Enterotoxigenic Bacteroides fragilis (ETBF) has emerged as a gut microbiome pathogen that can promote colitis associated cancer in humans. ETBF secretes the metalloprotease, B. fragilis toxin (BFT), which can induce ectodomain cleavage of E-cadherin and IL-8 secretion through the β-catenin, NF-κB, and MAPK pathways in intestinal epithelial cells. However, it is still unclear whether E-cadherin cleavage is required for BFT induced IL-8 secretion and the relative contribution of these signaling pathways to IL-8 secretion. Using siRNA knockdown and CRISPR knockout studies, we found that E-cadherin cleavage is required for BFT mediated IL-8 secretion. In addition, genetic ablation of β-catenin indicates that β-catenin is required for the BFT induced increase in transcriptional activity of NF-κB, p65 nuclear localization and early IL-8 secretion. These results suggest that BFT induced β-catenin signaling is upstream of NF-κB activation. However, despite β-catenin gene disruption, BFT still activated the MAPK pathway, suggesting that the BFT induced activation of the MAPK signaling pathway is independent from the E-cadherin/β-catenin/NF-κB pathway. These findings show that E-cadherin and β-catenin play a critical role in acute inflammation following ETBF infection through the inflammatory response to BFT in intestinal epithelial cells.

Osteoporosis is a common disease caused by an imbalance of processes between bone resorption by osteoclasts and bone formation by osteoblasts in postmenopausal women. The roots of Gentiana lutea L. (GL) are reported to have beneficial effects on various human diseases related to liver functions and gastrointestinal motility, as well as on arthritis. Here, we fractionated and isolated bioactive constituent(s) responsible for anti-osteoporotic effects of GL root extract. A single phytochemical compound, loganic acid, was identified as a candidate osteoprotective agent. Its anti-osteoporotic effects were examined in vitro and in vivo. Treatment with loganic acid significantly increased osteoblastic differentiation in preosteoblast MC3T3-E1 cells by promoting alkaline phosphatase activity and increasing mRNA expression levels of bone metabolic markers such as Alpl, Bglap, and Sp7. However, loganic acid inhibited osteoclast differentiation of primary-cultured monocytes derived from mouse bone marrow. For in vivo experiments, the effect of loganic acid on ovariectomized (OVX) mice was examined for 12 weeks. Loganic acid prevented OVX-induced bone mineral density loss and improved bone structural properties in osteoporotic model mice. These results suggest that loganic acid may be a potential therapeutic candidate for treatment of osteoporosis.

Enterotoxigenic Bacteroides fragilis (ETBF) is human intestinal commensal bacterium and a potent initiator of colitis through secretion of the metalloprotease Bacteroides fragilis toxin (BFT). BFT induces cleavage of E-cadherin in colon cells, which subsequently leads to NF-κB activation. Zerumbone is a key component of the Zingiber zerumbet (L.) Smith plant and can exhibit anti-bacterial and anti-inflammatory effects. However, whether zerumbone has anti-inflammatory effects in ETBF-induced colitis remains unknown. The aim of this study was to determine the anti-inflammatory effect of orally administered zerumbone in a murine model of ETBF infection. Wild-type C57BL/6 mice were infected with ETBF and orally administered zerumbone (30 or 60 mg/kg) once a day for 7 days. Treatment of ETBF-infected mice with zerumbone prevented weight loss and splenomegaly and reduced colonic inflammation with decreased macrophage infiltration. Zerumbone treatment significantly decreased expression of IL-17A, TNF-α, KC, and inducible nitric oxide synthase (iNOS) in colonic tissues of ETBF-infected mice. In addition, serum levels of KC and nitrite was also diminished. Zerumbone-treated ETBF-infected mice also showed decreased NF-κB signaling in the colon. HT29/C1 colonic epithelial cells treated with zerumbone suppressed BFT-induced NF-κB signaling and IL-8 secretion. However, BFT-mediated E-cadherin cleavage was unaffected. Furthermore, zerumbone did not affect ETBF colonization in mice. In conclusion, zerumbone decreased ETBF-induced colitis through inhibition of NF-κB signaling.

Osteoarthritis (OA) is a common degenerative disease that results in joint inflammation as well as pain and stiffness. A previous study has reported that Cornus officinalis (CO) extract inhibits oxidant activities and oxidative stress in RAW 264.7 cells. In the present study, we isolated bioactive compound(s) by fractionating the CO extract to elucidate its antiosteoarthritic effects. A single bioactive component, morroniside, was identified as a potential candidate. The CO extract and morroniside exhibited antiosteoarthritic effects by downregulating factors associated with cartilage degradation, including cyclooxygenase-2 (Cox-2), matrix metalloproteinase 3 (Mmp-3), and matrix metalloproteinase 13 (Mmp-13), in interleukin-1 beta (IL-1β)-induced chondrocytes. Furthermore, morroniside prevented prostaglandin E2 (PGE2) and collagenase secretion in IL-1β-induced chondrocytes. In the destabilization of the medial meniscus (DMM)-induced mouse osteoarthritic model, morroniside administration attenuated cartilage destruction by decreasing expression of inflammatory mediators, such as Cox-2, Mmp3, and Mmp13, in the articular cartilage. Transverse microcomputed tomography analysis revealed that morroniside reduced DMM-induced sclerosis in the subchondral bone plate. These findings suggest that morroniside may be a potential protective bioactive compound against OA pathogenesis.

Bone remodeling is a continuous process of bone synthesis and destruction that is regulated by osteoblasts and osteoclasts. Here, we investigated the anti-osteoporotic effects of morroniside in mouse preosteoblast MC3T3-E1 cells and mouse primary cultured osteoblasts and osteoclasts in vitro and ovariectomy (OVX)-induced mouse osteoporosis in vivo. Morroniside treatment enhanced alkaline phosphatase activity and positively stained cells via upregulation of osteoblastogenesis-associated genes in MC3T3-E1 cell lines and primary cultured osteoblasts. However, morroniside inhibited tartrate-resistant acid phosphatase activity and TRAP-stained multinucleated positive cells via downregulation of osteoclast-mediated genes in primary cultured monocytes. In the osteoporotic animal model, ovariectomized (OVX) mice were administered morroniside (2 or 10 mg/kg/day) for 12 weeks. Morroniside prevented OVX-induced bone mineral density (BMD) loss and reduced bone structural compartment loss in the micro-CT images. Taken together, morroniside promoted increased osteoblast differentiation and decreased osteoclast differentiation in cells, and consequently inhibited OVX-induced osteoporotic pathogenesis in mice. This study suggests that morroniside may be a potent therapeutic single compound for the prevention of osteoporosis.

Chronic inflammation has been linked to colitis-associated colorectal cancer in humans. The human symbiont enterotoxigenic Bacteroides fragilis (ETBF), a pro-carcinogenic bacterium, has the potential to initiate and/or promote colorectal cancer. Antibiotic treatment of ETBF has shown promise in decreasing colonic polyp formation in murine models of colon cancer. However, there are no reported natural products that have shown efficacy in decreasing polyp burden. In this study, we investigated the chemopreventive effects of oral administration of zerumbone in ETBF-colonized mice with azoxymethane (AOM)/dextran sulfate sodium (DSS)-induced tumorigenesis. Zerumbone significantly reduced the severity of disease activity index (DAI) scores as well as several parameters of colonic inflammation (i.e., colon weight, colon length, cecum weight and spleen weight). In addition, inflammation of the colon and cecum as well as hyperplasia was reduced. Zerumbone treatment significantly inhibited colonic polyp numbers and prevented macroadenoma progression. Taken together, these findings suggest that oral treatment with zerumbone inhibited ETBF-promoted colon carcinogenesis in mice indicating that zerumbone could be employed as a promising protective agent against ETBF-mediated colorectal cancer.