The mechanisms that promote an inflammatory environment and accelerated atherosclerosis in diabetes are poorly understood. We show that macrophages isolated from two different mouse models of type 1 diabetes exhibit an inflammatory phenotype. This inflammatory phenotype associates with increased expression of long-chain acyl-CoA synthetase 1 (ACSL1), an enzyme that catalyzes the thioesterification of fatty acids. Monocytes from humans and mice with type 1 diabetes also exhibit increased ACSL1. Furthermore, myeloid-selective deletion of ACSL1 protects monocytes and macrophages from the inflammatory effects of diabetes. Strikingly, myeloid-selective deletion of ACSL1 also prevents accelerated atherosclerosis in diabetic mice without affecting lesions in nondiabetic mice. Our observations indicate that ACSL1 plays a critical role by promoting the inflammatory phenotype of macrophages associated with type 1 diabetes; they also raise the possibilities that diabetic atherosclerosis has an etiology that is, at least in part, distinct from the etiology of nondiabetic vascular disease and that this difference is because of increased monocyte and macrophage ACSL1 expression.

Objective-Osteoprotegerin (OPG), a member of the tumor necrosis factor (TNF) superfamily of proteins, plays an important role in bone remodeling and is expressed in both mouse and human atherosclerotic lesions. The current study was designed to assess whether OPG plays a role in the progression and calcification of advanced atherosclerotic lesions in apoE Ϫ/Ϫ mice. Methods and Results-Atherosclerotic lesion area and composition and aortic calcium content were examined in mice deficient in both OPG and apolipoprotein E (OPG Ϫ/Ϫ .apoE Ϫ/Ϫ mice) at 20, 40, and 60 weeks of age. Littermate OPG ϩ/ϩ .apoE Ϫ/Ϫ mice were used as controls. The average cross-sectional area of lesions in the innominate arteries was increased in OPG Ϫ/Ϫ .apoE Ϫ/Ϫ mice at 40 and 60 weeks of age. The increase in lesion area was coupled with a reduced cellularity and an increase in connective tissue including laminated layers of elastin. Sixty-week-old OPG Ϫ/Ϫ .apoEmice also had an increase in the area of calcification of the lesions. There were no differences in markers of plaque stability. In vitro, OPG induced matrix metalloproteinase-9 (MMP-9) activity in macrophages and smooth muscle cells and acted as a survival factor for serum-deprived smooth muscle cells. Conclusion-OPG inhibits advanced plaque progression by preventing an increase in lesion size and lesion calcification.OPG may act as a survival factor and may modulate MMP9 production in vascular cells.

Background-S100A9 is constitutively expressed in neutrophils, dendritic cells, and monocytes; is associated with acute and chronic inflammatory conditions; and is implicated in obesity and cardiovascular disease in humans. Most of the constitutively secreted S100A9 is derived from myeloid cells. A recent report demonstrated that mice deficient in S100A9 exhibit reduced atherosclerosis compared with controls and suggested that this effect was due in large part to loss of S100A9 in bone marrow-derived cells. Methods and Results-To directly investigate the role of bone marrow-derived S100A9 in atherosclerosis and insulin resistance in mice, low-density lipoprotein receptor-deficient, S100A9-deficient bone marrow chimeras were generated. Neither atherosclerosis nor insulin resistance was reduced in S100A9-deficient chimeras fed a diet rich in fat and carbohydrates. To investigate the reason for this lack of effect, myeloid cells were isolated from the peritoneal cavity or bone marrow. S100A9-deficient neutrophils exhibited a reduced secretion of cytokines in response to toll-like receptor-4 stimulation. In striking contrast, S100A9-deficient dendritic cells showed an exacerbated release of cytokines after toll-like receptor stimulation. Macrophages rapidly lost S100A9 expression during maturation; hence, S100A9 deficiency did not affect the inflammatory status of macrophages. Conclusions-S100A9 differentially modifies phenotypic states of neutrophils, macrophages, and dendritic cells. The effect of S100A9 deficiency on atherosclerosis and other inflammatory diseases is therefore predicted to depend on the relative contribution of these cell types at different stages of disease progression. Furthermore, S100A9 expression in nonmyeloid cells is likely to contribute to atherosclerosis. (Circulation. 2011;123:1216-1226.)Key Words: atherosclerosis Ⅲ immunology Ⅲ macrophage Ⅲ S100 proteins S 100A9 and its binding partner, S100A8, are members of the S100 family of proteins and are promising novel markers of cardiovascular risk in humans. 1 Recent studies on mice demonstrate that S100A8/A9 promote atherosclerosis. 2 Thus, S100A9 appears to be both a marker and a mediator of atherosclerosis. Furthermore, circulating levels of S100A8/A9 are increased in a number of autoimmune and proinflammatory states, including type 1 diabetes mellitus 3,4 and obesity, 5 characterized by increased cardiovascular risk. Studies on S100A9-deficient mice suggest that S100A8/A9 have proinflammatory actions, eg, in sepsis 6,7 and pancreatitis. 8 Clinical Perspective on p 1226S100A8/A9 are abundantly and constitutively expressed in neutrophils and monocytes. Expression of S100A8/A9 is lost during differentiation of monocytes into macrophages, 9 yet some expression is sustained in dendritic cells (DCs). 10 S100A8/A9 promote migration of neutrophils through increased CD11b expression. 11 The effects of S100A9 deficiency in neutrophils might be due to the combined loss of S100A8 and S100A9 because S100A9-deficient neutrophils express S100A8 mRNA...

Rationale Macrophage accumulation in adipose tissue associates with insulin resistance and increased cardiovascular disease risk. We previously have shown that generation of reactive oxygen species (ROS) and monocyte chemotactic factors after exposure of adipocytes to saturated fatty acids (SFAs) such as palmitate occurs via translocation of NADPH oxidase 4 (NOX4) into lipid rafts (LRs). The anti-inflammatory effects of apolipoprotein A-I (apoA-I) and HDL on macrophages and endothelial cells appears to occur via cholesterol depletion of LRs. However, little is known concerning anti-inflammatory effects of HDL and apoA-I on adipocytes. Objective To determine whether apoA-I and HDL inhibit inflammation in adipocytes and adipose tissue, and whether this is dependent on LRs. Methods and Results In 3T3L-1 adipocytes, apoA-I, HDL and methyl-β-cyclodextrin inhibited chemotactic factor expression. ApoA-I and HDL also disrupted LRs, reduced plasma membrane cholesterol content, inhibited NOX4 translocation into LRs, and reduced palmitate-induced ROS generation and monocyte chemotactic factor expression. Silencing ABCA-1 abrogated the effect of apoA-I, but not HDL, while silencing ABCG-1 or SRB-1 abrogated the effect of HDL but not apoA-I. In vivo, apoA-I transgenic mice fed a high fat, high sucrose, cholesterol-containing diet showed reduced chemotactic factor and pro-inflammatory cytokine expression and reduced macrophage accumulation in adipose tissue. Conclusion ApoA-I and HDL have anti-inflammatory effects in adipocytes and adipose tissue similar to their effects in other cell types. These effects are consistent with disruption and removal of cholesterol from LRs, which are regulated by cholesterol transporters such as ABCA-1, ABCG-1 and SRB-1.