Upregulated NOTCH Signaling in the Lens of Patients With Pseudoexfoliation Syndrome Compared With Pseudoexfoliation Glaucoma Suggests Protective Role.

Abstract

NOTCH signaling is significantly upregulated in the lens capsules of eyes with pseudoexfoliation syndrome (PXF) but not in those with pseudoexfoliation glaucoma (PXG) when compared with healthy controls. NOTCH signaling has neuroprotective functions and altered NOTCH signaling is associated with neurodegenerative diseases with protein aggregation such as Alzheimer disease. As PXG is also a protein aggregate disease associated with neural degeneration, NOTCH molecular expression was explored in the lens capsules of patients with PXF, PXG, primary open-angle glaucoma (POAG), and healthy controls. Anterior lens capsules were collected from 106 patients (27 PXF, 24 PXG, 22 POAG, and 33 controls) undergoing cataract surgery. Gene expression profiling for NOTCH pathway molecules (ligands, receptors, and downstream target genes) was performed on the tissue using a quantitative reverse transcription-polymerase chain reaction. The results were confirmed by protein analysis using dot-blot or immunostaining techniques. There was no difference in the demographic characteristics between the groups. There was an increase in NOTCH4 receptor expression (>14-fold) in the PXF group as compared with the controls. Similarly, the Delta-like 3 and Delta-like 4 ligands were significantly elevated in the PXF group compared with controls (P<0.05). Downstream targets HES3, HES5, and HEY1 expression were significantly elevated (P<0.005) in PXF lens capsules, confirming a higher activity of NOTCH signaling in this cohort. Immunostaining also corroborated the gene expression profile. The finding that NOTCH signaling is significantly upregulated in the lens capsule of eyes with PXF and not in PXG or POAG patients suggests a possible protective role in the development of glaucoma.