Downregulated CD36 and oxLDL uptake and stimulated ABCA1/G1 and cholesterol efflux as anti-atherosclerotic mechanisms of interleukin-10.
OBJECTIVE
Marked anti-atheromatous effects of the anti-inflammatory cytokine interleukin-10 (IL-10) were observed in several lipid-driven animal models of arteriosclerosis. We therefore investigated whether IL-10 affects macrophage cholesterol handling.


METHODS
Human THP-1 cells and peripheral monocytes served as macrophage models. Specific mRNA was quantified by real-time RT-PCR, protein expression by flow cytometry and Western blotting. Cellular cholesterol handling was studied by lipoprotein-facilitated uptake and efflux assays. IL-10 effects were also studied in cells transfected with liver X receptor alpha (LXRalpha)-siRNA or a LXRalpha response element (LXRE) reporter construct.


RESULTS
Picomolar IL-10 suppressed basal and peroxisome proliferator-activated receptor gamma (PPARgamma)-stimulated transcription of the scavenger receptor CD36 due to reduced PPARgamma protein expression. In contrast, IL-10 stimulated transcription of the active cellular cholesterol exporters ATP-binding cassette transporters A1 and G1 (ABCA1, ABCG1) and the LDL receptor, whereas scavenger receptor-BI (SR-BI) was unchanged. The reduction of CD36 and stimulation of ABCA1 expression was confirmed in human monocytes. Thereby, IL-10 prevented cellular cholesterol overloading from oxidized LDL (oxLDL) and enhanced efflux to apoA-containing particles initiating reverse cholesterol transport. Experiments with inhibitors, LXRalpha silencing and the LXRE reporter gene construct supported the proximal transmission of the IL-10 effect on ABCA1 by the IL-10 receptor/signal transducer and activator of transcription 3 (STAT3) pathway and distal cross-talk to the LXRalpha and PPARalpha/retinoic acid X receptor (RXR) and cAMP/protein kinase A (PKA) pathways.


CONCLUSIONS
In addition to immune and anti-inflammatory actions, IL-10 redirects macrophage cholesterol handling towards reverse cholesterol transport, which contributes to its anti-atherosclerotic action.
Rubic
Tina
T
Institute for Prophylaxis of Cardiovascular Diseases, University of Munich, Germany, Pettenkoferstrasse 9, D-80336 Munich, Germany. trubic@web.de
Lorenz
Reinhard L
RL
D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D050197:Atherosclerosis / Q000276:immunology* / Q000378:metabolism; D015153:Blotting, Western / Q000379:methods; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D016753:Interleukin-10 / Q000502:physiology*; D008077:Lipoproteins, LDL / Q000378:metabolism*; D000071518:Liver X Receptors; D008264:Macrophages / Q000378:metabolism*; D057093:Orphan Nuclear Receptors; D047495:PPAR gamma / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D017463:Receptors, Complement 3b / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D014162:Transfection
C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D004268:DNA-Binding Proteins; D008077:Lipoproteins, LDL; D000071518:Liver X Receptors; C000605213:NR1H3 protein, human; D057093:Orphan Nuclear Receptors; D047495:PPAR gamma; D034741:RNA, Small Interfering; D017463:Receptors, Complement 3b; D018160:Receptors, Cytoplasmic and Nuclear; C099252:oxidized low density lipoprotein; D016753:Interleukin-10; D002784:Cholesterol