Selenium binding protein 1 protects renal tubular epithelial cells from ferroptosis by upregulating glutathione peroxidase 4.

Ferroptosis is a form of programmed cell death involved in various types of acute kidney injury (AKI). It is characterized by inactivation of the selenoprotein, glutathione peroxidase 4 (GPX4), and upregulation of acyl-CoA synthetase long-chain family member 4 (ACSL4). Since urinary selenium binding protein 1 (SBP1/SELENBP1) is a potential biomarker for AKI, this study investigated whether SBP1 plays a role in AKI. First, we showed that SBP1 is expressed in proximal tubular cells in normal human kidney, but is significant downregulated in cases of AKI in association with reduced GPX4 expression and increased ACSL4 expression. In mouse renal ischemia-reperfusion injury (I/R), the rapid downregulation of SBP1 protein levels preceded downregulation of GPX4 and the onset of necrosis. In vitro, hypoxia/reoxygenation (H/R) stimulation in human proximal tubular epithelial (HK-2) cells induced ferroptotic cell death in associated with an acute reduction in SBP1 and GPX4 expression, and increased oxidative stress. Knockdown of SBP1 reduced GPX4 expression and increased the susceptibility of HK-2 cells to H/R-induced cell death, whereas overexpression of SBP1 reduced oxidative stress, maintained GPX4 expression, reduced mitochondrial damage, and reduced H/R-induced cell death. Finally, selenium deficiency reduced GPX4 expression and promoted H/R-induced cell death, whereas addition of selenium was protective against H/R-induced oxidative stress. In conclusion, SBP1 plays a functional role in hypoxia-induced tubular cell death. Enhancing SBP1 expression is a potential therapeutic approach for the treatment of AKI.

Citrate attenuates vascular calcification in chronic renal failure rats.

Vascular calcification (VC) is a major contributor of cardiovascular dysfunction in chronic renal failure (CRF). Citrate binds calcium and inhibits the growth of calcium crystals. This present study intends to evaluate the effect of citrate on VC in adenine-induced CRF rats. The rats were randomly divided into five groups: the control group, the citrate control group, model group, model rats with low-dose treatment of citrate (216 mg/kg) and model rats with high-dose treatment of citrate (746 mg/kg). The rats were euthanized at 5 weeks with their blood and aorta in detection. The results showed that serum level of blood urea nitrogen, serum creatinine, phosphorus, calcium, and related renal failure function marker were elevated in the model group. Furthermore, the aortic calcium accumulation and alkaline phosphatase activity were significantly increased in the model group compared with control groups. Additionally, hematoxylin-eosin staining results demonstrated that the vascular calcification in aorta is significantly increased in the model group. Finally, the expression of VC-related proteins including bone morphogenetic protein and osteocalcin were increased in the model group, whereas alpha-smooth muscle actin was decreased in the model group compared with the control group. However, treatment with citrate caused a reversal effect of all the above events in a dose-dependent manner. In conclusion, citrate may attenuate vascular calcification in adenine-induced CRF rats.

Sodium Citrate Inhibits Endoplasmic Reticulum Stress in Rats with Adenine-Induced Chronic Renal Failure.

BACKGROUND/AIMS: Endoplasmic reticulum stress (ERS) is an important self-protective cellular response to harmful stimuli that contribute to various diseases, including chronic renal failure (CRF). Sodium citrate plays an important role in antioxidant and cellular immunity, but whether it improves ERS in CRF is unclear. METHODS: The rats were randomly divided into five groups: the control group, the sodium citrate control group, the model group, model rats with low dose sodium citrate (216 mg/kg), and model rats with a high dose of sodium citrate (746 mg/kg). The rats were euthanized at 6, 8, 12, and 16 weeks with their blood and renal tissue in detection. RESULTS: The increased concentrations of blood urea nitrogen and serum creatinine in the model group were significantly decreased by sodium citrate treatment. Hematoxylin-eosin and Masson staining showed that sodium citrate treatment apparently improved renal pathological changes in CRF rats. Western blot analysis showed that sodium citrate treatment decreased the protein levels of transforming growth factor-beta 1 and collagen type IV, which were increased in model rats. Moreover, immunohistochemical staining demonstrated that sodium citrate could effectively reduce the protein expression of glucose-regulated protein 78 kDa and CCAAT/enhancer-binding protein homologous protein in the model rats, which was consistent with western blot results. Additionally, the high dose of sodium citrate had a stronger protective effect in CRF rats than the low dose of sodium citrate. CONCLUSIONS: Sodium citrate has a protective effect on CRF through its effects on ERS.