title: OxLDL-mediated survival of macrophages does not require LDL internalization or signalling by major pattern recognition receptors.
abstract: Macrophages play a key role in the pathogenesis of atherosclerosis, in part by destabilizing plaques. We and others have shown that low concentrations of oxidized LDL (oxLDL) inhibit macrophage apoptosis. As oxLDL is present in lesions, this may be a mechanism by which macrophage populations in the intima are expanded. We have previously shown that oxLDL activates prosurvival signalling pathways such as the phosphoinositide 3-kinase (PI3K) pathway in bone marrow derived macrophages (BMDMs). However, little is known about more upstream signalling events especially at the receptor level. The endocytic pattern recognition receptors (PRRs), scavenger receptor A (SR-A) and CD36, are the main receptors on macrophages for uptake of oxLDL and are therefore important in foam cell formation. The signalling PRRs such as toll-like receptor (TLR) 2 and 4 also bind some types of oxLDL. This study was done to determine if any of the known PRRs are required for the anti-apoptotic effects of oxLDL in BMDMs. To do this, we tested the effect of oxLDL on viability of BMDMs lacking both SR-A and CD36 or lacking TLR2, TLR4, CD14, FcγRIIb, or RAGE. Our results indicate that none of these receptors are essential for activating the oxLDL prosurvival pathway. Furthermore, we show that the anti-apoptotic effect is not dependent on the uptake of oxLDL.
authors.affiliation: Department of Medicine, University of British Columbia, Vancouver, Canada. mriazy@interchange.ubc.ca
authors.forename: Maziar
authors.initials: M
authors.lastname: Riazy
authors.forename: Johnny H
authors.initials: JH
authors.lastname: Chen
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Yamamato
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamamato
authors.forename: Vincent
authors.initials: V
authors.lastname: Duronio
authors.forename: Urs P
authors.initials: UP
authors.lastname: Steinbrecher
mesh_terms: D000818:Animals; D017209:Apoptosis; D018955:CD36 Antigens / Q000235:genetics; D002470:Cell Survival; D002478:Cells, Cultured; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000378:metabolism / Q000494:pharmacology* / Q000502:physiology; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D000067759:Receptor for Advanced Glycation End Products; D017452:Receptors, IgG / Q000378:metabolism; D011971:Receptors, Immunologic / Q000378:metabolism; D051117:Scavenger Receptors, Class A / Q000235:genetics; D015398:Signal Transduction; D051193:Toll-Like Receptors / Q000378:metabolism*
chemical_list: D018955:CD36 Antigens; C499172:Fcgr2b protein, mouse; D018950:Lipopolysaccharide Receptors; D008077:Lipoproteins, LDL; D000067759:Receptor for Advanced Glycation End Products; D017452:Receptors, IgG; D011971:Receptors, Immunologic; D051117:Scavenger Receptors, Class A; D051193:Toll-Like Receptors; C099252:oxidized low density lipoprotein