1132 EFFECT OF ADENOSINE 2B RECEPTOR ANTAGONIST MRS1754 ON FIBROSIS PROGRESSION AND REGRESSION IN MICE

Abstract

during cancer and cirrhosis, but it also participates in the pathogenesis of metabolic syndrome. Recently, myostatin levels have been associated with fibrosis during NASH. However, no information is available on the possible direct role of myostatin in the biology of HSC. Aim of the study was to evaluate the effect of myostatin on biological actions and intracellular signaling in human HSC. Methods: We employed both an immortalized human HSC line (LX-2) and primary HSC isolated from human livers. Cell proliferation was evaluated by MTT. Cell migration was assessed with modified Boyden chambers. Gene expression and secretion of cytokines or ECM proteins were measured by qRT-PCR and ELISA, respectively. Intracellular signaling pathways were evaluated using phosphorylation-specific antibodies. Results: Transcripts for ActRIIB were expressed by HSC. Exposure to myostatin (50ng/ml) induced a significant increase in cell migration in both LX-2 and primary HSC, and time-dependently reduced cell proliferation. In addition, myostatin increased mRNA expression of TGF-beta and procollagen type1. We tested the ability of myostatin to activate intracellular signaling pathways in HSC. Myostatin rapidly and markedly induced phosphorylation of Smad3 and JNK. In contrast, p38MAPK and ERK1/2 were only modestly activated. Pretreatment of both LX-2 or primary HSC with the selective JNK inhibitor, SP600125 (20mM), caused a marked inhibition of myostatin-induced cell migration. Transcripts for myostatin and ActRIIB were measurable in normal liver. Induction of steatohepatitis by administration of a methionine and choline-deficient diet significantly increased the expression of both molecules. Conclusions: HSC express ActRIIB and respond to myostatin with increased chemotaxis, reduced proliferation, and increased expression of profibrogenic genes. At least some of these require JNK activation. Expression of myostatin and its receptor is present in the liver and up-regulated following chronic liver injury, indicating a possible role for this molecule in liver fibrosis. The first two Authors contributed equally to the present study.