Kalina Uwe, Koyama Noriko, Hosoda Tomoko, Nuernberger Heike, Sato Kazuto, Hoelzer Dieter, Herweck Frank, Manigold Tobias, Singer Manfred V, Rossol Siegbert, Böcker Ulrich
Department of Hematology, University Hospital Frankfurt, Germany.
Eur J Immunol. 2002 Sep;32(9):2635-43. doi: 10.1002/1521-4141(200209)32:9<2635::AID-IMMU2635>3.0.CO;2-N.
Expression of IL-18 in intestinal epithelial cells (IEC) has been implicated in Th1 cell-mediated chronic intestinal inflammation and anti-tumor immunity. However, physiological regulatory factors have not been identified. Besides their effects on proliferation and restitution, immunomodulatory functions have been attributed to short chain fatty acids (SCFA). We investigated the effect of SCFA (butyrate, propionate, acetate) on expression of IL-18 in IEC in vitro and in vivo. Expression of IL-18 mRNA and protein in human carcinoma-derived HT-29 and Caco-2 cells was analyzed by reverse transcription-PCR and Western blot. Transcriptional regulation of IL-18 gene expression was determined by transient transfection of wild-type and mutated IL-18 promoter. Further, in vivo expression of IL-18 in the intestine from butyrate-treated and untreated mice was assessed by immunohistochemistry. IL-18 mRNA and the IL-18 protein were expressed in IEC, while IL-18 secretion was not observed. Butyrate and acetate increased intracellular IL-18 content in a time- and dose-dependent fashion. In contrast to proinflammatory stimuli butyrate potently activated the IL-18 promoter, indicating that IL-18 is regulated at the transcriptional level by SCFA. Furthermore, a 108-bp sequence in the proximal region was identified to be essential for IL-18 promoter activation by butyrate. As proof of principle butyrate effects were confirmed in vivo by demonstration of increased IL-18 protein expression in IEC from butyrate-treated mice. In conclusion, SCFA up-regulate IL-18 protein expression in IEC, suggesting a potential regulatory contribution of these luminal constituents to T cell mediated inflammatory and neoplastic intestinal conditions.
白细胞介素-18（IL-18）在肠道上皮细胞（IEC）中的表达与Th1细胞介导的慢性肠道炎症及抗肿瘤免疫有关。然而，尚未确定其生理调节因子。除了对细胞增殖和修复的作用外，短链脂肪酸（SCFA）还具有免疫调节功能。我们研究了SCFA（丁酸、丙酸、乙酸）在体外和体内对IEC中IL-18表达的影响。通过逆转录聚合酶链反应（RT-PCR）和蛋白质印迹法分析了人癌源HT-29和Caco-2细胞中IL-18 mRNA和蛋白质的表达。通过野生型和突变型IL-18启动子的瞬时转染来确定IL-18基因表达的转录调控。此外，通过免疫组织化学评估了丁酸处理和未处理小鼠肠道中IL-18的体内表达。IEC中表达IL-18 mRNA和IL-18蛋白，但未观察到IL-18分泌。丁酸和乙酸以时间和剂量依赖的方式增加细胞内IL-18含量。与促炎刺激相反，丁酸能有效激活IL-18启动子，表明SCFA在转录水平上对IL-18有调节作用。此外，近端区域的一个108 bp序列被确定为丁酸激活IL-18启动子所必需。作为原理验证，通过证明丁酸处理小鼠的IEC中IL-18蛋白表达增加在体内证实了丁酸的作用。总之，SCFA上调IEC中IL-18蛋白表达，提示这些肠腔成分对T细胞介导的肠道炎症和肿瘤性疾病可能有调节作用。
