Effects Of Electromagnetic Radiation On Mitochondria
vrijdag, 16 september 2016 - Categorie: Onderzoeken
Wireless communications have increased significantly in modern times and concerns regarding their safety have grown as well. Wireless communications utilize high frequency radiation – radio frequencies and microwaves. Man-made electromagnetic radiation exerts numerous biological effects that begin at the molecular level and eventually lead to cellular, tissue and organ dysfunction. Electromagnetic radiation exerts its effects at the sub-cellular level by altering molecular rotation and vibration, increasing the collisions between molecules and breaking chemical bonds which ultimately affect structure and function (1). This has direct effects on energy production in the cell. Mitochondria are the organelles responsible for cellular energy production and numerous other cell functions and they are adversely affected by electromagnetic radiation in many inter-related ways.
Electromagnetic radiation causes structural damage to mitochondria. Exposure to radiation causes swelling and cavitation in mitochondria as well as broken, disorganized and sparse mitochondrial cristae or folds (1, 3). The damage increases with prolonged exposure time even though the dose of radiation was low, therefore, long-term, low-dose exposure leads to significant damage. After three hours of microwave radiation, visible swelling of mitochondria increased and after twenty four hours, there was mitochondrial degeneration (1). Damage caused by radiation is cumulative. Radiation also damages the mitochondrial membrane which causes a decrease in mitochondrial membrane potential (1), which is responsible for the proton motive force and energy production in mitochondria, which eventually leads to apoptosis (1, 4) or cell death, since apoptosis is regulated by mitochondria.
Calcium homeostasis is impaired by electromagnetic radiation. Mitochondrial are responsible for regulating calcium homeostasis within the cell. Normally, extracellular calcium is greater than intracellular calcium and most intracellular calcium is stored in the mitochondria and endoplasmic reticulum. Microwave radiation causes a significant increase in cytoplasmic calcium and this causes excess activation of the mitochondrial permeability transition pore (1), a nonspecific pore in the mitochondrial membrane, which leads to increased membrane permeability, disrupting metabolic gradients between mitochondria and the cytosol. This then leads to the uncoupling of oxidative phosphorylation (1), meaning oxidative phosphorylation is no longer yoked to the respiratory chain to synthesize ATP, so energy production ceases. Remaining ATP made by unaffected mitochondria also gets depleted and cell death ensues. Intracellular calcium increases also leads to swelling of mitochondria and if great, results in rupturing of mitochondria.
Oxidative stress and disturbed cellular signaling is caused by electromagnetic radiation. Oxidative stress occurs when there is an imbalance between free radical production and anti-oxidant defense mechanisms. There is a significant increase in reactive oxygen species, decreases in antioxidant enzymes glutathione peroxidase and superoxide dismutase and markers of lipid peroxidation and protein oxidation increase (1) when mitochondria are exposed to radiation. Radiation inhibits the mitochondrial respiratory chain by prolonging the lifespan of free radicals and impairing the anti-oxidant defense system (2). Enzyme functions and signaling pathways that are crucial to energy generation are disturbed by electromagnetic radiation. As mentioned above, calcium homeostasis is impaired and calcium is an important signaling molecule. The activity of cytochrome c oxidase, a critical enzyme in energy metabolism which transports electrons to oxygen to produce water and ATP, is suppressed (1). Oxidative stress and impaired signaling also affect mitochondrial gene expression.
Electromagnetic radiation damages mitochondrial genes and causes gene mutations. Mitochondrial DNA (mtDNA) are more susceptible to external stimuli than nuclear DNA (1) and they lack the repair mechanisms of nuclear DNA (2). Radiation induces mtDNA strand breaks and the excess reactive oxygen species production caused by radiation exposure also causes mtDNA mutations (1, 2). Exposure to radiation causes a decline in mtDNA copy number and mtRNA transcripts (2) which, when combined with mitochondrial mutations, adds further burden to the cell by way of more defective mitochondrial genes being passed onto future mitochondria. Mitochondrial gene mutations in turn amplify oxidative stress by encoding deficient critical proteins required for the respiratory chain (2). A vicious cycle is created by exposure to radiation whereby mitochondria are overwhelmed and cell death occurs.
Apoptosis increases after exposure to electromagnetic radiation (4). Exposure to radiation triggers a series of inter-related events – structural damage, impaired signaling, oxidative stress and gene mutations – that culminates in cell death. The cumulative damage causes an imbalance of pro-apoptotic and anti-apoptotic proteins which leads to a decrease in the mitochondrial membrane potential (4) and the release of cytochrome c which activates caspase-signaling pathways that lead to apoptotic cell death (1, 4). Although apoptosis may be beneficial in removing damaged cells, when it is excessive, it can be problematic because it can eventually lead to systemic dysfunction in the organism.
Excessive apoptosis caused by man-made electromagnetic radiation is problematic for the nervous system. The nervous system is very susceptible to the effects of radiation. The brain is more sensitive to electromagnetic radiation than other organs because it has a very high metabolic rate and a great demand for oxygen, making it very vulnerable to energy metabolism disorders (1). Numerous pathological changes can occur in the brain as a consequence of excessive radiation exposure such as structural damage, neurotransmitter disruption (1, 3), altered electrical activity and increased permeability of the blood-brain barrier (2, 4). How severely one is affected depends on the frequency, duration and intensity of the radiation exposure (1, 3). Everyone is or will be, in some way, negatively affected by man-made electromagnetic radiation. Because of the ever increasing amount of antennas and towers being installed by telecommunications companies, radio frequency and microwave radiation is nearly impossible to avoid nowadays and it poses a serious threat to public health. It will only get worse unless action is taken to remove and reduce and not simply avoid the sources of man-made radiation
1. Hao, Y., Zhao, L. & Peng, R. Effects of microwave radiation on brain energy metabolism and related mechanisms. Military Medical Research. 2015; 2:4. doi: 10.1186/s40779-015-0033-6.
2. Xu, S., Zhou, Z., Zhang, L., Yu, Z., Zhang, W., Wang, Y., Wang, X., Li, M., Chen, Y., Chen, C., He, M., Zhang, G. & Zhong, M. Exposure to 1800MHz radio frequency radiation induces oxidative damage to mitochondrial DNA in primary cultured neurons. Brain Research. 2010; 1311:189-196. doi: 10.1016/j.brainres.2009.10.062.
3. Zhao, L., Peng, R. Wang, S. Wang, L., Gao, Y., Dong, J., Li, X. & Su, Z. Relationship between Cognition Function and Hippocampus Structure after Long-term Microwave Exposure. Biomedical and Environmental Sciences. 2012; 25(2):182-188. doi: 10.3967/0895-3988.2012.02.009.
4. Zuo, H., Lin, T., Wang, D., Peng, R., Wang, S., Gao, Y., Xu, X., Li, Y., Wang, S., Zhao, L., Wang, L. & Zhou, H. Neural Cell Apoptosis Induced by Microwave Exposure Through Mitochondria-dependent Caspase-3 Pathway. International Journal of Medical Sciences.2014; 11(5):426–435. doi: 10.7150/ijms.6540.
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