Metabolic balance studies in hepatolenticular degeneration treated with diethyldithiocarbamate

Effect of copper and diethyldithiocarbamate combination therapy on the macular mouse, an animal model of Menkes disease

Menkes disease (MD) is a neurodegenerative disorder characterized by a copper deficiency in the brain. It is caused by the defective intestinal absorption of copper resulting from a deficiency of a copper-transporting ATPase, ATP7A. This gives rise to an accumulation of copper in the intestine. The copper deficiency in the brain of MD patients cannot be improved by copper injections, because the administered copper accumulates at the blood-brain barrier and is not transported across to the neurons. To resolve this problem, we investigated the effect of a combination therapy of copper and sodium diethyldithiocarbamate (DEDTC), a lypophilic chelator, in an animal model of MD, the macular mouse. Four-week-old macular mice treated with 50 mug of CuCl2 on the 7th day after birth were used. Experimental mice were given a subcutaneous injection of CuCl2 (4 microg) and an intraperitoneal injection of DEDTC (0.2 mg/g body weight) twice a week for 4 weeks and then sacrificed. Copper concentrations and cytochrome-c oxidase activity in the brains of treated mice were higher than those of control macular mice, which received only copper or saline. The ratios of brain noradrenaline to dopamine and of adrenaline to dopamine were also increased by the treatment, suggesting that the activity of dopamine beta-hydroxylase, a copper-dependent enzyme, was improved by the treatment. Liver and renal function tests showed no abnormalities in the treated mice, although copper concentrations in the kidneys of treated mice were higher than those of control macular mice. These results suggest that DEDTC facilitates the passage of copper across the blood-brain barrier and that the combination therapy of copper and DEDTC may be an effective treatment for the neurological disturbances suffered by patients with MD.

Drug targets in Menkes disease - prospective developments

Menkes disease (MNK) is an X-linked recessive disorder characterised by a copper-transporting ATPase defect. In the affected cells, copper transport from the cytosol to the Golgi apparatus is disturbed, resulting in a reduction of copper efflux. Orally-administered copper, which accumulates in the intestine, cannot be absorbed and thus a copper deficiency arises. The characteristic features of MNK are progressive neurological degeneration, connective tissue disorders and hair abnormalities, which are caused by a reduction in the activity of several copper-dependent enzymes, due to concomitant copper deficiency. Subcutaneous injections of copper-histidine complex, which currently forms the accepted mode of treatment, prevent the neurological degeneration in some patients when the treatment is initiated soon after birth. However, when the treatment is started later, the neurological degenerative processes are not prevented. Moreover, the treatment does not improve the connective tissue disorders that are caused by the low activity of lysyl oxidase. In order to solve these problems, a form of the treatment aimed at delivering copper into the Golgi apparatus should be studied. An attempt is made in this review to present what is currently known about MNK and its variants, the efficacy and problems of currently accepted treatments and finally therapeutic targets in MNK.

Cisplatin-induced loss of kidney copper and nephrotoxicity is ameliorated by single dose diethyldithiocarbamate, but not mesna

Platinum, copper, and zinc concentrations in kidney and liver were monitored following administration of cis-diamminedichloroplatinum (Cisplatin, CDDP) alone or in combination with diethyldithiocarbamate (DDC) or mercaptoethanesulfonate (mesna). Compounds were administered in saline to F344 female rats as single bolus ip doses: 7.5 mg CDDP/kg body wt; 500 mg DDC/kg body wt 1 hr after CDDP; and 100 mg mesna/kg body wt 1 hr before CDDP, at the same time as CDDP, or 1 hr after CDDP. Tissues were collected at 4 hr, 1 day, 4 days, and 7 days post-CDDP dosing. CDDP alone produced significant increases in blood urea nitrogen (fourfold) and plasma creatinine (threefold) concentrations by Day 4. Concurrent with the toxicity, CDDP lowered kidney copper (-71%) by Day 4, but had little effect on liver copper except in copper-pretreated rats. Copper-pretreated rats initially had a twofold higher kidney copper concentration and a fourfold higher liver copper concentration, but by Day 4, CDDP lowered copper concentrations in both organs to near the noncopper-treated levels. Platinum in kidney and liver rose 72-100% of peak levels within 4 hr post-CDDP and was relatively stable throughout the 7-day test period. Kidney zinc rose significantly by day 4 only in CDDP-treated rats. DDC protected against the kidney toxicity of CDDP and markedly changed kidney copper loss. Within 4 hr, DDC reduced kidney copper 60% while increasing kidney platinum to the highest concentration of any of the treatments. By Day 4, DDC-treated rats had approximately 50% lower kidney platinum while copper returned toward control levels. A single dose of mesna did not significantly protect against CDDP nephrotoxicity and had little effect on kidney platinum, copper, or zinc. The patterns of copper loss and toxicity from CDDP alone or with DDC suggest that copper be further evaluated for its role in the mechanism of CDDP cytotoxicity.

Diethyldithiocarbamate, a novel immunomodulator, prolongs survival in autoimmune MRL-lpr/lpr mice

MRL-lpr/lpr mice die at an early age from a spontaneously developing systemic lupus erythematosus-like disease and are characterized by massive lymphadenopathy, hyperproliferation of Lyt-2/L3T4 (null) T cells, decreased responses to mitogens, thymic atrophy, and very high serum autoantibody levels. Diethyldithiocarbamate (DTC), an immunomodulator suggested to enhance T cells, was used to treat 12-week-old female MRL-lpr/lpr mice (25 mg/kg/week). DTC treatment significantly prolonged survival (50% mortality, 43 weeks vs 20 weeks). Increased survival was associated with decreased lymphadenopathy, decreased proliferation of null cells, restoration of impaired mitogen responses, decreased thymic atrophy, and decreased serum levels of anti-DNA and anti-histone antibodies. Studies of cell surface antigen phenotype demonstrated increased expression of Lyt-2 and macrophage surface antigens. No effect on L3T4 single staining cells was observed. These results show that DTC significantly alters the disease course in these mice and suggest that DTC may be a useful treatment for autoimmune disease.

[Hepatolenticular degeneration. Apropos of 102 cases]

The author reports the clinical and laboratory findings in 102 patients of hepatolenticular degeneration (HLD) followed up in the Department of Neurology, University of São Paulo Medical School, since 1946. The problem of the early diagnosis of the relatives is analysed, the pathology of Wilson's disease is reviewed, and the relationship of HLD with other hepatocerebral diseases is examined. Etiopathogenesis is discussed according to current researches, the role of the decreased biliary copper excretion being emphasized. The results of treatment with D-penicillamine in 84 cases are commented.

Diethyldithiocarbamate inhibits scheduled and unscheduled DNA synthesis of rat thymocytes in vitro and in vivo--dose-effect relationships and mechanisms of action

In vitro as well as in animal models, diethyldithiocarbamate (DDC) modifies the tumoricidal activity of some antineoplastic agents. To gain further information about the mechanism of action of DDC, we measured (i) in vitro and (ii) in vivo changes in DNA synthesis of rat thymocytes. (i) In vitro, the scheduled (SDS) and unscheduled (UDS) incorporation of [3H]thymidine ([3H]dT) into DNA of rat thymic cells were biphasically inhibited in a dose range of 1-1000 micrograms DDC/ml. The UV-induced UDS was totally suppressed by 10 and 100 micrograms DDC/ml. (ii) In vivo, 1-4 h following intraperitoneal administration of 250-1000 mg DDC per kg body wt., SDS and UDS were inhibited up to about 80% in a dose-dependent manner. Nucleoid sedimentation, uptake of [3H]dT into the cells, and the pattern of phosphorylation of the intracellular [3H]dT following DDC treatment did not reveal any differences to the controls. A possible effect of DDC treatment on the ribonucleotide reductase and the DNA polymerase alpha is suggested.

In vivo radioprotective activities of diethyldithiocarbamate (DDC)

Studies were performed to determine whether diethyldithiocarbamate (DDC) protects against radiation damage to bone marrow, jejunal crypts, testicular tubules, hair follicles, tissues in the leg responsible for leg contractures, and a fibrosarcoma (FSA) of C3Hf/Kam mice. In most experiments, DDC at a dose of 400 mg/kg or 1000 mg/kg body weight was given i.p. 30 minutes before single doses of gamma radiation. DDC (1000 mg/kg) given 30 minutes before whole-body irradiation protected hematopoietic stem cells by a factor (PF) of 1.59, as assessed by the LD50/30 assay, and by PFs of 1.32-1.55, as assessed by the endogenous spleen colony assay. A dose of 400 mg/kg DDC was less effective. Protection was also significant against hair loss and leg contractures; PFs produced by 1000 mg/kg DDC were 1.44 and 1.38-1.51, respectively. Jejunum was protected by 400 mg/kg DDC (PF = 1.2), but not by 1000 mg/kg. The opposite was observed with testis: 1000 mg/kg was protective (PF = 1.2), but not 400 mg/kg. DDC also protected the FSa tumor, either as lung micrometastases or as a solitary tumor in the leg. Both 400 mg/kg and 1000 mg/kg DDC protected 4 day-old micrometastases by a PF of approximately 1.1. DDC at a dose of 1000 mg/kg protected 8 mm leg tumors by a PF of 1.24 at the TCD50 level. Therefore, DDC protected both normal tissues and FSA, but the degree of protection varied greatly. A therapeutic gain was achieved in some instances.

Combined effect of diethyldithiocarbamate (DDC) and modest hyperthermia on Chinese hamster (V79) cell survival and DNA strand break repair following photon irradiation

Previous studies from our institution have shown that 10(-4) M DDC enhances the effects of radiation and of hyperthermia treatment at 43 degrees C on the killing of Chinese hamster (DON) cells. We herein report studies on the combined effect seen at more modest temperatures (41 degrees C) which can be achieved in humans by whole body heating without the need for general anesthesia. Treatment of V79 cells with DDC for 60 minutes at 37 degrees C or 41 degrees C had minimal toxicity at concentrations up to 5 X 10(-5) M. When cells were irradiated with single doses up to 1000 rad (137Cs, 350 rad/min), pre-incubation with 10(-4) M DDC had no effect on cell survival at 37 degrees C, but markedly decreased survival at 41 degrees C (D37 = 475 rad without DDC, 270 rad with DDC). The mechanism of this increased cell killing is not known. We observed, however, that there is no repair of DNA single strand breaks in DNA from irradiated V79 cells previously held at 41 degrees C in the presence of 10(-4) M DDC. Without DDC, repair of SSB was similar at 37 degrees C and 41 degrees C.

An in vivo study of the radioprotective effect of diethyldithiocarbamate (DDC)

We have recently shown that diethyldithiocarbamate (DDC) protects plateau-phase cultures of mammalian cells from radiation. Experiments in vivo have extended our knowledge of the radioprotective properties of DDC and show that the LD50/30 in mice is increased from 780 rad to approximately 1400 rad when non-toxic concentrations of DDC are present prior to the irradiation. When DDC is present during irradiation, the pattern of death of the mice is similar to that seen in the absence of the drug and is quite different from that seen in animals dying of a gastrointestinal syndrome (LD50/7 congruent to 1700 rad). To confirm that the LD50/30 data represent bone marrow protection by DDC, we performed bone marrow CFUS assays with and without the presence of DDC, at the time of in vivo irradiation. The DO of the CFUS is increased from 80 rad in the control animals to 120 rad in the animals that have been pretreated with DDC. In experiments using 35S-labelled DDC, the tissue distribution of the drug in tumor-bearing mice indicates a preferential uptake of DDC in kidney, lung and bone marrow compared to tumor tissue. Based on data from both in vitro and in vivo studies, we believe that DDC shows promise as a radioprotective agent and should be considered for clinical trials.

Copper chelator enhancement of bleomycin cytotoxicity

Bleomycin's effects on DNA strand scission are inhibited by low concentration of some metal ions (including copper), greatly stimulated by ferrous (Fe+2) ions, and increased and probably mediated by the production of superoxide radicals (O2-), hydroxyl radicals (OH), and hydrogen peroxide (H2O2). However, the role of these mechanisms in overall bleomycin cytotoxicity is not known. For this reason, we have treated the Chinese hamster cell line (V79) cells with a copper chelator, diethyldithiocarbamate (DDC) and bleomycin in vitro DDC is known to inhibit superoxide dismutase (SOD), an enzyme responsible for the scavenging of O2-. The cytotoxicity is determined by the standard clonogenic survival method, which shows that DDC treated cells are more susceptible to bleomycin either as a function of bleomycin dose or as a function of bleomycin treatment time. These results support the notion that reducing Cu2+ levels and/or increasing O2- concentrations can modify the cytotoxicity of bleomycin.

Defective biliary excretion of copper in Wilson's disease

The biliary excretion of copper was measured in eight patients with Wilson's disease (three untreated, with hepatic dysfunction) and 10 control subjects (three with hepatic dysfunction). The duodenum was perfused with an amino-acid solution containing a non-absorbed marker, (51)CrCl(3), and juice was aspirated from the duodeno-jejunal junction. The mean concentration of copper in the duodenal aspirate in Wilson's disease was significantly lower than in the control group. The mean biliary copper excretion rate in Wilson's disease of 8.6 +/- 0.8 mug/20 min (SEM) was also significantly below that of the control group (16.4 +/- 0.8 mug/20 min). The presence of liver dysfunction made no significant difference to the excretion rates in either group of patients. These results suggest that the copper accumulation in Wilson's disease is due to the inability of the liver to excrete copper into bile in adequate amounts.