AGE-RAGE Axis Stimulates Oxidized LDL Uptake into Macrophages through Cyclin-Dependent Kinase 5-CD36 Pathway via Oxidative Stress Generation

Abstract

Advanced glycation end products (AGEs) are localized in macrophage-derived foam cells within atherosclerotic lesions, which could be associated with the increased risk of atherosclerotic cardiovascular disease under diabetic conditions. Although foam cell formation of macrophages has been shown to be enhanced by AGEs, the underlying molecular mechanism remains unclear. Since cyclin-dependent kinase 5 (Cdk5) is reported to modulate inflammatory responses in macrophages, we investigated whether Cdk5 could be involved in AGE-induced CD36 gene expression and foam cell formation of macrophages. AGEs significantly increased Dil-oxidized low-density lipoprotein (ox-LDL) uptake, and Cdk5 and CD36 gene expression in U937 human macrophages, all of which were inhibited by DNA aptamer raised against RAGE (RAGE-aptamer). Cdk5 and CD36 gene expression levels were correlated with each other. An antioxidant, N-acetyl-l-cysteine, mimicked the effects of RAGE-aptamer on AGE-exposed U937 cells. A selective inhibitor of Cdk5, (R)-DRF053, attenuated the AGE-induced Dil-ox-LDL uptake and CD36 gene expression, whereas anti-CD36 antibody inhibited the Dil-ox-LDL uptake but not Cdk5 gene expression. The present study suggests that AGEs may stimulate ox-LDL uptake into macrophages through the Cdk5–CD36 pathway via RAGE-mediated oxidative stress.

Glucose-Dependent Insulinotropic Polypeptide Suppresses Foam Cell Formation of Macrophages through Inhibition of the Cyclin-Dependent Kinase 5-CD36 Pathway

“…The floating cells were seeded onto 24-well dishes and incubated with 40 ng/mL PMA in RPMI 1640 medium containing 10% FCS at 37 • C in a humidified atmosphere with 5% CO 2 for 24 h. After twice rinsing gently by phosphate-buffer saline (PBS), adherent cells were prepared as differentiated macrophages. Previously, the adherent cells used like this experiment were differentiated from monocytes to macrophages by analysis of fluorescence-activated cell sorting (FACS) [25,32,[36][37][38][39][40]. U937 macrophages were treated with or without 1 nmol/L [D-Ala 2 ]GIP, or 0.215 µmol/L (R)-DRF053 in RPMI 1640 medium including 10% FCS at 37 • C in 5% CO 2 for 18 h.…”

“…The U937 cells were treated with 10 µg/mL Dil-ox-LDL in RPMI 1640 medium including 10% FCS at 37 • C in 5% CO 2 for 18 h [25,32,36]. After twice washing with PBS gently, immunofluorescence was observed using Keyence BZ-X710 microscope and analyzed with the Keyence BZ-X710 software (Osaka, Japan).…”

“…After twice washing with PBS gently, immunofluorescence was observed using Keyence BZ-X710 microscope and analyzed with the Keyence BZ-X710 software (Osaka, Japan). The quantification of fluorescent intensity of red color per cells was calculated as described previously [25,32,36].…”

“…Moreover, Cdk5 is abundantly expressed in macrophages and could mediate the lipopolysaccharide-induced inflammatory reactions [19]. Furthermore, we have recently found that advanced glycation end products (AGEs), aging molecules formed at an accelerated rate under diabetes, stimulate macrophage foam cell formation via the activation of Cdk5-CD36 pathway [25]. Since AGEs are localized in monocyte/macrophagederived foam cells within the atherosclerotic plaques, macrophage foam cell formation evoked by AGEs could cause the atherosclerotic plaque instability and resultantly increase the risk of CVD in diabetes [26][27][28][29][30].…”

The Role of Monocytes and Macrophages in Homeostasis and Disease and Novel Avenues for Putative Treatments

“…Thus, they concluded that this new compound does not increase the inflammatory response in the analyzed population of monocytes/macrophages and does not affect the dentin regeneration in which MMP-2 and MMP-9 are normally involved. The participation of macrophages/foam cells in the development of atherosclerosis was described by Yashima et al [ 19 ]. Advanced glycation end products (AGEs) localize to macrophage-derived foam cells within atherosclerotic lesions, which is associated with a higher risk of atherosclerotic cardiovascular disease under diabetic conditions.…”