Activation of Stretch-Activated Channels and Maxi-K+ Channels by Membrane Stress of Human Lamina Cribrosa Cells
Activation of Stretch-Activated Channels and Maxi-K+ Channels by Membrane Stress of Human Lamina Cribrosa Cells
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DOI：
10.1167/iovs.08-1937
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发表时间：
2009-01-01
影响因子：
4.4
通讯作者：
O'Brien, Colm J.
中科院分区：
文献类型：
--
作者：
Irnaten, Mustapha;Barry, Richard C.;O'Brien, Colm J.
目的。视神经头的筛板(LC)区域被认为是青光眼视神经病变的主要损害部位。当暴露在周期性拉伸中时，常驻LC细胞具有促纤维化的潜力。然而，这些细胞的机械敏感机制仍不清楚。在这里，作者研究了膜拉伸对细胞体积变化和离子通道活性的影响，并检测了细胞内钙离子([Ca(2+)](I))的相关变化。方法：作者使用来自正常供体眼的原代LC细胞。用共聚焦显微镜观察低张细胞膜牵张对细胞体积的影响。采用全细胞膜片钳技术和钙离子成像技术，分别观察低渗对钙离子通道(S)活性和[Ca(2+)](I)变化的影响。结果：在这项研究中，LC细胞对低张细胞肿胀有明显的体积变化。作者描述了LC细胞的大电导K(+)通道(MAXI-K(+))，并证明了在细胞膜低张拉伸过程中其活性增加。RT-PCR结果显示LC细胞中存在MAXI-K(+)标记。作者发现[Ca(2+)](I)和Maxi-K(+)通道依赖于细胞外的Ca(2+)，并被Gd抑制，后者可阻断牵张激活通道(SACs)。结论低渗应激可激活依赖SAC和Ca(2+)的Maxi-K(+)通道，细胞肿胀时[Ca(2+)](I)的升高主要来源于细胞外(或内质网外)。这些发现提高了对LC细胞如何响应细胞膜拉伸的理解。这一领域的进一步实验可能会揭示青光眼管理中新的治疗干预措施的未来目标。(投资眼科VS科学。2009年；50：194202DOI：10.1167/IOV.08-1937年
PURPOSE. The lamina cribrosa (LC) region of the optic nerve head is considered the primary site of damage in glaucomatous optic neuropathy. Resident LC cells have a profibrotic potential when exposed to cyclical stretch. However, the mechanosensitive mechanisms of these cells remain unknown. Here the authors investigated the effects of membrane stretch on cell volume change and ion channel activity and examined the associated changes in intracellular calcium ([Ca(2+)](i)).METHODS. The authors used primary LC cells obtained from normal human donor eyes. Confocal microscopy was used to investigate the effect of hypotonic cell membrane stretch on cell volume changes. Whole-cell patch-clamp and calcium imaging techniques were used to investigate the effect of hypotonicity on ion channel(s) activity and [Ca(2+)](i) changes, respectively. RT-PCR was used to examine for the maxi-K(+) signature in LC cells.RESULTS. In this study, LC cells showed significant volume changes in response to hypotonic cell swelling. The authors characterized a large conductance K(+) channel (maxi-K(+)) in LC cells and demonstrated its increased activity during cell membrane hypotonic stretch. RT-PCR revealed the presence of maxi-K(+) signature in LC cells. The authors showed the [Ca(2+)](i) and maxi-K(+) channels to be dependent on extracellular Ca(2+) and inhibited by gadolinium, which blocks stretch-activated channels (SACs). Pretreatment with thapsigargin, which blocks the release of Ca(2+) from endoplasmic reticulum stores, showed no significant difference in [Ca(2+)](i) concentration on hypotonic swelling.CONCLUSIONS. The results show that hypotonic stress of human LC cells activates SAC and Ca(2+)-dependent maxi-K(+) channels and that the increase in [Ca(2+)](i) during cell swelling was predominantly from extracellular sources (or intracellular stores other than the endoplasmic reticulum). These findings improve the understanding of how LC cells respond to cell membrane stretch. Further experiments in this area may reveal future targets for novel therapeutic intervention in the management of glaucoma. (Invest Ophthalmol Vis Sci. 2009; 50: 194-202) DOI: 10.1167/iovs.08-1937