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Combined pharmacological induction of Hsp70 suppresses prion protein neurotoxicity in Drosophila.

Zhang Y, Casas-Tinto S, Rincon-Limas DE, Fernandez-Funez P - PLoS ONE (2014)

Bottom Line: To validate the therapeutic potential of Hsp70, we treated flies with drugs known to induce Hsp70 expression, including the Hsp90 inhibitor 17-DMAG and the glucocorticoid dexamethasone.Although the individual treatment with these compounds produced no significant benefits, their combination significantly increased the level of inducible Hsp70, decreased the level of total PrP, reduced the accumulation of pathogenic PrP conformers, and improved locomotor activity.Thus, the combined action of two pharmacological activators of Hsp70 with distinct targets results in sustained high levels of inducible Hsp70 with improved behavioral output.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, McKnight Brain Institute, University of Florida, Gainesville, Florida, United States of America.

ABSTRACT
Prion diseases are rare and aggressive neurodegenerative disorders caused by the accumulation of misfolded, toxic conformations of the prion protein (PrP). Therapeutic strategies directed at reducing the levels of PrP offer the best chance of delaying or halting disease progression. The challenge, though, is to define pharmacologic targets that result in reduced PrP levels. We previously reported that expression of wild type hamster PrP in flies induces progressive locomotor dysfunction and accumulation of pathogenic PrP conformations, while co-expression of human Hsp70 delayed these changes. To validate the therapeutic potential of Hsp70, we treated flies with drugs known to induce Hsp70 expression, including the Hsp90 inhibitor 17-DMAG and the glucocorticoid dexamethasone. Although the individual treatment with these compounds produced no significant benefits, their combination significantly increased the level of inducible Hsp70, decreased the level of total PrP, reduced the accumulation of pathogenic PrP conformers, and improved locomotor activity. Thus, the combined action of two pharmacological activators of Hsp70 with distinct targets results in sustained high levels of inducible Hsp70 with improved behavioral output. These findings can have important therapeutic applications for the devastating prion diseases and other related proteinopathies.

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Related in: MedlinePlus

Dexamethasone has no effect on PrP expression.A, Flies expressing PrP ubiquitously (da>PrP-M9) were fed with 17-DMAG at 0, 6, 12, 24, and 48 µg/ml during development. Analysis of PrP levels in 1 day-old flies by western blot showed no significant changes. Tubulin was used as loading control to normalize protein levels. B, Quantification of triplicate experiment followed by analysis with ANOVA. No statistical differences were identified in these experiments.
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pone-0088522-g002: Dexamethasone has no effect on PrP expression.A, Flies expressing PrP ubiquitously (da>PrP-M9) were fed with 17-DMAG at 0, 6, 12, 24, and 48 µg/ml during development. Analysis of PrP levels in 1 day-old flies by western blot showed no significant changes. Tubulin was used as loading control to normalize protein levels. B, Quantification of triplicate experiment followed by analysis with ANOVA. No statistical differences were identified in these experiments.

Mentions: An alternative to using higher concentration of geldanamycin derivatives was to identify a second drug that could reinforce the activity of 17-DMAG. A literature search identified dexamethasone as an FDA-approved glucocorticoid that induces Hsp70 by promoting the stability of HSF1 on the Hsp70 promoter [26]. To examine the effect of dexamethasone on PrP accumulation, we raised flies expressing PrP ubiquitously as described above in fly media containing dexamethasone at concentrations from 6 to 48 µg/ml. Then, we collected 1 day-old flies, performed western blot, quantified the bands, and normalized the expression with tubulin to compare the three independent experiments. Overall, no dexamethasone treatment produced significant differences (Fig. 2 and Table 2). Although the 12 µg/ml treatment showed 30% higher levels of PrP, this difference was not significant (p = 0.07). Thus, neither 17-DMAG nor dexamethasone had significant effects on PrP steady-state levels when used alone.


Combined pharmacological induction of Hsp70 suppresses prion protein neurotoxicity in Drosophila.

Zhang Y, Casas-Tinto S, Rincon-Limas DE, Fernandez-Funez P - PLoS ONE (2014)

Dexamethasone has no effect on PrP expression.A, Flies expressing PrP ubiquitously (da>PrP-M9) were fed with 17-DMAG at 0, 6, 12, 24, and 48 µg/ml during development. Analysis of PrP levels in 1 day-old flies by western blot showed no significant changes. Tubulin was used as loading control to normalize protein levels. B, Quantification of triplicate experiment followed by analysis with ANOVA. No statistical differences were identified in these experiments.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3921213&req=5

pone-0088522-g002: Dexamethasone has no effect on PrP expression.A, Flies expressing PrP ubiquitously (da>PrP-M9) were fed with 17-DMAG at 0, 6, 12, 24, and 48 µg/ml during development. Analysis of PrP levels in 1 day-old flies by western blot showed no significant changes. Tubulin was used as loading control to normalize protein levels. B, Quantification of triplicate experiment followed by analysis with ANOVA. No statistical differences were identified in these experiments.
Mentions: An alternative to using higher concentration of geldanamycin derivatives was to identify a second drug that could reinforce the activity of 17-DMAG. A literature search identified dexamethasone as an FDA-approved glucocorticoid that induces Hsp70 by promoting the stability of HSF1 on the Hsp70 promoter [26]. To examine the effect of dexamethasone on PrP accumulation, we raised flies expressing PrP ubiquitously as described above in fly media containing dexamethasone at concentrations from 6 to 48 µg/ml. Then, we collected 1 day-old flies, performed western blot, quantified the bands, and normalized the expression with tubulin to compare the three independent experiments. Overall, no dexamethasone treatment produced significant differences (Fig. 2 and Table 2). Although the 12 µg/ml treatment showed 30% higher levels of PrP, this difference was not significant (p = 0.07). Thus, neither 17-DMAG nor dexamethasone had significant effects on PrP steady-state levels when used alone.

Bottom Line: To validate the therapeutic potential of Hsp70, we treated flies with drugs known to induce Hsp70 expression, including the Hsp90 inhibitor 17-DMAG and the glucocorticoid dexamethasone.Although the individual treatment with these compounds produced no significant benefits, their combination significantly increased the level of inducible Hsp70, decreased the level of total PrP, reduced the accumulation of pathogenic PrP conformers, and improved locomotor activity.Thus, the combined action of two pharmacological activators of Hsp70 with distinct targets results in sustained high levels of inducible Hsp70 with improved behavioral output.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, McKnight Brain Institute, University of Florida, Gainesville, Florida, United States of America.

ABSTRACT
Prion diseases are rare and aggressive neurodegenerative disorders caused by the accumulation of misfolded, toxic conformations of the prion protein (PrP). Therapeutic strategies directed at reducing the levels of PrP offer the best chance of delaying or halting disease progression. The challenge, though, is to define pharmacologic targets that result in reduced PrP levels. We previously reported that expression of wild type hamster PrP in flies induces progressive locomotor dysfunction and accumulation of pathogenic PrP conformations, while co-expression of human Hsp70 delayed these changes. To validate the therapeutic potential of Hsp70, we treated flies with drugs known to induce Hsp70 expression, including the Hsp90 inhibitor 17-DMAG and the glucocorticoid dexamethasone. Although the individual treatment with these compounds produced no significant benefits, their combination significantly increased the level of inducible Hsp70, decreased the level of total PrP, reduced the accumulation of pathogenic PrP conformers, and improved locomotor activity. Thus, the combined action of two pharmacological activators of Hsp70 with distinct targets results in sustained high levels of inducible Hsp70 with improved behavioral output. These findings can have important therapeutic applications for the devastating prion diseases and other related proteinopathies.

Show MeSH
Related in: MedlinePlus