Department of Physiology & Biophysics, SUNY at Stony Brook, Stony Brook, New York.
Invest Ophthalmol Vis Sci. 2013 Nov 1;54(12):7174-87. doi: 10.1167/iovs.13-12593.
Age-related nuclear cataracts involve denaturation and aggregation of intracellular proteins. We have documented age-dependent changes in membrane transport in the mouse lens to see what might initiate changes in the intracellular milieu.
Microelectrode-based intracellular impedance studies of intact lenses were used to determine gap junction coupling conductance, fiber and surface cell membrane conductances, effective extracellular resistivity, and intracellular voltage. Fiber cell connexin expression was detected by Western blotting. Intracellular hydrostatic pressure was measured with a microelectrode/manometer system. Concentrations of intracellular sodium and calcium were measured by intracellular injection of sodium-binding benzofuran isophthalate and Fura2, respectively.
In adult lenses, as age increased: fiber cell gap junction coupling conductance declined significantly, correlating with decreases in Cx46 and Cx50 labeling in Western blots; fiber and surface cell membrane conductances did not change systematically; effective extracellular resistivity increased monotonically; center to surface gradients for intracellular pressure, sodium, calcium, and voltage all increased, but in an interdependent manner that moderated changes. In newborn pup lenses, there were changes that did not simply fit with the above paradigm.
In newborn pup lenses, the observed changes may relate to growth factors that are not related to age-dependent changes seen in adult lenses. The major change in adult lenses was an age-dependent decrease in gap junction coupling, probably due to oxidative damage leading to degradation of connexin proteins. These changes clearly lead to compromise of intracellular homeostasis and may be a causal factor in age-related nuclear cataracts.
年龄相关性核性白内障涉及细胞内蛋白质的变性和聚集。我们记录了小鼠晶状体中膜转运的年龄依赖性变化，以了解可能引发细胞内环境变化的因素。
使用基于微电极的完整晶状体细胞内阻抗研究来确定缝隙连接偶联电导、纤维和表面细胞膜电导、有效细胞外电阻率和细胞内电压。通过 Western 印迹检测纤维细胞连接蛋白的表达。使用微电极/压力计系统测量细胞内静压。通过细胞内注射钠结合苯并呋喃异酞酸盐和 Fura2 分别测量细胞内钠和钙的浓度。
在成年晶状体中，随着年龄的增长：纤维细胞缝隙连接偶联电导显著下降，与 Western blot 中 Cx46 和 Cx50 标记物的减少相关；纤维和表面细胞膜电导没有系统地变化；有效细胞外电阻率单调增加；细胞内压力、钠、钙和电压的中心到表面梯度均增加，但以相互依赖的方式调节变化。在新生幼鼠晶状体中，观察到的变化不符合上述模式。
在新生幼鼠晶状体中，观察到的变化可能与生长因子有关，而与成年晶状体中观察到的年龄相关性变化无关。成年晶状体的主要变化是缝隙连接偶联的年龄依赖性下降，可能是由于氧化损伤导致连接蛋白降解。这些变化显然导致细胞内稳态受损，可能是年龄相关性核性白内障的一个因果因素。
