RAGE Mediates Cholesterol Efflux Impairment in Macrophages Caused by Human Advanced Glycated Albumin

Abstract

We addressed the involvement of the receptor for advanced glycation end products (RAGE) in the impairment of the cellular cholesterol efflux elicited by glycated albumin. Albumin was isolated from type 1 (DM1) and type 2 (DM2) diabetes mellitus (HbA1c > 9%) and non-DM subjects (C). Moreover, albumin was glycated in vitro (AGE-albumin). Macrophages from Ager null and wild-type (WT) mice, or THP-1 transfected with siRNA-AGER, were treated with C, DM1, DM2, non-glycated or AGE-albumin. The cholesterol efflux was reduced in WT cells exposed to DM1 or DM2 albumin as compared to C, and the intracellular lipid content was increased. These events were not observed in Ager null cells, in which the cholesterol efflux and lipid staining were, respectively, higher and lower when compared to WT cells. In WT, Ager, Nox4 and Nfkb1, mRNA increased and Scd1 and Abcg1 diminished after treatment with DM1 and DM2 albumin. In Ager null cells treated with DM-albumin, Nox4, Scd1 and Nfkb1 were reduced and Jak2 and Abcg1 increased. In AGER-silenced THP-1, NOX4 and SCD1 mRNA were reduced and JAK2 and ABCG1 were increased even after treatment with AGE or DM-albumin. RAGE mediates the deleterious effects of AGE-albumin in macrophage cholesterol efflux.

Persistent Effect of Advanced Glycated Albumin Driving Inflammation and Disturbances in Cholesterol Efflux in Macrophages

“…In human umbilical vascular endothelial cells, human glycated albumin differentially regulates proteins involved in endothelial dysfunction, namely related to apoptosis and oxidative stress and the NF-KB cascade downstream to AGE-RAGE signaling, which can be counteracted by soluble RAGE [ 23 ]. The deleterious effects of AGE-albumin in cholesterol homeostasis are mediated by RAGE—a highly expressed multi-ligand receptor in atherosclerotic plaques—since they were not observed in macrophages from RAGE knockout mice [ 24 ]. In another study, BMDMs from mice with DM presented a reduced cholesterol efflux to apoA-I and HDL, as compared to BMDMs from control animals.…”

Directed Transport of CRP Across In Vitro Models of the Blood-Saliva Barrier Strengthens the Feasibility of Salivary CRP as Biomarker for Neonatal Sepsis

“…Interestingly, mRNA expression of RAGE was not affected by addition of sRAGE to CRP in comparison to CRP alone in both models (data not shown) indicating that effects of sRAGE seemed to be restricted to the functional level of RAGE. In this context, it was shown that RAGE can mediate uptake as well as efflux transport processes [ 48 , 49 ]. In relation to our results, it could be speculated that RAGE mediates the uptake of CRP into saliva across the oral mucosa epithelium, whereas it is involved in efflux mechanisms to restrict exorbitant accumulation of CRP in saliva via the salivary gland epithelium.…”

Inflammation Meets Metabolism Roles: for the Receptor for Advanced Glycation End Products Axis in Cardiovascular Disease

“…Albumin was isolated from patients with type 1 and type 2 diabetes (T1D and T2D, respectively) and from non-diabetic control subjects. Macrophages were retrieved from Ager null and wild-type mice, or human THP1 cells were subjected to treatment with silencing RNAs to reduce the expression of AGER [ 63 ]. Compared to wild-type murine macrophages and control-treated THP1 cells, cholesterol efflux was reduced in response to albumin from T1D or T2D patients vs control albumin [ 63 ]; in parallel with increased intracellular lipid content.…”

“…Macrophages were retrieved from Ager null and wild-type mice, or human THP1 cells were subjected to treatment with silencing RNAs to reduce the expression of AGER [ 63 ]. Compared to wild-type murine macrophages and control-treated THP1 cells, cholesterol efflux was reduced in response to albumin from T1D or T2D patients vs control albumin [ 63 ]; in parallel with increased intracellular lipid content. These effects of the human diabetic albumin were reduced in macrophages lacking Ager; in that setting, cholesterol efflux and lipid staining were higher and lower, respectively, when compared to the control RAGE-expressing cells [ 63 ].…”

“…Compared to wild-type murine macrophages and control-treated THP1 cells, cholesterol efflux was reduced in response to albumin from T1D or T2D patients vs control albumin [ 63 ]; in parallel with increased intracellular lipid content. These effects of the human diabetic albumin were reduced in macrophages lacking Ager; in that setting, cholesterol efflux and lipid staining were higher and lower, respectively, when compared to the control RAGE-expressing cells [ 63 ]. These latter studies are important as they used in vivo-isolated vs in vitro-prepared AGEs; nevertheless, they indicate that the in vitro-prepared material behaves analogously to that of AGEs obtained directly from diabetic subjects.…”