Aquaporin 1 and aquaporin 4 expression in human brain after subarachnoid hemorrhage and in peritumoral tissue.

Aquaporins (AQPs) are a protein family of water channels which facilitate the water flux through the plasmatic membranes. The expression of AQPs has been described in rat brain by several studies. Despite recent reports that have shown an over-expression of AQP1 and 4 in human tumoral cells, little is known about AQP expression in human brain. The purpose of this study was to investigate the expression of AQP1 and AQP4 in human brain after subarachnoid hemorrhage (SAH) and in peritumoral tissue by western blot and immunohistochemistry. The results showed a marked increase of the expression of AQP1 and AQP4. This over-expression occurred on the astrocytic processes and polarization on astrocytic end-feet was lost. No expression was observed on neuronal cells. This study is the first demonstration of the induction of AQP1 and AQP4 on reactive astrocytes in an acute brain injury, such as SAH. These results reinforce the hypothesis that AQPs may be involved in the dynamics of brain edema formation or resolution. Further studies are needed to understand their functional role.