Environmental exposures, like those occurring at Superfund sites and Brownfields in Rhode Island, involve complex mixtures of hazardous chemicals. We have established a novel co-exposure paradigm to expand our mechanistic understanding of testicular injury resulting from such complex exposures. Model testicular toxicants are used as functional probes of the interacting cell types within the seminiferous epithelium: 2,5-hexanedione, carbendazim, and mono-(2-ethylhexyl) phthalate target Sertoli cells, and xirradiation and 1,2-dibromo-3-chloropropane target germ cells. Using the adult rat as the animal model, the co-exposure paradigm combines subacute exposure to 2,5-hexanedione with acute exposure to another Sertoli cell or germ cell toxicant.
In the initial funding period, dose-response behavior and phenotypic alterations were determined for the testicular toxicants. Compared with acute toxicant exposure alone, the co-exposure paradigm attenuated or enhanced the germ cell apoptotic response, the final common pathway of testicular injury, depending on dose and cellular target. Strikingly, the gene array analysis supports a positive correlation between a muted or exaggerated gene expression response and the extent of co-exposure attenuation or enhancement of germ cell apoptosis. These exciting results provide a phenotypic anchor for further molecular analyses, and underscore the ability of the co-exposure paradigm to provide new insight into the testicular response to complex exposures.
In the next funding period, laser capture microdissection will be used for cell-type and stage-specific
enrichment of mRNA and protein from the seminiferous epithelium, extending the co-exposure paradigm to
low doses. In addition, novel sperm biomarkers of effect will be identified for chronic cell-type specific
testicular injury. The work will be guided by the following working hypotheses: 1) co-exposure attenuation
or enhancement of toxicity depends upon dose, targeting, and the extent of molecular perturbation, and 2)
the testicular response to cell type specific toxicant exposure can be identified through molecular analysis of
- Elucidate the phenotypic and molecular features of testicular injury resulting from Sertoli cell plus germ cell toxicant co-exposure. Test 2,5-hexanedione co-exposure with x-irradiation or 1,2-dibromo-3-chloropropane, and determine molecular alterations at low doses.
- Identify the phenotypic and molecular characteristics of testicular injury caused by Sertoli cell plus Sertoli cell toxicant co-exposure. Examine 2,5-hexanedione co-exposure with carbendazim or mono-(2-ethylhexyl) phthalate, and use new bioinformatic techniques to analyze low dose effects.
- Develop sperm biomarkers of effect for Sertoli cell and germ cell toxicants. Discover novel sperm mRNA and epigenetic biomarkers of cell-type specific testicular injury.
Project Leader: Kim Boekelheide, M.D., Ph.D.
Lab Manager: Susan Hall
Graduate Researcher: Natasha Catlin