Pré-condicionamento com L-alanil-glutamina e neuroproteção contra a lesão cerebral de isquemia/reperfusão em ratos

Abstract

L-alanyl-glutamine preconditioning and neuroprotection against brain ischemia/reperfusion injury in rats. PAULO ROBERTO CAVALCANTE DE VASCONCELOS. Strictu Sensu Post-graduation in Surgery, Department of Surgery, School of Medicine, Federal University of Ceará (Degree of Doctorate of Medical and Surgical Sciences). April, 2014. Advisor: Prof. Sérgio Botelho Guimarães. This study aimed to evaluate the effects of the dipeptide l-alanyl-glutamine (l-ala-gln) as a preconditioning agent to potentially promote reduction in the intensity of the lesion or induction of resilience in rats subjected to global cerebral ischemia/reperfusion (I/R) injury. Cerebral edema, neuronal death and intracelular protein kinase signaling were studied. L-ala-gln was administered intravenously (0.75g/kg) 30 minutes before sham procedure or induction of global brain I/R injury. Cerebral tissue was analysed 1h and 24h after reperfusion. Brain edema, red neuron counting (cell death) and hippocampus concentrations of protein kinases (ERK/MAP quinase 1/2 (Thr185/Tyr187), Akt (Ser473), STAT3 (Ser727), JNK (Thr183/Tyr185), p70 S6 kinase (Thr412), STAT5A/B (Tyr694/699), CREB (Ser133), e p38 (Thr180/Tyr182) were determined. Results expressed as Mean±SD for normal results and Median±Percentil (25-75) for non parametric data. Significance established at p<0.05. Global I/R injury promoted increase in brain edema at 24 h after reperfusion, whereas preconditioning with l-ala-gln induced no change in edema. On the other hand, l-ala-gln preconditioning decreased significantly red neurons counting both at 1h and 24h post reperfusion. L-alanyl-glutamine promoted significant decreased concentrations of JNK after reperfusion as compared to I/R controls at 1h and at 24h post reperfusion. On the other hand, l-ala-gln preconditioning induced significant elevation of brain concentrations of P70 at 1h and at 24h post reperfusion, P38 at 1h after reperfusion and CREB at 24h post reperfusion. There was a significant precontitioning effect with l-alanyl-glutamine decreasing cell death (red neurons counting) at early (1h) and late reperfusion (24h) in the cerebral tissue. Decreased brain concentrations of JNK and elevated concentrations of P70, P38 and CREB induced by preconditioning with l-ala-gln indicate neuroprotective effects of by this peptide. More studies are necessary to confirm the present results and to investigate other intracelular pathways and other mechanisms envolved in this neuroprotective event. Key words: L-alanyl-glutamine; ischemia/reperfusion; apoptosis; rats