Phthalates are ubiquitous environmental contaminants present in soft plastics and PVC-containing devices, resulting in significant human exposure through contamination of food and medical products. The recently completed study by the National Toxicology Program Center for the Evaluation of Risks to Human Reproduction noted there was """"""""serious concern"""""""" that some human phthalate exposures are sufficiently high to adversely affect male reproductive function. Despite being the most studied testicular toxicant, the mechanism of phthalate-induced testicular injury is not known. Therefore, the long-term objective of this research is to determine the mechanism of phthalate-induced testicular injury in molecular detail. Hallmarks of phthalate testicular injury are an initial action on Sertoli cells, disruption of Sertoli cell FSH-induced cAMP generation, and the loss of Sertoli-germ cell adhesion. These historical data suggest that both signaling from G protein-coupled receptors and Sertoli-germ cell adhesion proteins are proximal targets of phthalate injury. Recently, putative Sertoli cell G protein-coupled receptors that are cell-cell adhesion proteins (flamingos) were discovered in testis, making such proteins attractive phthalate targets. The specific down-regulation of testicular flamingo mRNA during early stages of phthalate exposure confirmed that flamingo biology was compromised by phthalates. Because of these observations, this grant proposal investigates the mechanism of phthalate-induced testicular injury by examining the following working hypothesis: phthalates induce the phosphorylation, internalization and degradation of flamingo l and 2 protein leading to Sertoli-germ cell detachment and germ cell apoptosis.
Three specific aims will test this hypothesis by 1) localizing flamingo 1 and 2 to specific testis cell types, 2) examining both qualitative and quantitative changes in flamingo proteins during phthalate exposure, and 3) determining if disruption of flamingo protein mimics the phenotype produced by phthalate injury.

Agency
National Institute of Health (NIH)
Institute
National Institute of Environmental Health Sciences (NIEHS)
Type
Research Project (R01)
Project #
5R01ES011632-04
Application #
6711052
Study Section
Alcohol and Toxicology Subcommittee 4 (ALTX)
Program Officer
Heindel, Jerrold
Project Start
2002-06-25
Project End
2006-02-28
Budget Start
2004-03-01
Budget End
2005-02-28
Support Year
4
Fiscal Year
2004
Total Cost
$301,525
Indirect Cost
Name
The Hamner Institutes
Department
Type
DUNS #
040052250
City
Research Triangle Park
State
NC
Country
United States
Zip Code
27709
Lahousse, Stephanie A; Beall, Stephanie A; Johnson, Kamin J (2006) Mono-(2-ethylhexyl) phthalate rapidly increases celsr2 protein phosphorylation in HeLa cells via protein kinase C and casein kinase 1. Toxicol Sci 91:255-64
Johnson, Kamin J; Zecevic, Alma; Kwon, Eun J (2004) Protocadherin alpha3 acts at sites distinct from classic cadherins in rat testis and sperm. Biol Reprod 70:303-12
Richburg, John H; Johnson, Kamin J; Schoenfeld, Heidi A et al. (2002) Defining the cellular and molecular mechanisms of toxicant action in the testis. Toxicol Lett 135:167-83