Urban fine particulate matter (PM2.5) exposure destroys blood–testis barrier (BTB) integrity through excessive ROS-mediated autophagy

The effects of fine particulate matter on the blood-testis barrier and its potential mechanisms

With the rapid expansion of industrial scale, an increasing number of fine particulate matter (PM2.5) has bringing health concerns. Although exposure to PM2.5 has been clearly associated with male reproductive toxicity, the exact mechanisms are still unclear. Recent studies demonstrated that exposure to PM2.5 can disturb spermatogenesis through destroying the blood-testis barrier (BTB), consisting of different junction types, containing tight junctions (TJs), gap junctions (GJs), ectoplasmic specialization (ES) and desmosomes. The BTB is one of the tightest blood-tissue barriers among mammals, which isolating germ cells from hazardous substances and immune cell infiltration during spermatogenesis. Therefore, once the BTB is destroyed, hazardous substances and immune cells will enter seminiferous tubule and cause adversely reproductive effects. In addition, PM2.5 also has shown to cause cells and tissues injury via inducing autophagy, inflammation, sex hormones disorder, and oxidative stress. However, the exact mechanisms of the disruption of the BTB, induced by PM2.5, are still unclear. It is suggested that more research is required to identify the potential mechanisms. In this review, we aim to understand the adverse effects on the BTB after exposure to PM2.5 and explore its potential mechanisms, which provides novel insight into accounting for PM2.5-induced BTB injury.

A metabolomic perspective on the mechanisms by which environmental pollutants and lifestyle lead to male infertility

The incidence of male infertility (MI) is rising annually. According to epidemiological studies, environmental pollution (e.g., organic, inorganic, and air pollutants), occupational exposure (e.g., high temperature, organic solvents, and pesticides), and poor lifestyle (e.g., diet, sleep, smoking, alcohol consumption, and exercise) are important non-genetic causative factors of MI. Due to multiple and complex causative factors, the dose-effect relationship, and the uncertainty of pathogenicity, the pathogenesis of MI is far from fully clarified. Recent data show that the pathogenesis of MI can be monitored by the metabolites in serum, seminal plasma, urine, testicular tissue, sperm, and other biological samples. It is considered that these metabolites are closely related to MI phenotypes and can directly reflect the individual pathological and physiological conditions. Therefore, qualitative and quantitative analysis of the metabolome, the related metabolic pathways, and the identification of biomarkers will help to explore the MI-related metabolic problems and provide valuable insights into its pathogenic mechanisms. Here, we summarized new findings in MI metabolomics biomarkers research and their abnormal metabolic pathways triggered by the presented non-genetic risk factors, providing a metabolic landscape of semen and seminal plasma in general MI patients. Then, we compared the similarities and differences in semen and seminal plasma biomarkers between MI patients exposed to environmental and poor lifestyle factors and MI patients in general, and summarized some common biomarkers. We provide a better understanding of the biological underpinnings of MI pathogenesis, which might offer novel diagnostic, prognostic, and precise treatment approaches to MI.

Fine particulate matter (PM2.5) induces the stem cell-like properties of hepatocellular carcinoma by activating ROS/Nrf2/Keap1-mediated autophagy

Exposure to fine particulate matter (PM2.5) has been linked to an increased incidence and mortality of hepatocellular carcinoma (HCC). However, the impact of PM2.5 exposure on HCC progression and the underlying mechanisms remain largely unknown. This study aimed to investigate the effects of PM2.5 exposure on the stem cell-like properties of HCC cells. Our findings indicate that PM2.5 exposure significantly enhances the stemness of HCC cells (p < 0.01). Subsequently, male nude mice were divided into two groups (n = 8/group for tumor-bearing assay, n = 5/group for metastasis assay) for control and PM2.5 exposure. In vivo assays revealed that exposure to PM2.5 promoted the growth, metastasis, and epithelial-mesenchymal transition (EMT) of HCC cells (p < 0.01). Further exploration demonstrated that PM2.5 enhances the stemness of HCC cells by inducing cellular reactive oxygen species (ROS) generation (p < 0.05). Mechanistic investigation indicated that elevated intracellular ROS inhibited kelch-like ECH-associated protein 1 (Keap1) levels, promoting the upregulation and nucleus translocation of NFE2-like bZIP transcription factor 2 (Nrf2). This, in turn, induced autophagy activation, thereby promoting the stemness of HCC cells (p < 0.01). Our present study demonstrates the adverse effects of PM2.5 exposure on HCC development and highlights the mechanism of ROS/Nrf2/Keap1-mediated autophagy. For the first time, we reveal the impact of PM2.5 exposure on the poor prognosis-associated cellular phenotype of HCC and its underlying mechanism, which is expected to provide new theoretical basis for the improvement of public health.

PFOS exposure destroys the integrity of the blood-testis barrier (BTB) through PI3K/AKT/mTOR-mediated autophagy

Perfluorooctanesulfonate or perfluorooctane sulfonic acid (PFOS), a type of perfluorinated compound, is mainly found in consumer products. Exposure to PFOS could cause male reproductive toxicity by causing injury to the blood-testis barrier (BTB). However, the specific mechanisms through which PFOS affects male reproduction remain unclear. The mammalian target of rapamycin (mTOR) is a vital protein kinase that is believed to be a central regulator of autophagy. In this study, we established in vivo and in vitro models to explore the effects of PFOS on the BTB, autophagy, and the regulatory role of the mTOR signaling pathway. Adult mice were developmentally exposed to 0, 0.5, 5, and 10 mg/kg/day PFOS for five weeks. Thereafter, their testicular morphology, sperm counts, serum testosterone, expression of BTB-related proteins, and autophagy-related proteins were evaluated. Additionally, TM4 cells (a mouse Sertoli cell line) were used to delineate the molecular mechanisms that mediate the effects of PFOS on BTB. Our results demonstrated that exposure to PFOS induced BTB injury and autophagy, as evidenced by increased expression of autophagy-related proteins, accumulation of autophagosomes, observed through representative electron micrographs, and decreased activity of the PI3K/AKT/mTOR pathway. Moreover, treatment with chloroquine, an autophagy inhibitor, alleviated the effects of PFOS on the integrity of TM4 cells in the BTB and the PI3K/AKT/mTOR pathway. Overall, this study highlights that exposure to PFOS destroys the integrity of the BTB through PI3K/AKT/mTOR-mediated autophagy.

Adverse effects of exposure to petrol-generator exhaust fumes on the reproductive hormones, testis and spermatozoa in male dogs

There is evidence that sperm count has progressively declined in men over the recent decades. Exposure to air pollutants including petrol and diesel exhaust have been reported to impair male reproduction although there is little experimental evidence. This study investigated the effects of petrol-generator exhaust fumes (PGEF) on semen, sperm, gonadal structure and hormonal status in the dog. Sixteen adult male Basenji dogs were randomly assigned four to each of 4 groups as follows: an unexposed (Control) group and three groups exposed to graded levels of PGEF for 1, 2 or 3 h per day (hpd), respectively, for 90 days. Serum concentrations of testosterone (T), follicle stimulating hormone (FSH) and luteinizing hormone (LH) were measured on days 0 (baseline), 30, 60 and 90 of the study. At day 90, semen samples were collected for semen and sperm analysis. Testicular and epididymal tissues were subjected to gross, histopathological and histomorphometric evaluation. Graded exposure to PGEF resulted in increased serum concentration of T and decreased concentrations of FSH and LH, increased seminal plasma lipid peroxidation, seminiferous and epididymal tubular degeneration, germ cell depletion, lowered sperm concentration, decreased sperm motility and vitality, and increased sperm abnormal morphology. The close proximity between dogs and humans in exposed environments underscores the importance of these findings to human reproductive health and fertility. The findings suggest that with prolonged exposure, the impairment of reproductive functions will likely play significant roles in the decline in male fertility.

Epigenetic transgenerational effects of PM2.5 collected from southern Taiwan on sperm functions and DNA methylation in mouse offspring

During respiration, particulate matter with a diameter of 2.5 µm or less (PM2.5) suspended in the atmosphere enters the terminal alveoli and blood. PM2.5 particles can attach to toxic substances, resulting in health problems. Limited information is available regarding the effects of prenatal exposure to water-soluble PM2.5 (WS-PM2.5) and water-insoluble PM2.5 (WI-PM2.5) on male reproduction. In addition, whether exposure to these particles has transgenerational effects remains unknown. We investigated whether prenatal exposure to WS-PM2.5 and WI-PM2.5 disrupts sperm function in generations F1, F2, and F3 of male mice. Pregnant BALB/c mice were treated using intratracheal instillation on gestation days 7, 11, and 15 with 10 mg of a water extract or insoluble PM2.5. On postnatal day 105, epididymal sperm count, motility, morphology, mitochondrial membrane potential (MMP), reactive oxygen species (ROS) production, the sperm chromatin DNA fragmentation index (DFI), and testicular DNA methyltransferase (Dnmt) levels were evaluated in all generations. Whole-genome bisulfite sequencing was used to analyze the DNA methylation status of generation F3. According to the results, exposure to WS-PM2.5 affected sperm morphology, ROS production, and mean DFI in generation F1; ROS production and mean DFI in generation F2; and sperm morphology and MMP in generation F3. Similarly, exposure to WI-PM2.5 affected sperm morphology, ROS production, mean DFI, %DFI, and Dnmt1 expression in generation F1; sperm morphology, MMP, and ROS production in generation F2; and sperm morphology, ROS, and %DFI in generation F3. Two hypermethylated genes, PRR16 and TJP2, were observed in the WS-PM2.5 and WI-PM2.5 groups, two hypomethylated genes, NFATC1 and APOA5, were observed in the WS-PM2.5 group, and two hypomethylated genes, ZFP945 and GSE1, were observed in the WI-PM2.5 group. Hence, prenatal exposure to PM2.5 resulted in transgenerational epigenetic effects, which may explain certain phenotypic changes in male reproduction.

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.

Exposure to Fine Particulate Matter Constituents and Human Semen Quality Decline: A Multicenter Study

Exposure to fine particulate matter (PM < 2.5 μm in diameter [PM2.5]) may accelerate human sperm quality decline, although research on this association is limited. Our objective was to investigate the relationship between exposure to the chemical constituents of PM2.5 air pollution and decreased sperm quality and to further explore the exposure-response relationship. We conducted a multicenter population-based cohort study including 78,952 semen samples from 33,234 donors at 6 provincial human sperm banks (covering central, northern, southern, eastern, and southwestern parts of China) between 2014 and 2020. Daily exposure to PM2.5 chemical composition was estimated using a deep learning model integrating a density ground-based measure network at a 1 km resolution. Linear mixed models with subject- and center-specific intercepts were used to quantify the harmful impacts of PM2.5 constituents on semen quality and explore their exposure-response relationships. Per interquartile range (IQR) increase in PM2.5 exposure levels during spermatogenesis was significantly associated with decreased sperm concentration, progressive motility, and total motility. For PM2.5 constituents, per IQR increment in Cl- (β: -0.02, 95% CI: [-0.03, -0.00]) and NO3- (β: -0.05, 95% CI: [-0.08, -0.02]) exposure was negatively associated with sperm count, while NH4+ (β: -0.03, 95% CI: [-0.06, -0.00]) was significantly linked to decreased progressive motility. These results suggest that exposure to PM2.5 chemical constituents may adversely affect human sperm quality, highlighting the urgent need to reduce PM2.5 exposure.

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.

Diabetes-related perturbations in the integrity of physiologic barriers

One of the hallmarks of health is the integrity of barriers at the cellular and tissue levels. The two cardinal functions of barriers include preventing access of deleterious elements of the environment (barrier function) while facilitating the transport of essential ions, signaling molecules and nutrients needed to maintain the internal milieu (transport function). There are several cellular and subcellular barriers and some of these barriers can be interrelated. The principal physiologic barriers include blood-retinal barrier, blood-brain barrier, blood-testis barrier, renal glomerular/tubular barrier, intestinal barrier, pulmonary blood-alveolar barrier, blood-placental barrier and skin barrier. Tissue specific barriers are the result of the vasculature, cellular composition of the tissue and extracellular matrix within the tissue. Uncontrolled diabetes and acute hyperglycemia may disrupt the integrity of physiologic barriers, primarily through altering the vascular integrity of the tissues and may well contribute to the clinically recognized complications of diabetes. Although diabetes is a systemic disease, some of the organs display clinically significant deterioration in function while others undergo subclinical changes. The pathophysiology of the disruption of these barriers is not entirely clear but it may be related to diabetes-related cellular stress. Understanding the mechanisms of diabetes related dysfunction of various physiologic barriers might help identifying novel therapeutic targets for reducing clinically significant complications of diabetes.

Oxidative stress-induced apoptosis and autophagy: Balancing the contrary forces in spermatogenesis

Spermatogenesis is a complex process in the testis and is a cornerstone of male infertility. The abundance of unsaturated fatty acid and high cell division rate make male germs cells prone to DNA deterioration. ROS-mediated oxidative stress triggers DNA damage, autophagy, and apoptosis in male germ cells, which are critical causative factors that lead to male infertility. The complex connection and molecular crosstalk between apoptosis and autophagy is seen at multifaceted levels that interconnect the signaling pathways of these two processes. Multilevel interaction between apoptosis and autophagy is a seamless state of survival and death in response to various stressors. Interaction between multiple genes and proteins such as the mTor signaling pathway, Atg12 proteins, and the death adapter proteins, such as Beclin 1, p53, and Bcl-2 family proteins, validates such a link between these two phenomena. Testicular cells being epigenetically different from somatic cells, undergo numerous significant epigenetic transitions, and ROS modulates the epigenetic framework of mature sperm. Epigenetic deregulation of apoptosis and autophagy under oxidative stress conditions can cause sperm cell damage. The current review recapitulates the current role of prevailing stressors that generate oxidative stress leading to the induction of apoptosis and autophagy in the male reproductive system. Considering the pathophysiological consequences of ROS-mediated apoptosis and autophagy, a combinatorial approach, including apoptosis inhibition and autophagy activation, a therapeutic strategy to treat male idiopathic infertility. Understanding the crosslink between apoptosis and autophagy under stress conditions in male germ cells may play an essential role in developing therapeutic strategies to treat infertility.

Association between ambient PM1 and semen quality: A cross-sectional study of 27,854 men in China

BACKGROUND

Exposure to ambient fine and respirable particulate matter is associated with poor sperm quality, but evidence for particulate matter with an aerodynamic diameter ≤ 1 μm (PM₁) is scarce. We aimed to estimate the association between PM₁ exposure and sperm concentration, sperm count, sperm total motility, and sperm progressive motility in Chinese men.

METHODS

We conducted a cross-sectional study of 33,221 men attending an infertility clinic in Hubei, China, between 2014 and 2020. Daily concentrations of PM₁ data were estimated from a validated spatiotemporal artificial intelligence model. We used multivariate linear regression to estimate the association between PM₁ exposure and sperm parameters during the spermatogenesis period after adjusting for age, body mass index (BMI), education, ever having fathered a child, and season of semen collection. In addition, we performed stratified analysis to assess whether the association was varied by age, BMI, and educational attainment.

RESULTS

A total of 27,854 participants were included in the final analysis. An interquartile range (17.2 μg/m³) increase in PM₁ during the entire period of semen development was associated with declined semen concentration [-4.39% (95% CI: -7.67%, -1.12%)] and sperm count [-23.56% (95% CI: -28.95%, -18.18%)], reduced total motility [-0.86% (95% CI: -1.66%, -0.06%)] and progressive motility [-2.22% (95% CI: -3.00%, -1.43%)]. The associations were homogeneous across subgroups defined by age and education, but were more pronounced among men with underweight for sperm concentration and sperm count. We identified a critical exposure window of 0-9 lag days, 10-14 lag days, and 70-90 lag days before semen collection for sperm count and progressive motility.

CONCLUSIONS

Among men attending an infertility clinic in China, exposure to PM₁ was associated with poor semen quality, especially during the 70-90 days before ejaculation. These results suggest that exposure to PM₁ might be a novel risk factor for impaired semen quality.

Cell Death Pathways: The Variable Mechanisms Underlying Fine Particulate Matter-Induced Cytotoxicity

Recently, the advent of health risks due to the cytotoxicity of fine particulate matter (FPM) is concerning. Numerous studies have reported abundant data elucidating the FPM-induced cell death pathways. However, several challenges and knowledge gaps are still confronted nowadays. On one hand, the undefined components of FPM (such as heavy metals, polycyclic aromatic hydrocarbons, and pathogens) are all responsible for detrimental effects, thus rendering it difficult to delineate the specific roles of these copollutants. On the other hand, owing to the crosstalk and interplay among different cell death signaling pathways, precisely determining the threats and risks posed by FPM is difficult. Herein, we recapitulate the current knowledge gaps present in the recent studies regarding FPM-induced cell death, and propose future research directions for policy-making to prevent FPM-induced diseases and improve knowledge concerning the adverse outcome pathways and public health risks of FPM.

Perfluorooctanoic acid induces tight junction injury of Sertoli cells by blocking autophagic flux

Perfluorooctanoic acid (PFOA), a man-made chemical widely used in consumers, could cause male reproductive toxicity by disrupting blood-testis barrier (BTB) integrity. Autophagy in Sertoli cells is essential for regulation of spermatogenesis and BTB. However, it remains a mystery that whether PFOA-induced BTB injury is associated with autophagy in Sertoli cells. In this study, we found that PFOA dose-dependently disrupted tight junction (TJ) function in Sertoli cells in vivo and in vitro. Furthermore, the results from transmission electron microscopy, Western blot and immunofluorescence analysis revealed that PFOA induced the accumulation of autophagosome in testicular Sertoli cells as well as TM4 cells. Further study confirmed that autophagosome accumulation resulted from the blockage of autophagic degradation because of disruption of autophagosome and lysosome fusion via downregulation of the expression of α-SNAP. In parallel, the overexpressed MMP9 was also observed in vivo and in vitro. Conversely, overexpression of α-SNAP inhibited the expression of MMP9 in TM4 cells. In conclusion, PFOA blocks autophagic flux through downregulating the expression levels of α-SNAP in Sertoli cells, and then induces the accumulation of MMP9 leading to disruption of TJ function. This finding will provide clues for effective prevention and treatment of PFOA-induced male reproductive toxicity.

The role of stimulator of interferon genes-mediated AMPK/mTOR/P70S6K autophagy pathway in cyfluthrin-induced testicular injury

Cyfluthrin is widely used in the field of sanitary pest control by its wide insecticidal spectrum, high efficiency and low toxicity, low residue, and good biodegradability. But, as a double-edged sword, a large amount of cyfluthrin remains are still in the environment. The residual cyfluthrin is absorbed into the food chain through vegetation and then poses a risk to soil organisms and human health. Several studies have suggested that cyfluthrin is one of the main factors causing testicular damage, but the mechanism remains unclear. In this study, we established in vivo and in vitro models of testicular injury in rats and GC-2 cells exposed to cyfluthrin to explore whether stimulator of interferon genes (STING) gene mediates the regulation of AMPK/mTOR/p70S6K autophagy pathway, which lays a foundation for further study of the mechanism of testicular injury induced by cyfluthrin. The results showed that the activity of super oxide dismutase in testis decreased and the activity of malonic dialdehyde increased with the increase of concentration in vivo and in vitro. At the same time, the levels of mitochondrial damage and inflammation in the testis also increased, which further activated autophagy. In this process, the increased level of inflammation is related to the increased expression of STING gene, and AMPK/mTOR/p70S6K autophagy pathway is also involved. To sum up, cyfluthrin has certain reproductive toxicity, and long-term exposure can induce testicular cell damage. STING gene can participate in cyfluthrin-induced testicular injury through AMPK/mTOR/P70S6K autophagy pathway.

Lactoferrin Restores the Deoxynivalenol-Impaired Spermatogenesis and Blood-Testis Barrier Integrity via Improving the Antioxidant Capacity and Modifying the Cell Adhesion and Inflammatory Response

Deoxynivalenol (DON) is among the most prevalent contaminants in cereal crops and has been demonstrated to impair male spermatogenesis and induce oxidative stress, testicular apoptosis, and disruption of the blood-testis barrier (BTB). Lactoferrin (LF) is an iron-binding glycoprotein with multifunctions including anti-inflammation and antioxidation. Thus, this study aimed to investigate the effects of LF on the spermatogenesis and integrity of the BTB in DON-exposed mice. Thirty-two male mice were allotted to four groups for a 35-day feeding period: vehicle (basal diet), DON (12 mg/kg), LF (10 mg/d, p.o.), and DON + LF. The results showed that DON induced vacuolization of the spermatogenic epithelium, broke the adhesion junction between Sertoli cells and spermatids established by N-cadherin and induced testicular oxidative stress. LF administration restored sperm production, attenuated the DON-induced oxidative stress and reduced the breakages in adhesion junction. DON exposure enhanced the protein expression of occludin. Transcriptional profiling of the testis observed a disturbance in the expression profiles of cell adhesion and inflammatory response genes, and LF administration reversed these gene expressions. Furthermore, down-regulated signaling pathways, including the apical junction, TNFα signaling via NF-κB, and TGF-β in the DON group were observed. These were restored by LF. Enrichment analysis between DON + LF group and vehicle also confirmed the absence of these pathways. These findings indicated that LF eliminated the DON-induced detriment to spermatogenesis and cell connections between Sertoli cells and spermatids via improving antioxidant capacity and modifying the inflammatory response and cell adhesion genes.

Irisin Ameliorates PM2.5-Induced Acute Lung Injury by Regulation of Autophagy Through AMPK/mTOR Pathway

Background

PM2.5 exposure is one of the major inducements of various respiratory diseases and related mortality. Meanwhile, irisin, a metabolism and thermogenesis-related hormone, is found to be protective against acute lung injury induced by LPS, which indicates its therapeutic function in lung injury. However, the function and underlying mechanism of irisin in PM2.5-induced acute lung injury (ALI) are still unclear. This study is aimed to discover the potential mechanisms of irisin in PM2.5-induced acute lung injury.

Methods

Atg5 deficient mice and cells were established to clarify the relationship between irisin and autophagy in PM2.5-induced ALI. We also used Ad-mCherry-GFP-LC3B as a monitor of autophagy flux to claim the effects of irisin on autophagy. Western blotting and qPCR were used to reveal the molecular mechanism.

Results

As a result, PM2.5 exposure induced lung injury whereas mitigated by irisin. Moreover, PM2.5 hampered autophagy flux, characterized by accumulation of p62, and autophagosomes, as well as blocked autolysosomes. Irisin improved the disturbed autophagy flux, which was abrogated by deficiency of Atg5. Additionally, we demonstrated that irisin activated AMPK and inhibited mTOR, which indicated the enhanced autophagy. Moreover, blockage of AMPK by compound C terminated irisin's induction of autophagy in cultured MH-S cells.

Conclusion

Our findings reveal that irisin performs protective effects against PM2.5-induced ALI by activating autophagy through AMPK/mTOR signaling pathway.

Exposure to China dust exacerbates testicular toxicity induced by cyclophosphamide in mice

This study investigated the potential effects of China dust (CD) exposure on cyclophosphamide (CP)-induced testicular toxicity in mice, focusing on spermatogenesis and oxidative damage. CP treatment reduced testicular and epididymal weight and sperm motility and enhanced sperm abnormality. Histopathological examination presented various morphological alterations in the testis, including increased exfoliation of spermatogenic cells, degeneration of early spermatogenic cells, vacuolation of Sertoli cells, a decreased number of spermatogonia/spermatocytes/spermatids, along with a high number of apoptotic cells. In addition, the testis exhibited reduced glutathione (GSH) levels and glutathione reductase (GR) activity and enhanced malondialdehyde (MDA) concentration. Meanwhile, CD exposure exacerbated testicular histopathological alterations induced by CP. CD exposure also aggravated oxidative damage by increasing the lipid peroxidative product MDA and decreasing GSH levels and antioxidant enzyme activities in the testis. These results suggest that CD exposure exacerbates CP-induced testicular toxicity in mice, which might be attributed to the induction of lipid peroxidation and reduced antioxidant activity.

Impact of endocrine disrupting chemicals and pharmaceuticals on Sertoli cell development and functions

Sertoli cells play essential roles in male reproduction, from supporting fetal testis development to nurturing male germ cells from fetal life to adulthood. Dysregulating Sertoli cell functions can have lifelong adverse effects by jeopardizing early processes such as testis organogenesis, and long-lasting processes such as spermatogenesis. Exposure to endocrine disrupting chemicals (EDCs) is recognized as contributing to the rising incidence of male reproductive disorders and decreasing sperm counts and quality in humans. Some drugs also act as endocrine disruptors by exerting off-target effects on endocrine tissues. However, the mechanisms of toxicity of these compounds on male reproduction at doses compatible with human exposure are still not fully resolved, especially in the case of mixtures, which remain understudied. This review presents first an overview of the mechanisms regulating Sertoli cell development, maintenance, and functions, and then surveys what is known on the impact of EDCs and drugs on immature Sertoli cells, including individual compounds and mixtures, and pinpointing at knowledge gaps. Performing more studies on the impact of mixtures of EDCs and drugs at all ages is crucial to fully understand the adverse outcomes these chemicals may induce on the reproductive system.

Impacts of traffic-related particulate matter pollution on semen quality: A retrospective cohort study relying on the random forest model in a megacity of South China

BACKGROUND

Emerging evidence shows the detrimental impacts of particulate matter (PM) on poor semen quality. High-resolution estimates of PM concentrations are conducive to evaluating accurate associations between traffic-related PM exposure and semen quality.

METHODS

In this study, we firstly developed a random forest model incorporating meteorological factors, land-use information, traffic-related variables, and other spatiotemporal predictors to estimate daily traffic-related PM concentrations, including PM_2.5, PM₁₀, and PM₁. Then we enrolled 1310 semen donors corresponding to 4912 semen samples during the study period from January 1, 2019, and December 31, 2019 in Guangzhou city, China. Linear mixed models were employed to associate individual exposures to traffic-related PM during the entire (0-90 lag days) and key periods (0-37 and 34-77 lag days) with semen quality parameters, including sperm concentration, sperm count, progressive motility and total motility.

RESULTS

The results showed that decreased sperm concentration was associated with PM₁₀ exposures (β: -0.21, 95 % CI: -0.35, -0.07), sperm count was inversely related to both PM_2.5 (β: -0.19, 95 % CI: -0.35, -0.02) and PM₁₀ (β: -0.19, 95 % CI: -0.33, -0.05) during the 0-90 days lag exposure window. Besides, PM_2.5 and PM₁₀ might diminish sperm concentration by mainly affecting the late phase of sperm development (0-37 lag days). Stratified analyses suggested that PBF and drinking seemed to modify the associations between PM exposure and sperm motility. We did not observe any significant associations of PM₁ exposures with semen parameters.

CONCLUSION

Our results indicate that exposure to traffic-related PM_2.5 and PM₁₀ pollution throughout spermatogenesis may adversely affect semen quality, especially sperm concentration and count. The findings provided more evidence for the negative associations between traffic-related PM exposure and semen quality, highlighting the necessity to reduce ambient air pollution through environmental policy.

A comparison of fine particulate matter (PM2.5) in vivo exposure studies incorporating chemical analysis

The complex, variable mixtures present in fine particulate matter (PM_2.5) have been well established, and associations between chemical constituents and human health are expanding. In the past decade, there has been an increase in PM_2.5 toxicology studies that include chemical analysis of samples. This investigation is a crucial component for identifying the causal constituents for observed adverse health effects following exposure to PM_2.5. In this review, investigations of PM_2.5 that used both in vivo models were explored and chemical analysis with a focus on respiratory, cardiovascular, central nervous system, reproductive, and developmental toxicity was examined to determine if chemical constituents were considered in the interpretation of the toxicity findings. Comparisons between model systems, PM_2.5 characteristics, endpoints, and results were made. A vast majority of studies observed adverse effects in vivo following exposure to PM_2.5. While limited, investigations that explored connections between chemical components and measured endpoints noted significant associations between biological measurements and a variety of PM_2.5 constituents including elements, ions, and organic/elemental carbon, indicating the need for such analysis. Current limitations in available data, including relatively scarce statistical comparisons between collected toxicity and chemical datasets, are provided. Future progress in this field in combination with epidemiologic research examining chemical composition may support regulatory standards of PM_2.5 to protect human health.

Genome-wide alternation and effect of DNA methylation in the impairments of steroidogenesis and spermatogenesis after PM2.5 exposure

The effects of ambient fine particles on male reproductive health have raised widespread concern. The particular underlying mechanisms of the damage remain largely unclear and demand more research in new directions. Previous research has revealed that DNA methylation plays an important role in male reproductive development and is also vulnerable to environmental influences. However, there hasn't been enough investigation into the involvement of DNA methylation in PM_2.5-induced male reproductive toxicity. Here, we establish a real-time PM_2.5 exposure model and revealed that PM_2.5 exposure could lead to testicular dysfunction including spermatogenesis impairment and steroid hormone dysfunction. In particular, the decrease in the testicular global level of 5-methylcytosine (5mC) indicated a possible association of DNA methylation with testicular injury induced by PM_2.5 exposure. Further genome-wide methylation analysis revealed genomic hypomethylation of testicular DNA and identified more than 1000 differentially methylated regions in both CAP and UA versus FA, indicating that PM_2.5 exposure, even low-dose, could modulate the testicular methylome. Furthermore, integrated analysis of methylome and transcriptome identified some key methylated genes and networks, which may be involved in spermatogenesis and synthesis of steroid hormone. The testicular methylation levels of key genes especially Cyp11a1 and Pax8 raised, and their consequent reduced expression may impair the testosterone and sperm production process. Our research provides fundamental knowledge as well as novel insights into the possible involvement of DNA methylation in PM_2.5-induced male reproductive harm.

Exposure to automobile exhaust-derived PM2.5 induces spermatogenesis dysfunction by damaging UPRmt of prepubertal rats

Automobile exhaust-derived particulate matter 2.5 (PM2.5) can cause spermatogenic cell damage, potentially resulting in male infertility. This study uses male prepubertal Sprague Dawley (SD) rats to explore the molecular mechanisms by which automobile exhaust-derived PM2.5 causes spermatogenic cell damage and induces spermatogenesis dysfunction during sexual maturity by disrupting the mitochondrial unfolded protein response (UPR^mt) in spermatogenic cells. Male prepubertal SD rats were randomly divided into four groups: control (intratracheal instillation of normal saline), low-dose PM2.5 (5 mg/kg), high-dose PM2.5 (10 mg/kg), and PM2.5 10 mg/kg +Vit (100 mg/kg of vitamin C and 50 mg/kg of vitamin E). The rats were treated for four weeks, with five consecutive treatment days and two non-treatment days, followed by cohabitation. Testicular and epididymal tissues were harvested for analysis. The mitochondria in spermatogenic cells were observed under an electron microscope. UPR^mt-, oxidative stress-, and apoptosis-related markers in spermatogenic cells were examined. Spermatogenic cell numbers and conception rate declined significantly with increasing PM2.5 dose, with their mitochondria becoming vacuolated, swollen, and degenerated to varying degrees. The apoptosis of spermatogenic cells was abnormally enhanced in PM2.5 exposed groups compared to the control group. Spermatogenic cell numbers of conception rate gradually recovered, mitochondrial damage in spermatogenic cells was alleviated, and spermatogenic cell apoptosis was significantly reduced after vitamin intervention. In addition, protein levels of superoxide dismutase 1 (Sod1), nuclear factor erythroid 2-related factor 2 (Nrf2), and B-cell lymphoma 2 (Bcl-2) were significantly lower, while those of Bcl2-associated X apoptosis regulator (Bax), cleaved caspase 3 (Casp3), and cytochrome c (Cyt-c) and malondialdehyde (MDA) levels were significantly higher in the high-dose PM2.5 group than in the control group. The levels of UPR^mt-related proteins C/EBP homologous protein (Chop), heat shock protein 60 (Hsp60), and activating transcription factors 4 (Atf4) and 5 (Atf5) were higher in the low-dose PM2.5 group, lower in the high-dose PM2.5 group, and gradually recovered in PM2.5 10 mg/kg +Vit group. Our results show that exposure to automobile exhaust-derived PM2.5 induces oxidative stress responses, leads to post-sexual maturation UPR^mt dysfunction and mitochondrial impairment, and abnormally enhances spermatogenic cell apoptosis in prepubertal rats, resulting in male infertility.

PM2.5 exposure at different concentrations and modes induces reproductive toxicity in male rats mediated by oxidative and endoplasmic reticulum stress

The molecular mechanisms of PM_2.5 exposure in the male reproductive system, have scarcely been studied. Here, we demonstrate the possible relationship and molecular mechanisms between endoplasmic reticulum stress (ERS), oxidative stress, and reproductive toxicity caused by PM_2.5. A "PM_2.5 real-time online concentrated animal whole-body exposure system" was employed to expose male Wistar rats to PM_2.5 for 12 weeks, which could induce sperm quality decline, apoptosis, inflammation, oxidative stress, ERS, and histopathological damage in the testis. In vitro study on cultured primary testicular spermatogonia and Leydig cells confirmed that treatment with PM_2.5 (0-320 μg/mL) for 24 h decreased cell survival rate, increased reactive oxygen species, lactate dehydrogenase and 8-hydroxydeoxyguanosine levels, induced DNA damage, ERS and apoptosis, and inhibit the secretion and synthesis of testosterone in Leydig cells. These results clarified that ERS pathways triggered by oxidative stress could significantly induce CHOP and caspase-12 activation, which are significantly associated with cell apoptosis. However, oxidative stress and ERS inhibitors significantly inhibited the occurrence of these injuries. In conclusion, PM_2.5 triggers the ERS pathway and induces DNA damage in rat testicular cells through oxidative stress, ultimately leading to cellular apoptosis. Furthermore, high-concentration intermittent inhalation was more harmful than low-concentration continuous inhalation when the total mass of PM_2.5 exposure was the same.

Energy metabolism disorders and oxidative stress in the SH-SY5Y cells following PM2.5 air pollution exposure

Studies have shown that PM_2.5 exposure can induce neuronal apoptosis and neurobehavioral changes in animal experiments due partly to the mitochondria-mediated oxidative damage. How does it affect the mitochondrial energy metabolism as well as the neuronal damage, however, remain unclear. This study aimed to investigate the molecular processes of energy metabolism and oxidative damage induced by ambient PM_2.5 exposure in SH-SY5Y cells. SH-SY5Y cells were treated with PM_2.5 to establish a cytotoxicity model. A Seahorse Extracellular Flux Analyzer (XFp) was performed to evaluate the cellular mitochondrial respiratory and glycolysis after exposure to PM_2.5. The dose- and time-dependent effects of PM_2.5 on oxidative damage and apoptosis were analyzed. To further explore the relationship among oxidative damage, energy metabolism and apoptosis, SH-SY5Y cells were co-cultured with BHA and PM_2.5 for 24 h. The results demonstrated that the basic respiration and ATP production, the typical index of mitochondrial respiration as well as glycolysis, significantly reduced in SH-SY5Y cells with dose and time dependent. At the same time, the PM_2.5 could significantly decrease the cell viability and Mn-SOD activity, and increase the ROS levels and apoptosis rate as the escalation of dose and the extension of time. Importantly, the application of BHA could synchronously recover the PM_2.5 induced cell energy metabolism disorder, oxidative damage, and apoptosis. It seems that the abnormal cellular energy metabolism may be caused by oxidative damage following fine particles exposure, and further led to apoptosis.

Association between ambient air pollution and blood sex hormones levels in men

Concerns are growing over time on the adverse health effects of air pollution. However, the association between ambient air pollution and blood sex hormones in men is poorly understood. We included 72,917 men aged 20-55 years from February 2014 to December 2019 in Beijing, China in this study. Blood testosterone, follicle stimulating hormone, luteinizing hormone, estradiol, and prolactin levels of each participant were measured. We collected exposure data of daily ambient levels of particulate matter ≤10 μm (PM₁₀) and ≤2.5 μm (PM_2.5), nitrogen dioxide, sulfur dioxide (SO₂), carbon monoxide, and ozone. Generalized linear mixed models were used to analyze the potential association between ambient air pollution exposure and blood sex hormone levels. The results showed that both immediate and short-term cumulative PM_2.5, PM₁₀, and SO₂ exposure was related to altered serum sex hormone levels in men, especially testosterone. An increase of 10 μg/m³ in PM_2.5 and PM₁₀ in the current day was related to a 1.6% (95% confidence interval [CI]: 0.9%-2.3%) and 1.1% (95% CI: 0.5%-1.6%) decrease in testosterone, respectively, and a decreasing tendency of accumulated effects persisted within lag 0-30 days. The present study demonstrated that it is important to control ambient air pollution exposure to reduce effects on the reproductive health of men.

Role of angiotensin-converting enzyme 2 in fine particulate matter-induced acute lung injury

Fine particulate matter (PM2.5) pollution poses significant health concerns worldwide and can cause respiratory diseases. However, how it causes health problems is still poorly understood. Angiotensin-converting enzyme (ACE)2 is a terminal carboxypeptidase implicated in the functions of renin-angiotensin system (RAS) and plays a crucial role in the control of lung inflammation. To investigate whether ACE2 functions in PM2.5-induced lung inflammation, wild-type (WT) C57BL/6J mice and ACE2 knock-out (KO) mice were intratracheally instilled with PBS or PM2.5 suspension for 3 consecutive days, respectively. The concentrations of cytokines in bronchoalveolar lavage fluid (BALF) were determined by ELISA. The expression of ACE2 and ACE and activation of inflammatory signaling pathways in lung tissues were evaluated by immunofluorescence staining and Western blotting. We found that PM2.5 exposure increased ACE2 expression. Loss of ACE2 significantly elevated the levels of total proteins, total cells, and the concentrations of MCP-1, IL-1β in BALF after PM2.5 challenge. Additionally, loss of ACE2 enhanced lung pathologies, airway resistance, and inflammatory signaling activation. Collectively, loss of ACE2 exacerbates PM2.5-induced acute lung injury in mice.

Analysis by transcriptomics and metabolomics for the proliferation inhibition and dysfunction through redox imbalance-mediated DNA damage response and ferroptosis in male reproduction of mice and TM4 Sertoli cells exposed to PM2.5

Sertoli cells play a pivotal role in the complex spermatogenesis process. This study aimed to investigate the effects of PM_2.5 on Sertoli cells using the TM4 cell line and a real time whole-body PM_2.5 exposure mouse model, and further explore the underlying mechanisms through the application of metabolomics and transcriptomics. The results in vivo and in vitro showed that PM_2.5 reduced Sertoli cells number in seminiferous tubules and inhibited cell proliferation. PM_2.5 exposure also induced Sertoli cell dysfunction by increasing androgen binding protein (ABP) concentration, reducing the blood-testis barrier (BTB)-related protein expression, and decreasing glycolysis capacity and lactate production. The results of transcriptomics, metabolomics, and integrative analysis of multi-omics in the TM4 Sertoli cells revealed the activation of xenobiotic metabolism, and the disturbance of glutathione and purine metabolism after PM_2.5 exposure. Further tests verified the reduced GSH/GSSG ratio and the elevation of xanthine oxidase (XO) activity in the PM_2.5-exposed TM4 cells, indicating that excessive reactive oxygen species (ROS) was generated via metabolic disorder caused by PM_2.5. Moreover, the redox imbalance was proved by the increase in the mitochondrial ROS level, superoxide dismutase (SOD) and catalase (CAT) activity, as well as the activation of the Nrf2 antioxidative pathway. Further study found that the redox imbalance caused by PM_2.5 induced DNA damage response and cell cycle arrest. Additionally, PM_2.5 induced ferroptosis through iron overload and lipid peroxidation. Taken all together, our study provided new insights for understanding proliferation inhibition and dysfunction of TM4 Sertoli cells exposed to PM_2.5 via metabolic disorder and redox imbalance-mediated DNA damage response and ferroptosis.

Association of Exposure to Particulate Matter Air Pollution With Semen Quality Among Men in China

IMPORTANCE

The health effects of exposure to particulate matter (PM) on male fertility remain unclear. Although PM exposure has been linked with semen quality, the results were inconsistent.

OBJECTIVE

To examine the association of different size fractions of PM (<2.5 μm [PM2.5], 2.5-10 μm [PM2.5-10], and ≤10 μm [PM10]) exposure with semen quality in China.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study was conducted using data on men whose wives underwent assisted reproductive technology procedures in a tertiary hospital in Shanghai, China, from January 1, 2013, to December 31, 2019. Participants were from 340 prefecture-level cities of China and were followed up from the date of their first visit until December 31, 2019. Data were analyzed from December 1, 2020, to May 15, 2021.

EXPOSURES

Exposure to PM2.5, PM2.5-10, and PM10 during the entire period (0-90 days before semen ejaculation) and key periods of sperm development (0-9, 10-14, and 70-90 days before semen ejaculation).

MAIN OUTCOMES AND MEASURES

Semen quality, including sperm count, concentration, and motility.

RESULTS

A total of 33 876 men were included in the final analysis, with a mean (SD) age of 34.1 (5.7) years and large variation of PM exposure. For example, the median exposure to PM2.5 during the entire period of sperm development was 46.05 (IQR, 34.38-61.65) μg/m3. During the entire period of sperm development, exposures to higher levels of PM were significantly associated with lower total and progressive sperm motility. For total sperm motility, an IQR increase in PM2.5 exposure was associated with an estimated effect decrease of -3.60% (95% CI, -3.93% to -3.26%); an increase in PM2.5-10 exposure, with an estimated effect decrease of -0.45% (95% CI, -0.76% to -0.14%); and an increase in PM10 exposure, with an estimated effect decrease of -2.44% (95% CI, -2.91% to -1.96%). Similar results were observed for progressive motility. An IQR increase in PM2.5 or PM10 exposures was associated with an estimated effect decrease on sperm progressive motility of -1.87% (95% CI, -2.37% to -1.36%) and -1.05% (95% CI, -1.45% to -0.64%), respectively. However, no significant associations were observed between PM exposure during the entire period of sperm development and sperm count or concentration.

CONCLUSIONS AND RELEVANCE

These findings suggest that PM exposure may adversely affect sperm motility and highlight the need to reduce ambient particulate air pollution exposure for reproductive-aged men.

PM2.5 activated NLRP3 inflammasome and IL-1β release in MH-S cells by facilitating autophagy via activating Wnt5a

Particulate matter 2.5 (PM2.5)-induced pulmonary inflammation is an important issue worldwide. NLRP3 inflammasome activation has been found to be involved in pulmonary inflammation development. However, whether PM2.5 induces pulmonary inflammation by activating the NLRP3 inflammasome has not yet been fully elucidated. This study researched whether PM2.5 induces the NLRP3 inflammasomes activation to trigger pulmonary inflammation.

Mice and MH-S cells were exposed to PM2.5, BOX5, and Rapamycin. Hematoxylin and eosin staining was performed on the lung tissues of mice. M1 macrophage marker CD80 expression in the lung tissues of mice and LC3B expression in MH-S cells was detected by immunofluorescence. IL-1β level in the lavage fluid and MH-S cells were detected by enzyme-linked immunosorbent assay. Protein expression was detected by Western blot. Autophagy assay in MH-S cells was performed by LC3B-GFP punctae experiment.PM2.5 exposure induced the lung injury of mice and increased NLRP3, P62, Wnt5a, LC3BII/I, and CD80 expression and IL-1β release in the lung tissues. PM2.5 treatment increased NLRP3, pro-caspase-1, cleaved caspase-1, Pro-IL-1β, Pro-IL-18, P62, LC3BII/I, and Wnt5a expression, IL-1β release, and LC3B-GFP punctae in MH-S cells. However, BOX5 treatment counteracted this effect of PM2.5 on lung tissues of mice and MH-S cells. Rapamycin reversed the effect of BOX5 on PM2.5-induced lung tissues of mice and MH-S cells.PM2.5 activated the NLRP3 inflammasome and IL-1β release in MH-S cells by facilitating the autophagy via activating Wnt5a. The findings of this study provided a new clue for the treatment of pulmonary inflammation caused by PM2.5.

The activated ATM/p53 pathway promotes autophagy in response to oxidative stress-mediated DNA damage induced by Microcystin-LR in male germ cells

Microcystin-LR (MC-LR) is an intracellular toxin with multi-organ toxicity and the testis is one of its important target organs. Although there is increasing research on MC-LR in male reproductive toxicity, the association between DNA damage and autophagy induced by MC-LR in male germ cells are still unclear. Therefore, it is important to explore the mechanism of MC-LR-induced DNA damage and the role of the activated ATM/p53 signaling pathway in testicular toxicity. The present study showed that MC-LR exposure significantly reduced gonadal index and induced pathological damage of the testes in mice. In addition, MC-LR increased the oxidative stress-related indicator hydroxyl radical, accompanied by increased levels of DNA damage-related indicators gamma-H2AX, 8-hydroxy-2'-deoxyguanosine, the olive tail moment (OTM) and DNA content of comet tail (TailDNA%) in trailing cells. Moreover, MC-LR activated the ATM/p53 pathway by enhancing the phosphorylation levels of ATM, CHK2 and p53 proteins, and then led to cell autophagy, ultimately triggering disrupted testicular cell arrangement, reduced sperm count and spermatogenic cell shedding. Importantly, after pretreatment with the antioxidant NAC, the expression levels of DNA damage-related indicators and the extent of damage in male germ cells were significantly reduced. Furthermore, pretreatment with the ATM inhibitor KU55933 could reduce the occurrence of autophagy and mitigate testicular toxicity of MC-LR through inhibiting the activation of the ATM/p53 pathway. These results indicate that MC-LR-induced oxidative stress can activate the DNA damage-mediated ATM/p53 signalling pathway to induce autophagy in male germ cells. This study provides a novel insight to further clarify the reproductive toxicity caused by MC-LR and to protect male reproductive health.

Wu-Zi-Yan-Zong-Wan protects mouse blood-testis barrier from Tripterygium wilfordii Hook. f. multiglycoside-induced disruption by regulating proinflammatory cytokines

ETHNOPHARMACOLOGICAL RELEVANCE

Wu-Zi-Yan-Zong-Wan (WZYZW) is a classical traditonal Chinese herbal formula and a Chinese patent medicine used to treat male infertility. However, the chemical components of WZYZW and its mechanism are not yet fully clarified.

AIM OF THE STUDY

The purpose of this study is to observe the effect and underlying mechanism of WZYZW on ameliorating blood-testis barrier (BTB) dysfunction in mice with spermatogenic dysfunction induced by administration of Tripterygium wilfordii Hook. f. multiglycosides (GTW).

MATERIALS AND METHODS

WZYZW was administered by gavage to mice with GTW-induced spermatogenic dysfunction (kidney essence deficiency pattern) for 40 days. Testis tissues were obtained for subsequent histopathological analysis. Biotin tracing was used to evaluate the permeability of Sertoli cell tight junctions. The levels of proinflammatory cytokines including interleukin (IL)-6, IL-17A, IL-1α and tumor necrosis factor (TNF)-α were analyzed by ELISA. The expression levels of proteins related to tight junction including ZO-1, JAM-A and occludin were analyzed by western blotting. The ultrastructures of tight junctions were observed by transmission electron microscopy.

RESULTS

WZYZW ameliorated GTW-induced testicular spermatogenic dysfunction. Levels of IL-6, IL-17A, IL-1α, and TNF-α in the groups receiving low, medium, and high doses of WZYZW decreased in a dose-dependent manner. WZYZW impeded a biotin tracer from permeating the BTB, protecting its integrity in GTW-treated mice. In addition, our results showed no significant changes in the protein expressions of ZO-1, JAM-A, and occludin after WZYZW administration compared with the GTW group. Meanwhile, WZYZW exhibited a linear arrangement and restored the typical "sandwich" structure of BTB. No acute poisoning incidences were observed in all groups during the experiment.

CONCLUSIONS

Our findings demonstrate that WZYZW may ameliorate some GTW-induced BTB dysfunction, possibly by regulating proinflammatory cytokine levels. In vitro studies on the regulation of BTB permeability by WZYZW and its active components are further required.

Acute exposure to PM2.5 triggers lung inflammatory response and apoptosis in rat

Severe haze events, especially with high concentration of fine particulate matter (PM_2.5), are frequent in China, which have gained increasing attention among public. The purpose of our study was explored the toxic effects and potential damage mechanisms about PM_2.5 acute exposure. Here, the diverse dosages of PM_2.5 were used to treat SD rats and human bronchial epithelial cell (BEAS-2B) for 24 h, and then the bioassays were performed at the end of exposure. The results show that acute exposure to diverse dosages of PM_2.5 could trigger the inflammatory response and apoptosis. The severely oxidative stress may contribute to the apoptosis. Also, the activation of Nrf2-ARE pathway was an important compensatory process of antioxidant damage during the early stage of acute exposure to PM_2.5. Furthermore, the HO-1 was suppression by siRNA that promoted cell apoptosis triggered by PM_2.5. In other words, enhancing the expression of HO-1 may mitigate the cell apoptosis caused by acute exposure to PM_2.5. In summary, our findings present the first time that prevent or mitigate the damage triggered by PM_2.5 through antioxidant approaches was a promising strategy.

Astragaloside IV Protects from PM2.5-Induced Lung Injury by Regulating Autophagy via Inhibition of PI3K/Akt/mTOR Signaling in vivo and in vitro

Introduction

Prolonged exposure to air polluted with airborne fine particulate matter (PM2.5) can increase respiratory disease risk. Astragaloside IV (AS-IV) is one of the main bioactive substances in the traditional Chinese medicinal herb, Astragalus membranaceus Bunge. AS-IV has numerous pharmacological properties; whereas there are few reports on the prevention of PM2.5-induced lung injury by AS-IV through modulation of the autophagic pathway. This study aimed to investigate the protective effects and the underlying mechanisms of AS-IV in PM2.5-induced lung injury rats and rat alveolar macrophages (NR8383 cells).

Methods

The pneumotoxicity model was established by intratracheal injection of PM2.5 in rats, and PM2.5 challenge in NR8383 cells. The severity of lung injury was evaluated by wet weight to dry weight ratio and McGuigan pathology scoring. Inflammatory factors and oxidative stress were detected through ELISA. The expressions of p-PI3K, p-Akt, and p-mTOR proteins were analyzed by immunohistochemistry. Immunofluorescence and transmission electron microscopy were used to detect autophagosomes. The expressions of autophagy marker protein (LC3B and p62), PI3K/Akt/mTOR signaling and NF-κB translocation were detected by Western blot in lung tissue and NR8383 cells.

Results

After PM2.5 stimulation, rats showed severe inflammation and oxidative stress, along with inhibition of autophagy in lung tissue. AS-IV not only decreased pulmonary inflammation and oxidative stress by inhibiting nuclear factor kappa B translocation, but also regulated autophagy by inhibiting PI3K/Akt/mTOR signaling. After treatment with 3-methyladenine (a classic PI3K inhibitor, blocking the formation of autophagosomes), the protective effect of AS-IV on PM2.5-induced lung injury was further strengthened. In parallel, using Western blot, immunohistochemistry, and transmission electron microscopy, we demonstrated that AS-IV restore autophagic flux mainly through regulating the degradation of autophagosomes rather than suppressing the formation in vivo and in vitro.

Conclusion

Our data indicated that AS-IV protects from PM2.5-induced lung injury in vivo and in vitro by inhibiting the PI3K/Akt/mTOR pathway to regulate autophagy and inflammation.

PM2.5 Exposure of Mice during Spermatogenesis: A Role of Inhibitor κB Kinase 2 in Pro-Opiomelanocortin Neurons

BACKGROUND

Epidemiological studies have shown that exposure to ambient fine particulate matter with aerodynamic diameter less than or equal to 2.5 μm (PM2.5) correlates with a decrease in sperm count, but the biological mechanism remains elusive.

OBJECTIVES

This study tested whether hypothalamic inflammation, an emerging pathophysiological mediator, mediates the development of lower epididymal sperm count due to PM2.5 exposure.

METHODS

Inhibitor κB kinase 2 (IKK2) was conditionally knocked out either in all neurons or subtypes of hypothalamic neurons of mice. Effects of concentrated ambient PM2.5 (CAP) exposure on hypothalamic inflammation, the hypothalamic-pituitary-gonadal (HPG) axis, and epididymal sperm count of these mouse models were then assessed. Furthermore, to test whether hypothalamic inflammation is sufficient to decrease sperm production, we overexpressed constitutively active IKK2 (IKK2ca) either in all neurons or subtypes of hypothalamic neurons and assessed hypothalamic inflammation, the HPG axis, and sperm production of these overexpression mouse models.

RESULTS

CAP-exposed wild-type control mice vs. filtered air (FA)-exposed wild-type control mice had a higher expression of hypothalamic inflammatory markers, lower functional indexes of the HPG axis, and a lower epididymal sperm count. In contrast, all these measurements for CAP- vs. FA-exposed mice deficient of IKK2 in all neurons were comparable. We also found that overexpression of IKK2ca in either all neurons or pro-opiomelanocortin (POMC) neurons only, but not in Agouti-related protein (AgRP) neurons only, resulted in lower functional indexes of the HPG axis and a lower epididymal sperm count. Moreover, we showed that CAP- vs. FA-exposed mice deficient of IKK2 in POMC neurons had a comparable expression of hypothalamic inflammatory markers, comparable functional indexes of the HPG axis, and a comparable epididymal sperm count.

DISCUSSION

This mouse model study shows a causal role of IKK2 of POMC neurons in the development of lower epididymal sperm count due to PM2.5 exposure, providing a mechanistic insight into this emerging pathogenesis. https://doi.org/10.1289/EHP8868.

Lipid changes in extrapulmonary organs and serum of rats after chronic exposure to ambient fine particulate matter

Fine particulate matter (PM_2.5) is able to pass through the respiratory barrier to enter the circulatory system and can consequently spread to the whole body to cause toxicity. Although our previous studies have revealed significantly altered levels of phosphorylcholine-containing lipids in the lungs of rats after chronic inhalation exposure to PM_2.5, the effects of PM_2.5 on phosphorylcholine-containing lipids in the extrapulmonary organs have not yet been elucidated. In this study, we examined the lipid effects of chronic PM_2.5 exposure on various organs and serum by using a rat inhalation model followed by a mass spectrometry-based lipidomic approach. Male Sprague-Dawley rats were continuously exposed at the whole body level to nonfiltered and nonconcentrated ambient air from the outside environment of Taipei city for 8 months, while the control rats inhaled filtered air simultaneously. After exposure, serum samples and various organs, including the testis, pancreas, heart, liver, kidney, spleen, and epididymis, were collected for lipid extraction and analysis to examine the changes in phosphorylcholine-containing lipids after exposure. The results from the partial least squares discriminant analysis models demonstrated that the lipid profiles in the PM_2.5 exposure group were different from those in the control group in the rat testis, pancreas, heart, liver, kidney and serum. The greatest PM_2.5-induced lipid effects were observed in the testes. Decreased lyso-phosphatidylcholines (PCs) as well as increased unsaturated diacyl-PCs and sphingomyelins in the testes may be related to maintaining the membrane integrity of spermatozoa, antioxidation, and cell signaling. Additionally, our results showed that decreased PC(16:0/18:1) was observed in both the serum and testes. In conclusion, exposure to chronic environmental concentrations of PM_2.5 caused lipid perturbation, especially in the testes of rats. This study highlighted the susceptibility of the testes and suggested possible molecular events for future study.

Echinacoside Protects Against Dysfunction of Spermatogenesis Through the MAPK Signaling Pathway

Dysfunction at various levels of spermatogenesis (SD) is one of the important causes of infertility in men of reproductive age and requires advanced treatment strategies. Increasing evidence suggests that the therapeutic effects of echinacoside (ECH) mainly depend on their capacity to inhibit cell death. This study aimed to explore the therapeutic potential of ECH in SD rat models. Treatment with ECH reverted the morphological changes observed in testes with spermatogenesis dysfunction. It improved total sperm number, decreased the sperm deformity rate, and increased the sperm forward motility rate. The level of glutathione (GSH) was significantly higher in ECH-treated mice, whereas the lactate dehydrogenase (LDH) and SOD activities were improved compared with those in the spermatogenesis dysfunction model. Moreover, the increased expression of p38 and JNK was partially reversed by ECH. The number of normal TM3 cells increased gradually in an Echinacea dosage-dependent manner, suggesting that ECH promoted the proliferation of TM3 cells. In addition, treatment with ECH partially reversed the increased expression of p38 and JNK in TM3 cells. ECH protects against oxidative stress damage by activating antioxidant enzymes and MAPK signaling-related factors (p38 and JNK). It suggested that treatment with ECH alleviated spermatogenetic dysfunction of testes in male mice and it could be a promising strategy for patients suffering severe SD.

Cardamonin exerts a protective effect against autophagy and apoptosis in the testicles of diabetic male rats through the expression of Nrf2 via p62-mediated Keap-1 degradation

Cardamonin (CARD) is a chalconoid with anti-inflammatory and antioxidant properties, and it is present in several plants. We sought to explore whether CARD exerts any positive effects against hyperglycemia-induced testicular dysfunction caused by type 2 diabetes and aimed to identify its possible intracellular pathways. Adult male rats were subdivided into six groups: control, CARD, diabetic (DM), DM + glibenclamide (GLIB), DM + CARD and DM + GLIB + CARD. Type 2 DM induced a significant increase in blood glucose and insulin resistance, along with diminished serum insulin, testosterone and gonadotropins levels, which were associated with the impairment of key testicular androgenic enzymes and cellular redox balance. Administration of CARD at a dose of 80 mg/kg for 4 weeks effectively normalized all of these alterations, and the improvement was confirmed by epididymal sperm analysis. After treatment with CARD, the pathological changes in spermatogenic tubules were markedly improved. Significantly, CARD upregulated testicular glucose transporter-8 (GLUT-8) expression and had inhibitory effects on elevated autophagy markers and caspase-3 immunoreactive cells. Furthermore, our results revealed that CARD was able to attenuate damage via activation of Nrf2 through the p62-dependent degradation of testicular anti-Kelch-like ECH-associated protein-1 (Keap-1). In conclusion, this study suggests that CARD provides protection against diabetic stress-mediated testicular damage. The use of CARD with conventional anti-diabetic therapy was associated with improved efficacy compared with conventional therapy alone.

Air Pollution and COVID-19: A Possible Dangerous Synergy for Male Fertility

Several studies indicate that semen quality has strongly declined in the last decades worldwide. Air pollution represents a significant co-factor with the COVID-19 impact and has negative effects on the male reproductive system, through pro-oxidant, inflammatory and immune-dysregulating mechanisms. It has recently been reported that chronic exposure to PM2.5 causes overexpression of the alveolar ACE2 receptor, the entry route of SARS-CoV-2 into the organism shared by the lungs and testis where expression is highest in the body. In the testis, the ACE2/Ang-(1-7)/MasR pathway plays an important role in the regulation of spermatogenesis and an indirect mechanism of testicular damage could be due to the blockade of the ACE2 receptor by SARS-CoV-2. This prevents the conversion of specific angiotensins, and their excess causes inflammation with the overproduction of cytokines. PM2.5-induced overexpression of the alveolar ACE2 receptor, in turn, could increase local viral load in patients exposed to pollutants, producing ACE2 receptor depletion and compromising host defenses. By presenting an overall view of epidemiological data and molecular mechanisms, this manuscript aims to interpret the possible synergistic effects of both air pollution and COVID-19 on male reproductive function, warning that the spread of SARS-CoV-2 in the fertile years may represent a significant threat to global reproductive health. All of this should be of great concern, especially for men of the age of maximum reproductive capacity, and an important topic of debate for policy makers. Altered environmental conditions, together with the direct and indirect short- and long-term effects of viral infection could cause a worsening of semen quality with important consequences for male fertility, especially in those areas with higher environmental impact.

Micro- and Nanosized Substances Cause Different Autophagy-Related Responses

With rapid industrialization, humans produce an increasing number of products. The composition of these products is usually decomposed. However, some substances are not easily broken down and gradually become environmental pollutants. In addition, these substances may cause bioaccumulation, since the substances can be fragmented into micro- and nanoparticles. These particles or their interactions with other toxic matter circulate in humans via the food chain or air. Whether these micro- and nanoparticles interfere with extracellular vesicles (EVs) due to their similar sizes is unclear. Micro- and nanoparticles (MSs and NSs) induce several cell responses and are engulfed by cells depending on their size, for example, particulate matter with a diameter ≤2.5 μm (PM2.5). Autophagy is a mechanism by which pathogens are destroyed in cells. Some artificial materials are not easily decomposed in organisms. How do these cells or tissues respond? In addition, autophagy operates through two pathways (increasing cell death or cell survival) in tumorigenesis. Many MSs and NSs have been found that induce autophagy in various cells and tissues. As a result, this review focuses on how these particles interfere with cells and tissues. Here, we review MSs, NSs, and PM2.5, which result in different autophagy-related responses in various tissues or cells.

The role of different compounds on the integrity of blood-testis barrier: A concise review based on in vitro and in vivo studies

Sertoli cells are "nurturing cells'' in the seminiferous tubules of the testis which have essential roles in the development, proliferation and differentiation of germ cells. These cells also divide the seminiferous epithelium into a basal and an adluminal compartment and establish the blood-testis barrier (BTB). BTB shields haploid germ cells from recognition by the innate immune system. Moreover, after translocation of germ cells into the adluminal compartment their nutritional source is separated from the circulatory system being only supplied by the Sertoli cells. The integrity of BTB is influenced by several organic/ organometallic, hormonal and inflammatory substances. Moreover, several environmental contaminants such as BPA have hazardous effects on the integrity of BTB. In the current review, we summarize the results of studies that assessed the impact of these agents on the integrity of BTB. These studies have implications in understanding the molecular mechanism of male infertility and also in the male contraception.

Effects of PM2.5 exposure on reproductive system and its mechanisms

With the development of human society, haze has become an important form of air pollution. Haze is a mixture of fog and haze, and the main component of haze is fine particulate matter (PM_2.5), which is the most important indicator of composite air pollution. Epidemiological studies proved that PM_2.5 can break through the respiratory mucosal barrier and enter the human body, causing pathological effects on multiple systems of the body. In the past, people put more attention to PM_2.5 in the respiratory system, cardiovascular system, nervous system, etc, and relatively paid less attention to the reproductive system. Recent studies have shown that PM_2.5 will accumulate in the reproductive organs through blood-testis barrier, placental barrier, epithelial barrier and other barriers protecting reproductive tissues. In addition, PM_2.5 can disrupt hormone levels, ultimately affecting fertility. Prior studies have shown that oxidative stress, inflammation, apoptosis, and the breakdown of barrier structures are now considered to contribute to reproductive toxicity and may cause damage at the molecular and genetic levels. However, the exact mechanism remains to be elucidated. Our review aims to provide an understanding of the pathological effects of PM_2.5 on reproductive system and the existing injury mechanism.

Atmospheric PM2.5 blocking up autophagic flux in HUVECs via inhibiting Sntaxin-17 and LAMP2

Despite of growing evidence linking PM_2.5 exposure to autophagic activity in various human cells, the functional significance of PM_2.5 exposure affecting autophagy in the pathogenesis of human cardiovascular disease and the underlying molecular mechanisms remain unclear. In this study, the effects of ambient PM_2.5 (with final concentration 0, 1, 5, 25 µg/mL) on the autophagic activity in human umbilical vein endothelial cells (HUVECs) were systematically studied. The results showed that the internalized PM_2.5 mainly localized in the membrane-surrounded vacuoles in the cytoplasm. Compared with the negative control, dose-dependent increase of autophagosomes, puncta and protein levels of LC3-II and p62, and both dose- and time-dependent increase of AKT phosphorylation, with inversely time-dependent reduction of Beclin 1, ATG3 and ATG5 proteins, were presented in the PM_2.5-treated HUVECs, indicating a clear impairment of autophagic degradation in the PM_2.5-exposed HUVECs. Meanwhile, increase in lysosomes, LAMP1, proteases of CTSB and CTSD, and protein phosphorylation of ERK1/2 and TFEB was identified in the PM_2.5-treated HUVECs, showing a PM_2.5-mediated enhancement in lysosomal activity. A novel finding in this study is that both Sntaxin-17 and LAMP2, two key proteins involved in the control of membrane fusion between autophagosome and lysosome, were significantly decreased in the PM_2.5-exposed HUVECs, suggesting that the fusion of autophagosome-lysosome was blocked up. Collectively, ambient PM_2.5 exposure may block up the autophagic flux in HUVECs through inhibiting the expression of Sntaxin-17 and LAMP2. Autophagic activity in HUVECs is a useful biomarker for assessing risks of environmental factors to human cardiovascular health.

Analysis by Metabolomics and Transcriptomics for the Energy Metabolism Disorder and the Aryl Hydrocarbon Receptor Activation in Male Reproduction of Mice and GC-2spd Cells Exposed to PM2.5

Fine particulate matter (PM_2.5)-induced male reproductive toxicity arouses global public health concerns. However, the mechanisms of toxicity remain unclear. This study aimed to further investigate toxicity pathways by exposure to PM_2.5in vitro and in vivo through the application of metabolomics and transcriptomics. In vitro, spermatocyte-derived GC-2spd cells were treated with 0, 25, 50, 100 μg/mL PM_2.5 for 48 h. In vivo, the real-world exposure of PM_2.5 for mouse was established. Forty-five male C57BL/6 mice were exposed to filtered air, unfiltered air, and concentrated ambient PM_2.5 in Tangshan of China for 8 weeks, respectively. The results in vitro and in vivo showed that PM_2.5 exposure inhibited GC-2spd cell proliferation and reduced sperm motility. Mitochondrial damage was observed after PM_2.5 treatment. Increased Humanin and MOTS-c levels and decreased mitochondrial respiratory indicated that mitochondrial function was disturbed. Furthermore, nontargeted metabolomics analysis revealed that PM_2.5 exposure could disturb the citrate cycle (TCA cycle) and reduce amino acids and nucleotide synthesis. Mechanically, the aryl hydrocarbon receptor (AhR) pathway was activated after exposure to PM_2.5, with a significant increase in CYP1A1 expression. Further studies showed that PM_2.5 exposure significantly increased both intracellular and mitochondrial reactive oxygen species (ROS) and activated NRF2 antioxidative pathway. With the RNA-sequencing technique, the differentially expressed genes induced by PM_2.5 exposure were mainly enriched in the metabolism of xenobiotics by the cytochrome P450 pathway, of which Cyp1a1 was the most significantly changed gene. Our findings demonstrated that PM_2.5 exposure could induce spermatocyte damage and energy metabolism disorder. The activation of the aryl hydrocarbon receptor might be involved in the mechanism of male reproductive toxicity.

PM2.5-related cell death patterns

With the increasingly serious problem of environmental pollution, the health problems caused by PM2.5 are gradually coming into our line of sight. Previous researches have indicated that air pollution is nearly related to various diseases, but few studies have focused on the exact function mediated by particulate matter less than 2.5 (PM2.5) in these diseases. PM2.5 is known to induce multiple ways of cell death, including autophagy, necrosis, apoptosis, pyroptosis and ferroptosis. Therefore, it is of much importance to understand the different ways of cell death caused by PM2.5 in the pathogenesis and treatment of PM2.5-related diseases. This present review is an insight of multiple ways of PM2.5‑induced cell death in different diseases.

Fine particulate matter inhibits phagocytosis of macrophages by disturbing autophagy

Mounting evidence from epidemiological and clinical studies has revealed marked correlations between the air pollutant fine particulate matter (FPM) and respiratory diseases. FPM reaches distal airways and deposits in alveolar regions where it can act directly on alveolar macrophages. However, the detailed effect of FPM on the physiological function of alveolar macrophages and the underlying mechanisms remain unclear. In this study, we showed that exposing THP-1-derived macrophages to FPM led to autophagy dysfunction. FPM activated the extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway, which promoted the expression of autophagy-related 2A (ATG2A) and reactive oxygen species generation. The overexpression of ATG2A enhanced the synthesis of autophagic membranes, and the excessive production of reactive oxygen species caused autophagy flux inhibition through disrupting the lysosomal activity. More importantly, FPM impaired the phagocytic ability of macrophages on Escherichia coli and apoptotic neutrophils. Finally, we showed that restoring autophagy rescued the impairment of phagocytic ability induced by FPM. In summary, these results reveal the molecular mechanism of autophagy dysfunction caused by FPM and provide a novel approach to resolve the impaired function of macrophages in respiratory diseases induced by FPM.

Quercetin Intervention Alleviates Offspring's Oxidative Stress, Inflammation, and Tight Junction Damage in the Colon Induced by Maternal Fine Particulate Matter (PM2.5) Exposure through the Reduction of Bacteroides

The influences of maternal fine particulate matter (PM_2.5) exposure on intestinal oxidative stress, inflammation, tight junctions, and gut microbiota of offspring are not well understood. Moreover, research on the dietary intervention method has not been well studied. In our study, dams received PM_2.5 and quercetin intervention during gestation and lactation, and then inflammation biomarkers, oxidative stress indicators, tight junction proteins, and gut microbiota in the colon of offspring were analyzed. Compared with the control group, lower catalase (CAT) and superoxide dismutase (SOD) activities, higher interleukin-17A (IL-17A) and interleukin-22 (IL-22), decreased ZO-1 and occludin expressions, and higher Bacteroides abundance were observed in the offspring mice of the PM_2.5 group. However, higher CAT and SOD activities, lower IL-17A and IL-22 levels, increased ZO-1 and occludin expressions, and lower Bacteroides abundance were found in the quercetin groups. In addition, there was a negative correlation between Bacteroides abundance and CAT concentration. Additionally, Bacteroides abundance was positively related to IL-17A and IL-22 levels. These findings suggest that maternal PM_2.5 exposure may have some certain effects on intestinal oxidative stress, inflammation, and tight junctions. Quercetin administration may protect the offspring against these adverse effects. Changes of Bacteroides abundance play an important role in the process.

Ambient sulfur dioxide could have an impact on testicular volume from a observational study on a population of infertile male

Background

The effect of ambient pollutants on the male reproductive system is controversial. This retrospective study investigated the effect of environmental pollutants on male reproductive health.

Methods

Male patients with primary infertility (n = 282) were identified from a single center between January 2016 and December 2017. Patients were physically examined for the presence of varicocele and for the volume of both testicles. Semen quality was measured in terms of the total sperm count, sperm concentration, and the percentage of sperm cells with motility and normal morphology. Data were acquired on the concentration of ambient pollutants, namely particulate matters of diameter < 2.5 μm, sulfur dioxide (SO₂), nitrogen oxides (NO_x), and ozone (O₃), measured on daily and hourly basis, from the Environmental Protection Administration Executive Yuan, Taiwan. Individual exposure to pollutants was estimated based on the reported residential address of each participant. Statistical analysis indicated the effect of each pollutant on the testicular volume, sex hormone profile, and semen parameters.

Results

The mean ± standard deviation of age was 36.7 ± 7.3 years. The average sperm count and concentration were 41.9 million/mL and 34.1 million/mL, respectively. The mean levels of serum testosterone, follicle-stimulating hormone, and luteinizing hormone were 3.57 ± 1.68 ng/mL, 7.59 ± 6.3 IU/L, and 4.68 ± 3.49 IU/L, respectively. According to the multivariate linear regression model, NO_x exposure was a risk factor for decreased sperm concentration and motility (p = 0.043 and 0.032). Furthermore, SO₂ exposure was negatively associated and testicular volume (p < 0.01).

Conclusions

NO₂ and SO₂ exposure were negatively associated with the seminal parameter and decreased testicular volume, respectively, in a population of men with infertility. However, additional prospective studies are needed to ascertain the cause–effect relation of current results.

Chronic exposure to diesel exhaust particulate matter impairs meiotic progression during spermatogenesis in a mouse model

Exposure to ambient PM_2.5 may correlate with the decline of semen quality, and the underlying biological mechanism has not been fully understood. In the present study, mice were intratracheally instilled with diesel exhaust PM_2.5 (DEP), and its effects on the spermatogenic process as well as the alterations of testicular gene expression profile were assessed. Our results showed that chronic exposure to DEP impaired the fertility of male mice without influencing their libido. Compared with Vehicle-exposed group, the sperm count and motility from DEP-exposed mice were significantly decreased. In addition, immunohistological staining of γH2AX and DMC1, biomarkers for meiotic double strand breaks (DSBs), demonstrated that chronic exposure to DEP comprised the repair of meiotic DSBs, thus disrupting the spermatogenesis. Deep RNA sequencing test showed altered expressions of testicular genes including the GnRH signaling pathway. In summary, our research demonstrated that chronic exposure to DEP may disrupt spermatogenesis through targeting the meiotic recombination, providing a new perspective for the research on the male reproductive system damage caused by air pollution.

Identifying critical exposure windows for ambient air pollution and semen quality in Chinese men

Emerging studies documented the association between ambient air pollution exposure and semen quality, but the critical exposure windows have not been comprehensively studied. To identify susceptible windows for associations of exposure to ambient respirable particulate matter (PM₁₀), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and ozone (O₃) with sperm concentration, sperm count, total motility, and progressive motility, we recruited 1061 men attending an infertility clinic in Wuhan, China, between 2011 and 2013. We used a distributed lag multivariate linear regression to assess the exposure-lag-response relationship between semen quality and weekly air pollution exposure. The critical exposure windows were during the 6th to 12th sperm development weeks for PM₁₀, 10th to 11th weeks for O₃, and 0 to 5th weeks for SO₂. Over the entire 12 weeks of spermatogenesis period, an interquartile range increase (IQR) increase in PM₁₀ was associated with declined sperm concentration [-45.64% (95% CI: -59.97%, -26.18%) percent decrease], declined sperm count [-49.42% (95% CI: -64.42%, -28.09%) percent decrease], reduced total motility [-12.42 (95% CI: -20.47, -4.37)], and reduced progressive motility [-8.81 (95% CI: -16.00, -1.61)], SO₂ per IQR increase was associated with reduced sperm concentration [-39.73% (95% CI: -55.96%, -17.51%) percent decrease] and total motility [-8.64 (95% CI: -16.90, -0.38)], but NO₂ and O₃ were not associated with any of the four sperm quality parameters. Our findings suggest that exposure to PM₁₀ during spermatidogenesis period, exposure to SO₂ during spermatocytogenesis period, and exposure to O₃ during spermiogenesis period were associated with impaired semen quality, which implies air pollutants impair semen quality through varied pathways.