The pharmacology and therapeutic potential of (-)-huperzine A

Molecular modeling of multi-target analogs of huperzine A and applications in Alzheimer's disease

CONTEXT

Given the diverse pathophysiological mechanisms underlying Alzheimer's disease, it is improbable that a single targeted drug will prove successful as a therapeutic strategy. Therefore, exploring various hypotheses in drug design is imperative. The sequestration of Fe(II) and Zn(II) cations stands out as a crucial mechanism based on the mitigation of reactive oxygen species. Moreover, inhibiting acetylcholinesterase represents a pivotal strategy to enhance acetylcholine levels in the synaptic cleft. This research aims to investigate the analogs of Huperzine A, documented in scientific literature, considering of these two hypotheses. Consequently, the speciation chemistry of these structures with Fe(II) and Zn(II) was scrutinized using quantum chemistry calculations, molecular docking simulations, and theoretical predictions of pharmacokinetics properties. From the pharmacokinetic properties, only two analogs, HupA-A1 and HupA-A2, exhibited a theoretical permeability across the blood-brain barrier; on the other hand, from a thermodynamic standpoint, the enantiomers of HupA-A2 showed negligible chelation values. The enantiomers with the most favorable interaction parameters were S'R'HupA-A1 (ΔGBIND = -40.0 kcal mol-1, fitness score = 35.5) and R'R'HupA-A1 (ΔGBIND = -35.5 kcal mol-1, fitness score = 22.61), being compared with HupA (ΔGBIND = -41.75 kcal mol-1, fitness score = 39.95). From this study, some prime candidates for promising drug were S'R'HupA-A1 and R'R'HupA-A1, primarily owing to their favorable thermodynamic chelating capability and potential anticholinesterase mechanism.

METHODS

Quantum chemistry calculations were carried out at B3LYP/6-31G(d) level, considering the IEF-PCM(UFF) implicit solvent model for water. The coordination compounds were assessed using the Gibbs free energy variation and hard and soft acid theory. Molecular docking calculations were conducted using the GOLD program, based on the crystal structure of the acetylcholinesterase protein (PDB code = 4EY5), where the ChemScore function was employed with the active site defined as the region within a 15-Å radius around the centroid coordinates (X = -9.557583, Y = -43.910473, Z = 31.466687). Pharmacokinetic properties were predicted using SwissADME, focusing on Lipinski's rule of five.

Drug Treatment Attenuates Retinal Ganglion Cell Death by Inhibiting Collapsin Response Mediator Protein 2 Phosphorylation in Mouse Models of Normal Tension Glaucoma

Normal tension glaucoma (NTG) is a progressive neurodegenerative disease in glaucoma families. Typical glaucoma develops because of increased intraocular pressure (IOP), whereas NTG develops despite normal IOP. As a subtype of open-angle glaucoma, NTG is characterized by retinal ganglion cell (RGC) degeneration, gradual loss of axons, and injury to the optic nerve. The relationship between glutamate excitotoxicity and oxidative stress has elicited great interest in NTG studies. We recently reported that suppressing collapsin response mediator protein 2 (CRMP2) phosphorylation in S522A CRMP2 mutant (CRMP2 KIKI) mice inhibited RGC death in NTG mouse models. This study evaluated the impact of the natural compounds huperzine A (HupA) and naringenin (NAR), which have therapeutic effects against glutamate excitotoxicity and oxidative stress, on inhibiting CMRP2 phosphorylation in mice intravitreally injected with N-methyl-D-aspartate (NMDA) and GLAST mutant mice. Results of the study demonstrated that HupA and NAR significantly reduced RGC degeneration and thinning of the inner retinal layer, and inhibited the elevated CRMP2 phosphorylation. These treatments protected against glutamate excitotoxicity and suppressed oxidative stress, which could provide insight into developing new effective therapeutic strategies for NTG.

Alzheimer's disease therapy based on acetylcholinesterase inhibitor/blocker effects on voltage-gated potassium channels

Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder with progressive loss of memory and other cognitive functions. The pathogenesis of this disease is complex and multifactorial, and remains obscure until now. To enhance the declined level of acetylcholine (ACh) resulting from loss of cholinergic neurons, acetylcholinesterase (AChE) inhibitors are developed and successfully approved for AD treatment in the clinic, with a limited therapeutic effectiveness. At present, it is generally accepted that multi-target strategy is potently useful for designing novel drugs for AD. Accumulated evidence reveals that Kv channels, which are broadly expressed in brain and possess crucial functions in modulating the neuronal activity, are inhibited by several acetylcholinesterase (AChE) inhibitors, such as tacrine, bis(7)-tacrine, donepezil and galantamine. Inhibition of Kv channels by these AChE inhibitors can generate neuroprotective effects by either mitigating Aβ toxicity and neuronal apoptosis, or facilitating cell proliferation. These inhibitory effects provide additional explanations for clinical beneficial effectiveness of AChE inhibitors, meaning that Kv channel is a promising candidate target for novel drugs for AD therapy.

Perspectives on the Role of APOE4 as a Therapeutic Target for Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disease that is coupled with chronic cognitive dysfunction. AD cases are mostly late onset, and genetic risk factors like the Apolipoprotein E (APOE) play a key role in this process. APOE ɛ2, APOE ɛ3, and APOE ɛ4 are three key alleles in the human APOE gene. For late onset, APOE ɛ4 has the most potent risk factor while APOE ɛ2 plays a defensive role. Several studies suggests that APOE ɛ4 causes AD via different processes like neurofibrillary tangle formation by amyloid-β accumulation, exacerbated neuroinflammation, cerebrovascular disease, and synaptic loss. But the pathway is still unclear that which actions of APOE ɛ4 lead to AD development. Since APOE was found to contribute to many AD pathways, targeting APOE ɛ4 can lead to a hopeful plan of action in development of new drugs to target AD. In this review, we focus on recent studies and perspectives, focusing on APOE ɛ4 as a key molecule in therapeutic strategies.

Huperzine A and Its Neuroprotective Molecular Signaling in Alzheimer's Disease

Huperzine A (HupA), an alkaloid found in the club moss Huperzia serrata, has been used for centuries in Chinese folk medicine to treat dementia. The effects of this alkaloid have been attributed to its ability to inhibit the cholinergic enzyme acetylcholinesterase (AChE), acting as an acetylcholinesterase inhibitor (AChEI). The biological functions of HupA have been studied both in vitro and in vivo, and its role in neuroprotection appears to be a good therapeutic candidate for Alzheimer´s disease (AD). Here, we summarize the neuroprotective effects of HupA on AD, with an emphasis on its interactions with different molecular signaling avenues, such as the Wnt signaling, the pre- and post-synaptic region mechanisms (synaptotagmin, neuroligins), the amyloid precursor protein (APP) processing, the amyloid-β peptide (Aβ) accumulation, and mitochondrial protection. Our goal is to provide an integrated overview of the molecular mechanisms through which HupA affects AD.

One-Carbon Insertion and Polarity Inversion Enabled a Pyrrole Strategy to the Total Syntheses of Pyridine-Containing Lycopodium Alkaloids: Complanadine A and Lycodine

Complanadine A and lycodine are representative members of the Lycopodium alkaloids with a characteristic pyridine-containing tetracyclic skeleton. Complanadine A has demonstrated promising neurotrophic activity and potential for persistent pain management. Herein we report a pyrrole strategy enabled by one-carbon insertion and polarity inversion for concise total syntheses of complanadine A and lycodine. The use of a pyrrole as the pyridine precursor allowed the rapid construction of their tetracyclic skeleton via a one-pot Staudinger reduction, amine-ketone condensation, and Mannich-type cyclization. The pyrrole group was then converted to the desired pyridine by the Ciamician-Dennstedt rearrangement via a one-carbon insertion process, which also simultaneously introduced a chloride at C3 for the next C-H arylation. Other key steps include a direct anti-Markovnikov hydroazidation, a Mukaiyama-Michael addition, and a Paal-Knorr pyrrole synthesis. Lycodine and complanadine A were prepared in 8 and 11 steps, respectively, from a readily available known compound.

Acetylcholinesterase Inhibitors in the Treatment of Neurodegenerative Diseases and the Role of Acetylcholinesterase in their Pathogenesis

Acetylcholinesterase (AChE) plays an important role in the pathogenesis of neurodegenerative diseases by influencing the inflammatory response, apoptosis, oxidative stress and aggregation of pathological proteins. There is a search for new compounds that can prevent the occurrence of neurodegenerative diseases and slow down their course. The aim of this review is to present the role of AChE in the pathomechanism of neurodegenerative diseases. In addition, this review aims to reveal the benefits of using AChE inhibitors to treat these diseases. The selected new AChE inhibitors were also assessed in terms of their potential use in the described disease entities. Designing and searching for new drugs targeting AChE may in the future allow the discovery of therapies that will be effective in the treatment of neurodegenerative diseases.

Bioinspired Diversification Approach Toward the Total Synthesis of Lycodine-Type Alkaloids

Nitrogen heterocycles (azacycles) are common structural motifs in numerous pharmaceuticals, agrochemicals, and natural products. Many powerful methods have been developed and continue to be advanced for the selective installation and modification of nitrogen heterocycles through C-H functionalization and C-C cleavage approaches, revealing new strategies for the synthesis of targets containing these structural entities. Here, we report the first total syntheses of the lycodine-type Lycopodium alkaloids casuarinine H, lycoplatyrine B, lycoplatyrine A, and lycopladine F as well as the total synthesis of 8,15-dihydrohuperzine A through bioinspired late-stage diversification of a readily accessible common precursor, N-desmethyl-β-obscurine. Key steps in the syntheses include oxidative C-C bond cleavage of a piperidine ring in the core structure of the obscurine intermediate and site-selective C-H borylation of a pyridine nucleus to enable cross-coupling reactions.

Directing Stem Cell Fate: The Synthetic Natural Product Connection

Stem cells possess remarkable potential for the treatment of a broad array of diseases including many that lack therapeutic options. However, the use of cell-based products derived from stem cells as therapeutics has limitations including rejection, sufficient availability, and lack of appropriate engraftment. Chemical control of stem cells provides potential solutions for overcoming many of the current limitations in cell-based therapeutics. The development of exogenous molecules to control stem cell self-renewal or differentiation has arrived at natural product-based agents as an important class of modulators. The ex vivo production of cryopreserved cellular products for use in tissue repair is a relatively new area of medicine in which the conventional hurdles to implementing chemicals to effect human health are changed. Translational challenges centered on chemistry, such as pharmacokinetics, are reduced. Importantly, in many cases the desired human tissues can be evaluated against new chemicals, and approaches to cellular regulation can be validated in the clinically applicable system. As a result linking new and existing laboratory syntheses of natural products with findings of the compounds' unique abilities to regulate stem cell fate provides opportunities for developing improved methods for tissue manufacture, accessing probe compounds, and generating new leads that yield manufactured cells with improved properties. This review provides a summary of natural products that have shown promise in controlling stem cell fate and which have also been fully synthesized thereby providing chemistry platforms for further development.

Improvement in Long-Term Memory following Chronic Administration of Eryngium planum Root Extract in Scopolamine Model: Behavioral and Molecular Study

Eryngium planum L. (EP) is as a rare medicinal plant with a lot of potentials as pharmaceutical crops. The aim of our study was to assess the effect of subchronic (28-fold) administration of a 70% ethanol extract of EP roots (200 mg/kg, p.o.) on behavioral and cognitive responses in Wistar rats linked with acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), and beta-secretase (BACE-1) mRNA levels and AChE and BuChE activities in the hippocampus and frontal cortex. On the last day of experiment, 30 min after the last dose of EP or Huperzine A (HU), scopolamine (SC) was given at a dose of 0.5 mg/kg b.w. intraperitoneally. The results of a passive avoidance test showed an improvement in long-term memory produced by the EP extract in both scopolamine-induced rats and control group. EP caused an insignificant inhibition of AChE and BuChE activities in the frontal cortex and the hippocampus. EP decreased mRNA AChE, BuChE, and BACE-1 levels, especially in the cortex. Our results suggest that the EP extract led to the improvement of the long-term memory in rats coupled with total saponin content. The mechanism of EP action is probably complicated, since HPLC-MS analysis showed 64 chemical compounds (phenolics, saponins) in the extract of EP roots.

Neurotrophic natural products: chemistry and biology

Neurodegenerative diseases and spinal cord injury affect approximately 50 million people worldwide, bringing the total healthcare cost to over 600 billion dollars per year. Nervous system growth factors, that is, neurotrophins, are a potential solution to these disorders, since they could promote nerve regeneration. An average of 500 publications per year attests to the significance of neurotrophins in biomedical sciences and underlines their potential for therapeutic applications. Nonetheless, the poor pharmacokinetic profile of neurotrophins severely restricts their clinical use. On the other hand, small molecules that modulate neurotrophic activity offer a promising therapeutic approach against neurological disorders. Nature has provided an impressive array of natural products that have potent neurotrophic activities. This Review highlights the current synthetic strategies toward these compounds and summarizes their ability to induce neuronal growth and rehabilitation. It is anticipated that neurotrophic natural products could be used not only as starting points in drug design but also as tools to study the next frontier in biomedical sciences: the brain activity map project.