Potential effect of recombinant thrombomodulin on ischemia-reperfusion liver injury in rats

Thrombomodulin-mediated Inhibition of Neutrophil Extracellular Trap Formation Alleviates Hepatic Ischemia/Reperfusion Injury by Blocking TLR4 in Rats Subjected to Liver Transplantation

BACKGROUND

Hepatic ischemia/reperfusion injury (IRI) is an unavoidable outcome of liver transplantation, during which neutrophil extracellular traps (NETs) may play a critical role in the IRI-induced immune response to inflammation. The purpose of this study was to identify the function of recombinant human thrombomodulin (rTM) in the remission of hepatic IRI after liver transplantation and elucidate the specific mechanism.

METHODS

NET formation was detected in the serum of liver transplantation patients and rats following liver transplantation. Hematoxylin-eosin (HE) staining, terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) staining, immunohistochemistry and immunofluorescence were used to assess the effect of rTM on NET formation in vitro and in vivo.

RESULTS

We found that rTM markedly inhibited neutrophil formation in NETs, reduced apoptosis in hepatocytes, alleviated rat hepatic IRI and improved liver function. In vitro, rTM inhibited neutrophil formation in NETs, and lipopolysaccharide (LPS) (a Toll-like receptor (TLR)-4 agonist) reversed the inhibitory effect of rTM on NET formation. rTM blocked TLR-4 and the downstream extracellular signal-regulated kinase (ERK)/c-Jun NH2 terminal kinase (JNK) and nicotinamide adenine dinucleotide phosphate (NADPH)/ROS/peptidylarginine deiminase 4 (PAD4) signaling pathways to protect against hepatic IRI and inhibit NET formation. In addition, we demonstrated that combined treatment with rTM and an NADPH oxidative inhibitor had a better effect than either treatment alone.

CONCLUSIONS

NETs are a potential therapeutic target in hepatic IRI, and rTM could be used to prevent IR-induced hepatic injury. In addition, cotargeting NETosis-related signaling pathways might be a novel therapeutic strategy for hepatic IRI treatment.

The Impact of Dabigatran Treatment on Sinusoidal Protection Against Hepatic Ischemia/Reperfusion Injury in Mice

Thrombin is a key player in the coagulation cascade, and it is attracting much attention as a promotor of cellular injured signaling. In ischemia/reperfusion injury (IRI), which is a severe complication of liver transplantation, thrombin may also promote tissue damage. The aim of this study is to reveal whether dabigatran, a direct thrombin inhibitor, can attenuate hepatic IRI with focusing on a protection of sinusoidal endothelial cells (SECs). Both clinical patients who underwent hepatectomy and in vivo mice model of 60-minute hepatic partial-warm IRII, thrombin generation was evaluated before and after IRI. In next study, IRI mice were treated with or without dabigatran. In addition, hepatic SECs and hepatocytes pretreated with or without dabigatran were incubated in hypoxia/reoxygenation (H-R) environment in vitro. Thrombin generation evaluated by thrombin-antithrombin complex (TAT) was significantly enhanced after IRI in the clinical study and in vivo study. Thrombin exacerbated lactate dehydrogenase cytotoxicity levels in a dose-dependent manner in vitro. In an IRI model of mice, dabigatran treatment significantly improved liver histological damage, induced sinusoidal protection, and provided both antiapoptotic and anti-inflammatory effects. Furthermore, dabigatran not only enhanced endogenous thrombomodulin (TM) but also reduced excessive serum high-mobility group box-1 (HMGB-1). In H-R models of SECs, not hepatocytes, pretreatment with dabigatran markedly attenuated H-R damage, enhanced TM expression in cell lysate, and decreased extracellular HMGB-1. The supernatant of SECs pretreated with dabigatran protected hepatocytes from H-R damage and cellular death. Thrombin exacerbated hepatic IRI, and excessive extracellular HMGB-1 caused severe inflammation-induced and apoptosis-induced liver damage. In this situation, dabigatran treatment improved vascular integrity via sinusoidal protection and degraded HMGB-1 by endogenous TM enhancement on SECs, greatly ameliorating hepatic IRI.

The lectin-like domain of thrombomodulin is a drug candidate for both prophylaxis and treatment of liver ischemia and reperfusion injury in mice

Ischemia and reperfusion injury (IRI) can occur in any tissue or organ. With respect to liver transplantation, the liver grafts from donors by definition experience transient ischemia and subsequent blood reflow. IRI is a problem not only in organ transplantation but also in cases of thrombosis or circulatory disorders such as mesenteric ischemia, myocardial, or cerebral infarction. We have reported that recombinant human soluble thrombomodulin (rTM), which is currently used in Japan to treat disseminated intravascular coagulation (DIC), has a protective effect and suppresses liver IRI in mice. However, rTM may not be fully safe to use in humans because of its inherent anticoagulant activity. In the present study, we used a mouse liver IRI model to explore the possibility that the isolated lectin-like domain of rTM (rTMD1), which has no anticoagulant activity, could be effective as a therapeutic modality for IRI. Our results indicated that rTMD1 could suppress ischemia and reperfusion-induced liver damage in a dose-dependent manner without concern of associated hemorrhage. Surprisingly, rTMD1 suppressed the liver damage even after IR insult had occurred. Taken together, we conclude that rTMD1 may be a candidate drug for prevention of and therapy for human liver IRI without the possible risk of hemorrhage.

Recombinant thrombomodulin prevented hepatic ischemia-reperfusion injury by inhibiting high-mobility group box 1 in rats

Recombinant thrombomodulin (rTM) is a novel anticoagulant and anti-inflammatory agent that inhibits secretion of high-mobility group box 1 (HMGB1) from liver. We evaluated the protective effects of rTM on hepatic ischemia-reperfusion injury in rats. Ischemia was induced by clamping the portal vein and hepatic artery of left lateral and median lobes of the liver. At 30 min before ischemia and at 6 h after reperfusion, 0.3 ml of saline (IR group) or 0.3 ml of saline containing 6 mg/kg body weight of rTM (IR-rTM group) was injected into the liver through inferior vena cava or caudate vein. Blood flow was restored at 60 min of ischemia. Blood was collected 30 min prior to induction of ischemia and before restoration of blood flow, and at 6, 12, and 24 h after reperfusion. All the animals were euthanized at 24 h after reperfusion and the livers were harvested and subjected to biochemical and pathological evaluations. Serum levels of ALT, AST, and HMGB1 were significantly lower after reperfusion in the IR-rTM group compared to IR group. Marked hepatic necrosis was present in the IR group, while necrosis was almost absent in IR-rTM group. Treatment with rTM significantly reduced the expression of TNF-α and formation of 4-hydroxynonenal in the IR-rTM group compared to IR group. The results of the present study indicate that rTM could be used as a potent therapeutic agent to prevent IR-induced hepatic injury and the related adverse events.

Inhibition of glycogen synthase kinase 3β protects liver against ischemia/reperfusion injury by activating 5' adenosine monophosphate-activated protein kinase-mediated autophagy

AIM

Autophagy has been found to play an important role in hepatic ischemia/reperfusion (I/R) injury. Our previous study has also clarified that rictor deficiency aggravated hepatic I/R injury by suppressing autophagy. Here, we explore whether autophagy participates in glycogen synthase kinase 3β (GSK3β)-mediated cytoprotection in liver I/R.

METHODS

Mice were treated with SB216763 to inhibit GSK3β before being subjected to hepatic I/R. Liver injury was evaluated by liver and blood samples. Autophagy was measured by detecting expression of microtubule-associated protein 1 light chain-3B (LC3B) II and autophagy protein 5 (ATG-5), as well as the number of autophagosomes by transmission electron microscope. Primary hepatocytes pretreated with SB216763 for 2 h were subjected to hypoxia/reoxygenation to induce autophagy. The lactate dehydrogenase level was used to evaluate cell death and survival. Autophagy inhibitors and 5' adenosine monophosphate-activated protein kinase (AMPK) inhibitor were given in vivo or in vitro.

RESULTS

SB216763 significantly increased the number of autophagosomes and the protein levels of LC3B II and ATG-5 in liver I/R models, which was accompanied by a decline of hepatic necrosis and apoptosis. Consistent with the in vivo study, autophagy and cytoprotection were induced by the inhibition of GSK3β in the in vitro study. Moreover, pretreatment with autophagy inhibitors attenuated the cytoprotective role of autophagy in the GSK3β-treated liver I/R models. Further analysis showed that pretreatment with an AMPK inhibitor increased mammalian target of rapamycin (mTOR) activity, decreased autophagy, and abrogated GSK3β- mediated liver protection.

CONCLUSION

Autophagy was induced by GSK3β inhibition through the AMPK/mTOR pathway and could substantially ameliorate liver I/R injury. Therefore, our findings strongly renew the therapeutic value of the GSK3β/autophagy axis in hepatic I/R injury.

Plasma From Patients Undergoing Liver Transplantation Is Resistant to Anticoagulant Activity of Soluble Thrombomodulin

Recombinant human soluble thrombomodulin (ART-123) is an anticoagulant and anti-inflammatory agent clinically used for treatment of disseminated intravascular coagulation. Preclinical studies have shown that ART-123 reduces hepatic ischemia/reperfusion. Although ART-123 may therefore have clinical benefit in orthotopic liver transplantation, the substantial alterations in the hemostatic system may complicate its use in this setting. Here, we studied the in vitro effect of ART-123 on coagulation of patients with end-stage liver disease undergoing liver transplantation. Ten patients with end-stage liver disease undergoing liver transplantation were included in this study. Plasma samples of 10 healthy individuals were included to establish reference values. Different concentrations of ART-123 were added to plasma samples, and peak thrombin generation and clot lysis times (CLTs) were determined. In patient samples, plasma was profoundly resistant to the anticoagulant action of ART-123, as reflected by significantly higher median inhibitory concentration (IC₅₀ ) values of peak thrombin generation compared with controls. This might be partially explained by low levels of protein C, protein S, and elevated levels of factor VIII during transplantation. Intraoperative levels of thrombin activatable fibrinolysis inhibitor were significantly lower when compared with controls. However, ART-123-dependent prolongation of CLTs was not significantly different from healthy controls. In conclusion, this study suggests that ART-123 is unlikely to provoke bleeding in patients undergoing liver transplantation because proposed clinical dosages have a virtually absent anticoagulant effect in these patients. Clinical studies are required to confirm the safety of ART-123 and efficacy on alleviating ischemia/reperfusion injury during liver transplantation.

Damage-associated molecular patterns in intensive care unit patients with acute liver injuries: A prospective cohort study

Acute liver injury (ALI) is frequently detected in an intensive care unit (ICU) and reportedly affects prognosis. Experimental animal studies suggested that increased extracellular histone and high morbidity group box-1 (HMGB1) levels might contribute to ALI development. Whether these damage-associated molecular patterns (DAMPs) play a crucial role in ALI remains unclear in the human clinical setting.We consecutively enrolled the patients admitted to our ICU. The patients with ALI were included in the analysis together with those without ALI by using frequency matching. Extracellular histone, HMGB1, soluble thrombomodulin (sTM), and interleukin-6 (IL-6) levels were measured in plasma collected at ICU admission. ALI was defined as an acute elevation in serum aminotransferase levels to >200 IU/L.A total of 805 patients were enrolled. Twenty ALI and forty non-ALI patients were analyzed. Plasma histone levels were significantly higher in the ALI group than in the non-ALI group, whereas HMGB1 levels were significantly lower in the ALI group. Furthermore, sTM was significantly increased in the ALI patients, whereas IL-6 levels were comparable between the groups. Multivariate logistic regression analysis demonstrated that histones were independently associated with ALI. There was no significant impact of ALI on in-hospital mortality.Extracellular histones showed an independent association with ALI. Histone elevation might be one of the possible pathogenic mechanisms in the development of ALI of ICU patients.