Investigation of stress-induced microglial activation

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In the present study, we investigated microglial activation mechanism. With using microglia cell-line(MG6) as well as primary microglial cells, we employed RT-PCR, Western Blotting. Both in cell line and primary microglia, the expression of adrenergic receptor(AR) beta1 and beta2, but not beta3, was detected. Then, we administered an agonist for AR, isoproterenol. The result showed that isoproterenol did not affect the induction of interleukin-6.In addition, we studied an effect of adrenal steroid on microglial activation. It was shown that the expression of proinflammatory cytokines, such as interleukin-1, interleukin-6, was significantly inhibited by the adrenal steroid, dexamethazone. Furthermore, we studied the involvement of AR in microglial activation in vivo. In double knockout mouse that specifically lacks AR beta1 and beta2, microglial activation was not induced by exposure of restraint stress. The result was in contrast to that of wild type mouse which demonstrated significant stress-induced microglial activation in the brain. Thus, it was suggested that, in acute stress, microglial activation may be modulated through sympathetic nervous system, AR beta 1 and beta2.It was also suggested that adrenal glucocorticoids may play inhibitory roles in microglial activation.