3β, 6β-dichloro-5-hydroxy-5α-cholestane facilitates neuronal development through modulating TrkA signaling regulated proteins in primary hippocampal neuron

Differential Effects of the Processed and Unprocessed Garlic (Allium sativum L.) Ethanol Extracts on Neuritogenesis and Synaptogenesis in Rat Primary Hippocampal Neurons

Garlic (Allium sativum L.) is an aromatic herb known for its culinary and medicinal uses for centuries. Both unprocessed (white) and processed (black) garlic are known to protect against the pathobiology of neurological disorders such as Alzheimer's disease (AD) and Parkinson's disease (PD), which has been attributed to their anti-inflammatory and antioxidant properties. The information on the effects of processed and unprocessed garlic on neuronal process outgrowth, maturation, and synaptic development is limited. This study aimed at investigating and comparing the effects of the ethanol extracts of unprocessed (white garlic extract, WGE) and processed (black garlic extract, BGE) garlic on the maturation of primary hippocampal neurons. Neurite outgrowth was stimulated in a dose-dependent manner by both WGE and BGE and the most effective doses were 15 μg/mL and 60 μg/mL, respectively, without showing cytotoxicity. At this optimal concentration, both extracts promoted axonal and dendritic growth and maturation. Furthermore, both extracts substantially increased the formation of functional synapses. However, the effect of WGE was more robust at every developmental stage of neurons. In addition, the gas chromatography and mass spectrometry (GC-MS) analysis revealed a chemical profile of various bioactives in both BGE and WGE. Linalool, a compound that was found in both extracts, has shown neurite outgrowth-promoting activity in neuronal cultures, suggesting that the neurotrophic activity of garlic extracts is attributed, at least in part, to this compound. By using network pharmacology, linalool's role in neuronal development can also be observed through its modulatory effect on the signaling molecules of neurotrophic signaling pathways such as glycogen synthase kinase 3 (GSK3β), extracellular signal-regulated protein kinase (Erk1/2), which was further verified by immunocytochemistry. Overall, these findings provide information on the molecular mechanism of processed and unprocessed garlic for neuronal growth, survival, and memory function which may have the potential for the prevention of several neurological disorders.

Neuronal Differentiation and Outgrowth Effect of Thymol in Trachyspermum ammi Seed Extract via BDNF/TrkB Signaling Pathway in Prenatal Maternal Supplementation and Primary Hippocampal Culture

Reviving the neuronal functions in neurodegenerative disorders requires the promotion of neurite outgrowth. Thymol, which is a principal component of Trachyspermum ammi seed extract (TASE), is reported to have neuroprotective effects. However, the effects of thymol and TASE on neuronal differentiation and outgrowth are yet to be studied. This study is the first report investigating the neuronal growth and maturation effects of TASE and thymol. Pregnant mice were orally supplemented with TASE (250 and 500 mg/kg), thymol (50 and 100 mg/kg), vehicle, and positive controls. The supplementation significantly upregulated the expression of brain-derived neurotrophic factor (BDNF) and early neuritogenesis markers in the pups' brains at post-natal day 1 (P1). Similarly, the BDNF level was significantly upregulated in the P12 pups' brains. Furthermore, TASE (75 and 100 µg/mL) and thymol (10 and 20 µM) enhanced the neuronal polarity, early neurite arborization, and maturation of hippocampal neurons in a dose-dependent manner in primary hippocampal cultures. The stimulatory activities of TASE and thymol on neurite extension involved TrkB signaling, as evidenced by attenuation via ANA-12 (5 µM), which is a specific TrkB inhibitor. Moreover, TASE and thymol rescued the nocodazole-induced blunted neurite extension in primary hippocampal cultures, suggesting their role as a potent microtubule stabilizing agent. These findings demonstrate the potent capacities of TASE and thymol in promoting neuronal development and reconstruction of neuronal circuitry, which are often compromised in neurodegenerative diseases and acute brain injuries.

Mechanistic study of Coriandrum sativum on neuritogenesis and synaptogenesis based on computationally guided in vitro analyses

ETHNOPHARMACOLOGICAL RELEVANCE

Acceleration of neurite outgrowth and halting neurodegeneration are the most critical factors that are negatively regulated in various neurodegenerative diseases or injuries in the central nervous system (CNS). Functional foods or nutrients are considered alternative sources of bioactive components to alleviate various CNS injuries by promoting neuritogenesis and synaptogenesis, while their exact molecular mechanism remains unexplored.

AIM OF THE STUDY

Coriandrum sativum L. (CS) is one of the popular herbs in the Apiaceae family, of which CNS modulating action is a well-documented traditionally but detailed study on memory boosting function yet remains unexplored. Consequently, this study aims to analyze the neurogenic and synaptogenic modulation of CS aqueous ethanol (CSAE) extract in the primary hippocampal neurons.

MATERIALS AND METHODS

Primary hippocampal neurons were cultured and allowed to incubate with CSAE or vehicle. To observe the early neuronal differentiation, axonal and dendritic arborization, and synapse formation, neurons were immune-stained against indicated antibodies or stained directly with a lipophilic dye (1, 1'-dioctadecyl-3, 3, 3', 3'-tetramethyl indocarbocyanine perchlorate, DiL). Meanwhile, western blot was used to validate the synaptogenesis effect of CSAE compared to vehicle. Additionally, molecular docking and system pharmacology approaches were applied to confirm the possible secondary metabolites and pathways by which CSAE promotes neuritogenesis.

RESULTS

Results show that CSAE can induce neuritogenesis and synaptogenesis at 30 μg/mL concentration. The treatment impacts early neuronal polarization, axonal and dendritic arborization, synaptogenesis, and synaptic plasticity via NMDARs expressions in primary neurons. In silico network pharmacology of CS metabolites show that the CSAE-mediated neurogenic effect is likely dependent on the NTRK2 (TrkB) mediated neurotrophin signaling pathway. Indeed, the observed neurogenic activity of CSAE is markedly reduced upon the co-treatment with a TrkB-specific inhibitor. Furthermore, molecular docking following binding energy calculation shows that one of the CS metabolites, scoparone, has a high affinity to bind in the BDNF mimetic binding site of TrkB, suggesting its role in TrkB activation. Scoparone was found to enhance neuritogenesis, but not to the same extent as CSAE. Moreover, the expression of TrkB signaling-related proteins (BCL2, CASP3, GSK3, and BDNF), which was found to be modulated by scoparone, was significantly affected by the co-treatment of TrkB inhibitor (ANA-12). These results further suggest that the modulation of neuritogenesis by scoparone is TrkB-dependent.

CONCLUSIONS

This study provides deeper insights into the molecular mechanism of CS in boosting neuronal growth and memory function, which might implicate the prevention of many neurological disorders.

Protective Mechanisms of Nootropic Herb Shankhpushpi (Convolvulus pluricaulis) against Dementia: Network Pharmacology and Computational Approach

Convolvulus pluricaulis (CP), a Medhya Rasayana (nootropic) herb, is a major ingredient in Ayurvedic and Traditional Chinese formulae indicated for neurological conditions, namely, dementia, anxiety, depression, insanity, and epilepsy. Experimental evidence suggests various neuroactive potentials of CP such as memory-enhancing, neuroprotective, and antiepileptic. However, precise mechanisms underlying the neuropharmacological effects of CP remain unclear. The study, therefore, aimed at deciphering the molecular basis of neuroprotective effects of CP phytochemicals against the pathology of dementia disorders such as Alzheimer's (AD) and Parkinson's (PD) disease. The study exploited bioinformatics tools and resources, such as Cytoscape, DAVID (Database for annotation, visualization, and integrated discovery), NetworkAnalyst, and KEGG (Kyoto Encyclopedia of Genes and Genomes) database to investigate the interaction between CP compounds and molecular targets. An in silico analysis was also employed to screen druglike compounds and validate some selective interactions. ADME (absorption, distribution, metabolism, and excretion) analysis predicted a total of five druglike phytochemicals from CP constituents, namely, scopoletin, 4-hydroxycinnamic acid, kaempferol, quercetin, and ayapanin. In network analysis, these compounds were found to interact with some molecular targets such as prostaglandin G/H synthase 1 and 2 (PTGS1 and PTGS2), endothelial nitric oxide synthase (NOS3), insulin receptor (INSR), heme oxygenase 1 (HMOX1), acetylcholinesterase (ACHE), peroxisome proliferator-activated receptor-gamma (PPARG), and monoamine oxidase A and B (MAOA and MAOB) that are associated with neuronal growth, survival, and activity. Docking simulation further confirmed interaction patterns and binding affinity of selected CP compounds with those molecular targets. Notably, scopoletin showed the highest binding affinity with PTGS1, NOS3, PPARG, ACHE, MAOA, MAOB, and TRKB, quercetin with PTGS2, 4-hydroxycinnamic acid with INSR, and ayapanin with HMOX1. The findings indicate that scopoletin, kaempferol, quercetin, 4-hydroxycinnamic acid, and ayapanin are the main active constituents of CP which might account for its memory enhancement and neuroprotective effects and that target proteins such as PTGS1, PTGS2, NOS3, PPARG, ACHE, MAOA, MAOB, INSR, HMOX1, and TRKB could be druggable targets against dementia.

Neurotrophin-targeted therapeutics: A gateway to cognition and more?

Neurotrophins, such as brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF), are small proteins expressed in the brain and peripheral tissues, which regulate several key aspects of neuronal function, including neurogenesis, synaptic plasticity and neuroprotection, but also programmed cell death. This broad range of effects is a result of a complex downstream signaling pathway, with differential spatial and temporal activation patterns further diversifying their physiological effects. Alterations in neurotrophin levels, or known polymorphisms in neurotrophin genes, have been linked to a variety of disorders, including depression and Alzheimer's disease (AD). Historically, their therapeutic potential in these disorders has been hampered by the lack of suitable tool molecules for clinical studies. However, recent advancements have led to the development of new therapeutic candidates, which are now in clinical testing.

Unveiling the effect of Withania somnifera on neuronal cytoarchitecture and synaptogenesis: A combined in vitro and network pharmacology approach

Withania somnifera (WS), is known for its remarkable contribution in herbal medicine and Ayurveda, which is therapeutically applied to improve memory and anxiety in patients. However, the pharmacological details of this plant on memory boosting yet remained undefined. This study provides mechanistic insights on the effect of ethanol solution extract of the whole plant of WS (WSEE) on neuritogenesis by combining in vitro and in silico network pharmacology approaches. WSEE promoted significant neuronal growth through early differentiation, axodendritic arborization, and synaptogenesis on primary hippocampal neurons. The network pharmacological study confirmed that the neuritogenic activity is potentially mediated by modulating the neurotrophin signaling pathway, where NRTK1 (TrkA) was revealed as the primary target of WS secondary metabolites. This neurotrophic activity of WSEE was significantly stifled by the presence of TrkA inhibitor, which further confirms the TrkA-dependent activity of WSEE. In addition, a molecular docking study suggested steroidal lactones present in the WS might act as nerve growth factor (NGF)-mimetics, activating TrkA by binding to the NGF-binding domain. As a whole, the findings of the study suggest a significant role of WSEE on neuritogenesis and its potential to function as a therapeutic agent and in drug designing for the prevention and treatment of memory-related neurological disorders.

Chrysin restores memory deficit in hypothyroidism mice: Behavioral, neurochemical and computational approaches involving the neurotrophinergic system

Hypothyroidism is a condition that affects multiple systems, including the central nervous system, causing, for example, cognitive deficits closely related to Alzheimer's disease. The flavonoid chrysin is a natural compound associated with neuronal improvement in several experimental models. Here, we evaluated the effect of chrysin on cognitive impairment in hypothyroid female mice by exploring neuroplasticity. Hypothyroidism was induced by continuous exposure to 0.1% methimazole (MTZ) in drinking water for 31 days. On the 32nd day, the animals showed low plasma levels of thyroid hormones (hypothyroid mice) than the control group (euthyroid mice). Subsequently, mice were intragastrically administered with vehicle or chrysin (20 mg/kg) once a day for 28 consecutive days. At the end of the treatments, behavioral tests were performed: open-field test (OFT) and morris water maze (MWM). Then, the levels of neurotrophins (BDNF and NGF) in the hippocampus and prefrontal cortex were measured and tested the affinity of chrysin with neurotrophinergic receptors through molecular docking. Hypothyroid mice showed memory deficit in the MWM and reduced neurotrophins levels in the hippocampus and prefrontal cortex, meanwhile, the chrysin treatment was able to reversed the deficit of spatial memory function and increased the levels of BDNF in hipocamppus and NGF in both structures. Additionally, molecular docking analysis showed that chrysin potentially binds to the active site of the TrkA, TrkB, and p75NTR receptors. Together, these findings suggest that chrysin reversed behavioral and neurochemical alterations associated with memory deficit induced by hypothyroidism, possibly by modulating synaptic plasticity in the neurotrophinergic system.

Phytosterols: Targeting Neuroinflammation in Neurodegeneration

Plant-derived sterols, phytosterols, are well known for their cholesterol-lowering activity in serum and their anti-inflammatory activities. Recently, phytosterols have received considerable attention due to their beneficial effects on various non-communicable diseases, and recommended use as daily dietary components. The signaling pathways mediated in the brain by phytosterols have been evaluated, but little is known about their effects on neuroinflammation, and no clinical studies have been undertaken on phytosterols of interest. In this review, we discuss the beneficial roles of phytosterols, including their attenuating effects on inflammation, blood cholesterol levels, and hallmarks of the disease, and their regulatory effects on neuroinflammatory disease pathways. Despite recent advancements made in phytosterol pharmacology, some critical questions remain unanswered. Therefore, we have tried to highlight the potential of phytosterols as viable therapeutics against neuroinflammation and to direct future research with respect to clinical applications.

The beneficial role of the synthetic microneurotrophin BNN20 in a focal demyelination model

BNN20, a C17-spiroepoxy derivative of the neurosteroid dehydroepiandrosterone, has been shown to exhibit strong neuroprotective properties but its role in glial populations has not been assessed. Our aim was to investigate the effect of BNN20 on glial populations by using in vitro and in vivo approaches, taking advantage of the well-established lysophosphatidylcholine (LPC)-induced focal demyelination mouse model. Our in vivo studies, performed in male mice, showed that BNN20 treatment leads to an increased number of mature oligodendrocytes (OLs) in this model. It diminishes astrocytic accumulation during the demyelination phase leading to a faster remyelination process, while it does not affect oligodendrocyte precursor cell recruitment or microglia/macrophage accumulation. Additionally, our in vitro studies showed that BNN20 acts directly to OLs and enhances their maturation even after they were treated with LPC. This beneficial effect of BNN20 is mediated, primarily, through the neurotrophin receptor TrkA. In addition, BNN20 reduces microglial activation and their transition to their pro-inflammatory state upon lipopolysaccharides stimulation in vitro. Taken together our results suggest that BNN20 could serve as an important molecule to develop blood-brain barrier-permeable synthetic agonists of neurotrophin receptors that could reduce inflammation, protect and increase the number of functional OLs by promoting their differentiation/maturation.

Centella asiatica promotes early differentiation, axodendritic maturation and synaptic formation in primary hippocampal neurons

BACKGROUND

Centella asiatica is a 'medhya-rasayana (nootrophic or memory booster)' herb that has been indicated in Ayurveda for improving memory function and treating dementia disorders. Although the neuroprotective effects of C. asiatica have been reported in earlier studies, the information on whether this nootropic herb could promote early differentiation and development of axon and dendrites in primary hippocampal neurons is currently limited.

THE AIM OF THE STUDY

To investigate the effects of C. asiatica and asiatic acid, one of the principal active constituents of C. asiatica, on the various stages of neuronal polarity, including early neuronal differentiation, axonal outgrowth, dendritic arborization, axonal maturation, and synaptic formation.

MATERIALS AND METHODS

Embryonic rat hippocampal neurons were incubated with C. asiatica leaf extract (CAE) or asiatic acid. After an indicated time, neurons were fixed and immunolabeled to visualize the neuronal morphology. Morphometric analyses for early neuronal differentiation, axonal and dendritic maturation and synaptogenesis were performed using Image J software. Neuronal viability was determined using trypan blue exclusion assay.

RESULTS

CAE at varying concentrations ranging from 3.75 to 15 μg/mL enhanced neurite outgrowth with the highest optimal concentration of 7.5 μg/mL. The effects of CAE commenced immediately after cell seeding, as indicated by its accelerating effect on neuronal differentiation. Subsequently, CAE significantly elaborated dendritic and axonal morphology and facilitated synapse formation. Asiatic acid also facilitated neurite outgrowth, but to a lesser extent than CAE.

CONCLUSION

These findings revealed that CAE exerted its modulatory effects in every stage of neuronal development, supporting its previously claimed neurotrophic function and suggest that this natural nootropic and its active component asiatic acid can be further investigated to explore a promising solution for degenerative brain disorders and injuries.

Decreased miR-132 plays a crucial role in diabetic encephalopathy by regulating the GSK-3β/Tau pathway

Diabetic encephalopathy (DE) is a global concern and Gordian knot worldwide. miRNA-132 (miR-132) is a class of negative gene regulators that promote diabetic pathologic mechanisms and its complications. However, the molecular mechanisms of miR-132 in DE are elusive, thus an alternative therapeutic strategy is urgently in demand. The present study explored the protective effect and the underlying mechanism of miR-132 on DE via the GSK-β/Tau signaling pathway. Experimentally, a type 2 DM rat model was developed by incorporating a high-fat diet and streptozotocin injection. Further, the DE model was screened via the Morris Water Maze test. Primary hippocampal neurons and HT-22 cells were used for in vitro analysis. We found that hyperglycemia exacerbates cognitive impairment in T2DM rats. When we isolated the primary hippocampus neurons, the expression of miR-132 RNA was low in both the DE hippocampus and primary neurons. GSK-3β and Tau 404 were highly expressed in injured HT-22 cells and diabetic hippocampal tissues. miR-132 downregulated the expression of GSK-3β. Besides, a binding and colocalized relationship between GSK3β and Tau was also reported. These findings suggest that miR-132 exerts protective effects from DE injury by repressing GSK-3β expression and alleviating Tau hyperphosphorylation in HT-22 cells and hippocampus tissues.