Department of Physiological Sciences and Center for Environmental and Human Toxicology, University of Florida Genetics Institute, Interdisciplinary Program in Biomedical Sciences Neuroscience, College of Veterinary Medicine, University of Florida, Gainesville, FL, 32611, USA.
Department of Physiological Sciences and Center for Environmental and Human Toxicology, University of Florida Genetics Institute, Interdisciplinary Program in Biomedical Sciences Neuroscience, College of Veterinary Medicine, University of Florida, Gainesville, FL, 32611, USA.
Neurotoxicology. 2017 Dec;63:1-12. doi: 10.1016/j.neuro.2017.08.007. Epub 2017 Aug 24.
Mitochondria are sensitive targets of environmental chemicals. Dieldrin (DLD) is an organochlorine pesticide that remains a human health concern due to high lipid bioaccumulation, and it has been epidemiologically associated to an increased risk for Parkinson's disease (PD). As mitochondrial dysfunction is involved in the etiology of PD, this study aimed to determine whether DLD impaired mitochondrial bioenergetics in dopaminergic cells. Rat immortalized dopaminergic N27 cells were treated for 24 or 48h with one dose of either a solvent control, 2.5, 25, or 250μM DLD. Dopaminergic cells treated with 250μM DLD showed increased Casp3/7 activity at 24 and 48h. DLD also caused a dose dependent reduction in cell viability of ∼25-30% over 24h. No significant effects on cell viability, apoptosis, nor cytotoxicity were detected at 24 or 48h with 2.5μM DLD. Following a 24h exposure to 2.5 and 25μM DLD, viable cells were subjected to a mitochondrial stress test using the Seahorse XFe24 Extracellular Flux Analyzer. Following three independent experiments conducted for rigor, dopaminergic cells that were treated with 2.5 and 25μM DLD consistently showed a reduction in maximum respiration and spare capacity compared to the control group. Molecular responses were measured to determine mechanisms of DLD-induced mitochondrial dysfunction. There were no changes in transcripts associated with mitochondrial membrane potential and permeability (e.g. Ant, Hk1, Tspo, Vdac), nor PI3 K/Akt/mTor signaling or mitochondrial-associated apoptotic factors (Bax, Bcl2, Casp3). However, transcript levels for Chop/Gadd153 (DNA Damage Inducible Transcript 3), an apoptotic gene activated following endoplasmic reticulum (ER) stress, were 3-fold higher in N27 cells treated with DLD, suggesting that DLD-induced mitochondrial dysfunction is related to ER stress. Dopamine cells were also assessed for changes in tyrosine hydroxylase (TH) protein, which did not differ among treatments. This study demonstrates that DLD impairs oxidative respiration in dopamine cells, and ER stress is hypothesized to be associated with the DLD-induced mitochondrial dysfunction. This is important as ER stress is also linked to PD. This study presents mechanistic insight into pesticide-induced mitochondrial dysfunction using a chemical that is reported to be associated to a higher risk for neurodegenerative disease.
线粒体是环境化学物质的敏感靶点。狄氏剂（DLD）是一种有机氯农药，由于其高脂质生物蓄积性，仍然是人类健康关注的问题，并且已在流行病学上与帕金森病（PD）的风险增加相关。由于线粒体功能障碍与 PD 的病因有关，因此本研究旨在确定 DLD 是否会损害多巴胺能细胞中的线粒体生物能。用一种溶剂对照、2.5、25 或 250μM DLD 对大鼠永生化多巴胺能 N27 细胞进行 24 或 48 小时的处理。用 250μM DLD 处理的多巴胺能细胞在 24 和 48 小时时 Casp3/7 活性增加。DLD 还导致细胞活力在 24 小时内降低了约 25-30％。在 24 小时内用 2.5μM DLD 处理，未检测到细胞活力、凋亡或细胞毒性的显著影响。在 24 或 48 小时内用 2.5 和 25μM DLD 处理后，用 Seahorse XFe24 细胞外通量分析仪对存活细胞进行线粒体应激测试。在进行了三项严格的独立实验后，与对照组相比，用 2.5 和 25μM DLD 处理的多巴胺能细胞的最大呼吸和备用能力均持续降低。测量了分子反应以确定 DLD 诱导的线粒体功能障碍的机制。与线粒体膜电位和通透性相关的转录物（例如 Ant、Hk1、Tspo、Vdac）、PI3 K/Akt/mTor 信号或线粒体相关凋亡因子（Bax、Bcl2、Casp3）没有变化。但是，在 DLD 处理的 N27 细胞中，与内质网（ER）应激后激活的凋亡基因 Chop/Gadd153（DNA 损伤诱导转录物 3）的转录本水平高 3 倍，表明 DLD 诱导的线粒体功能障碍与 ER 应激有关。还评估了多巴胺细胞中酪氨酸羟化酶（TH）蛋白的变化，而处理之间没有差异。这项研究表明，DLD 会损害多巴胺能细胞的氧化呼吸，并且 ER 应激与 DLD 诱导的线粒体功能障碍有关。这很重要，因为 ER 应激也与 PD 有关。这项研究使用报告与神经退行性疾病风险增加相关的化学物质，为农药诱导的线粒体功能障碍提供了机制上的见解。
