Aspirin protected against endothelial damage induced by LDL: role of endogenous NO synthase inhibitors in rats.

AIM

To study the protective effect of aspirin on damages of the endothelium induced by low-density lipoprotein (LDL), and whether the protective effect of aspirin is related to reduction of nitric oxide synthase inhibitor level.

METHODS

Vascular endothelial injury was induced by a single injection of native LDL (4 mg/kg) in rats. Vasodilator responses to acetylcholine (ACh) in the isolated aortic rings were determined, and serum concentrations of asymmetric dimethylarginine (ADMA), malondialdehyde (MDA), tumour necrosis factor-alpha (TNF-alpha), and the activity of dimethylaminohydrolase (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-alpha, and decreased DDAH activity. Aspirin (30 or 100 mg/kg) markedly reduced the inhibition of vasodilator responses to ACh by LDL, and the protective effect of aspirin at the lower dose was greater compared with high-dose aspirin group. Aspirin inhibited the increased level of MDA and TNF-alpha induced by LDL. Aspirin at the dose of 30 mg/kg, but not at higher dose (100 mg/kg), significantly reduced the concentration of ADMA and increased the activity of DDAH.

CONCLUSION

Aspirin at the lower dose (30 mg/kg) protects the endothelium against damages elicited by LDL in vivo, and the protective effect of aspirin on endothelium is related to reduction of ADMA concentration by increasing DDAH activity.