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Renal fibrosis is a chronic pathological process that seriously endangers human health. However, the current therapeutic options for this disease are extremely limited. Previous studies have shown that signaling factors such as JAK2/STAT3, Smad3, and Myd88 play a regulatory role in renal fibrosis, and β-elemene is a plant-derived sesquiterpenoid organic compound that has been shown to have anti-inflammatory, anti-cancer, and immunomodulatory effects. In the present study, the anti-fibrotic effect of β-elemene was demonstrated by in vivo and in vitro experiments. It was shown that β-elemene inhibited the synthesis of extracellular matrix-related proteins in unilateral ureteral obstruction mice, and TGF-β stimulated rat interstitial fibroblast cells, including α-smooth muscle actin, vimentin, and connective tissue growth factor, etc. Further experiments showed that β-elemene reduced the expression levels of the above-mentioned fibrosis-related proteins by blocking the phosphorylation of JAK2/STAT3, Smad3, and the expression or up-regulation of MyD88. Notably, knockdown of MyD88 attenuated the phosphorylation levels of STAT3 and Smad3 in TGF-β stimulated NRK49F cell, which may be a novel molecular mechanism by which β-elemene affects renal interstitial fibrosis. In conclusion, this study elucidated the anti-interstitial fibrosis effect of β-elemene, which provides a new direction for future research and development of drugs related to chronic kidney disease. [ABSTRACT FROM AUTHOR]

Maslinic acid (MA), also named crategolic acid, is a pentacyclic triterpene extracted from fruits and vegetables. Although various beneficial pharmacological effects of MA have been revealed, its effect on renal fibrosis remains unclear. This study was designed to clarify whether MA could attenuate renal fibrosis and determine the putative underlying molecular mechanisms. We demonstrated that MA-treated mice with unilateral ureteral obstruction (UUO) developed a histological injury of low severity and exhibited downregulated expression of fibrotic markers, including α-smooth muscle actin (α-SMA), vimentin, and fibronectin by 38, 44 and 40%, and upregulated expression of E-cadherin by 70% as compared with untreated UUO mice. Moreover, MA treatment restored the expression levels of α-SMA, connective tissue growth factor, and vimentin to 10, 7.8 and 38% of those induced by transforming growth factor (TGF)-β in NRK49F cells. MA decreased expression of Smad2/3 phosphorylation and Smad4 in UUO kidneys and TGF-β treated NRK49F cells (p < 0.05, respectively). Notably, MA specifically interferes with MyD88, an adaptor protein, thereby mitigating Smad4 nuclear expression (p < 0.01 compared to TGF-β treated group) and ameliorating renal fibrotic changes (p < 0.01 for each fibrotic markers compared to TGF-β induced cells). In addition, in the UUO model and lipopolysaccharide-induced NRK49F cells, MA treatment decreased the expression of IL-1β, TGF-α and MCP-1, ICAM-1, associated with the suppression of NF-κB signaling. These findings suggest that MA is a potential agent that can reduce renal interstitial fibrosis, to some extent, via targeting TGF-β/Smad and MyD88 signaling. [ABSTRACT FROM AUTHOR]

Histone deacetylases have been a target of therapy for organ fibrosis. Here, we report the protective effect of CG200745 (CG), a novel histone deacetylase inhibitor, on tubulointerstitial fibrosis in Col4a3−/− mice, a murine model of Alport syndrome. Morphological analyses revealed CG treatment markedly alleviated kidney fibrosis in Col4a3−/− mice at the age of 7 weeks. CG prevented the activation of transforming growth factor β (TGFβ) and its downstream SMAD signaling in the kidney of Col4a3−/− mice. As critical upstream regulators of TGFβ signaling, immunoblotting of whole kidney lysate of Col4a3−/− mice reveled that intra-renal renin–angiotensin system (RAS) was activated with concurrent upregulation of inflammation and apoptosis, which were effectively suppressed by CG treatment. CG suppressed both activation of RAS and up-regulation of TGFβ signals in angiotensin II-stimulated HK-2 cells, a human kidney proximal tubular epithelial cell line. CG inhibited activation of TGFβ-driven signals and fibrosis in NRK-49F cells, a rat kidney fibroblast cell line, under angiotensin II-rich conditions. Collectively, CG was found to be effective both in proximal tubular epithelial cells by inhibiting local RAS and TGFβ signaling activation, as well as in fibroblasts by blocking their transition to myofibroblasts, attenuating renal fibrosis in a murine model of Alport syndrome. [ABSTRACT FROM AUTHOR]

TGF-β/Smad signaling is a major pathway in progressive fibrotic processes, and further studies on the molecular mechanisms of TGF-β/Smad signaling are still needed for their therapeutic targeting. Recently, peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) was shown to improve renal fibrosis, making it an attractive target for chronic kidney diseases (CKDs). Here, we show the mechanism by which PGC-1α regulates the TGF-β/Smad signaling pathway using HK-2 cell lines stably overexpressing empty vector (mock cells) or human PGC1α (PGC1α cells). Stable PGC-1α overexpression negatively regulated the expression of TGF-β-induced epithelial-mesenchymal transition (EMT) markers (fibronectin, E-cadherin, vimentin, and α-SMA) and EMT-related transcription factors (Snail and Slug) compared to mock cells, inhibiting fibrotic progression. Interestingly, among molecules upstream of Smad2/3 activation, the gene expression of only TGFβRI, but not TGFβRII, was downregulated in PGC-1α cells. In addition, the downregulation of TGFβRI by PGC-1α was associated with the upregulation of let-7b/c, miRNA for which the 3′ untranslated region (UTR) of TGFβRI contains a binding site. In conclusion, PGC-1α suppresses TGF-β/Smad signaling activation via targeting TGFβRI downregulation by let-7b/c upregulation. [ABSTRACT FROM AUTHOR]

Despite the wide use of angiotensin II receptor blockers in the treatment of Alport syndrome (AS), the mechanism as to how angiotensin II receptor blockers prevent interstitial fibrosis remains unclear. Here, we report that treatment of olmesartan effectively targets the feedback loop between the renin–angiotensin system (RAS) and transforming growth factor β (TGFβ) signals in tubular epithelial cells and preserves renal angiotensin-converting enzyme 2 (ACE2) expression in the kidney of Col4a3–/– mice, a murine model of experimental AS. Morphology analyses revealed amelioration of kidney fibrosis in Col4a3–/– mice by olmesartan treatment. Upregulation of TGFβ and activation of its downstream in Col4a3–/– mice were attenuated by olmesartan in Col4a3–/– mice. Intriguingly, TGFβ expression was preferentially upregulated in damaged tubular epithelial cells in Col4a3–/– mice. Concurrent upregulation of TNFα-converting enzyme and downregulation of ACE2 suggested RAS activation in Col4a3–/– mice, which was prevented by olmesartan. Mechanistically, olmesartan suppressed TGFβ-induced RAS activation in tubular epithelial cells in vitro. Collectively, we concluded that olmesartan effectively suppresses the progression of tubulointerstitial fibrosis in AS by interrupting RAS-TGFβ feedback loop to counterbalance intrarenal RAS activation. [ABSTRACT FROM AUTHOR]

PAI-1 and CTGF are overexpressed in kidney diseases and cause fibrosis of the lungs, liver, and kidneys. We used a rat model of unilateral ureteral obstruction (UUO) to investigate whether 6-BIO, a glycogen synthase kinase-3β inhibitor, attenuated fibrosis by inhibiting PAI-1 and CTGF in vivo. Additionally, TGFβ-induced cellular fibrosis was observed in vitro using the human kidney proximal tubular epithelial cells (HK-2), and rat interstitial fibroblasts (NRK49F). Expression of fibrosis-related proteins and signaling molecules such as PAI-1, CTGF, TGFβ, αSMA, SMAD, and MAPK were determined in HK-2 and NRK49F cells using immunoblotting. To identify the transcription factors that regulate the expression of PAI-1 and CTGF the promoter activities of AP-1 and SP-1 were analyzed using luciferase assays. Confocal microscopy was used to observe the co-localization of AP-1 and SP-1 to PAI-1 and CTGF. Expression of PAI-1, CTGF, TGFβ, and α-SMA increased in UUO model as well as in TGFβ-treated HK-2 and NRK49F cells. Furthermore, UUO and TGFβ treatment induced the activation of P-SMAD2/3, SMAD4, P-ERK 1/2, P-P38, and P-JNK MAPK signaling pathways. PAI-1, CTGF, AP-1 and SP-1 promoter activity increased in response to TGFβ treatment. However, treatment with 6-BIO decreased the expression of proteins and signaling pathways associated with fibrosis in UUO model as well as in TGFβ-treated HK-2 and NRK49F cells. Moreover, 6-BIO treatment attenuated the expression of PAI-1 and CTGF as well as the promoter activities of AP-1 and SP-1, thereby regulating the SMAD and MAPK signaling pathways, and subsequently exerting anti-fibrotic effects on kidney cells. [Display omitted] • 6-BIO inhibits UUO- and TGFβ induced kidney fibrosis. • 6-Bio reduces PAI-1 and CTGF expression associated with kidney fibrosis. • 6-BIO regulates AP-1 and SP-1 transcription activity in kidney cells. [ABSTRACT FROM AUTHOR]

[Display omitted] ACE inhibitors or angiotensin II receptor blockers (ACEi/ARBs) have been a cornerstone of the management in kidney disease, but their use is often limited by undesired systemic effects, such as symptomatic hypotension. To minimize the extra-renal effects of ACEi/ARBs, we formulated hydrophobically modified glycol chitosan (HGC) nanomicelles releasing olmesartan (HGC-Olm) that specifically accumulated in the kidney, and investigated whether kidney-specific delivery of olmesartan by HGC nanomicelles could ameliorate organ damage in Col4a3 −/− mouse, a murine model of progressive chronic kidney disease mimicking human Alport syndrome. Ex vivo tracing demonstrated that intravenously injected HGC-Olm nanomicelles were specifically delivered to the kidney, with sustained release of olmesartan for more than 48 h. Contrary to the conventional delivery of olmesartan via oral route, injection of HGC-Olm nanomicelles did not alter blood pressure in Col4a3 −/− mice. Immunohistochemistry revealed that HGC nanomicelles were diffusely distributed from the cortex and glomeruli to the outer medulla, sparing the inner medulla. Phenotypic analysis showed that the attenuation of kidney fibrosis in the kidney of Col4a3 −/− mice by HGC-Olm nanomicelles was comparable to that noted with conventionally delivered olmesartan. Therefore, our results suggest that HGC-Olm nanomicelles could be a safe and effective alternative drug delivery system for kidney diseases. [ABSTRACT FROM AUTHOR]