Neuron-glial cell communication in the traumatic stress-induced immunomodulation.

We have previously reported that neuron and glia could collaboratively govern the immunomodulation in traumatic rats. Herein, we characterized the sequential involvement of cortical neuron, microglia, and astrocytes in the traumatic stress-mediated neuroimmune modulation. At day 1 of trauma, transient extracellular signal related kinase 1/2 (ERK1/2) activation was initiated in neuron and microglia, which was accompanied by RSK-1 expression in the cytosol. At day 3 of trauma, persistent ERK1/2 activation occurred in astrocytes, which were destined for the nucleus leading to Elk-1 expression. Furthermore, the functional overlap of ERK1/2 and neuroligin 1 in astrocytes was strengthened at day 3 of trauma and responsible for the recovery from the immnosuppression. These effects could be disrupted by β-neurexin blockade. Altogether, we proposed the mechanism underlying the traumatic stress-induced immunosuppression, in which local activity ensured the initial establishment of neural circuitry in the frontal cortex. ERK1/2-signaling events are required for the temporal and spatial coordination between neuron and glial cells.