MicroRNA-143 Targets ATG2B to Inhibit Autophagy and Increase Inflammatory Responses in Crohn's Disease.

BACKGROUND

Dysfunctional autophagy is recognized as a contributing factor in many chronic inflammatory diseases, including Crohn's disease (CD). Genetic analyses have found that microRNA (miRNA) levels are altered in the intestinal tissues of CD patients.

METHODS

The Sequencing Alternative Poly-Adenylation Sites (SAPAS) method was used to compare the 3' end of the total mRNA sequence of 3 surgical specimens of CD patients (including inflamed tissues and corresponding noninflamed tissues in each case). The levels of autophagy-related 2B (ATG2B), LC3, and miR-143 were compared between inflamed tissues and noninflamed tissues using immunoblot and quantitative reverse transcription polymerase chain reaction. Luciferase assays were used to verify the interactions between miR-143 and ATG2B. Autophagy was measured by immunoblot analyses of LC3 and transmission electron microscopy. Inflammatory cytokines and IκBα were analyzed to evaluate the effect of miR-143 on inflammatory response.

RESULTS

The tandem repeat 3'-UTR of ATG2B was longer in inflamed tissues than in corresponding noninflamed tissues and contained an miR-143 target site. miR-143 expression was elevated, whereas ATG2B and LC3-II were downregulated in inflamed tissues. The direct interaction between miR-143 and ATG2B was verified by a 3'-UTR dual-luciferase reporter assay. Constitutive expression of miR-143 or depletion of ATG2B in cultured intestinal epithelial cells inhibited autophagy, reduced IκBα levels, and increased inflammatory responses.

CONCLUSIONS

miR-143 may induce bowel inflammation by regulating ATG2B and autophagy, suggesting that miR-143 might play a critical role in the development of CD. Therefore, miR-143 could be a promising novel target for gene therapy in CD patients.