Vaccinium bracteatum Improves Spatial Learning and Memory by Regulating N-methyl-D-aspartate Receptors and Tau Phosphorylation in Chronic Restraint Stress-Induced Memory Impaired Mice

Constituents of Stachys plants as potential dual inhibitors of AChE and NMDAR for the treatment of Alzheimer's disease: a molecular docking and dynamic simulation study

Alzheimer's disease (AD) is a chronic neurodegenerative condition characterized by progressive cognitive impairment. While the formation of β-amyloid plaques and neurofibrillary tangles are the hallmarks features of AD, the downstream consequence of these byproducts is the disruption of the cholinergic and glutamatergic neural systems. Growing evidence for the existence of interplay between AChE and NMDARs has opened up new venues for the discovery of novel ligands endowed with anticholinesterase and NMDAR-blocking activity. Plants belonging to the stachys genus have been extensively explored for having a broad range of therapeutic applications and have been used traditionally for millennia, to treat various CNS-related disorders, which makes them the ideal source of novel therapeutics. The present study was designed to identify natural dual-target inhibitors for AChE and NMDAR deriving from stachys genus for their potential use in AD. Using molecular docking, drug-likeness-profiling, MD simulation and MMGBSA calculations, an in-house database of biomolecules pertaining to the stachys genus was shortlisted based on their binding affinity, overall stability and critical ADMET parameters. Pre- and post-MD analysis revealed that Isoorientin effectively binds to AChE and NMDAR with various vital interactions, exhibits a stable behavior with minor fluctuations relative to two clinical drugs used as positive control, and displays strong and consistent interactions that lasted for the majority of the simulation. Findings from this study have elucidated the rationale behind the traditional use of Stachys plants for the treatment of AD and could provide new impetus for the development of novel dual-target therapeutics for AD treatment.Communicated by Ramaswamy H. Sarma.

Antidepressant effects of p-coumaric acid isolated from Vaccinium bracteatum leaves extract on chronic restraint stress mouse model and antagonism of serotonin 6 receptor in vitro

BACKGROUND

Vaccinium bracteatum Thunb. leaves (VBL) are used in traditional herbal medicines to treat various biological diseases. p-coumaric acid (CA), the main active component of VBL, has neuroprotective effects against corticosterone-induced damage in vitro. However, the effects of CA on immobility induced by chronic restraint stress (CRS) in a mouse model and 5-HT receptor activity have not been investigated.

HYPOTHESIS/PURPOSE

We investigated the antagonistic effects of VBL, NET-D1602, and the three components of Gαs protein-coupled 5-HT receptors. Additionally, we identified the effects and mechanism of action of CA, the active component of NET-D1602, in the CRS-exposed model.

METHODS

For in vitro analyses, we used 1321N1 cells stably expressing human 5-HT₆ receptors and CHO-K1 expressing human 5-HT₄ or 5-HT₇ receptors cell lines to study the mechanism of action. For in vivo analyses, CRS-exposed mice were orally administered CA (10, 50, or 100 mg/kg) daily for 21 consecutive days. The effects of CA were analyzed by assessing behavioral changes using a forced swim test (FST), measuring levels of hypothalamic-pituitary-adrenal (HPA) axis-related hormones in ntial therapeutic effects as 5-HT6 receptor antagonists for neurodegenerative diseases and depressioserum, and acetylcholinesterase (AChE), monoamines, including 5-HT, dopamine, and norepinephrine, using enzyme-linked immunosorbent assay kits. The underlying molecular mechanisms of the serotonin transporter (SERT), monoamine oxidase A (MAO-A), and extracellular signal-regulated kinase (ERK)/protein kinase B (Akt)/mTORC1 signaling were detected using western blotting.

RESULTS

CA was confirmed to be an active component in the antagonistic effects of NET-D1602 on 5-HT₆ receptor activity through decreases in cAMP and ERK1/2 phosphorylation. Moreover, CRS-exposed mice treated with CA showed a significantly reduced immobility time in the FST. CA also significantly decreased corticosterone, corticotropin-releasing hormone (CRH), and adrenocorticotropic hormone (ACTH) levels. CA enhanced 5-HT, dopamine, and norepinephrine levels in the hippocampus (HC) and prefrontal cortex (PFC) but decreased MAO-A and SERT protein levels. Similarly, CA significantly upregulated the ERK, Ca²⁺/calmodulin-dependent protein kinase II (CaMKII), Akt/mTOR/p70S6K/S6 signaling pathways in both HC and the PFC.

CONCLUSION

CA contained in NET-D1602 may play the antidepressant effects against CRS-induced depression-like mechanism and the selective antagonist effect of 5-HT₆ receptor.

Baicalein Preconditioning Cardioprotection Involves Pro-Oxidant Signaling and Activation of Pyruvate Dehydrogenase

Preconditioning has a powerful protective potential against myocardial ischemia-reperfusion injury (I/R). Our prior work demonstrated that baicalein, a flavonoid derived from the root of Scatellaria baicalensis Georgi (also known as Huangqin), confers this preconditioning protection. This study further explored the mechanisms of baicalein preconditioning (BC-PC) in mouse cardiomyocytes. Cells were treated with baicalein (10 μM) for a brief period of time (10 min) prior to simulated ischemia 90 min/reperfusion for 180 min. Baicalein triggered an induction of a small amount of mitochondrial reactive oxygen species (ROS) prior to the initiation of ischemia, assessed by 6-carboxy-2^', 7^'-dichlorodihydrofluorescein diacetate (6-carboxy-H₂DCFDA). It also significantly increased cell viability measured by propidium iodide (PI) and lactate dehydrogenase and preserved mitochondrial membrane potential assessed by TMRM fluorescence intensity. Myxothiazol, a mitochondrial electron transport chain complex III inhibitor, partially blocked ROS generation induced by BC-PC and reduced cell viability. BC-PC increased phosphorylation of Akt (Thr308 and Ser473) and eNOS Ser1177, and nitric oxide (NO) production measured using 4,5-diaminofluorescein diacetate (DAF-2 DA, 1 μM). Akt inhibitor API-2 abolished Akt phosphorylation and reduced DAF-2 production and cell viability. In addition, BC-PC decreased phosphorylation of pyruvate dehydrogenase (PDH) reflecting upregulated PDH activity, and increased ATP production at 30 min during reperfusion. Taken together, baicalein preconditioning-induced cardioprotection involves pro-oxidant generation, activates survival signaling Akt/eNOS/NO, and improves metabolic recovery after I/R injury. Our work provides new perspectives on the effect of baicalein on cardiac preconditioning against I/R injury.

Morin attenuates memory deficits in a rat model of Alzheimer's disease by ameliorating oxidative stress and neuroinflammation

This study aimed to investigate the effect of flavonoid morin on oxidative/nitrosative stress, neuroinflammation, and histological, molecular, and behavioral changes caused by amyloid-beta (Aβ)_1-42 in male Wistar rats (Alzheimer's disease model). Rats received morin (20 mg/kg, oral gavage) for 14 consecutive days after intrahippocampal injection of Aβ_1-42. Morin decreased the levels of malondialdehyde and nitric oxide, increased glutathione content, and enhanced catalase activity in the hippocampus of animals receiving Aβ_1-42. It also reduced the expression of tumor necrosis factor-α, interleukin-1β, interleukin-6, nuclear factor-kappa B, and N-methyl-D-aspartate receptor subunits 2A and 2B and increased the expression of brain-derived neurotrophic factor and α7 nicotinic acetylcholine receptor in the hippocampus of Aβ_1-42-injected rats. Besides, morin modified neuronal loss and histological changes in the CA1 region of the hippocampus. Morin allowed Aβ_1-42-infused rats to swim more time in the target quadrant in the Morris water maze test. It is concluded that morin may be suitable for the prevention and treatment of Alzheimer's disease by strengthening the antioxidant system, inhibiting neuroinflammation, preventing neuronal death, and enhancing memory function.

Isolation and Analytical Method Validation for Phytocomponents of Aqueous Leaf Extracts from Vaccinium bracteatum Thunb. in Korea

In this study, major phytochemical compounds of Vaccinium bracteatum Thunb. (VB) aqueous leaf extract were isolated and analyzed using a HPLC-based method, followed by method validation in accordance with the International Conference on Harmonisation (ICH) guidelines for drug development. Five major compounds were isolated in VB extract. Apart from vaccinoside, which had been the only compound isolated in VB extract to date, vanillic acid and protocatechuic acid were isolated for the first time. Isolation of orientin and isoorientin in the VB extract helped validate the reverse-phase analytical method. A new simple and rapid high-performance liquid chromatography (HPLC)-based method was developed for the validation of orientin and isoorientin in VB extract and was determinated according to the ICH guidelines. The analytical method was validated through a Waters Alliance HPLC System containing an e2695 separation module and a 2998 photodiode array (PDA) detector. The VB extract and solutions of orientin and isoorientin were analyzed using a reverse-phase Eclipse XDB-C18 column (4.6 × 250 mm ID, 5 µm, Waters), which was maintained at 30 °C. A mobile phase of methanol and 0.01% formic acid in water was used at a flow rate of 1.0 mL/min to achieve gradient elution. The linearity of the orientin and isoorientin was excellent results (R2 ≥ 0.9999) in the concentration range of 1.0–50.0 μg/mL. Precision values ranged 98.55–101.70% and 98.70–101.18%, respectively. The intra-day and inter-day relative standard deviation (RSD) values of the orientin and isoorientin were all <2.0%. The average recoveries of orientin ranged 98.30–101.57%, whereas isoorientin ranged 97.81–102.14% with RSD values <2.0%. Quantitative analysis found that VB extract contained 2.90 mg/g of orientin and 3.45 mg/g of isoorientin.

Chronic Restraint Stress-Induced Muscle Atrophy Leads to Fatigue in Mice by Inhibiting the AMPK Signaling Pathway

Currently, an increasing number of people are suffering from fatigue due to the state of their lifestyles, such as sedentary work in a relatively small space, irregular sleep patterns, or the lack of movement and exercise. The present study was designed to simulate the occurrence of fatigue in the above populations through a chronic restraint stress (CRS) model, and to reveal its dynamic processes and potential underlying molecular mechanisms. ICR mice were subjected to 8 h of restraint stress each day for 5, 10, or 15 days. It was found that the weight-loaded swimming performance, grip strength, and locomotor activity of the mice all decreased under CRS treatment, and that up to 15 days of CRS induced notable fatigue. Gastrocnemius muscle atrophy and some abnormal biochemical parameters related to fatigue under CRS were observed. Furthermore, transcriptome data showed that the changes in muscle cell metabolism and mitochondrial dysfunction were associated with the AMPK signaling pathway in CRS-treated mice. Western blotting analysis of the AMPK/PGC-1α signaling pathway revealed that CRS could decrease mitochondrial biogenesis and reduce the numbers of type I skeletal muscle fibers in the gastrocnemius of mice. CRS could also block the protective mitophagic flux to inhibit the abnormal clearance of damaged mitochondria. Our study suggests a critical link between muscle atrophy and CRS-induced fatigue in mice, suggesting that the pharmacological promotion of muscle and mitochondrial function can be used as a treatment for stress-induced fatigue.

Protective Effects of p-Coumaric Acid Isolated from Vaccinium bracteatum Thunb. Leaf Extract on Corticosterone-Induced Neurotoxicity in SH-SY5Y Cells and Primary Rat Cortical Neurons

Corticosterone (CORT)-induced oxidative stress and neurotoxicity can cause neuronal dysfunction and mental disorders. In the present study, we investigated the effects and mechanism of the HP-20 resin fraction of the water extract of Vaccinium bracteatum leaves (NET-D1602) and its bioactive compound p-coumaric acid on neuronal cell damage in SH-SY5Y cells and primary culture of rat cortical cells. NET-D1602 and p-coumaric acid significantly improved cell viability in CORT-induced neurotoxicity in SH-SY5Y cells and primary cultures of rat cortical cells, and increased the activities of antioxidant enzymes (superoxide dismutase and catalase) against CORT-induced neurotoxicity in SH-SY5Y cells. NET-D1602 and p-coumaric acid increased the phosphorylation levels of ERK1/2 and cAMP response element-binding protein (CREB) in cortical neurons. In addition, CREB phosphorylation by NET-D1602 and p-coumaric acid was dramatically reversed by PKA, c-Raf/ERK, PI3K, and mTOR inhibitors. Lastly, we demonstrated the neuroprotective effects of NET-D1602 (3 and 10 μg/mL) and p-coumaric acid (3 and 10 μM) via increased CREB phosphorylation in CORT-induced neurotoxicity mediated via the ERK1/2, Akt, and mTOR pathways. These results suggest that p-coumaric acid is a potential neuroprotective component of NET-D1602, with the ability to protect against CORT-induced neurotoxicity by regulating ERK1/2, Akt, and mTOR-mediated CREB phosphorylation.