The mu (μ) and delta (δ) opioid receptors modulate boar sperm motility

The Cation/Calcium Channel of Sperm (CatSper): A Common Role Played Despite Inter-Species Variation?

The main cation/calcium channel of spermatozoa (CatSper), first identified in 2001, has been thoroughly studied to elucidate its composition and function, while its distribution among species and sperm sources is yet incomplete. CatSper is composed of several subunits that build a pore-forming calcium channel, mainly activated in vivo in ejaculated sperm cells by intracellular alkalinization and progesterone, as suggested by the in vitro examinations. The CatSper channel relevance is dual: to maintain sperm homeostasis (alongside the plethora of membrane channels present) as well as being involved in pre-fertilization events, such as sperm capacitation, hyperactivation of sperm motility and the acrosome reaction, with remarkable species differences. Interestingly, the observed variations in CatSper localization in the plasma membrane seem to depend on the source of the sperm cells explored (i.e., epididymal or ejaculated, immature or mature, processed or not), the method used for examination and, particularly, on the specificity of the antibodies employed. In addition, despite multiple findings showing the relevance of CatSper in fertilization, few studies have studied CatSper as a biomarker to fine-tune diagnosis of sub-fertility in livestock or even consider its potential to control fertilization in plague animals, a more ethically defensible strategy than implicating CatSper to pharmacologically modify male-related fertility control in humans, pets or wild animals. This review describes inter- and intra-species differences in the localization, structure and function of the CatSper channel, calling for caution when considering its potential manipulation for fertility control or improvement.

Opioid replacement therapy with methadone or buprenorphine effects on male mice reproduction

RATIONALE

Opioid use disorders are commonly treated by long-acting agonist opioids including methadone and buprenorphine which could affect various aspects of male reproduction especially spermatogenesis.

OBJECTIVES

We aimed to determine whether detoxification with methadone or buprenorphine was associated with reproductive disorders in male mice.

METHODS

We orally induced morphine dependence in NMRI male mice, and then performed detoxification programs using either methadone or buprenorphine. Testis architecture and sperm parameters including sperm nuclear DNA integrity, mitochondrial activity, oxidative stress in seminal plasma, and routine sperm parameters were assessed to find the involved mechanisms.

RESULTS

The number of Leydig cells and the thickness of germinal epithelium reduced following morphine use and increased differently after detoxification with methadone or buprenorphine. Morphine dependence and detoxification with methadone and buprenorphine had different effects on sperm parameters. Morphine altered chromatin integrity, mitochondrial activity, and oxidative stress in sperm. Detoxification with methadone improved mitochondrial activity but worsened chromatin integrity, whereas detoxification with buprenorphine improved neither chromatin integrity nor mitochondrial activity. Seminal plasma oxidative stress was higher in the treated groups compared to control groups but was comparable among treatment groups. Our study revealed that long-term morphine use followed by detoxification with methadone or buprenorphine impairs testis structure and sperm parameters. Detoxification from morphine use with methadone and buprenorphine led to different preclinical outcomes in semen quality parameters, including chromatin integrity. Therefore, clinical detoxification protocols should be performed more cautiously, considering the desire of the individuals to reproduce.

The protective effect of zinc on morphine-induced testicular toxicity via p53 and Akt pathways: An in vitro and in vivo approach

BACKGROUND

Chronic use of morphine is associated with reproductive complications, such as hypogonadism and infertility. While the side effects of morphine have been extensively studied in the testis, much less is known regarding the effects of morphine on Sertoli cells and the effects of zinc on morphine-induced testicular injury as well as their underlying mechanisms. Therefore, the purpose of this study was to investigate the effect of morphine (alone and co-administered with zinc) on cell viability and apoptosis of the testicular (Sertoli) cells as well as the tumor suppressor p53 and phosphorylated-protein kinase B (p-Akt) protein levels in both in vitro and in vivo models.

METHODS

Cultured Sertoli cells were exposed to morphine (23 μM), zinc (8 μM), and zinc prior to morphine and their effects on Sertoli cell viability and apoptosis were investigated. Morphine (3 mg/kg) and zinc (5 mg/kg, 1 h before morphine) were also injected intraperitoneally to rats and then the apoptotic changes in the testis were evaluated.

RESULTS

Cell viability and p-Akt protein levels decreased in morphine-treated cells, while apoptosis and p53 protein expression increased in these cells. Pretreatment with zinc recovered morphine-induced apoptotic effects, as well as over-expression of p53 and down-regulation of p-Akt. These findings were supported by a subsequent animal study.

CONCLUSION

The present data indicated the protective effect of zinc against morphine-induced testicular (Sertoli) cell toxicity via p53/Akt pathways in both in vivo and in vitro models and suggested the clinical importance of zinc on infertility among chronic opioid users and addicted men.

Roles of CatSper channels in the pathogenesis of asthenozoospermia and the therapeutic effects of acupuncture-like treatment on asthenozoospermia

Rationale: Idiopathic asthenozoospermia (iAZS) is one of the major causes of male infertility and has no effective therapeutic treatment. Understanding the potential mechanisms that cause it may be helpful in seeking novel targets and treatment strategies for overcoming the problem of low sperm motility in iAZS individuals.

Methods: Computer-assisted semen analysis (CASA) was utilized to assess the sperm motility. RT-qPCR, Western blot, immunofluorescence staining, and calcium imaging analysis were performed to examine the expression and function of CatSper channels. Hyperactivation and acrosome reaction were used to evaluate the functional characteristics of epididymal sperm. In vivo fertility assay was applied to determine the fertility of rats. CatSper1 knockdown and overexpression experiments were performed to confirm the roles of CatSper channels in the pathogenesis of iAZS and the therapeutic effects of electroacupuncture (EA) treatment on AZS model rats.

Results: Here, we reported a functional down-regulation of CatSper channel from CatSper1 to CatSper 4 in the sperm of both iAZS patients and ornidazole (ORN)-induced AZS model rats, and an impaired sperm function characterized by a reduction of protein tyrosine phosphorylation, hyperactivation, and acrosome reaction in the epididymal sperm of AZS rats. Knockdown of CatSper1 in the testis tissues is sufficient to induce AZS in normal rats, and this action was validated by the reversal effects of CatSper1 overexpression. Transcutaneous electrical acupoint stimulation (TEAS) and electroacupuncture (EA) at 2 Hz frequency improve the sperm motility via enhancing the functional expression of CatSper channels in the sperm. Gene silencing CatSper1 in the sperm abolishes the therapeutic effects of 2 Hz-EA treatment on AZS rats.

Conclusions: We conclude that a functional down-regulation of CatSper channel in the sperm may be a contributor or a downstream indicator for a portion of AZS, especially iAZS, while 2 Hz-TEAS or EA treatment has a therapeutic effect on iAZS through inducing the functional up-regulation of CatSper channels in the sperm. This study provides a novel mechanism for the pathogenesis of some AZS especially iAZS, and presents a potential therapeutic target of CatSper for iAZS treatment. Acupuncture treatment like TEAS may be used as a promising complementary and alternative medicine (CAM) therapy for male infertility caused by iAZS in clinical practice.

Delta and kappa opioid receptors on mouse sperm cells: Expression, localization and involvement on in vitro fertilization

The endogenous opioid peptides have been reported to be involved in the regulation of reproductive physiology. Many of the studies conclude with sentences around the harmful effect of opioids in male fertility but, actually, there is only one study regarding the real fertility potential of spermatozoa that have been exposed to mu specific opioids. The aim of the present study was to see if the modulation of delta (OPRD1) and kappa (OPRK1) opioid receptors in mouse sperm during capacitation was able to vary the embryo production after in vitro fertilization (IVF). The presence of OPRD1 and OPRK1 in mouse mature spermatozoa was analyzed by RT-PCR and immunofluorescence. Incubating the sperm with, on one hand, the delta specific agonist DPDPE and/or antagonist naltrindole, and, on the other hand, the kappa specific agonist U-50488 and antagonist nor-binaltorphimine, we analyzed the involvement of OPRD1 and OPRK1 on IVF and preimplantational embryo development. We verified the presence of OPRD1 and OPRK1 in mouse mature spermatozoa, not only at the mRNA level but also at protein level. Moreover, the sperm incubation with DPDPE, before the IVF, had an effect on the fertilization rate of sperm and reduced the number of reached blastocysts, which was reverted by naltrindole. Instead, the use of the kappa agonist U-50488 and the antagonist nor-binaltophimine did not have any effect on the amount and the quality of the achieved blastocysts. Although nowadays the pure delta or kappa opioid ligands are not used for the clinic, clinical trials are being conducted to be used in the near future, so it would be interesting to know if the modulation of these receptors in sperm would generate any consequence in relation to fertilization capacity.

Mu opioid receptor expression and localisation in murine spermatozoa and its role in IVF

The endogenous opioid peptides are reported to be involved in the regulation of reproductive physiology. Many of the studies conclude with statements on the harmful effect of opioids on male fertility but, in fact, there are no studies regarding the real fertilisation potential of spermatozoa that have been exposed to opioids. The aim of the present study was to examine if modulation of mu opioid receptor (OPRM1) in murine spermatozoa during capacitation influenced embryo production after IVF. The presence of OPRM1 in murine mature spermatozoa was analysed by reverse transcription-polymerase chain reaction and immunofluorescence. We analysed the involvement of OPRM1 on IVF and pre-implantational embryo development by incubating the spermatozoa with the opioid agonist morphine and/or antagonist naloxone. We verified the presence of OPRM1 in murine mature spermatozoa, not only at the mRNA level but also the protein level. Moreover, incubation of the spermatozoa with morphine, before IVF, had an effect on the fertilisation rate of the spermatozoa and reduced the numbers of blastocysts, which was reversed by naloxone. Considering that opioids are widely used clinically, it is important to take into account their effect, via OPRM1, on the fertility of patients.

Endogenous Opiates and Behavior: 2016

This paper is the thirty-ninth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2016 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.

Effect of Thymoquinone on Reproductive Parameter in Morphine-treated Male Mice

BACKGROUND

Thymoquinone as the main active component of Nigella sativa might have a various pharmacological effects such as antiapoptotic and antioxidant. Morphine is commonly used for the treatment of severe pain that can increase the generation of free radicals and affects the spermatogenesis. This study was designed to evaluate protective effects of thymoquinone against morphine-induced damages, sperm viability, count, motility, morphology and testis histology, and nitric oxide and testosterone hormone of the mice.

MATERIALS AND METHODS

In this experimental study, we divided 48 mice into eight groups (n = 6); various doses of thymoquinone (2, 10, and 20 mg/kg) and morphine (20 mg/kg) plus thymoquinone (2, 10, and 20 mg/kg) were administered intraperitoneally to 48 male mice for 30 consequent days. Male reproductive parameters including testis weight, testosterone hormone, serum nitric oxide, germinal thickness, sperm morphology, count, viability, and motility were analyzed and compared.

RESULTS

The results indicated that morphine administration significantly decreased germinal thickness, testis weight, testosterone level, viability, morphology, count, and motility of sperm and increased nitric oxide as compared to saline group (P < 0.05). However, increasing the dose of thymoquinone in the thymoquinone and thymoquinone plus morphine groups significantly decreases nitric oxide level (P < 0.05) while significantly boosted motility, morphology, count, viability of sperm cells, germinal thickness, and testosterone hormone in all groups as compared to morphine group (P < 0.05).

CONCLUSION

It seems that thymoquinone administration could increase the quality some of spermatozoa and improves morphine-induced adverse effects on reproductive parameters in male mice.

The CatSper channel modulates boar sperm motility during capacitation

The cation channel of sperm (CatSper) comprises four transmembrane subunits specifically expressed in human, equine, murine and ovine spermatozoa, apparently implicated in capacitation, hyperactivation and acrosome exocytosis. Western blotting and immunocytochemistry showed hereby that CatSper subunits are also present in boar spermatozoa, primarily over the sperm neck, tail and cytoplasmic droplets; albeit CatSper -1 presented in addition some distribution over the membrane of the acrosome and CatSper -2 and -4 over the membrane of the post-acrosome. The role of the Catsper channel in boar spermatozoa was investigated by extending the spermatozoa in media containing different calcium (Ca²⁺) availability and exposure to the capacitation-trigger bicarbonate, to progesterone or CatSper inhibitors (Mibefradil and NNC 55-0396), separately or sequentially, at physiological and toxicological doses. Extracellular Ca²⁺ availability, combined with bicarbonate exposure (capacitation-inducing conditions) decreased sperm motility, similarly to when spermatozoa incubated in capacitation-inducing conditions was exposed to Mibefradil and NNC 55-0396. Exposure of these spermatozoa to progesterone did not cause significant changes in sperm motility and nor did it revert its decrease induced by CatSper antagonists. In conclusion, the CatSper channel regulates sperm motility during porcine capacitation-related events in vitro.

Glutathione Peroxidase 5 Is Expressed by the Entire Pig Male Genital Tract and Once in the Seminal Plasma Contributes to Sperm Survival and In Vivo Fertility

Glutathione peroxidase-5 (GPX5) is an H₂O₂-scavenging enzyme identified in boar seminal plasma (SP). This study attempted to clarify its origin and role on sperm survival and fertility after artificial insemination (AI). GPX5 was expressed (Western blot and immunocytochemistry using a rabbit primary polyclonal antibody) in testes, epididymis and accessory sex glands (6 boars). SP-GPX5 concentration differed among boars (11 boars, P < 0.001), among ejaculates within boar (44 ejaculates, P < 0.001) and among portions within ejaculate (15 ejaculates). The first 10 mL of the sperm rich fraction (SRF, sperm-peak portion) had a significantly lower concentration (8.87 ± 0.78 ng/mL) than the rest of the SRF and the post-SRF (11.66 ± 0.79 and 12.37 ± 0.79 ng/mL, respectively, P < 0.005). Sperm motility of liquid-stored semen AI-doses (n = 44, at 15–17°C during 72h) declined faster in AI-doses with low concentrations of SP-GPX5 compared to those with high-levels. Boars (n = 11) with high SP-GPX5 showed higher farrowing rates and litter sizes than those with low SP-GPX5 (a total of 5,275 inseminated sows). In sum, GPX5 is widely expressed in the boar genital tract and its variable presence in SP shows a positive relationship with sperm quality and fertility outcomes of liquid-stored semen AI-doses.