Oregonin inhibits inflammation and protects against barrier disruption in intestinal epithelial cells.

BACKGROUND AND AIMS: Oregonin, a major diarylheptanoid derivative isolated from Alnus japonica, exerts anti-inflammatory effects; however, little is known about the effect of oregonin in intestinal inflammation. The current study investigated the potential of oregonin for clinical applications in the treatment of inflammatory bowel disease (IBD) and elucidated its underlying molecular mechanisms. METHODS: The anti-inflammatory effect of oregonin in tumor necrosis factor-α (TNF-α)-stimulated human intestinal epithelial HT-29 cells was investigated. In addition, the protective effect of oregonin was determined against disruption of the intestinal barrier in tert-butyl hydroperoxide (t-BH)-stimulated human intestinal epithelial Caco-2 cells. RESULTS: Oregonin suppressed the expression of cyclooxygenase-2 (COX-2), intercellular adhesion molecule-1 (ICAM-1), IL-8, and IL-1ß, and inhibited activation of nuclear factor κB (NF-κB) in HT-29 cells stimulated with TNF-α. Oregonin increased heme oxygenase-1 (HO-1) expression through the ERK1/2 and JNK-dependent signaling pathway, which contributed to the oregonin-mediated suppression of COX-2 expression in the HT-29 cells stimulated with TNF-α. Moreover, oregonin induced AMP-activated protein kinase (AMPK) activation. Knockdown of AMPK abolished the induction of HO-1 protein by oregonin and suppression of oregonin-mediated ICAM-1 and COX-2 expression in the HT-29 cells stimulated with TNF-α. Oregonin prevented the t-BH-induced increase in monolayer permeability through inhibition of the reduction in expression of zonula occludens-1 and occludin in Caco-2 cells. Targeting HO-1 by siRNA transfection attenuated the oregonin-mediated prevention of loss of tight junction proteins and increase in permeability. CONCLUSION: The findings of this study suggest that oregonin is a potential candidate for treatment of IBD by preventing mucosal inflammation and barrier disruption.

Ameliorative effect of Alnus japonica ethanol extract on colitis through the inhibition of inflammatory responses and attenuation of intestinal barrier disruption in vivo and in vitro.

Inflammatory bowel disease (IBD) is chronic inflammation of the gastrointestinal tract caused by high levels of pro-inflammatory cytokines and epithelial barrier dysfunction. Alnus japonica Steud. (Betulaceae) has been used in traditional Asian medicine. However, the potential of A. japonica for the treatment of intestinal inflammation has not been investigated. This study investigated the effects of ethanol extract from A. japonica bark (AJE) on colonic mucosa injury in mice with dextran sodium sulfate (DSS)-induced colitis. Treatment with AJE ameliorated pathological damage and the histopathologic features of DSS-induced colitis. The administration of AJE also inhibits DSS-induced pro-inflammatory cytokines expression, including interleukin (IL)-1ß, IL-6, tumor necrosis factor (TNF)-α, and cyclooxygenase (COX)-2. Notably, AJE administration attenuated the reduction of tight junction proteins, zonula occludens (ZO)-1 and occludin, in DSS-induced colitis. In addition, AJE increased heme oxygenase (HO)-1 expression and prevented DSS-induced apoptosis in colonic epithelial cells. Furthermore, in vitro studies demonstrated that AJE inhibits TNF-α-induced IL-8, IL-1ß, and COX-2 expression in human intestinal epithelial HT-29 cells and tert-butyl hydroperoxide-induced reduction of ZO-1 and occludin expression in human intestinal epithelial Caco-2 cells. AJE-induced HO-1 protein expression was also found in both HT-29 and Caco-2 cells. Taken together, our findings demonstrated that AJE inhibits intestinal inflammation and protects against intestinal barrier disruption in mice with DSS-induced colitis in vivo and human intestinal epithelial cells in vitro. These results suggest that AJE might have beneficial effects for the treatment of IBD.

Isoliquiritigenin inhibits TNF-α-induced release of high-mobility group box 1 through activation of HDAC in human intestinal epithelial HT-29 cells.

The suppression of pro-inflammatory cytokine-induced inflammation responses is an attractive pharmacological target for the development of therapeutic strategies for inflammatory bowel disease (IBD). In the present study, we evaluated the anti-inflammatory properties of flavonoid isoliquiritigenin (ISL) in intestinal epithelial cells and determined its mechanism of action. ISL suppressed the expression of inflammatory molecules, including IL-8, IL-1ß and COX-2, in TNF-α-stimulated HT-29 cells. Moreover, ISL induced activation of Nrf2 and expression of its target genes, such as HO-1 and NQO1. ISL also inhibited the TNF-α-induced NF-κB activation in HT-29 cells. High-mobility group box 1 (HMGB1), which is one of the critical mediators of inflammation, is actively secreted from inflammatory cytokine-stimulated immune or non-immune cells. ISL inhibited HMGB1 secretion by preventing TNF-α-stimulated HMGB1 relocation, whereas the RNA and protein expression levels of cellular HMGB1 did not change in response to TNF-α or ISL. Moreover, we found that HMGB1 acetylation was associated with HMGB1 translocation to the cytoplasm and the extracellular release in TNF-α-stimulated HT-29 cells; however, ISL significantly decreased the amount of acetylated HMGB1 in both the cytoplasm and extracellular space of HT-29 cells. Histone deacetylase (HDAC) inhibition by Scriptaid abrogated ISL-induced HDAC activity and reversed the ISL-mediated decrease in acetylated HMGB1 release in TNF-α-stimulated HT-29 cells, suggesting that, at least in TNF-α-stimulated HT-29 cells, ISL suppresses acetylated HMGB1 release via the induction of HDAC activity. Together, the current results suggest that inhibition of HMGB1 release via the induction of HDAC activity using ISL may be a promising therapeutic intervention for IBD.

Heme oxygenase-1 promotes tumor progression and metastasis of colorectal carcinoma cells by inhibiting antitumor immunity.

Heme oxygenase-1 (HO-1) is upregulated in colorectal carcinoma (CRC) cells. However, the role of HO-1 in the metastatic potential of CRC remains to be elucidated. In this study, we investigated the potential of HO-1 to control the antitumor immunity of CRC. Intercellular adhesion molecule-1 (ICAM-1) plays an important role in the immune surveillance system. Hemin-induced HO-1 expression suppressed the expression of ICAM-1 in human CRC cells. HO-1 regulated ICAM-1 expression via tristetraprolin, an mRNA-binding protein, at the posttranscriptional level in CRC cells. The upregulated HO-1 expression in CRC cells markedly decreased the adhesion of peripheral blood mononuclear lymphocytes (PBMLs) to CRC cells and PBML-mediated cytotoxicity against CRC cells. Production of CXCL10, an effector T cell-recruiting chemokine, was significantly reduced by the increased HO-1 expression. The expression of the CXCL10 receptor, CXCR3, decreased significantly in PBMLs that adhered to CRC cells. HO-1 expression correlated negatively, although nonsignificantly, with ICAM-1 and CXCL10 expression in xenograft tumors. Taken together, our data suggest that HO-1 expression is functionally linked to the mediation of tumor progression and metastasis of CRC cells by inhibiting antitumor immunity.

Anti-fibrotic effect of PF2401-SF, a standardized fraction of Salvia miltiorrhiza, in thioacetamide-induced experimental rats liver fibrosis.

We previously reported the in vitro and in vivo hepatoprotective and anti-fibrotic effects of PF2401-SF, a standardized fraction of Salvia miltiorrhiza, against acute and subacute liver injury. The aim of this study was to investigate the effect of PF2401-SF on liver fibrosis induced by thioacetamide (TAA), a chronic liver injury model (12 weeks) that closely resembles fibrosis and cirrhosis in humans. Hepatoprotective activity was indicated by low serum levels of the markers aspartate amino transferase and alanine amino transferase .In addition, compared to the TAA-group livers, the PF2401-SF-treated liver tissues showed no fibrous tissue deposition in the portal areas, hepatocyte morphology more closely resembling normal tissue morphology, and significantly reduced collagen deposition. Furthermore, downregulation of collagen 1(α) and tissue inhibitor of metalloproteinase (TIMP)1 protein and mRNA expression also supports PF2401-SF's anti-fibrotic effect. We also observed reduced expression of α-smooth muscle actin (α-SMA), an important marker of hepatic stellate cells (HSCs) activation. From these results, we conclude that PF2401-SF's anti-fibrotic mechanism in the TAA model involves reduced HSC activation, and may be mediated by downregulation of central markers of fibrosis, including collagen 1(α), TIMP1, and α-SMA.