NOX4 and renal fibrosis: Meng et al. (2015) reported that NOX4/ROS activates the RhoA/ROCK1 signaling pathway, promotes lung fibroblast migration, promotes collagen synthesis, and increases pulmonary fibrosis. Interestingly, RhoA/ROCK1 is a signaling pathway upstream of NOX4/ROS that promotes the differentiation of renal muscle fibroblasts and aggravates renal fibrosis (Manickam et al., 2014). Although both RhoA/ROCK1 and NOX4/ROS are involved in the regulation of cell activation and fibrosis (Paik et al., 2014), the mutual regulation of RhoA/ROCK1 and NOX4/ROS in hepatic fibrosis has not been reported.