A Study to Validate the Relevance of Semen F2-Isoprostanes on Human Male Infertility

Evaluation of Known Markers of Ferroptosis in Semen of Patients with Different Reproductive Pathologies and Fertile Men

This study aims to investigate the role of ferroptosis, an iron-dependent form of regulated cell death, in male infertility. The motivation behind this research stems from the increasing recognition of oxidative stress and iron metabolism dysregulation as critical factors in male reproductive health. In this study, 28 infertile patients (grouped by the presence of urogenital infections or varicocele) and 19 fertile men were selected. Spermiograms were performed by light microscopy (WHO, 2021). Testosterone, ferritin, transferrin-bound iron, transferrin, and F2-isoprostanes (F2-IsoPs) were detected in seminal plasma. Glutathione peroxidase 4 (GPX4) and acyl coenzyme A synthetase long chain family member 4 (ACSL4) were also assessed in sperm cells using enzyme-linked immunosorbent assays (ELISA). All the variables were correlated (statistically significant Spearman's rank correlations) in the whole population, and then the comparison between variables of the different groups of men were carried out. Seminal ferritin and transferrin positively correlated with seminal F2-IsoPs, which had positive correlations with ACSL4 detected in sperm cells. Ferritin and ACSL4 negatively correlated with the seminal parameters. No correlation was detected for GPX4. Comparing the variables in the three examined groups, elevated levels of ACSL4 were observed in infertile patients with urogenital infections and varicocele; GPX4 levels were similar in the three groups. These results suggested a mechanism of ferroptosis, identified by increased ACSL4 levels and the occurrence of lipid peroxidation. Such events appear to be GPX4-independent in reproductive pathologies such as varicocele and urogenital infections.

A Possible Role for Nerve Growth Factor and Its Receptors in Human Sperm Pathology

Nerve growth factor (NGF) signalling affects spermatogenesis and mature sperm traits. In this paper, we aimed to evaluate the distribution and the role of NGF and its receptors (p75NTR and TrKA) on the reproductive apparatus (testis and epididymis) and sperm of fertile men (F) and men with different pathologies, namely varicocele (V) and urogenital infections (UGIs). We collected semen samples from 21 individuals (31-40 years old) subdivided as follows: V (n = 7), UGIs (n = 7), and F (n = 7). We submitted the semen samples to bacteriological analysis, leucocyte identification, and analysis of sperm parameters (concentration, motility, morphology, and viability). We determined the seminal plasma levels of NGF, interleukin 1β (IL-1β), and F2-isoprostanes (F2-IsoPs), and the gene and protein expression of NGF receptors on sperm. We also used immunofluorescence to examine NGF receptors on ejaculated sperm, testis, and epididymis. As expected, fertile men showed better sperm parameters as well as lower levels of NGF, F2-IsoPs, and IL-1β compared with men with infertility. Notably, in normal sperm, p75NTR and TrKA were localised throughout the entire tail. TrKA was also found in the post-acrosomal sheath. This localisation appeared different in patients with infertility: in particular, there was a strong p75NTR signal in the midpiece and the cytoplasmic residue or coiled tails of altered ejaculated sperm. In line with these findings, NGF receptors were intensely expressed in the epididymis and interstitial tissue of the testis. These data suggest the distinctive involvement of NGF and its receptors in the physiology of sperm from fertile men and men with infertility, indicating a possible role for new targeted treatment strategies.

Relevance of PUFA-derived metabolites in seminal plasma to male infertility

Aim

This study aims to investigate the biological effects of polyunsaturated fatty acid (PUFA)-derived metabolites in seminal plasma on male fertility and to evaluate the potential of PUFA as a biomarker for normozoospermic male infertility.

Methods

From September 2011 to April 2012, We collected semen samples from 564 men aged 18 to 50 years old (mean=32.28 years old)ch., residing in the Sandu County, Guizhou Province, China. The donors included 376 men with normozoospermia (fertile: n=267; infertile: n=109) and 188 men with oligoasthenozoospermia (fertile: n=121; infertile: n=67). The samples thus obtained were then analyzed by liquid chromatography-mass spectrometry (LC-MS) to detect the levels of PUFA-derived metabolites in April 2013. Data were analyzed from December 1, 2020, to May 15, 2022.

Results

Our analysis of propensity score-matched cohorts revealed that the concentrations of 9/26 and 7/26 metabolites differed significantly between fertile and infertile men with normozoospermia and oligoasthenozoospermia, respectively (FDR < 0.05). In men with normozoospermia, higher levels of 7(R)-MaR1 (HR: 0.4 (95% CI [0.24, 0.64]) and 11,12-DHET (0.36 (95% CI [0.21, 0.58]) were significantly associated with a decreased risk of infertility, while higher levels of 17(S)-HDHA (HR: 2.32 (95% CI [1.44, 3.79]), LXA5 (HR: 8.38 (95% CI [4.81, 15.24]), 15d-PGJ2 (HR: 1.71 (95% CI [1.06, 2.76]), and PGJ2 (HR: 2.28 (95% CI [1.42, 3.7]) correlated with an increased risk of infertility. Our ROC model using the differentially expressed metabolites showed the value of the area under the curve to be 0.744.

Conclusion

The PUFA-derived metabolites 7(R)-MaR1, 11,12-DHET, 17(S)-HDHA, LXA5, and PGJ2 might be considered as potential diagnostic biomarkers of infertility in normozoospermic men.

Human Sperm as an In Vitro Model to Assess the Efficacy of Antioxidant Supplements during Sperm Handling: A Narrative Review

Spermatozoa are highly differentiated cells that produce reactive oxygen species (ROS) due to aerobic metabolism. Below a certain threshold, ROS are important in signal transduction pathways and cellular physiological processes, whereas ROS overproduction damages spermatozoa. Sperm manipulation and preparation protocols during assisted reproductive procedures-for example, cryopreservation-can result in excessive ROS production, exposing these cells to oxidative damage. Thus, antioxidants are a relevant topic in sperm quality. This narrative review focuses on human spermatozoa as an in vitro model to study which antioxidants can be used to supplement media. The review comprises a brief presentation of the human sperm structure, a general overview of the main items of reduction-oxidation homeostasis and the ambivalent relationship between spermatozoa and ROS. The main body of the paper deals with studies in which human sperm have been used as an in vitro model to test antioxidant compounds, including natural extracts. The presence and the synergic effects of different antioxidant molecules could potentially lead to more effective products in vitro and, in the future, in vivo.

PUFAs and Their Derivatives as Emerging Players in Diagnostics and Treatment of Male Fertility Disorders

About 15% of couples worldwide are affected by infertility, with the male factor responsible for approximately 50% of reproductive failures. Male fertility can be influenced by various factors, including an unhealthy lifestyle and diet, often associated with oxidative stress. These changes are frequently the reason for spermatozoan dysfunction, malformations, and lowered count. However, sometimes even with proper semen parameters, fertilization does not occur, and this is referred to as idiopathic infertility. Of particular importance may be molecules contained in the spermatozoan membrane or seminal plasma, such as polyunsaturated fatty acids, including omega-3 (docosahexaenoic and eicosapentaenoic acids) and omega-6 (arachidonic acid) fatty acids and their derivatives (prostaglandins, leukotrienes, thromboxanes, endocannabinoids, isoprostanes), which are vulnerable to the effects of oxidative stress. In the present review, we discuss the influence of these molecules on human male reproductive health and its possible causes, including disrupted oxidative-antioxidative balance. The review also discusses the potential use of these molecules in the diagnostics and treatment of male infertility, with a particular focus on the innovative approach to isoprostanes as biomarkers for male infertility. Given the high occurrence of idiopathic male infertility, there is a need to explore new solutions for the diagnosis and treatment of this condition.

Arachidonic Acid Pathways and Male Fertility: A Systematic Review

Arachidonic acid (AA) is a polyunsaturated fatty acid that is involved in male fertility. Human seminal fluid contains different prostaglandins: PGE (PGE₁ and PGE₂), PGF_2α, and their specific 19-hydroxy derivatives, 18,19-dehydro derivatives of PGE₁ and PGE₂. The objective of this study is to synthesize the available literature of in vivo animal studies and human clinical trials on the association between the AA pathway and male fertility. PGE is significantly decreased in the semen of infertile men, suggesting the potential for exploitation of PGE agonists to improve male fertility. Indeed, ibuprofen can affect male fertility by promoting alterations in sperm function and standard semen parameters. The results showed that targeting the AA pathways could be an attractive strategy for the treatment of male fertility.

Oxidation of Polyunsaturated Fatty Acids as a Promising Area of Research in Infertility

In this review, the role of fatty acids (FA) in human pathological conditions, infertility in particular, was considered. FA and FA-derived metabolites modulate cell membrane composition, membrane lipid microdomains and cell signaling. Moreover, such molecules are involved in cell death, immunological responses and inflammatory processes. Human health and several pathological conditions are specifically associated with both dietary and cell membrane lipid profiles. The role of FA metabolism in human sperm and spermatogenesis has recently been investigated. Cumulative findings indicate F₂ isoprostanes (oxygenated products from arachidonic acid metabolism) and resolvins (lipid mediators of resolution of inflammation) as promising biomarkers for the evaluation of semen and follicular fluid quality. Advanced knowledge in this field could lead to new scenarios in the treatment of infertility.