Endotoxaemia and hepatic injury in 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.

Spontaneous remission of obstructive jaundice in rats: Selection of experimental models

The aim of the present study was to evaluate the prevalence and causes of spontaneous remission of obstructive jaundice in rats. Healthy male and female Wistar rats (180–220 g) were randomly assigned to receive common bile duct ligation (CBDL) and transection (group A), CBDL only (group B), or CBD dissection without ligation or transection (control group C; n=36 in each group). There was a difference in eye and skin jaundice prevalence between groups A and B from 14 days after surgery. The level of total bilirubin (TB) did not continue to increase in group A and began to decrease in the majority of rats in group B (P<0.05 vs. group B). At day 21 after surgery, the TB level returned to normal in group B and no significant difference was observed compared with group C. At day 21 after surgery, significant dilatation of bile ducts above the ligature was observed in group A following cholangiography with 38% meglumine diatrizoate and this contrast agent did not spread to other sites. Slight dilatation of the proximal bile ducts was observed in group B and the contrast agent entered the intestinal lumen through the omental ducts adhering to the porta hepatis. After 14 days of surgery, there were 36 rats in group A and B, and 17 rats exhibited spontaneous regression of jaundice. Overall, 47.2% (17/36) of rats experienced spontaneous remission of obstructive jaundice, 82.4% (14/17) of which underwent ligation only. The spontaneous remission of jaundice may have been caused by shunting through very small bile ducts or omental ducts adhering to the porta hepatis. If a model of biliary obstruction is to be established in future research, a model of CBDL and transection is preferable. In this case, jaundice reduction surgery should be performed 14 days after establishment of the model.

Hepatoprotective effect of water extract from Chrysanthemum indicum L. flower

Background

Chrysanthemum indicum L. flower (CIF) has been widely used as tea in Korea. This study aims to investigate the hepatoprotective effect of the hot water extract of CIF (HCIF) in in vitro and in vivo systems.

Methods

Hepatoprotective activities were evaluated at 250 to 1000 μg/mL concentrations by an in vitro assay using normal human hepatocytes (Chang cell) and hepatocellular carcinoma cells (HepG2) against CCl₄-induced cytotoxicity. Cytochrome P450 2E1, which is a key indicator of hepatic injury, was detected by western blot analysis using rabbit polyclonal anti-human CYP2E1 antibody. An in vivo hepatoprotective activity assay was performed at 1000 to 4000 μg/mL concentrations on CCl₄-induced acute toxicity in rats, and the serum levels of glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) were determined by standard enzyme assays.

Results

The hepatoprotective effects of HCIF significantly reduced the levels of GOT (60.1%, P = 0.000) and GPT (64.5%, P = 0.000) compared with the vehicle control group (CCl₄ alone). The survival rates of HepG2 and Chang cells were significantly improved compared with the control group [82.1% (P = 0.034) and 62.3% (P = 0.002), respectively]. HCIF [50 mg/kg body weight (BW)] treatment significantly reduced the serum levels of GOT (49.5%, P = 0.00), GPT (55.5%, P = 0.00), ALP (30.8%, P = 0.000) and LDH (45.6%, P = 0.000) compared with the control group in this in vivo study. The expression level of cytochrome P450 2E1 (CYP2E1) protein was also significantly decreased at the same concentration (50 mg/kg BW; P = 0.018).

Conclusion

HCIF inhibited bioactivation of CCl₄-induced hepatotoxicity and downregulates CYP2E1 expression in vitro and in vivo.

Protective effect of Lycium chinense fruit on carbon tetrachloride-induced hepatotoxicity

In the present study, we investigated the protective effect of Lycium chinense Miller (Solanaceae) fruit (LFE) against CCl(4)-induced hepatotoxicity and the mechanism underlying these protective effects in rats. The pretreatment of LFE has shown to possess a significant protective effect by lowering the serum aspartate and alanine aminotransferase (AST and ALT) and alkaline phosphatase (ALP). This hepatoprotective action was confirmed by histological observation. In addition, pretreatment of LFE prevented the elevation of hepatic malondialdehyde (MDA) formation and the depletion of reduced glutathione (GSH) content and catalase activity in the liver of CCl(4)-injected rats. The LFE also displayed hydroxide radical scavenging activity in a dose-dependent manner (IC(50) = 83.6 microg/ml), as assayed by electron spin resonance (ESR) spin-trapping technique. The expression level of cytochrome P450 2E1 (CYP2E1) mRNA and protein, as measured by reverse transcriptase-polymerase chain reaction (RT-PCR) and western blot analysis, was significantly decreased in the liver of LFE-pretreated rats when compared with that in the liver of control group. Based on these results, it was suggested that the hepatoprotective effects of the LFE might be related to antioxidative activity and expressional regulation of CYP2E1.

Bacterial translocation from the biliary tract to blood and lymph in rats with obstructive jaundice

BACKGROUND

The disruption of the hepatocyte tight junctions observed in biliary obstruction suggests altered permeability of the blood-bile barrier. In this study the role of biliary obstruction and increased biliary pressure on the translocation of bacteria from biliary tract to bloodstream and lymphatic system were evaluated.

MATERIALS AND METHODS

Rats underwent distal bile duct ligation (BDL, n = 33) for two weeks or a sham celiotomy (n = 21). Seventeen of the 33 BDL rats underwent subsequent biliary decompression by a choledochojejunostomy (CJ). Two weeks after the final operation, a laparotomy was performed again and the CBD, the thoracic duct, and the caval vein were canulated. Next, a suspension containing 10(8) Escherichia coli/ml was retrogradely infused in the CBD for 5 min at 5 or 20 cm H2O above the secretory biliary pressure.

RESULTS

A higher biliary infusion pressure resulted in a significant increase of cfu E.coli per milliliter of blood in all the three groups (Sham, BDL, CJ). BDL rats showed significantly more bacterial translocation to the bloodstream than the shams. After biliary decompression, translocation normalized to the control levels. At 5 cm H2O infusion pressure only one lymph culture was positive (CJ group). At 20 cm H2O overpressure, nine lymph cultures were E.coli positive (P = 0.03). These were found mainly in groups with a nonobstructed bile duct (Sham and CJ 40% vs BDL 10%).

CONCLUSION

Translocation of bacteria from biliary tract to bloodstream increased at higher intrabiliary pressures. Longstanding bile duct obstruction was an independent determinant for cholangiovenous reflux. Bacterial translocation to the lymphatic system did not parallel translocation to the bloodstream, although in the nonobstructed biliary tract, increased bacterial translocation to the lymphatic system was pressure related.

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.