Attenuation of oxidative stress, inflammation, and endothelial dysfunction in hypercholesterolemic rabbits by allicin

Abstract

Allicin, the active substance of garlic, exerts a broad spectrum of pharmacological activities and is considered to have potential therapeutic applications. The present study was designed to investigate the possible beneficial effects of allicin against oxidative stress, inflammation, and endothelial dysfunction in hypercholesterolemic rabbits. Male New Zealand white rabbits were used in this study. Rabbits randomly received 1 of the following treatments: normal chow diet for 4 weeks, 1% high cholesterol diet (HCD), HCD plus allicin (10 mg/kg/day), or HCD plus atorvastatin (10 mg/kg/day). Blood samples were collected at the end of experimental diets for measurement of serum total cholesterol (TC), triglycerides (TGs), high-density lipoprotein cholesterol (HDL-C), C-reactive protein (CRP), malondialdehyde (MDA), reduced glutathione (GSH), and superoxide dismutase (SOD). In addition, the aorta was removed for measurement of vascular reactivity, histopathological changes, intima/media (I/M) ratio, and immunohistochemical staining of both tumor necrosis-alpha (TNF-α) and nuclear factor (NF)-κB. HCD induced significant increases in serum TC, TGs, low-density lipoprotein cholesterol (LDL-C), CRP, and MDA. Moreover, HCD caused significant decrease in serum GSH and SOD. In addition, aortic relaxation response to acetylcholine (ACh) was impaired. Immunohistochemical staining of aortic specimens from HCD-fed rabbits revealed high expression levels of both TNF-α and the oxidant-induced transcription factor, NF-κB. Allicin supplementation significantly decreased serum MDA and CRP, increased serum HDL-C, GSH, and SOD levels while nonsignificantly affecting HCD-induced elevations in serum TC and LDL-C. Additionally, allicin significantly protected against HCD-induced attenuation of rabbit aortic endothelium-dependent relaxation to ACh and elevation in I/M ratio. This effect was confirmed by histopathological examination of the aorta. Moreover, allicin has substantially beneficial effects on aortic expression of TNF-α and NF-κB compared with HCD-fed rabbits. In conclusion, these findings demonstrate that allicin may be useful in reducing oxidative stress, inflammation, vascular dysfunction, and the aortic pathology in hypercholesterolemic rabbits.