of adenosine A 1 and A3 receptors in regulation of cardiomyocyte homeostasis after mitochondrial respiratory chain injury.

Apoptosis appears to be a central mechanism of cell death following reperfusion of the ischemic liver. The aim of this study was to determine the effect of decreased expression of the proapoptotic Bax gene on hepatic apoptotic warm ischemia/reperfusion (I/R) injury. Three groups of mice were studied: homozygotic knockout mice (Bax Ϫ/Ϫ ); heterozygotic (Bax ϩ/Ϫ ); and wild type (Bax ϩ/ϩ ). Isolated mouse livers were subjected to 90 minutes of ischemia (37°C) followed by 15 minutes of reperfusion. Bax and Bcl-2 expression in liver tissue homogenates was measured by Western blot. Serum liver enzyme levels were measured and intrahepatic caspase-3 activity was determined by fluorimetric assay. Oil red O (ORO) staining was performed for fat detection. Apoptotic cells were identified by morphological criteria, immunohistochemistry for caspase-3, and terminal deoxynucleotidyl transferase-mediated 2Ј-deoxyuridine 5Ј-triphosphate nick-end labeling (TUNEL) assay. At 1 minute of reperfusion, the ischemic (Bax Ϫ/Ϫ ) livers were characterized by statistically significantly lower liver enzyme levels and lower caspase-3 activity than the ischemic (Bax ϩ/ϩ ) livers (P Ͻ 0.05 for both). The reduction in postischemic apoptotic hepatic injury in the ischemic Bax Ϫ/Ϫ livers group was confirmed morphologically, by the significantly reduced microvesicular steatosis as determined by ORO staining, fewer apoptotic hepatocyte cells detected (P Ͻ 0.05); immunohistochemically, by the significantly weaker activation of caspase-3 compared to the ischemic group (P Ͻ 0.05); and by TUNEL assay (P Ͻ 0.05). Similar levels of antiapoptotic Bcl-2 protein expression were detected in all 3 groups of ischemic livers on Western blots. Bax protein was not expressed in Bax-deficient livers and was detected in Bax ϩ/ϩ normal livers. In the Bax ϩ/Ϫ livers, levels of the damage markers were moderate. In conclusion, The better tolerance of Bax knockout livers to I/R injury suggests that the Bax gene may serve as a potential target for therapeutic intervention in hepatic I/R injury.

CCPA in both modes of treatment and Cl-IB-MECA, especially in the injected mode, were beneficial in protecting the normal and hypertrophied perfused isolated rat heart subjected to normothermic cardioplegic ischemia. This protection was partially related to the increased phosphorylation of p38 MAPK.

No abstract

The aim of the present study was to investigate the protective role of pharmacological preconditioning on antioxidant enzymes using A(1) and A(3) adenosine receptor agonists in the recovery of the isolated myocardium after cardioplegic ischemia. Two different modes of preconditioning were studied: isolated rat hearts were perfused with A(1) receptor agonist 2-chloro-N(6)-cyclopentyladenosine (CCPA) or A(3) 2-chloro-N(6)-(3-iodobenzyl) adenosine-5'-N-methyluronamide (Cl-IB-MECA) (1 nM), followed by cardioplegic ischemia and reperfusion (30 min each) (perfusion mode), or CCPA or Cl-IB-MECA (100 micro g/kg) were injected intravenously 24 h before the experiment (injection mode). Hearts treated with CCPA improved in terms of mechanical function, infarct size, ATP levels, superoxide dismutase, and catalase (p < 0.005) in both modes of administration. Cl-IB-MECA was beneficial mainly in the injected group. Reduced damage to the mitochondria in the CCPA-treated hearts was observed using electron microscopy evaluation. In the Cl-IB-MECA-injected hearts, mitochondrial damage was moderate. CCPA in both modes of treatment and Cl-IB-MECA in the injected mode were beneficial in protecting the perfused isolated rat heart, subjected to normothermic cardioplegic ischemia. This protection was partially related to the higher myocardial activity of superoxide dismutase and catalase.