Figure 4.

Mitogen-activated protein kinase (MAPK) activation by double-stranded RNA in brain astrocytes. (a–c) Cells were incubated with 25 μg/ml poly(I:C) for the indicated times or left untreated. After the stimulation, cells were lysed by sonication and the lysates were analysed by Western blot using antibodies to phosphorylated extracellular signal-regulated kinase (p-ERK), ERK, p-p38, p38, phosphorylated c-Jun N-terminal kinase (p-JNK) and JNK. The fold induction was calculated as the ratio of phosphorylated MAPK to unphosphorylated MAPK. The data are representative of three separate experiments (a–c). (d) Astrocytes were preincubated with the indicated concentrations of U0126 (ERK inhibitor), SB203580 (p38 inhibitor), JNK inhibitor II (JNK inhibitor) or dimethyl sulphoxide (DMSO; control) for 30 min. After treatment, cells were cultured with 100 μg/ml poly(I:C) for 18 hr. The supernatant was collected and analysed by enzyme-linked immunosorbent assay for interleukin-6 (IL-6) production. *P< 0·05, significantly different from poly(I:C) control at varying concentrations.