Intestinal mucosal oxidative damage and bacterial translocation in cirrhotic rats

Organisms causing spontaneous bacterial peritonitis in children with liver disease and ascites in Southern Iran

AIM: To determine the causative agents of spontaneous bacterial peritonitis (SBP) in children with liver disease and ascites in our center.

METHODS: During a 2.5 year period, from September 2003 to March 2006, 12 patients with 13 episodes of SBP were studied. In all cases at the time of admission serum albumin and glucose, urinalysis and urine culture was performed. Analysis [white blood cell (WBC) count with differential, albumin, glucose], gram stain, culture by BACTEC method and antibiogram was done on ascitic fluids. Abdominal paracentesis was repeated after 48 h of antibiotic therapy for bacteriologic assay. The patients were followed for at least three months in a gastroenterology clinic.

RESULTS: There were 7 girls (58%) and 5 boys (42%) with a median age of 5.2 years (range, 6 mo to 16 years). All cases had positive ascitic fluid culture. Gram stain was positive in 5 (38.5%) of them. The isolated organisms were S. pneumoniae in 5 (38.5%), E. coli in 2 (15.3%), S. viridans in 2 (15.3%), and K. pneumoniae, H. influenza, Enterococci, and nontypable Streptococcus each in one (7.7%). All of them except Enterococci were sensitive to ciprofloxacin and ceftriaxone. All ascitic fluid cultures were negative after 48 h of antibiotic therapy.

CONCLUSION: S. pneumoniae is the most common cause of SBP in the pediatric age group and we recommend a third generation cephalosporine (e.g., Ceftriaxione or Cefotaxime) for empirical therapy in children with SBP.

Spontaneous bacterial peritonitis: a therapeutic update

Spontaneous bacterial peritonitis (SBP) is one of the main infectious complications of cirrhosis and occurs in 8-30% of hospitalized patients with ascites. SBP is characterized by infection of the ascitic fluid (AF) in the absence of any primary focus of intra-abdominal infection. The main route by which the AF becomes infected is the hematogenous route. The pathogenic mechanism by which infection develops is bacterial translocation from the intestinal flora to the mesenteric lymph nodes and from there to the bloodstream. Contributing factors are an increased growth of Gram-negative aerobic bacilli in the jejunum, changes in the intestinal barrier and in addition factors which could reduce the local flow of blood. For clinical diagnosis, patients with SBP may present signs of peritoneal irritation and pain, together with changes in gastrointestinal motility, sometimes with nausea, vomiting, diarrhea or ileus. Many patients, however, may not present any symptoms or signs as a result of the presence of SBP. Diagnostic paracentesis of the AF must be performed for every patient with cirrhosis, hospitalized with ascites. Laboratory diagnosis of SBP is carried out by polymorphonuclear count in the AF, together with a positive culture from the AF, which is characteristically monomicrobial. Escherichia coli has been the main bacterium isolated from AF as well as other Gram-negative bacteria from the Enterobacteriaceae family and Streptococcus genus. A more rapid diagnosis of SBP can be obtained via the use of leukocyte esterase, which is present in biological fluids and reacts with a component of the dipstick, changing its color. During the acute phase of SBP, antibiotics should be initiated promptly once the clinical and laboratory diagnosis of SBP has been made, before the result of AF culture. Cefotaxime or other third-generation cephalosporins have been considered the first-choice empirical antibiotics in the treatment of cirrhotic patients with SBP, and is efficacious in approximately 90% of cases. Broad-spectrum quinolones, which are almost completely absorbed after oral administration and diffuse rapidly through the AF, are currently used for oral treatment of uncomplicated SBP. Patients who have already had a previous episode of SBP, with a 69% probability of recurrence within a year, will benefit from prophylactic treatment. Cirrhotic patients with a high risk of SBP and other infections, such as those with gastrointestinal bleeding, also benefit from primary prophylaxis and norfloxacin has been used with success.

Intestinal permeability in rats with CCl4-induced portal hypertension

AIM: To investigate the intestinal barrier changes in rats with CCl₄-induced portal hypertension.

METHODS: The permeability of intestinal barrier detected by Lanthanum as a tracer was evaluated in rats. Bacterial translocation and plasma endotoxin were also determined.

RESULTS: The incidence of bacterial translocation was 85% in rats with CCl₄-induced portal hypertension, which was significantly higher than that in control rats (20%, P<0.01). Plasma endotoxin level was significantly higher in experimental group than in control group. Permeability of the epithelial mucosa and pathological alteration were increased in the ileum and the microvilli became shorter and thinner in rats with portal hypertension.

CONCLUSION: Bacterial translocation occurs in rats with CCl₄-induced portal hypertension and increased permeability between epithelial cells contributes to the translocation.

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Tumor necrosis factor-alpha induces apoptosis of enterocytes in mice with fulminant hepatic failure

AIM: To explore the alterations of intestinal mucosa morphology, and the effects of tumor necrosis factor α (TNFα) on enterocyte apoptosis in mice with fulminant hepatic failure (FHF).

METHODS: Liver damage was induced by lipopolysaccharide (LPS)/TNF-α in D-galactosamine (GalN) sensitized BALB/c mice. There were 40 mice in normal saline (NS)-treated group, 40 mice in LPS-treated group, 40 mice in GalN-treated group, 120 mice in GalN/ LPS-treated group and 120 mice in GalN/ TNFα-treated group. Each group was divided into five subgroups of eight mice each. Serum samples and liver, intestinal tissues were respectively obtained at 2, 6, 9, 12 and 24 h after administration. Anti-TNFα monoclonal antibody was injected intravenously into GalN/LPS-treated mice. Serum TNFα levels were determined by enzyme-linked immunosorbent assays (ELISA). Serum ALT levels were determined using an automatic analyzer. The intestinal tissues were studied under light microscope and electron microscope at 2, 6, 9, 12 and 24 h in mice with fulminant hepatic failure, respectively. Enterocyte apoptosis was determined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) method. The expression of tumor necrosis factor receptor 1 (TNFR1) in intestinal tissue was tested by immunohistochemistry Envision Two Steps.

RESULTS: Gut mucosa was morphologically normal at all time points in all groups, but typical apoptotic cells could be seen in all experimental groups under electron micro-scope. Apoptosis rate of gut mucosal epithelial cells were significantly increased at 6, 9 and 12 h, peaked at 12 h in mice with fulminant hepatic failure. TNFα induced apoptosis of enterocytes in mice with FHF. The integrated OD (IOD) levels of TNFα receptor 1 protein expressed in the intestine of mice with GalN/LPS and GalN/ TNFα-induced FHF at 2, 6, 9, 12 and 24 h after GalN/LPS and GalN/TNFα administration were 169.54±52.62/905.79±111.84, 11350.67±2133.26/28160.37±4601.67, 25781.00±2277.75/122352.30±49412.40, 5241.53±3007.24/49157.93±9804.88, 7086.13±1031.15/3283.45±127.67, respectively, compared with those in control groups (with NS, LPS and GalN administration, respectively). IOD level of TNFR1 changed significantly at 6, 9 and 12 h after GalN/LPS and GalN/TNFα administration. The expression of TNFR1 protein was significantly higher at 9 h after GalN/LPS and GalN/TNFα administration than that in control groups. Protein expression of TNFR1 was positively correlated with enterocyte apoptosis.

CONCLUSION: TNFα can induce apoptosis of enterocytes in mice with FHF. Anti-TNFα IgG can inhibit this role.

Infected and noninfected ascites in pediatric patients

OBJECTIVES

To determine the prevalence of spontaneous bacterial peritonitis, ascites with bacterial infection and noninfected ascites in pediatric patients with portal hypertensive ascites and to compare the clinical and laboratory features of infected and noninfected ascites.

METHODS

Forty-one episodes of portal hypertensive ascites (serum-ascites albumin gradient >1.1 g/dL) in 31 patients were studied. Median age was 2.9 years. Twenty-four (77.4%) patients were cirrhotic and 20 (83.3%) were classified as Child-Pugh C. Median pediatric end-stage liver disease score was 18.5. The following ascites features were assessed: polymorphonuclear neutrophil cell count, cytology, pH, concentration of glucose, lactic dehydrogenase, total protein and albumin, Gram stain and bacteriological culture. Blood was sampled for complete blood count, coagulation studies, liver and renal function tests. Groups were compared by Mann-Whitney and chi tests (P < 0.05).

RESULTS

Noninfected ascites were observed in 29 of 41 samples, spontaneous bacterial peritonitis in eight of 41 and ascites with bacterial infection in four of 41. The most prevalent clinical features were fever, voluminous ascites and encephalopathy, but there were no significant differences in the clinical features of the groups. All patients with infected ascites were cirrhotic. There was no statistical difference in Child-Pugh or pediatric end-stage liver disease status between patients with infected and noninfected ascites. Culture of ascetic fluid was positive in four of eight cases of spontaneous bacterial peritonitis. Gram-negative rods were the most prevalent bacteria cultured. Except for serum albumin, no statistical differences in biochemical markers were observed between patients with infected and noninfected ascites.

CONCLUSIONS

The prevalence of infected ascites was 29.2%. With the exception of serum albumin, there were no differences in the clinical and biochemical features of patients with infected ascites and noninfected ascites.

Bacterial translocation and its consequences in patients with cirrhosis

Bacterial translocation is the passage of viable bacteria from the intestinal lumen to mesenteric lymph nodes and other extraintestinal sites. Spontaneous bacterial peritonitis is the main clinical consequence of bacterial translocation in cirrhosis. Translocation of bacterial products of viable or non-viable bacteria, such as endotoxin and/or bacterial DNA, through the intestinal wall could stimulate the immune system and the hyperdynamic circulatory state in cirrhosis with clinical consequences that are under evaluation. Bacterial translocation is currently considered the passage of viable gut flora across the intestinal barrier to extraluminal sites. Aerobic Gram-negative bacilli are the most common translocating bacteria. Intestinal bacterial overgrowth, impairment in permeability of the intestinal mucosal barrier, and deficiencies in local host immune defences are the major mechanisms postulated to favour bacterial translocation in cirrhosis. Bacterial translocation is a key step in the pathogenesis of spontaneous bacteraemia and spontaneous bacterial peritonitis in cirrhosis. Translocation of intestinal bacterial products from viable or non-viable bacteria, such as endotoxin and bacterial DNA, has recently been associated with pathophysiological events, such as activation of the immune system and derangement of the hyperdynamic circulatory status in cirrhosis. Clinical consequences of these effects of bacterial products are presently under investigation.

Effect of TNF-α on tight junctions between the epithelial cells of intestinal mucosal barrier

AIM: To investigate the effect of TNF-α on tight junctions between the epithelial cells of the intestinal mucosal barrier.

METHODS: Colon cancer cell line (CaCo-2) was cultured. The localizations of zonula occluden-1 (ZO-1) in CaCo-2 epithelial cells were detected by immunofluorescence after exposure to TNF-α (0, 50, 100 and 200 mg/L) for 24 h and the TNF-α treatment with 100 mg/L for 0, 4, 8 and 24 h. The expression level of ZO-1 was analyzed by semi-quantitative reverse transcriptase-PCR after exposure to TNF-α with the above time and concentration.

RESULTS: Different expression levels of ZO-1 depended on different time and concentration of TNF-α treated on CaCo-2 epithelial cells. The integrity of tight junctions was disrupted and the expression level of ZO-1 decreased after treatment with TNF-α. The intensity of the immunofluorescent signal was less intensive after exposure to TNF-α 100 and 200 mg/L than that to 0 and 50 mg/L. The intensity of the immunofluorescent signal was less intensive after exposure to TNF-α 100 mg/L for 24 hours than those for 0 h, 4 h and 8 h. The RT-PCR results showed that after CaCo-2 cells were treated for 24h with the indicated concentrations (0, 50, 100 and 200 mg/L) of TNF-α and the TNF-α treatment with 100 mg/L for 0 h, 4 h, 8 h and 24 h, the expression levels of ZO-1 mRNA in CaCo-2 cells were decreased by TNF-α with 100 mg/L for 24 h, as compared with control (P < 0.01).

CONCLUSION: Tight junctions between the epithelial cells of the intestinal mucosal barrier can be destroyed by TNF-α, and decreased expression level of ZO-1 induced by TNF-α is one of the most important molecular mechanisms.

Portal hypertension

PURPOSE OF REVIEW

This review discusses the advances in the pathophysiology, diagnosis, and management of the complications of portal hypertension that have occurred in the past year.

RECENT FINDINGS

The specific topics reviewed are the pathophysiology of portal hypertension (including recent findings regarding intrahepatic vascular resistance and splanchnic vasodilatation) and experimental methods used to act on the mechanisms that lead to portal hypertension, as well as recent advances in the diagnosis and management of the complications of portal hypertension.

SUMMARY

The specific complications discussed in this review are varices and variceal bleeding (primary prophylaxis, treatment of the acute episode, and secondary prophylaxis), portal hypertensive gastropathy, ascites, hepatorenal syndrome, spontaneous bacterial peritonitis, the cardiopulmonary complications of portal hypertension (hepatopulmonary syndrome, portopulmonary hypertension, cardiac dysfunction), and hepatic encephalopathy.

Gut microflora in the pathogenesis of the complications of cirrhosis

The gut flora plays an important role in the pathogenesis of the complications of cirrhosis. Cirrhotic patients are prone to develop bacterial infections, mainly the 'spontaneous' infection of ascites or spontaneous bacterial peritonitis. Other complications of cirrhosis, such as variceal haemorrhage and ascites, occur mostly or solely as a consequence of portal hypertension. Portal pressure increases initially as a consequence of an increased intrahepatic resistance but, once collaterals have formed, high portal pressure is maintained by an increased splanchnic blood inflow secondary to vasodilatation. Splanchnic vasodilatation is the initiating event in the hyperdynamic circulatory state that aggravates the complications of cirrhosis. The gut flora plays a role in both the development of infections and in the hyperdynamic circulatory state of cirrhosis and, although less prominently, it also plays a role in the pathogenesis of hepatic encephalopathy. This chapter presents evidence regarding gut flora and its modification in the pathogenesis and management of these complications of cirrhosis.

Myeloperoxidase response to peritonitis in an experimental model

INTRODUCTION

Patients with peritonitis often exhibit systemic manifestations of sepsis, especially in the lungs. The aim of the present study was to evaluate the local and systemic effects of the neutrophil response to peritonitis in a rat model.

METHODS

Fifty Wistar rats were randomized to either a control group or a peritonitis group (5 mg zymosan intraperitoneal). Groups of five animals were killed at 4, 18, 24, 48 and 96 h for evaluation of the morphology of the peritoneum (mesothelial imprint), the number and phenotype of cells within peritoneal fluid (flow cytometry), and myeloperoxidase activity within the peritoneal fluid and distant organs (enzyme assay).

RESULTS

Zymosan produced macroscopic evidence of peritonitis and on microscopy there was disruption of peritoneal mesothelial cells. This was accompanied by an influx of neutrophils between 4 and 48 h (P < 0.001) and macrophages between 48 and 96 h (P < 0.001). There was also an increase in myeloperoxidase activity within peritoneal fluid between 4 and 48 h (P < 0.05), the lung at 4 h (P < 0.01) and the liver at 48 h (P < 0.001).

CONCLUSION

The present study has confirmed the validity of using zymosan to create a low-morbidity model of peritonitis. Besides the anticipated peritoneal response, there were distant effects of neutrophil activation within the lungs and liver. In the future, strategies that modulate neutrophil activation within these organs might play a useful adjunctive role in the management of patients with peritonitis.