Kleesattel David, Crish Samuel D, Inman Denise M
Invest Ophthalmol Vis Sci. 2015 Dec;56(13):8215-27. doi: 10.1167/iovs.15-17885.
Autophagy is a critical process, compromised in neurodegenerative disease, by which terminally differentiated cells like neurons manage cytoskeletal and organelle turnover. How autophagy relates to associated neurodegenerative pathologies remain unclear. We examined autophagy in optic neuropathy by investigating cytoskeletal degradation, mitochondria, and autophagic vesicles in the DBA2/J mouse model of glaucoma exhibiting differing levels of axon transport functionality.
DBA/2J and DBA/2J(wt-gpnmb) control mice 11 to 14 months of age were injected with cholera toxin-B (CTB) to assay anterograde axonal transport. Axonal mitochondria and autophagic vesicles were analyzed with respect to transport integrity in proximal and distal optic nerve using serial block face scanning electron microscopy (3D EM).
Several indices varied significantly between the DBA/2J and DBA/2J(wt-gpnmb) mice, including mitochondrial volume, average number of autophagic vesicles per axon, and mitochondrial cristae. However, there were no differences in mitochondrial cristae for axons with functional versus dysfunctional CTB transport, suggesting that mitochondrial dysfunction precedes overt transport blockade. Anterograde transport failure was accompanied by a dissociation of the relationship between mitochondrial and axon volumes. Autophagic vesicle profiles were significantly increased in optic nerve with transport deficit, consistent with greater autophagic activity. Mitochondria within autophagosomes, indicative of mitophagy, were observed in both proximal and distal axons.
Loss of anterograde transport in DBA/2J optic nerve is concomitant with diminished mitochondrial volume, increased cytoskeletal breakdown and autophagic activity, and accumulation of autophagic profiles, including signs of mitophagy, in proximal optic nerve. Axons with transport deficit are metabolically underserved, though not necessarily from mitophagy.
自噬是一个关键过程，在神经退行性疾病中会受到损害，通过这个过程，像神经元这样的终末分化细胞能够管理细胞骨架和细胞器的更新。自噬与相关神经退行性病变之间的关系仍不清楚。我们通过研究表现出不同轴突运输功能水平的青光眼DBA2/J小鼠模型中的细胞骨架降解、线粒体和自噬小泡，来检测视神经中的自噬。
给11至14月龄的DBA/2J和DBA/2J（野生型 - gpnmb）对照小鼠注射霍乱毒素B（CTB），以检测顺行轴突运输。使用连续块面扫描电子显微镜（3D EM）分析近端和远端视神经中轴突线粒体和自噬小泡的运输完整性。
DBA/2J和DBA/2J（野生型 - gpnmb）小鼠之间的几个指标有显著差异，包括线粒体体积、每个轴突的自噬小泡平均数量和线粒体嵴。然而，具有功能性与功能失调性CTB运输的轴突在线粒体嵴方面没有差异，这表明线粒体功能障碍先于明显的运输阻滞。顺行运输失败伴随着线粒体与轴突体积之间关系的解离。运输缺陷的视神经中自噬小泡轮廓显著增加，这与更高的自噬活性一致。在近端和远端轴突中均观察到自噬体中的线粒体，这表明存在线粒体自噬。
DBA/2J视神经中顺行运输的丧失与线粒体体积减小、细胞骨架分解增加和自噬活性增强以及近端视神经中自噬轮廓的积累（包括线粒体自噬的迹象）同时发生。运输缺陷的轴突代谢供应不足，尽管不一定是由于线粒体自噬。
