Degradation of endogenous bacterial cell wall polymers by the muralytic enzyme mutanolysin prevents hepatobiliary injury in genetically susceptible rats with experimental intestinal bacterial overgrowth

Microbial Players in Primary Sclerosing Cholangitis: Current Evidence and Concepts

Primary sclerosing cholangitis (PSC) is a rare cholestatic liver disease with progressive biliary inflammation, destruction of the biliary tract, and fibrosis, resulting in liver cirrhosis and end-stage liver disease. To date, liver transplantation is the only definitive treatment option for PSC. The precise etiology of PSC remains elusive, but it is widely accepted to involve a complex interplay between genetic predisposition, immunologic dysfunction, and environmental influence. In recent years, the gut-liver axis has emerged as a crucial pathway contributing to the pathogenesis of PSC, with particular focus on the role of gut microbiota. However, the role of the fungal microbiome or mycobiome has been overlooked for years, resulting in a lack of comprehensive studies on its involvement in PSC. In this review, we clarify the present clinical and mechanistic data and concepts concerning the gut bacterial and fungal microbiota in the context of PSC. This review sheds light on the role of specific microbes and elucidates the dynamics of bacterial and fungal populations. Moreover, we discuss the latest insights into microbe-altering therapeutic approaches involving the gut-liver axis and bile acid metabolism.

Role of the Gut–Liver Axis in the Pathobiology of Cholangiopathies: Basic and Clinical Evidence

The “Gut–Liver Axis” refers to the physiological bidirectional interplay between the gut and its microbiota and the liver which, in health, occurs thanks to a condition of immune tolerance. In recent years, several studies have shown that, in case of a change in gut bacterial homeostasis or impairment of intestinal barrier functions, cholangiocytes, which are the epithelial cells lining the bile ducts, activate innate immune responses against gut-derived microorganisms or bacterial products that reach the liver via enterohepatic circulation. Intestinal dysbiosis or impaired intestinal barrier functions cause cholangiocytes to be exposed to an increasing amount of microorganisms that can reactivate inflammatory responses, thus inducing the onset of liver fibrosis. The present review focuses on the role of the gut–liver axis in the pathogenesis of cholangiopathies.

The gut-liver axis in cholangiopathies: focus on bile acid based pharmacological treatment

PURPOSE OF REVIEW

This review analyses the main features of primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) and provides an overview of the currently available (bile acid) bile acid related treatments.

RECENT FINDINGS

In PBC, biliary injury is the consequence of a dysregulated intrahepatic and systemic immune response. Given the close association between PSC and inflammatory bowel disease (IBD), the microbiota represents an important factor in the development of PSC. Bile acid based pharmacological treatments could represent promising therapeutic strategies in the management of cholangiopathies.

SUMMARY

Cholangiopathies include a spectrum of diseases resulting in cholestasis, an impairment of bile flow in the biliary tree, leading to biliary obstruction and damage as well as liver inflammation and fibrosis. PSC and PBC are highly heterogeneous cholangiopathies and progressive disorders with defined pathophysiological mechanisms. Curative treatments have not been established, and although their prevalence is low, they are a frequent indication for liver transplantation in the advanced stages of cholangiopathies. These diseases still present with unmet therapeutic strategies, also taking into account that on average 30-40% of patients undergoing liver transplantation will have recurrence of the original illness.

The Role of Microbiota in Primary Sclerosing Cholangitis and Related Biliary Malignancies

Primary sclerosing cholangitis (PSC) is an immune-related cholangiopathy characterized by biliary inflammation, cholestasis, and multifocal bile duct strictures. It is associated with high rates of progression to end-stage liver disease as well as a significant risk of cholangiocarcinoma (CCA), gallbladder cancer, and colorectal carcinoma. Currently, no effective medical treatment with an impact on the overall survival is available, and liver transplantation is the only curative treatment option. Emerging evidence indicates that gut microbiota is associated with disease pathogenesis. Several studies analyzing fecal and mucosal samples demonstrate a distinct gut microbiome in individuals with PSC compared to healthy controls and individuals with inflammatory bowel disease (IBD) without PSC. Experimental mouse and observational human data suggest that a diverse set of microbial functions may be relevant, including microbial metabolites and bacterial processing of pharmacological agents, bile acids, or dietary compounds, altogether driving the intrahepatic inflammation. Despite critical progress in this field over the past years, further functional characterization of the role of the microbiota in PSC and related malignancies is needed. In this review, we discuss the available data on the role of the gut microbiome and elucidate important insights into underlying pathogenic mechanisms and possible microbe-altering interventions.

Bile Acids and Microbiota: Multifaceted and Versatile Regulators of the Liver-Gut Axis

After their synthesis from cholesterol in hepatic tissues, bile acids (BAs) are secreted into the intestinal lumen. Most BAs are subsequently re-absorbed in the terminal ileum and are transported back for recycling to the liver. Some of them, however, reach the colon and change their physicochemical properties upon modification by gut bacteria, and vice versa, BAs also shape the composition and function of the intestinal microbiota. This mutual interplay of both BAs and gut microbiota regulates many physiological processes, including the lipid, carbohydrate and energy metabolism of the host. Emerging evidence also implies an important role of this enterohepatic BA circuit in shaping mucosal colonization resistance as well as local and distant immune responses, tissue physiology and carcinogenesis. Subsequently, disrupted interactions of gut bacteria and BAs are associated with many disorders as diverse as Clostridioides difficile or Salmonella Typhimurium infection, inflammatory bowel disease, type 1 diabetes, asthma, metabolic syndrome, obesity, Parkinson’s disease, schizophrenia and epilepsy. As we cannot address all of these interesting underlying pathophysiologic mechanisms here, we summarize the current knowledge about the physiologic and pathogenic interplay of local site microbiota and the enterohepatic BA metabolism using a few selected examples of liver and gut diseases.

Inflammation and the Gut-Liver Axis in the Pathophysiology of Cholangiopathies

Cholangiocytes, the epithelial cells lining the bile ducts, represent the unique target of a group of progressive diseases known as cholangiopathies whose pathogenesis remain largely unknown. In normal conditions, cholangiocytes are quiescent and participate to the final bile volume and composition. Following exogenous or endogenous stimuli, cholangiocytes undergo extensive modifications of their phenotype. Reactive cholangiocytes actively proliferate and release a set of proinflammatory molecules, which act in autocrine/paracrine manner mediating the cross-talk with other liver cell types and innate and adaptive immune cells. Cholangiocytes themselves activate innate immune responses against gut-derived microorganisms or bacterial products that reach the liver via enterohepatic circulation. Gut microbiota has been implicated in the development and progression of the two most common cholangiopathies, i.e., primary sclerosing cholangitis (PSC) and primary biliary cholangitis (PBC), which have distinctive microbiota composition compared to healthy individuals. The impairment of intestinal barrier functions or gut dysbiosis expose cholangiocytes to an increasing amount of microorganisms and may exacerbate inflammatory responses thus leading to fibrotic remodeling of the organ. The present review focuses on the complex interactions between the activation of innate immune responses in reactive cholangiocytes, dysbiosis, and gut permeability to bacterial products in the pathogenesis of PSC and PBC.

Primary Sclerosing Cholangitis, Part 1: Epidemiology, Etiopathogenesis, Clinical Features, and Treatment

Primary sclerosing cholangitis (PSC) is a chronic, idiopathic cholangiopathy that can progress to cirrhosis, end-stage liver disease, hepatobiliary cancer, and/or colorectal cancer. The course of PSC is often complicated by portal hypertension, symptoms of cholestasis, and recurrent bacterial cholangitis, among other conditions, with a consequent decrease in survival (median, approximately 20 years) and quality of life. The etiopathogenesis of PSC remains poorly understood, and, as such, pharmacotherapy has yet to be definitively established. Despite its rarity, PSC is the fifth leading indication for liver transplantation (LT) in the United States. Although the only intervention known to extend survival of patients with PSC, LT is costly and invasive, and recurrent PSC affects approximately 30% of LT recipients. Over the past several years, owing in part to progress in the understanding of PSC, novel pharmacotherapeutics have been developed, some of which are currently in the PSC clinical trial pipeline. Here, in the first of a 2-part series, we provide a review and update of the epidemiology, etiopathogenesis, clinical features, and treatment of PSC. The second part of the series will focus on cancer risk, prevention, and surveillance of PSC.

Impact of Microbes on the Pathogenesis of Primary Biliary Cirrhosis (PBC) and Primary Sclerosing Cholangitis (PSC)

Primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) represent the major clinical entities of chronic cholestatic liver diseases. Both disorders are characterized by portal inflammation and slowly progress to obliterative fibrosis and eventually liver cirrhosis. Although immune-pathogenic mechanisms have been implicated in the pathogenesis of PBC and PSC, neither disorder is considered to be a classical autoimmune disease, as PSC and PBC patients do not respond to immune-suppressants. Furthermore, the decreased bile flow resulting from the immune-mediated tissue assault and the subsequent accumulation of toxic bile products in PBC and PSC not only perpetuates biliary epithelial damage, but also alters the composition of the intestinal and biliary microbiota and its mutual interactions with the host. Consistent with the close association of PSC and inflammatory bowel disease (IBD), the polyclonal hyper IgM response in PBC and (auto-)antibodies which cross-react to microbial antigens in both diseases, an expansion of individual microbes leads to shifts in the composition of the intestinal or biliary microbiota and a subsequent altered integrity of epithelial layers, promoting microbial translocation. These changes have been implicated in the pathogenesis of both devastating disorders. Thus, we will discuss here these recent findings in the context of novel and alternative therapeutic options.

The hepatocyte as a microbial product-responsive cell

Much research has focused on the responses to microbial products of immune cells such as monocytes, macrophages, and neutrophils. Although the liver is a primary response organ in various infections, relatively little is known about the antimicrobial responses of its major cell type, the hepatocyte. It is now known that the recognition of bacteria occurs via cell-surface proteins that are members of the Toll-like receptor (TLR) family. In addition, lipopolysaccharide (LPS) is bound by circulating LPS-binding protein (LBP) and presented to cell-surface CD14, which in turn interacts with TLR and transduces an intracellular signal. We investigated the CD14 and TLR2 responses of whole liver and isolated hepatocytes, and demonstrated that these cells can be induced to express the molecules necessary for responses to both Gram-positive and Gram-negative bacteria. Our findings may have clinical implications for pathological states such as sepsis.

Biliary Mucosal Barrier and Microbiome

Background

The biliary system is in continuous contact with the complex microbiota of the intestine. Microbial products have recently been proposed as potential triggers for biliary diseases.

Methods

The aim of this review is to provide a summary of the current knowledge regarding the role of the biliary and intestinal microbiome in biliary inflammatory diseases.

Results

Previously, it was suggested that the healthy biliary system is a sterile organ, while acute cholangitis and cholecystitis may occur from ascending infections. Although non-inflammatory biliary colonization by certain bacteria such as Salmonella spp. has been already recognized since several decades, human and animal studies indicated only very recently that the gallbladder harbors a complex microbiota also under non-pathologic conditions. Novel findings suggested that – similar to the situation in the intestine – the biliary mucosa features a chemical, mechanical, and immunological barrier, ensuring immunological tolerance against commensals. However, microbial triggers might influence acute and chronic inflammatory disease of the biliary system and the whole liver.

Conclusion

Although yet undefined, dysbiosis of the biliary or intestinal microbiota rather than a single microorganism may influence disease progression.

Primary sclerosing cholangitis - the Norwegian experience

Research related to primary sclerosing cholangitis (PSC) has since 1980 been a major activity at the Oslo University Hospital Rikshospitalet. The purpose of this publication is to describe the development of this research, the impact of this research on the clinical handling of the patients, and finally to describe what we believe are the most urgent, remaining problems to be solved. During the early years, our research dealt primarily with clinical aspects of the disease. The concomitant inflammatory bowel disease (IBD) seen in most patients with PSC was a major interest and we also started looking into genetic associations of PSC. Prognosis, malignancy development and treatment with special emphasis on transplantation have later been dealt with. These activities has had impact on several aspects of PSC management; when and how to diagnose PSC and variant forms of PSC, how to handle IBD in PSC and how to deal with the increased rate of malignancy? The problems remaining to be solved are many. What is the role of the gut and the gut microbiota in the development of PSC? Do the PSC patients have an underlying disturbance in the bile homeostasis? And how does the characteristic type of fibrosis in PSC develop? The genetic studies have supported a role for the adaptive immune system in the disease development, but how should this be dealt with? Importantly, the development of malignancy in PSC is still not understood, and we lack appropriate medical treatment for our patients.

Current research on the treatment of primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a progressive disease of the liver characterized by inflammation and destruction of the intra- and/or extra-hepatic bile ducts, leading to fibrosis and ultimately liver failure, cirrhosis and an increased risk of malignancy. The etiology of PSC is unclear. It is often associated with the inflammatory bowel diseases (IBD), particularly Ulcerative Colitis (UC); up to 75% of PSC patients have UC. PSC is more prevalent in men than in women. Ursodeoxycholic acid (UDCA) has been extensively studied in PSC in randomized clinical trials but failed to show a positive impact on the natural course of the disease. Currently, there is no effective medical therapy for PSC, and the majority of patients will eventually require liver transplantation. PSC is one of the leading indications for liver transplantation. In this paper, we review the current research on the potential therapeutic agents for the treatment of PSC.

Primary sclerosing cholangitis and the microbiota: current knowledge and perspectives on etiopathogenesis and emerging therapies

Primary sclerosing cholangitis (PSC) is a chronic, fibroinflammatory, cholestatic liver disease of unknown etiopathogenesis. PSC generally progresses to liver cirrhosis, is a major risk factor for hepatobiliary and colonic neoplasia, and confers a median survival to death or liver transplantation of only 12 years. Although it is well recognized that approximately 75% of patients with PSC also have inflammatory bowel disease (IBD), the significance of this association remains elusive. Accumulating evidence now suggests a potentially important role for the intestinal microbiota, and enterohepatic circulation of molecules derived therefrom, as a putative mechanistic link between PSC and IBD and a central pathobiological driver of PSC. In this concise review, we provide a summary of and perspectives regarding the relevant basic, translational, and clinical data, which, taken together, encourage further investigation of the role of the microbiota and microbial metabolites in the etiopathogenesis of PSC and as a potential target for novel pharmacotherapies.

Diagnosis and classification of primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a chronic cholestatic disease of the liver and that is characterized by progressive inflammation, fibrosis, and stricturing of the intrahepatic and extrahepatic bile ducts. It is progressive in most patients and leads to cirrhosis. It is a rare disease, mostly affecting people of northern European descent, males greater than females. The diagnosis is best established by contrast cholangiography, which reveals a characteristic picture of diffuse, multifocal strictures and focal dilation of the bile ducts, leading to a beaded appearance. Inflammatory bowel disease (IBD) is present in ~75% of the patients with PSC, mostly ulcerative colitis (~85% of the cases). In addition to biliary cirrhosis, complications of PSC include dominant strictures of the bile ducts, cholangitis, cholangiocarcinoma, colon dysplasia and cancer in patients with IBD, gallbladder polyps and cancer, and hepatic osteodystrophy. The etiology of PSC is not clear, but studies are ongoing. The median survival without liver transplantation is 12 to 15 years after diagnosis. Currently there are no effective treatments except liver transplantation. Immunosuppressive medications have not been shown to be effective but antibiotics and anti-fibrotic agents seem promising.

Role of the microbiota and antibiotics in primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is an idiopathic, progressive, cholestatic liver disease with considerable morbidity and mortality and no established pharmacotherapy. In addition to the long-recognized association between PSC and inflammatory bowel disease, several lines of preclinical and clinical evidence implicate the microbiota in the etiopathogenesis of PSC. Here we provide a concise review of these data which, taken together, support further investigation of the role of the microbiota and antibiotics in PSC as potential avenues toward elucidating safe and effective pharmacotherapy for patients afflicted by this illness.

Randomised clinical trial: vancomycin or metronidazole in patients with primary sclerosing cholangitis - a pilot study

BACKGROUND

Emerging data suggest that oral antibiotics may have therapeutic effects in primary sclerosing cholangitis (PSC), but published studies are limited.

AIMS

To investigate the safety and efficacy of oral vancomycin and metronidazole in patients with PSC.

METHODS

Thirty-five patients with PSC were randomised in a double-blind manner into four groups: vancomycin 125 mg or 250 mg four times/day, or metronidazole 250 mg or 500 mg three times/day for 12 weeks. The primary endpoint was decrease in alkaline phosphatase (ALK) at 12 weeks. Secondary end points included serum bilirubin and Mayo PSC risk score; pruritus; and adverse effects (AEs). Nonparametric tests were used for analysis.

RESULTS

The primary endpoint was reached in the low-dose (-43% change in ALK, P = 0.03) and high-dose (-40%, P = 0.02) vancomycin groups, with two patients in the former experiencing ALK normalisation. Bilirubin decreased significantly in the low-dose metronidazole group (-20%, P = 0.03) and trended towards significance in the low-dose vancomycin group (-33%, P = 0.06). Mayo PSC risk score decreased significantly in the low-dose vancomycin (-0.55, P = 0.02) and low-dose metronidazole group (-0.16, P = 0.03). Pruritus decreased significantly in the high-dose metronidazole group (-3.4, P = 0.03). AEs led to medication discontinuation in six patients, four of whom were receiving metronidazole.

CONCLUSIONS

Both vancomycin and metronidazole demonstrated efficacy; however, only patients in the vancomycin groups reached the primary endpoint, and with less adverse effects. Larger, longer-term studies are needed to further examine the safety and efficacy of antibiotics as a potential treatment for patients with primary sclerosing cholangitis (clinicaltrials.gov NCT01085760).

Immunomodulatory effect of vancomycin on Treg in pediatric inflammatory bowel disease and primary sclerosing cholangitis

Vancomycin has been shown to affect tumor necrosis factor-alpha (TNF-α) pathways as an immunomodulator; this is thought to be separate from its function as an antibiotic [1]. Previous studies have shown that oral vancomycin (OV) is an effective treatment for concomitant primary sclerosing cholangitis (PSC) and inflammatory bowel disease (IBD) in children [2, 3]. Since both diseases are associated with immune dysfunction, we hypothesized that vancomycin's therapeutic effect in IBD and PSC occurs through immunomodulation. Therefore, we examined the in vivo immunological changes that occur during OV treatment of 14 children with PSC and IBD. Within 3 months of OV administration, peripheral gamma-glutamyl transpeptidase (GGT) and alanine aminotransferase (ALT) concentrations, white blood cell (WBC) counts, and neutrophil counts normalized from elevated levels before treatment. Patients also demonstrated improved biliary imaging studies, liver biopsies and IBD symptoms and biopsies. Additionally, plasma transforming growth factor beta (TGF-β) levels were increased without concurrent shifts in Th1-or Th2-associated cytokine production. Peripheral levels of CD4 + CD25hiCD127lo and CD4 + FoxP3+ regulatory T (Treg) cells also increased in OV-treated PSC + IBD patients compared to pretreatment levels. A unique case study shows that the therapeutic effects of OV in the treatment of PSC + IBD do not always endure after OV discontinuation, with relapse of PSC associated with a decrease in blood Treg levels; subsequent OV retreatment was then associated with a rise in blood Treg levels and normalization of liver function tests (LFTs). Taken together, these studies support immune-related pathophysiology of PSC with IBD, which is responsive to OV.

Toll-like receptor 4-dependent Kupffer cell activation and liver injury in a novel mouse model of parenteral nutrition and intestinal injury

Infants with intestinal failure who are parenteral nutrition (PN)-dependent may develop cholestatic liver injury and cirrhosis (PN-associated liver injury: PNALI). The pathogenesis of PNALI remains incompletely understood. We hypothesized that intestinal injury with increased intestinal permeability combined with administration of PN promotes lipopolysaccharide (LPS)-Toll-like receptor 4 (TLR4) signaling dependent Kupffer cell (KC) activation as an early event in the pathogenesis of PNALI. We developed a mouse model in which intestinal injury and increased permeability were induced by oral treatment for 4 days with dextran sulphate sodium (DSS) followed by continuous infusion of soy lipid-based PN solution through a central venous catheter for 7 (PN7d/DSS) and 28 (PN28d/DSS) days. Purified KCs were probed for transcription of proinflammatory cytokines. PN7d/DSS mice showed increased intestinal permeability and elevated portal vein LPS levels, evidence of hepatocyte injury and cholestasis (serum aspartate aminotransferase, alanine aminotransferase, bile acids, total bilirubin), and increased KC expression of interleukin-6 (Il6), tumor necrosis factor α (Tnfα), and transforming growth factor β (Tgfβ). Markers of liver injury remained elevated in PN28d/DSS mice associated with lobular inflammation, hepatocyte apoptosis, peliosis, and KC hypertrophy and hyperplasia. PN infusion without DSS pretreatment or DSS pretreatment alone did not result in liver injury or KC activation, even though portal vein LPS levels were elevated. Suppression of the intestinal microbiota with broad spectrum antibiotics or ablation of TLR4 signaling in Tlr4 mutant mice resulted in significantly reduced KC activation and markedly attenuated liver injury in PN7d/DSS mice.

CONCLUSION

These data suggest that intestinal-derived LPS activates KC through TLR4 signaling in early stages of PNALI.

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.

Recurrence and rejection in liver transplantation for primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a chronic progressive inflammatory disease affecting the bile ducts, leading to fibrosis and eventually cirrhosis in most patients. Its etiology is unknown and so far no effective medical therapy is available. Liver transplantation (LTX) is the only curative treatment and at present PSC is the main indication for LTX in the Scandinavian countries. Close to half of the PSC patients experience one or more episodes of acute cellular rejection (ACR) following transplantation and approximately 1/5 of the transplanted patients develop recurrent disease in the graft. In addition, some reports indicate that ACR early after LTX for PSC can influence the risk for recurrent disease. For these important post-transplantation entities affecting PSC patients, we have reviewed the current literature on epidemiology, pathogenesis, treatment and the possible influence of rejection on the risk of recurrent disease in the allograft.

Update on primary sclerosing cholangitis

Early studies in primary sclerosing cholangitis (PSC) were concerned with disease characterization, and were followed by epidemiological studies of PSC and clinical subsets of PSC as well as a large number of treatment trials. Recently, the molecular pathogenesis and the practical handling of the patients have received increasing attention. In the present review we aim to give an update on the pathogenesis of PSC and cholangiocarcinoma in PSC, as well as to discuss the current opinion on diagnosis and treatment of PSC in light of the recent European Association for the Study of the Liver and the American Association for the Study of Liver Diseases practice guidelines.

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.

Alcohol, intestinal bacterial growth, intestinal permeability to endotoxin, and medical consequences: summary of a symposium

This report is a summary of the symposium on Alcohol, Intestinal Bacterial Growth, Intestinal Permeability to Endotoxin, and Medical Consequences, organized by National Institute on Alcohol Abuse and Alcoholism, Office of Dietary Supplements, and National Institute of Diabetes and Digestive and Kidney Diseases of National Institutes of Health in Rockville, Maryland, October 11, 2006. Alcohol exposure can promote the growth of Gram-negative bacteria in the intestine, which may result in accumulation of endotoxin. In addition, alcohol metabolism by Gram-negative bacteria and intestinal epithelial cells can result in accumulation of acetaldehyde, which in turn can increase intestinal permeability to endotoxin by increasing tyrosine phosphorylation of tight junction and adherens junction proteins. Alcohol-induced generation of nitric oxide may also contribute to increased permeability to endotoxin by reacting with tubulin, which may cause damage to microtubule cytoskeleton and subsequent disruption of intestinal barrier function. Increased intestinal permeability can lead to increased transfer of endotoxin from the intestine to the liver and general circulation where endotoxin may trigger inflammatory changes in the liver and other organs. Alcohol may also increase intestinal permeability to peptidoglycan, which can initiate inflammatory response in liver and other organs. In addition, acute alcohol exposure may potentiate the effect of burn injury on intestinal bacterial growth and permeability. Decreasing the number of Gram-negative bacteria in the intestine can result in decreased production of endotoxin as well as acetaldehyde which is expected to decrease intestinal permeability to endotoxin. In addition, intestinal permeability may be preserved by administering epidermal growth factor, l-glutamine, oats supplementation, or zinc, thereby preventing the transfer of endotoxin to the general circulation. Thus reducing the number of intestinal Gram-negative bacteria and preserving intestinal permeability to endotoxin may attenuate alcoholic liver and other organ injuries.

High prevalence of small intestinal bacterial overgrowth in patients with morbid obesity: a contributor to severe hepatic steatosis

BACKGROUND

With the increasing prevalence of obesity, non-alcoholic fatty liver disease (NAFLD) has become a major cause of liver diseases. Small intestinal bacterial overgrowth (SIBO) could be related to NAFLD. Our aim was to determine the prevalence of SIBO and its relationship with liver lesions in morbidly obese patients.

METHODS

A glucose hydrogen (H(2)) breath test (positive if fasting breath H(2) concentration > 20 ppm and/or an increase of > 10 ppm over baseline within the first 2 h) was performed in obese patients referred for bariatric surgery (body mass index [BMI] > 40 kg/m(2) or > 35 in association with comorbidities) and in healthy non-obese subjects. In obese patients, a surgical liver biopsy was performed.

RESULTS

One hundred and forty-six patients (129 women, age [mean+/-SE]: 40.7 +/- 11.4 years) were prospectively included in the study. The mean BMI was 46.1+/-6.4 kg/m(2). A liver biopsy was available in 137 patients and a breath test in 136. The frequency of positive breath tests was higher in obese patients (24/136, 17.1%) than in healthy subjects (1/40, 2.5%; P=0.031). In the univariate analysis, SIBO was not associated with clinical variables, but tended to be associated with more frequent severe hepatic steatosis (26.3 vs. 10.3%, P=0.127), whereas the frequency of sinusoidal or portal fibrosis, lobular necrosis and non-alcoholic steatohepatitis (NASH) were not different. In the multivariate analysis, SIBO (P=0.005) and the presence of a metabolic syndrome (P=0.006) were independent factors of severe hepatic steatosis.

CONCLUSION

In morbidly obese patients, bacterial overgrowth prevalence is higher than in healthy subjects and is associated with severe hepatic steatosis.

Primary sclerosing cholangitis: summary of a workshop

Primary sclerosing cholangitis (PSC) is a rare but important liver disease that leads to cirrhosis and need for liver transplantation in a high proportion of cases. The disease occurs in approximately 1 per 100,000 population per year, usually presents in adulthood, and affects men more often than women. Typical serum biochemical results, autoantibodies and liver biopsy are suggestive but not diagnostic of PSC, the diagnosis requiring cholangiographic demonstration of stricturing and dilatation of the intra- and/or extra-hepatic bile ducts. The natural history of PSC is variable, the average survival being 12 to 17 years. The cause of PSC is still unknown. Although considered an autoimmune disease, PSC has several atypical features and a strong genetic component. The therapy of PSC is unsatisfactory. Standard doses of ursodeoxycholic acid (UDCA) lead to improvements in biochemical abnormalities but not in histology, cholangiographic appearance or survival. Several innovative therapies have been tried in PSC, but with scant evidence of benefit. For patients with high grade strictures, endoscopic dilatation is beneficial. Liver transplantation is successful for end-stage liver disease due to PSC and improves survival. PSC may recur after transplantation but is rarely progressive. The most dreaded complication of PSC is cholangiocarcinoma. Diagnosis of this highly malignant tumor is difficult, and there are no biomarkers for its early detection. Liver transplantation for cholangiocarcinoma has an exceedingly poor outcome, although transplantation with neoadjuvant chemoirradiation holds promise in selected patients. Thus, significant opportunities remain for basic and clinical research into the cause, natural history, and therapy of PSC.

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.

Increased orocecal transit time in patients with nonalcoholic fatty liver disease

Intestinal bacterial overgrowth (IBO) has been suggested to play a pathogenic role in patients with nonalcoholic fatty liver disease (NAFLD). Delayed intestinal transit may contribute to IBO development. Ten nondiabetic patients with NAFLD and abnormal liver enzymes were recruited. Ten healthy individuals, matched by sex, age, and body mass index, were used as controls. Orocecal transit time (OCTT) was measured by the lactulose breath test. Anti-endotoxin core antibodies (EndoCAb) were determined. The effect of oral norfloxacin (400 mg BID during 2 weeks) on liver enzymes, lactulose breath test, and EndoCAb was also studied. NAFLD patients had higher basal breathed H2 and prolonged OCTT compared to controls (127 +/- 61 vs. 57 +/- 23 min, respectively; P = 0.0037). EndoCAb titers were similar in NAFLD patients and controls. Norfloxacin administration had no effect on ALT levels, lactulose breath test, or EndoCAb titers in patients with NAFLD. The present data show evidence of deranged intestinal motility in nondiabetic patients with NAFLD and support the hypothesis that NAFLD could be linked to endotoxin-induced liver damage of intestinal origin.

Characterization and quantification of C-polysaccharide in Streptococcus pneumoniae capsular polysaccharide preparations

Purified capsular polysaccharide preparations from Streptococcus pneumoniae that are used for vaccine production typically contain residual levels of C-polysaccharide (C-Ps). Residual C-Ps is typically found in one of two forms, either chemically linked to the capsular polysaccharide (bound) or present by itself (free). Two analytical methods have been developed and applied to determine the relative percentages of the two C-Ps forms present in various capsular polysaccharide preparations. Both methods differentiate the two forms of C-Ps according to the difference of their hydrodynamic sizes. One method is based on labeling C-Ps with a fluorescent tag and separating the two forms of C-Ps by high-performance size exclusion chromatography with on-line refractive index and fluorescence detection, and the other method is based on measuring self-diffusion rates of the two forms of C-Ps by nuclear magnetic resonance (NMR) and quantifying each form with deconvolution. Both methods were evaluated for relative accuracy, precision, and ease of application, and they were found to provide comparable results for a large number of pneumococcal polysaccharide preparations. These analyses, combined with other quantitative NMR measurement of total C-Ps in the polysaccharide powder, provide a more refined means of evaluating the amount of each form of C-Ps in polysaccharide preparations targeted for vaccine production.

Metronidazole and ursodeoxycholic acid for primary sclerosing cholangitis: a randomized placebo-controlled trial

No effective medical therapy is currently available for primary sclerosing cholangitis (PSC). Ursodeoxycholic acid (UDCA) improves liver enzymes, but its effect on liver histology is controversial. Metronidazole (MTZ) prevents PSC-like liver damage in animal models and reduces intestinal permeability. We recruited 80 patients with PSC into a randomized placebo-controlled study to evaluate the effect of UDCA and MTZ (UDCA/MTZ) compared with UDCA/placebo on the progression of PSC. Patients (41 UDCA/placebo and 39 UDCA/MTZ) were followed every third month. Assessment of liver function test, histological stage and grade, and cholangiography (via ERCP) at baseline showed no differences between the groups. After 36 months, serum aminotransferases gamma-glutamyltransferase, and alkaline phosphatase (ALP) decreased markedly in both groups, serum ALP more significantly in the UDCA/MTZ group (-337 +/- 54 U/L, P < .05) compared with the UDCA/placebo group. The New Mayo Risk Score decreased markedly only in the UDCA/MTZ group (-0.50 +/- 0.13, P < .01). The number of patients with improvement of stage (P < .05) and grade (P < .05) was higher in the combination group. ERCP findings showed no progression or improvement in 77% and 68% of patients on UDCA/MTZ and UDCA/placebo, respectively. In conclusion, combining MTZ with UDCA in PSC improved serum ALP levels and New Mayo Risk Score, but no statistically significant effect on disease progression as assessed via liver histology or ERCP was seen. Long-term studies using a higher dose of UDCA combined with MTZ in larger patient populations are indicated.

Antibiotic-resistant Propionibacterium acnes on the skin of patients with moderate to severe acne in Stockholm

The objective was to study the prevalence and antibiotic susceptibility patterns of Propionibacterium acnes strains isolated from patients with moderate to severe acne in Stockholm, Sweden and to determine the diversity of pulsed-field gel electrophoresis types among resistant P. acnes strains. One hundred antibiotic-treated patients and 30 non-antibiotic-treated patients with moderate to severe acne participated in the investigation. Facial, neck and trunk skin samples were taken with the agar gel technique. The susceptibility of P. acnes strains to tetracycline, erythromycin, clindamycin and trimethoprim-sulfamethoxazole was determined by the agar dilution method. The genomic profiles of the resistant strains were determined by pulsed-field gel electrophoresis. In the group of patients treated with antibiotics, resistant P. acnes strains were recovered in 37%, while in the non-antibiotic group of patients the incidence of resistant strains was 13%. Thus antibiotic-resistant P. acnes strains were significantly more often isolated from antibiotic-treated patients with moderate to severe acne than from non-antibiotic-treated patients (odds ratio, 3.8; P=0.01). There was a genetic diversity among the P. acnes strains. Forty-four different patterns of SpeI DNA digests were detected and two predominant clones were found. P. acnes strains exhibited different antibiotic susceptibility patterns and identical genotypes or vice versa. A person can be colonized with different strains with varying degrees of antibiotic resistance. The risk of increased resistance of P. acnes must be considered when treating acne patients with antibiotics, and especially long-term therapy should be avoided.

ENDOTOXIN-MEDIATED DISTURBANCE OF HEPATIC CYTOCHROME P450 FUNCTION AND DEVELOPMENT OF ENDOTOXIN TOLERANCE IN THE RAT MODEL OF DEXTRAN SULFATE SODIUM-INDUCED EXPERIMENTAL COLITIS

Hepatobiliary abnormalities have been described in patients with chronic inflammatory bowel diseases. Hepatic cytochrome P450 (P450)-dependent drug-metabolizing enzyme activities and susceptibility to a hepatotoxin, d-galactosamine, were determined in rats with dextran sulfate sodium (DSS)-induced colitis to assess whether liver function is affected in the model of inflammatory bowel disease. Colitis was induced by treatment of rats with 3% DSS in drinking water for 7 days. Liver microsomes for enzyme activities and serum for biological analysis were prepared from the rats with colitis, along with untreated and lipopolysaccharide (LPS)-treated rats. Other rats received intraperitoneal injection of d-galactosamine to assess their susceptibility to the toxin-induced liver injury. Treatment of rats with DSS resulted in not only colitis but also decreases in hepatic P450-dependent drug-metabolizing enzyme activities. Elevated endotoxin was found in portal blood, which was not associated with liver injury. The potency and the isoform selectivity in the suppression of the P450 enzymes by DSS treatment were similar to those of LPS-treated rats. Coadministration of antibiotics, polymyxin B or metronidazole, with DSS protected rats from decreases in some but not all P450 enzyme activities, indicating partial involvement of bacterial endotoxin in the P450 decreases. The rats with colitis were less susceptible than untreated rats to d-galactosamine-induced liver injury and TNF-alpha production, suggesting development of endotoxin tolerance in DSS-colitis. In conclusion, these results suggest that the DSS-colitis leads to endotoxin-mediated down-regulation of hepatic P450 enzymes and protection against d-galactosamine-induced liver injury, probably due to endotoxin tolerance.

Long-term evaluation of a rat model of chronic cholangitis resembling human primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a chronic cholestatic disorder with a presumed autoimmune aetiopathogenesis. We have recently described a novel organ-specific rat model of fibrosing cholangitis induced by intrabiliary administration of the hapten-reagent 2,4,6-trinitrobenzenesulfonic acid (TNBS) with similarities to human PSC. In the present report, we have evaluated the long-term outcome of TNBS-induced cholangitis in this model. Mild stenosis of the common bile duct of female Lewis rats (n = 18) was achieved by subtotal ligation and cholangitis induced by TNBS injection (50 mg/kg) into the dilated bile duct after a second laparotomy. After 8 and 12 months, we found no evidence of cholangitis in serum chemistry or histology or retrograde cholangiography of TNBS-treated rats. Antineutrophil cytoplasmic antibodies were positive in 75% of animals but were not predictive of liver damage. Tumour necrosis factor-alpha levels were not elevated in serum or in mononuclear spleen cell supernatants. Our findings suggest that a single initial insult is not sufficient to trigger chronic progressive inflammation. Rather, perpetuation of inflammation probably requires additional stimuli.

Microbial factors in inflammatory bowel disease

An unsolved puzzle in IBD research is whether germs, genes, or a combination of the two with excessive immune responses to gut-associated bacteria explains the pathogenesis of UC and CD. Whatever the answer, there is little doubt that microbial factors are involved intimately in IBD pathogenesis. Although a long search has failed to confirm a direct pathogenic role for a specific infectious agent, compelling evidence suggests that commensal enteric bacteria and their products provide a local environmental trigger that initiates and perpetuates IBD, reactivates quiescent disease, results in the frequent septic complications of CD, and contributes to the development of several extraintesinal manifestations. The most compelling evidence for involvement of the enteric flora in the pathogenesis of IBD has been generated from studies of animal models, which collectively support the view that IBD is due to genetically determined dysregulation of the mucosal immune response to luminal antigens derived from the normal bacterial flora. Although removing or dampening the dominant antigenic stimuli with antibiotics or probiotics is conceptually superior to the current array of immunosuppressive and anti-inflammatory agents that nonspecifically block the inflammatory cascade, more definitive, rigorously designed, controlled trials of treatments directed at the microflora are needed. Future research investigating mechanisms of tolerance to luminal bacteria and an understanding of how probiotics can manipulate the intestinal flora beneficially will bring clinicians closer to identifying potential therapeutic targets and unraveling the bacterial connection to IBD pathogenesis.

Hepatobiliary disease in inflammatory bowel disease

Many hepatobiliary diseases are seen in IBD. PSC is the most common, occurring in 7.5% of patients with UC. The cause of PSC is not well understood, but PSC seems to be associated with genetic susceptibility, sharing some immunologic abnormalities with UC. A characteristic cholangiogram in a patient with abnormal liver function tests usually establishes the diagnosis. Liver biopsy is not essential but can help make the diagnosis of small duct PSC in patients with a normal cholangiogram. There are no medications that treat PSC effectively. Endoscopic dilation of dominant strictures reduces the frequency of cholangitis and may improve survival. OLT remains the only proven treatment of advanced PSC. Cholangiocarcinoma is a feared complication of PSC that is difficult to diagnose. Cholelithiasis, PBC, portal vein thrombosis, and hepatic abscess are hepatobiliary disorders that occur less frequently in IBD patients.

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.

Hepatobiliary abnormalities and parenteral nutrition

Hepatobiliary dysfunctions (TPN-HBD) occur during parenteral nutrition. In older children these are usually reversible whereas in newborns and infants these hepatobiliary abnormalities play a significant role in the morbidity. Cholestasis is a commonly occurring TPN-HBD. It correlates directly with the decreasing gestational age, low birth weight and increasing duration of TPN therapy. The pathogenesis of cholestasis of TPN is multifactorial and predisposed by necrotising enterocolitis, sepsis, cardiac failure, shock, and hypotension. Diagnosis is made with exclusion of other causes of direct hyperbilirubinemia. Most TPN-HBD appear within 4 weeks of starting of TPN but severe complications manifest usually after the 16th week. Histologically there is intralobular cholestasis. In few cases there may be severe portal fibrosis followed by development of micronodular biliary cirrhosis. Enteral starvation, defective bile acid carriers, hypercaloric TPN are the major factors responsible for TPN-HBD, including cholestasis. Biliary complications of TPN-HBD are acalculous, cholecystitis, and cholelithiasis. Bile stasis is a major pathological factor for these. If the calories are provided only by glucose or glucose-containing electrolyte solutions it may lead to cholestasis and other TPN-HBD. Even small oral alimentation (continuous or bolus) during TPN, prevent TPN-HBD. Choleretic agents have been useful in the prevention and management of cholestasis and other parenteral nutrition induced hepatobiliary abnormalities.

Serum autoantibodies in patients with primary sclerosing cholangitis

BACKGROUND/AIM

Primary sclerosing cholangitis is a chronic cholestatic syndrome with a presumed autoimmune basis frequently associated with inflammatory bowel disease. The aim of this study was to determine the profile and significance of serum autoantibodies in patients with primary sclerosing cholangitis.

METHODS

Serum samples taken from 73 untreated patients (32 female and 41 male, median age 45 years) with well-defined primary sclerosing cholangitis, and from 75 healthy age- and sex-matched controls were assayed for 20 different autoantibodies.

RESULTS

Of 73 patients, 71 (97%) were positive for at least 1 autoantibody; whereas 59/73 patients (81%) were positive for > or =3 antibodies. Patients with primary sclerosing cholangitis had a significantly greater rate of positivity than controls for antinuclear, anticardiolipin, antineutrophil cytoplasmic, and antithyroperoxidase antibodies as well as rheumatoid factor. The rate of positivity and serum levels of any of these 20 autoantibodies were not significantly different between patients with primary sclerosing cholangitis and inflammatory bowel disease and those without inflammatory bowel disease. Anticardiolipins were the single group of antibodies that had a significant correlation with the Mayo risk score (r=0.49, p<0.001) and histologic stage of disease (r=0.30, p<0.01).

CONCLUSIONS

Primary sclerosing cholangitis is associated with a high proportion of non-organ specific autoantibodies. Anticardiolipin antibodies appear to be related to the severity of primary sclerosing cholangitis and may be a useful prognostic marker.

Primary biliary cirrhosis and primary sclerosing cholangitis

Primary biliary cirrhosis and primary sclerosing cholangitis are the most common chronic cholestatic liver diseases in adults that lead to biliary cirrhosis and its inherent complications such as portal hypertension and liver failure. Although important advances in the understanding of the pathogenesis of these conditions have been accomplished in the last two decades, much work is needed to uncover the interaction of genetic and immunologic mechanisms involved in their pathogenesis. Ursodeoxycholic acid at dosage of 13 to 15 mg/kg/d is the only agent that can currently be recommended in the treatment of PBC. No medical therapy aimed at disrupting disease progression is available for patients with primary sclerosing cholangitis, although several agents with different properties are currently under evaluation. Liver transplantation is the treatment of choice for patients with primary biliary cirrhosis and primary sclerosing cholangitis with end-stage liver disease.

Increased gut permeability after hemorrhage is associated with upregulation of local and systemic IL-6

Although intestinal barrier failure after hemorrhage is a well-documented event, the underlying mechanism is poorly understood. The aim of this study, therefore, was to determine whether altered intestinal permeability after hemorrhage is associated with upregulation of local and systemic interleukin-6 (IL-6). To study this, rats underwent laparotomy (i.e., trauma induced) and were bled to and maintained at a mean arterial pressure of 40 mm Hg until 40% of the shed blood volume was returned in the form of Ringer's lactate. The animals were then resuscitated with four times the volume of shed blood with Ringer's lactate over 60 min. At 1.5 h postresuscitation, an in vivo ligated loop of a distal small intestine was formed and the passage of 4-kDa fluorescein isothiocyanate-conjugated dextran (FD4) from the intestinal lumen into the portal vein and carotid artery blood was analyzed by fluorescence spectrometry. Samples from the portal vein and a carotid artery were collected and plasma IL-6 was assayed. Intraepithelial lymphocytes from a distal small intestine were isolated and cultured in vitro for 24 h with or without anti-rat CD3 monoclonal antibody stimulation. IL-6 activity in freshly isolated cells and its release by cultured lymphocytes were determined. Intestinal perfusion and portal blood flow were determined by radioactive microspheres in another set of parallel experiments. The results indicate that lumen-to-blood passage of FD4 through the wall of the small intestine increased significantly at 1.5 h after hemorrhage and resuscitation and was associated with decreased intestinal perfusion and portal blood flow. Plasma IL-6 levels in the portal vein and carotid artery markedly increased at 1.5 h after hemorrhage and resuscitation. In addition, a significant correlation was observed between plasma IL-6 and FD4 concentrations. Higher IL-6 activity in freshly isolated cells was found in hemorrhaged rats. Increased IL-6 release by cultured lymphocytes was also observed either with or without anti-rat CD3 monoclonal antibody stimulation. Thus, the increased intestinal permeability following trauma-hemorrhage and resuscitation appears to be associated with systemic and intestinal IL-6 upregulation.

A rat model of ileal pouch-rectal anastomosis

After colectomy and ileal pouch-rectal anastomosis, pouchitis may occur. Pouchitis is a poorly defined condition with unknown etiology. The aim of this study was to develop an animal model of pouchitis. Ileal pouch-rectal anastomosis was created in Lewis and Sprague-Dawley rats. Rats were studied 4 and 8 weeks after surgery, and pouchitis was assessed by stool output, histology, and tissue myeloperoxidase (MPO) levels. Some rats were treated with allopurinol or metronidazole beginning the day of surgery. Rats with pouches demonstrated inflammation with a monocytic infiltration, luminal exudate, mucosal ulcerations, and serosal inflammation. Rats with pouches had increased anaerobic bacterial flora compared with normal ileum. After creation of pouches, Lewis rats (histology score = 8.4 +/- 1.6; MPO = 17.3 +/- 3.6, mean +/- SD) developed more severe inflammation than Sprague-Dawley rats did (histology score = 4.3 +/- 1.8; MPO = 5.5 +/- 3.6) within 4 weeks, p < 0.001 and 8 weeks after surgery, p < 0.05. Stool output was also greater in Lewis (55 +/- 7 g/kg/day) compared with Sprague-Dawley rats with pouches (43 +/- 5 g/kg/day), p < 0.05. Metronidazole treatment reduced histology score (6.0 +/- 0.5) p < 0.05 and MPO (5.9 +/- 1.6) p < 0.001 in rats with pouches compared with rats with pouches that had no treatment. Allopurinol treatment in rats with pouches reduced histology score (4.0 +/- 1.7) and MPO (3.9 +/- 1.6), p < 0.001, compared with rats with pouches that had no treatment. Ileal pouch-rectal anastomosis in rats induced inflammation within 4 weeks, demonstrated differential host genetic susceptibility, and was associated with increased number of pouch bacteria. Anaerobes, especially bacteroides sp. and free radical, may mediate inflammation. Ileal pouch-rectal anastomosis surgery in rats may be a useful animal model for the study pouchitis.

The consequences of the intracellular retention of pathogen-derived T-cell-independent antigens on protein presentation to T cells

Intracellular pathogens can be considered as particulate antigens chemically composed of a complex mixture of T-cell-dependent antigens (TD) (peptides and proteins) and T-cell-independent antigens (TI) (glycolipids and complex polysaccharides). A large range of saccharides (from oligosaccharides to complex polysaccharides) derived from pathogenic microorganisms are being isolated and characterized. They are currently implicated in signaling systems and concomitant host-parasite relationships. However, there are not many structure-function relationships described for these pathogens. This is particularly true of polysaccharides. In this report we have reviewed the role of defined TI antigens in the processing and presentation of defined TD antigens to specific T cells by antigen-presenting cells (APC). We also considered the importance of some of the chemical characteristics shared by different carbohydrates implicated in the inhibition of antigen presentation. These findings are discussed in relation to the clear immunopathological consequences of long retention periods of complex carbohydrate molecules derived from intracellular parasites inside certain APC and the absence of antigen presentation impairment in physiological situations such as the removal of senescent or damaged red blood cells by splenic macrophages or intracellular accumulation of carbohydrates in colostrum and milk macrophages during lactation.

Inhibitory effects of thymus-independent type 2 antigens on MHC class II-restricted antigen presentation: comparative analysis of carbohydrate structures and the antigen presenting cell

The role of thymus-independent type 2 (TI-2) antigens (polysaccharides) on the MHC-II-restricted processing of protein antigens was studied in vitro. In general, antigen presentation is inhibited when both peritoneal and splenic macrophages (M phi) as well as Küpffer cells (KC) are preincubated with acidic polysaccharides or branched dextrans. However, the inhibitory effect of neutral polysaccharides was minimal when KC were used as antigen presenting cells (APC). Morphological evaluation of the uptake of fluoresceinated polysaccharides clearly correlates with this selective and differential interference. Polysaccharides do not block MHC-I-restricted antigen presentation. Some chemical characteristics shared by different saccharides seem to be specially related to their potential inhibitory abilities: (i) those where two anomeric carbon atoms of two interlinked sugars and (ii) those containing several sulfate groups per disaccharide repeating unit. No polysaccharide being inhibitory in M phi abrogated antigen processing in other APC: lipopolysaccharide-activated B cells, B lymphoma cells, or dendritic cells (DC). Using radiolabeled polysaccharides it was observed that DC and B cells incorporated less radioactivity as a function of time than M phi. Morphological evaluation of these different APC incubated for extended periods of time with inhibitory concentrations of polysaccharides revealed intense cytoplasmic vacuolization in M phi but not in B cells or DC. The large majority of M phi lysosomes containing polysaccharides fail to fuse with incoming endocytic vesicles and delivery of fluid-phase tracers was reduced, suggesting that indigestible carbohydrates reduced the fusion of these loaded lysosomes with endosomes containing recently internalized tracers. It is suggested that the main causes of this antigen presentation blockade are (i) the chemical characteristics of certain carbohydrates and whether the specific enzymatic machinery for their intracellular degradation exists; and (ii) the different phagocytic abilities of distinct APC populations, fluid-phase pinocytosis and receptor-mediated saccharide uptake, and existence of a differential antigen-processing pathway in M phi and DC or B cells, which could be based on a polysaccharide-inhibited step present in M phi but unaffected or irrelevant in both B cells and DC.

Normal luminal bacteria, especially Bacteroides species, mediate chronic colitis, gastritis, and arthritis in HLA-B27/human beta2 microglobulin transgenic rats

Genetic and environmental factors are important in the pathogenesis of clinical and experimental chronic intestinal inflammation. We investigated the influence of normal luminal bacteria and several groups of selected bacterial strains on spontaneous gastrointestinal and systemic inflammation in HLA-B27 transgenic rats. Rats maintained germfree for 3-9 mo were compared with littermates conventionalized with specific pathogen-free bacteria. Subsequently, germfree transgenic rats were colonized with groups of five to eight bacteria that were either facultative or strictly anaerobic. Transgenic germfree rats had no gastroduodenitis, colitis, or arthritis, but developed epididymitis and dermatitis to the same degree as conventionalized rats. Colonic proinflammatory cytokine expression was increased in transgenic conventionalized rats but was undetectable in germfree and nontransgenic rats. Colitis progressively increased over the first 4 wk of bacterial exposure, then plateaued. Only transgenic rats colonized with defined bacterial cocktails which contained Bacteroides spp. had colitis and gastritis. Normal luminal bacteria predictably and uniformly induce chronic colonic, gastric and systemic inflammation in B27 transgenic F344 rats, but all bacterial species do not have equal activities.