Mitochondrial and microtubule defects in Exfoliation Glaucoma

Abstract

Exfoliation Syndrome is an age-related systemic condition characterized by large aggregated fibrillar material deposition in the anterior eye tissues. This aggregate formation and deposition on the aqueous humor outflow pathway are significant risk factors for developing Exfoliation Glaucoma (XFG). XFG is a multifactorial late-onset disease that shares common features of neurodegenerative diseases, such as increased protein aggregation, impaired protein degradation, and oxidative and cellular stress. XFG patients display decreased mitochondrial membrane potential and mitochondrial DNA deletions. Here, using Tenon Capsule Fibroblasts (TFs) from patients without glaucoma (No Glaucoma, NG) and XFG patients, we found that XFG TFs have impaired mitochondrial bioenergetics and increased reactive oxygen species accumulation. These defects are associated with mitochondrial abnormalities as XFG TFs exhibit smaller mitochondria that contain dysmorphic cristae, with increased mitochondrial localization to lysosomes and slowed mitophagic flux. Mitochondrial dysfunction in the XFG TFs was associated with hyperdynamic microtubules, decreased acetylated tubulin, and increased HDAC6 activity. Treatment of XFG TFs with a mitophagy inducer, Urolithin A (UA), and a mitochondrial biogenesis inducer, Nicotinamide Ribose (NR), improved mitochondrial bioenergetics and reduced ROS accumulation. Our results demonstrate that XFG TFs have abnormal mitochondria and suggest that mitophagy inducers may represent a potential class of therapeutics for reversing mitochondrial dysfunction in XFG patients.