BACKGROUND: Non-alcoholic steatohepatitis (NASH) is a known progression factor for diabetes, however the molecular pathways involved are incompletely understood. While the glycoprotein CD147 has been implicated as a biomarker in liver fibrosis, its regulation in NASH and downstream effects (such as activation of matrix metalloproteinases: MMPs) have not yet been documented. We therefore investigated the hepatic response to high-fat diet (HFD) in a rodent model, complemented by in vitro studies, to elucidate a role for CD147 in hepatocyte injury. Whether microparticles (MPs) play a role in this process was also studied.
METHODS: Male C57Bl/6 mice were fed HFD (45%kCal fat) or chow. After 20 weeks, animals were terminated and livers were isolated. For in vitro studies the hepatocyte cell line (pH5CH8) were stimulated with palmitic acid (PA; 50µM). MPs were obtained by ultracentrifugation of culture supernatant, and quantified using NanoSightÔ . In some experiments CD147 was blocked by incubating cells or MPs with an anti-CD147 antibody. Gene expression of CD147 and MMPs were measured by qRT-PCR and proteins were measured by western blot and zymography respectively.
RESULTS: NanoSight data showed that hepatocyte MPs are below 300nm in diameter and particle concentration is unchanged after treatment with PA. However, such treatment did induce cell aggregation and increased expression of CD147, the latter was also reflected in the HFD model. Blocking MPs with anti-CD147 antibody prevented CD147-mediated induction of MMP-1, 2 and 14 and incubation of hepatocytes with antibody reversed the phenotype resulting from the stimulation with MPs isolated from PA treated cells.
CONCLUSION: Our findings show that CD147 is upregulated in NASH models similarly to chronic liver diseases, and that its expression in hepatocytes is regulated by lipids. Further, we show that MPs can induce hepatocyte injury and MMP induction in a CD147-dependent manner.