Centre de recherche en toxicologie de l'environnement (TOXEN), Département des sciences biologiques, Université du Québec à Montréal, C.P. 8888, Succursale Centre-ville, Montreal, QC H3C 3P8, Canada.
Environment Canada, St. Lawrence Centre, 105 McGill Street, Montreal, QC H2Y 2E7, Canada.
Sci Total Environ. 2016 Mar 1;545-546:289-98. doi: 10.1016/j.scitotenv.2015.12.110. Epub 2015 Dec 31.
A number of studies have reported altered circulating thyroid hormone levels in birds exposed either in controlled settings or in their natural habitat to ubiquitous organohalogen compounds including organochlorines (OCs) and polybrominated diphenyl ether (PBDE) flame retardants. However, limited attention has been paid to underlying homeostatic mechanisms in wild birds such as changes in the expression of genes in the hypothalamic-pituitary-thyroid (HPT) axis. The objective of the present study was to investigate the relationships between hepatic concentrations of major organohalogens (PBDEs and OCs), and circulating thyroid hormone (free and total thyroxine (T4) and triiodothyronine (T3)) levels and transcription of 14 thyroid-related genes in three tissues (thyroid, brain, and liver) of an urban-adapted bird exposed to high organohalogen concentrations in the Montreal area (QC, Canada), the ring-billed gull (Larus delawarensis). Positive correlations were found between liver concentrations of several polychlorinated biphenyls (PCBs), PBDEs as well as chlordanes and total plasma T4 levels. Hepatic concentrations of several PBDEs were negatively correlated with mRNA levels of deiodinase type 3, thyroid peroxidase, and thyroid hormone receptor β (TRβ) in the thyroid gland. Liver PCB (deca-CB) correlated positively with mRNA levels of sodium-iodide symporter and TRα. In brain, concentrations of most PBDEs were positively correlated with mRNA levels of organic anion transporter protein 1C1 and transthyretin, while PCBs positively correlated with expression of TRα and TRβ as well as deiodinase type 2. These multiple correlative linkages suggest that organohalogens operate through several mechanisms (direct or compensatory) involving gene transcription, thus potentially perturbing the HPT axis of this highly organohalogen-contaminated ring-billed gull population.
许多研究报告指出，在受控环境或自然栖息地中，暴露于普遍存在的有机卤代化合物（包括有机氯和多溴联苯醚（PBDE）阻燃剂）中的鸟类，其循环甲状腺激素水平发生了变化。然而，对于野生鸟类中的基本体内平衡机制，如下丘脑-垂体-甲状腺（HPT）轴中基因表达的变化，关注较少。本研究的目的是研究主要有机卤代物（PBDE 和 OCs）在肝中的浓度与循环甲状腺激素（游离和总甲状腺素（T4）和三碘甲状腺原氨酸（T3））水平以及三种组织（甲状腺、脑和肝）中 14 种甲状腺相关基因的转录之间的关系暴露于蒙特利尔地区（QC，加拿大）高有机卤浓度下的城市适应鸟类环嘴鸥（Larus delawarensis）。发现肝脏中几种多氯联苯（PCBs）、PBDE 以及氯丹和总血浆 T4 水平之间存在正相关。几种 PBDE 的肝浓度与甲状腺中脱碘酶 3、甲状腺过氧化物酶和甲状腺激素受体β（TRβ）的 mRNA 水平呈负相关。肝脏 PCB（十氯）与钠-碘转运体和 TRα 的 mRNA 水平呈正相关。在大脑中，大多数 PBDE 的浓度与有机阴离子转运蛋白 1C1 和转甲状腺素的 mRNA 水平呈正相关，而 PCBs 与 TRα 和 TRβ以及脱碘酶 2 的表达呈正相关。这些多重关联表明，有机卤代物通过几种机制（直接或补偿性）作用于基因转录，从而可能扰乱这种高度有机卤代污染的环嘴鸥种群的 HPT 轴。
