Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, 44 Thorez av., Saint Petersburg, Russia, 194223.
Biol Trace Elem Res. 2020 Oct;197(2):495-506. doi: 10.1007/s12011-019-01993-z. Epub 2019 Dec 3.
The study was designed to evaluate an influence of excessive fluoride (F) intake on cognitive capacities of adult rats and on proteins of memory-related calpain signaling in hippocampus. Control animals were given water with natural F content of 0.4 ppm; rats from other groups consumed the same water supplemented with 5, 20, and 50 ppm F (as NaF) for 12 months. The efficiency of learning and memory formation was evaluated by novel object recognition (NOR) and Morris water maze tests. The expression of enzymes of calpain-1 and calpain-2 signaling in hippocampus was detected by Western blotting. Excessive F consumption had moderate impact on short-term memory, but impaired spatial learning and long-term memory of animals. Intoxication of rats with 5-50 ppm F led to stimulation of calpain-1 in hippocampal cells and its translocation from cytosol to membranes, accompanied by activation of GTPase RhoA. Exposure to 20-50 ppm F resulted in proteolytic cleavage of phosphatase PHLPP1 and increased expression of phospho-ERK1/2 kinase with insignificant decline of total ERK1/2 activity. In contrast, F did not change the expression of calpain-2 and its substrates-phosphatase PTEN and kinase mTOR. However, F intake led to downregulation of cAMP-response element binding protein (CREB) and brain-derived neurotrophic factor (BDNF). Thus, altered expression of calpain-1 and its downstream effectors at a background of stable activity of calpain-2 indicates overstimulation of signaling pathways of early LTP phase and disrupted link between early and late LTP phases, most probably due to altered activity of transcriptional and neurotrophic factors.
这项研究旨在评估过量氟（F）摄入对成年大鼠认知能力的影响，以及对海马中与记忆相关的钙蛋白酶信号相关蛋白的影响。对照组动物饮用含有天然氟含量为 0.4ppm 的水；其他组的大鼠饮用相同的水，补充 5、20 和 50ppm 的 F（作为 NaF），为期 12 个月。通过新物体识别（NOR）和 Morris 水迷宫测试评估学习和记忆形成的效率。通过 Western blot 检测海马中钙蛋白酶-1 和钙蛋白酶-2 信号通路的酶表达。过量 F 摄入对短期记忆有中度影响，但会损害动物的空间学习和长期记忆。大鼠用 5-50ppm F 中毒会刺激海马细胞中的钙蛋白酶-1，并将其从细胞质转移到膜上，同时激活 GTPase RhoA。暴露于 20-50ppm F 会导致磷酸酶 PHLPP1 的蛋白水解切割，并增加磷酸化 ERK1/2 激酶的表达，而总 ERK1/2 活性没有明显下降。相比之下，F 不改变钙蛋白酶-2及其底物磷酸酶 PTEN 和激酶 mTOR 的表达。然而，F 摄入会下调 cAMP 反应元件结合蛋白（CREB）和脑源性神经营养因子（BDNF）。因此，钙蛋白酶-1及其下游效应物在钙蛋白酶-2稳定活性的背景下表达改变表明早期 LTP 阶段信号通路的过度刺激，以及早期和晚期 LTP 阶段之间的联系中断，最有可能是由于转录和神经营养因子的活性改变所致。
