👤 Nikitha Srikrishna

The Gastrointestinal (GI) microbiome and gut-brain axis are associated with the progression and pathology of Alzheimer's disease (AD). Amyloid deposition is thought to be a driver of AD, causing synaptic dysfunction and neuronal death in the brain. Chronic constipation is a common gastrointestinal (GI) dysmotility in AD patients, which impacts patient outcomes and quality of life. It is unknown if enteric amyloidosis disrupts myenteric neuron function and causes GI dysmotility. Untreated male and female APP/PS1 (a transgenic murine model of brain amyloidosis) and sex-matched control mice were followed until 12 months of age. A separate cohort of mice was treated with a vehicle or the beta-secretase (BACE1) inhibitor, lanabecestat, starting at 5 months of age until 7 months. GI motility was assessed in all mice by measuring whole GI transit in vivo. Propulsive colonic motility and GI smooth muscle contractions were measured ex vivo. At 7 or 12 months old, amyloidosis in the brain and myenteric plexus was determined by immunohistochemistry or ELISA; the myenteric neural density, including the cholinergic and nitrergic neurons, was evaluated by immune staining and RT-PCR; expression of pro-inflammatory factors in the GI wall was assessed by RT-PCR. By 7 months of age, male and female APP/PS1 mice developed abundant amyloid plaques in the brain. Aged untreated male APP/PS1 mice also demonstrated Aβ deposition in the colonic myenteric ganglia, which was associated with increased fecal output and faster whole GI transit starting at 4-7 months old, but vehicle- and lanabecestat-treated male APP/PS1 mice had similar GI motility to their non-genetic controls until 7 months old. None of the female APP/PS1 mice showed GI dysmotility or myenteric amyloidosis. Two months of lanabecestat treatment effectively reduced amyloid plaque burden in the brains of female APP/PS1 mice but not in male APP/PS1 mice. Treatment with lanabecestat did not affect myenteric Aβ intensity or GI motility in all APP/PS1 mice. All APP/PS1 mice did not show myenteric neuronal degeneration or inflammation until 12 months old. APP/PS1 mice do not recapitulate myenteric amyloidosis persistently and lack the phenotype of constipation observed in human AD patients; these mice should not be considered an adequate murine model for studying the role of myenteric amyloidosis in GI dysmotility. An adequate animal model with myenteric amyloidosis is required for further study. Show less

The complexity and multifaceted nature of Alzheimer's disease (AD) have driven us to further explore quinazoline scaffolds as multi-targeting agents for AD treatment. The lead optimization strategy was utilized in designing of new series of derivatives (AK-1 to AK-14) followed by synthesis, characterization, and pharmacological evaluation against human cholinesterase's (hChE) and β-secretase (hBACE-1) enzymes. Amongst them, compounds AK-1, AK-2, and AK-3 showed good and significant inhibitory activity against both hAChE and hBACE-1 enzymes with favorable permeation across the blood-brain barrier. The most active compound AK-2 revealed significant propidium iodide (PI) displacement from the AChE-PAS region and was non-neurotoxic against SH-SY5Y cell lines. The lead molecule (AK-2) also showed Aβ aggregation inhibition in a self- and AChE-induced Aβ aggregation, Thioflavin-T assay. Further, compound AK-2 significantly ameliorated Aβ-induced cognitive deficits in the Aβ-induced Morris water maze rat model and demonstrated a significant rescue in eye phenotype in the Aꞵ-phenotypic drosophila model of AD. Ex-vivo immunohistochemistry (IHC) analysis on hippocampal rat brains showed reduced Aβ and BACE-1 protein levels. Compound AK-2 suggested good oral absorption via pharmacokinetic studies and displayed a good and stable ligand-protein interaction in in-silico molecular modeling analysis. Thus, the compound AK-2 can be regarded as a lead molecule and should be investigated further for the treatment of AD. Show less

Inspite of established symptomatic relief drug targets, a multi targeting approach is highly in demand to cure Alzheimer's disease (AD). Simultaneous inhibition of cholinesterase (ChE), β secretase-1 (BACE-1) and Dyrk1A could be promising in complete cure of AD. A series of 18 diaryl triazine based molecular hybrids were successfully designed, synthesized, and tested for their hChE, hBACE-1, Dyrk1A and Aβ aggregation inhibitory potentials. Compounds S-11 and S-12 were the representative molecules amongst the series with multi-targeted inhibitory effects. Compound S-12 showed hAChE inhibition (IC Show less

Our present work demonstrates the molecular hybridization-assisted design, synthesis, and biological evaluation of 22 benzylpiperazine-linked 1,2,4-triazole compounds (PD1-22) as AD modifying agents. All the compounds were tested for their in vitro hChEs, hBACE-1, and Aβ-aggregation inhibition properties. Among them, compound PD-08 and PD-22 demonstrated good hChE and hBACE-1 inhibition as compared to standards donepezil and rivastigmine. Both compounds displaced PI from PAS at 50 µM concentration which was comparable to donepezil and also demonstrated anti-Aβ aggregation properties in self- and AChE-induced thioflavin T assay. Both compounds have shown excellent BBB permeation via PAMPA-BBB assay and were found to be non-neurotoxic at 80 µM concentration against differentiated SH-SY5Y cell lines. Compound PD-22 demonstrated an increase in rescued eye phenotype in Aβ-phenotypic drosophila AD model and amelioration of behavioral deficits in the Aβ-induced rat model of AD. The in-silico docking studies of compound PD-22 revealed a good binding profile towards CAS and PAS residues of AChE and the catalytic dyad of the BACE-1. The 100 ns molecular dynamics simulation studies of compound PD-22 complexed with AChE and BACE-1 enzymes suggested stable ligand-protein complex throughout the simulation run. Based on our findings compound PD-22 could further be utilized as a lead to design a promising candidate for AD therapy. Show less