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Title: Antiprion activity of DB772 and related monothiophene-and furan-based analogs in a persistently infected ovine microglia culture system

item DINKEL, KELCEY - Washington State University
item STANTON, JAMES - University Of Georgia
item BOYKIN, DAVID - Georgia State University
item STEPHENS, CHAD - Augusta University
item MADSEN-BOUTERSE, SALLY - Washington State University
item Schneider, David

Submitted to: Antimicrobial Agents and Chemotherapy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2016
Publication Date: 7/5/2016
Citation: Dinkel, K.D., Stanton, J.B., Boykin, D.W., Stephens, C.E., Madsen-Bouterse, S.A., Schneider, D.A. 2016. Antiprion activity of DB772 and related monothiophene-and furan-based analogs in a persistently infected ovine microglia culture system. Antimicrobial Agents and Chemotherapy. 60(9):5467-5482.

Interpretive Summary: Scrapie is the naturally transmissible prion disease of sheep and goats. Like the prion diseases of other species, scrapie infection is associated with a progressive accumulation of misfolded prion protein in cells of the central nervous system that ultimately results in fatal neurodegeneration. Currently, there is no effective treatment. We recently reported on the anti-prion activity of a novel compound, DB772, in cultured sheep microglia—a cell type of the central nervous system that is naturally infected by scrapie prions. Now, having similarly tested a library of compounds structurally related to DB772, we have identified eleven more DB compounds with similar or improved anti-prion activity. The data revealed structural elements key to the anti-prion activity of DB compounds and further suggests a mechanism of action targeting prion replication to reduce cellular accumulation of misfolded prion protein. This research provides an important advance in knowledge relevant to the development of an effective therapeutic agent for prion disease.

Technical Abstract: The transmissible spongiform encephalopathies are fatal neurodegenerative disorders characterized by the misfolding of the native cellular prion protein (PrP-C) into the accumulating, disease-associated isoform (PrP-Sc). Despite extensive research into the inhibition of prion accumulation, no effective treatment exists. Previously, we demonstrated the inhibitory activity of DB772, a monocationic phenyl-furan-benzimidazole, against PrP-Sc accumulation in sheep microglial cells. In an effort to determine the effect of structural substitutions on the anti-prion activity of DB772, we employed an in vitro strategy to survey a library of structurally-related, monothiophene/furan-based compounds for improved inhibitory activity. Eighty-nine compounds were screened at 1 µM for effects on cell viability and prion accumulation in a persistently infected ovine microglia culture system. Eleven compounds with equivalent or higher activity than DB772 were identified as preliminary hit compounds. For the preliminary hits, cytotoxicity and anti-prion activity were compared to calculate the tissue-culture selectivity index. A structure-activity relationship (SAR) analysis was performed to determine molecular components contributing to anti-prion activity. To investigate potential mechanisms of inhibition, effects on PrP-C and PrP-Sc were examined. While inhibition of total PrP-C was not observed, the results suggest that a potential target for inhibition at biologically relevant concentrations is through PrP-C misfolding to PrP-Sc. Further, SAR analysis suggested that two structural elements were associated with micromolar anti-prion activity. Taken together, the described data will provide a foundation for deeper investigation into previously untested DB compounds, and will aid in future design of effective therapeutics and the elucidation of mechanisms of prion diseases.