Cryotolerance of Stallion Spermatozoa Relies on Aquaglyceroporins rather than Orthodox Aquaporins.

Ariadna Delgado-Bermúdez,Sebastián Bonilla-Correal,Estela Garcia-Bonavila,Sergi Bonet,Federico Noto,Jordi Miró,Jaime Catalán,Marc Yeste,Marion Papas

doi:10.3390/biology8040085

Ariadna Delgado-Bermúdez, Sebastián Bonilla-Correal + Show 7 more

Open Access

https://doi.org/10.3390/biology8040085

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Journal: Biology	Publication Date: Nov 12, 2019
Citations: 14	License type: CC BY 4.0

Affiliation: University of Girona, Autonomous University of Barcelona

Abstract

Aquaporins (AQPs), a family of ubiquitous water channels divided into orthodox AQPs, aquaglyceroporins (GLPs), and superAQPs, are present in stallion spermatozoa. The aim of this study was to elucidate the functional relevance of each group of AQPs during stallion sperm cryopreservation through the use of three different inhibitors: acetazolamide (AC), phloretin (PHL) and propanediol (PDO). Sperm quality and function parameters were evaluated in the presence or absence of each inhibitor in fresh and frozen–thawed samples. In the presence of AC, different parameters were altered (p < 0.05), but not in a concentration- or time-depending manner. PHL was found to decrease sperm motility, viability, acrosome integrity, and the percentages of spermatozoa with low membrane lipid disorder, high mitochondrial membrane potential (MMP) and high intracellular levels of calcium and superoxides (p < 0.05). Finally, the sperm motility, viability, acrosome integrity, the percentages of spermatozoa with low membrane lipid disorder, high MMP and high intracellular calcium levels were higher (p < 0.05) in PDO treatments than in the control. The sperm response to AC, PHL and PDO indicates that GLPs, rather than orthodox AQPs, play a crucial role during stallion sperm cryopreservation. Furthermore, post-thaw sperm quality was higher in PDO treatments than in the control, suggesting that this molecule is a potential permeable cryoprotectant.

Highlights

The permeability of the plasma membrane to water and solutes is crucial for proper cell function and homeostasis
SYBR14+ /propidium iodide (PI− ) spermatozoa, viable cells; peanut agglutinin conjugated with fluorescein isothiocyanate (PNA-FITC− )/PI− spermatozoa, cells with an intact plasma membrane and acrosome; merocyanine 540 (M540− )/YO-PRO-1− spermatozoa, live cells with low mitochondrial membrane disorder; JC1 aggregates (JC1agg) spermatozoa, cells with high mitochondrial membrane potential (MMP); Fluo3+ /PI− spermatozoa, live cells with high intracellular calcium levels, mainly in the sperm mid-piece; Rhod5+ /YO-PRO-1− spermatozoa, live cells with high intracellular calcium levels, mainly in the sperm head; E+ /YO-PRO-1− spermatozoa, live cells with high superoxide (O2 − ) levels; 2’,7’-dichlorofluorescein (DCF+ )/PI− spermatozoa, live cells with high peroxide (H2 O2 ) levels
The effects of AQP inhibition rely on the specificity of each inhibitor for each AQPs group and its collateral effects on other sperm proteins

Summary

Introduction

The permeability of the plasma membrane to water and solutes is crucial for proper cell function and homeostasis. Because of the amphipathic nature of the plasma membrane, the simple diffusion of water molecules does not occur at high rates [1]. Aquaporins (AQPs) are a family of ubiquitous transmembrane proteins that allow for the facilitated diffusion of water. Some AQPs are permeable to small solutes [2]. 13 AQPs (AQP0–AQP12) have been identified in mammalian cells and have been classified into three different groups (orthodox AQPs, aquaglyceroporins (GLPs), and superAQPs), which differ in their sequence and solute permeability. The orthodox AQP group includes AQP0, AQP1, AQP2, AQP4, AQP5, AQP6, and AQP8, which are exclusively permeable

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