Ethanol increases astrocyte aquaporin-4 expression under hyper-sodium condition.

Ethanol increases brain aquaporin-4 (AQP4) expression after traumatic brain injury (TBI), leading to augment mortality and morbidity after TBI. AQP4 is regulated by sodium ion channels/transporters. Ethanol affects the ion channels/transporters. From these findings, we hypothesized that ethanol may have different effects on AQP4 expression in hypo- or hyper-sodium condition. In this study, rat primary astrocytes were incubated in iso-, hypo- or hyper-sodium MEM medium with 10% calf serum. Ethanol was added to each medium simultaneously. And to check whether hypo/hyper-sodium condition could change AQP4 expression after ethanol exposure or not, astrocytes were incubated in iso-sodium with ethanol, followed by changed to hypo/hyper-sodium with the same concentration of ethanol. Astrocyte AQP4 expression was increased in hypo-sodium exposure. Hypo-sodium with ethanol did not change AQP4 expression significantly, on the other hand, hyper-sodium with ethanol decreased AQP4 expression for short time exposure, and increased it for long time exposure. Hyper-sodium changing increased astrocyte AQP4 expression under EtOH exposure. These findings suggest that AQP4 expression is regulated by sodium ion or ion channels/transporters. And ethanol affects sodium ion channels/transporters, which is involved in AQP4 expression under ethanol.