Endotoxin levels in adult liver donors

Protective Effect of a Novel Technique for Liver Transplantation in the Rat

The rat orthotopic liver transplantation model with extremely short anhepatic phase was established to study its protective effect on the recipients and graft. One hundred fifty adult male Wistar rats were randomly divided into three groups: group A (n = 30), using magnetic rings for the suprahepatic vena cava reconstruction; group B (n = 30), using 7/0 Prolene sutures for suprahepatic vena cava running anastomosis as control; and a sham-operated group (n = 30) as a blank control group. The changes in liver enzyme, serum creatinine, endotoxin, and cytokine levels and histopathology were recorded. The serum creatinine, potassium, alanine transaminase, and alkaline phosphatase levels at different points in time in group A were lower than those in group B (P < .05). The level of portal vein blood endotoxin in group A was significantly lower than that in group B at each point (P < .01). At the same time, all the cytokines in group B were higher than those in group A, and the two groups were higher than those in the sham operation group. The mean levels of tumor necrosis factor-α (TNF-α), interferon-γ, (IFN-γ), and interleukin-1ß (IL-1ß) at 3 hours were higher than at 6 hours in group A. IL-10 and tissue inhibitor of metalloproteinase-1 (TIMP-1) were all higher at 3 hours in groups A and B. Levels of monocyte chemotactic protein-1, L-selectin, and TIMP-1 in group A and IL-10, monocyte chemotactic protein-1, L-selectin, and TIMP-1 in group B were higher in blood than in the liver. Levels of TNF-α, IFN-γ, IL-1, IL-10, and intracellular adhesion molecule-1 in group A and TNF-α, IFN-γ IL-1ß, and intracellular adhesion molecule-1 in group B were higher in the liver than in blood. We conclude that the extremely short anhepatic phase has protective effects on recipients and grafts in rat liver transplantation because it is related to alleviating ischemia-reperfusion injury and reducing the endotoxin release.

The role of macrophages in the development of biliary injury in a lipopolysaccharide-aggravated hepatic ischaemia-reperfusion model

INTRODUCTION

Endotoxins, in the form of lipopolysaccharides (LPS), are potent inducers of biliary injury. However the mechanism by which injury develops remains unclear. We hypothesized that hepatic macrophages are pivotal in the development of endotoxin-induced biliary injury and that no injury would occur in their absence.

MATERIAL AND METHODS

Clodronate liposomes were used to deplete macrophages from the liver. Forty-eight rats were equally divided across six study groups: sham operation (sham), liposome treatment and sham operation (liposomes+sham), 1mg/kg LPS i.p. (LPS), liposome treatment and LPS administration (liposomes+LPS), hepatic ischaemia-reperfusion injury with LPS administration (IRI+LPS) and liposome treatment followed by IRI+LPS (liposomes+IRI+LPS). Following 6h of reperfusion, blood, bile, and liver tissue was collected for further analysis. Small bile duct injury was assessed, serum liver tests were performed and bile composition was evaluated. The permeability of the blood-biliary barrier (BBB) was assessed using intravenously administered horseradish peroxidase (HRP).

RESULTS

The presence of hepatic macrophages was reduced by 90% in LPS and IRI+LPS groups pre-treated with clodronate liposomes (P<0.001). Severe small bile duct injury was not affected by macrophage depletion, and persisted in the liposomes+IRI+LPS group (50% of animals) and liposomes+LPS group (75% of animals). Likewise, BBB impairment persisted following macrophage depletion. LPS-induced elevation of the chemokine Mcp-1 in bile was not affected by macrophage depletion.

CONCLUSIONS

Depletion of hepatic macrophages did not prevent development of biliary injury following LPS or LPS-enhanced IRI. Cholangiocyte activation rather than macrophage activation may underlie this injury. This article is part of a Special Issue entitled: Cholangiocytes in Health and Diseaseedited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen.

Low-Dose Lipopolysaccharide Causes Biliary Injury by Blood Biliary Barrier Impairment in a Rat Hepatic Ischemia/Reperfusion Model

This study explored whether bacterial endotoxins, in the form of lipopolysaccharides (LPS), could have an injurious effect on the biliary tract in conjunction with ischemia. A total of 64 rats were randomly assigned to 4 groups: sham operation (sham group), 1 mg/kg LPS intraperitoneal (LPS group), hepatic ischemia/reperfusion (IR; IR group), and IR combined with LPS (IR+LPS group). Following 1 or 6 hours of reperfusion, serum liver tests, bile duct histology, immunofluorescence microscopy (zonula occludens-1 [ZO-1]), bile composition (bile salts, phospholipids, lactate dehydrogenase), hepatic gene expression (bile salt transporters and inflammatory mediators), as well as serum and biliary cytokine concentrations were quantified and compared between the study groups. In addition, the integrity of the blood biliary barrier (BBB) was assayed in vivo using horseradish peroxidase (HRP). LPS administration induced severe small bile duct injury following 6 hours of reperfusion. Furthermore, total bile salts and bilirubin concentrations in serum were increased in the LPS groups compared with sham controls (LPS, + 3.3-fold and +1.9-fold; IR+LPS, + 3.8-fold and +1.7-fold, respectively). The BBB was impaired in the LPS groups as evidenced by elevated levels of HRP in bile (+4.9-fold), and decreased expression of claudin 1 (-6.7-fold) and claudin 3 (-3.6-fold). LPS was found to be a potent inducer of small bile duct injury following hepatic ischemia and 6 hours of reperfusion. This injury was associated with increased permeability of the BBB and impaired hepatic bile salt clearance. Liver Transplantation 23 194-206 2017 AASLD.

Factors during Donor Care That May Affect Liver Transplantation Outcome

Publications are reviewed that identify factors during donor care and characteristics of the donor liver that may be associated with outcome following liver transplantation. The procurement coordinator has the opportunity to influence cold ischemia time, blood pressure, the serum sodium concentration and, perhaps, liver glycogen reserves. These variables may significantly affect postimplantation graft performance and graft or recipient survival. Summaries of those publications comprising this database are presented, and several limitations in their interpretation are discussed.

The endocannabinoid system and liver diseases

Endogenous cannabinoids (EC) are ubiquitous lipid signalling molecules provided by a number of central and peripheral effects, which are mainly mediated by the specific cannabinoid receptors CB(1) and CB(2). Although the expression of these receptors is very low or even absent in the healthy liver, a considerable series of experimental studies and some clinical observations have recognised the EC system as an important player in the pathophysiology of liver diseases. The EC system is highly up-regulated during chronic liver diseases and, to date, it has been implicated in the pathogenesis of non-alcoholic fatty liver disease, progression of fibrosis to cirrhosis and the development of the cardiovascular abnormalities of cirrhosis, such as the hyperdynamic circulatory syndrome and cirrhotic cardiomiopathy. Furthermore, the EC system influences the mechanisms responsible for cell damage and the inflammatory response during acute liver injury, such as that resulting from ischaemia-reperfusion. Thus, molecules targeting the CB(1) and CB(2) receptors may represent potential therapeutic agents for the treatment of liver diseases. At present, the CB(1) antagonists represent the most attractive pharmaceutical tool to resolve fat accumulation in patients with non-alcoholic fatty liver disease and to treat patients with cirrhosis, as they may slow the progression of fibrosis and attenuate the cardiovascular alterations associated with the advanced stage of the disease.

Factors during donor care that may affect liver transplantation outcome

Publications are reviewed that identify factors during donor care and characteristics of the donor liver that may be associated with outcome following liver transplantation. The procurement coordinator has the opportunity to influence cold ischemia time, blood pressure, the serum sodium concentration and, perhaps, liver glycogen reserves. These variables may significantly affect postimplantation graft performance and graft or recipient survival. Summaries of those publications comprising this database are presented, and several limitations in their interpretation are discussed.

Anti-endotoxin monoclonal antibodies are protective against hepatic ischemia/reperfusion injury in steatotic mice

Steatotic mice are particularly susceptible to hepatic ischemia/reperfusion injury compared with their lean littermates. We have previously demonstrated that livers of mice having a spontaneous mutation in the leptin gene (ob/ob), resulting in global obesity and liver steatosis, are ATP depleted, are endotoxin sensitive, and do not survive (I/R) injury. We hypothesize that administration of an anti-LPS monoclonal antibody (mAb) prior to initiation of I/R would be protective from that insult. Steatotic mice (ob/ob) were subjected to 15 min of ischemia via complete porta-hepatis occlusion and varying lengths of reperfusion with or without pre-treatment with an anti-LPS mAb. There was 14-31% survival of isotype matched control mAb treated ob/ob mice after 15 min of ischemia and 24 h of reperfusion. In contrast, 75-83% of ob/ob mice pre-treated with an anti-LPS mAb prior to initiation of I/R survived both ischemia and 24 h of reperfusion. Furthermore, there was a decrease in ALT and circulating endotoxin levels when treated with an anti-LPS mAb compared with control antibodies. Attenuation of the endotoxin load with anti-LPS mAb, prior to initiation of I/R, was cytoprotective and improved survival. Consequently, these studies might offer a solution to the problems associated with using steatotic livers in clinical transplantation.

Activation of the lipopolysaccharide signaling pathway in hepatic transplantation preservation injury

BACKGROUND

Endotoxin or lipopolysaccharide (LPS) initiates a cascade of complications of septic shock and multiple organ failure seen in Gram-negative bacterial infections. The first step of this pathway, which leads to activated nuclear factor (NF)-kappaB, activating protein (AP)-1, and other transcription factors, is the formation of the LPS receptor complex by LPS, LPS-binding protein (LBP), CD14, and toll-like receptor (TLR) 2 or 4. We examined whether the LPS signaling pathway is activated by hepatic ischemia/reperfusion injury in the transplant setting.

METHODS

Orthotopic syngeneic rat liver transplantation was performed with 0 to 18 hr of cold preservation in University of Wisconsin solution. Animals were killed 1 to 48 hr after reperfusion. Northern blot analysis for CD14, LBP, and TLR2 mRNA, immunohistochemistry for LBP, liver enzyme analysis, and gel shift assay for NF-kappaB and AP-1 were performed.

RESULTS

LPS levels were elevated early after reperfusion. Aspartate aminotransferase and alanine aminotransferase maximally increased 12 hr after transplantation. LBP mRNA and protein and CD14 mRNA were significantly up-regulated peaking at 6 to 12 hr after reperfusion. TLR2 mRNA was also increased. NF-kappaB activity showed a biphasic peak at 1 to 3 hr and 12 hr after reperfusion, whereas AP-1 activity showed a peak at 3 to 6 hr. The induction of CD14 mRNA correlated with the length of cold ischemia time.

CONCLUSIONS

These data indicate that multiple components of the LPS signaling pathway are activated during ischemia/reperfusion injury after liver transplantation.

Endotoxin-induced aggravation of preservation-reperfusion injury of rat liver and its modulation

BACKGROUND/AIMS

In clinical transplantation, exposure of donors to gut-derived endotoxin occurs frequently and may adversely affect liver transplantation therapy. The aim of this study was to investigate: 1) whether brief exposure of rats to endotoxin before liver procurement aggravates the early phase of reperfusion injury of hepatic explants; and if so 2) whether Kupffer cell activation is a contributing factor to liver injury; and 3) whether heparin and pentoxifylline could minimize this effect.

METHODS

Male Wistar rats were injected with 0.2-4.0 mg/kg of Escherichia coli lipopolysaccharide 2 h prior to liver harvest. After preservation in University of Wisconsin cold-storage solution, the livers were reperfused using a blood-free perfusion model. To inactivate Kupffer cells, some rats were pretreated with gadolinium chloride or liposome-encapsulated dichloromethylene-diphosphonate before lipopolysaccharide administration. The other rats received lipopolysaccharide with heparin or pentoxifylline.

RESULTS

In a dose-independent fashion, lipopolysaccharide impaired portal flow during graft reperfusion. In a dose-dependent way, lipopolysaccharide increased lactate dehydrogenase release into the perfusate and decreased bile flow and bromosulfophthalein excretion. Gadolinium chloride, liposomal dichloromethylene-diphosphonate, heparin, and pentoxifylline reduced lactate dehydrogenase release by 34%, 43%, 59%, and 64%, respectively, and improved functional parameters of the liver. A 52-fold increased neutrophil infiltration in the liver sinusoids after lipopolysaccharide exposure was not affected significantly by the drugs studied; however, heparin reduced markedly neutrophil activation.

CONCLUSIONS

The results of this investigation provide direct evidence that aggravation of preservation-reperfusion injury of rat liver by endotoxin is mediated by Kupffer cell-dependent mechanism(s) and it can be minimized by heparin and pentoxifylline.

Protection of sinusoidal endothelial cells against storage/reperfusion injury by prostaglandin E2 derived from Kupffer cells

BACKGROUND

In clinical liver transplants, grafts are frequently exposed to endotoxin (lipopolysaccharide, LPS) before harvest and may be predisposed to dysfunction. Because graft failure is linked to sinusoidal endothelial cell injury after storage/reperfusion, we investigated the effect of donor exposure to LPS on graft survival in relation to sinusoidal endothelial cell injury after storage/reperfusion in rats.

METHODS

Rats were injected with 0.5 mg/kg LPS. In some rats, 20 mg/kg GdCl3 or 5 mg/kg indomethacin was injected before LPS to ablate Kupffer cells and inhibit prostaglandin (PG) synthesis, respectively. Other rats were injected with 100 microg/kg dimethyl PGE2, a stable PGE2 analog. Rat livers were harvested, stored in cold UW solution and transplanted to non-treated rats for determination of survival and liver injury in recipients. Otherwise, after cold storage, the livers were reperfused briefly with physiological buffer containing trypan blue for determination of sinusoidal endothelial cell injury by counting trypan blue-positive nuclei in histological sections.

RESULTS

Donor treatment with LPS increased hepatic PGE2 production before storage and decreased recipient survival, but paradoxically decreased killing of sinusoidal endothelial cells after storage and reperfusion. Pretreatment of donors with GdCl3 or indomethacin prevented the protective preconditioning of sinusoidal endothelial cells by LPS, whereas pretreatment with dimethyl PGE2 protected sinusoidal endothelial cells to the same extent as LPS. Unlike LPS, however, PGE2 attenuated graft injury after liver transplants.

CONCLUSION

PGE2 derived from LPS-stimulated Kupffer cells protects sinusoidal endothelial cells against storage/reperfusion injury. Unlike LPS, PGE2 improves graft function after liver transplants. Thus, donor preconditioning with PGE2 may be beneficial in liver transplants.

Endotoxin levels in donors and recipients during orthotopic liver transplantation

BACKGROUND

The hypothesis being tested in this paper is that endotoxin levels in donors and in recipients during liver transplantation influences postoperative outcome.

METHODS

Endotoxin levels in systemic venous and portal venous blood were measured using in 46 adult donors and 44 adult recipients (47 liver transplants) during the period 1992-95. Endotoxin was measured using a modification of the Limulus amoebocyte lysate (LAL) assay.

RESULTS

In the donor, systemic endotoxin levels were above normal levels at 10.0 +/- 1.3 pg/mL from the start and rose to 15.8 +/- 2.9 pg/mL after dissection of the hilar structures, but fell to 10.6 +/- 0.8 pg/mL just prior to the removal of the liver (control = 7.8 pg/mL). The mean portal venous endotoxin levels were 18.2 +/- 3.4 pg/mL after dissection of the hilar structures and 12.6 +/- 0.9 pg/mL after cannulation of the portal vein. In the recipients, the highest level in the portal venous blood occurred at the end of the anhepatic phase (46.5 +/- 6.7 pg/mL). The systemic venous samples in the recipients were elevated to start with, but fell rapidly to 19.3 +/- 1.5 pg/mL 24 h postoperatively, and to 13.2 +/- 1.0 pg/mL by day 7. The endotoxin concentrations were higher in recipients who developed complications.

CONCLUSIONS

Endotoxin is elevated throughout the recipient transplantation procedure and up to 7 days postoperatively. High levels of endotoxin at induction, the anhepatic phase and at certain time points correlated with patients who developed postoperative complications.

Endotoxemia: methods of detection and clinical correlates

As an assay for endotoxin, the Limulus amebocyte lysate assay has several desirable properties: sensitivity, specificity, and potential for adaptation to a quantitative format. Several modifications have been developed to enhance its potential for clinical application. The modifications that allow quantitative measurement of endotoxin and also improve its application to blood samples are described in this review. In fluids other than blood, the detection of endotoxin with the Limulus amebocyte lysate assay can be used as an aid to identify the presence of gram-negative bacteria, and the assay has established utility. With blood, however, there are a range of factors that interfere with the detection of endotoxemia and there are disparate views with respect to the diagnostic and prognostic significance of the test results. In general, the clinical significance of the finding of endotoxemia broadly parallels the frequency and importance of gram-negative sepsis in the patient groups studied and a decline in endotoxin levels accompanies clinical improvement. However, with therapies designed to reduce levels of endotoxin, or to antagonize its effects, it is unclear whether clinical improvement occurs as a consequence of changes in the levels of endotoxemia.