Proinflammatory Cytokines Regulate LOX-1 Expression in Vascular Smooth Muscle Cells

Abstract

Objective-Atherogenesis represents a type of chronic inflammation and involves elements of the immune response, eg, the expression of proinflammatory cytokines. In advanced atherosclerotic lesions, lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is expressed in endothelial cells, macrophages, and smooth muscle cells (SMCs). In vitro, the expression of LOX-1 is induced by inflammatory cytokines like TNF-␣ and transforming growth factor (TGF)-␤. Therefore, LOX-1 is thought to be upregulated locally in response to cytokines in vivo. Methods and Results-We determined by reverse-transcription polymerase chain reaction (PCR) and Western blot analysis whether the mediators of the acute phase response in inflammation, IL-1␣, IL-1␤, and TNF-␣, regulate LOX-1 expression in cultured SMC, and whether this regulation is influenced by peroxisome proliferator-activated receptor ␥ (PPAR␥). We studied by immunohistochemistry whether these cytokines are spatially correlated with LOX-1 expression in advanced atherosclerotic lesions. We found upregulation of LOX-1 expression in SMC in a dose-and time-dependent manner after incubation with IL-1␣, IL-1␤, and TNF-␣. Simultaneous incubation with these cytokines at saturated concentrations had an additive effect on LOX-1 expression. The PPAR␥ activator, 15d-PGJ 2 , however, inhibited IL-1␤-induced upregulation of LOX-1. In the intima of atherosclerotic lesions regions of IL-1␣, IL-1␤, and TNF-␣ expression corresponded to regions of LOX-1 expression. Conclusion-We suppose that upregulated LOX-1 expression in SMC of advanced atherosclerotic lesions is a response to these proinflammatory cytokines. Moreover, the proinflammatory effects of these cytokines can be decreased by the antiinflammatory effect of PPAR␥.

Increased Levels of Lectin‐Like Oxidized Low‐Density Lipoprotein Receptor‐1 in Ischemic Stroke and Transient Ischemic Attack

“…Numerous in vitro studies have shown that oxidative as well as inflammatory stimuli increase OLR1 gene expression in macrophages, endothelial cells, and probably also in SMC 31, 32, 33, 34. In addition, different animal models have confirmed upregulation of OLR1 expression in the vasculature during inflammatory and oxidative conditions 30.…”

Regulation of Apoptotic Endonucleases by EndoG

“…The total protein extract from cells (10-100 mg) was dissolved in 50 mM Tris-HCl, pH 6.8, 1% sodium dodecyl sulfate, 2 mM EDTA, 1% 2-mercaptoethanol, 7.5% glycerol, and denatured by heating at 100°C for 10 min. Electrophoresis was performed at 100 V for 2 h. Proteins were transferred onto the nitrocellulose membrane in NuPAGE Ò transferring buffer (Invitrogen) at 40 V for 3 h. The membranes were stained with Ponseau S (SigmaAldrich) to control equal protein load as described elsewhere (Hofnagel et al, 2004). After soaking in the blocking solution overnight at 4°C, the membrane was incubated with polyclonal anti-DNase I antibody (Rockland, Gilbertsville, PA) diluted 1:1000, polyclonal anti-CAD antibody (Abbiotec, San Diego, CA) diluted 1:500, polyclonal anti-glyceraldehyde-3-phosphate dehydrogenase (GAPDH).…”

Lectin-Like Oxidized Low-Density Lipoprotein Receptor-1 Plays an Important Role in Vascular Inflammation in Current Smokers

“…Lectin-like low-density lipoprotein (LDL) receptor-1 (LOX-1) is an oxidized LDL (oxLDL) receptor expressed in endothelial cells 4) , smooth muscle cells 5) , cardiomyocytes 6) and monocytes 7) . The LOX-1 expression in the vascular wall is very low in its basal state and can be markedly induced by oxidative stress and inflammatory cytokines 4,5) .…”

“…The LOX-1 expression in the vascular wall is very low in its basal state and can be markedly induced by oxidative stress and inflammatory cytokines 4,5) . Activated LOX-1 initiates various atherogenic reactions, including the adhesion of monocytes to the endothelium and the transformation of macrophages into foam cells 7) , and it has also been suggested to be involved in destabilization and rupture of atherosclerotic plaques.…”