Abstract: Objective To explore the effect of sinomenine on the signal pathway of phosphatidyl-3 kinase(PI3K)/mammalian target of rapamycin(mTOR) and mesangial hyperplasia in renal tissue of rats with adriamycin-induced nephropathy and elucidate its protective mechanism.Methods A total of 50 SD rats were selected,10 rats were randomly injected with normal saline via caudal vein as control group,the other 40 rats were injected with adriamycin 5 mg/kg via caudal vein for 7 days to prepare nephrotic syndrome(NS) model.After successful modeling,the rats were randomly divided into the groups of model(NS),sinomenine low-dose(25 mg/kg),medium-dose(50 mg/kg) and high-dose(100 mg/kg) (n=10 each).Control and NS groups received normal saline through abdominal cavity and sinomenine groups were given corresponding doses of drugs once daily for 28 days.At 24 hours after the last administration,blood and urine samples of rats in each group were collected and rats sacrificed,renal tissue samples harvested,serum creatinine(Scr) and urea nitrogen(BUN) were measured by enzyme-linked immunosorbent assay(ELISA);24-hour urine protein was detected by Coomassie brilliant blue staining;hematoxylin-eosin staining(HE) was utilized for analyzing the pathological changes of kidney and mesangial matrix index(M/G);transmission electron microscopy for observing the thickening of glomerular basement membrane of kidney;Western blot for detecting the expressions of p-PI3K/PI3K,p-mTOR/mTOR,fibronectin(FN) and type IV collagen(COL4) in renal tissue.Results As compared with control group,there were pathological damages such as the increase of glomerular mesangial matrix,the expansion of renal tubule lumen and severe thickening of glomerular basement membrane.M/G and renal function indicators Scr,BUN,24-hour urine protein and renal tissue were elevated.The protein expressions of p-PI3K,p-mTOR,FN and COL4 rose markedly in NS group(P<0.05).As compared with NS group,sinomenine high/medium/low dose groups alleviated pathological damage such as glomerular basement membrane thickening,M/G,Scr,BUN,24-hour urine protein,renal tissue p-PI3K,expressions of mTOR,FN and COL4 proteins declined markedly in sinomenine low/medium/high-dose groups(P<0.05).As compared with low-dose sinomenine group,glomerular basement membrane thickening was the least pathologically damaged and M/G,Scr,BUN,24-hour urine protein,renal tissue p-PI3K,p-mTOR,FN and COL4 declined markedly in sinomenine medium/high-dose group(P<0.05).Conclusions Sinomenine may inhibit the activation of PI3K/mTOR signaling pathway,reduce the proliferation of glomerular mesangial cells and delay the process of nephrotic syndrome.