Inhibition of SIRT2 Alleviates Fibroblast Activation and Renal Tubulointerstitial Fibrosis via MDM2

Abstract

Background/Aims: Renal tubular epithelial cells and fibroblasts are the main sources of myofibroblasts, and these cells produce the extracellular matrix during tubulointerstitial fibrosis (TIF). Histone deacetylases (HDAC) inhibitors exert an antifibrogenic effect in the skin, liver and lung. Sirtuin 2 (SIRT2), which is a class III HDAC, is an important member of NAD⁺-dependent protein deacetylases. The current study evaluated the role of SIRT2 in renal TIF. Methods: Immunohistochemical staining and Western blot were performed to evaluate SIRT2 expression in TIF patients and unilateral urethral obstruction (UUO) mice. Western blot was used to assess the protein levels of SIRT2, α-SMA, collagen III, fibronectin, and MDM2 in tubular epithelial cells and fibroblasts. The specific inhibitor AGK2 was used to inhibit SIRT2 activity, and targeted siRNA was used to suppress SIRT2 expression. Results: SIRT2 expression increased in the tubulointerstitium of TIF patients and UUO mice. SIRT2 inhibition ameliorated TIF in UUO mice. SIRT2 expression in tubular cells was unchanged after exposure to TGF-β1. The SIRT2-specifc inhibitor AGK2 did not attenuate TGF-β1-induced tubular epithelial-mesenchymal transition. However, SIRT2 was upregulated in fibroblasts, and fibroblasts were activated after TGF-β1 treatment. Genetic knockdown and chemical inhibition of SIRT2 attenuated TGF-β1-induced fibroblast activation. We also explored the downstream signaling of SIRT2 during fibroblast activation. Genetic knockdown and chemical inhibition of SIRT2 suppressed TGF-β1-induced increase in MDM2 expression, and inhibition of the MDM2-p53 interaction using Nutlin-3 did not suppress SIRT2 upregulation. Conclusion: Our results suggest that SIRT2 participates in the activation of fibroblasts and TIF, which is mediated via regulation of the MDM2 pathway, and the downregulation of SIRT2 may be a therapeutic strategy for renal fibrosis.

Targeting MDM2 for novel molecular therapy: Beyond oncology

“…SIRT2 appears to promote fibroblast activation by enhancing TGF‐β1‐induced MDM2 expression, which leads to the subsequent inhibition of p53 (Figure ) . SIRT2 inhibition by genetic knockdown or pharmacological inhibitors has significantly reduced the fibroblast activation and suppressed the expression of MDM2 …”

“…Renal fibrosis (RF) is a common pathology of chronic kidney disease that is characterized by glomerulosclerosis and tubulointerstitial fibrosis (TIF) . He et al have found that SIRT2 is highly expressed in the tubulointerstitium from TIF patients and mice with unilateral ureteral obstruction, and SIRT2 plays an important role in activating fibroblasts and TIF. SIRT2 appears to promote fibroblast activation by enhancing TGF‐β1‐induced MDM2 expression, which leads to the subsequent inhibition of p53 (Figure ) .…”

“…He et al have found that SIRT2 is highly expressed in the tubulointerstitium from TIF patients and mice with unilateral ureteral obstruction, and SIRT2 plays an important role in activating fibroblasts and TIF. SIRT2 appears to promote fibroblast activation by enhancing TGF‐β1‐induced MDM2 expression, which leads to the subsequent inhibition of p53 (Figure ) . SIRT2 inhibition by genetic knockdown or pharmacological inhibitors has significantly reduced the fibroblast activation and suppressed the expression of MDM2 …”

Identification of fibroblast activation-related genes in two acute kidney injury models

“…Recently, some scholars have found that the activation of Sirtuin 2(SIRT2) promotes fibroblast activation and aggravates renal fibrogenesis (Ponnusamy et al, 2015). As expected, its inhibitor suppresses fibroblast activation through murine double minute2(MDM2), suggesting the SIRT2-MDM2 signaling pathway may be a therapeutic target for renal tubulointerstitial fibrosis (He et al, 2018). In the study of ischemic renal fibrosis, Cyr61 may not only inhibit the fibrotic phenotype of fibroblasts, but also inhibit the proliferation of fibroblasts through the p53/P21/Rb pathway (Liu et al, 2019).…”

Application of Histone Deacetylase Inhibitors in Renal Interstitial Fibrosis

“…SIRT1 and SIRT2 are found expressed in renal fibroblasts and tubular cell, while cellular distribution of other members in this subfamily is not clear. Studies have demonstrated the role of class III HDACs in tissue fibrosis, but results regarding SIRT1 in renal fibrosis are controversial, as both activation and inhibition of SIRT1 can attenuate renal fibrosis [25][26][27][28][29]. HDAC 11 is the sole member of class IV and is localized to the nucleus and may be involved in regulating the expression of interleukin 10.…”