Comparison of chemiluminescence and flow cytometry in the estimation of reactive oxygen and nitrogen species in human semen

Cell-type-specific determination of reactive oxygen species by flow cytometry

BACKGROUND

Seminal leukocyte-generated reactive oxygen species may have a significant impact on sperm intracellular reactive oxygen species levels, therefore contributing to oxidative damage and consequent functional impairment of spermatozoa. This relationship may be utilized for male urogenital inflammation-driven oxidative stress diagnostics.

OBJECTIVE

To obtain seminal cell-specific, reactive oxygen species-related fluorescence intensity cut-off values to differentiate leukocytospermic samples displaying reactive oxygen species overproduction (oxidative burst) from normozoospermic seminal samples.

MATERIAL AND METHODS

Ejaculates gained by masturbation were obtained from patients in the framework of andrology consultations. The results published in this paper were generated from samples for which the attending physician requested spermatograms and seminal reactive oxygen species laboratory tests. Routine seminal analyses were performed according to World Health Organization guidelines. Samples were divided into normozoospermic "non-inflamed," and leukocytospermic groups. The semen was stained by 2',7'-dichlorodihydrofluorescein diacetate and the reactive oxygen species-related fluorescence signal and the percentage of reactive oxygen species-positive spermatozoa within the living population were quantified by flow cytometry.

RESULTS

Reactive oxygen species-related mean fluorescence intensity was higher in both spermatozoa and leukocytes from leukocytospermic samples than in those from normozoospermic samples. Mean fluorescence intensity in spermatozoa was positively and linearly correlated with mean fluorescence intensity measured in leukocytes in both groups.

DISCUSSION

The capacity of spermatozoa to generate reactive oxygen species is at least three log lower than that of granulocytes. The question is whether the reactive oxygen species-producing machinery of spermatozoa is capable of causing autologous oxidative stress or whether leukocytes are the predominant source of seminal oxidative stress. Based on our observations, the reactive oxygen species production of leukocytes may have a significant impact on the overall reactive oxygen species levels measured in spermatozoa.

CONCLUSION

Reactive oxygen species-overproducing leukocytospermic and normozoospermic seminal samples can reliably be differentiated based on reactive oxygen species mean fluorescence intensity measurement.

Influence of trans-ferulic acid on the quality of ram semen upon cold preservation

BACKGROUND

Due to lower antioxidant capacity and higher amounts of polyunsaturated fatty acids, ram spermatozoa are very susceptible during cooling process.

OBJECTIVES

The objective was to examine the effect of the trans-ferulic acid (t-FA) on the ram semen during liquid preservation.

METHODS

Semen samples were collected from the Qezel rams, pooled, and extended with the Tris-based diluent. Pooled samples enriched with different amounts of the t-FA (0, 2.5, 5, 10, and 25 mM) and preserved at 4°C for 72 h. Spermatozoa's kinematics, membrane functionality, and viability were assessed by CASA system, hypoosmotic swelling test, and eosin-nigrosin staining, respectively. Moreover, biochemical parameters were measured at 0, 24, 48, and 72 h.

RESULTS

Results showed that 5 and 10 mM t-FA improved forward progressive motility (FPM) and curvilinear velocity compared to the other groups at 72 h (p < 0.05). Samples treated with 25 mM t-FA showed the lowest total motility, FPM, and viability at 24, 48, and 72 h of storage (p < 0.05). Higher total antioxidant activity levels were observed in the 10 mM t-FA-treated group compared to the negative control at 72 h (p < 0.05). Treatment with 25 mM t-FA increased malondialdehyde amounts and decreased superoxide dismutase activity compared to other groups at the final time assessment (p < 0.05). Nitrate-nitrite and lipid hydroperoxides values were not affected by treatment.

CONCLUSIONS

The current study indicates the positive and negative influences of different concentrations of t-FA on the ram semen upon cold storage.

Thiol oxidation by nitrosative stress: Cellular localization in human spermatozoa

Peroxynitrite is a highly reactive nitrogen species and when it is generated at high levels it causes nitrosative stress, an important cause of impaired sperm function. High levels of peroxynitrite have been shown to correlate with decreased semen quality in infertile men. Thiol groups in sperm are mainly found in enzymes, antioxidant molecules, and structural proteins in the axoneme. Peroxynitrite primarily reacts with thiol groups of cysteine-containing proteins. Although it is well known that peroxynitrite oxidizes sulfhydryl groups in sperm, the subcellular localization of this oxidation remains unknown. The main objective of this study was to establish the subcellular localization of peroxynitrite-induced nitrosative stress in thiol groups and its relation to sperm motility in human spermatozoa. For this purpose, spermatozoa from healthy donors were exposed in vitro to 3-morpholinosydnonimine (SIN-1), a compound which generates peroxynitrite. In order to detect peroxynitrite and reduced thiol groups, the fluorescent probes, dihydrorhodamine 123 and monobromobimane (mBBr), were used respectively. Sperm viability was analyzed by propidium iodide staining. Peroxynitrite generation and thiol redox state were monitored by confocal microscopy whereas sperm viability was evaluated by flow cytometry. Sperm motility was analyzed by CASA using the ISAS(®) system. The results showed that exposure of human spermatozoa to peroxynitrite results in increased thiol oxidation which is mainly localized in the sperm head and principal piece regions. Thiol oxidation was associated with motility loss. The high susceptibility of thiol groups to peroxynitrite-induced oxidation could explain, at least in part, the negative effect of reactive nitrogen species on sperm motility.

ABBREVIATIONS

DHR: dihydrorhodamine 123; mBBr: monobromobimane ONOO(-): peroxynitrite RNS: reactive nitrogen species RFI: relative fluorescence intensity SIN-1: 3-morpholinosydnonimine CASA: Computer-Aided Sperm Analysis PARP: poli ADP ribose polimerasa VCL: curvilinear velocity VSL: straight-line velocity VAP: average path velocity PRDXs: peroxiredoxins ODF: outer dense fiber ODF1: outer dense fiber 1 PI: propidium iodide DMSO: dimethyl sulfoxide SD: standard deviation

ANOVA

analysis of variance.

Evaluation of Lasting Effects of Heat Stress on Sperm Profile and Oxidative Status of Ram Semen and Epididymal Sperm

Higher temperatures lead to an increase of testicular metabolism that results in spermatic damage. Oxidative stress is the main factor responsible for testicular damage caused by heat stress. The aim of this study was to evaluate lasting effects of heat stress on ejaculated sperm and immediate or long-term effects of heat stress on epididymal sperm. We observed decrease in motility and mass motility of ejaculated sperm, as well as an increase in the percentages of sperm showing major and minor defects, damaged plasma and acrosome membranes, and a decrease in the percentage of sperm with high mitochondrial membrane potential in the treated group until one spermatic cycle. An increased enzymatic activity of glutathione peroxidase and an increase of stressed cells were observed in ejaculated sperm of the treated group. A decrease in the percentage of epididymal sperm with high mitochondrial membrane potential was observed in the treated group. However, when comparing immediate and long-term effects, we observed an increase in the percentage of sperm with low mitochondrial membrane potential. In conclusion, testicular heat stress induced oxidative stress that led to rescuable alterations after one spermatic cycle in ejaculated sperm and also after 30 days in epididymal sperm.

Influence of BHT inclusion on post-thaw attributes of human semen

The aim of this study was to determine the effect of butylated hydroxytoluene (BHT) supplemented cryopreservation medium on sperm parameters during the freeze-thaw process. In addition, sperm lipid peroxidation, DNA damage, and the amount of reactive oxygen species (ROS) were determined. Semen samples were obtained from 75 donors. Fifteen semen samples were used for optimizing BHT concentration and incubation time and 60 samples were used for the final experiments. After the determination of basic parameters, groups of three sample with similar parameters were pooled and processed by Pure Sperm gradient centrifugation. The semen samples were then diluted with normal freezing medium (control) or a medium containing 0.5 mM BHT (test) for 5 minute and stored in liquid nitrogen. Frozen cryovials were thawed individually for 20 seconds in a water bath (37°C) for evaluation. Freezing extenders supplemented with 0.5 mM BHT led to higher sperm motility and viability compared with control samples (p < 0.001). Furthermore, the addition of BHT decreased malondialdehyde (MDA) formation, DNA fragmentation, and ROS content compared with controls (p < 0.001). Our results showed that the addition of BHT to the freezing medium could be of advantage in reducing ROS and preventing the detrimental effect of ROS on the human sperm function.

Semen analysis: update on clinical value, current needs and future perspectives

At present, evaluation of male reproductive function consists primarily of routine semen analysis, a collection of conventional microscopic assessments ideally performed following the guidelines set by the World Health Organization. While providing some insight into testicular function, these long-performed tests are limited in the information that they impart; more specifically, they are unable to predict true fertility potential. As a consequence, there is a need for the appraisal and consideration of newer semen parameters that may be more indicative of reproductive success. Although various novel assays have been introduced that broaden the scope of information available to both researcher and clinician, the utility of these tests remains limited due to the lack of standardisation of protocols and the absence of clinically established, dependable reference ranges. As such, it is not surprising that most of these parameters and their associated methods remain recommended for ‘research purposes only’. With the burgeoning ‘omics’ revolution, nanotechnology and the development of new analytical instruments, there is now an opportunity for the identification and measurement of previously unknown features that may prove to be more indicative of each sperm's true functional status and capability. Once optimised, simplified, clinically validated and made more readily accessible, these new approaches hold the promise of forming the fulcrum upon which andrological investigations can enter a new era.

Relationship between reactive oxygen species production in human semen and sperm DNA damage assessed by Sperm Chromatin Structure Assay

AIM

The aim of this prospective study was to find possible relationship between ROS production measured by chemiluminescence and flow cytometry in human semen and sperm DNA damage estimated by Sperm Chromatin Structure Assay.

METHODS

Study included 39 men from infertile couples and 23 fertile volunteers who served as a control group. Aliquot of neat semen was used for ROS detection by chemiluminescence. Aliquot of sperm suspension in phosphate buffered saline was used for the detection of ROS by flow cytometry. Another aliquot of sperm suspension was used for SCSA to measure DNA fragmentation index and High DNA stainability.

RESULTS

DNA fragmentation index correlated negatively with sperm morphology and motility. High DNA stainability correlated positively with ROS production and negatively with sperm morphology and concentration. Although there were similar trends of rising DNA fragmentation index and ROS production among the three groups of men, the relationship did not reach statistical significance.

CONCLUSIONS

Higher values of DNA fragmentation index and high DNA stainability may also reflect developmental and/or environmental problems and not only oxidative stress.

Cytosolic and mitochondrial ROS: which one is associated with poor chromatin remodeling?

The aim of this study was to determine if there are any associations between impaired chromatin packaging and the origin of reactive oxygen species (ROS) production. Cytosolic ROS, mitochondrial ROS, DNA protamination, and apoptosis were evaluated with dichlorofluoresceindiacetate (DCFH-DA), dihydrorhodamine 123 (DHR123), chromomycin A3 (CMA3), and YO-Pro-1 (Y1)/propidium iodide (PI), respectively, by flow cytometry (FCM) in 40 infertile individuals. Percentages DCF+ and R123+ sperm were positively associated with percentage CMA3+ sperm and negatively associated with percentage apoptotic sperm. No correlation was observed between CMA3+ sperm and the percentage of apoptotic sperm. Under protamination of sperm is not associated with the origin of ROS production, but their relationship may suggest an association with general physiological dysfunction of sperm. Furthermore, under protamination does make sperm prone to apoptosis. Rather, it is likely that apoptosis is induced by ROS production. Considering that these conclusions are derived from correlative analyses, additional studies including an interventive approach are required.

The importance of semen analysis in the context of azoospermia

Azoospermia is a descriptive term referring to ejaculates that lack spermatozoa without implying a specific underlying cause. The traditional definition of azoospermia is ambiguous, which has ramifications on the diagnostic criteria. This issue is further compounded by the apparent overlap between the definitions of oligospermia and azoospermia. The reliable diagnosis of the absence of spermatozoa in a semen sample is an important criterion not only for diagnosing male infertility but also for ascertaining the success of a vasectomy and for determining the efficacy of hormonal contraception. There appears to be different levels of rigor in diagnosing azoospermia in different clinical situations, which highlights the conflict between scientific research and clinical practice in defining azoospermia.

DHR123: an alternative probe for assessment of ROS in human spermatozoa

The aim of this study was to assess the potential of dihydrorhodamine 123 (DHR123) to measure oxidative stress produced by human spermatozoa. The results were compared with 2', 7'-dichlorodihydrofluorescein diacetate (DCFH-DA) that is routinely used for assessment of H(2)O(2) produced by spermatozoa. Fluorescence intensity and percentage R123 and DCF positive sperm were measured by flow cytometry. The optimal condition for assessment of reactive oxygen species (ROS) produced by sperm with DHR123 was 0.05 µM for 1 million sperm per ml for 20 minutes. The results of ROS measurement by DHR123 showed a significant correlation (r= +0.818, P<0.001) with DCFH-DA staining. Immunofluorescence of sperm stained with DHR123 revealed ROS production in the sperm mid-piece. In addition a significant correlation was observed between oxidant production assessed by DHR123 and semen parameters. Therefore, DHR123 may be considered a suitable probe for estimating oxidants produced by human spermatozoa, and can present heterogeneity in oxidant production between different samples.