Identification of dibenzyl imidazolidine and triazole acetamide derivatives through virtual screening targeting amyloid beta aggregation and neurotoxicity in PC12 cells.

Aggregation and neurotoxicity of amyloid β (Aβ) protein is a hallmark characteristic of Alzheimer's disease (AD). In this study we compared the anti-aggregatory and neuroprotective effects of five synthetic compounds against Aβ protein; four of which possessed a five membered heterocycle ring scaffold (two dibenzyl phenyl imidazolidines and two triazole sulfanyl acetamides) and one with a fused five membered heterocycle (benzoxazole) ring, selected thorough virtual screening from ZINC database. Molecular docking of their optimized structures was used to study Aβ binding characteristics. As predicted from molecular docking, strong steric binding of imidazolidines and H-bonding of both triazoles to Aβ were translated into anti Aβ aggregation properties. Subsequent transmission electron microscopy (TEM) was used to assess their effects on Aβ1-42 fibril formation. Four compounds variably altered morphology of Aβ fibrils from long, intertwined fibrils to short, loose structures. Thioflavin T assay of Aβ fibrillisation kinetics demonstrated that one imidazolidine and both triazole compounds inhibited Aβ aggregation. Rat pheochromocytoma (PC12) cells were exposed to Aβ1-42, alone and in combination with the heterocyclic compounds to assess neuroprotective effects. Aβ1-42-evoked loss of neuronal cell viability was significantly attenuated in the presence of both imidazolidine compounds, while the triazole acetamides and benzoxazole compound were toxic to PC12 cells. These findings highlight the Aβ anti-aggregative and neuroprotective propensity of a dibenzyl phenyl imidazolidine scaffold (Compound 1 and 2). While the triazole sulfanyl acetamide scaffold also possessed Aβ anti-aggregation properties, they also demonstrated significant intrinsic neurotoxicity. Overall, the predictive efficacy of in silico methods enables the identification of novel imidazolidines that act both as inhibitors of Aβ aggregation and neurotoxicity, and may provide a further platform for the development of novel Alzheimer's disease-modifying pharmacotherapies.

Das S ，Smid SD 《-》

Novel cannabis flavonoid, cannflavin A displays both a hormetic and neuroprotective profile against amyloid β-mediated neurotoxicity in PC12 cells: Comparison with geranylated flavonoids, mimulone and diplacone.

Flavonoids form a diverse class of naturally occurring polyphenols ascribed various biological activities, including inhibition of amyloid β (Aβ) fibrillisation and neurotoxicity of relevance to Alzheimer's disease. Cannabis contains a unique subset of prenylated flavonoids, the cannflavins. While selected conventional flavonoids have demonstrated anti-amyloid and neuroprotective potential, any neuroprotective bioactivity of prenylated flavonoids has not been determined. We evaluated the in vitro neuroprotective and anti-aggregative properties of the novel geranylated cannabis-derived flavonoid, cannflavin A against Aβ1-42 and compared it to two similarly geranylated flavonoids, mimulone and diplacone, to compare the bioactive properties of these unique flavonoids more broadly. Neuronal viability were assessed in PC12 cells biochemically using the MTT assay in the presence of each flavonoid (1-200 µM) for 48 h. Sub-toxic threshold test concentrations of each flavonoid were then applied to cells, alone or with concomitant incubation with the lipid peroxidant tert-butyl hyrdroperoxide (t-bhp) or amyloid β (Aβ1-42; 0-2 µM). Fluorescent staining was used to indicate effects of Aβ1-42 on PC12 cellular morphology, while direct effects of each flavonoid on Aβ fibril formation and aggregation were assessed using the Thioflavin T (ThT) fluorometric kinetic assay and transmission electron microscopy (TEM) to visualise fibril and aggregate morphology. Cannflavin A demonstrated intrinsic hormetic effects on cell viability, increasing viability by 40% from 1 to 10 µM but displaying neurotoxicity at higher (>10-100 µM) concentrations. Neither mimulone nor diplacone exhibited such a biphasic effect, instead showing only concentration-dependent neurotoxicity, with diplacone the more potent (from >1 µM). However at the lower concentrations (<10 µM), cannflavin A increased cell viability by up to 40%, while 10 µM cannflavin A inhibited the neurotoxicity elicited by Aβ1-42 (0-2 µM), reducing Aβ aggregate adherence to PC-12 cells and associated neurite loss. The neuroprotective effects of cannflavin A were associated with a direct inhibition of Aβ1-42 fibril and aggregate density, evidenced by attenuated ThT fluorescence kinetics and microscopic evidence of both altered and diminished density of Aβ aggregate and fibril morphology via electron microscopy. These findings highlight a concentration-dependent hormetic and neuroprotective role of cannflavin A against Aβ-mediated neurotoxicity, associated with an inhibition of Aβ fibrillisation. The efficacy of the cannabis flavone may itself direct further lead development targeting neurodegeneration in Alzheimer's disease. However, the geranylated flavonoids generally displayed a comparatively potent neurotoxicity not observed with many conventional flavonoids in vitro.

Eggers C ，Fujitani M ，Kato R ，Smid S ... -  《-》

Structure-activity relationships for flavone interactions with amyloid β reveal a novel anti-aggregatory and neuroprotective effect of 2',3',4'-trihydroxyflavone (2-D08).

Naturally-occurring flavonoids have well documented anti-aggregatory and neuroprotective properties against the hallmark toxic protein in Alzheimer's disease, amyloid β (Aβ). However the extensive diversity of flavonoids has limited the insight into the precise structure-activity relationships that confer such bioactive properties against the Aβ protein. In the present study we have characterised the Aβ binding properties, anti-aggregatory and neuroprotective effects of a discreet set of flavones, including the recently described novel protein sumoylation inhibitor 2',3',4'-trihydroxyflavone (2-D08). Quercetin, transilitin, jaceosidin, nobiletin and 2-D08 were incubated with human Aβ1-42 for 48h in vitro and effects on Aβ fibrillisation kinetics and morphology measured using Thioflavin T (ThT) and electron microscopy respectively, in addition to effects on neuronal PC12 cell viability. Of the flavones studied, only quercetin, transilitin and 2-D08 significantly inhibited Aβ1-42 aggregation and toxicity in PC12 cells. Of those, 2-D08 was the most effective inhibitor. The strong anti-amyloid activity of 2-D08 indicates that extensive hydroxylation in the B ring is the most important determinant of activity against β amyloid within the flavone scaffold. The lack of efficacy of jaceosidin and nobiletin indicate that extension of B ring hydroxylation with methoxyl groups result in an incremental loss of anti-fibrillar and neuroprotective activity, highlighting the constraint to vicinal hydroxyl groups in the B ring for effective inhibition of aggregation. These findings reveal further structural insights into anti-amyloid bioactivity of flavonoids in addition to a novel and efficacious anti-aggregatory and neuroprotective effect of the semi-synthetic flavone and sumoylation inhibitor 2',3',4'-trihydroxyflavone (2-D08). Such modified flavones may facilitate drug development targeting multiple pathways in neurodegenerative disease.

Marsh DT ，Das S ，Ridell J ，Smid SD ... -  《-》

Bioactive polyphenol interactions with β amyloid: a comparison of binding modelling, effects on fibril and aggregate formation and neuroprotective capacity.

Das S ，Stark L ，Musgrave IF ，Pukala T ，Smid SD ... -  《-》

Cannabis terpenes display variable protective and anti-aggregatory actions against neurotoxic β amyloid in vitro: highlighting the protective bioactivity of α-bisabolol in motorneuronal-like NSC-34 cells.

Terpenes form a diverse class of naturally occurring chemicals ascribed various biological activities. Cannabis contains over 400 different terpenes of varying chemical complexity which may add to the known biological activities of phytocannabinoids of relevance to the increasing use of medical cannabis; however, to date have been incompletely characterized. We assessed three terpenes predominant in cannabis: α-bisabolol, myrcene and β-caryophyllene for neuroprotective and anti-aggregative properties in both undifferentiated and differentiated NSC-34 motorneuronal-like cells as a sensitive model for neurotoxicity to oxidative stress and amyloid β (Aβ1-42) protein exposure. Cell viability was assessed biochemically using the MTT assay in the presence of either α-bisabolol, myrcene and β-caryophyllene (1-1000 µM) for 48 hr. Sub-toxic threshold test concentrations of each terpene were then applied to cells, alone or with concomitant incubation with the lipid peroxidant tert-butyl hyrdroperoxide (t-BHP) or amyloid β (Aβ1-42; 0-1 µM) to assess neuroprotective effects. Direct effects of each terpene on Aβ fibril formation and aggregation were also evaluated using the Thioflavin T (ThT) fluorometric kinetic assay, circular dichroism and transmission electron microscopy (TEM) to visualise fibril and aggregate morphology. Terpenes were intrinsically benign to NSC-34 cells up to 100 µM. No significant antioxidant effects were observed following t-BHP administration with myrcene and β-caryophyllene, however α-bisabolol provided a modest but significant increase in cell viability in undifferentiated cells. α-bisabolol also demonstrated a significant neuroprotective effect against amyloid β exposure, with β-caryophyllene also providing a lesser, but significant increase in cell viability. Protective effects of terpenes were more pronounced in undifferentiated versus differentiated cells, attributable more so to an attenuated loss of cell viability in response to Aβ1-42 following NSC-34 cell differentiation. Neuroprotection was associated with a direct inhibition of Aβ1-42 fibril and aggregate density, evidenced by both attenuated ThT fluorescence kinetics and both spectral and microscopic evidence of altered and diminished density of Aβ aggregates. While myrcene and β-caryophyllene also elicited reductions in ThT fluorescence and alterations in Aβ aggregation, these were less well associated with neuroprotective capacity. These findings highlight a neuroprotective role of α-bisabolol against Aβ-mediated neurotoxicity associated with an inhibition of Aβ fibrillization and modest antioxidant effect against lipid peroxidation, while β-caryophyllene also provided a small but significant measure of protection to Aβ-mediated neurotoxicity. Anti-aggregatory effects were not directly correlated with neuroprotective efficacy. This demonstrates that bioactivity of selected terpenes should be a consideration in the emergent use of medicinal cannabis formulations for the treatment of neurodegenerative diseases.

Laws Iii JS ，Shrestha S ，Smid SD 《-》