Phytoestrogen arctigenin preserves the mucus barrier in inflammatory bowel diseases by inhibiting goblet cell apoptosis via the ERß/TRIM21/PHB1 pathway.

Intestinal mucus barrier dysfunction is closely involved in the pathogenesis of inflammatory bowel diseases (IBD). To investigate the protective effect and underlying mechanism of arctigenin, a phytoestrogen isolated from the fruits of Arctium lappa L., on the intestinal mucus barrier under colitis condition. The role of arctigenin on the intestinal mucus barrier and the apoptosis of goblet cells were examined by using both in vitro and in vivo assays. Arctigenin was demonstrated to promote the mucus secretion and maintain the integrity of mucus barrier, which might be achieved by an increase in the number of goblet cells via inhibiting apoptosis. Arctigenin selectively inhibited the mitochondrial pathway-mediated apoptosis. Moreover, arctigenin elevated the protein level of prohibitin 1 (PHB1) through blocking the ubiquitination via activation of estrogen receptor ß (ERß) to competitively interact with PHB1 and disrupt the binding of tripartite motif 21 (TRIM21) with PHB1. ERß knock down in the colons of mice with DSS-induced colitis resulted in significant reduction of the protection of arctigenin and DPN against the mucosal barrier. Arctigenin can maintain the integrity of the mucus barrier by inhibiting the apoptosis of goblet cells through the ERß/TRIM21/PHB1 pathway.

Oral administration of curcumin ameliorates pulmonary fibrosis in mice through 15d-PGJ2-mediated induction of hepatocyte growth factor in the colon.

Oral administration of curcumin has been shown to inhibit pulmonary fibrosis (PF) despite its extremely low bioavailability. In this study, we investigated the mechanisms underlying the anti-PF effect of curcumin in focus on intestinal endocrine. In bleomycin- and SiO2-treated mice, curcumin (75, 150 mg· kg-1 per day) exerted dose-dependent anti-PF effect when administered orally or rectally but not intravenously, implying an intestinal route was involved in the action of curcumin. We speculated that curcumin might promote the generation of gut-derived factors and the latter acted as a mediator subsequently entering the lungs to ameliorate fibrosis. We showed that oral administration of curcumin indeed significantly increased the expression of gut-derived hepatocyte growth factor (HGF) in colon tissues. Furthermore, in bleomycin-treated mice, the upregulated protein level of HGF in lungs by oral curcumin was highly correlated with its anti-PF effect, which was further confirmed by coadministration of c-Met inhibitor SU11274. Curcumin (5-40 µM) dose-dependently increased HGF expression in primary mouse fibroblasts, macrophages, CCD-18Co cells (fibroblast cell line), and RAW264.7 cells (monocyte-macrophage cell line), but not in primary colonic epithelial cells. In CCD-18Co cells and RAW264.7 cells, curcumin dose-dependently activated PPARγ and CREB, whereas PPARγ antagonist GW9662 (1 µM) or cAMP response element (CREB) inhibitor KG-501 (10 µM) significantly decreased the boosting effect of curcumin on HGF expression. Finally, we revealed that curcumin dose-dependently increased the production of 15-deoxy-Δ12, 14-prostaglandin J2 (15d-PGJ2) in CCD-18Co cells and RAW264.7 cells, which was a common upstream of the two transcription factors. Moreover, both the in vitro and in vivo effects of curcumin were diminished by coadministration of HPGDS-inhibitor-1, an inhibitor of 15d-PGJ2 generation. Together, curcumin promotes the expression of HGF in colonic fibroblasts and macrophages by activating PPARγ and CREB via an induction of 15d-PGJ2, and the HGF enters the lungs giving rise to an anti-PF effect.

Norisoboldine, a natural aryl hydrocarbon receptor agonist, alleviates TNBS-induced colitis in mice, by inhibiting the activation of NLRP3 inflammasome.

Although the etiology of inflammatory bowel disease is still uncertain, increasing evidence indicates that the excessive activation of NLRP3 inflammasome plays a major role. Norisoboldine (NOR), an alkaloid isolated from Radix Linderae, has previously been demonstrated to inhibit inflammation and IL-1ß production. The present study was to examine the effect of NOR on colitis and the underlying mechanism related to NLRP3 inflammasome activation. Our results showed that NOR alleviated colitis symptom in mice induced by 2, 4, 6-trinitrobenzene sulfonic acid (TNBS). Moreover, it significantly reduced expressions of cleaved IL-1ß, NLRP3 and cleaved Caspase-1 but not ASC in colons of mice. In THP-1 cells, NOR suppressed the expressions of NLRP3, cleaved Caspase-1 and cleaved IL-1ß but not ASC induced by lipopolysaccharide (LPS) and adenosine triphosphate (ATP). Furthermore, NOR could activate aryl hydrocarbon receptor (AhR) in THP-1 cells, inducing CYP1A1 mRNA expression, and promoting dissociation of AhR/HSP90 complexes, association of AhR and ARNT, AhR nuclear translocation, XRE reporter activity and binding activity of AhR/ARNT/XRE. Both siAhR and α-naphthoflavone (α-NF) markedly diminished the inhibition of NOR on NLRP3 inflammasome activation. In addition, NOR elevated Nrf2 level and reduced ROS level in LPS- and ATP-stimulated THP-1 cells, which was reversed by either siAhR or α-NF treatment. Finally, correlations between activation of AhR and attenuation of colitis, inhibition of NLRP3 inflammasome activation and up-regulation of Nrf2 level in colons were validated in mice with TNBS-induced colitis. Taken together, NOR ameliorated TNBS-induced colitis in mice through inhibiting NLRP3 inflammasome activation via regulating AhR/Nrf2/ROS signaling pathway.