Enterohepatic circulation of bacterial chemotactic peptide in rats with experimental colitis

Small duct primary sclerosing cholangitis: A discrete variant or a bridge to large duct disease, a practical review

The natural history, associations with inflammatory bowel disease (IBD), and long-term outcomes of large duct primary sclerosing cholangitis (ldPSC) have been well documented. Small duct primary sclerosing cholangitis (sdPSC) is a much less common and relatively more benign variant. The natural history of sdPSC has been difficult to characterize given the limited number of studies in the literature especially with regards to the subset of patients who progress to large duct involvement. It has been unclear whether sdPSC represented a subset of ldPSC, an earlier staging of ldPSC, or a completely separate and distinct entity of its own. Strong associations between sdPSC and IBD have been established with suspicion that concurrent sdPSC-IBD may be a key prognostic factor in determining which patients are at risk of progression to ldPSC. Little is known regarding the discrete circumstances that predisposes some patients with sdPSC to progress to ldPSC. It has been suspected that progression to large biliary duct involvement subjects this subset of patients to potentially developing life-threatening complications. Here the authors conducted a thorough review of the published sdPSC literature using Pubmed searches and cross-referencing to compile all accessible studies regarding cohorts of sdPSC patients in order better characterize the subset of sdPSC patients who progress to ldPSC and the associated outcomes.

The Role of the Intestine in the Pathogenesis of Primary Sclerosing Cholangitis: Evidence and Therapeutic Implications

The pathogenesis of primary sclerosing cholangitis (PSC), a progressive biliary tract disease without approved medical therapy, is not well understood. The relationship between PSC and inflammatory bowel disease has inspired theories that intestinal factors may contribute to the development and progression of hepatobiliary fibrosis in PSC. There is evidence from both fecal and mucosa-associated microbial studies that patients with PSC harbor an abnormal enteric microbiome. These organisms are thought to produce toxic byproducts that stimulate immune-mediated damage of hepatocytes and the biliary tree. The link between these mechanisms may be related to altered intestinal permeability leading to migration of bacteria or associated toxins to the liver through the portal circulation. In support of these concepts, early trials have demonstrated improved biochemical parameters and symptoms of PSC with oral antibiotics, ostensibly through manipulation of the enteric microbiota. This article reviews the published literature for evidence as well as gaps in knowledge regarding these mechanisms by which intestinal aberrations might drive the development of PSC. We also identify areas of future research that are needed to link and verify these pathways to enhance diagnostic and therapeutic approaches.

Hepatic Complications of Inflammatory Bowel Disease

Hepatobiliary disorders are commonly encountered in patients with inflammatory bowel disease (IBD). Although primary sclerosing cholangitis is the stereotypical hepatobiliary disorder associated with IBD, other diseases, including autoimmune hepatitis and nonalcoholic fatty liver disease, also are encountered in this population. Several agents used for treatment of IBD may cause drug-induced liver injury, although severe hepatotoxicity occurs infrequently. Furthermore, reactivation of hepatitis B virus infection may occur in patients with IBD treated with systemic corticosteroids and biologic agents.

Cutting edge issues in primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a chronic inflammatory liver disease characterized by the destruction of medium- to large-sized bile ducts and intense concentric fibrosis. Complications from PSC include bacterial cholangitis, cirrhosis, and cholangiocarcinoma and a therapy that might alter the natural history of the disease remains lacking. Our understanding of the pathogenesis of PSC also remains rudimentary but the strong association between PSC and inflammatory bowel disease suggest causal links between the diseases. The male predominance in PSC, lack of a defined, pathogenic auto-antigen, and the potential role of the innate immune system suggest that PSC may be due to dysregulation of immunity rather than a classic autoimmune disease. However, PSC shares several genetic susceptibility loci with other autoimmune diseases including the human leukocyte antigen DRB01*03 haplotype. The precise immune response of PSC is largely unknown but likely involves activation of the innate immune system by bacterial components delivered to the liver via the portal vein. Induction of adhesion molecules and chemokines leads to the recruitment of intestinal lymphocytes. Bile duct injury results from the sustained inflammation and production of inflammatory cytokines. Biliary strictures may cause further damage as a result of bile stasis and recurrent secondary bacterial cholangitis. Progress in our basic understanding of PSC is desperately needed in order to rationally design new therapeutic approaches to this disease.

Colorectal Oncogenesis and Inflammation in a Rat Model Based on Chronic Inflammation due to Cycling DSS Treatments

Inflammation is known to be linked with development of colorectal cancer, and the aim was to assess the malignant potential and degree of inflammation in a dextran-sulphate-sodium-(DSS-) induced cyclic colonic tumour model (CTM) in rats and to compare it with the azoxymethane-(AOM-) induced CTM model. Tumours developed in both groups, although, in the DSS group, the colonic mucosa appeared edematous and the number of haemorrhagic erosions and quantity of dysplastic lesions were higher as well as the mucosal concentration of myeloperoxidase and faecal viable count of Enterobacteriaceae. The livers were affected as evaluated by steatosis, parenchymal loss, haemorrhage, and inflammatory infiltrations, and higher proportions of acetate and lower proportions of butyrate in colonic content were found. The DSS model seems to mimic the clinical situation and may be valuable for investigation of inflammation-related dysplasia and colon cancer, as well as for altered liver function by endogenous inflammatory mediators.

The immunobiology of primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease histologically characterized by the presence of intrahepatic and/or extrahepatic biliary duct concentric, obliterative fibrosis, eventually leading to cirrhosis. Approximately 75% of patients with PSC have inflammatory bowel disease. The male predominance of PSC, the lack of a defined, pathogenic autoantigen, and the potential role of the innate immune system suggest that it may be due to dysregulation of immunity rather than a classic autoimmune disease. However, PSC is associated with several classic autoimmune diseases, and the strongest genetic link to PSC identified to date is with the human leukocyte antigen DRB01*03 haplotype. The precise immunopathogenesis of PSC is largely unknown but likely involves activation of the innate immune system by bacterial components delivered to the liver via the portal vein. Induction of adhesion molecules and chemokines leads to the recruitment of intestinal lymphocytes. Bile duct injury results from the sustained inflammation and production of inflammatory cytokines. Biliary strictures may cause further damage as a result of bile stasis and recurrent secondary bacterial cholangitis. Currently, there is no effective therapy for PSC and developing a rational therapeutic strategy demands a better understanding of the disease.

Atypical p-ANCA in PSC and AIH: a hint toward a "leaky gut"?

Primary sclerosing cholangitis (PSC) and autoimmune hepatitis (AIH) are enigmatic chronic inflammatory diseases of the liver, which are frequently associated with chronic inflammatory bowel diseases. Both types of liver disease share various distinct autoantibodies such as atypical perinuclear antineutrophil cytoplasmic antibodies (p-ANCA), and thus are considered autoimmune disorders with atypical features. The discovery that atypical p-ANCA recognize both tubulin beta isoform 5 in human neutrophils and the bacterial cell division protein FtsZ has renewed the discussion on the potential role of microorganisms in the pathogenesis of both diseases. In this paper, we review the evidence for microbial infection in PSC and AIH and discuss new concepts how cross-recognition between microbial antigens in the gut and host components by the immune system along with stimulation of pattern recognition receptors might give rise to chronic hepatic inflammatory disorders with features of autoimmunity.

Microbial influences in inflammatory bowel diseases

The predominantly anaerobic microbiota of the distal ileum and colon contain an extraordinarily complex variety of metabolically active bacteria and fungi that intimately interact with the host's epithelial cells and mucosal immune system. Crohn's disease, ulcerative colitis, and pouchitis are the result of continuous microbial antigenic stimulation of pathogenic immune responses as a consequence of host genetic defects in mucosal barrier function, innate bacterial killing, or immunoregulation. Altered microbial composition and function in inflammatory bowel diseases result in increased immune stimulation, epithelial dysfunction, or enhanced mucosal permeability. Although traditional pathogens probably are not responsible for these disorders, increased virulence of commensal bacterial species, particularly Escherichia coli, enhance their mucosal attachment, invasion, and intracellular persistence, thereby stimulating pathogenic immune responses. Host genetic polymorphisms most likely interact with functional bacterial changes to stimulate aggressive immune responses that lead to chronic tissue injury. Identification of these host and microbial alterations in individual patients should lead to selective targeted interventions that correct underlying abnormalities and induce sustained and predictable therapeutic responses.

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Intestinal permeability and bacterial growth of the small bowel in patients with primary sclerosing cholangitis

OBJECTIVE

Animal studies show that small intestinal bacterial overgrowth and infusion of bacterial antigens into portal blood cause hepatic histological changes similar to those seen in primary sclerosing cholangitis in man. It has been suggested that aa similar mechanism involving bacterial overgrowth with increased small-bowel permeability may play a pathogenic role in patients with primary sclerosing cholangitis (13 M, 9 F, median age 37 years, range 21-74 years), 19 of whom (83%) had quiescent inflammatory bowel disease, were included in the study along with 18 healthy volunteers (9 F, ( M, median age 36 years, range 23-80 years). Small-bowel bacterial overgrowth was defined as the presence of colonic flora>10(5) colony-forming units (cfu)/ml from duodenal aspirations. Small-bowel intestinal permeability was assessed as the differential urinary excretion of lactulose/L-rhamnose.

RESULTS

Bacterial overgrowth was evident in one patient with primary sclerosing cholangitis (4.5%) (Enterobacter) and in none of the controls. Intestinal permeability in patients with primary sclerosing cholangitis (0.034 (0.026-0.041) (median, interquartile range (IQR)) did not differ significantly from that of the controls (0.033 (0.025-0.041).

CONCLUSIONS

Small intestinal bacterial overgrowth and increased intestinal permeability does not seem to play an important pathogenic role in patients with primary sclerosing cholangitis.

Effect of mesalazine, metronidazole and gentamicin on bacterial translocation in experimental colitis

BACKGROUND AND AIM

In inflammatory bowel disease it has been established that enteric microorganisms are present in the final stage of the active inflammatory process. The purpose of the present study was to investigate the effects of mesalazine, and metronidazole-gentamicin combination, on bacterial translocation in an animal colitis model.

METHODS

Fifty rats were stratified into five groups. The control group (group NC) was given only 2 mL saline enema and the remaining four groups were given 2 mL acetic acid enema. Group CC was the diseased control group. The treatment regimens started on the fifth day: mesalazine enema in group MesC, metronidazole-gentamicin in group MGC, and mesalazine + metronidazole + gentamicin in group MesMGC. After death on day 10, 2.5-cm colonic segments from all groups were weighed separately. In all rats, histopathological scoring was done, and samples from feces, blood, liver and spleen underwent microbiological analyses.

RESULTS

For all diseased rats, both mean weight loss and colonic segment weight/bodyweight ratio was significantly higher than that in the sham group. As compared with other groups, body and colonic segment changes as well as histopathological scoring in rats receiving mesalazine enema either solely or in combination with the antibiotics were lower. No bacterial growth was found in the blood, liver and spleen of the rats in the control group while enteric bacteria, mainly Escherichia coli (35%) were the most common bacteria translocated to that in the latter. Antibiotic combination, alone or in combination with mesalazine was effective in reducing the bacterial translocation while mesalazine administration did not properly influence its regression.

CONCLUSIONS

Gram-negative enteric bacteria, predominantly E. coli, was the most common bacteria isolated in bacterial translocation occurring in acetic acid-induced colitis. This trial showed that mesalazine alone did not incorporate the reduction of infectious events, despite its beneficial effect on inflammatory changes in experimental colitis. Metronidazole and gentamicin combination given intraperitoneally was more effective than topical mesalazine in decreasing bacterial translocation.

The role of endogenous bacterial flora: bystander or the necessary prerequisite?

Abundant experimental and clinical data incriminate microbial factors in the pathogenesis of inflammatory bowel diseases. Commensal bacteria, and their products, provide the constant antigenic stimulus to disequilibrate the mucosal immune system towards an overly aggressive response in a genetically susceptible host with reduced tolerance towards the autologous flora. Not all bacteria have equal proinflammatory capabilities. Some may be even beneficial as demonstrated by the anti-inflammatory effects of so-called probiotics. Further investigations are needed to translate the clear experimental and clinical evidence into benefit for the patients.

Preparation and preliminary evaluation of 99mTc-EC-For-MLFK

For-Met-Leu-Phe-Lys (For-MLFK), a chemotactic peptide that binds with high affinity to granulocytes and monocytes, was labeled with 99mTc using ethylene dicysteine (EC) as the metal chelating system. EC was selected because of the rapid renal excretion of its 99mTc-complex and therefore, was expected to enhance the degree of urinary elimination of the peptide-conjugate. 99mTc-EC-For-MLFK was prepared using a preformed chelate approach. After incubation of 99mTc-EC-For-MLFK with total blood, 68.1% of the labeled peptide was associated with WBC and 86% of this cell-associated activity was bound to granulocytes. Biodistribution studies in normal mice revealed a very fast blood clearance (4.1% and 0.6% of I.D. in blood at respectively 5 and 60 min p.i.). However, elimination of the labeled peptide proceeds mainly via the hepatobiliary system (24.5% of I.D. in liver and 48.8% of I.D. in intestines at 60 min p.i.) and to a much lower degree via the kidneys (17.9% in renal system at 60 min p.i.). From these results, it is concluded that 99mTc-EC-For-MLFK is not suited to image infections, despite its high binding to granulocytes, since it leads to high, non-specific, abdominal activity.

Experimental colitis attenuates development of toxin-induced cholangitis in rats

Primary sclerosing cholangitis frequently occurs in association with ulcerative colitis. This close association may be due to colitis predisposing patients to bile ductular injury. Therefore, we determined the susceptibility of rats with experimental colitis to toxin-induced cholangitis. Sprague-Dawley rats received 2,4,6-trinitrobenzene-sulfonic-acid (TNBS) or ethanol vehicle intracolonically. Seven days later, rats received either the biliary epithelial cell toxin alpha-naphthylisothiocyanate (ANIT) or vehicle and were killed 24 hr later. Liver histology, serum biochemistries and tumor-necrosis factor-alpha (TNF-alpha), and hepatic interleukin-10 (IL-10) mRNA were determined. TNBS-treated rats showed extensive macroscopic colonic damage and a 10-fold increase in myeloperoxidase activity compared to ethanol-treated controls. ANIT-treated noncolitic rats showed portal inflammation centered on damaged bile ducts (cholangitis), which was markedly attenuated in ANIT-treated colitic rats. Hepatic IL-10 mRNA was twofold higher in colitic compared to noncolitic rats, with no difference in serum TNF-alpha. In conclusion, experimental colitis attenuates the development of toxin-induced cholangitis in rats, possibly by up-regulating hepatic IL-10 expression.

Animal models for primary sclerosing cholangitis

Since the aetiopathogenesis of primary sclerosing cholangitis (PSC) in humans remains undefined, investigators have studied a variety of animal models to gain insights into immunopathogenetic mechanisms associated with obliterative fibrous cholangitis of intra- and extra-hepatic bile ducts. To date, no animal model has been developed that exhibits all of the attributes of PSC. Rodent models instigated by bacterial cell components or colitis are promising because they may help to explain the strong association between PSC and inflammatory bowel disease (IBD). Other models of direct injury to biliary epithelia, peribiliary vascular endothelia or portal venous endothelia indicate that inflammation, chemokines and cytokines can produce diffuse sclerosis of bile ducts. Models of toxic, infectious or intra-luminal injury of the biliary tract also exhibit focal biliary sclerosis mediated by inflammation and cytokines. The histopathology of several models suggests a sequence of events beginning with secretion of proinflammatory cytokines by activated hepatic macrophages followed by peribiliary infiltration with CD4 and CD8 T cells with a T helper 1 phenotype. These results strongly suggest co-ordinated, pathogenetic roles for both the innate and adaptive immune responses. However, the stimuli that initiate and perpetuate peribiliary fibrosis remain unknown. Interestingly, several models are also associated with the development of anti-neutrophil cytoplasmic antibodies that react in a perinuclear and cytoplasmic pattern similar to that observed in patients with ulcerative colitis and/or PSC. Finally, models of extra-hepatic biliary obstruction continue to provide important information about the pathogenesis of portal fibrosis and secondary biliary cirrhosis that occurs in PSC and other diseases with obstruction of bile flow. Future studies in either existing or new animal models should advance our understanding of the pathogenesis of PSC, the major prerequisite for the development of effective therapies.

Influence of the bifunctional chelate on the biological behavior of (99m)Tc-labeled chemotactic peptide conjugates

Conjugates of For-MLFK and For-NleLFNleYK with S-benzyl mercaptoacetyl dipeptides containing, respectively, zero, one, and two carboxyl functions in their structures were prepared and labeled with (99m)Tc. In vitro binding studies using isolated human granulocytes indicated specific receptor binding of the radiolabeled conjugates. The fraction of granulocyte-associated activity was determined after incubation with total blood. Biodistribution studies of the (99m)Tc-peptides in normal mice revealed a very fast blood clearance proceeding mainly via the hepatobiliary system. Urinary excretion was higher for conjugates containing carboxyl functions in their ligand structures.

Disturbed bile secretion and cytochrome P450 function during the acute state of experimental colitis in rats

BACKGROUND/AIMS

A variety of hepatobiliary abnormalities has been described in patients with inflammatory bowel diseases. However, the pathophysiological mechanisms leading to these liver alterations are poorly understood. The aim of the present study was to investigate parameters of liver function in a trinitrobenzenesulfonic acid (TNB)-induced rat colitis model.

METHODS

Glucose output, bile acid secretion, bile acid uptake, and the cytochrome P-450 metabolic capacity during TNB-colitis were studied in the perfused liver model. Furthermore, hepatic bile acid- and glycogen content was measured. To evaluate the inflammatory response in the colon and liver, NF-kappaB/Rel was quantified by electrophoretic mobility shift assays. As an NF-kappaB/Rel regulated gene the inducible NO-synthase (NOS2) was evaluated by Western blot analysis. As possible mediators released from the inflamed colon into the portal vein, endotoxin and the stable metabolite of prostaglandin I2 (6-keto-prostaglandin-F1alpha) were determined.

RESULTS

Glucose output, bile acid secretion, bile acid uptake, and cytochrome P-450 metabolic capacity decreased on the first and second day of TNB-colitis. Hepatic bile acid content increased at day 14 of colitis. Glycogen content was reduced, most likely due to an inadequate chow intake of these animals. A low level of portal endotoxin was detectable during the first 2 days of colitis. In addition, 6-keto-prostaglandin-F1alpha was clearly increased in portal blood. NF-kappaB/Rel binding activity and inducible NOS2 were strongly positive in the colon during colitis. Although low levels of portal endotoxin were measured during the first 2 days of colitis, no significant NF-kappaB/Rel activity and NOS2 induction were detected in the liver.

CONCLUSION

Our results indicate that during the acute state of the TNB-colitis, bile acid secretion and cytochrome P-450 function are disturbed in the absence of distinct inflammatory changes in the liver.

Physiological assessment of epithelial function in damaged rat colon

OBJECTIVE

To assess colonic damage quantitatively by electrophysiological parameters such as membrane potential difference, short circuit current and transepithelial resistance, and by colonic membrane permeability (permeation clearance) of FITC-labelled dextran 4000.

MATERIALS AND METHODS

For experimental colitis models of rats, trinitrobenzene sulphonic acid-, acetic acid-, and dextran sulphate sodium-induced models were employed. The Ussing-type chamber was used for determination of the electrophysiological parameters and permeation clearance of FITC-labelled dextran 4000.

RESULTS

Reductions of all the above electrophysiological parameters were observed in trinitrobenzene sulphonic acid- and acetic acid-induced models. No good correlation between the reduction in the parameters and the intestinal damage score was found in any of the models. This shows that damage scores do not necessarily reflect precise changes in physiological epithelial function. In contrast, the electrophysiological parameters were well correlated with membrane permeability. The reduction in transepithelial resistance, i.e. reduction in barrier function, was supported by an increase in permeation clearance of FITC-labelled dextran 4000 and the plasma appearance of endotoxin in the trinitrobenzene sulphonic acid-induced model. Through the recovery of transepithelial resistance and permeation clearance of FITC-labelled dextran 4000 to control values in the acetic acid-induced model, automatic recovery of the model to normal occurred.

CONCLUSION

Examination of the electrophysiological parameters and permeation clearance of FITC-labelled dextran 4000 can provide a useful method of assessment of epithelial damage.

Primary biliary cirrhosis, primary sclerosing cholangitis, and autoimmune cholangitis

Primary biliary cirrhosis (PBC), and autoimmune cholangitis are presumed to be autoimmune cholestatic diseases, but the relevant antigens are unknown. Primary biliary cirrhosis is diagnosed by a positive serum mitochondrial antibody test. It usually affects women and has a very long course, culminating in liver transplantation or death. Ursodeoxycholic acid is probably the appropriate treatment. Primary sclerosing cholangitis (PSC) is marked by progressive destruction of extrahepatic and intrahepatic bile ducts. There is no specific diagnostic test or treatment. Cholangiocarcinoma is the dreaded complication and precludes liver transplantation, the only chance of a cure. Autoimmune cholangitis overlaps PBC and autoimmune chronic hepatitis. It is a rare condition, resembling PBC but with a negative serum mitochondrial antibody test; however, serum antinuclear antibodies and smooth muscle antibodies are present in high titers.

Hepatobiliary manifestations of inflammatory bowel disease

PSC is the most common of the clinically significant hepatobiliary diseases seen in association with IBD, with an incidence that varies from 2.5% to 7.5%. Conversely, 50% to 75% of patients with PSC have IBD. This high degree of association suggests a common pathogenetic mechanism; however, no causal relationship has been established. The etiopathogenesis of PSC remains poorly understood, despite a large number of studies looking at differing hypotheses. The diagnosis is usually established by cholangiography. Liver biopsy can sometimes be helpful in diagnosing pericholangitis. There is a significant overlap of the histology with chronic hepatitis. Serum markers have been studied for diagnosing PSC, particularly for early diagnosis of cholangiocarcinoma, but none have shown the high sensitivity and specificity needed to use them clinically. PSC usually progresses insidiously and eventually leads to cirrhosis. Despite progress in early recognition, optimal management of patients with PSC remains a challenge requiring a multidisciplinary approach among hepatologists, endoscopists, surgeons, and interventional radiologists. Colectomy for ulcerative colitis does not alter the natural history of PSC. There is a high (10% to 15%) incidence of cholangiocarcinoma in patients with PSC. This incidence along with the risk of colon cancer in patients with ulcerative colitis makes it necessary to follow these patients closely. A number of pharmacologic therapies have been evaluated, but none has proven successful in slowing the progression of PSC or prolonging survival. Endoscopic therapy has a proven utility in treating complications of recurrent cholangitis or worsening jaundice in the setting of a dominant stricture, but endoscopy has not been shown to improve survival or decrease the need for liver transplantation. Liver transplantation is life-saving for patients with advanced PSC. Pericholangitis, gallstones, and chronic hepatitis are additional disorders noted in association with IBD, but they are much less common and easier to manage than PSC.

Macrophages are essential for lymphocyte infiltration in formyl peptide-induced cholangitis in rat liver

BACKGROUND/AIMS

Cholangitis in rats induced by N-formyl L-methionine L-leucine L-tyrosine (fMLT) is characterized by infiltration of mononuclear cells around bile ducts in portal tracts.

METHODS

We investigated the initial process in fMLT-induced cholangitis histochemically.

RESULTS

Administration of fMLT into the colons of adult male Wistar rats with acetate-induced colitis resulted in an infiltration of mostly macrophages and granulocytes into the portal tracts on day 1. Abnormal peroxidation as demonstrated by the nitro blue tetrazolium (NBT) reaction occurred in bile duct cells as well, although no apparent necrosis of the bile duct cells was observed. On day 4, the majority of the inflammatory cells in the portal tracts were CD4+ or CD8+ T lymphocytes. The oxidative products of the NBT reaction also disappeared from the bile duct cells. Administration of carrageenan, a potent inhibitor of macrophage function, resulted in a significant decrease in lymphocyte infiltration into the portal tracts. On day 8, portal inflammation subsided.

CONCLUSIONS

In formyl peptide-induced cholangitis, macrophages and granulocytes may injure bile ducts transiently. Further, macrophages are necessary for the subsequent migration of T lymphocytes around the bile ducts.

Primary sclerosing cholangitis: a clinical review

Primary sclerosing cholangitis (PSC) is a cholestatic liver disease characterized by fibro-obliterative inflammation of the entire biliary tree. It is a slowly progressive disease with an undulating course, resulting in terminal biliary cirrhosis after a median period of about 12 years after diagnosis. The etiology of the disease is unknown and there is no effective therapy that can halt disease progression. Around 8% of PSC patients develop cholangiocarcinoma, which, by the time it is diagnosed, cannot be treated curatively. The purpose of this article is to review the current knowledge about primary sclerosing cholangitis and to speculate on future strategies to address the issues of etiology and therapy.

Sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a chronic, progressive cholestatic liver disease whose aetiopathogenesis is unknown. PSC is frequently associated with inflammatory bowel disease, in particular chronic ulcerative colitis, is most commonly observed in young males and is clinically characterized by fatigue, pruritus and jaundice. The diagnosis is supported by a cholestatic biochemical profile and histological abnormalities, and confirmed by visualization of an abnormal biliary tree. The natural history of the disease is currently being evaluated but is generally recognized to be slowly progressive, leading to complications of chronic cholestasis, portal hypertension and biliary cirrhosis. There is no specific medical treatment, and orthotopic liver transplantation remains the only definitive treatment for patients with end-stage PSC. A more rational approach to medical therapy will ensue upon a better understanding of the aetiopathogenesis of this disease.

Pericholangitis in a rabbit colitis model induced by injection of muramyl dipeptide emulsified with a long-chain fatty acid

Rabbit colitis has been induced by injection of muramyl dipeptide emulsified with a long-chain fatty acid. The muramyl dipeptide emulsion was injected submucosally at six portions of the rectum and colon, 10 cm proximal to the anus, using a flexible endoscope. Six rabbits were injected six times every 2 weeks and subsequently killed 2 weeks after the last injection. The histological changes of the colon that occurred in all 6 rabbits were mononuclear cell and histiocyte infiltration with sporadic eosinophils, transmural infiltration, and well-maintained goblet cell populations. These changes were different in degree. In 4 of 6 rabbits histological examination of the liver showed pericholangitis and periductal fibrosis mimicking the pericholangitis frequently seen in patients with inflammatory bowel disease. Fibrosis bridging between the portal and portal veins occurred in 2 rabbits, and noncaseating granuloma was seen in 1 rabbit. These histological changes in our model have led to the suggestion that continuous stimulation with bacterial cell wall fragments may be involved in chronic intestinal inflammation and extraintestinal manifestations such as pericholangitis.

Extraintestinal manifestations of granulomatous enterocolitis induced in rabbits by long-term submucosal administration of muramyl dipeptide emulsified with Freund's incomplete adjuvant

We examined whether extraintestinal manifestations of granulomatous enterocolitis in rabbits might be produced by the long-term administration of muramyl dipeptide which represents the basic fragment of the bacterial cell wall, emulsified with Freund's incomplete adjuvant. Muramyl dipeptide emulsion was injected submucosally at six sites in the rectum and colon, 10 cm proximal to the anus, each time with a flexible endoscope. Seven rabbits were injected nine times or more every month, and all were sacrificed 1 month after the last injection. The histological changes in the colon in the seven rabbits were mononuclear cell infiltration, epithelioid granulomas, granulomatous lesion, and denuded and regenerative epithelia, although the changes differed in degree. In five of the seven rabbits, histological examination of the liver showed pericholangitis and periductal fibrosis, findings analogous to sclerosing cholangitis in patients with inflammatory bowel disease. In four of the seven rabbits, fibrosis bridging mainly between portal and portal veins, and, in places, between portal and central veins, was seen. Two of the seven rabbits developed polyarthritis. The histological changes in our model suggest that continuous stimulation with bacterial cell wall fragments may be involved in the extraintestinal manifestations of chronic intestinal inflammation such as that seen in inflammatory bowel disease.

Increased permeability occurs in rat ileum following induction of pan-colitis

Acetic acid-induced pan colitis in rats leads not only to colonic injury but also to a bystander ileal injury, characterized by decreased fluid and electrolyte absorption without associated histological injury or infiltration of inflammatory cells. To examine the nature of this decreased ileal fluid and electrolyte absorption, we measured effect of acetic acid-induced pancolitis on ileal transmural sodium and chloride transport, as well as on ileal permeability to mannitol and inulin on mucosal sheets mounted in Ussing chambers. In addition, ileal tight junctional morphology was assessed by electron microscopy. In colitic animals, ileal serosal-to-mucosal sodium and chloride transmural fluxes were increased (P<0.05); compatible with the observed decrease in net fluid absorption. Mannitol and inulin ileal serosal-to-mucosal and mucosal-to-serosal ileal fluxes were similarly increased (P<0.05), suggesting that an increase in ileal permeability occurred during acetic acid-induced pancolitis. This increase in ileal permeability was not accompanied by changes in tight junctional ultrastructure. These results suggest that: (1) the decrease in ileal fluid and electrolyte absorption seen during acetic acid-induced rat pancolitis occurred in parallel with a rise in both transcellular and paracellular permeability, and (2) the ileal permeability changes were not accompanied by structural changes.

Effect of "co-ligand" on the biodistribution of 99mTc-labeled hydrazino nicotinic acid derivatized chemotactic peptides

Hydrazinonicotinamide (HYNIC) derivatized chemotactic peptides radiolabeled with 99mTc- (via 99mTc-glucoheptonate) have been demonstrated to be useful for infection imaging [J. Nucl. Med. 34, 1964-1974 (1993)]. Since HYNIC can occupy only two sites of the technetium co-ordination sphere, the labeled product most probably contains additional ligands. Thus we hypothesized that glucoheptonate serves this role by acting as a "'co-ligand'". Due to the low molecular weight of the chemotactic peptides, the "co-ligand" used for technetium labeling could have profound effects on biodistribution. To evaluate this possibility, we measured the biodistribution of 99mTc-labeled For-MLFK-HYNIC radiolabeled using four different "co-ligand"s: glucarate, glucoheptonate, mannitol and glucamine, providing a small series of hydroxyl-backbone ligands which differ in the number and type of ionizable functional groups present. Each preparation was injected into groups of 6 rats (approximately 10 microCi/rat) and biodistribution was determined at 5, 30, 60 and 120 min. Although small differences in biodistribution were detected in most tissues, the most prominent differences (P < 0.01) were observed in lung (glucoheptonate, glucarate > mannitol >> glucamine), liver (glucarate, glucoheptonate, mannitol >> glucamine), kidney (mannitol > glucarate, glucoheptonate, glucamine), spleen (glucarate >> glucoheptonate, mannitol >> glucamine) and GI-tract (glucarate, glucamine >> gluco-heptonate >> mannitol). These results provide support for the "co-ligand" hypothesis and indicate that the nature of the "co-ligand" can have profound effects on biodistribution. Although radiolabeling using glucamine as the "co-ligand" results in the lowest concentrations of radioactivity in most organs, the extremely low concentration of mannitol-labeled peptide in the GI-tract suggests that this may be the "co-ligand" of choice for most applications.

Small duct cholangitis induced by N-formyl L-methionine L-leucine L-tyrosine in rats

Primary sclerosing cholangitis (PSC) frequently accompanies inflammatory bowel diseases. In an attempt to increase our understanding of the pathogenesis of PSC, we studied bile duct changes in rats with colitis which had been given N-formyl L-methionine L-leucine L-tyrosine (fMLT) rectally; fMLT is one of the chemotactic peptides produced by Escherichia coli, and is secreted into the bile by hepatocytes after it enters the portal blood. Transrectal administration of fMLT induced a marked inflammation in the portal triad and mild hepatocyte necrosis on the 4th day. The infiltrating leukocytes in the portal tract were mostly mononuclear cells, which densely infiltrated around the bile ducts. These mononuclear cells appeared to attach to bile duct epithelial cells, and they were more numerous in the smaller bile ducts. Electron microscopy revealed that lymphocytes were in direct contact with bile duct lining cells and that some epithelial cells had degenerated or collapsed. These results suggest that this E. coli-derived peptide may induce cholangitis in the small bile duct through cell-mediated mechanisms. Since these pathologic changes resemble those of the bile duct observed in the early stage of PSC, it can be concluded that bacterial chemotactic peptides may play a role in the pathogenesis of small-duct PSC.

Current concepts in primary sclerosing cholangitis

OBJECTIVE

To describe primary sclerosing cholangitis (PSC) and its associated complications, as well as medical and surgical treatment.

DESIGN

A review of PSC and its associated etiopathologic factors is presented; numerous studies of agents that are used to treat patients with PSC are discussed.

RESULTS

PSC, a slowly progressive disease that often involves autoimmune damage to the biliary tree, is frequently associated with inflammatory bowel disease, usually chronic ulcerative colitis. Long-term follow-up of patients with PSC has revealed a high incidence of colon cancer and bile duct cancer, both of which are most likely related to the chronic inflammation involving these two organs. Although PSC is an unusual disease, it is now diagnosed with approximately the same frequency as is primary biliary cirrhosis. The histopathologic evolution of PSC results in irreversible damage to bile ducts, which ultimately leads to cholestasis, cirrhosis, liver failure, and premature death from liver failure unless liver transplantation is performed. Therefore, the best chance of achieving success is to treat patients with early-stage disease rather than those with irreversible end-stage cirrhotic disease. Although several medical therapies for PSC have been evaluated, only D-penicillamine, cyclosporine, methotrexate, and, most recently, ursodeoxycholic acid have been studied in controlled clinical trials. Furthermore, several surgical therapies for PSC and its associated complications have been assessed.

CONCLUSION

Currently, no therapy achieves a complete clinical, biochemical, or histologic remission in this disease. Until the etiopathogenesis of PSC is further defined, effective therapy is unlikely to be found. Thus, liver transplantation will continue to be an important therapeutic intervention for the management of patients with end-stage PSC.

Etiology and pathogenesis in primary sclerosing cholangitis

The etiology and pathogenesis of the inflammatory and fibrotic bile duct lesions characteristic of primary sclerosing cholangitis (PSC) is unknown, but several lines of evidence support the contention that genetic and immunologic factors are involved. There is an association with human leukocyte antigens (HLA) with an increased frequency of DR3, DR6, and DR2 positive haplotypes. DRB3*0101(DR52a) is the most strongly associated allele in some studies, but the HLA gene conferring the primary HLA associated susceptibility to PSC remains to be established. There is an aberrant expression of HLA class II antigens (DR and DP) on bile duct epithelial cells, with the potential to present antigens to the surrounding T-lymphocytes. A defective suppressor T-cell function has been suggested in some studies. The patients may have elevated levels of circulating immune complexes, immunoglobulins, and non-organ-specific autoantibodies. Antibodies to perinuclear antigens (pANCA) are present in about 80% of cases. Increased metabolism of complement C3, reduced clearance of immune complexes, and increased concentration of biliary immune complexes have been found. The strong association between PSC and ulcerative colitis (UC) has not been explained. The detection of circulating IgG antibodies against a specific epitope shared by epithelial cells in the bile ducts and colon in about two-thirds of PSC patients may be of importance. Portal bacteremia secondary to a diseased bowel may possibly contribute to development of liver disease in UC. Viral infections and toxic and ischemic factors have also been implicated in the pathogenesis of PSC. In conclusion, PSC seems to occur in genetically predisposed individuals, mediated by immunologic mechanisms. The primary event triggering the disease development is, however, unknown.

Prevalence of primary sclerosing cholangitis and other liver diseases in Japanese patients with chronic ulcerative colitis

An association between primary sclerosing cholangitis (PSC) and chronic ulcerative colitis (CUC) is well known in Western countries, but there have been no reports on this association in Japan. We reviewed 163 consecutive CUC patients (91 males and 72 females) diagnosed from 1984 to 1990 at Tokyo Women's Medical College. Abnormal liver function tests were found in 42 patients with CUC (25.8%), but chronic liver disease was only diagnosed in seven patients (4.3%). Among these seven patients, there were four with PSC, one with small-duct PSC, one with transfusion-associated chronic hepatitis and one with Type B liver cirrhosis. No relationship was found between the documented colonic manifestations of CUC and the presence of PSC. The four PSC patients did not have a longer history of CUC at the time of diagnosis of PSC than CUC patients without PSC. At the time of PSC diagnosis, two patients were asymptomatic, one presented with right upper quadrant pain, and the other had fatigue. Three patients were diagnosed as having CUC before the onset of PSC (range 2-13 years), and the other patient had both diseases simultaneously. All four had a good prognosis. Thus PSC was the most common chronic liver disease associated with CUC in our series, and it was present in all our CUC patients with alkaline phosphatase levels exceeding twice the upper limit of normal and mild transaminase elevation.

Acetic acid-induced colitis results in bystander ileal injury

The extent of the small intestinal injury following experimental acetic acid induction of colitis in rats was examined. Following intraluminal colonic administration of radiolabelled acetic acid, high levels of radioactivity were identified in the colon and in the liver, while low background levels were found in jejunum, ileum, caecum, and heart. The increased level of radioactivity in the liver relative to that of the heart suggests that a significant portion of the colonic intraluminal acetic acid was absorbed directly into the portal circulation. The colon, which was the only segment of intestine in direct contact with the acetic acid, had the highest levels of radiolabelled acetic acid, demonstrated a marked macroscopic mucosal ulceration, an enhanced myeloperoxidase activity, and a fall in in vivo fluid absorption. The jejunum, which demonstrated low levels of radiolabelled acetic acid was normal without evidence of injury. In contrast, the ileum, which displayed the same levels of radiolabelled acetic acid as did the jejunum, also demonstrated a significant fall in in vivo fluid absorption but showed no mucosal ulceration or increased myeloperoxidase activity. These studies have shown that acetic acid induction of colitis produces evidence of ileal injury but that this injury is not the result of inadvertent delivery of acetic acid or recruitment of neutrophils to the ileal mucosa.

Effects of inhalation of N-formyl-methionyl-leucyl-phenylalanine in the well elderly and in patients with chronic bronchitis

BACKGROUND

Inhalation of the bacterial peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP) produces bronchoconstriction in normal subjects. FMLP thus has a putative role as a mediator of bronchoconstriction associated with bacterial bronchial infection.

METHODS

The effects of FMLP inhalation were examined in ten subjects with a history of chronic bronchitis and ten age matched control subjects. Each subject inhaled FMLP doses from 0.025 to 0.8 mumol to determine the provocative dose of FMLP causing a 20% fall in FEV1(PD20FMLP). FEV1 was recorded every five minutes after the final FMLP inhalation until it had returned to 95% of baseline FEV1 or 60 minutes had elapsed. The time to return to 95% baseline FEV1 was recorded or extrapolated from the recovery curve as an index of rapidity of recovery. Total and differential white cell counts were performed on each subject at baseline and five and 15 minutes after the final FMLP inhalation.

RESULTS

The geometric mean PD20 FMLP in the patients with chronic bronchitis was 0.06 mumol (95% confidence interval 0.015-0.26), which was significantly lower than that in the control subjects (0.21 mumol (0.02-1.9)). PD20 FMLP in the patients with chronic bronchitis but not age matched controls (p = 0.35) was lower than that found previously in young normal subjects (0.35 mumol (0.07-1.8). The return to 95% baseline FEV1 occurred after 86(10) minutes in subjects with chronic bronchitis and in 81(23) minutes in their age matched controls, in both cases being much slower than that seen in young subjects (29(9) minutes).

CONCLUSION

Patients with chronic bronchitis may be especially susceptible to formyl peptides elaborated by bacteria during bacterial bronchial infection.

Isolation and purification of N-formylmethionine aminopeptidase from rat intestine

The intestinal mucosal epithelium is exposed to products of intestinal bacteria including potent inflammatory N-formylmethionyl oligopeptides. An N-formylmethionine aminopeptidase has been purified 2300-fold from rat intestine and was shown to degrade natural fMet oligopeptides from Escherichia coli culture supernatants with loss of bioactivity (release of specific granule constituents from human polymorphonuclear leucocytes) and immuno-reactivity (assessed using a polyclonal anti-fMet-Leu-Phe antiserum). The enzyme which was specific for N-terminal acyl-methionine residues had a native Mr of 340,000 and comprised four sub-units of Mr 82,000. The presence of this enzyme in intestinal mucosa could prevent absorption of intact bioactive fMet peptides produced by commensal bacteria in the gut lumen.

Hepatobiliary excretion of bacterial formyl-methionyl peptides in rat. Structure activity studies

The bacterial chemotactic peptide formyl-met-leu-phe and its radioiodinated analog formyl-met-leu-[125I]tyr are rapidly excreted by the liver into bile following portal or systemic venous infusions in rats or after absorption from the gut lumen. To determine the molecular structural requirements for hepatobiliary excretion of formyl-methionyl peptides, structure-activity studies using portal venous infusions of 24 structural analogs of formyl-met-leu-tyr were performed in rats with biliary cannulae. Hepatic extraction of peptides was studied in vivo using external gamma counting after portal infusion. Efficient hepatobiliary excretion was not restricted to bioactive formyl peptides, but showed a broad specificity for different amino-acylated (formyl, acetyl, propionyl, carbobenzoxy) di- and tripeptides and no requirement for methionine in position one or for a free carboxy terminus. However, nonacylated peptides and an acyl-amino acid showed little excretion. Hepatic extraction of peptide was also related to N-acylation. Hepatic extraction and excretion of N-acyl peptides were also related to hydrophobicity. Thus, the presence of an N-acyl group is the key determinant of biliary excretion of inflammatory bacterial f-met peptides in the rat.

Advances in primary sclerosing cholangitis

Primary sclerosing cholangitis is an increasingly recognized chronic cholestatic liver disease. It frequently occurs in association with chronic ulcerative colitis and is characterized by inflammation and fibrosis of the intrahepatic and extrahepatic bile ducts. The cause is unknown, although many mechanisms have been considered, including infectious, toxic, and immunologic. The prognosis varies. No adequate treatment exists, although a number of potential treatments have been evaluated in uncontrolled trials, and the results of controlled trials have only recently been reported. Liver transplantation has recently been shown to be an effective treatment for end-stage disease. These various advances in our understanding of primary sclerosing cholangitis are reviewed.

Antiinflammatory effects of various drugs on acetic acid induced colitis in the rat

The efficacy of various drugs used to treat ulcerative colitis, (sulfasalazine, 5-aminosalicylate, hydrocortisone) was investigated in a model of acetic acid-induced colitis in the rat. Subsequently, we tested the ability of antioxidant/5-lipoxygenase inhibitors (gossypol and nordihydroguiaretic acid [NDGA]) and a cyclooxygenase inhibitor (indomethacin) to attenuate the macroscopic colonic damage and/or neutrophil influx (myeloperoxidase activity [MPO]) associated with this model of colitis. Oral pretreatment with either sulfasalazine, gossypol, or NDGA significantly decreased colonic MPO activity induced by acetic acid. Intrarectal administration of such drugs resulted in an even larger reduction of the colonic inflammation, with gossypol being the most potent compound. Oral or intrarectal administration of corticosteroids (dexamethasone, hydrocortisone) also attenuated the parameters of acetic acid induced colitis. In contrast, pretreatment with indomethacin was ineffective, or when administered daily after colitis induction, indomethacin actually increased colonic neutrophil influx significantly. Our data suggest that both the route of drug administration and dosing regimen employed affect the antiinflammatory potency and/or efficacy of compounds on colitis induced by acetic acid in the rat. Drugs which were effective against this colitis may act by scavenging of oxygen derived free radicals.

Hepatic inflammation in rats with experimental small intestinal bacterial overgrowth

Hepatobiliary inflammation and other extraintestinal manifestations accompany certain intestinal disorders, perhaps because of proliferation or enhanced transport of luminal bacteria or their phlogistic cell-wall components. Using jejunal self-filling blind loops to create small bowel bacterial overgrowth, we compared biochemical and histological evidence of hepatic inflammation in 3 rat strains chosen for their variable inflammatory responses to bacterial cell wall polymers. Lewis and Wistar rats developed weight loss, hepatomegaly, and hepatic inflammation 4 and 12 wk, respectively, after creation of SFBL. Plasma aspartate aminotransferase levels in Lewis rats 4 wk (578 +/- 77 U/L) and Wistar rats 12 wk (220 +/- 35 U/L) after self-filling blind loops were significantly greater than in rats with self-emptying blind loops (112 +/- 24 U/L, p less than 0.001; 104 +/- 22, p less than 0.05) or sham-operated Lewis (84 +/- 24, p less than 0.001) or Wistar (78 +/- 10, p less than 0.001) rats. Randomized comparison using a histology grading score showed abnormalities that paralleled aminotransferase values. Lewis and Wistar rats with self-filling blind loops had hepatic injury with bile duct proliferation, fibrosis and acute and chronic periportal and focal parenchymal inflammation. Lewis and Wistar rats with self-emptying blind loops developed occasional mild histologic lesions. 50% of Lewis rats with self-filling blind loops for 4 wk died compared with only 15% in other groups. However, Buffalo rats with self-filling blind loops developed no weight loss, hepatomegaly, or hepatic injury. Anaerobic cultures of blood, peritoneum and liver were negative in all strains. Diet-restricted, sham-operated Wistar rats with weights similar to the Wistar rats with self-filling blind loops did not develop histologic abnormalities or elevated aminotransferase levels (76 +/- 31 U/L). These results show that experimental small bowel bacterial overgrowth causes significant hepatic inflammation leading to fibrosis in susceptible rat strains. Caloric deprivation and hepatic bacterial invasion are not etiologically responsible. We suggest that bacterial cell wall polymers or other bacterial toxins from the blind loop cause hepatic lesions in genetically susceptible hosts.

Radio-immunoassay for formyl methionyl leucyl phenylalanine. II. Demonstration of an enterohepatic circulation of immunoreactive bacterial chemotactic peptides in man

Bacterial chemotactic peptides (F-met-oligopeptides) are secreted by several species of commensal enteric bacteria and can be assayed by bioassay techniques in human colonic luminal fluid. We have previously demonstrated intestinal absorption and enterohepatic circulation of radiolabelled F-met peptides introduced into rat colon, and an eightfold increase in absorption and biliary excretion in rats with experimental colitis. This paper describes the application of a radio-immunoassay to measurements of formyl oligopeptides in human faecal dialysates, colonic and systemic venous blood and bile. All samples were fractionated by reverse-phase high performance liquid chromatography (HPLC) prior to assay. Immunoreactivity was found in faecal dialysates (5-700 nmol/L F-met-leu-phe equivalents) and bile samples (3-150 nmol/L) from normal subjects. After HPLC fractionation, up to five distinct peaks of immunoreactivity were identified. One of these co-chromatographed with authentic F-met-leu-phe; the others probably represented either closely related peptides or peptides of different chain lengths originating from the same F-met-leu-phe precursor protein. Colonic venous blood from two patients with ulcerative colitis contained immunoreactive peptide (10-30 nmol/L) and substantial immunoreactivity was found in ileostomy fluid and bile from two patients with primary sclerosing cholangitis. These results suggest the presence of an enterohepatic circulation of bacterial F-met oligopeptides in man and provide a basis for studies of the role of such pro-inflammatory peptides in patients with inflammatory bowel disease and associated hepatobiliary disorders.

Radio-immunoassay for formyl methionyl leucyl phenylalanine. I. Development and application to assessment of chemotactic peptide production by enteric bacteria

Bacterial chemotactic peptides are low molecular weight peptides which stimulate a wide range of neutrophil functions following binding to specific leucocyte receptors. Formyl methionyl leucyl phenylalanine (FMLP) is the major chemotactic peptide in Escherichia coli culture supernatants. This paper reports the development and validation of a radio-immunoassay (RIA) for FMLP and its application to the analysis of formyl peptide production by enteric bacteria in vitro. The assay was moderately sensitive (10 nmol/L FMLP) and highly specific showing cross reactivity with F-met-leu-tyr, F-nle-leu-phe and F-met-met-met sequences (ID50 = 200, 100 and 250 nmol/L, respectively) but no significant cross reactivity with non-formylated or other formylated di- and tri-peptides (ID50 = 10(5) nmol/L. Culture supernatants from five species of enteric bacteria were filtered, concentrated and fractionated by reverse phase high performance liquid chromatography before RIA. All five organisms produced immunoreactive F-met peptides. A major peak of immunoreactivity co-chromatographing with authentic FMLP was found in all supernatants, but additional peaks representing more hydrophobic peptides were found in Streptococcus faecalis and Bacteroides fragilis cultures. In E. coli culture supernatants, concentration of immunoreactive FMLP increased in a linear fashion during 3 h of log phase growth reaching 31.2 nmol/L(s.e.m. = 10) with final bacterial concentrations of 3 +/- 0.73 x 10(8)/mL (n = 6). These findings extend earlier work showing production of bioactive formyl oligopeptides by different species of enteric bacteria and suggest that a RIA for FMLP will be a useful tool for investigating the production and metabolic fate of such peptides in man.

Purification and amino acid sequencing of naturally occurring N-formyl-methionyl oligopeptides from Escherichia coli

A novel purification procedure for N-formyl methionyl oligopeptides from bacterial culture supernatants has been developed. C-terminal carboxypeptidase microsequencing of purified peptides from E. coli supernatants enabled identification of 6 naturally occurring formyl-oligopeptides.

Respiratory burst activity of intestinal macrophages in normal and inflammatory bowel disease

Macrophages isolated from normal mucosa (greater than 5 cm from tumour) and inflamed mucosa (from patients with inflammatory bowel disease) of colon and ileum were studied for their ability to undergo a respiratory burst as assessed by reduction of nitroblue tetrazolium to formazan. Using phorbol myristate acetate (PMA) and opsonised zymosan as triggers, only a minority (median: 8% for zymosan and 9% for PMA) of macrophages isolated from normal colonic mucosa demonstrated release of oxygen radicals. In contrast, a significantly greater (median: 17% for zymosan and 45% for PMA) proportion of macrophages isolated from inflamed colonic mucosa were able to undergo respiratory burst. Studies with normal and inflamed ileum showed similar results. Stimulation of macrophages isolated from normal colon with interferon-gamma produced only a small increase in the proportion of cells showing release of oxygen radicals. We conclude that the respiratory burst capacity of majority of macrophages isolated from normal colon and ileum is downregulated and a greater proportion of macrophages isolated from inflamed colon and ileum are able to undergo a respiratory burst.