LTA enhances MMP-9 promoter activity and astrocytic migration. a Cells were transiently cotransfected with pGL-MMP9-Luc and pGal for 24 h, pretreated with Gö, DPI, Apo, NAC and GR343 for 1 h, and then incubated with LTA for 16 h. The promoter activity was determined. b RBA-1 cells were plated on coverslips and grew to confluence; the coverslips were transferred to a new 10-cm dish containing serum-free medium for 24 h. Cells were pretreated with MMP2/9i, Gö, DPI, NAC or GR343 for 1 h, and then incubated with LTA (50 μg/ml) for 48 h. Phase contrast images of RBA-1 cells were taken. The number of LTA-induced cell migrations was counted. Data are expressed as the mean ± SEM of three independent experiments. #
P < 0.01, as compared with the cells stimulated with LTA alone. c Scheme of the LTA-mediated signaling pathways linked to MMP-9 expression and cell migration in brain astrocytes. Action of LTA to its receptors (TLR2) results in activation of PKCα/Nox2/ROS cascade. MMP-9 transcription is ATF-2/AP-1-dependently regulated by a ROS-dependent pathway. Moreover, p300 plays the role of an assistant mediator in these responses. This signaling pathway might contribute to sustained expression of MMP-9, which is required for cell migration in RBA-1 cells.