Unfortunately many publications referenced in this post are not public access. Many were obtained from Sci-Hub, whose public access is shaky.
Ki 2008
Purpose: In a previous study, we found that exposure to a 50 Hz magnetic field (MF) could activate stress-activated protein kinase (SAPK) and P38 mitogen-activated protein (MAP) kinase (P38 MAPK) in Chinese hamster lung (CHL) fibroblast cells, and simultaneous exposure to a ‘noise’ MF of the same intensity inhibited these effects. In order to explore the possible target sites and upstream signal transduction molecules of SAPK and P38 MAPK, and further validate the interference effects of ‘noise’ MF on 50 Hz MF, the effects of MF exposure on clustering of epidermal growth factor (EGF) receptors and Ras protein activation were investigated.
Materials and methods: CHL cells were exposed to a 50 Hz sinusoidal MF at 0.4 mT for different durations, and clustering of EGF receptors on cellular membrane and Ras protein activation were analyzed using immunofluorescence confocal microscopy and co-precipitation technology. EGF treatment served as the positive control.
Results: The results showed that, compared with sham-exposed cells, exposure to a 50 Hz MF at 0.4 mT for 5 min slightly induced EGF receptor clustering, whereas exposure for 15 min enhanced receptor clustering significantly. Corresponding to receptor clustering, Ras protein was also activated after exposure to the 50 Hz MF. Exposure to a ‘noise’ MF (with frequency ranges from 30 – 90 Hz) at the same intensity and durations, did not significantly affect EGF receptor clustering and Ras protein. However, by superimposing the ‘noise’ MF, receptor clustering and Ras activation induced by 50 Hz MF were inhibited.
Conclusion: The results suggested that membrane receptors could be one of the most important targets where extremely low frequency (ELF) MF interacts with cells, and Ras may participate in the signal transduction process of 50 Hz MF. Furthermore, a ‘noise’ MF could inhibit these effects caused by ELF-MF.
We’re going to come back to this image later in our browsing of abstracts in this post. The two blue “open hands” could be any growth factor receptor that “clusters” only when both hands bind a growth factor. As for RAF, MEK, and ERK, a kinase is an enzyme that transfers a phosphate group from adenosine triphosphate (ATP) to a serine, threonine, or tyrosine amino acid side chain of a protein. Phosphorylation is a common way of turning enzymes on. Phosphorylation, transfer of a phosphate group, may also occur in lipids.
This journey starts with the notion that 50 Hz from powerlines contributes to leukemia via ceramides in lipid membranes. It does so via interaction of PEMF with voltage gated Ca2+ channels. Signaling kinases related to changes in intracellular Ca2+ were examined. Another kinase, Akt, was found to be the signaling kinase … and intracellular store operated Ca2+ channel the source of endogenous Ca2+release. Far from leukemia, this pathway is important in muscle stretch.
Qiu 2016
Purpose To investigate the effects of a 50-Hz magnetic field (MF) exposure on ceramide metabolism, as well as the cascade downstream signaling pathways in human amniotic (FL) cells. Materials and methods FL cells were exposed to MF at 0.4 mT for different durations (from 5-60 min). The ceramides levels were analyzed with high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The activity of cathepsin D was assayed using a fluorometric assay kit, and the activity of protein phosphatase 2A (PP2A) was examined by Western blotting. After exposing to MF at 0.4 mT for 60 min with sequential culture for different durations (0, 3, 6, 12 or 36 h), the rate of cell apoptosis was assessed by flow cytometry. Results Exposing cells to MF at 0.4 mT for different durations caused a significant increase in ceramide production via de novo synthesis and hydrolysis of sphingomyelin (SM), and the effect was different according to the exposure time. However, no significant change in cell apoptosis was detected after MF exposure for 60 min with sequentially culturing for up to 36 h. In addition, increase in ceramide did not activate its downstream signal molecules, cathepsin D and PP2A, which are usually closely related to apoptosis of cells. Conclusions Exposure to a 50-Hz MF could raise ceramide levels but had no significant effect on apoptosis in cultured cells.
Lipid rafts are rigid regions in the cell membrane enriched in cholesterol and “sphingolipids. ” Rafts tend to be hot zones of “signal transduction” of growth hormone receptors on the outside of the cell to intracellular kinases and other signaling enzymes that tell the nucleus to respond to changes in the environment. This is where the desire to look at sphingolpids came from.
These are two possible routes to increasing ceramides in the FL cells of Qiu 2016. These authors did not differentiate between de novo synthesis via sphingosine or the salvage pathway via sphinomyelin in this particular publication. Sphingosine kinase phosphorylates sphingosine to sphingosine-1-phosphate, a signaling molecule that modulates endogenous release of Ca2+ via TRPC1 stretch activated Ca2+ that are coupled to intracellular (endogenous) stores.
Yang 2019
Previously, we found that exposure to a 50-Hz magnetic field (MF) could induce human amniotic epithelial (FL) cell proliferation and sphingosine kinase 1 (SK1) activation, but the mechanism was not clearly understood. In the present study, the possible signaling pathways which were involved in SK1 activation induced by 50-Hz MF exposure were investigated. Results showed that MF exposure increased intracellular Ca2+ which was dependent on the L-type calcium channel, and induced Ca2+ -dependent phosphorylation of extracellular regulated protein kinase (ERK), SK1, and protein kinase C α (PKCα). Also, treatment with U0126, an inhibitor of ERK, could block MF-induced SK1 phosphorylation, but had no effect on PKCα phosphorylation. Also, the inhibitor of PKCα, Gö6976, had no effect on MF-induced SK1 activation in FL cells. In addition, the activation of ERK and PKCα could be abolished by SKI II, the inhibitor of SK1. In conclusion, the intracellular Ca2+ mediated the 50-Hz MF-induced SK1 activation which enhanced PKCα phosphorylation, and there might be a feedback mechanism between SK1 and ERK activation in responding to MF exposure in FL cells.
Yi 2022
The mechanism underlying the biological effects caused by an extremely low-frequency electromagnetic field (ELF-EMF) is still unclear. Previously, we found that L-type calcium channel and sphingosine kinase 1 (SK1) were involved in 50-Hz MF exposure-induced cell proliferation. In the present study, the role of intracellular Ca2+ and signal molecules related to SK1 in cell proliferation induced by 50-Hz MF was investigated in human amniotic epithelial (FL) cells. Results showed that the intracellular Ca2+ chelator, BAPTA, could completely inhibit 50-Hz MF-induced cell proliferation, whereas NIF, the inhibitor of L-type calcium channel, only partly blocked it. When cells were cultured in calcium-free medium, MF exposure also increased intracellular Ca2+, activated SK1 and promoted cell proliferation although all of those increasing levels were lower than those in complete medium. Moreover, MF-activated SK1 could be completely inhibited by BAPTA, and MF-induced cell proliferation was abolished by SKI II, the specific inhibitor of SK1. Additionally, a 50-Hz MF exposure did not affect the activation of ERK and PKCα under the condition of calcium-free medium, but activated the Akt, which could be precluded entirely by BAPTA, but not be inhibited by NIF. Treatment of FL cells with LY294002, the inhibitor of Akt, could delete the MF-induced SK1 activation under the condition of calcium-free medium. Based on the data from the present experiment, it is concluded that endogenous Ca2+ release was involved in 50-Hz MF-induced cell proliferation via Akt-SK1 signal cascade.
It should be noted that PKCα is activated by increases in Ca2+. The additional twist is that enzyme activity of sphingosine kinase (SK1), PKCα, and PKCα’s target ERK kinase were traditionally assumed to be turned on by phosphorylation. Antibodies against kinase specific phosphorylation sites were used to determine if these kinases had been turned on.
- Go6976 an inhibitor of protein kinase C alpha, PKC
- Nifedipine (NIF), an L-type Ca2+ channel inhibitor.
- U0126 in an ERK inhibitor. Extracellular signal-Regulated Kinases transfer phosphate groups to serine or threonine amino acid side chains upon activated (phosphorylated) when growth factors bind extracellular receptors.
- SKI II is a sphingosine kinase inhibitor that reduces levels of sphingosine -1-phosphate.
Note that nothing was said in the abstract as to where this endogenous Ca2+ comes from if it is not through L-type voltage gated Ca2+ channels.
Formigli 2009, the link between sphingo and
Transient receptor potential canonical (TRPC) channels provide cation and Ca(2+) entry pathways, which have important regulatory roles in many physio-pathological processes, including muscle dystrophy. However, the mechanisms of activation of these channels remain poorly understood. Using siRNA, we provide the first experimental evidence that TRPC channel 1 (TRPC1), besides acting as a store-operated channel, represents an essential component of stretch-activated channels in C2C12 skeletal myoblasts, as assayed by whole-cell patch-clamp and atomic force microscopic pulling. The channel’s activity and stretch-induced Ca(2+) influx were modulated by sphingosine 1-phosphate (S1P), a bioactive lipid involved in satellite cell biology and tissue regeneration. We also found that TRPC1 was functionally assembled in lipid rafts, as shown by the fact that cholesterol depletion resulted in the reduction of transmembrane ion current and conductance. Association between TRPC1 and lipid rafts was increased by formation of stress fibres, which was elicited by S1P and abolished by treatment with the actin-disrupting dihydrocytochalasin B, suggesting a role for cytoskeleton in TRPC1 membrane recruitment. Moreover, TRPC1 expression was significantly upregulated during myogenesis, especially in the presence of S1P, implicating a crucial role for TRPC1 in myoblast differentiation. Collectively, these findings may offer new tools for understanding the role of TRPC1 and sphingolipid signalling in skeletal muscle regeneration and provide new therapeutic approaches for skeletal muscle disorders
So how does 50 Hz PEMF work?
I’ve no clue. The muscle stretch post made a case for a sphingosine-phosphate and the TRPC1 Ca2+ channel, which the former gates. This site has covered the QuantumTx activation of TRPC1 with their 15Hz near radio frequency pulses of PEMF. The CRY2 and TRPC1 post is one example. In this case the unpaired electron of the FAD functional group of cryptochrome 2 is the antenna for their brand of PEMF. Perhaps this is not the case for 50 Hz PEMF.
References
- Formigli L, Sassoli C, Squecco R, Bini F, Martinesi M, Chellini F, Luciani G, Sbrana F, Zecchi-Orlandini S, Francini F, Meacci E. (2009) Regulation of transient receptor potential canonical channel 1 (TRPC1) by sphingosine 1-phosphate in C2C12 myoblasts and its relevance for a role of mechanotransduction in skeletal muscle differentiation. J Cell Sci. 2009 May 1;122(Pt 9):1322-33. sci-hub free paper
- Ke XQ, Sun WJ, Lu DQ, Fu YT, Chiang H. 50-Hz magnetic field induces EGF-receptor clustering and activates RAS. Int J Radiat Biol. 2008 May;84(5):413-20. Sci-Hub free paper
- Qiu L, Feng B, Ni Z, Wu X, Sun W. (2016) Exposure to a 50-Hz magnetic field induced ceramide generation in cultured cells. Int J Radiat Biol. 2016;92(4):215-21. Sci-Hub free paper
- Yang X, Ye A, Chen L, Xia Y, Jiang W, Sun W. (2019) Involvement of calcium in 50-Hz magnetic field-induced activation of sphingosine kinase 1 signaling pathway. Bioelectromagnetics. 2019 Apr;40(3):180-187. Sci-hub free paper
- Ye AF, Liu XC, Chen LJ, Xia YP, Yang XB, Sun WJ. Endogenous Ca2+ release was involved in 50-Hz MF-induced proliferation via Akt-SK1 signal cascade in human amniotic epithelial cells. Electromagn Biol Med. 2022 Apr 3;41(2):142-151. PubMed
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