Study on Mechanism of Ginkgo biloba L. Leaves for the Treatment of Neurodegenerative Diseases Based on Network Pharmacology.

Ginkgo biloba L. leaves (GBLs), as widely used plant extract sources, significantly improve cognitive, learning and memory function in patients with dementia. However, few studies have been conducted on the specific mechanism of Neurodegenerative diseases (NDs). In this study, network pharmacology was employed to elucidate potential mechanism of GBLs in the treatment of NDs. Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP) was used to obtain the chemical components in accordance with the screening principles of oral availability and drug-like property. Potential targets of GBLs were integrated with disease targets, and intersection targets were exactly the potential action targets of GBLs for treating NDs; these key targets were enriched and analyzed by the protein protein interaction (PPI) analysis and molecular docking verification. Key genes were ultimately used to find the biological pathway and explain the therapeutic mechanism by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. Twenty-seven active components of GBLs may affect biological processes such as oxidative reactions and activate transcription factor activities. These components may also affect 120 metabolic pathways, such as the PI3K/AKT pathway, by regulating 147 targets, including AKT1, ALB, HSP90AA1, PTGS2, MMP9, EGFR and APP. By using the software iGEMDOCK, the main target proteins were found to bind well to the main active components of GBLs. GBLs have the characteristics of multi-component and multi-target synergistic effect on the treatment of NDs, which preliminarily predicted its possible molecular mechanism of action, and provided the basis for the follow-up study.

Chemical update on the potential for serotonin 5-HT6 and 5-HT7 receptor agents in the treatment of Alzheimer's disease.

Despite the better understanding of the mechanisms underlying Alzheimer's Disease (AD) and launched clinical trials, no AD-modifying treatment based on a synthetic drug has been introduced for almost twenty years. The serotonin 5-HT6 and 5-HT7 receptors turned out to be promising biological targets for modulation of central nervous system dysfunctions including cognitive impairment. Within this paper, we evaluate the pharmacological potency of both, 5-HT6R and 5-HT7R, agents in search for novel AD treatment. An overview of chemical structures of the 5-HTRs ligands with simultaneous procognitive action which have undergone preclinical and clinical studies within the last 10 years has been performed.

Metal Ions in Alzheimer's Disease: A Key Role or Not?

Despite tremendous research efforts in universities and pharmaceutical companies, effective drugs are still lacking for the treatment of Alzheimer's disease (AD). The biochemical mechanisms of this devastating neurodegenerative disease have not yet been clearly understood. Besides a small percentage of cases with early onset disease having a genetic origin (<5%, familial AD), most cases develop in the elderly as a sporadic form due to multiple and complex parameters of aging. Consequently, AD is spreading in all countries with a long life expectancy. AD is characterized by deposition of senile plaques made of ß-amyloid proteins (Aß) and by hyperphosphorylation of tau proteins, which have been considered as the main drug targets up to now. However, antibodies targeting amyloid aggregates, as well as enzyme inhibitors aiming to modify the amyloid precursor protein processing, have failed to improve cognition in clinical trials. Thus, to set up effective drugs, it is urgent to enlarge the panel of drug targets. Evidence of the link between AD and redox metal dysregulation has also been supported by post-mortem analyses of amyloid plaques, which revealed accumulation of copper, iron, and zinc by 5.7, 2.8, and 3.1 times, respectively, the levels observed in normal brains. Copper-amyloid complexes, in the presence of endogenous reductants, are able to catalyze the reduction of dioxygen and to produce reduced, reactive oxygen species (ROS), leading to neuron death. The possibility of using metal chelators to regenerate normal trafficking of metal ions has been considered as a promising strategy in order to reduce the redox stress lethal for neurons. However, most attempts to use metal chelators as therapeutic agents have been limited to existing molecules available from the shelves. Very few chelators have resulted from a rational design aiming to create drugs with a safety profile and able to cross the blood-brain barrier after an oral administration. In the human body, metals are handled by a sophisticated protein network to strictly control their transport and reactivity. Abnormal concentrations of certain metals may lead to pathological events due to misaccumulation and irregular reactivity. Consequently, therapeutic attempts to restore metal homeostasis should carefully take into account the coordination chemistry specificities of the concerned redox-active metal ions. This Account is focused on the role of the main biologically redox-active transition metals, iron and copper. For iron, the recent debate on the possible role of magnetite in AD pathogenesis is presented. The section devoted to copper is focused on the design of specific copper chelators as drug candidates able to regulate copper homeostasis and to reduce the oxidative damage responsible for the neuron death observed in AD brains. A short survey on non-redox-active metal ions is also included at the beginning, such as aluminum and its controversial role in AD and zinc which is a key metal ion in the brain.

Synthesis of furocoumarin-stilbene hybrids as potential multifunctional drugs against multiple biochemical targets associated with Alzheimer's disease.

A series of furocoumarin-stilbene hybrids has been synthesized and evaluated in vitro for inhibitory effect against acetylcholinesterase (AChE), butyrylcholinestarase (BChE), ß-secretase, cyclooxygenase-2 (COX-2), and lipoxygenase-5 (LOX-5) activities including free radical-scavenging properties. Among these hybrids, 8-(3,5-dimethoxyphenyl)-4-(3,5-dimethoxystyryl)furochromen-2-one 4h exhibited significant anticholinesterase activity and inhibitory effect against ß-secretase, COX-2 and LOX-5 activities. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and an in vitro cell-based antioxidant activity assay involving lipopolysaccharide induced reactive oxygen species production revealed that 4h has capability of scavenging free radicals. Molecular docking into AChE, BChE, ß-secretase, COX-2 and LOX-5 active sites has also been performed.

An evaluation of the genotoxicity and subchronic toxicity of the peel extract of Ponkan cultivar 'Ohta ponkan' (Citrus reticulata Blanco) that is rich in nobiletin and tangeretin with anti-dementia activity.

Nobiletin and tangeretin are major components of polymethoxylated flavones in the peels of citrus fruits such as Citrus reticulata. Because nobiletin and tangeretin have attracted attention due to their beneficial health properties, citrus peel extracts, in which they are concentrated, have the potential to serve as a functional food ingredient to prevent diseases. In this study, a series of toxicological studies on the peel extract of Ponkan cultivar 'Ohta ponkan' (Citrus reticulata Blanco), was conducted. No mutagenic activity was observed in a bacterial reverse mutation test, whereas chromosomal aberrations were induced in an in vitro mammalian chromosomal aberration test. No genotoxicity was observed in an in vivo mammalian micronucleus test. In a 90-day study at daily doses of 54, 180, or 540 mg/kg body weight (bw)/day, hyaline droplet nephropathy, which specifically occurs in adult male rats, was observed in males of 540 mg/kg bw/day group. No other adverse effects were observed in the 90-day study. The no adverse effect level in the 90-day study was considered to be 540 mg/kg bw/day for female rats and less than 540 mg/kg bw/day for male rats.

Pharmacokinetic and pharmacodynamic of the cognitive enhancer modafinil: Relevant clinical and forensic aspects.

Modafinil is a nonamphetamine nootropic drug with an increasingly therapeutic interest due to its different sites of action and behavioral effects in comparison to cocaine or amphetamine. A review of modafinil (and of its prodrug adrafinil and its R-enantiomer armodafinil) chemical, pharmacokinetic, pharmacodynamic, toxicological, clinical and forensic aspects was performed, aiming to better understand possible health problems associated to its unconscious and unruled use. Modafinil is a racemate metabolized mainly in the liver into its inactive acid and sulfone metabolites, which undergo primarily renal excretion. Although not fully clarified, major effects seem to be associated to inhibition of dopamine reuptake and modulation of several other neurochemical pathways, namely noradrenergic, serotoninergic, orexinergic, histaminergic, glutamatergic and GABAergic. Due its wake-promoting effects, modafinil is used for the treatment of daily sleepiness associated to narcolepsy, obstructive sleep apnea and shift work sleep disorder. Its psychotropic and cognitive effects are also attractive in several other pathologies and conditions that affect sleep structure, induce fatigue and lethargy, and impair cognitive abilities. Additionally, in health subjects, including students, modafinil is being used off-label to overcome sleepiness, increase concentration and improve cognitive potential. The most common adverse effects associated to modafinil intake are headache, insomnia, anxiety, diarrhea, dry mouth and raise in blood pressure and heart rate. Infrequently, severe dermatologic effects in children, including maculopapular and morbilliform rash, erythema multiforme and Stevens-Johnson Syndrome have been reported. Intoxication and dependence associated to modafinil are uncommon. Further research on effects and health implications of modafinil and its analogs is steel needed to create evidence-based policies.

Chemical and Biological Aspects of Montanine-Type Alkaloids Isolated from Plants of the Amaryllidaceae Family.

Plants of the Amaryllidaceae family are promising therapeutic tools for human diseases and have been used as alternative medicines. The specific secondary metabolites of this plant family, called Amaryllidaceae alkaloids (AA), have attracted considerable attention due to their interesting pharmacological activities. One of them, galantamine, is already used in the therapy of Alzheimer's disease as a long acting, selective, reversible inhibitor of acetylcholinesterase. One group of AA is the montanine-type, such as montanine, pancracine and others, which share a 5,11-methanomorphanthridine core. So far, only 14 montanine-type alkaloids have been isolated. Compared with other structural-types of AA, montanine-type alkaloids are predominantly present in plants in low concentrations, but some of them display promising biological properties, especially in vitro cytotoxic activity against different cancerous cell lines. The present review aims to summarize comprehensively the research that has been published on the Amaryllidaceae alkaloids of montanine-type.

Terpenoids, Cannabimimetic Ligands, beyond the Cannabis Plant.

Medicinal use of Cannabis sativa L. has an extensive history and it was essential in the discovery of phytocannabinoids, including the Cannabis major psychoactive compound-Δ9-tetrahydrocannabinol (Δ9-THC)-as well as the G-protein-coupled cannabinoid receptors (CBR), named cannabinoid receptor type-1 (CB1R) and cannabinoid receptor type-2 (CB2R), both part of the now known endocannabinoid system (ECS). Cannabinoids is a vast term that defines several compounds that have been characterized in three categories: (i) endogenous, (ii) synthetic, and (iii) phytocannabinoids, and are able to modulate the CBR and ECS. Particularly, phytocannabinoids are natural terpenoids or phenolic compounds derived from Cannabis sativa. However, these terpenoids and phenolic compounds can also be derived from other plants (non-cannabinoids) and still induce cannabinoid-like properties. Cannabimimetic ligands, beyond the Cannabis plant, can act as CBR agonists or antagonists, or ECS enzyme inhibitors, besides being able of playing a role in immune-mediated inflammatory and infectious diseases, neuroinflammatory, neurological, and neurodegenerative diseases, as well as in cancer, and autoimmunity by itself. In this review, we summarize and critically highlight past, present, and future progress on the understanding of the role of cannabinoid-like molecules, mainly terpenes, as prospective therapeutics for different pathological conditions.

Common fibrillar spines of amyloid-ß and human islet amyloid polypeptide revealed by microelectron diffraction and structure-based inhibitors.

Amyloid-ß (Aß) and human islet amyloid polypeptide (hIAPP) aggregate to form amyloid fibrils that deposit in tissues and are associated with Alzheimer's disease (AD) and type II diabetes (T2D), respectively. Individuals with T2D have an increased risk of developing AD, and conversely, AD patients have an increased risk of developing T2D. Evidence suggests that this link between AD and T2D might originate from a structural similarity between aggregates of Aß and hIAPP. Using the cryoEM method microelectron diffraction, we determined the atomic structures of 11-residue segments from both Aß and hIAPP, termed Aß(24-34) WT and hIAPP(19-29) S20G, with 64% sequence similarity. We observed a high degree of structural similarity between their backbone atoms (0.96-Å root mean square deviation). Moreover, fibrils of these segments induced amyloid formation through self- and cross-seeding. Furthermore, inhibitors designed for one segment showed cross-efficacy for full-length Aß and hIAPP and reduced cytotoxicity of both proteins, although by apparently blocking different cytotoxic mechanisms. The similarity of the atomic structures of Aß(24-34) WT and hIAPP(19-29) S20G offers a molecular model for cross-seeding between Aß and hIAPP.

Design and development of novel p-aminobenzoic acid derivatives as potential cholinesterase inhibitors for the treatment of Alzheimer's disease.

Based on the quantitative structure-activity relationship (QSAR), some novel p-aminobenzoic acid derivatives as promising cholinesterase enzyme inhibitors were designed, synthesized, characterized and evaluated to enhance learning and memory. The in vitro enzyme kinetic study of the synthesized compounds revealed the type of inhibition on the respective acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes. The in vivo studies of the synthesized compounds exhibited significant reversal of cognitive deficits in the animal models of amnesia as compared to standard drug donepezil. Further, the ex vivo studies in the specific brain regions like the hippocampus, hypothalamus, and prefrontal cortex regions also exhibited AChE inhibition comparable to standard donepezil. The in silico molecular docking and dynamics simulations studies of the most potent compound 22 revealed the consensual interactions at the active site pocket of the AChE.

Designing of promising medicinal scaffolds for Alzheimer's disease through enzyme inhibition, lead optimization, molecular docking and dynamic simulation approaches.

In the designed research work, a series of 2-furoyl piperazine based sulfonamide derivatives were synthesized as therapeutic agents to target the Alzheimer's disease. The structures of the newly synthesized compounds were characterized through spectral analysis and their inhibitory potential was evaluated against butyrylcholinesterase (BChE). The cytotoxicity of these sulfonamides was also ascertained through hemolysis of bovine red blood cells. Furthermore, compounds were inspected by Lipinki Rule and their binding profiles against BChE were discerned by molecular docking. The protein fluctuations in docking complexes were recognized by dynamic simulation. From our in vitro and in silico results 5c, 5j and 5k were identified as promising lead compounds for the treatment of targeted disease.

Physiological signature of a novel potentiator of AMPA receptor signalling.

We have synthesized a novel small molecule based on the pyrrolidinone-containing core structure of clausenamide, which is a candidate anti-dementia drug. The synthetic route yielded multi-gram quantities of an isomeric racemate mixture in a short number of steps. When tested in hippocampal slices from young adult rats the compound enhanced AMPA receptor-mediated signalling at mossy fibre synapses, and potentiated inward currents evoked by local application of l-glutamate onto CA3 pyramidal neurons. It facilitated the induction of mossy fibre LTP, but the magnitude of potentiation was smaller than that observed in untreated slices. The racemic mixture was separated and it was shown that only the (-) enantiomer was active. Toxicity analysis indicated that cell lines tolerated the compound at concentrations well above those enhancing synaptic transmission. Our results unveil a small molecule whose physiological signature resembles that of a potent nootropic drug.

New Positive Allosteric Modulator of AMPA Receptors: in vitro and in vivo Studies.

A new derivative of 3,7-diazabicyclo[3.3.1]nonane, which showed a high activity as a positive allosteric modulator of AMPA receptors of the CNS, was studied in electrophysiological experiments. At doses of 0.01 mg/kg, this compound significantly improved the memory of experimental animals disturbed by maximal electric shock. The results indicate that this compound is a promising candidate for preclinical trials and clinical studies as a drug for treatment of a number of psychoneurological diseases.

Mechanisms of recognition of amyloid-ß (Aß) monomer, oligomer, and fibril by homologous antibodies.

Alzheimer's disease is one of the most devastating neurodegenerative diseases without effective therapies. Immunotherapy is a promising approach, but amyloid antibody structural information is limited. Here we simulate the recognition of monomeric, oligomeric, and fibril amyloid-ß (Aß) by three homologous antibodies (solanezumab, crenezumab, and their chimera, CreneFab). Solanezumab only binds the monomer, whereas crenezumab and CreneFab can recognize different oligomerization states; however, the structural basis for this observation is not understood. We successfully identified stable complexes of crenezumab with Aß pentamer (oligomer model) and 16-mer (fibril model). It is noteworthy that solanezumab targets Aß residues 16-26 preferentially in the monomeric state; conversely, crenezumab consistently targets residues 13-16 in different oligomeric states. Unlike the buried monomeric peptide in solanezumab's complementarity-determining region, crenezumab binds the oligomer's lateral and edge residues. Surprisingly, crenezumab's complementarity-determining region loops can effectively bind the Aß fibril lateral surface around the same 13-16 region. The constant domain influences antigen recognition through entropy redistribution. Different constant domain residues in solanezumab/crenezumab/chimera influence the binding of Aß aggregates. Collectively, we provide molecular insight into the recognition mechanisms facilitating antibody design.

Intramembrane attenuation of the TLR4-TLR6 dimer impairs receptor assembly and reduces microglia-mediated neurodegeneration.

Recently, a single study revealed a new complex composed of Toll-like receptor 4 (TLR4), TLR6, and CD36 induced by fibrillary Aß peptides, the hallmark of Alzheimer's disease. Unlike TLRs located on the plasma membrane that dimerize on the membrane after ligand binding to their extracellular domain, the TLR4-TLR6-CD36 complex assembly has been suggested to be induced by intracellular signals from CD36, similar to integrin inside-out signaling. However, the assembly site of TLR4-TLR6-CD36 and the domains participating in Aß-induced signaling is still unknown. By interfering with TLR4-TLR6 dimerization using a TLR4-derived peptide, we show that receptor assembly is abrogated within the plasma membrane. Furthermore, we reveal that the transmembrane domains of TLR4 and TLR6 have an essential role in receptor dimerization and activation. Inhibition of TLR4-TLR6 assembly was associated with reduced secretion of proinflammatory mediators from microglia cells, ultimately rescuing neurons from death. Our findings support TLR4-TLR6 dimerization induced by Aß. Moreover, we shed new light on TLR4-TLR6 assembly and localization and show the potential of inhibiting TLR4-TLR6 dimerization as a treatment of Alzheimer's disease.

The structure of the human glutaminyl cyclase-SEN177 complex indicates routes for developing new potent inhibitors as possible agents for the treatment of neurological disorders.

Recent evidence links the role of human glutaminyl cyclase (hQC) to the amyloidogenic process involved in Alzheimer's disease (AD). hQC is a zinc enzyme present in neuronal tissue and its activity is responsible for the cyclization of N-terminal Gln or Glu ß-amyloid peptides, leading to N-pyroglutamic acid peptides (pE-Aß) that is probably a crucial event in the initiation and progress of the disease. Indeed, pE-containing peptides exhibit an elevated neurotoxicity and a tendency to aggregate. These observations render hQC inhibition an attractive strategy for developing new molecules active against AD. We present here the crystal structure of hQC in complex with SEN177, a newly designed molecule. The SEN177-binding mode to hQC differs from that of the known hQC inhibitors. SEN177 Ki on hQC is 20 nM, comparable or better than that of the most potent known hQC inhibitors PBD150 and PQ912. In addition, SEN177 already demonstrated relevant pharmacological properties in in vivo models of Huntington's disease. All these properties make SEN177 an important scaffold for developing molecules acting on AD and related diseases.

Aroylhydrazones constitute a promising class of 'metal-protein attenuating compounds' for the treatment of Alzheimer's disease: a proof-of-concept based on the study of the interactions between zinc(II) and pyridine-2-carboxaldehyde isonicotinoyl hydrazone.

With the increasing life expectancy of the world's population, neurodegenerative diseases, such as Alzheimer's disease (AD), will become a much more relevant public health issue. This fact, coupled with the lack of efficacy of the available treatments, has been driving research directed to the development of new drugs for this pathology. Metal-protein attenuating compounds (MPACs) constitute a promising class of agents with potential application on the treatment of neurodegenerative diseases, such as AD. Currently, most MPACs are based on 8-hydroxyquinoline. Recently, our research group has described the hybrid aroylhydrazone containing the 8-hydroxyquinoline group INHHQ as a promising MPAC. By studying the known structure-related ligand HPCIH, which does not contain the phenol moiety, as a simplified chemical model for INHHQ, we aimed to clarify the real impact of the aroylhydrazone group for the MPAC activity of a compound with potential anti-Alzheimer's activity. The present work describes a detailed solution and solid-state study of the coordination of HPCIH with Zn2+ ions, as well as its in vitro binding-ability towards this metal in the presence of the Aß(1-40) peptide. Similar to INHHQ, HPCIH is able to efficiently compete with Aß(1-40) for Zn2+ ions, performing as expected for an MPAC. The similarity between the behaviors of both ligands is remarkable. Taken together, the data presented herein point to aroylhydrazones, such as the compounds HPCIH and the previously published INHHQ, as encouraging MPACs for the treatment of AD.

New lignans attenuating cognitive deterioration of Aß transgenic flies discovered in Acorus tatarinowii.

Five new lignan racemates, (±)-tatarinoid D-H (1-5), and three known analogues (6-8) were isolated from the rhizomes of Acorus tatarinowii. Their structures were established by 1D, 2D-NMR, HR-MS, IR and optical spectral data. Among them, 1 and 6-8 can alleviate the cognitive deterioration of Aß transgenic flies.

Novel N-propylphthalimide- and 4-vinylbenzyl-substituted benzimidazole salts: Synthesis, characterization, and determination of their metal chelating effects and inhibition profiles against acetylcholinesterase and carbonic anhydrase enzymes.

The novel N-propylphthalimide-substituted and 4-vinylbenzyl-substituted N-heterocyclic carbene (NHC) precursors were synthesized by N-substituted benzimidazolium with aryl halides. The novel N-propylphthalimide-substituted and 4-vinylbenzyl-substituted NHC precursors have been characterized by using 1 H NMR, 13 C NMR, FTIR spectroscopy, and elemental analysis techniques. They were tested for the inhibition of AChE and hCA enzymes and demonstrated efficient inhibition profiles with Ki values in the range of 351.0-1269.9 nM against hCA I, 346.6-1193.1 nM against hCA II, and 19.0-76.3 nM against AChE. On the other hand, acetazolamide, a clinically used molecule, utilized as CA inhibitor, obtained a Ki value of 1246.7 nM against hCA I and 1407.6 nM against hCA II. Additionally, tacrine inhibited AChE and obtained a Ki value of 174.6 nM.

Synthesis and antioxidant, antixanthine oxidase, and antielastase activities of novel N,S-substituted polyhalogenated nitrobutadiene derivatives.

In this study, three substituted polyhalogenated nitrobutadiene derivatives were synthesized. Compound 1-[(2,3-dibromopropyl)sulfanyl]-1,3,4,4-tetrachloro-2-nitrobuta-1,3-diene (4) was synthesized before by our group. Compounds 8-{[1-[(2,3-dibromopropyl)sulfany]-3,4,4-trichloro-2-nitrobuta-1,3-butadien-1-yl}-1,4-dioxa-8-azaspiro[4.5]decane (5) and 1-[(2,3-dibromopropyl)sulfanyl]-3,4,4-trichloro-N-(4-methylpiperazin-1-yl)-2-nitrobuta-1,3-diene-1-amine (6) were synthesized in this work as original compounds. Xanthine oxidase, elastase inhibition abilities, and antioxidant activities were investigated in this work for compounds 4, 5, and 6. In this study, compounds 4, 5, and 6 exhibited antixanthine oxidase, antielastase, and antioxidant activities. Among the compounds screened, compound 4 exhibited xanthine oxidase and elastase inhibitor effect similar to the standard compound. Among the three tested compounds, compound 6 showed potent DPPH radical scavenging and reducing power activities. Therefore, these three compounds (4, 5, and 6) may be useful as an antixanthine oxidase, antielastase, and antioxidant agent in pharmaceutical and cosmetic industry.