Advanced glycation end products promote differentiation of CD4⁺ T helper cells toward pro-inflammatory response

Abstract

This study investigated the effect of advanced glycation end products (AGEs) on differentiation of naïve CD4⁺ T cells and the role of the receptor of AGEs (RAGE) and peroxisome proliferator-activated receptors (PPARs) activity in the process in order to gain insight into the mechanism of immunological disorders in diabetes. AGEs were prepared by the reaction of bovine serum albumin (BSA) with glucose. Human naïve CD4⁺ T cells, enriched from blood of healthy adult volunteers with negative selection assay, were cultured in vitro and treated with various agents including AGEs, BSA, high glucose, PGJ2 and PD68235 for indicated time. In short hairpin (sh) RNA knock-down experiment, naïve CD4⁺ T cells were transduced with media containing shRNA-lentivirus generated from lentiviral packaging cell line, Lent-X^TM 293 T cells. Surface and intracellular cytokine stainings were used for examination of CD4⁺ T cell phenotypes, and real-time PCR and Western blotting for detection of transcription factor mRNA and protein expression, respectively. The suppressive function of regulatory T (Treg) cells was determined by a [³H]-thymidine incorporation assay. The results showed that AGEs induced higher pro-inflammatory Th1/Th17 cells differentiated from naïve CD4⁺ T cells than the controls, whereas did not affect anti-inflammatory Treg cells. However, AGEs eliminated suppressive function of Treg cells. In addition, AGEs increased RAGE mRNA expression in naïve CD4⁺ T cells, and RAGE knock-down by shRNA eliminated the effect of AGEs on the differentiation of CD4⁺ T cells and the reduction of suppressive function of Treg cells. Furthermore, AGEs inhibited the mRNA expression of PPARγ, not PPARα PPARγ agonist, PGJ2, inhibited the effect of AGEs on naïve CD4⁺ T cell differentiation and reversed the AGE-reduced suppressive function of Treg cells; on the other hand, PPARγ antagonist, PD68235, attenuated the blocking effect of RAGE shRNA on the role of AGEs. It was concluded that AGEs may promote CD4⁺ T cells development toward pro-inflammatory state, which is associated with increased RAGE mRNA expression and reduced PPARγ activity.

Keywords

diabetes / advanced glycation end products / CD4⁺ T cell subsets / pro-inflammatory response

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