Tumor Necrosis Factor-α and C-C Motif Chemokine Ligand 18 Associate with Atherosclerotic Lipid Accumulation In situ and In vitro.

Atherosclerosis is regarded as a chronic inflammatory disease associated with changes in the innate immune system functioning and cytokine disturbances. Local inflammation in the arterial wall is an important component in the development and growth of atherosclerotic plaques. Inside the lesions, both pro- and antiinflammatory cytokines were detected, highlighting the complexity of the atherosclerotic process. However, little is known about the expression of these signaling molecules in early human atherosclerotic lesions. In this study, we explored localization of a pro-inflammatory cytokine, tumor necrosis factor-α (TNFα), and anti-inflammatory chemokine, C-C motif chemokine ligand 18 (CCL18), in the arterial wall of human aorta. We noticed differences in the intensity of staining for TNFα and CCL18 in atherosclerotic lesions and grossly normal areas, as well as differences in their localization. While CCL18 prevailed in the areas close to the aortic lumen, TNFα was localized in deeper layers of the intima. We next studied the expression of TNFα and CCL18 mRNA in lesions corresponding to different stages of atherosclerosis progression and found that it was maximal in lipofibrous plaques that are most enriched in lipids. To test the hypothesis that cytokine expression can be associated with lipid accumulation, we studied the TNFα and CCL18 expression profiles in primary human monocyte-derived macrophages after inducing lipid accumulation by incubating cultured cells with atherogenic LDL. We found that intracellular cholesterol accumulation was associated with upregulation of both TNFα and CCL18, confirming our hypothesis. These results encourage further investigation of cytokine expression in human atherosclerotic lesions and its role in the atherosclerosis progression.

Quantitative analysis of the expression of caspase 3 and caspase 9 in different types of atherosclerotic lesions in the human aorta.

The existing data on apoptotic processes in human atherosclerotic lesions is insufficient and is often contradictory. This study was undertaken to evaluate the levels of the expression of key apoptosis-related genes, namely, caspase 3 (CASP3) and caspase 9 (CASP9) in the normal (non-atherosclerotic) intima of the human aorta in comparison with those in different types of atherosclerotic lesions. Twenty-five autopsy samples of thoracic aorta were examined by polymerase chain reaction (PCR) analysis. The study revealed that the expressions of CASP3 and CASP9 genes were changed in different types of atherosclerotic lesions in course of the progression of the disease, but not in a unanimous way. The mRNA expression of CASP3 was found to be steadily decreasing with the progression of atherosclerosis while the expression of CASP9 showed a pattern which can be described as a "bell-shaped" relationship between gene mRNA expression and the type of atherosclerotic lesion, with the maximum being observed in fatty streaks. The fall in CASP3 expression may be associated with cellular senescence as well as with the domination of necrotic processes in atherosclerotic lesions, as shown by electron microscopic analysis. Our study provides novel quantitative data on the expression of CASP3 and CASP9 genes in different atherosclerotic lesions in the human aorta and thus, might assist in better understanding of the processes occurring during the development of lesions in human atherogenesis.