Consequences of dietary manganese and copper imbalance on neuronal apoptosis in a murine model of scrapie.

AIMS: Copper and manganese levels are altered in mice both lacking PrPc and prion-infected brains. The aim of this study was to analyse the effects of manganese and copper imbalance on neuronal apoptosis in a scrapie-infected Tga20 mouse model. METHODS: Immunoreactivities for the apoptotic proteins Bax and active caspase-3 were evaluated in nine regions of the brain of scrapie-infected and control Tga20 mice treated with one of several diets: depleted cooper (-Cu), loaded manganese (+Mn), depleted copper/loaded manganese (-Cu+Mn) and regular diet. Immunohistochemical determination of NeuN was used to detect possible neuronal loss. RESULTS: Intracellular Bax detection was significantly decreased in animals fed with modified diets, particularly in those treated with copper-depleted diets. A decrease in active caspase-3 was primarily observed in animals fed with enhanced manganese diets. Our results show that the -Cu, -Cu+Mn and +Mn diets protected against apoptosis in scrapie-infected mice. However, NeuN immunolabelling quantification revealed that no diet was sufficient to arrest neuronal death. CONCLUSIONS: With regard to apoptosis induction, the response of Tga20 mice to prion infection was similar to that reported for other mice models. Our results demonstrate the neuroprotective effects of -Cu, -Cu+Mn and +Mn diets in a murine model of scrapie. However, neuronal death induced by infection with prions seems to be independent of apoptosis marker signalling. Moreover, copper-modified diets were neuroprotective against the possible toxicity of the prion transgene in Tga20 control and infected mice even though manganese supplementation could not counteract this toxicity.

Approaches to Scrapie diagnosis by applying immunohistochemistry and rapid tests on central nervous and lymphoreticular systems.

Comparative studies evaluating the performance of Transmissible Spongiform Encephalopathies (TSE) rapid tests (validated for Bovine Spongiform Encephalopathy samples) on Scrapie samples have not been reported widely, particularly those dealing with lymphoreticular system tissues to a much lesser extent. The main objective of this study was to compare the ability of two current rapid tests (Western blot and Luminiscence Immunoassay Prionics-Check; WB and LIA, respectively) to detect PrPsc using central nervous system as well as lymphoreticular system samples corresponding to naturally infected animals. Thirty-four Scrapie-affected sheep, 26 with clinical signs of the disease, were included in the study. Tonsil, retropharyngeal lymph node and medulla oblongata were assessed by three tests: immunohistochemistry (confirmatory test), WB and LIA (rapid tests). The conclusion which can be drawn from this study is the fact that all animals involved in the study, including those at a preclinical stage, could be diagnosed regardless of the test used (with immunohistochemistry consistently showing higher sensitivity) only when the analyses of both the central nervous system and the lymphoreticular system were considered. The choice of these tissues for routine diagnosis is, therefore, proposed as a valuable tool to highly reduce the number of undetected positive cases.

Emboli in bulls killed in Spanish traditional bullfighting.

The finding of brain tissue fragments in blood and lungs of cattle stunned in slaughterhouses has raised concerns about food safety in the context of the bovine spongiform encephalopathy epidemic. In the present study, the possible occurrence of brain tissue emboli in animals killed in traditional Spanish bullfighting was investigated. Thorough histological analysis of multiple possible target organs was carried out in 434 bulls. No evidence of brain tissue embolism was obtained, but emboli from diverse sources were detected in pulmonary and hepatic tissue of a significant number of animals. These emboli seem to have been caused by the use of a long sword, which extensively disrupts intra-thoracic and intra-abdominal organs and vascular structures.

The effect of metal imbalances on scrapie neurodegeneration.

Environmental exposure to metal appears to enhance susceptibility to Transmissible Spongiform Encephalopathies (TSEs); however, published data are not conclusive. The current study focuses on assessing the effects of copper depletion and/or manganese enhancement in the diet on susceptibility to Scrapie and this disease progression. The degree of spongiosis was the highest in the animals that received a copper- depleted diet. These observations suggest that this diet contributes to the Scrapie lesions and to the worsening of the condition in animals that have been inoculated with Scrapie. The highest intensities of GFAP immunostaining were also associated with the copper- depleted diet. Dietary supplementation with manganese had a negative effect on neuronal counts. In conclusion, this study demonstrates that certain environmental factors may aggravate neuropathological Scrapie lesions. This is consistent with reports from other neurodegenerative diseases where some metalloenzymes play a pivotal protector role against the oxidative stress associated with pathogenesis.

Effect of the dimethoate administration on a Scrapie murine model.

Some authors have associated organophosphate compounds with susceptibility to transmissible spongiform encephalopathy (TSE) and even with the origin of this group of diseases. Nevertheless, the actual role played by these compounds still remains unclear. The aim of this study was to assess the effect of oral exposure to dimethoate (DMT) on the development of Scrapie using a genetically modified murine model. A total of 70 C57BL/6 mice over-expressing the PrP gene (Tg20) were included in the present study. A portion of the mice were intraperitoneally inoculated, while the rest were maintained as non-infected controls. Animals from the treated group were exposed to dimethoate dissolved in drinking water from the beginning of the experiment. Variables of incubation period, spongiosis, PrPsc deposits, glial over-expression, neuronal loss, and amyloid plaques were assessed in all animals. According to the results, a treatment consisting of a daily 15 mg/kg dose of DMT for 5 weeks did not show any effect on any of the variables assessed. Although more exhaustive studies for assessing different doses and organic compounds are required, this finding constitutes an empirical study that rules out the possibility that this compound may have a predisposing effect on TSEs.