Scavenging of reactive oxygen species in mitochondria induces myofibroblast differentiation.

The goal of this study was to investigate the possible role of reactive oxygen species (ROS) in signaling, in modulation of the cytoskeleton, and in differentiation of fibroblasts. For this purpose, we have applied a novel mitochondria-targeted antioxidant: plastoquinone conjugated with decyltriphenylphosphonium (SkQ1). This antioxidant at nanomolar concentration prevented ROS accumulation and cell death induced by H(2)O(2) in fibroblasts. We found that scavenging of ROS produced by mitochondria activated the Rho/ROCK/LIMK signaling pathway that was followed by phosphorylation of cofilin and stabilization of actin stress fibers. The mitochondria-targeted antioxidant induced differentiation of human subcutaneous fibroblasts to myofibroblasts as revealed by expression of fibronectin isoform (EDA-FN) and smooth muscle actin (α-SMA). This effect was shown to be mediated by transforming growth factor β1 (TGFβ1), which was activated by matrix metalloprotease 9 (MMP9) in the culture medium. Scavenging of ROS stimulated secretion of MMP9 rather than its processing. The same effect was achieved by the nontargeted antioxidant Trolox at higher concentration, but the thiol antioxidant N-acetylcysteine (NAC) inhibited MMP activity and was not able to induce myofibroblast differentiation. The myofibroblast phenotype was supported due to autocrine TGFβ1-dependent stimulation after removal of SkQ1. It is concluded that ROS scavenging in mitochondria induces TGFβ1-dependent myofibroblast differentiation.