Involvement of protein kinase C-gamma gamma in IL-1 beta-Induced cyclooxygenase-2 expression in human pulmonary epithelial cells

The signaling pathway of protein kinase C (PKC) is known to play a role in mediating the action of various cytokines. Here we examined the signal tran sduction pathway of PKC activation and the role of PKC isoforms in interleu kin-1 beta (IL-1 beta)-mediated cyclooxygenase-2 (COX-2) expression in huma n pulmonary epithelial cell line (A549). The tyrosine kinase inhibitors (ge nistein and tyrphostin AG126) and phosphatidylcholine-phospholipase C inhib itor (D-609) prevented IL-1 beta-induced prostaglandin E-2 (PGE(2)) release and COX-2 expression, whereas U-73122 (a phosphatidylinositol-phospholipas e C inhibitor) and propranolol (a phosphatidate phosphohydrolase inhibitor) had no effect. The PKC inhibitors (Go 6976 and Ro 31-8220) and NF-kappa B inhibitor, pyrrolidine dithiocarbamate, also attenuated IL-1 beta-induced P GE(2) release and COX-2 expression. Western blot analysis using PKC isoenzy me-specific antibodies indicated that A549 cells expressed PKC-alpha, -gamm a, -iota, -lambda, -zeta, and -mu. IL-1 beta caused the translocation of PK C-gamma but not other isoforms from cytosol to the membrane fraction. Moreo ver, the translocation of PKC-gamma was inhibited by genistein or D-609, bu t not by U-73122. IL-1 beta caused the translocation of p65 NF-kappa B from cytosol to the nucleus as well as the degradation of I kappa B-alpha in cy tosol. Furthermore, the translocation of p65 NF-kappa B was inhibited by ge nistein, Go 6976, Ro 31-8220, or pyrrolidine dithiocarbamate. These results indicate that in human pulmonary epithelial cells, IL-1 beta might activat e phosphatidylcholine-phospholipase C through an upstream tyrosine phosphor ylation to elicit PKC activation, which in turn initiates NF-kappa B activa tion, and finally induces COX-2 expression and PGE(2) release. Of the PKC i soforms present in A549 cells, only activation of PKC-gamma is involved in regulating IL-1 beta-induced responses.