Abstract 381: IL-19 Inhibits Atherosclerosis in LDLR-/- Mice by Modulating Cholesterol Uptake in Macrophages and Vascular Smooth Muscle Cells

Abstract

IL-19 is a recently described, putative anti-inflammatory cytokine which had previously been ascribed to be leukocyte specific. IL-19 is not detected in normal artery, but we detected IL-19 in multiple cell types in human atherosclerotic plaque suggesting a role for this interleukin in atherosclerosis. The purpose of this study was to determine whether administration of exogenous IL-19 could attenuate development of pre-formed atherosclerotic plaque, and to identify potential molecular mechanisms. LDLR-/- mice were fed high-fat diet for 12 weeks and then administered with 10ng/g/day IL-19 or PBS for an additional 8 weeks. En face analysis demonstrated that IL-19 could halt, but not reverse existing plaque (26.7+/-1.7%, 41.03+/-3.1%, 23.70+/-2.6% for baseline, PBS control, and IL-19-treated mice). Foam cell formation by macrophages and vascular smooth muscle cells (VSMC) is a hallmark event during atherosclerosis. Nothing has been reported regarding IL-19 effects on macrophage or VSMC lipid uptake; we therefore investigated whether IL-19 affects macrophage and VSMC cholesterol handling. Addition of IL-19 to wild-type bone marrow derived macrophages (BMDM) significantly promoted oxLDL uptake, conversely, BMDM from IL-19-/- mice had significantly less oxLDL uptake compared to wild-type BMDM. Addition of IL-19 to wild type BMDM significantly increased expression of scavenger receptor B1 (SR-B1), and decreased expression of inflammatory cytokines TNFα, IL-12b, MCP1. Interestingly, converse results were obtained with VSMC, as addition of IL-19 to wild-type VSMC decreased uptake of oxLDL ( p<0.05 ) and decreased expression of scavenger receptor CD36. VSMC isolated from IL-19-/- mice had increased uptake of oxLDL (p<0.0001). It is reported that M2 macrophages participate in plaque regression. IL-19 decreased IL-12b and significantly promoted the polarization of anti-inflammatory M2 phenotype in BMDM as evidenced by the increased expression of YM1 and IL-10 mRNA. These data demonstrate that IL-19 can inhibit progression of existing atherosclerotic plaque by modulating lipid metabolism in VSMC and macrophages and by promoting macrophage differentiation into an alternative, anti-inflammatory M2 phenotype.