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

Aim: 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.

Methods: Plasma and aqueous humor (AH) samples were collected from POAG patients (=100, age: 59.70±6.87y) and age-related cataract (ARC) patients (=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 (=7, 6-8wk). Finally, the IOP and ONOO in both eyes were measured 30min after the last drug treatment.

Results: ONOO levels of AH and plasma were significantly higher in the POAG group than in the ARC group (<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, <0.01 for AH; OR=1.004, 95%CI: 1.002-1.006, <0.001 for plasma]. Pearson correlation analysis showed that ONOO levels in AH or plasma were positively associated with visual field defects (=0.51, <0.01 for AH; =0.45, <0.001 for plasma), and ONOO levels in plasma and AH were correlated in the POAG group (=0.69, <0.001). However, administering MnTMPyP to mouse eyes reversed the elevated IOP caused by SIN-1 (<0.05).

Conclusion: 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.