Claulansine F promotes neuritogenesis in PC12 cells via the ERK signaling pathway

Unlocking the Therapeutic Potential of Natural Products for Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative condition marked by memory loss and cognitive decline. With current treatments offering limited effectiveness, researchers are turning to natural products that can target various aspects of AD pathology. Clinically approved natural products, such as galantamine and huperzine A, have shown success in AD treatments. Furthermore, compounds such as epigallocatechin gallate, quercetin, and resveratrol are in clinical trials. This Perspective examines nearly 100 natural compounds with promising neuroprotective effects in preclinical and clinical studies. These compounds exhibit diverse pharmacological actions that help to prevent neurodegeneration while improving cognitive functions. Their unique structures further enhance their biological activities, making them promising candidates for drug discovery. This Perspective stresses the importance of further clinical research to maximize the medical benefits of these compounds and highlights their potential as innovative remedies for AD. Continued exploration of these compounds is crucial to fully leverage their capabilities in combating AD.

Chemical profile of the roots of Clausena lansium and their inhibitory effects of the over-activation in BV-2 microglial cells

From the 95% ethanol aqueous extract of the roots of Clausena lansium, six previously undescribed alkaloids (1, 2a, 2b, 15, 24a, 24b), a pair of prenylated phenylpropenols (26a, 26b), two coumarins (27, 28), and two undescribed sesquiterpenes (37, 38) were isolated and identified using spectroscopic and electron circular dichroism data, together with thirty-two known compounds. The absolute configurations of three alkaloids (3a, 3b, 4a) were determined for the first time. In vitro assay showed that alkaloids 7, 10, 12, 19, and furanocoumarins 34, 35 displayed inhibitory effects on the production of nitric oxide in lipopolysaccharide (LPS)-induced BV-2 microglial cells, which were stronger than that of the minocycline (positive control). RT-PCR results indicated that indizoline (7) could inhibit the expression of pro-inflammatory factors (IL-1β, TNF-α, and IL-6) in LPS-treated BV-2 cells.

Neurotrophic Natural Products

Neurotrophins (NGF, BDNF, NT3, NT4) can decrease cell death, induce differentiation, as well as sustain the structure and function of neurons, which make them promising therapeutic agents for the treatment of neurodegenerative disorders. However, neurotrophins have not been very effective in clinical trials mostly because they cannot pass through the blood-brain barrier owing to being high-molecular-weight proteins. Thus, neurotrophin-mimic small molecules, which stimulate the synthesis of endogenous neurotrophins or enhance neurotrophic actions, may serve as promising alternatives to neurotrophins. Small-molecular-weight natural products, which have been used in dietary functional foods or in traditional medicines over the course of human history, have a great potential for the development of new therapeutic agents against neurodegenerative diseases such as Alzheimer's disease. In this contribution, a variety of natural products possessing neurotrophic properties such as neurogenesis, neurite outgrowth promotion (neuritogenesis), and neuroprotection are described, and a focus is made on the chemistry and biology of several neurotrophic natural products.

CZK, a novel alkaloid derivative from Clausena lansium, alleviates ischemic stroke injury through Nrf2-mediated antioxidant effects

Anti-oxidant stress is a potential strategy for the treatment of ischemic stroke. Here, we found a novel free radical scavenger termed as CZK, which is derived from alkaloids contained in Clausena lansium. In this study, we first compared cytotoxicity and biological activity between CZK and its parent's compound Claulansine F. It was found that CZK had lower cytotoxicity and improved anti-oxygen-glucose deprivation/reoxygenation (OGD/R) injury than its parent's compound. Free radical scavenging test showed that CZK had a strong inhibitory effect on hydroxyl free radicals with the IC₅₀ of 77.08 nM. Intravenous injection of CZK (50 mg/kg) significantly alleviated ischemia-reperfusion injury, manifested by reduced neuronal damage and decreased oxidative stress. Consistent with the findings, the activities of superoxide dismutase (SOD) and reduced glutathione (GSH) were increased. Molecular docking predicted that CZK might be combined with nuclear factor erythroid 2-related factor 2 (Nrf2) complex. Our results also confirmed that CZK upregulated the contents of Nrf2 and its target gene products Heme Oxygenase-1 (HO-1), and NAD(P)H: Quinone Oxidoreductase 1 (NQO1). In conclusion, CZK had a potential therapeutic effect for ischemic stroke by activating Nrf2-mediated antioxidant system.

Regulation of Neurogenesis and Neuronal Differentiation by Natural Compounds

Neuronal damage or degeneration is the main feature of neurological diseases. Regulation of neurogenesis and neuronal differentiation is important in developing therapies to promote neuronal regeneration or synaptic network reconstruction. Neurogenesis is a multistage process in which neurons are generated and integrated into existing neuronal circuits. Neuronal differentiation is extremely complex because it can occur in different cell types and can be caused by a variety of inducers. Recently, natural compounds that induce neurogenesis and neuronal differentiation have attracted extensive attention. In this paper, the potential neural induction effects of medicinal plant-derived natural compounds on neural stem/progenitor cells (NS/PCs), the cultured neuronal cells, and mesenchymal stem cells (MSCs) are reviewed. The natural compounds that are efficacious in inducing neurogenesis and neuronal differentiation include phenolic acids, polyphenols, flavonoids, glucosides, alkaloids, terpenoids, quinones, coumarins, and others. They exert neural induction effects by regulating signal factors and cell-specific genes involved in the process of neurogenesis and neuronal differentiation, including specific proteins (β-tubulin III, MAP-2, tau, nestin, neurofilaments, GFAP, GAP-43, NSE), related genes and proteins (STAT3, Hes1, Mash1, NeuroD1, notch, cyclin D1, SIRT1, reggie-1), transcription factors (CREB, Nkx-2.5, Ngn1), neurotrophins (BDNF, NGF, NT-3) and signaling pathways (JAK/STAT, Wnt/β-catenin, MAPK, PI3K/Akt, GSK-3β/β-catenin, Ca2+/CaMKII/ATF1, Nrf2/HO-1, BMP). The natural compounds with neural induction effects are of great value for neuronal regenerative medicine and provide promising prevention and treatment strategies for neurological diseases.

Aberrant canonical Wnt signaling: Phytochemical based modulation

BACKGROUND

Wnt signaling pathway plays a major role during development like gastrulation, axis formation, organ development and organization of body plan development. Wnt signaling aberration has been linked with various disease conditions like osteoporosis, colon cancer, hair follicle tumor, Leukemia, and Alzheimer's disease. Phytochemicals like flavonoid, glycosides, polyphenols, have been reported to directly target the markers of Wnt signaling in different disease models.

PURPOSE

The study deals in detail about the different phytochemical targeting key players of Wnt signaling pathway in diseases like Cancer, Osteoporosis, and Alzheimer's disease. We have focused on the Pharmacological basis of disease alleviation by phytochemical specifically targeting the Wnt signaling markers in this study.

METHODS

The study focused on the published articles from the preclinical rodent and invitro cell line studies related to Wnt signaling and Phytochemicals related to Cancer, Alzheimer's and Osteoporosis. The electronic databases Scopus, Web of Science and Pubmed database were used for the systematic search of literatures from 2005 up to 2019 using keywords Canonical Wnt signaling pathway, Cancer, Alzheimer's disease, Osteoporosis, Phytochemicals. The focus was to identify the target specific modulation of Wnt signaling mediated by phytochemicals.

RESULTS

Approximately 30 phytochemicals of different class have been identified to modulate Wnt signaling pathway acting through Axin, β-catenin translocation, GSK-3β, AKT, Wif-1 in various experimental studies. The down regulation of Wnt signaling is observed in Cancer mostly colorectal cancer, breast cancer mediated through mutations in APC and Axin genes. Different class of Phytochemicals such as flavonoid, glycosides, polyphenol, alkaloids etc. have been found to target Wnt signaling markers and alleviate Cancer. Similarly, Up regulation of Wnt signaling has been reported in Osteoporosis and neurodegenerative disease like Alzheimer's disease.

CONCLUSION

This review highlights the possibility of the Phytochemicals to target Wnt markers and its potential to either activate or deactivate the Wnt signaling pathway. It also describes the challenges in proper targeting of Wnt signaling and the potential risk and consequences of either up regulation or down regulation of the signaling pathway. This article highlights the possibility of Wnt signaling pathway as a therapeutic option in different diseases.

CZ-7, a new derivative of Claulansine F, promotes remyelination induced by cuprizone by enhancing myelin debris clearance

The mechanism of demyelinating diseases is controversial, while demyelination and remyeliantion disorder is the acknowledged etiology and therapeutic target. Untill now, there is no efficient therapy for these diseases. CZ-7, a new derivative of Claulansine F, which has been reported before, were investigated its pro-remyelination effect and its associated mechanism in cuprizone (CPZ)-induced demyelination model. In this study, male C57BL/6 mice were subjected to CPZ (300 mg/kg) through intragastric gavage and were orally administered CZ-7 (20 mg/kg) meanwhile. The results of weight monitoring and behavioral testing showed that CZ-7 can significantly improve behavior dysfunction in the demyelinating mice. Luxol-fast blue (LFB) staining, myelin basic protein (MBP) immunostaining, transmission electron microscopy (TEM) and QPCR results indicated the therapeutic effect of CZ-7 on CPZ mice model. Furthermore, degraded myelin basic protein (dMBP) immunofluorescent staining and oil red O staining showed that CZ-7 contributed to the clearance of degraded myelin debris. More microglia displayed phagocytic shape assembled in corpus callosum (CC) and there was an active process of phagocytosis in microglia after CZ-7 treatment. Immunofluorescent staining and QPCR analysis revealed the M2-polarized phenotype switch of microglia in the process of myelin debris removel, which demostrated the microenvironment improvement of CZ-7. Moreover, immunofluorescent staining of NG2 and O4 demonstated that more oligodendrocyte precursor cells (OPCs) existed in CC after CZ-7 treatment. In conclusion, our results demonstrated CZ-7 has a potential therapeutic effect for MS and other demyelinating diseases through enhancing myelin debris clearance to improve the microenvironment.

CZ-7, a new derivative of Claulansine F, ameliorates 2VO-induced vascular dementia in rats through a Nrf2-mediated antioxidant responses

Vascular dementia (VD) results from accumulated damage in the vascular system, which is characterized by progressive impairments in memory and cognition and is second only to Alzheimer's disease (AD) in prevalence among all types of dementia. In contrast to AD, there is no FDA-approved treatment for VD owing to its multiple etiologies. In this study, we investigated whether CZ-7, a new derivative of Claulansine F (Clau F) with verified neuroprotective activity in vitro, could ameliorate the cognitive impairment of rats with permanent occlusion of bilateral common carotid arteries (2VO) and its potential mechanisms of action. The 2VO rats were orally administered CZ-7 (10, 20, 40 mg/kg) from day 27 to day 53 post-surgery. Morris water maze tests conducted at day 48-51 revealed that CZ-7 administration significantly reduced the escape latency in 2VO rats. After the rats were sacrificed on day 53, morphological studies using Nissl and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining showed that administration of CZ-7 markedly attenuated the pathological changes in CA1-CA3 area of the hippocampus, including neuronal cell loss, nuclear shrinkage, and dark staining of neurons, and significantly decreased the chronic cerebral hypoperfusion-induced cell loss. Klüver-Barrera staining study revealed that CZ-7 administration significantly improved the white matter lesions. 8-OHdG and reactive oxygen species (ROS) immunofluorescent analyses showed that CZ-7 administration significantly decreased oxidative stress in CA1-CA3 area of the hippocampus. Finally, we found that the CZ-7-improved oxidative stress might be mediated via the Nrf2 pathway, evidenced by the double immunofluorescent staining of Nrf2 and the elevation of expression levels of oxidative stress proteins HO-1 and NQO1. In conclusion, CZ-7 has therapeutic potential for VD by alleviating oxidative stress injury through Nrf2-mediated antioxidant responses.

Claulansine F promoted the neuronal differentiation of neural stem and progenitor cells through Akt/GSK-3β/β-catenin pathway

The persistence of neurogenesis raises the idea that neurons produced by the resident or transplanted neural stem cells could replace the neurons lost from brain injury or neurodegenerative disease. Therefore, compounds or methods for promoting neuronal differentiation become the focus of neurodegenerative disease therapy research. Claulansine F (Clau F), a newly discovered carbazole alkaloid, has been showed to induce neuritogenesis in PC12 cells. Herein, we studied the effect of Clau F on neuronal differentiation of neural stem/progenitor cells (NS/PCs). The current study demonstrated that Clau F initiated neuronal differentiation with a significant increase of TuJ1-positive cells and TuJ1 protein levels. We also found that Clau F promoted the maturity and sustainability of neurons by increasing MAP2-positive cells and MAP2 protein levels. At the same time, Clau F significantly inhibited the proliferation of NS/PCs. The underlying mechanism of Clau F was preliminary explored. Clau F treatment resulted in a profound increase of phosphorylation of Akt and GSK-3β, which led to GSK-3β inhibition and subsequently the nuclear accumulation of β-catenin. Further, the interaction between β-catenin and p300 in the nucleus was enhanced and the transcription of p300/β-catenin responsive genes were increased significantly (c-jun, fra-1) by Clau F. Importantly, the positive effect of Clau F on neuronal differentiation was abolished by Akti-1/2, a specific inhibitor of Akt-1/2 kinase, which indicated the involvement of Akt/GSK-3β in Clau F-mediated neuronal differentiation. In conclusion, these data suggested that Clau F promoted neuronal differentiation through Akt/GSK-3β/β-catenin signaling pathway in NS/PCs.

Liraglutide Promotes Cortical Neurite Outgrowth via the MEK-ERK Pathway

Liraglutide is the glucagon-like peptide-1 (GLP-1) synthetic form which has been approved by the US Food and Drug Administration to be released onto the market. The metabolic benefits of incretin hormone as an anti-diabetic agent are widely recognized, but its potential extra-pancreatic effects of GLP-1 analog (liraglutide) in the central nerve system are less well known. To this purpose, we used immunofluorescence method to examine the effect of liraglutide on neurite outgrowth in primary cortical neuron culture by measuring neurite length and confirmed the promotion effect. Then, we investigated the potential mechanisms and found that liraglutide promoted neurite outgrowth in a dose-dependant manner, and this effect could be partially inhibited by MEK-ERK inhibitor U0126. Besides, liraglutide induced an increase of p-ERK/ERK expression, which could be blocked in the presence of U0126. Similarly, phosphorylated transcription factor (p-CREB) level shared the same trend with p-ERK/ERK ratio after liraglutide treatment. Collectively, our data illustrated that that liraglutide exerts neurotrophin-like activity partly via MEK-ERK pathway, which might offer a novel idea for treatment of axon-associated neurological diseases.

Robust Neuritogenesis-Promoting Activity by Bis(heptyl)-Cognitin Through the Activation of alpha7-Nicotinic Acetylcholine Receptor/ERK Pathway

AIMS

Neurodegenerative disorders are caused by progressive neuronal loss in the brain, and hence, compounds that could promote neuritogenesis may have therapeutic values. In this study, the effects of bis(heptyl)-cognitin (B7C), a multifunctional dimer, on neurite outgrowth were investigated in both PC12 cells and primary cortical neurons.

METHODS

Immunocytochemical staining was used to evaluate the proneuritogenesis effects, and Western blot and short hairpin RNA assays were applied to explore the underlying mechanisms.

RESULTS

B7C (0.1-0.5 μM) induced robust neurite outgrowth in PC12 cells, as evidenced by the neurite-bearing morphology and upregulation of growth-associated protein-43 expression. In addition, B7C markedly promoted neurite outgrowth in primary cortical neurons as shown by the increase in the length of β-III-tubulin-positive neurites. Furthermore, B7C rapidly increased ERK phosphorylation. Specific inhibitors of alpha7-nicotinic acetylcholine receptor (α7-nAChR) and MEK, but not those of p38 or JNK, blocked the neurite outgrowth as well as ERK phosphorylation induced by B7C. Most importantly, genetic depletion of α7-nAChR significantly abolished B7C-induced neurite outgrowth in PC12 cells.

CONCLUSION

B7C promoted neurite outgrowth through the activation of α7-nAChR/ERK pathway, which offers novel insight into the potential application of B7C in the treatment of neurodegenerative disorders.