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Reducing endoplasmic reticulum stress through a macrophage lipid chaperone alleviates atherosclerosis.

ABSTRACT: 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.

SUBMITTER: Erbay E

PROVIDER: S-EPMC2790330 | biostudies-literature | 2009 Dec

REPOSITORIES: biostudies-literature

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Reducing endoplasmic reticulum stress through a macrophage lipid chaperone alleviates atherosclerosis.

Erbay Ebru E Babaev Vladimir R VR Mayers Jared R JR Makowski Liza L Charles Khanichi N KN Snitow Melinda E ME Fazio Sergio S Wiest Michelle M MM Watkins Steven M SM Linton Macrae F MF Hotamisligil Gökhan S GS

Nature medicine 20091129 12

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 predomin ...[more]

PMID: 19966778

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Project description:BackgroundElevated plasma homocysteine levels, known as hyperhomocysteinemia, have been identified as an independent risk factor for atherosclerosis and related cardiovascular diseases. Macrophage pyroptosis-mediated inflammation is crucial in the development of atherosclerosis, but the underlying mechanisms remain unclear.MethodsA hyperhomocysteinemia atherosclerotic model with ApoE-/- mice fed with a high-methionine diet was constructed to investigate the role of plasma homocysteine in atherosclerosis. THP-1-derived macrophages were used to investigate the mechanisms by which Hcy regulates pyroptosis.ResultsWe found that hyperhomocysteinemia resulted in larger atherosclerotic plaques and more secretion of inflammatory cytokines, while these effects were attenuated in Caspase-1 knockdown mice. Likewise, in vitro experiments demonstrated that treatment of macrophages with homocysteine resulted in NLRP3 inflammasome activation and pyroptosis, as evidenced by cleavage of Caspase-1, production of downstream IL-1β, elevation of lactate dehydrogenase activity, and extensive propidium iodide-positive staining of cells. These were all inhibited by Caspase-1 inhibitor. In addition, excessive generation of reactive oxygen species was associated with mitochondrial dysfunction, characterized by loss of mitochondrial membrane potential and ATP synthesis. Moreover, further experiments revealed that homocysteine induced endoplasmic reticulum stress, enhanced communication between the endoplasmic reticulum and mitochondria, and consequently contributed to calcium disorder. Furthermore, the endoplasmic reticulum stress inhibitor, 4PBA, the calcium chelator, BAPTA, and calcium channel inhibitor, 2-APB significantly improved macrophage pyroptosis.ConclusionHomocysteine accelerates atherosclerosis progression by enhancing macrophages pyroptosis via promoting endoplasmic reticulum stress, endoplasmic reticulum-mitochondria coupling, and disturbing of calcium disorder.

Project description:Background: Anoectochilus roxburghii (Orchidaceae) is a traditional Chinese medicinal herb with anti-inflammatory, antilipemic, liver protective, immunomodulatory, and other pharmacological activities. Kinsenoside (KD), which shows protective effects against a variety types of liver damage, is an active ingredient extracted from A. roxburghii. However, the liver protective effects and potential mechanisms of KD in alcoholic liver disease (ALD) remain unclear. This study aimed to investigate the liver protective activity and potential mechanisms of KD in ALD. Methods: AML12 normal mouse hepatocyte cells were used to detect the protective effect of KD against ethanol-induced cell damage. An alcoholic liver injury model was induced by feeding male C57BL/6J mice with an ethanol-containing liquid diet, in combination with intraperitoneal administration of 5% carbon tetrachloride (CCl4) in olive oil. Mice were divided into control, model, silymarin (positive control), and two KD groups, treated with different doses. After treatment, hematoxylin-eosin and Masson's trichrome staining of liver tissues was performed, and serum alanine aminotransferase (ALT) and aspartate transaminase (AST) levels were determined to assess the protective effect of KD against alcoholic liver injury. Moreover, proteomics techniques were used to explore the potential mechanism of KD action, and ELISA assay, immunohistochemistry, TUNEL assay, and western blotting were used to verify the mechanism. Results: The results showed that KD concentration-dependently reduced ethanol-induced lipid accumulation in AML12 cells. In ALD mice model, the histological examination of liver tissues, combined with the determination of ALT and AST serum levels, demonstrated a protective effect of KD in the alcoholic liver injury mice. In addition, KD treatment markedly enhanced the antioxidant capacity and reduced the endoplasmic reticulum (ER) stress, inflammation, and apoptosis compared with those in the model group. Furthermore, KD increased the phosphorylation level of AMP-activated protein kinase (AMPK), inhibited the mechanistic target of rapamycin, promoted the phosphorylation of ULK1 (Ser555), increased the level of the autophagy marker LC3A/B, and restored ethanol-suppressed autophagic flux, thus activating AMPK-dependent autophagy. Conclusion: This study indicates that KD alleviates alcoholic liver injury by reducing oxidative stress and ER stress, while activating AMPK-dependent autophagy. All results suggested that KD may be a potential therapeutic agent for ALD.

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Reducing endoplasmic reticulum stress through a macrophage lipid chaperone alleviates atherosclerosis.

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Reducing endoplasmic reticulum stress through a macrophage lipid chaperone alleviates atherosclerosis.

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