Linear and non-linear relationships between sulfur dioxide and semen quality: A longitudinal study in Anhui, China

Sulfur dioxide increases testosterone biosynthesis by activating ERK1/2 pathway and disrupting autophagy in Leydig cells

Sulfur dioxide (SO2) is a ubiquitous environmental pollutant that has been shown to be toxic to the male reproductive system, but the underlying mechanism remains unclear. Therefore, the SO2-treated mice and primary Leydig cell models were established to investigate the effects of SO2 on the production of testosterone and its specific mechanism. The results demonstrated that SO2 activated the ERK1/2 signaling pathway, leading to increased key proteins expression of testosterone biosynthesis and elevated testosterone levels. The addition of ERK1/2 inhibitor U0126 attenuated SO2-induced increases in key testosterone biosynthetic gene mRNA levels of Star, Cyp17a1, Hsd3b1, and testosterone. Low doses of SO2 reduced the expression of BECLIN1 and LC3 proteins, increased P-4E-BP1 protein expression, and decreased autophagy in Leydig cells. Moreover, increasing doses of SO2 correlate with enhanced Leydig cell autophagy and testosterone levels initially. However, increasing the dose of SO2 resulted in a significant decrease in cell viability and ultimately decreased testosterone levels. These findings suggest that SO2 promotes testosterone production by activating ERK1/2 and disrupting autophagy. This study enriched the dose-effect relationship of SO2 on the male reproductive system and provided a theoretical reference for us to have a comprehensive and dynamic understanding of the SO2 toxic mechanism.

Can nutraceuticals counteract the detrimental effects of the environment on male fertility? A parallel systematic review and expert opinion

INTRODUCTION

Male fertility relies on a complex physiology that may be negatively influenced by lifestyle, diet, and environment. The beneficial effect of nutraceuticals on male fertility is a debated claim. The aim of this study was to assess if the positive effect of nutraceuticals can counteract the negative effects of the environment on male fertility.

EVIDENCE ACQUISITION

PubMed®/MEDLINE®, Embase and Cochrane Database were searched (September-October 2023), along with crosschecking of references and search for ongoing studies of the effects of the environment and nutraceuticals on male fertility, in accordance with the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).

EVIDENCE SYNTHESIS

Several environmental factors such as microplastic and other endocrine-disrupting chemicals and climate changes may affect the sperm quality in terms of reduction of sperm count number, mobility and altered morphology and thereby reduce male fertility. On the other hand, new evidence demonstrates that a balanced diet rich in antioxidants and essential nutrients, together with minimized exposure to environmental toxins, may improve male fertility and reproductive health. Several nutraceutical compounds proved a protective role against negative environmental effects on male fertility.

CONCLUSIONS

Available evidence confirms that the environment may negatively impact male fertility, and this impact is estimated to rise in the forthcoming years. On the other hand, new data indicate that nutraceuticals may have a protective role against the negative impact of environmental factors on male fertility. The need for future studies to monitor and explore these aspects of men's health cannot be underestimated.

Association of specific PM2.5 chemical constituents and ozone exposure with pregnancy outcomes in women undergoing assisted reproductive technology treatment in central China

The associations of air pollutants exposure with assisted reproductive technology (ART) pregnancy outcomes are mixed, and the effects of specific components of fine particulate matter (PM2.5) and ozone (O3) are not well understood. We conducted a retrospective longitudinal study to explore the association of PM2.5 constituents and O3 exposure with three ART outcomes among women undergoing ART treatment. The exposure window was segmented into five periods corresponding to the cycle of ovarian stimulation and oocyte retrieval procedure. Generalized linear mixed model (GLMM) was applied to explore the relationships between PM2.5 constituents, O3, Normalized Vegetation Index (NDVI) exposure and three ART outcomes. The combined effect of PM2.5 constituents was evaluated by the quantile g (qg)-computation. We also explored the modifying effect of different covariate. Elevated exposure level of PM2.5 (OR = 0.915, 95% CI: 0.859, 0.974) and its constituents (BC: 0.905, 95% CI: 0.840, 0.975; OM: 0.910, 95% CI: 0.848, 0.976; NO3-: 0.909, 95% CI: 0.850, 0.972, SO42-: 0.905, 95% CI: 0.846, 0.968, and NH4+: 0.902, 95% CI: 0.842, 0.966) exposure throughout the year before oocyte retrieval (period 1) was correlated with a reduced odds ratio (OR) of live birth with statistical significance. Similarly, for each interquartile range (IQR) increase in O3 exposure during periods 2 (85 days prior to oocyte retrieval), 3 (30 days prior to oocyte retrieval), 4 (oocyte retrieval to embryo transfer) and 5 (embryo transfer to hCG test) was significantly related to a decreased OR of live birth. Especially, participants who underwent fresh embryo transfer cycles and received two cleavage-stage embryo transfer, and were younger than 30 years old, showed a higher susceptibility to particulate matter. Findings from this study suggest that PM2.5 constituents and O3 exposure may have adverse effects on the ART outcomes, highlighting the importance of identifying critical exposure periods for various air pollutants and the need for meticulous management of particulate matter.

Critical windows for exposure to chemical composition of ambient particulate matter and human semen quality decline

BACKGROUND

Critical windows for exposure to chemical components of particulate matter (PM <2.5 μm in diameter [PM2.5]) associated with the human semen quality decline remain unclear.

OBJECTIVES

To address this gap, we developed a new analytical framework by integrating a Linear Mixed Model (LMM) with subject- and center-specific intercepts and a Distributed Lag Model (DLM) to fully account for correlations between finely vulnerable exposure windows based on complete profile of the spermatogenesis cycle.

METHODS

We constructed a multicenter cohort involving 33,234 sperm donors with 78,952 semen samples covering 6 representative regions across China from 2014 to 2020 to investigate the week-scale critical windows for the exposure. Daily exposure to PM2.5 chemical components of donors was derived from grid data based on 1-km spatial resolution surface measurements.

RESULTS

Decreased sperm count was significantly associated with NO3- and SO42- at 9-10 weeks (e.g., β: -0.05 %, 95%CI: [-0.10 %, -0.00 %] at the 9th week) and 0-2 weeks (e.g., β: -0.66 %, 95%CI: [-1.24 %, -0.07 %] at the 1st week), respectively. Critical windows of progressive motility decline were 0-10 weeks for BC (e.g., β: -0.07 %, 95%CI: [-0.11 %, -0.03 %] at the 5th week), Cl- at 1-4 weeks (e.g., β: -2.21 %, 95%CI: [-3.77 %, -0.66 %] at the 2nd week), 0-6 weeks and 9-10 weeks for NO3- (e.g., β: -0.05 %, 95%CI: [-0.09 %, -0.01 %] at the 4th week), 1-3 weeks and the 8th week for NH4+ (e.g., β: -0.06 %, 95%CI: [-0.11 %, -0.01 %] at the 2nd week). Total motility is significantly negatively associated with BC at entire windows, Cl- at 0-3 weeks, the 5th week and 9-10 weeks.

CONCLUSIONS

There are week-scale vulnerable windows of exposure to PM2.5 chemical components for human semen quality. This highlights the need for more targeted pollution control strategies addressing PM2.5 and its chemical components.

Environmental toxins and reproductive health: unraveling the effects on Sertoli cells and the blood-testis barrier in animals†

Environmental pollution is an inevitable ecological issue accompanying the process of socialization, with increasing attention to its impacts on individual organisms and ecological chains. The reproductive system, responsible for transmitting genetic material in animals, is one of the most sensitive systems to environmental toxins. Research reveals that Sertoli cells are the primary target cells for the action of environmental toxins. Different environmental toxins mostly affect the blood-testis barrier and lead to male reproductive disorders by disrupting Sertoli cells. Therefore, this article provides an in-depth exploration of the toxic mechanisms of various types of environmental toxins on the male testes. It reveals the dynamic processes of tight junctions in the blood-testis barrier affected by environmental toxins and their specific roles in the reconstruction process.

Negative association of atmospheric pollutants with semen quality: A cross-sectional study in Taiyuan, China

BACKGROUND

In recent decades, the quality of male semen has decreased worldwide. Air pollution has been linked to lower semen quality in several studies. However, the effects of atmospheric pollutants on different semen characteristics have not always been consistent. The aim of this study was to investigate the association between the Air Quality Index (AQI) and six atmospheric pollutants (PM2.5, PM10, SO2, NO2, CO, and O3), semen quality, and their key exposure window periods.

METHODS

This study included 1711 semen samples collected at the reproductive clinics of the First Affiliated Hospital of Shanxi Medical University in Taiyuan, Shanxi, China, from October 10, 2021, to September 30, 2022. We evaluated the association of AQI and six atmospheric pollutants with semen quality parameters throughout sperm development and three key exposure windows in men using single-pollutant models, double-pollutant models, and subgroup analyses of semen quality-eligible groups.

RESULTS

Both the single-pollutant model and subgroup analyses showed that PM, CO, and O3 levels were negatively correlated with total and progressive motility. At 70-90 d before semen collection, CO exposure and semen volume (β =-1.341, 95 % CI: -1.805, -0.877, P <0.001), total motility (β =-2.593, 95 % CI: -3.425, -1.761, P <0.001), and progressive motility (β =-4.658, 95 % CI: -5.556, -3.760, P <0.001) were negatively correlated. At 0-9 days before semen collection, CO was negatively correlated with normal morphology (β =-3.403, 95 % CI: -5.099, -1.708, P <0.001). Additionally, the AQI was adversely associated with total and progressive motility in subgroup analyses of the semen quality-eligible groups.

CONCLUSIONS

During the entire sperm development process, multiple air pollutants were determined to have an adverse correlation with semen quality parameters. AQI was significant marker for the combined effects of various atmospheric pollutants on male reproductive health.

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.

Does air pollution exposure affect semen quality? Evidence from a systematic review and meta-analysis of 93,996 Chinese men

Background

Air pollution may impair male fertility, but it remains controversial whether air pollution affects semen quality until now.

Objectives

We undertake a meta-analysis to explore potential impacts of six pollutants exposure during the entire window (0-90 days prior to ejaculation) and critical windows (0-9, 10-14, and 70-90 days prior to ejaculation) on semen quality.

Methods

Seven databases were retrieved for original studies on the effects of six pollutants exposure for 90 days prior to ejaculation on semen quality. The search process does not limit the language and search date. We only included original studies that reported regression coefficients (β) with 95% confidence intervals (CIs). The β and 95% CIs were pooled using the DerSimonian-Laird random effect models.

Results

PM2.5 exposure was related with decreased total sperm number (10-14 lag days) and total motility (10-14, 70-90, and 0-90 lag days). PM10 exposure was related with reduced total sperm number (70-90 and 0-90 lag days) and total motility (0-90 lag days). NO2 exposure was related with reduced total sperm number (70-90 and 0-90 lag days). SO2 exposure was related with declined total motility (0-9, 10-14, 0-90 lag days) and total sperm number (0-90 lag days).

Conclusion

Air pollution affects semen quality making it necessary to limit exposure to air pollution for Chinese men. When implementing protective measures, it is necessary to consider the key period of sperm development.

The impact of air pollution and endocrine disruptors on reproduction and assisted reproduction

PURPOSE OF REVIEW

Rapid increase in world population accompanied by global industrialization has led to an increase in deployment of natural resources, resulting in growing levels of pollution. Here, we review recent literature on the impact of environmental pollution on human reproductive health and assisted reproduction outcomes, focusing on two of the most common: air pollution and endocrine disruptors.

RECENT FINDINGS

Air pollution has been associated with diminished ovarian reserve, uterine leiomyoma, decreased sperm concentration and motility. Air pollution also correlates with decreased pregnancy rates in patients undergoing infertility treatment using in-vitro fertilization (IVF). Similarly, Bisphenol A (BPA), a well studied endocrine disrupting chemical, with oestrogen-like activity, is associated with diminished ovarian reserve, and abnormal semen parameters, while clinical implications for patients undergoing infertility treatment remain to be established.

SUMMARY

There is convincing evidence that environmental pollutants may have a negative impact on human health and reproductive potential. Air pollutions and endocrine disrupting chemicals found in water and food seem to affect male and female reproductive function. Large-scale studies are needed to determine the threshold values for health impact that may drive targeted policies.