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Macrophages show endoplasmic reticulum (ER) stress when exposed to lipotoxic signals associated with atherosclerosis, although the pathophysiological importance and the underlying mechanisms of this phenomenon remain unknown. Here we show that mitigation of ER stress with a chemical chaperone results in marked protection against lipotoxic death in macrophages and prevents macrophage fatty acid-binding protein-4 (aP2) expression. Using genetic and chemical models, we show that aP2 is the predominant regulator of lipid-induced macrophage ER stress. The absence of lipid chaperones incites an increase in the production of phospholipids rich in monounsaturated fatty acids and bioactive lipids that render macrophages resistant to lipid-induced ER stress. Furthermore, the impact of aP2 on macrophage lipid metabolism and the ER stress response is mediated by upregulation of key lipogenic enzymes by the liver X receptor. Our results demonstrate the central role for lipid chaperones in regulating ER homeostasis in macrophages in atherosclerosis and show that ER responses can be modified, genetically or chemically, to protect the organism against the deleterious effects of hyperlipidemia., Organelle-mediated stress, particularly ER stress, has recently emerged as a major pathophysiological paradigm underlying chronic metabolic diseases (1-8). In conjunction with its central role in protein synthesis, folding and transportation, [...]

The adipocyte fatty-acid-binding protein, aP2, has an important role in regulating systemic insulin resistance and lipid metabolism. Here we demonstrate that aP2 is also expressed in macrophages, has a significant role in their biological responses and contributes to the development of atherosclerosis. Apolipoprotein E (ApoE)-deficient mice also deficient for aP2 showed protection from atherosclerosis in the absence of significant differences in serum lipids or insulin sensitivity. aP2-deficient macrophages showed alterations in inflammatory cytokine production and a reduced ability to accumulate cholesterol esters when exposed to modified lipoproteins. Apoe[sup.-/-] mice with Ap2[sup.+/+] adipocytes and Ap2[sup.-/-] macrophages generated by bone-marrow transplantation showed a comparable reduction in atherosclerotic lesions to those with total aP2 deficiency, indicating an independent role for macrophage aP2 in atherogenesis. Through its distinct actions in adipocytes and macrophages, aP2 provides a link between features of the metabolic syndrome and could be a new therapeutic target for the prevention of atherosclerosis., Author(s): Liza Makowski [1, 7]; Jeffrey B. Boord [2, 7]; Kazuhisa Maeda [1]; Vladimir R. Babaev [2]; K. Teoman Uysal [1]; Maureen A. Morgan [5]; Rex A. Parker [5]; Jill [...]

The adipocyte fatty-acid?binding protein, aP2, has an important role in regulating systemic insulin resistance and lipid metabolism. Here we demonstrate that aP2 is also expressed in macrophages, has a significant role in their biological responses and contributes to the development of atherosclerosis. Apolipoprotein E (ApoE)-deficient mice also deficient for aP2 showed protection from atherosclerosis in the absence of significant differences in serum lipids or insulin sensitivity. aP2-deficient macrophages showed alterations in inflammatory cytokine production and a reduced ability to accumulate cholesterol esters when exposed to modified lipoproteins. Apoe-/- mice with Ap2+/+ adipocytes and Ap2-/- macrophages generated by bone-marrow transplantation showed a comparable reduction in atherosclerotic lesions to those with total aP2 deficiency, indicating an independent role for macrophage aP2 in atherogenesis. Through its distinct actions in adipocytes and macrophages, aP2 provides a link between features of the metabolic syndrome and could be a new therapeutic target for the prevention of atherosclerosis. [ABSTRACT FROM AUTHOR]