Mitochondrial dysfunction accounts for aldosterone-induced epithelial-to-mesenchymal transition of renal proximal tubular epithelial cells

Epithelial–mesenchymal transition (EMT) plays a pivotal role in the pathogenesis of renal tubulointerstitial fibrosis. We previously demonstrated that aldosterone (Aldo)-induced EMT is dependent on mitochondrial-derived oxidative stress. This study investigated whether mitochondrial dysfunction (MtD) is involved in the pathogenesis of EMT and whether peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), a major regulator of oxidative metabolism and mitochondrial function, prevents EMT by improving MtD. Aldo decreased PGC-1α expression while increasing its acetylation and induced MtD, as evidenced by oxidative stress, mitochondrial membrane potential collapse, mitochondrial DNA damage, and mitochondrial complex activity reduction. Aldo time-dependently induced p66Shc phosphorylation and expression. Mineralocorticoid receptor antagonist eplerenone and p66Shc short interfering RNA prevented Aldo-induced MtD and EMT, as evidenced by downregulation of α-smooth muscle actin and upregulation of E-cadherin. Mitochondrial DNA depletion by ethidium bromide or mitochondrial transcription factor A inhibitory RNA (RNAi) induced MtD, further promoting EMT. RNAi-mediated suppression of PGC-1α induced MtD and EMT, whereas overexpression of PGC-1α prevented Aldo-induced MtD and inhibited EMT. Similarly, overexpression of silent mating type information regulation 2 homolog 1 (SIRT1), a gene upstream of PGC-1α, or the SIRT1 activator resveratrol restored Aldo-induced MtD and EMT by upregulating PGC-1α. These findings, which implicate a role for MtD in EMT and suggest that SIRT1 and PGC-1α coordinate to improve mitochondrial function and EMT, may guide us in therapeutic strategies for renal tubulointerstitial fibrosis.

Graphical abstractAldosterone (Aldo) trigged p66Shc phosphorylation and the consequent mitochondrial ROS production, leading to the deterioration of mitochondrial function (mtDNA damage and mitochondrial enzymatic activity decrease) and further promoting epithelial-to-mesenchymal transition. Dotted lines indicate sites of interventions.Figure optionsDownload full-size imageDownload high-quality image (110 K)Download as PowerPoint slideHighlights► Aldo induces p66Shc phosphorylation, and further promoting MtD and EMT. ► Suppression of endogenous p66Shc by siRNA blocks Aldo-induced MtD and EMT. ► mtDNA depletion by EtBr or knockdown of PGC-1α or TFAM by RNAi induces MtD and EMT. ► Overexpression of PGC-1α prevents Aldo-induced MtD and inhibits EMT. ► SIRT1 overexpression or activation inhibits Aldo-induced MtD and EMT via PGC-1α.