Mitochondrial injury by disulfiram: two different mechanisms of the mitochondrial permeability transition

Disulfiram Inhibits Opsonin-Independent Phagocytosis and Migration of Human Long-Lived In Vitro Cultured Phagocytes from Multiple Inflammatory Diseases

Disulfiram (DSF), an anti-alcoholism medicine, exerts treatment effects in patients suffering from persistent Borreliosis and also exhibits anti-cancer effects through its copper chelating derivatives and induction of oxidative stress in mitochondria. Since chronic/persistent borreliosis is characterized by increased amounts of pro-inflammatory macrophages, this study investigated opsonin-independent phagocytosis, migration, and surface marker expression of in vivo activated and in vitro cultured human monocyte-derived phagocytes (macrophages and dendritic cells) with and without DSF treatment. Phagocytosis of non-opsonized Dynabeads® M-450 and migration of macrophages and dendritic cells were monitored using live cell analyzer Juli™ Br for 24 h, imaging every 3.5 min. To simultaneously monitor phagocyte function, results were analyzed by a newly developed software based on the differential phase contrast images of cells before and after ingestion of Dynabeads. DSF decreased the phagocytic capacities exhibited by in vitro enriched and long-lived phagocytes. Although no chemotactic gradient was applied to the test system, vigorous spontaneous migration was observed. We therefore set up an algorithm to monitor and quantify both phagocytosis and migration simultaneously. DSF not only reduced phagocytosis in a majority of these long-lived phagocytes but also impaired their migration. Despite these selective effects by DSF, we found that DSF reduced the expression densities of surface antigens CD45 and CD14 in all of our long-lived phagocytes. In cells with a high metabolic activity and high mitochondrial contents, DSF led to cell death corresponding to mitochondrial oxidative stress, whereas metabolically inactive phagocytes survived our DSF treatment protocol. In conclusion, DSF affects the viability of metabolically active phagocytes by inducing mitochondrial stress and secondly attenuates phagocytosis and migration in some long-lived phagocytes.

Disulfiram-Mitigating Unintended Effects

Lyme disease caused by infection with a multitude of vector-borne organisms can sometimes be successfully treated in its very early stages. However, if diagnosis is delayed, this infection can become disseminated and, like another spirochetal infection syphilis, can affect multiple organ systems in the body, causing a wide variety of life-altering symptoms. Conventional antibiotic therapy may not be effective in eradicating the symptoms of the disease we know as Lyme disease. The recent literature has suggested that disulfiram (DSM) may be a potent drug in the armamentarium of physicians who treat chronic Lyme disease. The use of disulfiram in the treatment of Lyme disease started with a researcher who determined that DSM is bactericidal to spirochete. Encouraged by published case reports of apparent recovery from chronic Lyme disease, having prescribed DSM ourselves in the past for alcoholics who had a desire to stop drinking and prescribing it now for patients with chronic Lyme disease, we observed both predictable and potentially avoidable side effects not necessarily related to the ingestion of alcohol. We reviewed the published literature in PubMed and Google Scholar, using the following key words: Lyme Disease; Borrelia burgdorferi treatment; and disulfiram toxicity. This paper outlines the results of that research to help avoid some of the pitfalls inherent in this novel use of an old and established medication in the practice of clinical medicine.

Disulfiram oxy-derivatives induce entosis or paraptosis-like death in breast cancer MCF-7 cells depending on the duration of treatment

BACKGROUND

Dithiocarbamates and derivatives (including disulfiram, DSF) are currently investigated as antineoplastic agents. We have revealed earlier the ability of hydroxocobalamin (vitamin В_12b) combined with diethyldithiocarbamate (DDC) to catalyze the formation of highly cytotoxic oxidized derivatives of DSF (DSFoxy, sulfones and sulfoxides).

METHODS

Electron and fluorescent confocal microscopy, molecular biology and conventional biochemical techniques were used to study the morphological and functional responses of MCF-7 human breast cancer cells to treatment with DDC and B_12b alone or in combination.

RESULTS

DDC induces unfolded protein response in MCF-7 cells. The combined use of DDC and B_12b causes MCF-7 cell death. Electron microscopy revealed the separation of ER and nuclear membranes, leading to the formation of both cytoplasmic and perinuclear vacuoles, with many fibers inside. The process of vacuolization coincided with the appearance of ER stress markers, a marked damage to mitochondria, a significant inhibition of 20S proteasome, and actin depolimerization at later stages. Specific inhibitors of apoptosis, necroptosis, autophagy, and ferroptosis did not prevent cell death. A short- time (6-h) exposure to DSFoxy caused a significant increase in the number of entotic cells.

CONCLUSIONS

These observations indicate that MCF-7 cells treated with a mixture of DDC and B_12b die by the mechanism of paraptosis. A short- time exposure to DSFoxy caused, along with paraptosis, a significant activation of the entosis and its final stage, lysosomal cell death.

GENERAL SIGNIFICANCE

The results obtained open up opportunities for the development of new approaches to induce non-apoptotic death of cancer cells by dithiocarbamates.

Mitochondria as the Target of Hepatotoxicity and Drug-Induced Liver Injury: Molecular Mechanisms and Detection Methods

One of the major mechanisms of drug-induced liver injury includes mitochondrial perturbation and dysfunction. This is not a surprise, given that mitochondria are essential organelles in most cells, which are responsible for energy homeostasis and the regulation of cellular metabolism. Drug-induced mitochondrial dysfunction can be influenced by various factors and conditions, such as genetic predisposition, the presence of metabolic disorders and obesity, viral infections, as well as drugs. Despite the fact that many methods have been developed for studying mitochondrial function, there is still a need for advanced and integrative models and approaches more closely resembling liver physiology, which would take into account predisposing factors. This could reduce the costs of drug development by the early prediction of potential mitochondrial toxicity during pre-clinical tests and, especially, prevent serious complications observed in clinical settings.

Approved drugs ezetimibe and disulfiram enhance mitochondrial Ca2+ uptake and suppress cardiac arrhythmogenesis

BACKGROUND AND PURPOSE

Treatment of cardiac arrhythmia remains challenging due to severe side effects of common anti-arrhythmic drugs. We previously demonstrated that mitochondrial Ca²⁺ uptake in cardiomyocytes represents a promising new candidate structure for safer drug therapy. However, druggable agonists of mitochondrial Ca²⁺ uptake suitable for preclinical and clinical studies are still missing.

EXPERIMENTAL APPROACH

Herewe screened 727 compounds with a history of use in human clinical trials in a three-step screening approach. As a primary screening platform we used a permeabilized HeLa cell-based mitochondrial Ca²⁺ uptake assay. Hits were validated in cultured HL-1 cardiomyocytes and finally tested for anti-arrhythmic efficacy in three translational models: a Ca²⁺ overload zebrafish model and cardiomyocytes of both a mouse model for catecholaminergic polymorphic ventricular tachycardia (CPVT) and induced pluripotent stem cell derived cardiomyocytes from a CPVT patient.

KEY RESULTS

We identifiedtwo candidate compounds, the clinically approved drugs ezetimibe and disulfiram, which stimulate SR-mitochondria Ca²⁺ transfer at nanomolar concentrations. This is significantly lower compared to the previously described mitochondrial Ca²⁺ uptake enhancers (MiCUps) efsevin, a gating modifier of the voltage-dependent anion channel 2, and kaempferol, an agonist of the mitochondrial Ca²⁺ uniporter. Both substances restored rhythmic cardiac contractions in a zebrafish cardiac arrhythmia model and significantly suppressed arrhythmogenesis in freshly isolated ventricular cardiomyocytes from a CPVT mouse model as well as induced pluripotent stem cell derived cardiomyocytes from a CPVT patient.

CONCLUSION AND IMPLICATIONS

Taken together we identified ezetimibe and disulfiram as novel MiCUps and efficient suppressors of arrhythmogenesis and as such as, promising candidates for future preclinical and clinical studies.

A Phase 1 dose-escalation study of disulfiram and copper gluconate in patients with advanced solid tumors involving the liver using S-glutathionylation as a biomarker

Background

Disulfiram and metals inactivate key oncoproteins resulting in anti-neoplastic activity. The goal of this study was to determine the maximum tolerated dose of copper when administered with disulfiram in patients with advanced solid tumors and liver involvement.

Methods

Disulfiram 250 mg was administered daily in 28-day cycles. Four doses of copper gluconate were tested (2, 4, 6, and 8 mg of elemental copper) in a standard 3 + 3 dose escalation design. Patients were evaluated for dose limiting toxicities and response. Protein S-glutathionylation was evaluated as a pharmacodynamic marker.

Results

Twenty-one patients were enrolled and 16 patients were evaluable for dose limiting toxicities. Among the 21 patients, there was a median of 4 lines of prior chemotherapy. Five Grade 3 toxicities were observed (anorexia, elevated aspartate aminotransferase or AST, elevated alkaline phosphatase, fever, and fatigue). Response data was available for 15 patients. Four patients had stable disease with the longest duration of disease control being 116 days. The median duration of treatment for evaluable patients was 55 days (range 28–124). Reasons for discontinuation included functional decline, disease progression, and disease-associated death. Increased S-glutathionylation of serum proteins was observed with treatment.

Conclusion

Disulfiram 250 mg daily with copper gluconate (8 mg of elemental copper) was well-tolerated in patients with solid tumors involving the liver and was not associated with dose limiting toxicities. While temporary disease stabilization was noted in some patients, no objective responses were observed. Treatment was associated with an increase in S-glutathionylation suggesting that this combination could exert a suppressive effect on cellular growth and protein function.

Trial registration

NCT00742911, first posted 28/08/2008.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08242-4.

Disulfiram as a Therapeutic Agent for Metastatic Malignant Melanoma-Old Myth or New Logos?

Simple Summary

In recent years, disulfiram has gained in attention as an anticancer drug due to its broad activity against various cancers, and its mechanisms and molecular targets have been deciphered in vitro and in vivo. One of these cancers is melanoma. Initial data from human studies show some benefit, but do not confirm its broad efficacy as a monotherapy. However, combination approaches could pave the way for exploiting the beneficial effects of disulfiram for cancer patients, including those with melanoma.

Abstract

New therapeutic concepts such as anti-PD-1-based immunotherapy or targeted therapy with BRAF and MEK inhibitors have significantly improved the survival of melanoma patients. However, about 20% of patients with targeted therapy and up to 50% with immunotherapies do not respond to their first-line treatment or rapidly develop resistance. In addition, there is no approved targeted therapy for certain subgroups, namely BRAF wild-type melanomas, although they often bear aggressive tumor biology. A repurposing of already approved drugs is a promising strategy to fill this gap, as it will result in comparatively low costs, lower risks and time savings. Disulfiram (DSF), the first drug to treat alcoholism, which received approval from the US Food and Drug Administration more than 60 years ago, is such a drug candidate. There is growing evidence that DSF has great potential for the treatment of various human cancers, including melanoma. Several mechanisms of its antitumor activity have been identified, amongst them the inhibition of the ubiquitin-proteasome system, the induction of reactive oxygen species and various death signaling pathways. This article provides an overview of the application of DSF in humans, its molecular mechanisms and targets in cancer therapy with a focus on melanoma. The results of clinical studies and experimental combination approaches of DSF with various cancer therapies are discussed, with the aim of exploring the potential of DSF in melanoma therapy.

Analysis of Time-Series Gene Expression Data to Explore Mechanisms of Chemical-Induced Hepatic Steatosis Toxicity

Non-alcoholic fatty liver disease (NAFLD) represents a wide spectrum of disease, ranging from simple fatty liver through steatosis with inflammation and necrosis to cirrhosis. One of the most challenging problems in biomedical research and within the chemical industry is to understand the underlying mechanisms of complex disease, and complex adverse outcome pathways (AOPs). Based on a set of 28 steatotic chemicals with gene expression data measured on primary hepatocytes at three times (2, 8, and 24 h) and three doses (low, medium, and high), we identified genes and pathways, defined as molecular initiating events (MIEs) and key events (KEs) of steatosis using a combination of a time series and pathway analyses. Among the genes deregulated by these compounds, the study highlighted OSBPL9, ALDH7A1, MYADM, SLC51B, PRDX6, GPAT3, TMEM135, DLGDA5, BCO2, APO10LA, TSPAN6, NEURL1B, and DUSP1. Furthermore, pathway analysis indicated deregulation of pathways related to lipid accumulation, such as fat digestion and absorption, linoleic and linolenic acid metabolism, calcium signaling pathway, fatty acid metabolism, peroxisome, retinol metabolism, and steroid metabolic pathways in a time dependent manner. Such transcription profile analysis can help in the understanding of the steatosis evolution over time generated by chemical exposure.

Calcium Induces Mitochondrial Oxidative Stress Because of its Binding to Adenine Nucleotide Translocase

Several studies have demonstrated that the mitochondrial membrane switches from selective to non-selective permeability because of its improved matrix Ca²⁺ accumulation and oxidative stress. This process, known as permeability transition, evokes severe dysfunction in mitochondria through the opening of a non-specific pore, whose chemical nature is still under discussion. There are some proposals regarding the components of the pore structure, e.g., the adenine nucleotide translocase and dimers of the F1 Fo-ATP synthase. Our results reveal that Ca²⁺ induces oxidative stress, which not only increases lipid peroxidation and ROS generation but also brings about both the collapse of the transmembrane potential and the membrane release of cytochrome c. Additionally, it is shown that Ca²⁺ increases the binding of the probe eosin-5-maleimide to adenine nucleotide translocase. Interestingly, these effects are diminished after the addition of ADP. It is suggested that pore opening is caused by the binding of Ca²⁺ to the adenine nucleotide translocase.

Recent Advances in Antabuse (Disulfiram): The Importance of its Metal-binding Ability to its Anticancer Activity

BACKGROUND

Considerable evidence demonstrates the importance of dithiocarbamates especially disulfiram as anticancer drugs. However there are no systematic reviews outlining how their metal-binding ability is related to their anticancer activity. This review aims to summarize chemical features and metal-binding activity of disulfiram and its metabolite DEDTC, and discuss different mechanisms of action of disulfiram and their contributions to the drug's anticancer activity.

METHODS

We undertook a disulfiram-related search on bibliographic databases of peerreviewed research literature, including many historic papers and in vitro, in vivo, preclinical and clinical studies. The selected papers were carefully reviewed and summarized.

RESULTS

More than five hundreds of papers were obtained in the initial search and one hundred eighteen (118) papers were included in the review, most of which deal with chemical and biological aspects of Disulfiram and the relationship of its chemical and biological properties. Eighty one (81) papers outline biological aspects of dithiocarbamates, and fifty seven (57) papers report biological activity of Disulfiram as an inhibitor of proteasomes or inhibitor of aldehyde dehydrogenase enzymes, interaction with other anticancer drugs, or mechanism of action related to reactive oxygen species. Other papers reviewed focus on chemical aspects of dithiocarbamates.

CONCLUSION

This review confirms the importance of chemical features of compounds such as Disulfiram to their biological activities, and supports repurposing DSF as a potential anticancer agent.

The protective effects of silybin on the cytotoxicity of thiram in human, rat and chicken cell cultures

The study objective was a determination of thiram cytotoxicity and silybin cytoprotective activity in course of the fungicide impact on cell metabolism and membrane integrity. Firstly, human, rat, chicken hepatoma cells and rat myoblasts cultures were incubated with thiram. The results showed higher sensitivity of myoblasts on thiram exposure than the hepatoma cells. Among hepatoma cells, the chicken cultures were the most sensitive on the fungicide endangering. The mitochondrial activity was the most thiram affected function within all types the cell lines used. When silybin co-acted with thiram, an increase of the cell viability was recorded. The EC₅₀-values were higher for thiram subjected to interaction with silybin than the effect of alone thiram action. The interaction mode between the studied compounds shown by combination index (CI) represented an antagonistic or an additive nature and was depended on thiram concentration, type of the cells and the assay used. Moreover, the morphology changes were dependent on silybin presence in the cell cultures subjected to thiram impact at the same time. Staining with Hoechst 33342 and propidium ioidium revealed the apoptosis cell death in the incubation cultures. Definitely, the results have shown a potential of silybin to protect the cultured cells in course of cytotoxicity induced by thiram. However, future studies taking into account other endpoints of thiram cytotoxicity pathways including species differences and the cytoprotection efficacy could be of interest.

Tamoxifen inhibits mitochondrial membrane damage caused by disulfiram

In this work, we studied the protective effects of tamoxifen (TAM) on disulfiram (Dis)-induced mitochondrial membrane insult. The results indicate that TAM circumvents the inner membrane leakiness manifested as Ca2+ release, mitochondrial swelling, and collapse of the transmembrane electric gradient. Furthermore, it was found that TAM prevents inactivation of the mitochondrial enzyme aconitase and detachment of cytochrome c from the inner membrane. Interestingly, TAM also inhibited Dis-promoted generation of hydrogen peroxide. Given that TAM is an antioxidant molecule, it is plausible that its protection may be due to the inhibition of Dis-induced oxidative stress.

The Importance of Patient-Specific Factors for Hepatic Drug Response and Toxicity

Responses to drugs and pharmacological treatments differ considerably between individuals. Importantly, only 50%-75% of patients have been shown to react adequately to pharmacological interventions, whereas the others experience either a lack of efficacy or suffer from adverse events. The liver is of central importance in the metabolism of most drugs. Because of this exposed status, hepatotoxicity is amongst the most common adverse drug reactions and hepatic liabilities are the most prevalent reason for the termination of development programs of novel drug candidates. In recent years, more and more factors were unveiled that shape hepatic drug responses and thus underlie the observed inter-individual variability. In this review, we provide a comprehensive overview of different principle mechanisms of drug hepatotoxicity and illustrate how patient-specific factors, such as genetic, physiological and environmental factors, can shape drug responses. Furthermore, we highlight other parameters, such as concomitantly prescribed medications or liver diseases and how they modulate drug toxicity, pharmacokinetics and dynamics. Finally, we discuss recent progress in the field of in vitro toxicity models and evaluate their utility in reflecting patient-specific factors to study inter-individual differences in drug response and toxicity, as this understanding is necessary to pave the way for a patient-adjusted medicine.

Strategies, models and biomarkers in experimental non-alcoholic fatty liver disease research

Non-alcoholic fatty liver disease encompasses a spectrum of liver diseases, including simple steatosis, steatohepatitis, liver fibrosis and cirrhosis and hepatocellular carcinoma. Non-alcoholic fatty liver disease is currently the most dominant chronic liver disease in Western countries due to the fact that hepatic steatosis is associated with insulin resistance, type 2 diabetes mellitus, obesity, metabolic syndrome and drug-induced injury. A variety of chemicals, mainly drugs, and diets is known to cause hepatic steatosis in humans and rodents. Experimental non-alcoholic fatty liver disease models rely on the application of a diet or the administration of drugs to laboratory animals or the exposure of hepatic cell lines to these drugs. More recently, genetically modified rodents or zebrafish have been introduced as non-alcoholic fatty liver disease models. Considerable interest now lies in the discovery and development of novel non-invasive biomarkers of non-alcoholic fatty liver disease, with specific focus on hepatic steatosis. Experimental diagnostic biomarkers of non-alcoholic fatty liver disease, such as (epi)genetic parameters and '-omics'-based read-outs are still in their infancy, but show great promise. In this paper, the array of tools and models for the study of liver steatosis is discussed. Furthermore, the current state-of-art regarding experimental biomarkers such as epigenetic, genetic, transcriptomic, proteomic and metabonomic biomarkers will be reviewed.

Oxidant stress, mitochondria, and cell death mechanisms in drug-induced liver injury: lessons learned from acetaminophen hepatotoxicity

Hepatotoxicity is a serious problem during drug development and for the use of many established drugs. For example, acetaminophen overdose is currently the most frequent cause of acute liver failure in the United States and Great Britain. Evaluation of the mechanisms of drug-induced liver injury indicates that mitochondria are critical targets for drug toxicity, either directly or indirectly through the formation of reactive metabolites. The consequence of these modifications is generally a mitochondrial oxidant stress and peroxynitrite formation, which leads to structural alterations of proteins and mitochondrial DNA and, eventually, to the opening of mitochondrial membrane permeability transition (MPT) pores. MPT pore formation results in a collapse of mitochondrial membrane potential and cessation of adenosine triphosphate synthesis. In addition, the release of intermembrane proteins, such as apoptosis-inducing factor and endonuclease G, and their translocation to the nucleus, leads to nuclear DNA fragmentation. Together, these events trigger necrotic cell death. Alternatively, the release of cytochrome c and other proapoptotic factors from mitochondria can promote caspase activation and apoptotic cell death. Drug toxicity can also induce an inflammatory response with the formation of reactive oxygen species by Kupffer cells and neutrophils. If not properly detoxified, these extracellularly generated oxidants can diffuse into hepatocytes and trigger mitochondrial dysfunction and oxidant stress, which then induces MPT and necrotic cell death. This review addresses the formation of oxidants and the defense mechanisms available for cells and applies this knowledge to better understand mechanisms of drug hepatotoxicity, especially acetaminophen-induced liver injury.

Central role of mitochondria in drug-induced liver injury

A frequent mechanism for drug-induced liver injury (DILI) is the formation of reactive metabolites that trigger hepatitis through direct toxicity or immune reactions. Both events cause mitochondrial membrane disruption. Genetic or acquired factors predispose to metabolite-mediated hepatitis by increasing the formation of the reactive metabolite, decreasing its detoxification, or by the presence of critical human leukocyte antigen molecule(s). In other instances, the parent drug itself triggers mitochondrial membrane disruption or inhibits mitochondrial function through different mechanisms. Drugs can sequester coenzyme A or can inhibit mitochondrial β-oxidation enzymes, the transfer of electrons along the respiratory chain, or adenosine triphosphate (ATP) synthase. Drugs can also destroy mitochondrial DNA, inhibit its replication, decrease mitochondrial transcripts, or hamper mitochondrial protein synthesis. Quite often, a single drug has many different effects on mitochondrial function. A severe impairment of oxidative phosphorylation decreases hepatic ATP, leading to cell dysfunction or necrosis; it can also secondarily inhibit ß-oxidation, thus causing steatosis, and can also inhibit pyruvate catabolism, leading to lactic acidosis. A severe impairment of β-oxidation can cause a fatty liver; further, decreased gluconeogenesis and increased utilization of glucose to compensate for the inability to oxidize fatty acids, together with the mitochondrial toxicity of accumulated free fatty acids and lipid peroxidation products, may impair energy production, possibly leading to coma and death. Susceptibility to parent drug-mediated mitochondrial dysfunction can be increased by factors impairing the removal of the toxic parent compound or by the presence of other medical condition(s) impairing mitochondrial function. New drug molecules should be screened for possible mitochondrial effects.

Drug-induced toxicity on mitochondria and lipid metabolism: mechanistic diversity and deleterious consequences for the liver

Numerous investigations have shown that mitochondrial dysfunction is a major mechanism of drug-induced liver injury, which involves the parent drug or a reactive metabolite generated through cytochromes P450. Depending of their nature and their severity, the mitochondrial alterations are able to induce mild to fulminant hepatic cytolysis and steatosis (lipid accumulation), which can have different clinical and pathological features. Microvesicular steatosis, a potentially severe liver lesion usually associated with liver failure and profound hypoglycemia, is due to a major inhibition of mitochondrial fatty acid oxidation (FAO). Macrovacuolar steatosis, a relatively benign liver lesion in the short term, can be induced not only by a moderate reduction of mitochondrial FAO but also by an increased hepatic de novo lipid synthesis and a decreased secretion of VLDL-associated triglycerides. Moreover, recent investigations suggest that some drugs could favor lipid deposition in the liver through primary alterations of white adipose tissue (WAT) homeostasis. If the treatment is not interrupted, steatosis can evolve toward steatohepatitis, which is characterized not only by lipid accumulation but also by necroinflammation and fibrosis. Although the mechanisms involved in this aggravation are not fully characterized, it appears that overproduction of reactive oxygen species by the damaged mitochondria could play a salient role. Numerous factors could favor drug-induced mitochondrial and metabolic toxicity, such as the structure of the parent molecule, genetic predispositions (in particular those involving mitochondrial enzymes), alcohol intoxication, hepatitis virus C infection, and obesity. In obese and diabetic patients, some drugs may induce acute liver injury more frequently while others may worsen the pre-existent steatosis (or steatohepatitis).

The ethanol metabolite acetaldehyde increases paracellular drug permeability in vitro and oral bioavailability in vivo

Alcohol consumption leads to the production of the highly reactive ethanol metabolite, acetaldehyde, which may affect intestinal tight junctions and increase paracellular permeability. We examined the effects of elevated acetaldehyde within the gastrointestinal tract on the permeability and bioavailability of hydrophilic markers and drug molecules of variable molecular weight and geometry. In vitro permeability was measured unidirectionally in Caco-2 and MDCKII cell models in the presence of acetaldehyde, ethanol, or disulfiram, an aldehyde dehydrogenase inhibitor, which causes acetaldehyde formation when coadministered with ethanol in vivo. Acetaldehyde significantly lowered transepithelial resistance in cell monolayers and increased permeability of the low-molecular-weight markers, mannitol and sucrose; however, permeability of high-molecular-weight markers, polyethylene glycol and inulin, was not affected. In vivo permeability was assessed in male Sprague-Dawley rats treated for 6 days with ethanol, disulfiram, or saline alone or in combination. Bioavailability of naproxen was not affected by any treatment, whereas that of paclitaxel was increased upon acetaldehyde exposure. Although disulfiram has been shown to inhibit multidrug resistance-1 P-glycoprotein (P-gp) in vitro, our data demonstrate that the known P-gp substrate paclitaxel is not affected by coadministration of disulfiram. In conclusion, we demonstrate that acetaldehyde significantly modulates tight junctions and paracellular permeability in vitro as well as the oral bioavailability of low-molecular-weight hydrophilic probes and therapeutic molecules in vivo even when these molecules are substrates for efflux transporters. These studies emphasize the significance of ethanol metabolism and drug interactions outside of the liver.

Identification of differentially expressed genes in the growth plate of broiler chickens with thiram-induced tibial dyschondroplasia

Tibial dyschondroplasia (TD) is characterized by expansion of the proximal growth plates of the tibiotarsus that fail to form bone, lack blood vessels, and contain non-viable cells. Thiram (a carbamate pesticide), when fed to young broiler chicks, induces TD with high regularity and precision. We used this experimental model to understand the cause of the defects associated with TD by selecting and identifying the genes differentially expressed in the TD growth plate of broiler chickens. Broiler chicks at 7 days of age were randomly divided into two groups. After fasting overnight, they were fed with regular diet (control) or the same diet containing 100 mg/kg thiram for 96 h to induce TD (thiram-fed). mRNA was purified from the growth plates of control and thiram-fed broilers. Forward and reverse-subtracted cDNA libraries were generated by suppression subtractive hybridization technology. Ten selected genes from cDNA libraries were identified by real-time quantitative polymerase chain reaction. All were differentially expressed in TD growth plates (P<0.05 or P<0.01). The levels of collagen type X (Col X), pro-alpha-1 collagen type I (Col I alpha1), collagen type IX (Col IX), NADH dehydrogenase (NADH DH), cytochrome C oxidase subunit III (COX III), enolase 1, alpha (ENO1), carbonic anhydrase II (CA2) and heat shock protein 90 (Hsp90) mRNA transcripts were up-regulated, while the expression levels of Matrilin 3 (MATN3) and chondromodulin-I (ChM-I) were down-regulated. Col I and Hsp90 were detected by immunohistochemistry at different stages. Given that these genes are involved in matrix formation, endochondral ossification, developmental regulation, electron transport in the mitochondrial respiratory chain and vascularization, our findings may provide new insights into understanding the pathogenesis of TD.

On the opening of an insensitive cyclosporin A non-specific pore by phenylarsine plus mersalyl

The purpose of this work was addressed to provide new information on the effect of thiol reagents on mitochondrial non-specific pore opening, and its response to cyclosporin A (CSA). To meet this proposal phenylarsine oxide (PHA) and mersalyl were employed as tools to induce permeability transition and CSA to inhibit it. PHA-induced mitochondrial dysfunction, characterized by Ca2+ efflux, swelling, and membrane de-energization, was inhibited by N-ethylmaleimide and CSA. Conversely, mersalyl failed to inhibit the inducing effect of phenylarsine oxide, it rather strengthened it. In addition, the effect of mersalyl was associated with cross-linking of membrane proteins. The content of membrane thiol groups accessible to react with PHA, mersalyl, and PHA plus mersalyl was determined. In all situations, permeability transition was accompanied by a significant decrease in the whole free membrane thiol content. Interestingly, it is also shown that mersalyl hinders the protective effect of cyclosporin A on PHA-induced matrix Ca2+ efflux.

Effect of glutathione depletion on apoptosis induced by thiram in Chinese hamster fibroblasts

Fungicide thiram, which is also known as an inducer of allergic contact dermatitis (ACD), was used as a model compound of thiuram chemicals, and its cellular effects were investigated in cultured Chinese hamster V79 cells. The level of intracellular reduced glutathione (GSH), protein sulfhydryl (PSH) groups, protein carbonyls (PC), membrane lipid peroxidation reflected by enhanced thiobarbituric acid reactive substrates (TBARS) production, as well as apoptotic effect were determined. The apoptosis induction was determined by assessing DNA fragmentation by TUNEL, annexin V binding, and caspases activation assays, using fluorescent microscope or flow cytometry, respectively. The concentrations of thiram required to induce cellular GSH depletion (by 40-50%), protein, and membrane lipid peroxidation (2-fold, and 1.7-fold, respectively), as well as to induce apoptosis in V79 Chinese hamster fibroblasts without causing necrosis through cytotoxic effects were between 50-100 microM. To investigate the role of decreased GSH content in the toxicity of thiram, GSH level was modified prior to exposure. Pretreatment of V79 cells with N-acetyl-L-cysteine (NAC), a GSH biosynthesis precursor, prevented GSH decrease, PC and TBARS production, as well as caspases activation induced by thiram exposure. On the other hand, thiram effects were enhanced by the previous depletion of cellular GSH by L-buthionine-(S,R)-sulfoximine (BSO).

Changes in the Tibial Growth Plates of Chickens with Thiram-induced Dyschondroplasia

Tibial dyschondroplasia (TD) is a metabolic cartilage disease of young poultry in which endochondral bone formation is disrupted leading to the retention of a non-calcified, avascular plug of cartilage in the tibial growth plate. Chicks aged 7 days were fed either a control diet or one containing thiram 100 ppm for 48 h to induce TD. Cell multiplication in the growth plate was determined thereafter with bromodeoxyuridine (BrdU) labelling, and metabolic changes by measuring alkaline phosphatase (ALP), tartrate-resistant acid phosphatase (TRAP), and glutathione (GSH) activities. The effect on chondrocyte maturation was examined by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of gene expression. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) and DNA fragmentation were used to determine the effects of thiram on cell survival. The results showed that thiram-induced TD was not due to the multiplication of cells in the post-proliferative zones. Thiram did not affect ALP activity, which would have indicated a loss of calcification potential, but it reduced both TRAP and the glutathione concentrations, suggesting that the growth plate metabolism and remodelling functions were adversely affected. Thiram appeared to have no effect on the expression of type X collagen, transglutaminase, RUNX2, or matrix metalloproteinase-2 (MMP) genes suggesting that it did not alter the maturation potential of chondrocytes. On the contrary, the expressions of MMP-13 and vascular endothelial growth factor (VEGF) genes were "up-regulated," suggesting that thiram has pro-angiogenic activity. However, TUNEL assay showed that thiram induced endothelial cell apoptosis in the capillary vessels of the growth plates, as early as 10 days of age, when TD was not visually evident. The vascular death increased on subsequent days accompanied by massive death of chondrocytes in the transition zone of the growth plate. The induction of apoptosis in the growth plate was also demonstrated by DNA fragmentation. It was concluded that thiram induced TD not through an increase in the multiplication of chondrocytes in the transition zone and not by altering the expression of genes causing the arrest of chondrocytes in a prehypertrophic state, but by creating a metabolic dysfunction which led to the destruction of blood capillaries in the transition zone chondrocytes.

Disulfiram inhibits activating transcription factor/cyclic AMP-responsive element binding protein and human melanoma growth in a metal-dependent manner in vitro, in mice and in a patient with metastatic disease

The thiocarbamate alcoholism drug disulfiram blocks the P-glycoprotein extrusion pump, inhibits the transcription factor nuclear factor-κB, sensitizes tumors to chemotherapy, reduces angiogenesis, and inhibits tumor growth in mice. Thiocarbamates react with critical thiols and also complex metal ions. Using melanoma as the paradigm, we tested whether disulfiram might inhibit growth by forming mixed disulfides with critical thiols in a mechanism facilitated by metal ions. Disulfiram given to melanoma cells in combination with Cu2+ or Zn2+ decreased expression of cyclin A and reduced proliferation in vitro at lower concentrations than disulfiram alone. In electrophoretic mobility shift assays, disulfiram decreased transcription factor binding to the cyclic AMP-responsive element in a manner potentiated by Cu2+ ions and by the presence of glutathione, suggesting that thiocarbamates might disrupt transcription factor binding by inducing S-glutathionylation of the transcription factor DNA binding region. Disulfiram inhibited growth and angiogenesis in melanomas transplanted in severe combined immunodeficient mice, and these effects were potentiated by Zn2+ supplementation. The combination of oral zinc gluconate and disulfiram at currently approved doses for alcoholism also induced &gt;50% reduction in hepatic metastases and produced clinical remission in a patient with stage IV metastatic ocular melanoma, who has continued on oral zinc gluconate and disulfiram therapy for 53 continuous months with negligible side effects. These findings present a novel strategy for treating metastatic melanoma by employing an old drug toward a new therapeutic use.

Physical and chemical aspects of long-term biodeterioration of some polymers and composites

A biodeterioration study was performed on synthetic polymeric materials including homogenous film made from poly(tetrafluorine ethylene), copolymer film made from tetrafluorine ethylene and perfluoromethyl vinyl ether, vulcanized rubber containing natural caoutchouc, and vulcanized rubber, the main component of which was synthetic butadiene nitrile caoutchouc. The materials were exposed for 12 years to the open air, in mycological containers, and in a cellar in maritime climate conditions: air humidity 72%-90% and seasonal average temperature of 17 degrees C in summer and -2.5 degrees C in winter. The studies of optical and electron microscopy revealed that microorganisms were able to develop not only on the surface of the materials but also to penetrate inside into deeper layers. The fungi that produced the most intensive deterioration in the fluorine polymers and vulcanized rubbers belonged to the Alternaria, Aspergillus, Aureobasidium, Cladosporium, Penicillium, Oidiodendron and Trichoderma genera. The fungi Aspergillus fumigatus, A. niger, Aureobasidium pullulans, and Trichoderma viride produced the most intensive deterioration in the fluorine films, whereas Alternaria tenuissima, Cladosporium herbarum, C. sphaerospermum, and fungi of the Oidiodendron genus were widespread on vulcanized rubbers. Fungi of the Aspergillus and Penicillium genera prevailed on both fluorine films and rubbers exposed in a cellar. Infrared spectroscopy indicated that the structures of poly(tetrafluorine ethylene) and the copolymer of tetrafluorine ethylene and perfluoromethyl vinyl ether did not change after the 12-year exposure; only insignificant changes in surface morphology were observed by optical microscopy. Vulcanized rubber made both from natural and from synthetic caoutchouc exposed for the same length of time showed rather evident changes in appearance and structure. X-ray graphical analysis revealed that new crystallization of the caoutchouc and a possible change in chemical composition of the fillers had occurred.

Comparative efficacy of different dithiocarbamates to induce tibial dyschondroplasia in poultry

Tibial dyschondroplasia (TD) is a metabolic cartilage disease in poultry the natural etiology of which is not known. In the absence of biomarkers to monitor the initiation and progression of the naturally occurring disease, experimentally induced TD can provide a suitable venue to study the mechanism of its pathogenesis. Therefore, the objective of this study was to establish a streamlined experimental protocol to induce TD using dithiocarbamates and to determine a time course of its progression. Three different dithiocarbamates, dimethyldithiocarbamate, pyrrolidine dithiocarbamate, and tetramethyl thiuram disulfide (thiram), were tested with respect to their abilities to induce TD and affect different physiological factors. Our results show that chickens fed thiram during the first 2 wk of age showed a maximum TD index. Thiram appeared to be the most potent of the 3 dithiocarbamates with dimethyldithiocarbamate having the least ability to induce TD and pyrrolidine dithiocarbamate showing an intermediate potency. A transient exposure to thiram for a day or 2 was sufficient to markedly increase the incidence of TD and produce lasting damage as determined by the presence of severe lesions in a high percentage of birds at 2 to 3 wk after the treatment. Thiram affected the chondrocyte morphology of maturing zone cartilage evident by nuclear shrinkage and emptied chondrocyte lacunae during later times and also involutions of capillary vessels. Such changes were not seen in prehypertrophic zone chondrocytes of the same growth plates. Thiram reduced the BW, increased blood heterophil-to-lymphocyte ratios, and elevated serum corticosterone concentrations indicating physiological stress. However, there was no change in relative liver weights or blood clinical chemistry including the serum concentrations of Ca, P, and Cu in thiocarbamate-fed chickens. Induction of TD in young chickens by means of a short feeding protocol with thiram may be useful to study the mechanisms of pathogenesis of TD and to identify micronutrients that can provide protection against this disease.

Effects of disulfiram on excitation-contraction coupling in rat soleus muscle

The aim of this study was to analyze whether disulfiram could affect excitation-contraction coupling in rat slow-twitch ( soleus) muscle.In small bundles of intact fibers, the amplitude and the time constant of relaxation of twitch and potassium contractures were dose-dependently and reversibly reduced by disulfiram at concentrations up to 27 microM. At larger concentrations (up to 67.5 microM) these effects were still present but less pronounced. In the presence of disulfiram (27 microM), the relationship between the amplitude of potassium contractures and membrane potential was shifted to more positive potentials whereas, the steady state inactivation curve was unchanged. These observations suggest that disulfiram has no effect on voltage sensors. In saponin-skinned fibers, the amount of Ca(2+) taken up, estimated by using the amplitude of 10 mM of caffeine contracture, was increased by disulfiram (27 microM). By contrast no significant modification was observed in the sensitivity of the ryanodine receptors to caffeine (contractures generated at 5 mM of caffeine) and in the myofibrillar Ca(2+) sensitivity (Triton X-100 skinned fibers). These results indicate that disulfiram induces a dose-dependent reversible effect on the contractile responses of soleus mammalian skeletal muscle by acting mainly on the sarcoplasmic reticulum Ca(2+)-ATPase activity.