CRITICAL TARGETS IN HYPEROXIC MITOCHONDRIAL INJURY

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Bronchopulmonary dysplasia (BPD) is a common, disabling and sometimes fatal chronic lung disease. It frequently accompanies premature birth and treatment of respiratory distress with artificial ventilation and high concentrations of inspired oxygen (hyperoxia). The biochemical basis of BPD is not well understood. In the baboon, exposure to hyperoxia is required treatment in both the ultra-premature (125 d) and premature (140) model of BPD. Hyperoxia damages mitochondria results in loss of aconitase activity, decreased mitochondrial and cell respiration, and loss of ATP. On that basis, this proposal's principal hypothesis is that adaptation to hyperoxic stress requires up-regulation of glycolytic, and/or glutaminolytic, enzymes. Because hexokinase rate- limits glycolysis in lung, it is hypothesized that expression of lung hexokinase(s) is up-regulated. Replacement of deficient mitochondrial anti-oxidants may alleviate early respiratory distress and resulting BPD and decrease up regulation of glycolytic enzymes. These hypotheses will be tested in these AIMS; 1) Determine differential expression of mRNA's encoding components of the mitochondrial porin complex-hexokinases (HKs), porins, and adenine nucleotide translocators (ANT), these same proteins, and relevant glycolytic and glutaminolytic enzymes; 2) Define early status of critical anti-oxidants (glutathione [GSH], thioredoxin [TRX], superoxide dismutases]), their precursors (S-adenosylmethionine), and oxidant target (aconitase) markers, and (3) Define the efficacy of early, continuous infusion of S-adenosylmethionine (AdoMet), a precursor of cellular and mitochondrial glutathione (GSH), on these markers and pulmonary histopathology of BPD. Hexokinase binding to, or release from, mitochondria will be quantitied using immunogold electron microscopy. Activities of HK, phosphofructokinase, and additional critical glycolytic and glutaminolytic enzymes also will be assayed. Lung GSH, TRX, and AdoMet, as well as circulating GSH, AdoMet, and sulfur amino acids will be measured early in the 125 d model. Together, these approaches will help define whether changes in hexokinase activity expression, known to occur in lungs of adult rats made oxygen-tolerant, also occur in the premature newborn baboon. In addition, they will indicate whether or not increased expression of pulmonary glutamine- utilizing enzymes also occurs during pulmonary oxidative stress and whether anti-oxidant stress and whether anti-oxidant supplementation modifies these adaptations.