Advanced Glycation End Products Induce Atherosclerosis via RAGE/TLR4 Signaling Mediated-M1 Macrophage Polarization-Dependent Vascular Smooth Muscle Cell Phenotypic Conversion

Abstract

Objective. The objective of this study was to investigate the involved mechanisms of advanced glycation end product- (AGE-) exacerbated atherosclerosis (AS). Methods. Toll-like receptor 4 (TLR4) inhibitor was administrated to type 2 diabetes mellitus (T2DM) AS rats. Atherosclerotic plaque, M1 macrophage infiltration, and VSMCs phenotypes were evaluated. AGE-exposed primary macrophages were treated with specific siRNAs knocking down receptor for AGEs (RAGE) and TLR4. Phenotypes of M1 macrophage and VSMCs were identified by fluorescent stains. Contact and noncontact coculture models were established. VSMCs and macrophages were cocultured in these models. ELISA was used to detect inflammatory cytokine concentrations. Relative mRNA expression levels were determined by real-time PCR. Relative protein expression and phosphorylation levels were evaluated by Western blots assays. Results. TLR4 inhibitor treatment significantly reduced arterial stenosis, infiltration of M1 polarized macrophages, and contractile-to-synthetic phenotype conversion of VSMCs in DM AS animals. RAGE and TLR4 silencing dramatically reduced AGE-induced macrophage M1 polarization, inflammatory cytokine secretion, and RAGE/TLR4/forkhead box protein C2 (FOXC2)/signaling which inhibited delta-like ligand 4 (Dll4) expression in macrophages. AGE-treated macrophages induced VSMC phenotypic conversion via activating Notch pathway in a contact coculture model rather than a noncontact model. The VSMC phenotypic conversion induction capability of macrophages was attenuated by RAGE and TLR4 silencing. Conclusions. AGEs induced activation of RAGE/TLR4/FOXC2 signaling, which featured macrophage with Dll4 high expression during M1 polarization. These macrophages promoted contractile-synthetic phenotypic conversion of VSMCs through the Dll4/Notch pathway after direct cell-to-cell contacts.

Endogenous advanced glycation end products in the pathogenesis of chronic diabetic complications

“…Delta-like ligand 4 (DLL4) expression is promoted by activated RAGE/TLR4 signaling. Dll4 expression on macrophage-treated vascular smooth muscle cells (VSMCs) results in contractile-phenotypic conversion via the Notch pathway, which contributes to atherosclerosis ( Xing et al, 2022 ). Additionally, AGE-RAGE interaction in monocytes-macrophages increases the synthesis of the following mediators: interleukin-1 (Il-1), tumor necrosis factor (TNF-a), platelet-derived growth factor (PDGF), and insulin-like growth factor-1 (IGF-1), all of which play a role in the pathogenesis of atherosclerosis ( Komplikacija and Tipa, 2015 ).…”

Role of advanced glycation end products on vascular smooth muscle cells under diabetic atherosclerosis

“…The stability of later period of atherosclerotic plaque was dominated by FAM172a, RAGE, galectin-3, autophagy and apoptosis ( 94 – 97 ). Trans-differentiation of VSMCs into a macrophage-like state to phagocytize lipids and form more foam cells are both an interfering factor affecting plaque stability ( 30 , 97 ). The above mechanisms of VSMCs in AS were summarized in Table 2 .…”

“…VSMCs play important roles in AS, the contractile-synthetic phenotypic of VSMCs conversion was critical in atherosclerotic plaque formation and development ( 30 ). Abnormally AGEs (resulted from hyperglycemia) lead to the differentiation of contractile VSMCs in vessel medium into synthetic VSMCs ( 169 ).…”

“…Binding of specific receptor for advanced glycation end-product (RAGE) and AGEs carries a big weight in the function of atherosclerotic VSMCs. RAGE expressed on VSMCs surface and mediates multiple damage mechanisms, thereby affecting the progression of AS ( 28 – 30 ). AGEs also have adverse effects on erectile dysfunction (ED), a risk factor for cardiovascular disease in diabetes, and diabetes retinopathy ( 31 , 32 ).…”

Vascular restenosis reduction with platelet membrane coated nanoparticle directed M2 macrophage polarization

“…Depending on the cytokines secreted and their functions, macrophages are mainly divided into two polarized types, including classically activated macrophages (M1 phenotype), also known as pro-inflammatory macrophages, and alternatively activated macrophages (M2 phenotype), also known as anti-inflammatory macrophages ( Orecchioni et al., 2019 ; Yang et al., 2020 ). Vascular injury mediates macrophage polarization to the M1 phenotype that secretes cytokines such as IL-1β, TNF-α, and IL-6 induces SMCs transformation to the secretory phenotype, which is active in proliferation and migration and eventually leads to restenosis ( Xing et al., 2022 ). On the other hand, the M2 phenotype reduces vascular restenosis by (1) reducing the secretion of inflammatory cytokines thereby inhibiting the secretory phenotype transformation of smooth muscle cells; (2) promoting endothelial repair to reduce inflammatory cell infiltration and inhibit smooth muscle cell proliferation and migration; (3) exosome-induced regulation in the proliferation and migration of smooth muscle cell ( Koelwyn et al., 2018 ; Yan et al., 2020 ).…”