Mechanisms of Reproductive Neuroendocrine Toxicity

描述（由申请人提供）：拟议研究的长期目标是确定神经内分泌干扰的主要原因和公共卫生关注的主要环境污染物的目标。在本延续提案中，将在鱼类模型大西洋黄花鱼中研究多氯联苯1254（PCB）诱导的色氨酸羟化酶（TPH）活性受损的近端原因和生殖神经内分泌后果。将在黄花鱼中检验以下总体假设：多氯联苯引起的控制生殖的促性腺激素-促性腺激素释放激素-促黄体激素（5-HT-GnRH-LH）神经内分泌途径受损涉及非共面同源物引起的TPH活性降低，这是氧化作用/损伤的结果。首先，一系列PCB浓度对TPH活性和下丘脑TPH蛋白及其mRNA水平的影响将进行研究，然后通过实验研究氧化损伤和神经内分泌干扰之间的关联。随后，维生素E（一种抗氧化剂）治疗对肾上腺素能功能的影响，以及其在逆转PCB对脂质过氧化、丙二醛-蛋白质加合物形成、TPH活性和神经内分泌功能的影响方面的功效，将进行研究。最后，一种共面二恶英类多氯联苯同系物（PCB 77）对TPH活性的影响将与两种非共面二邻位取代的多氯联苯同系物（PCB 47和PCB 153）所观察到的影响进行比较，以确定多氯联苯混合物中神经毒性效应的可能致病因子。还将研究PCB同源物诱导的下丘脑促性腺激素能功能受损对5-HT-GnRH-LH神经内分泌系统功能完整性的影响。具体目标是：i）确定PCB诱导的下丘脑TPH活性的降低是否伴随着TPH蛋白和mRNA水平的改变; ii）确定PCB诱导的TPH活性和5-HT-GnRH-LH功能的降低是否与氧化损伤相关，以及抗氧化剂在逆转这些效应中的功效; iii）确定多氯联苯混合物中的非共面二邻位取代多氯联苯同系物成分是否可以解释其对TPH活性和5-HT-GnRH-LH功能的毒性效应。现在有令人信服的证据表明，在环境或职业中接触多氯联苯或食用五大湖中受多氯联苯污染的鱼类与人类生殖和神经内分泌功能障碍及其子女的发育缺陷有关。然而，PCB神经毒性的机制仍然知之甚少。拟议的研究将探讨PCB神经毒性和神经内分泌毒性的新机制，这可能对其他神经功能（如与精神健康相关的神经功能）也具有重要意义。

DESCRIPTION (provided by applicant): The long-term goal of the proposed research is to determine the principal causes of neuroendocrine disruption and targets of the major environmental contaminants of public health concern. In this continuation proposal the proximal cause of Aroclor 1254 (PCB)-induced impairment of tryptophan hydroxylase (TPH) activity and the reproductive neuroendocrine consequences will be investigated in a fish model, Atlantic croaker. The following overall hypothesis will be tested in croaker: PCB-induced impairment of the serotonin-gonadotropin releasing hormone-luteinizing hormone (5-HT-GnRH-LH) neuroendocrine pathway controlling reproduction involves a non-coplanar congener-induced decrease in TPH activity, which is the result of oxidative effects/damage. Initially, the effects of a range of PCB concentrations on TPH activity and hypothalamic levels of the TPH protein and its mRNA will be investigated followed by experiments to investigate associations between oxidative damage and neuroendocrine disruption. Subsequently, the effects of vitamin E (an antioxidant) treatment on serotonergic functions, and its efficacy in reversing the effects of the PCB on lipid peroxidation, malondialdehyde-protein adduct formation, TPH activity, and neuroendocrine function, will be investigated. Finally, the effects of a coplanar dioxin-like PCB congener (PCB 77) on TPH activity will be compared to those observed with two non-coplanar di-ortho-substituted PCB congeners (PCB 47 and PCB 153) to identify likely causative agents of the neurotoxic effects in the PCB mixture. The consequences of PCB congener-induced impairment of hypothalamic serotonergic function on the functional integrity of the 5-HT-GnRH-LH neuroendocrine system will also be investigated. The specific objectives are to: i) determine whether the PCB-induced decrease in the hypothalamic TPH activity is accompanied by alterations in TPH protein and mRNA levels; ii) determine whether the PCB-induced decreases in TPH activity and 5-HT-GnRH-LH function are associated with oxidative damage, and the efficacy of an antioxidant in reversing these effects; iii) determine whether the non-coplanar di-ortho-substituted PCB congener component of PCB mixtures could account for their toxic effects on TPH activity and 5-HT-GnRH-LH function. There is now compelling evidence that the environmental or occupational exposure to PCBs or consumption of PCB-contaminated fish in the Great Lakes is associated with reproductive and neuroendocrine dysfunction in humans and developmental deficits in their children. However, the mechanisms of PCB neurotoxicity remain poorly understood. The proposed study will investigate a novel mechanism of PCB neurotoxicity and neuroendocrine toxicity which may also have significance for other neural functions such as those associated with mental health.