Margaret Hoper

The dextran sulphate sodium (DSS) model of colitis: an overview

The dextran sulphate sodium model of colitis has demonstrated several correlations with human inflammatory bowel disease and is deemed suitable for investigating pathogenesis, therapeutic options and the dysplasia–adenocarcinoma sequence of inflammatory bowel disease. It is widely applicable to mice, rats, hamsters and guinea pigs. This review explores the features of this model and identifies areas for further research studies.

Preliminary results of a prospective randomized trial of restrictive versus standard fluid regime in elective open abdominal aortic aneurysm repair.

Background:Open abdominal aortic aneurysm (AAA) repair is associated with a significant morbidity (primarily respiratory and cardiac complications) and an overall mortality rate of 4% to 10%. We tested the hypothesis that perioperative fluid restriction would reduce complications and improve outcome after elective open AAA repair. Methods:In a prospective randomized control trial, patients undergoing elective open infra-renal AAA repair were randomized to a “standard” or “restricted” perioperative fluid administration group. Primary outcome measure was rate of major complications (MC) after AAA repair and secondary outcome measures included: Sequential Organ Failure Assessment Score; FiO2/PO2 ratio; Urinary Albumin/Creatinine Ratio; Length-of-stay in, intensive care unit, high dependency unit, in-hospital. This prospective Randomized Controlled Trial was registered in a publicly accessible database and has the following ID number ISRCTN27753612. Results:Overall 22 patients were randomized, 1 was excluded on a priori criteria, leaving standard group (11) and restricted group (10) for analysis. No significant difference was noted between groups in respect to age, gender, American Society Anesthesiology class, Physiological and Operative Severity Score for the Enumeration of Mortality and Morbidity scores, operation time, and operation blood loss. There were no in-hospital deaths and no 30-day mortality. The cumulative fluid balance on day 5 postoperative was for standard group, 8242 ± 714 mL, compared with restricted group, 2570 ± 977 mL, P < 0.01. MC were significantly reduced in the restricted group (n = 10), 1 MC, compared with standard group (n = 11), 14 MC, P < 0.024. Total and postoperative length-of-stay in-hospital was significantly reduced in the restricted group, 9 ± 1 and 8 ± 1 days, compared with standard group, 18 ± 5 and 16 ± 5 days, P < 0.01 and P < 0.025, respectively. Conclusions:Serious complications are common after elective open AAA repair, and we have shown for the first time that a restricted perioperative fluid regimen can prevent MC and significantly reduce overall hospital stay.

Effect of Supplemental L-Arginine in a Chemical-Induced Model of Colorectal Cancer

Abstract. l -Arginine inhibits the development of spontaneous, transplantable solid tumors and chemically induced mammary tumors. The aim of the present study was to investigate the effect of l -arginine on chemically induced colorectal cancer in male Wistar rats. Colorectal cancer was induced in all animals by weekly subcutaneous injections of the colonic procarcinogen 1,2-dimethyhydrazine (DMH) at a dosage of 20 mg/kg body weight. Arginine was given in a 1% solution of drinking water. Group I was the DMH control; group II, arginine for 22 weeks; group III, arginine for the first 10 weeks only. Lymphocyte function was evaluated by measuring the thymic lymphocyte proliferative response to the T cell mitogen phytohemagglutinin. The results show that tumor incidence and tumor burden (tumors/rat and tumors/tumor-bearing rat) were significantly reduced in both groups of animals receiving arginine compared to DMH controls ( p < 0.05). The tumor areas and volumes were also reduced in both arginine groups ( p < 0.05). Thymic lymphocyte stimulation indices were significantly increased by arginine supplementation ( p < 0.05). These results would be in keeping with the reduction in colorectal tumor production due to a “nonspecific” stimulation of the host immune system by l -arginine.

Bactericidal/permeability-increasing protein attenuates systemic inflammation and acute lung injury in porcine lower limb ischemia-reperfusion injury.

ObjectiveTo investigate the role of recombinant bactericidal/permeability-increasing protein (rBPI21) in the attenuation of the sepsis syndrome and acute lung injury associated with lower limb ischemia–reperfusion (I/R) injury. Summary Background DataGut-derived endotoxin has been implicated in the conversion of the sterile inflammatory response to a lethal sepsis syndrome after lower torso I/R injury. rBPI21 is a novel antiendotoxin therapy with proven benefit in sepsis. MethodsAnesthetized ventilated swine underwent midline laparotomy and bilateral external iliac artery occlusion for 2 hours followed by 2.5 hours of reperfusion. Two groups (n = 6 per group) were randomized to receive, by intravenous infusion over 30 minutes, at the start of reperfusion, either thaumatin, a control-protein preparation, at 2 mg/kg body weight, or rBPI21 at 2 mg/kg body weight. A control group (n = 6) underwent laparotomy without further treatment and was administered thaumatin at 2 mg/kg body weight after 2 hours of anesthesia. Blood from a carotid artery cannula was taken every half-hour for arterial blood gas analysis. Plasma was separated and stored at −70°C for later determination of plasma tumor necrosis factor (TNF)-&agr;, interleukin (IL)-6 by bioassay, and IL-8 by enzyme-linked immunosorbent assay (ELISA), as a markers of systemic inflammation. Plasma endotoxin concentration was measured using ELISA. Lung tissue wet-to-dry weight ratio and myeloperoxidase concentration were used as markers of edema and neutrophil sequestration, respectively. Bronchoalveolar lavage protein concentration was measured by the bicinclinoic acid method as a measure of capillary-alveolar protein leak. The alveolar–arterial gradient was measured; a large gradient indicated impaired oxygen transport and hence lung injury. ResultsBilateral hind limb I/R injury increased significantly intestinal mucosal acidosis, intestinal permeability, portal endotoxemia, plasma IL-6 concentrations, circulating phagocytic cell priming and pulmonary leukosequestration, edema, capillary-alveolar protein leak, and impaired gas exchange. Conversely, pigs treated with rBPI21 2 mg/kg at the onset of reperfusion had significantly reduced intestinal mucosal acidosis, portal endotoxin concentrations, and circulating phagocytic cell priming and had significantly less pulmonary edema, leukosequestration, and respiratory failure. ConclusionsEndotoxin transmigration across a hyperpermeable gut barrier, phagocytic cell priming, and cytokinemia are key events of I/R injury, sepsis, and pulmonary dysfunction. This study shows that rBPI21 ameliorates these adverse effects and may provide a novel therapeutic approach for prevention of I/R-associated sepsis syndrome.

Glutamine Improves Intestinal Barrier Function in Experimental Biliary Obstruction

Objective: To determine the effects of enteral administration of glutamine on intestinal barrier function in experimental biliary obstruction. Background: Extrahepatic biliary obstruction is associated with the failure of intestinal barrier function, allowing bacteria and other substances from the intestine to enter the circulation and initiate a systemic inflammatory response, causing impairment of multiple organs. The amino acid glutamine has been shown to improve intestinal barrier function in other conditions, but its effects in biliary obstruction have not been fully examined. Methods: This study examined the effects of enteral administration of glutamine on intestinal permeability and on bacterial translocation from the intestine in a rodent model of biliary obstruction. Results: Glutamine was shown to reduce intestinal permeability measured as percentage excretion of 14C 7 days after biliary obstruction (0.35 ± 0.03 vs. 0.56 ± 0.085% in controls, p = 0.028), and glutamine administration was also associated with a decreased incidence of bacterial translocation to extra-intestinal sites (p = 0.03). Radiolabelled bacterial studies also demonstrated reduced translocation of bacterial fragments to extra-intestinal sites in glutamine-treated animals (p = 0.01). There was also some evidence of decreased exposure to endotoxin, reduced systemic inflammation and increased bacterial killing by the immune system in glutamine-treated animals. Conclusions: Glutamine modulates intestinal permeability and reduces bacterial translocation in an animal model of experimental biliary obstruction and may increase bacterial killing by the immune system.

The probiotic bacterium Lactobacillus plantarum species 299 reduces intestinal permeability in experimental biliary obstruction

Aims:  Extrahepatic biliary obstruction is associated with the failure of intestinal barrier function, allowing bacteria and other substances from the intestine to enter the circulation and initiate a systemic inflammatory response, causing impairment of organ function. Probiotic bacteria have been shown to have beneficial effects on intestinal barrier function in other conditions, but their effects have never been studied in biliary obstruction.

Metallothionein crypt-restricted immunopositivity indices (MTCRII) correlate with aberrant crypt foci (ACF) in mouse colon

Metallothionein (MT) crypt-restricted immunopositivity indices (MTCRII) are colonic crypt stem cell mutation markers that may be induced early and in abundance after mutagen treatment. Metallothionein is the endogenous reporter gene for MTCRII, but is not typically implicated in the classical pathway of colorectal tumorigenesis. Hence, the oncological relevance of MTCRII is unclear. This study tests the hypothesis that MTCRII induced by N-methyl-N-nitrosourea (MNU) and lambda carrageenan (λCgN) associate with aberrant crypt foci (ACF) in mouse colon. Undegraded λCgN and MNU were tested alone and in combination against MTCRII and ACF in Balb/c mice, at 20 weeks after the start of treatment. MTCRII were unaffected by λCgN alone. Combined λCgN/MNU treatments induced greater MTCRII (P<0.01) as well as greater number (P<0.001) and crypt multiplicity (P<0.01) of ACF than MNU alone. MTCRII were approximately 10-fold more numerous than ACF, although linear correlations were observed between these parameters (r=0.732; P<0.01). MTCRII are induced by λCgN/MNU interactions in sufficient numbers to provide statistical power from relatively small sample sizes and correlate with ACF formation. MTCRII could thus provide the basis for a novel medium-term murine bioassay relevant to early-stage colorectal tumorigenesis.

Hepatic cytokine response can be modulated using the Kupffer cell blocker gadolinium chloride in obstructive jaundice.

INTRODUCTION Depletion of Kupffer cells by gadolinium chloride (GdCl(3)) reduces the systemic response during sepsis. The study aim was to investigate the effect of this depletion on hepatic proinflammatory cytokine response to portal endotoxaemia. METHODS Sixteen Wistar rats were randomised to receive either saline IV (n = 8) or GdCl(3) (10 mg/kg IV, n = 8) six days after bile duct ligation (BDL). 24 h later the animals were perfused for 2 h, using isolated hepatic perfusion. Aliquots of effluent perfusate were collected at 20-min intervals for cytokine analysis. Sections of liver were sampled and the hepatic Kupffer cell number of each group was measured using ED1 immunohistochemistry. RESULTS Pre-treatment with GdCl(3) resulted in significantly reduced serum bilirubin concentrations but significantly elevated serum ALP and AST levels compared to the control group. It was also associated with a significant reduction in Kupffer cell numbers and a corresponding significant reduction in hepatic TNFα and IL-6 production in response to portal endotoxaemia. CONCLUSIONS Pre-treatment with GdCl(3) in jaundiced animals reduced Kupffer cell numbers, attenuated liver enzyme abnormalities and reduced TNFα and IL-6 in response to portal endotoxaemia. Hepatic Kupffer cells, therefore, play a significant role in the development of an exaggerated inflammatory response in obstructive jaundice.

The use of antiendotoxin peptides in obstructive jaundice endotoxemia.

Background Two novel antiendotoxin peptides, P6 and C1, may reduce the inflammatory response. This study aimed to determine the effect of endotoxin on hepatic cytokine response and to assess P6 and C1-related attenuation of the proinflammatory response to endotoxemia, in experimental biliary obstruction. Materials and methods 15 Male Wistar rats were randomized to one of three groups: bile duct ligation (BDL)+P6 (n=5), BDL+C1 (n=5), and BDL+no peptide (n=5). Rats were weighed and underwent BDL surgery on day 1. On day 8, the rats were reweighed and isolated hepatic perfusion was carried out. P6 or C1 peptide (10 &mgr;mol/l) was preincubated with 300 ml of endotoxin-containing Krebs perfusate. After perfusion of 10 min with endotoxin-free perfusate, the livers were perfused for another 10 min with 300 ml of perfusate-containing endotoxin on its own or endotoxin plus peptide. This was followed by a further 100 min of perfusion with endotoxin-free perfusate. Effluent perfusate was collected at 20-min intervals for subsequent biochemical and cytokine analyses. Results Perfusion with endotoxin+P6 or endotoxin+C1 resulted in no significant difference in weight loss, or interleukin-6 response compared with perfusion with endotoxin alone. However, perfusion with endotoxin+P6 or endotoxin+C1 significantly reduced the tumor necrosis factor-&agr; response to portal endotoxemia compared with perfusion with endotoxin alone. Conclusion This study demonstrates that novel antiendotoxin peptides may attenuate the hepatic inflammatory response in portal endotoxemia. In obstructive jaundice, preoperative peptide administration may reduce endotoxin-related postoperative complications.