INTRODUCTION: Advanced glycation endproducts (AGEs) are well-known inflammatory mediators, which are recognized by immune cells through their corresponding receptor RAGE and have been shown to participate in the pathophysiology of a variety of acute as well as chronic inflammatory diseases. Nevertheless, no data are available on the aftermath of AGE recognition on immune cells. MATERIALS AND METHODS: We used the monocytic cell line MonoMac6 as well as primary human monocytes for double stimulation experiments. We measured secreted as well as intracellular levels of TNF-α using ELISA and flow cytometry. In addition, gene expression of surface receptors (RAGE and TLR4) and TNF were measured by qPCR. RESULTS: Stimulation with AGE leads to a dose-dependent induction of self- and cross-tolerance in both primary monocytes as well as the MonoMac6 cell line. The AGE tolerance depended neither on a decreased expression of RAGE or TLR4, nor on a decrease of TNF-α expression. Nevertheless, intracellular TNF-α was decreased, hinting towards a posttranscriptional regulation. CONCLUSION: High levels of AGEs are capable to activate immune cells at first, but induce a secondary state of hypo-responsiveness in these cells. Based on the origin of its causal agent, we propose this phenomenon to be "metabolic tolerance".
INTRODUCTION: Advanced glycation endproducts (AGEs) are well-known inflammatory mediators, which are recognized by immune cells through their corresponding receptor RAGE and have been shown to participate in the pathophysiology of a variety of acute as well as chronic inflammatory diseases. Nevertheless, no data are available on the aftermath of AGE recognition on immune cells. MATERIALS AND METHODS: We used the monocytic cell line MonoMac6 as well as primary human monocytes for double stimulation experiments. We measured secreted as well as intracellular levels of TNF-α using ELISA and flow cytometry. In addition, gene expression of surface receptors (RAGE and TLR4) and TNF were measured by qPCR. RESULTS: Stimulation with AGE leads to a dose-dependent induction of self- and cross-tolerance in both primary monocytes as well as the MonoMac6 cell line. The AGE tolerance depended neither on a decreased expression of RAGE or TLR4, nor on a decrease of TNF-α expression. Nevertheless, intracellular TNF-α was decreased, hinting towards a posttranscriptional regulation. CONCLUSION: High levels of AGEs are capable to activate immune cells at first, but induce a secondary state of hypo-responsiveness in these cells. Based on the origin of its causal agent, we propose this phenomenon to be "metabolic tolerance".
Authors: Jianling Xie; José D Méndez; Verna Méndez-Valenzuela; María Montserrat Aguilar-Hernández Journal: Cell Signal Date: 2013-07-06 Impact factor: 4.315
Authors: Rajesh K Aneja; Allan Tsung; Hanna Sjodin; Julia V Gefter; Russell L Delude; Timothy R Billiar; Mitchell P Fink Journal: J Leukoc Biol Date: 2008-08-07 Impact factor: 4.962