Correlation between sKL and Nrf2 plasma levels and calcium oxalate urolithiasis.

OBJECTIVE: To investigate the relationship between plasma levels of sKL and Nrf2 and calcium oxalate calculi. METHODS: The clinical data of 135 patients with calcium oxalate calculi treated in the Department of Urology of the second affiliated Hospital of Xinjiang Medical University from February 2019 to December 2022, and 125 healthy persons who underwent physical examination in the same period were collected and divided into healthy group and stone group. The levels of sKL and Nrf2 were measured by ELISA. Correlation test was used to analyze the risk factors of calcium oxalate stones, logistic regression analysis was used to analyze the risk factors of calcium oxalate stones, and ROC curve was used to evaluate the sensitivity and specificity of sKL and Nrf2 in predicting urinary calculi. RESULTS: Compared with the healthy group, the plasma sKL level in the stone group decreased (111.53 ± 27.89 vs 130.68 ± 32.51), while the plasma Nrf2 level increased (300.74 ± 114.31 vs 246.74 ± 108.22). There was no significant difference in the distribution of age and sex between the healthy group and the stone group, but there were significant differences in plasma levels of WBC, NEUT, CRP, BUN, BUA, SCr, BMI, and eating habits. The results of correlation test showed that the level of plasma Nrf2 was positively correlated with SCr (r = 0.181, P < 0.05) and NEUT (r = 0.144 P < 0.05). Plasma sKL was not significantly correlated with Nrf2 (r = 0.047, P > 0.05), WBC (r = 0.108, P > 0.05), CRP (r = - 0.022, P > 0.05), BUN (r = - 0.115, P > 0.05), BUA (r = - 0.139, P > 0.05), SCr (r = 0.049, P > 0.05), and NEUT (r = 0.027, P > 0.05). Plasma Nrf2 was not significantly correlated with WBC (r = 0.097, P > 0.05), CRP (r = 0.045, P > 0.05), BUN (r = 0.122, P > 0.05), and BUA (r = 0.122, P > 0.05); (r = 0.078, P > 0.05) had no significant correlation. Logistic regression showed that elevated plasma sKL (OR 0.978, 95% CI 0.969 ~ 0.988, P < 0.05) was a protective factor for the occurrence of calcium oxalate stones, BMI (OR 1.122, 95% CI 1.045 ~ 1.206, P < 0.05), dietary habit score (OR 1.571, 95% CI 1.221 ~ 2.020, P < 0.05), and WBC (OR 1.551, 95% CI 1.423 ~ 1.424, P < 0.05). Increased NEUT (OR 1.539, 95% CI 1.391 ~ 1.395, P < 0.05) and CRP (OR 1.118, 95% CI: 1.066 ~ 1.098, P < 0.05) are risk factors for the occurrence of calcium oxalate stones. CONCLUSION: Plasma sKL level decreased and Nrf2 level increased in patients with calcium oxalate calculi. Plasma sKL may play an antioxidant role in the pathogenesis of calcium oxalate stones through Nrf2 antioxidant pathway.

Klotho inhibits the formation of calcium oxalate stones by regulating the Keap1-Nrf2-ARE signaling pathway.

PURPOSE: Oxidative damage is important in calcium oxalate (CaOx) stone development but occurs via multiple pathways. Studies have shown that klotho plays an essential role in ameliorating oxidative damage. This study aims to explore the role of klotho in CaOx stones and whether the underlying mechanism is related to the regulation of Keap1-Nrf2-ARE signaling. METHODS: The levels of GSH, SOD, CAT, MDA, and ROS were examined by ELISA. The klotho, Bcl-2, caspase-3, Keap1, Nrf2, HO-1, and NQO1 mRNA levels were measured by qRT‒PCR, and their protein levels were detected by Western blotting. Renal tissue apoptosis was examined by TUNEL staining, and crystal cell adherence and apoptosis in HKC cells were assessed based on the Ca2+ concentrations and by flow cytometry. The renal pathological changes and the adhesion of CaOx crystals in the kidneys were examined by hematoxylin-eosin and von Kossa staining, respectively. RESULTS: We constructed a CaOx kidney stone model in vitro. By regulating the klotho gene, klotho overexpression inhibited the CaOx-induced promotion of crystal cell adherence and apoptosis in HKC cells, and these effects were reversed by klotho knockdown. Moreover, our in vivo assay demonstrated that klotho overexpression alleviated glyoxylate administration-induced renal oxidative damage, renal apoptosis, and crystal deposition in the kidneys of mice, and these effects were also associated with activation of the Keap1-Nrf2-ARE pathway. CONCLUSION: Klotho protein inhibits the oxidative stress response of HKC cells through the Keap1-Nrf2-ARE signaling pathway, reduces the apoptosis of and adhesion of CaOx crystals to HKC cells, and decreases the occurrence of CaOx kidney stones. CLINICAL TRIAL REGISTRATION: 20220304.