Low power millimeter wave irradiation exerts no harmful effect on human keratinocytes in vitro

Abstract

Low power millimeter wave (LP-MW) irradiation has been successfully used in clinical practice as an independent and/or supplemental therapy in patients with various diseases. It is still not clear, however, whether exposed skin is directly affected by repeated LP-MW irradiation and whether cells of the epidermis can be activated by the absorbed energy. Keratinocytes, the most numerous component of the epidermis are believed to manifest functional responses to physical stimuli. In this study we analyzed whether LP-MW irradiation modulated the production of chemokines, including RANTES and IP-10 of keratinocytes in vitro. We also investigated whether LP-MW irradiation induces a heat stress reaction in keratinocytes, and stimulates heat shock protein 70 (Hsp70) production. Vital staining of keratinocytes with carboxyfluorescein succinimidyl ester and ethidium bromide was used to analyze the MW effect on the viability of adherent cells. In addition, we studied the effect of LP-MW irradiation on intercellular gap junctional communication in keratinocyte monolayers by Lucifer yellow dye transfer. We found no significant changes in constitutive RANTES and inducible IP-10 production following LP-MW irradiation. LP-MW exposure of keratinocyte monolayers did not alter Hsp70 production, unlike exposure to higher power MWs (HP-MW) or hyperthermia (43 degrees C; 1 h). LP-MW irradiation and hyperthermia did not alter the viability of adherent keratinocytes, while HP-MW irradiation induced cellular damage within the beam area. Finally, we found no alteration in the gap junctional intercellular communication of keratinocytes following LP-MW irradiation, which on the other hand, was significantly increased by hyperthermia. In summary, we detected no harmful effect of LP-MW irradiation on both keratinocyte function and structure in vitro, although these cells were sensitive to higher MW power that developed heat stress reaction and cellular damage. Our results provide further evidence that LP-MW irradiation does not induce evidence of skin inflammation or keratinocyte damage and that its clinical application appears to be safe.

Low‐power millimeter wave radiations do not alter stress‐sensitive gene expression of chaperone proteins

“…Our results suggest that MMW radiation at 60 GHz is not a stressor strong enough to modify stress-sensitive gene expression. These data confirm previously reported results [Szabo et al, 2003] showing that low-power MMW radiation has no proteotoxic effect.…”

Millimeter waves: Acoustic and electromagnetic

“…Significantly, apoptosis does not reveal itself until 24 h following the exposure. Therefore, studies looking for small effects should include observation lasting 24 h after the exposure [Szabo et al, 2003]. Most of the results of our studies on the effects of MMWs at therapeutic levels on the cell cultures of human keratinocytes were negative.…”

“…Extensive histological and histochemical studies of skin reveal that MMWs at therapeutic levels cause no damage to the skin [Szabo et al, 2003]. However, at higher intensities it is possible to see that apoptosis is induced in keratinocytes if the temperature exceeds 43 °C.…”

Gene Expression Changes in the Skin of Rats Induced by Prolonged 35 GHz Millimeter-Wave Exposure

“…Results from other investigations indicate that in vitro exposures of human keratinocytes to millimeter-wave frequencies of 42.22 or 61. 22 GHz, at or below incident power densities capable of inducing temperature rises, can cause increased production of interleukin 1 beta (12), up-regulation of heat-shock protein 70, cell injury (13), and externalization of phosphatidylserine at the cell membrane (14). It is not known whether these molecular changes, observed in in vitro systems, are also induced in vivo.…”