Abstract

Background and aim: Activated myofibroblast-like cells, originating from hepatic stellate cells (HSC/MFs) or other cellular sources, play a key profibrogenic role in chronic liver diseases (CLDs) that, as suggested by studies in animal models or rat HSC/MFs, may be modulated by reactive oxygen intermediates (ROI). In this study, human HSC/MFs, exposed to different levels of superoxide anion (O₂^•−) and, for comparison, hydrogen peroxide (H₂O₂), were analysed in terms of cytotoxicity, proliferative response, and migration.

Methods: Cultured human HSC/MFs were exposed to controlled O₂^•− generation by hypoxanthine/xanthine oxidase systems or to a range of H₂O₂ concentrations. Induction of cell death, proliferation, and migration were investigated using morphology, molecular biology, and biochemical techniques.

Results: Human HSC/MFs were shown to be extremely resistant to induction of cell death by O₂^•− and only high rates of O₂^•− generation induced either necrotic or apoptotic cell death. Non-cytotoxic low levels of O₂^•−, able to upregulate procollagen type I expression (but not tissue inhibitor of metalloproteinase 1 and 2), stimulated migration of human HSC/MFs in a Ras/extracellular regulated kinase (ERK) dependent, antioxidant sensitive way, without affecting basal or platelet derived growth factor (PDGF) stimulated cell proliferation. Non-cytotoxic levels of H₂O₂ did not affect Ras/ERK or proliferative response. A high rate of O₂^•− generation or elevated levels of H₂O₂ induced cytoskeletal alterations, block in motility, and inhibition of PDGF dependent DNA synthesis.

Conclusions: Low non-cytotoxic levels of extracellularly generated O₂^•− may stimulate selected profibrogenic responses in human HSC/MFs without affecting proliferation.