Oxidative profile and protease regulator potential to predict sperm functionality in donkey (Equus asinus)

Relationship between Oxidative Stress and Endometritis: Exploiting Knowledge Gained in Mares and Cows

Simple Summary

Endometritis is a widespread pathology in mares and cows and one of the leading causes of reproductive efficiency decline. Although localized in the innermost layer of the uterus, this inflammation involves the release of bioactive molecules and by-products related to molecular damage. Among the bioactive substances, a primary role is played by the reactive oxygen and nitrogen species, which, while exerting an antimicrobial effect, can amplify the inflammation, sometimes causing unwanted and self-aggravating effects. Part of these substances enters the bloodstream, with implications that range from sustaining distant effects on organs and tissues to being used as diagnostic biomarkers. The research carried out on this matter in cows and mares has maintained certain independence due to its species specificity. This review aims to collect and analyze the information available in these species to enhance diagnostics and provide new insights to prevent and treat this pathology.

Abstract

The etiopathogenesis of endometritis in mares and cows differs significantly; this could depend on a different sensitivity and reactivity of the uterus but also on endocrine and rearing factors and different stress sources. In both species, microorganisms and the immune system play a primary role in the generation of this pathology. Microbiological and cytological tests support clinical examination and significantly improve diagnostic accuracy. For both species, during the inflammation, immune cells invade the endometrium and release bioactive substances to contrast primary or secondary pathogen contamination. These molecules are traceable to cytokines, chemokines, and prostaglandins as well as reactive oxygen and nitrogen species (ROS and RNS), collectively known as RONS. The RONS-mediated oxidation causes morphological and functional alterations of macromolecules, such as proteins, lipids, and nucleic acids, with the consequent production of derivative compounds capable of playing harmful effects. These bioactive molecules and by-products, which have recently become increasingly popular as diagnostic biomarkers, enter the bloodstream, influencing the functionality of organs and tissues. This review has collected and compared information obtained in cows and mares related to the diagnostic potential of these biomarkers that are assessed by using different methods in samples from either blood plasma or uterine fluid.

Seminal Plasma Antioxidants Are Related to Sperm Cryotolerance in the Horse

The objective of this study was to determine the relationship of enzymatic (superoxide dismutase, SOD; glutathione peroxidase, GPX; catalase, CAT; and paraoxonase type 1, PON1) and non-enzymatic antioxidants (measured in terms of: Trolox equivalent antioxidant capacity, TEAC; cupric-reducing antioxidant capacity, CUPRAC; and ferric-reducing ability of plasma, FRAP), as well as the oxidative stress index (OSI) in seminal plasma (SP) with the resilience of horse sperm to freeze-thawing. Twenty-one ejaculates (one per individual) were collected and split into two aliquots: the first was used to harvest the SP and assess the activity levels of antioxidants and the OSI, and the second one was cryopreserved. The following post-thaw sperm quality parameters were evaluated: sperm motility, plasma membrane and acrosome integrity, mitochondrial membrane potential, intracellular levels of reactive oxygen species (ROS), and plasma membrane lipid disorder. Based on post-thaw total motility (TM) and plasma membrane integrity (SYBR14+/PI−), ejaculates were hierarchically (p < 0.001) clustered into two groups of good (GFE) and poor (PFE) freezability. The SP activity levels of PON1, SOD, and TEAC were higher (p < 0.05) in GFE than in PFE, showing a positive relationship (p < 0.05) with some sperm motility parameters and with plasma membrane (PON1 and TEAC) and acrosome (SOD and TEAC) integrity. In contrast, OSI was higher (p < 0.05) in the SP of PFE than in that of GFE, and was negatively correlated (p < 0.05) to some sperm motility parameters and to plasma membrane and acrosome integrity, and positively (p < 0.05) to the percentage of viable sperm with high plasma membrane lipid disorder. In conclusion, enzymatic (PON1 and SOD) and non-enzymatic (TEAC) antioxidants of SP are related to horse sperm cryotolerance. In addition, our results suggest that PON1 could be one of the main antioxidant enzymes involved in the control of ROS in this species. Further investigation is needed to confirm the potential use of these SP-antioxidants and OSI to predict sperm cryotolerance in horses.

Impact of Seminal Plasma Antioxidants on Donkey Sperm Cryotolerance

This study investigated whether the activities of the antioxidant components of donkey seminal plasma (SP)—both enzymatic (superoxide dismutase (SOD), catalase-like (CAT), glutathione peroxidase-like (GPX), and paraoxonase type 1 (PON1)) and non-enzymatic (measured in terms of total thiol, copper-reducing antioxidant capacity (CUPRAC), ferric-reducing ability of plasma (FRAP), and Trolox equivalent antioxidant capacity (TEAC))—and oxidative stress index (OSI) are related to sperm cryotolerance. For this purpose, 15 ejaculates from jackasses (one per individual) were collected and split into two aliquots. The first one was used for measuring the activities levels of enzymatic and non-enzymatic antioxidants and OSI in SP, whereas the other aliquot was cryopreserved. Before cryopreservation, sperm quality parameters (concentration, motility, and viability) were evaluated. After thawing, sperm motility, plasma membrane integrity, lipid disorder, mitochondrial membrane potential, reactive oxygen species (ROS), and calcium intracellular levels were also determined. Based on the percentages of total motility (TM) and of sperm with an intact plasma membrane (SYBR14⁺/PI⁻) after thawing, samples were classified as good-freezability (GFE) or poor-freezability (PFE) ejaculates through cluster analyses. The SP activity levels of enzymatic (SOD and PON1) and non-enzymatic antioxidants (CUPRAC, FRAP, and TEAC) were higher (p < 0.05) in GFE than in PFE, whereas SP-OSI was higher (p < 0.05) in PFE than in GFE. In addition, the activity levels of SOD, PON1, GPX, CUPRAC, FRAP, and TEAC were positively (p < 0.05) related to post-thaw sperm motility and plasma membrane integrity and negatively to intracellular ROS levels. The SP-OSI was negatively correlated (p < 0.05) to post-thaw sperm quality parameters and positively to intracellular ROS levels. It can thus be concluded that donkey SP antioxidants are related to sperm cryotolerance and that measurements of antioxidants PON1, SOD, CUPRAC, FRAP, and TEAC, as well as SP-OSI, could be used as markers of sperm cryotolerance. Further research addressing the relationship of these antioxidants and SP-OSI with sperm cryotolerance and their potential use as freezing markers is warranted.