Microplastics and nanoplastics (MNPs) are emerging environmental contaminants detected in human samples, and have raised concerns regarding their potential risks to human health, particularly neurotoxicity. This study aimed to investigate the deleterious effects of polystyrene nanoplastics (PS-NPs, 50 nm) and understand their mechanisms in inducing Parkinson's disease (PD)-like neurodegeneration, along with exploring preventive strategies. Following exposure to PS-NPs (0.5–500 μg/mL), we assessed cytotoxicity, mitochondrial integrity, ATP levels, and mitochondrial respiration in dopaminergic-differentiated SH-SY5Y cells. Molecular docking and dynamic simulations explored PS-NPs' interactions with mitochondrial complexes. We further probed mitophagy's pivotal role in PS-NP-induced mitochondrial damage and examined melatonin's ameliorative potential in vitro. We validated melatonin's intervention (intraperitoneal, 10 mg/kg/d) in C57BL/6 J mice exposed to 250 mg/kg/d of PS-NPs for 28 days. In our in vitro experiments, we observed PS-NP accumulation in cells, including mitochondria, leading to cell toxicity and reduced viability. Notably, antioxidant treatment failed to fully rescue viability, suggesting reactive oxygen species (ROS)-independent cytotoxicity. PS-NPs caused significant mitochondrial damage, characterized by altered morphology, reduced mitochondrial membrane potential, and decreased ATP production. Subsequent investigations pointed to PS-NP-induced disruption of mitochondrial respiration, potentially through interference with complex I (CI), a concept supported by molecular docking studies highlighting the influence of PS-NPs on CI. Rescue experiments using an AMPK pathway inhibitor (compound C) and an autophagy inhibitor (3-methyladenine) revealed that excessive mitophagy was induced through AMPK/ULK1 pathway activation, worsening mitochondrial damage and subsequent cell death in differentiated SH-SY5Y cells. Notably, we identified melatonin as a potential protective agent, capable of alleviating PS-NP-induced mitochondrial dysfunction. Lastly, our in vivo experiments demonstrated that melatonin could mitigate dopaminergic neuron loss and motor impairments by restoring mitophagy regulation in mice. Our study demonstrated that PS-NPs disrupt mitochondrial function by affecting CI, leading to excessive mitophagy through the AMPK/ULK1 pathway, causing dopaminergic neuron death. Melatonin can counteract PS-NP-induced mitochondrial dysfunction and motor impairments by regulating mitochondrial autophagy. These findings offer novel insights into the MNP-induced PD-like neurodegenerative mechanisms, and highlight melatonin's protective potential in mitigating the MNP’s environmental risk.

中文翻译：

---

聚苯乙烯纳米塑料暴露通过激活体内分化的 SH-SY5Y 细胞和多巴胺能神经元中的 AMPK/ULK1 途径诱导过度线粒体自噬

微塑料和纳米塑料（MNP）是在人类样本中检测到的新兴环境污染物，引起了人们对其对人类健康的潜在风险（特别是神经毒性）的担忧。本研究旨在调查聚苯乙烯纳米塑料（PS-NP，50 nm）的有害影响，了解其诱发帕金森病（PD）样神经变性的机制，并探索预防策略。暴露于 PS-NP (0.5–500 μg/mL) 后，我们评估了多巴胺能分化的 SH-SY5Y 细胞的细胞毒性、线粒体完整性、ATP 水平和线粒体呼吸。分子对接和动态模拟探索了 PS-NP 与线粒体复合物的相互作用。我们进一步探讨了线粒体自噬在 PS-NP 诱导的线粒体损伤中的关键作用，并在体外检查了褪黑激素的改善潜力。我们在暴露于 250 mg/kg/d PS-NP 28 天的 C57BL/6 J 小鼠中验证了褪黑素的干预作用（腹膜内，10 mg/kg/d）。在我们的体外实验中，我们观察到 PS-NP 在细胞（包括线粒体）中积累，导致细胞毒性和活力降低。值得注意的是，抗氧化剂治疗未能完全挽救活力，表明活性氧（ROS）独立的细胞毒性。PS-NPs 引起显着的线粒体损伤，其特征是形态改变、线粒体膜电位降低和 ATP 产生减少。随后的研究指出，PS-NP 可能通过干扰复合物 I (CI) 诱导线粒体呼吸中断，这一概念得到了分子对接研究的支持，强调了 PS-NP 对 CI 的影响。使用 AMPK 途径抑制剂（化合物 C）和自噬抑制剂（3-甲基腺嘌呤）进行的拯救实验表明，AMPK/ULK1 途径激活可诱导过度线粒体自噬，从而加剧分化的 SH-SY5Y 细胞中的线粒体损伤和随后的细胞死亡。值得注意的是，我们发现褪黑激素是一种潜在的保护剂，能够减轻 PS-NP 诱导的线粒体功能障碍。最后，我们的体内实验证明，褪黑激素可以通过恢复小鼠线粒体自噬调节来减轻多巴胺能神经元损失和运动障碍。我们的研究表明，PS-NPs 通过影响 CI 来破坏线粒体功能，通过 AMPK/ULK1 途径导致过度线粒体自噬，导致多巴胺能神经元死亡。褪黑激素可以通过调节线粒体自噬来抵消 PS-NP 诱导的线粒体功能障碍和运动障碍。这些发现为 MNP 诱导的 PD 样神经退行性机制提供了新的见解，并强调了褪黑激素在减轻 MNP 环境风险方面的保护潜力。