Modulation of inflammatory response by electromagnetic field in Neuronal and Microglial cells

Abstract

Neuroinflammation plays a key role in the development of CNS pathologies. This event encompasses a series of mechanisms involving the immune system and its cellular and molecular components. While it is necessary to activate the innate immune system during the early response to pathogens or traumas, persistent inflammation hinders neuronal recovery and contributes to the development of long-term neuronal complications. In this way, the application of pharmacological and non-pharmacological treatments is crucial to achieving better recovery of patients. We recently observed that the application of a low frequency electromagnetic field (EMF) decreases the expression of pro-inflammatory markers in an animal model of Traumatic Brain Injury in swine. To characterize this effect in terms of individualized response of neurons and microglial cells, we performed an in vitro model of pro-inflammatory damage by treating two different cell lines with tumor necrosis factor-α and then stimulating the cells with two frequencies of EMF. Transcriptional expression of inflammatory mediators was analyzed 24 and 48 hours after. Our results showed that both cell lines are susceptible to EMF, responding to the treatment by reducing the levels of the target genes in study. These observations further support the anti-inflammatory effect of EMF in the function of neurons and microglial cells and thus enhancing the recovery following traumatic brain injury, as observed under in vivo conditions in both experimental animals and human. These findings lay the foundation and warrants further preclinical and clinical studies to determine the effective frequency and duration of EMF stimulation in the healing of brain injury.

Keywords: Electromagnetic field; HCN2 cells; HMC3 cells; IL-1β; Microglial cells; Neurons; TNF-α; Traumatic Brain Injury.

Figure 1:

Effects of TNF-α and EMF exposition on the transcriptional expression of (A) NF-κB, (B) CASP1, (C) IL-1β, (D) IL-6 in HCN-2 cells. Cells were incubated with TNF-α (50 ng/mL) for 20 min and then exposed to EMFs of 2.5 or 5 Hz for 3 min. RT-PCR analysis were performed 24 h after the treatments. Data are presented as mean ± SD. Asterisks represent the statistical differences of each experimental condition compared to control untreated cells. Number signs represent the statistical differences among TNF-α treated cells. *(#) p<0.05, ** (##) p<0.01, *** (###) p<0.001. TNF-α: tumor necrosis factor alpha; EMF: electromagnetic field; NF-κB: nuclear factor kappa-light-chain-enhancer of activated B cells; CASP1: caspase 1; IL-1β: interleukin 1β; IL-6: interleukin 6.

Figure 2:

Effects of TNF-α and EMF exposition on the transcriptional expression of (A) NF-κB, (B) NLRP3, (C) CASP1 in HMC3 cells. Cells were incubated with TNF-α (50 ng/mL) for 20 min and then exposed to EMFs of 2.5 or 5 Hz for 3 min. RT-PCR analysis were performed 24 h and 48 h after the treatments. Data are presented as mean ± SD. Asterisks represent the statistical differences of each experimental condition compared to control untreated cells. Number signs represent the statistical differences among TNF-α treated cells. *(#) p<0.05, ** (##) p<0.01, *** (###) p<0.001. TNF-α: tumor necrosis factor alpha; EMF: electromagnetic field; NF-κB: nuclear factor kappa-light-chain-enhancer of activated B cells; NLRP3: nucleotide-binding oligomerization domain leucine rich repeat and pyrin domain-containing protein 3 CASP1: caspase 1.

Figure 3:

Effects of TNF-α and EMF exposition on the transcriptional expression of (A) IL-1β, (B) IL-18, (C) IL-6 in HMC3 cells. Cells were incubated with TNF-α (50 ng/mL) for 20 min and then exposed to EMFs of 2.5 or 5 Hz for 3 min. RT-PCR analysis were performed 24 h and 48 h after the treatments. Data are presented as mean ± SD. Asterisks represent the statistical differences of each experimental condition compared to control untreated cells. Number signs represent the statistical differences among TNF-α treated cells. *(#) p<0.05, ** (##) p<0.01, *** (###) p<0.001. TNF-α: tumor necrosis factor alpha; EMF: electromagnetic field; IL-1β: interleukin-1β; IL-18: interleukin 18; IL-6: interleukin 6.