Abstract
The present study is to investigate whether inflammatory cytokines inhibit ABCA1/ABCG1-mediated cholesterol efflux by regulating miR-33a-5P in THP-1 macrophages. We used interleukin-6 and tumor necrosis factor-alpha in the presence or absence of native low density lipoprotein (LDL) to stimulate THP-1 macrophages. THP-1 macrophages were infected by either control lentivirus vectors or lentivirus encoding miR-33a-5P or antisense miR-33a-5P. The effects of inflammatory cytokines, miR-33a-5P and antisense miR-33a-5P on intracellular lipids accumulation and intracellular cholesterol contents were assessed by oil red O staining and quantitative intracellular cholesterol assay. ApoA-I-mediated cholesterol efflux was examined using the fluorescent sterol (BODIPY-cholesterol). The gene and protein expressions of the molecules involved in cholesterol trafficking were examined using quantitative real-time polymerase chain reaction and Western blotting. Inflammatory cytokines or miR-33a-5P increased intracellular lipid accumulation and decreased apoA-I-mediated cholesterol efflux via decreasing the expression of ABCA1 and ABCG1 in the absence or presence of LDL in THP-1 macrophages. However, antisense miR-33a-5P reversed the effects of inflammatory cytokines on intracellular lipid accumulation, cholesterol efflux, and the expression of miR-33a-5P, ABCA1 and ABCG1 in the absence or presence of LDL in THP-1 macrophages. This study indicated that inflammatory cytokines inhibited ABCA1/ABCG1-mediated cholesterol efflux by up-regulating miR-33a-5P in THP-1 macrophages.
Highlights
Atherosclerosis is a complex disease in which the artery wall becomes thicker and thicker due to the accumulation of plaques along the walls that blocks blood flow
Total cholesterol (TC) and cholesterol ester (CE) were increased in inflammatory cytokine-treated cells in the plus low density lipoprotein (LDL)), 25 mg/ml LDL plus 40 ng/ml IL-6 (B, III, Con-Anti-miR plus IL-6 plus LDL), or 25 mg/ml LDL plus 40 ng/ml IL-6 (B, IV, Anti-miR-33a-5P plus IL6 plus LDL), followed by incubation at 37uC for 24 h. (A and B) The cells were examined for lipid inclusions by oil red O staining
Data are means 6 SD of duplicate wells from 6 experiments. *, P,0.05 compared with Con-miR or Con-miR plus LDL; **, P,0.01 compared with Con-miR plus LDL; #, P,0.05 compared with Con-Anti-miR plus IL-6 or Con-Anti-miR plus IL-6 plus LDL; ##, P,0.01 compared with Con- Anti-miR plus IL-6 or Con-Anti-miR plus IL-6 plus LDL
Summary
Atherosclerosis is a complex disease in which the artery wall becomes thicker and thicker due to the accumulation of plaques along the walls that blocks blood flow. Atherosclerosis can cause several conditions like aneurysm and rupturing of the arteries which lead to serious health problems, including heart attack, stroke and peripheral vascular disease, etc. These problems are the most common causes of worldwide morbidity and mortality [1]. Inflammation can facilitate arterial hyperplasia and lipid accumulation, and regulate aspects of plaque biology that triggers thrombotic complications of atherosclerosis, even in the absence of traditional risk factors. Inflammation provides a pathway that links alterations in traditional risk factors and modifications in the biology of the artery walls, leading to atherosclerosis and its complications [5], [6]
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