AGE-RELATED ALTERATION OF LEYDIG CELL REDOX ENVIRONMENT A RISK FACTOR FOR SUSCEPT

描述（由申请人提供）：越来越明显的是，定义代表对环境压力敏感性的风险因素的细胞环境变化对于改善我们研究潜在环境化学品和药物的方式至关重要。本项目的目标是确定老化过程中Leydig细胞氧化还原环境的改变是否代表对邻苯二甲酸二（2-乙基己基）酯（DEHP）诱导的类固醇生成抑制敏感性的风险因素。接触DEHP，一种众所周知的内分泌干扰物，可导致生殖健康问题，包括尿道下裂，睾丸癌和精液质量差。在发育过程中，雄激素在性器官形态发生和功能的编程中起着关键作用。在所有的发育阶段，雄激素的存在，在足够的数量是一个关键的决定因素的男性表型。因此，改变内分泌功能的环境化学品对人类和动物的生殖健康构成潜在风险。DEHP是一种常用的增塑剂，其松散地保持在聚合物基质的间隙之间，因此其及其代谢物是环境中普遍存在的污染物。人类通过食物、吸入、皮肤接触和医疗程序（如静脉滴注袋）接触DEHP，导致血液、尿液、精液和母乳中DEHP和代谢物的可测量水平。暴露于邻苯二甲酸单（2-乙基己基）酯（MEHP）（DEHP的活性代谢产物），可抑制纯化的成年大鼠Leydig细胞和MA-10小鼠肿瘤Leydig细胞的LH刺激类固醇形成。有趣的是，胎儿暴露于DEHP已被证明会导致窝仔数减少，并在以后的生活中，Leydig细胞增生，睾丸萎缩，血清睾酮水平降低，生育力降低。虽然人体接触DEHP的水平本身可能不会导致足够高的血清水平造成伤害，但有一些因素可能会加强其影响。例如，伴随衰老、轻度炎症和/或预先暴露于其他环境因子的细胞氧化剂系统的变化可能会增加对后续无毒剂量DEHP的敏感性。本提案的目标是确定：i）与年龄相关的氧化还原环境改变是否会增加间质细胞对DEHP的敏感性; ii）连续给予低剂量DEHP或稍后的第二次DEHP“撞击”是否会以单次低剂量不会影响睾酮产生的方式影响睾酮产生;以及iii）外部影响（如适度炎症）是否会增加间质细胞对低剂量DEHP的敏感性。这个项目的长期目标是使我成为一个既定的和高生产力的调查能够竞争和吸引R 01赠款支持伊丽莎白市州立大学（ECSU），少数民族服务机构。预计我与导师的机构，约翰霍普金斯大学彭博公共卫生学院（JHSPH）的参与将是建立JHSPH和ECSU之间更广泛合作的重要一步，使聪明的年轻少数民族学生在JHSPH继续接受生物医学科学的进一步培训。此外，我的实验室的成功将吸引ECSU的其他教师寻求资金，以发展他们在ECSU的研究和教学能力。从拟议项目中产生的出版物可能会导致如何评估潜在的环境化学品和药物的范式转变。

DESCRIPTION (provided by applicant): It is becoming increasingly evident that defining cellular environmental changes that represent risk factor for susceptibility to environment stressors is critical to improving the way we study potential environmental chemicals and pharmaceutical drugs. The goal of this project is to determine whether alteration of the Leydig cell redox environment during aging represents a risk factor for susceptibility to di-(2-ethylhexyl phthalate (DEHP)-induced inhibition of steroidogenesis. Exposure to DEHP, a well-known endocrine disruptor, can lead to reproductive health issues including hypospadias, testicular cancer, and poor semen quality. During development, androgen plays a critical role in programming sex organ morphogenesis and function. At all developmental stages, the presence of androgens in sufficient amounts is a critical determinant of the male phenotype. Consequently, environmental chemicals that alter endocrine function pose potential risks to the reproductive health of humans and animals. DEHP is a commonly used plasticizer that is loosely held between the interstices of the polymer matrix and thus it and its metabolites are ubiquitous contaminants of the environment. Human exposures to DEHP occur via food, inhalation, dermal contact and medical procedures (e.g. IV drip bags), which result in measurable levels of DEHP and metabolites in blood, urine, semen and breast milk. Exposure to mono-(2-ethylhexyl) phthalate (MEHP), the active metabolite of DEHP, was shown to inhibit LH-stimulated steroid formation by both purified adult rat Leydig cells and MA-10 mouse tumor Leydig cells. Interestingly, fetal exposures to DEHP have been shown to result in reduced litter size, and, later in life, Leydig cell hyperplasia, testicular atrophy, reduced serum levels of seru testosterone, and reduced fertility. Although the levels of human exposure to DEHP may not themselves result in high enough serum levels to cause harm, there are factors that may potentiate their effects. For example, changes in the cellular oxidant system that accompany aging, low grade inflammation and/or pre-exposure to other environmental agents may increase susceptibility to subsequent non-toxic doses of DEHP. The goals of this proposal are to determine whether: i) an age-related altered redox environment increases Leydig cell susceptibility to DEHP; ii) low doses of DEHP administered continuously, or second DEHP "hits" at later times, affect testosterone production in ways that single low doses do not; and iii) whether external influences such as modest inflammation might increase the susceptibility of Leydig cells to low doses of DEHP. The long term goal of this project is to enable me become an established and highly productive investigator capable of competing for and attracting R01 grant support to Elizabeth City State University (ECSU), a minority serving institution. It is expected that my involvement with the mentor's institution, The Johns Hopkins University, Bloomberg School of Public Health (JHSPH) will be a significant step in establishing a broader collaboration between JHSPH and ECSU to bring bright young minority students to pursue further training in biomedical science at JHSPH. In addition, the success of my laboratory will attract other faculty at ECSU to seek funding to develop their research and teaching capacities at ECSU. Publications that will rise from the proposed project could lead to a paradigm shift in how potential environmental chemicals and pharmaceutical drugs are evaluated.