Extremely low frequency electromagnetic fields activate the ERK cascade, increase hsp70 protein levels and promote regeneration in Planaria.
OBJECTIVE
To use regenerating Planaria Dugesia dorotocethala as a model to determine whether an intermittent modulated extremely low frequency electro-magnetic field (ELF-EMF) produces elevated levels of the heat shock protein hsp70 and stimulates intracellular pathways known to be involved in injury and repair. We focused on serum response element (SRE) binding through the extra-cellular signal-regulated kinase (ERK) cascade.


METHODS
Planaria were transected equidistant between the tip of the head and the tip of the tail. Individual head and tail portions from the same worm were exposed to a 60 Hertz 80 milliGauss ELF-EMF for 1 h twice daily for 15 days post-transection under carefully controlled exposure conditions. The regenerating heads and tails were photographed and the lengths measured at three-day intervals. In other experiments, the timing of the appearance of pigmented eyes was monitored in the tail portion at 12-h intervals following transection in both ELF-EMF exposed and sham control. In some experiments protein lysates were analysed for hsp70 levels, doubly phosphorylated (pp)-ERK, Elk-1 kinase activity and serum response factor (SRF)-SRE binding.


RESULTS
ELF-EMF exposure during the initial 3-days post-surgery caused a significant increase in regeneration for both heads and tails, but especially tails. The first appearance of eyes occurred at day seven post-transection in tail portions exposed to ELF-EMF. In the sham control tail samples the initial appearance of eyes occurred 48 h later. Concurrently, ELF-EMF-exposed heads and tails exhibited an elevation in the level of hsp70 protein, an activation of an ERK cascade, and an increase in SRF-SRE binding.


CONCLUSIONS
Exposures to a modulated sinusoidal ELF-EMF were delivered by a Helmholtz configuration at a frequency of 60 Hz and 80 mG twice a day for one hour. This is accompanied by an increase in hsp70 protein levels, activation of specific kinases and upregulation of transcription factors that are generally associated with repair processes.
Goodman
Reba
R
Department of Pathology, Columbia University, New York, NY 10032, USA. rmg5@columbia.edu
Lin-Ye
Avary
A
Geddis
Matthew S
MS
Wickramaratne
Priya J
PJ
Hodge
Susan E
SE
Pantazatos
Spiro P
SP
Blank
Martin
M
Ambron
Richard T
RT
D000818:Animals; D004574:Electromagnetic Fields; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000528:radiation effects*; D010932:Planarians / Q000502:physiology* / Q000528:radiation effects*; D012038:Regeneration / Q000528:radiation effects*; D013997:Time Factors
D018840:HSP70 Heat-Shock Proteins