STIMULATION OF INTERLEUKIN-8 PRODUCTION BY OKADAIC ACID AND VANADATE IN A HUMAN PROMYELOCYTE CELL-LINE, AN HL-60 SUBLINE - POSSIBLE ROLE OFMITOGEN-ACTIVATED PROTEIN-KINASE ON THE OKADAIC ACID-INDUCED NF-KAPPA-B ACTIVATION

Most types of cells can produce interleukin (IL)-8 in response to vari ous inflammatory stimuli, To study the role of protein phosphatases in the signal transduction leading to IL-8 production, a subline of HL-6 0 (C-15)was treated with okadaic acid (OA) and sodium orthovanadate (V A), inhibitors of phosphoserine/phosphothreonine phosphatase and phosp hotyrosine phosphatase, respectively, Both OA and VA dramatically incr eased IL-8 secretion up to 200-fold in the HL-60 cells, OA and VA stim ulation was accompanied by a marked increase in IL-8 mRNA expression a nd also by activation of a transcription factor, NP-KB. In addition, a n essential role of the NF-KB site in the IL-8 gene activation was con firmed by the chloramphenicol acetyltransferase assay,IL-8 production by OA or VA was inhibited by protein kinase inhibitors, including stau rosporine, H-7, R252a, herbimycin A, and genistein, Both OA and VA ind uced significant tyrosine phosphorylation of p44, which was presumed t o be Erk1, a member of the mitogen-activated protein kinase family, wi th concomitant activation of the mitogen-activated protein kinase acti vity, In parallel, rapid degradation of I kappa B-alpha, an inhibitory component. of NF-kappa B, was observed. Since OA-activated Erk1 phosp horylated recombinant I kappa B-alpha in vitro, we assumed that Erk1 i s involved in the phosphorylation and subsequent degradation of I kapp a B-alpha, thus leading to the activation of IL-8 gene transcription.