Activation of CREB-mediated autophagy by thioperamide ameliorates β-amyloid pathology and cognition in Alzheimer's disease

Rhoifolin, baicalein 5,6-dimethyl ether and agathisflavone prevent amnesia induced in scopolamine zebrafish (Danio rerio) model by increasing the mRNA expression of bdnf, npy, egr-1, nfr2α, and creb1 genes

The increasing attention towards age-related diseases has generated significant interest in the concept of cognitive dysfunction associated with Alzheimer's disease (AD). Certain limitations are associated with the current therapies, and flavonoids have been reported to exhibit multiple biological activities and anti-AD effects in several AD models owing to their antioxidative, anti-inflammatory, and anti-amyloidogenic properties. In this study, we performed an initial in silico predictions of the pharmacokinetic properties of three flavonoids (rhoifolin, baicalein 5,6-dimethyl ether and agathisflavone). Subsequently, we evaluated the antiamnesic and antioxidant potential of flavonoids in concentrations of 1, 3, and 5 μg/L in scopolamine (100 μM)-induced amnesic zebrafish (Danio rerio) model. Zebrafish behavior was analyzed by novel tank diving test (NTT), Y-maze, and novel object recognition test (NOR). Acetylcholinesterase (AChE) activity, brain antioxidant status and the expression of bdnf, npy, egr1, nrf2α, creb1 genes, and CREB-1 protein level was measured to elucidate the underlying mechanism of action. Our flavonoids improved memory and decreased anxiety-like behavior of scopolamine-induced amnesia in zebrafish. Also, the studied flavonoids reduced AChE activity and brain oxidative stress and upregulated the gene expression, collectively contributing to neuroprotective properties. The results of our study add new perspectives on the properties of flavonoids to regulate the evolution of neurodegenerative diseases, especially AD, by modulating the expression of genes involved in the regulation of synaptic plasticity, axonal growth, and guidance, sympathetic and vagal transmission, the antioxidant response and cell proliferation and growth.

The brain-protective mechanism of fecal microbiota transplantation from young donor mice in the natural aging process via exosome, gut microbiota, and metabolomics analyses

The natural aging process is accompanied by changes in exosomes, gut microbiota, and metabolites. This study aimed to reveal the anti-aging effect and mechanisms of fecal microbiota transplantation (FMT) from young donors on the natural aging process in mice by analyzing exosomes, gut microbiota, and metabolomics. Aging-relevant telomeric length, oxidative stress indexes in brain tissue, and serum cytokine levels were measured. Flow analysis of T-regulatory (Treg), CD4+, and CD8+ cells was performed, and the expression levels of aging-related proteins were quantified. High-throughput sequencing technology was used to identify differentially expressed serum exosomal miRNAs. Fecal microbiota was tested by 16 S rDNA sequencing. Changes in fecal metabolites were analyzed by UPLC-Q-TOF/MS. The results indicated that the expression of mmu-miR-7010-5p, mmu-miR-376b-5p, mmu-miR-135a-5p, and mmu-miR-3100-5p by serum exosomes was down-regulated and the abundance of opportunistic bacteria (Turicibacter, Allobaculum, Morganella.) was decreased, whereas the levels of protective bacteria (Akkermansia, Muribaculaceae, Helicobacter.) were increased after FMT. Metabolic analysis identified 25 potential biomarkers. Correlation analysis between the gut microbiota and metabolites suggested that the relative abundance of protective bacteria was positively correlated with the levels of spermidine and S-adenosylmethionine. The study indicated that FMT corrected brain injury due to aging via lipid metabolism, the metabolism of cofactors and vitamins, and amino acid metabolism.

AdipoRon promotes amyloid-β clearance through enhancing autophagy via nuclear GAPDH-induced sirtuin 1 activation in Alzheimer's disease

BACKGROUND AND PURPOSE

Amyloid-β (Aβ) peptide is one of the more important pathological markers in Alzheimer's disease (AD). The development of AD impairs autophagy, which results in an imbalanced clearance of Aβ. Our previous research demonstrated that AdipoRon, an agonist of adiponectin receptors, decreased the deposition of Aβ and enhanced cognitive function in AD. However, the exact mechanisms by which AdipoRon affects Aβ clearance remain unclear.

EXPERIMENTAL APPROACH

We studied how AdipoRon affects autophagy in HT22 cells and APP/PS1 transgenic mice. We also investigated the signalling pathway involved and used pharmacological inhibitors to examine the role of autophagy in this process.

KEY RESULTS

AdipoRon promotes Aβ clearance by activating neuronal autophagy in the APP/PS1 transgenic mice. Interestingly, we found that AdipoRon induces the nuclear translocation of GAPDH, where it interacts with the SIRT1/DBC1 complex. This interaction then leads to the release of DBC1 and the activation of SIRT1, which in turn activates autophagy. Importantly, we found that inhibiting either GAPDH or SIRT1 to suppress the activity of SIRT1 counteracts the elevated autophagy and decreased Aβ deposition caused by AdipoRon. This suggests that SIRT1 plays a critical role in the effect of AdipoRon on autophagic induction in AD.

CONCLUSION AND IMPLICATIONS

AdipoRon promotes the clearance of Aβ by enhancing autophagy through the AdipoR1/AMPK-dependent nuclear translocation of GAPDH and subsequent activation of SIRT1. This novel molecular pathway sheds light on the modulation of autophagy in AD and may lead to the development of new therapeutic strategies targeting this pathway.

PRG ameliorates cognitive impairment in Alzheimer's disease mice by regulating β-amyloid and targeting the ERK pathway

BACKGROUND

PRG is derived from Phellinus ribis and is a homogeneous polysaccharide with well-defined structural information. PRG was found to have significant in vitro neurotrophic and neuroprotective activities. Thus, PRG might be a potential treatment for Alzheimer's disease. However, the related mechanisms of action are still unclear, so deeper in vivo experimental validation and the potential mechanisms need to be investigated.

PURPOSE

The effects of PRG on AD mice were investigated using Senescence-accelerated SAMP8 mice as an AD model to elucidate the crucial molecular mechanisms.

METHODS

PRG was obtained from Phellinus ribis by water-alcohol precipitation, column chromatography, and ultrafiltration. The Morris water maze and novel object recognition behavioral assays were used to evaluate the effects of PRG in AD mice. Nissl staining, the TUNEL apoptosis assay, and Golgi staining were used to assess brain neuronal cell damage, apoptosis, and neuronal status. Enzyme-linked immunosorbent assays, Western blotting, and immunofluorescence were used to explore the impacts of correlated factors and protein pathways under relevant mechanisms.

RESULTS

The findings suggest that PRG improved learning ability and spatial memory capacity in SAMP8 mice. PRG hastened the disintegration of β-amyloid, reduced the content and abnormal accumulation of the toxic Aβ1-42 protein, and decreased apoptosis. PRG activated the BDNF/ERK/CREB signaling pathway through a cascade, exerted neurotrophic effects, regulated cell proliferation and differentiation, increased neuronal dendritic branching and spine density, and improved synaptic plasticity.

CONCLUSION

PRG promoted β-amyloid degradation to reduce neuronal damage and apoptosis. It exerted neurotrophic effects by activating the BDNF/ERK/CREB pathway, promoting neuronal dendritic branching and dendritic spine growth, regulating cell proliferation and differentiation, and improving synaptic plasticity, which improved AD. Taken together, as a novel natural active polysaccharide with a well-defined structure, PRG affected AD symptoms in senescence-accelerated mice by interacting with multiple targets. The results indicate that PRG is a promising potential anti-AD drug candidate.

Dysregulation of CREB5 Impairs Decidualization and Maternal-Fetal Interactions by Inhibiting Autophagy in Recurrent Spontaneous Abortion

BACKGROUND

Clinically, recurrent spontaneous abortion (RSA) is a pregnancy illness that is difficult to treat. Impaired decidualization is a documented cause of RSA, but the etiology and mechanism are still unknown. cAMP-responsive element binding protein 5 (CREB5) is a member of the ATF/CREB family. CREB5 has been reported to be related to pathological pregnancy, but there are few related studies on this topic in patients with RSA, and the underlying mechanism is unclear.

METHODS

We collected decidual tissues from RSA patients and healthy pregnant women to measure the expression level of CREB5, PRL, IGFBP1, ATG5, LC3B, and SQSTM/p62. Then, the changes in CREB5 expression and autophagy levels were measured in human endometrial stromal cells (hESCs) during decidualization. The expression levels of PRL and IGFBP1 were tested in sh-CREB5/ov-CREB5 hESCs after decidualization induction, and the autophagy level in sh-CREB5/ov-CREB5 hESCs was measured without decidualization induction. The decidualization ability of sh-CREB5 and ov-CREB5 hESCs treated with an autophagy inducer or inhibitor was measured. To investigate the effect of CREB5 in hESCs on the invasion and migration of HTR8/SVneo cells, we performed a coculture experiment. Finally, we examined the expression of CREB5 and autophagy key proteins in mouse decidual tissues by constructing an abortion mouse model.

RESULTS

In our study, we found that the expression of CREB5 was unusually elevated in the uterine decidua of RSA patients, but the expression of PRL, IGFBP1, and autophagy were decreased. During the decidualization of hESCs, the expression of CREB5 gradually decreases in a time-dependent manner with increasing autophagy. Moreover, by knocking down or overexpressing CREB5 in hESCs, it was found that CREB5 can impair decidualization and reduce autophagy in hESCs. Furthermore, the damage caused by CREB5 in terms of decidualization can be reversed by the addition of an autophagy inducer (rapamycin). In addition, CREB5 can increase the secretion of proteins (IL-1β and TGF-β1) in hESCs to inhibit trophoblast invasion and migration.

CONCLUSIONS

Our data support the supposition that CREB5 disturbs the decidualization of endometrial stromal cells and interactions at the maternal-fetal interface by inhibiting autophagy and that its abnormal upregulation and dysfunction may lead to RSA. It may function as a diagnostic and therapeutic target for RSA. Similarly, we found that in the spontaneous abortion mouse model, the expression of CREB5 in the decidual tissue of the abortion group was significantly increased, and autophagy was decreased.

Targeting Microglia in Neuroinflammation: H3 Receptor Antagonists as a Novel Therapeutic Approach for Alzheimer's Disease, Parkinson's Disease, and Autism Spectrum Disorder

Histamine performs dual roles as an immune regulator and a neurotransmitter in the mammalian brain. The histaminergic system plays a vital role in the regulation of wakefulness, cognition, neuroinflammation, and neurogenesis that are substantially disrupted in various neurodegenerative and neurodevelopmental disorders. Histamine H3 receptor (H3R) antagonists and inverse agonists potentiate the endogenous release of brain histamine and have been shown to enhance cognitive abilities in animal models of several brain disorders. Microglial activation and subsequent neuroinflammation are implicated in impacting embryonic and adult neurogenesis, contributing to the development of Alzheimer's disease (AD), Parkinson's disease (PD), and autism spectrum disorder (ASD). Acknowledging the importance of microglia in both neuroinflammation and neurodevelopment, as well as their regulation by histamine, offers an intriguing therapeutic target for these disorders. The inhibition of brain H3Rs has been found to facilitate a shift from a proinflammatory M1 state to an anti-inflammatory M2 state, leading to a reduction in the activity of microglial cells. Also, pharmacological studies have demonstrated that H3R antagonists showed positive effects by reducing the proinflammatory biomarkers, suggesting their potential role in simultaneously modulating crucial brain neurotransmissions and signaling cascades such as the PI3K/AKT/GSK-3β pathway. In this review, we highlight the potential therapeutic role of the H3R antagonists in addressing the pathology and cognitive decline in brain disorders, e.g., AD, PD, and ASD, with an inflammatory component.

Mitophagy activation by rapamycin enhances mitochondrial function and cognition in 5×FAD mice

Alzheimer's disease (AD) is the most prevalent form of dementia, characterized by severe mitochondrial dysfunction, which is an intracellular process that is significantly compromised in the early stages of AD. Mitophagy, the selective removal of damaged mitochondria, is a potential therapeutic strategy for AD. Rapamycin, a mammalian target of rapamycin (mTOR) inhibitor, augmented autophagy and mitigated cognitive impairment. Our study revealed that rapamycin enhances cognitive function by activating mitophagy, alleviating neuronal loss, and improving mitochondrial dysfunction in 5 ×FAD mice. Interestingly, the neuroprotective effect of rapamycin in AD were negated by treatment with 3-MA, a mitophagy inhibitor. Overall, our findings suggest that rapamycin ameliorates cognitive impairment in 5 ×FAD mice via mitophagy activation and its downstream PINK1-Parkin pathway, which aids in the clearance of amyloid-β (Aβ) and damaged mitochondria. This study reveals a novel mechanism involving mitophagy regulation underlying the therapeutic effect of rapamycin in AD. This study provides new insights and therapeutic targets for rapamycin in the treatment of AD. However, there are still some shortcomings in this topic; if we can further knock out the PINK1/Parkin gene in animals or use siRNA technology, we can further confirm the experimental results.

Exploring the memory: existing activity-dependent tools to tag and manipulate engram cells

The theory of engrams, proposed several years ago, is highly crucial to understanding the progress of memory. Although it significantly contributes to identifying new treatments for cognitive disorders, it is limited by a lack of technology. Several scientists have attempted to validate this theory but failed. With the increasing availability of activity-dependent tools, several researchers have found traces of engram cells. Activity-dependent tools are based on the mechanisms underlying neuronal activity and use a combination of emerging molecular biological and genetic technology. Scientists have used these tools to tag and manipulate engram neurons and identified numerous internal connections between engram neurons and memory. In this review, we provide the background, principles, and selected examples of applications of existing activity-dependent tools. Using a combination of traditional definitions and concepts of engram cells, we discuss the applications and limitations of these tools and propose certain developmental directions to further explore the functions of engram cells.

Neuroprotective Effects of Ferrostatin and Necrostatin Against Entorhinal Amyloidopathy-Induced Electrophysiological Alterations Mediated by voltage-gated Ca2+ Channels in the Dentate Gyrus Granular Cells

Alzheimer's disease (AD) is a progressive neurodegenerative disease that is the main form of dementia. Abnormal deposition of amyloid-beta (Aβ) peptides in neurons and synapses cause neuronal loss and cognitive deficits. We have previously reported that ferroptosis and necroptosis were implicated in Aβ25-35 neurotoxicity, and their specific inhibitors had attenuating effects on cognitive impairment induced by Aβ25-35 neurotoxicity. Here, we aimed to examine the impact of ferroptosis and necroptosis inhibition following the Aβ25-35 neurotoxicity on the neuronal excitability of dentate gyrus (DG) and the possible involvement of voltage-gated Ca2+ channels in their effects. After inducing Aβ25-35 neurotoxicity, electrophysiological alterations in the intrinsic properties and excitability were recorded by the whole-cell patch-clamp under current-clamp condition. Voltage-clamp recordings were also performed to shed light on the involvement of calcium channel currents. Aβ25-35 neurotoxicity induced a considerable reduction in input resistance (Rin), accompanied by a profoundly decreased excitability and a reduction in the amplitude of voltage-gated calcium channel currents in the DG granule cells. However, three days of administration of either ferrostatin-1 (Fer-1), a ferroptosis inhibitor, or Necrostatin-1 (Nec-1), a necroptosis inhibitor, in the entorhinal cortex could almost preserve the normal excitability and the Ca2+ currents. In conclusion, these findings suggest that ferroptosis and necroptosis involvement in EC amyloidopathy could be a potential candidate to prevent the suppressive effect of Aβ on the Ca2+ channel current and neuronal function, which might take place in neurons during the development of AD.

Hesperidin ameliorates Amyloid-β toxicity and enhances oxidative stress resistance and lifespan of Caenorhabditis elegans through acr-16 mediated activation of the autophagy pathway

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease in aged populations. Aberrant amyloid-beta accumulation is a common pathological feature in AD patients. Dysfunction of autophagy and impairment of α7nAChR functioning are associated with enhanced amyloid-beta (Aβ) accumulation in AD patients. Hesperidin, a flavone glycoside found primarily in citrus species, is known to have anti-inflammatory, antioxidant, and neuroprotective effects. However, the underlying molecular mechanisms of hesperidin as an antiaging and anti-Aβ phytochemical were unclear. In this study, we found that hesperidin upregulates the acr-16 expression level in C. elegans as evidenced by increased GFP-tagged ACR-16 and GFP-tagged pmyo-3:ACR-16 expression in muscle and ventral nerve cord. Further, hesperidin upregulates the autophagy genes in wild-type N2, evident by increased GFP-tagged LGG-1 foci. However, hesperidin failed to upregulate the autophagy genes level in acr-16 mutant worms that suggests autophagy activation is mediated through acr-16. In addition, hesperidin showed antiaging and anti-oxidative effects, as evidenced by positive changes in different markers necessary for health span and lifespan. Additionally, hesperidin could upregulate acr-16 and autophagy genes (lgg-1 & bec-1) and ameliorates Aβ-induced toxicity as observed with reduce ROS accumulation, paralysis rate, and enhanced lifespan even in worms AD model CL4176 and CL2006 strain. Our finding suggests that hesperidin significantly enhances oxidative stress resistance, prolongs the lifespan, and protects against Aβ-induced toxicity in C. elegans. Thus, acr-16 mediated autophagy and antioxidation is associated with anti-aging and anti-Aβ effect of hesperidin.

Toll-interacting protein participates in immunity and development of the lepidopteran insect Antheraea pernyi

Toll-interacting protein (Tollip) participates in multiple biological processes. However, the biological functions of Tollip proteins in insects remain to be further explored. Here, the genomic sequence of tollip gene from Antheraea pernyi (named Ap-Tollip) was identified with a length of 15,060 bp, including eight exons and seven introns. The predicted Ap-Tollip protein contained conserved C2 and CUE domains and was highly homologous to those tollips from invertebrates. Ap-Tollip was highly expressed in fat body compared with other determined tissues. As far as the developmental stages were concerned, the highest expression level was found at the 14th day in eggs or the 3rd day of the 1st instar. Ap-Tollip was also obviously regulated by lipopolysaccharide, polycytidylic acid or 20E in different tissues. In addition, the interaction between Ap-Tollip and ubiquitin was confirmed by western blotting and pull-down assay. RNAi of Ap-Tollip significantly affected the expression levels of apoptosis and autophagy-related genes. These results indicated that Ap-Tollip was involved in immunity and development of A. pernyi.

Galangin mitigates glucocorticoid-induced osteoporosis by activating autophagy of BMSCs via triggering the PKA/CREB signaling pathway

Glucocorticoid-induced osteoporosis (GIOP), one of the most common and serious adverse effects associated with glucocorticoid administration, manifests as decreased bone formation and increased bone resorption, eventually culminating in bone loss. Galangin (GAL) is a flavonoid extracted from the medicinal herbal galangal that possesses a variety of pharmacological activities and can inhibit osteoclastogenesis. However, the effects of GAL on GIOP remain unclear. Our study aims to explore the effects of GAL on GIOP in mice and the underlying mechanism. Our results show that GAL markedly mitigates the severity of dexamethasone (Dex)-induced osteoporosis in mice and potentiates osteogenic differentiation in mouse bone marrow-derived mesenchymal stem cells (BMSCs). Furthermore, GAL also significantly counteracts Dex-mediated suppression of osteogenic differentiation and autophagy in human BMSCs. GAL augments PKA/CREB-mediated autophagic flux in BMSCs and the bones of osteoporotic mice. GAL-mediated osteogenic differentiation in Dex-treated BMSCs is significantly decreased by the PKA inhibitor H89 and autophagy inhibitor 3-methyladenine. Collectively, our data indicate that GAL can ameliorate GIOP, partly by augmenting the mineralization of BMSCs by potentiating PKA/CREB-mediated autophagic flux, highlighting its potential therapeutic use in treating glucocorticoid-related osteoporosis.

PR-957 Suppresses Th1 and Th17 Cell Differentiation via Inactivating PI3K/AKT Pathway in Alzheimer's Disease

PR-957 [low molecular mass polypeptide (LMP)-7 selective inhibitor] regulates T helper (Th) cell differentiation and inflammatory response in multiple neurological diseases. Hence, this study aimed to explore the effect of PR-957 on Th1/Th2/Th17 cell differentiation, therapeutic efficacy and its potential mechanisms in Alzheimer's disease (AD). The LMP7 expressions in peripheral blood mononuclear cells from 30 AD patients and 30 healthy controls (HC) were detected. PR-957 was added for the incubation of naive cluster of differentiation (CD)4⁺ T cells from AD patients, then SC79 [phosphorylated protein kinase B (pAKT) agonist] was added. LMP7, Th1 cells, and Th17 cells were upregulated, while Th2 cells were downregulated in AD patients compared to HC. Also, LMP7 was positively related to Th1 cells and Th17 cells, but it did not correlate with Th2 cells in AD patients. PR-957 treatment downregulated Th1 cells, Th17 cells, and their secreted cytokines as well as phosphorylated phosphoinositide 3-kinase (pPI3K)/PI3K and pAKT/AKT expressions in AD CD4⁺ T cells. SC79 addition upregulated pAKT/AKT expression, Th1 cells, and Th17 cells, while downregulated Th2 cells; also SC79 could alleviate the effect of PR-957 on regulating PI3K/AKT pathway and Th1, Th2, and Th17 cell differentiation in AD CD4⁺ T cells. Furthermore, PR-957 attenuated cognitive impairment and neurofibrillary tangle; also it inhibited Th17 cell differentiation and PI3K/AKT pathway in the brain and spleen of AD mice. In conclusion, PR-957 suppresses Th1 and Th17 cell differentiation, attenuates neural injury and improves cognitive function via inactivating PI3K/AKT pathway in AD.

Neuroprotective effect of astragalin via activating PI3K/Akt-mTOR-mediated autophagy on APP/PS1 mice

As a small molecule flavonoid, astragalin (AST) has anti-inflammatory, anti-cancer, and anti-oxidation effects. However, the impact and molecular mechanism of AST in Alzheimer's disease (AD) are still not clear. This study aims to investigate the neuroprotective effect and mechanism of AST on APP/PS1 mice and Aβ25-35-injured HT22 cells. In this study, we found that AST ameliorated cognitive dysfunction, reduced hippocampal neuronal damage and loss, and Aβ pathology in APP/PS1 mice. Subsequently, AST activated autophagy and up-regulated the levels of autophagic flux-related protein in APP/PS1 mice and Aβ25-35-induced injury in HT22 cells. Interestingly, AST down-regulated the phosphorylation level of PI3K/Akt-mTOR pathway-related proteins, which was reversed by autophagy inhibitors 3-Methyladenine (3-MA) or Bafilomycin A1 (Baf A1). At the same time, consistent with the impacts of Akt inhibitor MK2206 and mTOR inhibitor rapamycin, inhibited levels of autophagy in Aβ25-35-injured HT22 cells were activated by the administration of AST. Taken together, these results suggested that AST played key neuroprotective roles on AD via stimulating PI3K/Akt-mTOR pathway-mediated autophagy and autophagic flux. This study revealed a new mechanism of autophagy regulation behind the neuroprotection impact of AST for AD treatment.

Jatrophane Diterpenoids from Euphorbia peplus Linn. as Activators of Autophagy and Inhibitors of Tau Pathology

Ten jatrophane diterpenoids were isolated from the whole plant Euphorbia peplus Linn. including seven new ones, named euphjatrophanes A-G (labeled compounds 1, 2, 4-8). Their structures were elucidated with a combination of spectroscopic and single-crystal X-ray crystallography, enabling the identification of compounds 3, 9, and 10 as the previously published euphpepluones G, K, and L, respectively. All compounds were evaluated for their bioactivity with flow cytometry in assays of autophagic flux in HM Cherry-GFP-LC3 (human microglia cells stably expressing the tandem monomeric mCherry-GFP-tagged LC3) cells. Euphpepluone K (9) significantly activated autophagic flux, an effect that was verified with confocal analysis. Moreover, cellular assays showed that euphpepluone K (9) induced autophagy and inhibited Tau pathology.

Neuroprotective effect of histamine H3 receptor blockade on methamphetamine-induced cognitive impairment in mice

OBJECTIVE

Methamphetamine (METH) exposure is commonly believed to result in cognitive impairment. Histamine H3 receptor (H3R) antagonists reportedly have potential applications for treating cognitive impairment accompanied by various neuropsychiatric disorders. The present study aimed to investigate the effect of H3R blockade by Thioperamide (THIO) on METH-induced cognitive impairment and the underlying mechanism.

METHODS

In Experiment 1, C57BL/6 mice received daily injections of saline or 5 mg/kg METH for 5 consecutive days. The Novel Object Recognition (NOR) and Morris water maze (MWM) tasks were used to assess cognitive functions of mice. H3R protein expression and apoptosis were subsequently measured in the hippocampus. In Experiment 2, HT22 cells were first treated with ddH₂O or 3 mM METH. The cell survival rate and H3R protein level were subsequently assessed. In Experiment 3, the animals were first treated with saline or 20 mg/kg THIO for 7 days, followed by co-administration of either saline or 5 mg/kg METH for an additional 5 days. The remaining experiments were carried out in the same manner as Experiment 1. In Experiment 4, HT22 cells were pretreated with either ddH₂O or 5 mM THIO for 2 h, followed by ddH₂O or 3 mM METH treatment for an additional 12 h. The remaining experiments were carried out in the same manner as Experiment 2. In Experiment 5, the changes in MEK1/2, p-MEK1/2, ERK1/2 and p-ERK1/2 protein levels were examined in the hippocampus of all mice from Experiment 3 and HT22 cells from Experiment 4.

RESULTS

METH-treated mice showed significantly worsened NOR and MWM performance, along with markably hippocampal apoptosis. A significantly lower cell survival rate was observed in METH-treated HT22 cells. Increased levels of H3R protein were found in both METH-treated mice and HT22 cells. THIO significantly improved METH-induced cognitive impairment in mice and toxicity in HT22 cells. METH significantly increased the level of p-MEK1/2 and p-ERK1/2 proteins in the hippocampus of mice and HT22 cells, which was reversed by THIO pretreatment.

CONCLUSION

Our findings reveal that H3R blockade by THIO yields a neuroprotective effect against METH-induced cognitive impairment in mice and toxicity in HT22 cells via the raf-MEK-ERK signaling pathway.

The Role of ERK1/2 Pathway in the Pathophysiology of Alzheimer's Disease: An Overview and Update on New Developments

Alzheimer's disease (AD) is the most common neurodegenerative disorder worldwide. Several findings suggest that correcting the dysregulated signaling pathways may offer a potential therapeutic approach in this disease. Extracellular signal-regulated kinase 1/2 (ERK1/2), a member of the mitogen-activated protein kinase family, plays a major role in regulation of cell proliferation, autophagy process, and protein synthesis. The available literature suggests dysregulated ERK1/2 in AD patients with potential implications in the multifaceted underlying pathologies of AD, including amyloid-β plaque formation, tau phosphorylation, and neuroinflammation. In this regard, in the current review, we aim to summarize the reports on the potential roles of ERK1/2 in AD pathophysiology.

Anti-inflammatory effects of new human histamine H3 receptor ligands with flavonoid structure on BV-2 neuroinflammation

OBJECTIVE

Microglia play an important role in the neuroinflammation developed in response to various pathologies. In this study, we examined the anti-inflammatory effect of the new human histamine H₃ receptor (H₃R) ligands with flavonoid structure in murine microglial BV-2 cells.

MATERIAL AND METHODS

The affinity of flavonoids (E243 -flavone and IIIa-IIIc-chalcones) for human H₃R was evaluated in the radioligand binding assay. The cytotoxicity on BV-2 cell viability was investigated with the MTS assay. Preliminary evaluation of anti-inflammatory properties was screened by the Griess assay in an in vitro neuroinflammation model of LPS-treated BV-2 cells. The expression and secretion of pro-inflammatory cytokines were evaluated by real-time qPCR and ELISA, respectively. The expression of microglial cell markers were determined by immunocytochemistry.

RESULTS

Chalcone derivatives showed high affinity at human H₃R with K_i values < 25 nM. At the highest nontoxic concentration (6.25 μM) compound IIIc was the most active in reducing the level of nitrite in Griess assay. Additionally, IIIc treatment attenuated inflammatory process in murine microglia cells by down-regulating pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) at both the level of mRNA and protein level. Our immunocytochemistry studies revealed expression of microglial markers (Iba1, CD68, CD206) in BV-2 cell line.

CONCLUSIONS

These results emphasize the importance of further research to accurately identify the anti-inflammatory mechanism of action of chalcones.

Drug repurposing: Clemastine fumarate and neurodegeneration

Neurodegenerative diseases have been a weighty problem in elder people who might be stricken with motor or/and cognition defects with lower life quality urging for effective treatment. Drugs are costly from development to market, so that drug repurposing, exploration of existing drugs for novel therapeutic purposes, becomes a wise and popular strategy to raise new treatment options. Clemastine fumarate, different from anti-allergic effect as H1 histamine antagonist, was screened and identified as promising drug for remyelination and autophagy enhancement. Surprisingly, fumarate salt also has similar effect. Hence, whether clemastine fumarate would make a protective impact on neurodegenerative diseases and what contribution fumarate probably makes are intriguing to us. In this review, we summarize the potential mechanism surrounding clemastine fumarate in current literature, and try to distinguish independent or synergistic effect between clemastine and fumarate, aiming to find worthwhile research direction for neurodegeneration diseases.

Molecular mechanisms of Alzheimer's disease: From therapeutic targets to promising drugs

Alzheimer's disease (AD) is a neurodegenerative disease characterized by cognitive impairment so widespread that it interferes with a person's ability to complete daily activities. AD is becoming increasingly common, and it is estimated that the number of patients will reach 152 million by 2050. Current treatment options for AD are symptomatic and have modest benefits. Therefore, considering the human, social, and economic burden of the disease, the development of drugs with the potential to alter disease progression has become a global priority. In this review, the molecular mechanisms involved in the pathology of AD were evaluated as therapeutic targets. The main aim of the review is to focus on new knowledge about mitochondrial dysfunction, oxidative stress, and neuronal transmission in AD, as well as a range of cellular signaling mechanisms and associated treatments. Important molecular interactions leading to AD were described in amyloid cascade and in tau protein function, oxidative stress, mitochondrial dysfunction, cholinergic and glutamatergic neurotransmission, cAMP-regulatory element-binding protein (CREB), the silent mating type information regulation 2 homolog 1 (SIRT-1), neuroinflammation (glial cells), and synaptic alterations. This review summarizes recent experimental and clinical research in AD pathology and analyzes the potential of therapeutic applications based on molecular disease mechanisms.

Myelin repair in Alzheimer's disease: a review of biological pathways and potential therapeutics

This literature review investigates the significant overlap between myelin-repair signaling pathways and pathways known to contribute to hallmark pathologies of Alzheimer's disease (AD). We discuss previously investigated therapeutic targets of amyloid, tau, and ApoE, as well as other potential therapeutic targets that have been empirically shown to contribute to both remyelination and progression of AD. Current evidence shows that there are multiple AD-relevant pathways which overlap significantly with remyelination and myelin repair through the encouragement of oligodendrocyte proliferation, maturation, and myelin production. There is a present need for a single, cohesive model of myelin homeostasis in AD. While determining a causative pathway is beyond the scope of this review, it may be possible to investigate the pathological overlap of myelin repair and AD through therapeutic approaches.

TFEB in Alzheimer's disease: From molecular mechanisms to therapeutic implications

Alzheimer's disease (AD), an age-dependent neurodegenerative disorder, is the most prevalent neurodegenerative disease worldwide. The primary pathological hallmarks of AD are the deposition of β-amyloid plaques and neurofibrillary tangles. Autophagy, a pathway of clearing damaged organelles, macromolecular aggregates, and long-lived proteins via lysosomal degradation, has emerged as critical for proteostasis in the central nervous system (CNS). Studies have demonstrated that defective autophagy is strongly implicated in AD pathogenesis. Transcription factor EB (TFEB), a master transcriptional regulator of autophagy, enhances the expression of related genes that control autophagosome formation, lysosome function, and autophagic flux. The study of TFEB has greatly increased over the last decade, and the dysfunction of TFEB has been reported to be strongly associated with the pathogenesis of many neurodegenerative disorders, including AD. Here, we delineate the basic understanding of TFEB dysregulation involved in AD pathogenesis, highlighting the existing work that has been conducted on TFEB-mediated autophagy in neurons and other nonneuronal cells in the CNS. Additionally, we summarize the small molecule compounds that target TFEB-regulated autophagy involved in AD therapy. Our review may yield new insights into therapeutic approaches by targeting TFEB and provide a broadly applicable basis for the clinical treatment of AD.

Pharmacological modulation of autophagy for Alzheimer’s disease therapy: Opportunities and obstacles

Alzheimer's disease (AD) is a prevalent and deleterious neurodegenerative disorder characterized by an irreversible and progressive impairment of cognitive abilities as well as the formation of amyloid β (Aβ) plaques and neurofibrillary tangles (NFTs) in the brain. By far, the precise mechanisms of AD are not fully understood and no interventions are available to effectively slow down progression of the disease. Autophagy is a conserved degradation pathway that is crucial to maintain cellular homeostasis by targeting damaged organelles, pathogens, and disease-prone protein aggregates to lysosome for degradation. Emerging evidence suggests dysfunctional autophagy clearance pathway as a potential cellular mechanism underlying the pathogenesis of AD in affected neurons. Here we summarize the current evidence for autophagy dysfunction in the pathophysiology of AD and discuss the role of autophagy in the regulation of AD-related protein degradation and neuroinflammation in neurons and glial cells. Finally, we review the autophagy modulators reported in the treatment of AD models and discuss the obstacles and opportunities for potential clinical application of the novel autophagy activators for AD therapy.

mTOR-mediated autophagy in the hippocampus is involved in perioperative neurocognitive disorders in diabetic rats

Introduction

Perioperative neurocognitive disorders (PND) are common neurological complications after surgery. Diabetes mellitus (DM) has been reported to be an independent risk factor for PND, but little is known about its mechanism of action. Mammalian target of rapamycin (mTOR) signaling is crucial for neuronal growth, development, apoptosis, and autophagy, but the dysregulation of mTOR signaling leads to neurological disorders. The present study investigated whether rapamycin can attenuate PND by inhibiting mTOR and activating autophagy in diabetic rats.

Methods

Male diabetic Sprague‐Dawley rats underwent tibial fracture surgery under isoflurane anesthesia to establish a PND model. Cognitive functions were examined using the Morris water maze test. The levels of phosphorylated mTOR (p‐mTOR), phosphorylated tau (p‐tau), autophagy‐related proteins (Beclin‐1, LC3), and apoptosis‐related proteins (Bax, Bcl‐2, cleaved caspase‐3) in the hippocampus were examined on postoperative days 3, 7, and 14 by Western blot. Hippocampal amyloid β (Aβ) levels were examined by immunohistochemistry.

Results

The data showed that surgical trauma and/or DM impaired cognitive function, induced mTOR activation, and decreased Beclin‐1 levels and the LC3‐II/I ratio. The levels of Aβ and p‐tau and the hippocampal apoptotic responses were significantly higher in diabetic or surgery‐treated rats than in control rats and were further increased in diabetic rats subjected to surgery. Pretreatment of rats with rapamycin inhibited mTOR hyperactivation and restored autophagic function, effectively decreasing tau hyperphosphorylation, Aβ deposition, and apoptosis in the hippocampus. Furthermore, surgical trauma‐induced neurocognitive disorders were also reversed by pretreatment of diabetic rats with rapamycin.

Conclusion

The results demonstrate that mTOR hyperactivation regulates autophagy, playing a critical role in the mechanism underlying PND, and reveal that the modulation of mTOR signaling could be a promising therapeutic strategy for PND in patients with diabetes.

The pleiotropic roles of autophagy in Alzheimer's disease: From pathophysiology to therapy

Autophagy is a lysosomal degradation pathway and the main clearance route of many toxic protein aggregates. The molecular pathology of Alzheimer's disease (AD) manifests in the form of protein aggregates-extracellular amyloid-β depositions and intracellular tau neurofibrillary tangles. Perturbations at different steps of the autophagy pathway observed in cellular and animal models of AD might contribute to amyloid-β and tau accumulation. Increased levels of autophagosomes detected in patients' brains suggest an alteration of autophagy in human disease. Autophagy is also involved in the fine-tuning of inflammation, which increases in the early stages of AD and possibly drives its pathogenesis. Mounting evidence of a causal link between impaired autophagy and AD pathology uncovers an exciting opportunity for the development of autophagy-based therapeutics.

Inhibition of Astrocytic Histamine N-Methyltransferase as a Possible Target for the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) represents the principal cause of dementia among the elderly. Great efforts have been established to understand the physiopathology of AD. Changes in neurotransmitter systems in patients with AD, including cholinergic, GABAergic, serotoninergic, noradrenergic, and histaminergic changes have been reported. Interestingly, changes in the histaminergic system have been related to cognitive impairment in AD patients. The principal pathological changes in the brains of AD patients, related to the histaminergic system, are neurofibrillary degeneration of the tuberomammillary nucleus, the main source of histamine in the brain, low histamine levels, and altered signaling of its receptors. The increase of histamine levels can be achieved by inhibiting its degrading enzyme, histamine N-methyltransferase (HNMT), a cytoplasmatic enzyme located in astrocytes. Thus, increasing histamine levels could be employed in AD patients as co-therapy due to their effects on cognitive functions, neuroplasticity, neuronal survival, neurogenesis, and the degradation of amyloid beta (Aβ) peptides. In this sense, the evaluation of the impact of HNMT inhibitors on animal models of AD would be interesting, consequently highlighting its relevance.

Thioperamide attenuates neuroinflammation and cognitive impairments in Alzheimer's disease via inhibiting gliosis

Alzheimer's disease (AD) is an age-related neurodegenerative disease, which characterized by deposition of amyloid-β (Aβ) plaques, neurofibrillary tangles, neuronal loss, and accompanied by neuroinflammation. Neuroinflammatory processes are well acknowledged to contribute to the progression of AD pathology. Histamine H3 receptor (H3R) is a presynaptic autoreceptor regulating histamine release via negative feedback way. Recently, studies show that H3R are highly expressed not only in neurons but also in microglia and astrocytes. H3R antagonist has been reported to have anti-inflammatory efficacy. However, whether inhibition of H3R is responsible for the anti-neuroinflammation in glial cells and neuroprotection on APPswe, PSEN1dE9 (APP/PS1 Tg) mice remain unclear. In this study, we found that inhibition of H3R by thioperamide reduced the gliosis and induced a phenotypical switch from A1 to A2 in astrocytes, and ultimately attenuated neuroinflammation in APP/PS1 Tg mice. Additionally, thioperamide rescued the decrease of cyclic AMP response element-binding protein (CREB) phosphorylation and suppressed the phosphorylated P65 nuclear factor kappa B (p-P65 NF-κB) in APP/PS1 Tg mice. H89, an inhibitor of CREB signaling, abolished these effects of thioperamide to suppress gliosis and proinflammatory cytokine release. Lastly, thioperamide alleviated the deposition of amyloid-β (Aβ) and cognitive dysfunction in APP/PS1 mice, which were both reversed by administration of H89. Taken together, these results suggested the H3R antagonist thioperamide improved cognitive impairment in APP/PS1 Tg mice via modulation of the CREB-mediated gliosis and inflammation inhibiting, which contributed to Aβ clearance. This study uncovered a novel mechanism involving inflammatory regulating behind the therapeutic effect of thioperamide in AD.

FOXO and related transcription factors binding elements in the regulation of neurodegenerative disorders

Neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, and others, are characterized by progressive loss of neuronal cells, which causes memory impairment and cognitive decline. Mounting evidence demonstrated the possible implications of diverse biological processes, namely oxidative stress, mitochondrial dysfunction, aberrant cell cycle re-entry, post-translational modifications, protein aggregation, impaired proteasome dysfunction, autophagy, and many others that cause neuronal cell death. The condition worsens as there is no effective treatment for such diseases due to their complex pathogenesis and mechanism. Mounting evidence demonstrated the role of regulatory transcription factors, such as NFκβ, FoxO, Myc, CREB, and others that regulate the biological processes and diminish the disease progression and pathogenesis. Studies demonstrated that forkhead box O (FoxO) transcription factors had been implicated in the regulation of aging and longevity. Further, the functions of FoxO proteins are regulated by different post-translational modifications (PTMs), namely acetylation, and ubiquitination. Various studies concluded that FoxO proteins exert both neuroprotective and neurotoxic properties depending on their regulation mechanism and activity in the brain. Thus, understanding the nature of FoxO expression and activity in the brain will help develop effective therapeutic strategies. Herein, firstly, we discuss the role of FoxO protein in cell cycle regulation and cell proliferation, followed by the regulation of FoxO proteins through acetylation and ubiquitination. We also briefly explain the activity and expression pattern of FoxO proteins in the neuronal cells and explain the mechanism through which FoxO proteins are rescued from oxidative stress-induced neurotoxicity. Later on, we present a detailed view of the implication of FoxO proteins in neurodegenerative disease and FoxO proteins as an effective therapeutic target.