Objective: To examine the potential effects of lifestyle factors on male reproductive health. Evidence of a global decline in human sperm quality over recent decades has been accumulating. Environm...

Lifestyle causes of male infertility.

The invasion of the male reproductive tract by microorganisms, and its subsequent consequences for sperm fertilizing potential, has been intensely discussed. The role of the bacteria that are responsible for the colonization and contamination of the male urogenital tract, rather than its infection, in diminished sperm parameters raises the most controversy. There are numerous premises suggesting that bacterial semen infection is associated with male infertility. However, the molecular mechanism by which the fertility is affected is complex and multifactorial, and still presents a puzzle. Some authors have suggested that direct interactions between bacteria and human spermatozoa facilitate sperm immobilization, affect sperm morphology, and thus weaken the ability of sperm to fertilize. On the other hand, the massive infiltration of activated leukocytes into the inflammatory site may be associated with impairment of sperm fertilizing potential, due to oxidative, apoptotic, and immune processes. This review presents current research trends and aims to summarize the present knowledge of semen inflammation and causative bacterial agents in the male urogenital tract, with its consequence on seminological parameters, and male fertility status.

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Mechanisms of the harmful effects of bacterial semen infection on ejaculated human spermatozoa: potential inflammatory markers in semen

Oxidative stress (OS) has been recognized as a significant cause of suboptimal assisted reproductive outcome. Many of the sperm preparation and manipulation procedures that are necessary in the in vitro environment can result in excessive production of reactive oxygen species (ROS) thereby exposing the gametes and growing embryos to significant oxidative damage. Antioxidants have long been utilized in the management of male subfertility as they can counterbalance the elevated levels of ROS inducing a high state of OS. Few studies have looked into the clinical effectiveness of antioxidants in patients undergoing assisted reproduction. While an overall favorable outcome has been perceived, the specific clinical indication and optimal antioxidant regimen remain unknown. The goal of our review is to explore the sources of ROS in the in vitro environment and provide a clinical scenario-based approach to identify the circumstances where antioxidant supplementation is most beneficial to enhance the outcome of assisted reproduction.

/pdf/role-of-antioxidants-in-assisted-reproductive-techniques-48r6uw3j7y.pdf

Role of Antioxidants in Assisted Reproductive Techniques.

Oxidative stress (OS) is a significant cause of DNA fragmentation and is associated with poor embryo development and recurrent miscarriage. The aim of this study was to compare two different methods for assessing seminal OS and their ability to predict sperm DNA fragmentation and abnormal semen parameters. Semen samples were collected from 520 men attending for routine diagnostic testing following informed consent. Oxidative stress was assessed using either a chemiluminescence assay to measure reactive oxygen species (ROS) or an electrochemical assay to measure oxidation reduction potential (sORP). Sperm DNA fragmentation (DFI) and sperm with immature chromatin (HDS) were assessed using sperm chromatin structure assay (SCSA). Semen analysis was performed according to WHO 2010 guidelines. Reactive oxygen species sORP and DFI are negatively correlated with sperm motility (p = 0.0012, 0.0002, <0.0001 respectively) and vitality (p < 0.0001, 0.019, <0.0001 respectively). The correlation was stronger for sORP than ROS. Reactive oxygen species (p < 0.0001), sORP (p < 0.0001), DFI (p < 0.0089) and HDS (p < 0.0001) were significantly elevated in samples with abnormal semen parameters, compared to those with normal parameters. Samples with polymorphonuclear leukocytes (PMN) have excessive ROS levels compared to those without (p < 0.0001), but sORP and DFI in this group are not significantly increased. DNA fragmentation was significantly elevated in samples with OS measured by ROS (p = 0.0052) or sORP (p = 0.004). The results demonstrate the multi-dimensional nature of oxidative stress and that neither assay can be used alone in the diagnosis of OS, especially in cases of leukocytospermia.

https://www.mdpi.com/2073-4425/10/3/236/pdf

A Comparison Between Two Assays for Measuring Seminal Oxidative Stress and their Relationship with Sperm DNA Fragmentation and Semen Parameters.

https://www.fertstert.org/article/S0015-0282(15)02121-4/pdf

Sperm DNA fragmentation and mitochondrial membrane potential combined are better for predicting natural conception than standard sperm parameters.

Summary
Measurement of reactive oxygen species (ROS) producing leukocytes in semen has been a standard component of the semen analysis, but its true significance remains still unknown. In this study, we have correlated the number of seminal leukocytes to various semen parameters. We found a negative correlation between the leukocyte number and sperm concentration (rs = −0.22; p = 0.01) and motility (rs = −0.20; p = 0.02). In contrast, a positive correlation between the number of leukocytes and both seminal ROS (rs = 0.70, p < 0.001; n = 125) and the number of spermatozoa with DNA fragmentation (rs = 0.43, p = 0.032; n = 25) was found. However, only a trend of positive correlation between ROS and the number of spermatozoa with TUNEL-detected DNA fragmentation was observed. Moreover, this latter was not correlated with loss of sperm mitochondrial membrane potential (MMP) (10% vs 35%, rs = 0.25, p = 0.08; n = 50). Overall these results indicate that the presence of high number of leukocytes in the ejaculate negatively affects key semen parameters, as sperm concentration and motility, associated with infertility conditions. Moreover, they suggest that leukocytes are the major source of the seminal ROS and cause of sperm DNA fragmentation. However, the absence of a clear correlation between ROS and sperm DNA fragmentation, and spermatozoa with damaged DNA and MMP loss, suggest that ROS produced by leukocytes might be not the only cause of DNA damage in spermatozoa and that intrinsic mitochondrial-dependent apoptotic pathways might not have a major impact on sperm DNA fragmentation.

M. G. Minasi

Papers

Involvement of seminal leukocytes, reactive oxygen species, and sperm mitochondrial membrane potential in the DNA damage of the human spermatozoa