Bicarbonate sensing in mouse cortical astrocytes during extracellular acid/base disturbances
Bicarbonate sensing in mouse cortical astrocytes during extracellular acid/base disturbances
复制标题
细胞外酸/碱干扰期间小鼠皮质星形胶质细胞的碳酸氢盐传感
DOI：
10.1113/jp273394
复制
发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Deitmer
中科院分区：
文献类型：
--
作者：
Theparambil;Naoshin;Defren;Schmälzle;Schneider;Deitmer
要点本研究表明，由碳酸酐酶 II (CAII) 支持的电化学钠-碳酸氢盐协同转运蛋白 NBCe1，提供了皮质星形胶质细胞中碳酸氢盐传感的有效机制。这种机制被认为在设置星形胶质细胞对细胞外酸/碱挑战的 pH 响应中发挥着重要作用。 NBCe1 有效地感知到等二氧化碳酸中毒和等水性低碳酸血症期间细胞外 [HCO3−] 的减少，或高碳酸血症期间细胞内 [HCO3−] 的增加，NBCe1 在这些条件下将碳酸氢盐带出细胞，并导致 WT 星形胶质细胞酸化和钠下降，但等碳酸血症、高碳酸血症和等水性低碳酸血症会在表达 NBCe1 和 CAII 的非洲爪蟾细胞中引起内向电流，但不会在天然卵母细胞中引起内向电流，这表明 NBCe1 在这些条件下以外向模式运行，与我们在星形胶质细胞中的发现一致。我们提出，星形胶质细胞的碳酸氢盐感应在细胞外酸/碱期间可能具有功能意义大脑的紊乱，因为它不仅改变星形胶质细胞的细胞内 pH/[HCO3−] 依赖性功能，而且还调节脑组织中的细胞外 pH/[HCO3−]。 摘要哺乳动物大脑的细胞外酸/碱状态在许多生理和病理事件中经历动态变化。尽管星形胶质细胞的细胞内 pH (pHi) 对细胞外酸/碱的变化做出反应，但介导这些变化的机制仍未解决。我们之前已经证明，生电钠-碳酸氢盐协同转运蛋白 NBCe1 是皮质星形胶质细胞中的高亲和力碳酸氢盐载体。在本研究中，我们研究了 NBCe1 是否在星形胶质细胞的碳酸氢盐传感以及确定 pH 值对细胞外酸/碱挑战的反应中发挥作用。我们使用离子选择性染料测量了野生型 (WT) 和 NBCe1 敲除 (KO) 小鼠星形胶质细胞在异碳酸血症、高碳酸血症和低碳酸血症期间细胞内 H+ 和 Na+ 的变化。我们还在类似条件下分析了非洲爪蟾细胞中 NBCe1 介导的膜电流。比较 WT 和 NBCe1-KO 星形胶质细胞，我们可以剖析 NBCe1 对 CO2 跨细胞膜扩散的贡献，以及在用乙氧基唑酰胺阻断碳酸酐酶 (CA) 活性后，CA 对酸/碱通量的幅度和速率的作用。我们的结果表明，星形胶质细胞中的 NBCe1 转运活性在 CA 活性的支持下，使星形胶质细胞在小鼠皮质中产生碳酸氢盐传感器。 NBCe1 通过感知跨膜 [HCO3−] 的变化将碳酸氢盐带入和带出细胞，无论细胞内和细胞外 pH 值如何变化，并在设置 pH 值对细胞外酸/碱挑战的响应中发挥了重要作用。我们提出，星形胶质细胞的碳酸氢盐感应可能在大脑细胞外酸/碱变化期间具有潜在的功能意义。
Key pointsThe present study suggests that the electrogenic sodium–bicarbonate cotransporter, NBCe1, supported by carbonic anhydrase II, CAII, provides an efficient mechanism of bicarbonate sensing in cortical astrocytes. This mechanism is proposed to play a major role in setting the pHiresponses to extracellular acid/base challenges in astrocytes.A decrease in extracellular [HCO3−] during isocapnic acidosis and isohydric hypocapnia, or an increase in intracellular [HCO3−] during hypercapnic acidosis, was effectively sensed by NBCe1, which carried bicarbonate out of the cells under these conditions, and caused an acidification and sodium fall in WT astrocytes, but not in NBCe1‐knockout astrocytes.Isocapnic acidosis, hypercapnic acidosis and isohydric hypocapnia evoked inward currents in NBCe1‐ and CAII‐expressingXenopus laevisoocytes, but not in native oocytes, suggesting that NBCe1 operates in the outwardly directed mode under these conditions consistent with our findings in astrocytes.We propose that bicarbonate sensing of astrocytes may have functional significance during extracellular acid/base disturbances in the brain, as it not only alters intracellular pH/[HCO3−]‐dependent functions of astrocytes, but also modulates the extracellular pH/[HCO3−] in brain tissue.AbstractExtracellular acid/base status of the mammalian brain undergoes dynamic changes during many physiological and pathological events. Although intracellular pH (pHi) of astrocytes responds to extracellular acid/base changes, the mechanisms mediating these changes have remained unresolved. We have previously shown that the electrogenic sodium–bicarbonate cotransporter, NBCe1, is a high‐affinity bicarbonate carrier in cortical astrocytes. In the present study, we investigated whether NBCe1 plays a role in bicarbonate sensing in astrocytes, and in determining the pHiresponses to extracellular acid/base challenges. We measured changes in intracellular H+and Na+in astrocytes from wild‐type (WT) and from NBCe1‐knockout (KO) mice, using ion‐selective dyes, during isocapnic acidosis, hypercapnic acidosis and hypocapnia. We also analysed NBCe1‐mediated membrane currents inXenopus laevisoocytes under similar conditions. Comparing WT and NBCe1‐KO astrocytes, we could dissect the contribution of NBCe1, of diffusion of CO2across the cell membrane and, after blocking carbonic anhydrase (CA) activity with ethoxyzolamide, of the role of CA, for the amplitude and rate of acid/base fluxes. Our results suggest that NBCe1 transport activity in astrocytes, supported by CA activity, renders astrocytes bicarbonate sensors in the mouse cortex. NBCe1 carried bicarbonate into and out of the cell by sensing the variations of transmembrane [HCO3−], irrespective of the changes in intra‐ and extracellular pH, and played a major role in setting pHiresponses to the extracellular acid/base challenges. We propose that bicarbonate sensing of astrocytes may have potential functional significance during extracellular acid/base alterations in the brain.
登录
查看更多内容
大鼠星形胶质细胞原代培养物中细胞内和细胞外 pH 值的关系。
DOI：
10.1152/ajpcell.1994.267.2.c581
发表时间：
1994
期刊：
The American journal of physiology
影响因子：
--
作者：
Mellergard,P;Ou-Yang,Y;Siesjo,BK
通讯作者：
Siesjo,BK
影响因子：
5.5
作者：
Stridh, Malin H.;Alt, Marco D.;Becker, Holger M.
通讯作者：
Becker, Holger M.
第 51 章 – 细胞内 pH 值的控制
DOI：
--
发表时间：
2008
期刊：
影响因子：
--
作者：
M. O. Bevensee;W. Boron
通讯作者：
W. Boron
影响因子：
4.8
作者：
Gawenis, Lara R.;Bradford, Emily M.;Shull, Gary E.
通讯作者：
Shull, Gary E.
Reeler 突变小鼠中的胶质细胞标记：生化和免疫组织学研究
影响因子：
4.7
作者：
M. S. Ghalidour;P. Derer;G. Labourdette;J. Delaunoy;O. Langley
通讯作者：
O. Langley