Glucose Modulates Macrophage Polarization By Glycating Adsorbed Albumin On Titanium

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Diabetes induces implant failure by macrophage M1-polarization, but whether high glucose modulates macrophage polarization via adsorbed protein is yet unknown. RAW264.7 cells, male SD rats (6-8 weeks) and bovine serum albumin were used in this study. Cells on pre-coated with albumin (3.5 mg/mL) or non-coated titanium plates were exposed to two variables: high (4.5 mg/mL) vs. low (1 mg/mL) glucose, presence (10% v/v) vs. absence of serum. Rats were injected with streptozotocin for 5 days before 3-day titanium implantation. Flow cytometry, qPCR and ROS fluorescent probes were for macrophage polarization assessment. Mass spectrometry was for adsorbed protein characterization. Albumin in high/low glucose were treated with or without DTPA (an anti-glycation agent) before 2-day glycation treatment. The Folin-Ciocalteu method, SDS-PAGE and CD spectroscopy were for albumin adsorption and conformation examination. Statistical analyses were performed by one-way ANOVA or Student’s t-test, p < 0.033 was defined as statistically significant. High glucose promoted macrophages’ M1-polarization by reducing albumin adsorption on titanium, as albumin inhibited macrophages’ M1-polarization. Reduced albumin adsorption was attributed to glycation-mediated structural deformation. Titanium pre-coated with non-glycated albumin effectively shifted the high glucose-induced polarization of macrophages in vivo and in vitro. High glucose inhibited albumin adsorption on titanium by glycation, thereby promoting macrophage M1-polarization. This study proposes a novel interfacial macrophage polarization mechanism, potentially facilitating the implant success in diabetic patients.

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