Gold concentrations in blood fractions of patients with rheumatoid arthritis treated with Myocrisin

Erythrocyte membrane gold levels after treatment with auranofin and sodium aurothiomalate

Triethylphosphine gold-2,3,4,6-tetra-o-acetyl-L-thio-D-glucopyranoside (auranofin and sodium aurothiomalate; Myocrisin are two chemically different gold compounds used to treat rheumatoid arthritis. This study highlights the interaction, in vivo, of these drugs with erythrocyte membrane in patients with rheumatoid arthritis. Fifty-eight patients with definite or classical rheumatoid arthritis were included in this study and randomly allocated to three groups as 18 patients in the Myocrisin group, 20 patients in the auranofin group, and 20 patients in the placebo group. The drugs appeared to react, in vivo, in different ways. With Myocrisin, the level of gold in erythrocyte membrane was, initially, very high and decayed exponentially afterwards, whereas auranofin produced a constant high level up to 36 weeks. The erythrocyte membrane gold level in nonsmokers was higher than that in smokers in the auranofin group, and it decreased with an increase in the number of cigarettes smoked (r = 0.836 P < 0.01); no such correlation was observed in the Myocrisin group. In a changeover study, auranofin appeared to change the nature of erythrocyte membrane after reacting with it and rendering it incapable of picking up any gold from Myocrisin. In the case of auranofin, the hemolysate membrane gold level was found to correlate with clinical improvement.

Gold stimulates Ca2+ entry into and subsequent suicidal death of erythrocytes

The suicidal death of erythrocytes, eryptosis, is characterized by cell shrinkage and cell membrane scrambling leading to phosphatidylserine exposure at the erythrocyte surface. Erythrocyte cell membrane scrambling is stimulated by increase of cytosolic Ca2+ concentration ([Ca2+](i)) and formation of ceramide. Phosphatidylserine (PS) exposing cells are rapidly cleared from circulating blood. Ca2+ entry and/or ceramide formation and thus eryptosis are triggered by lead, mercury, aluminium, and copper ions. The present study explored whether eryptosis could be similarly triggered by exposure to gold. To this end, erythrocytes from healthy volunteers were exposed to AuCl and phosphatidylserine exposure (annexin V binding), cell volume (forward scatter), [Ca2+](i) (Fluo3-dependent fluorescence), and ceramide formation (anti-ceramide-FITC fluorescence) were determined by flow cytometry. Exposure of erythrocytes to low concentrations of AuCl (> or =0.75microg/ml) increased [Ca2+](i) but did not affect ceramide formation. AuCl at concentrations > or =0.5microg/ml significantly increased the number of PS exposing erythrocytes and decreased forward scatter at low concentrations of AuCl pointing to cell shrinkage. Aurothiomalate (> or =1microg/ml), a gold containing drug effective against rheumatoid arthritis, similarly triggered PS exposure of erythrocytes. The present observations disclose a novel action of gold, which may well contribute to side effects during treatment with gold preparations.

Myocrisin-mediated oxidative stress

This study reports on the ability of myocrisin to mediate in the production and detoxification of oxidants (principally hydrogen peroxide) in the monocyte in-vivo and in-vitro. The hydrogen peroxide produced by the monocyte derived from rheumatoid arthritis patients being treated with myocrisin was found to be 14.9 +/- 1.6 nmoles/10(6) cells and is elevated above levels found in monocytes obtained from patients either being treated with non-steroidal anti-inflammatory drugs (NSAIDs) (11.3 +/- 0.4 nmoles/10(6) cells; P < 0.01) or normal healthy volunteers (11.2 +/- 1.2 nmoles/10(6) cells; P < 0.01). A comparative study on glutathione (GSH) oxidation indicated that levels of monocyte GSH were elevated in myocrisin-treated patients (2.4 +/- 0.49 mmol/l) over normal healthy volunteers (0.83 +/- 0.18 mM; P < 0.01) and that levels of monocyte diglutathione (GSSG) were depressed (myocrisin, 0.97 +/- 0.41 micromol/l; normal, 5.71 +/- 0.73 micromol/l; P < 0.01). The non-inhibition of glutathione reductase and the inhibition of glutathione peroxidase by gold provides the link between these two observations. Thus, gold therapy would seem to elevate monocyte hydrogen peroxide, increase monocyte reduced glutathione and decrease plasma glutathione peroxidase activity. Subsequently, the data from this small group of patients (n = 10) provides an indication that, in-vivo, myocrisin contributes to an increase in oxidative stress.

Innovative treatment approaches for rheumatoid arthritis. T-cell regulation

There is considerable evidence to implicate T cells in the pathogenesis of rheumatoid arthritis (RA). They initiate and sustain inflammation and therefore are attractive targets for immunotherapy. Several strategies targeting T cells have been tried in RA. The use of monoclonal antibodies to deplete T cells have been used extensively but with little success. Studies have shown that T cell depleting antibodies produce profound peripheral blood lymphopenia but they are less effective in depleting lymphocytes in the joint. Since clinical efficacy is likely to depend on depleting almost all synovial lymphocytes, high doses of monoclonal antibodies would have to be given. However, the invariably severe peripheral blood lymphopenia induced by such a regimen is likely to result in profound immunosuppression. Therefore, this strategy has been abandoned and recent attempts have been made to induce tolerance in RA. In animal models of RA, treatment with high dose non-depleting anti-CD4 monoclonal antibody protects them from arthritis induced by injection of streptococcal cell wall. In addition, it leads to a state of anergy which protects the animals from arthritis induction without further treatment with anti-CD4 monoclonal antibody. This is currently being used in clinical trials of RA. Other tolerance inducing treatment strategies include T cell or T cell receptor vaccination and oral tolerance. The former is particularly difficult since the rheumatoid arthritogenic antigen and the pathogenic T cell remain unknown. The latter has shown promise in placebo controlled trials although the ideal dosage remains unknown. The mechanism of action of oral tolerance involves either immunosuppressive T cell cytokines, T cell anergy or depletion.

A comparative study of the interaction of Myocrisin with albumin and gamma-globulin

The reactions of Myocrisin with albumin and gamma-globulin have been investigated using atomic absorption spectrometry and gel filtration. Albumin rapidly binds gold up to the levels predicted from the concentration of free sulphydryl groups present in the protein. However, in the presence of glutathione, gold incorporation is increased, suggesting that in vivo, free thiols (glutathione, thiomalate) may facilitate gold uptake by the protein. In comparison, gamma-globulin is found to be capable of binding up to one atom of gold per molecule of protein in a slow reaction which requires high Myocrisin concentrations.