Mercury (Hg) is a prominent environmental contaminant and can cause various subcellular effects. Elucidating the different subcellular toxicities of inorganic Hg (Hg²⁺) and methylmercury (MeHg) is critical for understanding their overall cytotoxicity. In this study, we employed aggregation-induced emission (AIE) probes to investigate the toxicity of Hg at the subcellular level using an aquatic embryonic zebrafish fibroblast cell line ZF4 as a model. The dynamic monitoring of lysosomal pH and the mapping of pH distribution during Hg²⁺ or MeHg exposure were successfully realized for the first time. We found that both Hg²⁺ and MeHg decreased the mean lysosomal pH, but with contrasting effects and mechanisms. Hg²⁺ had a greater impact on lysosomal pH than MeHg at a similar intracellular concentration. In addition, Hg²⁺ in comparison to MeHg exposure led to an increased number of lysosomes, probably because of their different effects on autophagy. We further showed that MeHg (200 nM) exposure had an inverse effect on mitochondrial respiratory function. A high dose (1000 nM) of Hg²⁺ increased the amount of intracellular lipid droplets by 13%, indicating that lipid droplets may potentially play a role in Hg²⁺detoxification. Our study suggested that, compared with other parameters, lysosome pH was most sensitive to Hg²⁺ and MeHg. Therefore, lysosomal pH can be used as a potential biomarker to assess the cellular toxicity of Hg in vitro.

汞（Hg）是一种重要的环境污染物，可引起各种亚细胞效应。阐明无机汞（Hg ²⁺）和甲基汞（MeHg）的不同亚细胞毒性对于理解它们的整体细胞毒性至关重要。在这项研究中，我们使用聚集诱导发射（AIE）探针，以水生胚胎斑马鱼成纤维细胞系ZF4作为模型，研究了亚细胞水平上Hg的毒性。首次成功实现了对Hg ²⁺或MeHg暴露过程中溶酶体pH的动态监测和pH分布图。我们发现，Hg ²⁺和MeHg均可降低平均溶酶体pH，但具有相反的作用和机制。汞²⁺在类似的细胞内浓度下，对溶酶体pH的影响比MeHg更大。此外，与MeHg暴露相比，Hg ²⁺导致溶酶体数量增加，可能是由于它们对自噬的影响不同。我们进一步表明，MeHg（200 nM）暴露对线粒体呼吸功能有反作用。高剂量（1000 nM）的Hg ²⁺使细胞内脂质小滴的数量增加13％，表明脂质小滴可能在Hg ^2+的解毒中起潜在作用。我们的研究表明，与其他参数相比，溶酶体pH对Hg ²⁺和MeHg最敏感。因此，溶酶体pH可以用作潜在的生物标志物，以评估汞在体外的细胞毒性。