SIRT3 inhibits Ang II-induced transdifferentiation of cardiac fibroblasts through ß-catenin/PPAR-γ signaling.

AIMS: Cardiac fibrosis is an inevitable process of numerous cardiovascular diseases in which the transdifferentiation of cardiac fibroblasts plays a pivotal role. Sirtuin3 (SIRT3) has been believed to protect against cardiac fibrosis. However, the mechanism underlying this beneficial effect has not yet been elucidated. In this study, we investigated the potential mechanism of SIRT3 on the inhibition of fibroblast-to-myoblast transdifferentiation. MAIN METHODS: Cells were stimulated by angiotension II (Ang II) with SIRT3 overexpression or knockdown. Also, PPARγ agonist (Pioglitazone PIO) and inhibitor (GW9662) were used to confirm the antifibrotic effect of PPARγ. Western blot, qRT-PCR, CCK-8 and immunofluorescence staining analysis were used for investigation. KEY FINDINGS: Our data demonstrated that overexpression of SIRT3 prevented the transdifferentiation of CFs while SIRT3 knockdown promoted the process. Simultaneously, SIRT3 overexpression increased total PPARγ expression and suppressed the acetylated PPARγ. Besides, pretreatment with PPARγ agonist, pioglitazone protected CFs from transdifferentiation while PPARγ inhibitor prevented the protective effect of SIRT3. In addition, we have found that SIRT3 upregulated the expression of PPARγ by degeration of ß-catenin. SIGNIFICANCE: Our findings indicate that this newly identified SIRT3/ß-catenin/PPAR-γ axis will provide novel insight into the understanding of the mechanism of transdifferentiation of CFs to myofibroblasts.

SIRT3-KLF15 signaling ameliorates kidney injury induced by hypertension.

Renal fibrosis participates in the progression of hypertension-induced kidney injury. The effect of SIRT3, a member of the NAD+-dependent deacetylase family, in hypertensive nephropathy remains unclear. In this study, we found that SIRT3 was reduced after angiotensin II (AngII) treatment both in vivo and in vitro. Furthermore, SIRT3-knockout mice aggravated hypertension-induced renal dysfunction and renal fibrosis via chronic AngII infusion (2000 ng/kg per minute for 42 days). On the contrary, SIRT3-overexpression mice attenuated AngII-induced kidney injury compared with wild-type mice. Remarkably, a co-localization of SIRT3 and KLF15, a kidney-enriched nuclear transcription factor, led to SIRT3 directly deacetylating KLF15, followed by decreased expression of fibronectin and collagen type IV in cultured MPC-5 podocytes. In addition, honokiol (HKL), a major bioactive compound isolated from Magnolia officinalis (Houpo), suppressed AngII-induced renal fibrosis through activating SIRT3-KLF15 signaling. Taken together, our findings implicate that a novel SIRT3-KLF15 signaling may prevent kidney injury from hypertension and HKL can act as a SIRT3-KLF15 signaling activator to protect against hypertensive nephropathy.