Abstract 585: Card9 Deficiency Accelerates Experimental Atherosclerosis

Introduction: There are accumulating evidences that innate and adaptive immunity play a major role in the development of atherosclerosis. Pattern-recognition receptors (PRRs) engagement including Toll-like receptors and Dectins are involved in the modulation of immune responses and atherosclerosis development but little is known about downstream signaling pathways. Card9 for Caspase recruitment domain-containing protein-9, is an adaptor protein expressed by antigen presenting cells required for PRRs-induced activation of myeloid cells. We hypothesized that Card9 pathway regulates systemic immune response and impacts on the development of atherosclerosis. Method and results: To evaluate the effect of Card9 deficiency on experimental atherosclerosis, Ldlr -/- mice were lethally irradiated and reconstituted with Card9 -/- or Card9 +/+ bone marrow cells and put under a high fat diet during 8 weeks. Animal weight and cholesterolemia were not different between groups. We observed an increase of atherosclerosis plaque size in the aortic sinus in chimeric Ldlr -/- Card9 -/- mice compared to chimeric Ldlr -/- Card9 +/+ mice (+32%, P=0.04). A more inflammatory plaque phenotype was found in chimeric Ldlr -/- Card9 -/- mice compared to control mice with an increase in both macrophage accumulation (+86%, P=0.0005) and necrotic core size (+102%, P=0.006). Card9 deficiency induced a deviation of the systemic immune response toward a pro-inflammatory profile. Lps/Ifn-γ-stimulated Card9 -/- bone marrow-derived macrophages (BMDM) produced less IL-10 (-22%, P<0.05) than Card9 +/+ BMDM. Lps/Ifn-γ-stimulated splenocytes from chimeric LDLr -/- Card9 -/- mice produced more IL-12p70 (+151%, P<0.01) than splenocytes from control mice. Anti-CD3 stimulated CD4 + T cells from chimeric Ldlr -/- Card9 -/- mice produced less Ifn-γ (-92%, P<0.05) and IL-17A (-100%, P<0.05) than control CD4 + T cells. A second atherosclerosis mouse model ApoE -/- Card9 -/- confirmed the protective role of Card9 with an increase in both atherosclerosis plaque size and macrophage accumulation in ApoE -/- Card9 -/- mice compared to ApoE -/- Card9 +/+ mice. Conclusion: Card9 deficiency accelerated atherosclerosis development in mice and induced a more inflammatory plaque phenotype.