Drp1-mediated mitochondrial fission promotes renal fibroblast activation and fibrogenesis

摘要

Excessive mitochondrial fission acts as a pro-proliferative marker in some cancers and organ fibrosis; its potential role in renal fibroblast activation and fibrogenesis has never been investigated. Here, we showed more pronounced fragmented mitochondria in fibrotic than in non-fibrotic renal fibroblast in humans and mice. In a mouse model of obstructive nephropathy, phosphorylation of Drp1 at serine 616 (p-Drp1S616) and acetylation of H3K27(H3K27ac) was increased in fibrotic kidneys; pharmacological inhibition of mitochondrial fission by mdivi-1 substantially reduced H3K27ac levels, fibroblasts accumulation, and interstitial fibrosis. Moreover, mdivi-1 treatment was able to attenuate the established renal fibrosis. In cultured renal interstitial fibroblasts, targeting Drp1 using pharmacological inhibitor or siRNA suppressed TGF-β1-elicited cell activation and proliferation, as evidenced by inhibiting expression of α-smooth muscle actin (α-SMA) and collagen I, as well as by reducing DNA synthesis. In contrast, Drp1 deletion enhanced cell apoptosis, along with decreased mitochondrial fragmentation, mtROS elevation, and glycolytic shift upon TGFβ1 stimulation. In Drp1 deletion fibroblasts, re-expression of wild-type Drp1 rather than Drp1S616A mutant restores the reduction of TGF-β-induced-Drp1 phosphorylation, H3K27ac, and cell activation. Moreover, TGF-β1 treatment increased the enrichment of H3K27ac at the promoters of α-SMA and PCNA, which was reversed in Drp1-knockdown fibroblasts co-transfected with empty vector or Drp1S616A, but not wild-type Drp1. Collectively, our results imply that inhibiting p-Drp1S616-mediated mitochondrial fission attenuates fibroblast activation and proliferation in renal fibrosis through epigenetic regulation of fibrosis-related genes transcription and may serve as a therapeutic target for retarding progression of chronic kidney disease.