Li Y Robert, Santo Arben, Zhu Hong, Jia Zhenquan, Trush Michael A
Department of Pharmacology, Campbell University Medical School, Buies Creek, NC 27506, USA.
Department of Pharmaceutical Sciences, Campbell University College of Pharmacy and Health Sciences, Buies Creek, NC 27506, USA.
React Oxyg Species (Apex). 2018 Sep;6(17):338-348. doi: 10.20455/ros.2018.855.
In this work, we investigated the effects of graphene quantum dots (GQDs) on copper redox-mediated free radical generation and cell injury. Using electron paramagnetic resonance (EPR) spectrometry in conjunction with 5,5-dimethyl-1-pyrroline -oxide (DMPO) as a spin trap, we found that GQDs at a concentration as low as 1 μg/ml significantly inhibited Cu(II)/HO-mediated hydroxyl radical formation. GQDs also blocked Cu(II)-catalyzed nucleophilic addition of HO to DMPO to form a DMPO-OH adduct in the absence of HO, suggesting a potential for GQDs to inhibit copper redox activity. Indeed, we observed that the presence of GQDs prevented HO-mediated reduction of Cu(II) to Cu(I) though GQDs themselves also caused the reduction of Cu(II) to Cu(I). To further investigate the effects of GQDs on copper redox activity, we employed the Cu(II)/hydroquinone system in which copper redox activity plays an essential role in the oxidation of hydroquinone to semiquinone radicals with consequent oxygen consumption. Using oxygen polarography as well as EPR spectrometry, we demonstrated that the presence of GQDs drastically blocked the oxygen consumption and semiquinone radical formation resulting from the reaction of Cu(II) and hydroquinone. These results suggested that GQDs suppressed free radical formation via inhibiting copper redox activity. Lastly, using cultured human cardiomyocytes, we demonstrated that the presence of GQDs also protected against Cu(II)/HO-mediated cardiac cell injury as indicated by morphological changes (e.g., cell shrinkage and degeneration). In conclusion, our work shows, for the first time, the potential for using GQDs to counteract copper redox-mediated biological damage.
在本研究中，我们调查了石墨烯量子点（GQDs）对铜氧化还原介导的自由基生成及细胞损伤的影响。通过电子顺磁共振（EPR）光谱联用5,5-二甲基-1-吡咯啉-N-氧化物（DMPO）作为自旋捕获剂，我们发现浓度低至1μg/ml的GQDs能显著抑制Cu（II）/HO介导的羟基自由基形成。在没有HO的情况下，GQDs还能阻止Cu（II）催化的HO对DMPO的亲核加成反应，从而形成DMPO-OH加合物，这表明GQDs具有抑制铜氧化还原活性的潜力。实际上，我们观察到GQDs的存在阻止了HO介导的Cu（II）还原为Cu（I），尽管GQDs本身也会导致Cu（II）还原为Cu（I）。为了进一步研究GQDs对铜氧化还原活性的影响，我们采用了Cu（II）/对苯二酚体系，在该体系中，铜氧化还原活性在对苯二酚氧化为半醌自由基并伴随耗氧的过程中起着至关重要的作用。通过氧极谱法和EPR光谱法，我们证明了GQDs的存在极大地阻止了Cu（II）与对苯二酚反应导致的耗氧和半醌自由基形成。这些结果表明，GQDs通过抑制铜氧化还原活性来抑制自由基形成。最后，我们使用培养的人类心肌细胞证明，GQDs的存在还能保护细胞免受Cu（II）/HO介导的心脏细胞损伤，这可通过形态学变化（如细胞收缩和变性）得以体现。总之，我们的研究首次表明了利用GQDs对抗铜氧化还原介导的生物损伤的潜力。
