Network pharmacology mechanisms and experimental verification of licorice in the treatment of ulcerative colitis

Ethnopharmacological relevance: Licorice is widely used in the treatment of ulcerative colitis (UC) and has good antioxidant and anti-inflammatory effects, but its specific active ingredients and mechanisms of action are still unknown. The purpose of the study: To elucidate the specific molecular mechanisms of licorice in the treatment of UC and to experimentally verify its activity. Methods: Through network pharmacology, the active ingredients of licorice and the molecular targets of UC were identified. A traditional Chinese medicine (TCM)-components-target-disease network diagram was established, and the binding energies of the active ingredient and targets of licorice were verified by molecular docking. A BALB/c mice model of UC was established by treatment with 3% dextran sulfate sodium (DSS). The effect of licorice on colon tissue injury was histologically assessed. The expression of IL-6 and IL-17 in colon tissue was detected by immunohistochemistry (IHC). Transmission electron microscopy (TEM) was used to observe morphological changes in mitochondria in the colon. Caco2 cells were treated with lipopolysaccharide (LPS) for 24 h to establish the cell inflammatory damage model, and cells were exposed to different concentrations of drugcontaining serum of Licorice (DCSL) for 24 h. In cells treated with the drug, the contents of oxidation markers were measured and ELISA was used to determine the levels of inflammatory factors in the cells. TEM was used to observe morphological changes in mitochondria. ZO-1 and occludin were detected by Western blotting. DCSL effects on autophagy were evaluated by treating cells with DCSL and autophagy inhibitor for 24 h after LPS injection. Small interfering ribonucleic acid (si-RNA) was used to silence Nrf2 gene expression in Caco2 cells to observe the effects of DCSL on autophagy through the Nrf2/PINK1 pathway. Nrf2, PINK1, HO-1, Parkin, P62, and LC3 were detected by Western blotting. Results: Ninety-one active ingredients and 339 action targets and 792 UC disease targets were identified, 99 of which were overlapping targets. Molecular docking was used to analyze the binding energies of liquiritin, liquiritigenin, glycyrrhizic acid, and glycyrrhetinic acid to the targets, with glycyrrhetinic acid having the strongest binding energy. In the UC mouse model, licorice improved colon histopathological changes, reduced levels of IL6 and IL-17 and repaired mitochondrial damage. In the LPS-induced inflammation model of Caco2 cells, DCSL decreased MDA, IL-1 beta, Il-6, and TNF-alpha levels and increased those of Superoxide Dismutase (SOD), glutathione peroxidase (GSH-PX), and IL-10, and improved the morphological changes of mitochondria. Increased expression of Nrf2, PINK1, Parkin, HO-1, ZO-1, occludin, P62, and LC3 promoted autophagy and reduced inflammation levels. Conclusion: Licorice improves UC, which may be related to the activation of the Nrf2/PINK1 signaling pathway that regulates autophagy.