Exposure to fine airborne particulate matters induces hepatic fibrosis in murine models

Background & Aims: Hepatic fibrosis, featured by the accumulation of excessive extracellular matrix in liver tissue, is associated with metabolic disease and cancer. Inhalation exposure to airborne particulate matter in fine ranges (PM2.5) correlates with pulmonary dysfunction, cardiovascular disease, and metabolic syndrome. In this study, we investigated the effect and mechanism of PM2.5 exposure on hepatic fibrogenesis. Methods: Both inhalation exposure of mice and in vitro exposure of specialized cells to PM2.5 were performed to elucidate the effect of PM2.5 exposure on hepatic fibrosis. Histological examinations, gene expression analyses, and genetic animal models were utilized to determine the effect and mechanism by which PM2.5 exposure promotes hepatic fibrosis. Results: Inhalation exposure to concentrated ambient PM2.5 induces hepatic fibrosis in mice under the normal chow or high-fat diet. Mice after PM2.5 exposure displayed increased expression of collagens in liver tissues. Exposure to PM2.5 led to activation of the transforming growth factor beta-SMAD3 signaling, suppression of peroxisome proliferator-activated receptor 7, and expression of collagens in hepatic stellate cells. NADPH oxidase plays a critical role in PM2.5-induced liver fibrogenesis. Conclusions: Exposure to PM2.5 exerts discernible effects on promoting hepatic fibrogenesis. NADPH oxidase mediates the effects of PM2.5 exposure on promoting hepatic fibrosis. (C) 2015 Published by Elsevier B.V. on behalf of the European Association for the Study of the Liver.