Longitudinal prostaglandin E(2) generation in various organs during evolution of experimental portal hypertension

It has been suggested that the arteriolar vasodilatation and hyperdynamic circulation observed in rats with partial portal vein ligation (PPVL) is caused by increased splanchnic and systemic delivery of vasodilator substances. The aims of our study were to determine organ-specific generation of prostaglandin E(2) (PGE(2)) in rats with PPVL during the evolution of portal hypertension. Rats with PPVL and sham-operated (S) rats were studied in the first, third, fourth and 14th postoperative days. They were anesthetized and splenic pulp pressure and blood pressure were measured. Spleen, colon and lungs were removed and the splenic, pulmonary and mucosal colonic PGE(2) were determined. All PPVL rats developed sequential hemodynamic changes compatible with evolving portal hypertension. Splenic pulp pressure was higher in PPVL rats compared with S rats during all days of the study. Within the group of PPVL the splenic pulp pressure was higher in the first postoperative day and decreased in the ensuing days. No changes in splenic and colonic PGE(2) generation were noted during the study period. Pulmonary PGE(2) generation increased significantly in the first postoperative day in PPVL rats compared with S rats. However, similar increase was observed on the third postoperative day in S rats. PGE(2) probably has no role in splanchnic hemodynamic changes during evolution of portal hypertension. Pulmonary PGE(2) generation may increase as a response to increased portal pressure, or to abdominal surgery.

Renal effects of nabumetone, a COX-2 antagonist: impairment of function in isolated perfused rat kidneys contrasts with preserved renal function in vivo

The constitutive cyclooxygenase (COX)-1 enzyme has been considered the physiologically important isoform for prostaglandin synthesis in the normal kidney. It has, therefore, been suggested that selective inhibitors of the 'inducible' isoform (COX-2) may be free from renal adverse effects. We studied the renal effects of the predominantly COX-2 antagonist nabumetone in isolated perfused kidneys. As compared with controls, kidneys removed after in vivo administration of oral nabumetone (15 mg/kg) disclosed altered renal function with reduced glomerular filtration rate, filtration fraction, and urine volume and enhanced hypoxic outer medullary tubular damage. By contrast, renal function and morphology were not affected in vivo by nabumetone or its active metabolite 6-methoxy-2-naphthylacetic acid. The latter agent (10-20 mg/kg i.v.) did not significantly alter renal microcirculation, as opposed to a selective substantial reduction in medullary blood flow noted with the nonselective COX inhibitor indomethacin (5 mg/kg i.v.). In a rat model of acute renal failure, induced by concomitant administration of radiocontrast, nitric oxide synthase, and COX inhibitors, the decline in kidney function and the extent of hypoxic medullary damage with oral nabumetone (80 mg/kg) were comparable to a control group, and significantly less than those induced by indomethacin. In rats subjected to daily oral nabumetone for 3 consecutive weeks, renal function and morphology were preserved as well. Both nabumetone and 6-methoxy-2-naphthylacetic acid reduced renal parenchymal prostaglandin E2 to the same extent as indomethacin. It is concluded that while nabumetone adversely affects renal function and may intensify hypoxic medullary damage ex vivo, rat kidneys are not affected by this agent in vivo, both in acute and chronic studies. COX selectivity may not explain the renal safety of nabumetone.

Ozone enema: a model of microscopic colitis in rats

Ozone is one of the most powerful oxidants available, with many applications in industry and medicine. Medically relevant features of ozone include bacterial and virucidal properties, disinfection, sterilization, circulatory stimulation, and disruption of malignant cells. Ozone therapy is administered in various ways, including intravenously, intramuscularly, and intrarectally. The latter modality is used for the treatment of colitis and hepatitis. Our aim was to examine the effect of ozone water enema on normal and inflamed rat colonic mucosa. Ozone water (20 microg/ml) was prepared via ozone generator and administered intrarectally (0.5 ml) daily. Rats were killed one, three, and seven days after rectal ozone water administration, and their colons resected, rinsed, and weighed (grams per 10 cm). Damage was assessed macro- and microscopically and tissue processed for myeloperoxidase and nitric oxide synthase activity. Rats receiving saline served as controls. In an additional experiment colitis was induced by intrarectal iodoacetamide. Ozone therapy caused no macroscopic damage. Ozone therapy induced microscopic colitis, which lasted for at least a week and was accompanied by increase in segmental weight, myeloperoxidase and nitric oxide activity, and prostaglandin E2 generation. Ozone therapy had no protective effect on inflamed mucosa. In conclusion, ozone water therapy had a deleterious effect on normal colonic mucosa, suggesting intrarectal administration be reevaluated. Ozone water enema may serve as a model of microscopic colitis.

Heparin and low-molecular-weight heparin (enoxaparin) significantly ameliorate experimental colitis in rats

BACKGROUND AND AIMS

The anticoagulants, unfractionated heparin and low-molecular-weight heparin, demonstrated anti-inflammatory effects in animal models and in humans. Because of its dual effects, high-dose heparin was proposed as a therapeutic modality for ulcerative colitis. We investigated whether a low dose of low-molecular-weight heparin-enoxaparin (Clexane, Rhône-Poulenc Rorer, France)-ameliorates the inflammatory response in two models of experimental colitis.

METHODS

Colitis was induced in rats by intrarectal administration of dinitrobenzene sulphonic acid. Enoxaparin (40, 80 and 200 microg/kg) or unfractionated heparin (100, 200 and 400 U/kg) were administered subcutaneously immediately after the induction of damage. Enoxaparin, 80 microg/kg, was also administered after induction of colitis by intrarectal administration of iodoacetamide. Rats were sacrificed 1, 3 or 7 days after induction of injury. Colonic damage was assessed macroscopically and histologically. Mucosal prostaglandin E2 generation, myeloperoxidase and nitric oxide synthase activities and tumour necrosis factor-alpha levels in blood were determined.

RESULTS

Enoxaparin and heparin significantly ameliorated the severity of dinitrobenzene sulphonic acid- and iodoacetamide-induced colitis as demonstrated by a decrease in mucosal lesion area, colonic weight and mucosal myeloperoxidase and nitric oxide synthase activities. The dose-response curve had a bell-shaped configuration: enoxaparin, 80 microg/kg, and unfractionated heparin, 200 U/kg, were the optimal doses.

CONCLUSIONS

Low-dose enoxaparin and unfractionated heparin ameliorate the severity of experimental colitis. This effect is related to their anti-inflammatory rather than anticoagulant properties.

Chronic exogenous hyperinsulinaemia-induced hypertension in pregnant rats: effect of chronic treatment with l-arginine

Recent studies have shown that maternal hyperinsulinaemia is a risk factor for the development of hypertension in pregnancy. Experimentally, pregnant rats with chronic exogenously induced hyperinsulinaemia (P-INS rats) have increased blood pressure at the end of gestation. This is associated with a blunted elevation of the excretion of the urinary metabolites of nitrate (UNO(x)). In the present study, we aimed to evaluate the mechanism(s) of the increase in blood pressure in this model. Four groups were studied: normal pregnant rats (P rats), P-INS rats, P-INS rats treated with L-arginine (2 g/l in the drinking water) (L-ARG rats) and hyperinsulinaemic virgin rats (V-INS rats). Systolic blood pressure (SBP), UNO(x) excretion (on ingestion of a controlled low-nitrate diet), urine noradrenaline (norepinephrine) and plasma endothelin levels were evaluated. Rats were killed on day 22 of pregnancy. Five P-INS rats were not killed at this time, in order to measure SBP 30 and 60 days after delivery. Fetal number and fetal body weight were evaluated. At the end of pregnancy, a 10+/-3% increase in SBP was found in P-INS rats, contrasting with a fall of -15+/-4% in P rats (P<0.01). In the L-ARG group at the end of pregnancy, SBP values had fallen by -14+/-2%, to values comparable with those of P rats. The increase in UNO(x) excretion was 175+/-38% in P rats, 106+/-12% in L-ARG rats and 41+/-8% in P-INS rats (P<0.01 compared with P and L-ARG groups). No differences were found in the urinary excretion of noradrenaline or in the plasma levels of endothelin-1 between the pregnant groups. Fetal number was similar in all groups, but fetal body weight was lower for P-INS rats compared with P and L-ARG rats. Thus the blood pressure response to L-arginine strongly suggests that a decrease in NO availability may be the main pathogenic mechanism involved in the development of hypertension in this model.

Substance P in rectal mucosa of children with chronic constipation

Substance P content was determined by radioimmunoassay in rectal mucosa of 17 children with idiopathic constipation and 9 with normal bowel movements who were used as controls. In children with chronic idiopathic constipation, rectal mucosa substance P levels were lower than levels in the control group: 47.6 +/- 11 vs. 79.4 +/- 11 pg/mg net weight respectively (differences not statistically significant). Substance P levels in rectal mucosa of children with soiling (11/17) did not differ from those of chronically constipated children without soiling (46.0 +/- 16 vs. 50.5 +/- 19 pg/mg net weight). In children with constipation, substance P levels did not correlate either with age or duration of symptoms. Substance P levels in normal controls were similar to levels previously observed in non-constipated adults, whereas levels in constipated children were intermediate between levels observed in healthy subjects and levels in adults with chronic constipation. These findings may point to a motility derangement as a possible factor in the pathogenesis of chronic constipation in childhood.

Dual effect of chronic nicotine administration: augmentation of jejunitis and amelioration of colitis induced by iodoacetamide in rats

Smoking has a dichotomous effect on inflammatory bowel disease, ameliorating disease activity in ulcerative colitis but having a deleterious effect on Crohn's disease. This effect is thought to be due to nicotine. We investigated the effect of chronic nicotine administration on the small and large bowel in iodoacetamide-induced jejunitis and colitis. Jejunitis was induced in Sprague-Dawley rats by intrajejunal administration of 0.1 ml 2% iodoacetamide and colitis by intrarectal administration of 0.1 ml 3% iodoacetamide. Nicotine was dissolved in drinking water (12.5 or 250 micrograms/ml), rats drinking ad libitum. Nicotine administration started 10 days prior to damage induction and throughout the experiment and had no effect on weight gain or daily food intake of rats. Rats were killed 5 days after iodoacetamide-induced colitis and 7 days after induction of jejunitis. The jejunum and colon were resected, rinsed, weighed, damage assessed macroscopically and microscopically and tissue processed for myeloperoxidase and nitric oxide synthase (NOS) activities and prostaglandin E2 (PGE2) generation. Effects of nicotine on gut microcirculation were also assessed. Nicotine by itself caused no damage to the colon. Nicotine had a dichotomous effect on jejunitis and colitis. At a dose of 12.5 micrograms/ml nicotine improved the macroscopic damage of colitis from 252 +/- 66 to 70 +/- 31 mm2, and segmental weight also declined significantly in the colon (from 1.7 +/- 0.2 to 1.2 +/- 0.1 g/10 cm). In contrast, the same dose of nicotine had a deleterious effect on iodoacetamide-induced jejunitis, increasing the macroscopic damage from 368 +/- 38 to 460 +/- 97 mm2 in rats treated with injury escalating to 970 +/- 147 in rats treated with 250 micrograms/ml nicotine. Nicotine treatment also significantly increased jejunal segmental weight. By itself nicotine did not change NOS activity or PGE2 generation compared to control rats, but it enhanced microcirculation in the colon, whereas in the jejunum nicotine decreased PGE2 generation and increased NOS activity but not jejunal microcirculation. Nicotine has opposite effects on iodoacetamide-induced colitis and jejunitis, which may be partly explained by decreased PGE2 generation and increased NOS activity in the jejunum and an increase in the colonic microcirculation.

Increased urinary N-telopeptide cross-linked type 1 collagen predicts bone loss in patients with inflammatory bowel disease

OBJECTIVE

Reduced bone mineral density (BMD) is common in patients with inflammatory bowel disease (IBD), but the factors associated with its longitudinal rate of change have not been established. We prospectively assessed the rate of change in BMD, and its association with biochemical markers of bone turnover.

METHODS

Twenty-two patients with Crohn's disease and 14 ulcerative colitis patients age 37.1 +/- 11.6 yr were followed for 2 yr. Lumbar spine (L2-L4) and femoral neck BMD were measured by dual x-ray absorptiometry at baseline and 24 months. Bone-specific alkaline phosphatase, osteocalcin, urinary N-telopeptide crosslinked type 1 collagen (NTx), parathyroid hormone, and 25-hydroxyvitamin-D were determined at baseline.

RESULTS

At baseline, 59% of Crohn's patients and 43% of ulcerative colitis patients were osteoporotic, with spine or femoral neck BMD T-score < -2.5. Spine BMD, and spine and femoral neck T-scores were lower and disease duration was longer in nine patients with ileal resection compared with nonoperated patients (0.84 +/- 0.15 g/cm2 vs 0.96 +/- 0.11 g/cm2, -3.0 +/- 1.5 vs -1.7 +/- 1.3, -3.2 +/- 1.5 vs -2.2 +/- 1.0, respectively; all p < 0.05). At 24 months, 13/36 (36%) and 14/36 (39%) patients experienced spinal and femoral neck bone loss, respectively, with mean annual percent BMD changes of -2.0% and -1.5%, respectively. NTx, a bone resorption marker, inversely correlated with spinal BMD rate of change (r = -0.4, p < 0.05). Using quartiles analysis, patients with the highest NTx (Q4) experienced the greatest decrease in spine BMD compared with patients with the lowest NTx (Q1).

CONCLUSIONS

Spine and femoral neck bone loss continues over time in more than one-third of IBD patients. Increased NTx level predicts spinal bone loss in IBD patients.

Cyclo-oxygenase-2 inhibitors ameliorate the severity of experimental colitis in rats

BACKGROUND

Both in experimental colitis and in inflammatory bowel disease, colonic eicosanoid generation is enhanced and may contribute to the pathogenesis of the inflammatory response.

AIMS

To evaluate the effect of selective cyclo-oxygenase-2 (COX-2) inhibitors on the extent and severity of two models of experimental colitis.

METHODS

Colitis was induced by intra-caecal administration of 2 ml 5% acetic acid or intra-colonic administration of 0.1 ml 3% iodoacetamide. Rats were treated intra-gastrically with nimesulide 2 x 10 mg/kg/day, or once with SC-236 6 mg/kg, and killed 1 or 3 days after damage induction. The colon was isolated, weighed, macroscopic damage was measured, and mucosal samples were obtained for histology and for determination of myeloperoxidase (MPO) and nitric oxide synthase (NOS) activities and eicosanoid generation. The serum levels of thromboxane B2 (TXB2), tumour necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) were determined.

RESULTS

Nimesulide significantly decreased the extent of colitis induced by acetic acid. Both nimesulide and SC-236 significantly decreased the extent of iodoacetamide-induced colonic damage. The decrease in the extent of colitis induced by nimesulide was accompanied by a significant decrease in mucosal MPO and NOS activities. Nimesulide and SC-236 decreased the enhanced colonic eicosanoid generation in acetic acid and iodoacetamide-induced colitis, and, in iodoacetamide-treated rats, nimesulide also decreased the elevated serum TNF-alpha and IL-1beta levels.

CONCLUSIONS

The effective nimesulide and SC-236-induced amelioration of the severity of the colitis in acetic acid and iodoacetamide-treated rats confirms the role of eicosanoids in their pathogenesis and suggests that COX-2 inhibitors may be of value in the treatment of inflammatory bowel disease.

Deferiprone, an oral iron chelator, ameliorates experimental colitis and gastric ulceration in rats

Iron is pivotal is producing tissue-damaging reactive oxygen metabolites. Our aim is to determine the antiinflammatory activity of deferiprone, an oral iron chelator, in experimental colitis and gastritis. Colitis was induced by intraceccal administration of 2 ml 5% acetic acid or by intracolonic administration of 0.1 ml 3% iodoacetamide, with or without cotreatment with deferiprone. Gastritis was induced by intragastric administration of ethanol or hydrochloric acid (HCl) and by subcutaneous injection of indomethacin, with and without deferiprone. Rats were killed 24 hours after acetic acid and iodoacetamide, 30 minutes after ethanol, one hour after HCl, and three hours after indomethacin administration. The colon or stomach was isolated, macroscopic damage was measured, and mucosal samples were obtained for determination of eicosanoid generation, myeloperoxidase (MPO), and nitric oxide synthase (NOS) activities. Deferiprone decreased iodoacetamide and acetic acid-induced macroscopic colonic damage by 67% and 69%, respectively, and macroscopic gastric damage by 91%, 68%, and 46% induced by ethanol, HCl, and indomethacin, respectively. The effect of deferiprone was accompanied by significant decrease in colonic and gastric, MPO and NOS activities, and colonic prostaglandin E2 (PGE2) generation, in acetic acid, ethanol, and indomethacin models, whereas in the iodoacetamide and HCl models attenuation of the decrease in PGE2 generation was seen. Deferiprone is protective in experimental colitis and gastritis, probably due to decreased production of iron-dependent oxygen-free radicals. Oral iron chelators may constitute a novel approach to ameliorate gastrointestinal inflammatory disorders.

Sulphydryl blocker-induced rat colitis is ameliorated by intravenous injection of antibody to colonic surfactant-like particle

A rat model of experimental colitis and jejunitis induced by iodoacetamide (IA), a sulphydryl blocker is accompanied by increased leukotriene, prostaglandin E2 (PGE2) generation, and nitric oxide synthase (NOS) activity. Rat small intestinal and colonic surfactant-like particles (SLP) that accumulate on the apical surface of mucosal cells have been identified and specific antibodies to them have been produced. The aim of this study was to evaluate a possible role of SLP in IA-induced colitis and jejunitis. Inflammation was induced in Sprague-Dawley rats either by intracolonic administration of 3% IA (0.1 ml) or by intrajejunal administration of 2% IA (0.1 ml). Antisera raised against either colonic SLP, pulmonary SP-A (a major protein associated with colonic SLP), or small intestinal SLP were injected into the tail vein of rats 48 h before, simultaneous with, or 24 h after IA administration. Rats were killed 2 or 10 days after IA was given, their colon or small intestine was isolated and rinsed, and a segment of colon (10 cm) or small bowel (30 cm) was weighed and processed for microscopy, NOS and myeloperoxidase (MPO) activities, and PGE2 generation. Intracolonic or jejunal IA resulted after 48 h in extensive macroscopic and microscopic damage, accompanied by increased segmental weight, MPO and NOS activity, and PGE2 generation. Colonic SLP antibody administration, either 48 h before or at the time of damage induction, significantly decreased macroscopic as well as microscopic damage, segmental weight, MPO activity, and PGE2 generation, but had no effect on NOS activity. Neither control sera nor antisera against SP-A had any protective effect, nor did injection of anti-colonic SLP antisera given 24 h after IA. Small bowel SLP antibody offered no protection against IA jejunitis. IA-induced colitis but not jejunitis is ameliorated by intravenous injection of SLP antibody by a mechanism yet to be determined. These data provide further evidence of a physiologic role for gastrointestinal SLP.

Mechanisms underlying gastric antiulcerative activity of nitroxides in rats

Reactive oxygen-derived species and redox-active metals are implicated in mediation of the pathogenesis of gastric mucosal damage and ulceration. Therefore, common strategies of intervention employ metal chelators, antioxidative enzymes, and low-molecular-weight antioxidants (LMWA). The aim of the present study was to elaborate the mechanism(s) responsible for the protection provided by nitroxide radicals in the experimental model of gastric ulceration. Fasted male rats were treated ig with 1 ml 96% ethanol, with or without ig pretreatment with nitroxide or hydroxylamine. In several experiments, rats were injected ip or iv with iron(III) or iron(II) prior to ethanol administration. Rats were sacrificed 10 min after ethanol administration, the stomach was removed, washed and lesion area measured. Pretreatment with iron(III) complexed to nitrilotriacetate or citrate, aggravated the extent of the gastric injury. Conversely, iron(II) inhibited the formation of lesions. The nitroxides were rapidly reduced to their respective hydroxylamines and demonstrated antiulcerative activity for rats treated with iron. However, injecting the hydroxylamine resulted in a similar tissue distribution of nitroxide/hydroxylamnine but did not provide protection. The results show that: (a) the nitroxide radicals, rather than their respective non-radical reduced form, are the active species responsible for protection; (b) nitroxides protect by dismutating O2*- and possibly indirectly increasing the NO level; (c) unlike classical LMWA which are reducing agents, nitroxides inhibit gastric damage by acting as mild oxidants, oxidizing reduced metals and pre-empting the Fenton reaction; and (d) the nitroxides act catalytically as recycling antioxidants.

Effect of chronic nicotine administration on trinitrobenzene sulphonic acid-induced colitis

BACKGROUND

Smoking, probably due to nicotine, has a bivalent effect on inflammatory bowel disease, ameliorating disease activity in ulcerative colitis and with a deleterious effect on Crohn's disease. The effect of nicotine patches in ulcerative colitis is controversial.

AIM

To investigate the effect of chronic nicotine use in a rat model of colitis.

METHODS

Colitis was induced in Sprague-Dawley rats by rectal administration of 30 mg trinitrobenzene sulphonic acid (TNBS) in 50% ethanol. Nicotine was dissolved in drinking water (2.5, 12.5, 25 and 250 microg/ml), with rats drinking ad libitum. Nicotine administration started 10 days prior to damage induction and had no effect on weight gain or daily food intake of rats. Rats were sacrificed 1 and 5 days after TNBS administration, their colons resected, rinsed, weighed, damage assessed macroscopically (mm2) and microscopically and tissue processed for myeloperoxidase (MPO) and nitric oxide synthase (NOS) activities, leukotriene B4 (LTB4), prostaglandin E2 (PGE2) generation and interleukin-1 (IL-1) serum levels.

RESULTS

Nicotine, by itself, caused no damage to the colon. Nicotine had a dose-dependent bivalent effect on colitis, significantly reducing macroscopic damage from 983 +/- 10 mm2 on TNBS alone to 429 +/- 118 mm2 on TNBS plus 12.5 microg/ml of nicotine, and escalating to 1086 +/- 262 mm2 on 250 microg/ml of nicotine. Segmental weight declined significantly (from 2.4 +/- 0.2 to 1.65 +/- 0.20 g/10 cm), on 12.5 microg/ml nicotine, as did MPO activity (from 3.2 +/- 0.4 to 0.7 +/- 0.1 units/g). All these parameters returned to the levels of TNBS alone when the dose of nicotine was increased to 250 microg/ml. Nicotine had no effect on NOS activity, PGE2 generation and serum IL-1 levels, but increased LTB4 generation.

CONCLUSIONS

Nicotine has a dose-dependent bivalent effect on TNBS-induced colitis which is not due to reduction in IL-1 serum levels or PGE2 generation, and is not NOS-mediated.

Hyperbaric oxygen: a novel modality to ameliorate experimental colitis

BACKGROUND

Hyperbaric oxygen (HBO) has been suggested to be beneficial in inflammatory bowel disease but the mechanisms responsible for its therapeutic effects have not been elucidated.

AIM

To assess the effect of HBO treatment on colonic damage in two models of experimental colitis, and to examine whether this effect is mediated by modulation of NO synthesis.

METHODS

Colitis was induced by either flushing the colon with 2 ml 5% acetic acid or intracolonic administration of 30 mg trinitrobenzenesulphonic acid (TNB) dissolved in 0.25 ml 50% ethanol. Rats were exposed to HBO (100% oxygen at 2.4 atmosphere absolute) for one hour twice on the day of colitis induction and once daily thereafter. Control rats were treated only with acetic acid or TNB. Rats were killed 24 hours after acetic acid administration or one and seven days after TNB treatment. The colon was isolated, washed, and weighed, the lesion area was measured, and mucosal scrapings were processed for determination of myeloperoxidase (MPO) and NO synthase (NOS) activities, prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) generation.

RESULTS

In control rats exposed for seven days to HBO, colonic NOS activity was significantly decreased by 61%, compared with its activity in untreated rats (2.93 (0.17) nmol/g/min). HBO significantly reduced by 51 and 62% the extent of injury induced by acetic acid and TNB respectively. The protection provided by HBO was accompanied by a significant decrease in colonic weight, PGE2 generation, MPO, and NOS activities. In acetic acid colitis, LTB4 generation was also significantly decreased.

CONCLUSIONS

(1) HBO effectively decreases colitis induced by acetic acid and TNB. (2) The decreased NOS activity induced by HBO suggests that reduction in NO generation may be among the mechanisms responsible for the anti-inflammatory effect of HBO. (3) HBO may be considered in the treatment of patients with refractory inflammatory bowel disease.

Femoral neck osteopenia in patients with inflammatory bowel disease

OBJECTIVE

The mechanism of bone loss in patients with inflammatory bowel disease (IBD) is not completely understood. The aim of this study was to assess indices of bone turnover and bone mineral density (BMD) in the lumbar spine and femoral neck in IBD patients.

METHODS

Sixty-three patients with Crohn's disease and 41 with ulcerative colitis were studied. Serum bone-specific alkaline phosphatase (B-ALP), osteocalcin, parathyroid hormone (PTH), 25 hydroxyvitamin D, interleukin-6 (IL-6), and urinary N-telopeptide cross linked type 1 collagen (NTX) were determined. BMD of the lumbar spine and femoral neck was determined by dual x-ray absorptiometry in 59 patients.

RESULTS

In the femoral neck 42% of the patients had osteopenia (-2.5 SD < BMD T score < -1 SD) and another 41% had osteoporosis (BMD T score < -2.5). In the spine 34% of the patients had osteopenia and additional 42% had osteoporosis. BMD T scores were lower in the femoral neck compared to the spine. Reduced BMD was unrelated to gender, disease type, lifetime corticosteroid dose, but inversely correlated with disease duration (r = -0.36, p < 0.05). Serum IL-6 was higher in IBD patients compared to controls. A reduced level of osteocalcin, a marker of bone formation, was present in 7% of patients and an increase in NTX, a marker of bone resorption, in 25% of them. Osteoporotic IBD patients (spine or hip BMD T score < -2.5) had increased serum IL-6, osteocalcin and PTH level compared to nonosteoporotic patients.

CONCLUSIONS

There is a high prevalence of reduced BMD at the spine and femoral neck in IBD patients, which is more severe in the hip. Bone turnover in osteoporotic IBD patients is associated with an increase in osteocalcin, PTH and IL-6. IL-6 may play a role in the pathogenesis of bone loss in IBD.

Direct determination of colonic nitric oxide level--a sensitive marker of disease activity in ulcerative colitis

OBJECTIVE

In active ulcerative colitis, colonic nitric oxide (NO) generation is enhanced and probably has an important role in its pathogenesis. We tested the reliability of an NO electrode in monitoring colonic NO levels in ulcerative colitis patients and control subjects and its possible usage as a marker of disease activity.

METHODS

Colonic NO level was determined by the NO detection system model NO-501 (InterMedical, Nagoya, Japan). The working electrode was inserted into a 7-mm diameter polyvinyl tube and introduced at a distance 6 cm from the anus. In each subject sigmoidoscopy was performed and mucosal biopsies were obtained. NO synthase (NOS) activity was determined by monitoring the conversion of 3H-arginine to citrulline.

RESULTS

Colonic NO level is significantly increased in patients with active ulcerative or Crohn's colitis--more than 2-fold higher than in control subjects. There was good correlation between colonic NO level and NOS activity and the clinical and endoscopic indices of disease activity.

CONCLUSION

Direct determination of colonic NO level is convenient, and reliable, and may help to monitor disease activity in ulcerative colitis.

Sulphydryl blocker induced small intestinal inflammation in rats: a new model mimicking Crohn's disease

BACKGROUND

Sulphydryl compounds are essential for maintaining mucosal integrity in the gastrointestinal tract.

AIM

To characterise a model of experimental inflammation in the small intestine induced by a sulphydryl blocker.

METHODS

Inflammation in the small intestine was induced in rats by intrajejunal administration of 0.1 ml 2% iodoacetamide. The possible amelioration of the damage induced was modulated by intragastric administration of TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl; 50 mg/100 g body weight), ketotifen (200 micrograms/100 g body weight), or by addition of L-NAME (NG-nitro-L-arginine methyl ester; 0.1 mg/ml) or apocynin (120 micrograms/ml) to the drinking water. Rats were sacrificed at various time intervals, the small intestine resected, weighed, macroscopic lesions were assessed, and mucosal generation of inflammatory mediators and nitric oxide synthase activity were determined.

RESULTS

Intrajejunal administration of iodoacetamide induced, after one week, multifocal mucosal erosions, ulcerations with granulomas and giant Langhans cells. At two weeks, the mucosa was almost macroscopically intact but histologically epithelial granuloma and giant cells were present. Myeloperoxidase activity was increased in the first 24 hours, one week later mucosal nitric oxide synthase activity and generation of leukotriene B4, leukotriene C4 and thromboxane B2 were increased, whereas prostaglandin E2 generation was decreased notably. Ketotifen and apocynin significantly decreased the extent of injury which was not affected by TEMPOL or L-NAME.

CONCLUSIONS

Jejunal inflammation induced by the sulphydryl blocker, iodoacetamide, resembles the pathological changes in Crohn's disease. The protective effect of ketotifen and apocynin indicates the contribution of O2- and pro-inflammatory mediators to the pathogenesis of the damage, and may be a novel approach to the treatment of inflammatory bowel disease.

Effect of colchicine and bisacodyl on rat intestinal transit and nitric oxide synthase activity

BACKGROUND

Bisacodyl and colchicine affect smooth-muscle contractility, intestinal water, and electrolyte transport. Nitric oxide (NO) stimulates intestinal electrolyte secretion and has an important role as a mediator of intestinal motility. We therefore studied, in rats, the effects of these agents on nitric oxide synthase (NOS) activity and gastrointestinal transit.

METHODS

Rats were treated with bisacodyl (10 mg/kg intragastrically) or colchicine (5 mg/kg intraperitoneally) with or without pretreatment with ketotifen (1 mg/kg intragastrically). Rats were killed after 1, 2, and 4 h. The intestine was isolated and rinsed, the mucosa scraped, and NOS activity determined. In all rats small-intestinal transit was measured 15 min after intragastric administration of charcoal.

RESULTS

Bisacodyl (10 mg/kg) and colchicine (5 mg/kg) induced a significant decrease in jejunal NOS activity. Pretreatment with the mast cell stabilizer ketotifen, which has been shown to attenuate the increased permeability induced by NO inhibition, prevented the decrease in colonic and jejunal NOS activity induced by bisacodyl and colchicine. Bisacodyl and colchicine significantly decreased intestinal transit time. Their effect on transit time was similar to that induced by intravenous administration of NG-nitro-L-arginine methyl ester (10 mg/kg).

CONCLUSIONS

It is suggested that the effect of bisacodyl and colchicine on intestinal transport is, at least partly, mediated through NO inhibition.

Decreased substance P content in the rectal mucosa of diabetics with diarrhea and constipation

Substance P (SP), vasoactive intestinal polypeptide (VIP), and somatostatin content in rectal mucosa were determined by radioimmunoassay (RIA) in 38 diabetic patients (12 with normal bowel function, 13 with diabetic diarrhea, and 13 with constipation) and in 10 nondiabetic controls with normal bowel function. SP content (picograms per milligram) in the rectal mucosa of diabetics with normal bowel function was significantly higher than that of nondiabetic controls (P < .05). SP content in the rectal mucosa of diabetics with diabetic diarrhea and constipation was significantly lower than in diabetics with normal bowel habits and nondiabetic controls (P < .05). No differences were found in the rectal mucosa content of VIP and somatostatin between the different groups of diabetics and controls. Diabetic diarrhea is a condition with an intermittent nature and frequently alternates with constipation. Our findings showing low levels of rectal mucosa SP in both conditions suggest a possible common role of SP in the pathogenesis of diabetic diarrhea and constipation.

The effect of ketotifen on nitric oxide synthase activity

1. We studied the effect of ketotifen, a second generation H1-receptor antagonist on nitric oxide synthase (NOS) activity in colonic mucosa and in renal tissues, and on rat renal haemodynamics in vivo. 2. Ketotifen (100 micrograms ml-1) increased human colonic NOS activity from 3.7 +/- 0.6 to 14.5 +/- 1.3 nmol g-1 min-1 (P < 0.005, ANOVA). In rat renal cortical and medullary tissues ketotifen increased NOS activity by 55% and 86%, respectively (P < 0.001). The stimulation of NOS activity was attenuated by NADPH deletion and by the addition of N omega nitro-L-arginine methyl ester (L-NAME) or aminoguanidine, but not by [Ca2+] deprivation. NOS activity was unaffected by two other H1-antagonists, diphenhydramine and astemizole, or by the structurally related cyproheptadine. Renal cortical NOS activity was also significantly stimulated 90 min after intravenous administration of ketotifen to anaesthetized rats. 3. Ketotifen administration to anaesthetized rats induced modest declines in blood pressure and reduced total renal, cortical and outer medullary vascular resistance. This is in contrast to diphenhydramine, which did not induce renal vasodilatation. 4. We conclude that ketotifen stimulates NOS activity by mechanisms other than H1-receptor antagonism. The association of this effect with therapeutic characteristics of ketotifen and the clinical implications of these findings are yet to be defined.

Anti-thyroid drugs decrease mucosal damage in a rat model of experimental colitis

BACKGROUND

Methimazole, an anti-thyroid drug, was recently found to be useful in the treatment of systemic lupus erythematosus and other autoimmune diseases. Moreover, decreased thyroid hormone production is associated with a variety of immunological manifestations, such as reduced activation of CD4+ cells, increased CD8+ cell activity and reduced soluble IL-2 receptors. In the present study we examined the effects of methimazole and propylthiouracil on a rat model of experimental colitis.

METHODS

Colitis was induced by intracolonic administration of 30 mg trinitrobenzene sulphonic acid (TNB). Two weeks prior to induction of colitis, rats were treated by either methimaziole (0.04%) or propylthiouracil (0.01%) in drinking water after a week of free access to water. Rats were sacrificed 48 h or 7 days after induction of colitis. The colon was isolated, rinsed with ice-cold water and weighed. Damage was assessed both macroscopically and microscopically and myeloperoxidase (MPO) activity determined.

RESULTS

All treated rats were hypothyroid as manifested by a significant elevation of thyroid stimulating hormone (TSH), by comparison with the control groups (mean -1.82 +/- 0.40 versus 0.11 +/- 0.02 mmol/L, respectively). The inflammatory response elicited by TNB resulted in severe mucosal damage 48 h after damage induction, which persisted for 7 days. Pre-treatment with either methimazole 0.04% or propylthiouracil 0.01% significantly decreased mucosal damage macroscopically (lesion area, lesion score and segmental weight) microscopically and also significantly decreased MPO level at both time points (P < 0.01).

CONCLUSIONS

Methimazole and propylthiouracil significantly reduce mucosal damage and colonic weight in a rat model of colitis. The mode by which they do so remains to be studied.

Sulphydryl blocker induced gastric damage is ameliorated by scavenging of free radicals

BACKGROUND

Sulphydryl compounds and nitric oxide are essential in maintaining gastric mucosal integrity.

AIMS

To characterise the gastric damage induced by a sulphydryl blocker, to evaluate the role of nitric oxide in its pathogenesis, and to reveal its possible prevention by scavenging of free radicals.

METHODS

Gastritis was induced in rats by addition of iodoacetamide (0.1%) to the drinking water, with and without daily intragastric administration of TEMPOL. After death, the stomach was resected, washed, lesion area assessed, and mucosal inflammatory mediators, myeloperoxidase and nitric oxide synthase activities were determined.

RESULTS

Administration of iodoacetamide induced gastric mucosal erosions present for up to two weeks. Myeloperoxidase activity was increased for up to seven days and nitric oxide synthase activity was significantly decreased for up to 14 days. Treatment for seven days with the free radical scavenger, TEMPOL, decreased by 68% the damage induced by iodoacetamide.

CONCLUSIONS

Gastric damage induced by iodoacetamide, a sulphydryl alkylator, accompanied by inhibition of nitric oxide synthase activity shows the important contribution of sulphydryl compounds and nitric oxide to the maintenance of gastric mucosal integrity. Nitric oxide donation and scavenging of free radicals may be a novel approach to prevent gastric damage.

Ketotifen is protective against indomethacin-induced intestinal ulceration in the rat

Ketotifen is an anti-allergic agent that was recently shown to prevent experimental gastric and colonic mucosal injury. We studied the effect of ketotifen on indomethacin-induced small intestinal ulceration in the rat. Ulceration was produced by s.c. injection of 30 mg/kg indomethacin, 30 min after refeeding 24 h fasted rats. Total ulcer area (mm2), prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) were measured 24 h after indomethacin administration. Study groups received ketotifen 100 micrograms/ 100 g body weight 30 min before and 5 h after indomethacin administration, either i.p. or orally. There were 7-9 animals in each group. Ulcer area was significantly reduced by oral administration of ketotifen from 229 +/- 26 to 146 +/- 28 mm2. PGE2 level was reduced by ketotifen from 505 +/- 73 to 228 +/- 68 ng/mg protein, and LTB4 was reduced from 289 +/- 68 to 59 +/- 26 ng/mg protein. Intraperitoneal administration of ketotifen had no effect on any of the measured parameters. Ketotifen had a definite protective effect on small intestinal mucosa in the rat, which was accompanied by a reduction of mucosal inflammatory mediators. Ketotifen may have a role in the prevention or treatment of small intestinal damage induced by nonsteroidal anti-inflammatory drugs.

Renal vasoactive mediator generation in portal hypertensive and bile duct ligated rats

BACKGROUND/METHODS

Vasoactive substances may have a role in the pathogenesis of functional renal abnormalities in patients with cirrhosis. We determined renal vasoactive mediators in rats with portal hypertension since the balance in each part of the kidney between the vasodilator activity of prostaglandin E2 and the vasospastic activity of thromboxane A2, leukotriene B4, leukotriene C4, endothelin-1 and platelet activating factor may determine renal function. Rats with partial portal vein ligation (n = 7), complete bile duct ligation (n = 6) and sham operated (n = 10) were studied. Three weeks following surgery renal function tests, including fractional excretion of sodium [Fe(Na)] were measured. Rats were anesthetized, splenic pulp pressure was measured, kidneys were removed, and cortex, medulla and papilla were separated and homogenized for determination of prostaglandin E2, thromboxane B2, leukotriene B4, leukotriene C4 and endothelin-1 by radioimmunoassay (ng/g) and platelet activating factor activity (pg/10 mg) by platelet aggregation.

RESULTS

Pulp pressure was > 13 mmHg in portal vein ligated and bile duct ligated and 6 mmHg in sham operated rats. In bile duct ligated rats there was a 70% decrease in Fe(Na) and a significant decrease in cortical and papillary prostaglandin E2, whereas cortical thromboxane B2 and platelet activating factor activity in the cortex, medulla and papilla were double that of sham operated rats. A similar but insignificant trend of changes was found in portal vein ligated rats. Medullary leukotriene B4 was significantly decreased in bile duct ligated rats. Papillary leukotriene B4 was not detected in bile duct ligated and portal vein ligated rats. Renal leukotriene C4 generation in the three groups was either unchanged (papilla) or beyond detection (cortex and medulla). Medullary and papillary endothelin-1 in portal vein ligated and bile duct ligated rats were 178%-130% higher than in sham operated rats. A significant negative correlation was found between Fe(Na) and cortical and medullary thromboxane B2 generation and medullary platelet activating factor activity.

CONCLUSIONS

1) In bile duct ligated rats enhanced intrarenal generation of thromboxane A2 and platelet activating factor may contribute to decreased renal sodium excretion. 2) The role of decreased intrarenal prostaglandin E2 and increased intrarenal endothelin-1 content in bile duct ligated rats is not yet understood. 3) Renal leukotriene generation is either decreased or undetected in portal vein ligated and bile duct ligated rats.

Gastric and colonic inflammatory and vasoactive mediators in experimental portal hypertension

Rats with portal hypertension and experimental liver disease may exhibit increased susceptibility of the gastric mucosa to damage by noxious agents, and increased bacterial translocation through the bowel wall. The aim of this study was to determine mucosal gastric and colonic generation of vasoactive substances, because they may contribute to the altered mucosal function. Rats with partial vein ligation (n = 7), complete bile duct ligation (n = 6) and sham-operated rats (n = 10) were studied. Three weeks following surgery rats were anesthetized, splenic pulp pressure was measured, stomachs and colons were removed and mucosa was extracted for determination of prostaglandin E2, thromboxane B2, leukotriene B4, leukotriene C4 and endothelin-1 by radioimmunoassay (ng/g) and platelet activating factor activity (pg/10 mg) by platelet aggregation. Pulp pressure was > 13 mmHg in partial vein ligated rats and bile duct ligated rats and 6 mmHg in sham-operated rats. No macroscopic or microscopic lesions were seen any of the removed tissues. Gastric mucosal prostaglandin E2 and thromboxane B2 generation were decreased by 35% and 7%, respectively, in bile duct ligated rats (bile duct ligated versus sham-operated, p < 0.05 for prostaglandin E2 and thromboxane B2). Gastric leukotriene B4 and C4 generation, platelet activating factor activity and endothelin-1 content did not differ significantly among the three groups. A different pattern of changes was observed in the colon. Colonic leukotriene B4 generation and endothelin-1 content were increased in bile duct ligated rats by 105% and 210%, respectively (bile duct ligated versus sham-operated, p < 0.05 for leukotriene B4 and endothelin-1). The decreased gastric mucosal prostaglandin E2 generation of bile duct ligated rats may render the gut mucosa of these animals relatively ischemic and vulnerable to damage by noxious agents. The increased colonic leukotriene B4 generation and the increased endothelin-1 content of the colonic mucosa of bile duct ligated rats may promote inflammatory and ischemic changes in the colonic mucosa and may enable bacterial translocation.

A stable nitroxide radical effectively decreases mucosal damage in experimental colitis

TEMPOL, a cyclic nitroxide stable radical blocks biological damage by breaking chain reactions through termination reaction with free radicals, and by inhibiting the catalytic effect of transition metals. This study tested its protective effect on two models of experimental colitis as free radicals play an important part in their pathogenesis. TEMPOL was given intragastrically immediately after induction of colitis with acetic acid or trinitrobenzene sulphonic acid (TNB) and mucosal damage was assessed one, three, or seven days later. Cellular partition of TEMPOL was determined by electron paramagnetic resonance spectroscopy. In vitro experiments showed that TEMPOL immediately penetrates colonic mucosa and, following its intragastric administration, it persists in both gastric and colonic mucosa for several hours. Intragastric administration of TEMPOL, 0.5 g/kg/bw, immediately after intracaecal administration of 5% acetic acid significantly decreased mucosal lesion area, myeloperoxidase activity, and leukotriene B4 and C4 generation when assessed 24 hours after damage induction. Intragastric administration of TEMPOL, 0.5 g/kg/bw, immediately after intracolonic administration of 30 mg TNB in 0.25 ml 50% ethanol, and once daily thereafter, significantly decreased mucosal lesion area assessed after one, three, and seven days, having no effect on LTC4 generation and affecting colonic weight, myeloperoxidase activity, and LTB4 generation only sporadically. In conclusion, TNB and acetic acid induced colitis can be pharmacologically manipulated by TEMPOL. TEMPOL may be beneficial in the treatment or prevention of inflammatory bowel disease.

Experimental colitis is ameliorated by inhibition of nitric oxide synthase activity

Enhanced nitric oxide (NO) generation by stimulated NO synthase (NOS) activity may, through its oxidative metabolism contribute to tissue injury in experimental colitis. In this study the possible amelioration of experimental colitis by NG-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NOS activity, was evaluated. Colitis was induced in rats by intracolonic administration of 30 mg trinitrobenzene sulphonic acid (TNB) dissolved in 0.25 ml 50% ethanol or by flushing the colon of capsaicin pretreated rats with 2 ml of 5% acetic acid. In several experiments, L-NAME 0.1 mg/ml was added to the drinking water at the time of colitis induction with TNB or seven days before acetic acid treatment. Rats were killed at various time intervals after induction of colitis. A 10 cm distal colonic segment was isolated, weighed, lesion area measured, and explants organ cultured for 24 hours for determination of NO generation by the Greiss reaction. The rest of the mucosa was scraped for determination of myeloperoxidase and NOS activities and leukotriene generation. In TNB treated rats mean arterial pressure was also determined up to 72 hours after damage induction, with or without cotreatment with nitroprusside. L-NAME significantly decreased the extent of tissue injury in TNB treated rats. Seven days after TNB treatment lesion area was reduced by 55%, colonic weight by 37%, and myeloperoxidase and NOS activity by 59% and 42%, respectively. Acetic acid induced colitis in capsaicin pretreated rats was also significantly decreased by L-NAME. Twenty four hours after acetic acid treatment lesion area was reduced by 61%, colonic weight by 21% and NOS activity by 39%. Mean (SEM) arterial blood pressure in TNB+L-NAME treated rats was 37.6 (8.1) mm Hg higher than in TNB treated rats, an effect that was only partially abolished by nitroprusside. These results show that inhibition of NO synthesis by an L-arginine analogue significantly ameliorates the extent of tissue injury in two models of experimental colitis, an effect that is not due only to its vasoconstrictor properties. Modulation of NO generation may be a novel therapeutic approach in inflammatory bowel disease.

Sulfhydryl blocker-induced rat colonic inflammation is ameliorated by inhibition of nitric oxide synthase

BACKGROUND & AIMS

Sulfhydryl compounds are essential in maintaining mucosal integrity, and nitric oxide may contribute to tissue injury. The aim of this study was to characterize experimental colitis induced by a sulfhydryl blocker.

METHODS

Colitis was induced in rats by intracolonic administration of 0.1 mL 3% iodoacetamide with and without addition of 0.1 mg/mL NG-nitro-L-arginine methyl ester (L-NAME) to the drinking water. After death, the distal colonic segment was resected and weighed, and mucosal inflammatory mediator, myeloperoxidase, and NO synthase activities were determined.

RESULTS

Iodoacetamide induced multifocal mucosal erosions and ulceration that were present for up to 1 week. At 3 weeks, the mucosa was almost intact. Colonic wet weight was maximal at 7 days. Myeloperoxidase activity and NO generation were increased in the first 72 hours, and NO synthase activity and prostaglandin E2 generation were increased up to 21 days. Leukotriene B4 and leukotriene C4 generation were increased up to 14 days. One week after iodoacetamide plus L-NAME treatment, lesion area was reduced by 85% and NO synthase activity by 52%.

CONCLUSIONS

Inflammatory mediators have an important contribution to the pathogenesis of colonic injury induced by a sulfhydryl alkylator. The protective effect of L-NAME indicates that NO contributes to tissue injury and that its modulation may be a novel approach to treat inflammatory bowel disease.

Nitric oxide-containing nerves in bowel segments of patients with Hirschsprung's disease

To assess the role of nerves that synthesize nitric oxide (NO) in Hirschsprung's Disease (HD), the authors studied the distribution of the enzyme NADPH diaphorase (NADPHd) in normal and diseased bowel segments. In the proximal (ganglionic) segment of the colon, NADPHd-positive neurons were present in both myenteric and submucosal plexuses. In the distal involved colonic segments from HD patients, the typical pattern of the neuronal network was completely missing in the regions of the two plexuses; instead, only disorganized NADPHd-positive nerve fibers were present and NADPHd-reactive neurons were absent. Mucosal NO synthase activity was 2.76 +/- 0.38 nmol/g/min in the proximal segment and only 0.83 +/- 0.49 nmol/g/min in the distal segment (P < .05, N = 3).

Ketotifen and nitroxides decrease capsaicin-augmented ethanol-induced gastric damage in rats

Systemic administration of capsaicin aggravates ethanol-induced injury of rat gastric mucosa. We evaluated the effect of subcutaneous administration of capsaicin on the gastric mucosa and on inflammatory mediators in saline- and ethanol-treated rats. Functional ablation of primary afferent C-fibers by capsaicin (total 100 mg/kg subcutaneous) tripled ethanol-induced damage. Pretreatment with ketotifen, a mast cell stabilizer (1 mg/kg) protected rat gastric mucosa from the amplified injury induced by capsaicin and ethanol. Tempol, a selective nontoxic cell-permeable nitroxide, completely prevented the amplified gastric ulceration induced by capsaicin and ethanol. This was accompanied by a significant decrease in leukotriene B4 and C4 generation. It is therefore suggested that mast cells and free radicals contribute to the amplified injury observed in rats pretreated with capsaicin and ethanol and that the pharmacological modulation of mast cell release and scavenging of free radicals may be of therapeutic efficacy in the prevention of gastric injury.

Enhanced colonic nitric oxide generation and nitric oxide synthase activity in ulcerative colitis and Crohn's disease

Recent studies have suggested that nitric oxide (NO.), the product of nitric oxide synthase in inflammatory cells, may play a part in tissue injury and inflammation through its oxidative metabolism. In this study the colonic generation of oxides of nitrogen (NOx) and nitric oxide synthase activity was determined in ulcerative colitis and Crohn's disease. Colonic biopsy specimens were obtained from inflammatory bowel disease patients and from normal controls. Mucosal explants were cultured in vitro for 24 hours and NOx generation was determined. Nitric oxide synthase activity was monitored by the conversion of [3H]-L-arginine to citrulline. Median NOx generation by inflamed colonic mucosa of patients with active ulcerative colitis and Crohn's colitis was 4.2- and 8.1-fold respectively higher than that by normal human colonic mucosa. In ulcerative colitis and Crohn's colitis nitric oxide synthase activity was 10.0- and 3.8-fold respectively higher than in normal subjects. Colonic NOx generation is significantly decreased by methylprednisolone and ketotifen. The decrease in NOx generation by cultured colonic mucosa induced by methylprednisolone suggests that NO synthase activity is induced during the culture and the steroid effect may contribute to its therapeutic effect. Enhanced colonic NOx generation by stimulated nitric oxide synthase activity in ulcerative colitis and Crohn's disease may contribute to tissue injury.

Transforming growth factor-beta gene therapy ameliorates experimental colitis in rats

OBJECTIVE

To modulate experimental colitis by the direct intramuscular injection of cDNA expression vector encoding transforming growth factor-beta 1.

METHODS

Colitis was induced in rats by the intracolonic administration of 0.25 ml 50% ethanol containing 30 mg trinitrobenzene sulfonic acid. Three and 10 days later the rats were injected intramuscularly with 200 micrograms transforming growth factor-beta 1 cDNA subcloned to the pRSV expression vector (pRSVTGF-beta 1). Control rats were injected with pRSVP2. The rats were sacrificed 2 weeks after trinitrobenzene sulfonic acid treatment and a 10 cm long distal colonic segment was resected, weighted, the lesion area measured, sections obtained for histology and the mucosa extracted for determination of myeloperoxidase activity and leukotriene generation.

RESULTS

In pRSVP2-treated rats (n = 17) the colon was inflamed and ulcerated with many adhesions to adjacent structures; the pRSVTGF-beta 1-treated rats (n = 21) had minimal swelling and inflammation in the colon. On histological examination 50% of the pRSVTGF-beta 1-treated rats had minimal or no ulceration, whereas 83% of the pRSVP2-treated rats had a maximal damage score. In pRSVTG-beta 1-treated rats the lesion area and wet weight were 21 and 52.5%, respectively, of the values for pRSVP2-treated rats (P < 0.05). The amelioration of tissue injury was accompanied by a significant decrease in mucosal leukotriene C4 generation.

CONCLUSIONS

Direct intramuscular transforming growth factor-beta 1 gene delivery effectively ameliorates trinitrobenzene sulfonic acid-induced colitis, suggesting that gene therapy with immunosuppressive cytokines may be a novel approach for the treatment of inflammatory bowel disease.

Ketotifen ameliorates capsaicin-augmented acetic acid-induced colitis

Capsaicin-sensitive afferent neurons are involved in maintaining the integrity of the gastrointestinal mucosa. These neurons are closely apposed to mast cells and could, therefore, lead to their activation. In the present study, the role of capsaicin-sensitive neurons in the pathogenesis of experimental colitis and the possible involvement of mast cells and nitric oxide were evaluated. Rats were treated with capsaicin subcutaneously, 20, 30, and 50 mg/kg, on three consecutive days, a regimen shown to ablate primary afferent neurons. Colitis was induced two weeks later by flushing 2 ml 5% acetic acid into the proximal colon. Control rats received saline, acetic acid, or capsaicin alone. Another group of rats received ketotifen (100 micrograms/100 g body wt x 2/day) intragastrically 48 hr prior to damage induction and thereafter. Rats were sacrificed 24 hr after damage induction, the colon isolated, damage assessed, explants were organ-cultured for 24 hr for determination of nitric oxide generation, and mucosa extracted for determination of leukotriene B4 generation and nitric oxide synthase activity. Significant increases in colonic weight, nitric oxide synthase activity, and nitric oxide and leukotriene B4 generation accompanied the near tripling of acetic acid-induced damage in capsaicin-pretreated rats. Ketotifen pretreatment significantly decreased the macroscopic damage and the increase in colonic weight. The protection provided by ketotifen was accompanied by a significant decrease in leukotriene B4 generation and nitric oxide synthase activity (80%).(ABSTRACT TRUNCATED AT 250 WORDS)

Therapeutic effect of colloid bismuth subcitrate in experimental colitis in the rat

Colloid bismuth subcitrate (CBS) has a protective effect on ulcerated gastric and duodenal mucosa. To investigate its effect on large intestinal mucosal injury, we used acetic acid-induced colitis in the rat. Colitis was produced in male Wistar rats by rectal instillation of 1 ml of 10% acetic acid followed immediately by 1.5 ml of NaCl 0.9% (saline) enema. 1.5 ml of saline containing 240 mg of CBS or saline alone were then administered rectally every 24 h for 5 days. Another group of animals received CBS only. On the sixth day the distal colon was examined macroscopically and histologically using a 0 (normal) to 3 (necrosis) score. Prostaglandin E2 (PGE2) was measured by RIA (ng/mg protein). CBS significantly reduced both macroscopic and microscopic scores from 2.09 to 1.25 (p < 0.02) and from 2.4 to 1.08 (p < 0.02) respectively. It also induced a significant reduction in PGE2 from 1.6 to 0.57 (p < 0.004) in the inflamed colonic mucosa. The significant protective effect of topical CBS, which is accompanied by a reduction of PGE2, indicates that CBS may have a role in the treatment of colitis.

Enhanced gastric nitric oxide synthase activity in duodenal ulcer patients

Nitric oxide, the product of nitric oxide synthase in inflammatory cells, may have a role in tissue injury through its oxidative metabolism. Nitric oxide may have a role in the pathogenesis of duodenal ulcer and may be one of the mechanisms responsible for the association between gastric infection with Helicobacter pylori and peptic disease. In this study, calcium independent nitric oxide synthase activity was detected in human gastric mucosa suggesting expression of the inducible isoform. In 17 duodenal ulcer patients gastric antral and fundic nitric oxide synthase activity was found to be two and 1.5-fold respectively higher than its activity in the antrum and fundus of 14 normal subjects (p < 0.05). H pylori was detected in the antrum of 15 of 17 duodenal ulcer patients and only in 7 of 14 of the control subjects. Antral nitric oxide synthase activity in H pylori positive duodenal ulcer patients was twofold higher than in H pylori positive normal subjects (p < 0.05). In duodenal ulcer patients antral and fundic nitric oxide synthase activity resumed normal values after induction of ulcer healing with ranitidine. Eradication of H pylori did not further affect gastric nitric oxide synthase activity. These findings suggest that in duodenal ulcer patients stimulated gastric mucosal nitric oxide synthase activity, though independent of the H pylori state, may contribute to the pathogenesis of the disease.

The effect of nizatidine on duodenal ulcer healing and on mucosal inflammatory mediators

The aim of this double-blind, randomized, placebo-controlled trial was to evaluate the effect of nizatidine on duodenal ulcer healing and generation of mucosal prostaglandin estradiol and inflammatory mediators. Fifty-five patients with endoscopically proven active duodenal ulcer received either nizatidine 300 mg or placebo, once nightly, for 4 weeks, when a second endoscopy was performed. Healing was defined as complete epithelialization of the ulcer crater. At both endoscopies mucosal biopsies were obtained for determination of prostanoids and inflammatory mediators. Nizatidine and placebo induced ulcer healing in 76% and 60.9% of the patients, respectively, but the difference did not reach statistical significance. Nizatidine treatment did not significantly affect mucosal leukotriene B4, leukotriene C4 or platelet activating factor generation. It is concluded, therefore, that the antisecretory effect is probably the main mechanism responsible for nizatidine's therapeutic effects in peptic ulcer disease.

A novel antiulcerogenic stable radical prevents gastric mucosal lesions in rats

The pathogenesis of gastric mucosal injury is still poorly understood. Recent reports implicate redox active metals and reactive oxygen species as mediators of gastric damage induced by ethanol or non-steroidal anti-inflammatory drugs. Attempts were made therefore to prevent gastric injury using chelators and the antioxidant enzymes catalase and superoxide dismutase. These attempts, at best, would only detoxify extracellular reactive species, such as those produced by activated circulating granulocytes and macrophages. This study utilises another strategy by pre-emption of both intra and extracellular reactive species using radical-radical annihilation reactions and by detoxifying redox active transition metals. Nitroxide, stable free radicals were shown to enter mucous cells, protect against the ethanol induced damage, and prevent gastric lesions induced by aspirin, indomethacin, 25% NaCl, or 0.6 N HCl. These findings confirm that gastric mucosal damage from the above agents is mediated by free radicals and, moreover, introduce a prototypical agent within a potential new class of gastric ulcer preventing drugs.

Somatostatin effectively prevents ethanol- and NSAID-induced gastric mucosal damage in rats

The interrelationship between somatostatin and its synthetic analog, sandostatin, with neuropeptides and inflammatory mediators, as well as their protection of gastric mucosal damage, were tested in rats. Rats were treated intragastrically with 1.0 ml of 96% ethanol with or without intravenous or intraperitoneal coadministration of somatostatin (1.0 microM/kg). Mucosal damage was also induced by the administration of either indomethacin (30 mg/kg subcutaneously) with or without intravenous sandostatin (10 micrograms/rat), given 30 min prior to damage induction. Somatostatin levels in ethanol-damaged gastric mucosa were significantly lower than in control rats. Substance P and vasoactive intestinal peptide (VIP) levels were significantly higher in the damaged mucosa in rats treated with ethanol, as was the mucosal generation of leukotriene B4 (LTB4) and cysteinyl-containing leukotrienes. The coadministration of somatostatin with ethanol significantly reduced gastric mucosal injury induced by ethanol alone. The protection of the mucosa was accompanied by reduction of mucosal substance P and VIP levels, as well as the generation of leukotrienes, an effect that was reversed by intraperitoneal or intravenous coadministration of somatostatin antagonist, cyclo-(7-aminoheptanoyl-PH-E-D-Trp-Lys-THR), 1.0 microM/100 g, with somatostatin (1.0 microM/kg) and ethanol. When given by itself somatostatin significantly reduced mucosal leukotriene generation compared with their generation in saline-treated rats. Sandostatin completely abolished gastric mucosal damage induced by indomethacin administration. In rats treated with somatostatin and indomethacin, this effect was accompanied by reduction of mucosal leukotriene generation. Administration of sandostatin to pylorus-ligated rats significantly reduced gastric acid output.(ABSTRACT TRUNCATED AT 250 WORDS)

Peroxynitrite-induced rat colitis--a new model of colonic inflammation

BACKGROUND

Excessive production of nitric oxide, characteristic of inflamed states, may have deleterious effects through its facile conversion (in the presence of O2) to peroxynitrite, which promotes lipid and sulfhydryl oxidation. This study assessed the effect of peroxynitrite on the rat colon.

METHODS

Peroxynitrite was administered intrarectally to rats. One, 3, 7, and 21 days after treatment, a distal colonic segment was isolated and tissue was obtained for histological evaluation and determination of myeloperoxidase activity and NOX, and eicosanoids generation.

RESULTS

Within 24 hours, the exposed segment was edematous and congested with occasional hemorrhagic mucosal ulceration. On day 7, the lumen was narrow; at day 21, there were signs of stenosis. Histological analysis showed transmucosal necrosis, acute inflammation, and exudative edema 24 hours after treatment. Surface re-epithelization and infiltration of granulation tissue were present at 1 week. Resolution of edema, mucin repletion, thickening of muscularis mucosa and propria, and fibrosis were observed at 3 weeks. Significant increase in NOX generation and myeloperoxidase and NO synthase activities were observed at 24 hours, whereas enhanced leukotriene generation was observed only at 21 days.

CONCLUSIONS

Peroxynitrite-induced colonic inflammation provides a novel model of NO-related tissue injury and offers the opportunity to further explore the potential role of NO in the pathogenesis of inflammatory bowel disease.

Ketotifen inhibits Clostridium difficile toxin A-induced enteritis in rat ileum

BACKGROUND

Clostridium difficile toxin A is the principal mediator of inflammatory enterocolitis in experimental animals. The purpose of this study was to explore the effect of ketotifen, an anti-inflammatory drug, on toxin A-induced enterotoxicity in rat ileum.

METHODS

The effects of intragastric administration of ketotifen on secretion, mannitol permeability, histological damage, and mucosal levels of leukotriene B4, leukotriene C4, and platelet activating factor in toxin A-exposed rat ileal loops were measured in vivo. The effects of ketotifen on toxin A-mediated release of rat mast cell protease II (rat mucosa mast cell product) release were also measured in rat ileal explants in vitro. The effect of ketotifen on neutrophil migration in vitro was also evaluated.

RESULTS

Ketotifen pretreatment inhibited toxin A-associated intestinal secretion by 42.5% and mannitol permeability by 56.3% and reduced epithelial cell inflammation and necrosis. These effects were associated with reduced levels of leukotriene B4 by 65.8%, leukotriene C4 by 88.8%, platelet activating factor by 77.8%, and inhibition of rat mast cell protease II by 58.4%. In addition, pretreatment of neutrophils with ketotifen inhibited neutrophil migration in vitro.

CONCLUSIONS

The protective effect of ketotifen in this animal model was associated with significant inhibition of release of mast cells and neutrophil derived mediators, supporting their involvement in C. difficile enteritis.

Role of vasoactive intestinal peptide (VIP) in pathogenesis of ethanol-induced gastric mucosal damage in rats

To elucidate the possible role of vasoactive intestinal peptide (VIP) in the pathogenesis of acute gastric mucosal damage, rats were treated intragastrically with 1.0 ml 96% ethanol with or without intravenous or intraperitoneal coadministration of VIP (1 nmol/liter to 1 mumol/liter/100 g). VIP was found to double the mean lesion area when compared with that induced by ethanol alone (P < 0.05), an effect that was prevented by VIP antagonist (1 mumol/liter/100 g). A substance P antagonist (1 mumol/liter/100 g) also reduced the extent of gastric damage induced by coadministration of VIP and ethanol. VIP antagonist or substance P antagonist significantly reduced ethanol-induced gastric mucosal damage. Gastric mucosal levels of LTB4, LTC4, VIP, and substance P were significantly increased in ethanol-treated rats as compared with saline-treated animals (P < 0.05). The augmentation of ethanol-induced damage by VIP was associated with increased gastric mucosal levels of LTB4. In VIP-treated rats, gastric mucosal levels of substance P were found to be significantly increased compared with control rats (P < 0.05). Administration of VIP to pyloric-ligated rats significantly increased gastric acid output and blood pepsinogen A levels as compared with saline treated rats (P < 0.05). Ketotifen, a mast cell stabilizer (100 micrograms/100 g), administered orally 30 min before damage induction by ethanol, with or without VIP, totally abolished the damage of the surface epithelium of the entire gastric mucosa and significantly reduced the mucosal levels of LTC4 and LTB4 (P < 0.05). It is suggested that VIP is involved in the pathogenesis of acute ethanol-induced gastric mucosal damage.(ABSTRACT TRUNCATED AT 250 WORDS)

Intestinal epithelial cells contribute to the enhanced generation of platelet activating factor in ulcerative colitis

Generation of platelet activating factor by intestinal mucosal epithelial cells and lamina propria mononuclear cells was evaluated to elucidate the possible role of this mediator in the pathogenesis of inflammatory bowel disease. Epithelial and lamina propria mononuclear cells were isolated from surgical specimens from control, Crohn's disease, and ulcerative colitis patients. Platelet activating factor was extracted from highly purified cell preparations with 80% ethanol after stimulation with and without 0.2 uM calcium ionophore A23187 and was measured by platelet aggregation assay. Both cell types generated platelet activating factor activity and this was generally comparable for epithelial and lamina propria cells. Basal and stimulated platelet activating factor activity of epithelial and lamina propria cells from ulcerative colitis but not Crohn's disease patients was appreciably higher than that of control. Stimulation with calcium ionophore increased appreciably platelet activating factor activity in lamina propria cells from all groups. In contrast, only epithelial cells from ulcerative colitis showed an appreciable increase after calcium ionophore induction. These results suggest that epithelial cells are important contributors to intestinal platelet activating factor generation under normal and inflammatory conditions and that epithelial cells actively play a part in the pathogenesis of ulcerative colitis.

Ketotifen--old drug, new indication: reduction of gastric mucosal injury

The objective of the present study was to determine the efficacy of ketotifen (Zaditen), an effective antiasthmatic drug, in preventing indomethacin-induced gastroduodenal mucosal injury in a two-arm prospective, randomized, double-blind, controlled and open study. Thirty healthy volunteers with endoscopic normal-appearing mucosa were randomly treated, double-blindly, for 1 week with either placebo or ketotifen, 2 mg twice daily. On day 7 indomethacin, 50 mg three times daily, was added. Two subjects, one from each group, were withdrawn from the study owing to non-compliance. Ten additional subjects received ketotifen, 2 mg twice daily, 24 h before indomethacin administration, in an open manner. A second endoscopy was performed 24 h after indomethacin was initiated. Mucosal damage in the stomach and duodenum (hemorrhages, erosions, ulcers) was scored in accordance with Lanza et al. or counted numerically. Adverse reactions were documented. Ketotifen reduced indomethacin-induced gastric mucosal damage, reducing the mean gastric lesion score from 2.85 +/- 0.20 in the placebo-treated group to 1.86 +/- 0.36 and in the subjects pretreated with ketotifen for 7 days. Ketotifen protected (lesion score < or = 1) 6 of 14 subjects pretreated for 7 days, whereas none of the 14 placebo-treated subjects were protected. Ketotifen had no statistically significant protective effects in the duodenum. In the open study lesion scores of patients pretreated with ketotifen for 24 h were similar to those pretreated for 7 days. Ketotifen is effective in the reduction of indomethacin-induced acute gastric mucosal injury. Further studies are required to verify these data in a more relevant clinical setting.

Octreotide effectively decreases mucosal damage in experimental colitis

The effect of octreotide, a synthetic analogue of somatostatin, on the modulation of the acetic acid model of experimental colitis was examined. Colitis was induced by intracolonic administration of 2 ml of 5% acetic acid. The inflammatory response elicited by the acetic acid resulted in increased colonic synthesis of platelet activating factor, leukotriene B4 and decreased mucosal somatostatin levels. Subcutaneous administration of octreotide (10 micrograms/rat) 1 hour before or immediately after damage induction, as well as 1 and 23 hours after acetic acid application, resulted in a significant reduction in mucosal damage. The protective effect was accompanied by a significant reduction in platelet activating factor activity, leukotriene B4, and vasoactive intestinal peptide concentrations. There were no significant changes in mucosal leukotriene C4 and calcitonin gene related peptide levels. This study shows that acetic acid induced colitis is pharmacologically manipulated by octreotide. The mechanism of action of octreotide has not yet been fully determined. The potential use of octreotide in treating active inflammatory bowel disease remains to be evaluated.

Substance P levels in the rectal mucosa of diabetic patients with normal bowel function and constipation

Substance-P content in rectal mucosa was determined by radioimmunoassay in 28 diabetic patients (17 with severe chronic constipation and 11 with normal bowel function), 24 non-diabetic patients with severe functional constipation, and 27 normal controls. Substance-P content (pg/mg) in the rectal mucosa of diabetics with normal bowel function was significantly higher than that of non-diabetic controls (p < 0.001). Substance-P content in the rectal mucosa of diabetics with constipation was more than double that of patients with non-diabetic functional constipation (p < 0.01) and lower than that of diabetics with normal bowel function (p < 0.0375). Diabetic patients (constipated and non-constipated) have higher substance-P content in the rectal mucosa than non-diabetics. Lower substance-P rectal mucosa content in constipated diabetic patients than in non-constipated diabetics supports a possible role of substance P in the pathogenesis of diabetic constipation.

Cytokines and platelet-activating factor in human inflamed colonic mucosa

Colonic biopsy specimens from patients with active ulcerative colitis and controls were incubated for four hours in the presence or absence of calcium ionophore or antihuman immunoglobulin E (IgE). Platelet-activating factor (PAF) was determined in the tissue by aggregation assay after extraction with 80% ethanol. PAF was not detected in normal mucosa, whereas A23187 and antihuman IgE stimulated its activity: mean +/- SE, 43.2 +/- 8.6 and 33.0 +/- 6.1 pg/10 mg wet weight, respectively. In active ulcerative colitis, A23187 and antihuman IgE induced significantly higher stimulation of PAF synthesis compared to their effects on normal mucosa. The enhanced stimulation of PAF induced by A23187 was dose-dependently inhibited by sulphasalazine, 5-aminosalicylic acid and prednisolone, but not by sulfapyridine. Colonic interleukin-1 content and release during 24 h of culture were significantly higher in patients with active ulcerative colitis and Crohn's disease compared to normal subjects. Prednisolone significantly and dose-dependently inhibited interleukin-1 release. These results suggest that colonic generation of PAF and interleukin-1 are elevated in patients with inflammatory bowel disease and, thus, may have a role in its pathogenesis. Pharmacological suppression of colonic PAF and interleukin-1 production may have beneficial therapeutic effects.

Ketotifen effectively prevents mucosal damage in experimental colitis

The effects of ketotifen, a 'mast cell stabiliser,' on two models of experimental colitis were examined. The inflammatory response elicited by either trinitrobenzene sulphonic acid or acetic acid resulted in increased colonic synthesis of platelet activating factor, prostaglandin E2, thromboxane B2, leukotrienes B4 and C4, and myeloperoxidase activity. Intragastric administration of ketotifen 100 micrograms/100 grams twice daily significantly decreased mucosal damage when given prophylactically 48 hours before the induction of colitis and then throughout the experiment. This effect was consistent in both models and was accompanied by a significant reduction in mucosal generation of platelet activating factor, prostaglandin E2, thromboxane B2, and leukotrienes C4 and B4. Myeloperoxidase activity was reduced as well, reaching significance only in the acetic acid model. This study shows that both trinitrobenzene sulphonic acid and acetic acid colitis can be pharmacologically manipulated by ketotifen. The mechanism of action of ketotifen has not yet been determined. Ketotifen's potential in the treatment of active inflammatory bowel disease or in the prevention of exacertations, or both, remains to be elucidated.

Effect of drugs on colonic eicosanoid accumulation in active ulcerative colitis

The effect of immunosuppressive drugs, 4-aminosalicylic acid (4-ASA), acetyl 5-aminosalicylic acid (5-ASA), and ketotifen on human colonic eicosanoid accumulation was evaluated in view of enhanced accumulation in patients with active ulcerative colitis. Azathioprine (100 micrograms/ml), cyclosporin (100 micrograms/ml), and methotrexate (100 micrograms/ml) significantly inhibited, by 25-35%, prostaglandin E2 (PGE2) accumulation by organ-cultured colonic mucosa of ulcerative colitis patients. Methotrexate was the only immunosuppressive drug that inhibited leukotriene B4 (LTB4) accumulation (50%), whereas azathioprine inhibited the accumulation of leukotriene C4 (LTC4) (25%). 5-ASA and its metabolite, acetyl 5-ASA, inhibited by 20-70% PGE2, LTB4, and LTC4 accumulation in the culture, supporting the contention that acetyl 5-ASA is as active as 5-ASA in these respects. 4-ASA had no effect on any of the eicosanoids. Ketotifen, a mast cell stabilizer, significantly inhibited the accumulation of PGE2, LTB4, and LTC4 by 33-60%. These results suggest a potential, new, unrecognized mode by which the immunomodulators induce part of their therapeutic effects in inflammatory bowel disease and support the contention that acetyl 5-ASA is as active as 5-ASA. The results obtained also indicate that ketotifen, used effectively in the prevention of bronchial asthma, inhibits the accumulation of colonic eicosanoids and, thus, may be of value in the treatment of inflammatory bowel disease.

Effect of aminophenols (5-ASA and 4-ASA) on colonic interleukin-1 generation

The effect of 5-ASA and 4-ASA, drugs used for the treatment of inflammatory bowel disease, on modulation of experimental colitis and on colonic generation of interleukin-1 was evaluated. Three weeks of treatment with 5-ASA or 4-ASA (50 micrograms/kg) and one week of treatment with 5-ASA significantly decreased colonic interleukin-1 generation and the extent and severity of inflammation in a rat model of colitis induced by trinitrobenzene sulphonic acid. Colonic biopsies were obtained from patients with active ulcerative colitis and organ cultured 24 hours in the absence or presence of the following drugs: sulphasalazine, sulphapyridine, 5-ASA and 4-ASA (25-100 micrograms/ml). Interleukin-1 content in tissue cultured in the presence of 5-ASA (100 micrograms/ml) was two-thirds of its content in tissue cultured in drug free medium and its release into the medium was decreased by 50%. Sulphasalazine 50 micrograms/ml significantly decreased by 33% the tissue content but did not affect interleukin-1 release and a higher dose was not more effective. Sulphapyridine and 4-ASA in doses up to 100 micrograms/ml did not affect either interleukin-1 colonic content or its release into the culture medium. We conclude that pharmacological suppression of colonic interleukin-1 generation may be one, although not the sole mechanism to explain the therapeutic efficacy of 5-ASA in the treatment of inflammatory bowel disease.