Role of neutrophils in sinusoidal endothelial cell injury after extensive hepatectomy in cholestatic rats

IL-22 promotes liver regeneration after portal vein ligation

Background

Insufficient remnant liver volume (RLV) after the resection of hepatic malignancy could lead to liver failure and mortality. Portal vein ligation (PVL) prior to hepatectomy is subsequently introduced to increase the remnant liver volume and improve the outcome of hepatic malignancy. IL-22 has previously been reported to promote liver regeneration, while facilitating tumor development in the liver via Steap4 upregulation. Here we performed PVL in mouse models to study the role of IL-22 in liver regeneration post-PVL.

Methods

Liver weight and volume was measured via magnetic resonance imaging (MRI). Immunohistochemistry for Ki67 and hepatocyte growth factor (HGF) was performed. IL-22 was analyzed by flow cytometry and quantitative polymerase chain reaction (qPCR) was used for acquisition of Il-33, Steap4, Fga, Fgb and Cebpd. To analyze signaling pathways, mice with deletion of STAT3 and a neutralizing antibody for IL-22 were used.

Results

The remnant liver weight and volume increased over time after PVL. Additionally, we found that liver regenerative molecules, including Ki67 and HGF, were significantly increased in remnant liver at day 3 post-PVL, as well as IL-22. Administration of IL-22 neutralizing antibody could reduce Ki67 expression after PVL. The upregulation of IL-22 after PVL was mainly derived from innate cells. IL-22 blockade resulted in lower levels of IL-33 and Steap4 in the remnant liver, which was also the case in mice with deletion of STAT3, the main downstream signaling molecule of IL-22, in hepatocytes.

Conclusion

IL-22 promotes liver regeneration after PVL. Thus, a combination of IL-22 supplementation and Steap4 blockade could potentially be applied as a novel therapeutic approach to boost liver regeneration without facilitating tumor progression after PVL.

Neutrophil-Induced Liver Injury and Interactions Between Neutrophils and Liver Sinusoidal Endothelial Cells

Neutrophils are the most abundant type of leukocytes with diverse functions in immune defense including production of reactive oxygen species, bacteriocidal proteins, neutrophil extracellular traps, and pro-inflammatory mediators. However, aberrant accumulation of neutrophils in host tissues and excessive release of bacteriocidal compounds can lead to unexpected injury to host organs. Neutrophil-mediated liver injury has been reported in various types of liver diseases including liver ischemia/reperfusion injury, nonalcoholic fatty liver disease, endotoxin-induced liver injury, alcoholic liver disease, and drug-induced liver injury. Yet the mechanisms of neutrophil-induced hepatotoxicity in different liver diseases are complicated. Current knowledge of these mechanisms are summarized in this review. In addition, a substantial body of evidence has emerged showing that liver sinusoidal endothelial cells (LSECs) participate in several key steps of neutrophil-mediated liver injury including neutrophil recruitment, adhesion, transmigration, and activation. This review also highlights the current understanding of the interactions between LSECs and neutrophils in liver injury. The future challenge is to explore new targets for selectively interfering neutrophil-induced liver injury without impairing host defense function against microbial infection. Further understanding the role of LSECs in neutrophil-induced hepatotoxicity would aid in developing more selective therapeutic approaches for liver disease.

Bile Acids Activated Receptors Regulate Innate Immunity

Once known exclusively for their role in nutrients absorption, primary bile acids, chenodeoxycholic and cholic acid, and secondary bile acids, deoxycholic and lithocholic acid, are signaling molecules, generated from cholesterol breakdown by the interaction of the host and intestinal microbiota, acting on several receptors including the G protein-coupled bile acid receptor 1 (GPBAR1 or Takeda G-protein receptor 5) and the Farnesoid-X-Receptor (FXR). Both receptors are placed at the interface of the host immune system with the intestinal microbiota and are highly represented in cells of innate immunity such as intestinal and liver macrophages, dendritic cells and natural killer T cells. Here, we review how GPBAR1 and FXR modulate the intestinal and liver innate immune system and contribute to the maintenance of a tolerogenic phenotype in entero-hepatic tissues, and how regulation of innate immunity might help to explain beneficial effects exerted by GPBAR1 and FXR ligands in immune and metabolic disorders.

Superoxide dismutase activity in portal vein endothelium after partial liver resection

PURPOSE

To investigate superoxide dismutase (SOD) activity in the portal vein endothelium and malondialdehyde acid (MDA) production in liver tissue of rats submitted to 70% hepatectomy.

METHODS

Twelve rats were distributed in two groups (hepatectomy and sham). Animals were sacrificed on post operative day 1 and portal vein, liver tissue and blood samples were collected. Portal vein SOD production was measured using lucigenin-amplified chemiluminescence assays. MDA measurement was used as an index of oxidative stress through the formation of TBARS (Thiobarbituric Acid Reactive Species).

RESULTS

There was no difference in post operative bilirubin, AST, ALT levels between groups. DHL level was higher in the hepatectomy group (p=0.01). MDA production in the remnant liver tissue and endothelial portal vein SOD activity were also significantly (p<0.05) elevated in the hepatectomy group when compared to control group. There was no correlation between MDA and SOD activity. SOD activity, on the other hand, showed a positive correlation with LDH level (p=0.038) and MDA levels showed a positive correlation with AST and ALT levels (p<0.001).

CONCLUSION

There is an increased production of malondialdehyde acid in liver tissue after partial hepatectomy and increased activity of superoxide dismutase in portal vein endothelium as well.

Early effects of portal flow modulation after extended liver resection in rat

INTRODUCTION

The incidence of small-for-size-liver-syndrome after liver transplantation and extended liver resection may be reduced by portal flow modulation. However, many aspects of the small-for-size-liver-syndrome pathogenesis are still unclear. In this experimental study we evaluated the early effects of portal flow modulation after 80% hepatic resection in rats.

MATERIALS AND METHODS

Rats were randomised in: sham operation (G1), conventional hepatic resection (G2), splenectomy and hepatic resection (G3), splenic transposition followed by hepatic resection after three weeks (G4). Six hours after operation, oxygen saturation of hepatic vein blood, glutathione, and standard liver markers were measured from hepatic venous blood. Glutathione measurement and histopatological examination were performed in the remnant liver.

RESULTS

Total bilirubin and liver glutathione did not show differences between groups. Aspartate aminotransferase and alanine aminotransferase significantly increased in G2-G4 groups. Blood glutathione and oxygen saturation of hepatic vein blood were lower in G2 than in other groups. A gradient of micro-vesicular degeneration was more severe in G2 compared with G3 and G4. Apoptosis, hemorrhagic necrosis, mitochondrial damage and leucocyte adhesion were evident in G2.

CONCLUSION

The portal flow modulation induced by splenectomy or splenic transposition was effective in limiting early damage after extended liver resection.

Biochemical and morphologic effects after extended liver resection in rats: preliminary results

After hepatic resection and transplantation with a partial graft, death and regeneration of the hepatocytes coexist in the liver. However, when the functional liver mass is inadequate to ensure a proper balance between regeneration vs functional and metabolic demands, small-for-size syndrome develops. We assessed the early effects of extended hepatic resection on liver function in a rat model. Six male Sprague-Dawley rats underwent 80% resection of the liver, and 6 rats served as a control group. At 6 hours after resection, blood samples were obtained from the hepatic vein for measurement of reduced glutathione (GSH), oxidized glutathione (GSSG), and hepatic venous oxygen saturation (Shvo(2)), and for standard liver function tests including determination of concentrations of alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transpeptidase, and total bilirubin. The remnant lobe was removed for GSH assay and histopathologic analysis. In the resection group, values were significantly higher for ALT (P = .002), AST (P = .002), and Shvo(2) (P = .01), whereas a significant decrease was observed for blood GSH (P = .009) but not liver GSH. Also in the resection group, we observed characteristic hepatocyte vacuolization with a gradient from periportal acinar zone 1 to the centrolobular area, the presence of hemorrhagic necrosis, and several leukocyte adhesions. The Shvo(2) and GSH data suggest early alteration of oxygen metabolism, as demonstrated by the reduction in oxygen uptake and decreased liver GSH secretion, with preservation of hepatic GSH. Mitochondrial dysfunction and oxidative injury seem to have a crucial role in early onset of liver damage.

Protective effect of methylprednisolone on warm ischemia-reperfusion injury in a cholestatic rat liver

BACKGROUND

Cholestasis has been identified as a risk factor for oxidative stress, and it potentially enhances after ischemic-reperfusion injury. The aim of this study was to evaluate the role of methylprednisolone on warm ischemia-reperfusion injury in the presence of cholestasis.

METHODS

A reversible cholestatic rat model was created. After 7 days, rats received 30 mg/kg of intravenous methylprednisolone 2 hours before ischemia, followed by 30 minutes of ischemia. Rats were euthanized 24 hours after ischemia. Serum aspartate aminotransferase and interleukin-6 were measured, and the liver was harvested for histology and myeloperoxidase estimation.

RESULTS

Methylprednisolone had a protective effect, with a statistically significant decrease in aspartate aminotransferase (P=.01) and a trend toward decreased levels of interleukin-6 (P=.07). Histology showed a significant difference in architectural distortion (P=.01), cytoplasmic vacuolation (P=.01), and nodular hepatocellular necrosis (P=.04).

CONCLUSIONS

Methylprednisolone attenuated the ischemic-reperfusion injury in the presence of cholestasis and can be considered for clinical use in the presence of cholestasis.

Inhibition of inducible nitric oxide synthase worsens liver damage regardless of lipopolysaccharide treatment in small-for-size liver transplantation

OBJECTIVE

In small-for-size liver transplantation, portal hypertension aggravates endotoxin from the gut which accelerates the activation of inducible nitric oxide synthase (iNOS). However, there is little knowledge as to the effects of iNOS inhibitors on small-for-size graft damage. Our study was designed to investigate the role of an iNOS inhibitor both with and without lipopolysaccharide (LPS) treatment in ischemia-reperfusion injury of small-for-size liver transplantation.

METHODS

Subjecting Sprague-Dawley rats to small-for-size grafts liver transplantation, we investigated the time course of changes in hepatic expression of iNOS and endothelial nitric oxide synthase (eNOS). Meantime, we also investigated the effects of iNOS inhibitor, both with and without LPS treatment, at 6h after reperfusion.

RESULTS

While iNOS mRNA expression reached a peak at 3h, the highest protein level occurred at 6h after reperfusion. Aminoguanidine (AG) significantly inhibited mRNA and protein expressions of iNOS, but not that of eNOS. However, LPS accelerated activation of iNOS, but suppressed the expression of eNOS. Meanwhile, compared with the untreated group, those treated with AG or LPS experienced worsened liver function and tissue damage, promoting neutrophil infiltration in the liver tissue. The difference between the LPS group and the LPS+AG group was found to be significant. In addition, AG and LPS treatments up-regulated the protein expression of ICAM-1 and NF-kappaB p65.

CONCLUSION

In a small-for-size model of rat liver transplantation, regardless of LPS treatment, the inhibitor of iNOS, AG, attenuated iNOS expression, but worsened liver function and tissue damage. The subsequent increased neutrophil infiltration in liver tissue may be associated with up-regulation of ICAM-1 and NF-kappaB expressions.

Neutrophil phenotype and function in partial hepatectomy in man

PURPOSE

Hepatic resections are still associated with considerable morbidity mainly because of postoperative infection. Adequate function of neutrophils is a crucial element in host defense. The aim of the study was to characterize neutrophils during partial hepatectomy.

METHODS

Fourteen patients undergoing partial liver resection were enrolled. Twenty-four hours pre-, intra- (after induction of anesthesia, after preparation of the liver, and 15 min after release of the Pringle maneuver), as well as postoperatively (3 h after Pringle; 24, 48, and 120 h after surgery), blood samples were obtained. In addition, healthy volunteers (n = 5) were investigated. Adhesion molecules (CD 62, CD 18), Fcy receptors (CD 16, CD 32), and phagocytosis by neutrophils were characterized by fluorescence-activated cell sorter analysis. Spontaneous and stimulated (formyl-methionyl-leucyl-phenylalanine) oxygen radical generation was measured by lucigenin-enhanced chemiluminescence.

RESULTS

Numeric upregulation of CD 62 and CD 18 on neutrophils was seen before the use of Pringle maneuver and persisted thereafter (p < 0.05). Spontaneous numeric expression of Fcy receptors (CD16 and CD 32) was unchanged during liver dissection but downregulated after Pringle maneuver was opened (p < 0.05). Although numeric Fcy receptors were downregulated, phagocytosis of heterologous opsonized Escherichia coli bacteria by neutrophils was unaffected. Spontaneous oxygen radical production peaked sharply 15 min after release of the Pringle maneuver (p < 0.05), contrary to stimulated oxygen radical production, which was depressed 3 h after the release of the Pringle maneuver (ns).

CONCLUSIONS

Uneventful partial hepatectomy in man resulted already in a significant change in the phenotype but in less significant changes in the functions of neutrophils.

Nuclear factor κB activity in patients with acute severe cholangitis

AIM: To determine the NF-κB activity in peripheral blood mononuclear cells (PBMC) in patients with acute cholangitis of severe type (ACST) and correlate the degree of NF-κB activation with severity of biliary tract infection and clinical outcome.

METHODS: Twenty patients with ACST were divided into survivor group (13 cases) and nonsurvivor group (7 cases). Other ten patients undergoing elective gastrectomy or inguinal hernia repair were selected as control group. Peripheral blood samples were taken 24 h postoperatively. PBMC were separated by density gradient centrifugation, then nuclear proteins were isolated from PBMC, and Electrophoretic Mobility Shift Assay (EMSA) used determined. The results were quantified by scanning densitometer of a Bio-Image Analysis System and expressed as relative optical density (ROD). The levels of TNF-α, IL-6, and IL-10 in the plasma of patients with ACST and healthy control subjects were determined by using an enzyme-linked immunoassay (ELISA).

RESULTS: The NF-κB activity was 5.02 ± 1.03 in nonsurvivor group, 2.98 ± 0.51 in survivor group and 1.06 ± 0.34 in control group. There were statistical differences in three groups (P < 0.05). The levels of TNF-α and IL-6 in plasma were (498 ± 53) ng·L^-1 and (587 ± 64) ng·L^-1 in nonsurvivor group, (284 ± 32) ng·L^-1 and (318 ± 49) ng·L^-1 in survivor group and (89 ± 11) ng·L^-1 and (102 ± 13) ng·L^-1 in control group. All patients with ACST had increased levels of TNF-α and IL-6, which were manyfold greater than those of control group, and there was an evidence of significantly higher levels in those of nonsurvivor group than that in survivor group (P < 0.05). The levels of IL-10 in plasma were (378 ± 32) ng·L^-1, (384 ± 37) ng·L^-1 and (68 ± 11) ng·L^-1 in three groups, respectively. All patients had also increased levels of IL-10 when compared with control group (P < 0.05), but the IL-10 levels were not significantly higher in nonsurvivors than in survivors (P > 0.05).

CONCLUSION: NF-κB activity in PBMC in patients with ACST increases markedly and the degree of NF-κB activation is correlated with severity of biliary tract infection and clinical outcome.

Liver sinusoidal endothelial cell injury by neutrophils in rats with acute obstructive cholangitis

AIM: The objective of this study is to elucidate the potential role of poly-morphonuclear neutrophils (PMN) in the development of such a sinusoidal endothelial cell (SEC) injury during early acute obstructive cholangitis (AOC) in rats.

METHODS: Twenty one Wistar rats were divided into three groups: the AOC group, the bile duct ligated group (BDL group), and the sham operation group (SO group). The common bile duct (CBD) of rats in AOC group was dually ligated and 0.2 mL of the E. coli O₁₁₁ B₄ (5 × 10⁹ cfu/mL) suspension was injected into the upper segment, in BDL group, only the CBD was ligated and in SO group, neither injection of E. coli suspension nor CBD ligation was done, but the same operative procedure. Such group consisted of seven rats, all animals were killed 6 h after the operation. Morphological changes of the liver were observed under light and electron microscope. Expression of intercellular adhesion molecule-1 (ICAM-1) mRNA in hepatic tissue was determined with reverse transcription polymerase chain reaction (RT-PCR). The serum levels of alanine aminotransferase (ALT) were determined with anutoanalyger and cytokine-induced neutrophil chemoattractant (CINC) was determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS: Neutrophils was accumulated in the hepatic sinusoids and sinusoidal endothelial cell injury existed in AOC group. In contrast, in rats of BDL group, all the features of SEC damage were greatly reduced. Expression of ICAM-1 mRNA in hepatic tissue in three groups were 7.54 ± 0.82, 2.87 ± 0.34, and 1.01 ± 0.12, respectively. There were significant differences among three groups (P < 0.05). The serum CINC levels in the three groups were 188 ± 21 ng•L⁻¹, 94 ± 11 ng•L⁻¹, and 57 ± 8 ng•L⁻¹, respectively. There were also significant differences among the three groups (P < 0.05). Activity of the serum ALT was 917 ± 167 nkat•L⁻¹, 901 ± 171 nkat•L⁻¹, and 908 ± 164 nkat•L⁻¹, respectively, (P > 0.05).

CONCLUSION: Hepatic SEC injury occurs earlier than hepatic parenchymal cells during AOC. Recruitments of circulating neutrophils in the hepatic sinusoidal space might mediate the SEC injury, and ICAM-1 in the liver may modulate the PMN of accumulation.