Adaptive response in mouse bone-marrow stromal cells exposed to 900-MHz radiofrequency fields: Gamma-radiation-induced DNA strand breaks and repair

The effect of exposure to radiofrequency LTE signal and coexposure to mitomycin-C in Chinese hamster lung fibroblast V79 cells

This study aims to investigate the cellular effects of radiofrequency exposure, 1950 MHz, long-term evolution (LTE) signal, administered alone and in combination with mitomycin-C (MMC), a well-known cytotoxic agent. Chinese hamster lung fibroblast (V79) cells were exposed/sham exposed in a waveguide-based system under strictly controlled conditions of both electromagnetic and environmental parameters, at specific absorption rate (SAR) of 0.3 and 1.25 W/kg. Chromosomal damage (micronuclei formation), oxidative stress (reactive oxygen species [ROS] formation), and cell cycle progression were analyzed after exposure and coexposure. No differences between exposed samples and sham-controls were detected following radiofrequency exposure alone, for all the experimental conditions tested and biological endpoints investigated. When radiofrequency exposure was followed by MMC treatment, 3 h pre-exposure did not modify MMC-induced micronuclei. Pre-exposure of 20 h at 0.3 W/kg did not modify the number of micronuclei induced by MMC, while 1.25 W/kg resulted in a significant reduction of MMC-induced damage. Absence of effects was also detected when CW was used, at both SAR levels. MMC-induced ROS formation resulted significantly decreased at both SAR levels investigated, while cell proliferation and cell cycle progression were not affected by coexposures. The results here reported provide no evidence of direct effects of 1950 MHz, LTE signal. Moreover, they further support our previous findings on the capability of radiofrequency pre-exposure to induce protection from a subsequent toxic treatment, and the key role of the modulated signals and the experimental conditions adopted in eliciting the effect.

Rejuvenation of Mesenchymal Stem Cells to Ameliorate Skeletal Aging

Advanced age is a shared risk factor for many chronic and debilitating skeletal diseases including osteoporosis and periodontitis. Mesenchymal stem cells develop various aging phenotypes including the onset of senescence, intrinsic loss of regenerative potential and exacerbation of inflammatory microenvironment via secretory factors. This review elaborates on the emerging concepts on the molecular and epigenetic mechanisms of MSC senescence, such as the accumulation of oxidative stress, DNA damage and mitochondrial dysfunction. Senescent MSCs aggravate local inflammation, disrupt bone remodeling and bone-fat balance, thereby contributing to the progression of age-related bone diseases. Various rejuvenation strategies to target senescent MSCs could present a promising paradigm to restore skeletal aging.

Assessment of Inflammation in 3D Reconstructed Human Skin Exposed to Combined Exposure to Ultraviolet and Wi-Fi Radiation

In the human environment, the increasing exposure to radiofrequency (RF) radiation, especially that emitted by wireless devices, could be absorbed in the body. Recently, mobile and emerging wireless technologies (UMTS, DECT, LTE, and Wi-Fi) have been using higher frequencies than 2G GSM systems (900/1800 MHz), which means that most of the circulating RF currents are absorbed into the skin and the superficial soft tissue. The harmful genotoxic, cytotoxic, and mutagenic effects of solar ultraviolet (UV) radiation on the skin are well-known. This study aimed at investigating whether 2422 MHz (Wi-Fi) RF exposure combined with UV radiation in different sequences has any effect on the inflammation process in the skin. In vitro experiments examined the inflammation process by cytokines (IL-1α, IL-6, IL-8) and MMP-1 enzyme secretion in a 3D full-thickness human skin model. In the first study, UV exposure was immediately followed by RF exposure to measure the potential additive effects, while in the second study, the possible protective phenomenon (i.e., adaptive response) was investigated when adaptive RF exposure was challenged by UV radiation. Our results suggest that 2422 MHz Wi-Fi exposure slightly, not significantly increased cytokine concentrations of the prior UV exposure. We could not detect the adaptive response phenomenon.

Inhibition of Autophagy Negates Radiofrequency-Induced Adaptive Response in SH-SY5Y Neuroblastoma Cells

In the last years, radiofrequency (RF) has demonstrated that it can reduce DNA damage induced by a subsequent treatment with chemical or physical agents in different cell types, resembling the adaptive response, a phenomenon well documented in radiobiology. Such an effect has also been reported by other authors both in vitro and in vivo, and plausible hypotheses have been formulated, spanning from the perturbation of the cell redox status, to DNA repair mechanisms, and stress response machinery, as possible cellular mechanisms activated by RF pre-exposure. These mechanisms may underpin the observed phenomenon, and require deeper investigations. The present study aimed to determine whether autophagy contributes to RF-induced adaptive response. To this purpose, SH-SY5Y human neuroblastoma cells were exposed for 20 h to 1950 MHz, UMTS signal, and then treated with menadione. The results obtained indicated a reduction in menadione-induced DNA damage, assessed by applying the comet assay. Such a reduction was negated when autophagy was inhibited by bafilomycin A1 and E64d. Moreover, CRISPR SH-SY5Y cell lines defective for ATG7 or ATG5 genes did not show an adaptive response. These findings suggest the involvement of autophagy in the RF-induced adaptive response in human neuroblastoma cells; although, further investigation is required to extend such observation at the molecular level.

900 MHz Radiofrequency Field Induces Mitochondrial Unfolded Protein Response in Mouse Bone Marrow Stem Cells

Objective: To examine whether exposure of mouse bone marrow stromal cells (BMSC) to 900 MHz radiofrequency fields used in mobile communication devices can induce mitochondrial unfolded protein response (UPR^mt). Methods: BMSCs were exposed to continuous wave 900 MHz radiofrequency fields (RF) at 120 μW/cm² power intensity for 4 h/d for 5 consecutive days. Cells in sham group (SH) were cultured in RF exposure system, but without RF radiation. The positive control cells were irradiated with 6 Gy X-ray at a dose rate of 1.103 Gy/min (XR). To inhibit the upstream molecular JNK2 of UPR^mt, cells in siRNA + RF, and siRNA + XR group were also pretreated with 100 nM siRNA-JNK2 for 48 h before RF/XR exposure. Thirty minutes, 4 h, and 24 h post-RF/XR exposure, cells were collected, the level of ROS was measured with flow cytometry, the expression levels of UPR^mt-related proteins were detected using western blot analysis. Results: Compared with Sham group, the level of ROS in RF and XR group was significantly increased 30 min and 4 h post-RF/XR exposure (P < 0.05), however, the RF/XR-induced increase of ROS level reversed 24 h post-RF/XR exposure. Compared with Sham group, the expression levels of HSP10/HSP60/ClpP proteins in cells of RF and XR group increased significantly 30 min and 4 h post-RF/XR exposure (P < 0.05), however, the RF/XR-induced increase of HSP10/HSP60/ClpP protein levels reversed 24 h post-RF exposure. After interfering with siRNA-JNK2, the RF/XR exposures could not induce the increase of HSP10/HSP60/ClpP protein levels any more. Conclusions: The exposure of 900 MHz RF at 120 μW/cm² power flux density could increase ROS level and activate a transient UPR^mt in BMSC cells. Mitochondrial homeostasis in term of protein folding ability is restored 24 h post-RF exposure. Exposure to RF in our experimental condition did not cause permanent and severe mitochondrial dysfunctions. However, the detailed underlying molecular mechanism of RF-induced UPR^mt remains to be further studied.

Evidence of bystander effect induced by radiofrequency radiation in a human neuroblastoma cell line

In previous studies we demonstrated that radiofrequency (RF) electromagnetic fields (EMF) is able to reduce DNA damage induced by a subsequent treatment with genotoxic agents, resembling the adaptive response, a phenomenon well known in radiobiology. In this study we report on the capability of the culture medium from SH-SY5Y neuroblastoma cells exposed to 1950 MHz to elicit, in recipient non-exposed cells, a reduction of menadione-induced DNA damage (P < 0.05; comet assay), indicating the capability of non-ionizing radiation to elicit a bystander effect. A comparable reduction was also detected in cultures directly exposed to the same EMF conditions (P < 0.05), confirming the adaptive response. In the same exposure conditions, we also evidenced an increase of heat shock protein 70 (hsp70) in culture medium of cells exposed to RF with respect to sham exposed ones (P < 0.05; western blot analysis), while no differences were detected in the intracellular content of hsp70. On the whole, our results evidence a protective effect of RF against menadione-induced DNA damage in directly and non-directly exposed cells, and suggest hsp70 pathway to be investigated as one of the potential candidate underpinning the interaction between RF exposure and biological systems.

Genetic effects of non-ionizing electromagnetic fields

This is a review of the research on the genetic effects of non-ionizing electromagnetic field (EMF), mainly on radiofrequency radiation (RFR) and static and extremely low frequency EMF (ELF-EMF). The majority of the studies are on genotoxicity (e.g., DNA damage, chromatin conformation changes, etc.) and gene expression. Genetic effects of EMF depend on various factors, including field parameters and characteristics (frequency, intensity, wave-shape), cell type, and exposure duration. The types of gene expression affected (e.g., genes involved in cell cycle arrest, apoptosis and stress responses, heat-shock proteins) are consistent with the findings that EMF causes genetic damages. Many studies reported effects in cells and animals after exposure to EMF at intensities similar to those in the public and occupational environments. The mechanisms by which effects are induced by EMF are basically unknown. Involvement of free radicals is a likely possibility. EMF also interacts synergistically with different entities on genetic functions. Interactions, particularly with chemotherapeutic compounds, raise the possibility of using EMF as an adjuvant for cancer treatment to increase the efficacy and decrease side effects of traditional chemotherapeutic drugs. Other data, such as adaptive effects and mitotic spindle aberrations after EMF exposure, further support the notion that EMF causes genetic effects in living organisms.

No Increased DNA Damage Observed in the Brain, Liver, and Lung of Fetal Mice Treated With Ethylnitrosourea and Exposed to UMTS Radiofrequency Electromagnetic Fields

The widespread use of mobile phones and Wi-Fi-based communication devices makes exposure to radiofrequency electromagnetic fields (RF-EMF) unavoidable. Previous experiments have revealed the tumor-promoting effects of non-ionizing RF-EMF in adult carcinogen-treated mice in utero. To extend these investigations, we tested whether these effects are due to the co-carcinogenicity of RF-EMF which would manifest as elevated DNA damage. Similar to previous experiments, pregnant mice were exposed to RF-EMF (Universal Mobile Telecommunication System [UMTS] standard, approximately 1,960 MHz) from day 7 post-conception (p.c.) at 0 (sham), 0.04, and 0.4 W/kg SAR. At day 14 p.c., the mice were injected with the carcinogen ethylnitrosourea (ENU, 40 mg/kg). At three time-points specifically 24, 36, and 72 h later, the pregnant females were sacrificed and the fetuses (n = 24-57) were removed. A dye (cy3) specific for adenyl adducts was used to detect DNA damage by fluorescence microscopy in the brain, liver, and lung of each fetus. Compared to control (0 W/kg SAR), exposure to RF-EMF had no effect on the formation of DNA adducts in the inspected tissues. We conclude that increased adenyl formation of DNA by RF-EMF exposure is not a valid explanation for the previously reported tumor-promoting effects of RF-RMF. Our findings may help to gain a deeper insight into the biological effects of RF-EMF exposure in the context of malignancy. © 2020 The Authors. Bioelectromagnetics published by Wiley Periodicals LLC on behalf of Bioelectromagnetics Society.

Treatment with 3-Aminobenzamide Negates the Radiofrequency-Induced Adaptive Response in Two Cell Models

In previous investigations, we demonstrated that pre-exposure of different cell cultures to radiofrequency fields can reduce the damage induced by genotoxic agents, an effect resembling the so-called adaptive response. In this study, we pre-exposed human peripheral blood lymphocytes and Chinese hamster lung fibroblast cell line to 1950 MHz, UMTS (Universal Mobile Telecommunication System) signal, for 20 h, and then treated cultures with Mitomycin-C. After confirming the induction of an adaptive response in terms of the reduction of micronuclei formation, we observed that such a response was negated by treatments with 3-aminobenzamide. Since 3-aminobenzamide is an inhibitor of poly (ADP-ribose) polymerase enzyme, which is involved in DNA repair, these results support the possible involvement of DNA repair mechanisms in radiofrequency-induced adaptive response.

Repeated 0.2-Gy γ-Ray Irradiation Attenuates the Inflammatory Process and Endotoxin Damage Induced by Lipopolysaccharides

Endotoxin damage is an acute, multi-organ disease, the most typical symptoms of which are liver injury and inflammatory cytokine storm. Endotoxin tolerance is described as the pretreatment of lipopolysaccharides (LPS) before the toxin invasion, which is consistent with the adaptive response induced by low-dose radiation (LDR). In this study, we verified that LDR could resist the endotoxin damage by suppressing the increase of inflammatory cytokines, including interleukin 6, tumor necrosis factor, and NO, to improve the survival and relieve the inflammatory cell infiltration, in which low dose of LPS performed consistently with LDR.

Role of NF-κB activation in mouse bone marrow stromal cells exposed to 900-MHz radiofrequency fields (RF)

Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is a primary transcription factor which plays a key role in several cellular processes including proliferation and survival. It is well known that exposure to non-ionizing radiofrequency fields (RFs), which are ubiquitous, resulted in interaction with cellular components. The aim of the study was thus to examine whether exposure of mouse bone marrow stromal cells (BMSC) to RF also resulted in cellular interactions. BMSC were exposed to 900 MHz RF at 120 μW/cm² power intensity for 4 hr/day for 5 consecutive days. The relative protein expression levels of NF-κB in the cytoplasm and nucleus of RF-exposed cells were compared to non-RF-exposed controls. At 30-min post-RF exposure, a significant decrease in protein expression of NF-κB in the cytoplasm was accompanied by a concomitant increase in nuclear NF-κB protein expression levels. Similar responses were noted in the cytoplasm and nuclear NF-κB levels at 2 hr with a return to control concentrations in primary transcription factor at 24-hr post-RF treatment. Daily incubation of BAY 11-7082, an inhibitor of NF-κB, for 90 min for 5 days followed by RF each day prevented the fall in cytoplasmic NF-κB and rise in nuclear primary transcription factor at 30 min and 2 hr. There were no marked alterations at 24 hr. Data showed that the effects of RF treatment on BMSC involved transient activation of NF-κB which may be attributed to RF-mediated cellular perturbation as evidenced by consequences of BAY 11-7082 inhibition.

Role of NF-κB activation in mouse bone marrow stromal cells exposed to 900 MHz radiofrequency fields (RF)

Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is a primary transcription factor which plays a key role in several cellular processes including proliferation and survival. It is well-known that exposure to non-ionizing radiofrequency fields (RF), which are ubiquitous, interact with cellular components. The aim of the study was thus to examine whether exposure of mouse bone marrow stromal cells (BMSC) to RF also resulted in cellular interactions. BMSC were exposed to 900 MHz RF at 120 μW/cm² power intensity for 4 hr/day for 5 consecutive days. The relative protein expression levels of NF-κB in the cytoplasm and nucleus of RF-exposed cells were compared to non-RF-exposed controls. At 30 min post-RF exposure a significant decrease in protein expression of NF-κB in the cytoplasm was accompanied by a concomitant increase in nuclear NF-κB protein expression levels. Similar responses were noted in the cytoplasm and nuclear NF-κB levels at 2 hr with a return to control concentrations in primary transcription factor at 24 hr post-RF treatment. Daily incubation of BAY 11-7082 an inhibitor of NF-κB for 90 min for 5 days followed by RF each day prevented the fall in cytoplasmic NF-κB and rise in nuclear primary transcription factor at 30 min and 2 hr. There were no marked alterations at 24 hr. Data showed that the effects of RF treatment on BMSC involved transient activation of NF-κB which may be attributed to RF-mediated cellular perturbation as evidenced by consequences of BAY 11-7082 inhibition.

Thermal and non-thermal health effects of low intensity non-ionizing radiation: An international perspective

Exposure to low frequency and radiofrequency electromagnetic fields at low intensities poses a significant health hazard that has not been adequately addressed by national and international organizations such as the World Health Organization. There is strong evidence that excessive exposure to mobile phone-frequencies over long periods of time increases the risk of brain cancer both in humans and animals. The mechanism(s) responsible include induction of reactive oxygen species, gene expression alteration and DNA damage through both epigenetic and genetic processes. In vivo and in vitro studies demonstrate adverse effects on male and female reproduction, almost certainly due to generation of reactive oxygen species. There is increasing evidence the exposures can result in neurobehavioral decrements and that some individuals develop a syndrome of "electro-hypersensitivity" or "microwave illness", which is one of several syndromes commonly categorized as "idiopathic environmental intolerance". While the symptoms are non-specific, new biochemical indicators and imaging techniques allow diagnosis that excludes the symptoms as being only psychosomatic. Unfortunately standards set by most national and international bodies are not protective of human health. This is a particular concern in children, given the rapid expansion of use of wireless technologies, the greater susceptibility of the developing nervous system, the hyperconductivity of their brain tissue, the greater penetration of radiofrequency radiation relative to head size and their potential for a longer lifetime exposure.

Protective effect of 1950 MHz electromagnetic field in human neuroblastoma cells challenged with menadione

This study aims to assess whether a 1950 MHz radiofrequency (RF) electromagnetic field could protect human neuroblastoma SH-SY5Y cells against a subsequent treatment with menadione, a chemical agent inducing DNA damage via reactive oxygen species formation. Cells were pre-exposed for 20 h to specific absorption rate of either 0.3 or 1.25 W/kg, and 3 h after the end of the exposure, they were treated with 10 µM menadione (MD) for 1 h. No differences were observed between sham- and RF-exposed samples. A statistically significant reduction in menadione-induced DNA damage was detected in cells pre-exposed to either 0.3 or 1.25 W/kg (P < 0.05). Moreover, our analyses of gene expression revealed that the pre-exposure to RF almost inhibited the dramatic loss of glutathione peroxidase-based antioxidant scavenging efficiency that was induced by MD, and in parallel strongly enhanced the gene expression of catalase-based antioxidant protection. In addition, RF abolished the MD-dependent down-regulation of oxoguanine DNA glycosylase, which is a critical DNA repairing enzyme. Overall, our findings suggested that RF pre-exposure reduced menadione-dependent DNA oxidative damage, most probably by enhancing antioxidant scavenging efficiency and restoring DNA repair capability. Our results provided some insights into the molecular mechanisms underlying the RF-induced adaptive response in human neuroblastoma cells challenged with menadione.

Risk management of free radicals involved in air travel syndromes by antioxidants

Frequent air travelers and airplane pilots may develop various types of illnesses. The environmental risk factors associated with air travel syndromes (ATS) or air travel-related adverse health outcomes raised concerns and need to be assessed in the context of risk management and public health. Accordingly, the aim of the present review was to determine ATS, risk factors, and mechanisms underlying ATS using scientific data and information obtained from Medline, Toxline, and regulatory agencies. Additional information was also extracted from websites of organizations, such as the International Air Transport Association (IATA), International Association for Medical Assistance to Travelers (IAMAT), and International Civil Aviation Organization (ICAO). Air travelers are known to be exposed to environmental risk factors, including circadian rhythm disruption, poor cabin air quality, mental stress, high altitude conditions, hormonal dysregulation, physical inactivity, fatigue, biological infections, and alcoholic beverage consumption. Consequences of ATS attributed to air travel include sleep disturbances (e.g., insomnia), mental/physical stress, gastrointestinal disorders, respiratory diseases, circulatory-related dysfunction, such as cardiac arrest and thrombosis and, at worst, mechanical and terrorism-related airplane crashes. Thus safety measures in the cabin before or after takeoff are undertaken to prevent illnesses or accidents related to flight. In addition, airport quarantine systems are strongly recommended to prepare for any ultimate adverse circumstances. Routine monitoring of environmental risk factors also needs to be considered. Frequently, the mechanisms underlying these adverse manifestations involve free radical generation. Therefore, antioxidant supplementation may help to reduce or prevent adverse outcomes by mitigating health risk factors associated with free radical generation.

Enhancement of X-ray Induced Apoptosis by Mobile Phone-Like Radio-Frequency Electromagnetic Fields in Mouse Spermatocyte-Derived Cells

To explore the combined effects of environmental radio-frequency (RF) field and X-ray, mouse spermatocyte-derived (GC-1) cells were exposed to 1950 MHz RF field at specific absorption rate (SAR) of 3 W/kg for 24 h combined with or without X-ray irradiation at 6 Gy. After treatment, the cell proliferation level was determined by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) Assay and 5-Bromo-2-deoxy Uridine (BrdU) enzyme linked immunosorbent (ELISA) Assay. The apoptosis level was detected by annexin V flow cytometry assay, transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) Assay and Caspase-3 Activity Assay. It was found that the proliferation and apoptosis level did not change in GC-1 cells after RF exposure alone. However, compared with the X-ray group, the proliferation level significantly decreased and the apoptotic rate significantly increased in the RF+X-ray group. Moreover, a significant decrease in Bcl-2 protein expression and increase in Bax protein expression were observed. The findings suggested that RF exposure at SAR of 3 W/kg did not affect apoptosis and proliferation in GC-1 cells by itself, but that it did enhance the effects of X-ray induced proliferation inhibition and apoptosis, in which B-cell lymphoma-2 (Bcl-2) and Bcl-2 associated X protein (Bax) might be involved.

Induction of Poly(ADP-ribose) Polymerase in Mouse Bone Marrow Stromal Cells Exposed to 900 MHz Radiofrequency Fields: Preliminary Observations

Background. Several investigators have reported increased levels of poly(ADP-ribose) polymerase-1 (PARP-1), a nuclear enzyme which plays an important role in the repair of damaged DNA, in cells exposed to extremely low dose ionizing radiation which does not cause measurable DNA damage. Objective. To examine whether exposure of the cells to nonionizing radiofrequency fields (RF) is capable of increasing messenger RNA of PARP-1 and its protein levels in mouse bone marrow stromal cells (BMSCs). Methods. BMSCs were exposed to 900 MHz RF at 120 μW/cm² power intensity for 3 hours/day for 5 days. PARP-1 mRNA and its protein levels were examined at 0, 0.5, 1, 2, 4, 6, 8, and 10 hours after exposure using RT-PCR and Western blot analyses. Sham-exposed (SH) cells and those exposed to ionizing radiation were used as unexposed and positive control cells. Results. BMSCs exposed to RF showed significantly increased expression of PARP-1 mRNA and its protein levels after exposure to RF while such changes were not observed in SH-exposed cells. Conclusion. Nonionizing RF exposure is capable of inducing PARP-1.