Changes in brain protein-expression of chaperones 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.

Rationale: Chaperones have been studied for their potential to protect the brain from ischemic injury. They protect from both global and focal ischemia in vivo and cell culture models of ischemia/reperfusion injury in vitro, the mechanism of protection however is not well understood. 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 chaperone 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.

Results: Hsp 90-chaperone Cdc37 is not detectable in 3 day-old control rats but was detected in all rats with PA at the same age.

Heat shock protein 75 kDa was significantly reduced in 3 week-old rats with perinatal asphyxia.

Heat-shock protein 105 kDa as well as 60 kDa heat shock protein, mitochondrial precursor was significantly reduced in 3 month-old rats with PA. Protein disulfide-isomerase A6 precursor (Calcium-binding protein 1) reduced in 3 months and 3 weeks in PA. T-complex protein 1, gamma subunit (Matricin) was significantly elevated in 3 Moths in PA.

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