Advanced Glycation End Products Enhance Murine Monocyte Proliferation in Bone Marrow and Prime Them into an Inflammatory Phenotype through MAPK Signaling

Abstract

Objective Increased monocytes, particularly the inflammatory subset, are associated with accelerated atherosclerosis in diabetes through thus far incompletely defined mechanisms. The present study tested the hypothesis that advanced glycation end products (AGEs) promote bone marrow monocytes to proliferate and drive them into an inflammatory phenotype. Methods and Results In vivo, AGEs (25 mg/kg i.p. for 7 days) increased proportions of CD115+ monocytes and the inflammatory subset, the CD115+Ly6Chigh cells, in murine bone marrow (flow cytometry analysis (FCM)), and enhanced gene expression of proinflammatory cytokines (IL-1β and TNF-α) but only slightly upregulated mRNA expression of anti-inflammatory cytokine (IL-10) (real-time PCR) in monocytes. In vitro, when the monocytes were treated with different dosages of AGEs (50, 150, and 300 μg/mL), we found that proliferation (CCK8) but not apoptosis (FCM) of the monocytes was induced; the mRNA expressions of proinflammatory cytokines (IL-1β and TNF-α) and GM-CSF were upregulated in a dose-dependent manner while mRNA levels of IL-10 and M-CSF were changed much less in monocytes (real-time PCR). Furthermore, AGEs (300 μg/mL) significantly enhanced the expression of Ki67 in monocytes (immunofluorescence staining (IF)), and this dose of AGEs markedly increased secretion of GM-CSF but not that of M-CSF (ELISA). For a pathway study, the monocytes were stimulated by 300 μg/mL AGEs for different periods of time (0, 15, 30, and 120 min) and the activation of the MAPK pathway was tested (FCM); the results showed the p38 and ERK pathways were activated but not JNK signaling. Pretreatment with an inhibitor of p38 (SB203580) or ERK (U0126) attenuated AGE-induced gene expression of proinflammatory cytokines and GM-CSF (real-time PCR), as well as reversing AGE-induced Ki67 expression (IF). Conclusions AGEs promote bone marrow monocytes to proliferate and drive them into an inflammatory phenotype through p38 and ERK activation.

In Vitro Methodologies to Study the Role of Advanced Glycation End Products (AGEs) in Neurodegeneration

“…Murine monocytes from mice treated with modified BSA showed an increased proportion of proinflammatory monocyte phenotype accompanied by an increased gene expression of proinflammatory cytokines such as IL-6 and TNF-α. However, no change was observed in the expression of anti-inflammatory cytokines [166]. However, the exact modifications that BSA underwent were not clear in this study.…”

“…However, the exact modifications that BSA underwent were not clear in this study. In the same study, they observed increased proliferation and expression of TNF-α, IL-6, which was MAPK dependent as proven by the incubation with MAPK inhibitors [166]. In another study, exposure of mouse peritoneal macrophages to glucose-, MGO-and glyoxylic acid-modified BSA increased the TNF-a secretion.…”

Amelioration of endothelial dysfunction by sodium glucose co‐transporter 2 inhibitors: pieces of the puzzle explaining their cardiovascular protection

“…During hyperglycaemia, binding of AGEs to RAGE elevates adhesion molecule expression, production of cytokines and growth factors via the activation of ERK, JNK and PI3K pathways. AGEs directly stimulate monocytes to produce inflammatory mediators such as the ILs and TNF‐α, and thereby further enhance local inflammation of the vascular wall (Jin et al, 2018). Moreover, excessive production of ROS induces vascular inflammation in ECs via up‐regulating the adhesion molecules ICAM‐1 and VCAM‐1 (Daiber et al, 2020).…”

Innate Immunity in Calcinosis Cutis

“…Various innate immune cells in the skin express RAGE, including mononuclear phagocytes, DCs, and keratinocytes [31,32]. AGE binding to mononuclear phagocytes stimulates their chemotaxis towards skin and the production of IL-1β and TNF-α [33,34]. In DCs, exposure to AGEs induces greater production of IL-6 and activation of the nuclear factor kappa B (NF-κB) pathway [35].…”