Abstract 029: Interleukin-35 Suppresses Endothelial Activation by Inhibiting Mitochondrial Reactive Oxygen Species Mediated Site-specific Acetylation of Histone 3 Lysine 14

Recently we reported that IL-35 is an inflammation-induced ant-inflammatory cytokine; thus, function as a HAMP (homeostasis associated molecular patterns). However, whether IL-35 affects endothelial cell activation and subsequent development of atherosclerosis is not known. Hence, we studied the expression of IL-35 during early atherosclerosis; and its roles and mechanisms in suppressing EC activation. Initially, we analyzed whether endogenous IL-35 levels and its receptor expression was increased in early atherosclerosis. Our data revealed that IL-35 level was significantly increased in the plasma of hyperlipidemic patients and apolipoprotein E (ApoE-/-) deficient mice. Further, the expression of IL-35 receptor components were increased in ApoE-/- mouse aortas. IL-35 inhibited monocyte recruitment on to human aortic endothelial cells (EC) activated by pro-atherogenic lysophosphatidylcholine (LPC). Furthermore, our RNA-Seq analysis showed that IL-35 selectively inhibited ICAM-1 expression that mediates EC activation. Further analysis by flowcytometry and electron spin resonance analysis revealed that IL-35 blocked LPC-mediated mitochondrial-reactive oxygen species (mtROS) production. The subsequent mass spectrometry, ChIP-Seq analysis and EMSA showed that LPC-mediated mtROS promotes acetylation of histone 3 lysine 14 (H3K14). Acetylation of histones facilitate the transcription of EC activation-related genes. We found that acetylated H3K14 increased the binding of pro-inflammatory transcription factor Ap-1 on to ICAM-1 promoter region and induction of ICAM-1 gene transcription. IL-35 mediated Inhibition of mtROS attenuated H3K14 acetylation, inhibited AP-1 binding to ICAM-1 promoter and suppressed ICAM-1 transcription. Finally, IL-35 cytokine treatment inhibited the progression and development of atherosclerosis in ApoE-/- mice. Our study concluded that IL-35 is induced during atherosclerosis and plays an anti-atherogenic role by suppressing EC activation through mtROS and H3K14 acetylation dependent mechanism.