Sensitivity of spiral ganglion neurons to damage caused by mobile phone electromagnetic radiation will increase in lipopolysaccharide-induced inflammation in vitro model

• Published in: Journal of neuroinflammation Vol. 12; no. 1; p. 105
• Main Authors: Zuo, Wen-Qi, Hu, Yu-Juan, Yang, Yang, Zhao, Xue-Yan, Zhang, Yuan-Yuan, Kong, Wen, Kong, Wei-Jia
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 29.05.2015; BioMed Central
• Subjects: Analysis; Animals; Animals, Newborn; Apoptosis Regulatory Proteins - metabolism; Beclin-1; Care and treatment; Cell Phone; Cells, Cultured; Disease Models, Animal; DNA Damage - drug effects; Dose-Response Relationship, Drug; Electric waves; Electromagnetic Phenomena; Electromagnetic radiation; Electromagnetic waves; Electromagnetism; Ganglion; Health aspects; In Vitro Techniques; Inflammation; Inflammation - etiology; Inflammation - metabolism; Inflammation - physiopathology; Lipopolysaccharides - adverse effects; Lipopolysaccharides - pharmacology; Microtubule-Associated Proteins - metabolism; Mitogens; Neurons; Neurons - cytology; Neurons - drug effects; Neurons - physiology; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species - metabolism; Risk factors; Spiral Ganglion - cytology; Spiral Ganglion - drug effects; Spiral Ganglion - physiology; Time Factors
• DOI: 10.1186/s12974-015-0300-1
• ISSN: 1742-2094

With the increasing popularity of mobile phones, the potential hazards of radiofrequency electromagnetic radiation (RF-EMR) on the auditory system remain unclear. Apart from RF-EMR, humans are also exposed to various physical and chemical factors. We established a lipopolysaccharide (LPS)-induced inflammation in vitro model to investigate whether the possible sensitivity of spiral ganglion neurons to damage caused by mobile phone electromagnetic radiation (at specific absorption rates: 2, 4 W/kg) will increase. Spiral ganglion neurons (SGN) were obtained from neonatal (1- to 3-day-old) Sprague Dawley® (SD) rats. After the SGN were treated with different concentrations (0, 20, 40, 50, 100, 200, and 400 μg/ml) of LPS, the Cell Counting Kit-8 (CCK-8) and alkaline comet assay were used to quantify cellular activity and DNA damage, respectively. The SGN were treated with the moderate LPS concentrations before RF-EMR exposure. After 24 h intermittent exposure at an absorption rate of 2 and 4 W/kg, DNA damage was examined by alkaline comet assay, ultrastructure changes were detected by transmission electron microscopy, and expression of the autophagy markers LC3-II and Beclin1 were examined by immunofluorescence and confocal laser scanning microscopy. Reactive oxygen species (ROS) production was quantified by the dichlorofluorescin-diacetate assay. LPS (100 μg/ml) induced DNA damage and suppressed cellular activity (P < 0.05). LPS (40 μg/ml) did not exhibit cellular activity changes or DNA damage (P > 0.05); therefore, 40 μg/ml was used to pretreat the concentration before exposure to RF-EMR. RF-EMR could not directly induce DNA damage. However, the 4 W/kg combined with LPS (40 μg/ml) group showed mitochondria vacuoles, karyopyknosis, presence of lysosomes and autophagosome, and increasing expression of LC3-II and Beclin1. The ROS values significantly increased in the 4 W/kg exposure, 4 W/kg combined with LPS (40 μg/ml) exposure, and H2O2 groups (P < 0.05, 0.01). Short-term exposure to radiofrequency electromagnetic radiation could not directly induce DNA damage in normal spiral ganglion neurons, but it could cause the changes of cellular ultrastructure at special SAR 4.0 W/kg when cells are in fragile or micro-damaged condition. It seems that the sensitivity of SGN to damage caused by mobile phone electromagnetic radiation will increase in a lipopolysaccharide-induced inflammation in vitro model.