Cytokine-induced vascular changes may contribute to the atherogenic process. We examined the effect of atherogenic diets on the aortic expression of genes for the cytokines interleukin-1 alpha and beta and tumor necrosis factor alpha. Male New Zealand White rabbits were fed one of the following diets for 10 wk: nonpurified diet, a semipurified diet with 10% corn oil, a semipurified diet with 1% corn oil and 9% partially hydrogenated coconut oil, or the 9% coconut oil diet supplemented with either 0.1, 0.3 or 0.9% added cholesterol (n = 6/group). At 10 wk, 3 rabbits per group received lipopolysaccharide (200 micrograms/kg) intravenously. After 1.5 h the rabbits were killed and their aortae removed and analyzed. Histologic examination showed that the 0.3% and 0.9% cholesterol-fed rabbits developed appreciable aortic lesions. Diet had no major effect on the basal levels of aortic cytokine mRNA as determined by polymerase chain reaction analysis of DNAs. However, aortic tissue from rabbits fed 0.3% and 0.9% cholesterol diets showed significantly enhanced lipopolysaccharide-evoked levels of mRNA encoding interleukin-1 alpha (392 +/- 91 for saturated fat vs. 759 +/- 191 and 800 +/- 120 fmoles/reaction for 0.3% and 0.9% cholesterol), interleukin-1 beta (99 +/- 10 vs. 353 +/- 80 and 355 +/- 86) and tumor necrosis factor alpha (195 +/- 15 vs. 594 +/- 78 and 667 +/- 97). Extracts of aortae from rabbits injected with lipopolysaccharide contained interleukin-1 and tumor necrosis factor alpha activity but differences in biological activity due to diet were not detectable at the 1.5 h time point (chosen for maximal mRNA expression). Increased local cytokine gene expression in response to acute stimulus might influence the evolution of the vascular response to diets rich in cholesterol and saturated fats.