Evidence that both cyclosporin and azathioprine prevent warm ischemia reperfusion injury to the rat liver

Heat shock preconditioning inhibits CD4+ T lymphocyte activation in transplanted fatty rat livers

Heat shock preconditioning (HPc) of fatty donor livers significantly increases recipient survival in rats. We investigated to what extent the blockade of Kupffer cells by gadolinium chloride (GdCl3) can mimic the effect of HPc and the involvement of liver CD4+ T lymphocytes in HPc. Fatty liver was experimentally induced in Lewis rats by a choline- and methionine-deficient diet. Fatty liver donors were pretreated with HPc (42.5 degrees C for 10 min), the Kupffer cell inhibitor GdCl3, or placebo (sham group). Donors were then harvested, stored in University of Wisconsin preservation solution for 12 h at 4 degrees C, and transplanted into normal syngeneic rats. Hepatic injury (alanine aminotransferase) and serum cytokines (interleukin-12p70, tumor necrosis factor-alpha, and interleukin-10) of recipients increased at 3 h, then decreased, and increased again at 24 h after transplantation. HPc treatment diminished both the early and later phases of this biphasic response and improved recipient survival. GdCl3 reduced these cytokines in the early but not the later phase and did not reduce neutrophil accumulation or improve the recipient survival. HPc, but not GdCl3 treatment, also reduced the number of liver CD4+ T lymphocytes and their interferon-gamma production. We conclude that HPc, but not GdCl3 treatment, prevents biphasic liver injury and the activation of liver CD4+ T lymphocytes in transplanted fatty donor livers.

Gene therapy for liver transplantation using adenoviral vectors: CD40-CD154 blockade by gene transfer of CD40Ig protects rat livers from cold ischemia and reperfusion injury

Liver injury induced by ischemia/reperfusion (I/R) is the prime factor in delayed or loss graft function following transplantation. CD4+ T lymphocytes are key cellular mediators of antigen-independent inflammatory response triggered by I/R. We attempted to modulate rat liver I/R injury by targeted gene therapy with CD40Ig, which blocks the CD40-CD154 costimulation pathway. One hundred percent of Ad-CD40Ig-pretreated orthotopic liver transplants (OLTs) subjected to 24 h of cold (4 degrees C) ischemia survived > 14 days (vs 50% in untreated/Ad-beta-gal groups). Ad-CD40Ig treatment decreased sGOT levels and depressed neutrophil infiltration, compared with controls. These functional data correlated with histological Suzuki's grading of hepatic injury, which in untreated/Ad-beta-gal groups showed severe necrosis (> 60%) and moderate to severe sinusoidal congestion; the Ad-CD40Ig-pretreated group revealed minimal sinusoidal congestion/necrosis. Unlike in controls, OLT expression of mRNA coding for IL-2/IFN-gamma remained depressed, whereas that of IL-4/IL-13 reciprocally increased in the Ad-CD40Ig group. Ad-CD40Ig reduced frequency of TUNEL+ cells and pro-apoptotic Caspase-3, but enhanced antioxidant HO-1 and anti-apoptotic Bcl-2/Bcl-xl expression. Thus, prolonged blockade of CD40-CD154 by CD40Ig exerts potent cytoprotection against hepatic I/R injury. These results provide the rationale for a novel gene therapy approach to maximize the organ donor pool through the safer use of liver transplants exposed to prolonged cold ischemia.

Molecular mechanisms of hepatic ischemia-reperfusion injury and preconditioning

Ischemia-reperfusion injury is, at least in part, responsible for the morbidity associated with liver surgery under total vascular exclusion or after liver transplantation. The pathophysiology of hepatic ischemia-reperfusion includes a number of mechanisms that contribute to various degrees in the overall injury. Some of the topics discussed in this review include cellular mechanisms of injury, formation of pro- and anti-inflammatory mediators, expression of adhesion molecules, and the role of oxidant stress during the inflammatory response. Furthermore, the roles of nitric oxide in preventing microcirculatory disturbances and as a substrate for peroxynitrite formation are reviewed. In addition, emerging mechanisms of protection by ischemic preconditioning are discussed. On the basis of current knowledge, preconditioning or pharmacological interventions that mimic these effects have the greatest potential to improve clinical outcome in liver surgery involving ischemic stress and reperfusion.

CD154-CD40 T-cell costimulation pathway is required in the mechanism of hepatic ischemia/reperfusion injury, and its blockade facilitates and depends on heme oxygenase-1 mediated cytoprotection

BACKGROUND

Ischemia/reperfusion (I/R) injury remains an important clinical problem that affects both early and later allograft outcome. This study was designed to analyze the role of T cells and CD154-CD40 T- cell costimulation pathway in a mouse liver I/R model.

METHODS AND RESULTS

Ninety minutes of warm ischemia followed by 4 h of reperfusion in wild-type (WT) mice resulted in a significant hepatic damage, as assessed by liver function (serum alanine aminotransferase [sALT] levels), local neutrophil accumulation (myeloperoxidase activity), and histology (Suzuki's score). In contrast, T-cell deficiency (in T-cell deficient [nu/nu] mice), disruption of the CD154 signaling (in knockout [KO] mice), or its blockade in WT recipients (after MR1 monoclonal antibody [mAb] treatment), virtually prevented hepatic I/R insult. Unlike CD154-deficient T cells, adoptive transfer of WT spleen cells fully restored hepatic I/R injury in nu/nu mice. Finally, the improved hepatic function in CD154 KO recipients, WT mice treated with CD154 mAb, or nu/nu mice infused with CD154-deficient cells resulted in consistently enhanced expression of heme oxygenase-1 (HO-1), a heat-shock protein with cytoprotective functions.

CONCLUSION

This study confirms the importance of T cells, and documents for the first time the role of CD154 costimulation signals in the mechanism of hepatic I/R injury. We also show that CD154 blockade-mediated cytoprotection results and depends on HO-1 overexpression. Our data provide the rationale for human trials to target CD154-CD40 costimulation in hepatic I/R injury, particularly in the transplant patient.

Immunodepressants ameliorate normothermic ischemia injury to the rat liver by down-regulating tumor necrosis factor, not by alleviation of lipid peroxidative injury

Mechanisms by which immunodepressants (Cyclosporine, CsA; FK 506, FK; Azanthioprine, AZA) ameliorate warm ischemic injury of the liver were examined. Female Sprague-Dawley rats were subjected to 60-min of normothermic liver ischemia. Animals were assigned to one of four groups: group I, control with vehicle treatment; groups II, III, and IV, treatment with CsA (10 mg/kg), FK (1 mg/kg), and AZA (1 mg/kg), respectively. The immunosuppressive agents were given per os for 4 consecutive days prior to the induction of hepatic ischemia. In addition to a survival study, plasma levels of endotoxin, serum activities of tumor necrosis factor-alpha (TNF), plasma levels of phosphatidylcholine hydroperoxide (PCOOH) as a lipid peroxide, and serum alanine aminotransferase (ALT) were investigated in blood samples collected from the suprahepatic vena cava. A 7-day survival period was significantly higher in the immunosuppressed animals. Serum TNF levels were elevated and peaked at 3 h following reperfusion. When, the peak values were compared, the animals given immunodepressants had significantly lower levels of TNF (217.0 +/- 40.6 pg/ml for group I, 67.6 +/- 13.7 for group II, 87.9 +/- 28.3 for group III and 89.1 +/- 19.9 for group IV; Mean +/- SEM). Plasma PCOOH levels were also elevated following reperfusion, but with no statistical difference among the groups. Our data suggest that immunodepressants ameliorate warm ischemia/reperfusion injury through modulation of TNF production and not through a diminution of lipid peroxidative injury.

Limited use of cyclosporin A in skeletal muscle ischemia--reperfusion injury

Reperfusion injury is propagated by an inflammatory-mediated tissue edema and damage after reestablishment of vascular flow following an initial ischemic insult. In the field of transplantation, cyclosporin A(CsA) provides protection against chronic graft rejection through lymphocyte immunosuppression. Evidence for an independent protective effect of CsA against ischemia-reperfusion (IR) injury during organ transfer has prompted studies showing the benefit of CsA in various ischemia-exposed visceral organs. The authors hypothesized that CsA administration may similarly benefit IR injury after skeletal muscle amputations. To determine the effects of CsA on IR injury the authors induced 4 hours of ischemia on the gracilis muscle in a rat model. CsA (15 mg per kilogram orally) was administered in two experimental groups: (1) preischemic (N = 6): 48, 24, and 3 hours before ischemia; and (2) postischemic (N = 6): 30 minutes after induction of ischemia. The effects of CsA on IR muscle injury were observed in each of the experimental groups as well as a control group (N = 6) exposed to similar ischemia and administered a saline vehicle. Muscle viability (nitro blue tetrazolium staining) and muscle edema (wet-to-dry weight ratio) were assessed 24 hours after reperfusion. The preischemic CsA-treated gracilis muscle group demonstrated improved muscle viability (39.1 +/- 4.8%) when compared with the ischemic control muscle group (23.8 +/- 7.1%; p = 0.039). Furthermore, the preischemic CsA-treated muscle group demonstrated decreased edema (1.137 +/- 0.095 times the contralateral nonischemic muscle) when compared with the control ischemic muscle group (1.248 +/- 0.045 times the contralateral nonischemic muscle; p = 0.011). Although a trend toward improved muscle viability (32.1 +/- 4.2%) and decreased edema formation (1.200 +/- 0.062 times the contralateral nonischemic muscle) was observed in the peri-ischemic CsA-treated group when compared with the control ischemic muscle group, these differences were not significant. These observations confirm the beneficial effects of preischemic CsA therapy observed in organ transplantation research and suggest limited clinical use of peri-ischemic CsA therapy for patients with musculoskeletal amputations.

Cold liver ischemia-reperfusion injury critically depends on liver T cells and is improved by donor pretreatment with interleukin 10 in mice

Kupffer cells are thought to mediate most of the deleterious effects of liver ischemia-reperfusion injury. The role of liver T cells and the impact of resident cell deactivation by interleukin 10 (IL-10) have never been addressed. Using a model of ex vivo liver cold ischemia and reperfusion, we assessed liver injury, tumor necrosis factor (TNF) and interferon gamma (IFN-gamma) release from livers of balb/c mice, nude mice, nude mice reconstituted with T cells, and gadolinium balb/c pretreated mice. The anti-inflammatory cytokine IL-10 was then used to define the best strategy of administration potentially able to modulate ischemia-reperfusion injury. For this purpose IL-10 was administered to the donor before liver harvesting, in the preservation medium during cold ischemia or during reperfusion. TNF and IFN-gamma were released time dependently and paralleled liver injury after reperfusion of cold preserved livers. Reperfused livers from nude or gadolinium pretreated mice disclosed a dramatic decrease in TNF and IFN-gamma release. Tissue injury was reduced by 51% in the absence of T cells and by 88% when Kupffer cells were deactivated. This effect was reverted by T-cell transfer to nude mice. Only donor pretreatment with IL-10 or IL-10 infusion during reperfusion led to a significant decrease in liver injury, TNF, and IFN-gamma release (-66% or -41%, -95% or -94%, and -70% or -70%, respectively). In conclusion, liver resident T cells are critically involved in cold ischemia-reperfusion injury and pretreatment of the donor with IL-10 decreases liver injury and the release of T-cell- and macrophage-dependent cytokines.

Protection by cyclosporine A against normothermic liver ischemia-reperfusion in pigs

BACKGROUND

Cyclosporine A (CYA) is primarily utilized as an immunosuppressant, but its mechanisms of action (including decreased neutrophilic free radical production and stabilization of mitochondrial and lysosomal membranes) may have beneficial effects in ischemia and reperfusion (IR) injury. This study was undertaken to examine the effect of CYA pretreatment on porcine liver histopathologic changes and enzymatic release caused by ischemia and reperfusion.

MATERIALS AND METHODS

CYA was administered orally for 4 days prior to surgery in two doses (10 or 20 mg/kg) while controls received only the control vehicle. Pigs were then exposed to 4 h of hepatic ischemia followed by 2 h of reperfusion.

RESULTS

Significant decreases in AST levels compared to controls were seen in high dose CYA pigs at the end of ischemia and at 30-min intervals during the reperfusion period. Controls exhibited necrotic hepatocytes and severe inflammatory cell infiltration, while high dose CYA animals demonstrated mild inflammatory cell infiltrates. Controls had decreased survival--20% did not survive reperfusion.

CONCLUSIONS

This study indicates that CYA may be useful in decreasing initial damage resulting from warm hepatic IR injury.

Immunosuppressants decrease neutrophil chemoattractant and attenuate ischemia/reperfusion injury of the liver in rats

BACKGROUND

Neutrophils may play an important role in the development of liver ischemia/reperfusion injury. We investigated the effects of the immunosuppressants azathioprine (AZA), cyclosporine A (CsA), tacrolimus (FK506), and rapamycin (RPM) on the expression of cytokine-induced neutrophil chemoattractant (CINC) after ischemia/reperfusion of the liver.

METHODS

Liver ischemia was induced in male Wistar rats by occluding the portal vein with a microvascular clip for 30 minutes. Rats received two intramuscular injections of AZA (4 mg/kg), CsA (5 mg/kg), FK506 (0.5 mg/kg), or RPM (0.5 mg/kg) 3 and 24 hours before ischemia/reperfusion of the liver.

RESULTS

Serum CINC concentrations in untreated animals increased, peaked 6 hours after reperfusion, and thereafter decreased gradually. Pretreatment with AZA, CsA, FK506, and RPM, however, inhibited the increase in serum CINC concentrations after reperfusion. CINC mRNA in liver tissue increased and peaked 3 hours after reperfusion, but was significantly lower in animals treated with AZA, CsA, FK506, and RPM. In vitro CINC production by Kupffer cells harvested from animals treated with AZA, CsA, FK506, or RPM 3 hours after reperfusion was also significantly lower than that observed in untreated animals. Both myeloperoxidase activity and the number of neutrophils accumulating in the liver 24 hours after reperfusion in animals treated with AZA, CsA, FK506, and RPM were significantly lower than in untreated animals. This correlated with lower serum aspartate transaminase, alanine transaminase, and lactate dehydrogenase levels in animals treated with AZA, CsA, FK506, and RPM 24 hours after reperfusion.

CONCLUSION

The immunosuppressants AZA, CsA, FK506, and RPM reduce neutrophil accumulation and attenuate ischemia/reperfusion injury of the liver.