Characterization of the Kupffer cell response to exogenous endotoxin in a rodent model of obstructive jaundice

Loss of bile salt export pump aggravates lipopolysaccharide-induced liver injury in mice due to impaired hepatic endotoxin clearance

BACKGROUND AND AIMS

Lipopolysaccharide (LPS) clearance is delayed in cholestatic liver diseases. While compromised clearance by Kupffer cells (KCs) is involved, the role of LPS uptake into hepatocytes and canalicular excretion remains unclear.

APPROACH AND RESULTS

Wild-type (WT) and bile salt export pump (Bsep) knockout (KO) mice were challenged i.p. with LPS. Liver injury was assessed by serum biochemistry, histology, molecular inflammation markers, and immune cell infiltration. LPS concentrations were determined in liver tissue and bile. Subcellular kinetics of fluorescently labeled LPS was visualized by intravital two-photon microscopy, and the findings in Bsep KO mice were compared to common bile duct-ligated (BDL) and multidrug resistance protein 2 (Mdr2) KO mice. Changes in gut microbiota composition were evaluated by 16S ribosomal RNA gene amplicon sequencing analysis. Bsep KO mice developed more pronounced LPS-induced liver injury and inflammatory signaling, with subsequently enhanced production of proinflammatory cytokines and aggravated hepatic immune cell infiltration. After LPS administration, its concentrations were higher in liver but lower in bile of Bsep KO compared to WT mice. Intravital imaging of LPS showed a delayed clearance from sinusoidal blood with a basolateral uptake block into hepatocytes and reduced canalicular secretion. Moreover, LPS uptake into KCs was reduced. Similar findings with respect to hepatic LPS clearance were obtained in BDL and Mdr2 KO mice. Pretreatment with the microtubule inhibitor colchicine inhibited biliary excretion of LPS in WT mice, indicating that LPS clearance is microtubule-dependent. Microbiota analysis showed no change of the gut microbiome between WT and Bsep KO mice at baseline but major changes upon LPS challenge in WT mice.

CONCLUSIONS

Absence of Bsep and cholestasis in general impair LPS clearance by a basolateral uptake block into hepatocytes and consequently less secretion into canaliculi. Impaired LPS removal aggravates hepatic inflammation in cholestasis.

Should preoperative biliary drainage be routinely performed for obstructive jaundice with resectable tumor?

Obstructive jaundice is a common clinical manifestation of malignant lesions adjacent to extrahepatic bile duct, ampulla or pancreatic head. Animal experiments and some clinical observations have demonstrated that preoperative biliary drainage could improve liver function as well as reduce endotoxemia, thereby reducing the incidence of perioperative complications. However, a number of randomized, controlled studies have found that preoperative biliary drainage failed to improve prognosis or reduce the incidence of perioperative complications; in contrast, it might increase the incidence of complications and cause extra financial burden on patients. Thus, whether preoperative biliary drainage should be performed or not is controversial. Since clinical randomized controlled studies are more relevant in clinical setting, we believe that preoperative biliary drainage should not be routinely performed for obstructive jaundice with resectable tumors. More randomized, controlled, prospective studies should be conducted for further exploration.

The quandary of preresection biliary drainage for pancreatic cancer

Surgery in patients with obstructive jaundice caused by a tumor in the pancreatic head area is associated with a higher risk of postoperative complications. Preoperative biliary drainage was introduced in an attempt to improve the general condition and reduce morbidity and mortality. Extensive experimental studies have been performed to analyze the beneficial effect of biliary drainage and showed improvement in liver function, nutritional status, and cell-mediated immune function as well as reduction in mortality. However, despite the results seen in the experimental studies, clinical studies reported both beneficial and adverse effects, and most studies advised against routinely performing preoperative biliary drainage. To add clarity to the ongoing controversy, a recent randomized controlled trial was performed and reported more overall complications in patients with jaundice who underwent preoperative biliary drainage followed by surgery compared to those who underwent surgery alone. Many of these complications were stent related. Like most clinical studies, a plastic stent was used to initiate biliary drainage. Patients with jaundice because of a tumor in the pancreatic head area without locoregional irresectability or metastases should be candidates for early surgery. Preoperative biliary drainage should not be performed routinely. However, some selected patients might benefit from preoperative biliary drainage, in cases of severe jaundice, neoadjuvant therapy, or postponed surgery due to logistics. In these cases, the use of metal biliary stents is indicated.

Cytokine response to portal endotoxaemia and neutrophil stimulation in obstructive jaundice

INTRODUCTION

An exaggerated proinflammatory response to endotoxaemia can occur in obstructive jaundice. The aims of this study were to determine the hepatic proinflammatory and anti-inflammatory cytokine response to endotoxaemia in experimental biliary obstruction and to determine the source of interleukin-6 (IL-6) using immunohistochemistry.

METHODOLOGY

Male Wistar rats were randomized into three groups: bile duct ligation (BDL), sham operation, and control groups. They were weighed before surgery and after 1 week. On day 8, hepatic perfusion was performed with endotoxin (Escherichia coli 0111:B4). Serial samples of blood, effluent, and influent perfusate were analyzed for proinflammatory and anti-inflammatory cytokines. Ultrastructural assessment of sections of the liver was performed.

RESULTS

BDL animals lost weight in the first week compared with the sham and the control animals that gained weight. Liver function tests were elevated in the BDL group. Effluent biochemistry did not reveal liver injury as a result of perfusion. Ultrastructurally, there was no evidence of liver injury, with only active Kupffer cells, preservation of liver architecture, and minimal liver injury being detected. Serum tumor necrosis factor-α was not detected in any group before perfusion; however, serum IL-6 was higher in the BDL group. Portal endotoxaemia resulted in an increase in tumor necrosis factor-α, IL-6, and IL-10 in the BDL group. Fluorescence immunohistochemistry demonstrated IL-6 in the sinusoidal spaces and the cytoplasm of Kupffer cells.

CONCLUSION

There is an exaggerated proinflammatory and anti-inflammatory cytokine response to portal endotoxaemia in animals with jaundice compared with the sham group.

Decreased hepatic peroxisome proliferator-activated receptor-γ contributes to increased sensitivity to endotoxin in obstructive jaundice

AIM: To investigate the role of hepatic peroxisome proliferator-activated receptor-γ (PPAR-γ) in increased susceptibility to endotoxin-induced toxicity in rats with bile duct ligation during endotoxemia.

METHODS: Male Sprague-Dawley rats were subjected to bile duct ligation (BDL). Sham-operated animals served as controls. DNA binding were determined by polymerase chain reaction, Western blotting analysis, and electrophoretic mobility shift assay, respectively. BDL and sham-operated rats received a non-lethal dose of intraperitoneal lipopolysaccharide (LPS) injection (3 mg/kg, i.p.). Additionally, the potential beneficial effects of the PPAR-γ agonist rosiglitazone were determined in BDL and sham-operated rats treated with a non-lethal dose of LPS. Survival was assessed in BDL rats treated with a non-lethal dose of LPS and in sham-operated rats treated at a lethal dose of LPS (6 mg/kg, i.p.).

RESULTS: PPAR-γ activity in rats undergoing BDL was significantly lower than in the sham-controls. Hepatic PPAR-γ gene expression was downregulated at both the mRNA and protein levels. In a parallel group, serum levels of pro-inflammatory cytokines were nearly undetectable in the sham-operated rats. When challenged with a non-lethal dose of LPS (3 mg/kg), the BDL rats had approximately a 2.4-fold increase in serum IL-6, a 2.7 fold increase in serum TNF-α, 2.2-fold increase in serum IL-1 and 4.2-fold increase in serum ALT. The survival rate was significantly lower as compared with that in sham-operated group. Additionally, rosiglitazone significantly reduced the concentration of TNF-α, IL-1β, IL-6 and ALT in sham-operated rats, but not in BDL rats, in response to LPS (3 mg/kg). Also, the survival was improved by rosiglitazone in sham-operated rats challenged with a lethal dose of LPS, but not in BDL rats, even with a non-lethal dose of LPS (3 mg/kg).

CONCLUSION: Obstructive jaundice downregulates hepatic PPAR-γ expression, which in turn may contribute to hypersensitivity towards endotoxin.

Hepatocyte nuclear factor-kappa beta (NF-kappaB) activation is protective but is decreased in the cholestatic liver with endotoxemia

BACKGROUND

Obstructive jaundice (OJ) is an important clinical consideration associated with a high risk of bacteremia. Hepatocyte nuclear factor-kappa B (NF-kappaB) activation confers an antiapoptotic function. Although the occurrence of hepatocyte apoptosis has been shown in OJ, the activation and role of NF-kappaB over the time course of OJ in conjunction with endotoxemia have not yet been well defined. We hypothesized that NF-kappaB activation may be decreased over the time course of OJ and endotoxemia, which leads to severe liver injury. The aim of the current study was to examine whether NF-kappaB activation can decrease hepatocyte apoptosis and liver injury over the time course of OJ in response to lipopolysaccharide (LPS) administration.

METHODS

Male C57BL/6 mice were subjected to bile duct ligation and were administered LPS intravenously at 3 days (OJ3) or 14 days (OJ14) after bile duct ligation. NF-kappaB activation; protein expressions of NF-kappaB p65, IkappaB-alpha, Ikappabeta-b, and Pin1; immunohistochemistry of poly adenosine diphosphate (ADP)-ribose polymerase p85 fragment (PARP); and serum alanine transaminase (ALT) levels were examined.

RESULTS

Hepatocyte NF-kappaB activation was observed during OJ. After LPS administration, the hepatic NF-kappaB activation defined by electrophoretic mobility shift assay was decreased in the OJ14 group compared with the OJ3 group, which is consistent with a decrease in NF-kappaB p65 protein expression. Changes in phosphorylated Ikappa-B-beta but not phosphorylated IkappaB-alpha mirrored these results. Significant hepatocyte apoptosis defined by PARP immunohistochemistry was observed in the LPS-treated OJ14 relative to the LPS-treated OJ3. Hepatic expressions of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in the LPS OJ14 mice were upregulated relative to those in the LPS OJ3. Serum ALT levels increased significantly in the LPS OJ14 relative to other mice. The survival rate was significantly less in the LPS OJ14 relative to other mice.

CONCLUSION

After prolonged OJ, exposure to endotoxemia was associated with a decrease in hepatocyte NF-kappaB activation and an increase in hepatocyte apoptosis and secondary necrosis, thus resulting in liver dysfunction.

Splanchnic Th(2) and Th(1) cytokine redistribution in microsurgical cholestatic rats

BACKGROUND

Long-term extrahepatic cholestasis in the rat induces ductular proliferation and fibrosis in the liver, portal hypertension, splenomegaly, portosystemic collateral circulation, and ascites. These splanchnic alterations could have an inflammatory pathophysiology.

MATERIAL AND METHODS

We measured serum levels of hepatobiliary injury markers and the acute phase proteins, alpha-1-major acid protein (alpha(1)-MAP) and alpha-1-acid glycoprotein (alpha(1)-GPA) in rats 6 wk after microsurgical extrahepatic cholestasis. We also assayed Th(1) (TNF-alpha and IL-1beta) and Th(2) (IL-4 and IL-10) cytokine levels in the liver, ileum, spleen, and mesenteric lymph complex by enzyme-linked immunosorbent assay (ELISA) techniques. Liver fibrosis was measured by Sirius red stain and by using an image system computer-assisted method and mast cell liver infiltration by Giemsa stain.

RESULTS

The cholestatic rats showed an increase (P<0.001) in serum levels of bile acids, total and direct bilirubin, AST, ALT, AST/ALT index, gamma-GT, alkaline phosphatase, alpha(1)- MAP, alpha(1)-GPA, and LDH (P<0.05) in relation to sham-operated rats. TNF-alpha, IL-1beta, IL-4, and IL-10 increased in the ileum (P<0.01) and mesenteric lymph complex (P<0.001), and decreased in the liver (P<0.001). A marked bile proliferation associated with fibrosis (P<0.001) and mast cell infiltration was also shown in the liver of cholestatic rats.

CONCLUSION

The splanchnic redistribution of cytokines, with an increase of Th(1) and Th(2) production in the small bowel and in the mesenteric lymph complex, supports the key role of inflammatory mechanisms in rats with secondary biliary fibrosis.

[Consequences of Kupffer cell blockade on endotoxin-induced inflammatory and hepatic microcirculatory reactions during experimental biliary obstruction]

INTRODUCTION/AIMS

In the clinical practice, biliary obstruction often leads to septic complications causing systemic and hepatic inflammatory reactions, which increases mortality and morbidity. Hepatic Kupffer cells (KC) play a pivotal role in this process. Herein we examined the consequences of bile duct ligation during endotoxaemia and the effects of KCs.

MATERIAL AND METHODS

In the first part of our experiment, the survival rate of male Wistar rats in 48-hr endotoxaemia with or without bile duct ligation was assessed. Time-dependent changes in pro-inflammatory TNF-alpha and IL-6 levels were also monitored. In the second series, hepatic capillary perfusion, neutrophil-endothelial interactions and KC activity were assessed using fluorescence intravital videomicroscopy. KC blockade was induced by gadolinium chloride (GdCl3) pretreatment.

RESULTS

Serum TNF-alpha and IL-6 levels were significantly increased in early endotoxaemia. Survival rate was deteriorated, while TNF-alpha and IL-6 releases, KC activity and leukocyte activation were increased if obstructive jaundice was also induced. KC blockade improved survival and reduced TNF-alpha and IL-6 productions without ameliorating perfusion failure.

CONCLUSIONS

In the presence of biliary obstruction, inflammatory and microcirculatory consequences of endotoxaemia are enhanced. The alleviating effect of KC blockade may underline the pathophysiological role of KCs in these conditions.

The effect of calcitonin gene-related peptide on healing of intestinal anastomosis in rats with experimental obstructive jaundice

PURPOSE

Intestinal anastomotic healing is a complex procedure in which several mediators and cytokines play roles. Calcitonin gene-related peptide is an important neuropeptide in inflammation. In this study we aimed to investigate the effect of calcitonin gene-related peptide on healing of intestinal anastomosis in rats with obstructive jaundice.

MATERIALS AND METHODS

Obstructive jaundice was induced in rats by the ligation and division of the common bile duct. Four days after the operation, intestinal anastomosis was performed, and either calcitonin gene-related peptide or 0.9% NaCl was administered intraperitoneally to these jaundiced rats and controls. The concentrations of serum tumor necrosis factor-alpha (TNF-alpha) and triglyceride levels of all rats were measured, and healing of the anastomosis was evaluated by measuring the bursting pressure and hydroxyproline content on the 7th postoperative day.

RESULTS

Calcitonin gene-related peptide was found to have positive effects on healing of the anastomosis by inhibiting the effects of TNF-alpha and increasing the bursting pressure and hydroxyproline content of the anastomosis.

CONCLUSION

Calcitonin gene-related peptide increases anastomotic wound healing in experimental anastomosis in the presence of obstructive jaundice in rats.

Preoperative biliary drainage in patients with obstructive jaundice: history and current status

RATIONALE

Preoperative biliary drainage (PBD) has been introduced to improve outcome after surgery in patients suffering from obstructive jaundice due to a potentially resectable proximal or distal bile duct/pancreatic head lesion. In experimental models, PBD is almost exclusively associated with beneficial results: improved liver function and nutritional status; reduction of systemic endotoxemia; cytokine release; and, as a result, an improved immune response. Mortality was significantly reduced in these animal models. Human studies show conflicting results.

FINDINGS

For distal obstruction, currently the "best-evidence" available clearly shows that routine PBD does not yield the appreciated improvement in postoperative morbidity and mortality in patients undergoing resection. Moreover, PBD harbors its own complications. However, most of the available data are outdated or suffer from methodological deficits.

CONCLUSION

The highest level of evidence for PBD to be performed in proximal obstruction, as well as over the preferred mode, is lacking but, nevertheless, assimilated in the treatment algorithm for many centers. Logistics and waiting lists, although sometimes inevitable, could be factors that might influence the decision to opt for PBD, as well as an extended diagnostic workup with laparoscopy (on indication) or scheduled preoperative chemotherapy.

LPS-binding protein mediates LPS-induced liver injury and mortality in the setting of biliary obstruction

It is generally accepted that low levels of lipopolysaccharide (LPS)-binding protein (LBP) augment the cell's response to LPS, whereas high levels of LBP have been shown to inhibit cell responses to LPS. Clinical studies and in vitro work by our group have demonstrated that, in the setting of liver disease, increased or acute-phase levels of LBP may actually potentiate rather than inhibit an overwhelming proinflammatory response. Therefore, in the present studies we sought to determine the role of acute-phase LBP in mediating morbidity and mortality in animals challenged with LPS in the setting of biliary obstruction. Using LBP-deficient mice and LBP blockade in wild-type mice, we demonstrate that high levels of LBP are deleterious in the setting of cholestasis. Following biliary obstruction and intraperitoneal LPS challenge, hepatic injury, hepatic neutrophil infiltration, and mortality were significantly increased in animals with an intact LBP acute-phase response. Kupffer cell responses from these animals demonstrated a significant increase in several inflammatory mediators, and Kupffer cell-associated LBP appears to be responsible for these differences, at least in part. Our results indicate that the role of LBP signaling in inflammatory conditions is complex and heterogeneous, and elevated levels of LBP are not always protective. Increased LBP production in the setting of cholestatic liver disease appears to be deleterious and may represent a potential therapeutic target for preventing overwhelming inflammatory responses to LPS in this setting.

Kupffer cell blockade improves the endotoxin-induced microcirculatory inflammatory response in obstructive jaundice

Cholestasis predisposes to hypersensitivity to LPS, leading to potential septic complications. We set out to characterize the involvement of Kupffer cell (KC) activation in the hepatic microcirculatory and structural consequences of obstructive jaundice in the presence and absence of acute endotoxemia. The hepatic microcirculatory consequences of 3-day extrahepatic bile duct ligation (BDL) were assessed in rats. The contributions of changes in hepatic perfusion, leukocyte influx, and proinflammatory cytokine release to the development of hepatic structural damage were also determined. Furthermore, the corresponding consequences of BDL in combination with acute (2-h) endotoxemia (1 mg kg(-1) LPS, i.v.) were compared with those observed after LPS alone. In a second series, the same protocols were applied in identical groups of rats where the KC function was inhibited with 24-h gadolinium chloride pretreatment (10 mg kg(-1), i.v.). Bile duct ligation induced minor inflammatory reactions but caused a marked reduction in hepatic sinusoidal perfusion and severe histological damage. LPS treatment, however, elicited an approximately 5-fold increase in leukocyte adherence in the central venules and pronounced IL-6 and TNF-alpha release, but without significant structural damage. The combination of BDL with LPS enhanced the perfusion failure, leukocyte sticking/deposition, and proinflammatory cytokine release; most of these changes can be effectively ameliorated by gadolinium chloride. In conclusion, when obstructive jaundice is followed by a second hit of LPS, perfusion failure, liver inflammation, and structural damage are enhanced, the KCs playing a decisive role in this scenario. Therapeutic strategies aimed at KC blockade can potentially reduce the risk of inflammatory complications in cholestasis.

Excessive inflammation but decreased immunological response renders liver susceptible to infection in bile duct ligated mice

BACKGROUND/AIMS

Obstructive jaundice (OJ) is associated with increased surgical morbidity and infectious complication. The aim of the current study was to clarify the mechanism of excessive inflammation and susceptibility to infection in OJ.

METHODS

C57/BL6 mice were subjected to bile duct ligation (BDL) or sham surgery. Expression tumor necrosis factor-alpha, macrophage inflammatory protein-2, monocyte chemoattractant protein-1, inducible protein-10, and interleukin (IL)-10, activation of nuclear factor kappa B, fluorescence activated cell sorter analysis, serum alanine aminotransferase levels, and histology were examined. Survival after lipopolysaccharide (LPS) administration or cecal ligation and puncture 3 or 14 d after surgery was determined. IL-1beta and interferon-gamma expression was examined after LPS administration.

RESULTS

OJ induced nuclear factor kappa B activation and increased expression of macrophage inflammatory protein-2, which caused significant increases in neutrophil recruitment. Serum alanine aminotransferase levels increased consistent with histological observations in OJ. Mononuclear cells were recruited in the liver after BDL associated with monocyte chemoattractant protein-1 up-regulation. The recruitment of NK and T cells was varied, consistent with IP-10 expression during the time course of OJ. IL-10 expression was significantly up-regulated 14 d after BDL. After LPS administration, the mice at 3 d after BDL and at 3 and 14 d after sham surgery were all still alive, but all mice at 14 d after BDL died. After LPS administration, IL-1beta significantly increased in the mice at 14 d after BDL.

CONCLUSIONS

Immune response such as expression of pro- and anti-inflammatory mediators and recruitment of immune cells may thus differ over the time course of OJ. Prolonged OJ may cause excessive inflammation, thus result in susceptibility to infection.

Effect of N-acetylcysteine on blood and tissue lipid peroxidation in lipopolysaccharide-induced obstructive jaundice

In obstructive jaundice, free radical production is increased and antioxidative activity is reduced. N-Acetylcysteine (NAC) has a beneficial effect with anti-inflammatory and antioxidant activity, acting as a free radical scavenger. NAC inhibits inducible nitric oxide synthase, suppresses cytokine expression/release, and inhibits adhesion molecule expression and nuclear factor kappa B. The aim of this study was to investigate the effects of NAC on liver/renal tissue and serum lipid peroxidation in lipopolysaccharide (LPS)-induced obstructive jaundice. We randomized 60 rats into 6 groups: group 1, Sham; group 2, obstructive jaundice (OJ) induced after bile-duct ligation; group 3, OJ + NAC (100 mg kg- 1 subcutaneously); group 4, OJ + LPS (10 mg kg-1); group 5, OJ + NAC + LPS; and group 6, OJ + LPS + NAC. For each group, the biochemical markers of lipid peroxidation and the antioxidant products were measured in serum and liver/renal tissue after sacrifice. Almost all lipid peroxidation products levels were increased and antioxidant products levels were decreased in groups who received LPS (groups 4, 5, and 6), but the effect was less remarkable when NAC was administered before LPS (group 5). The same trend was seen for groups with OJ +/- LPS who did not received NAC or received it after induced toxemia (groups 2, 4, and 6) as compared to groups 1 and 3. Moreover, in the case of OJ + LPS, rats treated with NAC before LPS (group 5) had lower lipid peroxidation products levels and higher antioxidant products levels as compared to those who did not received NAC (group 4). This phenomenon was not reproducible with NAC administered after LPS (group 6). Thus, results of this study showed that NAC prevents the deleterious effects of LPS in obstructive jaundice by reducing lipid peroxidation in serum and liver/renal tissue if administered before LPS. Nonetheless, NAC failed to prevent the lipid peroxidation in the case of established endotoxemia in obstructive jaundice.

The effect of aminoguanidine on blood and tissue lipid peroxidation in jaundiced rats with endotoxemia induced with LPS

Obstructive jaundice (OJ) is a severe condition that leads to several complications. One of the important problems in OJ is the increased incidence of endotoxemia, which is the result of bacterial translocation (BT) and defective host immune response. Lipid peroxidation (LP) is an important problem in OJ and sepsis in which nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) activity are increased and antioxidative activity is decreased. Formation of peroxynitrite (ONOO(-)) anion leads to cellular damage and apoptosis. In this experimental study, we explore the effect of specific iNOS inhibitor aminoguanidine (AG) on blood and tissue (liver and renal) LP and iNOS levels in jaundiced rats with endotoxemia induced with lipopolysaccharide (LPS). Rats were randomized into six groups; group A, sham; group B, obstructive jaundice (OJ); group C, OJ + LPS; group D, OJ + AG; group E, OJ + LPS + AG; group F, OJ + AG + LPS. Serum malondialdehyde (MDA) and serum myeloperoxidase (MPO) activity and liver and renal tissue MDA, MPO, and Na(+)/K(+)-ATPase activity levels were detected in biochemical methods. Liver and renal tissue iNOS levels were examined immunohistopathologically. Serum and tissue MDA and MPO levels and tissue iNOS expression were increased significantly in groups B, C, and E, while tissue ATPase levels were decreased significantly in the same groups. In the group treated with AG (group D), serum and tissue MDA and MPO levels and tissue iNOS expression were decreased while tissue ATPase levels were increased significantly. In group F, if AG was administrated before LPS, we observed that serum and tissue MDA and MPO levels and tissue iNOS expression were decreased while tissue ATPase levels were increased significantly. Thus, our study showed that AG had a protective effect when it was administrated before LPS, but it failed to prevent tissue iNOS expression and LP if there was established endotoxemia in OJ.

Phagocytosis and production of H2O2 by human peripheral blood mononuclear cells from patients with obstructive jaundice

BACKGROUND

The immune function is altered in jaundiced patients; here, the ability of their peripheral blood mononuclear cells to perform phagocytosis and to release H2O2 was analyzed.

METHODS

Cells from 53 patients before surgery for relief of cholestasis, from 38 patients 1 week and from 15 patients 2 weeks after surgery were separated and cultured for 1 h in the presence of phorbol myristate acetate. H2O2 release was evaluated colorimetrically and phagocytosis by the ingestion of Escherichia coli in vitro.

RESULTS

Before surgery for relief of cholestasis, the cells of the patients were unable to release H2O2, but, after surgery, an increasing percentage of patients had cells that were able to produce H2O2 (13% after 1 week; 33% after 2 weeks). This recovery did not correlate with bilirubinemia. When cultured for 1 week in the presence of normal or jaundiced plasma, regardless of collection time, cells of 12/12 patients released H2O2, but in lower levels if in the presence of jaundiced plasma. In contrast, H2O2 release by normal donor cells was enhanced in the presence of jaundiced plasma. Phagocytosis by cells of the patients was lower, but when present was associated with a significantly higher bactericidal activity.

CONCLUSION

These significant, but reversible alterations of monocyte function in jaundiced patients might contribute to their enhanced susceptibility to surgical complications.

Kupffer cells abrogate cholestatic liver injury in mice

BACKGROUND & AIMS

Biliary obstruction and cholestasis can cause hepatocellular apoptosis and necrosis. Ligation of the common bile duct in mice provides an excellent model in which to study the underlying mechanisms. Kupffer cells play a key role in modulating the inflammatory response observed in most animal models of liver injury. This study was performed to determine the role of Kupffer cells in the injury attending cholestasis.

METHODS

Mice were not treated or were rendered Kupffer cell-depleted by intravenous inoculation of multilamellar liposome-encapsulated dichloromethylene diphosphonate, the common bile duct was ligated and divided; sham-operated animals served as controls. Similarly, interleukin-6 (IL-6)-deficient and tumor necrosis factor-receptor-deficient mice underwent bile duct ligation (BDL) or sham operations.

RESULTS

Serum alanine transaminase levels were increased in all BDL mice at 3 days after surgery, but were significantly higher in IL-6-deficient mice or mice rendered Kupffer cell-depleted before ligation. Histologic examination of BDL livers showed portal inflammation, neutrophil infiltration, bile duct proliferation, and hepatocellular necrosis. Photoimage analyses confirmed more necrosis in the livers of Kupffer cell-depleted and IL-6-deficient animals. Purified Kupffer cells derived from BDL animals produced more IL-6 in culture. Similarly, Kupffer cells obtained by laser capture microdissection from the livers of BDL mice expressed increased levels of IL-6 messenger RNA. Recombinant mouse IL-6 administered 1 hour before BDL completely reversed the increased liver damage assessed otherwise in Kupffer cell-depleted mice.

CONCLUSIONS

These findings indicate that Kupffer cells abrogate cholestatic liver injury by cytokine-dependent mechanisms that include the production of IL-6.

Altered Kupffer cell function in biliary obstruction

BACKGROUND

An altered Kupffer cell (KC) response is thought to be responsible for the characteristic phenotype observed after biliary obstruction: a phenotype marked by a defect in the hepatic reticuloendothelial system and a hypersensitivity to endotoxin. Few studies, however, have directly examined KC function. We have sought to define the specific alterations in function and phenotype that occur in the KC after biliary obstruction.

METHODS

KCs were isolated from female C57BL/6 mice 4 days after a sham or common bile duct ligation (CBDL) operation. Phagocytosis, oxidative burst potential, and intracellular bacterial killing were measured as markers of reticuloendothelial system function. The KC response to endotoxin was assessed by measuring tumor necrosis factor alpha and interleukin 6 levels in the media after stimulation with lipopolysaccharide (LPS) or with LPS plus LPS-binding protein (LBP).

RESULTS

CBDL KCs demonstrated a significant increase in phagocytic ability and significantly decreased baseline oxidative stress, compared with Shams. The oxidative burst potential, however, was equivalent or higher for CBDL KCs. CBDL KCs also demonstrated increased numbers of viable intracellular bacteria after infection; however, it is unclear if this finding represents impaired intracellular bacterial killing or increased phagocytosis of bacteria. With respect to the KC response to endotoxin, CBDL KCs were found to be less sensitive to the stimulatory effects of LPS alone but were exquisitely sensitive to the effects of LBP. LBP levels were found to be significantly elevated in CBDL animals, and CBDL KCs demonstrated a dose-dependent, exaggerated tumor necrosis factor alpha and interleukin 6 response to LPS administered with LBP.

CONCLUSIONS

KC function is clearly altered after biliary obstruction. Phagocytic ability is actually increased, although the ability of CBDL KCs to kill bacteria within the phagosome remains ill defined. CBDL KCs are exquisitely sensitive to the effects of LBP, and LBP levels are elevated after biliary obstruction. LBP may be responsible for the increased proinflammatory response observed after endotoxin challenge in animals with biliary obstruction.

The isolated perfused liver response to a 'second hit' of portal endotoxin during severe acute pancreatitis

BACKGROUND/AIM

During severe acute pancreatitis (AP), the liver may show an exaggerated response to the inflammatory products of gut injury transported in the portal vein. Our aim was to explore liver proinflammatory mediator production after a 'second hit' of portal lipopolysaccharide (LPS) during AP.

METHODS

Twenty-four rats underwent one of three 'first-hit' scenarios: (1) severe AP induced by intraductal glycodeoxycholic acid injection and intravenous caerulein infusion, (2) sham laparotomy, or (3) no first intervention. Eighteen hours later, all animals received a 'second hit' of portal LPS in an isolated liver perfusion system. Tumour necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, and IL-6 concentrations were measured in portal and systemic serum, and in the perfusate 30 and 90 min after the 'second hit'. Neutrophil activation by the perfusate was assayed using dihydrorhodamine-123 fluorescence.

RESULTS

We observed a six-fold increase in IL-6 concentration across the liver during AP. All livers produced TNF-alpha after the portal LPS challenge, but this was not exaggerated by AP. No differential neutrophil activation by the perfusate was seen.

CONCLUSION

TNF-alpha, IL-1beta, IL-6 and neutrophil activator production by the isolated perfused liver, in response to a 'second hit' of portal LPS, does not appear to be enhanced during AP.

Microsurgical extrahepatic cholestasis in the rat: a long-term study

An experimental model of microsurgical cholestasis is studied as an alternative to the most frequently used surgical techniques, based on the section of the common bile duct. This microsurgical technique consists of the resection of the extrahepatic biliary tract, that is, of the common bile duct in continuity with the bile ducts that drain the four lobes of the rat liver. At 30 days of evolution, rats with microsurgical cholestasis do not develop biliary pseudocysts or intraperitoneal hilar hepatopulmonary abscesses and show an increase (p < 0.001) in total bilirubin (9.50 +/- 1.50 mg/dL vs. 1.60 +/- 0.35 mg/dL), bile acids (225 +/- 87 micromol/L vs. 12.5 +/- 14.50 micromol/L), gamma-glutamyltranspeptidase (375 +/- 143 U/L vs. 8 +/- 11 U/L), and alkaline phosphatase (73 +/- 25 U/L vs. 23 +/- 4 U/L) levels. The histological study shows fibrosis with biliary proliferation. The microsurgical cholestasis technique is a valid alternative to other techniques and can be an adequate experimental model for the study of etiopathogenic mechanisms of obstructive jaundice and especially to study extrahepatic biliary atresia.

The effect of N-acetylcysteine (NAC) on liver and renal tissue inducible nitric oxide synthase (iNOS) and tissue lipid peroxidation in obstructive jaundice stimulated by lipopolysaccharide (LPS)

Morbidity and mortality rates are very high in obstructive jaundice when it is associated with sepsis and multiple organ failure. Nitric oxide (NO) formation and increased expression of inducible nitric oxide synthase (iNOS) also take place in obstructive jaundice (OJ). N-Acetylcysteine (NAC) has a beneficial effect by demonstrating anti-inflammatory activity such as inhibits cytokine expression/release, inhibiting the adhesion molecule expression and inhibiting nuclear factor kappa B (NFkappaB). The aim of this study was to investigate the effects of NAC on liver and renal tissue iNOS, and liver tissue lipid peroxidation in lipopolysaccharide (LPS) induced obstructive jaundice. We randomized 48 rats into six groups. Group A: Sham group; group B: OJ group; group C: OJ+NAC; group D: OJ+LPS (Escherichia coli LPS serotype L-2630, 100mg, Sigma) group E: OJ+NAC+LPS; group F: OJ+LPS+NAC. NAC was started subcutaneously 100mg/kg. LPS was injected intraperitoneally and then at the tenth day we sacrificed the rats. Liver malondialdehyde (MDA) increased and liver ATPase decreased in groups B-D when compared to group A. After the administration of NAC (groups C-E), liver MDA levels decreased, tissue ATPase levels increased as compared to other groups. The liver and renal tissue iNOS expression was increased in groups B, D, and F. After the administration of NAC (groups C-E) the liver and renal tissue iNOS expression were decreased. Our results indicated that NAC prevented the deleterious effects of LPS in OJ by reducing iNOS expression via lipid peroxidation in liver and renal tissue; if it was administrated before LPS. But NAC failed to prevent the iNOS expression and lipid peroxidation if there was established endotoxemia in OJ.

High-fat enteral nutrition reduces endotoxin, tumor necrosis factor-alpha and gut permeability in bile duct-ligated rats subjected to hemorrhagic shock

BACKGROUND/AIMS

Cholestatic patients are prone to septic complications after major surgery due to an increased susceptibility to endotoxin and hypotension. High-fat enteral nutrition reduces endotoxin after hemorrhagic shock. However, it is unknown whether this nutritional intervention is protective in biliary obstruction. We investigated the effect of high-fat enteral nutrition on endotoxin, tumor necrosis factor-alpha (TNF-alpha) and intestinal permeability in cholestatic rats subjected to hemorrhagic shock.

METHODS

Bile duct-ligated (BDL) rats were fasted or fed with low-fat or high-fat enteral nutrition before hemorrhagic shock. Blood and tissue samples were taken after 90 min.

RESULTS

Plasma endotoxin decreased after hemorrhagic shock in BDL-rats fed with high-fat nutrition compared to fasted (P<0.01) and low-fat treated rats (P<0.05). Additionally, circulating TNF-alpha was reduced in BDL-rats pretreated with high-fat nutrition compared to fasted rats (P<0.01). The increased intestinal permeability to macromolecules was reduced by high-fat enteral nutrition, whereas bacterial translocation did not significantly change. Simultaneously, tight junction distribution in ileum and colon was disrupted in non-treated BDL-rats but remained unchanged in high-fat pretreated BDL-rats.

CONCLUSIONS

High-fat enteral nutrition protects against endotoxin-mediated complications independently of intraluminal bile. These results provide a potential new strategy to prevent endotoxin-mediated complications in cholestatic patients undergoing major surgery.

Étude de l’effet de l’antithrombine-III (AT-III) sur les modifications de l’épithélium intestinal liées à l’ictère obstructif : étude expérimentale chez le rat

PURPOSE

Bacterial translocation leading to sepsis is increased by obstructive jaundice(OJ). Antithrombin III (ATIII) mediates the promotion of prostaglandin release, an inhibitor of leucocyte activation and downregulator of many proinflammatory cytokines. We investigated the effect of ATIII on histopatology and villus morphology of small intestine.

MATERIAL AND METHODS

We designed an experimental study with 40 rats who were divided into four groups. The first one (control, n = 10) received saline, the second (n = 10) included normal rats who received ATIII, the third group (n = 10) was rats with OJ (ligation of common bile duct), and the fourth group included OJ rats receiving AT-III. AT-III (100 UI/kg intraperitoneally) was started at the third day following bile duct ligation and repeated for 5 days. At the 8 day, rats were scarified and ileum was analysed. Histopathological assessments were performed, using a grading scheme ranging from 0 to 10 (Chui et al).

RESULTS

Median histological score was found to be 2 in group 1, 1.71 in group 2, 5.43 in group 3 and 2.71 in group 4. The difference between group 3 and 4 was statistically significant. Mucosal thicknesses and villus lengths were found significantly lower in OJ group. Mucosal thicknesses and villus lengths were significantly preserved in jaundiced + AT-III group.

CONCLUSION

ATIII demonstrated a salutary effect on the histopathological changes caused by the OJ and prevented the adverse effects on histopathological and morphological parameters in ileal mucosa.

Superoxide and nitric oxide production by Kupffer cells in rats with obstructive jaundice: effect of internal and external drainage

BACKGROUND AND AIMS

The role of Kupffer cells in obstructive jaundice (OJ) has not been fully understood. The aims of the present study were to measure superoxide and nitric oxide (NO) production by Kupffer cells in experimental OJ in rats and to investigate the response to internal and external biliary drainage.

METHODS

Eighty male Sprague-Dawley rats were assigned to four groups: sham operation, OJ, and internal and external biliary drainage. Kupffer cells were isolated on day 7 in the sham operation and OJ group, and on day 7 after drainage procedures. Cells were cultured with or without lipopolysaccharide (LPS). Superoxide production was quantified in cultured Kupffer cells at 2 h and 48 h, respectively, after cell isolation using the superoxide dismutase inhibitable ferricytochrome c reduction method. Nitrite production in cell culture supernatants was measured 48 h later using Greiss reagents.

RESULTS

Without LPS stimulation, Kupffer cells produced comparable superoxide and nitrite in each group (P > 0.05). With LPS stimulation, Kupffer cells in the OJ group produced significantly higher superoxide anions than the other groups (P = 0.006). Nitrite production was significantly increased in the OJ group and external biliary drainage group compared to rats in the sham operation and internal drainage groups (P < 0.01).

CONCLUSIONS

Kupffer cells from rats with OJ produce great amounts of endotoxin-mediated oxidants. Both internal and external biliary drainage can decrease the elevated superoxide production. Internal drainage is superior to external drainage for reversing the distortional capacity of NO production by Kupffer cells.

Comparative study of macro- and microsurgical extrahepatic cholestasis in the rat

The long-term (5-week) evolution of two experimental models of extrahepatic cholestasis, i.e., macrosurgical by bile duct ligation (n = 20) and microsurgical by biliary tract resection (n = 13), is studied. All cholestatic animals showed jaundice, choluria, and portosystemic collateral circulation. Macrosurgical cholestasis causes greater hepatosplenomegaly, hilar biliary pseudocysts, and ascites. Microsurgical extrahepatic cholestasis occurs with a lower degree of hepatosplenomegaly as well as with serum increase (P < 0.001) of gamma-GT and alkaline phosphatase. The bile ductular proliferation in the four hepatic lobes is very intense (P < 0.001) in both experimental models. The differences between both experimental models may be considered secondary to the increase of the predisposition to infection in rats with bile duct ligation, that complicates their evolution. The microsurgical cholestasis model could be useful in studying cholestasis secondary to biliary atresia.

Surgical sepsis: dysregulation of immune function and therapeutic implications

Sepsis is defined clinically as the systemic inflammatory response of the host to the documented systemic infection. The pathophysiological disturbance involves both the innate and adaptive immune systems encompassing cellular immunity, humoral components and the complement system. Dendritic cells (antigen-presenting cells) are key cells involved in the regulation of the immune response in sepsis, in particular in activating T cells and especially inducing the production and secretion of specific cytokines. These are the main mediators in establishing prominent disturbances of inflammation in patients with sepsis. The clinical features of the sepsis syndrome may vary from minor clinical disturbances to severe multiple organ failure and death of the host. Appropriate therapeutic strategies for patients with sepsis utilise conventional therapy and new novel forms of treatment, which are showing promise for the future.

Systemic endotoxaemia following obstructive jaundice: the role of lactulose

BACKGROUND

Obstructive jaundice is often accompanied by bacterial translocation and subsequent sepsis. The effect of lactulose in preventing that process was evaluated in an experimental model. Obstructive jaundice was induced in 23 rabbits after common bile duct ligation.

METHODS

Animals were divided into two groups. Group A of 11 animals-controls and group B of 12 rabbits, which received 2 ml/kg of lactulose p.o. by a nasogastric tube. Blood was sampled daily, before and after operation. Samples were applied for culture and for estimation of endotoxins (LPS), tumor necrosis factor (TNFa), and malondialdehyde (MDA).

RESULTS

Mean (+/-SD) survival of animals of group A was 3.08+/-0.19 days compared to 5.36+/-0.41 days of animals of group B. Serum concentrations of LPS and TNFa of each day of treatment remain constant in animals of group A; they were steadily decreased in animals of group B reaching statistical significance on the fourth day. Similar changes were not found for MDA.

CONCLUSION

The administration of lactulose may prevent systemic endotoxaemia and the subsequent inflammatory response in an experimental model of obstructive jaundice, so as to extend survival. These results merit further clinical evaluation.

The effect of PARS inhibition on ileal histopathology, apoptosis and lipid peroxidation in LPS-induced obstructive jaundice

In our experimental study, we investigated the protective effect of 3-aminobenzamide (3-AB), the poly (ADP-ribose) synthetase (PARS inhibitor), on the ileal histopathology and the apoptosis in lipopolysaccharide (LPS)-induced inflammation in rats with obstructive jaundice (OJ). We randomized 40 rats into five groups. Group 1: sham group; Group 2: OJ group; Group 3: OJ+LPS; Group 4: OJ+3-AB+LPS; Group 5: OJ+LPS+3-AB. At the fifth day; the rats were jaundiced. In Group 3; 10 mg kg(-1) LPS was injected intraperitoneally at the fifth day and then after 6h the rats were sacrificed. In Group 4; 10 mg kg(-1) 3-AB was administrated intraperitoneally at the fifth day and repeated daily for 3 days and at the eighth day, 10 mg kg(-1) LPS was injected intraperitoneally. In Group 5, 10 mg kg(-1) LPS was injected intraperitoneally at the fifth day and after 6h 10 mg kg(-1) 3-AB was administrated intraperitoneally and repeated daily for 3 days. At the eighth day, rats were sacrificed. Blood samples were taken for detection of serum MDA levels. Ileum samples were taken after relaparotomy for histopathological examination to evaluate the endotoxin-related intestinal injury and Caspase-3 apoptosis and for detection of tissue MDA and ATPase activities. There was marked destruction of villous and crypt epithelial cells and extensive apoptosis in Groups 3 and 5 in histopathological examination. In Group 4, the scores of intestinal mucosal damage and apoptotic cells were reduced significantly (P<0.05). On the other hand, the scores of intestinal mucosal damage and apoptotic cells were not improved in Group 5. After the administration of 3-AB (Group 4), serum and ileal MDA levels decreased, ileal ATPase increased as compared to Groups 1 and 2. Our study showed that 3-AB prevented the mucosal damage and apoptotic loss of intestinal epithelial cells significantly if it was administrated before LPS. However, 3-AB failed to prevent the mucosal damage and apoptotic loss of intestinal epithelial cells significantly if there was established endotoxemia in OJ.

Infection by gram-negative organisms via the biliary route results in greater mortality than portal venous infection

Cholangitis requires bile duct obstruction and infection. Patients with cholangitis are often more affected than those with infections that reach the liver through the portal vein. We will attempt to study the influences of (i) route of entry and (ii) presence of bile duct obstruction on hepatic infection. C57BL/6 mice received injections of Escherichia coli or lipopolysaccharide into the obstructed bile duct or portal vein and were monitored for survival. Livers were assayed for bacteria, and cytokine mRNA was measured. In order to examine the effect of biliary obstruction on hepatic infection, animals were subjected to bile duct ligation 1 day prior to portal vein injection and were monitored for survival. The 50% lethal dose (LD(50)) for E. coli injected into the bile duct was 50 CFU/animal; the LD(50) for E. coli injected into the portal vein was 5 x 10(7) CFU/animal. Initial hepatic delivery of bacteria was equivalent 1 h after injection into the bile duct or portal vein. However, by 24 h, a significantly greater amount of bacteria was recovered from the livers of the bile duct-injected group. Interleukin 10 (IL-10) and IL-1RA mRNA was expressed at greater levels in the bile duct-injected group. Prior bile duct ligation followed by portal vein injection resulted in a higher incidence of death than when sham operation was performed prior to portal vein injection. Our data suggest that the increased mortality from cholangitis, compared with that from other hepatic infections, is related to the different route of delivery of pathogen and the maladaptive response (possibly involving IL-10 and IL-1RA) to biliary obstruction itself.

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.