Attenuation of the development of hypercholesterolemic atherosclerosis by thymoquinone.

Thymoquinone (TQ), derived from Nigella sativa seed, is an antioxidant. The present study investigated whether TQ attenuates the development of atherosclerosis, and/or reduces the serum lipid levels and oxidative stress in rabbits. New Zealand white female rabbits were assigned to four groups of six animals each: group I, control; group II, 1% cholesterol diet; group III, 1% cholesterol plus TQ (10 mg/kg/day; through a nasogastric tube) diet; and group IV, 1% cholesterol plus TQ (20 mg/kg/day; through a nasogastric tube) diet. Blood samples were collected at baseline and after four and eight weeks on the experimental diets for measurement of serum lipids, total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), TC/HDL-C ratio and oxidative stress biomarkers (malondialdehyde [MDA] and protein carbonyls). At the end of the eight weeks, the aorta was removed for the assessment of atherosclerotic changes, MDA and protein carbonyls. Group II animals developed atherosclerosis (45%±11% of the intimal surface of aorta was covered with atherosclerotic plaques), which was associated with an increase in the serum TC, TG, LDL-C, HDL-C, TC/HDL-C, MDA and protein carbonyls. In group III, TQ decreased serum TC, LDL-C, MDA and protein carbonyls by 26%, 29%, 85% and 62%, respectively, and aortic MDA by 73%, which was associated with a 40% reduction of the development of aortic atherosclerosis. The higher dose of TQ in group IV had effects similar to the lower dose (group III), except that this dose further decreased serum TG. It is concluded that TQ attenuates hypercholesterolemic atherosclerosis and this effect is associated with a decrease in serum lipids and oxidative stress.