Long-term exposure to a 40-GHz electromagnetic field does not affect genotoxicity or heat shock protein expression in HCE-T or SRA01/04 cells

Abstract

Millimeter waves are used in various fields, and the risks of this wavelength range for human health must be carefully evaluated. In this study, we investigated the effects of millimeter waves on genotoxicity and heat shock protein expression in human corneal epithelial (HCE-T) and human lens epithelial (SRA01/04) cells. We exposed the cells to 40-GHz millimeter waves at 1 mW/cm2 for 24 h. We observed no statistically significant increase in the micronucleus (MN) frequency or the level of DNA strand breaks in cells exposed to 40-GHz millimeter waves relative to sham-exposed and incubator controls. Heat shock protein (Hsp) expression also exhibited no statistically significant response to the 40-GHz exposure. These results indicate that exposure to 40 GHz millimeter waves under these conditions has little or no effect on MN formation, DNA strand breaks, or Hsp expression in HCE-T or SRA01/04 cells.

Keywords: comet assay; heat shock protein; human eye cells; micronucleus formation; millimeter waves.

Fig. 1.

The incubator for exposure equipped with applicators for exposure (right) and sham-exposure (left) (A). Illustration of the structure (B) and the photograph (C) of the applicator.

Fig. 2.

Micronucleus frequency in cells exposed to 40-GHz millimeter-wave radiation for 24 h: HCE-T cells (A) and SRA01/04 cells (B). The positive control was treatment with bleomycin (10 μg/ml). Data are presented as means ± SD from six independent experiments. **P < 0.01.

Fig. 3.

Representative micrographic photographs of control (A), sham (B), 40 GHz-exposed (C) and bleomycin-treated cells (D). Values of a comet parameter (tail moment) for cells exposed to 40-GHz millimeter-wave radiation for 24 h: HCE-T (E) and SRA01/04 (F). The positive control was treatment with bleomycin (10 μg/ml). Data are presented as means ± SD from six independent experiments. One asterisk and two asterisks indicate P < 0.05 and < 0.01, respectively.

Fig. 4.

(A) Expression of Hsp27 (1), Hsp70 (2), and Hsp90α (3) in HCE-T cells exposed to 40-GHz radiation for 24 h. Positive controls underwent heat treatment, as shown in the graphs. Data are presented as means ± SD from three independent experiments. **P < 0.01. (B) Expression of Hsp27 (1), Hsp70 (2) and Hsp90α (3) in SRA01/04 cells exposed to 40-GHz radiation for 24 h. Positive controls underwent heat treatment, as shown in the graphs. Data are presented as means ± SD from three independent experiments. **P < 0.01.