EPT Protects Against Low-density Lipoprotein-induced Endothelial Dysfunction By The DDAH/ADMA Pathway

Pericarpium trichosanthis, a Chinese herbel medicine, was used for treatment of coronary artery heart disease, angina pectoris. Recently, it has been reported that Extractive of pericarpium trichosanthis (EPT) has an effect of antioxidant and anti-inflammatory, which is benefit for preserving endothelial function and inhibition of atherogenesis. Hoever, the mechanisms need to be further investigated. Vascular endothelial injury is the formation of atherosclerosis initiating links. Many factors can injury the endothelial via direct and indirect pathway, ecpecialy, oxide low-density lipoprotein (ox-LDL) is an important factor contributing the event. L-arginine congener compounds asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase (NOS), is newly discoved to inhibit nitric oxide (NO) production. Previous work showed that a single injection of low-density lipoprotein (LDL) significantly lead to endothelial dysfunction concomitantly with increases the serum level of endogenous ADMA in rat; Incubation human umbilical vein endothelial cells (HUVECs) with ox-LDL in vitro, cause accumulation of ADMA via devitalization of dimethylarginine dimethylaminohydrolase (DDAH) which mainly response for hydrolase of ADMA. Based on the facts, in the present study we tested the protective effect of EPT on damages of the endothelium induced by Low-density lipoprotein (LDL), and whether the protective effect of EPT is related to the DDAH/ADMA pathway.METHODS:(1) Aortic ring model:the endoehilal injuried aortic ring was maded by a single dose of LDL (4 mg/kg) intravenously injected into the sublingual vein of male rat for 48 h, and physiological saline injection served as a control. Blood samples were collected from carotid artery in the state of anaesthetization. Vasodilator responses to acetylcholine (Ach) in the isolated aortic rings were determined, and serum concentrations of asymmetric dimethylarginine (ADMA), malondialdehyde (MDA), tumour necrosis factor-a (TNF-a), Nitric oxide (NO). (2) Cell culture and treatment:Incubation human umbilical vein endothelial cells (HUVECs) with ox-LDL (100μg/ml) for 24h, the medium levels of lactate dehydrogenase (LDH), ADMA, TNF-a, NO, MDA and the intracellular activity of DDAH were measured.RESULTS:A single injection of LDL (4 mg/kg) significantly decreased vasodilator responses to Ach, increased the serum level of ADMA, MDA and TNF-a, and decreased the serum level of NO. EPT (4ml/kg) with 70%ethanol elution markedly reduced the inhibition of vasodilator responses to Ach by LDL, and the protective effect of EPT with 70%ethanol elution was greater compared with the another ethanol elution group. EPT with 70%ethanol elution inhibited the increased level of ADMA, MDA and TNF-a induced by LDL, and increased the serum level of NO. Incubation of HUVECs with ox-LDL (100μg/ml) for 24h and treated with EPT (0.1mg/ml) markedly decreased the medium levels of LDH, ADMA, MDA and TNF-a, and increased the level of NO in the medium and the intracellular activity of DDAH.CONCLUSIONS:EPT can protect the endothelium against damages elicited by LDL in vivo and in culture, the mechanism of protective effect of EPT on endothelium may be related to the DDAH/ADMA pathway.