title: Sensitivity of spiral ganglion neurons to damage caused by mobile phone electromagnetic radiation will increase in lipopolysaccharide-induced inflammation in vitro model.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Otolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, People's Republic of China. zuowenqi@163.com.
authors.forename: Wen-Qi
authors.initials: WQ
authors.lastname: Zuo
authors.affiliation: Department of Otolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, People's Republic of China. safiner@gmail.com.
authors.forename: Yu-Juan
authors.initials: YJ
authors.lastname: Hu
authors.affiliation: Department of Otolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, People's Republic of China. yangyang_xiehe@163.com.
authors.forename: Yang
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Otolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, People's Republic of China. yaner_323@126.com.
authors.forename: Xue-Yan
authors.initials: XY
authors.lastname: Zhao
authors.affiliation: Department of Otolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, People's Republic of China. zyyellie@gmail.com.
authors.forename: Yuan-Yuan
authors.initials: YY
authors.lastname: Zhang
authors.affiliation: Department of Endocrinology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, People's Republic of China. wenly-kong@163.com.
authors.forename: Wen
authors.initials: W
authors.lastname: Kong
authors.affiliation: Department of Otolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, People's Republic of China. entwjkong@hust.edu.cn.|Institute of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, People's Republic of China. entwjkong@hust.edu.cn.
authors.forename: Wei-Jia
authors.initials: WJ
authors.lastname: Kong
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D000071186:Beclin-1; D040421:Cell Phone; D002478:Cells, Cultured; D004249:DNA Damage / Q000187:drug effects; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D055590:Electromagnetic Phenomena; D066298:In Vitro Techniques; D007249:Inflammation / Q000209:etiology* / Q000378:metabolism / Q000503:physiopathology; D008070:Lipopolysaccharides / Q000009:adverse effects* / Q000494:pharmacology*; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D013136:Spiral Ganglion / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D013997:Time Factors
chemical_list: D051017:Apoptosis Regulatory Proteins; D000071186:Beclin-1; D008070:Lipopolysaccharides; D008869:Microtubule-Associated Proteins; D017382:Reactive Oxygen Species; C512829:Becn1 protein, rat; C526109:Anxa3 protein, rat