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Modification of membrane fluidity in melanin-containing cells by low-level microwave radiation
A M Phelan1, D G Lange, H A Kues
1Department of Anesthesiology, Johns Hopkins Medical Institutions, Baltimore, Maryland 21205.
Abstract:
The treatment of a B16 melanoma cell line with 2.45-GHz pulsed microwaves (10 mW/cm2, 10-microseconds pulses at 100 pps, 1-h exposure; SAR, 0.2 W/kg) resulted in changes of membrane ordering as measured by EPR (electron paramagnetic resonance) reporter techniques. The changes reflected a shift from a more fluid-like phase to a more solid (ordered) state of the cell membrane. Exposure of artificially prepared liposomes that were reconstituted with melanin produced similar results. In contrast, neither B16 melanoma cells treated with 5-Bromo-2-Deoxyuridine (3 micrograms/day x 7 days) to render them amelanotic, nor liposomes prepared without melanin, exhibited the microwave-facilitated increase of ordering. Inhibition of the ordering was achieved by the use of superoxide dismutase (SOD), which strongly implicates oxygen radicals as a cause of the membrane changes. The data indicate that a significant, specific alteration of cell-membrane ordering followed microwave exposure. This alteration was unique to melanotic membranes and was due, at least in part, to the generation of oxygen radicals.
Insights
Pulsed microwaves alter cell membranes in melanotic melanoma cells, increasing membrane order. This effect, linked to oxygen radicals, was not observed in amelanotic cells or non-melanin liposomes.
Area of Science:
- Biophysics
- Cell Biology
- Melanoma Research
Background:
- Cell membranes are crucial for cellular function and signaling.
- Melanoma cells possess unique pigment (melanin) that may influence their response to external stimuli.
- Microwave exposure is increasingly studied for its biological effects.
Purpose of the Study:
- To investigate the impact of pulsed microwave exposure on the ordering of cell membranes in B16 melanoma cells.
- To determine if melanin plays a role in microwave-induced membrane alterations.
- To elucidate the mechanism behind microwave-induced membrane changes, particularly the involvement of oxygen radicals.
Main Methods:
- B16 melanoma cells and melanin-reconstituted liposomes were exposed to 2.45-GHz pulsed microwaves.
- Electron paramagnetic resonance (EPR) reporter techniques were used to measure changes in membrane ordering.
- Amelanotic melanoma cells and liposomes without melanin were used as controls.
- Superoxide dismutase (SOD) was employed to assess the role of oxygen radicals.
Main Results:
- Pulsed microwave exposure (10 mW/cm2) significantly increased the ordering (reduced fluidity) of cell membranes in B16 melanoma cells.
- Similar increases in membrane ordering were observed in liposomes containing melanin.
- No significant changes in membrane ordering were detected in amelanotic cells or liposomes lacking melanin.
- Superoxide dismutase inhibited the microwave-induced increase in membrane ordering, implicating oxygen radicals.
Conclusions:
- Specific alteration of cell membrane ordering occurs following pulsed microwave exposure in melanotic cells.
- Melanin is critical for this microwave-induced membrane effect.
- The generation of oxygen radicals is a key mechanism contributing to the observed changes in membrane ordering.