Effects of stress and the sympathetic nervous system on coronary artery atherosclerosis in the cynomolgus macaque

Abstract

Epidemiologic evidence increasingly implicates psychosocial variables in the development of coronary heart disease in human beings, an association that appears to be independent of the effects of other coronary disease risk factors. It has been hypothesized that behavioral influences on coronary heart disease are mediated by activation of the sympathetic nervous system, perhaps through exacerbation of coronary artery atherosclerosis. This article summarizes several studies of the effects of stress and sympathetic arousal on atherosclerosis in a nonhuman primate model of atherogenesis. The application of a behavioral stressor involving periodic reorganization of social group memberships resulted in worsened coronary atherosclerosis among male cynomolgus monkeys (Macaca fascicularis) fed a cholesterol-containing diet, relative to control animals housed in groups of fixed (stable) membership, but only among those monkeys that retained dominant social status during the course of the study. This effect could not be attributed to concomitant variability in blood pressure or serum lipid concentrations. When the same experimental procedures were applied to males fed a diet low in saturated fat and cholesterol, the manipulation of group memberships similarly led to development of greater atherosclerosis in the coronary arteries. In related observations, monkeys that exhibited the largest heart rate responses to a standardized behavioral challenge had more extensive coronary atherosclerosis than animals showing a less pronounced cardiac responsivity to stress. In a final investigation, we observed that the exacerbated atherosclerosis of dominant monkeys consuming an atherogenic diet and housed in unstable social groups could be prevented by long-term administration of a beta-adrenoreceptor-blocking agent, propranolol hydrochloride.