Del Turco Domenico, Paul Mandy H, Schlaudraff Jessica, Muellerleile Julia, Bozic Fran, Vuksic Mario, Jedlicka Peter, Deller Thomas
Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe University Frankfurt, Frankfurt, Germany.
Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Zagreb, Croatia.
Front Mol Neurosci. 2023 May 24;16:1118746. doi: 10.3389/fnmol.2023.1118746. eCollection 2023.
The cation-chloride cotransporters KCC2 and NKCC1 regulate the intracellular Cl concentration and cell volume of neurons and/or glia. The Cl extruder KCC2 is expressed at higher levels than the Cl transporter NKCC1 in mature compared to immature neurons, accounting for the developmental shift from high to low Cl concentration and from depolarizing to hyperpolarizing currents through GABA-A receptors. Previous studies have shown that KCC2 expression is downregulated following central nervous system injury, returning neurons to a more excitable state, which can be pathological or adaptive. Here, we show that deafferentation of the dendritic segments of granule cells in the outer (oml) and middle (mml) molecular layer of the dentate gyrus via entorhinal denervation leads to cell-type- and layer-specific changes in the expression of KCC2 and NKCC1. Microarray analysis validated by reverse transcription-quantitative polymerase chain reaction revealed a significant decrease in mRNA in the granule cell layer 7 days post-lesion. In contrast, mRNA was upregulated in the oml/mml at this time point. Immunostaining revealed a selective reduction in KCC2 protein expression in the denervated dendrites of granule cells and an increase in NKCC1 expression in reactive astrocytes in the oml/mml. The NKCC1 upregulation is likely related to the increased activity of astrocytes and/or microglia in the deafferented region, while the transient KCC2 downregulation in granule cells may be associated with denervation-induced spine loss, potentially also serving a homeostatic role via boosting GABAergic depolarization. Furthermore, the delayed KCC2 recovery might be involved in the subsequent compensatory spinogenesis.
阳离子-氯离子共转运体KCC2和NKCC1调节神经元和/或神经胶质细胞的细胞内氯离子浓度和细胞体积。与未成熟神经元相比,氯离子排出体KCC2在成熟神经元中的表达水平高于氯离子转运体NKCC1,这解释了氯离子浓度从高到低以及通过GABA-A受体的电流从去极化到超极化的发育转变。先前的研究表明,中枢神经系统损伤后KCC2表达下调,使神经元恢复到更易兴奋的状态,这可能是病理性的或适应性的。在这里,我们表明,通过内嗅神经去支配使齿状回外分子层(oml)和中分子层(mml)颗粒细胞的树突段去传入,会导致KCC2和NKCC1表达出现细胞类型和层特异性变化。通过逆转录定量聚合酶链反应验证的微阵列分析显示,损伤后7天颗粒细胞层的mRNA显著减少。相比之下,此时oml/mml中的mRNA上调。免疫染色显示,颗粒细胞去传入树突中KCC2蛋白表达选择性降低,oml/mml中反应性星形胶质细胞中NKCC1表达增加。NKCC1上调可能与去传入区域星形胶质细胞和/或小胶质细胞活性增加有关,而颗粒细胞中KCC2的短暂下调可能与去神经支配诱导的树突棘丢失有关,也可能通过增强GABA能去极化起到稳态作用。此外,KCC2的延迟恢复可能参与随后的代偿性树突棘生成。