MOLECULAR EPIDEMIOLOGY OF ATHEROSCLEROSIS

It has been hypothesized that mutational events may be involved in the atherogenetic process and that at least a portion of atherosclerotic plaques may develop according to an initiation-promotion process of ar terial smooth muscle cells, akin to benign tumors. We conducted a stud y to evaluate the occurrence of oxidative DNA damage and formation of DNA adducts in human atherosclerotic lesions and to assess the relatio nships of these promutagenic alterations with exposure to atherogenic risk factors. Pure DNA was extracted from the tunica media (composed m ainly of smooth muscle cells) of abdominal aorta fragments taken at su rgery from 85 patients suffering from severe atherosclerotic lesions. DNA adducts were detected by synchronous fluorescence spectrophotometr y and P-32 postlabeling after enrichment of adducts with either butano l or nuclease P1. 8-Hydroxy-2'-deoxguanosine (8-OH-dG), a typical indi cator of oxidative DNA damage, was measured by HPLC/electrochemical de tection. A complete questionnaire reporting general, clinical, and lab oratory characteristics was available for each patient. All 84 samples tested by P-32 postlabeling were positive by displaying the presence of diagonal radioactive zones and up to 9 individual DNA adducts. Of 5 2 samples tested, 32 (61.5%) yielded typical positive signals at synch ronous fluorescence spectrophotometry. All but one of 39 samples teste d had very high levels of 8-OH-dG, thus showing a remarkable oxidative DNA damage. Statistically significant correlations were found between the levels of molecular biomarkers and atherogenic risk factors inclu ding age, number of currently smoked cigarettes, ratio of total-to-hig h density lipoprotein blood cholesterol, blood triglycerides, and bloo d pressure. The DNA alterations detected in our study may be only one component of the genetic basis of atherogenesis. Moreover, no causal r ole in the atherogenetic process can be inferred from our results. How ever, DNA alterations, including oxidative damage and adduction of rea ctive molecules of either endogenous or exogenous source, were systema tically present in the smooth muscle cells of human atherosclerotic le sions and their intensity was significantly correlated with the occurr ence of atherogenic risk factors in the patients.