A highly sensitive fluorescent probe RN-NA reveals peroxynitrite as a novel biomarker for primary open angle glaucoma

To directly quantify peroxynitrite (ONOO^-) using a highly sensitive fluorescence resonance energy transfer probe RN-NA, investigate the association between ONOO^- and primary open angle glaucoma (POAG), and clarify whether RN-NA could be used as a potential tool for POAG diagnosis.

Plasma and aqueous humor (AH) samples were collected from POAG patients (n=100, age: 59.70±6.87y) and age-related cataract (ARC) patients (n=100, age: 61.15±4.60y) admitted to our hospital. Next, RN-NA was used to detect ONOO^- in plasma and AH samples, and the relationship between ONOO^- level and POAG was analyzed using binary logistic regression. Besides, Pearson correlation analysis was applied to characterize the correlation of the levels of ONOO^- with the patients' age, intraocular pressure (IOP), and mean deviation of visual field testing. The ONOO^- scavenger MnTMPyP was employed to treat the 3-morpholinosyndnomine (SIN-1)-induced ocular hypertension in mice (n=7, 6-8wk). Finally, the IOP and ONOO^- in both eyes were measured 30min after the last drug treatment.

ONOO^- levels of AH and plasma were significantly higher in the POAG group than in the ARC group (P<0.01). Additionally, ONOO^- levels were closely correlated with POAG in a binary logistic regression analysis [odds ratio (OR)=1.008, 95% confidence interval (CI): 1.002-1.013, P<0.01 for AH; OR=1.004, 95%CI: 1.002-1.006, P<0.001 for plasma]. Pearson correlation analysis showed that ONOO^- levels in AH or plasma were positively associated with visual field defects (R=0.51, P<0.01 for AH; R=0.45, P<0.001 for plasma), and ONOO^- levels in plasma and AH were correlated in the POAG group (R=0.69, P<0.001). However, administering MnTMPyP to mouse eyes reversed the elevated IOP caused by SIN-1 (P<0.05).

ONOO^- levels in AH and plasma, detected by RN-NA, are significantly related to POAG and positively correlated with visual field defects in POAG patients. Hence, ONOO^- is a potential biomarker of POAG, especially advanced POAG. Besides, anti-nitration compounds may be novel ocular hypotensive agents based on the animal study.