capacity to favor mesenchymal cell proliferation were shown in several other cell culture systems. [18][19][20] Thus, focalized MMP2 activity on the cell surface appears modulated by the pericellular microenvironment and might facilitate tumor progression and metastasis.…”

“…Specificity of all probes was previously shown by northern blot analyses. 12,[15][16][17] The optimization parameters of mRNA detection, to ensure analyses within the linear range, included cDNA probe concentration and specific activity, stringency washings, exposure time, film processing, and image analysis. Results were expressed as relative mRNA amounts, normalized for differences in RNA loading by comparison with the signal obtained for 18S rRNA.…”

Tumor hepatocytes and basement membrane–Producing cells specifically express two different forms of the endostatin precursor, collagen XVIII, in human liver cancers

“…3,7 The probes for albumin, collagen IV, laminin ␥1, ␣-smooth muscle actin (␣-SMA), matrix metalloproteinase-2, and 18S ribosomal RNA have been described. 6,13 Anti-a-SMA 14 16 Specimens were routinely processed for histology, i.e., hematoxylin-eosin-saffran and Sirius red staining.…”