Downregulation of Aquaporin 4 Expression through Extracellular Signal-regulated Kinases½ Activation in Cultured Astrocytes Following Scratch-injury

To investigate the role of extracellular signal-regulated kinase½ (ERK½) pathway in the regulation of aquaporin 4 (AQP4) expression in cultured astrocytes after scratch-injury. The scratch-injury model was produced in cultured astrocytes of rat by a 10-μL plastic pipette tip. The morphological changes of astrocytes and lactate dehydrogenase (LDH) leakages were observed to assess the degree of scratch-injury. AQP4 expression was detected by immunofluorescence staining and Western blot, and phosphorylated-ERK½ (p-ERK½) expression was determined by Western blot. To explore the effect of ERK½ pathway on AQP4 expression in scratch-injured astrocytes, 10 µmol/L U0126 (ERK½ inhibitor) was incubated in the medium at 30 min before the scratch-injury in some groups. Increases in LDH leakage were observed at 1, 12, and 24 h after scratch-injury, and AQP4 expression was reduced simultaneously. Decrease in AQP4 expression was associated with a significant increase in ERK½ activation. Furthermore, pretreatment with U0126 blocked both ERK½ activation and decrease in AQP4 expression induced by scratch-injury. These results indicate that ERK½ pathway down-regulates AQP4 expression in scratch-injured astrocytes, and ERK½ pathway might be a novel therapeutic target in reversing the effects of astrocytes that contribute to traumatic brain edema.