Dihydromyricetin protects against cerebral ischemia/reperfusion injury via suppressing microglia-mediated neuroinflammation and activation of ERK1/2-CREB signaling pathway

The influence of ferroptosis on the in vitro OGD/R model in rat microglia

OBJECTIVE

We aimed to explore the influence of ferroptosis on an oxygen-glucose deprivation/reoxygenation (OGD/R) model in primary rat microglia.

METHODS

Primary microglia were extracted from rats and cultured in vitro. The cells were subjected to a hypoxic environment for 6 h in a glucose-free medium, and then re-oxygenated for 24 h in DMEM/F12. Rat microglia were pretreated with the ferroptosis activator erastin and the ferroptosis inhibitor ferrostatin 1 for 24 h, followed by detection of cell cycle progression and apoptosis by flow cytometry. Intracellular total iron levels were measured. In addition, the relative levels of reactive oxygen species (ROS), malondialdehyde (MDA), and superoxide dismutase (SOD) were determined using enzyme-linked immunosorbent assay. The protein levels of 15-lox2, GPX4, SLC7A11, ACSL4, and TFR1 were examined by western blotting.

RESULTS

Compared with rat microglia subjected to OGD/R, pretreatment with erastin did not influence cell apoptosis but significantly enhanced total iron levels, MDA, and ROS levels, whereas it reduced SOD levels. Moreover, it upregulated ACSL4, TFR1, and 15-lox2 and downregulated GPX4 and SLC7A11. Pretreatment with ferrostatin 1 significantly inhibited cell apoptosis and cell cycle arrest in the G0/G1 phase. It significantly reduced total iron levels, MDA, and ROS levels and enhanced SOD levels, which also downregulated ACSL4, TFR1, and 15-lox2, and upregulated GPX4 and SLC7A11.

CONCLUSION

Our study showed that inhibition of ferroptosis is favorable against potential OGD/R-induced damage in rat microglia.

Regulatory mechanisms of natural compounds from traditional Chinese herbal medicines on the microglial response in ischemic stroke

BACKGROUND

Development of clinically effective neuroprotective agents for stroke therapy is still a challenging task. Microglia play a critical role in brain injury and recovery after ischemic stroke. Traditional Chinese herbal medicines (TCHMs) are based on a unique therapeutic principle, have various formulas, and have long been widely used to treat stroke. Therefore, the active compounds in TCHMs and their underlying mechanisms of action are attracting increasing attention in the field of stroke drug development.

PURPOSE

To summarize the regulatory mechanisms of TCHM-derived natural compounds on the microglial response in animal models of ischemic stroke.

METHODS

We searched studies published until 10 April 2023 in the Web of Science, PubMed, and ScienceDirect using the following keywords: natural compounds, natural products or phytochemicals, traditional Chinese Medicine or Chinese herbal medicine, microglia, and ischemic stroke. This review was prepared according to PRISMA (Preferred Reporting Item for Systematic Reviews and Meta-Analysis) guidelines.

RESULTS

Natural compounds derived from TCHMs can attenuate the M1 phenotype of microglia, which is involved in the detrimental inflammatory response, via inhibition of NF-κB, MAPKs, JAK/STAT, Notch, TLR4, P2X7R, CX3CR1, IL-17RA, the NLRP3 inflammasome, and pro-oxidant enzymes. Additionally, the neuroprotective response of microglia with the M2 phenotype can be enhanced by activating Nrf2/HO-1, PI3K/AKT, AMPK, PPARγ, SIRT1, CB2R, TREM2, nAChR, and IL-33/ST2. Several clinical trials showed that TCHM-derived natural compounds that regulate microglial responses have significant and safe therapeutic effects, but further well-designed clinical studies are needed.

CONCLUSIONS

Further research regarding the direct targets and potential pleiotropic or synergistic effects of natural compounds would provide a more reasonable approach for regulation of the microglial response with the possibility of successful stroke drug development.

Dihydromyricetin suppresses inflammatory injury in microglial cells to improve neurological behaviors of Alzheimer's disease mice via the TLR4/MD2 signal

AIM

We analyzed the role and mechanism of dihydromyricetin (DHM) in suppressing inflammatory injury in microglial cells via targeting MD2.

METHODS

In vitro, BV2 cells were used as the objects of study to induce inflammatory injury with LPS + ATP, then the cell apoptosis level was identified, inflammatory factor levels were measured by ELISA, TLR4 and MD2 were stained with fluorescence staining, and protein expression was determined using Western-blot (WB) assay. Afterwards, MD2 expression was knocked down n BV2 cells to construct the BV2-MD2^-/- cell line, so as to detect the role of DHM on BV2-MD2^-/-. Moreover, the binding of DHM to MD2 was analyzed via mall molecule-protein docking and pull-down assays. In-vivo, wild-type (WT) C67BL/6 mice and APP/PS1 (AD) mice were used as the objects of study, which were intervened with DHM to detect the changes in mouse cognition. In addition, the pathological changes of brain tissues were analyzed with H&E staining. In addition, the inflammatory factor and protein levels in brain tissues were also detected.

RESULTS

DHM suppressed inflammatory injury in BV2 cells, reduced the cell apoptosis rate and inflammatory factor levels, and suppressed the level of TLR4 and MD2. After MD2 knockdown, DHM was unable to further suppress BV2 cell injury. Results of small molecule-protein docking and pull-down assays suggested that DHM bound to MD2 to suppress the formation of TLR4 complex. In AD mice, DHM improved the cognitive disorder in mice, suppressed inflammatory injury in brain tissues and lowered the expression of TLR4 protein.

CONCLUSION

DHM targeted MD2 to suppress the formation of TLR4 protein complex, thereby suppressing inflammatory injury in microglial cells and improving the cognition in AD mice.

Dihydromyricetin attenuates intracerebral hemorrhage by reversing the effect of LCN2 via the system Xc- pathway

BACKGROUND

The limited understanding of the pathological mechanisms of intracerebral hemorrhage (ICH) and the absence of successful therapies lead to poor prognoses for patients with ICH. Dihydromyricetin (DMY) has many physiological functions, such as regulating lipid and glucose metabolism and modulating tumorigenesis. Moreover, DMY has been proven to be an effective treatment of neuroprotection. However, no reports to date have been made regarding the impact of DMY on ICH.

PURPOSE

This investigation aimed to identify the role of DMY on ICH in mice and the underlying mechanisms.

METHODS/RESULTS

This study demonstrated that DMY treatment effectively reduced hematoma size and cell apoptosis of brain tissue, and improved neurobehavioral outcomes in mice with ICH. Transcriptional and network pharmacological analyses revealed that lipocalin-2 (LCN2) was a potential target of DMY in ICH. After ICH, LCN2 mRNA and protein expression in brain tissue increased and DMY could inhibit the expression of LCN2. The rescue experiment with the implementation of LCN2 overexpression verified these observations. Furthermore, after DMY treatment, there was a significant decrease in cyclooxygenase 2 (COX2), phospho-extracellular regulated protein kinase (P-ERK), iron deposition, and the number of abnormal mitochondria, which were reversed by the overexpression of LCN2. Proteomics analysis suggests that SLC3A2 may be the downstream target of LCN2, promoting ferroptosis. Finally, LCN2 was shown to bind to SLC3A2 and regulate the downstream glutathione (GSH) synthesis and Glutathione Peroxidase 4 (GPX4) expression and glutathione (GSH) synthesis, as determined by molecular docking and co-immunoprecipitation analysis.

CONCLUSION

Our study confirmed for the first time that DMY might offer a favorable treatment for ICH through its action on LCN2. The possible mechanism for this could be that DMY reverses the inhibitory effect of LCN2 on the system Xc-, lessening ferroptosis in brain tissue. The findings of this study offer a greater understanding of how DMY affects ICH at a molecular level and could be conducive to developing therapeutic targets for ICH.

Deregulated Protein Kinases: Friend and Foe in Ischemic Stroke

Ischemic stroke is the third leading cause of mortality worldwide, but its medical management is still limited to the use of thrombolytics as a lifesaving option. Multiple molecular deregulations of the protein kinase family occur during the period of ischemia/reperfusion. However, experimental studies have shown that alterations in the expression of essential protein kinases and their pharmacological modulation can modify the neuropathological milieu and hasten neurophysiological recovery. This review highlights the role of key protein kinase members and their implications in the evolution of stroke pathophysiology. Activation of ROCK-, MAPK-, and GSK-3β-mediated pathways following neuronal ischemia/reperfusion injury in experimental conditions aggravate the neuropathology and delays recovery. Targeting ROCK, MAPK, and GSK-3β will potentially enhance myelin regeneration, improve blood-brain barrier (BBB) function, and suppress inflammation, which ameliorates neuronal survival. Conversely, protein kinases such as PKA, Akt, PKCα, PKCε, Trk, and PERK salvage neurons post-ischemia by mechanisms including enhanced toxin metabolism, restoring BBB integrity, neurotrophic effects, and apoptosis suppression. Certain protein kinases such as ERK1/2, JNK, and AMPK have favourable and unfavourable effects in salvaging ischemia-injured neurons. Targeting multiple protein kinase-mediated pathways simultaneously may improve neuronal recovery post-ischemia.

Flavonoids from edible fruits as therapeutic agents in neuroinflammation - a comprehensive review and update

Neuroinflammation is a key process in the pathogenesis of many neurological disorders, i.e. Alzheimer's disease and Parkinson's disease. However, there are no anti-inflammatory medical interventions recommended so far in the treatment of neuroinflammation-related brain disorders. Therefore, the burden of searching for effective and safe antineuroinflammatory agents is well founded, especially in the aging society. Compounds of plant origin, mainly (poly)phenols, have attracted considerable attention in recent years. Notably, the role of flavonoids in ameliorating neuroinflammation is in the limelight. Thus, we used comprehensive literature retrieval to summarize the effects and active components of edible fruits and their phenolic compounds. As a result, this review presents a valuable summary of results of in vitro, ex vivo, and in vivo studies on the antineuroinflammatory effects of edible fruits and their (poly)phenolic extracts as well as dietary flavonoids and other selected (poly)phenols based on the detailed description of foregoing studies. Additionally, problems resulting from the limited bioavailability of (poly)phenols were discussed.

Development and characterization of an inducible Dicer conditional knockout mouse model of Parkinson's disease: validation of the antiparkinsonian effects of a sigma-1 receptor agonist and dihydromyricetin

Parkinson's disease (PD) is a common neurodegenerative disease characterized by motor impairment and progressive loss of dopamine (DA) neurons. At present, the acute application of neurotoxic drugs such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine (6-OHDA) are commonly used to simulate the pathology of PD; however, it is difficult to induce the progressive pathogenesis of PD with these models. In this study, we employed DAT promoter-mediated Cre transgenic mice to establish tamoxifen-inducible Dicer conditional knockout (cKO) mice in an effort to mimic the progressive loss of DA neurons and the development of PD-like behavioral phenotypes. The results showed that Dicer cKO mice exhibited progressive loss of DA neurons in the substantia nigra (SN) following tamoxifen administration. Significant DA loss was observed 6 weeks after tamoxifen administration; accordingly, progressive motor function impairment was also observed. We also found that a significant neuroinflammatory response, as evidenced by microglial proliferation, another hallmark of PD pathogenesis, accompanied the loss of DA neurons. The acute application of levo-DOPA (L-DOPA) relieved the PD-like motor impairments in Dicer cKO mice to exert its antiparkinsonian action, indicating that the model can be used to evaluate the antiparkinsonian efficacy of PD drugs. To further elucidate the potential application of this novel PD animal model for PD drug development, we employed the powerful neuroprotective agent dihydromyricetin (DHM) (10 mg/kg) and the selective sigma-1 receptor agonist PRE-084 (1 mg/kg), both of which were previously shown to produce antiparkinsonian effects. The results indicated that the chronic administration of either DHM or PRE-084 attenuated the Dicer cKO-induced loss of DA neurons and motor impairments, although the two drugs acted through different mechanisms. These data indicate that the Dicer cKO mouse model may be a useful model for investigating the pathological development of PD and intervention-mediated changes. In conclusion, this transgenic mouse model appears to simulate the progressive pathogenesis of PD and may be a potentially useful model for PD drug discovery.

The protective effect of zeranol in cerebral ischemia reperfusion via p-CREB overexpression

AIMS

Cerebral ischemia reperfusion (I/R) is a neurovascular disease leading to cerebral damage. It was found that postmenopausal women are liable to more dangerous effects than men at same age in stroke. The objective of this study is to investigate the neuroprotective effect of zeranol against cerebral ischemia reperfusion in ovariectomized rats.

MAIN METHODS

36 female wistar rats divided in to 3 groups: sham group, I/R group (where I/R was induced 7 weeks after ovariectomy), zeranol group (0.5 mg/kg every 3 days for 5 weeks before I/R). Cerebral ischemia reperfusion (I/R) was performed by bilateral common carotid artery occlusion then de-ligated to restore blood flow. After 24 h of reperfusion, rats performed cylinder test to evaluate behavioral dysfunction followed by decapitation. Brain tissues were collected for biochemical measures such as oxidative stress marker malondialdehyde, antioxidant markers reduced glutathione, inflammatory markers (interleukin-1 beta, tumor necrosis factor alpha, and inducible nitric oxide synthase), matrix metalloproteinase-9, adenosine triphosphate, brain derived neurotrophic factor, glucose transporter-3, phosphorylated c-AMP response element binding protein and finally nissl staining for histopathological examination.

KEY FINDINGS

The zeranol administered group showed a reversal of neuronal damage caused by ischemia evidenced by the decrease in MDA, IL-1β, TNF-α, and MMP-9 levels, increase GSH, and ATP levels, decrease expression of iNOS in both regions cortex and hippocampus, increase protein level of p-CREB, GLUT-3 and BDNF, increase number of intact neuron cells in both regions and attenuated histological changes in both cortex and hippocampus regions.

SIGNIFICANCE

Zeranol has neuroprotective potential against cerebral ischemia reperfusion in ovariectomized rats.

Simultaneous quantitative analysis of 11 flavonoid derivatives with a single marker in persimmon leaf extraction and evaluation of their myocardium protection activity

An improved, reliable and comprehensive method for assessing the quality of the ethyl acetate extract from persimmon leaves (EAPL) and its commercial preparation, Naoxinqing (Brain and Heart Clear capsules), has been developed and validated. Based on HPLC-DAD-ESI-Q-TOF-MS analysis, myricetin-3-O-β-D-galactoside (1), myricetin-3-O-glucoside (2), quercetin-3-O-β-D-galactoside (3), quercetin-3-O-β-D-glucoside (4), quercetin-3-O-(2″-O-galloyl-β-D-galactoside) (5), quercetin-3-O-(2″-O-galloyl-β-D-glucoside) (6), kaempferol-3-O-β-D-galactoside (7), kaempferol-3-O-β-D-glucoside (8), kaempferol-3-O-(2″-O-galloyl-β-D-galactoside) (9), kaempferol-3-O-(2″-O-galloyl-β-D-glucoside) (10), quercetin (11) and kaempferol (12) were identified from 15 batch samples. A HPLC fingerprint analytical method was established. All compounds, with the exception of compound 2, were simultaneously quantified by the single standard to determine multi-components (SSDMC) method, using kaempferol-3-O-β-D-glucoside as the internal standard. The rate of analysis was found to be faster with the SSDMC method than with current acid hydrolysis method (Pharmacopoeia of the People's Republic of China 2015 edition) and the results were more intuitive and reliable. Three-dimensional principal component analysis revealed that there were similar characteristics in persimmon leaf from same district. Analysis of the myocardial cell protection activity of 11 monomeric compounds showed that compounds 12, 11 and 10 were the main active ingredients that produce pharmacologic functions in EAPL. Among these compounds, the bioactive constituent of myricetin-3-O-β-D-galactoside was determined for the first time in Diospyros khaki. Thus, we have established an effective assessment method that can be applied to the comprehensive quality evaluation of EAPL extract and Naoxinqing capsule.

Raf kinase inhibitor protein protects microglial cells against 1-methyl-4-phenylpyridinium-induced neuroinflammation in vitro

The Raf kinase inhibitor protein (RKIP), belonging to a member of the phosphatidylethanolamine-binding protein (PEBP) family, is involved in regulating neural development. However, the role of RKIP in microglial cells stimulated with 1-methyl-4-phenylpyridinium (MPP⁺) has not been determined. Thus, in the present study, we investigated the role of RKIP and its underlying mechanism in Parkinson's disease (PD). Our results showed that the expression of RKIP was significantly reduced in BV-2 cells treated with MPP⁺. Overexpression of RKIP markedly rescued cell viability and inhibited cell apoptosis in BV-2 cells exposed to MPP⁺. In addition, overexpression of RKIP inhibited MPP⁺-induced the production of pro-inflammatory molecules in BV-2 cells. Similar results were observed in primary microglial cells isolated from neonatal mice. Exploration of the underlying mechanisms of its action indicated that overexpression of RKIP prevented the activation of NF-κB and MEK/ERK pathways in MPP⁺-stimulated BV-2 cells. Taken together, these findings indicated that RKIP suppresses apoptosis and inflammation in MPP⁺-treated microglial cells through the inactivation of NF-κB and MEK/ERK signaling pathways. Thus, RKIP may be a promising target molecular involving in the pathogenesis of PD.

Nucleolin-Targeting AS1411-Aptamer-Modified Graft Polymeric Micelle with Dual pH/Redox Sensitivity Designed To Enhance Tumor Therapy through the Codelivery of Doxorubicin/TLR4 siRNA and Suppression of Invasion

In this article, a novel graft polymeric micelle with targeting function ground on aptamer AS1411 was synthesized. The micelle was based on chitosan-ss-polyethylenimine-urocanic acid (CPU) with dual pH/redox sensitivity and targeting effects. This micelle was produced for codelivering Toll-like receptor 4 siRNA (TLR4-siRNA) and doxorubicin (Dox). In vitro investigation revealed the sustained gene and drug release from Dox-siRNA-loaded micelles under physiological conditions, and this codelivery nanosystem exhibited high dual pH/redox sensitivity, rapid intracellular drug release, and improved cytotoxicity against A549 cells in vitro. Furthermore, the micelles loaded with TLR4-siRNA inhibited the migration and invasion of A549. Excellent tumor penetrating efficacy was also noted in the A549 tumor spheroids and solid tumor slices. In vivo, multiple results demonstrated the excellent tumor-targeting ability of AS1411-chitosan-ss-polyethylenimine-urocanic acid (ACPU) micelle in tumor tissues. The micelles exhibited excellent antitumor efficacy and low toxicity in the systemic circulation in lung-tumor-bearing BALB/c mice. These results conclusively demonstrated the great potential of the new graft copolymer micelle with targeting function for the targeted and efficient codelivery of chemotherapeutic drugs and genes in cancer treatment.

Dihydromyricetin exerts a rapid antidepressant-like effect in association with enhancement of BDNF expression and inhibition of neuroinflammation

RATIONALE

Major depressive disorder (MDD) is a highly prevalent illness that affects large populations across the world, and increasing evidence suggests that neuroinflammation and levels of brain-derived neurotrophic factor (BDNF) are closely related to depression. Dihydromyricetin (DHM) is a kind of flavonoid natural product that has been reported to display multiple pharmacological effects, including anti-inflammatory and anti-oxidative properties, and these may contribute to ameliorate MDD.

OBJECTIVE

This study investigated the effect of DHM on depression-related phenotypes in various experimental animal models.

METHODS

The antidepressant-like effect of DHM was validated via depression-related behavioral tests in naïve male C57BL/6 mice, as well as in the acute lipopolysaccharide-induced mouse model of depression. The chronic unpredicted mild stress (CUMS) mouse model of depression was also used to assess the rapid antidepressant-like effect of DHM by tail suspension test (TST), forced swimming test (FST), locomotor activity, and sucrose preference test (SPT). The expression of BDNF and inflammatory factors were determined through Western blotting and enzyme-linked immunosorbent assay, respectively.

RESULTS

DHM reduced immobility time in the TST and FST both in mice and the acute LPS-induced mouse model of depression. Seven days of DHM treatment ameliorated depression-related behaviors induced by CUMS, whereas similar treatment with the typical antidepressant venlafaxine did not. DHM activated the ERK1/2-CREB pathway and increased glycogen synthase kinase-3 beta (GSK-3β) phosphorylation at ser-9, with upregulation of BDNF expression, in both hippocampal tissues and cultured hippocampal cells.

CONCLUSION

The present data indicate that DHM exerts a more rapid antidepressant-like effect than does a typical antidepressant, in association with enhancement of BDNF expression and inhibition of neuroinflammation.