Hypoxia as a Factor Involved in the Regulation of the apoA-1, ABCA1, and Complement C3 Gene Expression in Human Macrophages (original) (raw)
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In this unifying hypothesis directed to the etiology and pathogenesis of atherosclerosis, the importance of focal arterial lesion-prone sites has been emphasized. Key initial participants in these sites include the focal intimal influx and accumulation of low-density lipoprotein (LDL) and a preferential recruitment of blood monocytes. Both are further enhanced in the presence of hyperlipidemia, when the quantity of intimal LDL and the oxidative potential of the intima exceed the capacity of macrophages to remove, via the non-down-regulating scavenger receptor, cytotoxic anionic (Ox-LDL) macromolecules. Foam cells, pathognomonic of the fatty streak, form during the receptor-mediated uptake of Ox-LDL by the macrophages. Interstitial free radicals and the excess of Ox-LDL particles injure and kill cells, including the foam cells, with the formation of the necrotic extracellular lipid core, a key transitional step in lesion progression. Monocyte-macrophage recruitment to the intima is l...
Arteriosclerosis, Thrombosis, and Vascular Biology, 2014
Objective— Advanced murine and human plaques are hypoxic, but it remains unclear whether plaque hypoxia is causally related to atherogenesis. Here, we test the hypothesis that reversal of hypoxia in atherosclerotic plaques by breathing hyperoxic carbogen gas will prevent atherosclerosis. Approach and Results— Low-density lipoprotein receptor–deficient mice (LDLR -/- ) were fed a Western-type diet, exposed to carbogen (95% O 2 , 5% CO 2 ) or air, and the effect on plaque hypoxia, size, and phenotype was studied. First, the hypoxic marker pimonidazole was detected in murine LDLR -/- plaque macrophages from plaque initiation onwards. Second, the efficacy of breathing carbogen (90 minutes, single exposure) was studied. Compared with air, carbogen increased arterial blood pO 2 5-fold in LDLR -/- mice and reduced plaque hypoxia in advanced plaques of the aortic root (−32%) and arch (−84%). Finally, the effect of repeated carbogen exposure on progression of atherosclerosis was studied in L...
Repetitive hypoxia increases lipid loading in human macrophages—a potentially atherogenic effect
Atherosclerosis, 2005
Obstructive sleep apnea (OSA) is characterized by repetitive episodes of hypoxia and is associated with an increase in cardiovascular disease. We, therefore, investigated the effect of repetitive hypoxia on two key early events in atherogenesis; lipid loading in foam cells and monocyte adhesion to endothelial cells. Human macrophages were loaded with acetylated low-density lipoproteins. During lipid loading, the cells were exposed to 30 min cycles of 2%/21% oxygen or control (room air, 5% CO 2 incubator). Human umbilical vein endothelial cells (HUVECs) were also exposed to 30 min cycles of repetitive hypoxia or control conditions and monocyte adhesion measured. Cell adhesion molecules E-selectin, ICAM-1 and VCAM-1 were measured by ELISA. Repetitive hypoxia increased cholesteryl ester uptake by macrophages (127 ± 5% compared to controls; p = 0.003). By contrast, monocyte adhesion to HUVECs and cell adhesion molecule expression were unchanged by exposure to repetitive hypoxia, compared to controls (p > 0.1). Repetitive hypoxia, at levels relevant to tissues such as the arterial wall, enhances lipid uptake into human macrophages. This may contribute to accelerated atherosclerosis in OSA patients.
Immune and Inflammatory Mechanisms of Atherosclerosis *
Annual Review of Immunology, 2009
Atherosclerosis is an inflammatory disease of the wall of large-and medium-sized arteries that is precipitated by elevated levels of lowdensity lipoprotein (LDL) cholesterol in the blood. Although dendritic cells (DCs) and lymphocytes are found in the adventitia of normal arteries, their number is greatly expanded and their distribution changed in human and mouse atherosclerotic arteries. Macrophages, DCs, foam cells, lymphocytes, and other inflammatory cells are found in the intimal atherosclerotic lesions. Beneath these lesions, adventitial leukocytes organize in clusters that resemble tertiary lymphoid tissues. Experimental interventions can reduce the number of available blood monocytes, from which macrophages and most DCs and foam cells are derived, and reduce atherosclerotic lesion burden without altering blood lipids. Under proatherogenic conditions, nitric oxide production from endothelial cells is reduced and the burden of reactive oxygen species (ROS) and advanced glycation end products (AGE) is increased. Incapacitating ROS-generating NADPH oxidase or the receptor for AGE (RAGE) has beneficial effects. Targeting inflammatory adhesion molecules also reduces atherosclerosis. Conversely, removing or blocking IL-10 or TGF-β accelerates atherosclerosis. Regulatory T cells and B1 cells secreting natural antibodies are atheroprotective. This review summarizes our current understanding of inflammatory and immune mechanisms in atherosclerosis.
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Journal of Pharmaceutical Research International
In atherosclerosis, apolipoprotein B-lipoproteins in blood artery matrix attract monocytes, which become macrophages and dendritic cells. Macrophages generated from recruited monocytes cause a maladaptive, non-resolving inflammatory response that increases subendothelial layer. Some lesions cause myocardial infarction, stroke, and sudden cardiac death. Modern atherosclerosis research focuses on the molecular biology of atherogenesis, although the disease's complex pathophysiology is still unknown. The goal of this research is to examine the mechanisms of atherosclerosis development, such as endothelial dysfunction, fatty streak formation, fibrous plaque formation, and plaque rupture (Fig. 1.). This article takes a thorough look at the pathophysiology of atherosclerosis, addressing the pathological and biochemical mechanisms of atherosclerotic plaque development and growth. Atherosclerosis pathogenesis and disease development are the primary topics of discussion in this review, w...