Analysis of Protein Oxidative Modifications in Follicular Fluid from Fertile Women: Natural Versus Stimulated Cycles.

Irantzu Pérez-Ruiz,José-Ignacio Ruiz-Sanz,María-Luisa Hérnandez,María-Begoña Ruiz-Larrea,Zaloa Larreategui,Susana Meijide,Marcos Ferrando,Rosaura Navarro

doi:10.3390/antiox7120176

Irantzu Pérez-Ruiz, José-Ignacio Ruiz-Sanz + Show 6 more

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https://doi.org/10.3390/antiox7120176

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Abstract

Oxidative stress is associated with obstetric complications during ovarian hyperstimulation in women undergoing in vitro fertilization. The follicular fluid contains high levels of proteins, which are the main targets of free radicals. The aim of this work was to determine specific biomarkers of non-enzymatic oxidative modifications of proteins from follicular fluid in vivo, and the effect of ovarian stimulation with gonadotropins on these biomarkers. For this purpose, 27 fertile women underwent both a natural and a stimulated cycle. The biomarkers, glutamic semialdehyde (GSA), aminoadipic semialdehyde (AASA), Nε-(carboxymethyl)lysine (CML), and Nε-(carboxyethyl)lysine (CEL), were measured by gas-liquid chromatography coupled to mass spectrometry. Results showed that follicular fluid contained products of protein modifications by direct metal-catalyzed oxidation (GSA and AASA), glycoxidation (CML and CEL), and lipoxidation (CML). GSA was the most abundant biomarker (91.5%). The levels of CML amounted to 6% of the total lesions and were higher than AASA (1.3%) and CEL (1.2%). In the natural cycle, CEL was significantly lower (p < 0.05) than in the stimulated cycle, suggesting that natural cycles are more protected against protein glycoxidation. These findings are the basis for further research to elucidate the possible relevance of this follicular biomarker of advanced glycation end product in fertility programs.

Highlights

Free radicals are highly reactive molecular species that are inherent to aerobic life
We described that controlled ovarian stimulation led to oxidative stress, mainly reflected by changes in the redox status of the serum in terms of total antioxidant activity, susceptibility to in vitro oxidation, and the levels of antioxidants such as tocopherol, bilirubin, uric acid, and albumin [18]
In the case of direct oxidations by free radicals, hydroxy-2-aminovaleric acid (HAVA) and hydroxy-2-aminocaproic acid (HACA) were used as standards, since during the reduction and acid hydrolysis processing of the samples the parent compounds are converted into HACA (GSA) and HAVA (AASA)

Summary

Introduction

Free radicals are highly reactive molecular species that are inherent to aerobic life. Proteins are one of the major targets of free radical attack, because of their high concentration in all compartments and because some amino acids (tyrosine, methionine, arginine, proline, and lysine) are prone to non-enzymatic modifications [1]. Proteins are involved in practically all physiological processes, and their oxidative modifications may have detrimental effects in an organism [2,3]. A hallmark of oxidative protein damage is the introduction of carbonyl groups into amino acid residues. Carbonyl groups in proteins may directly arise by metal-catalyzed oxidation of specific amino acids. During the protein glycation and the peroxidation of polyunsaturated fatty acids, Antioxidants 2018, 7, 176; doi:10.3390/antiox7120176 www.mdpi.com/journal/antioxidants

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