Homeostatic alterations related to total antioxidant capacity, elemental concentrations and isotopic compositions in aqueous humor of glaucoma patients

Marta Aranaz,Lara Lobo,Frank Vanhaecke,Marta Costas-Rodríguez,Montserrat García,Rosario Pereiro,Héctor González-Iglesias

doi:10.1007/s00216-021-03467-5

Abstract

Glaucoma is a multifactorial eye disease, characterized by progressive optic neurodegeneration. Elevation of the intraocular pressure is the main risk factor for glaucoma and is a consequence of an imbalance in the aqueous humor hydrodynamics, the physiology of which is influenced by the homeostatic equilibrium of essential elements, oxidative stress, and antioxidants. The aim of this work was to study local alterations in glaucomatous patients from two different, but connected, points of view: (i) the total antioxidant capacity (as an indicator of oxidative damage) and (ii) the concentration of mineral elements and their isotopic composition. Such objective was pursued using aqueous humor from patients diagnosed with pseudoexfoliation glaucoma (PEXG, n = 17) and primary open-angle glaucoma (POAG, n = 5) and age-matched control subjects (n = 16). The total antioxidant capacity (TAC) was examined in both aqueous humor and 60 serum samples (n = 20 controls, n = 20 for PEXG, and n = 20 for POAG), both showing higher TAC for the glaucoma population. The concentrations of the essential mineral elements (Cu, Fe, Mg, Na, P, and Zn) and the isotopic compositions of Cu and Zn were determined in aqueous humor using single-collector and multi-collector inductively coupled plasma–mass spectrometry, respectively. Significant differences were established for Mg and P levels when comparing the results for glaucomatous patients with those for the control population (p < 0.01 and p < 0.05 for Mg and P respectively, ANOVA and Kruskal-Wallis). The Zn isotopic composition was significantly shifted from that for the control population for PEXG patients. A significant difference in the isotopic composition of Zn was also established between the PEXG and POAG glaucoma cohorts.Graphical abstract

Highlights

Glaucoma comprises a complex group of neurodegenerative disorders, affecting nearly 80 million people worldwide, and is considered one of the leading causes of irreversible blindness [1]
Significant differences were obtained for Qt between the control group and pseudoexfoliation glaucoma (PEXG) in aqueous humor and between controls, primary open-angle glaucoma (POAG), and PEXG in serum
Elemental concentrations of Mg and P were established to be altered for the glaucoma cohorts as compared to the control group ( Cu, Fe, Na, and Zn were evaluated): POAG subjects showed higher levels of Mg compared with controls and PEXG patients presented higher levels of P in comparison with the control population

Summary

Introduction

Glaucoma comprises a complex group of neurodegenerative disorders, affecting nearly 80 million people worldwide, and is considered one of the leading causes of irreversible blindness [1]. This multifactorial disease is characterized by optic nerve damage and retinal ganglion cell (RGC) death, which leads to visual field loss. While its etiology remains so far unknown and its incidence increases with age, elevation of intraocular pressure (IOP) is the main risk factor for the development of glaucoma [1, 3]. The most prevalent subtypes of glaucoma include primary open-angle glaucoma (POAG) and pseudoexfoliation glaucoma (PEXG), sharing a dysfunction of the aqueous humor dynamics that results in elevated IOP. While POAG is usually associated with an alteration in the cell physiology of the trabecular meshwork [3], PEXG is characterized by the progressive accumulation of abnormal fibrillar protein aggregates in the anterior chamber of the eye [4]

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