Cerebroprotective Potential of Andrographolide Nanoparticles: In silico and In vivo Investigations

Ischemic stroke remains the leading cause of death and disability, while the main mechanisms of dominant neurological damage in stroke contain oxidative stress and inflammation. Docking studies revealed a binding energy of - 6.1 kcal/mol for AG, while the co-crystallized ligand (CCl) exhibited a binding energy of - 7.3 kcal/mol with NOS. AG demonstrated favourable hydrogen bond interactions with amino acids ASN A:354 and ARG A:388 and hydrophobic interactions with GLU A:377. Molecular dynamics simulations throughout 100 ns indicated a binding affinity of - 27.65±2.88 kcal/mol for AG, compared to - 18.01±4.02 kcal/mol for CCl. These findings suggest that AG possesses a superior binding affinity for NOS compared to CCl, thus complementing the stability of NOS at the docked site.AG has limited applications owing to its low bioavailability, poor water solubility, and high chemical and metabolic instability.The fabrication method was employed in the preparation of AGNP, SEM analysis confirmed spherical shape with size in 19.4±5 nm and investigated the neuroprotective effect in cerebral stroke rats induced by 30 min of carotid artery occlusion followed by 4 hr reperfusion, evaluated by infarction size, ROS/RNS via GSH, MPO, NO estimationand AchE activity, and monitoring EEG function. Cortex and hippocampal histology were compared between groups. AGNP treatment significantly decreased Infarction size and increased GSH levels (p<0.01**), decreased MPO (p<0.01**), NO (p<0.01**), AchE (p<0.01**), restored to normal EEG amplitude, minimizing unsynchronized polyspikes and histological data revealed that increased pyramidal cell layer thickness and decreased apoptotic neurons in hippocampus, cortex appeared normal neurons with central large vesicular nuclei, containing one or more nucleoli in compared to AG treatment. Based on brain biochemical, histopathology reports AGNP exhibited significant cerebroprotective activity compared to AG on ischemic rats.

Andrographolide Improves ApoE4-Mediated Blood-Brain Barrier Injury by Alleviating Inflammation

The pathological and physiological studies of Alzheimer's disease (AD) have been in-depth, and apolipoprotein E4 (ApoE4) has been proven to be highly correlated with AD, and clinical and experimental data show that ApoE4 can cause blood-brain barrier (BBB) injury, and the change of BBB permeability is an important factor affecting the development of AD. Andrographolide (Andro), as the active component of the natural plant Andrographis paniculata, has been proven to have anti-inflammatory and antioxidant effects, which have potential neuroprotective effects. To verify the protective effect of Andro on BBB in a short term, our research group used atorvastatin (Atorva)-mediated zebrafish brain injury model and the ApoE4-mediated cell co-culture model of BBB injury to explore the protective effects and mechanisms of Andro on BBB injury. Studies have shown that Andro can inhibit the activation of CypA/NF-κB/MMP-9 signaling pathway and has achieved the effect of antagonizing the inhibition of ApoE4 on intercellular tight junction proteins (occludin, claudin-5, and ZO-1). At the same time, Andro can inhibit the secretion of cell adhesion molecules (VCAM-1 and ICAM-1) in cells, thereby delaying the occurrence and progression of neuroinflammation and playing a protective role in BBB. In conclusion, Andro is a potent natural product which can protect the blood-brain barrier.

Impact of micronutrients and nutraceuticals on cognitive function and performance in Alzheimer's disease

Alzheimer's disease (AD) is a major global health problem today and is the most common form of dementia. AD is characterized by the formation of β-amyloid (Aβ) plaques and neurofibrillary clusters, leading to decreased brain acetylcholine levels in the brain. Another mechanism underlying the pathogenesis of AD is the abnormal phosphorylation of tau protein that accumulates at the level of neurofibrillary aggregates, and the areas most affected by this pathological process are usually the cholinergic neurons in cortical, subcortical, and hippocampal areas. These effects result in decreased cognitive function, brain atrophy, and neuronal death. Malnutrition and weight loss are the most frequent manifestations of AD, and these are also associated with greater cognitive decline. Several studies have confirmed that a balanced low-calorie diet and proper nutritional intake may be considered important factors in counteracting or slowing the progression of AD, whereas a high-fat or hypercholesterolemic diet predisposes to an increased risk of developing AD. Especially, fruits, vegetables, antioxidants, vitamins, polyunsaturated fatty acids, and micronutrients supplementation exert positive effects on aging-related changes in the brain due to their antioxidant, anti-inflammatory, and radical scavenging properties. The purpose of this review is to summarize some possible nutritional factors that may contribute to the progression or prevention of AD, understand the role that nutrition plays in the formation of Aβ plaques typical of this neurodegenerative disease, to identify some potential therapeutic strategies that may involve some natural compounds, in delaying the progression of the disease.

Andrographolide derivative Andro-III modulates neuroinflammation and attenuates neuropathological changes of Alzheimer's disease via GSK-3β/NF-κB/CREB pathway

Andrographolide has anti-inflammatory and neuroprotective effects, making it a potential therapeutic option for Alzheimer's disease (AD). Our research group optimized its structure in a previous study to minimize the risk of renal toxicity, which would beneficial for future clinical research. This study aims to examine the impact of Andro-III on enhancing cognitive learning ability in 3xTg-AD mice, as well as the mechanisms involved. Andro-III improved spatial learning ability, prevented the loss of Nysted's vesicles, reduced the accumulation of β-amyloid (Aβ) and tau proteins, and suppressed microglial activation. Further research found that the expression of nuclear factor kappa-B RelA (NF-κB p65) expression and glycogen synthase kinase-3β (GSK-3β) activity were inhibited, while CREB was upregulated in brain tissue treated with Andro-III. Moreover, Andro-III downregulated the expression of IBA1 and inflammatory factors in microglial cells of mice induced by Aβ. The regulation of the GSK-3β/NF-κB/CREB pathway was similar to that observed in 3xTg-AD mice. Therefore, Andro-III modulates neuroinflammation and attenuates neuropathological changes of AD via the GSK-3β/NF-κB/CREB pathway.

Therapeutic Potential of Natural Compounds from Herbs and Nutraceuticals in Alleviating Neurological Disorders: Targeting the Wnt Signaling Pathway

As an important signaling pathway in multicellular eukaryotes, the Wnt signaling pathway participates in a variety of physiological processes. Recent studies have confirmed that the Wnt signaling pathway plays an important role in neurological disorders such as stroke, Alzheimer's disease, and Parkinson's disease. The regulation of Wnt signaling by natural compounds in herbal medicines and nutraceuticals has emerged as a potential strategy for the development of new drugs for neurological disorders. Purpose: The aim of this review is to evaluate the latest research results on the efficacy of natural compounds derived from herbs and nutraceuticals in the prevention and treatment of neurological disorders by regulating the Wnt pathway in vivo and in vitro. A manual and electronic search was performed for English articles available from PubMed, Web of Science, and ScienceDirect from the January 2010 to February 2023. Keywords used for the search engines were "natural products,″ "plant derived products,″ "Wnt+ clinical trials,″ and "Wnt+,″ and/or paired with "natural products″/″plant derived products", and "neurological disorders." A total of 22 articles were enrolled in this review, and a variety of natural compounds from herbal medicine and nutritional foods have been shown to exert therapeutic effects on neurological disorders through the Wnt pathway, including curcumin, resveratrol, and querctrin, etc. These natural products possess antioxidant, anti-inflammatory, and angiogenic properties, confer neurovascular unit and blood-brain barrier integrity protection, and affect neural stem cell differentiation, synaptic formation, and neurogenesis, to play a therapeutic role in neurological disorders. In various in vivo and in vitro studies and clinical trials, these natural compounds have been shown to be safe and tolerable with few adverse effects. Natural compounds may serve a therapeutic role in neurological disorders by regulating the Wnt pathway. This summary of the research progress of natural compounds targeting the Wnt pathway may provide new insights for the treatment of neurological disorders and potential targets for the development of new drugs.

Molecular docking and dynamics simulations revealed the potential inhibitory activity of honey-iQfood ingredients against GSK-3β and CDK5 protein targets for brain health

Honey-iQfood is an herbal supplement made of a mixture of polyherbal extracts and wild honey. The mixture is traditionally claimed to improve various conditions related to brain cells and functions including dementia and Alzheimer's disease. Glycogen synthase kinase-3 beta (GSK-3β) and cyclin-dependent kinase 5 (CDK5) have been identified as being involved in the pathological hyperphosphorylation of tau proteins, which leads to the formation of neurofibrillary tangles and causes Alzheimer's disease. Therefore, this study was conducted to confirm the traditional claims by detection of active compounds, namely curcumin, gallic acid, catechin, rosmarinic acid, and andrographolide in the raw materials of Honey-iQfood through HPLC analysis, molecular docking, and dynamic simulations. Two potential compounds, andrographolide, and rosmarinic acid, produced the best binding affinities following the molecular docking of the active compounds against the GSK-3β and CDK5 targets. Andrographolide binds with GSK-3β at -8.2 kcal/mol, whereas rosmarinic acid binds to CDK5 targets at -8.6 kcal/mol. Molecular dynamics was further carried out to confirm the docking results and clarify their dynamic properties such as RMSD, RMSF, rGyr, SASA, PSA, and binding free energy. CDK5-andrographolide complexes had the best MM-GBSA score (-83.63 kcal/mol) compared to other complexes, indicating the better interaction profile and stability of the complex. These findings warrant further research into andrographolide and rosmarinic acid as efficient inhibitors of tau protein hyperphosphorylation to verify their therapeutic potential in brain-related illnesses.Communicated by Ramaswamy H. Sarma.

The Effects of Andrographis paniculata (Burm.F.) Wall. Ex Nees and Andrographolide on Neuroinflammation in the Treatment of Neurodegenerative Diseases

Neurodegenerative diseases (NDs) affect millions of people worldwide, and to date, Alzheimer's and Parkinson's diseases are the most common NDs. Of the many risk factors for neurodegeneration, the aging process has the most significant impact, to the extent that it is tempting to consider neurodegenerative disease as a manifestation of accelerated aging. However, genetic and environmental factors determine the course of neurodegenerative disease progression. It has been proposed that environmental stimuli influence neuroplasticity. Some clinical studies have shown that healthy lifestyles and the administration of nutraceuticals containing bioactive molecules possessing antioxidant and anti-inflammatory properties have a preventive impact or mitigate symptoms in previously diagnosed patients. Despite ongoing research efforts, the therapies currently used for the treatment of NDs provide only marginal therapeutic benefits; therefore, the focus is now directly on the search for natural products that could be valuable tools in combating these diseases, including the natural compound Andrographis paniculata (Ap) and its main constituent, andrographolide (Andro). Preclinical studies have shown that the aqueous extract of Ap can modulate neuroinflammatory and neurodegenerative responses, reducing inflammatory markers and oxidative stress in various NDs. Therefore, in this review, we will focus on the molecular mechanisms by which Ap and Andro can modulate the processes of neurodegeneration and neuroinflammation, which are significant causes of neuronal death and cognitive decline.

Utilizing Andrographis paniculata leaves and roots by effective usage of the bioactive andrographolide and its nanodelivery: investigation of antikindling and antioxidant activities through in silico and in vivo studies

To valorise the bioactive constituents abundant in leaves and other parts of medicinal plants with the objective to minimize the plant-based wastes, this study was undertaken. The main bioactive constituent of Andrographis paniculata, an Asian medicinal plant, is andrographolide (AG, a diterpenoid), which has shown promising results in the treatment of neurodegenerative illnesses. Continuous electrical activity in the brain is a hallmark of the abnormal neurological conditions such as epilepsy (EY). This can lead to neurological sequelae. In this study, we used GSE28674 as a microarray expression profiling dataset to identify DEGs associated with andrographolide and those with fold changes >1 and p-value <0.05 GEO2R. We obtained eight DEG datasets (two up and six down). There was marked enrichment under various Kyoto Encyclopaedia of Genes and Genomes (KEGG) and Gene Ontology (GO) terms for these DEGs (DUSP10, FN1, AR, PRKCE, CA12, RBP4, GABRG2, and GABRA2). Synaptic vesicles and plasma membranes were the predominant sites of DEG expression. AG acts as an antiepileptic agent by upregulating GABA levels. The low bioavailability of AG is a significant limitation of its application. To control these limitations, andrographolide nanoparticles (AGNPs) were prepared and their neuroprotective effect against pentylenetetrazol (PTZ)-induced kindling epilepsy was investigated using network pharmacology (NP) and docking studies to evaluate the antiepileptic multi-target mechanisms of AG. Andrographolide is associated with eight targets in the treatment of epilepsy. Nicotine addiction, GABAergic synapse, and morphine addiction were mainly related to epilepsy, according to KEGG pathway enrichment analysis (p < 0.05). A docking study showed that andrographolide interacted with the key targets. AG regulates epilepsy and exerts its therapeutic effects by stimulating GABA production. Rats received 80 mg/kg body weight of AG and AGNP, phenytoin and PTZ (30 mg/kg i.p. injection on alternate days), brain MDA, SOD, GSH, GABAand histological changes of hippocampus and cortex were observed. PTZ injected rats showed significantly (^***p < 0.001) increased kindling behavior, increased MDA, decreased GSH, SOD, GABA activities, compared with normal rats, while treatment AGNPs significantly reduced kindling score and reversed oxidative damage. Finally, we conclude that the leaves and roots of A. Paniculata can be effectively utilized for its major bioactive constituent, andrographolide as a potent anti-epileptic agent. Furthermore, the findings of novel nanotherapeutic approach claim that nano-andrographolide can be successfully in the management of kindling seizures and neurodegenerative disorders.

Age-Dependent Behavioral and Synaptic Dysfunction Impairment Are Improved with Long-Term Andrographolide Administration in Long-Lived Female Degus (Octodon degus)

In Octodon degus, the aging process is not equivalent between sexes and worsens for females. To determine the beginning of detrimental features in females and the ways in which to improve them, we compared adult females (36 months old) and aged females (72 months old) treated with Andrographolide (ANDRO), the primary ingredient in Andrographis paniculata. Our behavioral data demonstrated that age does not affect recognition memory and preference for novel experiences, but ANDRO increases these at both ages. Sociability was also not affected by age; however, social recognition and long-term memory were lower in the aged females than adults but were restored with ANDRO. The synaptic physiology data from brain slices showed that adults have more basal synaptic efficiency than aged degus; however, ANDRO reduced basal activity in adults, while it increased long-term potentiation (LTP). Instead, ANDRO increased the basal synaptic activity and LTP in aged females. Age-dependent changes were also observed in synaptic proteins, where aged females have higher synaptotagmin (SYT) and lower postsynaptic density protein-95 (PSD95) levels than adults. ANDRO increased the N-methyl D-aspartate receptor subtype 2B (NR2B) at both ages and the PSD95 and Homer1 only in the aged. Thus, females exposed to long-term ANDRO administration show improved complex behaviors related to age-detrimental effects, modulating mechanisms of synaptic transmission, and proteins.

The Flavonol Quercitrin Hinders GSK3 Activity and Potentiates the Wnt/β-Catenin Signaling Pathway

The Wnt/β-catenin signaling pathway dictates cell proliferation and differentiation during embryonic development and tissue homeostasis. Its deregulation is associated with many pathological conditions, including neurodegenerative disease, frequently downregulated. The lack of efficient treatment for these diseases, including Alzheimer’s disease (AD), makes Wnt signaling an attractive target for therapies. Interestingly, novel Wnt signaling activating compounds are less frequently described than inhibitors, turning the quest for novel positive modulators even more appealing. In that sense, natural compounds are an outstanding source of potential drug leads. Here, we combine different experimental models, cell-based approaches, neuronal culture assays, and rodent behavior tests with Xenopus laevis phenotypic analysis to characterize quercitrin, a natural compound, as a novel Wnt signaling potentiator. We find that quercitrin potentiates the signaling in a concentration-dependent manner and increases the occurrence of the Xenopus secondary axis phenotype mediated by Xwnt8 injection. Using a GSK3 biosensor, we describe that quercitrin impairs GSK3 activity and increases phosphorylated GSK3β S9 levels. Treatment with XAV939, an inhibitor downstream of GSK3, impairs the quercitrin-mediated effect. Next, we show that quercitrin potentiates the Wnt3a-synaptogenic effect in hippocampal neurons in culture, which is blocked by XAV939. Quercitrin treatment also rescues the hippocampal synapse loss induced by intracerebroventricular injection of amyloid-β oligomers (AβO) in mice. Finally, quercitrin rescues AβO-mediated memory impairment, which is prevented by XAV939. Thus, our study uncovers a novel function for quercitrin as a Wnt/β-catenin signaling potentiator, describes its mechanism of action, and opens new avenues for AD treatments.

Andrographolide, a natural anti-inflammatory agent: An Update

Botanicals have attracted much attention in the field of anti-inflammatory due to their good pharmacological activity and efficacy. Andrographis paniculata is a natural plant ingredient that is widely used around the world. Andrographolide is the main active ingredient derived from Andrographis paniculata, which has a good effect on the treatment of inflammatory diseases. This article reviews the application, anti-inflammatory mechanism and molecular targets of andrographolide in different inflammatory diseases, including respiratory, digestive, immune, nervous, cardiovascular, skeletal, and tumor system diseases. And describe its toxicity and explain its safety. Studies have shown that andrographolide can be used to treat inflammatory lesions of various systemic diseases. In particular, it acts on many inflammation-related signalling pathways. The future direction of andrographolide research is also introduced, as is the recent research that indicates its potential clinical application as an anti-inflammatory agent.

Study on the mechanism of andrographolide activation

Andrographolide is a natural antibiotic that has the ability to dispel heat, detoxify, reduce inflammation, and relieve pain. Recent research has shown that it can exert anti-inflammatory effects via multiple pathways and multiple targets (mediated by NF-κB, JAK/STAT, T cell receptor, and other signaling pathways). It can inhibit human lung cancer cells, colon cancer cells, osteosarcoma cells, and other tumor cells, as well as reduce bacterial virulence and inhibit virus-induced cell apoptosis. It can also regulate inflammatory mediator expression to protect the nervous system and effectively prevent mental illness. Additionally, andrographolide regulates the immune system, treats cardiovascular and cerebral vascular diseases, protects the liver, and the gallbladder. It is clear that andrographolide has a huge range of potential applications. The mechanism of andrographolide’s anti-inflammatory, antibacterial, antiviral, and nervous system defense in recent years have been reviewed in this article.

Lithium Enhances Hippocampal Glucose Metabolism in an In Vitro Mice Model of Alzheimer's Disease

Impaired cerebral glucose metabolism is an early event that contributes to the pathogenesis of Alzheimer's disease (AD). Importantly, restoring glucose availability by pharmacological agents or genetic manipulation has been shown to protect against Aβ toxicity, ameliorate AD pathology, and increase lifespan. Lithium, a therapeutic agent widely used as a treatment for mood disorders, has been shown to attenuate AD pathology and promote glucose metabolism in skeletal muscle. However, despite its widespread use in neuropsychiatric disorders, lithium's effects on the brain have been poorly characterized. Here we evaluated the effect of lithium on glucose metabolism in hippocampal neurons from wild-type (WT) and APPSwe/PS1ΔE9 (APP/PS1) mice. Our results showed that lithium significantly stimulates glucose uptake and replenishes ATP levels by preferential oxidation of glucose through glycolysis in neurons from WT mice. This increase was also accompanied by a strong increase in glucose transporter 3 (Glut3), the major carrier responsible for glucose uptake in neurons. Similarly, using hippocampal slices from APP-PS1 mice, we demonstrate that lithium increases glucose uptake, glycolytic rate, and the ATP:ADP ratio in a process that also involves the activation of AMPK. Together, our findings indicate that lithium stimulates glucose metabolism and can act as a potential therapeutic agent in AD.

Age- and Sex-Associated Glucose Metabolism Decline in a Mouse Model of Alzheimer’s Disease

Background: Alzheimer’s disease (AD) is characterized by a high etiological and clinical heterogeneity, which has obscured the diagnostic and treatment efficacy, as well as limited the development of potential drugs. Sex differences are among the risk factors that contribute to the variability of disease manifestation. Unlike men, women are at greater risk of developing AD and suffer from higher cognitive deterioration, together with important changes in pathological features. Alterations in glucose metabolism are emerging as a key player in the pathogenesis of AD, which appear even decades before the presence of clinical symptoms. Objective: We aimed to study whether AD-related sex differences influence glucose metabolism. Methods: We used male and female APPswe/PS1dE9 (APP/PS1) transgenic mice of different ages to examine glucose metabolism effects on AD development. Results: Our analysis suggests an age-dependent decline of metabolic responses, cognitive functions, and brain energy homeostasis, together with an increase of Aβ levels in both males and females APP/PS1 mice. The administration of Andrographolide (Andro), an anti-inflammatory and anti-diabetic compound, was able to restore several metabolic disturbances, including the glycolytic and the pentose phosphate pathway fluxes, ATP levels, AMPKα activity, and Glut3 expression in 8-month-old mice, independent of the sex, while rescuing these abnormalities only in older females. Similarly, Andro also prevented Aβ accumulation and cognitive decline in all but old males. Conclusion: Our study provides insight into the heterogeneity of the disease and supports the use of Andro as a potential drug to promote personalized medicine in AD.

Molecular Insights to the Wnt Signaling During Alzheimer's Disorder: a Potential Target for Therapeutic Interventions

In the adult brain, Wnt signaling is crucial for neurogenesis, and it also regulates neuronal development, neuronal maturation, neuronal differential, and proliferation. Impaired Wnt signaling pathways are associated with enhanced levels of amyloid-β, reduced β-catenin levels, and increased expression of GSK-3β enzyme, suggesting its direct association with the pathogenesis of Alzheimer's disorder (AD). These findings are consolidated by reports where activation of Wnt signaling by genetic factors and pharmacological intervention has improved the cognitive functions in animals and restored neurogenesis in the adult brain. Various natural and synthetic molecules have been identified that modulate Wnt signaling in the adult brain and promote neurogenesis and alleviate behavioral dysfunction. These molecules include lithium, valproic acid, ethosuximide, selenomethionine, curcumin, andrographolide, xanthoceraside, huperzine A, pyridostigmine, ginkgolide-B, ricinine, cannabidiol, and resveratrol. These molecules are associated with the DKK1 and GSK-3β inhibition and β-catenin stabilization along with their effects on neurogenesis, neuronal proliferation, and differentiation in the hippocampus through modulation of Wnt signaling and thereby could prove beneficial in the management of AD pathogenesis. Although modulation of the Wnt signaling seems to suggest to be promising in the management of AD, unfortunately, most of the literature available for the association of Wnt signaling and AD pathogenesis is either from preclinical studies or post-mortem brain. Therefore, it will be interesting to understand the role of Wnt signaling in AD patients, and a rigorous investigation could provide us with a better understanding of AD pathogenesis and the identification of novel targets for therapeutic interventions.

Neurobiological Promises of the Bitter Diterpene Lactone Andrographolide

Andrographolide (ANDRO), a bitter diterpene lactone found in Andrographis paniculata (Burm.f.) Nees, possesses several biological effects such as antioxidant, anti-inflammatory, and organo-protective effects. Scientific reports suggest that it also has neuroprotective capacity in various test systems. The purpose of this review was to synthesize the neuropharmacological properties of ANDRO and highlight the molecular mechanisms of action that highlight these activities. A careful search was done in PubMed and Google Scholar databases using specific keywords. Findings suggest that ANDRO possess neuroprotective, analgesic, and antifatigue effects. Prominent effects were stated on neuro-inflammation, cerebral ischemia, Alzheimer's and Parkinson's diseases, multiple sclerosis, and brain cancer in mice and rats. Furthermore, ANDRO and its derivatives can enhance memory and learning capacity in experimental animals (rats) without causing any toxicity in the brain. Thus, ANDRO may be one of the most promising plant-based psychopharmacological lead compounds for new drug development.

Menopause and development of Alzheimer's disease: Roles of neural glucose metabolism and Wnt signaling

Late onset Alzheimer´s disease (AD) is a neurodegenerative disease with gender differences in its onset and progression, being the prevalence predominant in women and at an earlier age than in men. The pathophysiology of the menopausal condition has been associated to this dementia, playing major roles regarding both endocrine and glucose metabolism changes, amongst other mechanisms. In the current review we address the role of estrogen deficiency in the processes involved in the development of AD, including amyloid precursor protein (APP) processing to form senile plaques, Tau phosphorylation forming neurofibrillary tangles, Wnt signaling and AD neuropathology, the role of glucose brain metabolism, Wnt signaling and glucose transport in the brain, and our research contribution to these topics.

Synthesis and Characterization of Andrographolide Derivatives as Regulators of βAPP Processing in Human Cells

Alzheimer's disease (AD) is a devastating neurodegenerative disorder, one of the main characteristics of which is the abnormal accumulation of amyloid peptide (Aβ) in the brain. Whereas β-secretase supports Aβ formation along the amyloidogenic processing of the β-amyloid precursor protein (βAPP), α-secretase counterbalances this pathway by both preventing Aβ production and triggering the release of the neuroprotective sAPPα metabolite. Therefore, stimulating α-secretase and/or inhibiting β-secretase can be considered a promising anti-AD therapeutic track. In this context, we tested andrographolide, a labdane diterpene derived from the plant Andrographis paniculata, as well as 24 synthesized derivatives, for their ability to induce sAPPα production in cultured SH-SY5Y human neuroblastoma cells. Following several rounds of screening, we identified three hits that were subjected to full characterization. Interestingly, andrographolide (8,17-olefinic) and its close derivative 14α-(5',7'-dichloro-8'-quinolyloxy)-3,19-acetonylidene (compound 9) behave as moderate α-secretase activators, while 14α-(2'-methyl-5',7'-dichloro-8'-quinolyloxy)-8,9-olefinic compounds 31 (3,19-acetonylidene) and 37 (3,19-diol), whose two structures are quite similar although distant from that of andrographolide and 9, stand as β-secretase inhibitors. Importantly, these results were confirmed in human HEK293 cells and these compounds do not trigger toxicity in either cell line. Altogether, these findings may represent an encouraging starting point for the future development of andrographolide-based compounds aimed at both activating α-secretase and inhibiting β-secretase that could prove useful in our quest for the therapeutic treatment of AD.

Andrographolide promotes hippocampal neurogenesis and spatial memory in the APPswe/PS1ΔE9 mouse model of Alzheimer's disease

In Alzheimer´s disease (AD) there is a reduction in hippocampal neurogenesis that has been associated to cognitive deficits. Previously we showed that Andrographolide (ANDRO), the main bioactive component of Andrographis paniculate, induces proliferation in the hippocampus of the APPswe/PSEN1ΔE9 (APP/PS1) mouse model of AD as assessed by staining with the mitotic marker Ki67. Here, we further characterized the effect of ANDRO on hippocampal neurogenesis in APP/PS1 mice and evaluated the contribution of this process to the cognitive effect of ANDRO. Treatment of 8-month-old APP/PS1 mice with ANDRO for 4 weeks increased proliferation in the dentate gyrus as evaluated by BrdU incorporation. Although ANDRO had no effect on neuronal differentiation of newborn cells, it strongly increased neural progenitors, neuroblasts and newborn immature neurons, cell populations that were decreased in APP/PS1 mice compared to age-matched wild-type mice. ANDRO had no effect on migration or in total dendritic length, arborization and orientation of immature neurons, suggesting no effects on early morphological development of newborn neurons. Finally, ANDRO treatment improved the performance of APP/PS1 mice in the object location memory task. This effect was not completely prevented by co-treatment with the anti-mitotic drug TMZ, suggesting that other effects of ANDRO in addition to the increase in neurogenesis might underlie the observed cognitive improvement. Altogether, our data indicate that in APP/PS1 mice ANDRO stimulates neurogenesis in the hippocampus by inducing proliferation of neural precursor cells and improves spatial memory performance.

Identification of poly(ADP-ribose)polymerase 1 and 2 (PARP1/2) as targets of andrographolide using an integrated chemical biology approach

Here, we describe the identification of PARP1/2 as direct binding proteins of andrographolide (Andro) using protein microarray, surface plasmon resonance (SPR), and enzyme activity assays. We then evaluated the proliferation inhibition, apoptosis, and cell migration effects of Andro on the MDA-MB-436 cell line in vitro. The final biological evaluation confirmed that Andro was a highly effective single agent in the MDA-MB-436 xenograft model and had a low hERG-mediated cardiac toxicity. Therefore, Andro represents the first natural product, non-amide member of a novel nanomolar-potency PARP1/2 inhibitor family.

Wnt signaling activation: targets and therapeutic opportunities for stem cell therapy and regenerative medicine

Wnt proteins are secreted morphogens that play critical roles in embryonic development, stem cell proliferation, self-renewal, tissue regeneration and remodeling in adults. While aberrant Wnt signaling contributes to diseases such as cancer, activation of Wnt/β-catenin signaling is a target of interest in stem cell therapy and regenerative medicine. Recent high throughput screenings from chemical and biological libraries, combined with improved gene expression reporter assays of Wnt/β-catenin activation together with rational drug design, led to the development of a myriad of Wnt activators, with different mechanisms of actions. Among them, Wnt mimics, antibodies targeting Wnt inhibitors, glycogen-synthase-3β inhibitors, and indirubins and other natural product derivatives are emerging modalities to treat bone, neurodegenerative, eye, and metabolic disorders, as well as prevent ageing. Nevertheless, the creation of Wnt-based therapies has been hampered by challenges in developing potent and selective Wnt activators without off-target effects, such as oncogenesis. On the other hand, to avoid these risks, their use to promote ex vivo expansion during tissue engineering is a promising application.

Hexane Extract of Chloranthus japonicus Increases Adipocyte Differentiation by Acting on Wnt/β-Catenin Signaling Pathway

Chloranthus japonicus has been heavily investigated for the treatment of various diseases. This paper attempts to show that Chloranthus japonicus can modulate adipocyte differentiation of preadipocytes. To establish this, we investigated the effects of Chloranthus japonicus extract in peroxisome proliferator-activated receptor γ (PPARγ) expression, adipogenesis, and the underlying molecular mechanisms in C3H10T1/2 and 3T3-L1 cells. Our data showed that Chloranthus japonicus methanol extract increased lipid accumulation and promoted adipocyte differentiation. Further studies on the fractionation with various solvents led to the identification of Chloranthus japonicus hexane extract (CJHE) as the most potent inducer of adipocyte differentiation. CJHE consistently increased lipid accumulation and adipocyte marker expression including Pparγ and it acted during the early stages of adipocyte differentiation. Mechanistic studies revealed that CJHE and a Wnt inhibitor similarly stimulated adipogenesis and were active in Wnt-selective reporter assays. The effects of CJHE were inhibited by Wnt3a protein treatment and were significantly blunted in β-catenin-silenced cells, further suggesting that CJHE acted on Wnt pathways to promote adipogenesis. We also showed that Chloranthus japonicus extracts generated from different plant parts similarly promoted adipocyte differentiation. These results identified Chloranthus japonicus as a pro-adipogenic natural product and suggest its potential use in metabolic syndrome.

Andrographolide restores glucose uptake in rat hippocampal neurons

Cerebral glucose hypometabolism is a common pathophysiological characteristic of many neurodegenerative diseases. This metabolic dysfunction includes alterations in glucose transport from the blood into the neurons by the facilitative glucose transporters (GLUTs). Several studies suggest that metabolic disturbances precede clinical symptoms and correlate with disease progression. Some groups have started to explore the use of therapeutic strategies that target decreased cerebral glucose metabolism to promote its availability. We selected Andrographolide (Andro), a natural product obtained from Andrographis paniculate that has both anti-hyperglycemic and anti-diabetic effects. Although it was shown to promote glucose uptake in vivo, the underlying mechanisms remain unclear. Here, we evaluated the acute effects of Andro on glucose transport and metabolism using primary rat hippocampal neuronal cultures. Our results showed that Andro enhances neuronal glucose uptake and stimulates glucose metabolism by inducing GLUT3 and 4 expression in neurons, as well as by promoting glycolysis. We also observed that Andro-mediated effects depend on the activity of AMP-activated protein kinase (AMPK), one of the central regulators of glucose metabolism. Our studies open the possibility to use Andro as a drug to restore glucose levels in neurodegenerative diseases.

Polypharmacology of andrographolide: beyond one molecule one target

Covering: 1951 to 2020Andrographolide is one of the most widely studied plant secondary metabolites, known to display diverse pharmacological actions. Current literature has documented a sizeable list of pharmacological targets for andrographolide, suggesting its multi-targeting nature. Many of these targets are central to the pathophysiology of highly prevalent diseases such as cardiovascular diseases, neurodegenerative disorders, autoimmunity, and even cancer. Despite its well-documented therapeutic efficacy in various disease models, for years, the discrepancies between in vivo bioavailability and bioactivity of andrographolide and the debate surrounding its multi-targeting properties (polypharmacology or promiscuity?) have hindered the development of this versatile molecule into a potential therapeutic agent. Is andrographolide a valuable lead for therapeutic development or a potential invalid metabolic panacea (IMP)? This perspective article aims to discuss this by considering various contributing factors to the polypharmacology of andrographolide.

Nature-derived compounds modulating Wnt/ -catenin pathway: a preventive and therapeutic opportunity in neoplastic diseases

The Wnt/β-catenin signaling is a conserved pathway that has a crucial role in embryonic and adult life. Dysregulation of the Wnt/β-catenin pathway has been associated with diseases including cancer, and components of the signaling have been proposed as innovative therapeutic targets, mainly for cancer therapy. The attention of the worldwide researchers paid to this issue is increasing, also in view of the therapeutic potential of these agents in diseases, such as Parkinson's disease (PD), for which no cure is existing today. Much evidence indicates that abnormal Wnt/β-catenin signaling is involved in tumor immunology and the targeting of Wnt/β-catenin pathway has been also proposed as an attractive strategy to potentiate cancer immunotherapy. During the last decade, several products, including naturally occurring dietary agents as well as a wide variety of products from plant sources, including curcumin, quercetin, berberin, and ginsenosides, have been identified as potent modulators of the Wnt/β-catenin signaling and have gained interest as promising candidates for the development of chemopreventive or therapeutic drugs for cancer. In this review we make an overview of the nature-derived compounds reported to have antitumor activity by modulating the Wnt/β-catenin signaling, also focusing on extraction methods, chemical features, and bio-activity assays used for the screening of these compounds.

Role of Wnt Signaling in Adult Hippocampal Neurogenesis in Health and Disease

Neurogenesis persists during adulthood in the dentate gyrus of the hippocampus. Signals provided by the local hippocampal microenvironment support neural stem cell proliferation, differentiation, and maturation of newborn neurons into functional dentate granule cells, that integrate into the neural circuit and contribute to hippocampal function. Increasing evidence indicates that Wnt signaling regulates multiple aspects of adult hippocampal neurogenesis. Wnt ligands bind to Frizzled receptors and co-receptors to activate the canonical Wnt/β-catenin signaling pathway, or the non-canonical β-catenin-independent signaling cascades Wnt/Ca2+ and Wnt/planar cell polarity. Here, we summarize current knowledge on the roles of Wnt signaling components including ligands, receptors/co-receptors and soluble modulators in adult hippocampal neurogenesis. Also, we review the data suggesting distinctive roles for canonical and non-canonical Wnt signaling cascades in regulating different stages of neurogenesis. Finally, we discuss the evidence linking the dysfunction of Wnt signaling to the decline of neurogenesis observed in aging and Alzheimer's disease.

Wnt Signaling Pathway Dysregulation in the Aging Brain: Lessons From the Octodon degus

Wnt signaling constitutes a fundamental cellular and molecular pathway, necessary from proper embryogenesis to function-maintenance of fully developed complex organisms. In this regard, Wnt pathway plays a crucial role in both the development of the central nervous system and in maintaining the structure and function of the neuronal circuits, and it has been suggested that its dysregulation is critical in the onset of several pathologies including cancer and neurodegenerative disorders, such as Alzheimer's disease (AD). Due to its relevance in the maintenance of the neuronal activity and its involvement in the outbreak of devastating diseases, we explored the age-related changes in the expression of Wnt key components in the cortex and hippocampus of 7 to 72-months-old Octodon degus (O. degus), a Chilean long-living endemic rodent that has been proposed and used as a natural model for AD. We found a down-regulation in the expression of different Wnt ligands (Wnt3a, Wnt7a, and Wnt5a), as well as in the Wnt co-receptor LRP6. We also observed an increase in the activity of GSK-3β related to the down-regulation of Wnt activity, a fact that was confirmed by a decreased expression of Wnt target genes. Relevantly, an important increase was found in secreted endogenous Wnt inhibitors, including the secreted-frizzled-related protein 1 and 2 (SFRP-1 and SFRP-2) and Dickkopf-1 (Dkk-1), all them antagonists at the cell surface. Furthermore, treatment with Andrographolide, a labdane diterpene obtained from Andrographis paniculata, prevents Wnt signaling loss in aging degus. Taken together, these results suggest that during the aging process Wnt signaling activity decreases in the brain of O. degus.

Stimulation of Melanocortin Receptor-4 (MC4R) Prevents Mitochondrial Damage Induced by Binge Ethanol Protocol in Adolescent Rat Hippocampus

Binge drinking is a common pattern of adolescent alcohol consumption characterized by a high alcohol intake within a short period of time; which may seriously affect brain function, triggering in some cases an addictive behavior. Current evidence indicates that alcohol addictive conduct is related to the impairment of the Melanocortin System (MCS). This system participates in the regulation of food intake and promotes anti-inflammatory response in the brain. However, the cellular mechanisms involved in the protective effects induced by MCS against binge-alcohol intoxication are still unknown. Here, we studied the effects of MCS activation on mitochondrial and oxidative damage induced by a binge-like protocol in the hippocampus of adolescent rats. We used a pharmacological activator of MC4R (RO27-3225) and evaluated its effects against oxidative injury, mitochondrial failure, and bioenergetics impairment induced by binge ethanol protocol in the hippocampus of adolescent's rats. Our results indicate that MC4R agonist reduces hippocampal oxidative damage promoting antioxidant (Nrf-2) and mitochondrial biogenesis (PGC1-alpha) pathways in animals subjected to the binge-like protocol. Additionally, MC4R activation prevented mitochondrial potential loss and increased mitochondrial mass that were significantly reduced by binge ethanol protocol. Finally, RO27-3225 treatment increased ATP production and mitochondrial respiratory complex expression in adolescent rats exposed to ethanol. Altogether, these findings show that activation of the MCS pathway through MC4R prevents these negative effects of binge ethanol protocol, suggesting a possible role of the MCS in the reduction of the neurotoxic effects induced by alcohol intoxication in adolescents.

Targeting the Wnt/β-catenin pathway in neurodegenerative diseases: recent approaches and current challenges

INTRODUCTION

Wnt/β-catenin signaling is an evolutionarily conserved pathway having a crucial role in embryonic and adult life. Specifically, the Wnt/β-catenin axis is pivotal to the development and homeostasis of the nervous system, and its dysregulation has been associated with various neurological disorders, including neurodegenerative diseases. Therefore, this signaling pathway has been proposed as a potential therapeutic target against neurodegeneration.

AREAS COVERED

This review focuses on the role of Wnt/β-catenin pathway in the pathogenesis of neurodegenerative diseases, including Parkinson's, Alzheimer's Diseases and Amyotrophic Lateral Sclerosis. The evidence showing that defects in the signaling might be involved in the development of these diseases, and the pharmacological approaches tested so far, are discussed. The possibilities that this pathway offers in terms of new therapeutic opportunities are also considered.

EXPERT OPINION

The increasing interest paid to the role of Wnt/β-catenin pathway in the onset of neurodegenerative diseases demonstrates how targeting this signaling for therapeutic purposes could be a great opportunity for both neuroprotection and neurorepair. Without overlooking some licit concerns about drug safety and delivery to the brain, there is growing and more convincing evidence that restoring this signaling in neurodegenerative diseases may strongly increase the chance to develop disease-modifying treatments for these brain pathologies.

Small Molecule Wnt Pathway Modulators from Natural Sources: History, State of the Art and Perspectives

The Wnt signaling is one of the major pathways known to regulate embryonic development, tissue renewal and regeneration in multicellular organisms. Dysregulations of the pathway are a common cause of several types of cancer and other diseases, such as osteoporosis and rheumatoid arthritis. This makes Wnt signaling an important therapeutic target. Small molecule activators and inhibitors of signaling pathways are important biomedical tools which allow one to harness signaling processes in the organism for therapeutic purposes in affordable and specific ways. Natural products are a well known source of biologically active small molecules with therapeutic potential. In this article, we provide an up-to-date overview of existing small molecule modulators of the Wnt pathway derived from natural products. In the first part of the review, we focus on Wnt pathway activators, which can be used for regenerative therapy in various tissues such as skin, bone, cartilage and the nervous system. The second part describes inhibitors of the pathway, which are desired agents for targeted therapies against different cancers. In each part, we pay specific attention to the mechanisms of action of the natural products, to the models on which they were investigated, and to the potential of different taxa to yield bioactive molecules capable of regulating the Wnt signaling.

The natural compound andrographolide inhibits human aortic valve interstitial cell calcification via the NF-kappa B/Akt/ERK pathway

Calcific aortic valve disease (CAVD) is caused by valve interstitial cells (VICs) initiating the thickening and calcification of valve leaflets. The present study aimed to investigate whether andrographolide (AGP) could attenuate the calcification of human valve interstitial cells (hVICs). hVICs stimulated by osteoblastic medium (OM) were treated with or without AGP. RNA sequencing was utilized to investigate changes in gene expression. Cell growth and calcification of hVICs were assessed using a CCK8 assay and Alizarin Red S staining, respectively. The expression of the two calcification-related markers, RUNX2 and ALP, were quantified by qRT-PCR, Western blotting, and immunofluorescent staining. The results indicate that hVICs treated with OM plus AGP exhibited decreased Alizarin Red S staining compared with cells treated with OM only in addition to down-regulation of ALP and RUNX2. Mappings of differentially expressed genes (DEGs) in different groups using Venn diagrams during analysis of gene expression profiles, 653 common DEGs were identified that displayed different biological functions and signaling pathways after treatment with AGP. RELA, a core factor of the NF-κB pathway was inhibited by AGP in addition to phosphorylation of AKT and ERK1/2. Thus, AGP attenuated calcification of hVICs. These results demonstrate that AGP, a promising natural product, can attenuate the process of CAVD.

Influence of Calcium Supplementation against Fluoride-Mediated Osteoblast Impairment in Vitro: Involvement of the Canonical Wnt/β-Catenin Signaling Pathway

Fluoride (F) is capable of promoting abnormal proliferation and differentiation in primary cultured mouse osteoblasts (OB cells), although the underlying mechanism responsible remains rare. This study aimed to explore the roles of wingless and INT-1 (Wnt) signaling pathways and screen appropriate doses of calcium (Ca²⁺) to alleviate the sodium fluoride (NaF)-induced OB cell toxicity. For this, we evaluated the effect of dickkopf-related protein 1 (DKK1) and Ca²⁺ on mRNA levels of wingless/integrated 3a (Wnt3a), low-density lipoprotein receptor-related protein 5 (LRP5), dishevelled 1 (Dv1), glycogen synthase kinase 3β (GSK3β), β-catenin, lymphoid enhancer binding factor 1 (LEF1), and cellular myelocytomatosis oncogene (cMYC), as well as Ccnd1 (Cyclin D1) in OB cells challenged with 10^-6 mol/L NaF for 24 h. The demonstrated data showed that F significantly increased the OB cell proliferation rate. Ectogenic 0.5 mg/L DKK1 significantly inhibited the proliferation of OB cells induced by F. The mRNA expression levels of Wnt3a, LRP5, Dv1, LEF1, β-catenin, cMYC, and Ccnd1 were significantly increased in the F group, while significantly decreased in the 10^-6 mol/L NaF + 0.5 mg/L DKK1 (FY) group. The mRNA expression levels of Wnt3a, LRP5, β-catenin, and cMYC were significantly decreased in the 10^-6 mol/L NaF + 2 mmol/L CaCl₂ (F+CaII) group. The protein expression levels of Wnt3a, Cyclin D1, cMYC, and β-catenin were significantly increased in the F group, whereas they were decreased in the F+CaII group. However, the mRNA and protein expression levels of GSK3β were significantly decreased in the F group while significantly increased in the F+CaII group. In summary, F activated the canonical Wnt/β-catenin pathway and changed the related gene expression and β-catenin protein location in OB cells, promoting cell proliferation. Ca²⁺ supplementation (2 mmol/L) reversed the expression levels of genes and proteins related to the canonical Wnt/β-catenin pathway.

Andrographolide Exerts Significant Antidepressant-Like Effects Involving the Hippocampal BDNF System in Mice

BACKGROUND

Major depressive disorder is a worldwide neuropsychiatric disorder associated with various symptoms, but current antidepressants used in clinical practice have various side effects and high failure rates. Andrographolide is the main bioactive ingredient of Andrographis paniculata and exhibits numerous pharmacological actions. This study aimed to evaluate the antidepressant-like effects of andrographolide in male C57BL/6J mice.

METHODS

The antidepressant-like effects of andrographolide in mice were explored in a forced swim test, tail suspension test, and chronic unpredictable mild stress model of depression. Western blotting and immunofluorescence were further performed to assess the effects of chronic unpredictable mild stress and andrographolide on the brain-derived neurotrophic factor signalling cascade and hippocampal neurogenesis. Moreover, a pharmacological inhibitor (K252a) and a lentiviral-short hairpin RNA (LV-TrkB-shRNA) were used to clarify the antidepressant-like mechanism of andrographolide.

RESULTS

Andrographolide exhibited antidepressant-like potential in the forced swim test and tail suspension test without influencing the locomotor activity of mice. Repeated andrographolide treatment not only produced significant antidepressant-like effects in the chronic unpredictable mild stress model but also prevented the decreasing effects of chronic unpredictable mild stress on hippocampal brain-derived neurotrophic factor signalling and neurogenesis in mice. Importantly, blockade of the hippocampal brain-derived neurotrophic factor system by K252a and TrkB-shRNA fully abolished the antidepressant-like effects of andrographolide in mice.

CONCLUSIONS

Andrographolide exerts antidepressant-like effects in mice via promoting the hippocampal brain-derived neurotrophic factor signalling cascade.

Dephosphorylation of clustered phosphoserine residues in human Grb14 by protein phosphatase 1 and its effect on insulin receptor complex formation

The physical interaction of the human growth factor receptor-bound protein 14 (hGrb14) and the insulin receptor (IR) represses insulin signaling. With respect to the recruiting mechanism of hGrb14 to IR respond to insulin stimulus, our previous reports have suggested that phosphorylation of Ser³⁵⁸ , Ser³⁶² , and Ser³⁶⁶ in hGrb14 by glycogen synthase kinase-3 repressed hGrb14-IR complex formation. In this study, we investigated phosphatase-mediated dephosphorylation of the hGrb14 phosphoserine residues. An in vitro phosphatase assay with hGrb14-derived synthetic phosphopeptides suggested that protein phosphatase 1 (PP1) is involved in the dephosphorylation of Ser³⁵⁸ and Ser³⁶² . Furthermore, coimmunoprecipitation experiments suggested that insulin-induced hGrb14-IR complex formation was repressed by the substitution of Ser³⁵⁸ or Ser³⁶² with glutamic acid. These findings suggested that phosphate groups on Ser³⁵⁸ and Ser³⁶² in hGrb14 are dephosphorylated by PP1, and the dephosphorylation facilitates hGrb14-IR complex formation.

Neuroprotective Effects of Ferruginol, Jatrophone, and Junicedric Acid Against Amyloid-β Injury in Hippocampal Neurons

Soluble amyloid-β (Aβ) oligomers have been recognized as early neurotoxic intermediates with a key role in the synaptic dysfunction observed in Alzheimer's disease (AD). Aβ oligomers block hippocampal long-term potentiation (LTP) and impair rodent spatial memory. Additionally, the presence of Aβ oligomers is associated with imbalanced intracellular calcium levels and apoptosis in neurons. In this context, we evaluated the effects of three diterpenes (ferruginol, jatrophone, and junicedric acid) that are found in medicinal plants and have several forms of biological activity. The intracellular calcium levels in hippocampal neurons increased in the presence of ferruginol, jatrophone, and junicedric acid, a result that was consistent with the observed increase in CA1 synaptic transmission in mouse hippocampal slices. Additionally, assays using Aβ peptide demonstrated that diterpenes, particularly ferruginol, restore LTP and reduce apoptosis. Recovery of the Aβ oligomer-induced loss of the synaptic proteins PSD-95, synapsin, VGlut, and NMDA receptor subunit 2A was observed in mouse hippocampal slices treated with junicedric acid. This cascade of events may be associated with the regulation of kinases, e.g., protein kinase C (PKC) and calcium/calmodulin-dependent protein kinase II (CaMKII), in addition to the activation of the canonical Wnt signaling pathway and could thus provide protection against Aβ oligomers, which trigger synaptic dysfunction. Our results suggest a potential neuroprotective role for diterpenes against the Aβ oligomers-induced neurodegenerative alterations, which make them interesting molecules to be further studied in the context of AD.

β-catenin aggregation in models of ALS motor neurons: GSK3β inhibition effect and neuronal differentiation

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by motor neuron death. A 20% of familial ALS cases are associated with mutations in the gene coding for superoxide dismutase 1 (SOD1). The accumulation of abnormal aggregates of different proteins is a common feature in motor neurons of patients and transgenic ALS mice models, which are thought to contribute to disease pathogenesis. Developmental morphogens, such as the Wnt family, regulate numerous features of neuronal physiology in the adult brain and have been implicated in neurodegeneration. β-catenin is a central mediator of both, Wnt signaling activity and cell-cell interactions. We previously reported that the expression of mutant SOD1 in the NSC34 motor neuron cell line decreases basal Wnt pathway activity, which correlates with cytosolic β-catenin accumulation and impaired neuronal differentiation. In this work, we aimed a deeper characterization of β-catenin distribution in models of ALS motor neurons. We observed extensive accumulation of β-catenin supramolecular structures in motor neuron somas of pre-symptomatic mutant SOD1 mice. In cell-cell appositional zones of NSC34 cells expressing mutant SOD1, β-catenin displays a reduced co-distribution with E-cadherin accompanied by an increased association with the gap junction protein Connexin-43; these findings correlate with impaired intercellular adhesion and exacerbated cell coupling. Remarkably, pharmacological inhibition of the glycogen synthase kinase-3β (GSK3β) in both NSC34 cell lines reverted both, β-catenin aggregation and the adverse effects of mutant SOD1 expression on neuronal differentiation. Our findings suggest that early defects in β-catenin distribution could be an underlying factor affecting the onset of neurodegeneration in familial ALS.

Wnt-induced activation of glucose metabolism mediates the in vivo neuroprotective roles of Wnt signaling in Alzheimer disease

Dysregulated Wnt signaling is linked to major neurodegenerative diseases, including Alzheimer disease (AD). In mouse models of AD, activation of the canonical Wnt signaling pathway improves learning/memory, but the mechanism for this remains unclear. The decline in brain function in AD patients correlates with reduced glucose utilization by neurons. Here, we test whether improvements in glucose metabolism mediate the neuroprotective effects of Wnt in AD mouse model. APPswe/PS1dE9 transgenic mice were used to model AD, Andrographolide or Lithium was used to activate Wnt signaling, and cytochalasin B was used to block glucose uptake. Cognitive function was assessed by novel object recognition and memory flexibility tests. Glucose uptake and the glycolytic rate were determined using radiotracer glucose. The activities of key enzymes of glycolysis such as hexokinase and phosphofructokinase, Adenosine triphosphate (ATP)/Adenosine diphosphate (ADP) levels and the pentose phosphate pathway and activity of glucose-6 phosphate dehydrogenase were measured. Wnt activators significantly improved brain glucose utilization and cognitive performance in transgenic mice. Wnt signaling enhanced glucose metabolism by increasing the expression and/or activity of hexokinase, phosphofructokinase and AMP-activated protein kinase. Inhibiting glucose uptake partially abolished the beneficial effects of Wnt signaling on learning/memory. Wnt activation also enhanced glucose metabolism in cortical and hippocampal neurons, as well as brain slices derived from APPswe/PS1E9 transgenic mice. Combined, these data provide evidence that the neuroprotective effects of Wnt signaling in AD mouse models result, at least in part, from Wnt-mediated improvements in neuronal glucose metabolism.

Chronic β-adrenergic stimulation reverses depressed Ca handling in mice overexpressing inhibitor-2 of protein phosphatase 1

RATIONALE

A higher expression/activity of type 1 serine/threonine protein phosphatase 1 (PP1) may contribute to dephosphorylation of cardiac regulatory proteins triggering the development of heart failure.

OBJECTIVE

Here, we tested the putatively protective effects of PP1 inhibitor-2 (I₂) overexpression using a heart failure model induced by chronic β-adrenergic stimulation.

METHODS AND RESULTS

Transgenic (TG) and wild-type (WT) mice were subjected to isoprenaline (ISO) or isotonic NaCl solution supplied via osmotic minipumps for 7 days. I₂ overexpression was associated with a depressed PP1 activity. Basal contractility was unchanged in catheterized mice and isolated cardiomyocytes between TG^NaCl and WT^NaCl. TG^ISO mice exhibited more fibrosis and a higher expression of hypertrophy marker proteins as compared to WT^ISO. After acute administration of ISO, the contractile response was accompanied by a higher sensitivity in TG^ISO as compared to WT^ISO. In contrast to basal contractility, the peak amplitude of [Ca]_i and SR Ca load were reduced in TG^NaCl as compared to WT^NaCl. These effects were normalized to WT levels after chronic ISO stimulation. Cardiomyocyte relaxation and [Ca]_i decay kinetics were hastened in TG^ISO as compared to WT^ISO, which can be explained by a higher phospholamban phosphorylation at Ser¹⁶. Chronic catecholamine stimulation was followed by an enhanced expression of GSK3β, whereas the phosphorylation at Ser⁹ was lower in TG as compared to the corresponding WT group. This resulted in a higher I₂ phosphorylation that may reactivate PP1.

CONCLUSION

Our findings suggest that the basal desensitization of β-adrenergic signaling and the depressed Ca handling in TG by inhibition of PP1 is restored by a GSK3β-dependent phosphorylation of I₂.

Discovery of Selective, Substrate-Competitive, and Passive Membrane Permeable Glycogen Synthase Kinase-3β Inhibitors: Synthesis, Biological Evaluation, and Molecular Modeling of New C-Glycosylflavones

Glycogen synthase kinase-3β (GSK-3β) is a key enzyme responsible for tau hyperphosphorylation and is a viable therapeutic target of Alzheimer's disease (AD). We developed a new class of GSK-3β inhibitors based on the 6- C-glycosylflavone isoorientin (1). The new inhibitors are passive membrane permeable and constitutively attenuate GSK-3β mediated tau hyperphosphorylation and amyloid neurotoxicity in an AD cellular model. Enzymatic assays and kinetic studies demonstrated that compound 30 is a GSK-3β substrate-competitive inhibitor with distinct kinase selectivity, isoform-selectivity and over 310-fold increased potency as compared to 1. Structure-activity relationship analyses and in silico modeling suggest the mechanism of actions by which the hydrophobic, π-cation, and orthogonal multipolar interactions of 30 with the substrate site are critical for the GSK-3β inhibition and selectivity. The results provide new insights into GSK-3β drug discovery. The new inhibitors are valuable chemical probes and drug leads with therapeutic potential to tackle AD and other GSK-3β relevant diseases.

Loss of canonical Wnt signaling is involved in the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia in the older population, however, the precise cause of the disease is unknown. The neuropathology is characterized by the presence of aggregates formed by amyloid-β (Aβ) peptide and phosphorylated tau; which is accompanied by progressive impairment of memory. Diverse signaling pathways are linked to AD, and among these the Wnt signaling pathway is becoming increasingly relevant, since it plays essential roles in the adult brain. Initially, Wnt signaling activation was proposed as a neuroprotective mechanism against Aβ toxicity. Later, it was reported that it participates in tau phosphorylation and processes of learning and memory. Interestingly, in the last years we demonstrated that Wnt signaling is fundamental in amyloid precursor protein (APP) processing and that Wnt dysfunction results in Aβ production and aggregation in vitro. Recent in vivo studies reported that loss of canonical Wnt signaling exacerbates amyloid deposition in a transgenic (Tg) mouse model of AD. Finally, we showed that inhibition of Wnt signaling in a Tg mouse previously at the appearance of AD signs, resulted in memory loss, tau phosphorylation and Aβ formation and aggregation; indicating that Wnt dysfunction accelerated the onset of AD. More importantly, Wnt signaling loss promoted cognitive impairment, tau phosphorylation and Aβ_1-42 production in the hippocampus of wild-type (WT) mice, contributing to the development of an Alzheimer's-like neurophatology. Therefore, in this review we highlight the importance of Wnt/β-catenin signaling dysfunction in the onset of AD and propose that the loss of canonical Wnt signaling is a triggering factor of AD.

Andrographolide Promotes Neural Differentiation of Rat Adipose Tissue-Derived Stromal Cells through Wnt/β-Catenin Signaling Pathway

Adipose tissue-derived stromal cells (ADSCs) are a high-yield source of pluripotent stem cells for use in cell-based therapies. We explored the effect of andrographolide (ANDRO, one of the ingredients of the medicinal herb extract) on the neural differentiation of rat ADSCs and associated molecular mechanisms. We observed that rat ADSCs were small and spindle-shaped and expressed multiple stem cell markers including nestin. They were multipotent as evidenced by adipogenic, osteogenic, chondrogenic, and neural differentiation under appropriate conditions. The proportion of cells exhibiting neural-like morphology was higher, and neurites developed faster in the ANDRO group than in the control group in the same neural differentiation medium. Expression levels of the neural lineage markers MAP2, tau, GFAP, and β-tubulin III were higher in the ANDRO group. ANDRO induced a concentration-dependent increase in Wnt/β-catenin signaling as evidenced by the enhanced expression of nuclear β-catenin and the inhibited form of GSK-3β (pSer9). Thus, this study shows for the first time how by enhancing the neural differentiation of ADSCs we expect that ANDRO pretreatment may increase the efficacy of adult stem cell transplantation in nervous system diseases, but more exploration is needed.

Andrographolide-loaded nanoparticles for brain delivery: Formulation, characterisation and in vitro permeability using hCMEC/D3 cell line

Andrographolide (AG) is a major diterpenoid of the Asian medicinal plant Andrographis paniculata which has shown exciting pharmacological potential for the treatment of inflammation-related pathologies including neurodegenerative disorders. Conversely, the low bioavailability of AG still represents a limiting factor for its use. To overcome these limitations, AG was loaded into human serum albumin based nanoparticles (HSA NPs) and poly ethylcyanoacrylate nanoparticles (PECA NPs). HSA NPs were prepared by thermal (HSAT AG NPs) and chemical cross-linking (HSAC AG NPs), while PECA AG NPs were produced by emulsion-polymerization. NPs were characterized in terms of size, zeta (ζ)-potential, polydispersity, and release studies of AG. In addition, the ability of free AG and AG-loaded in PECA and HSAT NPs to cross the blood-brain barrier (BBB) was assessed using an in vitro BBB model based on human cerebral microvascular endothelial cell line (hCMEC/D3). For BBB drug permeability assays, a quantitative UPLC-MS/MS method for AG in Ringer HEPES buffer was developed and validated according to international regulatory guidelines for industry. Free AG did not permeate the BBB model, as also predicted by in silico studies. HSAT NPs improved by two-fold the permeation of AG while maintaining the integrity of the cell layer, while PECA NPs temporarily disrupted BBB integrity.

Inhibition of Wnt signaling induces amyloidogenic processing of amyloid precursor protein and the production and aggregation of Amyloid-β (Aβ)42 peptides

Alzheimer's disease (AD) is the most common neurodegenerative disorder and the most frequent cause of dementia in the aged population. According to the amyloid hypothesis, the amyloid-β (Aβ) peptide plays a key role in the pathogenesis of AD. Aβ is generated from the amyloidogenic processing of amyloid precursor protein and can aggregate to form oligomers, which have been described as a major synaptotoxic agent in neurons. Dysfunction of Wnt signaling has been linked to increased Aβ formation; however, several other studies have argued against this possibility. Herein, we use multiple experimental approaches to confirm that the inhibition of Wnt signaling promoted the amyloidogenic proteolytic processing of amyloid precursor protein. We also demonstrate that inhibiting Wnt signaling increases the production of the Aβ₄₂ peptide, the Aβ₄₂ /Aβ₄₀ ratio, and the levels of Aβ oligomers such as trimers and tetramers. Moreover, we show that activating Wnt signaling reduces the levels of Aβ₄₂ and its aggregates, increases Aβ₄₀ levels, and reduces the Aβ₄₂ /Aβ₄₀ ratio. Finally, we show that the protective effects observed in response to activation of the Wnt pathway rely on β-catenin-dependent transcription, which is demonstrated experimentally via the expression of various 'mutant forms of β-catenin'. Together, our findings indicate that loss of the Wnt signaling pathway may contribute to the pathogenesis of AD.