Synergism between platelets and leukocytes in inducing endothelial cell apoptosis in the cold ischemic rat liver: a Kupffer cell-mediated injury

Transplantation of a human liver following 3 days of ex situ normothermic preservation

Current organ preservation methods provide a narrow window (usually <12 hours) to assess, transport and implant donor grafts for human transplantation. Here we report the transplantation of a human liver discarded by all centers, which could be preserved for several days using ex situ normothermic machine perfusion. The transplanted liver exhibited normal function, with minimal reperfusion injury and the need for only a minimal immunosuppressive regimen. The patient rapidly recovered a normal quality of life without any signs of liver damage, such as rejection or injury to the bile ducts, according to a 1-year follow up. This inaugural clinical success opens new horizons in clinical research and promises an extended time window of up to 10 days for assessment of viability of donor organs as well as converting an urgent and highly demanding surgery into an elective procedure.

microRNA-9-5p protects liver sinusoidal endothelial cell against oxygen glucose deprivation/reperfusion injury

Background

Maintenance of the function and survival of liver sinusoidal endothelial cells (LSECs) play a crucial role in hepatic ischemia/reperfusion (I/R) injury, a major cause of liver impairment during the surgical treatment. Emerging evidence indicates a critical role of microRNAs in I/R injury. This study aims to investigate whether miR-9-5p exerts a protective effect on LSECs.

Methods

We transfected LSECs with miR-9-5p mimic or mimic NC. LSECs were treated with oxygen and glucose deprivation (OGD, 5% CO₂, and 95% N₂), followed by glucose-free Dulbecco’s modified Eagle’s medium (DMEM) medium for 6 h and high glucose (HG, 30 mmol/L glucose) DMEM medium for 12 h. The biological role of miR-9-5p in I/R-induced LSEC injury was determined.

Results

In the in vitro model of OGD/HG injury in LSECs, the expression levels of miR-9-5p were significantly downregulated, and those of CXC chemokine receptor-4 (CXCR4) upregulated. LSEC I/R injury led to deteriorated cell death, enhanced oxidative stress, and excessive inflammatory response. Mechanistically, we showed that miR-9-5p overexpression significantly downregulated both mRNA and protein levels of CXCR4, followed by the rescue of LSECs, ameliorated inflammatory response, and deactivation of pro-apoptotic signaling pathways.

Conclusions

miR-9-5p promotes LSEC survival and inhibits apoptosis and inflammatory response in LSECs following OGD/HG injury via downregulation of CXCR4.

Gadolinium Chloride Inhibits the Production of Liver Interleukin-27 and Mitigates Liver Injury in the CLP Mouse Model

BACKGROUND

Liver macrophages play an important regulatory role in the inflammatory response of liver injury after severe infection. Interleukin- (IL-) 27 is an inflammatory cytokine that plays an important role in diseases caused by bacterial infection. However, the relationship between IL-27 and liver macrophages in liver injury after severe infection is not yet clear.

METHODS

A cecal ligation puncture (CLP) model was established in wild-type (WT) and IL-27 receptor- (WSX-1-) deficient (IL-27r-/-) mice, and recombinant IL-27 and gadolinium chloride (GdCl3) were injected into WT mice in the designated groups. The serum and liver IL-27, IL-6, tumor necrosis factor alpha (TNF-α), and IL-1β expression levels were evaluated by ELISA, quantitative PCR, or Western blotting; serum ALT and AST were detected by detection kits; and the severity of liver damage was evaluated by hematoxylin and eosin staining and the TUNEL assay of the liver tissue from the different groups. Liver macrophage polarization was evaluated by immunofluorescence. In addition, the polarization of peritoneal macrophage was evaluated by flow cytometry.

RESULTS

The serum and liver IL-27 expression levels were elevated in WT mice after CLP-induced severe infection, which were consistent with the changes in HE scores in the liver tissue. The levels of serum ALT, AST, liver IL-6, TNF-α, and IL-1β mRNA and liver pathological injury scores were further increased when pretreated with recombinant IL-27 in WT mice, but these levels were decreased in IL-27r-/- mice after CLP-induced severe infection compared to WT mice. In WT mice pretreated with GdCl3, liver pathological scores, serum ALT and AST, TUNEL-positive cell proportion from liver tissues, liver IL-27 expression, and the liver macrophages M1 polarization proportion decreased after CLP; however, the serum IL-27, IL-6, TNF-α, and IL-1β levels and the pathological lung and kidney scores were not significantly changed. When supplemented with exogenous IL-27, the liver pathological scores, serum ALT, AST, TUNEL-positive cell proportion of liver tissues, liver IL-27 expression, and the liver macrophage M1 polarization proportion increased. The in vitro, IL-27 expression increased in peritoneal macrophages when stimulated with LPS. Recombinant IL-27 together with LPS promoted the elevations in IL-6, TNF-α, and IL-1β levels in supernatant and the M1 polarization of peritoneal macrophages.

CONCLUSION

IL-27 is an important cytokine in the inflammatory response to liver injury after severe infection. The reduction of liver injury by gadolinium chloride in severe infection mice models may relate to the inhibition of liver IL-27 production. These changes may be mainly related to the decrease of liver macrophages M1 polarization. IL-27 may have a positive feedback on these macrophages.

Normothermic Ex Vivo Liver Perfusion Prevents Intrahepatic Platelet Sequestration After Liver Transplantation

BACKGROUND

The detrimental role of platelets in sinusoidal endothelial cell (SEC) injury during liver transplantation (LT) has been previously addressed after static cold storage (SCS), however, it is currently unknown after normothermic ex vivo liver perfusion (NEVLP).

METHODS

Pig LT was performed with livers from heart-beating donors or donation after circulatory death (DCD) donors subjected to SCS or NEVLP (n = 5/group).

RESULTS

All pigs except for 1 (DCD-SCS-group) survived 4 days. The heart-beating donor- and DCD-NEVLP-groups showed significantly lower aspartate transaminase-levels compared with the SCS-groups 3 hours post-LT (P = 0.006), on postoperative day (POD) 2 (P = 0.005), POD3 (P = 0.007), and on POD4 (P = 0.012). Post-LT total platelet count recovered faster in the NEVLP than in the SCS-groups at 12 hours (P = 0.023) and 24 hours (P = 0.0038). Intrahepatic sequestration of platelets was significantly higher in the SCS-groups 3 hours postreperfusion and correlated with severity of SEC injury. In both SCS-groups, levels of tumor growth factor-β were higher 3 hours post-LT, on POD1 and on POD3. Moreover, platelet factor 4 levels and platelet-derived extracellular vesicles were increased in the SCS-groups. Hyaluronic acid levels were significantly higher in the SCS-groups, indicating a higher grade of endothelial cell dysfunction. Platelet inhibition achieved by pretreatment with clopidogrel (n = 3) partly reversed the detrimental effects on SEC injury and therefore provided further evidence of the important role of platelets in ischemia/reperfusion injury and SEC injury.

CONCLUSIONS

Normothermic perfusion of liver grafts before transplantation effectively reduced platelet aggregation and SEC injury, which translated into an improved posttransplant organ function.

Amygdalin reduces lipopolysaccharide-induced chronic liver injury in rats by down-regulating PI3K/AKT, JAK2/STAT3 and NF-κB signalling pathways

This study was aimed to evaluate the anti-inflammatory potential of AG on lipopolysaccharide (LPS) -induced liver injury and investigate the underlying mechanism. Administration of LPSs in the rat produced rat liver injury model which was ascertained at histological and molecular levels. Those models were treated with a range of doses of LPSs (0.5, 1.0 and 1.5 mg/kg body weight), followed by measurement physical parameter and function of the liver. Within the max treatment doses, no toxicity was shown but protective effects of AG were evidenced by regulation of physical parameters and functions of the liver. Interestingly, nuclear factor kappa B (NF-κB) levels and inflammatory factors were down-regulated by AG. Furthermore, the histopathological analysis demonstrated that AG promoted recovery from dysfunction of liver tissue in the rats, which was further confirmed by observing expression changes of inflammation-associated proteins. Particularly, alteration in the PI3K/AKT and JAK2/STAT3 signalling pathway protein expression were regulated by AG in a dose-dependent manner, indicating the mechanism underlying the relief effect of AG in liver injury. Our study demonstrated the potential of AG in the management of complications related to liver injury.

Platelet and liver regeneration after liver surgery

The success of liver surgery, including resection and transplantation, is largely dependent on the ability of the liver to regenerate. Despite substantial improvement in surgical techniques and perioperative care, one of the main concerns is post-hepatectomy liver failure and early allograft dysfunction, both of which are associated with impaired liver regeneration. Recent studies have demonstrated the positive role of platelets in promoting liver regeneration and protecting hepatocytes; however, the underlying mechanisms responsible for these effects are not fully understood. In this review, we updated the accumulated evidence of the role of platelets in promoting liver regeneration, with a focus on liver resection and liver transplantation. The goal of these studies was to support the clinical implementation of platelet agents, such as thrombopoietin receptor agonists, to augment liver regeneration after liver surgery. This "platelet therapy" may become a treatment choice for post-hepatectomy liver failure and early allograft dysfunction.

Platelets and Platelet-Derived Extracellular Vesicles in Liver Physiology and Disease

Beyond their role in hemostasis, platelets are proposed as key mediators of several physiological and pathophysiological processes of the liver, such as liver regeneration, toxic or viral acute liver injury, liver fibrosis, and carcinogenesis. The effects of platelets on the liver involve interactions with sinusoidal endothelial cells and the release of platelet‐contained molecules following platelet activation. Platelets are the major source of circulating extracellular vesicles, which are suggested to play key roles in platelet interactions with endothelial cells in several clinical disorders. In the present review, we discuss the implications of platelet‐derived extracellular vesicles in physiological and pathophysiological processes of the liver.

Gadolinium chloride attenuates acetic acid-evoked colitis in mice by reducing neutrophil infiltration and pro-oxidative enzyme activity

This study investigated the potential of gadolinium chloride (GdCl₃), an inhibitor of kupffer cells on the myeloperoxidase (MPO) function, both in vivo on colon inflammation model and in vitro on thioglycollate-elicited peritoneal neutrophils. Colon inflammation was induced in mice (n = 7) by 4% acetic acid (AA) enema. GdCl₃ (10 mg/kg) treatment was given 24 h before AA challenge. Clinical changes during the protocol were scored. Colons were segmented into distal and proximal parts for histological and biochemical assessment. Furthermore, myeloperoxidase (MPO) enzymes were extracted and analyzed by western blot. Short-term GdCl₃ treatment inhibited dose-dependently superoxide anion (O₂^·-), alkaline phosphatase (ALP), and MPO release and promoted neutrophil apoptosis. In vivo, low-dose GdCl₃ improved colitis scores and inhibited acute phagocyte recruitment and colon damage within the mucosa as revealed by the decrease in MPO, nitric oxide (NO), and malondialdehyde (MDA) levels. At the same time, GdCl₃ restored catalase (CAT), superoxide dismutase (SOD) activities, and reduced glutathione (GSH) levels, thus reversing the MDA/GSH ratio in both distal and proximal colons. Compared to proximal, distal colon was more altered and displayed higher pathological manifestations. Lastly, the induction of apoptosis and regulation of the major nitrosative and oxidative functions of neutrophils by GdCl₃ suggests its consideration as a beneficial tool in attenuating colon inflammation.

Platelets as Modulators of Liver Diseases

Platelets are key players in thrombosis and hemostasis. Alterations in platelet count and function are common in liver disease, and may contribute to bleeding or thrombotic complications in liver diseases and during liver surgery. In addition to their hemostatic function, platelets may modulate liver diseases by mechanisms that are incompletely understood. Here, we present clinical evidence for a role of platelets in the progression of chronic and acute liver diseases, including cirrhosis, acute liver failure, and hepatocellular carcinoma. We also present clinical evidence that platelets promote liver regeneration following partial liver resection. Subsequently, we summarize studies in experimental animal models that support these clinical observations, and also highlight studies that are in contrast with clinical observations. The combined results of clinical and experimental studies suggest that platelets may be a therapeutic target in the treatment of liver injury and repair, but the gaps in our understanding of mechanisms involved in platelet-mediated modulation of liver diseases call for caution in clinical application of these findings.

Expression of tubulin folding cofactor B in mouse hepatic ischemia-reperfusion injury

The aim of the present study was to investigate the association between tubulin folding cofactor B (TBCB) expression and ischemia-reperfusion injury (IRI) in mice. A total of 48 C57BL/6 mice were randomly divided into a control group (Sham, n=6) and an ischemia-reperfusion group (n=42). The ischemia-reperfusion group was further divided into 6 subgroups as per different times after reperfusion (2, 4, 6, 8, 12 and 24 h), with 7 mice per subgroup. A hepatic IRI model was established in mice by clamping the hepatic hilum. Morphology, serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), interleukin 6 (IL-6) and tumor necrosis factor-α (TNF-α), and the expression level of TBCB were detected. Compared with the control group, the livers from the ischemia-reperfusion group were significantly changed, particularly at 12 h following ischemia-reperfusion, with obvious hepatic cell degeneration and necrosis. The ALT, AST, IL-6 and TNF-α levels in the sera of the mice in the hepatic ischemia-reperfusion group were increased at all time points following ischemia-reperfusion, and were the highest at 12 h, demonstrating statistically significant differences when compared with the control group (P<0.05). Furthermore, the expression levels of TBCB, TNF-α and IL-6 were significantly increased at all time-points following ischemia-reperfusion, and were the most significant at 12 h. At 24 h following ischemia-reperfusion, the expression levels had decreased. The present study indicated that TBCB expression is associated with TNF-α and IL-6 expression levels in mice with hepatic ischemia-reperfusion, and may be key in the development of liver injury during ischemia-reperfusion in mice.

Platelets in liver disease, cancer and regeneration

Although viral hepatitis treatments have evolved over the years, the resultant liver cirrhosis still does not completely heal. Platelets contain proteins required for hemostasis, as well as many growth factors required for organ development, tissue regeneration and repair. Thrombocytopenia, which is frequently observed in patients with chronic liver disease (CLD) and cirrhosis, can manifest from decreased thrombopoietin production and accelerated platelet destruction caused by hypersplenism; however, the relationship between thrombocytopenia and hepatic pathogenesis, as well as the role of platelets in CLD, is poorly understood. In this paper, experimental evidence of platelets improving liver fibrosis and accelerating liver regeneration is summarized and addressed based on studies conducted in our laboratory and current progress reports from other investigators. In addition, we describe our current perspective based on the results of these studies. Platelets improve liver fibrosis by inactivating hepatic stellate cells, which decreases collagen production. The regenerative effect of platelets in the liver involves a direct effect on hepatocytes, a cooperative effect with liver sinusoidal endothelial cells, and a collaborative effect with Kupffer cells. Based on these observations, we ascertained the direct effect of platelet transfusion on improving several indicators of liver function in patients with CLD and liver cirrhosis. However, unlike the results of our previous clinical study, the smaller incremental changes in liver function in patients with CLD who received eltrombopag for 6 mo were due to patient selection from a heterogeneous population. We highlight the current knowledge concerning the role of platelets in CLD and cancer and anticipate a novel application of platelet-based clinical therapies to treat liver disease.

Novel functions of platelets in the liver

Platelets contain not only proteins needed for hemostasis but also many growth factors that are required for organ development, tissue regeneration, and repair. Thrombocytopenia, which is frequently observed in patients with chronic liver disease (CLD) and cirrhosis, is due to various causes, such as decreased thrombopoietin production and accelerated platelet destruction caused by hypersplenism; however, the relationship between thrombocytopenia and hepatic pathogenesis and the role of platelets in CLD are poorly understood. Thus, in this paper, the experimental evidence for platelets improving liver fibrosis and accelerating liver regeneration is summarized and addressed based on studies conducted in our laboratory and current progress reports from other investigators. Platelets improve liver fibrosis by inactivating hepatic stellate cells to decrease collagen production. The level of intracellular cAMP is increased by adenosine through its receptors on hepatic stellate cells, thereby resulting in inactivation of these cells. Adenosine is produced by degradation of adenine nucleotides, which are stored in abundance within the dense granules of platelets. The regenerative effect of platelets in the liver consists of three mechanisms: a direct effect on hepatocytes, a cooperative effect with liver sinusoidal endothelial cells, and a collaborative effect with Kupffer cells. Based on these experiments, a clinical trial suggested that the increase in platelets induced by platelet transfusion improved liver function in patients with CLD in a clinical setting.We highlight the current knowledge concerning the role of platelets in CLD and expect to open a novel avenue for application of these clinical therapies to treat liver disease.

The Impact of Ischemia/Reperfusion Injury on Liver Allografts from Deceased after Cardiac Death versus Deceased after Brain Death Donors

BACKGROUND AND AIMS

The shortage of organs for transplantation has led to increased use of organs procured from donors after cardiac death (DCD). The effects of cardiac death on the liver remain poorly understood, however. Using livers obtained from DCD versus donors after brain death (DBD), we aimed to understand how ischemia/reperfusion (I/R) injury alters expression of pro-inflammatory markers ceramides and influences graft leukocyte infiltration.

METHODS

Hepatocyte inflammation, as assessed by ceramide expression, was evaluated in DCD (n = 13) and DBD (n = 10) livers. Allograft expression of inflammatory and cell death markers, and allograft leukocyte infiltration were evaluated from a contemporaneous independent cohort of DCD (n = 22) and DBD (n = 13) livers.

RESULTS

When examining the differences between transplant stages in each group, C18, C20, C24 ceramides showed significant difference in DBD (p<0.05) and C22 ceramide (p<0.05) were more pronounced for DCD. C18 ceramide is correlated to bilirubin, INR, and creatinine after transplant in DCD. Prior to transplantation, DCD livers have reduced leukocyte infiltration compared to DBD allografts. Following reperfusion, the neutrophil infiltration and platelet deposition was less prevalent in DCD grafts while cell death and recipients levels of serum aspartate aminotransferase (AST) of DCD allografts had significantly increased.

CONCLUSION

These data suggest that I/R injury generate necrosis in the absence of a strong inflammatory response in DCD livers with an appreciable effect on early graft function. The long-term consequences of increased inflammation in DBD and increased cell death in DCD allografts are unknown and warrant further investigation.

Hydrogen peroxide-activatable antioxidant prodrug as a targeted therapeutic agent for ischemia-reperfusion injury

Overproduction of hydrogen peroxide (H₂O₂) causes oxidative stress and is the main culprit in the pathogenesis of ischemia/reperfusion (I/R) injury. Suppression of oxidative stress is therefore critical in the treatment of I/R injury. Here, we report H₂O₂-activatable antioxidant prodrug (BRAP) that is capable of specifically targeting the site of oxidative stress and exerting anti-inflammatory and anti-apoptotic activities. BRAP with a self-immolative boronic ester protecting group was designed to scavenge H₂O₂ and release HBA (p-hydroxybenzyl alcohol) with antioxidant and anti-inflammatory activities. BRAP exerted potent antioxidant and anti-inflammatory activity in lipopolysaccharide (LPS)- and H₂O₂-stimulated cells by suppressing the generation of ROS and pro-inflammatory cytokines. In mouse models of hepatic I/R and cardiac I/R, BRAP exerted potent antioxidant, anti-inflammatory and anti-apoptotic activities due to the synergistic effects of H₂O₂-scavenging boronic esters and therapeutic HBA. In addition, administration of high doses of BRAP daily for 7 days showed no renal or hepatic function abnormalities. Therefore BRAP has tremendous therapeutic potential as H₂O₂-activatable antioxidant prodrug for the treatment of I/R injuries.

Tobacco and e-cigarette products initiate Kupffer cell inflammatory responses

Kupffer cells are liver resident macrophages that are responsible for screening and clearing blood of pathogens and foreign particles. It has recently been shown that Kupffer cells interact with platelets, through an adhesion based mechanism, to aid in pathogen clearance and then these platelets re-enter the general systemic circulation. Thus, a mechanism has been identified that relates liver inflammation to possible changes in the systemic circulation. However, the role that Kupffer cells play in cardiovascular disease initiation/progression has not been elucidated. Thus, our objective was to determine whether or not Kupffer cells are responsive to a classical cardiovascular risk factor and if these changes can be transmitted into the general systemic circulation. If Kupffer cells initiate inflammatory responses after exposure to classical cardiovascular risk factors, then this provides a potential alternative/synergistic pathway for cardiovascular disease initiation. We aimed to elucidate the prevalence of this potential pathway. We hypothesized that Kupffer cells would initiate a robust inflammatory response after exposure to tobacco cigarette or e-cigarette products and that the inflammatory response would have the potential to antagonize other salient cells for cardiovascular disease progression. To test this, Kupffer cells were incubated with tobacco smoke extracts, e-cigarette vapor extracts or pure nicotine. Complement deposition onto Kupffer cells, Kupffer cell complement receptor expression, oxidative stress production, cytokine release and viability and density were assessed after the exposure. We observed a robust inflammatory response, oxidative stress production and cytokine release after Kupffer cells were exposed to tobacco or e-cigarette extracts. We also observed a marginal decrease in cell viability coupled with a significant decrease in cell density. In general, this was not a function of the extract formulation (e.g. tobacco vs. e-cigarette products or the formulation of the cigarette product). These results indicate that Kupffer cells are responsive to classical cardiovascular risk factors and that an inflammatory response is initiated that may pass into the general systemic circulation.

Thrombocytopenia, Platelet Transfusion, and Outcome Following Liver Transplantation

Thrombocytopenia affects patients undergoing liver transplantation. Intraoperative platelet transfusion has been shown to independently influence survival after liver transplantation at 1 and 5 years. We examined the impact of thrombocytopenia and intraoperative platelet transfusion on short-term graft and overall survival after orthotopic liver transplantation (OLT). A total of 399 patients undergoing first OLT were studied. Graft and overall survival in patients with different degrees of thrombocytopenia and with or without intraoperative platelet transfusion were described. The degree of thrombocytopenia prior to OLT did not affect graft or overall survival after transplant. However, graft survival in patients receiving platelets was significantly reduced at 1 year (P= .023) but not at 90 days (P= .093). Overall survival was significantly reduced at both 90 days (P= .040) and 1 year (P= .037) in patients receiving platelets. We conclude that a consistently lower graft and overall survival were observed in patients receiving intraoperative platelet transfusion.

Gadolinium chloride suppresses acute rejection and induces tolerance following rat liver transplantation by inhibiting Kupffer-cell activation

The aim of the present study was to investigate the mechanism by which gadolinium chloride (GdCl₃) inhibits Kupffer cell (KC) activation and its ability to suppress acute rejection and induce tolerance following liver transplantation in rats. Rats were randomly divided into control, liver transplantation with GdCl₃ pretreatment and liver transplantation with normal saline pretreatment groups. The survival rate, liver function, hepatic pathological histology, cytokine levels in the liver and bile, activity of nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) in KCs, and expression levels of membranous molecules on the KCs were observed. It was identified that the one-month survival rate in the GdCl₃ group was significantly higher compared with that in the saline group (P<0.05). The liver function in the GdCl₃ group gradually recovered following transplantation surgery; however, it progressively deteriorated in the saline group. There were minor changes of hepatic pathological histology in the GdCl₃ group, whereas changes typical of acute rejection occurred in the saline group. In the GdCl₃ group, the levels of interferon γ and interleukin (IL)-2 were significantly lower whereas the levels of IL-10 were significantly higher compared with those in the control and saline groups (all P<0.01). The IL-4 levels in the GdCl₃ and control groups were similar. The activity of NF-κB in the saline group was significantly higher compared with those in the control and GdCl₃ groups (P<0.01). The expression levels of major histocompatibility complex-II, cluster of differentiation (CD)80 and CD86 on the KC membranes in the GdCl₃ group was significantly lower compared with those in the control group (P<0.05); however, these membranous proteins were highly expressed in the saline group. These data indicate that GdCl₃ efficiently inhibits the immunological activity of KCs, suppresses acute rejection and induces tolerance following liver allograft transplantation in rats.

Single-center transfusion rate for 555 consecutive liver transplantations: impact of two eras

Orthotopic liver transplantation (OLT) is the treatment of choice for patients with acute or chronic end-stage liver disease, irresectable primary liver tumor, and metabolic disorders. Historically, OLT has been associated with considerable blood loss and the need for transfusions. However, over the years there has been reduction is need for blood products. The aim of this article was to compare two distinct eras for perioperative blood transfusion rate among patients undergoing OLT; Era I, 200 transplantations in 188 patients, and Era II, 355 transplantations in 339 patients. The donor mean age was 33.70 (Era I) versus 35.34 (Era II). Cause of death in both eras was traumatic brain injury followed by cerebral vascular accident. Organ recipient data showed a mean age of 48.87 (Era I) versus 46.49 (Era II). During Era I patients with Child B (56.8%) prevailed, followed by Child C (35.4%) and Child A (7.8%). In Era II also patients with Child B (53.1%) prevailed, followed by Child C (39.6%) and Child A (7.3%). The prevalence of hepatocellular carcinoma (HCC) during Era I was 9% (18) and in Era II 20% (71). The use of blood products in the perioperative period: was as follows packed red blood cells 1.76 (Era I) versus 0.57 (Era II) units; fresh frozen plasma 1.89 (Era I) versus 0.49 (Era II) units; platelets 2.16 (Era I) versus 0.28 (Era II) units; and cryoprecipitate 0.08 (Era I) versus 0.03 (Era II) units. OLT using the piggyback technique was performed with a transfusion rate below <30%, and it reduced blood loss and prevented severe hemodynamic instability.

Protective Effects of N-acetylcysteine and a Prostaglandin E1 Analog, Alprostadil, Against Hepatic Ischemia: Reperfusion Injury in Rats

Ischemia–reperfusion (I/R) injury has a complex pathophysiology resulting from a number of contributing factors. Therefore, it is difficult to achieve effective treatment or protection by individually targeting the mediators or mechanisms. Our aim was to analyze the individual and combined effects of N-acetylcysteine (NAC) and the prostaglandin E1 (PGE1) analog alprostadil on hepatic I/R injury in rats. Thirty male Sprague-Dawley rats were randomly divided into five groups (six rats per group) as follows: Control group, I/R group, I/R + NAC group, I/R + alprostadil group, and I/R + NAC + alprostadil group. The rats received injections of NAC (150 mg/kg) and/or alprostadil (0.05 μg/kg) over a period of 30 min prior to ischemia. These rats were then subjected to 60 min of hepatic ischemia followed by a 60-min reperfusion period. Hepatic superoxide dismutase (SOD), catalase, and glutathione levels were significantly decreased as a result of I/R injury, but they were increased in groups treated with NAC. Hepatic malondialdehyde (MDA), myeloperoxidase (MPO), and nitric oxide (NO) activities were significantly increased after I/R injury, but they were decreased in the groups with NAC treatment. Alprostadil decreased NO production, but had no effect on MDA and MPO. Histological results showed that both NAC and alprostadil were effective in improving liver tissue morphology during I/R injury. Although NAC and alprostadil did not have a synergistic effect, our findings suggest that treatment with either NAC or alprostadil has benefits for ameliorating hepatic I/R injury.

Point of care perioperative coagulation management in liver transplantation and complete portal vein thrombosis

Liver transplantation (LT) is a serious hemostatic challenge in patients with portal vein thrombosis (PVT). Advances in monitoring systems have improved surgery in this setting. We report the successful application of a point-of-care (POC) rotational viscoelastic thromboelastometry-guided (TEM) testing system (ROTEM) which allowed management of coagulation during LT in a 64-year-old cirrhotic patient with a model for end-stage liver disease (MELD) score of 16. Perioperatively, the patient showed complete PVT, hepatomegaly, splenomegaly, recanalization of the umbilical vein, and portosystemic shunt. Macroscopic liver and spleen adherences with collateral circulation were evident. Coagulation factors and fibrinolysis were assessed preoperatively and at graft reperfusion to evaluate the need of hemostatic therapy. Based on ROTEM findings, the patient received 16 g of human fibrinogen concentrate, half preoperatively (with prothrombin complex concentrate 2000 IU, tranexamic acid 1 g, and platelets 2 IU), and two doses of 4 g before and after graft reperfusion; we achieved normalization of all monitored parameters. No ischemia-reperfusion syndrome was present. Postoperatively portal vein flux at Color-Doppler ultrasonography was normal. After a 3-day ICU stay, the patient was moved to the Department of Surgery and discharged on day 14. The postoperative course was uneventful and did not require any further haemostatic therapy.

Protective effect of heme oxygenase-1 on hepatic ischemia-reperfusion injury through inhibition of platelet adhesion to the sinusoids

BACKGROUND AND AIM

Heme oxygenase-1 (HO-1) acts as a protector against hepatic inflammatory injury. HO-1 catalyzes the conversion of heme protein to biliverdin, free iron, and carbon monoxide. Pro-inflammatory responses play critical roles in hepatic ischemia-reperfusion (I/R) injury, and carbon monoxide effectively downregulates I/R injury. The aim of this study was to evaluate the mechanism by which HO-1 reduces warm I/R injury.

METHODS

Sprague-Dawley rats were divided into two groups: the 20-min ischemia group (control group; n = 6) and the 20-min ischemia with cobalt protoporphyrin (CoPP group; n = 6). CoPP is an inducer of HO-1 in the sinusoids. Kupffer cells were labeled using the liposome entrapment method, and platelets were labeled with rhodamine-6G. The adherent platelets were observed for up to 120 min after reperfusion by intravital microscopy.

RESULTS

In the control group, the number of adherent platelets significantly increased than in the CoPP group. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive cells were observed after 120 min of reperfusion in the control group. They were not observed in the CoPP group. In the CoPP group, serum alanine transaminase and interleukin-6 levels reduced after reperfusion. Moreover, the flow velocity of platelets in the hepatic sinusoid markedly increased.

CONCLUSIONS

This study suggests that HO-1 inhibits platelet adhesion to sinusoids. Such inhibition leads to the prevention of hepatic I/R injury.

Hepatic sinusoidal endothelium avidly binds platelets in an integrin-dependent manner, leading to platelet and endothelial activation and leukocyte recruitment

Platelets have recently been shown to drive liver injury in murine models of viral hepatitis and promote liver regeneration through the release of serotonin. Despite their emerging role in inflammatory liver disease, little is known about the mechanisms by which platelets bind to the hepatic vasculature. Therefore, we referenced public expression data to determine the profile of potential adhesive receptors expressed by hepatic endothelium. We then used a combination of tissue-binding and flow-based endothelial-binding adhesion assays to show that resting platelets bind to human hepatic sinusoidal endothelial cells and that the magnitude of adhesion is greatly enhanced by thrombin-induced platelet activation. Adhesion was mediated by the integrins Gp1b, αIIbβIII, and αvβ3, as well as immobilized fibrinogen. Platelet binding to hepatic endothelial cells resulted in NF-κB activation and increased chemokine secretion. The functional relevance of platelet binding was confirmed by experiments that showed markedly increased binding of neutrophils and lymphocytes to hepatic endothelial cells under shear conditions replicating those found in the hepatic sinusoid, which was in part dependent on P-selectin expression. Thus the ability of platelets to activate endothelium and promote leukocyte adhesion may reflect an additional mechanism through which they promote liver injury.

Novel therapy for liver regeneration by increasing the number of platelets

Platelets are the smallest blood constitutes which contain three types of granules; alpha granules, dense granules, and lysosomal granules. Each granule contains various biophysiological substances such as growth factors, cytokines, etc. Platelets have been conventionally viewed as a trigger of inflammatory responses and injury in the liver. Some studies revealed that platelets have strong effects on promoting liver regeneration. This review presents experimental evidence of platelets in accelerating liver regeneration and describes three different mechanisms involved; (1) the direct effect on hepatocytes, where platelets translocate to the space of Disse and release growth factors through direct contact with hepatocytes, (2) the cooperative effect with liver sinusoidal endothelial cells, where the dense concentration of sphingosine-1-phosphate in platelets induces excretion of interleukin-6 from liver sinusoidal endothelial cells, and (3) the collaborative effect with Kupffer cells, where the functions of Kupffer cells are enhanced by platelets.

Mechanistic overview of reactive species-induced degradation of the endothelial glycocalyx during hepatic ischemia/reperfusion injury

Endothelial cells are covered by a delicate meshwork of glycoproteins known as the glycocalyx. Under normophysiological conditions the glycocalyx plays an active role in maintaining vascular homeostasis by deterring primary and secondary hemostasis and leukocyte adhesion and by regulating vascular permeability and tone. During (micro)vascular oxidative and nitrosative stress, which prevails in numerous metabolic (diabetes), vascular (atherosclerosis, hypertension), and surgical (ischemia/reperfusion injury, trauma) disease states, the glycocalyx is oxidatively and nitrosatively modified and degraded, which culminates in an exacerbation of the underlying pathology. Consequently, glycocalyx degradation due to oxidative/nitrosative stress has far-reaching clinical implications. In this review the molecular mechanisms of reactive oxygen and nitrogen species-induced destruction of the endothelial glycocalyx are addressed in the context of hepatic ischemia/reperfusion injury as a model disease state. Specifically, the review focuses on (i) the mechanisms of glycocalyx degradation during hepatic ischemia/reperfusion, (ii) the molecular and cellular players involved in the degradation process, and (iii) its implications for hepatic pathophysiology. These topics are projected against a background of liver anatomy, glycocalyx function and structure, and the biology/biochemistry and the sources/targets of reactive oxygen and nitrogen species. The majority of the glycocalyx-related mechanisms elucidated for hepatic ischemia/reperfusion are extrapolatable to the other aforementioned disease states.

Interaction between Kupffer cells and platelets in the early period of hepatic ischemia-reperfusion injury--an in vivo study

BACKGROUND

Hepatic ischemia-reperfusion (I/R) leads to activation of Kupffer cells (KCs). The activated KCs cause platelet and leukocyte adhesion to the sinusoidal endothelium. Previously, we reported that platelet-endothelium interactions occur earlier than leukocyte responses. The aim of this study was to evaluate the interaction between platelets and KCs in the hepatic microcirculation after I/R.

MATERIALS AND METHODS

Sprague-Dawley rats were divided into three groups: the no-ischemia group (control group; n = 6); the 20-min ischemia group (I/R group; n = 6); and the 20-min ischemia + anti-rat platelet serum group (APS group; n = 6). KCs were labeled using the liposome entrapment method. The number of adherent platelets was observed for up to 120 min after reperfusion by intravital microscopy. To investigate the effects of platelets on I/R injury, rats were injected intravenously with rabbit APS for platelet depletion.

RESULTS

In the I/R group, the number of adherent platelets increased significantly after I/R. More than 50% of the adherent platelets adhered to KCs. Electron microscopy indicated that the platelets attached to the KCs after hepatic ischemia. The histologic findings indicated liver damage and apoptosis of hepatocytes in zone 1. In the I/R group, but not in the control and APS groups, serum ALT increased immediately after reperfusion.

CONCLUSIONS

We succeeded in visualizing the dynamics of both KCs and platelets in the hepatic sinusoids. Liver ischemia induced the adhesion of platelets to KCs in the early period, which could play a key role in reperfusion injury of the liver.

FGL2/fibroleukin mediates hepatic reperfusion injury by induction of sinusoidal endothelial cell and hepatocyte apoptosis in mice

BACKGROUND & AIMS

Sinusoidal endothelial cell (SEC) and hepatocyte death are early, TNF-α mediated events in ischemia and reperfusion of the liver (I/Rp). We previously reported that TNF-α induced liver injury is dependent on Fibrinogen like protein 2 (FGL2/Fibroleukin) and showed that FGL2 binding to its receptor, FcγRIIB, results in lymphocyte apoptosis. In this study we examine whether I/Rp is induced by specific binding of FGL2 to FcγRIIB expressed on SEC.

METHODS

Hepatic ischemia and reperfusion was induced in wild type (WT) mice and in mice with deletion or inhibition of FGL2 and FcRIIB. Liver injury was determined by AST release, necrosis and animal death. Apoptosis was evaluated with caspase 3 and TUNEL staining.

RESULTS

FGL2 deletion or inhibition resulted in decreased liver injury as determined by a marked reduction in both levels of AST and ALT and hepatocyte necrosis. Caspase 3 staining of SEC (12% vs. 75%) and hepatocytes (12% vs. 45%) as well as TUNEL staining of SEC (13% vs. 60%, p=0.02) and hepatocytes (18% vs. 70%, p=0.03), markers of apoptosis, were lower in Fgl2(-/-) compared to WT mice. In vitro incubation of SEC with FGL2 induced apoptosis of SEC from WT mice, but not FcγRIIB(-/-) mice. Deletion of FcγRIIB fully protected mice against SEC and hepatocyte death in vivo. Survival of mice deficient in either Fgl2(-/-) (80%) or FcγRIIB(-/-) (100%) was markedly increased compared to WT mice (10%) which were subjected to 75min of total hepatic ischemia (p=0.001).

CONCLUSIONS

FGL2 binding to the FcγRIIB receptor expressed on SEC is a critical event in the initiation of the hepatic reperfusion injury cascade through induction of SEC and hepatocyte death.

Activation of human liver sinusoidal endothelial cell by human platelets induces hepatocyte proliferation

BACKGROUND & AIMS

We previously reported that platelets promote hepatocyte proliferation. In this study, we focused on the role of platelets in liver sinusoidal endothelial cells (LSECs) in addition to their role in hepatocyte in liver regeneration.

METHODS

Immortalized human LSECs (TMNK-1) were used. The LSECs were co-cultured with human platelets, and the proliferation of LSECs and the excretion of growth factors and interleukin-6 (IL-6) were subsequently measured. The main factor from platelets which induced the excretion of IL-6 from LSECs was determined using inhibitors of each component contained in the platelets. The need for direct contact between platelets and LSECs was investigated using cell culture inserts. The proliferation of human primary hepatocytes was measured after the addition of the supernatant of LSECs cultured with or without platelets.

RESULTS

The number of LSECs cocultured with platelets significantly increased. Excretion of IL-6 and vascular endothelial growth factor (VEGF) increased in LSECs with platelets. JTE-013, a specific antagonist for sphingosine 1-phosphate (S1P) 2 receptors, inhibited the excretion of IL-6 from LSECs after the addition of platelets. When the platelets and LSECs were separated by the cell culture insert, the excretion of IL-6 from LSECs was decreased. DNA synthesis was significantly increased in human primary hepatocytes cultured with the supernatant of LSECs with platelets.

CONCLUSIONS

Platelets promote LSEC proliferation and induce IL-6 and VEGF production. Direct contact between the platelets and LSECs and S1P, that are contained in platelets, were involved in the excretion of IL-6 from LSECs. IL-6 from LSECs induced proliferation of parenchymal hepatocytes.

Platelet adhesion in the sinusoid caused hepatic injury by neutrophils after hepatic ischemia reperfusion

Liver ischemia-reperfusion (I/R) injury is one of the most serious complications of hepatic surgery. In I/R, activated Kupffer cells cause platelet adhesion to sinusoidal endothelium as well as neutrophils and cause liver dysfunction. The aim of this study was to evaluate platelet dynamics in the hepatic microcirculation after I/R by intravital microscopy (IVM) and to clarify the relationship between platelet adhesion and neutrophil activation. Male Sprague-Dawley (SD) rats were divided into two groups: the control (administration of saline) group and the sivelestat group in which neutrophil activation was suppressed by sivelestat before I/R. The number of adherent platelets in sinusoid was observed up to 120 minutes after I/R by IVM. Samples of liver tissue and blood were taken for examination of histological findings, liver enzymes and inflammatory cytokines. The number of adherent platelets was significantly increased after I/R in both groups. Compared with the control group, the number of adherent platelets significantly decreased after hepatic I/R in the sivelestat group. Moreover, sivelestat improved changes of histological findings and elevation of liver enzymes. However, there was no significant difference in inflammatory cytokines of TNF-alpha, IL-1beta or IL-6. Platelet adhesion in the sinusoid is associated with liver dysfunction after I/R as well as neutrophils. Activated neutrophils induce platelet adhesion in the sinusoid of the liver.

Biological modulation of liver ischemia-reperfusion injury

PURPOSE OF REVIEW

This review gives a broad overview of the key factors of ischemic injury to the liver and presents the current modifications of preservation solutions and the few strategies of biological modulation in clinical use today.

RECENT FINDINGS

Protective effects in human-liver transplantation were shown by methylprednisolone treatment in decreased donors, and by inhalation of a nontoxic dose of nitric oxide in recipients. In addition, recent results showed rescue of pig livers, donated after cardiac death by application of a cocktail of substances addressing several previously identified mechanisms of ischemia-reperfusion injury.

SUMMARY

The future of a pharmacological approach attenuating or preventing ischemia-reperfusion injury lies in a combination of drugs acting simultaneously on several steps of the injury cascades. Applying these substances during flush, before, and during implantation appears as an attractive strategy to protect extended criteria liver grafts.

The hepatic microcirculation: mechanistic contributions and therapeutic targets in liver injury and repair

The complex functions of the liver in biosynthesis, metabolism, clearance, and host defense are tightly dependent on an adequate microcirculation. To guarantee hepatic homeostasis, this requires not only a sufficient nutritive perfusion and oxygen supply, but also a balanced vasomotor control and an appropriate cell-cell communication. Deteriorations of the hepatic homeostasis, as observed in ischemia/reperfusion, cold preservation and transplantation, septic organ failure, and hepatic resection-induced hyperperfusion, are associated with a high morbidity and mortality. During the last two decades, experimental studies have demonstrated that microcirculatory disorders are determinants for organ failure in these disease states. Disorders include 1) a dysregulation of the vasomotor control with a deterioration of the endothelin-nitric oxide balance, an arterial and sinusoidal constriction, and a shutdown of the microcirculation as well as 2) an overwhelming inflammatory response with microvascular leukocyte accumulation, platelet adherence, and Kupffer cell activation. Within the sequelae of events, proinflammatory mediators, such as reactive oxygen species and tumor necrosis factor-alpha, are the key players, causing the microvascular dysfunction and perfusion failure. This review covers the morphological and functional characterization of the hepatic microcirculation, the mechanistic contributions in surgical disease states, and the therapeutic targets to attenuate tissue injury and organ dysfunction. It also indicates future directions to translate the knowledge achieved from experimental studies into clinical practice. By this, the use of the recently introduced techniques to monitor the hepatic microcirculation in humans, such as near-infrared spectroscopy or orthogonal polarized spectral imaging, may allow an early initiation of treatment, which should benefit the final outcome of these critically ill patients.

Preconditioning, organ preservation, and postconditioning to prevent ischemia-reperfusion injury to the liver

Ischemia and reperfusion lead to injury of the liver. Ischemia-reperfusion injury is inevitable in liver transplantation and trauma and, to a great extent, in liver resection. This article gives an overview of the mechanisms involved in this type of injury and summarizes protective and treatment strategies in clinical use today. Intervention is possible at different time points: during harvesting, during the period of preservation, and during implantation. Liver preconditioning and postconditioning can be applied in the transplant setting and for liver resection. Graft optimization is merely possible in the period between the harvest and the implantation. Given that there are 3 stages in which a surgeon can intervene against ischemia-reperfusion injury, we have structured the review as follows. The first section reviews the approaches using surgical interventions, such as ischemic preconditioning, as well as pharmacological applications. In the second section, static organ preservation and machine perfusion are addressed. Finally, the possibility of treating the recipient or postconditioning is discussed.

Electron spin resonance and spin trapping technique provide direct evidence that edaravone prevents acute ischemia–reperfusion injury of the liver by limiting free radical-mediated tissue damage

A novel free radical scavenger, 3-methyl-1-phenyl-2-pyrazolin-5-one (edaravone), is used for the treatment of acute ischemic stroke and is protective in several animal models of organ injury. We tested whether edaravone is protective against acute liver warm ischemia/reperfusion injury in the rat by acting as a radical scavenger. When edaravone was administered prior to ischemia and at the time of initiation of the reperfusion, liver injury was markedly reduced. Production of oxidants in the liver in this model was assessed in vivo by spin-trapping/electron spin resonance (ESR) spectroscopy. Ischemia/reperfusion caused an increase in free radical adducts rapidly, an effect markedly blocked by edaravone. Furthermore, edaravone treatment blunted ischemia/reperfusion-induced elevation in pro-inflammatory cytokines, infiltration of leukocytes and lipid peroxidation in the liver. These results demonstrate that edaravone is an effective blocker of free radicals in vivo in the liver after ischemia/reperfusion, leading to prevention of organ injury by limiting the deleterious effects of free radicals.

Changing trends in transfusion practice in liver transplantation

PURPOSE OF REVIEW

Prevention of excessive blood loss is an important issue in the perioperative management of liver transplantation. This review describes changing trends in blood products use, risk predicting of blood transfusion, variability in use and practices, as well as transfusion safety during liver transplantation.

RECENT FINDINGS

Over the last 20 years, the average use of blood products per case has considerably decreased. There are marked interinstitutional differences in blood use. Differences in patient population characteristics and surgical techniques are a partial explanation, but differences in transfusion practices probably account for a substantial part of the variability. Recent data have sparked off ongoing controversy relating to volume replacement therapy and its impact on blood loss. New studies emphasize the risks associated with transfusion in liver transplantation.

SUMMARY

Recent studies call for continuing every reasonable effort to minimize the use of blood components and can guide us in new approaches to this vital problem.

The impact of intraoperative transfusion of platelets and red blood cells on survival after liver transplantation

BACKGROUND

Intraoperative transfusion of red blood cells (RBC) is associated with adverse outcome after orthotopic liver transplantation (OLT). Although experimental studies have shown that platelets contribute to reperfusion injury of the liver, the influence of allogeneic platelet transfusion on outcome has not been studied in detail. In this study, we evaluate the impact of various blood products on outcome after OLT.

METHODS

Twenty-nine variables, including blood product transfusions, were studied in relation to outcome in 433 adult patients undergoing a first OLT between 1989 and 2004. Data were analyzed using uni- and multivariate stepwise Cox's proportional hazards analyses, as well as propensity score-adjusted analyses for platelet transfusion to control for selection bias in the use of blood products.

RESULTS

The proportion of patients receiving transfusion of any blood component decreased from 100% in the period 1989-1996 to 74% in the period 1997-2004. In uni- and multivariate analyses, the indication for transplantation, transfusion of platelets and RBC were highly dominant in predicting 1-yr patient survival. These risk factors were independent from well-accepted indices of disease, such as the Model for End-Stage Liver Disease score and Karnofsky score. The effect on 1-yr survival was dose-related with a hazard ratio of 1.377 per unit of platelets (P = 0.01) and 1.057 per unit of RBC (P = 0.001). The negative impact of platelet transfusion on survival was confirmed by propensity-adjusted analysis.

CONCLUSION

This retrospective study indicates that, in addition to RBC, platelet transfusions are an independent risk factor for survival after OLT. These findings have important implications for transfusion practice in liver transplant recipients.

Platelets in liver transplantation: friend or foe?

Apart from the well-known role of blood platelets in hemostasis, there is emerging evidence that platelets have various nonhemostatic properties that play a critical role in inflammation, angiogenesis, tissue repair and regeneration, and ischemia/reperfusion (I/R) injury. All these processes may be involved in the (patho)physiological alterations occurring in patients undergoing liver transplantation. Experimental and clinical research points toward a dualistic role of platelets in patients undergoing liver transplantation, resulting in both beneficial and detrimental effects. Although a low platelet count is generally considered a risk factor for perioperative bleeding, recent studies have indicated that platelet function in patients with cirrhosis may not be as abnormal as previously assumed. Platelet transfusions are frequently considered in liver transplant recipients to correct low platelet counts and to prevent bleeding; however, evidence-based transfusion thresholds are lacking, and the other detrimental and nonhemostatic properties of platelets are generally not weighed in this respect. First, platelets have been shown to contribute to I/R injury of the liver graft via induction of sinusoidal endothelial cell apoptosis. Second, platelet transfusion has been identified as an independent risk factor for reduced survival via mechanisms that are not completely understood yet. On the other hand, recent studies indicate that platelets are critically involved in restoration after liver injury and in liver regeneration via serotonin-mediated mechanisms. These findings make platelets both friend and foe in liver transplantation. The scientific challenge will be to further dissect the mechanisms and clinical relevance of these contrasting roles of platelets in liver transplantation.

Diannexin, a novel annexin V homodimer, protects rat liver transplants against cold ischemia-reperfusion injury

Ischemia/reperfusion injury (IRI) remains an important problem in clinical transplantation. Following ischemia, phosphatidylserine (PS) translocates to surfaces of endothelial cells (ECs) and promotes the early attachment of leukocytes/platelets, impairing microvascular blood flow. Diannexin, a 73 KD homodimer of human annexin V, binds to PS, prevents attachment of leukocytes/platelets to EC, and maintains sinusoidal blood flow. This study analyzes whether Diannexin treatment can prevent cold IRI in liver transplantation. Rat livers were stored at 4 degrees C in UW solution for 24 h, and then transplanted orthotopically (OLT) into syngeneic recipients. Diannexin (200 microg/kg) was infused into: (i) donor livers after recovering and before reperfusion, (ii) OLT recipients at reperfusion and day +2. Controls consisted of untreated OLTs. Both Diannexin regimens increased OLT survival from 40% to 100%, depressed sALT levels, and decreased hepatic histological injury. Diannexin treatment decreased TNF-alpha, IL-1beta, IP-10 expression, diminished expression of P-selectin, endothelial ICAM-1, and attenuated OLT infiltration by macrophages, CD4 cells and PMNs. Diannexin increased expression of HO-1/Bcl-2/Bcl-xl, and reduced Caspase-3/TUNEL+ apoptotic cells. Thus, by modulating leukocyte/platelet trafficking and EC activation in OLTs, Diannexin suppressed vascular inflammatory responses and decreased apoptosis. Diannexin deserves further exploration as a novel agent to attenuate IRI, and thereby improve OLT function/increase organ donor pool.

Platelet dynamics in the early phase of postischemic liver in vivo

BACKGROUND

In liver surgery, ischemia/reperfusion injury occasionally leads to liver failure by activating Kupffer cells (KCs) and leukocytes. However, few reports have demonstrated a relationship between KCs and platelets in vivo. This study investigated the relationship between these cells using intravital microscopy.

MATERIALS AND METHODS

Male Wistar rats were divided into two groups: (1) KC+ group, receiving 1 mL saline; and (2) KC- group, intravenously injected with liposome-encapsulated dichloromethylene disphosphonate for elimination of KCs. At 48 h after administration, 20 min of total normothermic hepatic ischemia was induced. Rhodamine-6G-labeled platelets and sinusoidal alterations were monitored using intravital microscopy up to 120 min after reperfusion. P-selectin, accumulated leukocytes and morphological damage, and alanine aminotransferase were evaluated.

RESULTS

In the KC+ group, numbers of adherent platelets increased significantly within 30 min after reperfusion. Endothelial cells of sinusoids in which KCs were mainly located were destroyed and the sinusoids were significantly constricted after reperfusion. Conversely, in the KC- group, adherent platelets in sinusoids were suppressed, and sinusoidal perfusion, endothelial cell damage and serum alanine aminotransferase levels were significantly improved. P-selectin on sinusoidal endothelial cells was not observed up to 120 min after reperfusion in either group.

CONCLUSIONS

Adherent platelets appear to reflect activation of KCs and lead to leukocyte accumulation, resulting in sinusoidal perfusion disturbance and liver failure. Evaluation of adherent platelets in the microcirculation offers an important marker of hepatic injury.

Local interaction of apoptotic hepatocytes and Kupffer cells in a rat model of systemic endotoxemia

AIM

There is strong evidence that hepatocellular apoptosis is not only initiated by circulating blood cells which become adherent within the endotoxemic liver, but also contributes to further sustain the inflammatory cell-cell response.

METHODS

Because previous studies assumed the importance of the role of cellular cross-talk in mediating inflammatory liver injury, we herein examined the activation of Kupffer cells (KCs) and their spatial coincidence with intrahepatic leukocyte adherence and hepatocellular apoptosis at 6 h after intraperitoneal exposure of rats with lipopolysaccharide (10 mg/kg).

RESULTS

In vivo multifluorescence microscopy revealed liver injury including nutritive perfusion failure, tissue hypoxia, leukocyte accumulation, as well as KC activation and parenchymal apoptotic cell death. Detailed spatial analysis revealed frequent colocalization of activated KCs with apoptotic hepatocytes. Colocalization was absent in saline-treated controls.Colocalization was confirmed by histochemistry, which showed ED1-positive KCs neighboring and engulfing TUNEL-positive hepatocytes. Colocalization of KCs with leukocytes ranged between 4% and 5% and did not increase in endotoxemic animals. Taken together, the present results indicate that apoptotic cell death of hepatocytes may stimulate phagocytosis by neighboring KCs. Direct KC-leukocyte contact seems not to be mandatory for cellular communication in the process of hepatocellular apoptosis.

CONCLUSION

With respect to the fundamental importance of cell apoptosis, improved knowledge of these cell-cell interactions might allow the development of new therapeutic strategies through the regulation of apoptotic cell death.

Diannexin, a novel annexin V homodimer, provides prolonged protection against hepatic ischemia-reperfusion injury in mice

BACKGROUND AND AIMS

Ischemia-reperfusion injury (IRI) remains an important cause of liver failure after hepatic surgery or transplantation. The mechanism seems to originate within the hepatic sinusoid, with damage to endothelial cells, an early, reproducible finding. Sinusoidal endothelial cells (SECs), damaged during reperfusion, activate and recruit inflammatory cells and platelets. We hypothesized that a recombinant human annexin V homodimer, Diannexin, would protect SECs from reperfusion injury.

METHODS

We tested this proposal in a well-characterized in vivo murine partial hepatic IRI model.

RESULTS

Whether administered 5 minutes or 24 hours before or 1 hour after ischemia-reperfusion, Diannexin (100-1000 microg/kg) almost completely protected against liver injury. The protective efficacy conferred by Diannexin was highly visible at the microcirculatory level. Thus, although IR in this model is associated with early swelling and gap formation in SECs, Diannexin ameliorated these effects as shown by >80% reduction in alanine aminotransferase values during the early phase of reperfusion injury (2 hours) and near normalization of liver necrosis and inflammation in the late phase of inflammatory recruitment (24 hours). Consistent with the proposed role of SEC injury in hepatic IRI, Diannexin also decreased hepatic expression of proinflammatory molecules (MIP-2, ICAM-1, VCAM), abolished leukocyte and platelet adherence to damaged SECs, and, by in vivo microscopy, Diannexin preserved microcirculatory blood flow and hepatocyte integrity during reperfusion.

CONCLUSIONS

Diannexin is an apparently safe therapeutic protein that provides prolonged protection against hepatic IRI via cytoprotection of SECs, thereby interrupting secondary microcirculatory inflammation and coagulation.

Platelets and platelet-derived serotonin promote tissue repair after normothermic hepatic ischemia in mice

Hepatic ischemia and reperfusion (I/R) leads to the formation of leukocyte-platelet aggregates. Upon activation, platelets generate reactive oxygen species and release proapoptotic and proinflammatory mediators as well as growth factors. In cold hepatic ischemia, adhesion of platelets to endothelial cells mediates sinusoidal endothelial cell apoptosis. Furthermore, platelet-derived serotonin mediates liver regeneration. We hypothesized that platelets may contribute to reperfusion injury and repair after normothermic hepatic ischemia. The aim of this study was to assess the impact of platelets in normothermic hepatic I/R injury using models of impaired platelet function and immune thrombocytopenia. Inhibition of platelet function in mice was achieved via clopidogrel feeding. Immune thrombocytopenia was induced via intraperitoneal injection of anti-CD41 antibody. Platelet-derived serotonin was investigated using mice lacking tryptophan hydroxylase 1. Mice were subjected to 60 minutes of partial hepatic ischemia and various time points of reperfusion. Hepatic injury was determined via AST and histological analysis of the necrotic area as well as leukocyte infiltration. Liver regeneration was determined via proliferating cell nuclear antigen and Ki67 immunohistochemistry. Neither inhibition of platelet function nor platelet depletion led to a reduction of I/R injury. Liver regeneration and repair were significantly impaired in platelet-depleted animals. Mice lacking peripheral serotonin were deficient in hepatocyte proliferation, but otherwise displayed normal tissue remodeling.

CONCLUSION

Platelets have no direct impact on the pathogenesis of normothermic I/R injury. However, they mediate tissue repair and liver regeneration. Furthermore, platelet-derived serotonin is a mediator of hepatocyte proliferation in the postischemic liver, but has no impact on tissue remodeling.

Modulation of apoptosis as a target for liver disease

Apoptosis mediated via extrinsic or intrinsic pathways is essential for maintaining cellular homeostasis in the liver. The extrinsic pathway is triggered from the cell surface by engagement of death receptors as CD95, TRAIL (TNF-related apoptosis inducing ligand) and TNF (tumour necrosis factor) or TGF-beta (transforming growth factor beta) receptors. The intrinsic pathway is initiated from the mitochondria and can be influenced by Bcl-2 family members. Both pathways are intertwined and play a physiological role in the liver. Dysregulation of apoptosis pathways contributes to diseases as hepatocellular carcinoma, viral hepatitis, autoimmune hepatitis, ischaemia-reperfusion injury, iron or copper deposition disorders, toxic liver damage and acute liver failure. The apoptosis defects are often central pathogenetic events; hence molecular mechanisms of apoptosis give not only insight into disease mechanisms but also provide potential corresponding therapeutic candidates in liver disease. The focus of this review is the identification of apoptotic signalling components in the liver as therapeutic targets.

Rescue of the cold preserved rat liver by hypothermic oxygenated machine perfusion

The aim of the study was to investigate whether hypothermic oxygenated liver perfusion after cold liver preservation resuscitated metabolic parameters and whether this treatment had a benefit for liver viability upon reperfusion. We preserved rat livers either by cold storage (UW) for 10 h, or by perfusion for 3 h (oxygenated modified UW) after 10 h cold storage. We assessed viability of livers after preservation and after ischemic rewarming+normothermic reperfusion ex vivo. Ten hour cold storage reduced mitochondrial cytochrome oxidase and metabolically depleted the livers. Oxygenated perfusion after cold storage resulted in uploaded cellular energy charge and oxidized mitochondrial cytochrome oxidase. Reperfusion after 10 h cold storage increased formation of superoxid anions, release of cytosolic LDH, lipid peroxidation, caspase activities and led to disruption of sinusoidal endothelial cells. In contrast, reperfusion after 10 h cold storage+3 h hypothermic oxygenated perfusion resulted in no changes of lipid peroxidation, bile flow, energy charge, total glutathione, LDH release and of caspase activation, as compared to fresh resected livers. This study demonstrates, that a metabolically depleted liver due to cold storage can be energy recharged by short-termed cold machine perfusion. The machine perfused graft exhibited improved viability and functional integrity.

The Protective Effect of α-Tocopherol and GdCl3 Against Hepatic Ischemia/Reperfusion Injury

PURPOSE

To evaluate the combined effect of alpha-tocopherol and gadolinium chloride (GdCl3) in reducing lipid peroxidation after severe hepatic ischemia/reperfusion (IR) injury.

METHODS

Sixty male Wistar rats, 200-250 g, were randomly divided into six equal groups. There were two sham operation (SHAM) groups, two untreated IR groups, and two IR groups treated with GdCl3 and alpha-tocopherol (IRGT). After 60 min of total hepatic ischemia and 120 min reperfusion, one of each group was killed, liver samples were taken for malondialdehyde (MDA) and myeloperoxidase (MPO) analysis and light microscopy examination, and blood samples were analyzed for aspartate (AST) and alanine (ALT) transaminase, lactate dehydrogenase (LDH), and alpha-tocopherol content. The remaining groups were monitored for survival rate determination.

RESULTS

The mean MDA and MPO values in the SHAM, IR, and IRGT groups, respectively, were 1.117, 1.476, and 0.978 nmol/g wet tissue and 1.49, 6.26, and 1.78 (U/g). The mean alpha-tocopherol values in the SHAM, IR, and IRGT groups, respectively, were 10.4, 1.9, and 12 micromol/l. The mean serum AST, ALT, and LDH values were significantly higher in the IR group than in the SHAM group (P < 0.001), and significantly lower in the IRGT group than in the IR group (P < 0.001). Light microscopy examination revealed more severe congestion and vacuolization in the IR group than in the SHAM group, and minimal congestion and vacuolization in the IRGT group. Survival was significantly higher in the IRGT group than in the IR group.

CONCLUSION

The administration of GdCl3 and alpha-tocopherol is likely to protect the liver against lipid peroxidation by suppressing Kupffer cell and polymorphonuclear leukocyte activation and enhancing endogenous antioxidant activity.