Aust Sylvia, Thalhammer Theresia, Humpeler Susanne, Jäger Walter, Klimpfinger Martin, Tucek Gerhard, Obrist Peter, Marktl Wolfgang, Penner Edward, Ekmekcioglu Cem
Department of Pathophysiology, University of Vienna, Vienna, Austria.
J Pineal Res. 2004 Jan;36(1):43-8. doi: 10.1046/j.1600-079x.2003.00095.x.
Based on the fact that human bile and, particularly gallbladder bile, contains high physiological levels of the antioxidant melatonin, the aim of this study was to investigate whether the melatonin receptor MT1 is present in human gallbladder. Expression and localization of MT1 was assessed by RT-PCR, Western blotting and immunofluorescence analysis in gallbladder samples from patients with cholelithiasis and with advanced gallbladder carcinoma. Additionally, we monitored mRNA expression of the two key enzymes of melatonin synthesis, i.e. arylalkylamine-N-acetyltransferase (AANAT) and hydroxyindole-O-methyltransferase (HIOMT). MT1 mRNA and protein were present in all cholelithiasis (n = 10) and gallbladder carcinoma (n = 5) samples. As indicated from RT-PCR and Western blot studies, MT1 is located in gallbladder epithelia. Epithelial expression was further proven by immunofluorescence staining of MT1 in paraffin-embedded cholelithiasis and gallbladder carcinoma sections. Analysis of AANAT and HIOMT mRNA expression showed that HIOMT mRNA is present in gallbladder. Surprisingly, AANAT was not detectable under conditions where it was found in a human colon specimen. The absence of AANAT suggests that in human gallbladder, HIOMT might be involved in the formation of 5-hydroxytryptamine products other than melatonin. In summary, our results provide the first evidence for the presence of MT1 in human gallbladder epithelia. Therefore, in addition to its profound antioxidative effects in the biliary system, melatonin might also act through MT1-mediated signal transduction pathways. Thereby, it might be involved in the regulation of gallbladder function.
基于人体胆汁尤其是胆囊胆汁中含有生理水平的抗氧化剂褪黑素这一事实，本研究旨在探究褪黑素受体MT1是否存在于人体胆囊中。通过逆转录聚合酶链反应（RT-PCR）、蛋白质免疫印迹法和免疫荧光分析，对患有胆结石和晚期胆囊癌患者的胆囊样本中MT1的表达和定位进行了评估。此外，我们监测了褪黑素合成的两种关键酶，即芳基烷基胺-N-乙酰转移酶（AANAT）和羟基吲哚-O-甲基转移酶（HIOMT）的mRNA表达。MT1的mRNA和蛋白存在于所有胆结石样本（n = 10）和胆囊癌样本（n = 5）中。如RT-PCR和蛋白质免疫印迹研究所示，MT1位于胆囊上皮细胞中。通过对石蜡包埋的胆结石和胆囊癌切片进行MT1免疫荧光染色，进一步证实了其上皮表达。对AANAT和HIOMT mRNA表达的分析表明，HIOMT mRNA存在于胆囊中。令人惊讶的是，在人结肠标本中能检测到AANAT的条件下，在胆囊中却未检测到。AANAT的缺失表明，在人体胆囊中，HIOMT可能参与了除褪黑素之外的5-羟色胺产物的形成。总之，我们的结果首次证明了MT1在人体胆囊上皮细胞中的存在。因此，除了其在胆道系统中的强大抗氧化作用外，褪黑素还可能通过MT1介导的信号转导途径发挥作用。从而，它可能参与胆囊功能的调节。
