Effect of triptolide on expression of oxidative carbonyl protein in renal cortex of rats with diabetic nephropathy

The traditional Chinese medicine (Tripterygium wilfordiiHook.f., TWH) has been clinically used to treat primary and secondary renal diseases and proteinuria for nearly 40 years. However, there is a rare literature about the effect of triptolide (the main active ingredient of TWH) on the expression of oxidative carbonyl protein (OCP) in diabetic nephropathy (DN). This study aimed to provide experimental evidence for triptolide treatment on DN through its effect on the expression of OCP, in order to investigate the effects of triptolide on the expression of OCP in rats with DN. Sixty SD rats were randomly divided into five groups: control group, high-dose triptolide (Th) group, low-dose triptolide (Tl) group, DN model group, and positive control (benazepril) group. The DN model was established using streptozotocin. Urinary protein excretion, fasting blood glucose (FBG), superoxide dismutase (SOD) in renal homogenate, malondialdehyde (MDA) in renal homogenate and renal nitrotyrosine by immunohistochemistry, and the expression of OCP by oxyblotimmune blotting were detected. In the DN model group, rat urinary protein excretion and renal MDA were significantly increased, while renal SOD significantly decreased and nitrotyrosine expression was obviously upregulated in the kidney. After triptolide treatment, 24-h urinary protein excretion (61.96 +/- 19.00 vs. 18.32 +/- 4.78 mg/day, P < 0.001), renal MDA (8.09 +/- 0.79 vs. 5.45 +/- 0.68 nmol/L, P < 0.001), and nitrotyrosine expression were decreased. Furthermore, renal OCP significantly decreased, while renal SOD (82.50 +/- 19.10 vs. 124.00 +/- 20.52 U/L, P < 0.001) was elevated. This study revealed that triptolide can down-regulate the expression of OCP in the renal cortex of DN rats.