Effects on Synaptic Plasticity Markers in Fetal Mice and HT22 Neurons upon F-53B Exposure: The Role of PKA Cytoplasmic Retention

Chlorinated polyfluorinated ether sulfonate (F-53B), a chromium-fog depressant widely utilized as an alternative to perfluorooctanesulfonate, can transfer from mother to fetus. Recent research has demonstrated that prenatal exposure to F-53B results in synaptic damage in weaning mice. However, the mechanism underpinning F-53B-triggered synaptic damage during fetal development remains unclear. This study aims to investigate the role of the protein kinase A (PKA)/cAMP response element-binding protein (CREB) pathway, a crucial signaling mechanism known as "synaptic switch", in the early neurotoxicity of F-53B exposure both <i>in vivo</i> and <i>in vitro</i>. Here, C57BL/6 fetal mice were subjected to exposure to F-53B (0, 4, and 40 μg/L) from gestation days (GD) 0 to 14 to evaluate nerve injury prior to delivery. HT22 neurons exposed to F-53B (0, 0.016, 0.08, 0.4, 2, and 10 μmol/L) for 24 h were utilized to elucidate the underlying mechanism. Our results demonstrated that F-53B significantly increased the fluorescence intensity of Nestin (a neural stem cell marker) in the fetal brain hippocampus (GD14). Subsequently, we found that F-53B downregulated the expression of synaptic plasticity markers (SYP, GAP43, and BDNF) in the fetal brain and HT22 neurons. Further molecular docking analysis revealed that F-53B fits into the ligand-binding pockets of PKA and CREB1. Results showed that F-53B inhibited the translocation of PKA protein from the cytoplasm to the neuronal nuclei and reduced the levels of PKA, CREB1, p-PKA(α/β/γ)-Thr197, and p-CREB1-S133 in the nucleus. Furthermore, the expression of synaptic plasticity markers altered by F-53B could be reversed by a PKA agonist and was intensified by a PKA antagonist. In summary, our findings suggest that intrauterine exposure to F-53B can weaken the expression of synaptic plasticity markers in the fetal brain, with this neurotoxicity being mediated by the cytoplasmic retention of PKA.