Implications of Exposure to Air Pollution on Male Reproduction: The Role of Oxidative Stress

Air pollution, either from indoor (household) or outdoor (ambient) sources, occurs when there is presence of respirable particles in the form of chemical, physical, or biological agents that modify the natural features of the atmosphere or environment. Today, almost 2.4 billion people are exposed to hazardous levels of indoor pollution, while 99% of the global population breathes air pollutants that exceed the World Health Organization guideline limits. It is not surprising that air pollution is the world's leading environmental cause of diseases and contributes greatly to the global burden of diseases. Upon entry, air pollutants can cause an increase in reactive oxygen species (ROS) production by undergoing oxidation to generate quinones, which further act as oxidizing agents to yield more ROS. Excessive production of ROS can cause oxidative stress, induce lipid peroxidation, enhance the binding of polycyclic aromatic hydrocarbons (PAHs) to their receptors, or bind to PAH to cause DNA strand breaks. The continuous and prolonged exposure to air pollutants is associated with the development or exacerbation of pathologies such as acute or chronic respiratory and cardiovascular diseases, neurodegenerative and skin diseases, and even reduced fertility potential. Males and females contribute to infertility equally, and exposure to air pollutants can negatively affect reproduction. In this review, emphasis will be placed on the implications of exposure to air pollutants on male fertility potential, bringing to light its effects on semen parameters (basic and advanced) and male sexual health. This study will also touch on the clinical implications of air pollution on male reproduction while highlighting the role of oxidative stress.

Standards in semen examination: publishing reproducible and reliable data based on high-quality methodology

Biomedical science is rapidly developing in terms of more transparency, openness and reproducibility of scientific publications. This is even more important for all studies that are based on results from basic semen examination. Recently two concordant documents have been published: the 6th edition of the WHO Laboratory Manual for the Examination and Processing of Human Semen, and the International Standard ISO 23162:2021. With these tools, we propose that authors should be instructed to follow these laboratory methods in order to publish studies in peer-reviewed journals, preferable by using a checklist as suggested in an Appendix to this article.

Statins and Male Fertility: Is There a Cause for Concern?

The well-known 3-hydroxyl 3-methyl glutaryl-Coenzyme A reductase inhibitors, called statins, have been the main medication used in the treatment of hypercholesterolemia and some cases of cardiovascular diseases. The effectiveness of this drug in controlling cholesterol production is impeccable, however, patients often complain of a variety of side effects, such as myalgia, muscle atrophy, and in some cases, rhabdomyolysis. Not only has the use of statins caused the aforementioned side effects, but they are also shown to cause testicular discomfort, erectile dysfunction, altered semen parameters, and modified steroid hormone production. These reported adverse effects on male fertility are not generally agreed upon, as some have shown the use to be beneficial. Hence, this makes the aftermath effect of statin use on male fertility debatable and controversial. The negative effects have been associated with imbalanced or reduced steroid hormones, which are necessary for proper spermatogenesis and other sexual functions. Meanwhile, the beneficial effects are related to statin's anti-inflammatory and cardioprotective properties. These contradictory findings are in part due to the different age of users, concentrations of statins, the type and duration of treatment, and the underlying disease and/or comorbidities. Therefore, the current study aims to analyze the literature and gather evidence as to the effects of statin on male sexual health and reproductive parameters, and subsequently give recommendations for the direction of future studies.

Oxidative Stress and Male Infertility: Evidence From a Research Perspective

Male fertility potential can be influenced by a variety of conditions that frequently coincide. Spermatozoa are particularly susceptible to oxidative damage due to their limited antioxidant capacity and cell membrane rich in polyunsaturated fatty acids (PUFAs). The role of oxidative stress (OS) in the etiology of male infertility has been the primary focus of our Stellenbosch University Reproductive Research Group (SURRG) over the last 10 years. This review aims to provide a novel insight into the impact of OS on spermatozoa and male reproductive function by reviewing the OS-related findings from a wide variety of studies conducted in our laboratory, along with those emerging from other investigators. We will provide a concise overview of the production of reactive oxygen species (ROS) and the development of OS in the male reproductive tract along with the physiological and pathological effects thereof on male reproductive functions. Recent advances in methods and techniques used for the assessment of OS will also be highlighted. We will furthermore consider the current evidence regarding the association between OS and ejaculatory abstinence period, as well as the potential mechanisms involved in the pathophysiology of various systemic diseases such as obesity, insulin resistance, hypertension, and certain mental health disorders which have been shown to cause OS induced male infertility. Finally, special emphasis will be placed on the potential for transferring and incorporating research findings emanating from different experimental studies into clinical practice.

Cementing the relationship between conventional and advanced semen parameters

Background

Affordable conventional semen analysis remains a fundamental procedure to be performed routinely during the diagnosis of male infertility. Advanced semen analyses provide valuable clinical insights in treatment-related decision-making, but these are highly expensive and lack universal standardization. This study aimed at determining the relationship between conventional semen parameters, measured with assistance of computer-aided sperm analysis (CASA), and a set of advanced semen tests. Basic semen analysis (n = 124) was performed according to the World Health Organization (WHO) guidelines. Sperm DNA fragmentation and intracellular superoxide (O2−•) levels were assessed by flow cytometry. Seminal plasma thiobarbituric acid reactive substances (TBARS) levels as well as superoxide dismutase (SOD) and catalase (CAT) activity were measured by spectrophotometry. Spearman’s rank correlation coefficient was used, with significance set at p < 0.05.

Results

Semen pH correlated negatively with TBARS (p < 0.01). The proportions of total and progressively motile as well as rapid spermatozoa correlated positively with CAT activity (p < 0.05). Sperm viability correlated negatively with both O2−• (p < 0.05) and DNA fragmentation (p = 0.01), while normal morphology correlated negatively with O2−• levels (p < 0.05) and positively with CAT activity (p < 0.05). Straight-line velocity (VCL) and average-path velocity (VAP) correlated negatively with both O2−• (p < 0.01) and TBARS (p < 0.01). Amplitude of lateral head displacement (ALH) correlated negatively with O2−• (p < 0.01) and DNA fragmentation (p < 0.01), while its correlation with SOD activity was positive (p < 0.05).

Conclusion

The results obtained from this study support the validity of some CASA parameters as sensitive indicators of changes in sperm oxidative status and DNA integrity. Predicting advanced from conventional parameters through the building of linear regression models should be considered for future studies.

Taking a Leap of Faith: A Study of Abruptly Transitioning an Undergraduate Medical Education Program to Distance-Learning Owing to the COVID-19 Pandemic

The COVID-19 pandemic has forced universities worldwide to immediately transition to distance-learning. Although numerous studies have investigated the effect of the COVID-19 pandemic on universities in the Middle East, none have reflected on the process through which medical education programs for health professions underwent this transition. This study aimed to elucidate the rapid transition to distance-learning of an undergraduate medical program at the College of Medicine, Mohammad Bin Rashid University of Medicine and Health Sciences (Dubai, United Arab Emirates), owing to the COVID-19 pandemic. An action research approach constituted the foundation of this collaborative effort that involved investigations, reflections, and improvements of practice, through ongoing cycles of planning, acting, observing, and reflecting. Efforts of transitioning to distance-learning were grouped into four interrelated aspects: supporting faculty members in delivering the program content, managing curriculum changes, engaging with the students to facilitate distance-learning experiences, and conducting web-based assessments. Challenges included the high perceived uncertainty, need for making ad hoc decisions, lack of experiential learning and testing of clinical skills, and blurring of work-life boundaries. Our preliminary findings show the successful generation of a strong existing digital base, future prospects for innovation, and a cohesive team that was key to agility, rapid decision-making, and program implementation.

The effect of streptozotocin induced diabetes on sperm function: a closer look at AGEs, RAGEs, MAPKs and activation of the apoptotic pathway

This study was designed to (1) investigate the possible mechanisms through which diabetes-induced advanced glycation end products (AGEs) and receptor for AGEs (RAGE) activation can affect male reproductive function; and (2) corroborate the interaction of previously established independent pathways. Male albino Wistar rats (14-weeks old) weighing 250-300 g received either a single intraperitoneal injection of streptozotocin (30 mg/kg or 60 mg/kg), represented as STZ30 or STZ60 respectively, or citrate buffer (control). Diabetes mellitus (DM) was confirmed if plasma glucose levels were ≥ 14 mmol/L after 1 week. Animals were sacrificed after 8 weeks of treatment by an overdose of sodium pentobarbital (160 mg/kg body weight). The testes and epididymides were harvested. The testes were used for biochemical and Western blot analysis, while sperm was retrieved from the epididymis and analysed with computer-aided sperm analysis. The blood glucose levels of STZ60 animals were above the cut-off point and hence these animals were regarded as diabetic. Diabetic animals presented with a non-significant increase in AGE and RAGE expression. Diabetic animals showed a significant increase in the expression of cleaved caspase 3 compared to control (p < 0.001), and these animals also presented with an increase in the expression of JNK (p < 0.05), PARP (p = 0.059) and p38 MAPK (p = 0.1). Diabetic animals also displayed decreased catalase activity accompanied by a non-significant increase in malondialdehyde levels. Additionally, there was a significant decrease in the percentage of progressively motile spermatozoa (p < 0.05) in diabetic animals. This study has shed some light on the interplay between DM, AGE, RAGE and mitogen-activated protein kinase signalling in the testes of diabetic rats, which can result in altered sperm function and contribute to male infertility. However, more studies are needed to better understand this complicated process.

The Effect of Rooibos (Aspalathus linearis), Honeybush (Cyclopia intermedia) and Sutherlandia (Lessertia frutescens) on Testicular Insulin Signalling in Streptozotocin-Induced Diabetes in Wistar Rats

BACKGROUND

Testicular insulin signalling is altered in diabetic (DM) males. While unravelling the mechanism through which DM exert these detrimental effects, studies have shown the importance of insulin regulation in glucose homeostasis, and how a lack in insulin secretion indirectly led to reduced male fertility. The current study aimed to investigate the role of rooibos, honeybush and Sutherlandia on insulin signalling in the testicular tissue of type I diabetic rats.

METHODS

Animals (n=60) were randomly divided into six groups. The groups include a control group, a vehicle group, and diabetes was induced in the remainder of animals via a single intraperitoneal injection of STZ at 45mg/kg. The remaining four groups included a diabetic control (DC), diabetic + rooibos (DRF), diabetic + honeybush (DHB) and diabetic + Sutherlandia group (DSL). Animals were sacrificed after seven weeks of treatment, and blood and testes were collected.

RESULTS

All diabetic groups (DC, DRF, DHB, DSL) presented with a significant increase in blood glucose levels after diabetes induction compared to the control and vehicle (p<0.001). The DC animals presented with decreased testicular protein expression of IRS-1, PkB/Akt and GLUT4 compared to controls. DRF and DHB animals displayed an acute upregulation in IRS-1, while the DSL group showed improvement in IRS-2 compared to DC. Although, DRF animals presented with a decrease in PkB/Akt, DHB and DSL animals displayed upregulation (22.3%, 48%) compared to controls, respectively.

CONCLUSION

The results taken together, it can be suggested that these infusions may enhance insulin signalling through diverse pathways.

SARS-CoV-2 and the testis: similarity with other viruses and routes of infection

Since the start of the latest coronavirus (SARS-CoV-2) outbreak, the number of infected individuals and cases of coronavirus disease (COVID-19) has been increasing exponentially worldwide. Of interest is existing evidence that orchitis can develop due coronavirus infection. It is therefore not unreasonable to believe that SARS-CoV-2 could be transmitted by semen. Consequently, it is of paramount importance that individuals who could potentially be infected take all possible care to mitigate the likely risk of passing on the infection through sexual intercourse.

The Uruguayan semen donor population: A twenty-eight-year retrospective study

Several studies have reported a global decline in seminal quality over the years. The objective of this study was to describe the semen donor population of Uruguay through comparing data of successive samples banked by the same donors and the analysis of their semen and physical characteristics, ancestry origin and educational level. A total of 3,449 ejaculated samples collected from 71 donors, cryobanked between 1989 and March 2017 at Fertilab, were analysed. Results revealed a mean age of 23.90 ± 3.98 years, an average weight of 74.95 ± 1.09 kg and a mean height of 1.78 ± 0.06 m. The majority of the donors trace their origin to Europe (74.65%, 53/71) and 66.19% (47/71) have a level of education higher than secondary school. We observed longitudinal differences in two parameters, that is sperm concentration and semen volume. Sperm concentration declined, while semen volume increased significantly over the 28-year period. The results of the present study are in accordance with that of previous articles that also reported a decline in sperm concentration over time. However, no differences were observed in total sperm number per ejaculate due to the increase in semen volume values, thus reflecting no real changes in sperm production over time.

Modulation of Inflammatory Cytokines and Islet Morphology as Therapeutic Mechanisms of Basella alba in Streptozotocin-Induced Diabetic Rats

The mechanism of the previously reported antidiabetic effect of Basella alba is unknown. This study investigated the role of B. alba aqueous leaf extract in the modulation of inflammatory cytokines and islet morphology in streptozotocin-induced diabetic rats. Forty male Wistar rats, between 8 and 10 weeks old, were randomly divided into four groups (n = 10) and administered the following treatments: Healthy control (H-c) and Diabetic control (D-c) animals received normal saline 0.5 mL/100 g body weight daily, while Healthy Treatment (H-Ba) and Diabetic Treatment (D-Ba) rats received the plant extract 200 mg/kg body weight daily. All treatments were administered by oral gavage. Diabetes was induced in D-c and D-Ba rats by a single intraperitoneal injection of streptozotocin (55 mg/kg body). The body weight and fasting blood sugar (FBS) levels were recorded every week for 4 weeks, after which the rats were euthanized and samples collected for further analysis. After the experiment, FBS level was significantly reduced (p < 0.0001) in rats in the D-Ba group, but increased (p < 0.001) in rats in the D-c group. The absolute (H-c and H-Ba vs D-c, p < 0.05) and relative (D-Ba vs H-c, p < 0.05; D-Ba vs H-Ba, p < 0.005) weights of the pancreases were significantly higher after the experiment. The rats in the D-c group had significantly higher levels of serum interleukin-1β (p < 0.001 vs H-c; p < 0.05 vs H-Ba and D-Ba) and monocyte chemotactic protein-1 (p < 0.0001), but lower levels of interleukin-10 (p < 0.05) in comparison with the other groups. Histopathological examination revealed severe interstitial congestion, reduced islet area (p < 0.0001), and increased islet cell density in the D-c group compared with those in the D-Ba group. From these findings, it was concluded that the aqueous extract of B. alba stimulates the recovery of beta-islet morphology in streptozotocin-induced diabetic rats by modulating the peripheral production of inflammatory cytokines.

Revisiting The Relationship between The Ejaculatory Abstinence Period and Semen Characteristics

Variation in the ejaculatory abstinence period suggested by different guidance bodies have resulted in a growing concern among researchers and clinicians over what the precise period of ejaculatory abstinence ought to be for an optimal semen sample. Several studies have thus been undertaken to examine the association between the length of sexual abstinence and semen characteristics. Not all studies, however, have arrived at the same conclusions. This study aims to review all existing literature published during the past few decades pertaining to the influence of ejaculatory abstinence on semen quality. For the purpose of this systematic review, all data related to sexual abstinence duration and seminal parameters were re-analysed to homogenize the current data. Thorough PubMed, MEDLINE and Google Scholar, a literature search was conducted using the keywords "sexual abstinence", "ejaculatory abstinence", "semen", "spermatozoa", "semen analysis", "sperm parameters", "motility", "reactive oxygen species (ROS)" and "DNA fragmentation". After carefully reviewing all the literature, 30 relevant papers, both written in English and published between January 1979 and December 2016, were included in this review. The weight of the evidence suggests that the decline in semen volume and sperm concentration with shorter abstinence periods is accompanied by a substantial improvement in sperm motility characteristics, especially progressive motility and velocity. Nevertheless, available data are insufficient to support definitive conclusions regarding the influence of the ejaculatory abstinence period on advanced semen parameters (ROS, DNA fragmentation and seminal plasma antioxidant capacity) and pregnancy rates. In conclusion, taking all data into account, shortening of the abstinence period may be beneficial to sperm quality. Furthermore, we recommend that the current guidelines regarding the prescribed abstinence period should be revisited.

Contemporary evidence on the physiological role of reactive oxygen species in human sperm function

Reactive oxygen species (ROS) play an important role in male fertility. Overproduction of reactive oxygen species (ROS) has been associated with a variety of male fertility complications, including leukocytospermia, varicocele and idiopathic infertility. The subsequent oxidative insult to spermatozoa can manifest as insufficient energy metabolism, lipid peroxidation and DNA damage, leading to loss of motility and viability. However, various studies have demonstrated that physiological amounts of ROS play important roles in the processes of spermatozoa maturation, capacitation, hyperactivation and acrosome reaction. It is therefore crucial to define and understand the delicate oxidative balance in male reproductive cells and tissues for a better understanding of both positive as well as negative impact of ROS production on the fertilizing ability. This review will discuss the specific physiological roles, mechanisms of action and effects that ROS have on the acquisition of structural integrity and physiological activity of spermatozoa.

Proteomic analysis of seminal fluid from men exhibiting oxidative stress

BACKGROUND

Seminal plasma serves as a natural reservoir of antioxidants. It helps to remove excessive formation of reactive oxygen species (ROS) and consequently, reduce oxidative stress. Proteomic profiling of seminal plasma proteins is important to understand the molecular mechanisms underlying oxidative stress and sperm dysfunction in infertile men.

METHODS

This prospective study consisted of 52 subjects: 32 infertile men and 20 healthy donors. Once semen and oxidative stress parameters were assessed (ROS, antioxidant concentration and DNA damage), the subjects were categorized into ROS positive (ROS+) or ROS negative (ROS-). Seminal plasma from each group was pooled and subjected to proteomics analysis. In-solution digestion and protein identification with liquid chromatography tandem mass spectrometry (LC-MS/MS), followed by bioinformatics analyses was used to identify and characterize potential biomarker proteins.

RESULTS

A total of 14 proteins were identified in this analysis with 7 of these common and unique proteins were identified in both the ROS+ and ROS- groups through MASCOT and SEQUEST analyses, respectively. Prolactin-induced protein was found to be more abundantly present in men with increased levels of ROS. Gene ontology annotations showed extracellular distribution of proteins with a major role in antioxidative activity and regulatory processes.

CONCLUSIONS

We have identified proteins that help protect against oxidative stress and are uniquely present in the seminal plasma of the ROS- men. Men exhibiting high levels of ROS in their seminal ejaculate are likely to exhibit proteins that are either downregulated or oxidatively modified, and these could potentially contribute to male infertility.

New developments of the effect of melatonin on reproduction

In the past decades, a lot of advances in understanding the biochemistry and physiology of the pineal gland have been made. There is evidence that it interacts with many endocrine as well as non-endocrine tissues to influence their metabolic activity modulating many organs and functions. Melatonin is secreted by the pineal gland in the brain and plays an important role in regulating the neuroendocrine system. This hormone is one of the major role players in the regulation of the circadian sleep-wake cycle. It is normally released from the pineal gland during the night in response to environmental changes in light. Studies have shown that melatonin plays a role in the regulation of many reproductive processes such as puberty, gonadal function, and pregnancy. Beside these, melatonin has been shown to be able to directly neutralize a number of free radicals and reactive oxygen and nitrogen species. The main objective of this review is to provide comprehensive information about the new developments in melatonin research regarding its role in reproduction. A review of international scientific literature was done and a question-and-answer format was used in an attempt to convey comprehensive information in a simple manner. This review discusses evidence currently available relating to the effect of melatonin on reproductive processes. It deliberates the mechanism of action of melatonin, its effect on puberty, testicular and ova function, pregnancy, and oxidative stress. A growing body of scientific evidence is suggesting that melatonin plays an important role in reproductive function. It is therefore imperative to highlight the beneficial effects of this hormone in improving the reproductive processes.

Obesity: modern man's fertility nemesis

The obesity pandemic has grown to concerning proportions in recent years, not only in the Western World, but in developing countries as well. The corresponding decrease in male fertility and fecundity may be explained in parallel to obesity, and obesity should be considered as an etiology of male fertility. Studies show that obesity contributes to infertility by reducing semen quality, changing sperm proteomes, contributing to erectile dysfunction, and inducing other physical problems related to obesity. Mechanisms for explaining the effect of obesity on male infertility include abnormal reproductive hormone levels, an increased release of adipose-derived hormones and adipokines associated with obesity, and other physical problems including sleep apnea and increased scrotal temperatures. Recently, genetic factors and markers for an obesity-related infertility have been discovered and may explain the difference between fertile obese and infertile obese men. Treatments are available for not only infertility related to obesity, but also as a treatment for the other comorbidities arising from obesity. Natural weight loss, as well as bariatric surgery are options for obese patients and have shown promising results in restoring fertility and normal hormonal profiles. Therapeutic interventions including aromatase inhibitors, exogenous testosterone replacement therapy and maintenance and regulation of adipose-derived hormones, particularly leptin, may also be able to restore fertility in obese males. Because of the relative unawareness and lack of research in this area, controlled studies should be undertaken and more focus should be given to obesity as an etiolgy of male infertility.

The effect of obesity on sperm disorders and male infertility

The results of several studies point to an increased likelihood of abnormal semen parameters among overweight men, and an elevated risk for subfertility among couples in which the male partner is obese. Obesity is, therefore, associated with a higher incidence of male factor infertility. Several mechanisms might account for the effect of obesity on male infertility, both directly and indirectly, by inducing sleep apnea, alterations in hormonal profiles (reduced inhibin B and androgen levels accompanied by elevated estrogen levels) and increased scrotal temperatures, ultimately manifesting as impaired semen parameters (decreased total sperm count, concentration and motility; increased DNA fragmentation index). Neither the reversibility of obesity-associated male infertility with weight loss nor effective therapeutic interventions have been studied in-depth. The increasing prevalence of obesity calls for greater clinical awareness of its effects on fertility, better understanding of underlying mechanisms, and exploration into avenues of treatment.