Biaryl scaffold-focused virtual screening for anti-aggregatory and neuroprotective effects in Alzheimer's disease.

BACKGROUND: Alzheimer's disease (AD) is a primary cause of dementia in ageing population affecting more than 35 million people around the globe. It is a chronic neurodegenerative disease caused by defected folding and aggregation of amyloid beta (Aß) protein. Aß is formed by the cleavage of membrane embedded amyloid precursor protein (APP) by using enzyme 'transmembrane aspartyl protease, ß-secretase'. Inhibition of ß-secretase is a viable strategy to prevent neurotoxicity in AD. Another strategy in the treatment of AD is inhibition of acetylcholinesterase. This inhibition reduces the degradation of acetylcholine and temporarily restores the cholinergic function of neurons and improves cognitive function. Monoamine oxidase and higher glutamate levels are also found to be linked with Aß peptide related oxidative stress. Oxidative stress leads to reduced activity of glutamate synthase resulting in significantly higher level of glutamate in brain. The aim of this study is to perform in silico screening of a virtual library of biaryl scaffold containing compounds potentially used for the treatment of AD. Screening was done against the primary targets of AD therapeutics, acetylcholinesterase, ß-secretase (BACE1), Monoamine oxidases (MAO) and N-Methyl-D-aspartate (NMDA) receptor. Compounds were screened for their inhibitory potential by employing molecular docking approach using AutoDock vina. Binding energy scores were embodied in the heatmap to display varies strengths of interactions of the ligands targeting AD. RESULTS: Several ligands showed notable interaction with at least two targets, but the strong interaction with all the targets is shown by very few ligands. The pharmacokinetics of the interacting ligands was also predicted. The interacting ligands have good drug-likeness and brain availability essential for drugs with intracranial targets. CONCLUSION: These results suggest that biaryl scaffold may be pliable to drug development for neuroprotection in AD and that the synthesis of further analogues to optimize these properties should be considered.

Anti-neuroinflammatory Potential of Natural Products in Attenuation of Alzheimer's Disease.

Alzheimer's disease (AD) is a chronic progressive neurodegenerative disorder associated with dementia and cognitive impairment most common in elderly population. Various pathophysiological mechanisms have been proposed by numerous researcher, although, exact mechanism is not yet elucidated. Several studies have been indicated that neuroinflammation associated with deposition of amyloid- beta (Aß) in brain is a major hallmark toward the pathology of neurodegenerative diseases. So, there is a need to unravel the link of inflammatory process in neurodegeneration. Increased microglial activation, expression of cytokines, reactive oxygen species (ROS), and nuclear factor kappa B (NF-κB) participate in inflammatory process of AD. This review mainly concentrates on involvement of neuroinflammation and the molecular mechanisms adapted by various natural compounds, phytochemicals and herbal formulations in various signaling pathways involved in neuroprotection. Currently, pharmacologically active natural products, having anti-neuroinflammatory potential are being focused which makes them potential candidate to cure AD. A number of preclinical and clinical trials have been done on nutritional and botanical agents. Analysis of anti-inflammatory and neuroprotective phytochemicals such as terpenoids, phenolic derivatives, alkaloids, glycosides, and steroidal saponins displays therapeutic potential toward amelioration and prevention of devastating neurodegeneration observed in AD.

Antihyperalgesic Properties of Honokiol in Inflammatory Pain Models by Targeting of NF-κB and Nrf2 Signaling.

The present study investigates the possible anti-nociceptive effect of intraperitoneal (i.p.) honokiol: a phenolic compound originally isolated from Magnolia officinalis, in acute and chronic inflammatory pain models. Doses of 0.1, 5, and 10 mg/kg honokiol were administered in carrageenan induced pain and the dose (honokiol 10 mg/kg i.p.) with most significant response among behavioral tests was selected for further experiments. The i.p. administration of honokiol inhibits mechanical hyperalgesia, mechanical allodynia, and thermal hyperalgesia, without causing any apparent toxicity. To elucidate the effect of honokiol on various cytokines and antioxidant enzymes, quantitative real-time-PCR was performed to determine the expression levels of pro-inflammatory cytokines and antioxidant enzymes. It is demonstrated that honokiol significantly reduced the expression levels of tumor necrosis factor (TNF-α), interleukin-1ß (IL-1ß), interleukin-6 (IL-6), and vascular endothelial growth factor (VEGF). Similarly, honokiol was also found to potentiate the expression of nuclear factor erythroid 2-related factor 2 (Nrf2), superoxide dismutase 2 (SOD2), and heme oxygenase-1 (HO-1) levels. Additionally, honokiol significantly reduced plasma nitrite levels as compared to complete Freund's adjuvant (CFA) induced group. X-ray analysis and hematoxylin and eosin (H&E) staining of inflamed and treated paws showed that honokiol reduced the inflammation with significantly less leukocyte infiltration and soft tissue inflammation. In order to explore the possible mechanism of action of honokiol, agonists [piroxicam (5 mg/kg), tramadol (50 mg/kg), and gabapentin (5 mg/kg) i.p.] as well as antagonists [naloxone (4 mg/kg), olanzapine (10 mg/kg), and flumazenil (0.2 mg/kg) i.p.] were used to study involvement of various receptors on the anti-nociceptive effect of honokiol. The potential side effects of honokiol on muscle activity were assessed. An adverse effect testing of honokiol by liver and renal functions were also carried out. The effect of oral honokiol was also assessed on gastrointestinal (GIT) mucosa. Our results demonstrate that honokiol has a significant anti-nociceptive activity through inhibition of anti-inflammatory mediators.

Chemical Profiles and Anti-inflammatory Activity of the Essential Oils from Seseli gummiferum and Seseli corymbosum subsp. corymbosum.

The anti-inflammatory activity of the essential oils from Seseli corymbosum subsp. coiymbosum Pall. ex Sm. (SC) and Seseli gummiferum Boiss. & Heldr. subsp. corymbosum (SG) was investigated for the first time on lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. The main constituents (determined by GC-FID and GC-MS analyses) were germacrene D (54.1%) and sabinene (22.4%) in SG oil and ß-phellandrene (29.2%), α-phellandrene (8.2%) and germacrene D (2.5%) in SC oil. SC and SG oils inhibited nitric oxide (NO) production with IC50 values of 56.1 and 108.2 µg/mL, respectively. The oils also inhibited prostaglandin E2 (PGE2) with IC50 values of 49.4 µg/mL (SC oil) and 95.5 µg/mL (SG oil). The inhibitory effect of SC and SG oils was accompanied by dose-dependent decreases of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein expressions in LPS-induced RAW 264.7 cells. The research of the reporter gene assay on nuclear factor KB (NF-KB) showed that SC and SG oils inhibited NF-KB transcriptional activity. The obtained results suggest that SC and SG oils exert the anti-inflammatory effects in LPS-stimulated RAW 264.7 cells by suppressing NF-KB activation.

Preparative separation of minor saponins from Platycodi Radix by high-speed counter-current chromatography.

Platycosides (PSs), the saponins found in the root of Platycodon grandiflorum (Jacq.) A. DC. (Platycodi Radix), are typically composed of oleanene backbones with two side chains; one is a 3-O-glucose linked by a glycosidic bond, and the other is a 28-O-arabinose-rhamnose-xylose-apiose linked by an ester bond. Minor saponins, acetylated isomers of the major saponin on either the 2'' or 3'' position of rhamnose, were isolated from Platycodi Radix using a multi-step process including high-speed counter-current chromatography (HSCCC) and preparative reversed-phase high-performance liquid chromatography (RP-HPLC). After the separation of the major components, the enriched minor saponin fraction was used for this study. A two-phase solvent system consisting of chloroform-methanol-isopropanol-water (3:2:2:3, v/v) was used for HSCCC. HSCCC separation of the enriched minor saponin fraction yielded 2''-O-acetylplatycodin D, 3''-O-acetylpolygalacin D, 2''-O-acetylpolygalacin and a mixture of 3''-O-acetylplatycodin D and polygalacin D. The mixture fraction from HSCCC separation was further purified by preparative RP-HPLC, giving 3''-O-acetylplatycodin D and polygalacin D at a purity of over 98.9%. The developed method provides the preparative and rapid separation of minor saponins in the crude extract of Platycodi Radix. To the best of our knowledge, this is the first on the separation of acetylated PSs by HSCCC.

Detection of 2-O-sulfated iduronate and N-acetylglucosamine units in heparan sulfate by an antibody selected against acharan sulfate (IdoA2S-GlcNAc)n.

The snail glycosaminoglycan acharan sulfate (AS) is structurally related to heparan sulfates (HS) and has a repeating disaccharide structure of alpha-d-N-acetylglucosaminyl-2-O-sulfo-alpha-l-iduronic acid (GlcNAc-IdoA2S) residues. Using the phage display technology, a unique antibody (MW3G3) was selected against AS with a V(H)3, DP 47, and a CDR3 amino acid sequence of QKKRPRF. Antibody MW3G3 did not react with desulfated, N-deacetylated or N-sulfated AS, indicating that reactivity depends on N-acetyl and 2-O-sulfate groups. Antibody MW3G3 also had a high preference for (modified) heparin oligosaccharides containing N-acetylated glucosamine and 2-O-sulfated iduronic acid residues. In tissues, antibody MW3G3 identified a HS oligosaccharide epitope containing N-acetylated glucosamine and 2-O-sulfated iduronic acid residues as enzymatic N-deacetylation of HS in situ prevented staining, and 2-O-sulfotransferase-deficient Chinese hamster ovary cells were not reactive. An immunohistochemical survey using various rat organs revealed a distinct distribution of the MW3G3 epitope, which was primarily present in the basal laminae of most (but not all) blood vessels and of some epithelia, including human skin. No staining was observed in the glycosaminoglycan-rich tumor matrix of metastatic melanoma. In conclusion, we have selected an antibody that identifies HS oligosaccharides containing N-acetylated glucosamine and 2-O-sulfated iduronic acid residues. This antibody may be instrumental in identifying structural alterations in HS in health and disease.