Oxidation products of low-density lipoproteins have been suggested to promote inflammation during atherogenesis, and reticulocyte-type 15-lipoxygenase has been implicated to mediate this oxidation. In addition, the 5-lipoxygenase cascade leads to formation of leukotrienes, which exhibit strong proinflammatory activities in cardiovascular tissues. Here, we studied both lipoxygenase pathways in human atherosclerosis. The 5-lipoxygenase pathway was abundantly expressed in arterial walls of patients afflicted with various lesion stages of atherosclerosis of the aorta and of coronary and carotid arteries. 5-lipoxygenase localized to macrophages, dendritic cells, foam cells, mast cells, and neutrophilic granulocytes, and the number of 5-lipoxygenase expressing cells markedly increased in advanced lesions. By contrast, reticulocytetype 15-lipoxygenase was expressed at levels that were several orders of magnitude lower than 5-lipoxygenase in both normal and diseased arteries, and its expression could not be related to lesion pathology. Our data support a model of atherogenesis in which 5-lipoxygenase cascade-dependent inflammatory circuits consisting of several leukocyte lineages and arterial wall cells evolve within the blood vessel wall during critical stages of lesion development. They raise the possibility that antileukotriene drugs may be an effective treatment regimen in late-stage disease.arachidonic acid cascade ͉ coronary heart disease

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The degradation of platelet-activating factor (PAF) and lipid concentrations were measured in sera from 20 patients with insulin-dependent diabetes mellitus and from 20 age- and sex-matched healthy volunteers. The PAF-degrading capacity as well as triglycerides and total and very low density and low-density lipoprotein cholesterol were found to be significantly increased in the patients group, whereas the difference observed in high-density lipoprotein cholesterol was statistically nonsignificant. There were also a series of close relationships between the degradation of PAF and some lipid variables in the control group. These results confirm the parallel changes of lipoproteins and PAF-degrading capacity described previously in serum from atherosclerotic patients and extend it to patients suffering from diabetes mellitus.

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