D-penicillamine

Molecular Basis for the Interaction of Catalase with d-Penicillamine: Rationalization of Some of Its Deleterious Effects

d-Penicillamine (d-Pen) is a sulfur compound used in the management of rheumatoid arthritis, Wilson's disease (WD), and alcohol dependence. Many side effects are associated with its use, particularly after long-term treatment. However, the molecular basis for such side effects is poorly understood. Based on the well-known oxidase activity of hemoproteins and the participation of catalase in cellular H₂O₂ redox signaling, we posit that d-Pen could inactivate catalase, thus disturbing H₂O₂ levels. Herein, we report on the molecular basis that could partly explain the side effects associated with this drug compound, and we demonstrate that it induces the formation of compound II, a temporarily inactive state of the enzyme, through two distinct mechanisms. Initially, d-Pen reacts with native catalase and/or iron metal ions, used to mimic non-heme iron overload observed in long-term treated WD patients, to generate thiyl radicals. These radicals partake in a futile redox cycle, thus producing superoxide radical anions O₂^•- and hydrogen peroxide H₂O₂. Then, either H₂O₂ unexpectedly reacts with reduced CAT-Fe(II) to produce compound II or both aforementioned reactive oxygen species intervene in compound II generation through compound I formation and then reduction. These findings support the evidence that d-Pen could perturb H₂O₂ redox homeostasis through transient but recurring catalase inactivation, which may in part rationalize some deleterious effects observed with this therapeutic agent, as discussed.

Application of 9.4T MRI in Wilson Disease Model TX Mice With Quantitative Susceptibility Mapping to Assess Copper Distribution

In the current study, we used 9.4-tesla magnetic resonance imaging (9.4T MRI) and inductively coupled plasma mass spectrometry (ICP-MS) to investigate the distribution of copper in the brain samples of a murine model of Wilson's disease (WD) following penicillamine (PCA) treatment. We also evaluated if the distribution of copper in the brain samples of mice was correlated with behavioral symptoms. Results from the behavioral experiments showed that 7 days of PCA treatment decreased the total distance traveled in the open field and the number of rearing and climbing instances among the toxic milk (TX) mice as compared with model group. We also observed that the open arm ratio in the elevated plus-maze (EPM) was reduced, escape latency in the Barnes maze test was increased, and avoidance in the open field was enhanced in TX mice following 14 days of PCA treatment as compared with those in untreated TX mice. We found that PCA treatment for 21-28 days improved the cognitive abilities, exploratory behavior, and movement behavior of TX mice. The PCA-treated mice also exhibited varying degrees of magnetic susceptibilities in the cortex, corpus striatum, hippocampus, and amygdaloid nucleus across the treatment period. Low copper concentrations were found in all of the analyzed brain regions of PCA-treated mice after 21-28 days as compared with the model group (P < 0.05). However, copper concentrations were increased in the primary motor cortex and cerebellum at 7 days post-PCA treatment as compared with those in the model group (P < 0.05). After 14 days of PCA treatment, the copper concentrations in the sensorimotor cortex, corpus striatum, hippocampus, and amygdaloid nucleus were higher than those detected without treatment. The results from a Pearson's correlation analysis revealed that there was a significant (P < 0.05) correlation between copper concentrations and magnetic susceptibility in all of the brain regions that were analyzed. Therefore, our results indicate that copper concentration and magnetic susceptibility are associated with alterations in mood-related behavior, recognition memory, and movement behaviors in TX mice that are treated with PCA. The redistribution of copper in the TX mouse brain during PCA treatment may aggravate changes in behavioral performance.

An unexpected antioxidant and redox activity for the classic copper-chelating drug penicillamine

Penicillamine has been widely-used clinically as a copper-chelating drug for the treatment of copper-overload in Wilson's disease. In this study, we found that penicillamine provided marked protection against cytotoxicity induced by tetrachlorohydroquinone (TCHQ), a major toxic metabolite of the well-known wood preservative pentachlorophenol, while other classic copper-chelating agents do not. We found, unexpectedly, that both TCHQ autooxidation and tetrachlorosemiquinone radical (TCSQ^•-) formation were remarkably delayed by penicillamine. Further investigation showed that TCSQ^•- was reduced back to TCHQ by penicillamine, with the concurrent formation of its corresponding disulfide. These data demonstrated that the protection by penicillamine against TCHQ-induced toxicity was not due to its classic Cu-chelating property, but rather to its reduction of the reactive TCSQ^•- to the much less-reactive TCHQ. This is the first report of an unexpected antioxidant and redox activity for penicillamine, which might prove highly relevant to its biological activities.

Cystic kidney disease in a patient with systemic toxicity from long-term D-penicillamine use

D-penicillamine, used to treat cystinuria, is known to cause impaired collagen deposition and dysfunction in elastic fibers. D-penicillamine also has been associated with glomerular abnormalities, typically membranous glomerulonephritis. We describe a patient with severe bilateral cystic kidney disease that developed after long-term D-penicillamine use for treatment of cystinuria. The cysts in the kidneys were noted during an evaluation for acute kidney injury. The patient had no evidence of cysts on prior renal imaging at a time when his kidney function was normal. Simultaneously, he presented with multiorgan manifestations of D-penicillamine toxicity, including the skin findings of cutix laxa and elastosis perforans serpiginosa. Consequently, D-penicillamine treatment was discontinued, after which the progression of cystic kidney disease gradually ceased, along with the other systemic manifestations of toxicity. To our knowledge, this is the first report of cystic kidney disease associated with and perhaps caused by long-term d-penicillamine therapy. The proposed mechanism of cyst formation is the malfunction of the extracellular matrix of the kidney by d-penicillamine that leads to an impaired repair process after kidney injury.

Therapeutic potential of copper chelation with triethylenetetramine in managing diabetes mellitus and Alzheimer's disease

This article reviews recent evidence, much of which has been generated by my group's research programme, which has identified for the first time a previously unknown copper-overload state that is central to the pathogenesis of diabetic organ damage. This state causes tissue damage in the blood vessels, heart, kidneys, retina and nerves through copper-mediated oxidative stress. This author now considers this copper-overload state to provide an important new target for therapeutic intervention, the objective of which is to prevent or reverse the diabetic complications. Triethylenetetramine (TETA) has recently been identified as the first in a new class of anti-diabetic molecules through the original work reviewed here, thus providing a new use for this molecule, which was previously approved by the US FDA in 1985 as a second-line treatment for Wilson's disease. TETA acts as a highly selective divalent copper (Cu(II)) chelator that prevents or reverses diabetic copper overload, thereby suppressing oxidative stress. TETA treatment of diabetic animals and patients has identified and quantified the interlinked defects in copper metabolism that characterize this systemic copper overload state. Copper overload in diabetes mellitus differs from that in Wilson's disease through differences in their respective causative molecular mechanisms, and resulting differences in tissue localization and behaviour of the excess copper. Elevated pathogenetic tissue binding of copper occurs in diabetes. It may well be mediated by advanced-glycation endproduct (AGE) modification of susceptible amino-acid residues in long-lived fibrous proteins, for example, connective tissue collagens in locations such as blood vessel walls. These AGE modifications can act as localized, fixed endogenous chelators that increase the chelatable-copper content of organs such as the heart and kidneys by binding excessive amounts of catalytically active Cu(II) in specific vascular beds, thereby focusing the related copper-mediated oxidative stress in susceptible tissues. In this review, summarized evidence from our clinical studies in healthy volunteers and diabetic patients with left-ventricular hypertrophy, and from nonclinical models of diabetic cardiac, arterial, renal and neural disease is used to construct descriptions of the mechanisms by which TETA treatment prevents injury and regenerates damaged organs. Our recent phase II proof-of-principle studies in patients with type 2 diabetes and in nonclinical models of diabetes have helped to define the pathogenetic defects in copper regulation, and have shown that they are reversible by TETA. The drug tightly binds and extracts excess systemic Cu(II) into the urine whilst neutralizing its catalytic activity, but does not cause systemic copper deficiency, even after prolonged use. Its physicochemical properties, which are pivotal for its safety and efficacy, clearly differentiate it from all other clinically available transition metal chelators, including D-penicillamine, ammonium tetrathiomolybdate and clioquinol. The studies reviewed here show that TETA treatment is generally effective in preventing or reversing diabetic organ damage, and support its ongoing development as a new medicine for diabetes. Trientine (TETA dihydrochloride) has been used since the mid-1980s as a second-line treatment for Wilson's disease, and our recent clinical studies have reinforced the impression that it is likely to be safe for long-term use in patients with diabetes and related metabolic disorders. There is substantive evidence to support the view that diabetes shares many pathogenetic mechanisms with Alzheimer's disease and vascular dementia. Indeed, the close epidemiological and molecular linkages between them point to Alzheimer's disease/vascular dementia as a further therapeutic target where experimental pharmacotherapy with TETA could well find further clinical application.

Copper(II)-selective chelation improves function and antioxidant defences in cardiovascular tissues of rats as a model of diabetes: comparisons between triethylenetetramine and three less copper-selective transition-metal-targeted treatments

AIMS/HYPOTHESIS

Treatment with the Cu(II)-selective chelator triethylenetetramine (TETA) improves cardiovascular disease in human patients, and cardiac and vascular/renal disease in rats used as a model of diabetes. Here we tested two hypotheses: first, that TETA elicits greater improvement in organ function than less Cu-selective transition-metal-targeted treatments; second, that the therapeutic actions of TETA are consistent with mediation through suppression of oxidative stress.

METHODS

Rats were made diabetic with streptozotocin (55 mg/kg, i. v.) and treated from 8 weeks after disease induction for the following 8 weeks with effective dosages of oral TETA, or one of three less Cu-selective transition-metal-targeted treatments: D-penicillamine, deferiprone or Zn acetate. Treatment effects were measured in ex vivo cardiac and aortic tissues, plasma and urine.

RESULTS

Diabetes damaged both cardiac and renal/vascular function by impairing the ability of cardiac output to respond physiologically to rising afterload, and by significantly elevating the urinary albumin/creatinine ratio. Diabetes also lowered total antioxidant potential and heparan sulphate levels in cardiac and arterial tissues, and serum ferroxidase activity, whereas it elevated urinary heparan sulphate excretion. TETA treatment rectified or partially rectified all these defects, whereas the other three experimental treatments were ineffectual. By contrast, none of the four drug treatments lowered diabetes-mediated elevations of plasma glucose or lipid concentrations.

CONCLUSIONS/INTERPRETATION

TETA may limit the cardiac and renal/vascular damage inflicted by diabetes through its actions to reinforce antioxidant defence mechanisms, probably acting through selective chelation of 'loosely-bound'/chelatable Cu(II). It may also improve heparan sulphate homeostasis and bolster antioxidant defence by increasing vascular extracellular superoxide dismutase activity. Urinary albumin/creatinine ratio might prove useful for monitoring TETA treatment.

Enhanced intracellular delivery of the reactive oxygen species (ROS)-generating copper chelator D-penicillamine via a novel gelatin--D-penicillamine conjugate

D-Penicillamine (D-pen) is an established copper chelator. We have recently shown that the copper-catalyzed D-pen oxidation generates concentration-dependent hydrogen peroxide (H 2O 2). Additionally, D-pen coincubated with cupric sulfate resulted in cytotoxicity in human leukemia and breast cancer cells due to the extracellular generation of reactive oxygen species (ROS). The inherent physicochemical properties of D-pen such as its short in vivo half-life, low partition coefficient, and rapid metal catalyzed oxidation limit its intracellular uptake and the potential utility as an anticancer agent in vivo. Therefore, to enhance the intracellular delivery and to protect the thiol moiety of D-pen, we designed, synthesized, and evaluated a novel gelatin-D-pen conjugate. D-pen was covalently coupled to gelatin with a biologically reversible disulfide bond with the aid of a heterobifunctional cross-linker ( N-succinimidyl-3-(2-pyridyldithio)-propionate) (SPDP). Additionally, fluorescein-labeled gelatin-D-pen conjugate was synthesized for cell uptake studies. D-pen alone was shown not to enter leukemia cells. In contrast, the qualitative intracellular uptake of the conjugate in human leukemia cells (HL-60) was shown with confocal microscopy. The conjugate exhibited slow cell uptake (over the period of 48 to 72 h). A novel HPLC assay was developed to simultaneously quantify both D-pen and glutathione in a single run. The conjugate was shown to completely release D-pen in the presence of glutathione (1 mM) in approximately 3 h in PBS buffer, pH 7.4. The gelatin-D-pen conjugate resulted in significantly greater cytotoxicity compared to free D-pen, gelatin alone, and a physical mixture of gelatin and D-pen in human leukemia cells. Further studies are warranted to assess the potential of D-pen conjugate in the delivery of D-pen as a ROS generating anticancer agent.

Penicillamine determination using a tyrosinase micro-rotating biosensor

Tyrosinase [EC 1.14.18.1], immobilized on a rotating disk, catalyzed the oxidation of catechols to o-benzoquinone, whose back electrochemical reduction was detected on glassy carbon electrode surface at -150mV versus Ag/AgCl/NaCl 3M. Thus, when penicillamine (PA) was added to the solution, this thiol-containing compound participate in Michael type addition reactions with o-benzoquinone to form the corresponding thioquinone derivatives, decreasing the reduction current obtained proportionally to the increase of its concentration. This method could be used for sensitive determination of PA in drug and human synthetic serum samples. A linear range of 0.02-80 microM (r=0.999) was obtained for amperometric determination of PA in buffered pH 7.0 solutions (0.1 M phosphate buffer). The biosensor has a reasonable reproducibility (R.S.D.<4.0%) and a very stable amperometric response toward this compound (more than 1 month).

Plasma d-penicillamine redox state evaluation by capillary electrophoresis with laser-induced fluorescence

D-Penicillamine (D-Pen) is a thiol drug used in the treatment of Wilson's disease, rheumatoid arthritis, metal intoxication and cystinuria. We have recently described a new capillary electrophoresis (CE) method to measure physiological thiols, in which separation of total plasma homocysteine, cysteine, cysteinylglycine, glutathione is achieved using the organic base N-methyl-D-glucamine in the run buffer. In this paper, we present an improvement of our method that allows a baseline separation of total plasma D-Pen from the physiological thiols. Moreover, reduced, free and protein-bound forms of drug are measured by varying the order of disulfide reduction with tributylphosphine and proteins precipitation with 5-sulphosalicylic acid (SSA). After derivatization with 5-iodoacetamidofluorescein (5-IAF), samples are separated and measured by capillary electrophoresis with laser-induced fluorescence in an uncoated fused-silica capillary (57 x 75 microm i.d.) using a phosphate/borate run buffer pH 11.4. In these conditions, the migration time of D-Pen is about 7 min and the time required for each analysis is roughly 10 min. The proposed method has been utilized to measure the various forms of the drug in a D-Pen administered Wilson's disease patient.

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.

Penicillamine-induced bullous dermatoses

The successful therapeutic use of D-penicillamine (DPA) has been hindered by its many adverse effects. Autoimmune bullous syndromes are among the less common adverse DPA reactions; they are not dose dependent and appear late in the treatment of diseases of altered immunity, most often rheumatoid arthritis. The majority of the DPA-induced bullous syndromes belong to the pemphigus spectrum, usually pemphigus foliaceus or erythematosus, have a lower prevalence of demonstrable tissue-fixed or circulating antibodies than spontaneously occurring pemphigus, display abnormal direct immunofluorescent patterns, and have a generally favorable prognosis. However, many cases do exhibit a full-blown chronic disease, unaffected by DPA withdrawal. DPA-induced cicatricial pemphigoid is a severe disease of both mucous and cutaneous involvement with a prognosis similar to the spontaneous disease. Cases of DPA-induced epidermolysis bullosa acquisita and DPA-induced bullous pemphigoid were not sufficiently substantiated by immunofluorescence or immunoprecipitation criteria.