On sperm nuclear zinc and chromatin decondensation : an in vitro study on the physiology of the ejaculated human spermatozoon

Ejaculated human spermatozoa were studied in vitro with respect to their capacity to decondense the chromatin in sodium dodecyl sulfate (SDS). The content of zinc in sperm heads was studied in epididymal, vasal, and ejaculated human spermatozoa. These were the main results: (1) Soon after ejaculation most spermatozoa decondensed the chromatin in SDS with zinc-chelating EDTA. Only few spermatozoa decondensed in SDS alone. (2) During storage, many spermatozoa lost the capacity to decondense in SDS-EDTA. Half of all spermatozoa lost this capacity within the first hour after ejaculation whether they were washed and stored in a buffered salt solution (BSS) within 20 minutes after ejaculation, or simply stored in the original seminal plasma. During prolonged storage (24 hours) the capacity was better retained among spermatozoa stored in BSS, than in those stored in seminal plasma. Furthermore, among spermatozoa treated with EDTA before storage, the loss of capacity for decondensation during storage was enhanced. In contrast, the initial capacity for decondensation was completely prevented in spermatozoa supplemented with zinc during 24 h storage in BSS. (3) The ejaculated human sperm head contained significant amounts of zinc bound within the nuclear matrix. With EDTA-treatment, 90% of sperm head zinc could be removed soon after ejaculation. After 24 h storage in seminal plasma significantly less zinc could be released by exposure to EDTA. (4) Epididymal and vasal sperm heads had significantly lower contents of zinc than ejaculated sperm heads. (5) The zinc content of ejaculated sperm heads from various portions of split­ ejaculates was neither correlated to the total seminal plasma zinc concentration, nor to the concentrations of measured subfractions of zinc bound to various groups of zinc-ligands. However, most of the variations in sperm head zinc could be explained by variations in total sperm number and concentration of fructose secreted by the seminal vesicles. The results seem to justify the conclusion that the human spermatozoon takes up zinc at ejaculation from the concomitantly expelled prostatic fluid, and that zinc subsequently acts as a reversible stabilizer of the sperm chromatin. The results also imply that inappropriate stabilization by zinc of the sperm chromatin is likely to occur in spermatozoa from men with prostatic dysfunction, men expelling the spermatozoa mainly in vesicular fluid, and men expelling high total numbers of spermatozoa. The possibility is discussed that zinc stabilizes the quarternary structure of the sperm chromatin by chelating between e.g. amino- and thiol-groups of adjacent nucleoprotein fibers. Concomitantly, zinc would protect these thiol-groups from being comitted into superstabilizing disulfide-bridge crosslinks. Thereby would zinc preserve a potential of the chromatin for rapid decondensation in the ooplasm

Sperm Nuclear Zinc, Chromatin Stability, and Male Fertility

Zinc excreted from the human prostate secures a high content of zinc in the sperm nucleus and contributes to the stability of the quaternary structure of the chromatin. After ejaculation, in vitro, a second type of stability, most probably involving disulfide- bridge crosslinks, supersedes the zinc-dependent stability. Normally, the nucleus of the ejaculated spermatozoon remains stable, i.e., it does not decondense when exposed to a detergent (e.g., sodium dodecyl sulfate -SDS), whereas a spermatozoon which has been exposed to a zinc- chelating medium becomes destabilized and decondenses in SDS. Spontaneous decondensation in SDS, i.e., without prior treatment with zinc-chelators, occurs among many spermatozoa from some infertile men, especially men with impaired secretory function of the prostate. This indicates that spontaneously decondensing spermatozoa have an inadequate content of zinc at ejaculation. Here, zinc in the sperm nucleus and chromatin stability was studied in semen samples from a group of men living in marriages with hitherto unexplained cause for infertility, and a group of fertile donors, who participated in an insemination program. Sperm nuclear zinc was studied with X-ray microanalysis and chromatin stability was assessed as percentage spermatozoa with stable sperm heads after exposure to SDS. Fertile donors had higher content of zinc in the sperm nuclei and had also higher proportions spermatozoa with a stabilized chromatin, than had the men living in infertile marriages. A positive rank- correlation was found between percentage of stable spermatozoa and sperm nuclear zinc. Zinc may stabilize the chromatin by forming salt-bridges between thiol-and amino- residues of adjacent nucleoprotamine-fibers

Male reproductive health statement:(XIIIth international symposium on Spermatology, May 9th--12th 2018, Stockholm, Sweden

International audienc

Improving standard practices in studies using results from basic human semen examination

: The purpose of this article is to provide an explanation of the background behind a checklist that declares the laboratory methods used in a scientific study. It focuses primarily on implementing laboratory procedures to yield reliable results in basic semen examinations. While the World Health Organization (WHO) and international standards provide recommendations for basic semen examination, manuscripts submitted to Andrology frequently lack transparency regarding the specific techniques used. In addition, the terminology used for semen examination results often fails to provide a clear definition of the groups under study. Furthermore, the WHO's reference limits are often misinterpreted as strict boundaries between fertility and infertility. It is important to note that valid clinical andrological diagnoses and treatments cannot rely solely on semen examination results; they require proper laboratory procedures as a foundation for diagnosing and treating male patients. Therefore, scientific journals should promote the adoption of robust laboratory practices and an accurate definition of patient groups. A checklist can facilitate the design of high-quality studies and the creation of informative publications. Further, it can help journals assess submitted manuscripts and improve the overall quality of their publications

Esomeprazole reduces sperm motility index by targeting the spermic cholinergic machinery : A mechanistic study for the association between use of proton pump inhibitors and reduced sperm motility index

Recent studies have linked prolonged use of the most commonly prescribed proton pump inhibitors (PPIs) with declined human sperm function and infertility. Here, we report for the first time the most plausible underlying mechanism for this unwarranted secondary mode of action. We followed up on a recent serendipitous discovery in our laboratory regarding PPIs' off-target action and performed detailed pharmacodynamic analyses by combining in silico and in vitro studies to determine the off-target effect of one of the most commonly used PPI, esomeprazole, on the key human acetylcholine biosynthesizing enzyme, choline acetyltransferase (ChAT; EC 2.3.1.6). A pivotal enzyme in the spermic cholinergic system that governs the sperm motility, concentration and quality. Our results were conclusive and showed that both the racemic form, omeprazole and its pure S-enantiomer, esomeprazole, acted as potent mixed-competitive inhibitor of human ChAT with a global inhibition constant (Ki) of 88 nM (95%CI: 10-167 nM) for esomeprazole and 178 nM (95%CI: 140-230 nM) for the racemic drug omeprazole. Most importantly, esomeprazole substantially reduces both total number of motile sperm (by 36%, p < 0.001; and 21% p < 0.0001, at 10 and 100 nM, respectively) as well as the total number of sperm with progressive motility (by 42% p < 0.0016 and by 26% p < 0.0001, respectively) after 60 min relative to 20 min incubation in our ex vivo functional assay performed on ejaculated human sperm. In conclusion, this study presents a completely new perspective regarding PPIs secondary mode of action/unwarranted side effects and calls for further mechanistic and larger clinical studies to elucidate the role of PPIs in infertility