BACKGROUND AND PURPOSEChemotherapeutic agents, including 5-fluorouracil (5-FU), frequently cause intestinal mucositis resulting in severe diarrhoea and morphological mucosal damage. 5-HT3 receptor antagonists are clinically effective in the treatment of nausea and emesis during cancer chemotherapy. Therefore we here have examined the effects of 5-HT3 receptor antagonists on 5-FU-induced intestinal mucositis in mice. EXPERIMENTAL APPROACHIntestinal mucositis was induced in male C57BL/6 mice by daily administration of 5-FU (50 mg·kg ), on the accompanying histology, cytokine production and apoptosis were assessed. KEY RESULTSContinuous administration of 5-FU to mice caused severe intestinal mucositis, which was histologically characterized by the shortening of villi and destruction of intestinal crypts, accompanied by body weight loss and diarrhoea. Daily ramosetron administration dose-dependently reduced the severity of intestinal mucositis, body weight loss and diarrhoea. Similar beneficial effects were observed with ondansetron. The number of apoptotic, caspase-3-and caspase-8-activated cells increased 24 h after the first 5-FU administration, and these responses were reduced by ramosetron. The up-regulation of TNF-a, IL-1b and IL-6 following 5-FU treatment was also attenuated by ramosetron. CONCLUSIONS AND IMPLICATIONS5-HT3 receptor antagonists ameliorated 5-FU-induced intestinal mucositis in mice, and this action could result from suppression of apoptotic responses in the intestinal crypt cells via inhibition of cytokine expression. Thus, 5-HT3 receptor antagonists may be useful for preventing not only nausea and emesis but also intestinal mucositis during 5-FU chemotherapy.

. Potential role of the NADPH oxidase NOX1 in the pathogenesis of 5-fluorouracil-induced intestinal mucositis in mice. Am J Physiol Gastrointest Liver Physiol 302: G1133-G1142, 2012. First published March 7, 2012 doi:10.1152/ajpgi.00535.2011.-Although NADPH oxidase 1 (NOX1) has been shown to be highly expressed in the gastrointestinal tract, the physiological and pathophysiological roles of this enzyme are not yet fully understood. In the present study, we investigated the role of NOX1 in the pathogenesis of intestinal mucositis induced by the cancer chemotherapeutic agent 5-fluorouracil (5-FU) in mice. Intestinal mucositis was induced in Nox1 knockout (Nox1KO) and littermate wild-type (WT) mice via single, daily administration of 5-FU for 5 days. In WT mice, 5-FU caused severe intestinal mucositis characterized by a shortening of villus height, a disruption of crypts, a loss of body weight, and diarrhea. In Nox1KO mice, however, the severity of mucositis was significantly reduced, particularly with respect to crypt disruption. The numbers of apoptotic caspase-3-and caspase-8-activated cells in the intestinal crypt increased 24 h after the first 5-FU administration but were overall significantly lower in Nox1KO than in WT mice. Furthermore, the 5-FU-mediated upregulation of TNF-␣, IL-1␤, and NOX1 and the production of reactive oxygen species were significantly attenuated in Nox1KO mice compared with that in WT mice. These findings suggest that NOX1 plays an important role in the pathogenesis of 5-FU-induced intestinal mucositis. NOX1-derived ROS production following administration of 5-FU may promote the apoptotic response through upregulation of inflammatory cytokines.

Clinical chemotherapy frequently causes intestinal mucositis as a side effect, which is accompanied by severe diarrhea. We recently showed that the cytokine-mediated apoptotic pathway might be important for the development of intestinal mucositis induced by 5-fluorouracil (5-FU). Saireito, the traditional Japanese herbal (Kampo) medicine, is widely used to treat diarrhea and various inflammatory diseases in Japan. In the present study, we investigated the effect of saireito on 5-FU-induced intestinal mucositis in mice, especially in relation to apoptosis in the intestinal crypt. Male C57BL/6 mice were given 5-FU (50 mg/kg), i.p. once daily for 6 days. Intestinal mucositis was evaluated histochemically. Saireito (100–1000 mg/kg) was administered p.o. twice daily for 6 days. Repeated 5-FU treatment caused severe intestinal mucositis including morphological damage, which was accompanied by body weight loss and diarrhea. Daily administration of saireito reduced the severity of intestinal mucositis in a dose-dependent manner. Body weight loss and diarrhea during 5-FU treatment were also significantly attenuated by saireito administration. The number of apoptotic and caspase-3-activated cells in the intestinal crypt was increased, and was accompanied by up-regulated tumor necrosis factor (TNF)-α and interleukin (IL)-1β mRNA within 24 h of the first 5-FU injection. However, all of these measures were significantly lower after saireito administration. These results suggest that saireito attenuates 5-FU-induced intestinal mucositis. This action may come from the reduction of apoptosis in the intestinal crypt via suppression of the up-regulation of inflammatory cytokines. Therefore, saireito may be clinically useful for the prevention of intestinal mucositis during cancer chemotherapy.

These findings indicate that an up-regulation of TRPV4 channels in vascular endothelial cells contributes to the progression of colonic inflammation by increasing vascular permeability. Thus, TRPV4 is an attractive target for the treatment of inflammatory bowel diseases.

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BACKGROUND AND PURPOSE5-HT (serotonin) regulates various physiological functions, both directly and via enteric neurons. The present study investigated the role of endogenous 5-HT and 5-HT 3 receptors in the pathogenic mechanisms involved in colonic inflammation, especially in relation to substance P (SP) and the neurokinin-1 (NK 1 ) receptor. EXPERIMENTAL APPROACHThe effects of 5-HT 3 and NK 1 receptor antagonists were examined in dextran sulphate sodium (DSS)-induced colitis in mice. Inflammatory mediator expression and the distribution of 5-HT 3 and NK 1 receptors were also determined. KEY RESULTSDaily administration of ramosetron and ondansetron (5-HT 3 antagonists) dose-dependently attenuated the severity of DSSinduced colitis and up-regulation of inflammatory mediator expression. Immunohistochemical analysis showed 5-HT 3 receptors are mainly expressed in vesicular ACh transporter-positive cholinergic nerve fibres in normal colon. DSS increased the number of colonic nerve fibres that were double positive for 5-HT 3 receptors and SP but not of those that were double positive for 5-HT 3 receptors and vesicular ACh transporter. DSS increased colonic SP levels and SP-positive nerve fibres; these responses were attenuated by ramosetron. DSS-induced colitis and up-regulation of inflammatory mediators were attenuated by aprepitant, an NK 1 antagonist. Immunohistochemical studies further revealed that DSS treatment markedly increased NK 1 receptor expression in CD11b-positive cells. CONCLUSIONS AND IMPLICATIONSThese findings indicate that the 5-HT/5-HT 3 receptor and SP/NK 1 receptor pathways play pathogenic roles in colonic inflammation. 5-HT acts via 5-HT 3 receptors to up-regulate inflammatory mediators and promote colonic inflammation. These effects may be further mediated by activation of macrophage NK 1 receptors via SP released from 5-HT 3 receptor-positive nerve fibres. The 5-HT 3 receptor is a ligand-gated cation channel and is widely distributed in brain and spinal cord neurones, as well as in the gastrointestinal tract (Farber et al., 2004). In the gastrointestinal tract, the 5-HT 3 receptor is involved in secretory, peristaltic, emetic and pain responses (Siriwardena et al., 1993;Jackson and Yakel, 1995;Hansen, 2003). Indeed, 5-HT 3 receptor antagonists have been used clinically for the treatment of chemotherapy-induced nausea/emesis and irritable bowel syndrome with diarrhoea (Minami et al., 1997;Kozlowski et al., 2000;Fukudo et al., 2014). We recently found that 5-HT 3 receptor antagonists such as ramosetron and ondansetron ameliorated intestinal injuries induced by the anticancer agent, 5-fluorouracil (5-FU), and the nonsteroidal anti-inflammatory drug, indomethacin (Kato et al., 2012;Yasuda et al., 2013). Several studies further showed that 5-HT 3 receptor antagonists reduced the severity of postoperative ileus and colitis (Mousavizadeh et al., 2009;Motavallian et al., 2013;Maehara et al., 2015). These findings suggest that endogenous 5-HT has pro-inflammatory effects that are mediated via 5-HT 3 ...

COVID-19, caused by SARS-CoV-2, has spread worldwide with a dire disaster situation.To urgently investigate the pathogenicity of COVID-19 and develop vaccines and therapeutics, animal models that are highly susceptible to SARS-CoV-2 infection are needed. In the present study, we established an animal model highly susceptible to SARS-CoV-2 via the intratracheal tract infection in CAG-promoter-driven human angiotensin-converting enzyme 2 transgenic (CAG-hACE2) mice. The CAG-hACE2 mice showed several severe symptoms of SARS-CoV-2 infection, with definitive weight loss and subsequent death. Acute lung injury with elevated cytokine and chemokine levels was observed at an early stage of infection in CAG-hACE2 mice infected with SARS-CoV-2. The analysis of the hACE2 gene in CAG-hACE2 mice revealed that more than 15 copies of hACE2 genes were tandemly integrated into the mouse genome, supporting the high susceptibility to SARS-CoV-2. In the developed model, immunization with viral antigen or injection of plasma from immunized mice prevented body weight loss and lethality due to infection with SARS-CoV-2. These results indicate that a highly susceptible model of SARS-CoV-2 infection in CAG-hACE2 mice via the intratracheal tract is suitable for evaluating vaccines and therapeutic medicines.

Transient receptor potential (TRP) vanilloid 1 (TRPV1) and TRP ankyrin 1 (TRPA1), which are non-selective cation channels, play important roles in the sensation of pain. This study investigated the roles of TRPV1 and TRPA1 in dextran sulfate sodium (DSS)-induced murine colitis. DSS (2%) administered for 7 days caused severe colitis that was significantly less severe in TRPV1-deficient (TRPV1KO) and TRPA1-deficient (TRPA1KO) mice than that in wild-type (WT) mice. Similar colitis attenuations were observed in TRPV1KO and TRPA1KO mice but not in WT mice that had been transplanted with bone marrow cells from WT, TRPA1KO, or TRPV1KO mice. DSS treatment upregulated calcitonin gene-relative peptide (CGRP)- and substance P (SP)-positive nerve fibers in the colonic mucosa of WT mice. TRPV1KO and TRPA1KO mice showed significant reductions in the DSS-induced upregulation of SP, but the DSS-induced upregulation of CGRP was not reduced. Sensory deafferentation evoked by pretreatment with high doses of capsaicin markedly exacerbated DSS-induced colitis with reductions in DSS-induced upregulation of SP- and CGRP-positive nerve fibers. These findings suggest that neuronal TRPV1 and TRPA1 contribute to the progression of colonic inflammation. While these responses may be mediated by the upregulation of SP-mediated deleterious mechanisms, CGRP may be associated with protective mechanisms.