Klotho Stabilizes the Podocyte Actin Cytoskeleton in Idiopathic Membranous Nephropathy through Regulating the TRPC6/CatL Pathway.

INTRODUCTION: The aim of this study was to explore the renoprotective effects of Klotho on podocyte injury mediated by complement activation and autoantibodies in idiopathic membranous nephropathy (IMN). METHODS: Rat passive Heymann nephritis (PHN) was induced as an IMN model. Urine protein levels, serum biochemistry, kidney histology, and podocyte marker levels were assessed. In vitro, sublytic podocyte injury was induced by C5b-9. The expression of Klotho, transient receptor potential channel 6 (TRPC6), and cathepsin L (CatL); its substrate synaptopodin; and the intracellular Ca2+ concentration were detected via immunofluorescence. RhoA/ROCK pathway activity was measured by an activity quantitative detection kit, and the protein expression of phosphorylated-LIMK1 (p-LIMK1) and p-cofilin in podocytes was detected via Western blotting. Klotho knockdown and overexpression were performed to evaluate its role in regulating the TRPC6/CatL pathway. RESULTS: PHN rats exhibited proteinuria, podocyte foot process effacement, decreased Klotho and Synaptopodin levels, and increased TRPC6 and CatL expression. The RhoA/ROCK pathway was activated by the increased phosphorylation of LIMK1 and cofilin. Similar changes were observed in C5b-9-injured podocytes. Klotho knockdown exacerbated podocyte injury, while Klotho overexpression partially ameliorated podocyte injury. CONCLUSION: Klotho may protect against podocyte injury in IMN patients by inhibiting the TRPC6/CatL pathway. Klotho is a potential target for reducing proteinuria in IMN patients.

Derlin-1 promotes ubiquitylation and degradation of the epithelial Na+ channel, ENaC.

Ubiquitylation of the epithelial Na+ channel (ENaC) plays a critical role in cellular functions, including transmembrane transport of Na+, Na+ and water balance, and blood pressure stabilization. Published studies have suggested that ENaC subunits are targets of ER-related degradation (ERAD) in yeast systems. However, the molecular mechanism underlying proteasome-mediated degradation of ENaC subunits remains to be established. Derlin-1, an E3 ligase mediator, links recognized target proteins to ubiquitin-mediated proteasomal degradation in the cytosol. In the present study, we found that derlin-1 suppressed the expression of ENaC at the protein level and that the subunit α-ENaC (also known as SCNN1A) physically interacted with derlin-1 at the membrane-anchored domains or the loop regions, and that derlin-1 initiated α-ENaC retrotranslocation. In addition, HUWE1, an endoplasmic reticulum (ER)-resident E3 ubiquitin ligase, was recruited and promoted K11-linked polyubiquitylation of α-ENaC and, hence, formation of an α-ENaC ubiquitin-mediated degradation complex. These findings suggest that derlin-1 promotes ENaC ubiquitylation and enhances ENaC ubiquitin- mediated proteasome degradation. The derlin-1 pathway therefore may represent a significant early checkpoint in the recognition and degradation of ENaC in mammalian cells.

Effectiveness of Zhibai Dihuang pill (Chinese herbal formula) in combination with western drugs in the treatment of recurrent aphthous stomatitis: A systematic review and meta-analysis.

BACKGROUND: The pain caused by recurrent aphthous stomatitis (RAS) and the recurrent nature of RAS lead to diminished quality of life for RAS patients. An alternative treatment for RAS is the oral administration of the Chinese herbal medicine Zhibai Dihuang pill (ZBDHP). Our study aims to investigate the clinical efficacy of ZBDHP when used in combination with Western medicine (WM) for the treatment of RAS and its effectiveness in preventing the recurrence of RAS. METHODS: Following the PRISMA 2020 guidelines, we conducted a literature search on 7 electronic databases according to predefined criteria. The methodological quality of randomized controlled trials (RCTs) was evaluated based on the Cochrane Handbook, and data analysis was performed using RevMan 5.3 software. RESULTS: A meta-analysis which included 7 studies and 669 participants in total was carried out in this study. The quantitative analysis revealed that the combined treatment of ZBDHP and WM has witnessed significantly improved overall clinical efficacy (RR = 1.20, 95% CI [1.12, 1.28], P < .05), reduced recurrence rate (RR = 0.24, 95% CI [0.13, 0.45], P < .05), decreased ulcer area (MD = -0.75, 95% CI [-0.91, -0.59], P < .05), and reduced pain visual simulation score (MD = -0.42, 95% CI [-0.52, -0.33], P < .05). No significant heterogeneity was observed among the studies. Qualitative analysis showed that the combination therapy significantly reduced serum levels of tumor necrosis factor-α (TNF-α), interleukin-6 and interleukin-10, shortened ulcer healing time and pain disappearance time, with no adverse effects observed. CONCLUSION: It was found that the combination of ZBDHP and WM is more effective in treating RAS than the use of WM alone, which thus provides clinicians with a more optimal treatment option. However, due to limitations in the methodological quality of the included original studies and the small sample size, we hold the opinion that more rigorous and scientific clinical trials are needed to further evaluate the efficacy of ZBDHP in treating RAS.

Estrogen negatively regulates the renal epithelial sodium channel (ENaC) by promoting Derlin-1 expression and AMPK activation.

The main functions of the epithelial sodium channel (ENaC) in the kidney distal nephron are mediation of sodium and water balance and stabilization of blood pressure. Estrogen has important effects on sodium and water balance and on premenopausal blood pressure, but its role in the regulation of ENaC function is not fully understood. Female Sprague-Dawley rats were treated with 17ß-estradiol for 6 weeks following bilateral ovariectomy. Plasma estrogen, aldosterone, creatinine, and electrolytes were analyzed, and α-ENaC and derlin-1 protein expression in the kidney was determined by immunohistochemistry and western blotting. The expression levels of α-ENaC, derlin-1, AMPK, and related molecules were also examined by western blotting and real-time PCR in cultured mouse renal collecting duct (mpkCCDc14) epithelial cells following estrogen treatment. Immunofluorescence and coimmunoprecipitation were performed to detect α-ENaC binding with derlin-1 and α-ENaC ubiquitination. The results demonstrated that the loss of estrogen elevated systolic blood pressure in ovariectomized (OVX) rats. OVX rat kidneys showed increased α-ENaC expression but decreased derlin-1 expression. In contrast, estrogen treatment decreased α-ENaC expression but increased derlin-1 expression in mpkCCDc14 cells. Moreover, estrogen induced α-ENaC ubiquitination by promoting the interaction of α-ENaC with derlin-1 and evoked phosphorylation of AMPK in mpkCCDc14 cells. Our study indicates that estrogen reduces ENaC expression and blood pressure in OVX rats through derlin-1 upregulation and AMPK activation.