Gold sodium thiomalate and chloroquine inhibit cytokine production in monocytic THP-1 cells through distinct transcriptional and posttranslational mechanisms.

Gold sodium thiomalate (GST), chloroquine (CQ), and methotrexate have been widely used in the therapy of rheumatoid arthritis and other inflammatory conditions. Using the human monocytic cell line THP-1 we have analyzed effects of these drugs on cytokine production and intracellular signaling. GST and CQ were equally effective in reducing lipopolysaccharide (LPS)-induced IL-1 beta release while CQ was a more effective inhibitor of TNF-alpha production than GST. Methotrexate did not affect production of these cytokines. CQ reduced IL-1 beta mRNA expression and strongly inhibited phosphorylation of mitogen-activated protein kinase (MAPK) p38, and to a lesser extent c-Jun N-terminal kinase and extracellular signal-regulated kinase 1/2. In contrast, GST did not affect cytokine mRNA expression or MAPK activation. However, GST selectively inhibited the activity of the interleukin-1 converting enzyme (ICE)/caspase-1. These data demonstrate that CQ inhibits IL-1 beta release from monocytes by interfering with pretranscriptional signaling and TNF-alpha release by posttranslational events whereas GST downregulates IL-1 beta secretion by interfering with posttranslational IL-1 beta processing.

Focal adhesion kinase and mitogen-activated protein kinases are involved in chondrocyte activation by the 29-kDa amino-terminal fibronectin fragment.

The 29-kDa amino-terminal fibronectin fragment (FN-f) has a potent chondrolytic effect and is thought to be involved in cartilage degradation in arthritis. However, little is known about signal transduction pathways that are activated by FN-f. Here we demonstrated that FN-f induced nitric oxide (NO) production from human articular chondrocytes. Expression of inducible nitric-oxide synthase (iNOS) mRNA and NO production were observed at 6 and 48 h after FN-f treatment, respectively. Interleukin-1beta (IL-1beta) mRNA up-regulation was stimulated by FN-f in human chondrocytes. To address the possibility that FN-f-induced NO release is mediated by IL-1beta production, the effect of IL-1 receptor antagonist (IL-1ra) was determined. IL-1ra partially inhibited FN-f-induced NO release although it almost completely inhibited IL-1beta-induced NO release. Tyrosine phosphorylation of focal adhesion kinase was induced transiently by FN-f treatment. Blocking antibodies to alpha(5) or beta(1) integrin and Arg-Gly-Asp-containing peptides did not inhibit FN-f-induced NO production. PP2, a Src family kinase inhibitor, or cytochalasin D, which selectively disrupts the network of actin filaments, inhibited both FAK phosphorylation and NO production induced by FN-f, but the phosphatidylinositol 3-kinase inhibitor wortmannin had no effect. Analysis of mitogen-activated protein kinases (MAPK) showed activation of extracellular signal-regulated kinase (ERK), c-Jun NH(2)-terminal kinase, and p38 MAPK. High concentrations of SB203580, which inhibit both JNK and p38 MAPK, and PD98059 a selective inhibitor of MEK1/2 that blocks ERK activation, inhibited FN-f induced NO production. These data suggest that focal adhesion kinase and MAPK mediate FN-f induced activation of human articular chondrocytes.