Ischemic preconditioning decreases C-X-C chemokine expression and neutrophil accumulation early after liver transplantation in rats

Advances in research on the protective mechanisms of ischemic postconditioning against hepatic ischemia-reperfusion injury

Liver transplantation is the only effective treatment for end-stage liver diseases. Ischemia-reperfusion injury remains a major cause of post-transplantation liver dysfunction and even failure. Ischemic postconditioning is defined as rapid intermittent periods of reperfusion and ischemia in the early phase of repefusion after long ischemia of the tissues and organs. Many investigations have demonstrated that ischemic postconditioning has a protective effect against hepatic ichemia-reperfusion injury. Ischemic postconditioning exerts protective effects through many possible mechanisms such as oxygen free radicals, calcium overload, polymorphonuclear neutrophils, cytokines, cell apoptosis and mitochondria.

Selectin Inhibition Modulates NF-κ B and AP-1 Signaling After Liver Ischemia/Reperfusion

The infiltration of neutrophils after ischemia and reperfusion (I/R) is facilitated by the expression of adhesion molecules on the surface of both leukocytes and endothelial cells. Adhesion molecules of the selectin family are of particular importance at the onset of neutrophil mediated injury, as demonstrated by the occurrence of many cellular interactions with the final extravasation of inflammatory leukocytes at the site of I/R damage. Previous studies demonstrated a prevention of neutrophil extravasation and protection of ischemic damage when a small anti-selectin molecule was used. In this study, we tested a new small anti-selectin compound (OC-229) in a murine model of partial hepatic I/R. The aim of this study was to determine the effect of OC-229 on liver function and histology after I/R and to evaluate its role in the modulation of the inflammatory molecular signaling pathways of NF-kappa B and AP-1 under the same experimental condition. Mice subjected to 90 min of partial (70-80%) hepatic ischemia and 3 h of reperfusion were divided into three groups (n = 9/group): sham, ischemic control, and treated group, which received 25 mg/kg of the anti-selectin small molecule OC-229. These groups were studied when the treatment was given at the time of reperfusion (no pretreatment was given). The parameters measured at 3 h of reperfusion included liver function tests (ALT and AST), liver histology, and liver tissue electrophoretic mobility shift assay (EMSA) for NF-kappa B and AP-1. It was demonstrated that the multiselectin inhibitor OC-229 offered significant protection for the ischemic liver when given at 25 mg/kg at the time of reperfusion. ALT and AST serum levels significantly decreased when the ischemic control and the group receiving OC-229 were compared (p = .01). Treated animals demonstrated better histological findings as well. The EMSA showed dissociation of NF-kappa B and AP-1 activity in the liver nuclear extracts after selectin inhibition treatment. A reduction in the activity of AP-1 and an increment in NF-kappa B activation was seen. In this work, we obtained evidence that the small-molecule selectin inhibitor OC-229 offered functional and histological protection of the ischemic liver when given at 25 mg/kg at the time for reperfusion. There was dissociation in the activation signals of NF-kappa B and AP-1. Increase in NF-kappa B and reduction of the activation of AP-1 were noted at 3 h of reperfusion.

Molecular Biology of Apoptosis in Ischemia and Reperfusion

This study reviews the current understanding of the mechanisms that mediate the complex processes involved in apoptosis secondary to ischemia and reperfusion (I/R) and is not intended as a complete literature review of apoptosis. Several biochemical reactions trigger a cascade of events, which activate caspases. These caspases exert their effect through downstream proteolysis until the final effector caspases mediate the nuclear features characteristic of apoptosis, DNA fragmentation and condensation. Within the context of ischemia, the hypoxic environment initiates the expression of several genes involved in inflammation, the immune response, and apoptosis. Many of these same genes are activated during reperfusion injury in response to radical oxygen species generation. It is plausible that inhibition of specific apoptotic pathways via inactivation or downregulation of those genes responsible for the initiation of inflammation, immune response, and apoptosis may provide promising molecular targets for ameliorating reperfusion injury in I/R-related processes. Such inhibitory mechanisms are discussed in this review. Important targets in I/R-related pathologies include the brain during stroke, the heart during myocardial infarction, and the organs during harvesting and/or storage for transplantation. In addition, we present data from our ongoing research of specific signal transduction-related elements and their role in ischemia/reperfusion injury. These data address the potential therapeutic application of anti-inflammatory and anti-ischemic compounds in the prevention of I/R damage.

Protection of Veratrum nigrum L. var. ussuriense Nakai alkaloids against ischemia-reperfusion injury of the rat liver

AIM: To investigate the protective effects and possible mechanisms of Veratrum nigrum L.var. ussuriense Nakai alkaloids (VnA) on hepatic ischemia/reperfusion (I/R) injury in rats.

METHODS: Forty male Wistar rats were randomly divided into four experimental groups (n = 10 in each): (A) Control group (the sham operation group); (B) I/R group (pretreated with normal saline); (C) Small-dose (10 μg/kg) VnA pretreatment group; (D) Large-dose (20 μg/kg) VnA pretreatment group. Hepatic ischemia/reperfusion (Hepatic I/R) was induced by occlusion of the portal vein and the hepatic artery for 90 min, followed by reperfusion for 240 min. The pretreatment groups were administered with VnA intraperitoneally, 30 min before surgery, while the control group and I/R group were given equal volumes of normal saline. Superoxide dismutase (SOD) activity, myeloperoxidase (MPO) activity and nitric oxide (NO) content in the liver tissue at the end of reperfusion were determined and liver function was measured. The expression of intercellular adhesion molecule-1 (ICAM-1) and E-selectin (ES) were detected by immunohistochemical examinations and Western blot analyses.

RESULTS: The results showed that hepatic I/R elicited a significant increase in the plasma levels of alanine aminotransferase (ALT: 74.53 ± 2.58 IU/L vs 1512.54 ± 200.76 IU/L, P < 0.01) and lactic dehydrogenase (LDH: 473.48 ± 52.17 IU/L vs 5821.53 ± 163.69 IU/L, P < 0.01), as well as the levels of MPO (1.97 ± 0.11 U/g vs 2.57 ± 0.13 U/g, P < 0.01) and NO (69.37 ± 1.52 μmol/g protein vs 78.39 ± 2.28 μmol/g protein, P < 0.01) in the liver tissue, all of which were reduced by pretreatment with VnA, respectively (ALT: 1512.54 ± 200.76 IU/L vs 977.93 ± 89.62 IU/L, 909.81 ± 132.76 IU/L, P < 0.01, P < 0.01; LDH: 5821.53 ± 163.69 IU/L vs 3015.44 ± 253.01 IU/L, 2448.75 ± 169.4 IU/L, P < 0.01, P < 0.01; MPO: 2.57 ± 0.13 U/g vs 2.13 ± 0.13 U/g, 2.07 ± 0.05 U/g, P < 0.01, P < 0.01; NO: 78.39 ± 2.28 μmol/g protein vs 71.11 ± 1.73 μmol/g protein, 68.58 ± 1.95 μmol/g protein, P < 0.05, P < 0.01). The activity of SOD (361.75 ± 16.22 U/mg protein vs 263.19 ± 12.10 U/mg protein, P < 0.01) in the liver tissue was decreased after I/R, which was enhanced by VnA pretreatment (263.19 ± 12.10 U/mg protein vs 299.40 ± 10.80 U/mg protein, 302.09 ± 14.80 U/mg protein, P < 0.05, P < 0.05). Simultaneously, the histological evidence of liver hemorrhage, polymorphonuclear neutrophil infiltration and the overexpression of ICAM-1 and E-selectin in the liver tissue were observed, all of which were attenuated in the VnA pretreated groups.

CONCLUSION: The results demonstrate that VnA pretreatment exerts significant protection against hepatic I/R injury in rats. The protective effects are possibly associated with enhancement of antioxidant capacity, reduction of inflammatory responses and suppressed expression of ICAM-1 and E-selectin.

Avaliação bioquímica dos efeitos do pré-condicionamento isquêmico após isquemia e reperfusão hepática em ratos

OBJETIVO: Comparar a lesão hepatocelular ocasionada pelo emprego do pré-condicionamento isquêmico e de duas outras modalidades de clampeamento tríade portal: clampeamento contínuo e intermitente. MÉTODO: Quarenta ratos Wistar foram divididos em quatro grupos de 10 animais cada. No Grupo Sham nenhuma espécie de clampeamento foi adotada. Nos outros três, provocamos isquemia de quarenta minutos por meio do clampeamento do pedículo hepático. No Grupo I esta isquemia foi contínua. No Grupo II, também contínua, mas precedida de cinco minutos de isquemia e 10 minutos de reperfusão (précondicionamento isquêmico). No Grupo III foi realizada isquemia intermitente em ciclos de 10 min de isquemia e cinco minutos de reperfusão. Para avaliar a lesão hepatocelular foi adotada a dosagem de transaminase glutâmico oxalacética (TGO), glutâmico pirúvica (TGP) e lactato desidrogenase (LDH), aferidas no início e no final dos procedimentos. RESULTADOS: Não houve diferença estatística nos valores basais das enzimas estudadas, demonstrando uniformidade nos grupos. Os quatro grupos apresentaram variação significativa de todas as enzimas entre os dois momentos de coleta, porém de forma diferenciada. A variação no Grupo Sham foi menor que a do grupo II. Este foi semelhante ao grupo III e em todos a elevação foi significativamente menor que no grupo I (D do Sham CONCLUSÕES: Em ratos Wistar o clampeamento contínuo do pedículo hepático, precedido de um ciclo de cinco minutos de isquemia e 10 minutos de reperfusão (pré-condicionamento isquêmico) provoca menor lesão hepática do que o clampeamento contínuo e apresenta resultados comparáveis aos obtidos através da utilização do clampeamento intermitente, em fígados normais submetidos a um período de isquemia hepática de 40 minutos e um tempo total de cirurgia de 60 minutos.

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