TNF-α-mediated podocyte injury via the apoptotic death receptor pathway in a mouse model of IgA nephropathy.

BACKGROUND: IgA nephropathy (IgAN) is the most common primary glomerular disease worldwide and it is characterized by mesangial IgA deposits. Proteinuria is a common clinical feature of IgAN, which has a critical connection to podocyte injury and has been used as a clinical prognostic factor for IgAN. Evidence has shown that TNF-α released from mesangial cells may lead to podocyte apoptosis. METHODS: Forty male BALB/c mouse were randomly divided into the control group and IgAN group. A mice model of IgAN was developed by oral administration of bovine serum albumin (BSA) combined with Staphylococcus Enterotoxin B (SEB) tail vein injection. Urinary protein concentrations, renal function, renal morphological, IgA deposition, apoptosis situation, and the mRNA and protein expression of nephrin, podocin, TNF-α, TNFR1, caspase-8 and caspase-3, were detected after 12 weeks. RESULTS: BSA and SEB can successfully establish an IgAN mouse model, and the main pathological changes are the IgA immune complex deposition in the mesangial area. The gene and protein expression levels of nephrin and podocin were found to be downregulated, and death receptor pathway-related indicators were upregulated, and they were involved in TNF-α-activated podocyte injury and apoptosis in IgAN mice. CONCLUSION: TNF-α may play an important role in the pathogenesis of podocyte apoptosis in IgAN, and its effects may be mediated through the apoptotic death receptor pathway.

Huangqi Guizhi Wuwu Decoction attenuates Podocyte cytoskeletal protein damage in IgA nephropathy rats by regulating AT1R/Nephrin/c-Abl pathway.

ETHNOPHARMACOLOGICAL RELEVANCE: Huangqi Guizhi Wuwu Decoction(HQGZWWD) is a Traditional Chinese Medicine formula from Synopsis of Golden Chamber used to treat blood arthralgia. According to the principle that the same treatment can be used for different diseases, HQGZWWD has proven effective for IgA nephropathy (IgAN) associated with spleen and kidney yang deficiency. AIM OF THE STUDY: In this study, we investigated the mechanism by which HQGZWWD alleviates proteinuria and protects renal function in rats with IgAN by regulating the AT1R/Nephrin/c-Abl pathway. METHODS: Rats were randomly divided into six groups: control, IgAN model, IgAN model treated with low-dose HQGZWWD, IgAN model treated with medium-dose HQGZWWD, IgAN model treated with high-dose HQGZWWD, and IgAN model treated with valsartan. IgAN was induced using bovine γ-globulin. We evaluated the mediating effects of HQGZWWD on podocyte cytoskeletal proteins, the AT1R/Nephrin/c-Abl pathway, upstream tumor necrosis factor-α (TNF-α), and TNF-α receptor-1 (TNFR1). RESULTS: The IgAN rats displayed proteinuria, IgA deposition in the mesangial region, and podocyte cytoskeletal protein damage. The expression of TNF-α, TNFR1, AT1R, and c-Abl was increased in the IgAN rat kidney, whereas the expression of nephrin, podocin, ACTN4, and phosphorylated nephrin (p-nephrin) was reduced. HQGZWWD treatment significantly alleviated podocyte cytoskeletal protein damage in the IgAN rats, upregulated the expression of nephrin, podocin, and ACTN4, and the colocalized expression of F-actin and nephrin. This study demonstrates that HQGZWWD attenuates podocyte cytoskeletal protein damage by regulating the AT1R-nephrin- c-Abl pathway, upregulating the expression of p-nephrin, and downregulating the expression of AT1R and c-Abl. CONCLUSIONS: These results indicate that HQGZWWD attenuates podocyte cytoskeletal protein damage in IgAN rats by regulating the AT1R/Nephrin/c-Abl pathway, providing a potential therapeutic approach for IgAN.

Reactive oxygen species induced by uric acid promote NRK­52E cell apoptosis through the NEK7­NLRP3 signaling pathway.

Increasing uric acid (UA) could induce renal tubular epithelial cell (NRK­52E) injury. However, the specific mechanism by which UA induces renal tubular epithelial cell injury remains unknown. It was hypothesized that UA induces renal tubular epithelial cell injury through reactive oxygen species (ROS) and the Never in mitosis gene A (NIMA)­related kinase 7 (NEK7)/NLR family pyrin domain containing 3 (NLRP3) signaling pathway. TUNEL assay and flow cytometry were applied to measure apoptosis, and the results of the present study showed that UA treatment induced apoptosis of NRK­52E cells in a concentration­dependent manner. Western blotting was performed to determine the expression levels of cleaved caspase­3, Bax and Bcl­xl, it was found that levels were significantly increased after UA treatment in NRK­52E cells. ROS and apoptosis were predominantly induced in NRK­52E cells and there was an association between ROS and apoptosis. Enhanced expression of NEK7, NLRP3, apoptosis­associated speck­like and caspase­1 were observed in NRK­52E cells treated with UA. The ROS inhibitor, N­acetyl­l­cysteine, exerted a protective effect on the UA­induced apoptosis of tubular epithelial cells by reducing excess ROS production, which significantly inhibited NEK7 and NLRP3 inflammasome activation. These results indicated that UA activates ROS and induces apoptosis of NRK­52E cells. The mechanism might be related to the regulation of the NEK7/NLRP3 signaling pathway.

Siwu Granules and Erythropoietin Synergistically Ameliorated Anemia in Adenine-Induced Chronic Renal Failure Rats.

OBJECTIVE: Renal anemia in patients with end-stage chronic kidney disease is closely related to the deterioration of cardiac function, renal function, and quality of life. This study involved adenine-induced renal anemic rat models and evaluated the treatment effect of Siwu granules and/or erythropoietin (EPO). METHODS: Fifty SD rats were randomly divided into 5 groups: control, model, Siwu, EPO, and Siwu plus EPO groups. The expression levels of NO, MDA, SOD, CAT, IL-6, TNF-α, EPO, EPOR, α-SMA, and TGF-ß1 were detected in rats after 8 weeks of treatment with Siwu granules and/or EPO. RESULTS: After modeling, 47 rats entered the stage of treatment. Siwu plus EPO treatment significantly increased the rat hemoglobin content (p < 0.05) and reduced blood urea nitrogen (p < 0.05) and serum creatinine (p < 0.001). Compared with the control group, the expression of EPO and EPOR in the kidney of rats with renal failure was significantly decreased (p < 0.05). Moreover, the Siwu plus EPO group improved the level of oxidative stress in rats with chronic renal failure and reduced the expression of inflammatory factors. The expression of α-SMA and TGF-ß1 in rats with renal failure was higher, but there was no expression in the control group. CONCLUSION: Combined treatment of Siwu granules with EPO increased the expression of EPO and EPOR in the renal tissues and inhibited oxidative stress and inflammatory factors, improving the renal function and anemia.

Effect and Mechanism of ShiZhiFang on Uric Acid Metabolism in Hyperuricemic Rats.

OBJECTIVE: To explore the effect and mechanism of ShiZhiFang on uric acid metabolism. METHODS: 40 rats were divided into normal group, model group, ShiZhiFang group, and benzbromarone group. The hyperuricemic rat model was induced by yeast gavage at 15 g/kg and potassium oxonate intraperitoneal injection at 600 mg/kg for two weeks. During the next two weeks, ShiZhiFang group rats were given ShiZhiFang by gavage, and benzbromarone group rats were given benzbromarone by gavage. The serum uric acid, creatinine, blood urea nitrogen, XOD activity, urinary uric acid, urinary ß2-MG, and histopathological changes were observed in the rats of each group after treatment. RESULTS: The hyperuricemic model was established successfully and did not show the increase of serum creatinine and blood urea nitrogen. Compared with the model group, the serum uric acid, serum XOD activity, and urinary ß2-MG were significantly decreased (p < 0.05), and 24 h urinary uric acid excretion was significantly decreased (p < 0.01) in ShiZhiFang group, whereas the two treatment groups were of no statistical significant in above indicators (p > 0.05); renal histopathology showed that the lesions in two treatment groups were reduced compared to the model groups. The gene and protein expression of uric acid anion transporters rOAT1 and rOAT3 in the kidney was significantly higher than that in model group (p < 0.01). CONCLUSION: The model is suitable for the study of primary hyperuricemia. The mechanisms of ShiZhiFang on uric acid metabolism in hyperuricemic rats may be involved in reducing the activity of serum XOD and promoting the transcription and expression of rOAT1 and rOAT3 in the kidney.

Effects of Shizhifang on NLRP3 Inflammasome Activation and Renal Tubular Injury in Hyperuricemic Rats.

OBJECTIVE: Uric acid (UA) activates the NLRP3-ASC-caspase-1 axis and triggers cascade inflammatory that leads to hyperuricemic nephropathy and hyperuricemia-induced renal tubular injury. The original study aims to verify the positive effects of the traditional Chinese medicinal formula Shizhifang (SZF) on ameliorating the hyperuricemia, tubular injury, and inflammasome infiltration in the kidneys of hyperuricemic lab rats. METHOD: Twenty-eight male Sprague-Dawley rats were divided into four groups: control group, oxonic acid potassium (OA) model group, OA + SZF group, and OA + Allopurinol group. We evaluated the mediating effects of SZF on renal mitochondrial reactive oxygen species (ROS) and oxidative stress (OS) products, protein expression of NLRP3-ASC-caspase-1 axis, and downstream inflammatory factors IL-1ß and IL-18 after 7 weeks of animals feeding. RESULT: SZF alleviated OA-induced hyperuricemia and inhibited OS in hyperuricemic rats (P < 0.05). SZF effectively suppressed the expression of gene and protein of the NLRP3-ASC-caspase-1 axis through accommodating the ROS-TXNIP pathway (P < 0.05). CONCLUSION: Our data suggest that SZF alleviates renal tubular injury and inflammation infiltration by inhibiting NLRP3 inflammasome activation triggered by mitochondrial ROS in the kidneys of hyperuricemic lab rats.