Changes in brain protein-expression after perinatal asphyxia in a rat model at different ages

Background: Perinatal asphyxia (PA) is a major determinant of neurological morbidity in the pediatric population. Animal studies focusing on the subacute sequelae have uncovered a variety of morphological, neurochemical, behavioral and cognitive changes following PA, including deficits of the protein synthetic machinery and aberrant expression of individual brain proteins. The developing brain is uniquely vulnerable to hypoxic-ischemic injury, with a complex evolution of injury that affords opportunities for intervention. This susceptibility of the developing brain to hypoxia among others depends on the presence of antioxidant defense.

Rationale: Reviewing developmental studies, the susceptibility of the fetal brain to hypoxia appears to increase with brain development as gestation approaches term indicating that the status of the anti-oxidant enzymes among other is determining the sensitivity of the developing brain to hypoxia. We therefore decided to systematically study expression-levels of brain proteins in various age groups in control rats and rats that underwent a period of PA, aiming to extend our understanding of the effects of PA on antioxidant protein expression in a time-dependent way.

Methods: Hippocampal tissue of rats with and without PA (at 20 minutes of PA) was dissected from brain at three different time points: 3 days, 3 weeks and 3 months of age, using a proteomic method. Proteins were run on two-dimensional gel electrophoresis with in-gel-digestion and subsequent identification of proteins by MALDI-TOF followed by quantification of protein spots by specific software. 18 antioxidant proteins were identified and quantified.

Results: In 3 days old asphyxiated rats significantly higher expression of thioredoxin peroxidase 1, which turned to significantly reduced expression at 3 weeks and reached normal level at 3 months was observed. Electron transfer flavoprotein alpha-subunit (mitochondrial precursor) was not detected at 3 days but at 3 weeks and 3 months showing comparable expression in both groups, asphyxiated and control. At three weeks the flavoprotein subunit of succinate-ubiquinone reductase was also reduced in asphyxiated rats. At three months peroxiredoxin 6 presented with elevated expression in asphyxiated rats. In contrast, the serotransferin (precursor) was reduced in asphyxiated rats at this time-point.

Conclusion: PA leads to derangements of antioxidant proteins at different stages of development. Aberrant protein expression may provide evidence for involvement of individual antioxidant proteins in the pathomechanisms of PA. As expression of the majority of antioxidant-proteins remained unchanged, these findings can be considered specific and not simply due to protein derangement by the deficient protein machinery per se.