SIRT3 Deficiency Sensitizes Angiotensin-II-Induced Renal Fibrosis

Background: Sirtuin 3 (SIRT3) has a crucial role in the cardiovascular diseases. Our previous study revealed that SIRT3 knockout (SIRT3KO) promoted cardiac pericyte-fibroblast transition. In this study, we investigated the involvement of pericyte and iron in angiotensin II (Ang-II)-mediated renal fibrosis in the SIRT3KO mice. Methods and Results: NG2-DsRed mice and NG2-DsRed-SIRT3 knockout (SIRT3KO) mice were infused with saline or Ang-II (1000 ng/kg/min) for 4 weeks. Renal fibrosis, iron content and reactive oxygen species (ROS) were measured. Masson's trichrome staining showed that SIRT3KO enhanced Ang-II-induced renal fibrosis. Immunostaining showed that Ang-II treatment increased the number of NG2-DsRed+ cells in the kidney, and SIRT3KO further enhanced NG2-DsRed+ cells. Moreover, SIRT3KO promoted pericyte differentiation into fibroblasts as evidenced by co-staining NG2-DsRed/FSP-1. Furthermore, DsRed/FSP-1+ and DsRed/transforming growth factor-beta 1 (TGF-beta 1)+ fibroblasts were elevated by SIRT3KO after Ang-II infusion. Ang-II-induced collagen I and TGF-beta 1 expression was also enhanced in the SIRT3KO mice. SIRT3KO significantly exacerbated Ang-II-induced iron accumulation. This was accompanied by an increase in acetyl-p53, HO-1 and FPN expression. Further, SIRT3KO sensitized Ang-II-induced upregulation of p47phox and gp91phox together with increased ROS formation in the kidney. Conclusion: Our study suggests that SIRT3 deficiency sensitized Ang-II-induced renal fibrosis by the mechanisms involved in promoting differentiation of pericytes into fibroblasts, exacerbating iron overload and accelerating NADPH oxidase-derived ROS formation.