This study was undertaken to evaluate effects of acute and chronic ELF-MF exposure on serum lipid profile, lipid peroxidation, antioxidant system, and paraoxonase activity as mediators protecting against atherogenesis and atherosclerosis.
According to the results of our study, ELF-MF exposure changed lipid profile, increased lipid peroxidation, and affected antioxidant system.
Paraoxonase, HDL and serum total antioxidant capacity parallel alterations reflects their similar functions as measurements of antioxidant system. In this study, one time acute exposure to ELF-MF slightly increased their serum levels which showed that antioxidant system has been evoked. These mediators levels were normalized after 3 days in short time exposure, however after chronic exposure, antioxidant capacity remained low after 72 hours. Antioxidant capacity could be repaired after exposure, but its’ ability to repair is dependent on duration and continuity of ELF-MF exposure. It should be noted that observed differences in HDL levels were not clinically significant; clinical significance of the above statistically observed differences needs further evaluation.
To the best of our knowledge, this is the first study evaluating the paraoxonase alterations after acute and chronic ELF-MF exposure. According to the results of Torres-Duran et al. serum HDL levels were increased after acute one time exposure to ELF- MF (Hz). Their results were in accordance with our findings.  It has been shown that paraoxonase has antioxidant properties and could prevent cell-mediated oxidative modification of low density lipoprotein ; hence, impaired paraoxonase activity could increase risk of atherosclerosis due to increased lipoprotein peroxidation .
LDL seems to be the impervious particle in this study. No significant differences were observed between LDL levels of different groups. Although increased levels of free fatty acids in our study might indicate that metabolism of lipids were increased after ELF-MF exposure. Most previous reports suggest that ELF-MF exposure might increase lipid metabolism . Torres-Duran et al. observed that one time exposure to ELF-MF significantly decreased total cholesterol levels and increased lipid peroxide content in the liver. Serum free fatty acids level were increased in their exposed rats compared to their control sham exposed rats . Nitric oxide synthase stimulation by ELF-MF may explain these findings. CD and MDA levels were increased after ELF-MF exposure in our study. Surprisingly, even one time exposure to ELF-MF increased CD levels as an early stage marker of lipid peroxidation. While after 72 hours, CD levels were normalized but MDA levels increased as the late stage marker of peroxidation. Chronic exposure tends to increased levels of CD and MDA. Due to the kinetic of CD particle, its serum levels were normalized after 72 hours but MDA serum levels remained high. This was predictable due to short half life of CD particles as early markers of lipid peroxidation. MDA prolonged half life explains observed steady state of MDA levels after 72 hours.
According to the study by Zwirska-Korczala et al., ELF-MF exposure increased lipid peroxidation in cultured 3 T3-L1 pre-adipocyte . Erdal et al. suggested that ELFMF exposure could increase nitrosative-oxidative stress in liver tissue . Ayata et al. showed that Exposure to mobile phone waves increased lipid peroxidation and fibrosis in Rat skin . Lee et al. suggested that ELF-MF exposure affects antioxidant system by production of free reactive oxygen species ROS . Atherosclerosis is a chronic process, and chronic lipid peroxidation by ELF-MF exposure theoretically might increase the risk of atherosclerosis.
It is well known that inflammation and oxidative stress are closely linked while oxidative stress evokes inflammation; on the other hand inflammation increases oxidative stress via production of reactive oxygen species through inflammatory cells. In a recent published study by Jonai et al. ELF-MF exposure decreased TNF-α production in the human peripheral blood mononuclear cells (h-PBMCs). Interleukin 1-B production was increased and Interferon-γ production was decreased at some point of exposure . IL-1 is an inflammatory stimulating cytokine; increased production of IL-1 could increase oxidative stress. Surprisingly, there are some reports suggesting ELF-MF as anti-inflammatory mediator in treatment of inflammatory conditions [18,19]. However as we mentioned above, most of recent published articles are in line with the results obtained in our study implying ELF-MF exposure as mediator of oxidative stress [4,10,16,20]. Akdag et al. showed that ELF-MF exposure (100 and 500 micro T) implemented oxidative stress, diminished antioxidant defense system and had toxic effects on brain of exposed rats . According to the results of a recent published study by Jelenkovic et al., ELF-MF exposure increased lipid peroxidation in frontal cortex, forebrain and basal areas in the brain of exposed rats. Superoxide anion production was also increased in all areas of brain in exposed rats. They suggested that NO2 signaling pathways might be affected by NO2 reaction with superoxide onions .
According to the results of our study, one time ELF-MF exposure increased lipid peroxidation (CD and MDA) and increased antioxidant serum activity (HDL, paraoxonase activity, and serum total antioxidant capacity). Chronic ELF-MF exposure increased lipid peroxidation and affected antioxidant system. Free fatty acids levels were increased after both one time and two weeks exposure. Chronic exposure made irreversible changes while acute exposure tended to reversible alterations on above mentioned parameters. It seems that ELF-MF exposure implements an effect which evokes antioxidant system to recompense toxic effects of reactive oxygen species; however, in chronic ELF-MF exposure antioxidant system is exhausted and oxidative stress and resulted lipid peroxidation is dramatically increased as a consequence.
Glutathion peroxidase levels as a valuable marker of oxidative stress were not measured in this study. Clinical significance of observed changes in measured parameters needs further evaluations.
Oxidant-antioxidant pathways are extremely complex and it should keep in mind that uncontrolled and over the counter consumption of any supplement could accompany by several unfavorable and hazardous effects . Manipulation and modification of oxidant-antioxidants pathway needs accurate knowledge of this complex system. Hence, our findings and even the results of larger clinical studies do not warranty benefits of antioxidants consumption.
In conclusion, ELF- MF exposure could impair oxidant-antioxidant balance and might increase oxidative stress and lipid peroxidation. Antioxidant defect could be repaired after exposure; however it might depends on the duration and continuity of ELF-MF exposure.
All performed experiments and procedures were in accordance with the guidelines for animal care and use of ethics committee of Tehran University of Medical Sciences and ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments. The study protocol was approved by the ethics committee of Endocrinology and Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences.