Intranasal administration of sodium dimethyldithiocarbamate induces motor deficits and dopaminergic dysfunction in mice.

The primary etiology of Parkinson's disease (PD) remains unclear, but likely reflects a combination of genetic and environmental factors. Exposure to some pesticides, including ziram (zinc dimethyldithiocarbamate), is a relevant risk factor for PD. Like some other environmental neurotoxicants, we hypothesized that ziram can enter the central nervous system from the nasal mucosa via the olfactory nerves. To address this issue, we evaluated the effects of 1, 2 or 4 days of intranasal (i.n., 1 mg/nostril/day) infusions of sodium dimethyldithiocarbamate (NaDMDC), a dimethyldithiocarbamate more soluble than ziram, on locomotor activity in the open field, neurological severity score and rotarod performance. We also addressed the effects of four daily i.n. NaDMDC infusions on olfactory bulb (OB) and striatal measures of cell death, reactive oxygen species (ROS), tyrosine hydroxylase, and the levels of dopamine, noradrenaline, serotonin, and their metabolites. A single i.n. administration of NaDMDC did not significantly alter the behavioral measures. Two consecutive days of i.n. NaDMDC administrations led to a transient neurological deficit that spontaneously resolved within a week. However, the i.n. infusions of NaDMDC for 4 consecutive days induced motor and neurological deficits for up to 7 days after the last NaDMDC administration and increased striatal TH immunocontent and dopamine degradation within a day of the last infusion. Pharmacological treatment with the anti-parkinsonian drugs l-DOPA and apomorphine improved the NaDMDC-induced locomotor deficits. NaDMDC increased serotonin levels and noradrenaline metabolism in the OB 24 h after the last NaDMDC infusion, ROS levels in the OB 2 h after the last infusion, and striatum 2 and 24 h after the last infusion. These results demonstrate, for the first time, that i.n. NaDMDC administration induces neurobehavioral and neurochemical impairments in mice. This accords with evidence that dimethyldithio-carbamate exposure increases the risk of PD and highlights the possibility that olfactory system could be a major route for NaDMDC entry to central nervous system.

The influence of co-exposure to dimethyldithiocarbamate on butadiene metabolism.

Treatment of rats and mice with a single oral dose of dimethyldithiocarbamate (DMDTC; 250 mg/kg) had a marked effect on hepatic CYP2E1 and aldehyde dehydrogenase activities, measured in vitro, for up to 24 h after dosing. The same treatment did not affect CYP2A6, glutathione S-transferase, epoxide hydrolase, alcohol dehydrogenase activities or hepatic glutathione levels. As a consequence of the loss of CYP2E1 activity, butadiene metabolism in liver fractions from DMDTC treated rats and mice was markedly reduced, as was the metabolism of the mono-epoxide to the di-epoxide in mouse liver. The conversion of the mono-epoxide to the diol by epoxide hydrolases was not affected by DMDTC treatment. Urinary excretion of radioactivity, following dosing with DMDTC and exposure to 200 ppm C-14 butadiene for 6 h, was markedly reduced in rats, but increased in mice. The profiles of urinary metabolites were qualitatively similar from mice exposed to butadiene to those exposed after dosing with DMDTC. In the rat, pre-dosing with DMDTC resulted in the formation of three additional urinary metabolites following exposure to butadiene. Overall, DMDTC appears to impact qualitatively and quantitatively on the metabolism of butadiene. The nature and full significance of these changes has yet to be characterised.

Blockade of ovulation in the rat by systemic and ovarian intrabursal administration of the fungicide sodium dimethyldithiocarbamate.

Dithiocarbamates, acting as inhibitors of catecholamine synthesis, have been reported to block ovulation in female rats following systemic administration by suppressing the neural noradrenergic signaling involved in triggering the ovulatory surge of luteinizing hormone. The ovaries also synthesize norepinephrine and receive noradrenergic input via sympathetic innervation, and it has been suggested that such input may play a role in follicular maturation and ovulation. The current experiments investigated whether the dithiocarbamate fungicide dimethyldithiocarbamate (DMDTC) would block oocyte release in normally cycling rats when administered systemically during the proestrous presurge period, and if so, would the compound also have a comparable direct ovarian effect on ovulation in response to a local intrabursal exposure of one ovary late on the day of vaginal proestrus. The results showed that a dose-related suppression of oocyte release was present in response to both intraperitoneal and intrabursal (IB) injections. But these effects appear to be mediated through different mechanisms. The unilateral IB injections were effective only on the exposed side for each ovarian pair, while no alterations were seen in ovarian norepinephrine. IB administration 24 h earlier blocked ovulation on both sides, while hCG injections were able to restore ovulation on the noninjected side only, implying that diestrous DMDTC was inhibiting the LH surge. The data indicate that while an effect on hypothalamic catecholamine synthesis may underlie the ovulatory blockade following intraperitoneal DMDTC administration, it does not appear to be involved in the response to local ovarian exposure. Moreover, the blockade in response to the diestrous IB exposure likely involves two separate mechanisms, one attributable to an alteration in ovarian hormonal feedback to the brain (or pituitary), inhibiting the LH surge, and the other associated with a direct, as yet undetermined, effect on local preovulatory events within the ovary.

Enhancement of cytotoxicity of bleomycin by dithiocarbamates: formation of bis(dithiocarbamato) cu(II).

Properties of the reactions of dithiocarbamates and their Cu(II) or Fe(III) complexes with Ehrlich cells were determined and related to their effects on the inhibition of cell proliferation caused by bleomycin and Cu bleomycin. In complete culture medium containing Eagle's minimal essential medium plus Earles salts and 2.5% fetal calf serum, dimethyl- and diethyldithiocarbamates and their copper complexes inhibit cell proliferation and cause cell death. The copper complexes are more effective agents. Ferric tris-diethyldithiocarbamate is also a cytotoxic species. In contrast, when cells are exposed to dimethyldithiocarbamate or its copper complex in Ringer's buffer under metal-restricted condition, washed, and then placed in complete medium, the copper complex is much more active in inhibiting cell growth. The difference is magnified when dihydroxyethyldithiocarbamate and N-methylglucamine dithiocarbamate and their copper complexes are compared in complete media. Incubation of bleomycin or copper bleomycin with Ehrlich cells in Ringer's buffer with or without dimethyldithiocarbamate or bis-dimethyldithiocarbamato Cu(II) leads to no enhancement of cytotoxicity from combinations of agents, except when the two copper complexes are present. Diethyl- or dimethyldithiocarbamate readily extracts copper from Cu(II)bleomycin and iron from Fe(III)bleomycin when ethylacetate is present to remove the tris-dithiocarbamato Fe(III) complex from aqueous solution. When bis-dimethyldithiocarbamato Cu(II) is incubated with Ehrlich cells, copper is released from the complex and bound to high molecular weight and metallothionein fractions. A reductive mode of dissociation of the copper complexes in cells is supported by ESR experiments. Reactions of diethyl- and dimethyldithiocarbamato Cu(II) with thiol compounds demonstrates one possible mechanism of reduction of these complexes.

Antipseudomonal effects of selected dithiocarbamates alone and in combination with gentamicin or aztreonam.

The antipseudomonal effects conferred by combinations of substituted dithiocarbamates, gentamicin or aztreonam (Azactam) were measured and compared to those produced by single agents alone in female BALB/C mice bearing overwhelming Pseudomonas aeruginosa infections. Dimethyldithiocarbamate (DMDTC), diethyldithiocarbamate (DEDTC), and sodium N-methyl-D-glucamine dithiocarbamate (NMGDTC) were chosen as representative substituted dithiocarbamates. All three dithiocarbamates rescued some cisplatin-immunosuppressed mice from pseudomonal infections but DMDTC and NMGDTC produced better results than DEDTC. Single daily injections of DMDTC at doses of 5 mg/kg/day or higher for a total of 7 days rescued 14 of 18 mice given 10(6) viable Pseudomonas aeruginosa by tail vein inoculation. Similar dose regimens of 10 mg/kg/day or higher NMGDTC for a total of 7 days rescued 15 of 18 mice. DEDTC at doses of 5 mg/kg/day or higher for 7 days rescued 7 of 18 mice. Combinations of DMDTC or NMGDTC with gentamicin failed to produce better results than each agent alone in mice immunosuppressed with methyl-prednisolone (Solumedrol) at the dose range evaluated in mice inoculated with 10(6) viable organisms via tail veins. Combinations of DMDTC and aztreonam were effective in mice immunosuppressed with methylprednisolone and given overwhelming numbers of viable Pseudomonas aeruginosa (10(7) or more, ip). Combinations of 6 mg/kg/day or higher of each agent with multiple daily injections rescued 11 of 18 mice. The results yielded by either agent alone were not impressive. Similar results were obtained when mice immunosuppressed with cisplatin were given ip injections of 10(8) or more viable bacteria. No mice were rescued by the use of DMDTC, NMGDTC, aztreonam or gentamicin only. Combinations of DMDTC (6 mg/kg) and aztreonam (6 mg/kg) with multiple daily injections for seven days rescued 11 of 20 infected mice while combinations of NMGDTC with aztreonam were less effective (3 of 20 rescued). The concurrent administration of DMDTC and aztreonam offers considerable promise in the treatment of overwhelming pseudomonal infections in mice and may prove to be of value in human patients as well.