Effects of electromagnetic radiation on morphology and TGF-β3 expression in mouse testicular tissue

Effects of radiofrequency electromagnetic field (RF-EMF) exposure on male fertility: A systematic review of experimental studies on non-human mammals and human sperm in vitro

BACKGROUND

The World Health Organization is coordinating an international project aimed at systematically reviewing the evidence regarding the association between radiofrequency electromagnetic field (RF-EMF) exposure and adverse health effects. Reproductive health outcomes have been identified among the priority topics to be addressed.

OBJECTIVES

To evaluate the effect of RF-EMF exposure on male fertility of experimental mammals and on human sperm exposed in vitro.

METHODS

Three electronic databases (PubMed, Scopus and EMF Portal) were last searched on September 17, 2022. Two independent reviewers screened the studies, which were considered eligible if met the following criteria: 1) Peer-reviewed publications of sham controlled experimental studies, 2) Non-human male mammals exposed at any stage of development or human sperm exposed in vitro, 3) RF-EMF exposure within the frequency range of 100 kHz-300 GHz, including electromagnetic pulses (EMP), 4) one of the following indicators of reproductive system impairment:Two reviewers extracted study characteristics and outcome data. We assessed risk of bias (RoB) using the Office of Health Assessment and Translation (OHAT) guidelines. We categorized studies into 3 levels of overall RoB: low, some or high concern. We pooled study results in a random effects meta-analysis comparing average exposure to no-exposure and in a dose-response meta-analysis using all exposure doses. For experimental animal studies, we conducted subgroup analyses for species, Specific Absorption Rate (SAR) and temperature increase. We grouped studies on human sperm exposed in vitro by the fertility status of sample donors and SAR. We assessed the certainty of the evidence using the GRADE approach after excluding studies that were rated as "high concern" for RoB.

RESULTS

One-hundred and seventeen papers on animal studies and 10 papers on human sperm exposed in vitro were included in this review. Only few studies were rated as "low concern" because most studies were at RoB for exposure and/or outcome assessment. Subgrouping the experimental animal studies by species, SAR, and temperature increase partly accounted for the heterogeneity of individual studies in about one third of the meta-analyses. In no case was it possible to conduct a subgroup analysis of the few human sperm in vitro studies because there were always 1 or more groups including less than 3 studies. Among all the considered endpoints, the meta-analyses of animal studies provided evidence of adverse effects of RF-EMF exposure in all cases but the rate of infertile males and the size of the sired litters. The assessment of certainty according to the GRADE methodology assigned a moderate certainty to the reduction of pregnancy rate and to the evidence of no-effect on litter size, a low certainty to the reduction of sperm count, and a very low certainty to all the other meta-analysis results. Studies on human sperm exposed in vitro indicated a small detrimental effect of RF-EMF exposure on vitality and no-effect on DNA/chromatin alterations. According to GRADE, a very low certainty was attributed to these results. The few studies that used EMP exposure did not show effects on the outcomes. A low to very low certainty was attributed to these results.

DISCUSSION

Many of the studies examined suffered of severe limitations that led to the attribution of uncertainty to the results of the meta-analyses and did not allow to draw firm conclusions on most of the endpoints. Nevertheless, the associations between RF-EMF exposure and decrease of pregnancy rate and sperm count, to which moderate and low certainty were attributed, are not negligible, also in view of the indications that in Western countries human male fertility potential seems to be progressively declining. It was beyond the scope of our systematic review to determine the shape of the dose-response relationship or to identify a minimum effective exposure level. The subgroup and the dose-response fitting analyses did not show a consistent relationship between the exposure levels and the observed effects. Notably, most studies evaluated RF-EMF exposure levels that were higher than the levels to which human populations are typically exposed, and the limits set in international guidelines. For these reasons we cannot provide suggestions to confirm or reconsider current human exposure limits. Considering the outcomes of this systematic review and taking into account the limitations found in several of the studies, we suggest that further investigations with better characterization of exposure and dosimetry including several exposure levels and blinded outcome assessment were conducted.

PROTOCOL REGISTRATION

Protocols for the systematic reviews of animal studies and of human sperm in vitro studies were published in Pacchierotti et al., 2021. The former was also registered in PROSPERO (CRD42021227729 https://www.crd.york.ac.uk/prospero/display_record.php?RecordID = 227729) and the latter in Open Science Framework (OSF Registration DOI https://doi.org/10.17605/OSF.IO/7MUS3).

Molecular Hydrogen Reduces Electromagnetic Pulse-Induced Male Rat Reproductive System Damage in a Rodent Model

Infertility has got to be a broadly concerned social issue these days, in which the malefactor cannot be overlooked. Numerous studies have shown that electromagnetic pulse (EMP) radiation may have seriously damaging effects on reproductive health, through nonthermal effects and oxidative stress. Molecular hydrogen, a selective hydroxyl radical scavenger, explains the protective effects against many diseases closely associated with oxidative damage, such as ionizing radiation (IR). We sought to characterize the beneficial effects of molecular hydrogen on the male reproductive system in a rodent EMP exposure model. The 8-week-old male Sprague-Dawley rats were exposed to EMP (peak intensity 1000 kV/m, pulse edge 20 ns, pulse width 200 ns, 1 Hz, and 200 pulses), with or without hydrogen-rich water. The pathological structure of the testis, the rate of apoptosis of the testis, the serum testosterone level, the sperm parameters, and the activity of the antioxidant enzymes of the testis were measured. Then, transcriptomic and untargeted metabolomic analyses were applied to uncover the underlying mechanism. Exposure to EMP increased testicular apoptosis rate and apoptosis protein level, decreased sperm viability and motility, decreased serum testosterone levels, and diminished testicular antioxidant capacity. Molecular hydrogen-alleviated damage decreased the testicular apoptosis rate and apoptosis protein level, increased sperm motility, increased serum testosterone levels, and improved antioxidative capacity. Omics results showed that molecular hydrogen has a strong influence on metabolic pathways, and EMP affects mainly oxidative phosphorylation, TNF signaling pathways, and cytokine-receptor interactions. The mechanism of molecular hydrogen's effect may be related to the reversal of some metabolite levels. These observations warrant molecular hydrogen as an innovative approach for potential protection against EMP.

Biochemical, immunohistochemical and morphometrical investigation of the effect of thymoquinone on the rat testis following exposure to a 900-MHz electromagnetic field

Long-term use of cell phones emitting electromagnetic fields (EMFs) have raised concerns regarding public health in recent year. We aimed to investigate the possible effects of 900 MHz EMF exposure (60 min/day for 28 days) on the rat testis. Another objective was to determine whether the deleterious effect of EMF radiation would be reduced by the administration of thymoquinone (TQ) (10 mg/kg/day). Twenty-four male adult Wistar albino rats were randomly selected, then assigned into four groups as followControl, EMF, TQ and EMF + TQ. Testicular samples were analyzed using histological, stereological, biochemical and immunohistochemical techniques. Total numbers of primary spermatocytes and spermatids as well as Leydig cells were significantly decreased in the EMF group compared to the Control group (p < 0.05). In the EMF + TQ group, the total number of primary spermatocytes was significantly increased compared to the EMF group (p < 0.05). Superoxide dismutase (SOD) activity was significantly increased in the EMF group compared to the Control group (p < 0.05). Also, serum testosterone levels and wet weight of testes were significantly decreased in the EMF group compared to the Control group (p < 0.05). Our findings suggested that exposure to a 900 MHz EMF had adverse effects on rat testicular tissue and that the administration of TQ partially mitigated testicular oxidative damages caused by EMF radiation.

Effects of 220 MHz Pulsed Modulated Radiofrequency Field on the Sperm Quality in Rats

Under some occupational conditions, workers are inevitably exposed to high-intensity radiofrequency (RF) fields. In this study, we investigated the effects of one-month exposure to a 220 MHz pulsed modulated RF field at the power density of 50 W/m² on the sperm quality in male adult rats. The sperm quality was evaluated by measuring the number, abnormality and survival rate of sperm cells. The morphology of testis was examined by hematoxylin-eosin (HE) staining. The levels of secreting factors by Sertoli cells (SCs) and Leydig cells (LCs) were determined by enzyme linked immunosorbent assay (ELISA). The level of cleaved caspase 3 in the testis was detected by immunofluorescence staining. Finally, the expression levels of the apoptosis-related protein (caspase 3, BAX and BCL2) in the testis were assessed by Western blotting. Compared with the sham group, the sperm quality in the RF group decreased significantly. The levels of secreting factors of SCs and the morphology of the testis showed an obvious change after RF exposure. The level of the secreting factor of LCs decreased significantly after RF exposure. The levels of cleaved caspase 3, caspase 3, and the BAX/BCL2 ratio in the testis increased markedly after RF exposure. These data collectively suggested that under the present experimental conditions, 220 MHz pulsed modulated RF exposure could impair sperm quality in rats, and the disruption of the secreting function of LCs and increased apoptosis of testis cells induced by the RF field might be accounted for by this damaging effect.

Editor's Highlight: Effects of Intraperitoneal Injection of SnS2 Flowers on Mouse Testicle

SnS2 nanoflowers (SnS2 NFs) have been widely used in photoelectric and catalytic applications. However, its explosure and reproductive toxicity is unknown. The aim of this study was to investigate the effect of exposure to 3 different sized-SnS2 flowers (dose: 38 mg/kg; size: 50, 80, and 200 nm) in testes of mice for 4 weeks by intraperitoneal injection. Though the body weight of mice treated or not with SnS2 NFs was not different, and SnS2 NFs were distributed to the organs including liver, kidney, spleen, heart, brain, and testis, more distribution SnS2 NFs (50 and 80 nm) were found in testicle tissues compared with SnS2 flowers (200 nm) in those tissues. The results of sperm count and survival analysis, histopathological evaluation, and qRT-PCR detection showed that there was moderate reproductive toxicity induced by the small-sized SnS2 NFs in testicle tissues. Furthermore, elevated malondialdehyde level and decreased superoxide dismutase activity were also observed in the SnS2 NFs (dose: 38 mg/kg; size: 50 and 80 nm) treated groups. Likewise, the qRT-PCR data indicated that SnS2 NFs can induce apoptosis and inflammation responses. Although the pro-inflammation marker of TNF-α, IL-1β, iNOS, and COX-2 at the mRNA levels were higher expression in 50 and 80 nm groups than that in control and 200 nm group, no statistical significance existed between 50 and 80 nm groups. Accordingly, the repeated-dose toxicity of SnS2 NFs in testicle tissues was also observed in a dose-dependent manner by intraperitoneal injection of SnS2 NFs (size: 50 nm; 0.38, 3.8, and 38 mg/kg) for 4 weeks, when determined by sperm count, survival rate, and qRT-PCR analysis. In addition, transmission electron microscopy showed that the ultrastructural abnormalities formed by the small-sized SnS2 NFs in testes were more severe than those formed by the large-sized SnS2 in testes. Taken together, these findings implied that the SnS2 NFs activated inflammation responses that signified apoptosis in murine testes. This study provided useful information for risk analysis and regulation of SnS2 NFs by administration agencies.

Radiations and male fertility

During recent years, an increasing percentage of male infertility has to be attributed to an array of environmental, health and lifestyle factors. Male infertility is likely to be affected by the intense exposure to heat and extreme exposure to pesticides, radiations, radioactivity and other hazardous substances. We are surrounded by several types of ionizing and non-ionizing radiations and both have recognized causative effects on spermatogenesis. Since it is impossible to cover all types of radiation sources and their biological effects under a single title, this review is focusing on radiation deriving from cell phones, laptops, Wi-Fi and microwave ovens, as these are the most common sources of non-ionizing radiations, which may contribute to the cause of infertility by exploring the effect of exposure to radiofrequency radiations on the male fertility pattern. From currently available studies it is clear that radiofrequency electromagnetic fields (RF-EMF) have deleterious effects on sperm parameters (like sperm count, morphology, motility), affects the role of kinases in cellular metabolism and the endocrine system, and produces genotoxicity, genomic instability and oxidative stress. This is followed with protective measures for these radiations and future recommendations. The study concludes that the RF-EMF may induce oxidative stress with an increased level of reactive oxygen species, which may lead to infertility. This has been concluded based on available evidences from in vitro and in vivo studies suggesting that RF-EMF exposure negatively affects sperm quality.

Changes in testicular morphology and oxidative stress biomarkers in 60-day-old Sprague Dawley rats following exposure to continuous 900-MHz electromagnetic field for 1 h a day throughout adolescence

The purpose of this study was to investigate the 60-day-old male rat testis following exposure to continuous 900-megahertz (MHz) electromagnetic field (EMF) throughout the adolescent period using histopathological and biochemical analysis methods. Twenty-four Sprague Dawley rats aged 21 days were randomly and equally (n = 8) divided into three groups. No procedure was performed on the control group rats. The sham group rats were held in an EMF-cage without exposure to EMF. The EMF group rats were exposed to continuous 900-MHz EMF for 1 h each day inside the EMF-cage during adolescence. On postnatal day 60 the testes were extracted and divided into right and left halves. The right half was used for histopathological evaluation and the left half for biochemical analyses. Our results show that changes may occur in morphology and oxidative stress biomarkers in the rat testis following exposure to continuous 900-MHz EMF throughout the adolescent period.

Fine particle matter disrupts the blood-testis barrier by activating TGF-β3/p38 MAPK pathway and decreasing testosterone secretion in rat

Fine particle matter (PM) is correlated with male reproductive dysfunction in animals and humans, but the underlying mechanisms remain unknown. To investigate the toxic mechanism of PM, 32 male Sprague-Dawley (SD) rats were exposed to saline or PM_2.5 with the doses of 1.8, 5.4, and 16.2 mg/kg.b.w. via intratracheal instillation, respectively, one time every 3 days, in total times for 30 days. Sperm concentration, hormone level, the expressions of BTB-associated protein and the mitogen-activated protein kinase (MAPK) pathway, tumor necrosis factor α and transforming growth factor β3 levels were detected. The results showed a decrease in sperm number, testosterone and luteinizing hormone levels and altered ultrastructure of BTB in testis of rat after exposure to PM_2.5 . The protein levels of N-Cadherin, Occludin, Claudin-11, and Connexin-43 were significantly decreased in the testes. TGF-β3 content in testes showed increase, with the p-p38/p38 MAPK ratio also increasing after PM_2.5 exposure. These results demonstrate that PM_2.5 restrained the expressions of BTB-associated proteins through activating TGF-β3/p38 MAPK pathway and decreasing testosterone secretion, and therefore lead to the damage of BTB resulting in the decrease of sperm quality, which might be the potential reasons for its negative effects on spermatogenesis and male reproduction.

Effects of Simulated Mobile Phone Electromagnetic Radiation on Fertilization and Embryo Development

This study investigated the effects of 935-MHz electromagnetic radiation (ER) on fertilization and subsequent embryonic development in mice. Ovulating mice were irradiated at three ER intensities for 4 h/day (d) or 2 h/d for three consecutive days; the ova were then harvested for in vitro fertilization to observe the 6-h fertilization rate (6-FR), 72-h morula rate (72-MR), and 110-h blastula rate (110-BR). Compared with the control group, the 6-FR, 72-MR, and 110-BR were decreased in the low ER intensity group, but the differences were not significant; in the mid- and high-intensity ER groups, 72-MR and 110-BR in the 4 h/d and 2 h/d subgroups were decreased, showing significant differences compared with the control group. Moreover, the comparison between 4 h/d and 2 h/d subgroups showed significant differences. Mid- and high-intensity ER at 935 MHz can reduce the fertilization rate in mice, and reduce the blastulation rate, thus reducing the possibility of embryo implantation.

Effects of Electromagnetic Radiation from Smartphones on Learning Ability and Hippocampal Progenitor Cell Proliferation in Mice

OBJECTIVES

Nonionizing radiation is emitted from electronic devices, such as smartphones. In this study, we intended to elucidate the effect of electromagnetic radiation from smartphones on spatial working memory and progenitor cell proliferation in the hippocampus.

METHODS

Both male and female mice were randomly separated into two groups (radiated and control) and the radiated group was exposed to electromagnetic radiation for 9 weeks and 11 weeks for male and female mice, respectively. Spatial working memory was examined with a Y maze, and proliferation of hippocampal progenitor cells were examined by 5-bromo-2'-deoxyuridine administration and immunohistochemical detection.

RESULTS

When spatial working memory on a Y maze was examined in the 9(th) week, there was no significant difference in the spontaneous alternation score on the Y maze between the two groups. In addition, there was no significant difference in hippocampal progenitor cell proliferation. However, immunoreactivity to glial fibrillary acidic protein was increased in exposed animals. Next, to test the effect of recovery following chronic radiation exposure, the remaining female mice were further exposed to electromagnetic radiation for 2 more weeks (total 11 weeks), and spontaneous alternation was tested 4 weeks later. In this experiment, although there was no significant difference in the spontaneous alternation scores, the number of arm entry was significantly increased.

CONCLUSION

These data indicate that although chronic electromagnetic radiation does not affect spatial working memory and hippocampal progenitor cell proliferation it can mediate astrocyte activation in the hippocampus and delayed hyperactivity-like behavior.

Injury to the blood-testis barrier after low-dose-rate chronic radiation exposure in mice

Exposure to ionising radiation induces male infertility, accompanied by increasing permeability of the blood-testis barrier. However, the effect on male fertility by low-dose-rate chronic radiation has not been investigated. In this study, the effects of low-dose-rate chronic radiation on male mice were investigated by measuring the levels of tight-junction-associated proteins (ZO-1 and occludin-1), Niemann-Pick disease type 2 protein (NPC-2) and antisperm antibody (AsAb) in serum. BALB/c mice were exposed to low-dose-rate radiation (3.49 mGy h(-1)) for total exposures of 0.02 (6 h), 0.17 (2 d) and 1.7 Gy (21 d). Based on histological examination, the diameter and epithelial depth of seminiferous tubules were significantly decreased in 1.7-Gy-irradiated mice. Compared with those of the non-irradiated group, 1.7-Gy-irradiated mice showed significantly decreased ZO-1, occludin-1 and NPC-2 protein levels, accompanied with increased serum AsAb levels. These results suggest potential blood-testis barrier injury and immune infertility in male mice exposed to low-dose-rate chronic radiation.

Perfluorooctanoic acid disrupts the blood-testis barrier and activates the TNFα/p38 MAPK signaling pathway in vivo and in vitro

Perfluorooctanoic acid (PFOA) is correlated with male reproductive dysfunction in animals and humans, but the underlying mechanisms for this remain unknown. To explore the potential reproductive toxicity of PFOA, we studied blood-testis barrier (BTB) damage using in vivo and in vitro models. Male mice were gavage-administered PFOA (0-20 mg/kg/d) for 28 consecutive days, and breeding capacity and permeability of the Sertoli cell-based BTB were estimated. Primary Sertoli cells (SCs) were exposed to PFOA (0-500 μM) for 48 h, and transepithelial electrical resistance (TER) was assessed. Furthermore, BTB-associated protein expression, TNFα content, and phosphorylation and protein levels of the mitogen-activated protein kinase (MAPK) pathway were detected. An apparent decrease in mated and pregnant females per male mouse as well as litter weight was observed. Marked BTB damage was evidenced by increased red biotin fluorescence in the lumen tubular of the testes and the decrease in TER in SCs in vitro. The protein levels of claudin-11, connexin-43, N-cadherin, β-catenin, and occludin were significantly decreased in the testes and also in the SCs in vitro except for N-cadherin and β-catenin. TNFα content showed a dose-dependent increase in the testes and a dose- and time-dependent increase in the SCs, with the p-p38/p38 MAPK ratio also increasing in testes and SCs after PFOA exposure. Moreover, PFOA altered expressions of claudin-11, connexin-43, TNFα, and p-p38 MAPK were recovered 48 h after PFOA removal in the SCs. The SCs appeared to be target to PFOA, and the disruption of the BTB may be crucial to PFOA-induced reproductive dysfunction in mice.