Abstract 44: Interleukin-27 Signaling is a Critical Regulator of Inflammation in Atherosclerosis

Abstract

Atherosclerosis is chronic inflammatory disease, which affects blood vessels. While the pro-atherogenic role of various inflammatory cytokines was broadly investigated, less is known about contribution of anti-inflammatory cytokines with regard to their ability to control inflammation in vivo. Interleukin 27 (IL-27) was shown to play immunosuppressive function via multiple mechanisms. We tested whether IL-27 signaling is important to restrain inflammation in mouse models of atherosclerosis. We transplanted bone marrow from Il27ra -/- or Il27ra +/+ mice into atherosclerosis prone Ldlr -/- littermates. Recipients of Il27ra -/- marrow showed significantly larger atherosclerotic lesions in aortic roots, aortic arches and, most strikingly, in the abdominal aorta. Aortas contained more CD45 + leukocytes and CD4 + T cells, which produced pro-atherogenic cytokines IL-17A and TNF-α. Concomitantly, the levels of IL-17A and IL-6 were significantly elevated in aortic tissue. These cytokines normally suppressed by IL-27, regulated the expression of CCL2 and other chemokines, which in turn led to accumulation of myeloid CD11b + and CD11c + cells in aortas, atherosclerotic plaque growth and disease progression. Moreover, using our recently developed live imaging by two-photon microscopy, we found enhanced interaction between antigen presenting cells and T cells in the arterial wall of Il27ra deficient mice. Overall, IL-27 signaling in bone marrow-derived cells regulates atherosclerosis by controlling interaction of antigen presenting cells and T cells in the arterial wall and therefore curbing Th17 and Th1 lineage differentiation, TNF and IL-17 dependent chemokine expression and subsequent myeloid cell accumulation. Thus, our work establishes the importance of anti-inflammatory cytokine signaling in atherosclerosis and demonstrates novel anti-atherogenic role of IL-27.