Abstract
The aim of this study was to investigate the possible biological effects of extremely low frequency field (ELF-EMF) by implementing three approaches - colony assay, cDNA microarray, and flow cytometry to evaluate the variation of cell survival rates, gene expression profiles, and cell cycle as well as apoptosis, respectively. Each in-house gene chip consisted of four replicated spots of each of 7334 sequence-verified human genes. We chose keratinocytes to analyze the biological effects of ELF-EMF because keratinocytes were the first line of self-defense of human body against to the environmental stress. Cells were exposed to ELF-EMF for 3 hours with or without pre-irradiation of 2 Gyγ-ray. The result of colony assay demonstrated that ELF-EMF exposure did not alter cell survival with or without priorγ-ray irradiation. However, the microarray data illustrated that ELF-EMF treatment repressed the expression of DNA helicase-related and DNA replication genes, as well as regulated the expression of several cell cycle-related and apoptotic genes. Moreover, data showed that when γ-ray irradiated keratinocytes were treated with additional ELF-EMF exposure, the DNA helicase-related and DNA replication genes were further down-regulated. However, the cell cycle- and apoptosis-related genes did not display similar regulatory characteristics. In flow cytometry approach, our results demonstrated that the cell cycle distributions affected by ELF-EMF were dependent on the cell density. Therefore, no firm conclusion can be drawn from the available data. Apoptotic analysis revealed that ELF-EMF exposure had not induce significant levels of apoptotic death in keratinocytes. In conclusion, our microarray data has shown for the first time that the expression of several group of genes were affected by ELF-EMF exposure, including cell survival-, cell cycle- and apoptosis-related genes as well as DNA helicase-related genes. Although colony assay and flow cytometry analysis had not detect any notable biological effects, this may imply that microarray analysis is a more sensitive screening tool to investigate minor biological effects caused by ELF-EMF exposure.