Red LED Light Acts on the Mitochondrial Electron Chain of Mammalian Sperm via Light-Time Exposure-Dependent Mechanisms

Swimming trapper decreases the proportion of chromosomally unbalanced spermatozoa in human Robertsonian translocation carriers

BACKGROUND

Carriers of reciprocal translocations often have more unbalanced spermatozoa and higher DNA fragmentation rates, elevating reproductive risk. The simple swim-up method (SSUM) can decrease the amount of spermatozoa with abnormal chromatin structure and fragmented DNA, however, it has limited efficacy in eliminating chromosomally unbalanced sperm.

METHODS

The spermatozoa of eight Robertsonian translocation (Rob) carriers were split into three groups: original raw semen group (control group); SSUM and swimming trapper method group (STM) processed semen samples. After different semen preparation procedures, semen qualities, sperm chromosomal aneuploidy, and sperm fragmented DNA were evaluated.

RESULTS

Although spermatozoa with higher motility was obtained by both SSUM and STM, the population of faster forward moving sperm was greater with STM as compared to SSUM. While the rates of DNA fragmentation were statistically much lower in both groups than ejaculated semen sample, our data showed better effect on the decrease of DNA fragmentation index (DFI) after selection by STM for patients who have high DFI (>20%) in neat semen. For all patients, significant decrease in the frequency of chromosomally unbalanced spermatozoa was observed after selection using STM. Although similar trends can be seen in the SSUM group, a significant difference was identified in one patient only.

CONCLUSIONS

Use of swimming trapper (STM) is superior for enriching high-motile and genetically competent sperm in comparison with SSUM.

Applications of laser technology in the manipulation of human spermatozoa

The application of laser technology in the field of assisted reproductive technology (ART) has experienced rapid growth over the past decades owing to revolutionary techniques such as intracytoplasmic sperm injection (ICSI), preimplantation genetic testing (PGT), and in vitro manipulation of gametes and embryos. For male gametes, in vitro manipulation techniques include spermatozoa selection, sorting, immobilization, and quality assessment. A number of studies have been conducted to investigate the application of different laser technologies in the manipulation of human spermatozoa. However, there is a lack of a unified understanding of laser application in the in vitro manipulation of sperm and safety considerations in ART and, subsequently, the inability to make clear and accurate decisions on the clinical value of these laser technologies. This review summarizes the advancements and improvements of laser technologies in the manipulation of human spermatozoa, such as photobiomodulation therapy, laser trap systems for sperm analysis and sorting, laser-assisted selection of immotile sperm and laser-assisted immobilization of sperm prior to ICSI. The safety of those technologies used in ART is also discussed. This review will provide helpful and comprehensive insight into the applications of laser technology in the manipulation of human spermatozoa.

Cell bioenergetics and ATP production of boar spermatozoa

Cellular metabolism is an important feature of spermatozoa that deserves more insights to be fully understood, in particular in porcine semen physiology. The present study aims to characterize the balance between glycolytic and oxidative metabolism in boar sperm cells. Agilent Seahorse technology was used to assess both oxygen consumption rate (OCR), as an oxidative metabolism index, and extracellular acidification rate (ECAR), as a glycolytic index. Different metabolic parameters were studied on freshly ejaculated sperm cells (identified as day zero sample, d0) and after one day of storage at 17 °C in Androhep extender (d1). Mitochondrial ATP production rate (MitoATP) was higher than the glycolytic ATP production rate (glycoATP) at both d0 and d1 while at d1 the amount of ATP production decreased, in particular, due to OXPHOS reduction. Conversely, glycoATP was not significantly different between d0 and d1. Interestingly, OCR profile showed no different bioenergetic parameters (i.e. ATP turnover, basal or maximal respiration, and spare respiration) between d0 and d1, thus indicating that sperm cell metabolism was reversibly decreased by preservation conditions. Other metabolic parameters showed the same trend, irrespective of the storage time: under stressed conditions (oligomycin plus FCCP), spermatozoa showed an increase in mitochondrial respiration while the metabolic potential of glycolysis did not undergo variations when compared to baseline metabolism. The rate of oxidation of fuel substrates - glucose, fatty acids, and glutamine - showed that sperm reliance on glucose oxidation to maintain baseline respiration was higher than fatty acids or glutamine. Interestingly spermatozoa demonstrated to have a low "capacity" parameter, which indicates that they cannot use only a single fuel substrate to produce energy. This feature of sperm metabolism to be unable to increase oxidation of a particular fuel to compensate for inhibition of alternative fuel pathway(s) was demonstrated by the negative value of "flexibility". Our results showed that ATP production in boar sperm cells relied on mitochondrial oxidative metabolism in freshly ejaculated cells, while, under liquid storage conditions, their oxidative metabolism decreased while the glycolysis remained constant. These results open new fields of research in the preservation techniques of boar sperm cells.

Study of mitochondrial function in thawed bull spermatozoa using selective electron transfer chain inhibitors

Bull spermatozoa depend equally on glycolysis and oxidative phosphorylation for the maintenance of the energy necessary for their proper functioning. The aim of the present work was to delineate the mitochondrial activity of bull spermatozoa after incubation with specific inhibitors of the different mitochondrial complexes and evaluate their ROS production. Thawed bull sperm cells (30 × 106 mL-1 in Tyrode's extender) were incubated 1 and 3h at 37 °C with rotenone 5 μM (ROT), complex I inhibitor; dimethyl-malonate 10 mM (DMM), complex II inhibitor; carbonyl cyanide m-chlorophenyl hydrazine 5 μM (CCCP), uncoupling agent; antimycin A 1 μg/mL (ANTI), complex III inhibitor; oligomycin 5 μM (OLIGO), ATP synthase inhibitor, and 0.5% DMSO, vehicle (CTR). Sperm motility and kinematics were assessed by Hamilton Thorn IVOS 12.0. Mitochondrial membrane potential, mitochondrial O2•- production and H2O2 intracellular content were evaluated by BD FACSCalibur flow cytometer, and sperm viability (SYBR-14/PI) and mitochondrial activity (JC-1/SYBR-14/PI) were assessed by epifluorescence microscopy. A multivariate analysis was performed on the results. In addition, sperm kinematic features, registered for each motile spermatozoon, were studied by cluster analysis. The incubation during 1 or 3 h in presence of the inhibitors of mitochondrial functionality only had a minor effect on motility parameters, decreasing the proportion of the SP1 (fast progressive) subpopulation after 3 h of incubation with ROT, ANTI or OLIGO. The percentage of live spermatozoa with active mitochondria was reduced under the effect of ANTI and CCCP both at 1 and 3 h. In conclusion, mitochondrial function is somehow impaired in frozen thawed bull sperm as not all live cells showed active mitochondria. These results support the findings that bull spermatozoa can alternatively rely on oxidative phosphorylation or glycolysis for energy obtainment and that their mitochondria are less affected by ETC inhibitors.

Effect of monochromatic light on the behavior of the ctenophore Mnemiopsis leidyi (A. Agassiz, 1865)

Ctenophores are invertebrate, gelatinous predators that perform complex movements due to their numerous ciliary comb plates. We investigated the behavioral responses of the ctenophore Mnemiopsis leidyi A. Agassiz, 1865 to red, green, and blue lights of different powers and fluxes emitted by LEDs or lasers. White LEDs were used to mimic natural sunlight. When laser light was directed to the aboral organ, the animals tended to leave the illumination zone. The blue-light reaction was six times faster than the red-light reaction. The behavioral strategy of the animals changed significantly when their freedom of maneuvering was restricted. Typical locomotions were ranked according to the laser beam avoidance time from the beginning of exposure to going into darkness. The minimum reaction time was required for turning and moving the ctenophore, while moving along the laser beam and turning around required more time. Typical patterns of behavior of M. leidyi in the light flux were established using cluster analysis. Three preferential behavioral strategies were identified for avoiding laser irradiation: 1) body rotation; 2) shifting sideways; and 3) movement with deviation from the beam. The elementary ability of ctenophores to make decisions in situative conditions has been demonstrated.

Glucose Starvation Inhibits Ferroptosis by Activating the LKB1/AMPK Signaling Pathway and Promotes the High Speed Linear Motility of Dairy Goat Sperm

In mammals, sperm acquire fertilization ability after capacitation in vitro or when in the female reproductive tract. The motility patterns of sperm undergo continuous changes from the moment of ejaculation until fertilization in the female reproductive tract. In vitro, hyperactivated motility can be induced through high glucose mediums, while in vivo, it is induced by oviduct fluids. Conversely, sperm maintain linear motility in seminal plasma or uterine fluids that contain low glucose levels. In dairy goat sperm, energy metabolism associated with capacitation depends on the energy sources in vitro, seminal plasma, or the female reproductive tract, especially the glucose levels. However, there is little experimental knowledge that glucose levels affect sperm energy metabolism in dairy goats. To clarify these hypotheses, we incubated dairy goat spermatozoa with different concentrations of rotenone-glucose (ROT), carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP), and tigecycline (TIG) in vitro. Sperm motility attributes, ATP content, pyruvate and lactate levels, mitochondrial permeability transition pore fluorescence intensity, mitochondrial membrane potential (MMP), and protein synthesis were analyzed. Sperm motility patterns changed from circular to linear under low glucose conditions compared with those in high glucose conditions and showed a significant improvement in progressive motility and straight line speed, whereas lactate and pyruvate levels and MMP decreased remarkably. Incubation of spermatozoa with ROT, FCCP, and TIG inhibited sperm mitochondrial activity, protein synthesis, oxidative phosphorylation, and ATP levels, thereby reducing sperm motility, including the progressive motility, straight line speed, and total motility. Simultaneously, incubation of spermatozoa with Compound C under low glucose conditions significantly decreased the ATP levels and MMP, as well as liver kinase B1 and AMPK protein expression. Under low glucose conditions, sperm mainly produce ATP through mitochondrial OXPHOS to achieve high speed linear movement, inhibit ferroptosis through the LKB1/AMPK signaling pathway, and further maintain energy metabolism homeostasis.

Effects of photobiomodulation therapy on human sperm function

INTRODUCTION

Sperm motility is a crucial factor in male infertility and it depends on mitochondrial tail movements. Photobiomodulation light therapy allows the cells to produce their energy through activation of the mitochondria. The aim of the present study was to examine the impact of photobiomodulation on sperm motility in astenozoospermic individuals.

MATERIALS AND METHODS

Following semen analyses of 20 astenozoospermic individuals, collected semen samples were centrifuged. Pellet was obtained and homogenized through mixing with culture media in 1:1 ratio. Each semen samples were divided into 3 groups. In the first group, control samples were not exposed to laser irradiation. The Group 2 and Group 3 were exposed to 650nm wavelength of photobiomodulation from 10cm distance in dark environment via a 36cm² aperture sizer with 200mW output power for 30 and 60min duration, respectively. Sperm motilities were evaluated and chromatin condensation of sperms was determined.

RESULTS

Sperm motilities were significantly increased in photobiomodulation groups compared with the controls. Sperm motilities tended to be different between the 30 and 60min red light exposure groups; however, it was not statistically significant. When the motility grades were compared, no significant difference was observed in non-progressive motility sperms. While immotile sperms decreased significantly in the photobiomodulation groups compared to the control group, progressive sperms increased.

CONCLUSIONS

The results of the present study demonstrated that the photobiomodulation is an efficient method to increase the sperm motility of astenozoospermic individuals independent of the duration of exposure.

Effects of cryopreservation on the mitochondrial bioenergetics of bovine sperm

This study evaluated the bioenergetic map of mitochondria metabolism in cryopreserved bovine sperm. The detected oligomycin-sensitive basal respiration supported ATP production; frozen-thawed spermatozoa were found to have a coupling efficiency higher than 0.80. Cell respiration, however, was not stimulated by the protonophoric action of FCCP, as its titration with 1, 2, 4 and 6 μM did not stimulate the uncoupling activity on oxidative phosphorylation as highlighted by unresponsive oxygen consumption. The unusual effect on the stimulation of maximal respiration was not related to fibronectin- or PDL-coated plates used for cellular metabolism analysis. Conversely, irradiation of frozen-thawed bovine sperm with the red light improved mitochondrial parameters. In effect, the maximal respiration of red-light-stimulated sperm in PDL-coated plates was higher than the non-irradiated. In spite of this, red-light irradiation had no impact on membrane integrity and mitochondrial activity evaluated by epifluorescence microscopy.

The effects of red LED light on pig sperm function rely upon mitochondrial electron chain activity rather than on a PKC-mediated mechanism

While irradiation with red LED light has been reported to modulate sperm function in different mammalian species, the mechanisms underlying their response are poorly understood. This work sought to provide new insights into whether this effect relies on a direct action upon mitochondrial electron chain and/or on PKC-linked mechanisms such as those related to opsins. For this purpose, pig semen was light-stimulated for 1, 5 or 10 min in the presence/absence of antimycin A, an inhibitor of the mitochondrial electron chain, or PKC 20–28^® (PKCi), a PKC inhibitor. Antimycin A completely blocked the effects of light at all the performed irradiation patterns. This effect was linked to a complete immobility of sperm, which was accompanied with a significant (p < 0.05) drop in several markers of mitochondrial activity, such as JC-1 staining and O₂ consumption rate. Antimycin A, however, did not affect intracellular ATP levels, intramitochondrial calcium, total ROS, superoxides or cytochrome C oxidase (CCO) activity. In the case of PKCi, it did also counteract the effects of light on motility, O₂ consumption rate and CCO activity, but not to the same extent than that observed for antimycin A. Finally, the effects observed when sperm were co-incubated with antimycin A and PKCi were similar to those observed with antimycin A alone. In conclusion, red LED light acts on sperm function via a direct effect on mitochondrial electron chain. Additionally, light-activated PKC pathways have a supplementary effect to that observed in the electron chain, thereby modulating sperm parameters such as motility and CCO activity.

Assessment of sperm mitochondrial activity by flow cytometry and fluorescent microscopy: a comparative study of mitochondrial fluorescent probes in bovine spermatozoa

CONTEXT

While conventional semen analysis is a simple, time-saving, and economical means to evaluate sperm quality, it leaves biochemical and metabolic characteristics of spermatozoa aside. To address this issue, the use of fluorescent probes assessing functional sperm parameters, such as JC-1, DiOC6 (3) and MitoTracker, has increased over the last decades. Apparently contradictory observations have nevertheless fostered an ongoing debate on their sensitivity and ability to evaluate the mitochondrial membrane potential (MMP) of sperm cells, thus warranting a re-examination of these probes.

AIMS

The present study aims to elucidate the suitability and sensitivity of each probe to evaluate the MMP of bovine spermatozoa by flow cytometry.

METHODS

Cryopreserved spermatozoa from ten bulls were thawed, stained with JC-1/SYTOXRed, DiOC6 (3)/propidium iodide (PI) or MitoTracker Deep Red (MTDR)/PI, and evaluated with flow cytometry and fluorescence microscopy.

KEY RESULTS

DiOC6 (3), JC-1 and MTDR can be simultaneously co-stained with a viability marker. The results of the present study support the ability of DiOC6 (3)/PI and JC-1/SYTOXRed, but not that of MTDR/PI, to monitor the MMP of spermatozoa.

CONCLUSIONS

JC-1/SYTOXRed assessed by flow cytometry was found to be the most sensitive and robust fluorescent probe to assess MMP. Moreover, DiOC6 (3)/PI could be a suitable alternative when the flow cytometer is not equipped with a red laser and/or an adequate optical filter.

IMPLICATIONS

Both DiOC6 (3) and JC-1, but not MTDR, could be used as probes to assess the mitochondrial membrane potential of bovine spermatozoa.

Photo Stimulation of Seminal Doses with Red LED Light from Duroc Boars and Resultant Fertility in Iberian Sows

Simple Summary

The main objective of breeding Iberian pigs is the production of high-quality dry cured meat products. As this breed shows a reduced litter size in comparison to the commercial breeds, some previous studies have reported the use of photostimulation of seminal doses as a method for improving the farrowing rate and litter size. The aim of this study was to explore whether the application of a photostimulation procedure to Duroc seminal doses has any beneficial effect on fertility and litter size. Semen samples were obtained from 38 fertile Duroc boars and the fertility study was conducted on two commercial farms using multiparous Iberian sows (farm A, n = 824; farm B, n = 2131), that were randomly assigned to LED (L) or control (C) groups. Post-cervical insemination took place 0 and 24 h after the diagnosis of estrus, with seminal doses from the same ejaculate and same treatment. The photostimulation of the seminal doses had no effect on the reproductive performance (farrowing rate: 91.72% C vs. 90.09% L, litter size: 8.71 ± 0.06 piglets C vs. 8.70 ± 0.05 L, p > 0.05).

Abstract

In pigs, it has been reported that increased farrowing rates and litter size have been induced by photostimulating the seminal doses for artificial insemination with red LED light. As the reproductive characteristics, production system, and outcome parameters of Iberian breed pigs are different from other commercial breeds, the aim of this study was to evaluate the possible effect of illuminating seminal doses from Duroc boars with red LED light and the fertility outcomes of Iberian females. Semen samples were obtained from 38 fertile Duroc boars. Photostimulation of the artificial insemination (AI) seminal doses was carried out by illuminating the samples with a red LED for 10 min, followed by 10 min of darkness, and finally 10 additional minutes of red light. The fertility study was conducted on two commercial farms using multiparous Iberian sows (farm A, n = 824; farm B, n = 2131), that were randomly assigned to LED (L) or control (C) groups. No differences were found between L and C groups in both farms (p > 0.05) for parity, pregnancy rate, duration of pregnancy, farrowing rate, and litter size (total, alive, and stillborn piglets). Farrowing rates in farm A were 88.8% (n = 383) for control and 89.6% (n = 441, p = 0.67) for the LED group. In farm B, farrowing rates were C:90.5% (n = 1030) and L: 90.1% (n = 1101, p = 0.48). In farm A, total born piglets were 8.69 ± 0.11 for C and 8.71 ± 0.11 for L (p = 0.87). In farm B, the results were 8.72 ± 0.7 for C and 8.70 ± 0.06 (p = 0.82) for L. Under the production conditions for the Iberian breed, the photostimulation with red LED light using Duroc pig seminal doses was not effective in improving the fertility of Iberian sows.

The Effects of Red Light on Mammalian Sperm Rely upon the Color of the Straw and the Medium Used

Simple Summary

Several studies have shown that the exposure of semen to red light improves sperm quality and fertilizing ability, which could improve the efficiency of assisted reproductive techniques with irradiated semen. However, despite being considered as possible sources of variation, the effects of the color of the container (straws) or the medium have not yet been evaluated. In this study, 13 ejaculates from different stallions were split into equal fractions, diluted either with Kenney or Equiplus extender, and subsequently packed into straws of five different colors. After storage at 4 °C for 24 h, the sperm were irradiated and different variables, including sperm motility, plasma membrane integrity, and mitochondrial membrane potential, were evaluated. Our results confirm that irradiation increases some motion characteristics and mitochondrial membrane potential without affecting sperm viability and demonstrate that the effects depend on the color of the straw and the extender used.

Abstract

Previous research has determined that irradiation of mammalian sperm with red light increases motility, mitochondrial activity, and fertilization capacity. In spite of this, no study has considered the potential influence of the color of the straw and the extender used. Therefore, this study tests the hypothesis that the response of mammalian sperm to red light is influenced by the color of the straw and the turbidity/composition of the extender. Using the horse as a model, 13 ejaculates from 13 stallions were split into two equal fractions, diluted with Kenney or Equiplus extender, and stored at 4 °C for 24 h. Thereafter, each diluted fraction was split into five equal aliquots and subsequently packed into 0.5-mL straws of red, blue, yellow, white, or transparent color. Straws were either nonirradiated (control) or irradiated with a light–dark–light pattern of 3–3–3 (i.e., light: 3 min, dark: 3 min; light: 3 min) prior to evaluating sperm motility, acrosome and plasma membrane integrity, mitochondrial membrane potential, and intracellular ROS and calcium levels. Our results showed that irradiation increased some motion variables, mitochondrial membrane potential, and intracellular ROS without affecting the integrities of the plasma membrane and acrosome. Remarkably, the extent of those changes varied with the color of the straw and the extender used; the effects of irradiation were more apparent when sperm were diluted with Equiplus extender and packed into red-colored straws or when samples were diluted with Kenney extender and packed into transparent straws. As the increase in sperm motility and intracellular ROS levels was parallel to that of mitochondrial activity, we suggest that the impact of red light on sperm function relies upon the specific rates of energy provided to the mitochondria, which, in turn, vary with the color of the straw and the turbidity/composition of the extender.