Rottlerin, a PKC isozyme-selective inhibitor, affects signaling events andcytokine production in human monocytes

The implication of select protein kinase C (PKC) isoenzymes in cytokine pro duction by human monocytes was investigated using an isozyme-selective inhi bitor of PKC, rottlerin, We found that lipopolysaccharide (LPS) triggers cy tosol-to-membrane translocation of PKC alpha and delta isoenzymes, whereas phorbol ester (PMA) induces translocation of several PKC isoforms, Moreover , we show that in LPS- and PMA-stimulated monocytes rottlerin affects sever al cellular responses. (1) At low (15 mu M) concentration it blocks translo cation of PKC delta, diminishes DNA binding activity of AP-1 transcription factor, and attenuates cytokine production [tumor necrosis factor alpha (TN F-alpha) > interleuldn-1 beta (IL-1 beta)], (2) At high (50 mu M) concentra tion it prevents translocation of PKCa, and subsequently inhibits ERK1/ERK2 phosphorylation, DNA binding activities of AP-1 and nuclear factor-KB tran scription factors, and the production of both tested cytokines. Thus, we pr opose that cytosol-to-membrane translocation of PKC alpha ard PK delta isoe nzymes may represent early steps in the signaling cascades that lead to TNF -alpha and IL-1 beta production in human monocytes.