MicroRNA-31 Reduces Inflammatory Signaling and Promotes Regeneration in Colon Epithelium, and Delivery of Mimics in Microspheres Reduces Colitis in Mice.

BACKGROUND & AIMS: Levels of microRNA 31 (MIR31) are increased in intestinal tissues from patients with inflammatory bowel diseases and colitis-associated neoplasias. We investigated the effects of this microRNA on intestinal inflammation by studying mice with colitis. METHODS: We obtained colon biopsy samples from 82 patients with ulcerative colitis (UC), 79 patients with Crohn's disease (CD), and 34 healthy individuals (controls) at Shanghai Tenth People's Hospital. MIR31- knockout mice and mice with conditional disruption of Mir31 specifically in the intestinal epithelium (MIR31 conditional knockouts) were given dextran sulfate sodium (DSS) or 2,4,6-trinitrobenzene sulfonic acid (TNBS) to induce colitis. We performed chromatin immunoprecipitation and luciferase assays to study proteins that regulate expression of MIR31, including STAT3 and p65, in LOVO colorectal cancer cells and organoids derived from mouse colon cells. Partially hydrolyzed alpha-lactalbumin was used to generate peptosome nanoparticles, and MIR31 mimics were loaded onto their surface using electrostatic adsorption. Peptosome-MIR31 mimic particles were encapsulated into oxidized konjac glucomannan (OKGM) microspheres, which were administered by enema into the large intestines of mice with DSS-induced colitis. Intestinal tissues were collected and analyzed by histology and immunohistochemistry. RESULTS: Levels of MIR31 were increased in inflamed mucosa from patients with CD or UC, and from mice with colitis, compared with controls. STAT3 and nuclear factor-κB activated transcription of MIR31 in colorectal cancer cells and organoids in response to tumor necrosis factor and interleukin (IL)6. MIR31-knockout and conditional-knockout mice developed more severe colitis in response to DSS and TNBS, with increased immune responses, compared with control mice. MIR31 bound to 3' untranslated regions of Il17ra and Il7r messenger RNAs (RNAs) (which encode receptors for the inflammatory cytokines IL17 and IL7) and Il6st mRNA (which encodes GP130, a cytokine signaling protein). These mRNAs and proteins were greater in MIR31-knockout mice with colitis, compared with control mice; MIR31 and MIR31 mimics inhibited their expression. MIR31 also promoted epithelial regeneration by regulating the WNT and Hippo signaling pathways. OKGM peptosome-MIR31 mimic microspheres localized to colonic epithelial cells in mice with colitis; they reduced the inflammatory response, increased body weight and colon length, and promoted epithelial cell proliferation. CONCLUSIONS: MIR31, increased in colon tissues from patients with CD or UC, reduces the inflammatory response in colon epithelium of mice by preventing expression of inflammatory cytokine receptors (Il7R and Il17RA) and signaling proteins (GP130). MIR31 also regulates the WNT and Hippo signaling pathways to promote epithelial regeneration following injury. OKGM peptosome-MIR31 microspheres localize to the colon epithelium of mice to reduce features of colitis. Transcript Profiling: GSE123556.

The Antagonistic Action of Abscisic Acid and Cytokinin Signaling Mediates Drought Stress Response in Arabidopsis.

As sessile organisms, plants encounter a variety of environmental stresses and must optimize their growth for survival. Abscisic acid (ABA) and cytokinin antagonistically regulate many developmental processes and environmental stress responses in plants. However, the molecular mechanism underlying this antagonism remains poorly defined. In this study, we demonstrated that Sucrose nonfermenting1-related kinases SnRK2.2, SnRK2.3, and SnRK2.6, the key kinases of the ABA signaling pathway, directly interact with and phosphorylate type-A response regulator 5 (ARR5), a negative regulator of cytokinin signaling. The phosphorylation of ARR5 Ser residues by SnRK2s enhanced ARR5 protein stability. Accordingly, plants overexpressing ARR5 showed ABA hypersensitivity and drought tolerance, and these phenotypes could not be recapitulated by overexpressing a non-phosphorylated ARR5 mimic. Moreover, the type-B ARRs, ARR1, ARR11 and ARR12, physically interacted with SnRK2s and repressed the kinase activity of SnRK2.6. The arr1,11,12 triple mutant exhibited hypersensitivity to ABA. Genetic analysis demonstrated that SnRK2s act upstream of ARR5 but downstream of ARR1, ARR11 and ARR12 in mediating ABA response and drought tolerance. Taken together, this study unravels the antagonistic actions of several molecular components of the ABA and cytokinin signaling pathways in mediates drought stress response, providing significant insights into how plants coordinate growth and drought stress response by integrating multiple hormone pathways.