title: miR-195 plays a role in steroid resistance of ulcerative colitis by targeting Smad7.
abstract: An imbalance in pro- and anti-inflammation is an important mechanism of steroid resistance in UC (ulcerative colitis), and miRNAs may participate in this process. The present study aimed to explore whether miRNAs play a role in the steroid resistance of UC by regulating gene expression of the inflammation signal pathway. SS (steroid-sensitive) patients, SR (steroid-resistant) patients and healthy individuals were recruited. In vivo miRNA profiles of serum samples showed that miR-195 was decreased significantly in the SR group compared with the SS group (P<0.05). This result was confirmed by qPCR (quantitative real-time PCR) and miRNA ISH (in situ hybridization) in serum and colon tissue samples. Online software was used to identify Smad7 mRNA as a potential target of miR-195. The direct interaction of miR-195 and Smad7 mRNA was investigated using a biotinylated miR-195 pull-down assay. Overexpression of a miR-195 precursor lowered cellular levels of Smad7 protein; conversely, antagonism of miR-195 enhanced Smad7 translation without disturbing Smad7 mRNA levels. A luciferase reporter assay revealed a repressive effect of miR-195 via a single Smad7 3'-UTR target site, and point mutation of this site prevented miR-195-induced repression of Smad7 translation. Furthermore, increased levels of miR-195 led to a decrease in c-Jun and p65 expression. In contrast, transfection with anti-miR-195 led to increased levels of c-Jun and p65 protein. The decrease in miR-195 led to an increase in Smad7 expression and corresponding up-regulation of p65 and the AP-1 (activator protein 1) pathway, which might explain the mechanism of steroid resistance in UC patients.
authors: Peking University People's Hospital, 11 Xizhimen South Street, Beijing 100044, China.
authors: Guodong
authors: G
authors: Chen
authors: Peking University People's Hospital, 11 Xizhimen South Street, Beijing 100044, China.
authors: Shan
authors: S
authors: Cao
authors: Peking University People's Hospital, 11 Xizhimen South Street, Beijing 100044, China Peking University Hepatology Institute, 11 Xizhimen South Street, Beijing 100044, China.
authors: Feng
authors: F
authors: Liu
authors: Peking University People's Hospital, 11 Xizhimen South Street, Beijing 100044, China liuyulan@pkuph.edu.cn.
authors: Yulan
authors: Y
authors: Liu
mesh_terms: D020413:3' Untranslated Regions; D000328:Adult; D018938:Caco-2 Cells; D003093:Colitis, Ulcerative / Q000097:blood / Q000188:drug therapy / Q000235:genetics*; D004351:Drug Resistance / Q000235:genetics*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D008297:Male; D035683:MicroRNAs / Q000096:biosynthesis / Q000097:blood / Q000235:genetics*; D008875:Middle Aged; D016755:Proto-Oncogene Proteins c-jun / Q000096:biosynthesis / Q000097:blood; D015398:Signal Transduction / Q000235:genetics; D051906:Smad7 Protein / Q000096:biosynthesis / Q000097:blood / Q000235:genetics*; D013256:Steroids / Q000627:therapeutic use*; D018808:Transcription Factor AP-1 / Q000096:biosynthesis / Q000097:blood; D019892:eIF-2 Kinase / Q000096:biosynthesis / Q000097:blood
chemical_list: D020413:3' Untranslated Regions; C552722:MIRN195 microRNA, human; D035683:MicroRNAs; D016755:Proto-Oncogene Proteins c-jun; C497806:SMAD7 protein, human; D051906:Smad7 Protein; D013256:Steroids; D018808:Transcription Factor AP-1; D019892:eIF-2 Kinase
keywords: Smad7; miRNA; post-transcriptional regulation; steroid resistance; ulcerative colitis