Reproductive infertility is characterized by the inability to achieve pregnancy after a year or more of unprotected sexual intercourse. This review highlights the significant impact of exposure to both types of heavy metals (essential and non-essential) on the reproductive performance of various species, particularly humans. Heavy metals present a high atomic density and weight, including lead, mercury, cadmium, nickel, chromium, and arsenic, and are delivered into the environment through natural and human activities, posing a threat to ecological systems and human reproductive health. These heavy metals have the potential for bioaccumulation and can adversely affect male fertility and sperm quality due to their role in disrupting endocrine functions, altering hormone levels responsible for sperm production, and inducing oxidative stress. The elevated production of reactive oxygen species (ROS) exceeds the capability of antioxidants and can lead to the alteration of sperm quality. Seminal fluid contains antioxidants like vitamin C, vitamin E, zinc, and selenium to counteract the impacts of ROS and also to preserve the sperm function. This review aims also to explore the impact of heavy metals on sperm quality and their relationship with antioxidant imbalance and ROS. The exposure to heavy metals whether through occupational or environmental means increases the production of ROS and therefore leads to an imbalance of antioxidants production. All these factors have no doubt an impact on male reproductive health.

Oocyte activation is a fundamental event in mammalian fertilization and is initiated by a cascade of calcium signaling and oscillation pathways. Phospholipase C zeta (PLCζ) is involved in modulating cortical granule exocytosis, releasing oocyte meiotic arrest, regulating gene expression, and early embryogenesis. These processes are considered to be initiated and controlled by PLCζ activity via the inositol-1,4,5-triphosphate pathway. The decrease or absence of functional PLCζ due to mutational defects in protein expression or maintenance can impair male fertility. In this literature review, we highlight the significance of PLCζ as a sperm factor involved in oocyte activation, its mechanism of action, the signaling pathway involved, and its close association with oocyte activation. Finally, we discuss the relationship between male infertility and PLCζ deficiency.

This study aimed to describe phospholipase C zeta (PLCζ) deficiency from patients who experienced oocyte fertilization failure following intracytoplasmic sperm injection (ICSI) and to investigate the relationship between sperm DNA fragmentation, chromatin decondensation, and PLCζ. A total of 135 patients participated in this study—65 fertile men and 70 infertile patients— and semen samples were obtained to analyze concentration, motility, and morphology. PLCζ protein levels were assessed by immunofluorescence and quantitative techniques, DNA fragmentation by TUNEL essay, and chromatin decondensation by aniline blue staining. The proportion of spermatozoa presenting PLCζ was significantly lower in infertile patients (18.41 ± 18.84%) compared to fertile controls (67.31 ± 13.79%) (p < 0.001). A significant decrease in PLCζ protein levels was observed in infertile patients compared to fertile controls, which was the same for localization patterns for each region (acrosomal, equatorial, and combination of these regions). Significant correlations were also observed between sperm parameters and PLCζ levels, DNA fragmentation, and chromatin decondensation. Furthermore, a statistically significant correlation was detected between the percentage of spermatozoa presenting PLCζ and DNA integrity (p < 0.001). In summary, DNA fragmentation and chromatin decondensation are associated with alterations in the localization patterns and reduced protein levels of PLCζ, which may contribute to total fertilization failure.

Background: The IL-6 levels in seminal plasma have an important impact on sperm quality. This study aimed to evaluate the correlation between IL-6 levels in seminal plasma and sperm parameters for Moroccan population. Methods: This is a case control study. Semen samples were obtained from patients who consulted the Medical Analysis Laboratory and Reproductive Biology Labomac, Casablanca, Morocco from Apr 2022 to Jun 2023, among them 50 presenting azoospermia, 25 severe oligo-astheno-teratozoospermia and 25 normozoospermia. Results: Significant differences regarding age of azoospermic patients (P=0.008) and BMI for OATS and azoospermic (P=0.032, P=0.047 respectively), also for physical activity azoospermic P<0.01 and P=0.02 for OATS patients same difference for micronutrient intake especially for zinc. Sperm parameters present also statistically significant in terms of motility, concentration, and morphology (P < 0.05). Semen interleukin-6 levels showed a significant difference for azoospermic patients (P=0.045) also for OATS (P=0.001). On the other hand, leucoscreen analysis revealed a significantly higher mean leukocytes concentration in azoospermic and OATS patients (P=0.004 and P<0.001 respectively). Conclusion: The seminal plasma IL-6 assay could be used as a sensitive biomarker of silent infection or inflammation of the male genital tract.

Mammalian fertilization involves the migration of spermatozoa through the female reproductive system. Early embryonic development is a consequence of several steps and signaling pathways being activated, as well as biochemical and morphological modifications of spermatozoa that enable them to penetrate the membrane of mature oocytes. There are some crucial steps known to clearly explain the process of fertilization, starting with hyperactivation of spermatozoa, mutual recognition, and binding of gametes mediated by receptors located on the surface membranes of both gametes. The final step is followed by oocyte activation, which is primarily triggered via sperm-derived factors, inducing a sharp increase in intracellular calcium levels, eventually leading to polyspermy block. This review integrates current knowledge of the molecular and physiological events governing fertilization, emphasizing how ion regulation and signaling pathways converge to enable sperm function and oocyte activation. Special attention is given to sperm-derived factors such as phospholipase C zeta (PLCζ) and post-acrosomal sheath WW domain-binding protein (PAWP), which play essential roles in triggering calcium release and supporting early embryonic development.