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INCREASED APOPTOSIS IN ORGANOGENESIS-STAGED MOUSE EMBRYOS INDUCED BY DISINFECTION BY-PRODUCTS
Citation:
Hunter III, E S., E H. Rogers, AND K. Ward. INCREASED APOPTOSIS IN ORGANOGENESIS-STAGED MOUSE EMBRYOS INDUCED BY DISINFECTION BY-PRODUCTS. Presented at Society of Toxicology, San Francisco, CA, March 25-29, 2001.
Description:
Increased apoptosis in organogenesis-staged mouse embryos induced by disinfection by-products. Sid Hunter1,2, Ellen Rogers1 and Keith Ward2, 1 Developmental Biology Branch, Reproductive Toxicology Division, NHEERL, US EPA, RTP, NC; 2 Curriculum in Toxicology, UNC Chapel Hill, Chapel Hill, NC
Neurulation is one of the earliest morphogenetic events in brain development. Development of the neural plate includes an epithelio-mesenchymal transformation of the neuroectoderm to form the migratory neural crest (NC) cells as well as formation of the neural tube. Xenobiotic-induced cell death in neuroepithelial and NC cells have been associated with neural tube and craniofacial defects. Day 8 (plug day = 0) early somite staged (4-6 pairs of somites) CD-1 mouse conceptuses in whole embryo culture, exposed to the haloacetic acids (HAs) dichloroacetate, bromochloroacetate or dibromoacetate exhibit craniofacial dysmorphogenesis after a 24 hour culture period. These effects include a lack of neural tube closure as well as prosencephalic and pharyngeal arch hypoplasia. Based on the morphology both NC cells and neural tube closure appear susceptible to HA-induced toxicity. To characterize the pathogenic effects produced by HAs, vital staining was used to evaluate cell death and flow cytometry was used to determine the distribution of cells in the cell cycle. Lysotracker staining and whole mount evaluation indicated that cell death was present in the neuroepithelium, but was especially widespread in the pharyngeal arches following a 24 hour exposure to HAs. No changes in the distribution of nuclei in the cell cycle were detected. The co-localization of defect and cell death, especially in the first pharyngeal arch, suggests that these may be causally related. Based on studies in adult tissues, our working hypothesis is that HA-induced dysmorphogenesis is the result of altered signal transduction. Embryos exposed to staurosporine, a broad spectrum kinase inhibitor, exhibit dysmorphology and high levels of cell death. Staurosporine perturbed NC cell development and induced high levels of cell death in primary NC cell culture. The adverse effects of staurosporine on the embryo and NC cells are consistent with our hypothesis that altered signal transduction pathways may be responsible for HA-induced defects; however the critical pathway(s) for neurulation remains to be determined. This abstract does not present EPA policy.