UCD School of Medicine and Medical Science, University College Dublin, Ireland.
Exp Eye Res. 2013 Oct;115:224-9. doi: 10.1016/j.exer.2013.07.022. Epub 2013 Jul 29.
The connective tissue plates of the lamina cribrosa (LC) region are continuously exposed to a mechanically dynamic environment. To study how the LC cells respond to these mechanical forces, we measured the mechano-sensitive calcium dependent maxi-K(+) ion channel current in the cell membrane of LC cells of glaucoma and normal subjects. Primary culture LC cells from 7 normal and 7 age matched glaucoma donors were studied. Perfusion of cells with hypotonic solution was used to stretch the cell membrane. Whole-cell patch-clamp technique was used to measure the basal (non stretched) and hypotonic stretch-induced changes in maxi-K(+) ion channel activity in normal and glaucoma LC cells. The role of membrane-type Ca(2+) entry channel inhibition (verapamil) and internal Ca(2+) store re-uptake blockade (2-APB) on maxi-K(+) activity was also examined. Basal and stretched-induced maxi-K(+) current were significantly elevated in the glaucoma LC cells compared to normal controls (p < 0.05). In normal LC cells hypotonic stretch elevated the mean maxi-K(+) current from 18.5 ± 5.7 pA/pF (at Vp = +100 mV) to 88.4 ± 12.4 pA/pF (P < 0.05), and from 39.5 ± 7.3 pA/pF to 133.1 ± 18.5 pA/pF in glaucoma LC cells (P < 0.02). Verapamil and 2-APB significantly reduced basal maxi-K(+) current in glaucoma LC cells (33.1 ± 8.2 pA/pF to 17.9 ± 5.6 pA/pF; and 32.2 ± 8.3 pA/pF to 17.3 ± 5.4 pA/pF, P < 0.05, respectively) but not in normal LC cells (P > 0.05). Following hypotonic stretch, verapamil and 2-APB significantly (P < 0.05) reduced the maxi-K(+) current in both normal and glaucoma LC cells. Baseline and hypotonic stretch induced Ca(2+)-dependent maxi-K(+) channel activity are elevated in LC cells of glaucoma patients, which may result from the abnormally high levels of intracellular calcium in glaucoma LC cells.
小梁网层的连接组织板（LC）区域持续暴露于机械动态环境中。为了研究 LC 细胞如何应对这些机械力，我们测量了青光眼和正常受试者 LC 细胞细胞膜中机械敏感钙依赖性 maxi-K(+)离子通道电流。研究了来自 7 名正常和 7 名年龄匹配的青光眼供体的原代 LC 细胞培养物。使用低渗溶液灌注细胞以拉伸细胞膜。全细胞膜片钳技术用于测量正常和青光眼 LC 细胞中基础（未拉伸）和低渗拉伸诱导的 maxi-K(+)离子通道活性变化。还研究了膜型 Ca(2+)内流通道抑制（维拉帕米）和细胞内 Ca(2+)储存再摄取阻断（2-APB）对 maxi-K(+)活性的作用。与正常对照相比，青光眼 LC 细胞中的基础和拉伸诱导的 maxi-K(+)电流显着升高（p<0.05）。在正常 LC 细胞中，低渗拉伸使平均 maxi-K(+)电流从+100 mV 时的 18.5±5.7 pA/pF 升高至 88.4±12.4 pA/pF（P<0.05），而在青光眼 LC 细胞中从 39.5±7.3 pA/pF 升高至 133.1±18.5 pA/pF（P<0.02）。维拉帕米和 2-APB 显着降低了青光眼 LC 细胞中的基础 maxi-K(+)电流（33.1±8.2 pA/pF 至 17.9±5.6 pA/pF；32.2±8.3 pA/pF 至 17.3±5.4 pA/pF，P<0.05），但在正常 LC 细胞中没有（P>0.05）。低渗拉伸后，维拉帕米和 2-APB 显着降低了正常和青光眼 LC 细胞中的 maxi-K(+)电流（P<0.05）。青光眼患者 LC 细胞中的基础和低渗拉伸诱导的 Ca(2+)依赖性 maxi-K(+)通道活性升高，这可能是由于青光眼 LC 细胞中细胞内钙水平异常升高所致。
