DIOXINS AND HYPOTHALAMIC APPETITE NEUROPEPTIDES

这笔小额赠款的主要假设是，发育期间(即围产期)暴露于多氯芳香烃(PCAHs)或PCAHs混合物会扰乱对摄食行为的中央控制。多氯二苯并-二恶英(PCDDs)、联苯(PCbs)和二苯并呋喃(PCDF)等多环芳烃是一类广泛存在的异类化合物，具有较长的生物半衰期和生物积累潜力。在围产期接触PCAHs混合物的儿童中，它们在母乳中的丰度和潜在的神经发育毒性，包括生长迟缓，被记录在案。毒性最大的是(2，3，7，8-四氯二苯并-Rho-二恶英)或TCDD。TCDD是一种非常有效的厌食症和致瘦药物；在动物研究中，PCAH暴露的一个特征是“消耗综合征”，包括生长速度下降和吞噬减少。多环芳烃抑制摄食行为的毒性和作用部位的潜在机制(S)尚不清楚。我们提出的假设是，由于发育过程中暴露于PCAH，控制摄食行为的下丘脑中枢神经肽的动态平衡被破坏，这是PCAH诱导的吞噬减少的一个机制。我们将首先测量在妊娠期或妊娠期和哺乳期给予TCDD对下丘脑两种刺激性神经肽：神经肽Y(NPY)和黑色素浓缩激素(MCH)以及两种抑制神经肽：α-黑素细胞刺激素(α-MSH)和促肾上腺皮质激素释放激素(CRH)表达的影响。如果我们没有观察到TCDD单独对妊娠或妊娠+哺乳期实验中提出的一种或多种下丘脑神经肽的影响(S)，那么我们将测试由2，3，7，8-TCDD，2，3，7，8-TCDF，1，2，3，7，8-PeCDD，1，2，3，7，8-PeCDF，2，3，4，7，8-PeCDF，OCDF，以及多氯联苯77、126和169组成的PCAH混合物在妊娠期间或妊娠和哺乳期给予的影响。我们将测量参与食物摄取调节的其他下丘脑神经肽的表达，如甘丙素、刺鼠相关肽和食欲素。我们将通过Northern杂交和狭缝印迹分析以及放射免疫分析来测量PCAHs对下丘脑显微解剖区域神经肽表达的影响。如果我们发现在PCAH治疗期间，下丘脑神经肽表达水平的变化并不是PCAH引起的吞噬减少的基础，我们将检验另一种假说，即PCAH扰乱了下丘脑NPY、食欲素和α-MSH受体的表达。我们试图证明参与下丘脑摄食行为控制的神经肽或神经肽受体的稳态改变是PCAHs厌食作用的一个机制。

The primary hypothesis for this small grant is that developmental exposure (ie, perinatal) to PolyChlorinated Aromatic Hydrocarbons (PCAHs) or to mixtures of PCAHs disrupts the central control of feeding behavior. PCAHs, such as polychlorinated dibenzo-rho-dioxins (PCDDs), biphenyls (PCBs) and dibenzofurans (PCDFs) represent a diverse group of widespread xenobiotics with long biological half lives and potential for bioaccumulation. Their abundance in human milk and potent neurodevelopmental toxicity, including growth retardation, in children exposed perinatally to mixtures of PCAHs is documented. The most toxic of the PCAHs is (2,3,7,8-tetrachlorodibenzo-rho-dioxin) or TCDD. TCDD is an exceedingly potent anorexic and leptogenic agent; a hallmark of PCAH exposure in animal studies is the " wasting syndrome" which includes depressed growth rates and hypophagia. The underlying mechanism(s) of toxicity and site of action for the inhibitory action of PCAHs on feeding behavior is not known. We propose the hypothesis that disruption in the homeostasis of neuropeptides in hypothalamic centers that control ingestive behavior, by developmental exposure to PCAHs, is a mechanism for PCAH-induced hypophagia. We will initially measure the effects of TCDD given either during gestation or during both gestation and lactation on hypothalamic expression of two stimulatory neuropeptides: neuropeptide Y (NPY) and melanin-concentrating hormone (MCH) and of two inhibitory neuropeptides: alpha-melanocyte-stimulating hormone (alpha-MSH) and corticotrophin-releasing hormone (CRH). If we do not observe an effect(s) of TCDD alone on one or more of the of hypothalamic neuropeptides as proposed in either the gestation or gestation plus lactation experiments, we will then test the effects of a mixture of PCAHs composed of 2,3,7,8-TCDD, 2,3,7,8-TCDF,1,2,3,7,8-PeCDD, 1,2,3,7,8-PeCDF, 2,3,4,7,8-PeCDF, OCDF, and PCBs 77, 126 and 169 given either during gestation or during gestation and lactation. We will measure expression of other hypothalamic neuropeptides involved in regulation of food intake such as galanin, agouti-related peptide and the orexins. We will measure the effects of PCAHs on neuropeptide expression in micro-dissected hypothalamic regions by means of Northern and slot blotting analyses and by radioimmunoassays. If we find that changes in expression levels of hypothalamic neuropeptides do not underlie the PCAH-induced hypophagia during PCAH treatment, we will test an alternate hypothesis that PCAHs disrupt hypothalamic expression of receptors for NPY, orexins and alpha-MSH. We intend to demonstrate that alteration in the homeostasis of neuropeptides or of neuropeptide receptors involved in hypothalamic control of feeding behavior is a mechanism underlying the anorectic action of PCAHs.