6:2 fluorotelomer sulfonamide alkylbetaine (6:2 FTAB) is a major component of Forafac^®1157, a novel perfluorooctane sulfonate (PFOS) alternative used globally in aqueous film forming foams (AFFFs). Although 6:2 FTAB has been recently detected in the aquatic environment, its toxic effects on aquatic organisms remain unclear. Here, zebrafish embryos were exposed to various concentrations of 6:2 FTAB (0, 5, 10, 20, 40, 60, 80, and 100 mg/L) from 6 to 120 h post-fertilization (hpf) to investigate its developmental toxicity and possible mechanism of action. Results showed that exposure to 40 mg/L or higher concentrations of 6:2 FTAB significantly decreased the survival percentage and increased the malformation percentage. The median lethal concentration (LC₅₀) at 120 hpf was 43.73 ± 3.24 mg/L, and the corresponding benchmark dose lower limit (BMDL) of lethal effect was 33.79 mg/L. These values were both higher than those for PFOS, supporting the notion that 6:2 FTAB is less toxic than PFOS to zebrafish embryos. The most common developmental defect in 6:2 FTAB-treated embryos was rough-edged skin/fins. TUNEL assay showed that 6:2 FTAB exposure induced cell apoptosis in the tail region compared with that of the control, which might explain the rough-edged skin/fins. The increased transcriptional levels of p53, bax, and apaf1 and the increased activities of caspase-3, -8, and -9 provided further evidence of 6:2 FTAB-induced apoptosis. We also analyzed the effects of 6:2 FTAB on oxidative stress and the immune system. Results showed that reactive oxygen species and malondialdehyde accumulated in concentration-dependent manners after exposure to 6:2 FTAB, and antioxidant enzyme activities (catalase and glutathione peroxidase) also changed. Exposure to 6:2 FTAB also altered the transcriptional levels of ccl1, il-1β, il-8, tnfα, ifn, and cxcl-c1c, which play important roles in the innate immune system. Collectively, our data suggest that 6:2 FTAB exposure can induce cell apoptosis, oxidative stress, and immunotoxicity, thus highlighting the developmental toxicity of 6:2 FTAB in zebrafish embryos.

6：2的氟化调聚物磺酰胺烷基甜菜碱（6：2 FTAB）是FORAFAC的主要成分^® 1157，在水性成膜泡沫（AFFFs）全球使用的新型全氟辛烷磺酸（PFOS）替代。尽管最近在水生环境中发现了6：2 FTAB，但它对水生生物的毒性作用仍不清楚。在这里，斑马鱼的胚胎在受精后6到120 h（hpf）暴露于不同浓度的6：2 FTAB（0、5、10、20、40、60、80和100 mg / L），以研究其发育毒性和可能的​​作用机理。结果表明，暴露于40 mg / L或更高浓度的6：2 FTAB会显着降低存活率并增加畸形率。致死浓度中位数（LC ₅₀）在120 hpf下为43.73±3.24 mg / L，相应的致死基准剂量下限（BMDL）为33.79 mg / L。这些值均高于全氟辛烷磺酸，这支持了6：2 FTAB对全斑马鱼胚胎的毒性小于全氟辛烷磺酸的观点。经FTAB处理的6：2胚胎中最常见的发育缺陷是粗糙的皮肤/鳍。TUNEL分析显示，与对照组相比，6：2 FTAB暴露导致尾巴区域的细胞凋亡，这可能解释了粗糙的皮肤/鳍。p53，bax和apaf1的转录水平增加caspase-3，-8和-9的活性增加提供了6：2 FTAB诱导的细胞凋亡的进一步证据。我们还分析了6：2 FTAB对氧化应激和免疫系统的影响。结果表明，暴露于6：2 FTAB后，活性氧和丙二醛以浓度依赖的方式积累，抗氧化酶活性（过氧化氢酶和谷胱甘肽过氧化物酶）也发生了变化。暴露于6：2 FTAB也会改变ccl1，il-1β，il-8，tnfα，ifn和cxcl-c1c的转录水平，在先天免疫系统中起重要作用。总的来说，我们的数据表明6：2 FTAB暴露可以诱导细胞凋亡，氧化应激和免疫毒性，从而突出了6：2 FTAB在斑马鱼胚胎中的发育毒性。