School of Biological Sciences, University of Auckland, Auckland, New Zealand.
Department of Physiology, School of Medical Sciences, University of Auckland, Auckland, New Zealand.
Exp Eye Res. 2019 Jul;184:146-151. doi: 10.1016/j.exer.2019.04.016. Epub 2019 Apr 17.
Tryptophan-derived UV filters are predominantly found in the lenses of primates and humans. While protective against UV radiation, aging alters the complement and spatial distributions of human lens UV filters, and a role for UV filters has been suggested in age-related cataract formation. To establish how the spatial distributions of UV filters change in normal human lens aging, matrix assisted laser desorption/ionisation-imaging mass spectrometry (MALDI-IMS) was utilised to map the locations and relative abundance of multiple UV filters simultaneously. Frozen human lenses were cryosectioned axially, and the 20 μm-thick sections coated with MALDI matrix via robotic sprayer and analysed using negative ion mode MALDI-Fourier transform-ion cyclotron resonance MS. While signal for many UV filters was detected throughout the lenses, signal intensity was generally highest in the central (embryonic) nucleus and decreased uniformly in outer (foetal, juvenile, adult) nuclear and cortical regions, and many UV filter signals declined with age. In contrast, two antioxidant-conjugated UV filters (Cys-3-OHKG and GSH-3-OHKG) were restricted to the lens nucleus and their relative signal increased with increasing lens age. The enhanced spatial resolution of MALDI-IMS over manual trephine dissection techniques and its multiplex capability allowed the spatial relationships between lens UV filters to be established and explored in relation to aging. Together these results confirmed that the complement of UV filters in each lens is dynamic and undergoes significant age-related changes. In the future, this information could be used to compare with other lens biomolecule changes to better understand the lens aging process and age-related cataract formation.
色氨酸衍生的紫外线滤光剂主要存在于灵长类动物和人类的晶状体中。虽然这些滤光剂能起到防护紫外线辐射的作用，但随着年龄的增长，人类晶状体中的紫外线滤光剂的补体和空间分布会发生改变，并且有人提出紫外线滤光剂在年龄相关性白内障的形成中起作用。为了确定正常人类晶状体老化过程中紫外线滤光剂的空间分布如何变化，本研究利用基质辅助激光解吸/电离成像质谱（MALDI-IMS）同时对多种紫外线滤光剂的位置和相对丰度进行了映射。对冷冻的人类晶状体进行轴向冷冻切片，通过机器人喷雾器将 MALDI 基质涂覆在 20μm 厚的切片上，并采用负离子模式 MALDI-傅里叶变换离子回旋共振 MS 进行分析。尽管在整个晶状体中都检测到了许多紫外线滤光剂的信号，但信号强度通常在中央（胚胎）核中最高，并在外核（胎儿、幼年、成年）和皮质区均匀降低，而且许多紫外线滤光剂的信号随年龄的增长而下降。相比之下，两种抗氧化剂缀合的紫外线滤光剂（Cys-3-OHKG 和 GSH-3-OHKG）局限于晶状体核，其相对信号随晶状体年龄的增加而增加。与手动环钻切割技术相比，MALDI-IMS 的空间分辨率更高，并且具有多重检测能力，能够建立和探索晶状体紫外线滤光剂之间的空间关系及其与老化的关系。这些结果共同证实了每个晶状体中的紫外线滤光剂的组成是动态的，并随着年龄的增长发生显著变化。将来，这些信息可用于与其他晶状体生物分子变化进行比较，以更好地了解晶状体老化过程和年龄相关性白内障的形成。
