Esperanza Marta, Houde Magali, Seoane Marta, Cid Ángeles, Rioboo Carmen
Laboratorio de Microbiología, Facultad de Ciencias, Universidade da Coruña, Campus de A Zapateira s/n 15071. A Coruña, Spain.
Environment and Climate Change Canada, Aquatic Contaminants Research Division, 105 McGill Street, Montreal, QC, H2Y 2E7, Canada.
Aquat Toxicol. 2017 Aug;189:184-193. doi: 10.1016/j.aquatox.2017.06.015. Epub 2017 Jun 19.
The aim of this study was to investigate the impacts and modes of action of a chemical and nutrient deprivation on the cellular senescence process of Chlamydomonas reinhardtii. Several molecular and cellular parameters related to senescence phenomena were monitored in C. reinhardtii cells exposed for 24h to a sublethal concentration (0.25μM) of the herbicide atrazine and in unexposed 96h cells in an early stationary phase of growth. All endpoints showed the same pattern of response between treatments, except for the intracellular level of calcium, where a significant increase was observed in 24h-exposed cultures compared to 24h-log controls. Results also indicated that cell viability remained above 98% for all conditions. Reactive oxygen species (ROS) levels and caspase activity increased in all experimental cultures with respect to 24h-log controls and alterations in the nuclear morphology and cells with auto-phagosomes were observed in all treatments. However, a decrease in lipid peroxidation was detected which could be related to the observed increment of autophagic vacuoles that recycle damaged material, such as altered lipids in microalgal membranes. Furthermore, responses at the molecular level were also investigated. Gene transcription analyses, carried out by RT-qPCR technique, indicated an increase in transcripts for genes encoding glutathione S-transferase (GST) and ascorbate peroxidase (APX I) and a decrease for those encoding catalase (CAT), glutathione peroxidase (GPX) and Mn-superoxide dismutase (SOD-1) in both experimental treatments. Overall molecular and cellular results suggest that a short-term exposure to a sublethal concentration of atrazine may induce senescence features in microalgal cells which are the base of aquatic food webs.
本研究的目的是调查化学物质和营养剥夺对莱茵衣藻细胞衰老过程的影响及作用模式。在暴露于亚致死浓度（0.25μM）除草剂莠去津24小时的莱茵衣藻细胞以及处于生长早期稳定期未暴露的96小时细胞中，监测了与衰老现象相关的几个分子和细胞参数。除细胞内钙水平外，所有终点在处理之间均显示出相同的反应模式，与24小时对数生长期对照相比，在暴露24小时的培养物中观察到细胞内钙水平显著增加。结果还表明，在所有条件下细胞活力均保持在98%以上。相对于24小时对数生长期对照，所有实验培养物中的活性氧（ROS）水平和半胱天冬酶活性均增加，并且在所有处理中均观察到核形态改变和出现自噬体的细胞。然而，检测到脂质过氧化作用降低，这可能与观察到的自噬泡增加有关，自噬泡可回收受损物质，如微藻膜中改变的脂质。此外，还研究了分子水平的反应。通过RT-qPCR技术进行的基因转录分析表明，在两种实验处理中，编码谷胱甘肽S-转移酶（GST）和抗坏血酸过氧化物酶（APX I）的基因转录本增加，而编码过氧化氢酶（CAT）、谷胱甘肽过氧化物酶（GPX）和锰超氧化物歧化酶（SOD-1）的基因转录本减少。总体分子和细胞结果表明，短期暴露于亚致死浓度的莠去津可能会在作为水生食物网基础的微藻细胞中诱导衰老特征。
