Common and specific effects of gadolinium and yttrium separately, and jointly with nifedipine, on the bivalve mollusc Unio tumidus

Environmental concentrations of rare earth elements (REEs) are increasing rapidly due to their unique properties and widespread application in modern technologies. Since the biological effects of REEs are expected to be similar to those of essential metals and cause oxidative stress, the goal of this study was to verify these directions of their impact in the bivalve mollusc Unio tumidus. The mussels were treated with gadolinium (Gd, 30 nM), yttrium (Y, 30 nM), and their mixture (Mix) with the Ca-channel blocker nifedipine (NFD, 10 µM) for 14 days. The distribution of zinc (Zn), involving metallothioneins (MT), as well as the redox state and signs of toxicity, was analysed in the digestive gland. The visible changes due to Gd accumulation, unlike those of Y, were observed in the tissue and were accompanied by a decrease in lysosomal integrity. Both Gd and Y increased the total MT (MTSH) concentration without increasing ZnMT levels. The presence of NFD alleviated the effects of single exposures to Gd or Y on MT and Gd accumulation. It induced approximately 2-fold increases in Cyp450-dependent EROD, caspase-3, and GTPase activities, indicating a Ca-dependent and Zn-related mode of action for the studied REEs. All exposures elevated GSH, GSSG, NAD, and NAD+ levels, as well as the NADH/NAD+ ratio, while decreasing lipid peroxidation (TBARS), indicating a reductive shift and cholinesterase inhibition. Discriminant analysis separated toxicant groups, and IBRv2 showed that the Gd group had the most significant impact on molluscs.由于稀土元素（Rare Earth Elements, REEs）独特的理化性质与在现代科技中的广泛应用，其环境浓度正快速攀升。鉴于学界推测稀土元素的生物学效应与必需金属类似，并可引发氧化应激，本研究旨在验证稀土元素对双壳类软体动物圆顶珠蚌（Unio tumidus）的上述影响路径。实验将受试贻贝分别暴露于钆（Gadolinium, Gd，30 nM）、钇（Yttrium, Y，30 nM）及其混合液（Mix），并联合钙通道阻滞剂硝苯地平（Nifedipine, NFD，10 µM）处理14天。研究人员对其消化腺中锌（Zinc, Zn）的分布（涉及金属硫蛋白（Metallothioneins, MT））、氧化还原状态及毒性表征进行了分析。与钇处理组不同，钆的积累可引发组织出现肉眼可见的病理改变，并伴随溶酶体完整性受损。钆与钇均可提升总金属硫蛋白（Total Metallothioneins, MTSH）的浓度，但未改变锌结合型金属硫蛋白（ZnMT）的水平。硝苯地平的存在可缓解单次暴露于钆或钇对金属硫蛋白及钆积累所产生的影响。其可使细胞色素P450依赖的乙氧基试卤灵-O-脱乙基酶（EROD）、半胱天冬酶-3（caspase-3）及GTP酶的活性提升约2倍，这表明本研究涉及的稀土元素的作用模式依赖钙离子且与锌相关。所有暴露组均提升了还原型谷胱甘肽（GSH）、氧化型谷胱甘肽（GSSG）、烟酰胺腺嘌呤二核苷酸（NAD）、氧化型烟酰胺腺嘌呤二核苷酸（NAD+）的水平及NADH/NAD+比值，同时降低了脂质过氧化产物（硫代巴比妥酸反应物，TBARS）的含量，这表明体系发生了还原偏移并伴随胆碱酯酶活性受抑。判别分析可有效区分各毒物处理组，而整合生物标志物响应指数2（IBRv2）分析结果显示，钆处理组对软体动物的影响最为显著。