Inhibition of C5a-induced neutrophil chemotaxis and macrophage cytokine production in vitro by a new C5a receptor antagonist.

A cyclic peptide, Phe-[Orn-Pro-D-Cyclohexylalanine-Trp-Arg] (F-[OPdChaWR]), was recently shown in vitro to antagonise the binding of C5a to its receptor (CD88) on human polymorphonuclear leukocytes (PMNs) and in vivo to inhibit the neutropenia associated with septic shock induced by lipopolysaccharide (LPS) in rats. The aim of this study was to investigate whether F-[OPdChaWR] inhibits C5a-mediated chemotaxis of human PMNs using a modified Boyden chamber and C5a-stimulated release of cytokines from human monocytes in vitro. Approximately 50% of the chemotactic activity induced by 10 nM C5a was inhibited by 76 nM F-[OPdChaWR]. This correlated with inhibition of C5a-induced polarisation of PMNs by F-[OPdChaWR]. C5a alone failed to induce release of the inflammatory cytokines interleukin(IL)-1beta, tumour necrosis factor (TNF)-alpha, and IL-6 from human monocytes at concentrations up to 100 nM. However, in the presence of low concentrations of LPS (50 ng/mL), both IL-1beta and TNF-alpha were stimulated by 1 nM C5a. This co-stimulation was inhibited by F-[OPdChaWR] with IC(50)s of 0.8 and 6.9 nM for release of TNF-alpha and IL-1beta, respectively. No agonist activity was detected for F-[OPdChaWR] in either the chemotaxis or cytokine release assays at concentrations up to 50 microM. These results show that F-[OPdChaWR] inhibits several important inflammatory activities of C5a and suggest that C5a receptor antagonists may be effective in the treatment of inflammatory diseases mediated by C5a.

A comparison of the disease-modifying and cytokine-regulating activities of tenidap, piroxicam and cyclosporin-A using the adjuvant-induced model of arthritis in rats.

This study compared the antiarthritic activity of tenidap, piroxicam and cyclosporin-A (CsA) using the model of adjuvant-induced arthritis in rats. The aim of the study was to correlate any disease-modifying effects of tenidap with its in-vivo regulation of cytokines.Both tenidap and piroxicam reduced arthritic disease when administered orally from the time the first signs of arthritis are expressed. Disease suppression correlated with a significant reduction in interleukin-6 production and a slight reduction in interleukin-1 and tumour necrosis factor production. When coadministered with the adjuvant, tenidap and CsA prevented disease in 50% and 100% of animals, respectively, whereas piroxicam had no effect. This disease prevention induced by tenidap and CsA coincided with reduced interferon-gamma and interleukin-2 production by lymph node cells one day following initiation of adjuvant disease. This inhibition of T-cell cytokines might be consistent with tenidap acting as a disease-modifying drug.