MMP‐13 deletion decreases profibrogenic molecules and attenuates N‐nitrosodimethylamine‐induced liver injury and fibrosis in mice

Abstract

Connective tissue growth factor (CTGF) is involved in inflammation, pathogenesis and progression of liver fibrosis. Matrix metalloproteinase‐13 (MMP‐13) cleaves CTGF and releases several fragments, which are more potent than the parent molecule to induce fibrosis. The current study was aimed to elucidate the significance of MMP‐13 and CTGF and their downstream effects in liver injury and fibrosis. Hepatic fibrosis was induced using intraperitoneal injections of N‐nitrosodimethylamine (NDMA) in doses of 10 μg/g body weight on three consecutive days of each week over a period of 4 weeks in both wild‐type (WT) and MMP‐13 knockout mice. Administration of NDMA resulted in marked elevation of AST, ALT, TGF‐β1 and hyaluronic acid in the serum and activation of stellate cells, massive necrosis, deposition of collagen fibres and increase in total collagen in the liver of WT mice with a significant decrease in MMP‐13 knockout mice. Protein and mRNA levels of CTGF, TGF‐β1, α‐SMA and type I collagen and the levels of MMP‐2, MMP‐9 and cleaved products of CTGF were markedly increased in NDMA‐treated WT mice compared to the MMP‐13 knockout mice. Blocking of MMP‐13 with CL‐82198 in hepatic stellate cell cultures resulted in marked decrease of the staining intensity of CTGF as well as protein levels of full‐length CTGF and its C‐terminal fragments and active TGF‐β1. The data demonstrate that MMP‐13 and CTGF play a crucial role in modulation of fibrogenic mediators and promote hepatic fibrogenesis. Furthermore, the study suggests that blocking of MMP‐13 and CTGF has potential therapeutic implications to arrest liver fibrosis.

A positive feedback loop bi-stably activates fibroblasts

“…9 ) 40 – 42 . In accordance with this hypothesis based on computational analysis, several MMP-deficient mice were documented as displaying a persistently activated fibroblast phenotype associated with fibrotic diseases in multiple organs 43 – 45 . Therefore, the next challenge will be to uncover this negative regulator, which is crucial in maintaining the homeostasis of fibroblasts during wound healing.…”

Stevia rebaudianatea prevents experimental cirrhosis via regulation of NF‐κB, Nrf2, transforming growth factor beta, Smad7, and hepatic stellate cell activation

“…On the other hand, MMPs are important regulators of the ECM (Duarte et al, ), which is the main reservoir of fibrogenic molecules by binding growth factors such as TGF‐β and CTGF (Higashi et al, ). MMP13 is primarily responsible for the cleavage of CTGF (George, Tsutsumi, & Tsuchishima, ), whereas the high proteolytic activities of MMP2 and 9 promote the dissociation of IL‐1β and tumor necrosis factor‐alpha from the ECM (Bauvois, ), leading to exacerbation of the inflammatory process. In summary, AES exerts its antifibrotic effects by downregulating TGF‐β and CTGF, leading to the repression of collagen synthesis by HSCs and modulation of ECM turnover, subsequently regulating pro‐inflammatory and profibrogenic pathways.…”

Molecular mechanisms in the pathogenesis of N-nitrosodimethylamine induced hepatic fibrosis

“…The process of hepatic fibrosis is initiated with cellular oxidative stress and production of reactive oxygen species (ROS) that serve as mediators of molecular events involved in the pathogenesis of hepatic fibrosis 7–10 . These processes results in cellular injury and release a variety of cytokines and growth factors that induce activation of resting hepatic stellate cells (HSCs) into myofibroblast-like cells with the expression of α-smooth muscle actin filaments as a characteristic marker 11–14 . The activated stellate cells lose their lipid droplets (vitamin A), rapidly proliferate and dramatically upregulate a number of genes, especially for collagens, fibronectins, laminin, hyaluronic acid, and start increased synthesis of connective tissue proteins, markedly collagens 15–17 .…”