Published online Mar 15, 2023. doi: 10.4239/wjd.v14.i3.222
Peer-review started: September 22, 2022
First decision: December 26, 2022
Revised: January 8, 2023
Accepted: February 15, 2023
Article in press: February 15, 2023
Published online: March 15, 2023
Processing time: 174 Days and 7.9 Hours
Nε-(carboxymethyl)lysine (CML) is a representative of advanced glycation end products. CML could promote the lipid uptake of macrophages. The receptor for advanced glycation end products (RAGE) and cluster of differentiation 36 (CD36) are receptors of CML. It is necessary to explore the relationship between RAGE and CD36 and their roles in the lipid uptake of macrophages.
CML was reported an atherogenic factor. CML can promote the lipid uptake of macrophages and the formation of foam cells. RAGE and CD36 are important for the pathogenesis of CML. RAGE and CD36 have also been reported to promote atherosclerosis. Therefore, RAGE and CD36 may be involved in the lipid uptake of macrophages. The different roles of RAGE and CD36 are also worth exploring.
We aimed to clarify the role of RAGE and CD36 in CML-induced macrophage uptake and to explore the relationship and difference between RAGE and CD36 in this process.
Raw264.7 cells were divided into control group and CML group. Cells of the CML group were incubated with oxidized low-density lipoprotein and CML to test the effect of CML on lipid uptake. The expressions of RAGE and CD36 were determined by western blot and quantitative polymerase chain reaction. Immunoprecipitation and radioactive receptor-ligand binding assays were performed to exam the binding of CML to RAGE and CD36. A receptor-ligand binding model was constructed to predict binding sites. The uptake of lipid and CML was tested after the cells were preincubated with Anti-RAGE or Anti-CD36.
CML significantly promotes lipid uptake by macrophages. The expression of CD36 and RAGE was also significantly upregulated under CML stimulation. Immunoprecipitation showed that CML could interact with CD36 and RAGE. Radioreceptor ligand binding assay also confirmed the binding of CML to CD36 and RAGE. Moreover, the affinity of CML with CD36 was significantly higher than that of RAGE. The receptor-ligand binding model found that the binding sites of CML and CD36 may be ARG82, ASN71, and THR70. The binding of CML to cells was significantly reduced after pre-incubation with Anti-CD36 or Anti-RAGE. Furthermore, Anti-CD36 and Anti-RAGE significantly inhibited lipid uptake by macrophages.
CML promotes lipid uptake by macrophages, and its binding to CD36 and RAGE plays a key role in this process.
The current study provides clues for the pathogenesis of metabolic toxic product CML, and also suggests a promising intervention target for the prevention and treatment of atherosclerosis.