Nanoparticle-Encapsulated Bryostatin-1 Activates α-Secretase and PKC Isoforms In vitro and Facilitates Acquisition and Retention of Spatial Learning in an Alzheimer's Disease Mouse Model

BACKGROUND

Alzheimer's disease (AD) animal models have revealed neuroprotective actions of Bryostatin-1 mediated by activation of novel PKC isoforms, suppression of beta-amyloid and downregulation of inflammatory and angiogenic events, making Bryostatin-1 an attractive candidate for attenuating AD-associated neural, vascular, and cognitive disturbances.

OBJECTIVE

To further enhance Bryostatin-1 efficacy, nanoparticle-encapsulated Bryostatin-1 formulations were prepared.

METHODS

We compared nano-encapsulated and unmodified Bryostatin-1 in in vitro models of neuronal PKC-d, PKC-e isoforms, α-secretase and studied nano-encapsulated Bryostatin-1 in an AD mouse model of spatial memory (BC3-Tg (APPswe, PSEN1 dE9) 85Dbo/J mice).

RESULTS

We found that nanoencapsulated Bryostatin-1 formulations displayed activity greater or equal to that of unmodified Bryostatin-1 in PKC-δ and -ε and α-secretase activation assays. We next evaluated how treatment with a nanoencapsulated Bryostatin-1 formulation facilitated spatial learning in the Morris water maze. AD transgenic mice (6.5 to 8 months of age) were treated with nanoparticle encapsulated Bryostatin-1 formulation (1, 2.5, or 5 μg/mouse) three times the week before testing and then daily for each of the 5 days of testing. Across the acquisition phase, mice treated with nanoencapsulated Bryostatin-1 had shorter latencies, increased % time in the target zone and decreased % time in the opposite quadrant. The mice were given retention testing after a 2-week period without drug treatment. Mice treated with nanoencapsulated Bryostatin-1 had shorter latencies to find the escape platform, indicating retention of spatial memory.

CONCLUSION

These data suggest that cognitive deficits associated with AD could be treated using highly potent nanoparticle-encapsulated formulations of Bryostatin-1.

Measurement of nanoparticle concentration using quartz crystal microgravimetry

Various nanoscale items (e.g., nanoparticles and nanotubes) have been actively investigated due to their unique physicochemical properties. A common issue encountered in such studies is accurate expression of nanoparticle concentration. Given the critical importance of the dose-response relationship, we present the use of quartz crystal microgravimetry (QCM) to accurately measure nanoparticle concentration in a colloidal suspension. Application of a small drop of the nanoparticle suspension in a volatile solvent to the crystal surface leaves a dry nanoparticle residue after solvent evaporation after which the shift in the crystal resonant frequency is recorded. The instrument was calibrated using a set of serial dilutions of Si and Ag nanopowder in methanol, rhodamine B in methanol, and ferrocene in cyclohexane. Using QCM, a linear response for nanoparticle concentrations up to 1300 μg/mL was determined. The developed method was used to determine the concentrations of size-selected, octyl-terminated Si nanocrystal samples with median diameters in the range 1.1-14.8 nm and also to calculate size-dependent nanocrystal extinction coefficients.