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Interleukin-6 (IL-6) and interleukin-8 (IL-8) are implicated in the pathogenesis of rheumatic diseases. In affected joints fibroblast-like synoviocytes (FLS) are the major source of these pro-inflammatory cytokines. We have previously found that production of both cytokines is inhibited in vitro by taurine chloramine (Tau-Cl). Heme oxygenase (HO-1) activity was also reported to restrict synthesis of various inflammatory mediators, including IL-6 and IL-8. The aim of present study was to investigate whether this enzyme activity is implicated in the mechanism of Tau-Cl suppressive effect. We have shown that in rheumatoid FLS both hemin (known HO-1 inducer) and Tau-Cl significantly up-regulate HO-1 expression at the mRNA and protein levels and simultaneously inhibit IL-1 beta-triggered production of pro-inflammatory cytokines. However, the inhibitory potency of these compounds differs, because hemin is more potent inhibitor of IL-8 than IL-6 production, while Tau-Cl exerts opposite effect. Importantly, pretreatment of the cells with HO-1 inhibitor completely reverses the inhibitory effect of hemin on both cytokines production. However, in Tau-Cl treated cells this inhibitor fully restores only IL-8 secretion but has weaker effect on IL-6 response. Thus, the present results: (i) support HO-1 activity to be relevant to negatively control production of pro-inflammatory cytokines, and (ii) underline implication of HO-1 in mediating Tau-Cl inhibitory action.

The effect of taurine (Tau) and taurine chloramine (Tau-Cl) on the production of TNF-α, IL-1β, and IL-6 by peripheral blood mononuclear cells of healthy volunteers was examined. Cells were stimulated with bacterial lipopolysaccharide (LPS) in the presence of either Tau or Tau-Cl. After 24 h culture the cytokine concentrations were measured in both culture supernatants (secreted) and cell lysates (cell-associated) using ELISA. In LPS-stimulated cells Tau-Cl inhibited both the secreted and cell-associated IL-1β and IL-6, while exerted dual effect on TNF-α production: raising it slightly at low and reducing at higher concentration. By contrast, Tau had no significant effect on the cytokine production. These results indicate that Tau-Cl modulates synthesis of pro-inflammatory cytokines, and therefore it may play a role in the initiation and propagation of immune response.

Taurine chloramine (TauCl), a product of neutrophil myeloperoxidase - halide system, formed by a reaction of taurine with HOCl, is known as an anti-microbial and anti-inflammatory long-lived oxidant. We previously reported that TauCl inhibits in vitro the production of proinflammatory cytokines (IL-6, IL-8) by RA synoviocytes. Therefore we performed this study to investigate the effect of TauCl treatment on the development of collagen-induced arthritis (CIA) in DBA1/J mice. Early administration of TauCl (after primary immunization) resulted in the delay of the onset of CIA, but had no effect on severity of arthritis. TauCl, given daily for 21 days after booster immunization, did not reduce the symptoms of arthritis in those mice, which already developed CIA, but significantly diminished incidence of the disease (55% vs. 90% of placebo mice). The mechanism of this effect is unknown. This is the first in vivo study suggesting that TauCl may be used for immune intervention in chronic inflammatory diseases.

Taurine chloramine (TauCl) and taurine bromamine (TauBr) are products of activated neutrophils and eosinophils, respectively. It has been reported that TauCl, has strong anti-inflammatory properties. In a number of separate studies it has been shown that heme oxygenase-1 (HO-1), a stress inducible protein, exerts similar anti-inflammatory effects. In this study we investigated the influence of HO-1 on TauCl/TauBr mediated suppression of NO generation in J774.2 macrophages. Expression of HO-1 and inducible nitric oxide synthase (NOS-2) in LPS stimulated J774.2 cells provides an opportunity for determining these interactions. TauCl and TauBr, at non-cytotoxic concentrations, in a similar, dose-dependent manner, inhibited the expression of NOS-2, as evidenced by western blotting technique. Surprisingly, TauCl and TauBr induced expression of HO-1 in both non-activated and LPS-activated macrophages. Importantly, the fall in NOS-2 protein level was associated with a concomitant, dose-dependent induction of HO-1. In addition, an inhibitor of HO-1 activity, chromium III mesoporhyrin (CrMP), attenuated the inhibitory activity of TauBr but not that of TauCl, as measured by nitrite accumulation. These results suggest that at a site of inflammation, TauCl and TauBr may provide a link between taurine-dependent and HO-1-dependent cytoprotective mechanisms.