Kumar Anoop, Husain Nazim, Anbazhagan Arivarasu N, Jayawardena Dulari, Priyamvada Shubha, Singhal Megha, Jain Charu, Kaur Prabhdeep, Guzman Grace, Saksena Seema, Dudeja Pradeep K
Jesse Brown VA Medical Center, Research and Development, Chicago, IL, USA.
Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois Chicago, Chicago, IL, USA.
Inflamm Bowel Dis. 2025 Mar 3;31(3):625-635. doi: 10.1093/ibd/izae271.
Down-Regulated in Adenoma (DRA) plays a critical role in intestinal chloride absorption and a decrease in its expression is a key event in diarrheal disorders. Recently, DRA has emerged as an Inflammatory Bowel Disease (IBD) susceptibility gene. Therefore, the strategies to upregulate DRA expression are potentially novel approaches to not only treat IBD-associated diarrhea but also gut inflammation. In this study, the effect of dexamethasone (DEX), an anti-inflammatory corticosteroid on DRA expression was investigated.
GR (glucocorticoid receptor) overexpressed Caco-2 cells and C57BL/6/J mice and anti-αIL-10R mAb model of IBD were used. Protein expression was assessed by immunoblotting and immunofluorescence. Transcript levels were assessed by quantative-real-time polymerase chain reaction (qRT-PCR) and promoter activity was measured by luciferase assays.
Our results showed that DEX significantly increased DRA mRNA and protein expression in GR overexpressing Caco-2 cells. DEX-induced upregulation of DRA was GR dependent and appeared at least in part to occur via a transcriptional mechanism, as promoter activity of the DRA construct (-1183/+114 bp) was significantly increased in response to DEX. The increase in DRA mRNA was abrogated in the presence of MKP-1 inhibitor, triptolide. Administration of DEX (2 mg/kg body weight) to mice for 24 and 48 hours significantly increased the DRA expression in mouse colon. DEX treatment to mice for 7 days in the αIL-10R mAb model of colitis was able to significantly attenuate the gut inflammation and associated decrease in DRA expression.
We demonstrate that DEX stimulates DRA expression via transcriptional mechanisms and suggest that upregulation of DRA may contribute to both anti-inflammatory and pro-absorptive effects of DEX.
腺瘤下调基因（DRA）在肠道氯化物吸收中起关键作用，其表达降低是腹泻性疾病的关键事件。最近，DRA已成为炎症性肠病（IBD）的易感基因。因此，上调DRA表达的策略不仅是治疗IBD相关性腹泻的潜在新方法，也是治疗肠道炎症的潜在新方法。在本研究中，研究了抗炎皮质类固醇地塞米松（DEX）对DRA表达的影响。
使用糖皮质激素受体（GR）过表达的Caco-2细胞和C57BL/6/J小鼠以及IBD的抗αIL-10R单克隆抗体模型。通过免疫印迹和免疫荧光评估蛋白质表达。通过定量实时聚合酶链反应（qRT-PCR）评估转录水平，并通过荧光素酶测定法测量启动子活性。
我们的结果表明，DEX显著增加了GR过表达的Caco-2细胞中DRA mRNA和蛋白质的表达。DEX诱导的DRA上调依赖于GR，并且至少部分似乎是通过转录机制发生的，因为DRA构建体（-1183/+114 bp）的启动子活性响应DEX而显著增加。在存在MKP-1抑制剂雷公藤内酯醇的情况下，DRA mRNA的增加被消除。给小鼠施用DEX（2mg/kg体重）24小时和48小时显著增加了小鼠结肠中DRA的表达。在αIL-10R单克隆抗体结肠炎模型中，给小鼠DEX处理7天能够显著减轻肠道炎症以及相关的DRA表达降低。
我们证明DEX通过转录机制刺激DRA表达，并表明DRA的上调可能有助于DEX的抗炎和促吸收作用。
