Crespo-Lopez María Elena, Costa-Malaquias Allan, Oliveira Edivaldo H C, Miranda Moysés S, Arrifano Gabriela P F, Souza-Monteiro José R, Sagica Fernanda Espirito-Santo, Fontes-Junior Enéas A, Maia Cristiane S F, Macchi Barbarella M, do Nascimento José Luiz M
Laboratório de Farmacologia Molecular, Instituto de Ciências Biológicas, Universidade Federal do Pará, 66075-110 Belém (Pará), Brasil.
Laboratório de Cultura de Tecidos e Citogenética, Departamento de Meio Ambiente, Instituto Evandro Chagas, 67030-000 Ananindeua (Pará), Brasil.
PLoS One. 2016 Sep 13;11(9):e0162822. doi: 10.1371/journal.pone.0162822. eCollection 2016.
Human exposure to relatively low levels of methylmercury is worrying, especially in terms of its genotoxicity. It is currently unknown as to whether exposure to low levels of mercury (below established limits) is safe. Genotoxicity was already shown in lymphocytes, but studies with cells of the CNS (as the main target organ) are scarce. Moreover, disturbances in the cell cycle and cellular proliferation have previously been observed in neuronal cells, but no data are presently available for glial cells. Interestingly, cells of glial origin accumulate higher concentrations of methylmercury than those of neuronal origin. Thus, the aim of this work was to analyze the possible genotoxicity and alterations in the cell cycle and cell proliferation of a glioma cell line (C6) exposed to a low, non-lethal and non-apoptotic methylmercury concentration. Biochemical (mitochondrial activity) and morphological (integrity of the membrane) assessments confirmed the absence of cell death after exposure to 3 μM methylmercury for 24 hours. Even without promoting cell death, this treatment significantly increased genotoxicity markers (DNA fragmentation, micronuclei, nucleoplasmic bridges and nuclear buds). Changes in the cell cycle profile (increased mitotic index and cell populations in the S and G2/M phases) were observed, suggesting arrest of the cycle. This delay in the cycle was followed, 24 hours after methylmercury withdrawal, by a decrease number of viable cells, reduced cellular confluence and increased doubling time of the culture. Our work demonstrates that exposure to a low sublethal concentration of MeHg considered relatively safe according to current limits promotes genotoxicity and disturbances in the proliferation of cells of glial origin with sustained consequences after methylmercury withdrawal. This fact becomes especially important, since this cellular type accumulates more methylmercury than neurons and displays a vital role protecting the CNS, especially in chronic intoxication with this heavy metal.
人类接触相对低水平的甲基汞令人担忧，尤其是考虑到其遗传毒性。目前尚不清楚接触低水平汞（低于既定限值）是否安全。淋巴细胞中已显示出遗传毒性，但针对中枢神经系统（作为主要靶器官）细胞的研究却很少。此外，此前在神经元细胞中观察到了细胞周期和细胞增殖的紊乱，但目前尚无关于神经胶质细胞的数据。有趣的是，神经胶质来源的细胞比神经元来源的细胞积累更高浓度的甲基汞。因此，本研究的目的是分析暴露于低浓度、非致死且非凋亡的甲基汞环境下的胶质瘤细胞系（C6）的可能遗传毒性以及细胞周期和细胞增殖的变化。生化（线粒体活性）和形态学（膜完整性）评估证实，在暴露于3μM甲基汞24小时后细胞没有死亡。即使没有促进细胞死亡，这种处理也显著增加了遗传毒性标志物（DNA片段化、微核、核质桥和核芽）。观察到细胞周期谱的变化（有丝分裂指数增加以及S期和G2/M期的细胞群体增加），表明细胞周期停滞。在甲基汞撤离24小时后，细胞周期的这种延迟伴随着活细胞数量减少、细胞汇合度降低以及培养物倍增时间增加。我们的研究表明，根据当前限值被认为相对安全的低亚致死浓度甲基汞暴露会促进神经胶质来源细胞的遗传毒性和增殖紊乱，并且在甲基汞撤离后会产生持续影响。这一事实变得尤为重要，因为这种细胞类型比神经元积累更多的甲基汞，并且在保护中枢神经系统方面发挥着至关重要的作用，尤其是在这种重金属的慢性中毒情况下。
