Rationale: Inflammation impairs macrophage cholesterol clearance from vascular tissues and promotes atherosclerosis. Inflammatory macrophages suppress expression of the transcription cofactor interferon regulatory factor 2–binding protein 2 (IRF2BP2), and genetic variants near IRF2BP2 associate with ischemic heart disease progression in humans. Objectives: To test whether IRF2BP2 in macrophages affects atherosclerosis in mice and humans. Methods and Results: We generated mice that delete IRF2BP2 in macrophages. IRF2BP2-deficient macrophages worsened atherosclerosis in irradiated low-density lipoprotein receptor null-recipient mice and in apolipoprotein E null mice. IRF2BP2-deficient macrophages were inflammatory and had impaired cholesterol efflux because of their inability to activate the cholesterol transporter ABCA1 in response to cholesterol loading. Their expression of the anti-inflammatory transcription factor Krüppel-like factor 2 was markedly reduced. Promoter studies revealed that IRF2BP2 is required for MEF2-dependent activation of Krüppel-like factor 2. Importantly, restoring Krüppel-like factor 2 in IRF2BP2-deficient macrophages attenuated M1 inflammatory and rescued M2 anti-inflammatory gene activation and improved the cholesterol efflux deficit by restoring ABCA1 activation in response to cholesterol loading. In a cohort of 1066 angiographic cases and 1011 controls, homozygous carriers of a deletion polymorphism (rs3045215) in the 3′ untranslated region sequence of human IRF2BP2 mRNA had a higher risk of coronary artery disease (recessive model, odds ratio [95% confidence interval]=1.560 [1.179–2.065], P =1.73E-03) and had lower IRF2BP2 (and Krüppel-like factor 2) protein levels in peripheral blood mononuclear cells. The effect of this deletion polymorphism to suppress protein expression was confirmed in luciferase reporter studies. Conclusion: Ablation of IRF2BP2 in macrophages worsens atherosclerosis in mice, and a deletion variant that lowers IRF2BP2 expression predisposes to coronary artery disease in humans.

Mitochondria, the dynamic organelles and power house of eukaryotic cells function as metabolic hubs of cells undergoing continuous cycles of fusion and fission. Recent findings have made it increasingly apparent that mitochondria essentially involved in energy production have evolved as principal intracellular signaling platforms regulating not only innate immunity but also inflammatory responses. Perturbations in mitochondrial dynamics, including fusion/fission, electron transport chain (ETC) architecture and cristae organization have now been actively correlated to modulate metabolic activity and immune function of innate and adaptive immune cells. Several newly identified mitochondrial proteins in mitochondrial outer membrane such as mitochondrial antiviral signaling protein (MAVS) and with mitochondrial DNA acting as danger-associated molecular pattern (DAMP) and mitochondrial ROS generated from mitochondrial sources have potentially established mitochondria as key signaling platforms in antiviral immunity in vertebrates and thereby orchestrating adaptive immune cell activations respectively. A thorough understanding of emerging and intervening role of mitochondria in toll-like receptor-mediated innate immune responses and NLRP3 inflammasome complex activation has gained lucidity in recent years that advocates the imposing functions of mitochondria in innate immunity. Fascinatingly, also how the signals stemming from the endoplasmic reticulum cooperate with the mitochondria to activate the NLRP3 inflammasome is now looked ahead as a stage to unravel as to how different mitochondrial and associated organelle stress responses cooperate to bring about inflammatory consequences. This has also opened avenues of research for revealing mitochondrial targets that could be exploited for development of novel therapeutics to treat various infectious, inflammatory, and autoimmune disorders. Thus, this review explores our current understanding of intricate interplay between mitochondria and other cellular processes like autophagy in controlling mitochondrial homeostasis and regulation of innate immunity and inflammatory responses.

Touyz RM, Schiffrin EL. Resistance artery remodeling in deoxycorticosterone acetate-salt hypertension is dependent on vascular inflammation: evidence from M-CSF-deficient mice. Am J Physiol Heart Circ Physiol 292: H1789 -H1795, 2007. First published December 1, 2006; doi:10.1152/ajpheart.01118.2006.-Deoxycorticosterone acetate (DOCA)-salt hypertension has an important endothelin-1 (ET-1)-dependent component. ET-1-induced vascular damage may be mediated in part by oxidative stress and vascular inflammation. Homozygous osteopetrotic (Op/Op) mice, deficient in macrophage colonystimulating factor (m-CSF), exhibit reduced inflammation. We investigated in osteopetrotic (Op/Op) mice the effects of DOCA-salt hypertension on vascular structure, function, and oxidative stress, the latter as manifested by reduced nicotinamide adenine dinucleotide phosphate [NAD(P)H] oxidase activity. Mice were implanted with DOCA (200 mg/mouse, under 5% isofluorane anesthesia) and given saline for 14 days. Systolic blood pressure (mmHg) was significantly increased (146 Ϯ 2 and 138 Ϯ 1; P Ͻ 0.001 vs. basal 115 Ϯ 3 and 115 Ϯ 3, respectively) by DOCA-salt in wild-type (ϩ/ϩ) and heterozygous (Op/ϩ) mice, but not in Op/Op mice (130 Ϯ 1 vs. basal 125 Ϯ 3). Norepinephrine contractile response was significantly enhanced, while acetylcholine endothelium-dependent vasodilation was significantly impaired in DOCA-salt-treated ϩ/ϩ and Op/ϩ mice compared with control mice. No changes in norepinephrine-induced contraction and acetylcholine-induced relaxation were observed in DOCA-salt Op/Op mice. DOCA-salt ϩ/ϩ and Op/ϩ mice had significantly increased mesenteric resistance artery media-to-lumen ratio and media cross-sectional area, neither of which were altered in Op/Op mice. Basal vascular superoxide production and NAD(P)H oxidase activity, vascular cell adhesion molecule-1 expression, and macrophage infiltration were significantly increased only in DOCAsalt ϩ/ϩ mice. Thus m-CSF-deficient mice developed less endothelial dysfunction, vascular remodeling, and oxidative stress induced by DOCA-salt than ϩ/ϩ and Op/ϩ mice, suggesting that inflammation may play a role in DOCA-salt hypertension, a model that results in part from effects of ET-1, which has proinflammatory actions. endothelial dysfunction; reactive oxygen species; macrophage/monocyte THE ROLE OF INFLAMMATION through recruitment, activation, survival, and proliferation of mononuclear phagocytes in the vascular wall has been increasingly recognized in atherosclerosis and hypertension (18). This proinflammatory state is mediated through increased expression of several mediators, including leukocyte adhesion molecules, chemokines, and specific growth factors, and may be triggered by vasoactive agents such as endothelin-1 (ET-1) and angiotensin II (ANG II) (4, 22).Macrophage colony-stimulating factor (m-CSF) regulates the differentiation, proliferation, and survival of macrophages (20). Osteopetrotic mice are homozygous for a naturally occurring recessive frame shift mutation (Op) in the m-CSF gene ...

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