ABSTRACT
Penitrem A is a fungal neurotoxin that recurrently causes intoxication in animals, and occasionally also in humans. We have previously reported that penitrem A induced the production of reactive oxygen species (ROS) in rat cerebellar granule cells, opening for a new mechanism of action for the neurotoxin. The aim of this study was to examine the potential of penitrem A to induce ROS production in isolated human neutrophil granulocytes, and to study possible mechanisms involved. Penitrem A significantly increased the production of ROS in human neutrophils at concentrations as low as 0.25µM (40% increase over basal levels), as measured with the DCF fluorescence assay. The EC50 determined for the production of ROS by penitrem A was 3.8µM. The maximal increase in ROS production was approximately 330% over basal levels at a concentration of 12.5µM. ROS formation was significantly inhibited by the antioxidant vitamin E (50µM), the intracellular Ca+2 chelator BAPTA-AM (5µM), the mitogen activated protein kinase kinase (MEK) 1/2 and 5 inhibitor U0126 (1 and 10µM), the p38 mitogen activated protein kinase (MAPK) inhibitor SB203580 (1µM), the c-Jun amino-terminal kinase (JNK) inhibitor SP600125 (10µM), and the calcineurin inhibitors FK-506 and cyclosporine A (1.5 and 0.5µM, respectively). These finding suggest that penitrem A is able to induce an increase in ROS production in neutrophils via the activation of several MAPK-signalling pathways. We suggest that this increase may partly explain the pathophysiology generated by penitrem A neuromycotoxicosis in both humans and animals.
Subject(s)
Mycotoxins/toxicity , Neurotoxins/toxicity , Neutrophils/drug effects , Reactive Oxygen Species/metabolism , Anthracenes/pharmacology , Antioxidants/pharmacology , Calcineurin/pharmacology , Cell Line , Cyclosporine/pharmacology , Granulocytes/drug effects , Granulocytes/metabolism , Humans , Imidazoles/pharmacology , Inhibitory Concentration 50 , JNK Mitogen-Activated Protein Kinases/antagonists & inhibitors , JNK Mitogen-Activated Protein Kinases/metabolism , Neutrophils/metabolism , Pyridines/pharmacology , Tacrolimus/pharmacology , Vitamin E/pharmacology , p38 Mitogen-Activated Protein Kinases/antagonists & inhibitors , p38 Mitogen-Activated Protein Kinases/metabolismABSTRACT
The fungal neurotoxin penitrem A has previously been found to cause neurological disorders in animals and humans after ingestion of contaminated food and/or feed. It penetrates the blood-brain-barrier and causes cerebellar pathology in rats, including mild effects on granule neurons. The aim of the current study was to investigate the potential toxicity of penitrem A in rat cerebellar granule neurons in vitro, and to examine the involvement of the GABAA, AMPA and NMDA receptors, intracellular signalling pathways as well as the role of oxidative stress in penitrem A-induced neuronal death. Cerebellar granule cells were exposed to penitrem A, alone or together with different pharmacological agents, before cell survival was assessed with the MTT assay or formation of reactive oxygen species (ROS) was investigated with the DCF assay. Penitrem A caused a time- and concentration-dependent reduction in cell survival, as well as a concentration-dependent increase in ROS production. Co-incubation with diazepam, GABA, BAPTA-AM, vitamin E, SP600125 and cyclosporine A significantly reduced cell death. Our results show that penitrem A is toxic to cerebellar granule neurons in vitro. Further, ROS production and the GABAA receptor are likely to be involved in the induction of neuronal death following penitrem A exposure. A disruption of calcium homeostasis and activation of the JNK pathway may also play a role in penitrem A neurotoxicity.
Subject(s)
Cerebellum/drug effects , Mycotoxins/toxicity , Neurons/drug effects , Oxidative Stress/drug effects , Receptors, GABA-A/drug effects , Animals , Animals, Newborn , Calcium/metabolism , Cell Death/drug effects , Cells, Cultured , Cerebellum/metabolism , Cerebellum/pathology , Cytoprotection , Dose-Response Relationship, Drug , Female , JNK Mitogen-Activated Protein Kinases/metabolism , Male , Neurons/metabolism , Neurons/pathology , Neuroprotective Agents/pharmacology , Rats , Rats, Wistar , Reactive Oxygen Species/metabolism , Receptors, GABA-A/metabolism , Signal Transduction/drug effects , Time FactorsABSTRACT
Fungi in the genus Penicillium, particularly P. crustosum, produce tremorgenic mycotoxins, as well as suspected tremorgenic compounds. The accidental intoxication of six dogs with such toxins are reported. The clinical signs included vomiting, convulsions, tremors, ataxia, and tachycardia, all of which are indicators of intoxications affecting the nervous system. This symptomatology caused us to think that the dog poisoning was the result of tremorgenic mycotoxins. One dog was euthanized in the acute phase, while three others recovered completely within a few days. However, neurological symptoms were still observed four months after the poisoning of two of the dogs. One of these recovered completely within the next 2-3 months, while the other still suffers from ataxia three years later. Available samples of feed, stomach content and/or tissues from the intoxications were subjected to mycological and chemical analysis. Penitrem A was found in all reported poisonings and roquefortine C in all cases when this toxin was included in the analysis. The producer of these toxins, Penicillium crustosum, was detected in all cases where material suitable for mycological examinations (feed or vomit) was available. To our knowledge, this is the first report documenting the presence of penitrems and roquefortine C in organs from poisoned dogs. Furthermore, the report indicates that the recovery period after severe poisonings with P. crustosum may be protracted.
