Therapeutic activity of inhibition of the soluble epoxide hydrolase in a mouse model of scrapie

Abstract

Aims: The misfolding and the aggregation of specific proteins are key features of neurodegenerative diseases, specifically Transmissible Spongiform Encephalopathies (TSEs). In TSEs, neuronal loss and inflammation are associated with the accumulation of the misfolded isoform (PrP(sc)) of the cellular prion protein (PrP(c)). Therefore we tested the hypothesis that augmenting a natural anti-inflammatory pathway mediated by epoxygenated fatty acids (EpFAs) will delay lethality. EpFAs are highly potent but enzymatically labile molecules produced by the actions of a number of cytochrome P450 enzymes. Stabilization of these bioactive lipids by inhibiting their degradation mediated by the soluble epoxide hydrolase (sEH) results in potent anti-inflammatory effects in multiple disease models.

Main methods: Mice were infected with the mouse-adapted RML strain of scrapie by intracerebral or intraperitoneal routes. Animals received the sEH inhibitor, by oral route, administrated in drinking water or vehicle (PEG400). Infected mice were euthanized at a standard clinical end point. Histopathological, immunohistochemical and Western blot analyses of brain tissue confirmed the presence of pathology related to prion infection.

Key findings: Oral administration of the sEHI did not affect the very short survival time of the intracerebral prion infection group. However, mice infected by intraperitoneal route and treated with t-AUCB survived significantly longer than the control group mice (p<0.001).

Significance: These findings support the idea that inhibition of sEH or augmentation of the natural EpFA signaling in the brain offers a potential and different route to understand prion diseases and may become a therapeutic strategy for diseases involving neuroinflammation.

Fig. 1

Inhibition of sEH by orally administered inhibitor delays lethality of prion infection. A) Mice inoculated by intracerebroventricular (i.c.) route and administered vehicle (PEG400, 1% in drinking water) displayed median survival time of 163 days which was not significantly different than the group receiving 1 mg/kg/day t-AUCB which had a median survival time of 165 days (log-rank test p = 0.86). B) Mice inoculated by intraperitoneal (i.p.) route and administered vehicle (PEG400, 1% in drinking water) displayed a delayed median survival time of 207 days compared to i.c. inoculation. This survival time was further delayed in the t-AUCB (1 mg/kg/day in drinking water) treatment groups which had a median survival time of 216 days (log-rank test p = 0.025).

Fig. 2

Analysis of brain of mice by Western-blotting demonstrates equal prion load in t-AUCB and vehicle treated mice. All samples were treated with proteinase K prior to SDS–PAGE separation. All animals were subjected to Western blot analysis with positive results (n = 15 for vehicle and n = 14 for t-AUCB group). Representative samples are shown in the figure. In the first column from the left brain homogenates of con-firmed positive control prion infected mice are displayed. The second column displays brain samples of negative control mice inoculated (i.p.) with brain homogenates of healthy mice. In subsequent columns α1–6 denote i.p. infected + vehicle animals and β1–7 denote i.p. infected + t-AUCB treated animals.