Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0004153 (atherosclerosis)
 77,401 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

beta-Amyloid accumulation is associated with pathologic changes in the brain in Alzheimer's disease and has recently been identified in plaques of another chronic inflammatory disorder, atherosclerosis. The class B scavenger receptor, CD36, mediates binding of fibrillar beta-amyloid to cells of the monocyte/macrophage lineage, including brain macrophages (microglia). In this study, we demonstrate that in microglia and other tissue macrophages, beta-amyloid initiates a CD36-dependent signaling cascade involving the Src kinase family members, Lyn and Fyn, and the mitogen-activated protein kinase, p44/42. Interruption of this signaling cascade, through targeted disruption of Src kinases downstream of CD36, inhibits macrophage inflammatory responses to beta-amyloid, including reactive oxygen and chemokine production, and results in decreased recruitment of microglia to sites of amyloid deposition in vivo. The finding that engagement of CD36 by beta-amyloid initiates a Src kinase-dependent production of inflammatory mediators in cells of the macrophage lineage reveals a novel receptor-mediated pro-inflammatory signaling pathway of potential therapeutic importance.
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PMID:A CD36-initiated signaling cascade mediates inflammatory effects of beta-amyloid. 1223 21

Scavenger receptors recognize modified low-density lipoproteins (LDLs) such as acetylated LDL and oxidized LDL. Advanced glycation end products (AGE), which are generated through long-term exposure of proteins to glucose, also behave as active ligands for some scavenger receptors, including class A scavenger receptor (SR-A) and class B scavenger receptors such as CD36 and scavenger receptor, class B, type I (SR-BI). SR-BI, the first identified high-density lipoprotein (HDL) receptor, plays key roles in reverse cholesterol transport by promoting selective uptake of cholesteryl esters (CE) in HDL by hepatocytes, and cholesterol efflux of unesterified cholesterol from peripheral cells to HDL. Using Chinese hamster ovary cells overexpressing SR-BI (CHO-SR-BI cells), it was demonstrated that AGE-bovine serum albumin binds to SR-BI and inhibits selective uptake of HDL-CE by CHO-SR-BI cells as well as cholesterol efflux from CHO-SR-BI cells to HDL, suggesting potential roles of AGE in diabetic dyslipidemia and accelerated atherosclerosis in diabetes.
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PMID:Scavenger receptors that recognize advanced glycation end products. 1224 49

Caveolae are 50-100 nm plasma membrane invaginations, which function in cell signaling, in transcytosis, and in regulating cellular cholesterol homeostasis. These subcompartments of the plasma membrane are characterized by the presence of caveolin proteins. Recent studies have indicated that caveolae may be involved in the regulation of cellular cholesterol efflux to high-density lipoproteins (HDL), as well as selective cholesteryl ester uptake mediated by scavenger receptor class B type I (SR-BI). In the present studies, we show that caveolin-1 expression in HEK-293T cells has no effect on SR-BI-mediated cellular cholesterol efflux to reconstituted HDL. However, SR-BI-mediated selective cholesteryl ester uptake is significantly inhibited by caveolin-1. Interestingly, we also found that SR-BI, but not CD36, can induce the dramatic stabilization of the caveolin-1 protein, independently of its transcriptional control. On the other hand, caveolin-1 has little effect on SR-BI stability, but clearly increases CD36 stability. Since SR-BI expression has been shown to increase cellular cholesterol levels, we next examined the effect of cholesterol itself on caveolin-1 stabilization and localization. When cells were loaded with cholesterol, we observed the dramatic stabilization of caveolin-1 with significant clustering of caveolin-1 at the cell surface. In addition, a palmitoylation-deficient caveolin-1 mutant was still responsive to cholesterol-induced stabilization, indicating that palmitoylation of caveolin-1 is not required for the cholesterol-induced stabilization of caveolin-1. These results suggest an important role for cholesterol and SR-BI in the regulation of caveolin functioning, especially in cell types such as endothelial cells and macrophages, which can be dramatically affected by changes in their cholesterol content during the development of atherosclerosis.
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PMID:Stabilization of caveolin-1 by cellular cholesterol and scavenger receptor class B type I. 1226 38

FAT/CD36 is involved in various processes including uptake of fatty acid into the heart and of oxidized low density lipoprotein (LDL) into macrophages. Expression of the FAT/CD36 gene is regulated in a tissue-specific manner, and loss or inadequately regulated expression of FAT/CD36 is thought to be one of the causes of some diseases such as cardiomyopathy and atherosclerosis. We recently found that the mouse and human FAT/CD36 genes have two independent promoters. To elucidate the physiological significance of the two promoters, we characterized the peroxisome proliferator-activated receptor ligand-responsive new promoter that is located 14 kb upstream of the previously reported promoter of the human gene. We found several SNPs in this region some of which were found only when analyzing DNA samples from the patients lacking FAT/CD36 totally or in a cell-type-specific manner. However, we could not detect any negative effect of these SNPs on the transcription by transient transfection analysis, suggesting that the identified SNPs alone are not directly linked to low transcriptional activities.
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PMID:Structural and functional analysis of a new upstream promoter of the human FAT/CD36 gene. 1241 63

Advanced glycation end products (AGEs) are nonenzymatically glycosylated proteins, which accumulate in vascular tissues in aging and diabetes. Receptors for AGEs include scavenger receptors, which recognize acetylated low density lipoproteins (Ac-LDL) such as scavenger receptor class AI/AII (SR-A), cell surface glycoprotein CD36, scavenger receptor class B type I (SR-BI), and lectin-like oxidized low density lipoprotein receptor-1. The broad ligand repertoire of these receptors as well as the diversity of the receptors for AGEs have prompted us to examine whether AGEs are also recognized by the novel scavenger receptors, which we have recently isolated from a cDNA library prepared from human umbilical vein endothelial cells, such as the scavenger receptor expressed by endothelial cells-I (SREC-I); the fasciclin EGF-like, laminin-type EGF-like, and link domain-containing scavenger receptor-1 (FEEL-1); and its paralogous protein, FEEL-2. At 4 degrees C, (125)I-AGE-bovine serum albumin (BSA) exhibited high affinity specific binding to Chinese hamster ovary (CHO) cells overexpressing FEEL-1 (CHO-FEEL-1) and FEEL-2 (CHO-FEEL-2) with K(d) of 2.55 and 1.68 microg/ml, respectively, but not to CHO cells expressing SREC (CHO-SREC) and parent CHO cells. At 37 degrees C, (125)I-AGE-BSA was taken up and degraded by CHO-FEEL-1 and CHO-FEEL-2 cells but not by CHO-SREC and parent CHO cells. Thus, the ability to bind Ac-LDL is not necessarily a prerequisite to bind AGEs. The (125)I-AGE-BSA binding to CHO-FEEL-1 and CHO-FEEL-2 cells was effectively inhibited by Ac-LDL and polyanionic SR-A inhibitors such as fucoidan, polyinosinic acids, and dextran sulfate but not by native LDL, oxidized LDL, or HDL. FEEL-1, which is expressed by the liver and vascular tissues, may recognize AGEs, thereby contributing to the development of diabetic vascular complications and atherosclerosis.
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PMID:FEEL-1 and FEEL-2 are endocytic receptors for advanced glycation end products. 1247 45

Evidence is accumulating that cellular lipid binding proteins are playing central roles in cellular lipid uptake and metabolism. Membrane-associated fatty acid-binding proteins putatively function in protein-mediated transmembrane transport of fatty acids, likely coexisting with passive diffusional uptake. The intracellular trafficking of fatty acids, bile acids, and other lipid ligands, may involve their interaction with specific membrane or protein targets, which are unique properties of some but not of all cytoplasmic lipid binding proteins. Recent studies indicate that these proteins not only facilitate but also regulate cellular lipid utilization. For instance, muscle fatty acid uptake is subject to short-term regulation by translocation of fatty acid translocase (FAT)/CD36 from intracellular storage sites to the plasma membrane, and liver-type cytoplasmic fatty acid-binding protein (L-FABPc) functions in long-term, ligand-induced regulation of gene expression by directly interacting with nuclear receptors. Therefore, the properties of the lipid-protein complex, rather than those of the lipid ligand itself, determine the fate of the ligand in the cell. Finally, there are an increasing number of reports that deficiencies or altered functioning of both membrane-associated and cytoplasmic lipid binding proteins are associated with disease states, such as obesity, diabetes and atherosclerosis. In conclusion, because of their central role in the regulation of lipid metabolism, cellular lipid binding proteins are promising targets for the treatment of diseases resulting from or characterised by disturbances in lipid metabolism, such as atherosclerosis, hyperlipidemia, and insulin resistance.
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PMID:Cellular lipid binding proteins as facilitators and regulators of lipid metabolism. 1247 62

Fatty acid translocase (FAT)/CD36 has been associated with diverse normal and pathologic processes. These include scavenger receptor functions (uptake of apoptotic cells and modified lipid), lipid metabolism and fatty acid transport, adhesion, angiogenesis, modulation of inflammation, transforming growth factor-beta activation, atherosclerosis, diabetes and cardiomyopathy. Although CD36 was identified more than 25 years ago, it is only with the advent of recent genetic technology that in vivo evidence has emerged for its physiologic and pathologic relevance. As these in vivo studies are expanded, we will gain further insight into the mechanism(s) by which CD36 transmits a cellular signal, and this will allow the design of specific therapeutics that impact on a particular function of CD36.
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PMID:The impact of overexpression and deficiency of fatty acid translocase (FAT)/CD36. 1247 85

Chondroitin sulfate (CS) used for treatment of osteoarthritis exerts distinct effects on human articular chondrocytes in vitro. We performed a binding analysis with 99mTc-labeled CS (Condrosulf, a commercial CS preparation containing calcium stearate) and cultured human chondrocytes in order to evaluate the presence of specific receptors. Saturation binding at 37 degrees C for 2 h revealed the presence of high-affinity binding sites for CS with a Kd of 2.3 x 10(-9) mol/L and a Bmax of 5.0 x 10(8). Extensive dialysis of Chondrosulf led to a decrease of the binding affinity by 52.5 +/- 19.5% and of the number of CS binding sites/cell by 62.0 +/- 14.0%, demonstrating that the additive present in the Condrosulf preparation enhances CS binding. The nature of the binding site is not yet known but evidence exists in the literature that the scavenger receptor CD36, thoroughly investigated on macrophages, is also found on chondrocytes and might be involved in CS binding. Therefore, we undertook a comparative binding study with human monocytes and labelled LDL and oxidized LDL, the latter being a postulated atherogenic agent in atherosclerosis. For [125I]-LDL binding we found a Kd of 0.45 x 10(-8) mol/L and a Bmax of 0.14 x 10(6) on quiescent monocytes and for [125I]-(ox)LDL binding a Kd of 1.8 x 10(-8) mol/L and a Bmax of 1.3 x 10(6) using LPS-activated monocytes. These data are comparable to the binding affinity found for lipoprotein-proteoglycan-complexes and hence are an indication but not a proof that CD36 is involved in CS binding to human chondrocytes.
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PMID:Binding of [99mTc]chondroitin sulfate to scavenger receptors on human chondrocytes as compared to binding of oxidized [125I]LDL on human macrophages. 1250 34

Protease inhibitors decrease the viral load in HIV patients, however the patients develop hypertriglyceridemia, hypercholesterolemia, and atherosclerosis. It has been assumed that protease inhibitor-dependent increases in atherosclerosis are secondary to the dyslipidemia. Incubation of THP-1 cells or human PBMCs with protease inhibitors caused upregulation of CD36 and the accumulation of cholesteryl esters. The use of CD36-blocking antibodies, a CD36 morpholino, and monocytes isolated from CD36 null mice demonstrated that protease inhibitor-induced increases in cholesteryl esters were dependent on CD36 upregulation. These data led to the hypothesis that protease inhibitors induce foam cell formation and consequently atherosclerosis by upregulating CD36 and cholesteryl ester accumulation independent of dyslipidemia. Studies with LDL receptor null mice demonstrated that low doses of protease inhibitors induce an increase in the level of CD36 and cholesteryl ester in peritoneal macrophages and the development of atherosclerosis without altering plasma lipids. Furthermore, the lack of CD36 protected the animals from protease inhibitor-induced atherosclerosis. Finally, ritonavir increased PPAR-gamma and CD36 mRNA levels in a PKC- and PPAR-gamma-dependent manner. We conclude that protease inhibitors contribute to the formation of atherosclerosis by promoting the upregulation of CD36 and the subsequent accumulation of sterol in macrophages.
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PMID:HIV protease inhibitors promote atherosclerotic lesion formation independent of dyslipidemia by increasing CD36-dependent cholesteryl ester accumulation in macrophages. 1256 55

Uptake of modified low density lipoprotein (LDL) by monocyte-macrophages is mediated by the scavenger receptor CD36, which is upregulated in vitro by high glucose concentrations and oxidatively modified LDL. We hypothesised that monocyte CD36 expression would be higher in Type 2 diabetes, and would increase during acute hyperglycaemia. Sixteen subjects with Type 2 diabetes and 11 controls underwent a 75 g oral glucose load. Monocyte CD36 expression (by laser flow cytometry), plasma LDL diene conjugates, plasma LDL hydroxyoctadecadienoic acid-13 (a peroxisome proliferator activator receptor gamma agonist) were measured at 0, 2 and 4 h. Mean monocyte CD36 expression at baseline was 34% higher in the diabetes group (P=0.01), did not change during acute hyperglycaemia and plasma LDL conjugated diene concentration was the only variable directly related to CD36 expression (F=4.53; P=0.05; r=0.51). Higher baseline CD36 expression in Type 2 diabetes could reflect increased post-transcriptional efficiency of CD36 mRNA in response to chronic hyperglycaemia and could be a proatherogenic mechanism in Type 2 diabetes.
Atherosclerosis 2003 Mar
PMID:Increased expression of a scavenger receptor (CD36) in monocytes from subjects with Type 2 diabetes. 1261 77


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