Hypercholesterolemia,
cholesterol-enriched diet and oxidative stress have been shown to increase serum total
cholesterol (TC) and
low density lipoprotein-cholesterol (
LDL-C) levels resulting in development of
atherosclerosis.
Antioxidants play an important role in inhibiting and scavenging
free radicals, thus providing protection to humans against infectious and degenerative diseases. The present study was undertaken to examine the possible protective effects of
propolis (a resinous hive product collected by honeybees from various plant sources) and
thymoquinone (TQ, active constituent of Nigella. Sativa seeds oil) on serum
lipid levels and early atherosclerotic lesions in hypercholestrolemic rabbits. New Zealand rabbits were fed on either standard chow or atherogenic diet during four weeks and concomitantly received either
propolis or TQ. At the end of experiment period, serum samples were collected to determine
lipid profile, kidney functions and
antioxidant status. Tissues from aorta, pulmonary artery and kidney were taken for histopathological examination. The
cholesterol-enriched diet induced a significant increase in serum TC,
triglycerides,
LDL-C,
thiobarbituric acid-reactive substances concentrations and a significant decrease in
high density lipoprotein-cholesterol and in
reduced glutathione levels compared to control group. Administration of
propolis or TQ with
cholesterol-enriched diet significantly (p < 0.05) reduced TC,
LDL-C,
triglycerides and
thiobarbituric acid-reactive substances concentrations, while increased
high density lipoprotein-cholesterol concentration, as well as
glutathione content compared to high
cholesterol (HC) control group. Kidney function parameters were significantly affected by
cholesterol diet and both
propolis and TQ counterregulated the
cholesterol-induced changes. Histopathologically, early atherosclerotic changes were observed in HC control group represented by endothelial damage and thickened foam cells while
propolis or TQ provided protection against the HC-induced damage. In conclusion, the present study suggests the potential beneficial effects of both
propolis and TQ in diminishing the risk of
atherosclerosis via
antioxidant mechanism.