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Carla J Siegfried, Ying-Bo Shui, Ying Liu, Andrew J W Huang, Paul L Kaufman; Aqueous humor biomarker of oxidative damage and antioxidant status: Correlations with oxygen and racial differences. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4901.
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© ARVO (1962-2015); The Authors (2016-present)
Our previous studies identified significantly higher levels of oxygen (pO2) in anterior segments of patients with prior vitrectomy/cataract surgeries as well as patients of African American background. This prospective, cross-sectional study explores correlations of a biomarker of oxidative damage and antioxidant status in aqueous humor (AH) of human subjects as well as experimental monkey eyes.
Patients undergoing glaucoma and/or cataract surgery (n=219) were consented and recruited. Intraocular pO2 measurements were taken prior to surgery with a fiberoptic probe (Oxford Optronix, UK) at five locations in the anterior segment. AH was collected and stored in liquid nitrogen container. Ascorbic acid (AsA) and total reactive antioxidant potential (TRAP) were measured and 8-hydroxy-2'-deoxyguanosine (8-OHdG), a biomarker of oxidative damage, was detected by ELISA (Oxiselect™). Five rhesus monkeys underwent pars plana vitrectomy followed by lens extraction over two-year period. AsA, TRAP and 8-OHdG were measured as in human subjects. T-test/ANOVA and multivariate regression were used for statistical analysis.
Human AH showed AsA and TRAP levels that were significantly lower and pO2 higher in groups with previous vitrectomy and vitrectomy plus cataract extraction (p<0.05, 0.01 respectively) compared to cataract extraction only (1.4±0.6 mM, 479.3±146.7 Trolox units) with no differences between African American vs. Caucasians. Monkeys showed the same results in AsA, TRAP and pO2 as humans. However, 8-OHdG was significantly increased after vitrectomy (p=0.03) followed by lens extraction (p=0.04). Preliminary data of human aqueous indicated a significant increase in African American (n=11) compared to Caucasians (n=17;p=0.015). Additional human specimen collection and analysis is ongoing with further subgroup analysis.
Decreased antioxidant levels in human subject and monkey AH following vitrectomy and lensectomy may correlate with increased pO2. Increased 8-OHdG in monkey AH may provide direct evidence of oxidative damage in structures surrounding the anterior chamber specifically trabecular meshwork. Also, increased 8-OHdG AH levels in African Americans may serve as a biomarker and aid our understanding this population's higher risk and severity of open angle glaucoma.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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