Hypoxia And Mitochondrial Dysfunction In Developing CNS

FISZER DE PLAZAS S; GIUSTI S; CONVERSO D; PODEROSO JJ

Insbruck, Austria

Congreso; 20th Biennial Meeting of the International Society For Neurochemistry jointly with the European Society for Neurochemistry; 2005

In some hypoxia models an increase of intracellular levels of nitric oxide (NO) has been described which in turn, stimulates the mitochondrial production of reactive oxygen species like superoxide anion (O2-) and peroxynitrite (ONOO-). The aim of this paper is to determinate whether hypoxia/reoxygenation events during embryonic development induce the expression of neuronal nitric oxide synthase (nNOS), and putative effects in nitrosylation/nitration of proteins and mitochondrial function. For this purpose, 12-embryonic-day old chicken embryos were used which underwent sever hypoxia (8% [O2], 60 minutes), followed by different reoxygenation periods: 1h, 2h, 3h and 4h. nNOS expression potentation and mitochondrial complex content wasdetected by Western blot in cytosolic and mitochondrial fractions. Activity of respiratory complexes I (CI) and IV (CIV) was recorded by monitoring oxidation of specific substrates. During hypoxia a 50% transient increase of nNOS was observed (P,0.05) in cytosolic fraction and during the first hour reoxygenation period together with an increase of the content of nitrated proteins. Surprisingly, nNOS was traslocated to mitochondria (3 fold increase respct to control, P,0.01) during the first two hours followed by intense nitration. Decreased Complex I activity was detected after the first reoxygenation hour without changes in protein expression. In conclusion, the increase of nNOS levels and formation of peroxynitrite should explain protein nitration and reduction of CI activity in developmental hypoxia.