Department of Neurochemistry, Mossakowski Medical Research Centre, Polish Academy of Sciences, Pawinskiego 5, 02-106, Warsaw, Poland.
Department of Physiology, Institute of Pharmacology, Polish Academy of Sciences, Smetna 12, 31-343, Krakow, Poland.
Chemosphere. 2019 May;223:64-73. doi: 10.1016/j.chemosphere.2019.02.032. Epub 2019 Feb 8.
The brominated flame retardant tetrabromobisphenol A (TBBPA) is toxic to cultured brain neurons, and glutamate receptors partially mediate this effect; consequently, the depolarizing effect of TBBPA on neurons is to be expected, but it is yet to be actually demonstrated. The aim of this study was to detect TBBPA-evoked depolarization and identify the underlying mechanisms. The plasma membrane potential of rat cerebellar granule cells (CGC) in cerebellar slices or in primary cultures was measured using whole-cell current clamp recordings, or the fluorescent probe oxonol VI, respectively. The contribution of NMDA and AMPA receptors, voltage-gated sodium channels and intracellular calcium mobilization was tested using their selective antagonists or inhibitors. Direct interactions of TBBPA with NMDARs were tested by measuring the specific binding of radiolabeled NMDAR ligands to isolated rat cortical membrane fraction. TBBPA (25 μM) strongly depolarized CGC in cerebellar slices, and at ≥ 7.5 μM concentration-dependently depolarized primary CGC cultures. Depolarization of the primary CGC by 25 μM TBBPA was partly reduced when MK-801 was applied alone or in combination with either TTX or CNQX, or where bastadin 12 was applied in combination with ryanodine, whereas depolarization was completely prevented when MK-801, CNQX and TTX where combined. TBBPA had no effect on the specific binding of NMDAR radio-ligands to isolated cortical membranes. These results demonstrate the depolarizing effect of TBBPA on CGC, which is mainly mediated by ionotropic glutamate receptors, while voltage-gated sodium channels are also involved. We found no evidence for the direct activation of NMDARs by TBBPA.
溴化阻燃剂四溴双酚 A（TBBPA）对培养的脑神经元有毒性，谷氨酸受体部分介导了这种作用；因此，预计 TBBPA 会对神经元产生去极化作用，但尚未得到实际证明。本研究旨在检测 TBBPA 诱发的去极化并确定潜在机制。使用全细胞膜片钳记录或荧光探针 oxonol VI 分别测量小脑颗粒细胞（CGC）在小脑切片或原代培养物中的质膜电位。使用其选择性拮抗剂或抑制剂测试 NMDA 和 AMPA 受体、电压门控钠通道和细胞内钙动员的贡献。通过测量放射性标记的 NMDA 配体与分离的大鼠皮质膜部分的特异性结合来测试 TBBPA 与 NMDA 受体的直接相互作用。25μM 的 TBBPA 强烈去极化小脑切片中的 CGC，并在≥7.5μM 浓度依赖性地去极化原代 CGC 培养物。当单独或与 TTX 或 CNQX 联合应用 MK-801，或当 bastadin 12 与 Ryanodine 联合应用时，25μM TBBPA 对原代 CGC 的去极化部分减少，而当 MK-801、CNQX 和 TTX 联合应用时，去极化完全被阻止。TBBPA 对分离的皮质膜中 NMDA 放射性配体的特异性结合没有影响。这些结果表明 TBBPA 对 CGC 的去极化作用主要是通过离子型谷氨酸受体介导的，而电压门控钠通道也参与其中。我们没有发现 TBBPA 直接激活 NMDA 受体的证据。
