Effects Of EMP Exposure On Brain Microglia And Its Mechanism

Electromagnetic Pulse (EMP) is a short high-voltage pulse with a fastrising time and a broad bandwidth. Because of its unusual characters, EMP hasraised much concern about its biological effects. In our previous study, we foundthat brain was one of the sensitive targets of EMP, EMP exposure could increasethe permeability of Blood-Brain Barrier (BBB), and caused the leakage ofalbumin from blood to brain. It was reported that albumin could activatemicroglia in vitro. It was well known that microglia are the immune cells inbrain, which play very important role in maintaining the homeostasis of brain.Till now, the effect of EMP on brain microglia is unclear.In this study, immunohistochemistry, ELISA, Western Blotting andRT-PCR were used to investigate the effect and its mechanism of EMP on brainmicroglia, in vivo and in vitro.AIMSTo investigate the effects and its mechanism of EMP on brain microglia. METHODS1. Adult male SD rats, primary cultured brain microglia cells and mouseBV-2cells were exposed to EMP at200kV/m for200pulses respectively.2. Microglia cells morphology was observed by CD11bimmunohistochemisty after EMP exposure.3. Levels of NO, TNF-α, IL-10and IL-1βin rat cortex and cell supernatantwere determined by nitrate reductase method and ELISA.4. Protein and phosphorylated protein levels of p38, ERK and JNK in ratcortex and cells were detected by Western Blotting.5. Levels of NO, TNF-α, IL-10and IL-1β in cell supernant weredetermined at different time points after EMP exposure when the cells werepretreated with p38inhibitor (SB203580) before EMP exposure.RESULTS1. The expression of CD11b in rat brain cortex and the number of CD11bimmuno-positive cells increased significantly at1h (p<0.05), reached the peak at6h (p<0.05), began to recover at12h (p<0.05) and recovered to sham grouplevel at24h; The number of avtivated microglia cells both in primary culturedmicroglia and BV-2cells increased significantly at1h (p<0.05), reached thepeak at6h (p<0.05) and recovered to sham group level at24h after EMPexposure.2. In rat brain cortex, the levels of NO and TNF-αincreased significantly at1h (p<0.05), reached the peak at6h (p<0.05) and recovered to sham group levelat24h after EMP exposure; IL-10increased obviously at1,6h (P<0.05) andrecovered to sham group level at12h; IL-1βdid not change obviously after EMPexposure. In primary cultured microglia supernatant, NO increased significantlyat1,6,12h(p<0.05) and recovered to sham group level at24h after EMP exposure; TNF-αdecreased significantly at6h (p<0.05); IL-1βdecreased at at1h (p<0.05), reached the peak at6h (p<0.05), began to recover at12h (p<0.05)and recovered to sham group level at24h; IL-10increased at1,6h (p<0.05) andrecovered to sham group level at12h. In BV-2cells supernatant, NO levelincreased obviously at1,6,12h (p<0.05) recovered to sham group level at24hafter EMP exposure; levels of TNF-α, IL-1βand IL-10did not change obviouslyafter EMP exposure.3. The protein level of p38and phosphorylated p38increased significantlyboth in cortex and culturel cells after EMP exposure (p<0.05) and recovered tosham level at12and24hour respectively; the protein levels of ERK, JNK,P-ERK, P-JNK did not change obviously.4. SB203580(p38inhibitor) partly prevented the change of NO, IL-10,IL-1β, TNF-αlevel induced by EMP exposure.CONCLUSIONS1. EMP exposure could activate brain microglia in rat brain both in vivoand in vitro.2. EMP exposure could affect the secretion function of microglia.3. p38pathway is involved in EMP-induced microglia activation and thechange of secretion function.4. p38inhibitor can protect brain microglia injuries caused by EMPexposure.