Differential effects of protein kinase C inhibitors on chemokine production in human synovial fibroblasts

Abstract

1 Rheumatoid arthritis is associated with the accumulation and activation of selected populations of inflammatory cells within the arthritic joint. One putative signal for this process is the production, by resident cells, of a group of inflammatory mediators known as the chemokines. 2 The chemokines interleukin-8 (IL-8), monocyte chemotactic protein-1 (MCP-1) and RANTES (regulated on activation normal T-cell expressed and presumably secreted) are target-cell specific chemoattractants produced by synovial fibroblasts in response to stimulation with interleukin-la (IL-la) or tumour necrosis factor a (TNFa). The signalling pathways involved in their production are not well defined. We therefore used four different protein kinase C inhibitors to investigate the role of this kinase in the regulation of chemokine mRNA and protein expression in human cultured synovial fibroblasts. 3 The non-selective PKC inhibitor, staurosporine (1-300 nM) significantly increased the production of IL-la-induced IL-8 mRNA and protein. A specific PKC inhibitor, chelerythrine chloride (0.1-3 gM), also caused a small concentration-dependent increase in IL-8 mRNA and protein production. In contrast, 3-[1-[3-(amidinothio)propyl]-3-indoly]-4-(1-methyl-3-indolyl)-1H-pyrrole-2,5-dione methanesulphonate (Ro 31-8220) and 2[1-(3-dimethylaminopropyl)-1H-indol-3-yl]-3-(lH-indol-3-yl)-maleimide (GF 109203X), two selective PKC inhibitors of the substituted bisindolylmaleimide family had a concentration-dependent biphasic effect on IL-la or TNFa-induced chemokine expression. At low concentrations they caused a stimulation in chemokine production, which was especially evident at the mRNA level. At higher concentrations both inhibited IL-la or TNFa-induced chemokine mRNA and protein production. Ro 31-8220 was 10 fold more potent than GF 109203X, with an IC50 of 1.6+0.08 ,M (mean+s.e.mean, n=4) for IL-la induced IL-8 production. Ro 31-8220 also inhibited the expression of IL-la or TNFa-induced MCP-1 and RANTES mRNA with a similar potency. 4 The stimulatory effect of staurosporine is discussed in relation to the known poor selectivity of this inhibitor for PKC. It is proposed that activation of an isoform of PKC, possibly PKC epsilon or zeta, which is inhibited by higher concentrations of the bisinodolylmaleimides, plays a role in the regulation of chemokine expression induced by IL-la or TNFa in synovial cells. 5 The inhibition of chemokine production by bisindolylmaleimide compounds heralds a novel approach for future anti-inflammatory therapies.

ML-7, Chelerythrine and Phorbol Ester Increase Outflow Facility in the Monkey Eye

“…The evidence might therefore seem to support PKC, rather than MLCK, as the target kinase. However, although CHEL has been widely used as a speci®c PKC inhibitor, the relative newness of this compound and the difference in experimental systems precludes certainty as to its speci®city for PKC (Jordan et al, 1996) in the relevant ocular cells.…”

A2B Adenosine and P2Y2 Receptors Stimulate Mitogen-activated Protein Kinase in Human Embryonic Kidney-293 Cells

“…Both compounds have been reported to be potent and selective PKC inhibitors. Nevertheless, it has been recently noted that these two PKC inhibitors have differential actions and distinct pharmacological properties (41)(42)(43)(44). Ro 31-8220 is a much more potent inhibitor of PKC (106 -169 nM versus 5800 nM) than is GF 109203X (45-48), whereas they are almost equipotent as inhibitors of other PKC isoforms.…”

Octreotide regulates CC but not CXC LPS-induced chemokine secretion in rat Kupffer cells

“…Differential regulation of CC and CXC chemokines has been previously shown following stimulation of intestinal epithelial cell lines with INFg and TNFa, in which case upregulation of CC chemokines was found, while there was no effect on CXC chemokine expression (Kim et al, 2002). Moreover, differential inhibition patterns of CC and CXC chemokine production have been reported following treatment with protein kinase C inhibitors of different specificity (Jordan et al, 1996). The differential inhibitory effect of octreotide observed in the present study represents an interesting observation relevant to previously published data on chemokine regulation that requires further study.…”