Selective inhibition of class IIa histone deacetylases alleviates renal fibrosis.

In this study, we examined the effect of MC1568, a selective class IIa histone deacetylase (HDAC) inhibitor, on the development and progression of renal fibrosis in a murine model of renal fibrosis induced by unilateral ureteral obstruction (UUO). All 4 class IIa HDAC isoforms, in particular HDAC4, were up-regulated in renal epithelial cells of the injured kidney. Administration of MC1568 immediately after UUO injury reduced expression of α-smooth muscle actin (α-SMA), fibronectin, and collagen 1. MC1568 treatment or small interfering RNA-mediated silencing of HDAC4 also suppressed expression of those proteins in cultured renal epithelial cells. Mechanistically, MC1568 abrogated UUO-induced phosphorylation of Smad3, NF-κB, and up-regulation of integrin ɑVß6 in the kidney and inhibited TGF-ß1-induced responses in cultured renal epithelial cells. MC1568 also increased renal expression of klotho, bone morphogenetic protein 7, and Smad7. Moreover, delayed administration of MC1568 at 3 d after ureteral obstruction reversed the expression of α-SMA, fibronectin, and collagen 1 and increased expression of matrix metalloproteinase (MMP)-2 and -9. Collectively, these results suggest that selectively targeting class IIa HDAC isoforms (in particular HDAC4) may inhibit development and progression of renal fibrosis by suppressing activation and expression of multiple profibrotic molecules and increasing expression of antifibrotic proteins and MMPs.-Xiong, C., Guan, Y., Zhou, X., Liu, L., Zhuang, M. A., Zhang, W., Zhang, Y., Masucci, M. V., Bayliss, G., Zhao, T. C., Zhuang, S. Selective inhibition of class IIa histone deacetylases alleviates renal fibrosis.

WITHDRAWN: Salvianolate attenuates renal fibrosis in rat models of diabetic nephropathy by inhibiting inflammation and oxidative stress mechanisms.

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Pharmacological inhibition of Src kinase protects against acute kidney injury in a murine model of renal ischemia/reperfusion.

Activation of Src kinase has been implicated in the pathogenesis of acute brain, liver, and lung injury. However, the role of Src in acute kidney injury (AKI) remains unestablished. To address this, we evaluated the effects of Src inhibition on renal dysfunction and pathological changes in a murine model of AKI induced by ischemia/reperfusion (I/R). I/R injury to the kidney resulted in increased Src phosphorylation at tyrosine 416 (activation). Administration of PP1, a highly selective Src inhibitor, blocked Src phosphorylation, improved renal function and ameliorated renal pathological damage. PP1 treatment also suppressed renal expression of neutrophil gelatinase-associated lipocalin and reduced apoptosis in the injured kidney. Moreover, Src inhibition prevented downregulation of several adherens and tight junction proteins, including E-cadherin, ZO-1, and claudins-1/-4 in the kidney after I/R injury as well as in cultured renal proximal tubular cells following oxidative stress. Finally, PP1 inhibited I/R-induced renal expression of matrix metalloproteinase-2 and -9, phosphorylation of extracellular signal-regulated kinases1/2, signal transducer and activator of transcription-3, and nuclear factor-κB, and the infiltration of macrophages into the kidney. These data indicate that Src is a pivotal mediator of renal epithelial injury and that its inhibition may have a therapeutic potential to treat AKI.

Pharmacological targeting of BET proteins inhibits renal fibroblast activation and alleviates renal fibrosis.

Bromodomain and extra-terminal (BET) protein inhibitors have been shown to effectively inhibit tumorgenesis and ameliorate pulmonary fibrosis by targeting bromodomain proteins that bind acetylated chromatin markers. However, their pharmacological effects in renal fibrosis remain unclear. In this study, we examined the effect of I-BET151, a selective and potent BET inhibitor, on renal fibroblast activation and renal fibrosis. In cultured renal interstitial fibroblasts, exposure of cells to I-BET151, or silencing of bromodoma in-containing protein 4 (Brd4), a key BET protein isoform, significantly reduced their activation as indicated by decreased expression of α-smooth muscle actin, collagen 1 and fibronectin. In a murine model of renal fibrosis induced by unilateral ureteral obstruction (UUO), administration of I-BET151 suppressed the deposition of extracellular matrix proteins, renal fibroblast activation and macrophage infiltration. Mechanistically, I-BET151 treatment abrogated UUO-induced phosphorylation of epidermal growth factor receptor and platelet growth factor receptor-ß. It also inhibited the activation of Smad-3, STAT3 and NF-κB pathways, as well as the expression of c-Myc and P53 transcription factors in the kidney. Moreover, BET inhibition resulted in the reduction of renal epithelial cells arrested at the G2/M phase of cell cycle after UUO injury. Finally, injury to the kidney up-regulated Brd4, and I-BET151 treatment abrogated its expression. Brd4 was also highly expressed in human fibrotic kidneys. These data indicate that BET proteins are implicated in the regulation of signaling pathways and transcription factors associated with renal fibrogenesis, and suggest that pharmacological inhibition of BET proteins could be a potential treatment for renal fibrosis.

Enhancer of Zeste Homolog 2 Inhibition Attenuates Renal Fibrosis by Maintaining Smad7 and Phosphatase and Tensin Homolog Expression.

Enhancer of zeste homolog 2 (EZH2) is a methyltransferase that induces histone H3 lysine 27 trimethylation (H3K27me3) and functions as an oncogenic factor in many cancer types. However, the role of EZH2 in renal fibrogenesis remains unexplored. In this study, we found high expression of EZH2 and H3K27me3 in cultured renal fibroblasts and fibrotic kidneys from mice with unilateral ureteral obstruction and humans with CKD. Pharmacologic inhibition of EZH2 with 3-deazaneplanocin A (3-DZNeP) or GSK126 or siRNA-mediated silencing of EZH2 inhibited serum- and TGFß1-induced activation of renal interstitial fibroblasts in vitro, and 3-DZNeP administration abrogated deposition of extracellular matrix proteins and expression of α-smooth muscle actin in the obstructed kidney. Injury to the kidney enhanced Smad7 degradation, Smad3 phosphorylation, and TGFß receptor 1 expression, and 3-DZNeP administration prevented these effects. 3-DZNeP also suppressed phosphorylation of the renal EGF and PDGFß receptors and downstream signaling molecules signal transducer and activator of transcription 3 and extracellular signal-regulated kinase 1/2 after injury. Moreover, EZH2 inhibition increased the expression of phosphatase and tensin homolog (PTEN), a protein previously associated with dephosphorylation of tyrosine kinase receptors in the injured kidney and serum-stimulated renal interstitial fibroblasts. Finally, blocking PTEN with SF1670 largely diminished the inhibitory effect of 3-DZNeP on renal myofibroblast activation. These results uncovered the important role of EZH2 in mediating the development of renal fibrosis by downregulating expression of Smad7 and PTEN, thus activating profibrotic signaling pathways. Targeted inhibition of EZH2, therefore, could be a novel therapy for treating CKD.