Endothelin(A) receptor blockade reduces ischemia/reperfusion injury in pig pancreas transplantation

Dynamic Nomogram for Predicting Thrombocytopenia in Adults with Acute Pancreatitis

Objective

Thrombocytopenia increases the risk of hemorrhage in patients with acute pancreatitis (AP), leading to poor clinical outcomes. Currently, there is no reliable tool for the early assessment of thrombocytopenia in these patients. We aimed to develop a nomogram based on available clinical parameters and validate its efficacy in predicting thrombocytopenia.

Methods

This was a retrospective study. All the data were extracted from an electronic database from May 2018 to May 2019. Patients with a diagnosis of AP and staying in the intensive care unit for more than 3 days were retrospectively analyzed. A clinical signature was built based on reproducible features, using the least absolute shrinkage and selection operator method (LASSO), and logistic regression established the model (P < 0.05). Nomogram performance was determined by its discrimination, calibration, and clinical usefulness.

Results

A total of 594 eligible patients were enrolled, of whom 399 were allocated to the training sets and the 195 in the test sets. The clinical features, including blood urea nitrogen (BUN), fibrinogen (FIB), and antithrombase III, were significantly associated with the incidence of thrombocytopenia after acute pancreatitis (p < 0.05) in training sets. The individualized nomogram showed good discrimination in the training sample (area under the receiver operating characteristic curve [AUC], 0.881) and in the validation sample (AUC, 0.883) with good calibration.

Conclusion

The proposed nomogram has good performance for predicting thrombocytopenia in patients with acute pancreatitis and may facilitate clinical decision-making.

Melatonin role preventing steatohepatitis and improving liver transplantation results

Liver steatosis is a prevalent process that is induced due to alcoholic or non-alcoholic intake. During the course of these diseases, the generation of reactive oxygen species, followed by molecular damage to lipids, protein and DMA occurs generating organ cell death. Transplantation is the last-resort treatment for the end stage of both acute and chronic hepatic diseases, but its success depends on ability to control ischemia-reperfusion injury, preservation fluids used, and graft quality. Melatonin is a powerful endogenous antioxidant produced by the pineal gland and a variety of other because of its efficacy in organs; melatonin has been investigated to improve the outcome of organ transplantation by reducing ischemia-reperfusion injury and due to its synergic effect with organ preservation fluids. Moreover, this indolamine also prevent liver steatosis. That is important because this disease may evolve leading to an organ transplantation. This review summarizes the observations related to melatonin beneficial actions in organ transplantation and ischemic-reperfusion models.

Potential benefits of melatonin in organ transplantation: a review

Organ transplantation is a useful therapeutic tool for patients with end-stage organ failure; however, graft rejection is a major obstacle in terms of a successful treatment. Rejection is usually a consequence of a complex immunological and nonimmunological antigen-independent cascade of events, including free radical-mediated ischemia-reperfusion injury (IRI). To reduce the frequency of this outcome, continuing improvements in the efficacy of antirejection drugs are a top priority to enhance the long-term survival of transplant recipients. Melatonin (N-acetyl-5-methoxytryptamine) is a powerful antioxidant and ant-inflammatory agent synthesized from the essential amino acid l-tryptophan; it is produced by the pineal gland as well as by many other organs including ovary, testes, bone marrow, gut, placenta, and liver. Melatonin has proven to be a potentially useful therapeutic tool in the reduction of graft rejection. Its benefits are based on its direct actions as a free radical scavenger as well as its indirect antioxidative actions in the stimulation of the cellular antioxidant defense system. Moreover, it has significant anti-inflammatory activity. Melatonin has been found to improve the beneficial effects of preservation fluids when they are enriched with the indoleamine. This article reviews the experimental evidence that melatonin is useful in reducing graft failure, especially in cardiac, bone, otolaryngology, ovarian, testicular, lung, pancreas, kidney, and liver transplantation.

Interleukin-17 expression in murine pressure ulcer tissues

To explore the process of pressure ulcer formation, interleukin (IL)-17 expression levels were observed in a mouse model of pressure ulcers. Twenty mice were divided into experimental and control groups (10 mice per group). A mouse model of pressure ulcers was established by inducing ischemia-reperfusion injury on local tissue in the experimental group. Pressure ulcer tissues in the experimental group and normal mouse tissue in the control group were stained using hematoxylin and eosin (H&E) and observed using light microscopy. The protein and mRNA expression levels of IL-17, in mouse pressure ulcer tissues from the experimental group and in the normal tissue from the control group, were determined using real-time PCR and western blot analysis, respectively. The mRNA and protein expression levels of IL-17 were compared between the two groups. H&E staining indicated that striated muscle was arranged orderly and cellular structure was intact in the control group, whilst inflammatory cell infiltration was observed in the muscle tissue of the experimental group. The expression levels of IL-17 mRNA were 0.307±0.058 ng in the experimental group and 0.112±0.042 ng in the control group (P<0.05). The expression levels of the IL-17 protein were 0.434±0.097 ng in the experimental group and 0.181±0.040 ng in the control group (P<0.05). IL-17 expression levels were increased in pressure ulcers, which suggests that IL-17 may be associated with pressure ulcers.

Altered cellular membrane fluidity levels and lipid peroxidation during experimental pancreas transplantation

Although the pathogenesis of ischemia reperfusion (IR) injury is based on complex mechanisms, free radicals play a central role. We evaluated membrane fluidity and lipid peroxidation during pancreas transplantation (PT) performed in 12 pigs (six donors and six recipients). Fluidity was measured by fluorescence spectroscopy, and malondialdehyde (MDA) and 4-hydroxyalkenals (4-HDA) concentrations were used as an index of lipid oxidation. Pancreatic tissues were collected as follows: (A) donor, immediately before vascular clamping; (B) graft, following perfusion lavage with University of Wisconsin preservation fluid; (C) graft, after 16 h of cold ischemia; and (D) recipient, 30 min vascular postreperfusion. Fluidity and MDA and 4-HDA concentrations were similar in cases A, B, and C. However, there was significant membrane rigidity and increased lipid peroxidation after reperfusion (D). These findings suggest that reperfusion exaggerates oxidative damage and may account for the rigidity in the membranes of allografts during PT.

Role of hepatic stellate cells on graft injury after small-for-size liver transplantation

BACKGROUND AND AIM

Small-for-size grafts are prone to mechanical injury and a series of chemical injuries that are related to hemodynamic force. Hepatic stellate cells activate and trans-differentiate into contractile myofibroblast-like cells during liver injury. However, the role of hepatic stellate cells on sinusoidal microcirculation is unknown with small-for-size grafts.

METHODS

Thirty-five percent of small-for-size liver transplantation was performed with rats as donors and recipients. Endothelin-1 levels as well as hepatic stellate cells activation-related protein expression, endothelin-1 receptors, and ultrastructural changes were examined. The cellular localizations of two types of endothelin-1 receptors were detected. Furthermore, liver function and sinusoidal microcirculation were analyzed using two different selective antagonists of endothelin-1 receptor.

RESULTS

Intragraft expression of hepatic stellate cells activation-related protein such as desmin, crystallin-B and smooth muscle α-actin was upregulated as well as serum endothelin-1 levels and intragraft expression of the two endothelin receptors. The antagonist to endothelin-1 A receptor not to the endothelin-1 B receptor could attenuate microcirculatory disturbance and improve liver function.

CONCLUSIONS

Small-for-size liver transplantation displayed increased hepatic stellate cells activation and high level of endothelin-1 binding to upregulation of endothelin-1 A receptor on hepatic stellate cells, which contracted hepatic sinusoid inducing graft injury manifested as reduction of sinusoidal perfusion rate and elevation of sinusoidal blood flow.

Melatonin prolongs graft survival of pancreas allotransplants in pigs

Oxidative stress is involved in ischemia-reperfusion injury and allograft rejection after transplantation. We studied two well-known antioxidants, melatonin and ascorbic acid (AA), in relation to the survival of a pancreas transplantation model without immunosuppression. Forty-eight Landrace pigs were divided into three groups (n = 16 each; eight donors and eight recipients) that received melatonin, AA, or no antioxidant therapy (controls). Melatonin and AA were administered (10 mg/kg body weight) intravenously to donors and recipients during surgery and on postoperative days 1-7. The molecules were also added (5 mm) to a University of Wisconsin preservation solution during organ cold storage. Melatonin significantly delayed acute rejection and prolonged allograft survival (25.1 ± 7.7 days) compared with the controls (8.1 ± 0.8 days, P = 0.013) and the AA group (9.4 ± 1.6 days, P = 0.049). Melatonin reduced indicators of oxidative stress, malondialdehyde, and 4-hydroxyalkenals, in pancreatic samples collected during procurement, cold ischemia, and reperfusion. Melatonin also reduced serum pig-major acute-phase protein/inter-α-trypsin inhibitor heavy chain 4 (pMAP/ITIH(4)) in the early post-transplantation period. AA only partially reduced oxidative damage 30 min postreperfusion and failed to prevent pMAP/ITIH(4) elevations. These findings suggested that melatonin may be a useful therapeutic tool for organ transplantation.

Multidrug strategies are effective in the treatment of severe experimental pancreatitis

BACKGROUND

Trypsinogen activation, oxygen radicals, cytokines, leukocyte infiltration, and pancreatic ischemia are important steps in the pathogenesis of necrotizing pancreatitis and associated systemic complications. Several drugs that inhibit those pathogenetic steps attenuated biochemical and histologic changes, while survival remained low. The aim of the present study was to evaluate the benefit of multidrug approaches compared to monotherapies on organ injury and survival in acute experimental pancreatitis in the rat model of retrograde bile injection combined with intravenous cerulein.

METHODS

Necrotizing pancreatitis was induced in rats. After a therapy-free interval of 6 hours, 10 treatment regimens were evaluated: multidrug regimen 1, which contained the protease inhibitor gabexate mesilate, oxygen-free radical scavengers, nitric oxide donor L-arginine, a platelet-activating factor antagonist, and antibodies against intracellular adhesion molecule-1 (ICAM-1) dissolved in dextran, was compared to multidrug regimen 2 (dextran, acetylcysteine, L-arginine, and anti-ICAM-1), monotherapies of each of the drugs, and standard intravascular volume replacement.

RESULTS

Both multidrug regimens significantly reduced pancreatic and systemic injury and microcirculatory disturbances compared to any of the monotherapies. Treatment with regimen 1 decreased 24-hour mortality to 0% and increased long-term survival to 85% (standard therapy, 70% and 15%, respectively). Multidrug regimen 2 was as effective as regimen 1.

CONCLUSION

Treatment of acute necrotizing pancreatitis with multidrug regimens significantly decreases short-term mortality compared to monotherapies. Moreover, multidrug strategies are still effective after a wide therapeutic window. Key to this effective therapy is the inhibition of microcirculatory disturbances and of the systemic inflammatory response. The experimental superiority of the multidrug approach should be confirmed in a clinical trial.

The role of interleukin-6, endothelins, and apoptotic genes in small bowel transplantation, in a swine model of ischemia and reperfusion injury

IRI is closely related to sepsis in ITx setting. Complete understanding of the mechanisms involved in IRI development may improve outcomes. Ortothopic ITx without immunosuppression was performed in order to characterize IRI-associated mucosal damage. Twenty pigs underwent ITx. Two groups were assigned to different CI times: G1: 90 min and, G2: 180 min. Euro-Collins was used as preservation solution. Jejunal fragments were collected at donor laparotomy, 30 min, and 3 days after reperfusion. IRI assessment involved: histopathologic analysis, quantification of MPO-positive cells through immunohistochemical studies, quantification of epithelial apoptotic cells using TUNEL staining, and quantification of IL-6, ET-1, Bak, and Bcl-XL genes expression by RT-PCR. Neutrophilic infiltration increased in a similar fashion in both groups, but lasted longer in G2. Apoptosis detected by TUNEL staining increased and anti-apoptotic gene Bcl-XL expression decreased significantly in G1, 3 days after surgery. Endothelin-1 and IL-6 genes expression increased 30 min after the procedure and returned to baseline 3 days after surgery. In conclusion, IL-6 and ET-1 are involved precociously in the development of intestinal IRI. Apoptosis was more frequently detected in G1 grafts by TUNEL-staining and by RT-PCR.

Repeated gene transfection impairs the engraftment of transplanted porcine neonatal pancreatic cells

BACKGROUND

Previously, we reported that neonatal porcine pancreatic cells transfected with hepatocyte growth factor (HGF) gene in an Epstein-Barr virus (EBV)-based plasmid (pEBVHGF) showed improved proliferation and differentiation compared to those of the control. In this study, we examined if pancreatic cells transfected repeatedly with pEBVHGF can be successfully grafted to control blood glucose in a diabetes mouse model.

METHODS

Neonatal porcine pancreatic cells were cultured as a monolayer and were transfected with pEBVHGF every other day for a total of three transfections. The transfected pancreatic cells were re-aggregated and transplanted into kidney capsules of diabetic nude mice or normal nude mice. Blood glucose level and body weight were measured every other day after transplantation. The engraftment of the transplanted cells and differentiation into beta cells were assessed using immunohistochemistry.

RESULTS

Re-aggregation of the pancreatic cells before transplantation improved engraftment of the cells and facilitated neovascularization of the graft. Right before transplantation, pancreatic cells that were transfected with pEBVHGF and then re-aggregated showed ductal cell marker expression. However, ductal cells disappeared and the cells underwent fibrosis in a diabetes mouse model two to five weeks after transplantation; these mice also did not show controlled blood glucose levels. Furthermore, pancreatic cells transplanted into nude mice with normal blood glucose showed poor graft survival regardless of the type of transfected plasmid (pCEP4, pHGF, or pEBVHGF).

CONCLUSION

For clinical application of transfected neonatal porcine pancreatic cells, further studies are required to develop methods of overcoming the damage for the cells caused by repeated transfection and to re-aggregate them into islet-like structures.

Incidence of pancreas graft thrombosis using low-molecular-weight heparin

INTRODUCTION

Simultaneous pancreas-kidney transplantation is the current treatment of choice for patients with type I diabetes and end stage renal disease. Vascular graft thrombosis (VGT) after pancreas transplantation is the main cause of early graft loss.

METHODS

A total of 188 consecutive pancreas transplantations were performed between January 2000 and December 2006. A retrospective study was carried out in order to compare incidence of VGT and relaparotomy-for-bleeding rate of once daily fixed dose low-molecular-weight-heparin (LMWH) to dose-adjusted intravenous unfractionated heparin (UFH).

RESULTS

Fifty-eight patients receiving LMWH and 129 receiving UFH were identified. There were 7% (4/58) VGTs in the LMWH and 17% (22/129) in the UFH group (p = 0.047). The frequency of major bleeding requiring relaparatomy was not significantly different in the groups related to LMWH and UFH, respectively (6.9% vs. 7.8%). One yr patient and pancreas graft survival was 98.9/89.6% in the LMWH and 97.8/74.4% in the UFH group. Donor and recipient characteristics were similar.

CONCLUSION

In our experience once daily fixed dose LMWH might not be inferior to dose-adjusted intravenous heparin in preventing pancreas graft thrombosis.

Pathophysiological role of platelets and platelet system in acute pancreatitis

The most successful approach for restoring normal long-term glucose homeostasis in type I diabetes mellitus is whole-organ pancreas transplantation. Graft pancreatitis is observed in up to 20% of patients and may lead to loss of the transplanted organ. Several pathophysiological events have been implicated in this form of pancreatitis. The most important cause of early graft pancreatitis is ischemia/reperfusion (I/R)-related disturbance of microvascular perfusion with subsequent hypoxic tissue damage. Recently, considerable evidence accumulated that, among a variety of other pathophysiological events, the activation of platelets can contribute to I/R injury in the course of acute pancreatitis experimentally and clinically. This review summarizes the events affecting platelet function and, therefore, pancreatic microcirculation leading to acute pancreatitis. Therapeutic approaches and own results are presented.

Induction of heme oxygenase-1 improves the survival of pancreas grafts by prevention of pancreatitis after transplantation

BACKGROUND

Ischemia/reperfusion (I/R) injury after pancreas transplantation might result in graft pancreatitis. The role of heme oxygenase-1 (HO-1) in pancreas transplantation and prevention of graft pancreatitis is unknown.

METHOD

We studied the impact of HO-1 induction with cobalt protoporphyrin (CoPP) in experimental pancreas transplantation with moderate (6 hr) and prolonged (20 hr) cold ischemic time (CIT). Donor animals received CoPP 5 mg/kg intraperitoneal at 48 hr or intraperitoneal saline injections in the corresponding control groups before procurement. Harvested grafts were perfused with HTK solution and stored at 4 degrees C.

RESULTS

After prolonged CIT, graft survival was 100% with CoPP pretreatment in contrast to only 37.5% without pretreatment. CoPP-pretreated grafts demonstrated an unimpaired endocrine graft function at moderate and prolonged CIT. Serum lipase activity as a sign of exocrine preservation was significantly lower. In addition, morphological architecture was well preserved. CoPP pretreatment markedly increased HO-1 gene expression in donor pancreas (130-fold increase) by means of quantitative reverse transcriptase -polymerase chain reaction. Immunohistochemical examinations showed that the increase of HO-1 on the protein level was related to HO-1-positive donor macrophages in the pancreas grafts. HO-1 overexpression was accompanied by significant decrease of proinflammatory cytokines such as tumor necrosis factor-alpha, interleukin (IL)-2, IL-6, interferon-y, and by significant increase of the anti-inflammatory cytokine IL-10 and less expression of adhesion molecules such as e- and p-selectins.

CONCLUSIONS

HO-1 is highly inducible in the allograft rat pancreas and associated with a survival benefit and good graft function after transplantation. This study contributes to the beneficial potentials of HO-1 for the prevention of graft pancreatitis.

Endothelin-1 and pancreatic islet vasculature: studies in vivo and on isolated, vascularly perfused pancreatic islets

Endothelin-1 (ET-1) is a potent endothelium-derived vasoconstrictor, which also stimulates insulin release. The aim of the present study was to evaluate whether exogenously administered ET-1 affected pancreatic islet blood flow in vivo in rats and the islet arteriolar reactivity in vitro in mice. Furthermore, we aimed to determine the ET-receptor subtype that was involved in such responses. When applying a microsphere technique for measurements of islet blood perfusion in vivo, we found that ET-1 (5 nmol/kg) consistently and markedly decreased total pancreatic and especially islet blood flow, despite having only minor effects on blood pressure. Neither endothelin A (ET(A)) receptor (BQ-123) nor endothelin-B (ET(B)) receptor (BQ-788) antagonists, alone or in combination, could prevent this reduction in blood flow. To avoid confounding interactions in vivo, we also examined the arteriolar vascular reactivity in isolated, perfused mouse islets. In the latter preparation, we demonstrated a dose-dependent constriction in response to ET-1. Administration of BQ-123 prevented this, whereas BQ-788 induced a right shift in the response. In conclusion, the pancreatic islet vasculature is highly sensitive to exogenous ET-1, which mediates its effect mainly through ET(A) receptors.

Influence of Salvia miltiorrhiza on the changes of plasma endothelin and P-selectin in patients with acute pancreatitis

AIM: To explore the changes of plasma endothelin and P-selectin as well as the effects of Salvia miltiorrhiza (SM) in patients with acute pancreatitis (AP).

METHODS: A total of 82 patients with acute pancreatitis were divided into group A (n = 40) and B (n = 42), treated with general method and SM, respectively. Anther 20 normal individuals were used as normal controls. The levels of plasma endothelin (ET) and P-selectin were measured by radioimmunoassay.

RESULTS: The levels of ET and P-selectin in patients with severe acute pancreatitis (SAP) were significantly higher than those in the cases with mild acute pancreatitis (MAP) and normal controls (ET: 147.56 ± 10.65 ng/L vs 85.13 ± 9.47, 52.27 ± 6.23 ng/L, P < 0.01; P-selectin: 85.32 ± 6.21 µg/L vs 30.01 ± 4.82, 10.26 ± 2.57 µg/L, P < 0.01), and the levels of ET and P-selectin were positively correlated in SAP (r = 0.705, P < 0.01). After treatment, the levels of ET and P-selectin in group B were obviously decreased as compared with those before treatment (ET: 69.77 ± 7.65 ng/L vs 100.54 ± 11.41 ng/L, P < 0.01; P-selectin: 4.07 ± 4.75 µg/L vs 54.52 ± 9.79 µg/L, P < 0.01). The average in-hospital time of group B was distinctly shorter than that of group A (9.76 ± 1.77 d vs 14.27 ± 2.55 d, P < 0.01).

CONCLUSION: Endothelin and P-selectin may be involved in the pathogenesis of AP, and SM is effective in the treatment of AP.

Absolute oxygen tension (pO(2)) in murine fatty and muscle tissue as determined by EPR

The absolute partial pressure of oxygen (pO(2)) in the mammary gland pad and femoral muscle of female mice was measured using EPR oximetry at 700 MHz. A small quantity of lithium phthalocyanine (LiPc) crystals was implanted in both mammary and femoral muscle tissue of female C3H mice. Subsequent EPR measurements were carried out 1-30 days after implantation with or without control of core body temperature. The pO(2) values in the tissue became stable 2 weeks after implantation of LiPc crystals. The pO(2) level was found to be higher in the femoral muscle than in the mammary tissue. However, the pO(2) values showed a strong dependence on the core body temperature of the mice. The pO(2) values were responsive to carbogen (95% O(2), 5% CO(2)) breathing even 44-58 days after the implantation of LiPc. The LiPc linewidth was also sensitive to changes in the blood supply even 60 days after implantation of the crystals. This study further validates the use of LiPc crystals and EPR oximetry for long-term non-invasive assessment of pO(2) levels in tissues, underscores the importance of maintaining normal body core temperature during the measurements, and demonstrates that mammary tissue functions at a lower pO(2) level than muscle in female C3H mice.

Attenuation of proinflammatory gene expression and microcirculatory disturbances by endothelin A receptor blockade after orthotopic liver transplantation in pigs

BACKGROUND

Endothelin-1 (ET-1), a very potent mediator of vasoconstriction, leads to microcirculatory disturbances and release of proinflammatory cytokines under pathophysiologic conditions. Our aim was to evaluate the effect of a selective ET(A)-receptor antagonist (ET(A)-RA) on cold ischemia/reperfusion (I/R) injury in a pig model.

METHODS

Twenty pigs revealed orthotopic liver transplantation. The animals were randomized into 2 groups: control pigs received isotonic saline; the treated group received the selective ET(A)-RA BSF 208075 at the beginning of reperfusion. On postoperative days 4 and 7, animals were re-laparotomized to obtain tissue specimens. Liver tissue samples were collected and quantitative mRNA expression for prepro-ET-1, ET(A) receptor, pro-IL-1beta, pro-IL-6, pro-TNF-alpha, and endothelial nitric oxide synthase was analyzed using the TaqMan system. Additionally, immunohistochemical analysis for ET-1 was performed. Hepatic microcirculation was evaluated by laser Doppler flow measurement and partial pressure of oxygen and carbon dioxide measurements with the Paratrend sensor. Postischemic liver damage was monitored by measurement of liver enzymes and by histologic analysis using a semiquantitative scoring classification.

RESULTS

Treatment with the ET(A)-RA significantly reduced the severity of I/R injury evidenced by lower serum AST, ALT and GLDH. Analysis of partial pressure of oxygen and blood flow revealed a significant improvement of capillary perfusion and blood flow in the treated group and was associated with a relevant reduction of tissue injury. One hour after reperfusion, quantitative RT-PCR revealed significantly lower expression of prepro-ET-1, ET(A) receptor, endothelial nitric oxide synthase, pro-TNF-alpha, pro-IL-1beta and pro-IL-6 in the therapy group. Immunohistochemical analysis demonstrated significantly reduced ET-1 immunostaining after therapy. Histologic investigation suggested less tissue damage in treated animals.

CONCLUSIONS

Treatment with the selective ET(A)-RA BSF 208075 has protective effects on microcirculation after liver transplantation. ET(A)-RA not only affects the expression of vasoactive genes, but also decreases gene expression of proinflammatory cytokines such as TNF-alpha, IL-1beta and IL-6.

The endothelin/nitric oxide balance determines small-for-size liver injury after reduced-size rat liver transplantation

Small-for-size (SFS) liver graft injury is probably related to microcirculatory disorders due to an imbalance of vasoconstricting, e.g. endothelin (ET)-1, and vasorelaxing mediators, e.g. nitric oxide (NO). We studied the role of ET-1/NO balance and the effect of an endothelin A receptor (ETAR) antagonist on SFS injury after liver resection and reduced-size liver transplantation (RSLT). One hundred twenty-six Lewis rats were divided into five groups: (I) 70% liver resection, (II) 70% liver resection treated with the ETAR antagonist LU 135252 (1 mg/kg b.w. i.v.), (III) RSLT (30% residual liver volume), (IV) RSLT treated with the ETAR antagonist, (V) sham operation. Liver microcirculation was measured by intravital microscopy. ET-1, ETAR, endothelial NO-synthase (eNOS), activation of Kupffer cells (KCs) and parenchymal injury were studied by immunohistology. Survival and liver function were followed up to 14 days. RSLT led to increased ET-1, ETAR and decreased eNOS protein expression, accompanied by activation of KC, reduced perfusion rate, vasoconstriction and elevated sinusoidal blood flow, as well as hepatocellular damage, impaired liver function and impaired survival. ETAR blockade (groups II + IV) improved the ET-1/NO balance, attenuated microcirculatory disorders and improved hepatocellular apoptosis and liver function. Microcirculatory disorders related to an ET-1/NO imbalance may contribute to SFS liver injury. Maintenance of ET-1/NO balance by blocking ETAR reduces SFS injury by protecting liver microcirculation, thus reducing hepatocellular damage.

Amelioration of microcirculatory damage by an endothelin A receptor antagonist in a rat model of reversible acute liver failure

BACKGROUND/AIMS

Hepatocellular damage in acute liver failure (ALF) is aggravated by proinflammatory and cytotoxic mediators released from sinusoidal-lining cells. We studied a selective endothelin A receptor (ETAR) antagonist for its potential influence on the microcirculation in the setting of ALF.

METHODS

Seventy Wistar rats were divided into five groups: (I) induction of ALF by a 70% liver resection combined with injection of 400 microg/kg endotoxin, (II) ALF treated with the ETAR antagonist LU 135252 (1 mg/kg b.w. i.v.), (III) sham operation, (IV) injection of endotoxin, (V) 70% liver resection. Liver microcirculation was measured by intravital microscopy. Parenchymal injury, growth fractions, endothelin (ET)-1 and ETAR were studied by histology and immunohistology. Survival, liver function, and morphology were followed up to 14 days.

RESULTS

100% mortality, impaired liver function, widespread endothelial lesions, highest ET-1 and ETAR levels, a decreased perfusion rate, reduced sinusoidal diameter, as well as an increase in both leukocyte-endothelium interactions and sinusoidal blood flow were observed after induction of ALF. ETAR antagonist-treated rats showed decreased ET-1 and ETAR levels as well as improved microcirculatory function, morphology, liver function, and 85% survival.

CONCLUSIONS

Microcirculatory disturbances correlate with liver dysfunction in ALF. ETAR blockade represents a new therapeutic approach to ALF by reducing microcirculatory lesions and their sequelae.