Department of Basic Medical Sciences, National Institute for Minamata Disease, Kumamoto, Japan.
Department of Clinical Medicine, National Institute for Minamata Disease, Kumamoto, Japan.
Toxicol Appl Pharmacol. 2015 Feb 1;282(3):259-66. doi: 10.1016/j.taap.2014.12.008. Epub 2014 Dec 26.
Methylmercury (MeHg) is an environmental toxin which induces cell death specific for the nervous systems. Here we show that MeHg causes neuronal cell death through the suppression of the tropomyosin receptor kinase A (TrkA) pathway, and that compounds activating the TrkA pathway prevent MeHg-induced nerve damage in vitro and in vivo. We first investigated the mechanism of MeHg-induced neurotoxicity in differentiating neurons using PC12 cells. Exposure to 100nM MeHg for 1day induced apoptosis in differentiating PC12 cells. Further, MeHg-induced apoptosis was preceded by inhibition of neurite extension, as determined by ELISA analyses of the neurite-specific protein neurofilament triplet H protein (NF-H). To determine the mechanism of MeHg-induced apoptosis, we evaluated the effects of MeHg on the TrkA pathway, which is known to regulate neuronal differentiation and viability. Western blot analysis demonstrated that, like the TrkA phosphorylation inhibitor K252a, MeHg inhibited phosphorylation of TrkA and its downstream effectors. Furthermore, GM1 ganglioside and its analog MCC-257, which enhance TrkA phosphorylation, overcame the effect of MeHg in neurons, supporting the involvement of the TrkA pathway in MeHg-induced nerve damage. Finally, we demonstrated that MCC-257 rescued the clinical sign and pathological changes in MeHg-exposed rats. These findings indicate that MeHg-induced apoptosis in neuron is triggered by inhibition of the TrkA pathway, and that GM1 ganglioside and MCC-257 effectively prevent MeHg-induced nerve damage.
甲基汞（MeHg）是一种环境毒素，可特异性诱导神经系统细胞死亡。在这里，我们表明 MeHg 通过抑制原肌球蛋白受体激酶 A（TrkA）途径引起神经元细胞死亡，并且激活 TrkA 途径的化合物可预防体外和体内 MeHg 诱导的神经损伤。我们首先使用 PC12 细胞研究了 MeHg 在分化神经元中引起神经毒性的机制。用 100 nM MeHg 处理 1 天会诱导分化 PC12 细胞发生细胞凋亡。此外，通过 ELISA 分析神经丝三联体 H 蛋白（NF-H）测定的神经突特异性蛋白，MeHg 诱导的细胞凋亡之前先抑制神经突延伸。为了确定 MeHg 诱导细胞凋亡的机制，我们评估了 MeHg 对 TrkA 途径的影响，该途径已知可调节神经元分化和存活。Western blot 分析表明，与 TrkA 磷酸化抑制剂 K252a 一样，MeHg 抑制了 TrkA 及其下游效应物的磷酸化。此外，GM1 神经节苷脂及其类似物 MCC-257 可增强 TrkA 磷酸化，可克服 MeHg 对神经元的作用，支持 TrkA 途径参与 MeHg 诱导的神经损伤。最后，我们证明 MCC-257 挽救了暴露于 MeHg 的大鼠的临床症状和病理变化。这些发现表明，MeHg 诱导神经元凋亡是由 TrkA 途径的抑制触发的，GM1 神经节苷脂和 MCC-257 可有效预防 MeHg 诱导的神经损伤。
