Novel therapeutic strategy for neurodegeneration by blocking Aß seeding mediated aggregation in models of Alzheimer's disease.

Aß accumulation plays a central role in the pathogenesis of Alzheimer's disease (AD). Recent studies suggest that the process of Aß nucleated polymerization is essential for Aß fibril formation, pathology spreading and toxicity. Therefore, targeting this process represents an effective therapeutic strategy to slow or block disease progression. To discover compounds that might interfere with the Aß seeding capacity, toxicity and pathology spreading, we screened a focused library of FDA-approved drugs in vitro using a seeding polymerization assay and identified small molecule inhibitors that specifically interfered with Aß seeding-mediated fibril growth and toxicity. Mitoxantrone, bithionol and hexachlorophene were found to be the strongest inhibitors of fibril growth and protected primary cortical neuronal cultures against Aß-induced toxicity. Next, we assessed the effects of these three inhibitors in vivo in the mThy1-APPtg mouse model of AD (8-month-old mice). We found that mitoxantrone and bithionol, but not hexachlorophene, stabilized diffuse amyloid plaques, reduced the levels of Aß42 oligomers and ameliorated synapse loss, neuronal damage and astrogliosis. Together, our findings suggest that targeting fibril growth and Aß seeding capacity constitutes a viable and effective strategy for protecting against neurodegeneration and disease progression in AD.

Effect of urinary alkalinisation and acidification on the tissue distribution of hexachlorophene in rats.

1. Urinary alkalinisation may be helpful in treating acute poisoning with uncouplers of oxidative phosphorylation containing a phenolic hydroxyl (pKa 4-6) or other acidic moiety. 2. We studied the effects of urine alkalinisation and acidification on the tissue distribution of hexachlorophene (HCP, pKa 5.7) in male Sprague Dawley rats (10 rats/group). 3. Ammonium chloride (10 mL kg-1, 2% m/v) or sodium bicarbonate (10 mL kg-1, 2% m/v) were administered by gavage on three occasions over 24 h, prior to a single gavage dose of HCP (180 mg kg-1). Controls received aqueous sodium chloride (10 mL kg-1, 0.9% m/v) followed by either HCP (180 mg kg-1) or vehicle alone. 4. Urine pH, body mass and body temperature were monitored during the study and, at the conclusion of the experiment (12 h post-HCP dose), organ mass (liver, kidney, brain), and plasma, urine and tissue HCP concentrations were measured. 5. No clinical features of toxicity were observed in any group. However, sodium bicarbonate significantly reduced median HCP in liver--median plasma and kidney HCP concentrations were also reduced but not significantly. Conversely, ammonium chloride significantly increased median HCP concentrations in liver and kidney--median plasma HCP was also increased but not significantly. 6. The results provide some support for the hypothesis that blood pH influences the tissue distribution of uncouplers of oxidative phosphorylation containing an acidic moiety. Urinary alkalinisation may be useful in treating acute poisoning with these compounds.

Effect of short-term exposure to hexachlorophene on rat brain cell specific marker enzymes.

Seven cell specific marker enzymes in brain and optic nerve and morphological evaluation by light microscopy were used to characterize the neurotoxicity associated with exposure of rats to hexachlorophene (HCP; 40 mg/kg/day, po, for 9 days). In vitro exposure to HCP at concentrations up to 100 microM had no direct inhibitory effect on the marker enzymes, validating their use in evaluating brain function in vivo. Rats exhibited a reduction in body weight gain, weakness, and ataxia of the hind limbs by the ninth day of HCP exposure. At 24 hr following the last day of exposure to HCP, the activities of the three neuron specific enzymes, glutamic acid decarboxylase, tyrosine hydroxylase, and choline acetyltransferase, in rat brain were unchanged from those of the vehicle-treated control group. Of the two astroglial enzyme markers measured, a small but significant increase was observed in the activity of nonneuronal enolase in the cerebellum and glutamine synthetase in the hippocampus of HCP-treated rats. The optic nerve appeared to be the most sensitive tissue in that the activity of both the astroglial marker, nonneuronal enolase, and the myelin marker, 2',3'-cyclic nucleotide phosphohydrolase, was significantly decreased following HCP exposure. This decrease in enzyme activity is consistent with the histological observations demonstrating extensive vacuolization and edema in the optic nerve after exposure to HCP.