Department of Physiology, Harbin Medical University, Harbin, China.
Department of Genetics, Harbin Medical University, Harbin, China.
Acta Physiol (Oxf). 2021 Jul;232(3):e13672. doi: 10.1111/apha.13672. Epub 2021 Jun 22.
Glial fibrillary acidic protein (GFAP) molecularly associates with aquaporin 4 (AQP4) in astrocytic plasticity. Here, we further examined how AQP4 modulates osmotic effects on vasopressin (VP) neurons in rat supraoptic nucleus (SON) through interactions with GFAP in astrocytes.
Brain slices from adult male rats were kept under osmotic stimulation. Western blot, co-immunoprecipitation, immunohistochemistry and patch-clamp recordings were used for analysis of expressions and interactions between GFAP and AQP4, astrocyte-specific proteins in the SON, as well as their influence on VP neuronal activity. Data were analysed using SPSS software.
Hyposmotic challenge (HOC) of acute SON slices caused an early (within 5 minutes) and transient increase in the colocalization of AQP4 with GFAP filaments. This effect was prominent at astrocytic processes surrounding VP neuron somata and was accompanied by inhibition of VP neuronal activity. Similar HOC effect was seen in the SON isolated from rats subjected to in vivo HOC, wherein a transiently increased molecular association between GFAP and AQP4 was detected using co-immunoprecipitation. The late stage rebound excitation (10 minutes) of VP neurons in brain slices subjected to HOC and the associated astrocytic GFAP's 'return to normal' were both hampered by 2-(nicotinamide)-1,3,4-thiadiazole, a specific AQP4 channel blocker that itself did not influence VP neuronal activity. Moreover, this agent prevented hyperosmotic stress-evoked excitation of VP neurons and associated reduction in GFAP filaments.
These findings indicate that osmotically driven increase in VP neuronal activity requires the activation of AQP4, which determines a retraction of GFAP filaments.
胶质纤维酸性蛋白（GFAP）在星形胶质细胞可塑性中与水通道蛋白 4（AQP4）分子结合。在这里，我们通过星形胶质细胞中 GFAP 与 AQP4 的相互作用，进一步研究了 AQP4 如何调节血管加压素（VP）神经元对渗透压的影响。
将成年雄性大鼠的脑片置于渗透压刺激下。使用 Western blot、免疫共沉淀、免疫组织化学和膜片钳记录来分析 GFAP 和 AQP4 之间的表达和相互作用，以及它们对 VP 神经元活性的影响。使用 SPSS 软件分析数据。
急性 SON 切片的低渗刺激（HOC）导致 AQP4 与 GFAP 纤维的早期（5 分钟内）和短暂的共定位增加。这种效应在围绕 VP 神经元胞体的星形胶质细胞突起中更为明显，并伴有 VP 神经元活性的抑制。在体内 HOC 处理的大鼠中，也观察到类似的 HOC 效应，其中使用免疫共沉淀检测到 GFAP 和 AQP4 之间的瞬时增加的分子相关性。在 HOC 处理的脑片中，VP 神经元的后期反弹兴奋（10 分钟）以及相关的星形胶质细胞 GFAP 的“恢复正常”均受到 2-（烟酰胺）-1,3,4-噻二唑（一种特异性 AQP4 通道阻断剂）的阻碍，而该阻断剂本身并不影响 VP 神经元活性。此外，该试剂可防止高渗应激引起的 VP 神经元兴奋以及相关的 GFAP 纤维减少。
这些发现表明，渗透压驱动的 VP 神经元活性增加需要 AQP4 的激活，这决定了 GFAP 纤维的回缩。
