Environmental Chemistry and Toxicology Laboratory, Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720;
Department of Entomology, College of Agricultural and Environmental Science, University of California, Davis, CA 95616; and.
Proc Natl Acad Sci U S A. 2014 Jun 10;111(23):8607-12. doi: 10.1073/pnas.1407379111. Epub 2014 May 27.
Use of the highly toxic and easily prepared rodenticide tetramethylenedisulfotetramine (TETS) was banned after thousands of accidental or intentional human poisonings, but it is of continued concern as a chemical threat agent. TETS is a noncompetitive blocker of the GABA type A receptor (GABAAR), but its molecular interaction has not been directly established for lack of a suitable radioligand to localize the binding site. We synthesized [(14)C]TETS (14 mCi/mmol, radiochemical purity >99%) by reacting sulfamide with H(14)CHO and s-trioxane then completion of the sequential cyclization with excess HCHO. The outstanding radiocarbon sensitivity of accelerator mass spectrometry (AMS) allowed the use of [(14)C]TETS in neuroreceptor binding studies with rat brain membranes in comparison with the standard GABAAR radioligand 4'-ethynyl-4-n-[(3)H]propylbicycloorthobenzoate ([(3)H]EBOB) (46 Ci/mmol), illustrating the use of AMS for characterizing the binding sites of high-affinity (14)C radioligands. Fourteen noncompetitive antagonists of widely diverse chemotypes assayed at 1 or 10 µM inhibited [(14)C]TETS and [(3)H]EBOB binding to a similar extent (r(2) = 0.71). Molecular dynamics simulations of these 14 toxicants in the pore region of the α1β2γ2 GABAAR predict unique and significant polar interactions for TETS with α1T1' and γ2S2', which are not observed for EBOB or the GABAergic insecticides. Several GABAAR modulators similarly inhibited [(14)C]TETS and [(3)H]EBOB binding, including midazolam, flurazepam, avermectin Ba1, baclofen, isoguvacine, and propofol, at 1 or 10 μM, providing an in vitro system for recognizing candidate antidotes.
使用剧毒且易于制备的灭鼠剂四亚甲基二砜四胺（TETS）在数千例意外或故意的人类中毒后被禁用，但由于其作为化学威胁剂的持续存在，仍令人担忧。TETS 是非竞争性 GABA 型 A 受体（GABAAR）阻断剂，但由于缺乏合适的放射性配体来定位结合位点，其分子相互作用尚未直接确定。我们通过将磺酰胺与 H(14)CHO 和 s-三氧杂环己烷反应，然后用过量 HCHO 完成顺序环化反应，合成了 [(14)C]TETS（14 mCi/mmol，放射化学纯度>99%）。加速质谱（AMS）的出色放射性碳灵敏度允许将 [(14)C]TETS 与大鼠脑膜中的神经受体结合研究与标准 GABAAR 放射性配体 4'-乙炔基-4-n-[(3)H]丙基双环邻苯二甲酸酯 ([(3)H]EBOB)（46 Ci/mmol）进行比较，说明了 AMS 用于表征高亲和力 [(14)C]放射性配体结合位点的用途。在 1 或 10 μM 下测定的 14 种具有广泛化学结构的非竞争性拮抗剂均以相似的程度抑制 [(14)C]TETS 和 [(3)H]EBOB 与结合（r(2) = 0.71）。这些 14 种毒物在 α1β2γ2 GABAAR 孔区的分子动力学模拟预测 TETS 与 α1T1'和 γ2S2'具有独特且显著的极性相互作用，而 EBOB 或 GABA 类杀虫剂则没有观察到这些作用。几种 GABAAR 调节剂，包括咪达唑仑、氟西泮、阿维菌素 Ba1、巴氯芬、异瓜氨酸和丙泊酚，在 1 或 10 μM 时同样抑制 [(14)C]TETS 和 [(3)H]EBOB 结合，为识别候选解毒剂提供了体外系统。
