The role of the NF-κB, SAPK/JNK, and TLR4 signalling pathways in the responses of RAW 264.7 cells to extremely low-intensity microwaves

Abstract

Purpose: To investigate the role of the toll-like receptor 4 (TLR4), nuclear factor κB (NF-κB), and stress activated protein kinases/Jun N-terminal kinase (SAPK/JNK) signalling pathways in the responses of RAW 264.7 macrophages to low-intensity microwaves (MW).

Materials and methods: Three inhibitors of TLR4, SAPK/JNK, and NF-κB signalling, namely CLI-095, SP600125, and IKK Inhibitor XII, respectively, were added to cultured RAW 264.7 macrophages before MW treatment.

Results: MW exposure resulted in stimulation of RAW 264.7 cell activity manifested by increases in cytokine production and the stimulation of cell signalling. The blocking of a key kinase of the NF-κB pathway by IKK Inhibitor XII resulted in decreased MW-induced TLR4 expression and increased SAPK/JNK and NF-κB phosphorylation in irradiated cells. In addition, IKK Inhibitor XII significantly decreased tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin 1α (IL-1α), interleukin 6 (IL-6), and interleukin 10 (IL-10) production in both exposed and unexposed RAW 264.7 macrophages. Inhibitor SP6000125 did not prevent an MW effect on signal proteins with the exception of decreased SAPK/JNK phosphorylation in RAW 264.7 cells. Cytokine production was markedly decreased in MW-exposed cells cultured with SP6000125. The inhibitor of TLR4, CLI-095, did not affect signal proteins and cytokine production changes in MW-exposed cells.

Conclusions: The results suggest that low-intensity MW promotes macrophage activity via mechanisms involving cellular signalling, particularly the NF-κB pathway.

Keywords::

• NF-κB
• SAPK/JNK
• TLR4
• microwaves
• RAW 264.7 cells

Acknowledgements

The work was supported by Program of Russian Academy of Sciences “Molecular and Cellular Biology” and by Russian Foundation for Basic Research, Grant Nos. 14-44-03558 and 15-04-01307. The authors would like to thank Elsevier WebShop Language Service for help with language editing.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.