Age dependent accumulation patterns of advanced glycation end product receptor (RAGE) ligands and binding intensities between RAGE and its ligands differ in the liver, kidney, and skeletal muscle

Abstract

Background: Much evidence indicates receptor for advanced glycation end products (RAGE) related inflammation play essential roles during aging. However, the majority of studies have focused on advanced glycation end products (AGEs) and not on other RAGE ligands. In the present study, the authors evaluated whether the accumulation of RAGE ligands and binding intensities between RAGE and its ligands differ in kidney, liver, and skeletal muscle during aging.

Results: In C57BL/6 N mice aged 12 weeks, 12 months, and 22 months, ligands accumulation, binding intensities between RAGE and its ligands, activated macrophage infiltration, M1/M2 macrophage expression, glyoxalase-1expression, and signal pathways related to inflammation were evaluated. The RAGE ligands age-associated accumulation patterns were found to be organ dependent. Binding intensities between RAGE and its ligands in kidney and liver increased with age, but those in skeletal muscle were unchanged. Infiltration of activated macrophages in kidney and liver increased with age, but infiltration in the skeletal muscle was unchanged. M1 expression increased and M2 and glyoxalase-1 expression decreased with age in kidney and liver, but their expressions in skeletal muscle were not changed.

Conclusion: These findings indicate patterns of RAGE ligands accumulation, RAGE/ligands binding intensities, or inflammation markers changes during aging are organs dependent.

Keywords: AGEs; Aging; Macrophage activation; RAGE; RAGE ligands.

Fig. 1

Age-related RAGE ligands expression difference in kidney, liver and skeletal muscle. The level of RAGE ligands including AGEs, HMGB1, and S100β in the a kidney, b liver and c skeletal muscle of young, middle-aged, old mice were validated by In-direct ELISA. Ratios represented in the graphs represent fold levels of AGEs versus young mice. **; p < 0.01 versus young mice, $$; p < 0.01 versus middle-aged mice

Fig. 2

Age-dependent binding affinities between RAGE with RAGE ligands in kidney, liver and skeletal muscle. The binding levels of RAGE-RAGE ligands, which are, AGEs, HMGB1 and S100β in a kidney, b liver and c skeletal muscle of young, middle-aged, and old age mice were determined by Sandwich ELISA. Ratios in graphs represented fold of RAGE-AGEs binding levels versus young mice. **; p < 0.01 versus young mice, $$; p < 0.01 versus middle-aged mice

Fig. 3

Age-related expressions of total, M1, and M2 macrophages in kidney, liver and skeletal muscle. The Expression of total, M1 and M2 macrophages were determined by Immunohistochemistry and Immunoblotting. The level of Iba1 represented total macrophage expression in a kidney, b liver and c skeletal muscle. The level of iNOS represented M1 macrophage expression in d kidney, e liver and f skeletal kidney. The level of arginase 1 (Arg 1) represented M2 macrophage expression in d kidney, e liver and f skeletal kidney. Ratios in graphs are folds levels versus young mice. Scale bar = 100 um, *; p < 0.05 and **; p < 0.01 versus young mice

Fig. 4

Age-related changes in the levels of GLO-1 in kidney, liver and skeletal muscle. Levels of Glo-1 in a kidney, b liver and c skeletal muscle of the young, middle-aged, and old groups were validated by qRT-PCR. Ratios in graphs represented fold levels versus young mice. Expressions of NF_KB and IL-1β were determined by immunoblotting in d kidney, e liver and f skeletal muscle. **; p < 0.01 versus young mice, $$; p < 0.01 versus middle-aged mice