5-HT₃ receptor antagonists ameliorate 5-fluorouracil-induced intestinal mucositis by suppression of apoptosis in murine intestinal crypt cells

BACKGROUND AND PURPOSE

Chemotherapeutic 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 APPROACH

Intestinal mucositis was induced in male C57BL/6 mice by daily administration of 5-FU (50 mg·kg⁻¹) for 5 days. Effects of 5-HT₃ receptor antagonists, ramosetron (0.01-0.1 mg·kg⁻¹) and ondansetron (5 mg·kg⁻¹), on the accompanying histology, cytokine production and apoptosis were assessed.

KEY RESULTS

Continuous 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-α, IL-1β and IL-6 following 5-FU treatment was also attenuated by ramosetron.

CONCLUSIONS AND IMPLICATIONS

5-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.

Cinacalcet, a calcimimetic, prevents nonsteroidal antiinflammatory drug-induced small intestinal damage in rats

The extracellular calcium-sensing receptor (CaSR), a G protein-coupled cell receptor cloned from bovine parathyroid, has been demonstrated to play a regulatory role in various functions of the gastrointestinal tract. In the present study, we examined the effect of cinacalcet, a drug that acts as a calcimimetic through the allosteric activation of CaSR, on the loxoprofen-induced small intestinal lesions and investigated the mechanisms involved in the protective action. Male Sprague-Dawley rats were used without fasting. The animals were administered loxoprofen p.o. and euthanized 24 hours later and the intestinal mucosa was examined for lesions. Cinacalcet was given p.o. twice, 30 min before and 6 h after loxoprofen. Loxoprofen caused hemorrhagic lesions in the small intestine, accompanied by the upregulation of enterobacterial invasion, myeloperoxidase (MPO) activity and inducible nitric oxide synthase (iNOS)/tumor necrosis factor α (TNF-α) expression as well as the downregulation of Muc2 expression. Prior administration of cinacalcet dose-dependently and significantly reduced the severity of these lesions in response to loxoprofen, with concomitant suppression of the changes in bacterial invasion, iNOS/TNF-α as well as Muc2 expression, and myeloperoxidase activity. Cinacalcet also significantly reversed a decrease in mucus secretion and fluid secretion in the small intestine caused by loxoprofen, but had no effect on the intestinal hypermotility or prostaglandin E₂ deficiency caused by loxoprofen. These results suggest that cinacalcet protects the small intestine against loxoprofen-induced damage, and this effect may be functionally associated with an increase in fluid secretion and a reversal of downregulation of Muc2 expression caused by loxoprofen, resulting in suppression of bacterial invasion and iNOS/TNF-α expression, the major pathogenic events in nonsteroidal antiinflammatory drugs-induced small intestinal ulceration.

An Adaptor Molecule Afadin Regulates Lymphangiogenesis by Modulating RhoA Activity in the Developing Mouse Embryo

Afadin is an intracellular binding partner of nectins, cell-cell adhesion molecules, and plays important roles in the formation of cell-cell junctions. Afadin-knockout mice show early embryonic lethality, therefore little is known about the function of afadin during organ development. In this study, we generated mice lacking afadin expression in endothelial cells, and found that the majority of these mice were embryonically lethal as a result of severe subcutaneous edema. Defects in the lymphatic vessels of the skin were observed, although the morphology in the blood vessels was almost normal. Severe disruption of VE-cadherin-mediated cell-cell junctions occurred only in lymphatic endothelial cells, but not in blood endothelial cells. Knockout of afadin did not affect the differentiation and proliferation of lymphatic endothelial cells. Using in vitro assays with blood and lymphatic microvascular endothelial cells (BMVECs and LMVECs, respectively), knockdown of afadin caused elongated cell shapes and disruption of cell-cell junctions among LMVECs, but not BMVECs. In afadin-knockdown LMVECs, enhanced F-actin bundles at the cell periphery and reduced VE-cadherin immunostaining were found, and activation of RhoA was strongly increased compared with that in afadin-knockdown BMVECs. Conversely, inhibition of RhoA activation in afadin-knockdown LMVECs restored the cell morphology. These results indicate that afadin has different effects on blood and lymphatic endothelial cells by controlling the levels of RhoA activation, which may critically regulate the lymphangiogenesis of mouse embryos.

ROS evaluation for a series of CNTs and their derivatives using an ESR method with DMPO

Carbon nanotubes (CNTs) are important materials in advanced industries. It is a concern that pulmonary exposure to CNTs may induce carcinogenic responses. It has been recently reported that CNTs scavenge ROS though non-carbon fibers generate ROS. A comprehensive evaluation of ROS scavenging using various kinds of CNTs has not been demonstrated well. The present work specifically investigates ROS scavenging capabilities with a series of CNTs and their derivatives that were physically treated, and with the number of commercially available CNTs. CNT concentrations were controlled at 0.2 through 0.6 wt%. The ROS scavenging rate was measured by ESR with DMPO. Interestingly, the ROS scavenging rate was not only influenced by physical treatments, but was also dependent on individual manufacturing methods. Ratio of CNTs to DMPO/ hydrogen peroxide is a key parameter to obtain appropriate ROS quenching results for comparison of CNTs. The present results suggest that dangling bonds are not a sole factor for scavenging, and electron transfer on the CNT surface is not clearly determined to be the sole mechanism to explain ROS scavenging.

Prophylactic effect of egualen sodium, a stable azulene derivative, on gastrointestinal damage induced by ischemia/reperfusion, double antiplatelet therapy and loxoprofen in rats

We examined the effect of egualen, a stable azulene derivative, against gastric damage induced by ischemia/reperfusion (I/R), gastric bleeding induced by double antiplatelet therapy with aspirin (ASA) plus clopidogrel, and small intestinal damage generated by loxoprofen, and investigated the possible mechanisms involved in its protective action. Male C57BL/6 mice or SD rats were used under urethane anesthesia (gastric lesions) or in a conscious (intestinal lesions) state. I/R-induced gastric injury was produced in mice by clamping the celiac artery for 30 min, followed by reperfusion for 60 min. Gastric bleeding was induced in rats by luminal perfusion with 25 mM ASA+50 mM HCl for 2 hours in the presence of clopidogrel (30 mg/kg). To produce small intestinal lesions the rats were given loxoprofen (60 mg/kg) p.o. and killed 24 hours later. Egualen was given i.d. 60 min before I/R or ASA perfusion, while given p.o. twice 30 min before and 6 hours after loxoprofen. Egualen significantly prevented the I/R-induced gastric damage, and the effect was equivalent to that of seratrodast (TXA2 antagonist). This agent also significantly suppressed gastric bleeding induced by ASA plus clopidogrel, similar to PGE2. Likewise, egualen significantly prevented loxoprofen-induced damage in the small intestine, accompanied by an increase in the secretion of mucus and suppression of bacterial invasion as well as iNOS expression. These results suggest that egualen has a prophylactic effect against various lesions in the gastrointestinal mucosa, probably through its characteristic pharmacological properties, such as TXA2 antagonistic action, local mucosal protection, and stimulation of mucus secretion.

[A case of duodenal epithelioid hemangioma causing gastrointestinal bleeding]

A case of epithelioid hemangioma of the duodenum causing bleeding was encountered. A 32-year-old man was admitted because of anemia. Endoscopic examination revealed a submucosal tumor with central depression in the 2nd portion of the duodenum. It was considered to be the bleeding focus of anemia. A partial resection of the duodenum was performed. The macro- and microscopic examination of the specimen revealed an epithelioid hemangioma. Hemangiomas of the intestinal tract are rare, representing only 0.3% of all tumors of the intestinal tract, and among them, hemangiomas of the duodenum are extremely rare, representing only 3.4% of those of the intestinal tract. Most hemangiomas of the duodenum are cavernous hemangiomas or capillary hemangiomas. We report the first case of epithelioid hemangioma of the duodenum.

CD44 with variant exons 8-10 in colorectal tumors

Using a fusion protein encoded by variant exon (v) 8-10 of CD44, a monoclonal antibody (mAb) 44-1V reactive with v9 product was generated. Western immunoblots and reverse transcriptase-polymerase chain reaction/Southern blot revealed that a 130 kilodalton component containing v8-10 products was specifically expressed in colorectal and gastric cancer cell lines. Immunohistological examination of 179 pairs of colorectal cancer and normal tissues revealed that about 47% of cancers expressed the CD44 variant (CD44v8-10), and its expression correlated with hematogenous and lymph node metastasis. These findings suggest the usefulness of CD44v8-10 in the prediction of colorectal cancer metastasis.

Sialyl-lewis-x antigen immunoreaction of colorectal-cancer and its relationship to hematogenous metastasis

The adhesion of cancer cells to endothelial cells of the target organ is one of the most important steps of hematogenous metastasis. Especially, sialyl Le(X) plays an important role in defining the metastasis. The expression of sialyl Le(X) antigen in colorectal cancer and its usefulness not only as an indicator of metastatic potential but also as a prognostic factor was studied immunohistochemically. Fifty-five (32.4%) sialyl Le(X) antigen-positive tumors were found in 170 colorectal cancers. There was a significant correlation between the expression of sialyl Le(X) antigen and the histological tumor type, venous invasion, lymph node metastasis, as well as liver metastasis. Hematogenous metastases were significantly more frequent in patients with sialyl Le(X)-positive tumor than in those with sialyl Le(X)-negative tumor; and prognosis was significantly poorer in the former. The results suggest that sialyl Le(X) antigen plays a role in hematogenous metastasis of colorectal cancer, and that the expression of sialyl Le(X) is associated with poor prognosis.

Domain 5 of high molecular weight kininogen inhibits collagen-mediated cancer cell adhesion and invasion in association with α-actinin-4

High molecular weight kininogen (HK) is a plasma glycoprotein with multiple functions, including the regulation of coagulation. We previously demonstrated that domain 5 (D5(H)), a functional domain of HK, and its derived peptides played an important role in the vitronectin-mediated suppression of cancer cell adhesion and invasion. However, the underlying mechanisms of the D5(H)-mediated suppressive effects remain to be elucidated. Here, we showed that D5(H) and its derivatives inhibited the collagen-mediated cell adhesion and invasion of human osteosarcoma MG63 cells. Using purified D5(H) fused to glutathione-S-transferase (GST) and D5(H)-derived peptides for column chromatography, an actin-binding protein, α-actinin-4, was identified as a binding protein of D5(H) with high-affinity for P-5m, a core octapeptide of D5(H). Immunofluorescence microscopy demonstrated that D5(H) co-localized with α-actinin-4 inside MG63 cells. In addition, exogenous GST-D5(H) added to the culture media was transported into MG63 cells, although GST alone as a control was not. As α-actinin-4 regulates actin polymerization necessary for cell adhesion and is related to the integrin-dependent attachment of cells to the extracellular matrix, our results suggest that D5(H) may modulate cell adhesion and invasion together with actinin-4.