Enhancement of monocyte antimycobacterial activity by diethyldithiocarbamate (DTC)

Oxidative Stress Response Tips the Balance in Aspergillus terreus Amphotericin B Resistance

In this study, we characterize the impact of antioxidative enzymes in amphotericin B (AmB)-resistant (ATR) and rare AmB-susceptible (ATS) clinical Aspergillus terreus isolates. We elucidate expression profiles of superoxide dismutase (SOD)- and catalase (CAT)-encoding genes, enzymatic activities of SODs, and superoxide anion production and signaling pathways involved in the oxidative stress response (OSR) in ATS and ATR strains under AmB treatment conditions. We show that ATR strains possess almost doubled basal SOD activity compared to that of ATS strains and that ATR strains exhibit an enhanced OSR, with significantly higher sod2 mRNA levels and significantly increased cat transcripts in ATR strains upon AmB treatment. In particular, inhibition of SOD and CAT proteins renders resistant isolates considerably susceptible to the drug in vitro In conclusion, this study shows that SODs and CATs are crucial for AmB resistance in A. terreus and that targeting the OSR might offer new treatment perspectives for resistant species.

Copper and Antibiotics: Discovery, Modes of Action, and Opportunities for Medicinal Applications

Copper is a ubiquitous element in the environment as well as living organisms, with its redox capabilities and complexation potential making it indispensable for many cellular functions. However, these same properties can be highly detrimental to prokaryotes and eukaryotes when not properly controlled, damaging many biomolecules including DNA, lipids, and proteins. To restrict free copper concentrations, all bacteria have developed mechanisms of resistance, sequestering and effluxing labile copper to minimize its deleterious effects. This weakness is actively exploited by phagocytes, which utilize a copper burst to destroy pathogens. Though administration of free copper is an unreasonable therapeutic antimicrobial itself, due to insufficient selectivity between host and pathogen, small-molecule ligands may provide an opportunity for therapeutic mimicry of the immune system. By modulating cellular entry, complex stability, resistance evasion, and target selectivity, ligand/metal coordination complexes can synergistically result in high levels of antibacterial activity. Several established therapeutic drugs, such as disulfiram and pyrithione, display remarkable copper-dependent inhibitory activity. These findings have led to development of new drug discovery techniques, using copper ions as the focal point. High-throughput screens for copper-dependent inhibitors against Mycobacterium tuberculosis and Staphylococcus aureus uncovered several new compounds, including a new class of inhibitors, the NNSNs. In this review, we highlight the microbial biology of copper, its antibacterial activities, and mechanisms to discover new inhibitors that synergize with copper.

Antitubercular activity of disulfiram, an antialcoholism drug, against multidrug- and extensively drug-resistant Mycobacterium tuberculosis isolates

The antimycobacterial activities of disulfiram (DSF) and diethyldithiocarbamate (DDC) against multidrug- and extensively drug-resistant tuberculosis (MDR/XDR-TB) clinical isolates were evaluated in vitro. Both DSF and DDC exhibited potent antitubercular activities against 42 clinical isolates of M. tuberculosis, including MDR/XDR-TB strains. Moreover, DSF showed remarkable bactericidal activity ex vivo and in vivo. Therefore, DSF might be a drug repurposed for the treatment of MDR/XDR-TB.

DETC induces Leishmania parasite killing in human in vitro and murine in vivo models: a promising therapeutic alternative in Leishmaniasis

Background

Chemotherapy remains the primary tool for treatment and control of human leishmaniasis. However, currently available drugs present serious problems regarding side-effects, variable efficacy, and cost. Affordable and less toxic drugs are urgently needed for leishmaniasis.

Methodology/Principal Findings

We demonstrate, by microscopy and viability assays, that superoxide dismutase inhibitor diethyldithiocarbamate (DETC) dose-dependently induces parasite killing (p<0.001) and is able to “sterilize” Leishmania amazonensis infection at 2 mM in human macrophages in vitro. We also show that DETC-induced superoxide production (p<0.001) and parasite destruction (p<0.05) were reverted by the addition of the antioxidant N-acetylcysteine, indicating that DETC-induced killing occurs through oxidative damage. Furthermore, ultrastructural analysis by electron microscopy demonstrates a rapid and highly selective destruction of amastigotes in the phagosome upon DETC treatment, without any apparent damage to the host cell, including its mitochondria. In addition, DETC significantly induced parasite killing in Leishmania promastigotes in axenic culture. In murine macrophages infected with Leishmania braziliensis, DETC significantly induced in vitro superoxide production (p = 0.0049) and parasite killing (p = 0.0043). In vivo treatment with DETC in BALB/C mice infected with Leishmania braziliensis caused a significant decrease in lesion size (p<0.0001), paralleled by a 100-fold decrease (p = 0.0087) in parasite burden.

Conclusions/Significance

Due to its strong leishmanicidal effect in human macrophages in vitro, its in vivo effectiveness in a murine model, and its previously demonstrated in vivo safety profile in HIV treatment, DETC treatment might be considered as a valuable therapeutic option in human leishmaniasis, including HIV/Leishmania co-infection.

Pyrrolidine dithiocarbamate and diethyldithiocarbamate are active against growing and nongrowing persister Mycobacterium tuberculosis

Diethyldithiocarbamate (DETC) and pyrrolidine dithiocarbamate (PDTC) were highly active against tubercle bacilli, with MICs of 8 microg/ml and 0.13 microg/ml, respectively. DETC and PDTC were active against old cultures, enhanced pyrazinamide or pyrazinamide/rifampin activity, and had serum inhibitory titers of 1:2 and 1:4, respectively, in mice given 100 mg/kg orally.

Inhibition of Japanese encephalitis virus infection by diethyldithiocarbamate is independent of its antioxidant potential

Diethyldithiocarbamate (DDTC), a low molecular weight dithiol, has been described as an immunomodulator and modifier of diverse biological actions in human and animal models, and has also been shown to be effective in several disease conditions. Therefore, we studied the therapeutic aspect of DDTC in providing inhibition of Japanese encephalitis virus (JEV) infection. DDTC tested at various doses (10-100 micromol/kg) revealed that administration at low concentration (10 micromol/kg; i.p.) on alternate days prolonged the average survival time (AST) of mice infected with lethal dose of JEV (102 LD50, i.c.) and delayed progression of the disease. The low dose also provided > 80% survival in sub-clinical (10(5) LD50, i.c.) JEV infection. Administration of DDTC to JEV-infected mice enhanced the inducible nitric oxide synthase (iNOS) activity in brain and level of serum tumour necrosis factor-alpha (TNF-alpha). We have recently demonstrated the production of nitric oxide (NO) via induction of iNOS activity is meditated by circulating macrophage-derived factor (MDF), which may be responsible for the delayed progression of the disease. DDTC-mediated inhibition of JEV is believed to involve the augmentation of protective role of MDF as evidenced by the observation that pretreatment with anti-MDF antibody significantly decreased the AST of mice and together with the inhibition of iNOS activity. Interestingly, DDTC alone did not stimulate iNOS and TNF-alpha in mock-infected normal mice. These results show that DDTC may have a possible therapeutic role during JEV infection.

Modulating effect of sodium diethyldithiocarbamate on neutrophils in normal, febrile and cold-stressed rabbits

The studies were conducted on normal, febrile and cold-stressed rabbits. Fever was induced by a single intravenous injection of 1 micrograms/kg of E. coli lipopolysaccharide (LPS). The animals were submerged in ice-water for 20 s and then were kept at -15 degrees C for approx. 8 min., until their body temperature dropped by 3 degrees C. Sodium diethyldithiocarbamate (DTC) was injected i.v. to normal, febrile and cold-stressed rabbits, in a single dose of 2 or 20 mg/kg. The effect of DTC on body temperature, the number of neutrophils in blood, phagocytic activity of neutrophils and their ability to reduce nitroblue tetrazolium (NBT) were evaluated. It was found that DTC administered in a dose of 2 or 20 mg/kg did not affect the body temperature of rabbits. In normal rabbits, DTC did not change the number of neutrophils, but increased their phagocytic activity and ability to reduce NBT. In febrile rabbits, DTC depending on the dose, shortened the stimulating effect of LPS on neutrophil ability to reduce NBT but enhanced and prolonged the effect of pyrogen on neutrophil phagocytic activity. The rabbits treated with DTC prior to hypothermia exhibited shorter neutrophilia resulting from cold stress. In addition, DTC administered to the rabbits before their exposure to cold stress proved to be a partial or even total protection against the decrease in NBT reducing ability and phagocytic activity of blood neutrophils.