The protective effect of alpha-tocopherol against dichromate-induced renal tight junction damage is mediated via ERK1/2

Renal tight junctions (TJ) play a central role in modulating the paracellular pathway. We examined the function, quantity and distribution of TJ proteins: occludin and claudin-2 (cln-2), on proximal tubule in a model of acute renal failure (ARF) associated with oxidative damage. Since ERK1/2-p modulates TJ integrity, we studied their participation in dichromate (Cr⁶⁺) toxicity. We evaluated whether co-administration of the antioxidant alpha-tocopherol (α-TOC) prevents Cr⁶⁺ toxicity in TJ. Female Wistar rats received potassium dichromate 15 mg/kg, sc (5.3 mg/kg of Cr⁶⁺) single dose, with or without α-TOC (125 mg/kg, po, daily). Two and 7 days after Cr⁶⁺treatment, oxidative damage was assessed by renal lipid peroxidation (LPO), proximal function was estimated by sodium and glucose fractional excretions. Occludin, cln-2, and ERK1/2-p were detected by immunofluorescence and Western blot. ARF induced by Cr⁶⁺ provoked augment in the sodium and glucose urinary looses, increases in occludin quantity (6.6- and 15-fold on days 2 and 7, respectively) and the mislocation of cln-2. Electrophoresis migration showed a higher molecular weight band only in the Cr⁶⁺-administered groups, suggesting occludin hyperphosphorylation. α-TOC treatment diminished the LPO, improved tubular function, and preserved TJ location and expression. In summary, we show disruption of occludin and cln-2 in ARF induced by Cr⁶⁺-intoxication. This study provides evidence of the beneficial effect of α-TOC on TJ structure and function undergoing oxidative damage, and we suggest the participation of ERK1/2 in the mechanisms leading to protection by the antioxidant.