Advanced glycation end-products reduce lipopolysaccharide uptake by macrophages

PLoS One. 2021 Jan 25;16(1):e0245957. doi: 10.1371/journal.pone.0245957. eCollection 2021.

Abstract

Hyperglycaemia provides a suitable environment for infections and the mechanisms of glucose toxicity include the formation of advanced glycation end-products (AGEs), which comprise non-enzymatically glycosylated proteins, lipids, and nucleic acid amino groups. Among AGE-associated phenotypes, glycolaldehyde-derived toxic AGE (AGE-3) is involved in the pathogenesis of diabetic complications. Internalisation of endotoxin by various cell types contributes to innate immune responses against bacterial infection. An endotoxin derived from Gram-negative bacteria, lipopolysaccharide (LPS), was reported to enhance its own uptake by RAW264.7 mouse macrophage-like cells, and an LPS binding protein, CD14, was involved in the LPS uptake. The LPS uptake induced the activation of RAW264.7 leading to the production of chemokine CXC motif ligand (CXCL) 10, which promotes T helper cell type 1 responses. Previously, we reported that AGE-3 was internalised into RAW264.7 cells through scavenger receptor-1 Class A. We hypothesized that AGEs uptake interrupt LPS uptake and impair innate immune response to LPS in RAW264.7 cells. In the present study, we found that AGE-3 attenuated CD14 expression, LPS uptake, and CXCL10 production, which was concentration-dependent, whereas LPS did not affect AGE uptake. AGEs were reported to stimulate the receptor for AGEs and Toll-like receptor 4, which cause inflammatory reactions. We found that inhibitors for RAGE, but not Toll-like receptor 4, restored the AGE-induced suppression of CD14 expression, LPS uptake, and CXCL10 production. These results indicate that the receptor for the AGE-initiated pathway partially impairs the immune response in diabetes patients.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Survival / drug effects
  • Chemokine CXCL10 / metabolism
  • Glycation End Products, Advanced / pharmacology*
  • Lipopolysaccharide Receptors / metabolism
  • Lipopolysaccharides / pharmacology*
  • Macrophages / drug effects
  • Macrophages / metabolism*
  • Mice
  • RAW 264.7 Cells
  • Toll-Like Receptor 4 / metabolism

Substances

  • Chemokine CXCL10
  • Glycation End Products, Advanced
  • Lipopolysaccharide Receptors
  • Lipopolysaccharides
  • Toll-Like Receptor 4

Grants and funding

This work was supported by the Japan Society for the Promotion of Science (JSPS) Grants-in-Aid for Early-Career Scientists (17K16766), Scientific Research (C) (18K06905), by Japan Agency for Medical Research and Development (AMED) (15LK0201014h0003), by the Ministry of Education, Culture, Sports, Science and Technology (MEXT)-Supported Program for the Strategic Research Foundation at Private Universities (S1411037). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.