Department of Ophthalmology, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China.
Hunan Clinical Research Center of Ophthalmic Disease, Changsha, Hunan, China.
Invest Ophthalmol Vis Sci. 2024 Nov 4;65(13):12. doi: 10.1167/iovs.65.13.12.
Aging alters the function of the lacrimal gland and disrupts the balance of the microenvironment on the ocular surface, eventually leading to aqueous-tear-deficient dry eye. Mitophagy has been reported to play an important role in aging, but the underlying mechanism remains unclear.
The young (6 weeks) and middle-aged (12 months) male C57BL/6J mice were used in this study, and mitophagy agonist rapamycin and inhibitor Mdivi-1 were used in in vivo experiments. Hematoxylin and eosin, Masson, Oil Red O, and reactive oxygen species (ROS) staining were used to detect histological changes and lipids in lacrimal gland. Changes in the expression of proteins were identified by Western blotting of lacrimal gland lysates. Transmission electron microscopy and immunofluorescence staining were used to assess mitophagy. The single-cell RNA sequencing (scRNA-seq) and bioinformatics analyses were used to detect transcription signature changes during aging.
In this study, we discovered that aging increased oxidative stress, which increased apoptosis, and generated ROS in acinar epithelial cells. Furthermore, activation of PINK1/Parkin-mediated mitophagy by rapamycin reduced lacrimal gland ROS concentrations and prevented aging-induced apoptosis of acinar cells, thereby causing histological alterations, microstructural degradation, and increasing tear secretion associated with ROS accumulation. By contrast, Mdivi-1 aggregates mitochondrial function and thereafter leads to lacrimal gland function impairment by inhibiting mitochondrial fission and giving rise to mitophagy.
Overall, our findings suggested that aging could impair mitochondrial function of acinar cells, and age-related alterations may be treated with therapeutic approaches that enhance mitophagy while maintaining mitochondrial function.
衰老改变了泪腺的功能，并破坏了眼表面微环境的平衡，最终导致水样液缺乏性干眼症。自噬已被报道在衰老中发挥重要作用，但潜在机制尚不清楚。
本研究使用年轻（6 周）和中年（12 个月）雄性 C57BL/6J 小鼠，体内实验使用自噬激动剂雷帕霉素和抑制剂 Mdivi-1。苏木精和伊红、马松、油红 O 和活性氧（ROS）染色用于检测泪腺的组织学变化和脂质。通过对泪腺裂解物进行 Western blot 分析来鉴定蛋白质表达的变化。透射电子显微镜和免疫荧光染色用于评估自噬。单细胞 RNA 测序（scRNA-seq）和生物信息学分析用于检测衰老过程中的转录特征变化。
在这项研究中，我们发现衰老增加了氧化应激，从而增加了 ROS 在腺泡上皮细胞中的凋亡。此外，雷帕霉素激活 PINK1/Parkin 介导的自噬减少了泪腺 ROS 浓度，并防止了衰老引起的腺泡细胞凋亡，从而导致组织学改变、微结构降解，并增加与 ROS 积累相关的泪液分泌。相比之下，Mdivi-1 聚集线粒体功能，通过抑制线粒体分裂和引发自噬，从而导致泪腺功能障碍。
总的来说，我们的研究结果表明，衰老可能会损害腺泡细胞的线粒体功能，而与年龄相关的改变可能可以通过增强自噬同时保持线粒体功能来治疗。
