Gold determination in biological fluids by atomic absorption spectrophotometry: application to chrysotherapy in rheumatoid arthritis patients

Contamination from Syringes and Blood Container Pots in Trace Element Analysis

Syringes, blood container pots and test tubes have been investigated to determine whether they act as sources of contaminants during trace element analyses. Urine containers were investigated to decide which materials do not absorb mercury from dilute solutions.

No copper and little magnesium contamination was found. Zinc contamination was unpredictable. Very large amounts of zinc leached from the rubber end cap of the piston of disposable, plastic sterile syringes.

The B.S.I. Standards for disposable syringes were shown to be unacceptable for heavy metals.

Interaction and Aggregation of Sodium Aurothiomalate and Poly l-Lysine

This report describes the interaction and aggregation of sodium aurothiomalate with polylysine, a potentially useful property, both as a model for drug-protein interaction and as a means of reversibly immobilizing sodium aurothiomalate. Sodium aurothiomalate formed stable precipitates with polylysine at neutral pH, ionic strengths below 1m NaCl, and optimally, at sodium aurothiomalate to lysine ratios of less than one. The interaction could be demonstrated both by precipitation (which was sensitive to the size of polylysine polymer) and by using polylysine immobilized to Sepharose. Precipitation could be inhibited by addition of the organic thiomalate moiety alone. These findings indicate that the interaction of sodium aurothiomalate with polylysine is by electrostatic bonding of the thiomalate (mercaptosuccinate) moiety and the ε-amino groups of lysine residues. At suitable molar ratios this will link together many polylysine chains leading to precipitation. This represents a potentially valuable interaction for immobilization of the drug and in the formation of conjugates.

Immunomodulatory effects of therapeutic gold compounds. Gold sodium thiomalate inhibits the activity of T cell protein kinase C

Previous studies have shown that the gold compounds, gold sodium thiomalate (GST) and auranofin (AUR), which are effective in the treatment of rheumatoid arthritis, inhibit functional activities of a variety of cells, but the biochemical basis of their effect is unknown. In the current studies, human T cell proliferation and interleukin 2 production by Jurkat cells were inhibited by GST or AUR at pharmacologically relevant concentrations. Because it has been documented that protein kinase C (PKC) is involved in T cell activation, the capacity of gold compounds to inhibit PKC partially purified from Jurkat cells was assayed in vitro. GST was found to inhibit PKC in a dose-dependent manner, but AUR caused no significant inhibition of PKC at pharmacologically relevant concentrations. The inhibitory effect of GST on PKC was abolished by 2-mercaptoethanol. To investigate the effect of GST on the regulation of PKC in vivo, the levels of PKC activity in Jurkat cells were examined. Cytosolic PKC activity decreased slowly in a concentration- and time-dependent manner as a result of incubation of Jurkat cells with GST. To ascertain whether GST inhibited PKC translocation and down-regulation, PKC activities associated with the membrane and cystosolic fractions were evaluated after phorbol myristate acetate (PMA) stimulation of GST incubated Jurkat cells. Translocation of PKC was markedly inhibited by pretreatment of Jurkat cells with GST for 3 d, but the capacity of PMA to down-regulate PKC activity in Jurkat cells was not altered by GST preincubation. The functional impact of GST-mediated downregulation of PKC in Jurkat cells was examined by analyzing PMA-stimulated phosphorylation of CD3. Although GST preincubated Jurkat cells exhibited an increased density of CD3, PMA-stimulated phosphorylation of the gamma chain of CD3 was markedly inhibited. Specificity for the inhibitory effect of GST on PKC was suggested by the finding that GST did not alter the mitogen-induced increases in inositol trisphosphate levels in Jurkat cells. Finally, the mechanism of the GST-induced inhibition of PKC was examined in detail, using purified PKC subspecies from rat brain. GST inhibited type II PKC more effectively than type III PKC, and also inhibited the enzymatic activity of the isolated catalytic fragment of PKC. The inhibitory effect of GST on PKC activity could not be explained by competition with phospholipid or nonspecific interference with the substrate. These data suggest that the immunomodulatory effects of GST may result from its capacity to inhibit PKC activity.

Thiol-containing compounds inhibit the production of monocyte/macrophage-derived angiogenic activity

Macrophage (M phi)-mediated angiogenesis is believed to play an important role in the pathogenesis of rheumatoid arthritis. Gold sodium thiomalate, which is used in the treatment of rheumatoid arthritis, is a potent inhibitor of the production of m phi-derived angiogenic activity. To determine the mechanism of this inhibition, we studied the effects of thiol containing compounds (TCCs) on elicited mouse peritoneal m phi and lipopolysaccharide stimulated normal human monocytes. Monocyte/m phi conditioned media were potently angiogenic when assayed in rat corneas, while conditioned media from viable monocyte/m phi s treated with TCCs (at concentrations of 8.3-16.6 x 10(-5) M) were not. TCCs inhibited production of angiogenic activity by the m phi s rather than affecting other components of the angiogenic response such as the angiogenic factors or the target microvasculature of the rat cornea. Levels of the angiogenic mediator tumor necrosis factor-alpha (TNF-alpha) were not decreased in conditioned media of monocyte/m phi s treated with TCCs. We conclude that TCCs are potent inhibitors of the production of m phi-mediated angiogenic activity. This action of TCCs on m phi s may be in part responsible for the mechanism of action of therapeutic gold compounds in rheumatoid arthritis.

Low-dose gold compounds inhibit fibroblast proliferation and do not affect interleukin-1 secretion by macrophages

We examined the effect of low concentrations of gold compounds on the proliferation of human fibroblasts. Gold sodium thiomalate (GST) inhibited both basal and interleukin-1-induced tritiated thymidine incorporation into fibroblasts in a dose- and time-dependent manner. Significant inhibition was observed at the level of 5 micrograms/ml GST, and greater than 50% inhibition was attained at 10 micrograms/ml. These concentrations are attainable in the serum of treated patients. Similar inhibition was observed when less than 1 micrograms/ml auranofin, which is also within a serum-attainable range, was added. Low concentrations of GST (0-10 micrograms/ml) did not affect interleukin-1 secretion from lipopolysaccharide-stimulated human mononuclear phagocytes (M phi) when assessed by both human fibroblast and C3H/HeJ mouse thymocyte proliferation assays. When M phi precultured for 48 hours with GST (0-10 micrograms/ml) were added to the fibroblast culture in the presence or absence of lipopolysaccharide, there was no significant inhibition of M phi-induced DNA synthesis of fibroblasts. In contrast, when fibroblasts were precultured with GST (0-10 micrograms/ml) for 48 hours and freshly separated M phi were added, significant inhibition was observed in M phi-induced fibroblast proliferation at 5 micrograms/ml. These results suggest that low concentrations of GST directly cause a reduction of fibroblast proliferation, but do not affect the capability of M phi for induction of fibroblast proliferation. Therefore, gold compounds may play a role in the inhibition of the growth of rheumatoid pannus by direct inhibition of fibroblast proliferation.

Effect of gold salt treatment on the receptor binding activity of monocytes and macrophages isolated from rats with adjuvant arthritis

We investigated the effect of chrysotherapy on the Fc and complement receptor binding activity of peripheral blood (PB) monocytes and peritoneal (PE) macrophages isolated from normal rats and rats with adjuvant induced arthritis. The adjuvant induced severe disease in Dark Agouti (DA) rats and less marked disease in J. C. Lewis (JC) rats. Gold treatment reduced the disease in DA rats but exacerbated the disease in JC rats. PB monocytes generally exhibited increased receptor activity after adjuvant injection. Gold treatment resulted in a simultaneous reduction of the PB monocyte receptor activity and increased the PE macrophage receptor activity. This was considered to be due to a direct effect of gold, since the Fc receptor activity of PE macrophages increased after in vitro gold treatment.

Antiarthritic synergism of combined oral and parenteral chrysotherapy. I. Studies in adjuvant-induced arthritis in rats

In comparative clinical studies of auranofin (AF, oral gold) and parenteral gold in the treatment of rheumatoid arthritis, no difference in efficacy was detected. Since the pharmacologic profiles of these compounds are different, we studied their combined effect on adjuvant arthritis (AA). The effect of AF alone and combined with gold sodium thiomalate (GTM) or gold sodium thiosulfate (GTS) on the excretion of urinary hydroxyproline (UHP) and urinary calcium (UCa), and the articular index of arthritic rats was followed during five weeks of treatment. The excretion of UHP and UCa was significantly inhibited (P less than 0.005) in rats treated with AF combined with GTM or GTS as compared with animals treated with the individual gold compounds. However, the articular index only decreased significantly (P less than 0.02) in the group of rats treated with AF + GTS. The present studies open the possibility that combined treatment with oral and injectable gold provide a new approach for chrysotherapy with an increased antiarthritic potency.

Inhibition of human endothelial cell proliferation by gold compounds

Neovascularization has a role in the propagation of rheumatoid synovitis because the spread of mononuclear cell infiltration and the growth of pannus are dependent on the growth of new blood vessels. Growth of such vessels requires local endothelial cell (EC) proliferation. Inhibition of synovial EC proliferation, therefore, would have the potential to diminish rheumatoid inflammation. We have, therefore, studied the effects of gold sodium thiomalate (GST), auranofin, and gold chloride on the proliferation of human umbilical vein EC. GST suppressed both basal and EC growth factor-induced tritiated thymidine incorporation into EC in a dose-dependent fashion. Inhibition was observed with concentrations as low as 1 microgram/ml GST, 5 micrograms/ml gold chloride, and 0.1 microgram/ml auranofin, levels attainable in blood and synovium of patients. These results suggest that gold compounds have an antiangiogenic effect. The low concentrations inhibiting EC proliferation suggest that gold compounds may suppress rheumatoid synovitis by reducing the number of small blood vessels available for mononuclear cell infiltration and synovial tissue proliferation.

Collagenase production by human mononuclear cells in culture: inhibition by gold containing compounds and other antirheumatic agents

Human peripheral blood mononuclear cells in adherent cultures have been shown to synthesise and secrete collagenase. In the present study we have examined the modulation of collagenase production in these cultures by several antirheumatic agents. Incubation of monocytes in serum free medium with sodium aurothiomalate in concentrations varying from 7.7 X 10(-7) to 7.7 X 10(-3) mol/l resulted in marked dose dependent inhibition of the collagenase production. This inhibition was apparently selective in that total protein synthesis or the viability of the cells were not affected. Similar inhibition of the collagenase production was also noted with auranofin, aurothioglucose, and chloroauric acid. The inhibition with auranofin was achieved with a concentration as low as 7.4 X 10(-8) mol/l. To examine the mechanisms of the inhibition of the collagenase activity induced by sodium aurothiomalate the production of prostaglandin E2 was also measured in the same cell cultures. Sodium aurothiomalate in concentrations greater than 7.7 X 10(-4) mol/l significantly inhibited the prostaglandin E2 production; the prostaglandin E2 production was not inhibited, however, in 7.7 X 10(-5) mol/l concentration, while the collagenase production was reduced by 51.0%. Also, exogenous prostaglandin E2 added to the cultures only slightly reversed the inhibition of the collagenase production by sodium aurothiomalate. Thus the inhibition of collagenase production by sodium aurothiomalate in human adherent mononuclear cell cultures appears to be independent of the inhibition of prostaglandin E2 production. The inhibition of collagenase produced by monocyte-macrophages, as shown here in vitro, may contribute to the clinical efficacy of the compounds tested in the treatment of rheumatoid arthritis.

Clinical pharmacokinetics of oral and injectable gold compounds

The pharmacokinetics of oral gold (auranofin) in some respects resemble, and in other respects differ from, those of existing parenteral gold compounds such as gold sodium thiomalate (GST). This may in part relate to physicochemical differences as GST is a water-soluble polymeric compound in vitro whereas auranofin is lipid-soluble and characteristically monomeric. Furthermore, intramuscularly administered gold is greater than 95% bioavailable, whereas only 20 to 30% of an orally administered dose of auranofin is absorbed. Following a standard 50mg intramuscular injection of GST, serum gold concentrations rise sharply, peaking between 4 and 8 mg/L in approximately 2 hours and declining to an average of 3 mg/L by 7 days. With repeated injections of GST stable serum concentrations of gold (3 to 5 mg/L) are eventually achieved (usually within 5 to 8 weeks) although absolute concentrations may vary widely between patients. On the other hand, long term treatment with auranofin is associated with lower and more stable serum concentrations of gold (0.5 to 0.7 mg/L), on the standard dosing regimen of 6 mg daily. Both compounds are retained within the body for prolonged periods. However, the amount of gold retained with auranofin is significantly less compared with GST (less than 5% of a tracer dose of auranofin--about 20% of the absorbed dose--is retained by 100 days whereas the retention for a single labelled dose of GST over a similar interval is greater than 50%). Excretory patterns of GST and auranofin also differ. Most of an absorbed dose of GST (greater than 70%) is excreted by the kidneys whereas only 50% of an absorbed (15% of an administered) dose of auranofin is excreted in the urine. Both compounds are avidly bound by plasma proteins and auranofin shows a particularly strong association with circulating cellular elements. In human subjects, parenterally administered gold is widely distributed among bodily tissues, showing a predilection for tissues of the reticuloendothelial system as well as the kidney and adrenal cortex. Comparable studies in humans are not available for auranofin but animal studies have shown comparatively less affinity for the liver, kidney and spleen. Valuable insight has been gained in analysing the comparative pharmacokinetics of oral and injectable gold compounds. Unfortunately, attempts to correlate pharmacokinetic findings with clinical response or pharmacodynamic changes, as a whole, remain largely unsuccessful with these agents.

Auranofin. A preliminary review of its pharmacological properties and therapeutic use in rheumatoid arthritis

Auranofin is the first orally active gold compound for the treatment of rheumatoid arthritis. Like other chrysotherapeutic agents, its exact mechanism of action is unknown, but it probably acts via immunological mechanisms and alteration of lysosomal enzyme activity. Although long term clinical experience with auranofin is limited, its efficacy appears to approach that of sodium aurothiomalate. Further comparative studies with aurothioglucose, hydroxychloroquine and D-penicillamine are required before definitive statements can be made regarding the relative efficacy of auranofin and these agents. While patients have demonstrated clinical remission of rheumatoid arthritis in response to auranofin therapy, radiological studies have been inconclusive regarding its effect on the occurrence or progression of erosive lesions. Auranofin is relatively well tolerated in most patients, but diarrhoea, skin rash, and pruritus are sometimes troublesome, and thrombocytopenia and proteinuria are potentially serious side effects which may occur during therapy. Whereas mucocutaneous side effects are more frequent with injectable gold compounds, gastrointestinal reactions are the most common adverse effect seen with auranofin. The frequency of side effects has been similar with auranofin and sodium aurothiomalate, but they are generally less severe with auranofin. While some of the side effects are controlled by a reduction in dosage, temporary or permanent withdrawal of auranofin may be necessary. Auranofin is clearly a useful addition to the limited list of agents with disease-modifying potential presently available for the treatment of rheumatoid arthritis. It will doubtless generate much interest as its final place in therapy becomes better defined through additional well-designed studies and wider clinical experience.

Inhibition of polyclonally induced immunoglobulin secretion by aurothiomalate

The influence of sodium aurothiomalate on the secretion of immunoglobulins by normal human lymphocytes in vitro was investigated by means of a reverse hemolytic plaque forming cell (PFC) assay. Aurothiomalate inhibited the PFC response induced by pokeweed mitogen (PWM) and by Epstein-Barr virus (EBV) in a dose dependent manner. The inhibition was irreversible, as pre-incubation for 2 h with the drug followed by extensive washing and further culture in gold salt-free medium still caused an inhibition of the PFC response to PWM and to EBV. Cell proliferation was not significantly affected, suggesting that the inhibition of PFC formation was not due to cytotoxicity. Pre-incubation of monocytes/macrophages (Mø's), T lymphocytes and B lymphocytes with the gold compound prior to culture with PWM showed that Mø's and B cells were highly sensitive, whereas T lymphocytes were resistant to the drug. The findings indicate that aurothiomalate inhibits the polyclonally induced PFC response by interfering with accessory Mø function and by affecting the B lymphocyte itself.

Auranofin versus injectable gold. Comparison of pharmacokinetic properties

The new oral gold compound auranofin differs pharmacokinetically from the existing injectable gold compounds such as gold sodium thiomalate. Following a standard 50 mg intramuscular injection of gold sodium thiomalate, plasma gold levels rise sharply, peak between 400 and 800 micrograms/dl in approximately two hours, then decline to approximately 300 micrograms/dl by seven days. With repeated 50 mg weekly injections, stable plasma concentrations are gradually achieved, although absolute levels vary greatly among individual subjects. On the other hand, auranofin is associated with lower (50 to 70 micrograms/dl) and more predictable plasma concentrations. Single-dose kinetic studies using isotopically labelled gold show that the plasma disappearance half-time for gold sodium thiomalate is relatively rapid (approximately six days) compared with 17 days for auranofin. Both compounds are retained within the body over prolonged periods. Retention of auranofin is much less, about 1 percent of the original tracer dose remaining at 180 days, compared with more than 30 percent retention of gold sodium thiomalate. Excretory pathways are notable different. The majority of gold sodium thiomalate (greater than 70 percent) is excreted by the kidneys, with the remaining fraction appearing erratically in the stool. In contrast, the enteric pathway represents the major excretory route for auranofin, with nearly 85 percent of the dose eventually recoverable in the stool and less than 15 percent in the urine. In human subjects, parenterally administered gold is almost universally dispersed among body tissues, although highest concentrations occur in the organs of the reticuloendothelial system and the adrenal and renal cortices. Comparable studies are not available for auranofin, but animal studies show comparatively less affinity for liver, kidney, and spleen. To date, attempts to correlate the pharmacokinetics of the injectable gold compounds with clinical response and toxicity have been largely unsuccessful. The distinctive pharmacokinetic profile of auranofin, when compared with gold sodium thiomalate, may nonetheless account in part for the clinical and pharmacologic differences between these compounds.

Mechanisms of action of gold

Since the successful introduction of injectable gold compounds for the treatment of rheumatoid arthritis over 50 years ago, numerous studies on the possible mechanism of action have been performed. This heavy metal has been show to possess a bewildering array of biological effects. Studies using gold performed both in vitro and in vivo can be grouped into anti-microbial, anti-immunologic, anti-inflammatory, anti-enzymatic and other effects. In this survey, we have analyzed these multiple approaches to the study of the mechanism of action of injectable gold preparations and apply the findings to rheumatoid arthritis.

Assessment of immune response during chrysotherapy. Comparison of gold sodium thiomalate vs. auranofin

Auranofin (AF) differs significantly from gold sodium thiomalate (GST) in formulation, i.e., aurous gold is stabilized by dual sulfur and phosphorus ligands, has hydrophobic rather than hydrophilic characteristics, and lacks ionic charge. These attributes facilitate: oral absorption of AF, plasma membrane penetration, increase in intracellular lymphocyte gold concentration and perhaps thereby influence lymphocyte function. AF therapy was observed to affect primarily T rather than B lymphocyte function in 16 RA subjects receiving 6 mg of AF per day for an average of 45 weeks (range 20-74 weeks) compared with GST-treated RA subjects. Lymphocytes from AF-treated subjects manifested prompt and sharp declines in mitogen-induced lymphoproliferative response (LPR); suppressed response to skin testing with dinitrochlorobenzene (DNCB); and blebbing of lymphocyte membranes as shown by scanning electron microscopy. Suppression of LPR with AF was approximately 60% after the first week and 80% after 20 weeks of therapy, contrasting with 0% and 30% for the respective intervals in GST-treated subjects. DNCB skin testing of AF patients, indicated 11 of 14, failed to respond, whereas all GST patients responded. Local or systemic fungal, bacterial and/or opportunistic infections were not encountered. The effect of AF on B cell effector function, e.g., suppression of immunoglobulins and rheumatoid factor titer, was less marked when contrasted with GST therapy in RA subjects, as previously reported.

Binding of gold to bovine serum albumin using flameless atomic absorption

A graphite furnace atomic absorption spectrophotometric assay capable of accurately determining nanogram amounts of gold in biological fluids was developed. The presence of bovine serum albumin and/or phosphate in the sample reduced the method sensitivity without affecting the linear response. Binding of gold was studied by ultrafiltration using cones with a molecular weihght cutoff of 25,000. The binding of gold at various concentrations to 2 and 4% bovine serum albumin in 0.1 M phosphate buffer, pH 7.4, was independent of the gold and protein concentrations. In the 2-10 microgram/ml range, the overall binding values (mean +/- SD) of gold to 2 and 4% bovine serum albumin were 98 +/- 1.6 (n = 35) and 99 +/- 1.0% (n = 15), respectively. When ultrafiltration cones with a molecular weight cutoff of 50,000 were used, the extent of binding to 2% bovine serum albumin was 85.4 +/- 1.6% (n=11). This statistically significant difference (p less than 0.001) was due to variations in the protein retention of the two cone types. Interaction studies showed that gold was not displaced from the binding sites by salicylic acid (200 microgram/ml) or vice versa.

Inhibitory effects of a new oral gold compound on HeLa cells

Auranofin (AF), a recently introduced oral antirheumatic coordinated gold compound, was investigated for its antitumor potential. Due to certain similarities with the antitumor-coordinated compound, cis-Diamminedichloroplatinum II, we studied the effects of AF on cell proliferation. These studies included assessing DNA, RNA, and protein synthesis as measured by incorporation of 3H-thymidine, 3H-uridine, and 3H-leucine, respectively, into HeLa cells. AF was shown to exert a dose-dependent inhibition on DNA synthesis and to inhibit 3H-thymidine uptake more rapidly and persistently than 3H-uridine or 3H-leucine uptake at a gold concentration of 75--100 micrograms/dl. These three parameters were inhibited with a 24-hour exposure to 100 micrograms/dl. The inhibition of 3H-thymidine uptake in HeLa pretreated for 6 hours with 50 or 100 micrograms/dl of gold was found to be irreversible. No change in tracer uptake was observed in the acid-soluble pool or in the uptake of 3H-2-deoxy-D-glucose in these cells. Furthermore, HeLa cells demonstrated marked reductions in viability and oxygen uptake after exposure to AF. Dose-dependent surface morphological changes, e.g., blebbing, pitting, were noted in these cells after a brief treatment period. These results suggest this coordinated gold compount exerts a significant inhibitory effect on essential biological processes and functions.

Chrysotherapy. Suppression of immunoglobulin synthesis

Forty-four subjects with classic or definite rheumatoid arthritis who were on individualized chrysotherapy were observed for changes in serum protein electrophoresis, immunoglobulins, and circulating lymphocyte counts. By paired variate analysis, significant declines from pretreatment values were recorded for the following--electrophoretic protein fractions: gamma, alpha-1, alpha-2, (P less than 0.05); immunoglobulins: IgM--53% (P less than 0.001), IgG--37% (P less than 0.01), IgA--34% (P less than 0.001). Rheumatoid factor decreased in 29 of 39 subjects, 15 becoming seronegative (P less than 0.001); circulating lymphocytes decreased by 27% (P less than 0.001). The maximal suppressive effect on IgG and IgM was not achieved until the third and fourth years of therapy by sustained weekly administration of gold sodium thiomalate (one year cumulative dosage, mean 2106 mg, range 1065-2,885; greater than or equal to 4 year cumulative dosage, mean 8747 mg, range 5,385-15,160 mg). An immunosuppressive effect is suggested by these results.

Rapid determination of gold in whole blood of arthritis patients using flameless atomic absorption spectrophotometry

An assay for gold in whole blood of arthritis patients was developed using the graphite furnace atomic absorption spectrophotometer. This method involves no pretreatment of the whole blood except for simple dilution, thereby eliminating some variables and saving laboratory time and expense.

Determination of gold in plasma and plasma fractions by atomic absorption spectrometry and by neutron activation analysis

Three techniques of gold analysis, flame and electrothermal atomic absorption spectrometry and neutron activation analysis, have been compared, using plasma and plasma fractions (derived by gel chromatography) from rheumatoid patients receiving aurothiomalate therapy and from plasma samples incubated with aurothiomalate in vitro. The three methods correlated well in the analysis of gold in whole plasma, but only neutron activation analysis was suitable for the assay of all the plasma fractions. The susceptibility of the two atomic absorption methods to interference by sodium chloride was investigated.

A double-blind trial of high versus conventional dosages of gold salts for rheumatoid arthritis

In a double-blind study, patients were randomly selected for treatment using conventional doses (CD; 50 mg) or high doses (HD; 150 mg) of sodium aurothiomalate given weekly by injection. Twenty-three patients were assigned to the CD group and 24 to the HD group. Neither efficacy nor toxicity correlated with serum gold concentrations. Conventional doses were as efficacious as high doses with respect to both rapidity and degree of response. However, side effects were much more frequent and severe in the HD group. Thus there is no reason to recommend a 150 mg weekly dosage regimen.

Comparison of two dosage schedules of gold salts in the treatment of rheumatoid arthritis. Relationship of serum gold levels to therapeutic response

Two doses of gold sodium thiomalate were compared for their effect on rheumatoid arthritis. Thirty-seven patients with active disease for longer than 6 months were treated with 25 mg of gold sodium thiomalate for an average of 29.6 weeks, then at biweekly or monthly intervals to complete 2 years of treatment. Thirty-eight patients were given more than twice as much gold salt at the same intervals on a flexible dose schedule that produced serum gold levels which averaged 332 microgram/dl during the weekly injection phase. No differences were observed in the therapeutic responses of the two groups. Therefore the minimal dose of gold sodium thiomalate required to induce a response in rheumatoid arthritis is 25 mg or less per week. Serum gold levels in the steady state varied between 95 and 386 microgram/dl and were not related to response. Serum half-life for gold was calculated for patients who had an excellent response and for those who were treatment failures. The rate at which gold disappeared from serum was not related to therapeutic responses.

Effect of auranofin, a new antiarthritic agent, on immune complex-induced release of lysosomal enzymes from human leukocytes

Auranofin, an oral chrysotherapeutic agent effective in the treatment of rheumatoid arthritis (RA), was found to be a potent, noncytotoxic inhibitor of IgG-RF immune complex-induced lysosomal enzyme release (LER) from human leukocytes. At a concentration of 1 microg Au/ml (5 microM), auranofin produced a marked reduction in beta-glucuronidase (100%), acid phosphatase (88%), and lysozyme (72%) release. In contrast, gold sodium thiosulfate (GST, an injectable gold compound) had no inhibitory activity on LER at equivalent gold concentrations (i.e., 1 microg Au/ml) and only modest activity (less than 36% inhibition) at concentrations as high as 40 microg Au/ml. The 50% inhibitory dose (LD50) of auranofin on LER was calculated to be 3-4 microM (0.6-0.8 microg Au/ml). Blood gold levels in auranofin-treated RA patients were found to be within the range required for in vitro inhibition of LER, and correlated with decreases in IgG, RF titers, and IgG-RF immune-complex formation in vitro. These results suggest that the therapeutic action of auranofin may be caused, at least in part, by inhibition of LER and/or decreases in immune-complex formation.

Inhibition of antigen- and mitogen-induced human lymphocyte proliferation by gold compounds

Gold sodium thiomalate (GST) inhibited in vitro antigen- and mitogen-triggered human lymphocyte DNA synthesis. Inhibition of responsiveness was observed with concentrations of GST equivalent to gold levels found in serum or tissues of patients receiving chrysotherapy, Inhibition was dependent upon the gold ion itself since GST and gold chloride were both inhibitory whereas thiomalic acid was not. Inhibition could not be explained by nonspecific killing of cells or by an alteration in the kinetics of the responses. GST inhibited mitogen-induced proliferation most effectively when present from the initiation of culture and could not inhibit the responsiveness of cells which previously had been activated by concanvalin A. These findings indicated that GST blocked a critical early step in lymphocyte activation. The degree of GST-induced inhibition of proliferation was increased in cultures of cells partially depleted of monocytes. Moreover, inhibition was reversed by supplementation of these cultures with purified monocytes. These observations suggested that GST blocked thymus-derived (T)-lymphocyte activation by interfering with a requisite function of the monocyte population in initiating such responses. Prolonged incubation of peripheral blood mononuclear cells with GST resulted in diminished mitogen responsiveness upon subsequent culture in the absence of gold. The addition of fresh monocytes restored responsiveness to these populations. Furthermore, preincubation of purified monocytes with GST rendered them deficient in their ability to support mitogen-induced T-lymphocyte proliferation on subsequent culture. These observations indicate that the major effect of GST results from interference with the functional capability of the monocyte population.

Auranofin. New oral gold compound for treatment of rheumatoid arthritis

Eight patients with rheumatoid arthritis were treated with SK & F D-39162 (auranofin), a new oral gold compound which was effective in suppressing adjuvant-induced arthritis in rats. Clinical and humoral parameters were studied during a 3-month period of drug administration followed by a 3-month period under placebo. The drug was absorbed, well tolerated, and its action was manifested by a drop in the mean IgG blood levels in the third week of treatment accompanied by clinical improvement after 5 weeks of oral gold intake. Together with IgG changes, an increase of the albumin ratio was observed, as well as a decrease of alpha2-globulin and rheumatoid factor titres. From a total number of 60 swollen joints found initially in the 8 patients only 17 were swollen at week 12 and 9 at week 15. Although the number of patients treated was too small to allow definite conclusions, a follow-up study under placebo of clinical and laboratory changes in the same patients during another 3-month period showed that IgG serum levels rapidly reverted preceding a flare up of disease activity after withdrawal of the drug. This confirmed a direct role in cause-effect relation played by the new oral gold compound.

Effects of gold salts and prednisolone on inflammatory cells. II. Suppression of inflammation and phagocytosis in the rat

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Effects of gold salts and prednisolone on inflammatory cells. I. Phagocytic activity of macrophages and polymorphs in inflammatory exudates studied by a "skin-window" technique in rheumatoid and control patients

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