Numb ameliorates necrosis and inflammation in acute kidney injury induced by cisplatin.

Cisplatin induces acute renal failure in humans and mice.Tubular apoptosis, necrosis and inflammation are the primary pathogenesis of cisplatin-induced acute kidney injury(AKI). We previously reported that the depletion of Numb from proximal tubules exacerbates tubular cells apoptosis in cisplatin-induced AKI, however, the role of Numb in tubular necrosis and renal inflammation in cisplatin-induced AKI remains unclear. A mouse model of AKI was produced by cisplatin intraperitoneally injection in mice from proximal tubule-specific depletion of Numb (PT-Nb-KO) and their wild-type littermates (PT-Nb-WT) respectively. Renal Numb expression was determined by Western blotting. Renal morphological damage was examined by hematoxylin and eosin staining (H&E staining). Tubular necrosis was evaluated by histological study and the protein level of renal Mixed lineage kinase domain-like protein (MLKL) which is a molecular marker of necrosis. Leukocyte infiltration and pro-inflammatory cytokines was determined by immunostaining and quantitative real-time PCR (qRT-PCR) respectively.The protein level of Numb was dramatically decreased in kidneys of PT-Nb-KO mice compared with PT-Nb-WT mice. After cisplatin injection, a significant increase of tubular injury score and the protein level of renal MLKL were detected in PT-Nb-KO mice compared with those in PT-Nb-WT. In addition, the number of F4/80-positve and CD3-positive cells, markers for macrophages and neutraphils respectively, showed significantly increased in kidneys from PT-Nb-KO mice compared with those in PT-Nb-WT mice. Consistently, the gene expression of pro-inflammatory cytokines including TNF-α and MCP-1 in the kidneys was higher in PT-Nb-KO mice than those in PT-Nb-WT mice. Numb play additional protective role in cisplatin-induced AKI through ameliorating tubular necrosis and renal inflammation besides attenuating cisplatin-induced tubular apoptosis.

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