Abstract 553: Expression of TNFalfa and CCL18 is Increased as a Result of Cholesterol Accumulation in Macrophages

Abstract

Innate immunity plays important role in atherogenesis. Immune reaction in artery wall involves both pro-and anti-inflammatory cytokines. We investigated cytokines’ mRNA expression in uninvolved and atherosclerotic human aortic intima. TNF-α and CCL18 were localized in autopsy aortic samples using immunohistochemistry. Expression of cytokine mRNA was measured by PCR or qPCR in the same samples. Primary culture of blood-derived monocytes/macrophages from healthy donors was used to study TNF-α and CCL18 mRNA expression induced by IFN-gamma and IL-4, respectively. Intracellular lipid accumulation was induced by incubation of cultured cells with atherogenic modified LDL isolated from blood of patients with documented coronary atherosclerosis. Immunohistochemistry demonstrated that the number of cytokine-positive cells (both TNF-α and CCL18) were increased in atherosclerotic lesions as compared with unaffected aortic intima. Cytokines were associated with different cell types including macrophages and non-macrophage cells. Both TNF-α and CCL18 were manly occurred in macrophages. Rice of both cytokines’ mRNA expression measured by PCR was observed in atherosclerotic lesion. In lipid-rich atherosclerotic lesion cytokine expression was the most considerable. Correlation between lipid content in aortic intima and cytokine expression was found. To elucidate the mechanism of elevation of lipid-associated cytokine expression, cell culture study was performed. Cultured monocytes/macrophages were incubated with atherogenic modified LDL of atherosclerotic patients and non-atherogenic LDL from healthy donors. In contrast to non-atherogenic LDL patients’ LDL induced intracellular cholesterol accumulation and increased mRNA expression of both TNF-α and CCL18 in cell culture. Thus, i ntracellular lipid accumulation caused by atherogenic modified LDL from atherosclerotic patients induces overexpression of TNFa and CCL18. This finding can explain the elevation of TNF-α and CCL18 expression in lipid-rich atherosclerotic lesions of human aorta.