Presence and function of dopamine transporter (DAT) in stallion sperm: dopamine modulates sperm motility and acrosomal integrity

Brushing rams before and during electroejaculation improves sperm motility and kinetics with slight changes in stress biomarkers

The aim of this study was to determine whether brushing rams before and during electroejaculation (EE) reduces their stress response and improves the characteristics of the ejaculate. A single person brushed each ram for 5 min daily, for 15 days, in an individual pen. Semen was collected from five rams brushed before and during EE by the same brusher, while the other five were electroejaculated without being brushed. The treatments were exchanged three days later, so semen was collected from all the rams with both treatments. Brushing increased mass motility (P = 0.05), and curvilinear (P = 0.001), linear (P = 0.02), and average path (P = 0.01) velocities of sperm, as well as the average amplitude of lateral displacement of the sperm head (P = 0.05), and tended to increase sperm concentration (P = 0.09). Brushing tended to reduce the cortisol concentration (P = 0.06) and the duration of head movements when 2 V pulse series V was applied (P = 0.1). Brushing increased creatine kinase concentration (P = 0.04) and tended to increase rectal (P = 0.06) and maximum eye surface temperatures (P = 0.1), total time, and number of electrical pulses administered (P = 0.07 for both variables), as well as the sum of pulses per voltage applied during EE (P = 0.06). In rams accustomed to being brushed by the same person, brushing them before and during EE improved semen quality, with slight changes in the stress responses.

An association weight matrix identified biological pathways associated with bull fertility traits in a multi-breed population

Using seven indicator traits, we investigated the genetic basis of bull fertility and predicted gene interactions from SNP associations. We used percent normal sperm as the key phenotype for the association weight matrix-partial correlation information theory (AWM-PCIT) approach. Beyond a simple list of candidate genes, AWM-PCIT predicts significant gene interactions and associations for the selected traits. These interactions formed a network of 537 genes: 38 genes were transcription cofactors, and 41 genes were transcription factors. The network displayed two distinct clusters, one with 294 genes and another with 243 genes. The network is enriched in fertility-associated pathways: steroid biosynthesis, p53 signalling, and the pentose phosphate pathway. Enrichment analysis also highlighted gene ontology terms associated with 'regulation of neurotransmitter secretion' and 'chromatin formation'. Our network recapitulates some genes previously implicated in another network built with lower-density genotypes. Sequence-level data also highlights additional candidate genes relevant to bull fertility, such as FOXO4, FOXP3, GATA1, CYP27B1, and EBP. A trio of regulatory genes-KDM5C, LRRK2, and PME-was deemed core to the network because of their overarching connections. This trio probably influences bull fertility through their interaction with genes, both known and unknown as to their role in male fertility. Future studies may target the trio and their target genes to enrich our understanding of male fertility further.

Biogenic amines in the testis: sources, receptors and actions

Biogenic amines are signaling molecules with multiple roles in the central nervous system and in peripheral organs, including the gonads. A series of studies indicated that these molecules, their biosynthetic enzymes and their receptors are present in the testis and that they are involved in the regulation of male reproductive physiology and/or pathology. This mini-review aims to summarize the current knowledge in this field and to pinpoint existing research gaps. We suggest that the widespread clinical use of pharmacological agonists/antagonists of these signaling molecules, calls for new investigations in this area. They are necessary to evaluate the relevance of biogenic amines for human male fertility and infertility, as well as the potential value of at least one of them as an anti-aging compound in the testis.

Dopamine receptor D2 regulates genes involved in germ cell movement and sperm motility in rat testes†

The function of dopamine receptor D2 (D2R) is well associated with sperm motility; however, the physiological role of D2R present on testicular cells remains elusive. The aim of the present study is to delineate the function of testicular D2R. Serum dopamine levels were found to decrease with age, whereas testicular D2R expression increased. In rat testicular sections, D2R immunolabeling was observed in interstitial cells, spermatogonia, spermatocytes and mature elongated spermatids, whereas tyrosine hydroxylase immunolabeling was selectively detected in Leydig cells. In vitro seminiferous tubule culture following bromocriptine (D2R agonist) treatment resulted in decreased cAMP levels. Microarray identified 1077 differentially expressed genes (511 up-regulated, 566 down-regulated). The majority of differentially expressed genes were present in post-meiotic cells including early and late spermatids, and sperm. Gene ontology elucidated processes related to extra-cellular matrix to be enriched and was supported by differential expression of various collagens and laminins, thereby indicating a role of dopamine in extra-cellular matrix integrity and transport of spermatids across the seminiferous epithelium. Gene ontology and enrichment map also highlighted cell/sperm motility to be significantly enriched. Therefore, genes involved in sperm motility functions were further validated by RT-qPCR. Seven genes (Akap4, Ccnyl1, Iqcf1, Klc3, Prss55, Tbc1d21, Tl18) were significantly up-regulated, whereas four genes (Dnah1, Dnah5, Clxn, Fsip2) were significantly down-regulated by bromocriptine treatment. The bromocriptine-stimulated reduction in seminiferous tubule cyclic AMP and associated changes in spermatid gene expression suggests that dopamine regulates both spermatogenesis and spermiogenesis within the seminiferous epithelium, and spermatozoa motility following spermiation, as essential processes for fertility.

Pathogenesis of the crosstalk between reproductive function and stress in animals-part 1: Hypothalamo-pituitary-adrenal axis, sympatho-adrenomedullary system and kisspeptin

Stress is defined as a disruption of the body homeostasis in response to modest as well as perceived challenge. Two main physiological routes, the hypothalamic-pituitary-adrenal system (HPA) and the sympatho-adrenomedullary system (SAM), aim to maintain or restore homeostasis by mutual interaction. SAM is quickly-reacting as it primarily works through the nervous system-the sympathetic nervous system. In response to stress, signals are sent to activate the adrenal medulla which releases catecholamines (primarily adrenaline and norepinephrine). The catecholamines have a momentary effect on the body's organs that are prepared for a fight situation. At the same time, the stressor activates the HPA axis by signals from the brain causing secretion of the pituitary hormone adrenocorticotropic hormone (ACTH). ACTH acts on the adrenal cortex, which secretes glucocorticoids, including cortisol. Since HPA primarily works through hormones, the system is slightly slower than SAM and gives rise to a metabolic effect. While short-term stress response is an adaptive and beneficial process, chronic or excessive stress can lead to a range of negative health outcomes including reproductive disorders and infertility. Several mechanisms have been proposed to explain the link between stress and reproduction. This includes in particular kisspeptin, which is closely related to reproduction, as it is a powerful stimulator of the Hypothalamic-pituitary-gonadal (HPG) system. The present review, through current knowledge in various male and female species, deals with the role of the SAM and the HPA, including the major action of kisspeptin and glucocorticoids that trigger the consequences of psychological or physiological stress on reproductive function.

Methylmercury exposure-induced reproductive effects are mediated by dopamine in Caenorhabditis elegans

Methylmercury (MeHg) is a neurotoxicant that exists in the natural environment, which level can be greatly increased because of human activity. MeHg exposures have the risk of being detrimental to the development of the nervous system. Studies on MeHg toxicity have largely focused on the mechanisms of its neurotoxicity following developmental exposures. Additionally, reproductive toxicity of developmental MeHg exposures has been noted in rodent models. The model organism Caenorhabditis elegans (C. elegans) is a self-fertilizing animal which has a short lifespan around 20 days. Most C. elegans are hermaphrodites that can generate both sperm and oocytes. To investigate the effects of developmental MeHg exposures on the reproduction in C. elegans, larvae stage 1 worms were exposed to MeHg (0, 0.01 or 0.05 μM) for 24 h. The laid eggs and oocytes were compared during each day at adult stages for 6 days. We showed that MeHg exposure significantly induced an increased number of eggs in day 1 adults without an effect on the timing of egg laying or the total number of eggs or oocytes over the 6-day period. The expression of dat-1 and cat-2 and dopamine levels were increased in worms exposed to MeHg. Supplementation with 100 μM dopamine recapitulated the effect of MeHg on the number of eggs present in day 1 adults. Furthermore, the effect of MeHg on the number of eggs was abrogated in the cat-2 mutant worms CB1112. The number of oocytes in the 6-day adult stages was decreased by MeHg in the dat-1 mutant RM2702. MeHg exposures did not change the mating rate or the number of offspring from mating. Combined, these novel findings show that developmental exposure to low levels of MeHg has limited effects on the reproduction in C. elegans. Furthermore, our data support a modulatory role of dopamine in MeHg-induced effects on reproduction in this model system.

Metabolomics of Human Semen: A Review of Different Analytical Methods to Unravel Biomarkers for Male Fertility Disorders

Background: Human life without sperm is not possible. Therefore, it is alarming that the fertilizing ability of human spermatozoa is continuously decreasing. The reasons for that are widely unknown, but there is hope that metabolomics-based investigations may be able to contribute to overcoming this problem. This review summarizes the attempts made so far. Methods: We will discuss liquid chromatography–mass spectrometry (LC-MS), gas chromatography (GC), infrared (IR) and Raman as well as nuclear magnetic resonance (NMR) spectroscopy. Almost all available studies apply one of these methods. Results: Depending on the methodology used, different compounds can be detected, which is (in combination with sophisticated methods of bioinformatics) helpful to estimate the state of the sperm. Often, but not in all cases, there is a correlation with clinical parameters such as the sperm mobility. Conclusions: LC-MS detects the highest number of metabolites and can be considered as the method of choice. Unfortunately, the reproducibility of some studies is poor, and, thus, further improvements of the study designs are needed to overcome this problem. Additionally, a stronger focus on the biochemical consequences of the altered metabolite concentrations is also required.

Spermatozoan Metabolism as a Non-Traditional Model for the Study of Huntington’s Disease

Huntington’s Disease (HD) is a fatal autosomal dominant neurodegenerative disease manifested through motor dysfunction and cognitive deficits. Decreased fertility is also observed in HD animal models and HD male patients, due to altered spermatogenesis and sperm function, thus resulting in reduced fertilization potential. Although some pharmaceuticals are currently utilized to mitigate HD symptoms, an effective treatment that remedies the pathogenesis of the disease is yet to be approved by the FDA. Identification of genes and relevant diagnostic biomarkers and therapeutic target pathways including glycolysis and mitochondrial complex-I-dependent respiration may be advantageous for early diagnosis, management, and treatment of the disease. This review addresses the HD pathway in neuronal and sperm metabolism, including relevant gene and protein expression in both neurons and spermatozoa, indicated in the pathogenesis of HD. Furthermore, zinc-containing and zinc-interacting proteins regulate and/or are regulated by zinc ion homeostasis in both neurons and spermatozoa. Therefore, this review also aims to explore the comparative role of zinc in both neuronal and sperm function. Ongoing studies aim to characterize the products of genes implicated in HD pathogenesis that are expressed in both neurons and spermatozoa to facilitate studies of future treatment avenues in HD and HD-related male infertility. The emerging link between zinc homeostasis and the HD pathway could lead to new treatments and diagnostic methods linking genetic sperm defects with somatic comorbidities.

Progesterone, Myo-Inositol, Dopamine and Prolactin Present in Follicular Fluid Have Differential Effects on Sperm Motility Subpopulations

Considering the challenges surrounding causative factors in male infertility, rather than relying on standard semen analysis, the assessment of sperm subpopulations and functional characteristics essential for fertilization is paramount. Furthermore, the diagnostic value of sperm interactions with biological components in the female reproductive tract may improve our understanding of subfertility and provide applications in assisted reproductive techniques. We investigated the response of two sperm motility subpopulations (mimicking the functionality of potentially fertile and sub-fertile semen samples) to biological substances present in the female reproductive tract. Donor semen was separated via double density gradient centrifugation, isolated into high (HM) and low motile (LM) sperm subpopulations and incubated in human tubal fluid (HTF), capacitating HTF, HD-C medium, progesterone, myo-inositol, dopamine and prolactin. Treated subpopulations were evaluated for vitality, motility percentages and kinematic parameters, hyperactivation, positive reactive oxygen species (ROS), intact mitochondrial membrane potential (MMP) and acrosome reaction (AR). While all media had a significantly positive effect on the LM subpopulation, dopamine appeared to significantly improve both subpopulations' functional characteristics. HD-C, progesterone and myo-inositol resulted in increased motility, kinematic and hyperactivation parameters, whereas prolactin and myo-inositol improved the LM subpopulations' MMP intactness and reduced ROS. Furthermore, progesterone, myo-inositol and dopamine improved the HM subpopulations' motility parameters and AR. Our results suggest that treatment of sub-fertile semen samples with biological substances present in follicular fluid might assist the development of new strategies for IVF treatment.

Prepubertal arsenic exposure alters phosphoproteins profile, quality, and fertility of epididymal spermatozoa in sexually mature rats

Arsenic intoxication affects male reproductive parameters of prepubertal rats. Besides, morphological and functional alterations in their testis and epididymis may remain after withdrawal of arsenic insult, causing potential impairment in male fertility during adulthood. In this study, we aimed at analyzing the effect of prepubertal arsenic exposure on the fecundity of epididymal sperm from sexually mature Wistar rats, assessing fertility indexes, sperm parameters, and sperm phosphoproteins content. Male pups on postnatal day (PND) 21 received filtered water (controls, n = 10) and 10 mg L^-1 arsenite (n = 10) daily for 30 days. From PND52 to PND81, rats from both groups received filtered water. During this period, the males mated with non-exposed females between PND72 and PND75. Our results showed that sexually mature rats presented low sperm production, epididymal sperm count, motility, and quality after prepubertal arsenic exposure. These findings possibly contributed to the low fertility potential and high preimplantation loss. Epididymal sperm proteome detected 268 proteins, which 170 were found in animals from both control and arsenic groups, 27 proteins were detected only in control animals and 71 proteins only in arsenic-exposed rats. In these animals, SPATA 18 and other five proteins were upregulated, whereas keratin type II cytoskeletal 1 was downregulated (q < 0.1). The results of KEGG pathway analysis demonstrated an enrichment of pathways related to dopaminergic response, adrenergic signaling, protein degradation, and oocyte meiosis in arsenic-exposed animals. Moreover, 26 proteins were identified by phosphoproteomic with different phosphorylation pattern in animals from both groups, but SPATA18 was phosphorylated only in arsenic-exposed animals. We concluded that prepubertal exposure to arsenic is deleterious to sperm quality and male fertility, altering the sperm phosphoproteins profile.

Effects of quetiapine administration on sperm quality and testicular histology

Quetiapine is one of the most commonly prescribed antipsychotics to treat schizophrenia in adults, in particular. In this study, quetiapine's effects were assessed on healthy sperm production in rats at repeated-pharmacological doses. Additionally, the effects of quetiapine on oxidative status and hormonal balance were also evaluated in rats. Quetiapine was administered to rats orally at 10, 20, and 40 mg/kg body weight doses for 28 days. At the end of this period, body and organ weights were measured, sperm concentration, motility, and morphology were determined, sperm damage was assessed, and histopathological analysis of testicular tissue was performed. Additionally, serum FSH, LH, and testosterone levels as male reproductive hormones were measured. Catalase, superoxide dismutase, glutathione, and malondialdehyde levels were determined for evaluating the oxidative status of testicular tissue. The findings obtained in this study showed that relative epididymis weights and sperm concentration decreased and abnormal sperm morphology increased in quetiapine-administered rats. Irregularity of typical architecture of the seminiferous tubules and germinal cell disorganization was observed in testicular sections of 20 and 40 mg/kg quetiapine-administered rats. Further, serum LH and testosterone levels decreased in 20 and 40 mg/kg quetiapine-administered rats. Additionally, decreased catalase and superoxide dismutase activities in testicular tissue of quetiapine-administered rats and increased malondialdehyde levels in testicular tissue of 40 mg/kg quetiapine-administered rats were measured. In conclusion, quetiapine treatment decreased sperm quality, altered hormone levels, and induced oxidative stress may be considered potential contributors to this adverse effect.

Photostimulation and thermotaxis of sperm: Overview and practical implications in porcine reproduction

The journey of mammalian sperm through the female genital tract requires the existence of a myriad of mechanisms that allow cells to reach the oviduct in a timely manner from the place of semen deposition. Several biochemical mechanisms such as signaling through molecules like bicarbonate, neurotransmitters or even glycosaminoglycanes are known and have been studied by several relevant groups worldwide. However, biophysical mechanisms for sperm transport are much less studied and understood. Thermotaxis, for example, is a powerful, physical signaling system that is known to direct sperm inside the female genital tract, although the intimate mechanisms by which this effect is launched are yet to be elucidated. This review is focuses on the analysis of thermotaxis and its possible relationship with another phenomenon that has been observed in sperm from a variety of species, namely photostimulation. An overall review on sperm thermotaxis and putative mechanism/s that can be involved in this phenomenon is developed, followed by a description of the most recent findings on the mechanisms underlying sperm photostimulation, highlighting its possible relationship with thermotactic mechanisms. Finally, an overview regarding some practical implications of the phototactic/thermotactic phenomenon has been included in order to evaluate the possible use of techniques based on these phenomena as tools for improving pig reproduction.

Ritalinic Acid Stimulates Human Sperm Motility and Maintains Vitality In Vitro

Purpose

To evaluate the in vitro impact of ritalinic acid (RA), a major metabolite of methylphenidate (drug to treat attention-deficit hyperactivity disorder), on sperm motility, vitality and oxidative stress.

Materials and Methods

Semen samples (n=13) were collected from healthy donors and a semen analysis was performed according to World Health Organization. Density gradient centrifugation was performed to isolate motile sperm. Samples were incubated with different concentrations (0, 1, 10, 100, and 1,000 ng/mL) of RA. The non-exposed group (0 ng/mL) was defined as the control group. Samples were analyzed for motility at different time points (0, 60, 150, 240, and 300 minutes) and for vitality and oxidation reduction potential (ORP) (at 0, 240, and 300 minutes). Sperm motility was assessed manually and motion kinetic parameters were recorded by computer aided semen analysis.

Results

RA at any tested concentration significantly increased sperm motility compared to the control in a time-dependent manner with a maximum increase after 240 minutes. Motion kinetic parameters were not comparable. For sperm vitality, supplementation with RA significantly maintained survival at higher levels, while non-treated sperm gradually died. These higher levels of vitality were maintained with rising RA concentrations of up to 1,000 ng/mL. A non-significant trend of increased ORP was observed in all study groups.

Conclusions

RA increases sperm motility and maintains vitality at any concentration tested. Therefore, RA might be utilized to improve sperm quality in asthenozoospermic specimens. However, further investigation is ongoing to evaluate the effect of RA on other sperm parameters.

Sperm count and motility are quantitatively affected by functional polymorphisms of HTR2A, MAOA and SLC18A

Spermatozoa and neurones share similar membrane characteristics and features. Associations of multiple polymorphisms traditionally related to neurotransmission were investigated. Infertile men were grouped into controls with normospermia (n = 182) and idiopathic infertile men with asthenozoospermia (n = 103), and analysed as a case-control study and as a quantitative association of each genotype. Ten neurotransmission-associated genetic variants were mapped by SNP analysis using quantitative polymerase chain reaction with TaqMan probes. Men with HTR2A rs6313 had a higher risk of asthenozoospermia (OR = 2.14; P = 0.04). MAOA rs3788862 G carriers displayed an increased risk of asthenozoospermia (OR = 2.29; P = 0.02). The SLC18A1 rs1390938 G allele was more frequent among such cases (0.75 versus 0.87; P < 0.01 and P < 0.01 for Armitage trend test); for SLC18A1 rs2270641 P = 0.02 (case-control frequency) and P = 0.01 (Armitage trend test). MAOA rs3788862 was correlated with sperm motility (Spearman ρ = 0.14; P = 0.02); SLC18A1 rs1390938 was correlated with sperm count and motility (Spearman ρ = 0.20; P < 0.01). Gene polymorphisms of HTR2A, MAOA and SLC18A1, related to neurotransmission, are individually associated with asthenozoospermia through variation in sperm count and motility, without detectable allelic or genotype interaction.

Bupropion promotes alterations in the spermatogenesis of mice and congenital malformations in the offspring

Bupropion hydrochloride (BUP) has been associated with male sexual dysfunction. The aim of this study was to evaluate the effects of BUP on the reproductive function of male mice and to evaluate offspring development. The mice were distributed into BUP group (40 mg kg−1) and control group (saline). On Day 35 of treatment the males were placed to mate with females and then killed on Day 46 for evaluation of reproductive function. On Day 18 of pregnancy, pregnant females were killed for evaluation of congenital malformations in the offspring. The BUP group showed a decrease in the Johnsen score (Control, 9.354 ± 0.092; BUP, 7.615 ± 0.147), Sertoli (Control, 5.623 ± 0.184; BUP, 4.215 ± 0.097) and Leydig (Control, 11.430 ± 0.817; BUP, 7.531 ± 0.213) cell counts, testosterone levels (Control, 783.5 ± 154.2 ng dL−1; BUP, 201.4 ± 54.8 ng dL−1) and sperm production (Control, 2.852 ± 0.211; BUP, 1.988 ± 0.116) and increased morphological alterations of the sperm head (Control, 8.134%; BUP, 10.423%) and tail (Control, 4.96%; BUP, 16.211%). The congenital malformations observed in BUP-derived offspring were: kyphosis (Control, 0.00%; BUP, 5.26%), retroverted rear legs (Control, 14.43%; BUP, 53.68%), incomplete ossification of the supraoccipital and exoccipital (Control, 21.82%; BUP, 86.00%) and sternum (Control, 25.45%; BUP, 82.00%). BUP had toxic effects on testicular function and teratogenic potential.

Survey on basal blood plasma catecholamine concentrations in Martina Franca donkey (Equus asinus)

BACKGROUND

Catecholamines are among the most frequently investigated parameters for studying sympathoadrenal activity in response to stress conditions.

OBJECTIVES

To evaluate basal plasma concentrations of catecholamines (adrenaline, noradrenaline and dopamine) in healthy donkeys.

STUDY DESIGN

Cross-sectional study.

METHODS

Catecholamine concentrations from 440 Martina Franca donkeys were determined: 269 females and 171 entire males, aged from 4 months to 24 years. Animals were subdivided into four age categories: under 12 months old (64 males and 54 females), from 13 to 36 months (56 males and 75 females), from 37 to 120 months (49 males and 80 females) and over 120 months (24 males and 38 females). Indwelling jugular catheters were inserted at least 12 h before drawing blood. The data set was subjected to analysis of variance considering age, sex and the two-way interaction between them as independent variables. Pearson's correlation coefficients between the three catecholamines were evaluated.

RESULTS

Confidence intervals (CI) for noradrenaline concentration ranged between 239.98 and 255.07 ng/L (mean 247.52 ng/L), for adrenaline between 129.27 and 137.90 ng/L (mean 133.59 ng/L), dopamine concentrations between 149.62 and 160.80 ng/L (mean 155.21 ng/L) and noradrenaline/adrenaline ratio between 1.91 and 2.05 (mean 1.98). Catecholamine plasma concentrations were not influenced by sex. Donkeys older than 37 months had lower adrenaline and noradrenaline plasma concentrations (P<0.001) and higher noradrenaline/adrenaline ratios (P<0.01) than younger animals.

MAIN LIMITATIONS

Indwelling catheters and blood drawing procedures may have influenced catecholamine levels.

CONCLUSIONS

Catecholamine concentrations were established within a large group of healthy Martina Franca donkeys.

Neuronal signaling repertoire in the mammalian sperm functionality

The common embryonic origin has been a recurrent explanation to understand the presence of "neural receptors" in sperm. However, this designation has conditioned a bias marked by the classical neurotransmission model, dismissing the possibility that neurotransmitters can play specific roles in the sperm function by themselves. For instance, the launching of acrosome reaction, a fundamental sperm function, includes several steps that recall the process of presynaptic secretion. Unlike of postsynaptic neuron, whose activation is mediated by molecular interaction between neurotransmitter and postsynaptic receptors, the oocyte activation is not mediated by receptors, but by cytosolic translocation of sperm phospholipase (PLCζ). Thus, the sperm has a cellular design to access and activate the oocyte and restore the ploidy of the species by an "allogenic pronuclear fusion." At subcellular level, the events controlling sperm function, particularly the capacitation process, are activated by chemical signals that trigger ion fluxes, sterol oxidation, synthesis of cyclic adenosine monophosphate, protein kinase A activation, tyrosine phosphorylations and calcium signaling, which correspond to second messengers similar to those associated with exocytosis and growth cone guidance in neurons. Classically, the sperm function associated with neural signals has been analyzed as a unidimensional approach (single ligand-receptor effect). However, the in vivo sperm are exposed to multidimensional signaling context, for example, the GABAergic, monoaminergic, purinergic, cholinergic, and melatoninergic, to name a few. The aim of this review is to present an overview of sperm functionality associated with "neuronal signaling" and possible cellular and molecular mechanisms involved in their regulation.