Induction of stress proteins by electromagnetic fields in cultured HL-60 cells

Abstract

HL‐60 cells in culture were exposed for 2 h to a sinusoidal 0.1 or 1 mT (1 or 10 Gauss) magnetic field at 60 Hz and pulse labeled after exposure with radioactive isotopes by incubation by using either [35S]methionine, [3H]leucine, or [33P]phosphate. The radioactive labels were incorporated into cellular proteins through synthesis or phosphorylation. Proteins were extracted from electrostatically sorted nuclei, and the heat shock/stress proteins (sp) were analyzed for synthesis and phosphorylation by two‐dimensional polyacrylamide gel electrophoresis. In the control cultures (no exposure to the magnetic field), sp 72c (cognate form) was faintly observed. A 0.1 mT exposure did not show sp metabolism to be different from that of the controls; however, after a 1 mT exposure of the HL‐60 cells, sp 70i (inducible form) was synthesized ([35S]methionine incorporation). Sp 90 was not synthesized at either field level, but was phosphorylated ([33P]phosphate incorporation) in the 1 mT exposure. Sp 27 (isoforms a and b) was induced after a 1 mT exposure as reflected by labeling with [3H]leucine. These sps were not detected after a 0.1 mT exposure. After a 1 mT exposure and labeling with [33P], sp 27 isoforms b and c were phosphorylated whereas isoform ‘a‘ was not observed. Sps 70i, 72c, and 90 were identified by commercial sp antibodies. Likewise, polypeptides a, b, and c were verified as sp 27 isoforms by Western blotting. Statistical evaluation of sp areas and densities, determined from fluorographs by Western‐blot analysis, revealed a significant increase in sps 90 and 27a after a 1 mT magnetic field exposure. The 1 mT magnetic field interacts at the cellular level to induce a variety of sp species. Bioelectromagnetics 20:347–357, 1999. Published 1999 Wiley‐Liss, Inc.

Power-line frequency electromagnetic fields do not induce changes in phosphorylation, localization, or expression of the 27-kilodalton heat shock protein in human keratinocytes.

“…In human breast cells, they found that a 1-hr EMF exposure or a repeated 20-min EMF exposure led to 30-40% increases in HSP70 protein (30). More recently, Pipkin et al (44) reported that both HSP70 and HSP27 were induced in HL-60 cells after a 1 mT EMF exposure for 2 hr.…”

The influence of extremely low frequency magnetic fields on cytoprotection and repair

“…Miyakawa et al [2001] found that the temperature required for a given expression of a reporter gene (lacZ) under HSP16 promoter control in transgenic nematode worms was reduced after exposure to a 60 Hz magnetic field at up to 0.5 T. Leszczynski et al [2002] saw an increase in protein phosphorylation and Hsp27 expression after exposure to a 900 MHz GSM signal. Other reports, discussed previously, have found magnetic field influences on Hsp16 activity in nematodes [Junkersdorf et al, 2000], as well as Hsp27 in cell cultures [Pipkin et al, 1999;Tokalov and Gutzeit, 2004]. Controversy exists for studies of HSP27 as well, and no effect was seen in several papers [Guisasola et al, 2002;Shi et al, 2003;Coulton et al, 2004;Lim et al, 2005].…”

“…The magnetic field exposure was also able to enhance the HSP response following 43 8C heat stress. Pipkin et al [1999] found no response from a 2-h 60 Hz exposure at 100 mT, but did see an increase in Hsp70, as well as some other heat shock proteins (Hsp27, Hsp90) at 1 mT. At that field strength, the authors found their coils were heating the incubator and employed a water cooling system to counter that problem.…”

Bioelectric Effects of Low-Frequency Modulated Microwave Fields on Nervous System Cells

“…Hsps proteins play a critical role in the regulation of the cell cycle, proliferation and apoptosis. The synthesis of Hsp can be produced under several stress conditions: alcohol, oxidative stress, osmotic pressure change, toxic chemicals and exposure to low-frequency EMF (Pipkin et al, 1999;Leszczynski et al, 2002). Our future research will be devoted to study the quantification of Hsp-70, Bcl-2 and Cx43 proteins, in control and irradiated samples, possible increased [Ca 2+ ] i concentration process and the implication of the anti-apoptotic increase of Bcl-2 protein promoting cell survival (Takuma et al, 2004). 3.…”