Lipid and protein oxidation levels in spermatozoa and seminal plasma of Asian Elephants (Elephas maximus) and their relationship with semen parameters

Physiological changes in captive elephants in northern Thailand as a result of the COVID-19 tourism ban-stress biomarkers

The international travel ban instituted by the Thai government in March 2020 in response to the COVID-19 pandemic greatly affected how tourist camp elephants were managed, with reductions in exercise opportunities, longer chaining hours, and diminished food provisioning. This study was conducted to determine how those changes affected health and welfare biomarkers in individual elephants over the 2 years of the countrywide lockdown (April 2020-April 2022). Blood and fecal samples were collected from 58 elephants at six camps (monthly in Year 1, quarterly in Year 2) and analyzed for stress biomarkers - fecal glucocorticoid metabolites (fGCM), serum oxidative stress [malondialdehyde (MDA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG)], and stress leukograms. Overall, fGCM concentrations increased within the first few months and remained higher than pre-COVID levels, as did the H/L ratio, a measure affected by cortisol. Serum 8-OHdG, an indicator of DNA oxidative damage, also increased over time, while monocytosis and lymphopenia further suggested alterations in immune function as a result of stress. By contrast, another marker of oxidative stress, serum MDA, declined, possibly in response to reduced roughage and supplement intake. A notable finding was a seasonal pattern of fGCM that was significantly different from previous studies. Whereas higher fGCM during the rainy season were observed in this study, previously, concentrations were highest during the winter, high tourist season. Thus, ironically, both the presence and absence of tourists have been associated with increased fGCM concentrations, albeit for different reasons. Camp management factors negatively affecting stress outcomes included shorter chain lengths, longer chain hours, lack of exercise, and reduced roughage and supplements. Overall, it was clear that camps struggled to maintain adequate care for elephants during the COVID-19 pandemic, highlighting the importance of tourist income and need for contingency plans to cope with potential future disruptions to tourism.

Seasonal patterns of oxidative stress markers in captive Asian elephants in Thailand and relationships to elephant endotheliotropic herpesvirus shedding

Introduction

Oxidative stress refers to an imbalance between oxidant and antioxidant activity and accumulation of reactive oxygen species, which can have detrimental effects on animal health. Annual fluctuations in oxidative stress status can occur, increasing disease susceptibility during certain time periods. However, a full understanding of factors related to oxidative stress in Asian elephants and how to mitigate the negative consequences is lacking.

Methods

This study measured six serum oxidative stress markers [reactive oxygen species (ROS), malondialdehyde (MDA), 8-hydroxydeoxyguanosine (8-OHdG), albumin, glutathione peroxidase (GPx), and catalase] and two stress markers [serum cortisol and fecal glucocorticoid metabolites (fGCM)] in 23 captive Asian elephants in Thailand over a 12 months period to examine relationships with age and season.

Results

Seasonal variations were observed, with several markers exhibiting significantly higher concentrations in the summer (ROS, MDA, 8-OHdG, albumin) and lower values during the rainy/winter seasons (MDA, 8-OHdG, albumin, catalase). By contrast, GPx was the only marker to be highest during the rainy season. For the stress markers, higher fGCM concentrations were noted during the rainy season, which contrasts with earlier studies showing more activity in the winter (tourist season). Positive correlations were found between the temperature-humidity index and ROS, GPx, and fGCM, while a negative correlation was observed with serum albumin. Elephant endotheliotropic herpesvirus (EEHV) shedding events were associated with higher concentrations of ROS and MDA. A moderate negative correlation was observed between 8-OHdG and the PCR threshold cycle of EEHV shedding (Ct), indicating DNA damage may be involved in EEHV shedding in elephants.

Discussion

Results revealed significant age and seasonal effects on several oxidative stress markers, indicating those factors should be considered in study design and data interpretation. There also may be physiological adaptations in oxidative stress conditions in relation to environmental changes that could impact health outcomes.

Effect of Electroejaculation Protocols on Semen Quality and Concentrations of Testosterone, Cortisol, Malondialdehyde, and Creatine Kinase in Captive Bengal Tigers

The Bengal tiger (Panthera tigris tigris) is critically endangered, so assisted reproductive technologies, including artificial insemination, are important conservation tools. For wild and domestic felids, electroejaculation (EE) is the most common semen collection method, with protocols optimized to obtain sufficient amounts of viable sperm for artificial insemination. However, less attention has been paid to ensuring animal wellbeing during the process. This study examined the effects of three EE protocols (Low, 2-5 volts; Medium, 3-6 volts; High, 4-7 volts) on semen quality, testicular size, serum testosterone, creatine kinase (CK), and malondialdehyde (MDA) concentrations, and serum cortisol as a proxy for stress. Blood samples were collected before, during, and after each EE series. Seminal plasma pH, and sperm motility, viability, and morphology were evaluated after each procedure. Seminal plasma and sperm pellet MDA concentrations were also determined. Primary sperm abnormalities and seminal plasma MDA were higher in the Low compared to Medium and High voltage groups (p < 0.05). Serum CK in the High voltage group increased during the EE series (p < 0.05), suggesting the potential for muscle damage. However, no significant changes were observed for serum cortisol, testosterone, or MDA concentrations. Results suggest the Medium voltage protocol produced good quality samples at lower voltages than the High protocol with no negative effect on muscle function, which might be better for animal welfare.

Measures of Oxidative Status Markers in Relation to Age, Sex, and Season in Sick and Healthy Captive Asian Elephants in Thailand

Oxidative stress is a pathological condition that can have adverse effects on animal health, although little research has been conducted on wildlife species. In this study, blood was collected from captive Asian elephants for the assessment of five serum oxidative status markers (reactive oxygen species (ROS) concentrations; malondialdehyde, MDA; albumin; glutathione peroxidase, GPx; and catalase) in healthy (n = 137) and sick (n = 20) animals. Health problems consisted of weakness, puncture wounds, gastrointestinal distress, eye and musculoskeletal problems, and elephant endotheliotropic herpesvirus hemorrhagic disease (EEHV-HD). Fecal samples were also collected to assess glucocorticoid metabolites (fGCMs) as a measure of stress. All data were analyzed in relation to age, sex, sampling season, and their interactions using generalized linear models, and a correlation matrix was constructed. ROS and serum albumin concentrations exhibited the highest concentrations in aged elephants (>45 years). No sex differences were found for any biomarker. Interactions were observed for age groups and seasons for ROS and catalase, while GPx displayed a significant interaction between sex and season. In pairwise comparisons, significant increases in ROS and catalase were observed in summer, with higher ROS concentrations observed only in the adult female group. Lower catalase activity was exhibited in juvenile males, subadult males, adult females, and aged females compared to subadult and adult elephants (males and females) in winter and the rainy season. There was a positive association between catalase activity and fGCMs (r = 0.23, p < 0.05), and a number of red blood cell parameters were positively associated with several of these biomarkers, suggesting high oxidative and antioxidative activity covary in red cells (p < 0.05). According to health status, elephants with EEHV-HD showed the most significant changes in oxidative stress markers, with MDA, GPx, and catalase being higher and albumin being lower than in healthy elephants. This study provides an analysis of understudied health biomarkers in Asian elephants, which can be used as additional tools for assessing the health condition of this species and suggests age and season may be important factors in data interpretation.

OXIDATIVE STRESS AND REPRODUCTIVE FUNCTION: The impact of oxidative stress on reproduction: a focus on gametogenesis and fertilization

In brief

Many aspects of the reproductive process are impacted by oxidative stress. This article summarizes the chemical nature of reactive oxygen species and their role in both the physiological regulation of reproductive processes and the pathophysiology of infertility.

Abstract

This article lays out the fundamental principles of oxidative stress. It describes the nature of reactive oxygen species (ROS), the way in which these potentially toxic metabolites interact with cells and how they impact both cellular function and genetic integrity. The mechanisms by which ROS generation is enhanced to the point that the cells' antioxidant defence mechanisms are overwhelmed are also reviewed taking examples from both the male and female reproductive system, with a focus on gametogenesis and fertilization. The important role of external factors in exacerbating oxidative stress and impairing reproductive competence is also examined in terms of their ability to disrupt the physiological redox regulation of reproductive processes. Developing diagnostic and therapeutic strategies to cope with oxidative stress within the reproductive system will depend on the development of a deeper understanding of the nature, source, magnitude, and location of such stress in order to fashion personalized treatments that meet a given patient's clinical needs.

Impact of Oxidative Stress on Male Reproduction in Domestic and Wild Animals

Oxidative stress occurs when the levels of reactive oxygen species (ROS) overcome the antioxidant defenses of the organism, jeopardizing several biological functions, including reproduction. In the male reproductive system, oxidative stress not only impairs sperm fertility but also compromises offspring health and survival, inducing oxidative damage to lipids, proteins and nucleic acids. Although a clear link between oxidative stress and male fertility disorders has been demonstrated in humans and laboratory rodents, little information is available about the implications of impaired redox homeostasis in the male fertility of domestic and wild animals. Therefore, this review aims to provide an update regarding the intrinsic and extrinsic factors that are associated with oxidative stress in the male reproductive system and their impact on the reproductive performance of domestic and wild animals. The most recent strategies for palliating the detrimental effects of oxidative stress on male fertility are reviewed together with their potential economic and ecological implications in the livestock industry and biodiversity conservation.

Down-regulation of miR-383-5p suppresses apoptosis in oxidative stress rat hepatocytes by targeting Bcl2

miRNAs are a class of small non-coding RNAs that are involved in various biological processes. In the preliminary work of the laboratory, found that miR-383-5p was down-regulated in the liver tissue of acute cold stress rats and has been shown to be an important regulatory factor in tumour proliferation, but there are very few studies involving the mediation of cold stress in rat liver tissues. Therefore, the purpose of this study was to determine the effect of miR-383-5p on the livers of cold stress rats by simulating the cold stress state of rat liver tissues in vitro using H₂ O₂ to induce rat hepatocyte oxidative stress. The results showed that MDA content, Caspase 3 and Cyto C protein levels increased significantly; GPx activity and SOD1 protein levels decreased significantly and miR-383-5p expression was significantly down-regulated in rat liver tissues after cold stress. Different concentrations of H₂ O₂ was added to rat hepatocytes, and the results showed that the expression of miR-383-5p, the ROS level, and the apoptosis rate in rat hepatocytes was increased significantly in a concentration-dependent fashion. Transfection of miR-383-5p inhibitor revealed that the apoptosis rate of rat hepatocytes, and the protein level of apoptosis-related protein Caspase 3 were reduced; the results of the dual-luciferase reporter gene assay showed that miR-383-5p targeted regulation of Bcl2. The results suggested that the expression of miR-383-5p was up-regulated in oxidative stress rat hepatocytes and may aggravate the apoptosis of rat hepatocytes induced by targeting inhibition of Bcl2 translation.

Total antioxidant capacity and protein peroxidation intensity in seminal plasma of infertile and fertile dogs

The aim of this study was to evaluate the total antioxidant capacity and protein peroxidation intensity in seminal plasma of infertile and fertile dogs. The study was conducted on 10 infertile and 10 fertile dogs of various breeds. Infertility was defined as conception failure at least three matings with different bitches. Semen was collected by manual manipulation. The sperm concentration and motility parameters were evaluated using CASA Hamilton Thorne, Vers. IVOS 12.3. The morphology of spermatozoa and the percentage of live and dead sperm cells were assessed microscopically, total antioxidant capacity and the content of SH-groups in seminal plasma were determined spectrophotometrically, the contents of protein peroxidation markers in seminal plasma, bityrosine and formylokinurenine, were determined using spectrofluorimetric methods. Sperm concentration and total sperm count were significantly (p < 0.05) lower in infertile dogs than in fertile dogs (99.92 ± 3 0.05 × 10⁶ /ml vs. 282.07 ± 48.27 × 10⁶ /ml; 214.19 ± 114.74 × 10⁶ vs. 747.57 ± 210.94 × 10⁶ , respectively). The percentage of spermatozoa with normal morphology and the most determined motility parameters differed significantly (p < 0.05) between both groups. The mean values of total antioxidant capacity in the seminal plasma were significantly (p < 0.05) lower (19.95 ± 20.94 vs. 25.66 ± 23.18 µmol/g protein), whereas the mean contents of bityrosine and formylokinurenine in seminal plasma were significantly (p < 0.05) higher in infertile dogs than in fertile dogs (3.71 ± 4.83 µg/mg protein vs. 1.55 ± 2.00 µg/mg protein and 0.37 ± 0.45 µg/mg protein vs. 0.14 ± 0.08 µg/mg protein, respectively). In conclusion, the obtained results suggest that the poor semen quality and infertility in dogs could be associated with lowered total antioxidant capacity and increased protein peroxidation in seminal plasma as a consequence of oxidative stress.