Department of Physiological Chemistry, Faculty of Chemistry, University of Vienna, Althanstraße 14, 1090 Vienna, Austria.
Food Funct. 2018 Jul 17;9(7):3906-3915. doi: 10.1039/c8fo01045e.
Advanced glycation end products (AGEs) are frequently encountered in a western diet, in addition to their formation in vivo. N-Epsilon-carboxymethyllysine (CML), one of the chemically diverse compounds formed in the reaction between reducing carbohydrates and amines, is often used as a marker of advanced glycation, and has been shown to stimulate serotonin release from cells representing the central (SH-SY5Y cells) and the peripheral (Caco-2 cells) serotonin system in vitro. Here, we investigated the effect of glyoxal, free CML, and protein-linked AGE-BSA on serotonin release from human gastric tumour cells, which originate from an adenocarcinoma of the stomach and have recently been shown to be capable of serotonin synthesis and release. Microarray experiments showed both CML and glyoxal to alter genes associated with serotonin receptors. Furthermore, treatment with glyoxal resulted in a small change in RAGE expression while CML did not alter its expression. On a functional level, treatment with 500 μM CML increased extracellular serotonin content by 341 ± 241%, while treatment with 1 mg mL-1 AGE-BSA led to a reduction by 49 ± 11% compared to non-treated cells. The CML-induced serotonin release was reduced by the HTR3 antagonist granisetron. Incubation with the RAGE antagonist FPS-ZM1 abolished the effect of AGE-BSA on serotonin release, while no impact on CML-induced serotonin release was observed. Furthermore, treatment with 5 mM CML stimulated proton secretion as a functional outcome measure, assessed using a pH sensitive dye. Taken together, these results indicate a likely HTR3-mediated, RAGE-independent effect of free CML on serotonin release and a RAGE-dependent mechanism for the protein linked AGE-BSA.
晚期糖基化终产物（AGEs）在西方饮食中很常见，除了在体内形成之外。N-ε-羧甲基赖氨酸（CML）是还原糖和胺之间反应形成的化学结构多样的化合物之一，通常用作晚期糖基化的标志物，并且已被证明能够刺激代表中枢（SH-SY5Y 细胞）和外周（Caco-2 细胞）的细胞释放 5-羟色胺。在这里，我们研究了乙二醛、游离 CML 和蛋白结合的 AGE-BSA 对源自胃腺癌的人胃肿瘤细胞释放 5-羟色胺的影响，这些细胞最近被证明能够合成和释放 5-羟色胺。微阵列实验表明 CML 和乙二醛均改变了与 5-羟色胺受体相关的基因。此外，用乙二醛处理会导致 RAGE 表达略有改变，而 CML 则不会改变其表达。在功能水平上，用 500μM CML 处理会使细胞外 5-羟色胺含量增加 341±241%，而用 1mg/mL AGE-BSA 处理会导致与未处理细胞相比减少 49±11%。HTR3 拮抗剂格兰司琼可减少 CML 诱导的 5-羟色胺释放。用 RAGE 拮抗剂 FPS-ZM1 孵育可消除 AGE-BSA 对 5-羟色胺释放的影响，而对 CML 诱导的 5-羟色胺释放没有影响。此外，用 5mM CML 处理可刺激质子分泌作为功能测定指标，使用 pH 敏感染料进行评估。综上所述，这些结果表明游离 CML 可能通过 HTR3 介导、RAGE 不依赖的机制影响 5-羟色胺释放，并且 AGE-BSA 通过 RAGE 依赖的机制发挥作用。
