Activation of mammalian target of rapamycin protein and acute kidney injury induced by hexavalent chromium in rats / 中国药理学与毒理学杂志

ABSTRACT

OBJECTIVE: To explore the role of the mammalian target of rapamycin (mTOR) protein in acute kidney injury (AKI) induced by hexavalent chromium [Cr(VI)] in rats. METHODS: Forty-two male SD rats were randomly divided into normal control (single ip with saline), different-dose Cr(VI) groups (single ip with Cr(VI) 5 or 10 mg·kg-1], Rap intervention group (ip with Rap 2 mg·kg-1once every other day (totally four times) before being treated with Cr(VI) 5 or 10 mg·kg-1], and NAC intervention group (ip with NAC 300 mg·kg-1for 3d (once per day), followed by treatment with Cr(VI) 5 or 10 mg-kg-1]. After 48 h of Cr(VI) treatment, body mass and kidney mass of rats were detected to calculate the kidney coefficient. HE staining of renal tissues was performed, and the percentage of the renal tubular injury area was calculated by AutoCAD software under the microscope. The levels of serum creatinine (Scr) and urinary neutrophil gelatinase-associated lipocalin (NGAL) were detected by ELISA, while the levels of glutathione (GSH) and malondialdehyde (MDA) in kidney tissues were measured by spectrophotometric colorimetry assay. The protein levels of phosphorylated mTOR (p-mTOR), phosphorylated p70 ribosomal protein S6 kinase (p-p70S6K) and cleaved-caspase 3 in renal tissues were analyzed by Western blotting. RESULTS: After treatment with Cr(VI) 10 mg·kg-1for 48 h, rats showed not only an elevation of kidney mass and kidney coefficient, but also higher levels of Scr and urinary NGAL, as well as higher percentage of the renal tubular injury area and MDA compared with normal control (P<0.05). Also, Cr(VI) induced significant upregulation of p-mTOR, p-p70S6K or cleaved-caspase 3, but a significant decrease in GSH content in kidney tissues compared with that of normal control (P<0.05). Further more, compared with single Cr(VI) treatment of 5 or 10 mg· kg-1, the corresponding intervention of Rap or NAC decreased the levels of Scr and the percentage of the renal tubular injury area, and significantly down-regulated the expressions of p-mTOR, p-p70S6K or cleaved-caspase 3 protein in kidney tissues (P<0.05). Rap intervention reduced the levels of Scr, the percentage of the renal tubular injury area and cleaved-caspase 3 protein levels more significantly than NAC intervention (P<0.05). CONCLUSION: Cr(VI) induces the activation of p-mTOR protein, and mTOR inhibitor Rap can antagonize effectively renal tubular damage elicited by Cr(VI) in rats.