Author(s):
Ding C*, Wang H, Yang C, Hang Y, Zhu S, Cao Y.
* Department of Hygiene Toxicology, School of Public Health, Medical College of Soochow University, Suzhou.
China
Published in:
Electromagn Biol Med 2024: 1-11 [im Druck]
Published: 20.09.2024
on EMF:data since 11.11.2024
Further publications: Studie gefördert durch:

National Natural Science Foundation of China [81373025].

Keywords for this study:
Medical/biological studies
Go to EMF:data assessment

Radiofrequency field inhibits RANKL-induced osteoclast differentiation in RAW264.7 cells via modulating the NF-κB signaling pathway.

Original Abstract

In this study, we investigated the inhibitory effects of radiofrequency exposure on RANKL-induced osteoclast differentiation in RAW264.7 cells, along with the underlying mechanisms. RAW264.7 cells were subjected to radiofrequency exposure at three distinct power densities: 50 µW/cm², 150 µW/cm², and 450 µW/cm². The results showed that, among the three dosage levels, exposure to 150 µW/cm² of radiofrequency radiation significantly reduced the proliferation capacity of RAW264.7 cells. RF exposure at three power densities resulted in significant increases in the level of osteoclast apoptosis and notable decreases in osteoclast differentiation. Notably, the most pronounced effects on apoptosis, differentiation in RAW 264.7 cells were observed at the 150 µW/cm² power density. These effects were accompanied by concurrent decreases in mRNA and protein levels of osteoclast-specific genes, including RANK, NFATc1, and TRACP. Furthermore, radiofrequency exposure at power density of 150 µW/cm² induced a significant decrease in cytoplasmic NF-κB protein levels while increasing its nuclear fraction, thereby counteracting the effects of RANKL-induced NF-κB activation. These data suggest that radiofrequency exerts inhibitory properties on RANKL-induced NF-κB transcriptional activity, subsequently indirectly suppressing the expression of downstream NF-κB target genes, such as NFATc1 and TRACP. In conclusion, our study demonstrates that radiofrequency radiation effectively inhibits osteoclast differentiation by modulating the NF-κB signaling pathway. These findings have important implications for potential therapeutic interventions in osteoporosis.

Keywords

NF-κB | RANKL | RAW 264.7 cells | Radiofrequency field | osteoclast differentiation

Exposure:

900 MHz
Leistungsdichte: 50; 150; 450 µW/cm²

EMF:data assessment

Summary

Bone is a dynamic organ undergoing constant remodeling, regulated by a delicate balance between osteoblast-mediated formation and osteoclast-mediated resorption. Osteoclasts are unique multinucleated macrophages derived from hematopoietic stem cells that are solely responsible for bone resorption. This delicate homeostasis is critical for healthy bone tissue and is disrupted in conditions such as osteoporosis. The RANK/RANKL signaling pathway is particularly important for bone metabolism, as the interaction of RANKL with RANK initiates the differentiation of precursor cells into osteoclasts. Excessive formation of mature multinucleated osteoclasts is a key event in the progression of osteoporosis. Previous studies have shown that various doses of pulsed electromagnetic fields can reduce bone loss in osteoporotic rats. Based on this, the authors of this publication hypothesized that radiofrequency (RF) might exert energy-dependent effects on osteoclast differentiation. This study therefore examined the effects of RF on RANKL-induced osteoclast differentiation in RAW264.7 cells and investigated underlying molecular mechanisms.

Source: ElektrosmogReport - Issue 4/2024

Study design and methods

The RAW264.7 mouse macrophage cell line was subjected to three distinct power intensities (0.5 W/m² = LRF; 1.5 W/m² = MRF; 4.5 W/m² = HRF) for 4 hours/day over a five-day period, with the cells being exposed to a 900 MHz radiofrequency electromagnetic field. Sham-exposed cells were used as controls. For the osteoclast differentiation experiment, the cells were treated with RANKL. To assess the role of the pro-inflammatory transcription factor NF-κB in mediating the RF effect, the cell line was treated with an NF-κB inhibitor. As a positive control for RF effects on osteoclast formation, the authors used 17ß-estradiol (E2). They analyzed cell viability, apoptosis, osteoclast markers, and components of the RANK/RANKL as well as NF-κB signaling pathways.

Results

Neither low-dose (0.5 W/m²) nor high-dose (4.5 W/m²) 900 MHz radiofrequency affected the viability of RANKL-induced osteoclasts. However, the medium dose (1.5 W/m²) showed an inhibitory effect of osteoclast cell division comparable to E2 administration. Conversely, apoptosis and osteoclast marker tests revealed that all three 900 MHz doses were capable of inducing apoptosis during osteoclast differentiation. Thus, radiofrequency radiation exerts significant inhibitory effects on RANKL-induced osteoclast differentiation, with the most pronounced inhibition observed at the medium RF dose. Analysis of RANKL signaling pathway components RANK and TRCAP revealed a significant decrease in mRNA and protein levels following exposure to 1.5 W/m². This suggests that RF may impair the capacity for differentiation by inhibiting the formation of differentiation markers. Finally, the effect of 900 MHz exposure at 1.5 W/m² on NF-κB was investigated. RF exposure impaired the translocation of NF-κB into the nucleus, which in turn inhibited the NF-κB-regulated transcription factor NFATc1. These findings indicate that RF might impair genes associated with osteoclast differentiation via the NF-κB signaling pathway and NFATc1.

Conclusions

The researchers concluded that 900 MHz RF exposure at a power density of 1.5 W/m² can inhibit the differentiation of RAW264.7 cells into osteoclasts. On a molecular level, this inhibition appears to be caused by the prevention of NF-κB translocation into the nucleus, which subsequently impairs differentiation markers. This finding suggests that RF might offer a potential non-invasive approach to effective osteoporosis treatment. (The results of this study indicate that 900 MHz exposure at moderate intensity can significantly affect the differentiation of hematopoietic stem cells. While the authors focused on the therapeutic potential, they also highlight the biological effects of sub-thermal RF exposure on differentiation processes in vitro. It is noteworthy that, the authors mention a "window effect" in their publication, which follows a non-linear dose-response relationship where specific RF intensities produce more significant biological effects than lower or higher intensities. These phenomena may help explain the heterogeneity in research findings regarding RF and health and underscore the need for a more comprehensive understanding to assess potential health risks for humans. Editor’s note) (RH)