| Developmental toxicity is the potential of a drug or chemical to cause adverse effects in the developing organism, embryo, fetus or newborn and is important to consider in any health risk assessment for humans and wildlife (World Health Organization). This information is most commonly derived from experimental studies in which pregnant lab animals are exposed to various compounds during critical stages of development. However, new experimental approaches are being implemented to detect, understand and predict novel pathways leading to developmental toxicity. A correlation between developmental toxicity and mitochondrial dysfunction has been implicated in the pathogenesis of a number of developmental diseases. The research presented here was aimed at attaining a better understanding of how molecular pathways involved in stress-induced mitochondrial dysfunction lead to developmental toxicity. The overall hypothesis of this dissertation is that mitochondrial dysfunction by environmental chemicals triggers p53 release from the mitochondrion as an intracellular signal for downstream stress-response pathways of the cell.;The following dissertation addresses three main questions: What is the response of mitochondrial-p53 to rotenone-induced mitochondrial dysfunction? Can we assess differences in post-translational modifications of mitochondrial p53 versus non-mitochondrial p53 pools? And, can we determine if Bzrp/TSPO is involved in the regulation of mitochondrial toxicities? This dissertation is divided into four Chapters and establishes an in vitro model with which further studies can be conducted to further evaluate mechanisms of developmental toxicity. Chapter one is an overall general discussion about the dynamic and multifunctional roles of the tumor suppressor TP53 because previous research indicates that functional inactivation of this protein can cause a defect in mitochondrial oxidative capacity that is linked to dysmorphogenesis of embryos and increased risk for defects. Chapter one also discusses mechanisms of how the mitochondrial drug PK11195, a ligand of the oxygen-sensing tryptophan rich sensory protein, may lead to anti-teratogenic and anti-disease action during development in mice. Chapter two discusses the establishment of an in vitro model that suggests a connection between p53 activity and mitochondrial function. Chapter three focuses on determining possible molecular and cellular mechanisms of rotenone-induced mitochondrial dysfunction and the connection to p53 activity. Chapter four concludes with an overall summary, hypothesis and future directions for follow up studies. In summary, the data implies a connection between p53 activity and mitochondrial function. For instance, rotenone-induced mitochondrial dysfunction in mitochondrial targeted p53 cells caused emission of p53 from the mitochondrial to the nucleus. Pharmacological relevant concentrations of PK11195, a Bzrp/TSPO antagonist, can suppress the emission of p53 from the mitochondria. Furthermore, these findings also suggest changes in post-translational status may accompany the redistribution of p53. Together, this dissertation examines mitochondrion-specific changes; however, the data suggest that release of p53 from mitochondria is part of a signaling cascade that is initiated by mitochondrial dysfunction and resembles the DNA damage response. Collectively, these studies characterize a potential 'toxicity pathway' in murine embryo fibroblasts that may be applied toward discovering novel modes of intervention for human prenatal developmental toxicity. |
