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

The implication of select protein kinase C (PKC) isoenzymes in cytokine production by human monocytes was investigated using an isozyme-selective inhibitor of PKC, rottlerin, We found that lipopolysaccharide (LPS) triggers cytosol-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 several cellular responses. (1) At low (15 mu M) concentration it blocks translocation of PKC delta, diminishes DNA binding activity of AP-1 transcription factor, and attenuates cytokine production [tumor necrosis factor alpha (TNF-alpha) > interleuldn-1 beta (IL-1 beta)], (2) At high (50 mu M) concentration it prevents translocation of PKCa, and subsequently inhibits ERK1/ERK2 phosphorylation, DNA binding activities of AP-1 and nuclear factor-KB transcription factors, and the production of both tested cytokines. Thus, we propose that cytosol-to-membrane translocation of PKC alpha ard PK delta isoenzymes may represent early steps in the signaling cascades that lead to TNF-alpha and IL-1 beta production in human monocytes.