Protective effects of Ligularia fischeri root extracts against ulcerative colitis in mice through activation of Bcl-2/Bax signalings

BACKGROUND

Ulcerative colitis (UC) is a chronic inflammatory bowel disease characterized by high levels of proinflammatory cytokines and epithelial barrier dysfunction. The root of Ligularia fischeri (Ledeb.) Turcz. is a traditional Chinese medicinal herb with diverse therapeutic properties, which has been successfully used to treat inflammation-related diseases. However, little is known about its effect and mechanism against UC.

PURPOSE

To investigate the efficacy and mechanism of L. fischeri root extracts against UC.

METHODS

L. fischeri root samples were prepared using the alcohol extraction method and liquid-liquid extraction method. A dextran sodium sulfate-induced UC mouse model and a lipopolysaccharide (LPS)-induced inflammatory cell model were employed in the present study. Cell apoptosis was detected by TUNEL staining, and an enzyme-linked immunosorbent assay was used to quantify the abundance of inflammatory factors in tissues. Hematoxylin and eosin staining and Masson staining were employed to analyze drug toxicity to the liver and kidney. A myeloperoxidase (MPO) assay kit was used to detect neutrophil infiltration in colon tissues. RT-qPCR was then employed to quantify the transcriptional levels of proinflammatory and apoptotic-related genes, while tight junction and apoptosis-related proteins were quantified via western blotting. Gas Chromatography/Mass Spectrometry analysis was then performed to identify the natural compounds in L. fischeri root extracts.

RESULTS

The water decoction extract, methanol extract, and especially the chloroform extract (CE) exerted potent therapeutic effects in UC mice. Similar to the positive control group (5-aminosalicylic acid), oral administration of CE (30, 60, and 90 mg/kg/d) elicited distinct therapeutic effects on UC mice in the medium- and high-dose groups. CE decreased disease activity index, histopathological score, and MPO level significantly, and effectively retained the colon length. Furthermore, CE significantly reduced the levels of proinflammatory cytokines, including interleukin (IL)-1β, IL-6, and tumor necrosis factor-α and enhanced the expression of tight junction proteins, such as zonula occludens (ZO)-1, ZO-2, claudin-1, and occludin, as well as the transcriptional levels of mucins, such as MUC-1 and MUC-2, in UC mice. Notably, CE prevented apoptosis of colonic epithelial cells by up-regulating Bcl-2 and down-regulating Bax. Also, CE inhibited the secretion of pro-inflammatory cytokines and apoptosis in LPS-induced RAW264.7 macrophages via the activation of Bcl-2/Bax signals.

CONCLUSIONS

Collectively, L. fischeri root extracts, especially CE, have obvious therapeutic effects against UC. CE reduces inflammation and protects the intestinal epithelial cells and intestinal epithelial barrier via activation of the Bcl-2/Bax signaling pathway, and may be a promising therapeutic agent for UC treatment.