Stimulation of interleukin-8 production by okadaic acid and vanadate in a human promyelocyte cell line, an HL-60 subline - Possible role of mitogen-activated protein kinase on the okadaic acid-induced NF-kappa B activation

Most types of cells can produce interleukin (IL)-8 in response to various inflammatory stimuli, To study the role of protein phosphatases in the signal transduction leading to IL-8 production, a subline of HL-60 (C-15)was treated with okadaic acid (OA) and sodium orthovanadate (VA), inhibitors of phosphoserine/phosphothreonine phosphatase and phosphotyrosine phosphatase, respectively, Both OA and VA dramatically increased IL-8 secretion up to 200-fold in the HL-60 cells, OA and VA stimulation was accompanied by a marked increase in IL-8 mRNA expression and also by activation of a transcription factor, NP-KB. In addition, an essential role of the NF-KB site in the IL-8 gene activation was confirmed by the chloramphenicol acetyltransferase assay,IL-8 production by OA or VA was inhibited by protein kinase inhibitors, including staurosporine, H-7, R252a, herbimycin A, and genistein, Both OA and VA induced significant tyrosine phosphorylation of p44, which was presumed to be Erk1, a member of the mitogen-activated protein kinase family, with concomitant activation of the mitogen-activated protein kinase activity, In parallel, rapid degradation of I kappa B-alpha, an inhibitory component. of NF-kappa B, was observed. Since OA-activated Erk1 phosphorylated recombinant I kappa B-alpha in vitro, we assumed that Erk1 is involved in the phosphorylation and subsequent degradation of I kappa B-alpha, thus leading to the activation of IL-8 gene transcription.