OBJECTIVETo investigate the involvement of PI3K/Akt signaling pathway in the changes of urine protein in adriamycin-induced nephropathic rats treated with dexamethasone and LY294002 (a PI3K inhibitor).

METHODSSD rats were randomized into normal control group, ariamycin-induced nephropathy group (ADR group), ariamycin+dexamethasone group (DEX group), and ADR+DEX+LY294002 group (LY294002 group). On days 7, 14 and 28 after the treatments, 24-h urine was collected from the rats to analyze the total urine proteins. The renal tissues were obtained on day 28 to examine the expressions of p-AKT, AKT and Bad proteins in the cortical tissues using Western blotting; the expression of Bad mRNA in the cortical tissues was measured by QPCR.

RESULTSUrine protein increased progressively in ADR group accompanied by significantly reduced p-AKT/AKT ratio and increased Bad mRNA expression in comparison with those in the normal control group (P<0.05). Urine protein was obviously reduced in DEX group with comparable p-AKT/AKT ratio and Bad mRNA expression level with those in the control group (P>0.05). Urine protein showed no significant reduction in LY294002 group, but the p-AKT/AKT ratio was significantly reduced and Bad mRNA expression was increased compared with those in DEX group (P<0.05).

CONCLUSIONDexamethasone increases the expression of Bad mRNA and reduces urine protein in adriamycin-induced nephropathic rats by activating PI3K/Akt signaling pathway. LY294002 can inhibit PI3K/Akt signaling pathway to block the effect of dexamethasone, suggesting that PI3K/Akt signaling pathway is one of the signaling pathways that mediate the effect of dexamethasone on proteinuria.