Effects of radiofrequency field exposure on glutamate-induced oxidative stress in mouse hippocampal HT22 cells

Perceptions and Experiences About Device-Emitted Radiofrequency Radiation and Its Effects on Selected Brain Health Parameters in Southwest Nigeria

Introduction

Radiofrequency radiation (RFR) is a form of non-ionising radiation that is used or emitted by a number of technologies and innovative devices including mobile phones and computers and gadgets. Exposure to RFR has been reported to have certain negative effects on human health. It is clear that quality and reliable data will be required with respect to the specific nature of RFR effects on mental health. This research considered the perceptions and exposure-related experiences of people within a Nigerian population with respect to RFR.

Methods

Structured and validated questionnaires were used to profile self-reported patterns of behaviour and sleep in humans. Questionnaire administration-electronic was opened for exactly one week, consisting of 25 specific questions and five open-ended questions [total = 30 questions]. A total population approach was adopted [N=~240]. Bivariate analysis using Chi-square tests were conducted to determine the association between knowledge of electronic gadgets as a source of radiofrequency radiation and sociodemographic characteristics of respondents. Binary logistic regression was used to determine the factors associated with good knowledge of electronic gadgets as a source of radiofrequency radiation. The level of statistical significance was set at p ≤ 0.05.

Results

The response rate was approximately 84%. Fatigue/tiredness [69.6%], attention deficit [69.1%] and headache [62.4%] ranked top amongst RFR-associated negative effects on mental health. Among the respondents, 29 (56.9%) among those above 20 years had good knowledge of radiofrequency radiation from electronic gadgets compared to 72 (47.2%) aged 20 years and below (X² = 1.285, p = 0.257). Also, 45 (59.2%) of persons who lived in a town/village had good knowledge of radiofrequency radiation from electronic gadgets compared to 56 (44.4%) who lived in the city (X² = 4.135, p = 0.042). Persons who lived in a town/village had nearly two times the odds of having good knowledge of RFR from electronic gadgets.

Conclusion

The study showed that respondents had experienced significant and negative effects of RFR on their mental health. The current level of knowledge and awareness on the nature of RFR and exposures was just about average, indicating a critical and urgent need to educate the public on the subject.

Effects of 1800 MHz radiofrequency fields on signal transduction and antioxidant proteins in human A172 glioblastoma cells

PURPOSE

To assess the effects of 1800 MHz radiofrequency electromagnetic field (RF-EMF) exposure on the expression of signal transduction and antioxidant proteins in a human-derived A172 glioblastoma cell line.

MATERIALS AND METHODS

Adherent human-derived A172 glioblastoma cells (1.0 × 105 cells per 35 mm culture dish, containing 2 mL DMEM media) were exposed to 1800 MHz continuous-wave (CW) or GSM-modulated RF fields, in the presence or absence of serum for 5, 30 or 240 min at a specific absorption rate (SAR) of 0 (sham) or 2.0 W/kg. Concurrent negative (vehicle) and positive controls (1 µg/mL anisomycin) were included in each experiment. Cell lysates were collected immediately after exposure, stabilized by protease and phosphatase inhibitors in lysis buffer, then frozen and maintained at -80 °C until analysis. The relative expression levels of phosphorylated- and total-signal transduction proteins (CREB, JNK, NF-κB, ERK1/2, Akt, p70S6K, STAT3 and STAT5) and antioxidant proteins (SOD1, SOD2, CAT, TRX1, PRX2) were assessed using Milliplex magnetic bead array panels and a MagPix Multiplex imaging system.

RESULTS

In cells exposed to 1800 MHz continuous-wave RF-EMF with the presence of serum in the culture medium, CAT expression was statistically significantly decreased after a 30 min exposure, total JNK was decreased at both 30 and 240 min of exposure, STAT3 was decreased after 240 min of exposure and phosphorylated-CREB expression was decreased after 30 min of exposure. In cells exposed to 1800 MHz GSM-modulated RF-EMF in serum-free cultures, the expression level of total STAT5 was decreased after 30 and 240 min of exposure. These observed changes were detected sporadically across time-points, culture conditions and RF-EMF exposure conditions indicating the likelihood of false positive events. When cells were treated with anisomycin for 15 min as a positive control, dramatic increases in the expression of phosphorylated signaling proteins were observed in both serum-starved and serum-fed A172 cells, with larger fold change increases in the serum-free cultures. No statistically significant differences in the expression levels of SOD1, SOD2 or TRX1 were observed under any tested conditions after exposure to RF-EMF.

CONCLUSIONS

The current study found no consistent evidence of changes in the expression of antioxidant proteins (SOD1, SOD2, CAT or TRX2) or a variety of signal transductions proteins (CREB, JNK, NF-κB, ERK1/2, Akt, p70S6K, STAT3, STAT5) in a human-derived glioblastoma A172 cell line in response to exposure to 1800 MHz continuous-wave or GSM-modulated RF-EMF for 5, 30 or 240 min in either serum-free or serum-containing cultures.

Manmade Electromagnetic Fields and Oxidative Stress-Biological Effects and Consequences for Health

Concomitant with the ever-expanding use of electrical appliances and mobile communication systems, public and occupational exposure to electromagnetic fields (EMF) in the extremely-low-frequency and radiofrequency range has become a widely debated environmental risk factor for health. Radiofrequency (RF) EMF and extremely-low-frequency (ELF) MF have been classified as possibly carcinogenic to humans (Group 2B) by the International Agency for Research on Cancer (IARC). The production of reactive oxygen species (ROS), potentially leading to cellular or systemic oxidative stress, was frequently found to be influenced by EMF exposure in animals and cells. In this review, we summarize key experimental findings on oxidative stress related to EMF exposure from animal and cell studies of the last decade. The observations are discussed in the context of molecular mechanisms and functionalities relevant to health such as neurological function, genome stability, immune response, and reproduction. Most animal and many cell studies showed increased oxidative stress caused by RF-EMF and ELF-MF. In order to estimate the risk for human health by manmade exposure, experimental studies in humans and epidemiological studies need to be considered as well.

Effects of radiofrequency electromagnetic radiation emitted from a mobile phone base station on the redox homeostasis in different organs of Swiss albino mice

This study was designed to investigate the possible effects of exposure to mobile phone base station (MPBS) emits 1800-MHz RF-EMR on some oxidative stress parameters in the brain, heart, kidney and liver of Swiss albino mice under exposures below thermal levels. Mice were randomly assigned to three experimental groups which were exposed to RF-EMR for 6 hr/day, 12 hr/day and 24 hr/day for 45 consecutive days, respectively, and a control group. The glutathione (GSH) levels and activities of glutathione-s-transferase (GST) and superoxide dismutase (SOD) were significantly reduced in mice brain after exposure to RF-EMR for 12 hr and 24 hr per day. Exposure of mice to RF-EMR for 12 hr and 24 hr per day also led to a significant increase in malondialdehyde (an index of lipid peroxidation) levels in mice brain. On the contrary, exposures used in this study did not induce any significant change in various oxidative stress-related parameters in the heart, kidney and liver of mice. Our findings showed no significant variations in the activities of aspartate amino-transferase (AST), alanine amino-transferase (ALT), and on the level of creatinine (CRE) in the exposed mice. This study also revealed a decrease in RBC count with an increase in WBC count in mice subjected to 12 hr/day and 24 hr/day exposures. Exposure to RF-EMR from MPBS may cause adverse effects in mice brain by inducing oxidative stress arising from the generation of reactive oxygen species (ROS) as indicated by enhanced lipid peroxidation, and reduced levels and activities of antioxidants.

Dexmedetomidine Attenuates Glutamate-Induced Cytotoxicity by Inhibiting the Mitochondrial-Mediated Apoptotic Pathway

Background

Glutamate (GLU) is the most excitatory amino acid in the central nervous system and plays an important role in maintaining the normal function of the nervous system. During cerebral ischemia, massive release of GLU leads to neuronal necrosis and apoptosis. It has been reported that dexmedetomidine (DEX) possesses anti-oxidant and anti-apoptotic properties. The objective of this study was to investigate the effects of DEX on GLU-induced neurotoxicity in PC12 cells.

Material/Methods

PC12 cells were treated with 20 mM GLU to establish an ischemia-induced injury model. Cell viability was accessed by MTT assay. MDA content and SOD activity were analyzed by assay kits. Apoptosis rate, ROS production, intracellular Ca²⁺ concentration, and MMP were evaluated by flow cytometry. Western blot analysis was performed to analyze expressions of caspase-3, caspase-9, cyt-c, bax, and bcl-2.

Results

PC12 cells treated with GLU exhibited reduced cell viability and increased apoptosis rates, which were ameliorated by pretreatment with DEX. DEX significantly increased SOD activity, reduced content of MDA, and decreased production of ROS in PC12 cells. In addition, DEX clearly reduced the level of intracellular Ca²⁺ and attenuated the decline of MMP. Moreover, DEX notably reduced expressions of caspase-3, caspase-9, cyt-c, and bax and increased expression of bcl-2.

Conclusions

Our findings suggest that DEX can protect PC12 cells against GLU-induced cytotoxicity, which may be attributed to its anti-oxidative property and reduction of intracellular calcium overload, as well as its ability to inhibit the mitochondria-mediated apoptotic pathway.

Peroxiredoxin 4 attenuates glutamate-induced neuronal cell death through inhibition of endoplasmic reticulum stress

High concentrations of glutamate induce neurotoxicity by eliciting reactive oxygen species (ROS) generation and intracellular Ca²⁺ influx. The disruption of Ca²⁺ homeostasis in the endoplasmic reticulum (ER) evokes ER stress, ultimately resulting in neuronal dysfunction. Additionally, glutamate participates in the development of neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases. Peroxiredoxins (Prxs) are members of a family of antioxidant enzymes that protect cells from neurotoxic factor-induced apoptosis by scavenging hydrogen peroxide (H₂O₂). Prx4 is located in the ER and controls the redox condition within the ER. The present study investigated the protective effects of Prx4 against glutamate-induced neurotoxicity linked to ER stress. HT22 cells in which Prx4 was either overexpressed or silenced were used to elucidate the protective role of Prx4 against glutamate toxicity. The expression of Prx4 in HT22 cells was significantly increased in response to glutamate treatment, while ROS scavengers and ER chemical chaperones reduced Prx4 levels. Moreover, Prx4 overexpression reduces glutamate-induced apoptosis of HT22 cells by inhibiting ROS formation, Ca²⁺ influx, and ER stress. Therefore, we conclude that Prx4 has protective effects against glutamate-induced HT22 cell damage. Collectively, these results suggest that Prx4 could contribute to the treatment of neuronal disorders.

Dexmedetomidine Protects Against Chemical Hypoxia-Induced Neurotoxicity in Differentiated PC12 Cells Via Inhibition of NADPH Oxidase 2-Mediated Oxidative Stress

Dexmedetomidine (Dex) is a widely used sedative in anesthesia and critical care units, and it exhibits neuroprotective activity. However, the precise mechanism of Dex-exerted neuroprotection is not clear. Increased neuronal NADPH oxidase 2 (NOX2) contributes to oxidative stress and neuronal damage in various hypoxia-related neurodegenerative disorders. The present study investigated whether Dex regulated neuronal NOX2 to exert its protective effects under hypoxic conditions. Well-differentiated PC12 cells were exposed to cobalt chloride (CoCl₂) to mimic a neuronal model of chemical hypoxia-mediated neurotoxicity. The data showed that Dex pretreatment of PC12 cells significantly suppressed CoCl₂-induced neurotoxicity, as evidenced by the enhanced cell viability, restoration of cellular morphology, and reduction in apoptotic cells. Dex improved mitochondrial function and inhibited CoCl₂-induced mitochondrial apoptotic pathways. We further demonstrated that Dex attenuated oxidative stress, downregulated NOX2 protein expression and activity, and inhibited intracellular calcium ([Ca²⁺]i) overload in CoCl₂-treated PC12 cells. Moreover, knockdown of the NOX2 gene markedly improved mitochondrial function and attenuated apoptosis under hypoxic conditions. These results demonstrated that the protective effects of Dex against hypoxia-induced neurotoxicity in neural cells were mediated, at least partially, via inhibition of NOX2-mediated oxidative stress.

Protective Effect of miR-374a on Chemical Hypoxia-Induced Damage of PC12 Cells In Vitro via the GADD45α/JNK Signaling Pathway

To explore the effect of microRNA-374a (miR-374a) on chemical hypoxia-induced pheochromocytoma (PC12) cell damage by mediating growth arrest and the DNA damage-45 alpha (GADD45α)/c-Jun N-terminal kinase (JNK) signaling pathway. PC12 cells were divided into a Control group (no treatment), Model group (treated with CoCl₂ for 24 h), negative control (NC) group (transfected with miR-374a negative control sequence and treated with CoCl₂ for 24 h), and miR-374a mimic group (transfected with miR-374a mimics and treated with CoCl₂ for 24 h). The viability and apoptosis of PC12 cells were determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and flow cytometry, while the mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) content were assessed by Rh123 and dichloro-dihydro-fluorescein diacetate (DCFH-DA) methods. The expression of miR-374a and GADD45α/JNK proteins was detected using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and Western blot. A significant decrease was found in the survival rate, MMP and miR-374a expression, while an increase was shown in the ROS content and GADD45α and p-JNK expression in hypoxic PC12 cells (all P < 0.05). A luciferase reporter gene assay demonstrated that GADD45α is the target gene of miR-374a. When transfected with miR-374a mimics, hypoxic PC12 cells showed an obvious elevation in survival rate and MMP but a great reduction in cell apoptosis and ROS content, as well as in the expression of GADD45α and p-JNK proteins (all P < 0.05). MiR-374a can protect PC12 cells against hypoxia-induced injury by inhibiting the GADD45α/JNK pathway, enhancing cell viability, suppressing oxidative stress, and inhibiting cell apoptosis, thereby becoming a potential therapeutic target for hypoxic damage.