Microglia M1/M2 polarization contributes to electromagnetic pulse-induced brain injury

Area of Science:

• Neuroscience
• Immunology
• Biophysics

Background:

• Electronic technology advancements raise concerns about electromagnetic fields (EMFs) and electromagnetic pulse (EMP) biological effects.
• The neurotoxic or neuroprotective impact of EMP on conditions like cerebral ischemia is debated.
• Microglia, brain's immune cells, can be either neurotoxic (M1 phenotype) or neuroprotective (M2 phenotype), influencing central nervous system diseases.

Purpose of the Study:

• To investigate the effects of EMP irradiation on neuronal apoptosis and microglia polarization.
• To elucidate the role of the Toll-like receptor-4 (TLR4)/MyD88/NFκB pathway in EMP-induced microglia activation.
• To differentiate the outcomes of short-term versus long-term EMP exposure on neural tissue.

Main Methods:

• In vivo and in vitro experiments were conducted using a specific EMP (400 kV/m, 1 Hz, 200 pulses).
• Microglia polarization (M1/M2 states) was assessed following EMP exposure.
• Neuronal apoptosis, inflammatory cytokine levels (IL-6, IL-1β, TNF-α), and neuroprotective factors (IL-10, TGF-β, BDNF) were measured.

Main Results:

• Short EMP irradiation (≤24 h) induced M1 microglia polarization, activated the TLR4/MyD88/NFκB pathway, increased inflammatory cytokines, and caused neuronal apoptosis.
• Long EMP irradiation (3 days) promoted M2 microglia polarization, reduced apoptosis and inflammation, and elevated neuroprotective factors.
• EMP exposure demonstrated a dual effect, inducing both neuronal damage and recovery by modulating M1/M2 microglia polarization.

Conclusions:

• EMP irradiation exhibits a dose-dependent effect on neural tissue, with short exposure being detrimental and long exposure potentially beneficial.
• The switch between M1 and M2 microglia polarization, mediated by the TLR4/MyD88/NFκB pathway, is a key mechanism in EMP's dual neurobiological effects.
• Understanding EMP's impact on microglia is crucial for developing therapeutic strategies for neurological injuries like cerebral ischemia.