Enhanced endothelial cell injury by activated neutrophils in patients with obstructive jaundice

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.

Neutrophil extracellular traps enhance procoagulant activity and thrombotic tendency in patients with obstructive jaundice

BACKGROUND & AIMS

Patients with obstructive jaundice (OJ) are considered to be prothrombotic with increased risk of thromboembolism complications. The role of neutrophil extracellular traps (NETs) in procoagulant activity (PCA) and thrombosis risk in patients with OJ is unclear. In this study, we investigated NETs formation in OJ patients and the role of elevated unconjugated bilirubin (UCB) in inducing NETs, resulting in enhanced PCA and endothelial injury.

METHODS

NETs of OJ patients and healthy controls were measured. NETs PCA was assessed via coagulation time (CT), fibrin formation and purified coagulation complex production assays. Visualization of NETs and mitochondrial reactive oxygen species (MitoROS) were performed with a fluorescence microscope. We further used confocal microscopy to quantify the exposure of phosphatidylserine (PS), fibrin strands and FVa/Xa on Human umbilical vein endothelial cells (HUVECs).

RESULTS

Assessment of NETs components levels revealed greater NETs production in OJ patients than in healthy controls. Importantly, OJ-NETs were responsible for enhanced PCA. UCB induced NETs formation via MitoROS accumulation and mitochondrial mobilization. HUVECs cocultured with OJ NETs lost their cell-cell junctions and consequently converted to a procoagulant phenotype. The PCA was attenuated by using DNase I alone or in combination with lactadherin.

CONCLUSIONS

Our results suggest that UCB-induced NETs play a prominent role in promoting the hypercoagulable and prothrombotic state in OJ patients. The increased MitoROS accumulation in neutrophils initiated NETosis. NETs are promising targets for indicating or improving coagulation disorders in OJ patients.

The Preventive Effect of Dexmedetomidine Against Postoperative Intra-abdominal Adhesions in Rats

This study aimed to determine the possible preventive effects of dexmedetomidine on postoperative intra-abdominal adhesions. Dexmedetomidine is a highly selective and potent α2 adrenergic agonist with sedative, analgesic, anxiolytic, sympatholytic, hemodynamic, and diuretic properties. In recent years, investigations have shown that dexmedetomidine possesses secondary antioxidant and also anti-inflammatory effects. Thirty Wistar albino male rats were randomized and divided into 3 groups of 10 animals each: group 1, sham-operated; group 2, cecal abrasion + peritoneal dissection; group 3, cecal abrasion + peritoneal dissection followed by daily intravenous injection of 10 μg/kg dexmedetomidine for 10 days. The animals were killed on postoperative day 21. Blood and cecal samples were taken for biochemical and histopathologic evaluation. In this study, biochemical and pathologic parameters were significantly better in the cecal abrasion + peritoneal dissection + dexmedetomidine group when compared with the cecal abrasion + peritoneal dissection group. Tissue malondialdehyde, myeloperoxidase, total sulfhydryl, and catalase were found to be significantly different between the cecal abrasion/peritoneal dissection + dexmedetomidine and the cecal abrasion/peritoneal dissection groups. Plasma malondialdehyde and total sulfhydryl values were also statistically different between these groups (P < 0.05). Statistical analyses of mean pathologic scores showed that the histopathologic damage in the cecal abrasion/peritoneal dissection + dexmedetomidine group was significantly less than the damage in the control group (P < 0.05 for all pathologic parameters). The results of this study show that dexmedetomidine had a significant preventive effect on postoperative intra-abdominal adhesions. We concluded that these effects might be due to antioxidant and anti-inflammatory activities.

Effects of sulfasalazine on lipid peroxidation and histologic liver damage in a rat model of obstructive jaundice and obstructive jaundice with lipopolysaccharide-induced sepsis

BACKGROUND

Sulfasalazine, an inhibitor of cyclooxygenase, 5-lipoxygenase, and nuclear factor κB (NF-κB), has been found to alleviate oxidative damage, proinflammatory cytokine production, bile-duct proliferation, neutrophil infiltration, and fibrosis. Therefore, it may have a potential effect in attenuating lipid peroxidation and histologic liver damage in patients with biliary obstruction and biliary obstruction with sepsis.

OBJECTIVE

The aim of this study was to investigate the effect of sulfasalazine on lipid peroxidation and histologic liver damage due to obstructive jaundice (OJ) and to OJ with lipopolysaccharide (LPS)-induced sepsis in an experimental model.

METHODS

Male Wistar rats, weighing 150 to 220 g, were randomized into 6 groups: OJ; OJ + LPS; OJ + sulfasalazine; OJ + sulfasalazine + LPS (sulfasalazine administered before sepsis); OJ + LPS + sulfasalazine (sulfasalazine administered after sepsis); and sham. Liver malondialdehyde (MDA) and myeloperoxidase (MPO) activities were assessed to monitor lipid peroxidation and neutrophil infiltration in liver tissue. Histologic liver damage was evaluated with hematoxylin-eosin stained slides. Liver tissue NF-κB and caspase-3 expression were studied immunohistopathologically to evaluate lipid peroxidation, liver damage, and hepatocyte apoptosis.

RESULTS

Forty-eight rats were evenly randomized into 6 groups of 8. MDA (P = 0.001), MPO (P = 0.001), NF-κB (P = 0.003), caspase-3 expression (P = 0.002), and liver injury scores (P = 0.002) increased significantly in the OJ group compared with the sham group. Compared with the OJ group, MDA (P = 0.030) and MPO levels (P = 0.001), and liver injury scores (P = 0.033) were decreased significantly in the OJ + sulfasalazine group. In the OJ + sulfasalazine + LPS and OJ + LPS + sulfasalazine groups, MDA (P = 0.008 and P = 0.023, respectively) and MPO (both, P = 0.001) were significantly decreased; however, liver NF-κB, caspase-3 expression, and liver injury scores were not significantly different compared with the OJ + LPS group. There was no significant difference between the OJ + LPS + sulfasalazine and OJ + sulfasalazine + LPS groups in regard to all end points when comparing the effects of sulfasalazine administered before or after sepsis.

CONCLUSIONS

Sulfasalazine was associated with decreased neutrophil accumulation and lipid peroxidation in these rats with OJ. Administration of sulfasalazine before or after LPS-induced sepsis was associated with a reduction in lipid peroxidation and neutrophil accumulation; however, it did not attenuate histologic liver damage. There was no difference between the findings when sulfasalazine was administered before or after sepsis in OJ.

Bile duct ligation in neonatal rats: is it a valid experimental model for biliary atresia studies?

BA is the most important disease requiring liver transplantation in children. Common BDL in rats is a classic experimental model to study biliary obstruction. The response of the neonatal animal to BDL has yet to be completely understood and few reports have focused on the behavioral differences of the liver between neonatal and adult animals. Ninety newborn Wistar rats aged six days, weighing 8.0-13.9 g, and 90 adult Wistar rats weighing 199.7-357.0 g, were submitted to BDL. After surgery, they were randomly divided and killed on the 3rd, 5th, 7th, 14th, 21st and 28th day post-BDL. Hepatic biopsies were obtained and the following were measured: (i) semiquantification of the bile ductule proliferation and inflammatory infiltrate by HE stain, (ii) quantification of portal and periportal fibrosis with the Sirius-red stain. Although the initial response of ductule proliferation and inflammatory infiltrate were less intense in the newborn animal, the portal and periportal fibrosis were higher when compared with adult animals (p < 0.0491). These findings may contribute to the understanding of the pathophysiology of BA.

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.

Does Pharmaconutrition with L-Arginine and/or α-Tocopherol Improve the Gut Barrier in Bile Duct Ligated Rats?

BACKGROUND/AIM

Nitric oxide supplementation and antioxidant therapy modulate gut barrier function, but the relationships between enhanced nitric oxide production, antioxidant administration, and biliary obstruction remain unclear. We evaluated the role of nitric oxide and alpha-tocopherol supplementation in bile duct ligated rats.

METHODS

Fifty male Wistar albino rats underwent sham operation (group I; control animals) or bile duct ligation (groups II, III, IV, and V). The ligation groups received the following regimens: standard pellet diet (group II), pellet diet plus intramuscularly administered alpha-tocopherol (group III), and L-arginine-enriched pellet diet without (group IV) or with (group V) alpha-tocopherol. Nitric oxide, malondialdehyde, and alpha-tocopherol concentrations were assessed at the end of 3 weeks. Liver and intestinal samples were scored histologically. Mesenteric lymph node and liver cultures were assessed for bacterial translocation.

RESULTS

The liver malondialdehyde concentration was highest in group III. The nitric oxide content in the liver was higher in groups III and V, as were the blood alpha-tocopherol levels. Bacterial translocation was evident following bile duct ligation, but did not differ among the treatment groups. Intestinal histology revealed that group III had the lowest villus height, that group V had the least villus count, and that group II had the highest mucous cell count. The fibrosis scores were higher in groups IV and V.

CONCLUSIONS

An obvious effect of alpha-tocopherol (with or without L-arginine) on the gut barrier could not be demonstrated. Moreover, the L-arginine-enriched diet promoted fibrosis in the liver. Thus, while biliary duct obstruction triggers bacterial translocation, nitric oxide and/or alpha-tocopherol supplementation did not seem to improve the gut barrier in our model.

The effects of antithrombin-III on inducible nitric oxide synthesis in experimental obstructive jaundice. An immunohistochemical study

The absence of bile in the gastrointestinal tract stimulates bacterial overgrowth and bacterial translocation. In the response to endotoxin and LPS-induced endotoxemia which may be prevented by antithrombin-III (AT-III); endothelial cells; and various cells release cytokines, nitric oxide (NO) and other mediators. The purpose of this study was to examine blood NO levels and renal inducible NO synthase (iNOS) expression and determine whether AT-III has an inhibiting effect on renal injury and iNOS expression in obstructive jaundice (OJ). Forty rats were randomized into four groups: group A (Sham), group B (Sham+AT-III, 250 IU kg(-1)), group C (OJ), group D (OJ+AT-III, 250 IU kg(-1)). All animals were sacrificed on the 10th day and blood samples were taken for bilirubin and NO level determination. In addition, iNOS expression of the renal tissues was evaluated immunohistochemically. Blood NO levels were found to be 32.99 micromol l(-1) in group A, 32.26 micromol l(-1) in group B, 46.33 micromol l(-1) in group C, and 34.71 micromol l(-1) in group D. The intensity of iNOS staining in the OJ+AT-III group was less than the intensity of iNOS staining in the OJ group in the renal tissue. This study shows that OJ causes increased production of NO in blood and increased iNOS expression in the kidney. AT-III inhibits iNOS expression and reduces the level of blood NO. Thus, our findings indicate that under conditions of OJ, AT-III limits renal cellular injury by inhibiting LPS-induced iNOS expression.

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

BACKGROUND AND AIMS

The authors have shown previously that sinusoidal endothelial cell injury developed concomitantly with the accumulation of neutrophils in the hepatic sinusoidal space in cholestatic rats after extensive hepatectomy. The aim of the present study was to investigate the role of neutrophils in the development of this kind of endothelial cell injury.

METHODS

Rats underwent 78% partial hepatectomy after 2 weeks of cholestasis, and subsequent external biliary drainage for 5 days. To decrease the number of neutrophils, antirat neutrophil serum was administered intraperitoneally. Some serum parameters and histological specimens were examined 48 h after partial hepatectomy.

RESULTS

Anti-neutrophil serum significantly reduced the number of accumulated neutrophils in the hepatic sinusoids. Although the purine nucleoside phosphorylase: alanine aminotransferase ratio, a marker of non-parenchymal cell injury, was increased in cholestatic-hepatectomized rats, this abnormality was significantly attenuated by the treatment with antineutrophil serum. Electron microscopically, focal detachment of cytoplasms of sinusoidal endothelial cells was observed occasionally in cholestatic-hepatectomized rats, but was not found in the antirat neutrophil serum-treated rats.

CONCLUSION

These results indicate that accumulated neutrophils might be important effector cells in the pathogenesis of sinusoidal endothelial cell injury after extensive hepatectomy in cholestatic rats, even after appropriate external biliary drainage.

Enhanced polymorphonuclear neutrophil-mediated endothelial cell injury and its relation to high surgical mortality rate in cirrhotic patients

OBJECTIVE

A high incidence of complications has been documented in patients with cirrhosis after operations. Recently, polymorphonuclear neutrophils (PMN) have been revealed to have the capacity to injure vascular endothelium and to cause organ damage. Furthermore, the altered function of PMN has been shown in patients with cirrhosis. However, there are few reports investigating the interaction between PMN and endothelial cells and its relation to a high incidence of postoperative complications in cirrhosis. The aim of this study was to evaluate PMN-mediated endothelial cell injury in patients with cirrhosis.

METHODS

Patients were divided into two groups: those who had normal liver with metastatic liver carcinoma and those who had cirrhosis with hepatocellular carcinoma. All patients in both groups underwent hepatic resection. PMN were isolated from patients before operation. Human umbilical vein endothelial cells and PMN were cocultured after addition of phorbol myristate acetate. The release of lactate dehydrogenase (LDH) and thrombomodulin in the cocultured medium and the elastase activity in PMN suspension were measured.

RESULTS

The release of both LDH and thrombomodulin in the group with cirrhosis was significantly higher than in the group with normal liver. The elastase activity was similarly higher in the group with cirrhosis than in the group with normal liver. The surgical morbidity rate was remarkably higher in the group with cirrhosis (50%) than in the group with normal liver (0%).

CONCLUSIONS

This study shows that PMN have an enhanced potential to cause endothelial cell injury in patients with cirrhosis. This PMN "priming" may be responsible for the occurrence of postoperative complications in patients with cirrhosis after hepatectomy.