Physiological role of reactive oxygen species in testis and epididymal spermatozoa

Chronic stress disturbs neuroendocrine control of reproduction and fertility in male rats

Currently, stress is considered one of the risk factors for infertility in male humans, altering sperm function. Sperm production and maturation depends on the hypothalamic-pituitary-testis axis control. Therefore, the objective of the current study was to evaluate the effects of chronic stress on the neuroendocrine control of male reproduction, the oxidative status in the epididymis, and male fertility. Adult male rats were assigned to control or chronic stress groups. Chronically stressed males were exposed to cold-water immersion (CWI) for 50 consecutive days. After euthanasia, the hypothalamus was dissected for Kisspeptin (Kiss1) and Gonadotropin releasing hormone (GnRH) evaluation; serum luteinizing hormone (LH), testosterone (T), and corticosterone concentrations were determined. In the epididymis, reactive oxygen species (ROS), lipid peroxides, and content of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx4) were assessed. Sperm motility, viability, concentration, morphology and acrosomal reaction were assessed. Epididymal sperm were used for in-vitro fertilization with oocytes from intact female rats. Stressed males showed lower hypothalamic Kiss1 and GnRH content, lower LH and T concentration, together with higher serum corticosterone concentration. ROS production, and lipid peroxides increased in all epididymal regions, while SOD, CAT, and GPx4 content decreased after chronic stress; sperm quality was also lower. The percentage of fertilized oocytes decreased, and embryonic development was low, compared to controls. Together, these results show that chronic stress disrupts neuroendocrine control of male reproduction and generates oxidative stress in the epididymis. These effects disturb sperm quality, leading to low fertilizing potential and poor embryonic development.

Characteristic analysis of N6-methyladenine in different parts of yak epididymis

BACKGROUND

The epididymis is essential for sperm maturation. During sperm maturation, markable alterations of the payload of small noncoding RNAs are observed in the epididymis, which indicated the role of epigenetic alterations in sperm maturation. However, the N6-Methyladenosine (m6A) modification profile of the epididymis remains unelucidated. Therefore, in this study, we assessed the m6A modification levels in the caput, corpus, and cauda of the yak epididymis using a combination of methylated RNA immunoprecipitation and RNA sequencing.

RESULTS

The m6A levels were significantly increased in the corpus of the epididymis. Functional enrichment analysis of differentially methylated RNA (DMR) between the corpus and caput group revealed the significant enrichment of DMRs in the gap junction, ErbB signaling pathway, and mTOR signaling pathway, which participate in cell communication and sperm maturation. In addition, the DMRs of cauda-vs-corpus group were enriched in apoptosis, the FoxO signaling pathway, the PI3K-Akt signaling pathway, and the tumor necrosis factor signaling pathway that were associated with sperm autophagy, oxidative stress, and sperm maturation. Furthermore, we identified the key genes exhibiting significant changes in m6A levels but with no differences in RNA levels, including YY1-associated factor 2, forkhead box J2, and forkhead box O1. This finding indicated that m6A modifications affect these genes during translation, thereby participating in sperm maturation.

CONCLUSIONS

In summary, we generated the m6A profile of the yak epididymis, which will aid in further elucidating the maturation process of sperm and reveal more information related to male infertility.

Exploring the impact of lipid stress on sperm cytoskeleton: insights and prospects

The decline in male fertility correlates with the global rise in obesity and dyslipidaemia, representing significant public health challenges. High-fat diets induce metabolic alterations, including hypercholesterolaemia, hepatic steatosis and atherosclerosis, with detrimental effects on testicular function. Testicular tissue, critically dependent on lipids for steroidogenesis, is particularly vulnerable to these metabolic disruptions. Excessive lipid accumulation within the testes, including cholesterol, triglycerides and specific fatty acids, disrupts essential sperm production processes such as membrane formation, maturation, energy metabolism and cell signalling. This leads to apoptosis, impaired spermatogenesis, and abnormal sperm morphology and function, ultimately compromising male fertility. During spermiogenesis, round spermatids undergo extensive reorganization, including the formation of the acrosome, manchette and specialized filamentous structures, which are essential for defining the final sperm cell shape. In this Perspective, we examine the impact of high-fat diets on the cytoskeleton of spermatogenic cells and its consequences to identify the mechanisms underlying male infertility associated with dyslipidaemia. Understanding these processes may facilitate the development of therapeutic strategies, such as dietary interventions or natural product supplementation, that aim to address infertility in men with obesity and hypercholesterolaemia. The investigation of cytoskeleton response to lipid stress extends beyond male reproduction, offering insights with broader implications.

Dibutyl phthalate disrupts [Ca2+]i, reactive oxygen species, [pH]i, protein kinases and mitochondrial activity, impairing sperm function

To explore the mechanism of sperm dysfunction caused by dibutyl phthalate (DBP), the effects of DBP on intracellular [Ca2+] and [pH], reactive oxygen species (ROS), lipid peroxidation (LPO), mitochondrial permeability transition pore (mPTP) opening, mitochondrial membrane potential (MMP), adenosine triphosphate (ATP) levels, phosphorylation of protein kinase A (PKA) substrate proteins and phosphotyrosine (p-Tyr) proteins, sperm motility, spontaneous acrosome reaction, and tail bending were examined in mouse spermatozoa. At 100 µg/mL, DBP significantly increased tail bending and [Ca2+]i. Interestingly, DBP showed biphasic effects on [pH]i. DBP at 10-100 µg/mL significantly decreased sperm motility. Similarly, Ca2+ ionophore A23187 decreased [pH]i sperm motility, suggesting that DBP-induced excessive [Ca2+]i decreased sperm motility. DBP significantly increased ROS and LPO. DBP at 100 µg/mL significantly decreased mPTP closing, MMP, and ATP levels in spermatozoa, as did H2O2, indicative of ROS-mediated mitochondrial dysfunction caused by DBP. DBP as well as H2O2 increased p-Tyr sperm proteins and phosphorylated PKA substrate sperm proteins. DBP at 1-10 µg/mL significantly increased the spontaneous acrosome reaction, suggesting that DBP can activate sperm capacitation. Altogether, DBP showed a biphasic effect on intracellular signaling in spermatozoa. At concentrations relevant to seminal ortho-phthalate levels, DBP activates [pH]i, protein tyrosine kinases and PKA via physiological levels of ROS generation, potentiating sperm capacitation. DBP at high doses excessively raises [Ca2+]i and ROS and disrupts [pH]i, impairing the mitochondrial function, tail structural integrity, and sperm motility.

Disulfide Bridges Assessment in the Sperm Chromatin by Flow Cytometry

The evaluation of the status of sperm chromatin is essential to deepen the male fertility study, but, despite its proven impact on fertility and the embryo, it is not routinely analyzed in andrology labs. One of the factors related to sperm functionality is the stability that disulfide bonds (DB) provide to the chromatin, which can be indirectly studied by analyzing the reduction of DB to free thiols. Monobromobimane (mBBr) is a fluorescent dye specific for the study of DB. It is a rapid and highly specific technique, easy to perform, and repeatable, and the total DB can be calculated from the direct fluorescent signal of free thiols. This chapter summarizes how to perform the mBBr technique in spermatozoa of multiple mammal species.

Physiological and pathological aspects of epididymal sperm maturation

In mammals, sperm that leave the testes are nonfunctional and require a complex post-testicular maturation process to acquire their ability to recognize and fertilize the egg. The crucial maturation changes that provide sperm their fertilizing capability occur while passing through the epididymis. Due to the widespread use of assisted reproductive technologies to address male infertility, there has been a significant decrease in research focusing on the mechanisms underlying the maturation process over the past decades. Considering that up to 40% of male infertility is idiopathic and could be reflecting sperm maturation defects, the study of post-testicular sperm maturation will clearly contribute to a better understanding of the causes of male infertility and to the development of both new approaches to maturing sperm in vitro and safer male contraceptive methods. Based on this, the present review focuses on the physiopathology of the epididymis as well as on current approaches under investigation to improve research in sperm maturation and as potential therapeutic options for male infertility.

Effects of Reactive Oxygen and Nitrogen Species on Male Fertility

Significance: In recent decades, male fertility has been severely reduced worldwide. The causes underlying this decline are multifactorial, and include, among others, genetic alterations, changes in the microbiome, and the impact of environmental pollutants. Such factors can dysregulate the physiological levels of reactive species of oxygen (ROS) and nitrogen (RNS) in the patient, generating oxidative and nitrosative stress that impairs fertility. Recent Advances: Recent studies have delved into other factors involved in the dysregulation of ROS and RNS levels, such as diet, obesity, persistent infections, environmental pollutants, and gut microbiota, thus leading to new strategies to solve male fertility problems, such as consuming prebiotics to regulate gut flora or treating psychological conditions. Critical Issues: The pathways where ROS or RNS may be involved as modulators are still under investigation. Moreover, the extent to which treatments can rescue male infertility as well as whether they may have side effects remains, in most cases, to be elucidated. For example, it is known that prescription of antioxidants to treat nitrosative stress can alter sperm chromatin condensation, which makes DNA more exposed to ROS and RNS, and may thus affect fertilization and early embryo development. Future Directions: The involvement of extracellular vesicles, which might play a crucial role in cell communication during spermatogenesis and epididymal maturation, and the relevance of other factors such as sperm epigenetic signatures should be envisaged in the future.

Apigenin supplementation substantially improves rooster sperm freezability and post-thaw function

This pioneering research investigated apigenin potential to augment rooster sperm cryosurvival in an extender model. Apigenin is a natural antioxidant flavonoid showing promise for improved post-thaw sperm function. However, its effects on avian semen cryopreservation remain unexplored. This first study supplemented rooster sperm Lake extender with 0, 50, 100, 200, 400 μmol/L apigenin to determine the optimal concentrations for post-thaw quality. Supplementation with 100 μmol/L apigenin resulted in significant enhancements in total motility (from 41.5% up to 71.5%), progressive motility (18.1% to 29.1%) (p < 0.05), membrane integrity (40% to 68%), mitochondrial function (p < 0.001), viability (37% to 62%) and total antioxidant capacity (p < 0.001) compared to the control. It also substantially reduced percentages of abnormal morphology, reactive oxygen species and apoptosis (p < 0.001). Although 200 μmol/L apigenin significantly enhanced some attributes, effects were markedly lower than 100 μmol/L. Higher doses did not improve cryoprotective parameters. This indicates 100 μmol/L as the optimal apigenin concentration. This represents the first report of apigenin protecting rooster sperm from cryodamage. The natural antioxidant improved post-thaw sperm quality, likely by suppressing oxidative stress and apoptosis. Apigenin shows promise for enhancing rooster sperm cryosurvival.

2,4-D mediated moderation of aluminum tolerance in Salvinia molesta D. Mitch. with regards to bioexclusion and related physiological and metabolic changes

We examined the efficacy of 2,4-dichlorophenoxy acetic acid (2,4-D; 500 µM) in enhancing the potential of Salvinia species for tolerance to aluminum (Al) toxicity (240 and 480 µM, seven days). Salvinia showed better efficacy in removal of toxicity of Al by sorption mechanism with changes of bond energy shifting on cell wall residues and surface structure. Plants recorded tolerance to Al concentration (480 µM) when pretreated with 2,4-D through adjustment of relative water content, proline content, osmotic potential, and improved the pigment fluorescence for energy utilization under Al stress. Photosynthetic activities with regards to NADP-malic enzyme and malic dehydrogenase and sugar metabolism with wall and cytosolic invertase activities were strongly correlated with compatible solutes. A less membrane peroxidation and protein carbonylation had reduced ionic loss over the membrane that was studied with reduced electrolyte leakage with 2,4-D pretreated plants. Membrane stabilization was also recorded with higher ratio of K+ to Na+, thereby suggesting roles of 2,4-D in ionic balance. Better sustenance of enzymatic antioxidation with peroxidase and glutathione metabolism reduced reactive oxygen species accumulation and save the plant for oxidative damages. Moreover, gene polymorphism for antioxidant, induced by 2,4-D varied through Al concentrations would suggest an improved biomarker for tolerance. Collectively, analysis and discussion of plant's responses assumed that auxin herbicide could be a potential phytoprotectant for Salvinia as well as improving the stability to Al toxicity and its bioremediation efficacy.

Plantain-based diet decreases oxidative stress and inflammatory markers in the testes of rats exposed to atrazine

Exposure to the herbicide atrazine (ATZ) has deleterious effects on male fertility. This fact underscores the need for measures to protect against the detrimental impact of atrazine exposure on male fertility. The study assessed the protective effects of plantain-based diet (PBD) on rat testes exposed to ATZ by exploring oxid-inflammatory homeostasis. The study evaluated the preventive and therapeutic effects of PBD in a two-phased experiment. Male rats were randomized into seven groups for therapeutic model (Control, ATZ only, ATZ recovery, ATZ + 50% PBD, ATZ + 25% PBD, ATZ + 12.5% PBD and ATZ + quercetin-QUE) while the preventive model had ten groups (Control, ATZ, 50% PBD + ATZ, 25% PBD + ATZ, 12.5% PBD + ATZ and QUE + ATZ). The oxidative stress parameters (DNA fragmentation and MDA level), purinergic activity (ATPase), acetylcholine esterase, and inflammatory markers (NO level, MPO activity, and TNF-α) were increased while the Nrf2 levels were decreased by the ATZ treatment. However, the PBD was able to restore the oxido-inflammatory parameters in the rat testes. The chemical fingerprint of the diet revealed that the diets contained 16 bioactive compounds with quercetin being the most prominent compound. Overall, treatment with PBD was able to protect and prevent the toxicity caused by ATZ by modulating the redox and inflammatory status as well as purinergic activity in the rat testes.