NEURAL AND ENDOCRINE EFFECTS OF ENVIRONMENTAL EXPOSURE TO CHEMICALS

环境中接触化学品对神经和内分泌的影响

• 批准号: 6217752
• 负责人: GLORIA V CALLARD
• 金额: $ 14.49万
• 依托单位: BOSTON UNIVERSITY MEDICAL CAMPUS
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-04-01 至 2000-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6217752
• 关键词: Sertoli cells; apoptosis; blood testis barrier; cadmium; complementary DNA; disease /disorder model; environmental contamination; genetic library; male reproductive system disorder; meiosis; membrane permeability; metal poisoning; metallothionein; nervous system; neurotoxins; sharks; stem cells; sulfated glycoprotein 2

Epidemiological studies indicate that male gametes and the complex, hormone-regulated processes by which germ cell proliferation, development and survival are controlled, may be threatened. By virtue of a long biological half-life, cadmium (Cd) exemplifies a trace environmental pollutant with potential as a cumulative toxicant. Although spermatogenesis is exquisitely sensitive to Cd toxicity, which may be related to increased permeability of the blood-testis barrier and high constitutive expression of metallothionein (Mt), attempts to pinpoint sensitive stages, cell-types and mechanisms of action have been hampered by the complex testicular organization of common laboratory mammals. A technically advantageous alternative is the shark testis, which facilitates analysis of spermatogenesis stage-by-stage in vivo and allows intact germinal units (spermatocysts), comprising stage-synchronized germ cell/Sertoli cell clones, to be isolated for experimentation and analysis in vitro. Initial studies indicate that Cd increases permeability of a functional barrier in meiotic and postmeiotic stages but is preferentially concentrated in tissues at premeiotic stages, where it increases synthesis of a Mt-like protein, increases the percentage of germinal clones undergoing programmed cell death (apoptosis), and increases secretion of SGP-2, a frequent marker of apoptosis in somatic cells. We propose to examine the hypothesis that Cd has direct access to germ cells in early developmental st ages, is taken up by an active Cd-accumulating mechanisms that is further amplified by enhanced mt expression, and activates a cell death program by perturbing normal control mechanisms. Cd-mediated defects early in development would have profound consequences for all subsequent stages and the final number of mature spermatozoa. Using the shark testis model and in vivo and in vitro approaches, we will (1) define kinetics of Cd uptake and retention stage-by-stage and identify cellular and nuclear vs. cytosolic sites of accumulation; (2) relate Cd exposure to intracellular levels and to Cd effects on barrier permeability, Mt and SGP- 2 expression, and to the extent and timing of apoptosis; (3) elucidate the relationship between apoptosis and DNA replication/repair and reproductive/hormonal status in response to Cd; (4) initiate studies to determine pathways by which Cd activates apoptosis in the stem cell/spermatogonial germ cell population; and (5) evaluate the utility of cultured premeiotic spermatocysts for identifying spermatogenic toxicants that affect programmed (apoptotic) vs. unregulated (necrotic) death of male germ cells.

流行病学研究表明，雄配子和复杂的， 生殖细胞增殖、发育的激素调节过程 生存受到控制，可能受到威胁。 凭借着长久以来 生物半衰期，镉 (Cd) 是微量环境的例证 具有累积毒物潜力的污染物。 虽然 精子发生对镉毒性极其敏感，这可能是 与血睾屏障通透性增加和高 金属硫蛋白（Mt）的组成型表达，试图查明 敏感阶段、细胞类型和作用机制受到阻碍 常见实验室哺乳动物的复杂睾丸组织。 一个 技术上有利的替代方案是鲨鱼睾丸，它有助于 体内精子发生的逐阶段分析并允许完整 生发单位（精囊），包括阶段同步的胚芽 细胞/支持细胞克隆，用于分离实验和分析 体外。 初步研究表明，镉会增加渗透性 减数分裂和减数分裂后阶段的功能屏障，但优先 集中在减数分裂前阶段的组织中，增加合成 Mt 样蛋白，增加生发克隆的百分比 经历程序性细胞死亡（细胞凋亡），并增加分泌 SGP-2，体细胞凋亡的常见标志物。 我们建议 检查镉在早期可直接进入生殖细胞的假设 发育阶段，被活跃的 Cd 积累机制所占据 通过增强 mt 表达进一步放大，并激活细胞 通过扰乱正常的控制机制来实现死亡程序。 镉介导的缺陷 早期发展将对所有后续产生深远的影响 阶段和成熟精子的最终数量。 使用鲨鱼睾丸 模型以及体内和体外方法，我们将（1）定义动力学 逐步吸收和保留 Cd，并识别细胞和细胞核 与细胞溶质的积累位点相比； (2) 将镉暴露与 细胞内水平以及 Cd 对屏障通透性、Mt 和 SGP 的影响 2表达，以及细胞凋亡的程度和时间； (3) 阐明 细胞凋亡与DNA复制/修复之间的关系 对镉的反应的生殖/荷尔蒙状态； (4) 开展研究 确定 Cd 激活茎细胞凋亡的途径 细胞/精原生殖细胞群； (5) 评估效用 培养的减数分裂前精囊用于鉴定生精毒物 影响男性程序性（细胞凋亡）与不受控制（坏死）死亡 生殖细胞。