Effect of Cordyceps sinensis on expressions of HIF-1α and VEGF in the kidney of rats with diabetic nephropathy

Abstract

To examine the expressions of hypoxia inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) in the kidney of rats with diabetic nephropathy before and after the treatment of Cordyceps sinensis, and to explore the mechanism of Cordyceps sinensis against hypoxia. The diabetes model was produced by intraperitoneal injection of 60 mg/kg streptozotocin, then the rats whose 24 h urine protein level was above 30 mg/d were thought to have suffered diabetic nephropathy. Thirty rats were randomly divided into a diabetic nephropathy group (DN group, n=15) and a Cordyceps sinensis group (CS group, n=15), and another 15 normal rats served as a normal control group (NC group, n=15). The CS group were intragastrically administered Cordyceps sinensis extract liquid [5.0 g/(kg.d)], the other groups were intragastrically administered drinking water of equal volume. Five rats in each group were killed after 2, 4, and 6 weeks. The 24 h urine protein excretion, urine β-N-acetyl glucosaminidase (NAGase) and serum creatinine were measured; the renal pathological changes were evaluated by HE and Masson staining; the mRNA and protein expressions of HIF-1α and VEGF were dectected by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. Compared with the normal control group, the renal tubular vacuolar degeneration was obvious, and the glomerular mesangial matrix increased in the DN group. The 24 h urinary protein excretion, urine NAGase and serum creatinine also increased significantly (all P<0.05); the expressions of HIF-1α and VEGF in the renal tissue gradually increased with time, and the expression of HIF-1α was correlated with that of VEGF in the 2 groups (r=0.850, r=0.887, both P<0.05) . Compared with the DN group, the pathological changes were relieved, the 24 h urinary protein excretion, urine NAGase and serum creatinine level were decreased, and the expressions of HIF-1α and VEGF decreased in the CS group (all P<0.05), but they were still higher than those in the normal contral group (P<0.05). There was no significant difference in the mRNA and protein expression of HIF-1α between the 4th week and the 6th week after the treatment of CS (P>0.05). The expressions of HIF-1α and VEGF increase in the kidney of rats with diabetic nephropathy, and the positive correlation suggests that there is chronic hypoxia in the renal tissue of diabetic nephropathy. Cordyceps sinensis may protect against chronic hypoxia injury in diabetic nephropathy by lowering the expressions of HIF-1α and VEGF.