Rapid increase in the activity of enzymes of eicosanoid synthesis in hepatic and extrahepatic tissues after experimental liver transplantation

Preliminary observations of an ex vivo normothermic whole blood machine perfusion in an experimental liver transplant porcine model

BACKGROUND

Even though transplantation is an essential treatment with no viable alternatives, a significant worldwide donor shortage persists. In this study, we assessed the metabolism of livers that underwent extended periods of circulatory death and subsequently conducted functional validation through transplantation to explore the feasibility of using livers from an uncontrolled donor after circulatory death (u-DCD).

METHODS

A donor model simulating u-DCD was constructed using pigs. The prolonged warm ischemia time (WIT) was set to 60, 120, and 180 minutes, and the liver function was evaluated after 24 hours of perfusion using an originally developed normothermic perfusion system. Based on the results, functional confirmation by transplantation was performed on the 2 groups with prolonged WIT of 60 and 180 minutes.

RESULTS

Based on the 24-hour perfusion of the liver alone, we evaluated the function by transplanting the WI 60-minute model and 180-minute model (N = 3 each). Warm ischemia was 73.5 ± 3.7 minutes and 188 ± 3 minutes in the 60-minute model and 180-minute model, respectively. In the model with 60 minutes of WI, one case survived until the endpoint, and 2 cases survived between 8 and 12 hours, whereas, in the model with 180 minutes of WI, they died within 6 hours.

CONCLUSION

We constructed a completely uncontrolled circulatory arrest model without anticoagulation and showed the possibility of using u-DCD livers by ex vivo machine perfusion and transplantation.

Analysis of polyunsaturated fatty acids and the omega-6 inflammatory pathway in hepatic ischemia/re-perfusion injury

The aim of the present study was to assess omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acids (PUFAs) in liver tissue and evaluate changes in the n‑6-associated inflammatory pathway following liver ischemia/re‑perfusion (IR) injury. Male Wistar rats which were allowed free access to standard rat chow were included in the study. Blood vessels supplying the median and left lateral hepatic lobes were occluded with an arterial clamp for 60 min, followed by 60 min of re‑perfusion. Levels of arachidonic acid (AA, C20:4n‑6), dihomo‑gamma‑linolenic acid (DGLA, C20:3n‑6), eicosapentaenoic acid (EPA, C20:5n‑3) and docosahexaenoic acid (DHA, C22:6n‑3) in liver tissue were determined by an optimized multiple reaction monitoring method using ultra fast‑liquid chromatography coupled with tandem mass spectrometry. Phospholipase A2 (PLA2), cyclooxygenase (COX) and prostaglandin E2 (PGE2) were measured in tissue samples to evaluate changes in the n‑6 inflammatory pathway. Total histopathological score of cellular damage were significantly increased following hepatic IR injury. n‑3 and n‑6 PUFA levels were significantly increased in post‑ischemic liver tissue compared to those in non‑ischemic controls. No significant difference was observed in the AA/DHA and AA/EPA ratio in post‑ischemic liver tissues compared with that in the control. Tissue activity of PLA2 and COX as well as PGE2 levels were significantly increased in post‑ischemic liver tissues compared to those in non‑ischemic controls. The results of the present study suggested that increased hydrolysis of fatty acids via PLA2 triggers the activity of COX and leads to increased PGE2 levels. Future studies evaluating agents which block the formation of eicosanoids derived from n‑6 PUFAs may facilitate the development and application of treatment strategies in liver injury following IR.

Inhibition of neutral sphingomyelinase decreases arachidonic acid mediated inflammation in liver ischemia-reperfusion injury

This study aimed to determine the role of selective neutral sphingomyelinase (N-SMase) inhibition on arachidonic acid (AA) mediated inflammation following liver ischemia-reperfusion (IR) injury. Selective N-SMase inhibitor was administered via intraperitoneal injections. Liver IR injury was created by clamping blood vessels supplying the median and left lateral hepatic lobes for 60 min, followed by 60 min reperfusion. Levels of AA in liver tissue were determined by multiple reaction monitoring (MRM) using ultra fast-liquid chromatography (UFLC) coupled with tandem mass spectrometry (MS/MS). Phospholipase A₂ (PLA₂), cyclooxygenase (COX) and prostaglandin E₂ (PGE₂) were measured in liver tissue. Arachidonic acid levels, activity of PLA₂, COX and PGE₂ levels were significantly increased in postischemic liver tissue compared to nonischemic controls. N-SMase inhibition significantly decreased COX activity and PGE₂ levels in postischemic liver. Future studies evaluating agents blocking N-SMase activity can facilitate the development of treatment strategies to alleviate inflammation in liver I/R injury.

Effects of a bradykinin B(2) receptor antagonist on ischemia-reperfusion injury in a canine lung transplantation model

BACKGROUND

This study investigated the effects of a bradykinin B(2) receptor antagonist, FR173657 (FR), on ischemia-reperfusion (I/R) injury in a canine lung transplantation model.

METHODS

Eighteen pairs of weight-matched dogs were randomly divided into 3 groups. Six pairs were assigned to the FR(D+R) group, in which FR (100 nmol/kg/h) was administered to the transplant donor continuously beginning 30 minutes before ischemia until the onset of ischemia, and FR was administered to the transplant recipient beginning 30 minutes before reperfusion and continuing for 2 hours after reperfusion. Another 6 pairs of dogs were assigned to the FR(R) group, in which FR was administered only to the recipient in the same manner as in the FR(D+R) group. The other pairs were assigned to the control group, in which vehicle alone was administered. Orthotopic left lung transplantation was performed after 12-hour cold storage in Euro-Collins solution. Fifteen minutes after reperfusion, the right pulmonary artery and the right stem bronchus were ligated. The animals were measured for 4 hours after reperfusion for left pulmonary vascular resistance (L-PVR), cardiac output (CO), arterial oxygen pressure (PaO(2)) and alveolar-arterial oxygen pressure difference (A-aD(O(2))). Lung specimens were harvested for measurement of the wet-to-dry lung weight ratio (WDR), histopathologic studies and polymorphonuclear neutrophil (PMN) count.

RESULTS

Compared with the control group, PaO(2), A-aDO(2), L-PVR and CO were all significantly (p < 0.05) improved and WDR significantly (p < 0.05) lower in both the FR(D+R) and FR(R) groups. Moreover, in the FR-treated groups, histologic tissue edema was mild, and PMN infiltration was significantly (p < 0.05) reduced.

CONCLUSIONS

The bradykinin B(2) receptor antagonist, FR173657, ameliorates I/R injury in lung grafts, indicating that protection of lung grafts can be achieved by the administration of FR solely to the transplant recipient.

Kupffer cells play an important role in the cytokine production and activation of nuclear factors of liver grafts from non-heart-beating donors

In the non-heart-beating donor (NHBD) deterioration of microcirculation of the liver graft is strongly associated with secretion of cytokines and eicosanoids. In this study we investigated the excretion of cytokines, eicosanoids, and DNA binding activity of transcription factors in the grafts from NHBD and evaluated the effects of the elimination of Kupffer cells on them. The purpose of this study was to clarify the impact of Kupffer cells on transcription factor activity and the that of cytokine and eicosanoid production on reperfusion injury of liver grafts from NHBD. Wistar rats were allocated to four groups: (a). control group: livers were extracted under heart-beating conditions and perfused without cold storage, (b). heart beating (HB) group: livers extracted under heart-beating conditions were perfused after 6 h of cold storage, (c). non-heart-beating (NHB) group: livers extracted after cardiac arrest were perfused after cold storage, (d). Kupffer cell eliminated (KE) group: liposome-encapsulated dichloromethylene diphosphonate was intravenously administered to eliminate Kupffer cells before extraction, and the liver was perfused after cold storage. Cytokines and eicosanoids in perfusate were measured. DNA binding activity of nuclear factor kappa B, activating protein 1, and nuclear factor-interleukin 6 of tissue were investigated. Concentrations of interleukin 1 beta and thromboxane B(2) in the perfusate were significantly higher in NHB group, but they were completely suppressed in the KE group. A rise in binding activity of nuclear factor kappa B and activating protein 1 was not observed during cold storage in any groups, but these activities did increase remarkably after reperfusion. Significant buildup of those activities were recognized in the NHB group, and this phenomenon was inhibited in the KE group. The histological structures of the sinusoid in the KE group were well maintained, as with those of the control group. These results indicate that cytokines, eicosanoids, and the DNA binding activity of the transcripton factor are strongly associated with reperfusion injury, and Kupffer cells play an important role in this mechanism in grafts from NHBDs.

The effect of a selective cyclooxygenase-2 inhibitor in extended liver resection with ischemia in dogs

BACKGROUND

Pringle's procedure is commonly used during liver surgery, and it sometimes causes liver failure. Metabolites of arachidonic acid, which are converted by cyclooxygenase (Cox), are involved in ischemia-reperfusion injury. This study evaluated the effects of FK 3311, which selectively inhibits Cox-2, on ischemia-reperfusion injury during liver resection in dogs.

MATERIALS AND METHODS

The animals were divided into four groups and subjected to 60 min of warm ischemia by partial inflow occlusion. The FK-treated groups (FK0.2: 0.2 mg/kg, FK1: 1 mg/kg, FK3: 3mg/kg) received FK3311, and the control group received vehicle. Following reperfusion, the nonischemic lobes were resected and remnant liver function was evaluated.

RESULTS

Tissue blood flow and serum glutamic oxaloacetic transaminase, glutamic pyruvic transaminase, and lactate dehydrogenase were significantly better in the FK1 and FK3 groups, especially FK1, than in the control group. Thromboxane B(2) was significantly lower in the FK1 and FK3 groups than in the control group. The level of 6-keto-prostaglandin F(1alpha) was significantly lower in the FK3 group and relatively unchanged in the FK1 group. Histological damage was milder in the FK1 group. There were significantly fewer polymorphonuclear neutrophils in the FK1 group than in the control group.

CONCLUSIONS

FK3311 ameliorates the ischemia-reperfusion injury caused by Pringle's procedure during extensive liver resection. This agent may be clinically useful in extended liver surgery involving vascular isolation.

Effects of FK3311 on pulmonary ischemia-reperfusion injury in a canine model

BACKGROUND

This study investigated the effects of a selective COX-2 inhibitor, FK3311, on warm ischemia-reperfusion (I/R) injury in the canine lung.

MATERIALS AND METHODS

Sixteen adult mongrel dogs were used in this study. In the FK group (n = 8), FK (1 mg/kg) was administered intravenously 15 min before ischemia and 15 min before reperfusion. In the control group (n = 8), a vehicle was injected in the same manner. Warm ischemia was induced for 3 h by clamping the left pulmonary artery, veins, and bronchus. Five-minute clamping tests of the right pulmonary artery were performed before ischemia and 30 min after reperfusion. During the test, left pulmonary vascular resistance (L-PVR), cardiac output (CO), and arterial oxygen pressure (PaO(2)) were measured. The lung specimens were simultaneously harvested for wet-to-dry weight ratio (WDR) measurements, histopathological studies, and polymorphonuclear neutrophil (PMN) counts. Serum thromboxane (Tx) B(2) and 6-keto-prostaglandin (PG) F(1alpha) (stable metabolites of TxA(2) and PGI(2), respectively) were also measured 30 min after reperfusion.

RESULTS

L-PVR, CO, PaO(2), and WDR were significantly (P < 0.05) better in the FK group than in the control group. Histological tissue edema was mild, and PMN infiltration was significantly (P < 0.05) reduced in the FK group compared to the control group. The serum TxB(2) levels were significantly (P < 0.05) lower in the FK group than in the control group, while 6-keto-PGF(1alpha) levels were not significantly (P < 0.05) reduced. Two-day survival rate was significantly (P < 0.05) better in the FK group than in the control group.

CONCLUSIONS

FK has protective effects on pulmonary I/R injury stemming from marked inhibition of TxA(2).

Anti-ICAM-1 blockade reduces postsinusoidal WBC adherence following cold ischemia and reperfusion, but does not improve early graft function in rat liver transplantation

BACKGROUND/AIM

The present in vivo study investigated the impact of a monoclonal antibody directed against the intercellular adhesion molecule-1 (ICAM-1) on initial microvascular reperfusion injury after liver transplantation.

METHODS

Orthotopic, syngeneic liver transplantation including arterial reconstruction was performed in male Lewis rats after 24 h graft storage in University of Wisconsin (UW) solution at 4 degrees C. Animals received either an anti-ICAM-1 antibody (n=7), an IgG1 control antibody (n=8) or saline only (n=7). Hepatic microvascular alterations during the initial 90 min of reperfusion were assessed using intravital fluorescence microscopy. Early graft dysfunction was determined by analysis of bile flow.

RESULTS

After treatment with anti-ICAM-1 mAb, hepatic microvascular perfusion was found improved when compared with that of IgG1- and saline-treated controls. In addition, anti-ICAM-1 mAb effectively reduced the number of permanently adherent white blood cells in postsinusoidal venules (284.4+/-59.1 mm(-2) vs IgG1: 371.9+/-26.7 mm(-2) and saline: 431.8+/-46.4 mm(-2); p<0.05). In contrast, the number of stagnant white blood cells in sinusoids was higher (p<0.05) in liver grafts with blocked ICAM-1 (320.6+/-17.2 mm(-2)) compared with that of IgG1- (215.2+/-11.1 mm(-2)) and saline-treated controls (226.4+/-14.0 mm(-2)). Measurement of hepatic uptake of fluorescent-labeled latex particles did not reveal significant differences in phagocytic activity. Finally, bile flow also did not differ between the three groups studied.

CONCLUSION

Together these results indicate that ICAM-1 is involved in the process that mediates white blood cells adherence in postsinusoidal venules, whereas in hepatic sinusoids other mechanisms apart from ICAM-1-mediated white blood cells adherence seem to be fundamental for posttransplant white blood cells accumulation. Our data further suggest that white blood cells adherence in postsinusoidal venules via ICAM-1 does not make a major contribution to the pathogenesis of early cold ischemia/reperfusion injury after liver transplantation.

Metabolism of prostaglandins in porcine liver transplantation with a graft harvested after 30- and 60-minute warm ischemia

The influence of warm ischemia on the metabolism of prostaglandins was investigated using a pig liver transplantation model employing the temporary portal arterialization technique. Eighteen pigs were divided into three groups according to warm ischemia time: 0 min (group I, n = 6), 30 min (group II, n = 6), and 60 min (group III, n = 6). During portal arterialization, the hepatic venous prostaglandin E2 (PGE2) level in group III (3356.0 +/- 1011.8 pg/ml) was significantly higher than that in group I (831.7 +/- 182.1 pg/ml; P = 0.0285). The hepatic venous PGE2 levels were significantly higher than the arterial counterparts in all groups both at the beginning and during portal arterialization. At 60 min after portal revascularization, the arterial PGE2 level in group III (886.7 +/- 268.0 pg/ml) was significantly higher than that in group I (99.0 +/- 18.6 pg/ml; P = 0.0116) and II (204.2 +/- 65.4 pg/ml; P = 0.0282). Neither thromboxane B2 (TXB2) nor 6-keto PGF1 alpha showed any significant differences. In conclusion, the intraoperative changes of PGE2 thus reflected the degree of warm ischemic damage, and PGE2 could also be released from the graft. On the other hand, the increased levels of TXB2 and 6-keto PGF1 alpha were thought to have an extrahepatic origin.

Effect of thromboxane synthetase inhibitor on non-heart-beating donors in rat orthotopic liver transplantation

BACKGROUND

The use of non-heart-beating donors could relieve donor organ shortage provided that the outcome of the recipients is not jeopardized.

METHODS

In this study we evaluated the effect of thromboxane synthetase inhibitor (OKY-046) on non-heart-beating donors in orthotopic liver transplantation in rodents. OKY-046 (OKY group, n = 8) or vehicle (control group, n = 8) was given to the donor animals for 60 minutes before the induction of 30 minutes of warm ischemia to the liver before transplantation and survival, and several parameters were compared between the two groups.

RESULTS

All recipients in the control group died within 2 days, whereas 67% of those of the OKY group had a 2-day survival and 44% had a 2-week survival (p < 0.01). Bile output from the allograft for 2 hours after reperfusion was significantly larger in the OKY group at all time points (p < 0.05). Furthermore, serum transaminase levels 10 minutes after reperfusion were significantly lower in the OKY group (p < 0.05), although those 120 minutes after reperfusion were comparable between the two groups. The thromboxane B2 level in liver tissue 10 and 120 minutes after reperfusion was significantly lower in the OKY group compared with the control group (p < 0.02 and p < 0.05, respectively).

CONCLUSIONS

These results indicate that OKY-046 given to the donor before the induction of warm ischemia could ameliorate ischemia/reperfusion injury of the hepatic allograft by reducing thromboxane A2 production after reperfusion.

Identification of novel metabolites of prostaglandin E2 formed by isolated rat hepatocytes

The metabolism of prostaglandin E2 (PGE2) in isolated rat hepatocytes led to the formation of four major as well as several minor products which were structurally characterized using electrospray tandem mass spectrometry. The major metabolites identified included dinor-PGE1, dinor-PGE2, and tetranor-PGE1 and the taurine conjugates of dinor-PGE1 and dinor-PGE2. Several minor metabolites including the taurine conjugates of PGE2 and tetranor PGE1 along with a glucuronide conjugate of PGE2 were also identified. These taurine conjugates had not been previously identified in studies of PGE2 metabolism, yet comprised nearly 50% of the mixture of metabolites after 40-min incubations. Experiments carried out with deuterium-labeled PGE2 ([3,3,4,4-D4]PGE2) resulted in the complete loss of all deuterium atoms in dinor-PGE1, dinor-PGE2, and tetranor metabolites during incubation with hepatocytes. Metabolism via classic beta-oxidation pathways would predict one deuterium atom retained by dinor-PGE1 and two deuterium atoms retained by dinor-PGE2. When PGE2 was incubated with isolated rat hepatocytes in buffer containing 30% D2O, substantial incorporation (30%) of one deuterium atom could be observed in the dinor metabolites along with 10% incorporation into the tetranor and residual PGE2. Deuterium-labeled PGE1 ([3,3,4,4-D4]PGE1) was metabolized to D2-dinor-PGE1, tetranor-PGE1, and the taurine conjugate of D2-dinor-PGE1 by isolated rat hepatocytes. The loss of deuterium during metabolism of the deuterated substrates of PGE2, but not PGE1, as well as the incorporation of deuterium atoms from the aqueous solvent into PGE2 metabolites suggested that the delta 5 double bond and sequential isomerization reactions lead to eventual exchange of the protons from carbon atom 4 of PGE2 with water.

Role of leukotrienes B4 and C4 in liver allograft rejection

Previous studies have shown that eicosanoids may act in vitro as immunoregulatory substances. In this study, the concentrations of leukotriene B4 (LTB4) and leukotriene C4 (LTC4) were measured in a model of allograft rejection. Six orthotopic allotransplants of the liver were performed in dogs without the administration of immunosuppressives. LTB4 levels showed an increase coinciding with the start of rejection, significant differences being present between the basal levels and those measured 24 h post-revascularization (P < 0.05), and every day from the 3rd postoperative day (P < 0.01). LTB4 rose before the parameters generally used in evaluating rejection. LTC4 levels increased significantly (P < 0.001) in the first 24 h, and experienced no further variations. LTB4 may play an important role in the mechanisms which bring about the response to the allograft. This substance could be a specific and early marker for rejection.