Metabolism of Nifurtimox and the Drug-Drug Interaction Potential Including its Major Metabolites.

Background: Nifurtimox is an effective treatment for patients with Chagas disease, but knowledge of its biotransformation and excretion is limited.

Objective: This study aimed to better understand the fate of oral nifurtimox .

Methods: We investigated the exposure and excretion pathways of [C]-labeled nifurtimox and its metabolites in rats.

Emodepside targets SLO-1 channels of Onchocerca ochengi and induces broad anthelmintic effects in a bovine model of onchocerciasis.

Onchocerciasis (river blindness), caused by the filarial worm Onchocerca volvulus, is a neglected tropical disease mostly affecting sub-Saharan Africa and is responsible for >1.3 million years lived with disability. Current control relies almost entirely on ivermectin, which suppresses symptoms caused by the first-stage larvae (microfilariae) but does not kill the long-lived adults.

Energy metabolism modulation by biguanides in comparison with rotenone in rat liver and heart.

The biguanide metformin, a widely used antidiabetic drug, has received great interest in oncology research in recent years after an epidemiological study showed a link between metformin treatment and a reduced cancer risk in diabetic patients. Since mitochondrial metabolism has become a target for possible cancer therapeutic approaches, especially for tumors relying on oxidative metabolism, mitochondrial complex I inhibition is under discussion to be responsible for the anti-cancer effect of metformin. Rotenone, a well-known strong mitochondrial complex I inhibitor, yet associated with toxic effects, has also shown anti-cancer activity.

Consensus statement on the need for innovation, transition and implementation of developmental neurotoxicity (DNT) testing for regulatory purposes.

This consensus statement voices the agreement of scientific stakeholders from regulatory agencies, academia and industry that a new framework needs adopting for assessment of chemicals with the potential to disrupt brain development. An increased prevalence of neurodevelopmental disorders in children has been observed that cannot solely be explained by genetics and recently pre- and postnatal exposure to environmental chemicals has been suspected as a causal factor. There is only very limited information on neurodevelopmental toxicity, leaving thousands of chemicals, that are present in the environment, with high uncertainty concerning their developmental neurotoxicity (DNT) potential.

Mechanistic Investigations of the Mitochondrial Complex I Inhibitor Rotenone in the Context of Pharmacological and Safety Evaluation.

Inhibitors of the mitochondrial respiratory chain complex I are suggested to exert anti-tumor activity on those tumors relying on oxidative metabolism and are therefore of interest to oncology research. Nevertheless, the safety profile of these inhibitors should be thoroughly assessed. Rotenone, a proven complex I inhibitor, has shown anti-carcinogenic activity in several studies.

International STakeholder NETwork (ISTNET): creating a developmental neurotoxicity (DNT) testing road map for regulatory purposes.

A major problem in developmental neurotoxicity (DNT) risk assessment is the lack of toxicological hazard information for most compounds. Therefore, new approaches are being considered to provide adequate experimental data that allow regulatory decisions. This process requires a matching of regulatory needs on the one hand and the opportunities provided by new test systems and methods on the other hand.

Relationship of cellular topoisomerase IIα inhibition to cytotoxicity and published genotoxicity of fluoroquinolone antibiotics in V79 cells.

Fluoroquinolone (FQ) antibiotics are bacteriocidal through inhibition of the bacterial gyrase and at sufficient concentrations in vitro, they can inhibit the homologous eukaryotic topoisomerase (TOPO) II enzyme. FQ exert a variety of genotoxic effects in mammalian systems through mechanisms not yet established, but which are postulated to involve inhibition of TOPO II enzymes. To assess the relationship of inhibition of cell nuclear TOPO II to cytotoxicity and reported genotoxicity, two FQ, clinafloxacin (CLFX) and lomefloxacin (LOFX), having available genotoxicity data showing substantial differences with CLFX being more potent than LOFX, were selected for study.

Cyclophosphamide and etoposide canine studies demonstrate the cross-species potential of the flow cytometric peripheral blood micronucleated reticulocyte endpoint.

Erythrocyte-based micronucleus tests have traditionally been performed with bone marrow specimens, since, in most preclinical animal models, the spleen can efficiently remove aberrant erythrocytes from the circulation. Even so, evidence is mounting that by examining tens of thousands of young (CD71-positive) circulating reticulocytes for the presence of micronuclei via flow cytometry, a sensitive assay of cytogenetic damage is realized. The work described herein was designed to test this hypothesis further, using an important preclinical toxicology model, the beagle dog.

The use of Fluoro-Jade in primary neuronal cell cultures.

Fluoro-Jade (FJ) and its derivatives are widely used for histological staining of neurons undergoing neurodegeneration. With this dye, the entire structure of these neurons can be stained in a fast and reliable way in histopathological slices of the brain, with results comparable to those obtained with other methods such as the Nissle technique or silver staining. The question arose as to whether this method might be useful for in vitro neuronal cell cultures.

Assessment of DNA double-strand breaks and gammaH2AX induced by the topoisomerase II poisons etoposide and mitoxantrone.

Double-strand breaks (DSBs) are highly deleterious DNA lesions as they lead to chromosome aberrations and/or apoptosis. The formation of nuclear DSBs triggers phosphorylation of histone H2AX on Ser-139 (defined as gammaH2AX), which participates in the repair of such DNA damage. Our aim was to compare the induction of gammaH2AX in relation to DSBs induced by topoisomerase II (TOPO II) poisons, etoposide (ETOP) and mitoxantrone (MXT), in V79 cells.

Screening for estrogenicity and anti-estrogenicity: a critical evaluation of an MVLN cell-based transactivation assay.

Concerns have been raised whether natural and man-made chemicals might have the potential to adversely interfere with the endocrine system of humans and wildlife. This issue initiated intense research over the past years with a focus on interactions with the estrogen receptor (ER) as for several natural and anthropogenic compounds an estrogenic potential could be demonstrated. Transactivation assays have contributed much to the characterization of compounds with estrogen-like activity.

Improvements in an in-vitro assay for excitotoxicity by measurement of early gene (c-fos mRNA) levels.

Quantitative, real-time reverse transcription-polymerase chain reaction (RT-PCR) measurements were made to investigate the levels of c-fos mRNA as one measure of the expression of the c-fos gene. Exposure of mouse cerebellar granule cells to excitotoxic concentrations of glutamate (Glu) and aspartate (Asp) led to a changed time profile for mRNA expression, from a transient c-fos expression at 15-30 min to a delayed, elevated and sustained expression at later time points which was prevented by selective antagonism of the NMDA receptor but not of the AMPA/kainate receptor demonstrating that this c-fos induction was mediated through the specific activation of the NMDA Glu receptor subtype. The question as to whether c-fos expression changes could be used to predict excitotoxicity was addressed by testing the c-fos response of the cultures to several compounds, at low (and therefore non-toxic) and high (toxic) concentrations at two suitable time-points of exposure (30 and 240 min), in the presence and absence of Glu receptor antagonists.

Effects of the carbamates fenoxycarb, propamocarb and propoxur on energy supply, glucose utilization and SH-groups in neurons.

Carbamates belonged to an older insecticide group, with propoxur being representative of this group. However, today carbamates with hormonal effects on insects, like fenoxycarb, or with fungicide properties, like propamocarb, are also used. The goal was a comparison of three structurally and functional different carbamates with a possibly common toxicological mechanism.

Effects of the new herbicide fentrazamide on the glucose utilization in neurons and erythrocytes in vitro.

Treatment of rats with fentrazamide for 2 years at 3000 ppm (males) and 4000 ppm (females) led to an increased incidence and degree of axonal degeneration in sciatic nerve as well as to effects on red blood cells. The mechanism underlying these effects was investigated in vitro using various cell cultures (permanent rodent cell lines from the nervous system, liver, kidney, skeletal and heart muscle and fibroblasts, primary cortical neurons and erythrocytes from the rat). Added to cultured rat cortical neurons for 1 week, fentrazamide considerably decreased glucose consumption, ATP levels and mitochondrial membrane potential and lowered the GSH level, however, it had little impact on viability and neurofilaments and did not induce oxidative stress (ROS) over the first 2 h.

Critical analysis of potential body temperature confounders on neurochemical endpoints caused by direct dosing and maternal separation in neonatal mice: a study of bioallethrin and deltamethrin interactions with temperature on brain muscarinic receptors.

The present investigation was conducted to understand better possible confounding factors caused by direct dosing of neonatal mice during the pre-weaning developmental period. By direct dosing, pups might encounter thermal challenges when temporarily removed from their 'natural habitat'. Typically, this leads to a cold environment and food deprivation (impaired lactation) and modulation of the toxic potency of the substance administered.

Effects of the dithiocarbamate fungicide propineb in primary neuronal cell cultures and skeletal muscle cells of the rat.

After repeated-dose toxicity studies with the fungicide propineb, reversible effects on muscle functions were found. Therefore, mechanistic investigations should contribute to clarification of its mode of action in relation to disulfiram and diethyldithiocarbamate neurotoxicity or direct effects on muscle cells. In principle, besides the dithiocarbamate effects, two different mechanisms have been discussed for this fungicide.

Neurotoxic mode of action of artemisinin.

We recently described a screening system designed to detect neurotoxicity of artemisinin derivatives based on primary neuronal brain stem cell cultures (G. Schmuck and R. K.