NOX4 and Hepatic fibrosis: NOX4 may play a key role in liver fibrosis development, downstream TGF-β, at two different levels: i) in vitro experiments reveal that NOX4 is required for both HSC activation and maintenance of the activated phenotype in MFBs and ii) hepatocytes respond to TGF-β by inducing NOX4 that is required for its pro-apoptotic response, which might be relevant to blunt regeneration and create a pro-fibrogenic microenvironment.