Circulating immune complex, endotoxin, and biliary infection in patients with biliary obstruction

Sequestration of Intestinal Acidic Toxins by Cationic Resin Attenuates Pancreatic Cancer Progression through Promoting Autophagic Flux for YAP Degradation

Simple Summary

Annually, more than 450,000 people are diagnosed with pancreatic cancer worldwide with over 430,000 mortalities. Pancreatic ductal carcinoma (PDAC) accounts for around 80% of pancreatic cancer cases with an extremely high mortality rate. Emerging research has demonstrated that gut dysbiosis is closely associated with pancreatic cancer, while the underlying mechanisms remain elusive. In this study, we found that elevated levels of endotoxin (LPS) and bile acids were associated with malignant progression in Kras-driven pancreatic cancer mice. Importantly, oral administration of cationic resins to sequestrate intestinal endotoxins and bile acids efficiently attenuated tumor progression. Thus, sequestration of intestinal acidic toxins by oral administration of cationic resins may have potential as an intervention strategy for pancreatic malignancy.

Abstract

Pancreatic cancer is driven by risk factors such as diabetes and chronic pancreatic injury, which are further associated with gut dysbiosis. Intestinal toxins such as bile acids and bacterial endotoxin (LPS), in excess and persistence, can provoke chronic inflammation and tumorigenesis. Of interest is that many intestinal toxins are negatively charged acidic components in essence, which prompted us to test whether oral administration of cationic resin can deplete intestinal toxins and ameliorate pancreatic cancer. Here, we found that increased plasma levels of endotoxin and bile acids in Pdx1-Cre: LSL-Kras^G12D/+ mice were associated with the transformation of the pancreatic ductal carcinoma (PDAC) state. Common bile-duct-ligation or LPS injection impeded autolysosomal flux, leading to Yap accumulation and malignant transformation. Conversely, oral administration of cholestyramine to sequestrate intestinal endotoxin and bile acids resumed autolysosomal flux for Yap degradation and attenuated metastatic incidence. Conversely, chloroquine treatment impaired autolysosomal flux and exacerbated malignance, showing jeopardization of p62/ Sqxtm1 turnover, leading to Yap accumulation, which is also consistent with overexpression of cystatin A (CSTA) in situ with pancreatic cancer cells and metastatic tumor. At cellular levels, chenodeoxycholic acid or LPS treatment activated the ligand–receptor-mediated AKT-mTOR pathway, resulting in autophagy-lysosomal stress for YAP accumulation and cellular dissemination. Thus, this work indicates a potential new strategy for intervention of pancreatic metastasis through sequestration of intestinal acidic toxins by oral administration of cationic resins.

Streptococcus bovis endocarditis, a silent sign for colonic tumour

AIM

An association between colonic carcinoma and Streptococcus bovis endocarditis/bacteraemia was first suggested in 1951. This knowledge has great clinical implications, yet we found scant awareness amongst general surgical trainees. The aim of this article was to review the evidence available in the literature and explore the pathophysiology behind this association.

METHOD

The literature was reviewed, between 1950 and 2008, using Pubmed, Embase and Ovid database searches. We utilized different combinations of the keywords: Streptococcus bovis, endocarditis, septicaemia and colon cancer/carcinoma. Quality assessment was determined using the Oxford Centre for Evidence-based Medicine Levels of Evidence (May 2001). Studies were selected based on their relevance to the aims to be addressed.

RESULTS

We included nine case reports and found 24 studies demonstrating an association between S. bovis bacteraemia/endocarditis and colon cancer; the reported incidence in studies was variable (6-67%). The majority of studies (20) were retrospective analysis of data; only four studies were prospective. A total of 12 of 24 studies also reported an association with extra-colonic malignancy (1-22%) and 12 with liver disease (3-57%). Eight studies relevant to the pathophysiology of this association were identified.

CONCLUSION

Streptococcus bovis endocarditis and/or bacteraemia is an early clue to the likely presence of colorectal cancer. Whilst further studies are required to determine the precise pathophysiology, clinicians should be aware of this association. It is advisable to investigate rigorously for colon cancer in all patients presenting with S. bovis endocarditis/bacteraemia; such patients may also present with liver disease or, occasionally, extra-colonic malignancy.

The association of Streptococcus bovis bacteremia and gastrointestinal diseases: a retrospective analysis

There is a well-established association between Streptococcus bovis bacteremia (SBB) and colorectal cancer. However, SBB is also frequently associated with chronic liver disease and has been described with other gastrointestinal disorders. The aim of the study was to evaluate the prevalence of gastrointestinal disease in patients with SBB. Retrospective analysis of the microbiology database at Jackson Memorial Medical Center, Miami, Florida, between 1992 and 2002, was performed. Patients' clinical records were reviewed, with special focus on underlying gastrointestinal disease or other major comorbidities. Thirty-eight patients (83%) were adults and eight (17%) were pediatric patients. Nineteen patients presented with gastrointestinal disorders associated with SBB (41%). Nine adult patients (19%) had end-stage liver disease (five female). Six patients had alcohol-induced liver disease (one with concomitant chronic hepatitis C), with the remaining three cases related to autoimmune hepatitis, primary biliary cirrhosis, and nonalcoholic steatohepatitis. Colonic neoplasms (adenocarcinoma in 3 and adenomatous polyps in 3) were found in 6 of 10 adult patients in whom colonoscopic evaluation was performed. Seven adult patients had acquired immunodeficiency syndrome (AIDS) (18%). Mortality in the patients with AIDS and SBB was high (71%). No significant association with gastrointestinal diseases was found in the pediatric population. Bacteremia due to S. bovis in adults is frequently associated with hepatic dysfunction (1:4), colonic neoplasms (1:6), and AIDS (1:6). This association was valid for our adult population only. SBB is an early clue to the likely presence of these serious underlying conditions and warrants rigorous investigation when recognized.

Haemodynamic alterations and their morphological basis in biliary obstruction

The relationship between the haemodynamic alterations and morphological changes in the liver caused by biliary obstruction was investigated in rats after ligation of the common bile duct. In these rats, the portal vein pressure was markedly elevated, and the differences in blood pressure between the portal vein and the terminal portal venule and between the terminal portal venule and the terminal hepatic venule were greater than in the sham-operated rat. The livers showed narrowing of the most peripheral branches of the portal vein due to compression by proliferated bile ductules and sinusoidal stenosis due to enlarged liver cells, but there was no perceptible change in the hepatic vein branches. These data suggest that hepatic circulatory disturbance in biliary obstruction is caused by deformation of the peripheral portal vein branches and sinusoidal stenosis.

Defense system in the biliary tract against bacterial infection

Bacteria can invade the biliary tract by ascending from the duodenum and via the hematogenous route from the hepatic portal venous blood. The sphincter of Oddi, situated at the junction of the biliary tract and the upper gastrointestinal tract, forms an effective mechanical barrier to duodenal reflex and ascending bacterial infection. Conversely, Kupffer cells and the tight junctions between hepatocytes help prevent bacteria and toxic metabolites from entering the hepatobiliary system from the portal circulation. The continuous flushing action of bile and the bacteriostatic effects of bile salts keeps the biliary tract sterile under normal conditions. Secretory immunoglobulin A (sIgA), the predominant immunoglobulin in the bile, and mucus excreted by the biliary epithelium probably function as antiadherence factors, preventing microbial colonization. When barrier mechanisms break down, as in surgical or endoscopic sphincterotomy and with insertion of biliary stents, pathogenic bacteria enter the biliary system at high concentrations and take up residence on any foreign bodies. Intrabiliary pressure is a key factor in the development of cholangitis. Chronic biliary obstruction raises the intrabiliary pressure. This adversely influences the defensive mechanisms such as the tight junctions, Kupffer cell functions, bile flow, and sIgA production in the system, resulting in a higher incidence of septicemia and endotoxemia in these patients. Knowledge of biliary defense against infection is still quite primitive. Unclear are the roles of sIgA in the bile, mechanism of bacterial adhesion to the biliary epithelium, Kupffer cell function in biliary obstruction, and the antimicrobial activity of bile salts.

The triad of Streptococcus bovis bacteremia, colonic pathology, and liver disease

The association of Streptococcus bovis endocarditis and colon carcinoma has been reported previously in small series in the medical, but not surgical, literature. Although the fecal carriage rate of S. bovis increases with colonic pathology, no explanation exists for the development of bacteremia in these cases. To explore the possible contribution of hepatic dysfunction to the development of portal and systemic bacteremia, the incidence of both colonic pathology and liver disease or dysfunction was determined in 92 patients with S. bovis endocarditis and/or bacteremia. Colonic and liver evaluation had been undertaken in 47% and 93% of patients, respectively. Among these patients, colonic pathology was identified in 51%, and liver disease or dysfunction was documented in 56%. Either the underlying colonic disease or alterations in hepatic secretion of bile salts or immunoglobulins may promote the overgrowth of S. bovis and its translocation from the intestinal lumen into the portal venous system. A compromised hepatic reticuloendothelial system may then contribute to the development of S. bovis septicemia and subsequent endocarditis. We conclude that S. bovis bacteremia is an indication to the clinician of the possibility of underlying liver disease as well as colon pathology.

Effects of percutaneous transhepatic biliary drainage on blood-bile permeability and selective IgA transport in patients with biliary obstructions

Biliary obstruction induces a increase in the permeability between blood and bile, and a decrease in the rate of immunoglobulin A (IgA) transport into bile. We investigated the effects of percutaneous transhepatic biliary drainage (PTBD) on these derangements. PTBD reduced the extent of elevation of the bile-to-serum ratio of Immunoglobulin G (IgG; IgG-BS ratio) in patients with obstructive jaundice. Because IgG is known to be passively transported from serum to bile, the results indicate that PTBD restores the blood-bile barrier function. The IgA-BS ratio/IgG-BS ratio index (IgA/IgG index) and the IgM/IgG index, which indicated the function of selective transport of IgA and IgM into bile, initially decreased and then returned to the normal range 17 days after PTBD in patients who experienced a rapid resolution of hyperbilirubinemia. However these indices remained low in patients who did not experience this resolution. The serum secretory IgA levels in patients who did not experienced rapid resolution of hyperbilirubinemia markedly increased before PTBD. The serum secretory IgA levels in the patients who did and those who did not experience rapid resolution of hyperbilirubinemia, after initially increasing, decreased after PTBD. However the level returned to the control range only in patients who experienced a rapid resolution. These results indicate that the secretory IgA level is a sensitive indicator of hepatobiliary function, and measurement of the level of secretory IgA could predict the effect of PTBD.

Endotoxaemia and hepatic injury in obstructive jaundice

To examine whether endotoxaemia contributes to the development of bile infarction and whether obstructive jaundice enhances endotoxin hepatotoxicity, the present study was undertaken in rats. The development of bile infarction and the elevation of serum transaminase activities in rats following ligation of the common bile duct were not prevented by administration of polymyxin B, neomycin, or lactulose, which have anti-endotoxin properties. Moreover, the morphological and functional changes in obstructive jaundice were not enhanced by administration of endotoxin. These data indicate that endotoxaemia does not contribute to the development of bile infarction. On the other hand, the administration of a small dose of endotoxin to rats with biliary obstruction--a dose which does not induce abnormalities of liver function tests or any morphological changes in the liver in non-jaundiced rats--led to focal hepatocellular coagulative necrosis and elevation of serum transaminase levels. These data indicate that endotoxin-induced hepatic injury is potentiated in obstructive jaundice.

Effects of sera from patients with obstructive jaundice on the generation of oxygen intermediates by normal polymorphonuclear leukocytes

Recently it has been suggested that oxygen intermediates play an important role in the pathogenesis of tissue damage. The effect of sera from patients with obstructive jaundice on the generation of oxygen intermediates by normal polymorphonuclear leukocytes (PMNs) was investigated. Sera from patients with obstructive jaundice increased superoxide anion (O2-), hydrogen peroxide (H2O2) and hydroxol radical (OH.) generation compared with sera from healthy individuals or patients with biliary tract stones and/or tumors of the biliary tract or pancreas (without obstructive jaundice). In particular, the hydroxyl radical, which is one of the most potent oxidants capable of causing tissue damage, was produced in large quantities. Sera from patients with obstructive jaundice have a strong capacity to induce production of oxygen intermediates from PMNs, and oxygen intermediates may play a role in the pathogenesis of hepatic and other organ injury in obstructive jaundice.