T. Diamond

Changes in gastrointestinal morphology associated with obstructive jaundice.

Bacterial translocation has been consistently demonstrated in experimental models of obstructive jaundice. An important factor which promotes this phenomenon is physical injury of the intestinal mucosa. Some previous studies have presented suggestive evidence of this, following bile duct ligation. The aims of this study were to analyse objectively intestinal mucosal morphometric characteristics, to examine for evidence of bacterial translocation, and to assess enterocytes for ultrastructural abnormalities. Adult female Wistar rats were assigned to one of three groups: control (n=8), bile duct ligation (BDL; n=11), or sham operation (n=10). One week later, portal blood, mesenteric lymph nodes, liver, and spleen were harvested and cultured aerobically and anaerobically for evidence of bacterial translocation. Segments of jejunum, ileum, caecum, and large bowel were examined histologically, using light microscopy and morphometrically, using an image analysis system. Electron microscopy was performed on regions of the gastrointestinal tract where significant morphometric alterations had been identified. Significant bacterial translocation was identified following BDL (63.6% BDL vs. 0% sham vs. 0% control, p<0.01, Fishers exact test). There was a significant reduction in total mucosal thickness (standard error) [650 µm (23) BDL vs. 731 µm (27) sham vs. 744 µm (95) control] and villous height [451 µm (20) BDL vs. 515 µm (18) sham vs. 559 µm (79) control] in jaundiced animals, compared with sham‐operated and control animals (p<0.02, Mann–Whitney U‐test). Electron microscopy revealed oedematous change associated with mild inflammation, disruption of desmosomes, and the formation of lateral spaces between enterocytes. In addition, enterocytes showed vacuolation of their cytoplasm and mitochondrial swelling. Increased numbers of bacteria appeared to be attached to the mucosa. These data provide evidence of physical disruption of intestinal mucosa in jaundiced animals, most marked in the distal ileum. Significant bacterial translocation occurs following bile duct ligation and this supports the hypothesis of gut barrier dysfunction with obstructive jaundice. Copyright

Host immune responses and intestinal permeability in patients with jaundice.

Systemic endotoxaemia is implicated in the development of complications associated with obstructive jaundice. The aims of these studies were to assess the systemic immune response to intervention in patients with jaundice and to compare the effects of surgical and non‐surgical biliary drainage on host immune function and gut barrier function.

Endotoxaemia in Obstructive Jaundice

Surgical procedures in patients with obstructive jaundice are associated with significant morbidity and mortality1. This is due, to a large extent, to the development of postoperative complications such as sepsis, bleeding disorders and renal failure24. Clinical and experimental studies have suggested several aetiological factors for these complications including hypotension, impaired nutritional status, impaired immune function and the presence of potential toxic substances in the circulation such as bilirubin and bile acids1’5’6. However, in recent years, there has been an increasing recognition of the role of circulating endotoxins in the development of complications in obstructive jaundice4’7-9. The focus of this review will be the proposed association between the presence of systemic endotoxaemia in obstructive jaundice and the subsequent development of systemic complications. The experimental and clinical evidence for the existence of portal and systemic endotoxaemia in obstructive jaundice will be reviewed, followed by an outline of the current theory on the origin and mechanisms of development of endotoxaemia. The effects of endotoxaemia in jaundiced animals and patients, and the mechanisms by which these may be produced, will then be reviewed. The recognition of endotoxaemia as a possible cause of complications in obstructive jaundice and other pathological situations has led to the development of a variety of therapeutic strategies, including the use of anti-endotoxin agents, and these will be discussed.

Tryptophan catabolites in mesenteric lymph may contribute to pancreatitis-associated organ failure

Multiple organ failure (MOF) is the key determinant of mortality in acute pancreatitis (AP). Mesenteric lymph cytotoxicity contributes to organ failure in experimental models of systemic inflammation. The aim of this study was to evaluate the mesenteric lymph pathway and the lymph injury proteome in experimental AP‐associated MOF, and to test the hypothesis that immunoregulatory tryptophan catabolites contribute to mesenteric lymph cytotoxicity.

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.

The isolated perfused liver response to a 'second hit' of portal endotoxin during severe acute pancreatitis.

Background/Aim: During severe acute pancreatitis (AP), the liver may show an exaggerated response to the inflammatory products of gut injury transported in the portal vein. Our aim was to explore liver proinflammatory mediator production after a ‘second hit’ of portal lipopolysaccharide (LPS) during AP. Methods: Twenty-four rats underwent one of three ‘first-hit’ scenarios: (1) severe AP induced by intraductal glycodeoxycholic acid injection and intravenous caerulein infusion, (2) sham laparotomy, or (3) no first intervention. Eighteen hours later, all animals received a ‘second hit’ of portal LPS in an isolated liver perfusion system. Tumour necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6 concentrations were measured in portal and systemic serum, and in the perfusate 30 and 90 min after the ‘second hit’. Neutrophil activation by the perfusate was assayed using dihydrorhodamine-123 fluorescence. Results: We observed a six-fold increase in IL-6 concentration across the liver during AP. All livers produced TNF-α after the portal LPS challenge, but this was not exaggerated by AP. No differential neutrophil activation by the perfusate was seen. Conclusion: TNF-α, IL-1β, IL-6 and neutrophil activator production by the isolated perfused liver, in response to a ‘second hit’ of portal LPS, does not appear to be enhanced during AP.

Differential Preservation of Lipopolysaccharide-Induced Chemokine/Cytokine Expression during Experimental Pancreatitis-Associated Organ Failure in Rats Shows a Regulatory Expressed Phenotype

Background: Altered lipopolysaccharide (LPS)-responsiveness is a key feature of acute pancreatitis (AP)-associated multiple organ failure (AP-MOF) in rats and humans. Aim: To determine the differential expression of 16 cytokines and chemokines in response to delayed LPS administration in established experimental AP-MOF in rats. Methods: In a cubic factorial group design (12 groups, n = 6 rats/group), 0, 6 and 30 µg/kg Escherichia coli 0111:B4 LPS was administered intra-arterially, 18 h into experimental AP-MOF or sham laparotomy. AP was induced by intraductal glycodeoxycholic acid and intravenous caerulein. Central venous serum concentrations of 16 cytokines and chemokines were measured by Searchlight™ multiplex ELISA. Results: Four patterns were observed: (1) TNF-α, IL-1α, IL-1β, IL-6, IFN-γ, MCP-1, MIP-2α, MIP-3α, fractalkine and RANTES showed a diminished LPS response in AP versus sham (p < 0.001, ANOVA); (2) IL-2, IL-4 and GM-CSF levels were undetectable; (3) CINC-2α and GRO/KC showed little or no difference between AP and controls, and (4) IL-10 concentrations after 0 and 6 µg/kg, but not 30 µg/kg LPS injection were significantly higher in AP than controls (p < 0.001, ANOVA). Conclusion: Experimental AP-MOF in rats results in differential preservation of the cytokine and chemokine response to LPS challenge, with a predominantly regulatory expressed phenotype.

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.

Kupffer cell depletion does not significantly reduce the hepatic proinflammatory cytokine response to portal endotoxaemia in obstructive jaundice

ConclusionsThe data suggest that, although Kupffer cells appear to initiate the inflammatory response to endotoxin in obstructive jaundice, other hepatic cells release proinflammatory cytokines subsequently.