Department of Occupational and Environmental Health, School of Public Health, China Medical University, Shenyang, Liaoning, People's Republic of China.
Program of Environmental Toxicology, School of Public Health, China Medical University, Shenyang, Liaoning, People's Republic of China.
Neurochem Int. 2019 Jan;122:73-84. doi: 10.1016/j.neuint.2018.11.009. Epub 2018 Nov 14.
Emerging evidence indicates that nonylphenol (NP), a widely diffused and stable environmental contaminant, causes damage to the central nervous system (CNS). Although NP could cross the blood-brain barrier (BBB) and accumulate in key brain regions, little is known about the direct effects of NP on neurons. In this study, we aimed to investigate the direct effects of NP exposure on induction of apoptosis and autophagy in primary cortical neurons. Results showed that exposure to NP decreased the cell viability in a concentration-dependent manner. The exposure led to both the increase of TUNEL-positive neurons and the activation of caspase-3. Increased levels of endoplasmic reticulum (ER) stress-related proteins, GRP78, CHOP, ATF4, and casepase-12, were observed in neurons exposed to NP. At the same time, the exposure decreased Bcl-2/Bax ratio and mitochondrial transmembrane potential, and increased the release of Cytochrome-C. In addition, NP exposure enhanced LC3-II conversion, decreased levels of SQSTM1/p62, and increased levels of Beclin-1 and LAMP2. NP exposure also reduced the protein levels of p-mTOR, and did not change the levels of total mTOR. Furthermore, to investigate the role of autophagy in NP-induced apoptosis, both the autophagy inhibitor chloroquine (CQ) and the autophagy inducer rapamycin (RAP) were applied to modulate autophagy activation in primary cortical neurons. The inhibition of autophagy caused by CQ enhanced NP-induced apoptosis; conversely, RAP-induced autophagy remarkably suppressed it. In conclusion, our findings demonstrate that NP exposure induced apoptosis with a concomitant increase of autophagic flux in primary cortical neurons, which supports the idea that this potential neurotoxin has direct effects of on neurons. Both ER stress and mitochondrial pathways may be involved in NP-induced apoptosis in neurons. Furthermore, our results also suggest that autophagy activation might be a protective strategy to ameliorate NP-induced apoptosis in neurons.
新兴证据表明，壬基酚（NP）作为一种广泛存在且稳定的环境污染物，会对中枢神经系统（CNS）造成损害。尽管 NP 能够穿过血脑屏障（BBB）并在关键的脑区积累，但人们对 NP 对神经元的直接影响知之甚少。在这项研究中，我们旨在研究 NP 暴露对原代皮质神经元凋亡和自噬的直接影响。结果表明，NP 暴露以浓度依赖的方式降低细胞活力。暴露导致 TUNEL 阳性神经元数量增加和 caspase-3 激活。NP 暴露的神经元中内质网（ER）应激相关蛋白 GRP78、CHOP、ATF4 和 caspase-12 的水平增加。同时，暴露降低了 Bcl-2/Bax 比值和线粒体跨膜电位，并增加了 Cytochrome-C 的释放。此外，NP 暴露增强了 LC3-II 的转化，降低了 SQSTM1/p62 的水平，增加了 Beclin-1 和 LAMP2 的水平。NP 暴露还降低了 p-mTOR 的蛋白水平，而总 mTOR 的水平没有变化。此外，为了研究自噬在 NP 诱导的凋亡中的作用，我们应用自噬抑制剂氯喹（CQ）和自噬诱导剂雷帕霉素（RAP）来调节原代皮质神经元中的自噬激活。CQ 抑制自噬增强了 NP 诱导的凋亡；相反，RAP 诱导的自噬显著抑制了它。总之，我们的研究结果表明，NP 暴露诱导原代皮质神经元凋亡，并伴有自噬流的增加，这支持了这种潜在神经毒素对神经元有直接作用的观点。内质网应激和线粒体途径可能都参与了 NP 诱导的神经元凋亡。此外，我们的结果还表明，自噬激活可能是一种保护策略，可以改善 NP 诱导的神经元凋亡。
