Benzyl quinolone carboxylicacid (BQCA) is a recently described cholinergic muscarinic M1 receptor positive allosteric modulator having potential as cognitive enhancer in Alzheimer's disease (AD). The clinical failures of most of the potentially effective therapeutics to treat the CNS disorders are often not due to a lack of drug potency but rather shortcomings in the method by which the drug is delivered. The limitations imposed by the blood-brain barrier (BBB) and the non-selective distribution of drugs in the brain have hindered the effective treatment of AD and may result in severe side effects on the normal brains. Dual functional ligands are a crucial component of the dual targeted delivery system. To overcome the first barrier of AD treatment, targeting ligands must be chosen to overcome the BBB. Accordingly, TGNYKALHPHNG (denoted as TGN) was employed as the first-order ligand for targeting and penetrating the BBB. Aβ 1-42 in the amyloid plaques is a target for AD therapy. A D-enantiomeric peptide, QSHYRHISPAQV (denoted as QSH), binds Aβ 1-42 in the sub-micromolar range and stains Aβ 1-42 deposits in the brains of both AD model rat and humans. In this study, we constructed a dual-functional targeted poly lactide-co-glycolide (PLGA) nanoparticle system (NPs), modified with both TGN and QSH for delivering BQCA loaded NPs to AD brain lesions and evaluated for in vitro cytotoxicity using SK-N-SH cells (a human neuroblastoma cell line), tissue and brain distribution studies and Morris Water Maze Test to evaluate learning and memory capacities in streptozotocin-induced rat model. The developed NPs did not cause any inhibition of growth and were non-toxic to the SK-N-SH cells and hence safe for brain delivery and also achieved enhanced and precise targeted delivery to amyloid plaque in the brains of AD model rat compared to the unmodified NPs and the free drug. When administration of dual ligand conjugated PLGA NPs of BQCA in streptozotocin-induced animals significantly decreased escape latency (Fig 1). A dual-functional drug delivery system was developed to target AD lesions using TGN and QSH appended to the surface of BQCA loaded PLGA NPs and demonstrate might be a valuable targeting system for treatment of AD. Treatment with BQCA and BQCA loaded NPs in STZ induced rats reverses the reference and working memory deficits in Radial Arm Maze task. Data expressed as mean ± SD (n=10). Significance was determined by two-way ANOVA followed by Bonferroni post-test. ###P < 0.001, ##P < 0.01 vs sham control, ***P < 0.001, **P < 0.01, *P < 0.05 vs negative control were considered significant. (A) Reference memory errors, (B) correct working memory errors and (C) incorrect working memory errors. Treatment with BQCA and BQCA loaded NPs in STZ induced rats reverses the spatial learning deficits in HB task. Data expressed as mean ± SD (n =10). Significance was determined by two-way ANOVA followed by Bonferroni post-test. ###P < 0.001, ##P < 0.01 vs sham control, ***P < 0.001, **P < 0.01, *P < 0.05 vs negative control were considered significant. (A) Number of hits, (B) number of errors and (C) trial completion time.

A comparative pharmacokinetic analysis and tissue distribution of BQCA in rat plasma visceral organs.

Benzyl quinolone carboxylic acid (BQCA) is a novel highly selective allosteric potentiator of M1 Muscarinic acetylcholine receptor over other subtypes in a way that effectively enhancing the cognitive effect by reducing Aβ42 peptides without producing unwanted cholinergic side effects and increases activity of medial prefrontal cortical neurons and restores impairments in reversal learning. Central nervous system drug efficacy depends upon the ability of a drug to cross the blood-brain barrier and reach therapeutic concentrations in brain following systemic administration. The clinical failures of most of the potentially effective therapeutics to treat the central nervous system disorders are often not due to a lack of drug potency but rather shortcomings in the method by which the drug is delivered. Drugs deliver through nano-drug delivery could enhance neuroprotection by rapid accumulation of drugs in the brain and a slow metabolism of the compound. Hence, considering the importance of treating AD, we made an attempt to target the allosteric potentiator BQCA in the brain by using poly lactide-co-glycolide (PLGA) nanoparticles (NPs) coated with polysorbate-80 and evaluated brain targeting efficacy of BQCA after intravenous injection in rats as BQCA was administered alone, bound to NPs and also bound to NPs coated with polysorbate-80 and also evaluated influence of developed NPs of BQCA on learning and memory capacities, Morris Water Maze Test was performed in streptozotocin-induced rat model. In the brain a significant increase in BQCA concentration was observed in the case of polysorbate-80 coated PLGA NPs compared to the uncoated NPs and the free drug. Administration of BQCA solution in streptozotocin-induced animals did not result in any noticeable improvement in learning and memory capacities, whereas administration of polysorbate-80 coated PLGA NPs of BQCA in streptozotocin-induced animals significantly (P < 0.05) decreased escape latency. These results indicated that, compared to BQCA solution polysorbate-80 coated PLGA NPs of BQCA resulted in faster memory regain in streptozotocin-induced animals. In conclusion, these results demonstrate the effectiveness of developed NPs of BQCA in brain targeting and preventing the cognitive deficits caused by streptozotocin-induced in rats and its potential in the treatment of AD.