JAM-1 expression and the integrity of the blood-brain barrier after microwave radiation exposure

Objective To investigate the expression of JAM-1 after microwave irradiation and its correlation with blood-brain barrier integrity. Methods A total of 160 male Wistar rats were divided into a sham radiation group and a radiation group. The radiation group was subdivided into three sub-groups treated with micrewaves at average power densities of 10, 30 and 100 mW/cm2. Rats in each group were sacrificed and their brain tissue sampled at 6 hours and 1, 3, 7 and 14 days after the irradiation. Evans blue ( EB ) dye, laser confocal microscopy,Western blotting, RT-PCR and image analysis were used to test the permeability of the blood-brain barrier and the expression of JAM-1 in protein and at the gene level in the rats' hippocampus and cortex. Results There was an increase of EB in the hippocampus 3 to 14 days after 10 and 100 mW/cm2 microwave irradiation. The EB level increased progressively in the 10 and 30 mW/cm2 groups within 7 d after irradiation but recovered by the 14th day. It also increased progressively in the 100 mW/cm2 group within 14 d after irradiation. In the hippocampus, EB was observed only in the lumens of the blood vessels in the sham group, but EB had diffused out of the blood vessels in the irradiated groups by the 3rd day after irradiation. After 10 or 30 mW/cm2 microwave irradiation, JAM-1 protein in the hippocampus and cortex decreased significantly within 7 d after irradiation but recovered by the 14th day. It decreased progressively in the 100 mW/cm2 group within 14 d after irradiation. The expression of JAM-1 mRNA in the hippocampus decreased significantly at 6 h after irradiation at all power levels, but it recovered within 7 days in the 10 and 30 mW/cm2 groups. Conclusions Microwave radiation can decrease the expression of JAM-1 in the hippocampus and cortex. The degree of decrease is positively correlated with the microwave radiation power. The change might involve increasing the permeability of the blood-brain barrier. Key words: Microwaves; Rats; Junctional adhesion molecule-1; Blood-brain barrier