miR-21 antagonist alleviates colitis and angiogenesis via the PTEN/PI3K/AKT pathway in colitis mice induced by TNBS.

Background: The pathogenesis of Crohn's disease (CD) is unknown; however, angiogenesis is known to play an important role in the disease. The present research suggests that microRNA-21 (miR-21) may play a positive regulatory role in disordered angiogenesis in CD. Methods: C57 wild-type mice were divided into 6 groups. On day 0, all mice in the 2,4,6-trinitrobenzenesulfonic acid (TNBS) group were given an enema at the concentration of TNBS 100 mg/kg mouse body weight (solvent 50% alcohol). In the control group, the enema was performed with 50% alcohol. On day 0, 2, 4, and 6, the mice of the agomir-21 + TNBS group and the agomir control + TNBS group were injected with 200 µL, 5 nmol agomir-21 or agomir control [dissolved in ribonuclease (RNase)-free water] by tail vein injection, while the antagomir-21 + TNBS group and the antagomir control + TNBS group were injected with 200 µL, 20 nmol antagomir-21 or antagomir control (dissolved in RNase-free water). The body weight and disease activity index (DAI) score were recorded daily. The colons were obtained to assess macro and microscopic colon damage. The inferior vena cava and the accompanying abdominal aorta were chosen to detect the protein expression of the phosphatase and tensin homolog (PTEN)/phosphoinositide 3-kinase (PI3K)/serine/threonine kinase (AKT)/vascular endothelial growth factor (VEGF) axis through western blotting. Serum interleukin-1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) were detected by enzyme-linked immunosorbent assay (ELISA). The distribution and expression of neovascularization were demonstrated by cluster of differentiation 31 (CD31) immunohistochemistry. Results: Compared with the only-TNBS group, the agomir-21 + TNBS group showed significantly severer colitis symptoms and more abnormal vascular hyperplasia, while the antagomir-21 + TNBS group showed symptom relief and reduced vascular hyperplasia. In addition, agomir-21 obviously inhibited the expression of PTEN and activated the PI3K/AKT/VEGF pathway in mice induced by TNBS, while antagomir-21 effectively antagonized this effect. Conclusions: miR-21 can promote the progression of colitis in mice induced by TNBS and aggravate the disordered angiogenesis by regulating the PTEN/PI3K/AKT axis. Intravenous injection of miR-21 antagonists can effectively relieve the symptoms of colitis and inhibit colonic angiogenesis.