Abstract
DEP domain containing mTOR-interacting protein (DEPTOR) was originally identified as an in vivo dual inhibitor of mechanistic target of rapamycin (mTOR). It was recently reported to be involved in renal physiology and pathology in vitro; however, its detailed roles and mechanisms in vivo are completely unknown. We observed that DEPTOR expression in the kidney was markedly increased on day 3 after cisplatin treatment, at which time cell apoptosis peaked, implicating DEPTOR in cisplatin-induced acute kidney injury (AKI). We then used the Cre–LoxP system to generate mutant mice in which the DEPTOR gene was specifically deleted in the proximal tubule cells. DEPTOR deficiency did not alter the renal histology or functions in the saline-treated group, indicating that DEPTOR is not essential for kidney function under physiological conditions. Interestingly, DEPTOR deletion extensively preserved the renal histology and maintained the kidney functions after cisplatin treatment, suggesting that the absence of DEPTOR ameliorates cisplatin-induced AKI. Mechanistically, DEPTOR modulated p38 MAPK signaling and TNFα production in vivo and in vitro, rather than mTOR signaling, thus moderating the inflammatory response and cell apoptosis induced by cisplatin. Collectively, our findings demonstrate the roles and mechanisms of DEPTOR in the regulation of the renal physiology and pathology, and demonstrate that the loss of DEPTOR in the proximal tubules protects against cisplatin-induced AKI.
Highlights
Acute kidney injury (AKI), which often results from ischemia/reperfusion, sepsis, or nephrotoxins, is a major kidney disease characterized by the rapid loss of renal function, leading to the accumulation of metabolic wastes and imbalances in electrolytes and body fluids[1,2,3]
We demonstrate that DEPTOR knockout protected the proximal tubules from cisplatin-induced AKI, and that this protection was probably mediated by reduced cell death through the inhibition of p38 mitogen-activated protein kinase (MAPK) signaling and the production of tumor necrosis factor α (TNFα)
A western blotting analysis showed that DEPTOR expression in the renal cortex was almost constant from day 0 to day 2 after cisplatin treatment, but increased sharply on day 3, indicating that DEPTOR is involved in cisplatin-induced AKI, in its later stage (Fig. 1f)
Summary
Acute kidney injury (AKI), which often results from ischemia/reperfusion, sepsis, or nephrotoxins, is a major kidney disease characterized by the rapid loss of renal function, leading to the accumulation of metabolic wastes and imbalances in electrolytes and body fluids[1,2,3]. It is associated with high rates of morbidity and mortality. The nephrotoxicity of cisplatin mainly involves the death of the tubule cells, including both apoptosis and necrosis, because it activates complex signaling pathways[8,9].
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