Abstract:

Objective Aquaporin 4(AQP4) is the predominant water channel protein in the brain, and plays important roles in the development of brain edema. However the mechanisms regulating changes of AQP4 expression after brain injury are not known. In this study, we investigated the change of AQP4 expression in cultured rat astrocyte after scratch injury and explored the effects of pretreatment with mitogenactivated protein kinases(MAPKs) inhibitors. Methods Secondary cultured astrocyte at 10 days were used to prepare scratch injury model, the morphologic change of astrocyte was observed through phase contrast microscope, and immunostaining of antiglial fibriliary acidic protein(GFAP) was performed. Meanwhile, the AQP4 mRNA level in astrocyte was determined by real-time fluorescent quantitative reverse transcription polymerase chain reaction. Results Without injury the cultured astrocyte were uniformly thin and flat, while 12 h after scratch injury, the astrocyte became irregularly shaped and the cell processes along the margin of the wound extended to the cellfree area. Also,the immunostaining showed stronger GFAP staining at 12 h after injury, and hypertrophic astrocyte occurred. The level of AQP4 mRNA in astrocyte decreased significantly at 12 h after scratch injury(P<0.05), which was antagonized by pretreatment with ERK inhibitor U0126, p38 MAPK inhibitor SB203580 and JNK inhibitor SP600125 respectively(P<0.05). Conclusion Our results demonstrate that scratch injury on astrocyte directly down-regulated AQP4 mRNA expression, and MAPKs inhibitors can antagonize the response. These findings suggest that MAPKs signal transduction pathway may be involved in the regulation of AQP4 expression after injury.

Key words: astrocyte, aquaporin 4, scratch injury, mitogenactivated protein kinases