Inhibition of mitogen-induced response of human peripheral blood mononuclear cells by bucillamine, a new antirheumatic sulfhydryl drug

Expert opinion on emerging urate-lowering therapies

INTRODUCTION

There has been a resurgence in gout therapeutics in the last decade, not only for the management of gout flares, but also for the treatment of hyperuricemia. This editorial summarizes new, emerging therapies for people with gout. Areas covered: We review several new therapies for gout, including those that are focused on lowering serum urate (levotofisopam, ulodesine, verinurad, merbarone, KUX-1151, UR-1102, FYU-981, SEL-212), or treating gout flares (canakinumab, bucillamine) or both (arhalofenate, diacerein). Expert opinion: Among therapies with both urate lowering and anti-inflammatory action, arhalofenate seems promising, but more data are needed. Examining therapies aimed at treating gout flares [anti-inflammatory action], bucillamine has some potential, but more data and Phase III studies are needed, to better understand its efficacy and safety. Among the urate-lowering therapies (ULTs), verinurad seems to be the most promising, while levotofisopam and ulodesine require more data. A uricase-replacement therapy with improved immune reaction (SLE-212) is in a Phase II trial. A number of ULTs including KUX-1151, UR-1102 and FYU-981 are in early development and more will be known once initial data and studies are published.

Therapeutic effects of the combination of methotrexate and bucillamine in early rheumatoid arthritis: a multicenter, double-blind, randomized controlled study

Disease-modifying antirheumatic drug (DMARD) combination therapies are used widely, but there have been few reports clearly demonstrating that combination therapy is more effective than DMARD monotherapy. We conducted a multicenter, double-blind controlled trial in order to clarify that the combination of methotrexate and bucillamine is more effective than either alone. The subjects of this study were 71 patients with active rheumatoid arthritis within 2 years of onset. Dosages were 8 mg methotrexate with 5 mg folic acid per week (MTX group), 200 mg bucillamine per day (BUC group), or both MTX and BUC (combination group). Clinical effects and adverse reactions were observed for 96 weeks. The ACR 20 response rate was 79.2% in the combination group, significantly higher than the rates of 43.5% for the MTX group (P = 0.008) and 45.8% for the BUC group (P = 0.0178). The cumulative survival curve of maintaining the ACR 20 response was significantly higher in the combination group than in the MTX and BUC groups (P = 0.0123 and P = 0.0088, respectively). The mean increase in the total Sharp score over 96 weeks was 12.6 +/- 9.0 in the combination group, significantly lower (P = 0.0468) than the value of 28.0 +/- 28.3 for the single DMARD (combined MTX and BUC) group. The incidence of adverse reactions did not differ significantly between the three groups. It was concluded that the combination therapy with MTX and BUC showed significantly higher clinical efficacy than either of the single DMARD therapies.

Inhibitory effects of bucillamine on increased blood-retinal barrier permeability in streptozotocin-induced diabetic rats

PURPOSE

To investigate the effect of bucillamine for prevention of increasing blood-retinal barrier (BRB) permeability in streptozotocin (STZ)-induced diabetic rats.

METHODS

The groups included control and STZ-induced diabetic rats treated with or without bucillamine. Six months after intervention, the concentrations of reduced and oxidative glutathione (GSH and GSSG) in the retina were measured biochemically. In addition, vitreous fluorescein, which leaks from the vessels after intravenous injection of fluorescein sodium, was measured to evaluate BRB permeability. To evaluate the scavenging ability against the reactive oxygen species (ROS) in vitro, the second-order rate constant for the reaction of bucillamine with ROS was estimated from the kinetics based on the rate constant for the reaction of ROS.

RESULTS

The BRB permeability was significantly higher (p = 0.01) in diabetic rats not treated with bucillamine, and bucillamine inhibited the BRB permeability. The GSH concentration and the GSH/GSSG ratio in the retinas decreased in diabetic rats not treated with bucillamine; bucillamine inhibited the decrease of the GSH concentrations. The ROS scavenging activity of bucillamine was similar with that of GSH.

CONCLUSIONS

In diabetic retinas, oxidative stress might increase, which may be one of the causes of BRB breakdown. The antioxidant effects of bucillamine might take part in inhibition of increased permeability of the BRB in diabetes.

Inhibitory effect of bucillamine on laser-induced choroidal neovascularization in rats

PURPOSE

We investigated the inhibitory effects of bucillamine on formation of laser-induced choroidal neovascularization (CNV) in a rat model.

METHODS

Bucillamine administration (approximately 150 mg/kg/day) was started 1 week before photocoagulation and continued to the end of the study. Control groups received drinking water. Two weeks after photocoagulation, choroidal neovascularization development was evaluated using simultaneous fluorescein and indocyanine green angiography, and the maximal thickness of the lesions was measured histologically.

RESULTS

The incidence of CNV formation was 99.5 +/- 0.2% [mean +/- standard deviation (SD)] in control rats and 64.3 +/- 15.1% with bucillamine (P < 0.01). Histological study showed that the thickness of the CNV lesions was 23.4 +/- 6.5 microm (mean +/- SD) in the bucillamine-treated rats, which was significantly decreased compared to that in controls (60.8 +/- 9.2 microm) (P < 0.01).

CONCLUSIONS

Our results suggest that bucillamine may inhibit the development of laser-induced CNV in rats.

Effects of KE-758; an active metabolite of the new anti-rheumatic drug KE-298, D-penicillamine, bucillamine and auranofin on the proliferation of murine lymphocytes, and the production of nitric oxide by murine macrophages

2-Mercaptomethyl-4-(4-methylphenyl)-4-oxobutanoic acid (KE-758), which is the active metabolite of 2-acetylthiomethyl-4-(4-methylphenyl)-4-oxobutanoic acid (KE-298), is a novel sulphydryl anti-rheumatic drug. In this study we analyzed the effect of KE-758 on the proliferation of murine lymphocytes, and on the production of nitric oxide (NO) by RAW264.7 murine macrophage cells. We compared its effect with other sulphydryl drugs such as D-penicillamine, bucillamine and auranofin. The proliferation of lymphocytes was measured by 3H-thymidine incorporation assay. Nitrite was measured using Griess Reagent. In the absence of copper ions, KE-758, D-penicillamine and bucillamine rarely affected the proliferation of concanavarin A (ConA) activated murine splenocytes. However, in the presence of copper, pharmacological concentrations of KE-758 but not D-penicillamine and bucillamine suppressed the proliferation of murine splenocytes through a hydrogen peroxide-dependent mechanism. Auranofin markedly suppressed the proliferation regardless of the presence of copper ions by reducing the cellular viability. Furthermore, only KE-758 markedly suppressed the proliferation of phorbol myristate acetate (PMA) plus ionomycin activated murine whole blood lymphocytes (WBL) even in the absence of exogenous copper ions by a hydrogen peroxide-independent mechanism. Meanwhile, lipopolysaccharide (LPS) or LPS plus interferon-gamma (IFN-gamma) induced NO production by RAW264.7 cells were suppressed by KE-758 and auranofin but not by D-penicillamine and bucillamine. In conclusion, KE-758 is a novel immunosuppressive drug, which inhibits both lymphocyte and macrophage functions and its unique anti-rheumatic profile is distinct from that of D-penicillamine, bucillamine and auranofin.

Effects of germanium oxide and other chemical compounds on phenylmercury acetate-induced genotoxicity in cultured human lymphocytes

Phenylmercury acetate (PMA), which not only causes an elevation of sister chromatid exchanges (SCEs) but also induces high frequency of endoreduplication in human lymphocytes, may be genotoxic to humans. The major aim of our study was to investigate the effects of germanium oxide (GeO2), D-penicillamine (D-PA), dimercaprol (BAL), and diltiazem (DTM) on PMA-induced genotoxicity as quantified by SCEs. All concentrations of the four chemical compounds tested alone did not induce genotoxicity in cultured human lymphocytes. However, GeO2 significantly inhibited PMA-induced genotoxicity in a concentration-dependent manner. Similarly, D-PA at concentrations of 3 microM and 10 microM, and BAL at a concentration of 30 microM produced the antigenotoxic effects. In addition, GeO2 (1.5 microM) significantly reversed an increase of endoreduplication frequency caused by PMA. In a cell cycle kinetic study, GeO2 (0.5-5.0 microM) reversed the inhibition of PMA on the proliferating rate index (PRI) of lymphocytes. On the contrary, both D-PA and DTM at concentrations of 30-300 microM markedly potentiated PMA-induced inhibition of PRI. These findings show that GeO2, D-PA and BAL could antagonize PMA-induced genotoxicity, and GeO2 appears to be the most effective.

The mechanisms of action of disease-modifying antirheumatic drugs: a review with emphasis on macrophage signal transduction and the induction of proinflammatory cytokines

1. Rheumatoid arthritis (RA) is probably the most common source of treatable disability. A major problem in modern rheumatology is that the mechanism(s) of action of the currently used disease-modifying antirheumatic drugs (DMARDs) remain unclear. Many of these drugs entered rheumatology mainly through clinical intuition and have been used for decades. 2. The former T-cell-centered paradigm of rheumatoid inflammation has given way to a model of inflammation highlighting the macrophage and its proinflammatory cytokines. In particular, tumor necrosis factor alpha (TNF-alpha) has gained prominence as a central proinflammatory mediator in RA, and antibodies against TNF-alpha have been successfully used in patients with RA. 3. This review will summarize the recent advances in determining the mechanisms of action of the currently used DMARDs, with particular emphasis on their effects on the induction of TNF-alpha and interleukin 1 (IL-1) in mononuclear phagocytes. Although some DMARDs, such as auranofin, antimalarials and tenidap, act as inhibitors of the induction of these cytokines in monocytes or macrophages or both, other drugs, such as methotrexate, D-penicillamine and aurothiomalate, do not seem to affect either TNF-alpha or IL-1. 4. The drugs' effects on proinflammatory cytokine induction are correlated to those on other macrophage responses.