Sueiras Vivian M, Devaux Floriane, Smith Benjamin, Lai James, Batchelor Wyndham, Likht Nikita Y, Moy Vincent T, Ziebarth Noël M
Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, FL.
Florida Lions Eye Bank, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL.
Mol Vis. 2019 Oct 14;25:593-xxx. eCollection 2019.
To quantify the partition coefficient and the diffusion coefficient of metal-carrier proteins in the human lens capsule as a function of age.
Whole lenses from human donors were incubated overnight in a solution of fluorescently labeled transferrin, albumin, or ceruloplasmin. In the central plane of the capsule thickness, fluorescence recovery after photobleaching (FRAP) experiments were conducted to measure the diffusion of the protein within the lens capsule. The anterior portion of the lens was recorded before the FRAP experiments to locate the boundaries of the anterior lens capsule and to measure the partition coefficient of the labeled proteins. The partition coefficient (P), the time to half maximum recovery of the fluorescent intensity (τ), and the diffusion coefficient (D) for each protein were analyzed as a function of donor age.
There was no statistically significant relationship between the half maximum recovery time or the diffusion coefficient and age for transferrin (molecular weight [MW]=79.5 kDa, τ=17.26±4.840 s, D=0.17±0.05 μm/s), serum albumin (MW=66.5 kDa, τ=18.45±6.110 s, D=0.17±0.06 μm/s), or ceruloplasmin (MW=120 kDa, τ=36.57±5.660 s, D=0.08±0.01 μm/s). As expected, the larger protein (ceruloplasmin) took longer to recover fluorescent intensity due to its slower movement within the lens capsule. The partition coefficient statistically significantly increased with age for each protein (P: 0.09-0.71, P: 0.42-0.95, P: 0.19-1.17).
The diffusion of heavy-metal protein carriers within the anterior lens capsule is not dependent on age, but it is dependent on the size of the protein. The permeability of the lens capsule to these heavy-metal protein carriers increases with age, suggesting that there will be a higher concentration of heavy metals in the older lens. This behavior may favor the formation of cataract, because heavy metals enhance protein oxidation through the Fenton reaction.
量化金属载体蛋白在人晶状体囊中的分配系数和扩散系数随年龄的变化情况。
将来自人类供体的完整晶状体在荧光标记的转铁蛋白、白蛋白或铜蓝蛋白溶液中孵育过夜。在囊厚度的中心平面进行光漂白后荧光恢复（FRAP）实验，以测量蛋白质在晶状体囊内的扩散。在FRAP实验之前记录晶状体的前部，以定位前囊膜的边界并测量标记蛋白质的分配系数。分析每种蛋白质的分配系数（P）、荧光强度恢复到最大值一半的时间（τ）和扩散系数（D）随供体年龄的变化情况。
转铁蛋白（分子量[MW]=79.5 kDa，τ=17.26±4.840秒，D=0.17±0.05μm/s）、血清白蛋白（MW=66.5 kDa，τ=18.45±6.110秒，D=0.17±0.06μm/s）或铜蓝蛋白（MW=120 kDa，τ=36.57±5.660秒，D=0.08±0.01μm/s）的荧光强度恢复到最大值一半的时间或扩散系数与年龄之间均无统计学上的显著关系。正如预期的那样，较大的蛋白质（铜蓝蛋白）由于在晶状体囊内移动较慢，荧光强度恢复所需时间更长。每种蛋白质的分配系数随年龄增长在统计学上显著增加（P：0.09 - 0.71，P：0.42 - 0.95，P：0.19 - 1.17）。
重金属蛋白载体在前囊膜内的扩散不依赖于年龄，而是依赖于蛋白质的大小。晶状体囊对这些重金属蛋白载体的通透性随年龄增加，这表明老年晶状体中重金属的浓度会更高。这种行为可能有利于白内障的形成，因为重金属通过芬顿反应增强蛋白质氧化。
