Neuroprotective effects of tenuigenin on neurobehavior, oxidative stress, and tau hyperphosphorylation induced by intracerebroventricular streptozotocin in rats

Natural Products Targeting Tau Protein Phosphorylation: A Promising Therapeutic Avenue for Alzheimer's Disease

Alzheimer's disease is a progressive neurodegenerative disorder characterized by tau protein hyperphosphorylation and neurofibrillary tangle formation, which are central to its pathogenesis. This review focuses on the therapeutic potential of natural products in targeting tau phosphorylation, a key factor in Alzheimer's disease progression. It comprehensively summarizes current research on various natural compounds, including flavonoids, alkaloids, saponins, polysaccharides, phenols, phenylpropanoids, and terpenoids, highlighting their multitarget mechanisms, such as modulating kinases and phosphatases. The ability of these compounds to mitigate oxidative stress, inflammation, and tau pathology while enhancing cognitive function underscores their value as potential anti-Alzheimer's disease therapeutics. By integrating recent advances in extraction methods, pharmacological studies, and artificial intelligence-driven screening technologies, this review provides a valuable reference for future research and development of natural product-based interventions for Alzheimer's disease.

Insulin signaling disruption exacerbates memory impairment and seizure susceptibility in an epilepsy model with Alzheimer's disease-like pathology

Alzheimer's disease (AD) and epilepsy exhibit a complex bidirectional relationship. Curiously, diabetes as a comorbidity increases the risk of epilepsy among AD patients. Recently, we reported that the Wistar audiogenic rat (WAR) strain, a genetic model of epilepsy, displays a partial AD-like phenotype, including brain insulin resistance. We also assessed seizure susceptibility in an AD model created through intracerebroventricular injections of streptozotocin (icv-STZ), which induces AD features via brain insulin resistance. Our goal was to explore how disrupted brain insulin signaling influences AD-like features and seizure susceptibility in the WAR strain. Adult male WARs received a single intracerebroventricular injection of streptozotocin (icv-STZ) (1.5 mg/kg) or vehicle (saline). Two weeks post-injection, spatial memory was assessed using the Barnes Maze (BM) test. Three weeks later, the rats underwent an audiogenic kindling (AuK) protocol (20 acoustic stimuli, 2 per day) to evaluate seizure frequency and severity. Seizures were analyzed using the Categorized Severity Index and Racine's scale and Western blot analysis was performed on hippocampal tissue. Our findings revealed that icv-STZ significantly worsened memory performance, increased seizure frequency, and reduced seizure onset relative to vehicle. Furthermore, icv-STZ decreased Akt activation and increased Glycogen Synthase Kinase-3 (GSK3) phosphorylation, indicating disrupted insulin signaling. Notably, icv-STZ decreased tau phosphorylation without altering amyloid β precursor protein (AβPP) levels. In conclusion, a low-dose icv-STZ injection exacerbates memory deficits and seizure susceptibility in the WAR strain by disturbing downstream proteins involved in insulin signaling. This highlights the implications of brain insulin resistance in both AD and epilepsy.

The effects of nitric oxide in Alzheimer's disease

Alzheimer's disease (AD), the most prevalent cause of dementia, is a progressive neurodegenerative condition that commences subtly and inexorably worsens over time. Despite considerable research, a specific drug that can fully cure or effectively halt the progression of AD remains elusive. Nitric oxide (NO), a crucial signaling molecule in the nervous system, is intimately associated with hallmark pathological changes in AD, such as amyloid-beta deposition and tau phosphorylation. Several therapeutic strategies for AD operate through the nitric oxide synthase/NO system. However, the potential neurotoxicity of NO introduces an element of controversy regarding its therapeutic utility in AD. This review focuses on research findings concerning NO's role in experimental AD and its underlying mechanisms. Furthermore, we have proposed directions for future research based on our current comprehension of this critical area.

Aqueous extract of Spirulina exerts neuroprotection in an experimental model of Alzheimer sporadic disease in mice induced by Streptozotocin

Alzheimer's disease (AD) is a progressive neurodegenerative disease that causes gradual memory loss and cognitive impairment. Intracerebroventricular injections of streptozotocin (ICV-STZ) have been used as an experimental model of sporadic Alzheimer's disease (SAD) because they produce deficits in brain insulin signaling, oxidative stress, neuroinflammation, and neurodegeneration, resulting in cognitive decline and memory impairment. Spirulina platensis (SPI) is a nutraceutical with anti-inflammatory, antioxidant, and neuroprotective properties. The objective of this work was to study the effects of SPI on cognitive deficits and neuronal damage in mice submitted to the experimental model of SAD induced by ICV-STZ. Male Swiss mice (25-35 g) received ICV-STZ (3 mg/Kg) bilaterally on days 1 and 3, SPI (50 and 100 mg/Kg, o.p.) or vehicle (saline) was administered 2 h after the second surgery, and once a day for 16 days. SPI treatment prevented working, episodic, spatial, and aversive memory deficits. Locomotor activity was not altered. ICV-STZ caused an increase in MDA, nitrite, and superoxide anion, while decreasing GSH. SPI treatment protected against GSH increase in the prefrontal cortex and hippocampus, and inhibited AChE activity in the prefrontal cortex. SPI prevented astrogliosis and microgliosis induced by ICV-STZ. These findings highlight the therapeutic potential of SPI for the treatment of SAD, indicating that its neuroprotective action is linked to antioxidant, anti-inflammatory, and AChE inhibitory activity.

Prevention and Treatment of Alzheimer's Disease Via the Regulation of the Gut Microbiota With Traditional Chinese Medicine

Alzheimer's disease (AD) is caused by a variety of factors, and one of the most important factors is gut microbiota dysbiosis. An imbalance in the gut mincrobiota have been shown to change the concentrations of lipopolysaccharide and short-chain fatty acids. These microorganisms synthesize substances that can influence the levels of a variety of metabolites and cause multiple diseases through the immune response, fatty acid metabolism, and amino acid metabolism pathways. Furthermore, these metabolic changes promote the formation of β-amyloid plaques and neurofibrillary tangles. Thus, the microbiota-gut-brain axis plays an important role in AD development. In addition to traditional therapeutic drugs such as donepezil and memantine, traditional Chinese medicines (TCMs) have also showed to significantly decrease the severity of AD symptoms and suppress the underlying related mechanisms. We searched for studies on the effects of different herbal monomers, single herbs, and polyherbal formulas on the gut microbiota of AD patients and identified the relevant pathways through which the gut microbiota affected AD. We conclude that improvements in the gut microbiota not only decrease the occurrence of inflammatory reactions but also reduce the deposition of central pathological products. Herbal monomers have a stronger effect on improving of central pathology. Polyherbal formulas have the most extensive effect on the gut microbiota in patients with AD. Among the effects of formulas, the anti-inflammatory effect is the most essential and is also the main concern regarding the use of TCMs in treating AD from the viewpoint of the gut microbiota. We hope that this review will be helpful for providing new ideas for the clinical application of TCMs in the treatment of AD.

The Protective Effects of Polygala tenuifolia and Tenuifolin on Corticosterone-Evoked Ferroptosis, Oxidative Stress, and Neuroinflammation: Insights from Molecular Dynamics Simulations and In Vitro Experiments

Excessive stress is a well-established contributor to neurological damage, insomnia, and depression, imposing a significant burden on individuals and society. This underscores the urgent need for effective stress-relief strategies. The main purpose of this study was to explore the protective effects of Polygala tenuifolia (PT) and its bioactive compound, tenuifolin, against corticosterone-induced neurotoxicity, with a focus on ferroptosis, oxidative stress, and neuroinflammation. Both PT extracts and tenuifolin mitigated corticosterone-induced cellular damage. Tenuifolin reversed the corticosterone-induced dysregulation of ferroptosis-associated proteins, such as SLC7A11, GPX4, and Nrf2, leading to a marked reduction in ferroptosis levels. Molecular dynamics simulations revealed that corticosterone significantly altered the conformation and binding energy of the SLC7A11/SLC3A2 complex, critical for ferroptosis regulation. These changes were reversed by tenuifolin. Additionally, tenuifolin alleviated corticosterone-induced oxidative stress and neuroinflammation, both of which accelerated ferroptosis. In conclusion, these results indicate that tenuifolin attenuates corticosterone-induced neurotoxicity by modulating ferroptosis, oxidative stress, and neuroinflammation. This study provides a theoretical foundation for the application of PT and tenuifolin in stress-induced nerve damage.

Saponin components in Polygala tenuifolia as potential candidate drugs for treating dementia

Objective

This study aims to elucidate the intervention effects of saponin components from Polygala tenuifolia Willd (Polygalaceae) on dementia, providing experimental evidence and new insights for the research and application of saponins in the field of dementia.

Materials and Methods

This review is based on a search of the PubMed, NCBI, and Google Scholar databases from their inception to 13 May 2024, using terms such as "P. tenuifolia," "P. tenuifolia and saponins," "toxicity," "dementia," "Alzheimer's disease," "Parkinson's disease dementia," and "vascular dementia." The article summarizes the saponin components of P. tenuifolia, including tenuigenin, tenuifolin, polygalasaponins XXXII, and onjisaponin B, as well as the pathophysiological mechanisms of dementia. Importantly, it highlights the potential mechanisms by which the active components of P. tenuifolia prevent and treat diseases and relevant clinical studies.

Results

The saponin components of P. tenuifolia can reduce β-amyloid accumulation, exhibit antioxidant effects, regulate neurotransmitters, improve synaptic function, possess anti-inflammatory properties, inhibit neuronal apoptosis, and modulate autophagy. Therefore, P. tenuifolia may play a role in the prevention and treatment of dementia.

Conclusion

The saponin components of P. tenuifolia have shown certain therapeutic effects on dementia. They can prevent and treat dementia through various mechanisms.

I-C-F-6 attenuates chronic cerebral hypoperfusion-induced neurological injury in mice by modulating microglia polarization

Chronic cerebral hypoperfusion (CCH) is the leading cause of chronic cerebral dysfunction syndrome with its complex pathological mechanisms involving cortical and hippocampal neuronal loss, white matter lesions, and neuroinflammation. I-C-F-6 is a septapeptide, which has anti-inflammatory and anti-fibrotic effects. This study aimed to evaluate the neuroprotective effect of I-C-F-6 in chronic cerebral hypoperfusion (CCH)-induced neurological injury. C57BL/6 J mice were subjected to bilateral common carotid artery stenosis (BCAS), and BV2 microglia cells were induced with oxygen-glucose deprivation (OGD). In vivo, mice were divided randomly into four groups: Sham, BCAS, GBE (30 mg/kg), and I-C-F-6 (0.5 mg/kg). In vitro, microglia were divided randomly into four groups: control, OGD, I-C-F-6 (25 μg/mL), and Shikonin (800 nmol/L). Through LFB, TUNEL, and NeuN staining, we found that I-C-F-6 was able to mitigate myelin pathology and reduce the number of apoptotic neurons. Furthermore, immunofluorescence staining revealed that I-C-F-6 was able to reduce microglia clustering and downregulate NF-κB p65. We also observed a significant downregulation of M1 phenotype microglia signature genes, such as TNF-α, iNOS, and upregulation of anti-inflammatory cytokines, such as Arg-1 and IL-10, indicating that I-C-F-6 may mainly reduce polarization towards the M1 phenotype in microglia. Notably, I-C-F-6 downregulated the expression of NF-κB signaling pathway-related proteins IKK-β and NF-κB p65, as well as pro-inflammatory cytokines IL-1β and iNOS. In conclusion, I-C-F-6 can improve neurological damage, alleviate neuroinflammation, and inhibit microglia polarization to the M1 phenotype via the NF-κB signaling pathway.

Tenuigenin promotes non-rapid eye movement sleep via the GABAA receptor and exerts somnogenic effect in a MPTP mouse model of Parkinson's disease

Sleep disturbances are commonly non-motor symptoms in Parkinson's diseases (PD). However, standard dopamine replacement therapies for the treatment of motor symptoms often prove inadequate in combating sleep disturbances. Previous studies conducted by our research group have reported the neuroprotective effects of tenuigenin, a natural extract from Polygala tenuifolia root, which has been traditionally employed in treating insomnia. The objective of this study was to investigate the potential of tenuigenin in modulating sleep-wake behaviors and elucidate the underlying mechanisms. We employed EEG/EMG recordings to evaluate the impact of tenuigenin on sleep-wake profiles. Furthermore, we utilized c-Fos immunostaining, whole-cell patch clamping and local field potentials (LFP) recording to explore the mechanisms involved in sleep-promoting effects of tenuigenin. Additionally, we examined the effects of tenuigenin on sleep-promoting in MPTP PD mice. Here, we found tenuigenin demonstrated a significant increase in NREM sleep and a reduction in sleep latency in mice, without altering the EEG power density. Moreover, tenuigenin increased c-Fos expression in the ventrolateral preoptic area (VLPO) and stimulated sleep-promoting neurons in VLPO. The sleep-promoting effects of tenuigenin were abolished when mice were pretreated with flumazenil, an antagonist at the benzodiazepine site of the GABAA receptor. Furthermore, tenuigenin was found to ameliorate sleep disturbances in MPTP-induced mice. The results suggesting that tenuigenin facilitated a type of NREM sleep comparable to physiological NREM sleep through interaction with the GABAA receptor. Additionally, tenuigenin demonstrated improvements in sleep disturbances in MPTP-induced PD mice, suggesting its potential as a sleep-promoting substance, particularly for PD patients experiencing sleep disturbances.

Selected plant triterpenoids and their amide derivatives in cancer treatment: A review

Medicinal plants have been used to treat different diseases throughout the human history namely in traditional medicine. Most of the plants mentioned in this review article belong among them, including those that are widely spread in the nature, counted frequently to be food and nutrition plants and producing pharmacologically important secondary metabolites. Triterpenoids represent an important group of plant secondary metabolites displaying emerging pharmacological importance. This review article sheds light on four selected triterpenoids, oleanolic, ursolic, betulinic and platanic acid, and on their amide derivatives as important natural or semisynthetic agents in cancer treatment, and, in part, in pathogenic microbe treatment. A literature search was made in the Web of Science for the given key words covering the required area of secondary plant metabolites and their amide derivatives. The most recently published findings on the biological activity of the selected triterpenoids, and on the structures and biological activity of their relevant amide derivatives have been summarized therein. Mainly anti-cancer effects, and, in part, antimicrobial and other effects of the four selected triterpenoids and their amide derivatives have also been reviewed. A comparison of the effects of the parent plant products and those of their amide derivatives has been made.

Medicinal Herbs and Their Derived Ingredients Protect against Cognitive Decline in In Vivo Models of Alzheimer’s Disease

Alzheimer’s disease (AD) has pathological hallmarks including amyloid beta (Aβ) plaque formation. Currently approved single-target drugs cannot effectively ameliorate AD. Medicinal herbs and their derived ingredients (MHDIs) have multitarget and multichannel properties, engendering exceptional AD treatment outcomes. This review delineates how in in vivo models MHDIs suppress Aβ deposition by downregulating β- and γ-secretase activities; inhibit oxidative stress by enhancing the antioxidant activities and reducing lipid peroxidation; prevent tau hyperphosphorylation by upregulating protein phosphatase 2A expression and downregulating glycogen synthase kinase-3β expression; reduce inflammatory mediators partly by upregulating brain-derived neurotrophic factor/extracellular signal-regulated protein kinase 1/2-mediated signaling and downregulating p38 mitogen-activated protein kinase (p38 MAPK)/c-Jun N-terminal kinase (JNK)-mediated signaling; attenuate synaptic dysfunction by increasing presynaptic protein, postsynaptic protein, and acetylcholine levels and preventing acetylcholinesterase activity; and protect against neuronal apoptosis mainly by upregulating Akt/cyclic AMP response element-binding protein/B-cell lymphoma 2 (Bcl-2)-mediated anti-apoptotic signaling and downregulating p38 MAPK/JNK/Bcl-2-associated x protein (Bax)/caspase-3-, Bax/apoptosis-inducing factor-, C/EBP homologous protein/glucose-regulated protein 78-, and autophagy-mediated apoptotic signaling. Therefore, MHDIs listed in this review protect against Aβ-induced cognitive decline by inhibiting Aβ accumulation, oxidative stress, tau hyperphosphorylation, inflammation, synaptic damage, and neuronal apoptosis in the cortex and hippocampus during the early and late AD phases.

Neuroprotective Effects and Mechanisms of Senegenin, an Effective Compound Originated From the Roots of Polygala Tenuifolia

Senegenin is the main bioactive ingredient isolated from the dried roots of Polygala tenuifolia Willd. In recent years, senegenin has been proved to possess a variety of pharmacological activities, such as anti-oxidation, anti-inflammation, anti-apoptosis, enhancement of cognitive function. Besides, it has a good development prospect for the treatment of neurodegenerative diseases, depression, osteoporosis, cognitive dysfunction, ischemia-reperfusion injury and other diseases. However, there is no systematic literature that fully demonstrates the pharmacological effects of senegenin. In order to meet the needs of new drug research and precise medication, this review summarized the neuroprotective effects, mechanisms and gastrointestinal toxicity of senegenin based on the literatures published from the past 2 decades. In addition, an in-depth analysis of the existing problems in the current research as well as the future research directions have been conducted in order to provide a basis for the clinical application of this important plant extract.

Xi-Xian-Tong-Shuan capsule alleviates vascular cognitive impairment in chronic cerebral hypoperfusion rats by promoting white matter repair, reducing neuronal loss, and inhibiting the expression of pro-inflammatory factors

BACKGROUND

While the number of cases of vascular cognitive impairment caused by chronic cerebral hypoperfusion (CCH) has been increasing every year, there are currently no clinically effective treatment methods. At present, Xi-Xian-Tong-Shuan capsule is predominantly used in patients with acute cerebral ischemia; however, its protective effect on CCH has rarely been reported.

OBJECTIVE

To explore the underlying mechanisms by which Xi-Xian-Tong-Shuan capsule alleviates cognitive impairment caused by CCH.

METHODS

A model of CCH was established in specific-pathogen-free (SPF)-grade male Sprague-Dawley (SD) rats using bilateral common carotid artery occlusion (BCCAO). Xi-Xian-Tong-Shuan capsules were intragastrically administered for 42 days after the BCCAO surgery. We then assessed for changes in cognitive function, expression levels of pro-inflammatory factors, and coagulation function as well as for the presence of white matter lesions and neuronal loss. One-way ANOVA and Tukey's test were used to analyze the experimental data.

RESULTS

The rats showed significant cognitive dysfunction after the BCCAO surgery along with white matter lesions, a loss of neurons, and elevated levels of inflammatory factors, all of which were significantly reversed after intervention with Xi-Xian-Tong-Shuan capsules.

CONCLUSION

Xi-Xian-Tong-Shuan capsules can ameliorate vascular cognitive impairment in CCH rats by preventing damage of white matter, reducing neuronal loss, and inhibiting the expression of pro-inflammatory factors. Our study provides a new reference for the clinical treatment of chronic cerebral ischemia with Xi-Xian-Tong-Shuan capsules.

Neuroprotective Effect of Fucoxanthin against Intracerebroventricular Streptozotocin (ICV-STZ) Induced Cognitive Impairment in Experimental Rats

BACKGROUND

Alzheimer's disease (AD) is a neurological disorder characterized by loss of memory and cognitive functions caused by oxidative stress, neuroinflammation, change in neurotransmitter levels, and excessive deposition of Aβ_(1-42) plaques. Fucoxanthin is a carotenoid with potential antioxidant, anti-inflammatory, and neuroprotective actions.

OBJECTIVE

In the present study, fucoxanthin was employed as a protective strategy in Intracerebroventricular Streptozotocin (ICV-STZ) induced experimental model of cognitive impairment.

METHODS

STZ was injected twice ICV (3 mg/kg) on alternate days 1 and 3, and Wistar rats were evaluated for the memory analysis using Morris water maze and elevated plus-maze. Fucoxanthin at low 50 mg/kg, p.o. and high dose 100 mg/kg, p.o. was administered for 14 days. All animals were sacrificed on day 29, and brain hippocampus tissue after isolation was used for biochemical (MDA, nitrite, GSH, SOD and Catalase), neuroinflammatory (TNF-α, IL-1β, and IL-6), neurotransmitters (ACh, GABA Glutamate), Aβ_(1-42) and Tau protein measurements.

RESULTS

STZ-infused rats showed significant impairment in learning and memory, increased oxidative stress (MDA, nitrite), reduced antioxidant defense (GSH, SOD and Catalase), promoted cytokine release, and change in neurotransmitters level. However, fucoxanthin improved cognitive functions, restored antioxidant levels, reduced inflammatory markers dose-dependently, and restored neurotransmitters concentration.

CONCLUSION

The finding of the current study suggests that fucoxanthin could be the promising compound for improving cognitive functions through antioxidant, anti-inflammatory, and neuroprotective mechanisms, and inhibition of acetylcholinesterase (AChE) enzyme activities, Aβ_(1-42) accumulation, and tau protein.

Toxic Substance-induced Hippocampal Neurodegeneration in Rodents as Model of Alzheimer’s Dementia

BACKGROUND: Alzheimer’s Dementia (AD) cases are increasing with the global elderly population. To study the part of the brain affected by AD, animal models for hippocampal degeneration are still necessary to better understand AD pathogenesis and develop treatment and prevention measures. AIM: This study was a systematic review of toxic substance-induced animal models of AD using the Morris Water Maze method in determining hippocampal-related memory impairment. Our aim was reviewing the methods of AD induction using toxic substances in laboratory rodents and evaluating the report of the AD biomarkers reported in the models. METHODS: Data were obtained from articles in the PubMed database, then compiled, categorized, and analyzed. Eighty studies published in the past 5 years were included for analysis. RESULTS AND DISCUSSION: The most widely used method was intracerebroventricular injection of amyloid-β _substances. However, some less technically challenging techniques using oral or intraperitoneal administration of other toxic substances also produce successful models. Instead of hippocampal neurodegeneration, many studies detected biomarkers of the AD pathological process while some reported inflammation, oxidative stress, neurotrophic factors, and changes of cholinergic activity. Female animals were underrepresented despite a high incidence of AD in women. CONCLUSION: Toxic substances may be used to develop AD animal models characterized with appropriate AD pathological markers. Characterization of methods with the most easy-handling techniques and more studies in female animal models should be encouraged.

Discovery of a Novel Lineage Burkholderia cepacia ST 1870 Endophytically Isolated from Medicinal Polygala paniculata Which Shows Potent In Vitro Antileishmanial and Antimicrobial Effects

In this study, we report the isolation and identification of an endophytic strain of Burkholderia cepacia (COPS strain) associated with Polygala paniculata roots. Polygala plants are rich sources of promising microbiomes, of which the literature reports several pharmacological effects, such as trypanocidal, antinociceptive, anesthetic, anxiolytics, and anticonvulsant activities. B. cepacia COPS belongs to a new sequence type (ST 1870) and harbors a genome estimated in 8.3 Mbp which exhibits the aminoglycosides and beta-lactams resistance genes aph(3′)-IIa and bla_TEM-116, respectively. Analysis performed using MLST, average nucleotide identity, and digital DNA-DNA hybridization support its species-level identification and reveals its novel housekeeping genes alleles gyrB, lepA, and phaC. The root endophyte B. cepacia COPS drew our attention from a group of 14 bacterial isolates during the primary screening for being potentially active against Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212, Micrococcus luteus ATCC 9341, Escherichia coli ATCC 25922, and Candida albicans ATCC 10231 and exhibited the broad-spectrum activity against phytopathogenic fungi. In addition, COPS strain showed production of protease, lipase, and esterase in solid media, and its natural product extract showed potent inhibition against fungal plant pathogens, such as Moniliophthora perniciosa, whose antagonism index (89.32%) exceeded the positive control (74.17%), whereas Sclerotinia sclerotiorum and Ceratocystis paradoxa showed high percentages of inhibition (85.53% and 82.69%, respectively). COPS crude extract also significantly inhibited S. epidermidis ATCC 35984, E. faecium ATCC 700221 (MIC values of 32 μg/mL for both), E. faecalis ATCC 29212 (64 μg/mL), and S. aureus ATCC 25923 (128 μg/mL). We observed moderate antagonistic activity against A. baumannii ATCC 19606 and E. coli ATCC 25922 (both at 512 μg/mL), as well as potent cytotoxic effects on Leishmania infantum and Leishmania major promastigote forms with 78.25% and 57.30% inhibition. In conclusion, this study presents for the first time the isolation of an endophytic B. cepacia strain associated with P. paniculata and enough evidence that these plants may be considered a rich source of microbes for the fight against neglected diseases.

Polygala tenuifolia: a source for anti-Alzheimer's disease drugs

Context: Alzheimer's disease (AD) is a chronic neurodegenerative disease that originates from central nervous system lesions or recessions. Current estimates suggest that this disease affects over 35 million people worldwide. However, lacking effective drugs is the biggest handicap in treating AD. In traditional Chinese medicine (TCM), Polygala tenuifolia Willd. (Polygalaceae) is generally used to treat insomnia, memory dysfunction and neurasthenia.Objective: This review article explores the role of P. tenuifolia and its active components in anti-Alzheimer's disease.Methods: Literature for the last ten years was obtained through a search on PubMed, SciFinder, CNKI, Google Scholar, Web of Science, Science Direct and China Knowledge Resource Integrated with the following keywords: Polygala tenuifolia, polygalasaponin XXXII (PGS 32), tenuifolin, polygalacic acid, senegenin, tenuigenin, Alzheimer's disease.Results: Polygala tenuifolia and its active components have multiplex neuroprotective potential associated with AD, such as anti-Aβ aggregation, anti-Tau protein, anti-inflammation, antioxidant, anti-neuronal apoptosis, enhancing central cholinergic system and promote neuronal proliferation.Conclusions: Polygala tenuifolia and its active components exhibit multiple neuroprotective effects. Hence, P. tenuifolia is a potential drug against Alzheimer's disease, especially in terms of prevention.

Investigation of Low Dose Cabazitaxel Potential as Microtubule Stabilizer in Experimental Model of Alzheimer's Disease: Restoring Neuronal Cytoskeleton

BACKGROUND

Neuronal Microtubule (MT) tau protein, providing cytoskeleton to neuronal cells, plays a vital role, including maintenance of cell shape, intracellular transport, and cell division. Tau hyperphosphorylation mediated MT destabilization results in axonopathy, additionally neurotransmitter deficit and ultimately causing Alzheimer's disease. Pre-clinically, streptozotocin (3mg/kg, 10μl/ unilateral, ICV) stereotaxically mimics the behavioral and neurochemical alterations similar to Alzheimer's tau pathology resulting in MT assembly defects further lead to neuropathological cascades.

OBJECTIVE

Clinically approved medications such as Donepezil (DNP), rivastigmine, and Memantine (MEM) are responsible for symptomatic care only, but there is no specific pharmacological intervention that directly interacts with the neuronal microtubule destabilization.

METHODS

The current study focused on the involvement of anti-cancer agent microtubule stabilizer cabazitaxel at a low dose (0.5 and 2 mg/kg) alone and in combination with standard drugs DNP (5 mg/kg), MEM (10 mg/kg) and microtubule stabilizer Epothilone D (EpoD) (3 mg/kg) in the prevention of intracerebroventricular streptozotocin (ICV-STZ) intoxicated microtubule-associated tau protein hyperphosphorylation.

RESULTS

Chronic treatment of CBZ at a low dose alone and in combination with standard drugs showing no side effect and significantly improve the cognitive impairment, neurochemical alterations along with reducing the level of hyperphosphorylated tau by preventing the breakdown of the neuronal cytoskeleton, respectively.

CONCLUSION

The above findings suggested that CBZ at low dose show neuroprotective effects against ICV-STZ induced microtubule-associated tau protein hyperphosphorylation in rats and may be an effective agent for the preventive treatment of AD.

A review on the phytopharmacological studies of the genus Polygala

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Polygala, the most representative genus of the Polygalaceae family, comprises more than 600 species from all over the world of which around 40 are distributed in China, some of them, being used in the Traditional Chinese Medicine system.

AIM OF THE REVIEW

We intend to discuss the current knowledge about the traditional uses, and the newest phytochemical and pharmacological achievements with tentative elucidation of the mechanism of action on the genus Polygala covering the period 2013-2019 to provide a scientific support to the traditional uses, and to critically analyze the reported studies to obtain new insights for further researches.

MATERIALS AND METHODS

The data were systematically collected from the scientific electronic data bases including SciFinder, Scopus, Elsevier, PubMed and Google Scholar.

RESULTS

This literature overview reported several traditional uses of different species of Polygala, mainly against wounds, inflammation, cardiovascular and central nervous system disorders. P. altomontana, P caudata, P. flavescens, P. glomerata, P. japonica, P. molluginifolia, P. sibirica, P. tenuifolia are the main species which have been studied in the last few years. Phytochemical studies showed that they contain triterpene saponins, triterpenes, terpenoids, xanthones, flavonoids, coumarins, oligosaccharide esters, styryl-pyrones, benzophenones, and polysaccharides. Pharmacological in vitro and in vivo studies and proposal of the mechanisms of action indicated that pure constituents and extracts of Polygala ssp exhibited significant anti-inflammatory, neuroprotective, antiischemic, antidepressant, sedative, analgesic, antiatherosclerosis, antitumor and enzyme inhibitory properties.

CONCLUSION

This review on traditional uses and phytopharmacological potential of the genus Polygala revealed updated insights which can be explored for further mechanism-based pharmacological activities and structure/activity relationships studies and a better comprehension of the development of Chinese medicine preparations. However some pharmacological studies showed several gaps such as incomplete methodologies and ambiguous findings. More high scientific quality preclinical studies with pharmacokinetic considerations will be required in the future to assess the traditional uses of some species of this genus. This might lead to efficacy and safety issues in clinical trials and to potential medicinal applications.

The Effects of Yuan-Zhi Decoction and Its Active Ingredients in Both In Vivo and In Vitro Models of Chronic Cerebral Hypoperfusion by Regulating the Levels of Aβ and Autophagy

Chronic cerebral hypoperfusion (CCH) is closely related to the occurrence of Alzheimer's disease (AD) in the elderly. CCH can induce overactivation of autophagy, which increases the deposition of amyloid-β (Aβ) plaques in the brain, eventually impairing the cognitive function. Yuan-Zhi decoction (YZD) is a traditional Chinese medicine (TCM) formulation that is used to treat cognitive dysfunction in the elderly, but the specific mechanism is still unclear. In this study, we simulated CCH in a rat model through bilateral common carotid artery occlusion (BCCAO) and treated the animals with YZD. Standard neurological tests indicated that YZD significantly restored the impaired cognitive function after BCCAO in a dose-dependent manner. Furthermore, YZD also decreased the levels of Aβ aggregates and the autophagy-related proteins ATG5 and ATG12 in their hippocampus. An in vitro model of CCH was also established by exposing primary rat hippocampal neurons to hypoxia and hypoglycemia (H-H). YZD and its active ingredients increased the survival of these neurons and decreased the levels of Aβ1-40 and Aβ1-42, autophagy-related proteins Beclin-1 and LC3-II, and the APP secretases BACE1 and PS-1. Finally, both Aβ aggregates showed a positive statistical correlation with the expression levels of the above proteins. Taken together, YZD targets Aβ, autophagy, and APP-related secretases to protect the neurons from hypoxic-ischemic injury and restore cognitive function.

Design and synthesis of pentacyclic triterpene conjugates and their use in medicinal research

Triterpenoids are natural products from plants and many other organisms that have various biological activities, such as antitumor, antiviral, antimicrobial, and protective activities. This review covers the synthesis and biological evaluation of pentacyclic triterpene (PT) conjugates with other molecules that have been found to increase the IC₅₀ or improve the pharmacological profile of the parent PT. Some of these molecules are designed to target specific proteins or cellular organelles, which has resulted in highly selective lead structures for drug development. Other PT conjugates are useful for investigating their mechanism of action. This concept has been very successful: 1) Many compounds, especially mitochondria-targeting PT conjugates, have reached a selective cytotoxicity at low nanomolar concentrations in cancer cells. 2) A number of PT conjugates have had high activity against HIV or the influenza virus. 3) Fluorescent PT conjugates have been able to visualize the PT in living cells, which has allowed quantification of the uptake and distribution of the PT within the cell. 4) Biotinylated PT conjugates have been used to identify target proteins, which may help to show their mechanism of action. 5) A large number of PT conjugates with polyethylene glycol (PEG), polyamines, etc. form nanometer-sized micelles that have a much better pharmacological profile than the PT alone. In summary, the connection of a PT to an appropriate modifying molecule has resulted in extremely useful semisynthetic compounds with a high potential to treat cancer or viral infections or compounds that are useful for the study of the mechanism of action of PTs at the molecular level.

Neuroprotective Approach of Anti-Cancer Microtubule Stabilizers Against Tauopathy Associated Dementia: Current Status of Clinical and Preclinical Findings

Neuronal microtubule (MT) tau protein provides cytoskeleton to neuronal cells and plays a vital role including maintenance of cell shape, intracellular transport, and cell division. Tau hyperphosphorylation mediates MT destabilization resulting in axonopathy and neurotransmitter deficit, and ultimately causing Alzheimer’s disease (AD), a dementing disorder affecting vast geriatric populations worldwide, characterized by the existence of extracellular amyloid plaques and intracellular neurofibrillary tangles in a hyperphosphorylated state. Pre-clinically, streptozotocin stereotaxically mimics the behavioral and biochemical alterations similar to AD associated with tau pathology resulting in MT assembly defects, which proceed neuropathological cascades. Accessible interventions like cholinesterase inhibitors and NMDA antagonist clinically provides only symptomatic relief. Involvement of microtubule stabilizers (MTS) prevents tauopathy particularly by targeting MT oriented cytoskeleton and promotes polymerization of tubulin protein. Multiple in vitro and in vivo research studies have shown that MTS can hold substantial potential for the treatment of AD-related tauopathy dementias through restoration of tau function and axonal transport. Moreover, anti-cancer taxane derivatives and epothiolones may have potential to ameliorate MT destabilization and prevent the neuronal structural and functional alterations associated with tauopathies. Therefore, this current review strictly focuses on exploration of various clinical and pre-clinical features available for AD to understand the neuropathological mechanisms as well as introduce pharmacological interventions associated with MT stabilization. MTS from diverse natural sources continue to be of value in the treatment of cancer, suggesting that these agents have potential to be of interest in the treatment of AD-related tauopathy dementia in the future.

Apelin-13 Suppresses Neuroinflammation Against Cognitive Deficit in a Streptozotocin-Induced Rat Model of Alzheimer's Disease Through Activation of BDNF-TrkB Signaling Pathway

Alzheimer’s disease (AD), a progressive neurodegenerative disease characterized by impairments of cognitive function as a result of synaptic deficits and neuronal loss, is associated with inflammation. Apelin-13, a predominant neuropeptide with inhibiting effect on inflammation, has beneficial effects on cognition memory and neuronal damage. However, whether apelin-13 can protect neurons to ameliorate cognitive deficits in AD by inhibiting the inflammatory response remains largely unknown. To test this hypothesis, rats were intracerebroventricularly (ICV) injected with streptozotocin (3 mg/kg) alone or in combination with apelin-13 (2 μg). And tyrosine receptor kinase B (TrkB) blocker K252a (200 nM) was administrated 10 min before apelin injection. Furthermore, cognitive performance was assessed by new object recognition (NOR) and Y-maze tests. Protein expression of apelin, APJ, microglial marker (IBA1), astroglia marker (GFAP), interleukin 1 beta (IL-1β), tumor necrosis factor-α (TNF-α), synaptophysin (SYP), brain-derived neurotrophic factor (BDNF), TrkB, phospho-TrkB (p-TrkB) in the hippocampus were examined by western blotting or immunohistochemistry. And the gene expression of IBA1, GFAP, IL-1β, TNF-α, and SYP were detected by real-time quantitative polymerase chain reaction (PCR). Inflammatory disorder in the hippocampus was tested by hematoxylin and eosin (H&E) staining. The enzyme-linked immunosorbent assay (ELISA) was used to study the expression level of acetylcholine. And the activity of acetylcholinesterase was detected by Acetylcholinesterase Assay Kit. We observed that apelin/APJ signaling was downregulated in the hippocampus of rats administrated with STZ. Apelin-13 was found to significantly ameliorate STZ-induced AD-like phenotypes including congnitive deficit, cholinergic disfunction and the damage of neuron and synaptic plasticity. Moreover, apelin-13 inhibited microglia and astrocyte activation, reduced IL-1β and TNF-α expression and hippocampal BDNF/TrkB expression deficit in AD rats. Finally, apelin-13-mediated effects were blocked by TrkB receptor antagonist K252a. These results suggest that apelin-13 upregulates BDNF/TrkB pathway against cognitive deficit in a STZ-induced rat model of sporadic AD by attenuating inflammation.