Lead (Pb) is an environmental contaminant that primarily affects the central nervous system, particularly the developing brain. Recently, increasing evidence indicates the important roles of histone deacetylases (HDACs) in Pb-induced neurotoxicity. However, the precise molecular mechanisms involving HDAC4 remains unknown. The purpose of this study was to investigate the role of HDAC4 in Pb-induced neurotoxicity both in vivo and in vitro. In vitro study, PC12 cells were exposed to Pb (10 μM) for 24 h, then the mRNA and protein levels of HDAC4 were analyzed. In vivo study, pregnant rats and their female offspring were treated with lead (50 ppm) until postnatal day 30. Then the pups were sacrificed and the mRNA and protein levels of HDAC4 in the hippocampus were analyzed. The results showed that HDAC4 was significantly increased in both PC12 cells and rat hippocampus upon Pb exposure. Blockade of HDAC4 with either LMK-235 (an inhibitor of HDAC4) or shHDAC4 (HDAC4-knocking down plasmid) ameliorated the Pb-induced neurite outgrowth deficits. Interestingly, HDAC4 was aberrantly accumulated in the nucleus upon Pb exposure. By contrast, blocking the HDAC4 shuffling from the cytosol to the nucleus with ΔNLS2-HDAC4 (the cytosol-localized HDAC4 mutant) was able to rescue the neuronal impairment. In addition, Pb increased PP1 (protein phosphatase 1) expression which in turn influenced the subcellular localization of HDAC4 by dephosphorylation of specific serine/threonine residues. What’s more, blockade of PP1 with PP1-knocking down construct (shPP1) ameliorated Pb-induced neurite outgrowth deficits. Taken together, nuclear accumulation of HDAC4 by PP1-mediated dephosphorylation involved in Pb-induced neurotoxicity. This study might provide a promising molecular target for medical intervention with environmental cues.

铅 (Pb) 是一种环境污染物，主要影响中枢神经系统，尤其是发育中的大脑。最近，越来越多的证据表明组蛋白去乙酰化酶 (HDAC) 在铅诱导的神经毒性中的重要作用。然而，涉及 HDAC4 的精确分子机制仍然未知。本研究的目的是研究 HDAC4 在体内和体外 Pb 诱导的神经毒性中的作用。在体外研究中，将 PC12 细胞暴露于 Pb (10 μM) 24 小时，然后分析 HDAC4 的 mRNA 和蛋白质水平。在体内研究中，怀孕的大鼠及其雌性后代用铅 (50 ppm) 处理直到出生后第 30 天。然后处死幼崽并分析海马中 HDAC4 的 mRNA 和蛋白质水平。结果表明，Pb 暴露后，PC12 细胞和大鼠海马中的 HDAC4 均显着增加。用 LMK-235（HDAC4 抑制剂）或 shHDAC4（HDAC4 敲低质粒）阻断 HDAC4 可改善 Pb 诱导的神经突生长缺陷。有趣的是，HDAC4 在铅暴露后异常积累在细胞核中。相比之下，用 ΔNLS2-HDAC4（细胞质定位的 HDAC4 突变体）阻止 HDAC4 从细胞质到细胞核的改组能够挽救神经元损伤。此外，Pb 增加了 PP1（蛋白磷酸酶 1）表达，进而通过特定丝氨酸/苏氨酸残基的去磷酸化影响 HDAC4 的亚细胞定位。更重要的是，用 PP1 敲低构建体 (shPP1) 阻断 PP1 改善了 Pb 诱导的神经突生长缺陷。综合起来，HDAC4 通过 PP1 介导的去磷酸化在核内积累，参与 Pb 诱导的神经毒性。这项研究可能为环境线索的医学干预提供一个有希望的分子靶点。