Complex formation equilibria of Cu(II) and Zn(II) with triethylenetetramine and its mono- and di-acetyl metabolites.

Triethylenetetramine (TETA) dihydrochloride, or trientine, is a therapeutic molecule that has long been used as a copper-chelating agent for the second-line treatment of patients with Wilson's disease. More recently, it has also been employed as an experimental therapeutic molecule in diabetes where it improves cardiac structure in patients with diabetic cardiomyopathy and left-ventricular hypertrophy. TETA is metabolized by acetylation, which leads to the formation of two main metabolites in humans and other mammals, monoacetyl-TETA (MAT) and diacetyl-TETA (DAT). These metabolites have been identified in the plasma and urine of healthy and diabetic subjects treated with TETA, and could themselves play a role in TETA-mediated copper chelation and restoration of physiological copper regulation in diabetes. In this regard, a potentiometric and spectrophotometric study of Cu(II)-complex formation equilibria of TETA, MAT and DAT is presented here, to provide a comprehensive evaluation of the stoichiometries of the complexes formed and of their relative stability constants. A potentiometric study has also been conducted on the corresponding Zn(II) complexes, to evaluate any possible interference with TETA-mediated Cu(II) binding by this second physiological transition-metal ion, which is present in similar concentrations in human plasma and which also binds to TETA. An ESI-MS study of these systems has both confirmed the complex formation mechanisms established from the potentiometric and spectrophotometric results, and in addition provided direct information on the stoichiometry of the complexes formed in solution. These data when taken together show that the 1 : 1 complexes formed with Cu(II) and Zn(II) have different degrees of protonation. The stability of the Cu(II) and Zn(II) complexes with the three ligands, evaluated by the parameters pCu and pZn, decreases with the introduction of the acetyl groups. Nevertheless the stability of Cu(II) complexes with MAT is sufficiently high to enable its participation in copper scavenging from the patient. A speciation study of the behavior of TETA and MAT with Cu(II) in the presence of Zn(II) at peri-physiological plasma concentrations is also presented. While Zn(II) did not hinder copper binding, the possibility is raised that prolonged TETA treatment could possibly alter the homeostatic regulation of this essential metal ion. The lack of reliable literature stability constants concerning the Cu(II) and Zn(II) interaction with the major transport proteins in plasma is also briefly considered.

Determination of triethylenetetramine (TETA) and its metabolites in human plasma and urine by liquid chromatography-mass spectrometry (LC-MS).

A liquid chromatography-mass spectrometry (LC-MS) method has been developed to measure triethylenetetramine (TETA) and its metabolites in human samples. We identified two metabolites of TETA, N1-acetyltriethylenetetramine (MAT) and N1,N10-diacetyltriethylenetetramine (DAT), the latter being novel. We further developed this LC-MS method for the measurement of TETA and these metabolites in human plasma and urine in a single injection. Separation of analytes was achieved on a cyano column using 15% acetonitrile, 85% water (18 M Omega), and 0.1% heptafluorobutyric acid as the mobile phase. Simultaneous MS detection was performed at [M+H]+ values of 147, 189, 231 and 245, corresponding to TETA, MAT, DAT, and N1-acetylspermine as the internal standard, respectively. This method was successfully applied to measure TETA, MAT and DAT in plasma and urine of humans receiving oral drug treatment.

Triethylenetetramine and metabolites: levels in relation to copper and zinc excretion in urine of healthy volunteers and type 2 diabetic patients.

Triethylenetetramine (TETA), a selective Cu(II)-chelator used in the treatment of Wilson's disease, is now undergoing clinical trials for the treatment of heart failure in diabetes. Despite decades of clinical use, knowledge of its pharmacology in human subjects remains incomplete. Here, we first used liquid chromatography-mass spectrometry (LC-MS) to detect and identify major metabolites of TETA in human plasma and urine, and then used this method to measure concentrations of TETA and its metabolites in the urine of healthy and diabetic subjects who were administered increasing doses (300, 600, 1200, and 2400 mg) of TETA orally. Twenty-four-hour urine collections were performed before and after dosing participants. Two major metabolites of TETA were detected in human urine, N(1)-acetyltriethylenetetramine (MAT) and N(1),N(10)-diacetyltriethylenetetramine, the latter being novel. Both metabolites were verified with synthetic standards by LC-MS. The proportion of unchanged TETA excreted as a fraction of total urinary drug-derived molecules was significantly higher in healthy than in matched diabetic subjects, consistent with a higher rate of TETA metabolism in the latter. TETA-evoked increases in urinary Cu excretion in nondiabetic subjects were more closely correlated with parent drug concentrations than in diabetic subjects, whereas, by contrast, urinary Cu was more closely associated with the sum of TETA and MAT. These findings are consistent with the hypothesis that MAT could play a significant role in the molecular mechanism by which TETA extracts Cu(II) from the systemic compartment in diabetic subjects.

Effects of interactions between drugs on the renal excretion of trientine in rats--acetazolamide and furosemide increase trientine excretion.

PURPOSE: To elucidate the effects of drug interactions on the urinary excretion of trientine in rats. METHOD: Trientine and various other drugs were intravenously administered to rats and the urinary excretion of trientine was investigated. To clarify the mechanisms of drug-drug interactions, we also investigated the effects of various drugs on spermine uptake by rat renal brushborder membrane vesicles. RESULTS: Cimetidine, a substrate of the H+/organic cation antiporter, and aminoglycoside antibiotics did not affect trientine excretion, while acetazolamide and furosemide, which increase the concentration of sodium ions in renal proximal tubules, increased the excretion of trientine. However, trichlormethiazide, which acts in renal distal tubules, did not affect trientine excretion. Acetazolamide and furosemide did not directly affect the Na+/spermine transporter because these diuretics had no effect on the uptake of spermine into the rat renal brush-border membrane vesicles. CONCLUSIONS: There is no interaction between trientine and the substrate of the H+/organic cation antiporter or aminoglycoside antibiotics. However, drugs that change the concentration of sodium ions in renal proximal tubules, such as diuretics, can increase the trientine excretion since the increase in the luminal concentration of sodium ion accelerates the Na+/spermine antiporter.

The mechanism of excretion of trientine from the rat kidney: trientine is not recognized by the H+/organic cation transporter.

Trientine dihydrochloride is used to treat Wilson's disease by chelating copper and increasing its urinary excretion. The mechanism of renal excretion of trientine has been investigated in-vivo and in-vitro. Trientine clearance in the rat-was significantly faster than creatinine clearance. When trientine and the same number of moles of copper ions were administered simultaneously to the rat, however, trientine clearance decreased to almost the same level as the creatinine clearance. To clarify this active excretion system for trientine, the uptake of trientine and a physiological polyamine compound, spermine, was investigated using rat renal brush-border membrane vesicles. Although, because trientine and spermine are organic cations, the H+/organic cation transporter is expected to recognize these compounds, neither an outwardly directed H+ gradient nor an inward Na+ gradient stimulated trientine uptake. [14C]Spermine uptake was, nevertheless, trans-stimulated by both unlabelled spermine and trientine and the trans-stimulating effect of spermine on trientine uptake was, furthermore, completely abolished by addition of copper ions to the incubation medium. These results suggest that there is a specific transport system for spermine and trientine on the renal brushborder membrane. This transport system contributes to the secretion of trientine in the kidney proximal tubule but does not recognize the trientine-copper complex.

Metabolism of administered triethylene tetramine dihydrochloride in humans.

Triethylene tetramine dihydrochloride (trien 2HCl) has been used for the treatment of Wilson's disease, which is characterized by the accumulation of copper in various organs. We previously developed an HPLC system for analyzing trien, and found a trien metabolite in the urine when trien was orally given to humans. In this study, the metabolite was identified as 1-N-acetyltriethylene tetramine (acetyltrien) by FAB-MS and 1H-NMR spectroscopy. Trien and acetyltrien were capable of combining with copper, iron and zinc. However, the chelating activity of acetyltrien was significantly lower than that of trien. When trien was given to healthy adults, the amount of trien excreted in the urine was about 1% of the administered trien, whereas that of acetyltrien was about 8%. Most of the trien was excreted within the first 6 hours after the administration, while acetyltrien was excreted for over 26 hours. The urinary copper, iron and zinc levels all increased in parallel with the trien excretion.

[A study of trientine therapy in Wilson's disease with neurological symptoms].

D-penicillamine, an orally-administered chelating agent, is effective for Wilson's disease (WD). However 25% of WD patients showed serious adverse reactions to D-penicillamine cause this drug to be discontinued after months or years of treatment. For these cases, trientine-2HCl and trientine-4HCl, less toxic agents, are investigated. Three patients with WD, associated with neurological symptoms, were given either trientine-2HCl or trientine-4HCl. These patients had been on therapy with D-penicillamine. Severe adverse reactions had developed during the course of therapy, and D-penicillamine was discontinued, pancytopenia in case 1, nephrotic syndrome in case 2, and myasthenia gravis in case 3. Trientine-2HCl for case 1, and trientine-4HCl for cases 2 and 3 were instituted and continued. The neurological findings in all patients were extremely improved without side effects by trientine therapy. Though the chelating action on copper is weaker than that of D-penicillamine, it is efficient in improvement of the clinical neurological symptoms.

Fate of orally administered triethylenetetramine dihydrochloride: a therapeutic drug for Wilson's disease.

Triethylenetetramine dihydrochloride (TETA) is a therapeutic drug for Wilson's disease. We developed a simple fluorometric method for detection of TETA in biological fluids by using high-performance liquid chromatography (HPLC), and examined TETA concentrations in the serum and urine of two healthy adults who were given TETA orally. No TETA peak was detected in the serum. The amount of TETA in the urine of the two adults was only 1.6 and 1.7% of the dose administered. However, a large unidentified peak appeared in the urine after oral administration. This peak was not observed in a mixture of TETA and control urine or in urine before TETA administration. When the urine after TETA administration was analyzed after hydrolysis with HCl, the unidentified peak disappeared, while the TETA peak increased. These findings indicate that the substance which yielded the unidentified peak is a metabolite of TETA, suggesting that most of the TETA administered is metabolized and then excreted in the urine.

Comparison of disposition behavior and de-coppering effect of triethylenetetramine in animal model for Wilson's disease (Long-Evans Cinnamon rat) with normal Wistar rat.

The disposition behaviors and de-coppering effect of triethylenetetramine dihydrochloride (trientine), a selective chelating agent for copper and an 'orphan drug' for Wilson's disease, have been evaluated in an animal model, Long-Evans Cinnamon (LEC) rats, and normal rats (Wistar). In LEC rats, urinary excretion of trientine was remarkably lower than that of Wistar rats. The absorption rates from the jejunal loop and in vitro metabolism in the liver S9 fraction (supernatant of 9000 x g) were approximately the same for both strains. The decline of urinary excretion of trientine in LEC rats is thought to be due mainly to the lowering of the functional activity of the kidney, because urinary excretion of creatinine and phenolsulfonphthalein were significantly lower in LEC rats than those in Wistar rats. Both acceleration of urinary excretion of copper and reduction of hepatic copper levels were observed with treatment of trientine in LEC rats aged 6 weeks. In LEC rats aged 13 weeks, however, no de-coppering effect from the liver was observed, though urinary excretion of copper was increased. These results suggest that trientine has a pharmacological effect in disease state, especially in the early stages of hepatitis.

[Intestinal absorption and urinary excretion of triethylenetetramine for Wilson's disease in rat].

Triethylenetetramine.2.HCl (trientine, TE) is an orphan drug for the treatment of Wilson's disease. There has been no reports regarding the absorption, distribution, metabolism, and excretion in the body. In the current study, the absorption and excretion of TE in rats were examined. The observed mean percentage amount of TE absorbed at the jejunum and ileum with the loop method for 1 h was 42.0% and 22.5%, respectively. Tight junction blocking agent inhibited the absorption of TE from the jejunum loop with 27%, but the absorption of TE from the ileum loop was not affected by this blocking agent. Therefore, the main absorption route for TE might be permeation across the plasma membrane of intestinal epithelial cells. TE and amikacin, a polycationic compound like TE, bound to the brush border membrane (BBM) of rat small intestine in the absence of inorganic ions such as Na+, K+, Ca2+, Mg2+ and Cu2+. But the binding of TE to BBM was inhibited markedly under the physiological concentration of these ions. The bioavailability of TE was below 10% and the plasma levels of TE in non-fasted rats were significantly lower than that observed in fasted rats. The urinary excretion of unchanged TE during 24 h was only 3.5% of the orally administered dose. However, the urinary excretion of total TE including metabolites, though they have not been identified, was 35.7%. These results suggest that low bioavailability of TE might be due to the rapid metabolism in the body after absorption from the gastrointestinal tract.