Intrauterine hypoxia is a leading cause of fetal morbidity and mortality. Fetuses may be exposed to hypoxia if the mother lives at high altitude, smokes, or is subject to intrauterine stress such as preeclampsia, uterine ischemia, or placental dysfunction. Adaptation of the fetal cardiovascular system to hypoxic stress is essential for survival. Chronic hypoxia in the adult heart has been reported to upregulate the oxygen- sensitive gene expression of both inducible nitric oxide synthase (iNOS) and proinflammatory cytokines. Further, proinflammatory cytokine release has been shown to be stimulated by cyclic GMP. Therefore we hypothesize that chronic hypoxia increases proinflammatory cytokine production in fetal hearts via upregulation of the iNOS pathway. We will expose pregnant guinea pigs to either normoxia (room air) or chronic hypoxia (10.5%O2) for 14d prior to term (65d) and remove fetuses for study at 60d gestation (near term). Fetal hearts will be excised from anesthetized fetuses for analysis and the effect of fetal hypoxia on cardiac iNOS and cytokine gene expression will be quantified. Real-time PCR and Western blot will be used to measure mRNA and protein expression, respectively, of the iNOS/NO/cGMP pathway and proinflammatory cytokines in intact fetal hearts and isolated cardiomyocytes. Aim 1: To test the hypothesis that there is a link between hypoxia-induced upregulation of the iNOS pathway and proinflammatory cytokine expression in the fetal heart. The first aim will demonstrate the effects of chronic hypoxia exposure resulting in sustained gene expression in the intact fetal heart. Aim 2: To test the hypothesis that proinflammatory cytokine release from isolated fetal cardiomyocytes is regulated by the cGMP pathway. Using isolated fetal cardiomyocytes, the second aim will demonstrate how chronic hypoxia initiates a cascade of events in which the iNOS/NO/cGMP pathway is activated in a cell specific manner resulting in proinflammatory cytokine release. Both aims will provide new information for understanding the mechanism by which chronic hypoxia alters gene expression of the iNOS/NO/cGMP and cytokine pathways in the fetal heart. If the fetus is unable to adapt to a hypoxic stress, the fetus could suffer long-term effects such as neurological injury and heart dysfunction due to proinflammatory cytokine damage or apoptosis. These proposed studies will aid in our understanding of the underlying mechanisms associated with cardioprotection, injury, as well as fetal programming during intrauterine stress.
NIH ExPorter
NIH ExPorter