EV71 induces COX-2 expression via c-Src/PDGFR/PI3K/Akt/p42/p44 MAPK/AP-1 and NF-kappaB in rat brain astrocytes

Enterovirus 71 (EV71) induces the expression of cyclooxgenase (COX)-2 served as a major neurotoxic factor in CNS injury. However, the mechanisms underlying EV71-initiated intracellular signaling pathways leading to COX-2 expression remain unknown. Therefore, we investigated the mechanisms underlying EV71-induced COX-2 expression and prostaglandin E(2) (PGE(2)) production in rat brain astrocytes (RBA)-1, determined by Western blotting, RT-PCR, and promoter assay. Here, we reported that EV71-induced COX-2 expression and PGE(2) production were attenuated by pretreatment with the inhibitors of c-Src (PP1), PDGFR (AG1296), PI3K (Wortmannin), MEK1/2 (PD98059), NF-kappaB (helenalin), and AP-1 (Tanshinone) and transfection with shRNA or siRNA of c-Src, PDGFR, p85, c-Jun, c-Fos, ERK1, or ERK2. We further observed that EV71-induced activation of Akt and p42/p44 MAPK were mediated via c-Src and PDGFR. Pretreatment with PP1 attenuated EV71-stimulated phosphorylation of Src, PDGFR, Akt, and p42/p44 MAPK. Inhibition of PI3K by Wortmannin attenuated EV71-induced Akt and p42/p44 MAPK phosphorylation, but had no effect on PDGFR phosphorylation, suggesting that PDGFR is an upstream and p42/p44 MAPK is a downstream component of PI3K/Akt in these responses. EV71-stimulated NF-kappaB translocation from the cytoplasm to the nucleus, IkappaBalpha degradation and NF-kappaB promoter activity were attenuated by pretreatment with helenalin, but not AG1296, Wortmannin, and PD98059. EV71-induced c-Jun mRNA expression was attenuated by pretreatment with PD98059, AG1296, or Wortmannin. These results demonstrate that in RBA-1 cells, EV71-induced COX-2 expression associated with PGE(2) production is mediated through activation of c-Src/PDGFR/PI3K/Akt/p42/p44 MAPK to initiate the expression of AP-1.