Increased levels of inducible HSP70 in cells exposed to electromagnetic fields.
Because reports in the literature on the effects of electromagnetic fields (EMFs) on expression of the 70-kDa heat-shock protein (HSP70) are somewhat contradictory, we studied the influence of low-frequency EMFs on the accumulation of inducible HSP70 in several cell models. Some of the cell types tested showed increased levels of HSP70 protein when exposed for 24 h to 50 Hz, 680 microT EMFs. In endothelial cells, EMFs alone induced only a poor and transient activation of the heat-shock transcription factor 1 (HSF1); however, neither the level of HSP70 mRNA nor the synthesis of HSP70 appeared to be altered significantly. Accordingly, transfection experiments involving HSP70 promoter showed that gene transcription was not affected. We also noted a marked reduction in proteasome activities in cell extracts exposed to EMFs. Interestingly, the heat-shock-induced levels of HSP70 mRNA and protein were increased by a concomitant weak stressor like EMFs. Taken together, our results indicate that in EMF-exposed endothelial cells, HSP70 gene transcription and translation are unaffected; however, EMFs alone promoted accumulation of the inducible HSP70 protein, probably by increasing its stability, and it enhanced accumulation and translation of the heat-induced HSP70 mRNA when applied in concert with heat shock.
Alfieri
Roberta R
RR
Sezione di Patologia Molecolare ed Immunologia, Dipartimento di Medicina Sperimentale, Università degli Studi di Parma, Parma 43100, Italy. roberta.alfieri@unipr.it
Bonelli
Mara A
MA
Pedrazzi
Giuseppe
G
Desenzani
Silvia
S
Ghillani
Mario
M
Fumarola
Claudia
C
Ghibelli
Lina
L
Borghetti
Angelo F
AF
Petronini
Pier Giorgio
PG
D000818:Animals; D002478:Cells, Cultured; D004307:Dose-Response Relationship, Radiation; D004560:Electricity; D004574:Electromagnetic Fields; D042783:Endothelial Cells / Q000378:metabolism* / Q000528:radiation effects*; D004781:Environmental Exposure; D005786:Gene Expression Regulation / Q000528:radiation effects; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D011829:Radiation Dosage; D013552:Swine
D018840:HSP70 Heat-Shock Proteins