Hideaki Tsukada

Effects of the anti‐ICAM‐1 monoclonal antibody on dextran sodium sulphate‐induced colitis in rats

Increased expression of intercellular adhesion molecule‐1 (ICAM‐1) in the colon of inflammatory bowel disease (IBD) has been reported. We evaluated the effects of monoclonal antibodies to ICAM‐1 on acute colitis induced by dextran sodium sulphate (DSS) in rats. Colitis was induced by feeding rats 3% DSS for 7 days. Anti‐ICAM‐1 antibody or vehicle alone was injected intraperitoneally in rats daily from day 0 to day 6. On day 7 the rats were killed and colitis was evaluated histologically. Prophylactic treatment with anti‐ICAM‐1 significantly attenuated colonic damage, neutrophil infiltration and the shortening of the colon in DSS colitis. Our findings demonstrate that ICAM‐1 plays an important role in this model of inflammatory bowel disease. Although this study does not directly address the effect of anti‐ICAM‐1 therapy in IBD, our findings encourage experiments using therapies that target ICAM‐1 in rats with already developed disease.

Adrenomedullin promotes epithelial restitution of rat and human gastric mucosa in vitro

We have investigated the effect of adrenomedullin (AM) on restitution of mucosal integrity following damage in rat and human gastric mucosa, measuring the potential difference (PD) on a mucosal strip mounted on an Ussing chamber. Mucosal damage was induced by 0.5, 1.0, and 2.0 M NaCl solution, and it caused an immediate and significant decrease in PD. In the rat AM group, PD recovered significantly more than in control group at 120 min after exposure to 0.5 M (p < 0.01) and 1.0 M (p < 0.05) NaCl solution. In the human AM group, PD completely recovered at 120 min after exposure to 0.5 M (p < 0.05) NaCl solution. In rat mucosa damaged by 0.5 M NaCl solution, the effect was inhibited by human (h)-CGRP(8-37) and there was no significant difference between the h-CGRP(8-37) group and control group. On immunohistochemical examination of rat gastric mucosa, AM was detected within the chief cell. AM probably promotes epithelial restitution primarily through the CGRP receptor, but it does not ameliorate more severe damage of gastric mucosa in vitro.

Aminoguanidine has both an anti-inflammatory effect on experimental colitis and a proliferative effect on colonic mucosal cells

BACKGROUND The aim of this study was to assess the effect of aminoguanidine (AG) on developed colitis and cell proliferation. METHODS Colitis was induced by means of trinitrobenzene sulphonic acid (TNB) in male Wistar rats weighing about 250 g. Seven days after induction of TNB colitis the rats were divided into two groups at random, and one group was orally treated with 1.5 micromol/kg AG each day. We assessed the effect of AG by measuring the mucosal damage, the ulcer area, myeloperoxidase (MPO) activity, inducible nitric oxide synthase (iNOs) activity, and nitrogen oxide in serum 7 days after the beginning of treatment. RESULTS AG significantly ameliorated the macroscopic damage score (AG versus control, 5.25 +/- 0.80 versus 7.50 +/- 0.50), the microscopic damage score (5.88 +/- 1.13 versus 9.25 +/- 0.31), ulcer area (0.57 +/- 0.14 versus 1.24 +/- 0.17 cm2), decreased MPO activity (51.5 +/- 9.4 versus 192.2 +/- 60 units/g tissue), and nitrogen oxide in serum (27.2 +/- 1.4 versus 32.3 +/- 1.8 microM) but did not decrease iNOs activity (8732 +/- 435 versus 8672 +/- 357 cpm/g tissue). Moreover, AG accelerated T84 cell proliferation in a dose-dependent manner. CONCLUSIONS These results suggest that AG ameliorates TNB colitis not only by its anti-inflammatory effect but also by accelerating the proliferation of colonic mucosal cells. AG, accordingly, might well be a useful new medicine to ameliorate inflammatory bowel disease.

Effects of a Thromboxane A2 Receptor Antagonist in an Animal Model of Inflammatory Bowel Disease

BACKGROUND/AIMS We evaluated the effects of an antagonist of the thromboxane A2 receptor (ONO-NT-126) in an animal model of inflammatory bowel disease (IBD). METHODS Colitis was induced by intracolonic instillation of trinitrobenzenesulfonic acid/ethanol in male Wistar rats. ONO-NT-126 or vehicle alone was administered intraluminally via anus once a day. The rats were killed after 7 days for assessment of colonic damage by the colonic damage score. RESULTS AND CONCLUSION ONO-NT-126 markedly reduced the colonic damage. Our findings suggest that the thromboxane-thromboxane receptor system plays an important role in this model of IBD and that antagonism of the thromboxane A2 receptor may prove useful for the treatment of IBD.

Effect of adrenomedullin on ion transport and muscle contraction in rat distal colon

We have investigated the effects of adrenomedullin (AM) on mucosal ion transport using the Ussing method and smooth muscle contraction using the Magnus method in rat. Our results indicate that AM increases Isc (short-circuit current) for Cl- secretion (100 nM:170.0 +/- 41.2%, 1 microM:193.8 +/- 45.5%, 100% Isc:28.2 +/- 3.1 microA/cm2) with an initial small decrease of Isc, inhibiting Na+ absorption. Tetrodotoxin (TTX) inhibits the Isc response elicited by AM (86%). In addition, AM relaxes potassium-induced contraction (10 nM:11.1 +/- 8.51%, 100 nM:33.4 +/- 12.7%, 100% contraction: 1.8 +/- 0.22 g), and TTX inhibits the response elicited by AM (90%). We conclude that AM modulates water and ion transport as well as bowel movement, mainly through the colonic nervous system.

Effects of okadaic acid on rat colon

Effects of okadaic acid (OA) on mucosal damagewere examined in rat colon. OA was sprinkled on ratcolon mucosa under observation with anelectronic-endoscopic system, and OA was also applied tothe in vivo microscopic field. The OA-induced changesin transepithelialconductance (Gt) weremeasured by the Ussing voltage clamp technique. Byendoscopic observation, the luminal sprinkling of OA (60nmol/kg) evoked transient microthrombi in the submucosalvenule, which was followed by mucosal edema.Histological study after endoscopic observation showedsubmucosal fluid retention, suggesting an increase of vascular permeability. The microthrombi werealso detected by in vivo microscopy. Byelectrophysiological study after endoscopic observationwith and without OA addition, the basal Gtvalues were 54 ± 6.2 and 36.2 ± 4.2 mS/cm2,respectively (P < 0.01). Furthermore in control rats,the serosal addition of OA evoked an increase inGt in a concentration-dependent mannerwithout increasing lactate dehydrogenase release. 2,4,6-Triaminopyrimidinium inhibitedOA-induced Gt change by 60%. These resultsindicate that OA evokes an increase in paracellularpermeability of epithelium. We conclude that thedeveloped microthrombi are the first key event of OA-induced mucosaldamage, followed by an increase in permeability in thesubmucosal venule and in the paracellular pathway of theepithelium.

Influence of Water-Immersion Stress on Synthesis of Mucus Glycoprotein in the Rat Gastric Mucosa

Gastric mucous cells of rats subjected to water-immersion stress were incubated with [3H]-palmitic acid and [14C]-N-acetylgalactosamine. The peptidyl-tRNA released by gastric polysomes was precipitated with cold ethanol and then the content was determined. A 70% reduction in the peptidyl-tRNA isolated was observed in the stressed rats, as compared with in control rats. The peptide recovered from the peptidyl-tRNA showed 30-50% less [3H]-palmitic acid and [14C]-N-acetylgalactosamine incorporation in the stressed rats than in normal controls. It was thus suggested that translation, acylation and glycosylation of the peptides in the ribosomes of the gastric mucosa were remarkably affected by the stress.

Effect of argatroban on trinitrobenzene sulfonic acid-induced colitis.

Background : Recent studies have suggested that heparin is effective for treatment of inflammatory bowel disease (IBD) and its various effects (in addition to the anticoagulant effect). We evaluated the effects of argatroban as an antithrombin drug on trinitrobenzene sulfonic acid (TNB)‐induced colitis, an established model of IBD.

Simultaneous measurement of colonic ion transport and muscle contraction

Thus far, studies of mucosal ion transport and muscle contraction have been conducted separately. 1 We have devised a new tnethod by which we can measure both short circuit current (Isc) and muscle contraction simultaneously. In this study, we employed this method to investigate the effects of endothelin-1 (ET1) on the rat distal colon. Endothelin was originally identified as a potent vasoconstrictive peptide in culture media conditioned by porcine aortic endothelial cells. 2 Three isopeptides of ET, now named ET-1, ET2, and ET-3, were subsequently identified by analysis of human genomic library. 3 These ET isopeptides exert various pharmacological actions, such as producing transient vasodilation and prolonged contraction of bronchial, intestinal, and uterine smooth muscles. 4

Effects of an aldose reductase inhibitor on gastroenteropathy in streptozotocin-diabetic rats.

We investigated the effects of epalrestat, an aldose reductase inhibitor (ARI), on gastric emptying, fecal water content, and electrolyte transport in distal colon in streptozotocin (STZ)-induced diabetic rats. We measured gastric emptying time by acetaminophen method and short-circuit-current (Isc) in colonic mucosa using an Ussing chamber. The Isc in response to electric-field-stimulation (EFS) was decreased in untreated rats due to suppression by Cl- secretion. ARI treatment alleviated this suppression (2.7 +/- 0.6 vs. 7.4 +/- 1.1 microA/0.38 cm2 at 8 weeks after treatment, 1.1 +/- 0.2 vs. 7.0 +/- 1.0 at 12 weeks after treatment, P<0.05). In addition, the percentage of fecal water content in untreated rats was significantly lower than in ARI-treated rats (58.0 +/- 2.0 vs. 67.6 +/- 0.8% at 8 weeks, 56.9 +/- 2.1 vs. 63.4 +/- 1.4 at 12 weeks, P<0.05). From STZ injection to 8 weeks, the serum levels of acetaminophen in the diabetic rats were significantly lower than in controls, indicating delayed gastric emptying. At 12 weeks in the diabetic rats treated with ARI, the serum levels of acetaminophen were significantly higher than in the untreated diabetic rats (6.6 +/- 0.4 vs. 3.5 +/- 0.5 microg/ml, P<0.05). ARI-treatment ameliorated delayed gastric emptying without improving glycemic control. These findings show that ARI partially prevented progression of impaired gastric emptying, ion transport, and water transport, and suggest that epalrestat might be useful in the treatment of diabetic gastroenteropathy.