A 50-Hz magnetic-field exposure promotes human amniotic cells proliferation via SphK-S1P-S1PR cascade mediated ERK signaling pathway

The Frequency of a Magnetic Field Reduces the Viability and Proliferation of Numerous Tumor Cell Lines

The frequency of a magnetic field has led to the development of physicochemical interaction models and to the consideration of the role of frequency as a fundamental parameter in the change of cell behavior. The main objective of this article is to find a frequency window to decrease the viability and proliferation of different tumor cell lines to compare the frequency response of each. For this purpose, tumor cell lines PC12 (rat), B16F10 (mouse), SKBR3 (human), MDA-MB-231 (human), and the non-tumor cell line 3T3 (mouse) are exposed to a magnetic field of 100 µT for 24, 48, and 72 hours in frequency windows contained in the range [20-100] Hz, and their viability and proliferation behavior is evaluated. The results show a frequency-, exposure-time-, and cell-line-dependent behavior, with the most pronounced changes for most cell lines at frequencies of 45, 50, and 55 Hz. It is concluded that each cell type could respond to specific frequency codes that allow the modification of its behavior in vital cellular processes related to tumor development. Knowledge of these codes would allow for the therapeutic application of magnetic fields in oncological pathologies.

The Cellular Response Is Determined by a Combination of Different ELF-EMF Exposure Parameters: A Scope Review

Since the establishment of regulations for exposure to extremely low-frequency (0-300) Hz electromagnetic fields, scientific opinion has prioritised the hypothesis that the most important parameter determining cellular behaviour has been intensity, ignoring the other exposure parameters (frequency, time, mode, waveform). This has been reflected in the methodologies of the in vitro articles published and the reviews in which they are included. A scope review was carried out, grouping a total of 79 articles that met the proposed inclusion criteria and studying the effects of the different experiments on viability, proliferation, apoptosis, oxidative stress and the cell cycle. These results have been divided and classified by frequency, intensity, exposure time and exposure mode (continuous/intermittent). The results obtained for each of the processes according to the exposure parameter used are shown graphically to highlight the importance of a good methodology in experimental development and the search for mechanisms of action that explain the experimental results, considering not only the criterion of intensity. The consequence of this is a more than necessary revision of current exposure protection regulations for the general population based on the reductionist criterion of intensity.

Extremely low-frequency electromagnetic field induces acetylation of heat shock proteins and enhances protein folding

The pervasive weak electromagnetic fields (EMF) inundate the industrialized society, but the biological effects of EMF as weak as 10 µT have been scarcely analyzed. Heat shock proteins (HSPs) are molecular chaperones that mediate a sequential stress response. HSP70 and HSP90 provide cells under undesirable situations with either assisting covalent folding of proteins or degrading improperly folded proteins in an ATP-dependent manner. Here we examined the effect of extremely low-frequency (ELF)-EMF on AML12 and HEK293 cells. Although the protein expression levels of HSP70 and HSP90 were reduced after an exposure to ELF-EMF for 3 h, acetylations of HSP70 and HSP90 were increased, which was followed by an enhanced binding affinities of HSP70 and HSP90 for HSP70/HSP90-organizing protein (HOP/STIP1). After 3 h exposure to ELF-EMF, the amount of mitochondria was reduced but the ATP level and the maximal mitochondrial oxygen consumption were increased, which was followed by the reduced protein aggregates and the increased cell viability. Thus, ELF-EMF exposure for 3 h activated acetylation of HSPs to enhance protein folding, which was returned to the basal level at 12 h. The proteostatic effects of ELF-EMF will be able to be applied to treat pathological states in humans.

Residential exposure to magnetic fields from high-voltage power lines and risk of childhood leukemia

BACKGROUND

Several studies have suggested an excess risk of leukemia among children living close to high-voltage power lines and exposed to magnetic fields. However, not all studies have yielded consistent results, and many studies may have been susceptible to confounding and exposure misclassification.

METHODS

We conducted a case-control study to investigate the risk of leukemia associated with magnetic field exposure from high-voltage power lines. Eligible participants were children aged 0-15 years residing in the Northern Italian provinces of Modena and Reggio Emilia. We included all 182 registry-identified childhood leukemia cases diagnosed in 1998-2019, and 726 age-, sex- and province-matched population controls. We assessed exposure by calculating distance from house to nearest power line and magnetic field intensity modelling at the subjects' residence. We used conditional logistic regression models to estimate odds ratios (ORs) and 95% confidence intervals (CIs), with adjustment for potential confounders (distance from nearest petrol station and fuel supply within the 1000 m-buffer, traffic-related particulate and benzene concentrations, presence of indoor transformers, percentage of urban area and arable crops).

RESULTS

In multivariable analyses, the OR comparing children living <100 m from high-voltage power-lines with children living ≥400 m from power-lines was 2.0 (95% CI 0.8-5.0). Results did not differ substantially by age at disease diagnosis, disease subtype, or when exposure was based on modeled magnetic field intensity, though estimates were imprecise. Spline regression analysis showed an excess risk for both overall leukemia and acute lymphoblastic leukemia among children with residential distances <100 m from power lines, with a monotonic inverse association below this cutpoint.

CONCLUSIONS

In this Italian population, close proximity to high-voltage power lines was associated with an excess risk of childhood leukemia, particularly among the youngest children.

Endogenous Ca2+ release was involved in 50-Hz MF-induced proliferation via Akt-SK1 signal cascade in human amniotic epithelial cells

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.

Combined effect of co-exposure to di (2-ethylhexyl) phthalates and 50-Hz magnetic-fields on promoting human amniotic cells proliferation

Di (2-ethylhexyl) phthalate (DEHP) and extremely low-frequency electromagnetic fields (ELF-EMFs) exist far and wide in our surroundings. Studies have reported that both of DEHP and ELF-EMFs could promote cell proliferation which is related with adverse bioeffects. In this study, we investigated whether there is the combined effect between DEHP and 50-Hz magnetic fields (MFs) on cell proliferation in human amniotic (FL) cells. Results revealed that the low-concentration DEHP (1 μM) could promote FL cell proliferation, whereas the high-dose DEHP (100 μM) inhibited cell proliferation. When FL cells were treated jointly by a 50-Hz, 0.2-mT MF and 0.1 μM DEHP, the proliferation rate of cells was significantly higher than that of single factor exposure. Additionally, co-exposure to under-threshold MF and DEHP could cooperatively activate protein kinase B (Akt), sphingosine kinase 1 (SphK1) and extracellular signal regulated kinase (ERK) in a cascade manner, and finally mediate cell proliferation. Taken together, the findings of this study indicated that the co-exposure to under-threshold MF and DEHP could jointly promote cell proliferation through activating proliferation-related signal pathway, which warned us that it should be cautious about assessing the underlying health hazards of co-exposure to MFs and DEHP at under-threshold levels.

SphK1 Promotes Cancer Progression through Activating JAK/STAT Pathway and Up-Regulating S1PR1 Expression in Colon Cancer Cells

BACKGROUND

SphK1 is a conserved lipid kinase, which can catalyze formation of tumor promoting factor sphingosine phosphate-1 (S1P).

OBJECTIVE

To investigate effect of SphK1 on proliferation/migration of colon cancer cells and associated mechanisms.

METHODS

Transcription of SphK1 gene in colon cancer cells was detected. Gene transcription of SphK1 was inhibited by transfecting with si-SphK1 gene in colon cancer cells. Effects of SphK1 inhibition (si-SphK1) on cell migration/proliferation were detected using transwell system and MTS. Gene transcription of SIP, S1PR1, S1PR2, S1PR3, and activation of JAK/STAT3 pathway were examined using RT-PCR and western blot assay. S1PR1 over-expressing plasmid was constructed and transfected into cells. Effects of S1PR1 over-expression on migration/proliferation of si-SphK1 transfected colon cancer cells and activation of JAK/STAT3 pathway were determined using RT-PCR and western blotting.

RESULTS

Gene transcription of SphK1 in SW480 and HT-29 colon cancer cells was significantly inhibited by transfection of si-SphK1 gene. Transwell migration and MTS findings showed that si-SphK1 transfection (si-SphK1 group) could reduce migration quantity and cell viability of colon cancer cells compared to negative control (NC) (p<0.0001). SphK1 inhibition (si-SphK1 group) significantly down-regulated S1PR1 and S1PR3 gene transcription in SW480 and HT-29 cells (p<0.0001), and decreased activation level of JAKSTAT3 signaling pathway compared to NC group (p<0.05). Over-expression of S1PR1 reversed inhibitory effects of si-SphK1 on migration/proliferation of SW480 and activation of JAK/Stat3.

CONCLUSION

SphK1 promoted proliferation and migration of colon cancer cells through promoting JAK/STAT activation and up-regulating S1PR1 expression.

30 Hz, Could It Be Part of a Window Frequency for Cellular Response?

Many exogenous and endogenous risk factors have been proposed as precursors of brain tumors, including the exposure to non-ionizing electromagnetic fields. Nevertheless, there is still a debate among the scientific community about the hazard of the effects produced by non-ionizing radiation (NIR) because conflicting results have been found (number of articles reviewed >50). For that reason, to provide new evidence on the possible effects produced by exposure to NIR, we performed different studies with several combinations of extremely low frequencies, times, and field intensities in tumoral and non-tumoral cells. The results of our studies showed that cell viability was frequency dependent in glioblastoma cells. In fact, our results revealed that a frequency of 30 Hz-or even other frequencies close to 30 Hz-could constitute a window frequency determinant of the cellular response in tumoral and non-tumoral cells.

Anti-Inflammatory Effect of Geniposide on Regulating the Functions of Rheumatoid Arthritis Synovial Fibroblasts via Inhibiting Sphingosine-1-Phosphate Receptors1/3 Coupling Gαi/Gαs Conversion

The activated Gα protein subunit (Gαs) and the inhibitory Gα protein subunit (Gαi) are involved in the signal transduction of G protein coupled receptors (GPCRs). Moreover, the conversion of Gαi/Gαs can couple with sphingosine-1-phosphate receptors (S1PRs) and have a critical role in rheumatoid arthritis (RA). Through binding to S1PRs, sphingosine-1-phosphate (S1P) leads to activation of the pro-inflammatory signaling in rheumatoid arthritis synovial fibroblasts (RASFs). Geniposide (GE) can alleviate RASFs dysfunctions to against RA. However, its underlying mechanism of action in RA has not been elucidated so far. This study aimed to investigate whether GE could regulate the biological functions of MH7A cells by inhibiting S1PR1/3 coupling Gαi/Gαs conversion. We use RASFs cell line, namely MH7A cells, which were obtained from the patient with RA and considered to be the main effector cells in RA. The cells were stimulated with S1P (5 μmol/L) and then were treated with or without different inhibitors: Gαi inhibitor pertussis toxin (0.1 μg/mL), S1PR1/3 inhibitor VPC 23019 (5 μmol/L), Gαs activator cholera toxin (1 μg/mL) and GE (25, 50, and 100 μmol/L) for 24 h. The results showed that GE may inhibit the abnormal proliferation, migration and invasion by inhibiting the S1P-S1PR1/3 signaling pathway and activating Gαs or inhibiting Gαi protein in MH7A cells. Additionally, GE could inhibit the release of inflammatory factors and suppress the expression of cAMP, which is the key factor of the conversion of Gαi and Gαs. GE could also restore the dynamic balance of Gαi and Gαs by suppressing S1PR1/3 and inhibiting Gαi/Gαs conversion, in a manner, we demonstrated that GE inhibited the activation of Gα downstream ERK protein as well. Taken together, our results indicated that down-regulation of S1PR1/3-Gαi/Gαs conversion may play a critical role in the effects of GE on RA and GE could be an effective therapeutic agent for RA.

RAC1 Involves in the Radioresistance by Mediating Epithelial-Mesenchymal Transition in Lung Cancer

Radiation therapy is a common and acceptable approach for lung cancer. Although the benefit of ionizing radiation (IR) is well-established, cancer cells can still survive via pro-survival and metastasis signaling pathways. Ras related C3 botulinum toxin substrate1 (RAC1), a member of Rho family GTPases, plays important roles in cell migration and survival. In the present study, we investigated the effects of RAC1 on the survival of lung cancer cells treated with irradiation. The results showed RAC1 is overexpressed in lung cancer cells and promoted cell proliferation and survival. Furthermore, IR induced RAC1 expression and activity via the activation of PI3K/AKT signaling pathway, and then enhancing cell proliferation, survival, migration and metastasis and increasing levels of epithelial-to-mesenchymal transition (EMT) markers, which facilitated the cell survival and invasive phenotypes. In addition, overexpression of RAC1 attenuated the efficacy of irradiation, while inhibition of RAC1 enhanced sensitivity of irradiation in xenograft tumors in vivo. Collectively, we further found that RAC1 enhanced radioresistance by promoting EMT via targeting the PAK1-LIMK1-Cofilins signaling in lung cancer. Our finding provides the evidences to explore RAC1 as a therapeutic target for radioresistant lung cancer cells.