ABSTRACT
Although IPC (ischaemic preconditioning) is considered as a protective strategy in HI/R (hepatic ischaemia/reperfusion), the mechanisms for this effect have not been fully elucidated. In the present study we investigate whether PPC (pharmacological preconditioning) by transient activation of A(1)R (adenosine A(1) receptor) protects against long-term HI/R and whether the protective effects of IPC depend on A(1)R activation and whether both preconditionings affect remote organs. Wistar rats underwent IPC and long-term HI/R. Another set of animals were pharmacologically preconditioned with the A(1)R-agonist CCPA [2-chloro-N(6)-cyclopentyladenosine; 0.1 mg/kg of body weight, i.p. (intraperitoneally)] 24 h before HI/R. In other groups, rats received an A(1)R-antagonist, DPCPX (1,3-dipropyl-8-cyclopentylxanthine; 0.1 mg/kg of body weight, i.p.) 24 h before HI/R. Hepatic damage was evaluated by transaminase [AST (aspartate transaminase), ALT (alanine transaminase)] release; inflammation was assessed by hepatic MPO (myeloperoxidase) and serum TNFalpha (tumour necrosis factor alpha) and NO; oxidative stress was estimated by MDA (malondialdehyde) and 4-HDA (4-hydroxyalkenals), SOD (superoxide dismutase) activity, GSH and ADA (adenosine deaminase) as adenosine metabolism. Both preconditionings protected liver and lung against HI/R as indicated by the reduction in transaminases, MPO, MDA+4-HDA, NO, TNFalpha and ADA activity as compared with HI/R (P<0.05). However, pre-treatment with DPCPX abolished the protective effects of IPC and PPC. Preconditionings induced a significant increase in hepatic MnSOD (manganese SOD) activity and NO generation compared with the sham group, and this activity was abolished by DPCPX pre-treatment. A(1)R activation induced hepatic delayed preconditioning and blockade of A(1)R abolished hepatic IPC. IPC, as well as PPC, were able to prevent lung damage. These protective effects are associated with a reduction in oxidative stress, inflammation and endogenous antioxidant preservation.
Subject(s)
Adenosine/analogs & derivatives , Ischemic Preconditioning/methods , Liver/blood supply , Receptor, Adenosine A1/physiology , Reperfusion Injury/prevention & control , Adenosine/antagonists & inhibitors , Adenosine/therapeutic use , Adenosine A1 Receptor Agonists , Adenosine A1 Receptor Antagonists , Animals , Antioxidants/metabolism , Drug Evaluation, Preclinical/methods , Female , Glutathione/metabolism , Liver/enzymology , Oxidation-Reduction , Oxidative Stress/drug effects , Peroxidase/metabolism , Rats , Rats, Wistar , Reperfusion Injury/metabolism , Superoxide Dismutase/metabolism , Tumor Necrosis Factor-alpha/metabolism , Xanthines/pharmacologyABSTRACT
The liver is damaged by sustained ischemia in liver transplantation, and the reperfusion after ischemia results in further functional impairment. Ozone oxidative preconditioning (OzoneOP) protected the liver against ischemia/reperfusion (I/R) injury. The aim of this study was to investigate the role of A(1) adenosine receptor on the protective actions conferred by OzoneOP in hepatic I/R. By using a specific agonist and antagonist of the A(1) subtype receptor (2-chloro N6 cyclopentyladenosine, CCPA and 8-cyclopentyl-1,3-dipropylxanthine, DPCPX respectively), we studied the role of A(1) receptor in the protective effects of OzoneOP on the liver damage, nitiric oxide (NO) generation, adenosine deaminase activity and preservation of the cellular redox balance. Immunohistochemical analysis of nuclear factor-kappa B (NF-kappaB), tumor necrosis factor alpha (TNF-alpha) and heat shock protein-70 (HSP-70) was performed. OzoneOP prevented and/or ameliorated ischemic damage. CCPA showed a similar effect to OzoneOP + I/R group. A(1)AR antagonist DPCPX blocked the protective effect of OzoneOP. OzoneOP largely reduced the intensity of the p65 expression, diminished TNF-alpha production, and promoted a reduction in HSP-70 immunoreactivity. In summary, OzoneOP exerted protective effects against liver I/R injury through activation of A(1) adenosine receptors (A(1)AR). Adenosine and (.)NO produced by OzoneOP may play a role in the pathways of cellular signalling which promote preservation of the cellular redox balance, mitochondrial function, glutathione pools as well as the regulation of NF-kappaB and HSP-70.
Subject(s)
Ischemic Preconditioning/methods , Liver Transplantation/methods , Liver/blood supply , Ozone/therapeutic use , Receptor, Adenosine A1/metabolism , Reperfusion Injury/prevention & control , Adenosine/analogs & derivatives , Adenosine/pharmacology , Adenosine A1 Receptor Antagonists , Animals , Biomarkers/metabolism , Disease Models, Animal , HSP72 Heat-Shock Proteins/metabolism , Immunohistochemistry , Male , NF-kappa B/metabolism , Nitric Oxide/biosynthesis , Oxidants, Photochemical/therapeutic use , Oxidative Stress/drug effects , Oxidative Stress/physiology , Purinergic P1 Receptor Antagonists , Rats , Rats, Wistar , Reperfusion Injury/metabolism , Reperfusion Injury/pathology , Treatment Outcome , Tumor Necrosis Factor-alpha/metabolism , Xanthines/pharmacologyABSTRACT
The liver is damaged by sustained ischaemia during liver transplantation, and the reperfusion after ischaemia results in further functional impairment. Ozone oxidative preconditioning (OzoneOP) protected the liver against ischaemia/reperfusion (I/R) injury through different mechanisms. The aim of this study was to investigate the influence of the inhibition of protein synthesis on the protective actions conferred by OzoneOP in hepatic I/R. Rats were treated with cycloheximide (CHX) in order to promote protein synthesis inhibition after OzoneOP treatment. Plasma transaminases, malondialdehyde and 4-hydroxyalkenals and morphological characteristics were measured as an index of hepatocellular damage; Cu/Zn-superoxide dismutase (SOD), Mn-SOD, catalase, total hydroperoxides and glutathione levels as markers of endogenous antioxidant system. OzoneOP increased Mn-SOD isoform and ameliorated mitochondrial damage. CHX abrogated the protection conferred by OzonoOP and decreased Mn-SOD activity. Cellular redox balance disappeared when CHX was introduced. Protein synthesis is involved in the protective mechanisms mediated by OzoneOP. Ozone treatment preserved mitochondrial functions and cellular redox balance.
