Endotoxin, endotoxin-neutralizing-capacity, sCD14, sICAM-1, and cytokines in patients with various degrees of alcoholic liver disease

CHRONIC ALCOHOLISM CAUSES DELETERIOUS CONDITIONING OF INNATE IMMUNITY

AIMS

To examine the immune consequences of chronic alcoholism in man, in relation to the known association between alcoholism and raised incidence and severity of infections.

METHODS

In 36 alcoholics without liver disease, at the point of commencing withdrawal from alcohol, the following measures of immune competence were measured: the immunophenotypes of cells, acute phase proteins, the endotoxin-neutralizing capacity (ENC) of the serum, titers of anti-lipopolysaccharide (LPS) antibodies, and ex vivo cytokine inducibility in T cells and monocytes (TNFalpha, IL1beta, IL1RA, IL4, IL6, IL8, IL10 and IL12). The results were compared to those from healthy volunteers (day controls). Measures were repeated after 8-13 days of abstinence.

RESULTS

LPS-binding protein (LBP) and soluble CD14 (sCD14) were significantly increased in patients' sera at the outset of withdrawal, whereas reduced titers of anti-LPS IgG (P = 0.012) and a reduced ENC (P = 0.001) were measured. Only ENC rapidly returned to normal values after withdrawal therapy. Cytokine induction with phorbol ester showed no significant alterations in patients' T cells. Patients' monocytes, however, responded to LPS stimulation with enhanced IL1beta-, but reduced TNFalpha- and IL12-production (P = 0.004, P = 0.0042 and P = 0.001, respectively). While IL1- and TNFalpha-responses normalized after the withdrawal period, impairment of the IL12 response persisted throughout the observation period of 2 weeks.

CONCLUSIONS

Alcoholism results in a prolonged LPS-mediated hypoinflammatory conditioning of the innate but not the adaptive immune system, which is not reversed immediately after withdrawal. This alcohol-induced status of the immune system predisposes to infections and sepsis by blunting initial response to the pathogens.

Lack of sexual dimorphism in alcohol-induced liver damage (ALD) in rats treated chronically with ethanol-containing low carbohydrate diets: The role of ethanol metabolism and endotoxin

Evidence has been presented suggesting that females are significantly more susceptible to alcohol-induced liver damage (ALD) than males. In the current study, we examined sexual dimorphism in hepatic pathology, metabolism and cytokine profiles using two different rat models of ALD. Male and female Sprague-Dawley or Wistar rats were fed ethanol-containing low-carbohydrate liquid diets using oral or intragastric methods for 42 or 60 days. In both models, ethanol treatment produced similar significant liver hyperplasia accompanied by increases in plasma ALT, steatosis, inflammation and necrosis (p < 0.05). Greater pathology scores were observed in the intragastrically infused rats. Males did not differ significantly from females in serum ALT values or pathology despite greater elevations in TNFalpha and IL-1beta mRNAs in ethanol-treated female rat livers (p < 0.05). Furthermore, there was no sexual dimorphism in blood ethanol concentrations or CYP2E1-induction even though sexually dimorphic alterations in other hepatic cytochrome P450 enzymes were observed. These data do not support previous observations that female rats have a greater susceptibility to ethanol-induced hepatotoxicity than males.

Recent Advances in Alcoholic Liver Disease I. Role of intestinal permeability and endotoxemia in alcoholic liver disease

A significant body of evidence indicates that endotoxemia and endotoxin-mediated hepatocellular damage play a crucial role in the pathogenesis of alcoholic liver disease. A close correlation between endotoxemia and the severity of alcohol-induced liver injury is supported by a number of clinical and experimental studies. Elevated intestinal permeability appears to be the major factor involved in the mechanism of alcoholic endotoxemia and the pathogenesis of alcoholic liver disease. Ethanol and its metabolic derivatives, acetaldehyde in particular, alter intracellular signal-transduction pathways leading to the disruption of epithelial tight junctions and an increase in paracellular permeability to macromolecules. Studies addressing the mechanisms of such epithelial disruption and the protective factors that prevent ethanol and acetaldehyde-mediated disruption of epithelial tight junctions are critically important in the investigations toward the search of preventive and therapeutic strategies for alcoholic liver disease.

Recent insights into the role of the innate immune system in the development of alcoholic liver disease

The innate immune system is responsible for the rapid, initial response of the organism to potentially dangerous stresses, including pathogens, tissue injury, and malignancy. Pattern-recognition receptors of the toll-like receptor (TLR) family expressed by macrophages provide a first line of defense against microbial invasion. Activation of these receptors results in a stimulus-specific expression of genes required to control the infection, including the production of inflammatory cytokines and chemokines, followed by the recruitment of neutrophils to the site of infection. The early stages in the development of alcoholic liver disease (ALD) follow a pattern characteristic of an innate immune response. Kupffer cells, the resident macrophages in the liver, are activated in response to bacterial endotoxins (lipopolysaccharide, LPS), leading to the production of inflammatory and fibrogenic cytokines, reactive oxygen species, as well as the recruitment of neutrophils to the liver. One mechanism by which chronic ethanol can turn the highly regulated innate immune response into a pathway of disease is by disrupting the signal transduction cascades mediating the innate immune response. Recent studies have identified specific modules in the TLR-4 signaling cascade that are disrupted after chronic ethanol exposure, including CD14 and the mitogen-activated protein kinase family members, ERK1/2 and p38. Enhanced activation of these TLR-4 dependent signaling pathways after chronic ethanol likely contributes to the development of alcoholic liver disease.

Serum hyaluronate correlates with histological progression in alcoholic liver disease

OBJECTIVES

Chronic alcohol consumption may lead to the development of liver cirrhosis. Serum concentrations of hyaluronate were suggested as a predictor in chronic liver disease, but its power to distinguish between severity of fibrosis and inflammation had not been assessed. In order to evaluate hyaluronate as a marker to detect early stages of alcoholic liver disease and to establish a possible correlation with hepatic histology, serum concentrations were measured by radioimmunoassay in 87 patients with biopsy-proven fatty liver, fatty liver and mild fibrosis, fatty liver and inflammation, severe fibrosis and inflammation, and cirrhosis, and in 12 non-alcoholic control subjects. In addition, serum hyaluronate was determined in 40 non-cirrhotic alcoholic patients with either a normal serum aspartate aminotransferase (AST) or an AST elevated at least two-fold.

RESULTS

Serum hyaluronate increased significantly with advanced stages of alcoholic liver disease, while levels in patients with fatty liver were elevated only slightly without reaching significance. Hyaluronate correlated well with histological stage and was highly sensitive for detecting fibrosis in general and perivenular fibrosis as an indicator of progression to cirrhosis. Hyaluronate levels were not influenced by AST levels.

CONCLUSION

Serum hyaluronate is a good predictor of the presence of even moderate hepatic fibrosis in alcoholic liver disease, justifying its clinical use to assess morphological alterations of the liver in alcoholics.

Combination of steroids with infliximab or placebo in severe alcoholic hepatitis: a randomized controlled pilot study

BACKGROUND/AIMS

The aim of this study is to evaluate the tolerance and effects of infliximab combined with steroids in severe alcoholic hepatitis (AH).

METHODS

Twenty patients with biopsy-proven severe AH (Maddrey's score>32) received prednisone 40 mg/day for 28 days and either infliximab 5mg/kg IV (group A) or placebo (group B) at day 0. Histology, plasma interleukin-6 (IL-6) and interleukin-8 (IL-8) were measured at baseline and at day 10.

RESULTS

Infliximab was well tolerated. Histology showed no significant changes. At day 28, Maddrey's score significantly improved in group A (39 (32-53) to 12 (7-52), P<0.05 vs. baseline) but not in group B (44 (33-50) to 22 (2-59), P=NS). At day 10, IL-6 and IL-8 decreased in group A (25 pg/ml (10-85 pg/ml) to 4.5 pg/ml (2-25 pg/ml); 301 pg/ml (107-1207 pg/ml) to 14 6 pg/ml (25-252 pg/ml), P<0.01, P<0.05 vs. baseline, respectively). In group B, changes were not significant (38 pg/ml (13-116 pg/ml) to 16 pg/ml (4-128); 315 pg/ml (26-1698 pg/ml) to 110 pg/ml (27-492 pg/ml)).

CONCLUSIONS

In severe AH, infliximab was well tolerated and associated with significant improvement in Maddrey's score at day 28. Although the size of this study does not allow comparison between groups, these promising results should encourage larger trials assessing the effects of this therapy on survival.

Endotoxin and its binding proteins in chronic liver disease: the effect of transjugular intrahepatic portosystemic shunting

BACKGROUND

Gut-derived endotoxin is insufficiently cleared by the diseased liver, and thus, is elevated in plasma of patients with chronic liver disease (CLD). Endotoxin action might be modified by binding to soluble CD14 (sCD14) and lipopolysaccharide-binding protein (LBP), both of which have not yet been sufficiently studied in CLD.

METHODS

Endotoxin, sCD14 and LBP have been determined in peripheral blood of 72 patients and 39 control subjects, and in portal and hepatic venous blood of 12 patients during transjugular intrahepatic portosystemic shunt (TIPS) implantation.

RESULTS

Peripheral endotoxin (average 3-fold increased compared to controls), LBP, and sCD14 plasma levels were elevated in chronic liver disease irrespective of Child stage m, preserve/absence of cirrhosis or aetiology. LBP, and sCD14. Furthermore, endotoxin levels in the portal vein (38.1 +/- 6.1 pg/ml) were only slightly elevated compared to the hepatic vein (29.2 +/- 4.4 pg/ml), and peripheral endotoxin levels did not increase after TIPS.

CONCLUSIONS

Decreased hepatocellular function rather than hepatic blood shunting might be responsible for endotoxemia. The elevation in LBP and sCD14 levels may be a consequence of endotoxemia.

Intraperitoneal protein injection in the axolotl: the amphibian kidney as a novel model to study tubulointerstitial activation

BACKGROUND

A substantial body of experimental evidence suggests that protein loading causes activation of proximal tubular epithelial cells with consecutive interstitial fibrosis. These studies have mostly been performed using mammalian in vivo models of glomerular damage or tissue cultures of mammalian tubulointerstitial cells. The kidney of the axolotl contains not only closed nephrons, but also nephrons with ciliated peritoneal funnels called nephrostomes that have access to the peritoneal fluid. Injection of protein into the peritoneal cavity fails to expose closed nephrons to a protein load, but causes selective uptake and transient storage of proteins in tubular epithelial cells of nephrons with nephrostomes. The purpose of the present study was to determine whether (a) the axolotl kidney can be used as a model to assess protein uptake by tubular cells in vivo in the absence of glomerular damage, and (b) this is accompanied by any evidence of tubular epithelial cell activation and interstitial fibrosis.

METHODS

Male and female axolotl (80 to 120 g of weight) were given a daily intraperitoneal injection of 1.5 mL endotoxin-free calf serum or saline as control. Kidneys were harvested after 4 or 10 days using perfusion fixation for light microscopy (fibrous tissue stain) and saline perfusion for immunohistochemistry (fibronectin, TGF-beta and collagen I).

RESULTS

The findings document selective storage of protein and lipids, progressive with time, in proximal tubular epithelial cells of nephrons draining the coelomic cavity. In addition, progressive focal accumulation of fibrous tissue was noted around protein-storing tubules. Immunohistochemical staining demonstrated the presence of fibronectin and TGF-beta in the tubular epithelial cells and interstitial cells.

CONCLUSION

The axolotl kidney provides a novel in vivo model to study tubulointerstitial activation and induction of interstitial fibrosis by protein loading. The findings are independent of alterations of glomerular function that may have potential confounding effects on peritubular hemodynamics, pO2, cell traffic, etc.

Lipopolysaccharide induced synthesis of CD14 proteins and its gene expression in hepatocytes during endotoxemia

AIM: To observe synthesis of CD14 protein and expression of CD14 mRNA in hepatic tissue and hepatocytes of rats during endotoxemia.

METHODS: The endotoxemia model of Wistar rat was established by injection of a dose of lipopolysaccharide (LPS) (5 mg·kg^-1, Escherichia coli O111:B4) via the tail vein, and then the rats were sacrificed after 3, 6, 12 and 24 h in batches. Hepatocytes were isolated from normal and LPS-injected rats by in situ collagenase perfusion technique and were collected to measure the expression of CD14 mRNA and synthesis of CD14 protein by reverse transcript-polymerase chain reaction (RT-PCR) or Western blot analysis. The binding of fluorescein isothiocyanate (FITC)-CD14 polyclonal antibody to isolated hepatocytes was also assessed by flow cytometric analysis (FCM).

RESULTS: In the rats with endotoxemia, the expressions of CD14 mRNA in hepatic tissue and isolated hepatocytes were stronger at 3, 6, and 12 h than that in control rats (3.48 ± 0.15, 5.89 ± 0.62, 4.33 ± 0.18, vs 1.35 ± 0.14 in hepatic tissue, P < 0.01; 4.12 ± 0.17, 6.24 ± 0.64, 4.35 ± 0.18, vs 1.87 ± 0.15 in hepatocytoes, P < 0.01).The synthesis of CD14 protein in hepatic tissue and isolated hepatocytes increases also obviously in 6 and 12 h when compared to that in control rats (13.27 ± 1.27, 17.32 ± 1.35, 11.42 ± 1.20,vs 7.34 ± 0.72 in hepatic tissue, P < 0.01; 14.68 ± 1.30, 17.95 ± 1.34, 11.65 ± 1.19, vs 7.91 ± 0.70 in hepatocytes, P < 0.01). FCM showed that mean fluorescence intensity (MFI) and numbers of FITC-CD14 positive cells in the rats with endotoxemia increased obviously at 3, 6, 12 and 24 h when compared with normal control group (43.4%, 70.2%, 91.4%, 32.6% vs 4.5%, P < 0.01).

CONCLUSION: LPS can markedly promote the synthesis of CD14 protein and up-regulate the expression of CD14 mRNA in isolated hepatocytes and hepatic tissue. Liver might be a main source for soluble CD14 production during endotoxemia.

Expression of lipopolysaccharide binding protein and its receptor CD14 in experimental alcoholic liver disease

AIM: To evaluate the relationship between the expression of lipopolysaccharides (LPS) binding protein (LBP) and CD14 mRNA and the severity of liver injury in alcohol-fed rats.

METHODS: Twenty Wistar rats were divided into two groups: ethanol-fed group (group E) and control group (group C). Group E was fed with ethanol (5-12 g·kg¯¹·d¯¹) and group C received dextrose instead of ethanol. Rats of the two groups were sacrificed at 4 wk and 8 wk. Levels of endotoxin and alanine transaminase (ALT) in blood were measured, and liver pathology was observed under light and electronic microscopy. Expressions of LBP and CD14 mRNA in liver tissues were determined by RT-PCR analysis.

RESULTS: Plasma endotoxin levels were increased more significantly in group E (129 ± 21) ng·L¯¹ and (187 ± 35) ng·L¯¹ at 4 and 8 wk than in control rats (48 ± 9) ng·L¯¹ and (53 ± 11) ng·L¯¹, respectively (P < 0.05). Mean values of plasma ALT levels were (1867 ± 250) nkat·L¯¹ and (2450 ± 367) nkat·L¯¹ in Group E. The values were increased more dramatically in ethanol-fed rats than in Group C after 4 and 8 wk. In liver section from ethanol-fed rats, there were marked pathological changes (steatosis, cell infiltration and necrosis). In ethanol-fed rats, ethanol administration led to a significant increase in LBP and CD14 mRNA levels compared with the control group (P < 0.05).

CONCLUSION: Ethanol administration led to a significant increase in endotoxin levels in serum and LBP and CD14 mRNA expressions in liver tissues. The increase of LBP and CD14 mRNA expression might wake the liver more sensitive to endotoxin and liver injury.

S-Adenosylmethionine modulates inducible nitric oxide synthase gene expression in rat liver and isolated hepatocytes

BACKGROUND/AIMS

Hepatocellular availability of S-adenosylmethionine, the principal biological methyl donor, is compromised in situations of liver damage. S-Adenosylmethionine administration alleviates experimental liver injury and increases survival in cirrhotic patients. The mechanisms behind these beneficial effects of S-adenosylmethionine are not completely known. An inflammatory component is common to many of the pathological conditions in which S-adenosylmethionine grants protection to the liver. This notion led us to study the effect of S-adenosylmethionine administration on hepatic nitric oxide synthase-2 induction in response to bacterial lipopolysaccharide and proinflammatory cytokines.

METHODS

The effect of S-adenosylmethionine on nitric oxide synthase-2 expression was assessed in rats challenged with bacterial lipopolysaccharide and in isolated rat hepatocytes treated with proinflammatory cytokines. Interactions between S-adenosylmethionine and cytokines on nuclear factor kappa B activation and nitric oxide synthase-2 promoter transactivation were studied in isolated rat hepatocytes and HepG2 cells, respectively.

RESULTS

S-Adenosylmethionine attenuated the induction of nitric oxide synthase-2 in the liver of lipopolysaccharide-treated rats and in cytokine-treated hepatocytes. S-Adenosylmethionine accelerated the resynthesis of inhibitor kappa B alpha, blunted the activation of nuclear factor kappa B and reduced the transactivation of nitric oxide synthase-2 promoter.

CONCLUSIONS

Our findings indicate that the hepatoprotective actions of S-adenosylmethionine may be mediated in part through the modulation of nitric oxide production.