Human sperm displays rapid responses to diet

The global rise in obesity and steady decline in sperm quality are two alarming trends that have emerged during recent decades. In parallel, evidence from model organisms shows that paternal diet can affect offspring metabolic health in a process involving sperm tRNA-derived small RNA (tsRNA). Here, we report that human sperm are acutely sensitive to nutrient flux, both in terms of sperm motility and changes in sperm tsRNA. Over the course of a 2-week diet intervention, in which we first introduced a healthy diet followed by a diet rich in sugar, sperm motility increased and stabilized at high levels. Small RNA-seq on repeatedly sampled sperm from the same individuals revealed that tsRNAs were up-regulated by eating a high-sugar diet for just 1 week. Unsupervised clustering identified two independent pathways for the biogenesis of these tsRNAs: one involving a novel class of fragments with specific cleavage in the T-loop of mature nuclear tRNAs and the other exclusively involving mitochondrial tsRNAs. Mitochondrial involvement was further supported by a similar up-regulation of mitochondrial rRNA-derived small RNA (rsRNA). Notably, the changes in sugar-sensitive tsRNA were positively associated with simultaneous changes in sperm motility and negatively associated with obesity in an independent clinical cohort. This rapid response to a dietary intervention on tsRNA in human sperm is attuned with the paternal intergenerational metabolic responses found in model organisms. More importantly, our findings suggest shared diet-sensitive mechanisms between sperm motility and the biogenesis of tsRNA, which provide novel insights about the interplay between nutrition and male reproductive health.

The role of cyclic AMP, calcium and filamentous actin in adenosine modulation of Fc receptor-mediated phagocytosis in human neutrophils

The role of cyclic AMP, calcium and filamentous actin (F-actin) content during adenosine modulation of Fc receptor (FcR)-mediated phagocytosis in adherent human neutrophils was investigated. Phagocytosis of IgG-opsonized yeast particles was found to be enhanced by pico- to nanomolar concentrations of adenosine or the A1-agonist N6-cyclopentyl-adenosine (CPA) but reduced by micromolar concentrations of adenosine or the A2-agonist 5'-N-ethylcarboxamidoadenosine (NECA). NECA, in the presence of the cAMP-specific phosphodiesterase inhibitor Ro 20-1724, increased the intracellular content of cAMP during phagocytosis. Ro 20-1724 potentiated the NECA-induced reduction of the phagocytic capacity. These observations indicate that cAMP elevations are involved in A2-receptor-mediated inhibition of phagocytosis. NECA, in the presence of Ro 20-1724, markedly enhanced the action polymerization associated with adhesion to the substrate and contact with the phagocytic prey. During advanced phagocytosis, however, the F-actin content reached levels clearly below those observed in control cells. This prolonged depolymerization phase correlated with the A2-receptor-induced cAMP elevation. Depletion of intracellular free calcium abolished the cAMP-elevating effects of NECA, and also completely abrogated the A1- and A2-receptor-mediated effects on phagocytosis. However, since NECA reduced the F-actin content even in Ca(2+)-depleted cells, A2-receptor-mediated inhibition of phagocytosis could not be directly coupled to changes in the overall content of F-actin. Our results indicate that adenosine modulates FcR-mediated phagocytosis in a calcium-dependent way, and does so through 'stimulatory' A1 and 'inhibitory' A2 receptors, and also that cAMP elevation is linked to the A2-receptor-induced inhibition of phagocytosis.

Platelets enhance Fc(gamma) receptor-mediated phagocytosis and respiratory burst in neutrophils: the role of purinergic modulation and actin polymerization

The interaction of platelets with neutrophil granulocytes is considered to play an important role in the inflammatory process, and the present study was focused on platelet-induced modulation of Fcgamma receptor-mediated functions in neutrophils. We found that phagocytosis and the respiratory burst (measured as luminol-enhanced chemiluminescence), triggered in neutrophils by immunoglobulin G (IgG)-opsonized yeast particles, were potentiated by platelets and that maximal enhancement was achieved at a physiological neutrophil/platelet ratio of about 1:50 to 1:100. Platelets both increased the intra- and extracellular generation of oxygen radicals as well as the release of myeloperoxidase from stimulated neutrophils. The presence of platelets also induced a cortical actin polymerization in neutrophils, which might explain the increased phagocytic capacity. Platelets appear to affect neutrophil function in a contact-independent manner that most likely involves ATP, indicated by the following: (1) platelet supernatants, but not fixed platelets, affected neutrophil function in the same way as viable platelets; (2) platelets raised the extracellular ATP level four- to fivefold; (3) exogenous ATP mimicked the effects of platelets on actin polymerization, phagocytosis, and the respiratory burst in neutrophils; (4) hydrolysis of extracellular ATP with apyrase or blocking of ATP receptors with suramin reversed the platelet-induced enhancement of neutrophil function. An increased accumulation of extracellular adenosine, induced by inhibiting endogenous adenosine deaminase or adding exogenous adenosine, reversed the effects of platelets. The platelet-induced potentiation of the respiratory burst was inhibited by the tyrosine kinase inhibitor genistein, suggesting that tyrosine phosphorylation is involved. However, platelets did not significantly affect the Fcgamma receptor-triggered calcium response in neutrophils. In conclusion, we show that platelets, through an ATP-dependent mechanism, potentiate IgG-mediated ingestion and production of oxygen metabolites in neutrophils.

Adenosine inhibits actin dynamics in human neutrophils: evidence for the involvement of cAMP

The mechanisms by which adenosine regulates the inflammatory reaction are poorly characterized. In this study, we investigated the effects of adenosine on neutrophil actin polymerization elicited by the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (fMLP) or IgG-opsonized yeast particles. We used bodipy-phallacidin staining in combination with flow cytometry and found that adenosine markedly reduced actin polymerization triggered by IgG-yeast, whereas the effect on the fMLP-response was less pronounced. Similar or even more pronounced effects were obtained with the adenosine A2 receptor agonist 5'-N-ethylcarboxamidoadenosine (NECA), suggesting an A2 receptor-mediated mechanism. The following observations indicate that the A2 receptor-induced effects involve the cAMP-protein kinase A (PKA) signaling pathway: (1) a combination of NECA and the cAMP-specific phosphodiesterase (PDE) inhibitor Ro 20-1724 raised the cAMP content in both unstimulated and stimulated neutrophils and also further inhibited the actin dynamics; (2) the PKA inhibitor H89 reversed the inhibitory effects of NECA on the actin dynamics; (3) Ro 20-1724, isoproterenol and dibutyryl cAMP (DBcAMP) reduced actin polymerization in almost the same way as NECA did. NECA together with Ro 20-1724 impaired the fMLP-induced shape changes and cortical accumulation of actin filaments. In contrast, H89 potentiated the fMLP-induced formation of a submembranous ring of actin filaments. Neutrophils phagocytosing yeast particles in the presence of NECA and Ro 20-1724 were predominantly round in shape, and their ability to extend actin-rich pseudopods around the prey was reduced. These effects were partly antagonized by H89. In correlation with the effects on actin polymerization, NECA more effectively diminished IgG-induced upregulation of the beta2 integrin CD11b/CD18 than such upregulation induced by fMLP. The inhibitory effects of A2-receptor activation on actin dynamics and beta2 integrin expression in neutrophils exposed to IgG-yeast were also associated with a cAMP-dependent reduction of the phagocytic capacity. In conclusion, we show that adenosine inhibits actin dynamics and shape changes in neutrophils via a cAMP-dependent pathway. This finding further characterizes the mechanisms by which adenosine functions as an important modulator of the inflammatory response.

Platelets enhance neutrophil locomotion: evidence for a role of P-selectin

It has been suggested that the accumulation of platelets at sites of vascular damage and inflammation regulates the function of leukocytes. In this study, we investigated the effects of platelets on the transmigration of neutrophil granulocytes through microporous membranes. We demonstrate that platelets markedly enhance both the random and the chemotactic migration of neutrophils. Stimulatory effects were acquired by adding paraformaldehyde-fixed platelets or the supernatants of platelets; however, the effects were lower or significantly higher, respectively, compared with viable platelets. The increased neutrophil migration was associated with an amplified polymerization of actin filaments and expression of CD11b/CD18. Previous investigations indicate that the initial adhesion between platelets and neutrophils is mediated by P-selectin exposed on the surface of platelets. In this study, the following observations suggest a role for P-selectin in the platelet-induced enhancement of neutrophil motility: (i) platelet supernatants contained substantial amounts of P-selectin, (ii) filtration of platelet supernatants markedly reduced the content of P-selectin and simultaneously decreased the potentiating effects on neutrophil motility, (iii) inhibition of P-selectin-mediated cell cell adhesion with sialyl Lewis X or by incubation in calcium-free medium reduced the enhancing effects of platelets on neutrophil responses, and (iv) purified and recombinant P-selectin mimicked the effects of platelets on neutrophil locomotion. In conclusion, we propose that platelets through P-selectin promote accumulation and emigration of neutrophils during inflammatory and thrombotic processes.

Modulation of the chemotactic peptide- and immunoglobulin G-triggered respiratory burst in human neutrophils by exogenous and endogenous adenosine

The effects of exogenous and endogenous adenosine on the production of oxygen metabolites in neutrophils triggered by the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (fMLP) or immunoglobulin G (IgG)-opsonized yeast particles, were investigated. By using luminol-enhanced chemiluminescence, we found that adenosine A1 receptor activation did not affect, whereas adenosine A receptor activation, through a mechanism involving the cyclic AMP (cAMP)-protein kinase A signalling pathway, both inhibited the fMLP- and IgG-triggered respiratory burst. The adenosine-induced inhibition was however more pronounced after exposure to fMLP than to IgG-yeast. Stimulation with fMLP caused an extracellular accumulation of endogenous adenosine, which indicates that this event is a negative-feedback mechanism preventing an uncontrolled activation of chemoattractant-stimulated neutrophils. On the contrary, exposure of neutrophils to IgG-yeast did not appear to accumulate extracellular adenosine, probably due to increased adenosine deaminase activity during phagocytosis. In conclusion, this work accentuates the importance of adenosine, both exogenously applied and endogenously formed, as an inflammatory agent modulating the respiratory burst during the different phases in neutrophil activation.

Sulfatide-induced L-selectin activation generates intracellular oxygen radicals in human neutrophils: modulation by extracellular adenosine

The sulfated form of galactocerebrosides (sulfatides) have recently been established as ligands for L-selectin. In this study we show that exposure of human neutrophils to sulfatides induces a transient generation of oxygen radicals, revealed by the luminol-enhanced chemiluminescence (CL) technique. The CL response was mainly located intracellularly, and was dependent on sulfation of the galactose ring, since non-sulfated galactocerebrosides had no effect. Sulfatides also dramatically amplified the CL response triggered by the chemotactic peptide formylmethionyl-leucyl-phenylalanine (fMLP). This effect was primarily due to an increased (up to 10-fold) intracellular generation of oxygen metabolites. Removal or blocking of L-selectin with chymotrypsin and monoclonal antibodies, respectively, markedly reduced the effects of sulfatides. Furthermore, sulfatides amplified the CL response triggered by ionomycin, whereas the response induced by phorbol-12-myristate-13-acetate was slightly reduced. The tyrosine kinase inhibitor, genistein, markedly inhibited the oxygen radical production induced by sulfatides, and totally abolished the potentiating effects of sulfatides in fMLP- and ionomycin-stimulated neutrophils. Sulfatides also triggered a transient rise in the intracellular free calcium concentration, [Ca2+]i. Consequently, L-selectin activation through sulfatides appear to affect oxidase activity through a Ca(2+)-dependent pathway involving tyrosine phosphorylation. Adenosine is an anti-inflammatory agent predominately released from the vascular endothelium which might suppress an inappropriate activation of the oxidase during L-selectin-mediated rolling of neutrophils. Indeed, we found that adenosine inhibited the oxidative burst induced by sulfatides, mainly by attenuating the intracellular generation of oxygen radicals. However, 10-100 times higher concentration of exogenous adenosine was required to inhibit the CL response induced by sulfatides to the same extent as the adenosine-mediated inhibition of the fMLP-induced response. This difference in sensitivity to adenosine could be explained by various expression of extracellular adenosine deaminase (ADA), since we found that the ADA-inhibitor erythro-9-(2-hydroxy-3-nonyl)-adenine (EHNA) markedly reduced the oxygen radical production caused by sulfatides and almost totally abolished the potentiating effects of sulfatides on the fMLP-induced respiratory burst. In contrary, EHNA only slightly reduced the fMLP-triggered CL response. We suggest that the initial activation of L-selectin prepare the neutrophil for an effective microbicidal activity in the extravascular space. This process might be dependent on a L-selectin-mediated increase in the expression and activity of ADA, which locally reduces the extracellular level of adenosine.

Cross-talk between adenosine and the oxatriazole derivative GEA 3175 in platelets

We examined the interplay between adenosine and the nitric oxide (NO)-containing oxatriazole derivative GEA 3175 in human platelets. The importance of cyclic guanosine 3'5'-monophosphate (cGMP)-inhibited phosphodiesterases (PDEs) was elucidated by treating the platelets with adenosine combined with either GEA 3175 or the PDE3-inhibitor milrinone. The drug combinations provoked similar cyclic adenosine 3'5'-monophosphate (cAMP) responses. On the contrary, cGMP levels were increased only in GEA 3175-treated platelets. Both drug combinations reduced P-selectin exposure, platelet adhesion and fibrinogen-binding. However, adenosine together with GEA 3175 was more effective in inhibiting platelet aggregation and ATP release. Thrombin-induced rises in cytosolic Ca2+ were suppressed by the two drug combinations. Adenosine administered with GEA 3175 was, however, more effective in reducing Ca2+ influx. In conclusion, the interaction between adenosine and GEA 3175 involves cGMP-mediated inhibition of PDE3. The results also imply that inhibition of Ca2+ influx represent another cGMP-specific mechanism that enhances the effect of adenosine.

Release of oxygen metabolites from chemoattractant-stimulated neutrophils is inhibited by resting platelets: role of extracellular adenosine and actin polymerization

The effect of human platelets on chemoattractant-induced generation of oxygen metabolites in neutrophils was investigated, using luminol-enhanced chemiluminescence (CL). Resting platelets inhibited the extracellular, but not the intracellular, production of oxygen radicals in formyl-methionyl-leucyl-phenylalanine (fMet-Leu-Phe)-stimulated neutrophils. Maximal effect was obtained at the physiological neutrophil/platelet ratio of 1/50. Similar results were acquired by adding supernatants of platelets, indicating a role for a soluble factor. Removal of extracellular adenosine by adenosine deaminase (ADA), or blocking of adenosine-receptors by theophylline, antagonized the inhibitory effects of platelets (or the equivalent supernatant) on the neutrophil respiratory burst. In contrast, accumulation of adenosine by apyrase enhanced the inhibition. Exogenous adenosine mimicked the effects of platelets on the fMet-Leu-Phe-induced respiratory burst. To further assess the role of platelet-derived adenosine, the platelets were fixed with paraformaldehyde. We found that fixed platelets, as well as their supernatant, inhibited the fMet-Leu-Phe-induced CL-response to the same extent as viable cells. These effects were also reversed by ADA and theophylline, respectively. A prior removal of adenosine in the platelet suspension by ADA, followed by treatment with erythro-9-(2-hydroxy-3-nonyl)-adenine (EHNA) to inactivate ADA, did not reverse the inhibitory action of platelets on the fMet-Leu-Phe-induced CL-response in neutrophils. However, if adenosine receptors of neutrophil at the same time were blocked with theophyline, the inhibition was significantly reduced. Platelets markedly increased the generation of adenosine in a neutrophil suspension. The effect was antagonized by S-(4-Nitrobenzyl)-6-thioguanosine (NBTG), but unaffected by alpha, beta-methyl-eneadenosine5'diphosphate (AMP-CP), indicating that the platelet-dependent accumulation of adenosine is due to an increased release of endogenous adenosine from neutrophils and not to a degradation of extracellular AMP. In correlation, NBTG, but not AMP-CP, reversed the platelet-mediated inhibition of the fMet-Leu-Phe-induced CL-response in neutrophils. Consequently, these data suggest that a platelet-derived factor increases the release of endogenously formed adenosine from neutrophils, terminating the production of oxygen radicals. The inhibition of oxidase activity was also associated with a platelet-induced polymerization of actin in the margin of the neutrophils. Treatment of neutrophils with cytochalasin B reversed the effects of platelets, both on F-actin content and CL-response. In summary, resting platelets limit the release of oxygen radicals from chemoattractant-stimulated neutrophils, thus preventing excessive damage to host tissues in the vascular space. This effect is suggested to be associated with an increase generation of neutrophil-derived adenosine enhancing an autoregulatory inhibitory pathway, and a peripheral accumulation of actin filaments forming a barrier for extracellular release of reactive oxygen radicals.

Intravaginal exposure to seminal plasma after ovum pick-up does not increase live birth rates after in vitro fertilization or intracytoplasmic sperm injection treatment: a double-blind, placebo-controlled randomized trial

OBJECTIVE

To detect whether intravaginal exposure to prepared seminal plasma led to an absolute increase in live birth rate (LBR) after in vitro fertilization (IVF) by 10% compared with placebo. It has been suggested that intravaginal deposition of seminal plasma after ovum pick-up (OPU) for IVF treatment, increases pregnancy and LBRs.

DESIGN

Double-blind, placebo-controlled prospective study. An outcome assessment was made before the type of intervention was unblinded. The outcome data were analyzed according to an intention-to-treat protocol.

SETTING

University Hospital.

PATIENTS

Couples scheduled for an IVF treatment cycle: in total, 792 couples (393 in the seminal plasma group and 399 in the control group) were recruited over a 5-year period of inclusion in a single-center setting.

INTERVENTION

On the day of OPU, the couples were randomized into groups receiving either vaginal deposition of prepared seminal plasma from the partner or saline. Both participants and the physician were blind to the grouping.

MAIN OUTCOME MEASURES

The primary outcome was a live birth (LB). The secondary outcomes were a positive pregnancy test, defined as human chorionic gonadotropin identified in urine 3 weeks after OPU , and clinical pregnancy, defined as an intrauterine viable pregnancy assessed using transvaginal sonography after 5-7 weeks.

RESULTS

In the index group, 35.4% had a positive pregnancy test (relative risk [RR],0.93; 95% confidence interval {CI} 0.78-1.10), 28.8% had a clinical pregnancy (RR 1.00, 95% CI 0.97-1.03), and 26.5% had a LB (RR 0.86; 95% CI 0.70-1.07), adjusted for day of transfer, female age, and number of fertilized oocytes. Corresponding rates in the control group were 37.3%, 33.6%, and 29.8%. No statistically significant differences regarding outcomes between the two intervention groups were found.

CONCLUSION

Prepared seminal plasma applied in the vagina directly after OPU did not increase the rates of LB or clinical pregnancies. The importance of immunological factors to allow the implantation of an embryo is not questioned, but no improvement in the LBRs in IVF treatment by introducing the male partner's prepared seminal plasma after OPU could be found.

CLINICAL TRIAL REGISTRATION NUMBER

Clinicaltrials.gov, ID NCT02716753. Registration date 17 March, 2016, first enrollment November, 2016, completed March, 2023.