Circadian Rhythmicity of Antioxidant Markers in Rats Exposed to 1.8 GHz Radiofrequency Fields
Cao H, Qin F, Liu X, Wang J, Cao Y, Tong J, Zhao H. Circadian Rhythmicity of Antioxidant Markers in Rats Exposed to 1.8 GHz Radiofrequency Fields. Int J Environ Res Public Health. 2015 Feb 12;12(2):2071-2087.
Background: The potential health risks of exposure to Radiofrequency Fields (RF) emitted by mobile phones are currently of considerable public interest, such as the adverse effects on the circadian rhythmicities of biological systems. To determine whether circadian rhythms of the plasma antioxidants (Mel, GSH-Px and SOD) are affected by RF, we performed a study on male Sprague Dawley rats exposed to the 1.8 GHz RF.
Methods: All animals were divided into seven groups. The animals in six groups were exposed to 1.8 GHz RF (201.7 μW/cm2 power density, 0.05653 W/kg specific absorption rate) at a specific period of the day (3, 7, 11, 15, 19 and 23 h GMT, respectively), for 2 h/day for 32 consecutive days. The rats in the seventh group were used as sham-exposed controls. At the end of last RF exposure, blood samples were collected from each rat every 4 h (total period of 24 h) and also at similar times from sham-exposed animals. The concentrations of three antioxidants (Mel, GSH-Px and SOD) were determined. The data in RF-exposed rats were compared with those in sham-exposed animals.
Results: circadian rhythms in the synthesis of Mel and antioxidant enzymes, GSH-Px and SOD, were shifted in RF-exposed rats compared to sham-exposed animals: the Mel, GSH-Px and SOD levels were significantly decreased when RF exposure was given at 23 and 3 h GMT.
Conclusion: The overall results indicate that there may be adverse effects of RF exposure on antioxidant function, in terms of both the daily antioxidative levels, as well as the circadian rhythmicity.
... in recent years, evidence is emerging on non-thermal biological effects of RF exposures at different frequencies and SARs/power densities [9,10,11,12].
There are, however, very few reports thus far taking into account circadian associated effects from RF radiation due to mobile phone exposure on different biological systems, especially on the oxidative damage. Reactive oxygen species (ROS) were reported to be directly involved in causing oxidative damage in cellular macromolecules such as lipids, proteins, and nucleic acids in tissues leading to oxidative stress which was suggested to play an important role in several human health conditions such as atherosclerosis, cardiovascular diseases, neurodegenerative disorders, cancer and the aging process . Nonetheless, cells have developed protective mechanisms to scavenge ROS through the production of antioxidant enzymes such as glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), catalase (CAT), etc. However, when ROS generation is outweighed, the endogenous antioxidative defense system is likely to be perturbed . Recent reports have also suggested that melatonin (Mel) is a potent anti-oxidant that exerts many receptor-mediated and receptor-independent activities  and regulates the expression of several genes involved in the production of numerous antioxidant enzymes . In mammals, Mel is synthesized by the pineal gland in the brain in a circadian rhythm and was reported to play an important role in physiological detoxification of ROS and thus, acts as an antioxidant [17,18,19].
Since people generally hold mobile phones near to head when they are making a phone call or answering the phone, their brains are being exposed more to RF than other parts of the body, many studies have reported that people using mobile phone present with changed levels of Mel. But thus far, there were controversial reports, in animals and humans, indicating a decrease, no significant change or an increase in Mel synthesis as well as antioxidant levels following exposure to RF [20,21,22,23,24,25]. Although preliminary results of these studies have shown that RF may change antioxidant levels, as well as increase oxidative stress [26,27], the daily circadian alterations of antioxidant markers under RF exposure have not been demonstrated so far. In this study, we have exposed male rats to 1.8 GHz RF used for mobile phone communications at different times of the day (Greenwich mean time, GMT) to examine the impact on circadian rhythmicity of Mel synthesis as well as GSH-Px and SOD concentrations. The rationale being that the antenna of mobile phones is held close to the head and hence, may have an effect on the brain and perhaps on the pineal gland, which synthesizes Mel.
The FDTD analysis indicated that the numerical whole body SAR distribution was 0.0145W/kg with reference input power density 0.001327 W/m2 as shown in Figure 2 ... As mentioned above, SARE are approximately 0.05653 W/Kg calculated in Equation (1). SARE is lower than the threshold of whole-body SAR recommended by Non-Ironizing Radiation Protection guidelines , so the non-thermal effect inside the rats in RF groups played an important role in the experiments.
There were several controversial reports in the peer-reviewed scientific literature between exposure to RF frequencies used for mobile communications and adverse human health effects: these include increased genotoxicity, brain tumors and neurodegenerative diseases [34,35,36]. While the cellular mechanisms underlying such effects have not been completely elucidated, one of the putative mechanisms proposed for the observed effects was the induction of ROS/free radicals in RF-exposed cells [26,27]. There is well-documented evidence indicating that ROS induces oxidative damage in major cell macromolecules such as lipids and nucleic acids, which have been implicated in tissue injury . However, cells have developed inherent protective measures by synthesizing antioxidant enzymes such as GSH-Px, SOD, CAT, etc. . Thus, the biological antioxidant capacity was suggested to be dependent upon such antioxidant enzymes. Significant decreases in the activity levels of these antioxidant enzymes have been reported in rats exposed to 1.8 GHz RF resulting in increased oxidative stress. There is also ample evidence suggesting that Mel synthesized in the pineal gland in the brain performs the function of antioxidant [39,40]. In experimental animals, pinealectomy was shown to disrupt the circadian rhythm of Mel synthesis leading to decreased antioxidant levels  and thus, antioxidant capacity . In a previous study, we reported a robust circadian rhythm for melatonin in rat blood plasma with peak synthesis observed at ZT19 (GMT 2) .
Although the adverse effects on the circadian rhythmicity in Mel and antioxidant enzymes (SOD and GSH-Px) were observed after 1.8 GHz RF exposure in this experiment, it is of interest for us to examine the signaling mechanism of RF exposure on the circadian rhythmicity of anti-oxidant markers. In our experiment, Mel is more sensitive to RF exposure than the other two anti-oxidant markers, SOD and GSH-Px. Mel is synthesized by the pineal gland in the brain in a circadian rhythm which is synchronous with clock gene expression in the pineal gland, as previously reported by our group . The endogenous clock oscillations rely upon genetic mechanisms involving clock genes coding for transcription factors working in negative and positive feedback loops . A major positive loop consists of the basic helix-loop-helix/PAS-type transcriptional activators BMAL1 and CLOCK or its paralog NPAS2, while two cryptochrome (CRY) and three period proteins (PER) are involved in the negative control of the oscillator . Recently, a CRY-dependent pathway was reported to be involved in disrupting negative geotaxis in Drosophila by electromagnetic field . Mel synthesis is also controlled by clock genes , though whether CLOCK genes play any role in the adverse effects of RF has not, to our knowledge, been studied yet.
This study provides evidence implicating circadian rhythmicity in Mel and the antioxidant enzymes SOD and GSH-Px, as well as the effects of RF exposure on the alterations in antioxidant markers. The adverse effects of RF radiation are present in both the average daily levels of antioxidant markers, and their alterations in a 24-h period (circadian rhythm). Although this study clearly shows that RF exposure induces antioxidant circadian rhythm changes in rats, the next work will be mostly performed to study molecular mechanisms of the regulation of circadian rhythm by clock-controlled genes.
Joel M. Moskowitz, Ph.D., Director
Center for Family and Community Health
School of Public Health
University of California, Berkeley
Electromagnetic Radiation Safety
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