Age-progressive neurodegenerative pathologies, including Alzheimer's disease (AD), are distinguished and diagnosed by disease-specific components of intra-or extracellular aggregates. Increasing evidence suggests that neuroinflammation promotes protein aggregation, and is involved in the etiology of neurological diseases. We synthesized and tested analogs of the naturally occurring tubulin-binding compound, combretastatin A-4. One such analog, PNR502, markedly reduced the quantity of Alzheimer-associated amyloid aggregates in the BRI-Aβ 1-42 mouse model of AD, while blunting the ability of the pro-inflammatory cytokine IL-1β to raise levels of amyloid plaque and its protein precursors in a neuronal cell-culture model. In transgenic Caenorhabditis elegans (C. elegans) strains that express human Aβ 1-42 in muscle or neurons, PNR502 rescued Aβ-induced disruption of motility (3.8-fold, P < 0.0001) or chemotaxis (1.8-fold, P < 0.05), respectively. Moreover, in C. elegans with neuronal expression of Aβ 1-42 , a single day of PNR502 exposure reverses the chemotaxis deficit by 54% (P < 0.01), actually exceeding the protection from longer exposure. Moreover, continuous PNR502 treatment extends nematode lifespan 23% (P ≤ 0.001). Given that PNR502 can slow, prevent, or reverse Alzheimer-like protein aggregation in human-cell-culture and animal models, and that its principal predicted and observed binding targets are proteins previously implicated in Alzheimer's, we propose that PNR502 has therapeutic potential to inhibit cerebral Aβ 1-42 aggregation and prevent or reverse neurodegeneration.
Morphine‐6‐O‐sulfate (M6S) is as a mixed‐action mu/delta (μ/δ) opioid receptor agonist with high potency and analgesic efficacy. These studies used assays of drug discrimination and schedule‐controlled responding to assess abuse‐liability, tolerance, and physical dependence as compared to morphine in rats. Attempts to train 0.3 mg/kg (IP) M6S from saline failed, but all rats rapidly acquired the discrimination when the training dose was changed to 3.0 mg/kg morphine, and substitution tests showed that morphine and fentanyl both fully substituted for the training dose, M6S and M3A6S (3‐O‐acetyl ester of M6S) only partially substituted, and salvinorin A did not elicit morphine‐like effects. Tolerance to response rate‐decreasing effects was studied in rats administered either 1.0 or 3.0 mg/kg morphine or M6S before food‐reinforced operant sessions. At both unit doses, tolerance to M6S‐elicited rate suppression developed more slowly than tolerance to morphine‐induced reductions in response rates. To assess dependence, rats were maintained on 1.0 mg/kg morphine or 1.0 mg/kg M6S until food‐reinforced response rates were stable for at least 5 days. Rats were then administered saline or increasing doses of the opioid antagonist naltrexone (NTX) (0.3, 1.0, 3.0, or 10.0 mg/kg) in order to determine antagonist‐precipitated withdrawal. NTX precipitated withdrawal was similar in both morphine‐maintained and M6S‐maintained rats. In conclusion, the mixed μ/δ agonist activity of M6S failed to completely protect against the development of physical dependence, but delayed tolerance development to behavioral effects and resulted in decreased morphine‐like subjective effects, perhaps implying a decreased abuse liability over μ agonists.
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