DL0410 ameliorates cognitive disorder in SAMP8 mice by promoting mitochondrial dynamics and the NMDAR-CREB-BDNF pathway

Qiangji decoction mitigates neuronal damage, synaptic and mitochondrial dysfunction in SAMP8 mice through the regulation of ROCK2/Drp1-mediated mitochondrial dynamics

ETHNOPHARMACOLOGICAL RELEVANCE

Qiangji Decoction (QJD), a Chinese medicine, is widely used in Traditional Chinese Medicine to treat amnesia and Alzheimer's disease (AD), showing significant anti-AD effects. However, the precise mechanisms behind these effects are not well understood and require more research.

AIM OF THE STUDY

This study aims to elucidate the mechanisms by which QJD ameliorates neuronal damage, synaptic dysfunction, and mitochondrial impairment in AD through the regulation of ROCK2/Drp1-mediated mitochondrial dynamics.

MATERIALS AND METHODS

UPLC-Q-TOF-MS/MS was used to identify active components in QJD extract. The study used SAMP8 mice for AD modeling and SAMR1 mice as controls. Cognitive function in SAMP8 mice was assessed with the Morris Water Maze after following treatment with QJD and the mitochondrial fission inhibitor Mdivi-1. Nissl and FJB staining evaluated QJD's effect on hippocampal injury. Synaptic integrity was examined with Golgi-Cox staining, transmission electron microscopy, and immunofluorescence. Mitochondrial function in hippocampal neurons was assessed using electron microscopy, JC-1 staining, and reagent kits. Western blot analyzed expression of proteins related to mitochondrial fission (ROCK2, Drp1, Fis1, Mff) and fusion (Mfn1, Mfn2, OPA1).

RESULTS

The analysis of QJD extract via UPLC-Q-TOF-MS/MS led to the identification of 46 active compounds. In SAMP8 mice, administration of QJD resulted in decreased escape latency, increased platform crossings, and extended duration in the target quadrant. Additionally, QJD exhibited neuroprotective effects on the hippocampus of SAMP8 mice, effectively preventing neuronal loss and damage. QJD also facilitated the extension and thickening of dendritic spines, enhanced the ultrastructure of hippocampal synapses, and upregulated synaptic function-related proteins, including PSD95 and SYN1. Furthermore, QJD ameliorated mitochondrial damage, improved mitochondrial membrane potential and ATP content, and reduced ROS expression in hippocampal neurons of SAMP8 mice. These effects were mediated through the downregulation of ROCK2, phosphorylated Drp1 (Ser616), Fis1, and Mff, as well as the upregulation of Mfn1, Mfn2, and OPA1.

CONCLUSIONS

QJD may reduce neuronal damage, synaptic dysfunction, and mitochondrial impairment in SAMP8 mice by regulating mitochondrial dynamics through the ROCK2/Drp1 pathway.

Uncovering the intricacies of O-GlcNAc modification in cognitive impairment: New insights from regulation to therapeutic targeting

O-linked β-N-acetylglucosamine (O-GlcNAc) represents a post-translational modification that occurs on serine or threonine residues on various proteins. This conserved modification interacts with vital cellular pathways. Although O-GlcNAc is widely distributed throughout the body, it is particularly enriched in the brain, where most proteins are O-GlcNAcylated. Recent studies have established a causal link between O-GlcNAc regulation in the brain and alterations in neurophysiological function. Alterations in O-GlcNAc levels in the brain are associated with the pathogenesis of several neurogenic diseases that can lead to cognitive impairment. Remarkably, manipulation of O-GlcNAc levels demonstrated a protective effect on cognitive function. Although the precise molecular mechanism of O-GlcNAc modification in the nervous system remains elusive, its regulation is fundamental to multiple neural and cognitive functions, fluctuating levels during normal and pathological cognitive processes. In this review, we highlight the significant functional importance of O-GlcNAc modification in pathological cognitive impairments and the potential application of O-GlcNAc as a promising target for the intervention or amelioration of cognitive impairments.

Mitochondrial Dysfunction in Neurodegenerative Diseases: Mechanisms and Corresponding Therapeutic Strategies

Neurodegenerative disease (ND) refers to the progressive loss and morphological abnormalities of neurons in the central nervous system (CNS) or peripheral nervous system (PNS). Examples of neurodegenerative diseases include Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS). Recent studies have shown that mitochondria play a broad role in cell signaling, immune response, and metabolic regulation. For example, mitochondrial dysfunction is closely associated with the onset and progression of a variety of diseases, including ND, cardiovascular diseases, diabetes, and cancer. The dysfunction of energy metabolism, imbalance of mitochondrial dynamics, or abnormal mitophagy can lead to the imbalance of mitochondrial homeostasis, which can induce pathological reactions such as oxidative stress, apoptosis, and inflammation, damage the nervous system, and participate in the occurrence and development of degenerative nervous system diseases such as AD, PD, and ALS. In this paper, the latest research progress of this subject is detailed. The mechanisms of oxidative stress, mitochondrial homeostasis, and mitophagy-mediated ND are reviewed from the perspectives of β-amyloid (Aβ) accumulation, dopamine neuron damage, and superoxide dismutase 1 (SOD1) mutation. Based on the mechanism research, new ideas and methods for the treatment and prevention of ND are proposed.

The Mitochondrial Blueprint: Unlocking Secondary Metabolite Production

Mitochondrial metabolism plays a pivotal role in regulating the synthesis of secondary metabolites, which are crucial for the survival and adaptation of organisms. These metabolites are synthesized during specific growth stages or in response to environmental stress, reflecting the organism's ability to adapt to changing conditions. Mitochondria, while primarily known for their role in energy production, directly regulate secondary metabolite biosynthesis by providing essential precursor molecules, energy, and reducing equivalents necessary for metabolic reactions. Furthermore, they indirectly influence secondary metabolism through intricate signaling pathways, including reactive oxygen species (ROS), metabolites, and redox signaling, which modulate various metabolic processes. This review explores recent advances in understanding the molecular mechanisms governing mitochondrial metabolism and their regulatory roles in secondary metabolite biosynthesis, which highlights the involvement of transcription factors, small RNAs, and post-translational mitochondrial modifications in shaping these processes. By integrating current insights, it aims to inspire future research into mitochondrial regulatory mechanisms in Arabidopsis thaliana, Solanum tuberosum, Nicotiana tabacum, and others that may enhance their secondary metabolite production. A deeper understanding of the roles of mitochondria in secondary metabolism could contribute to the development of new approaches in biotechnology applications.

GPx1-ERK1/2-CREB pathway regulates the distinct vulnerability of hippocampal neurons to oxidative stress via modulating mitochondrial dynamics following status epilepticus

Glutathione peroxidase-1 (GPx1) and cAMP/Ca2+ responsive element (CRE)-binding protein (CREB) regulate neuronal viability by maintaining the redox homeostasis. Since GPx1 and CREB reciprocally regulate each other, it is likely that GPx1-CREB interaction may play a neuroprotective role against oxidative stress, which are largely unknown. Thus, we investigated the underlying mechanisms of the reciprocal regulation between GPx1 and CREB in the male rat hippocampus. Under physiological condition, L-buthionine sulfoximine (BSO)-induced oxidative stress increased GPx1 expression, extracellular signal-regulated kinase 1/2 (ERK1/2) activity and CREB serine (S) 133 phosphorylation in CA1 neurons, but not dentate granule cells (DGC), which were diminished by GPx1 siRNA, U0126 or CREB knockdown. GPx1 knockdown inhibited ERK1/2 and CREB activations induced by BSO. CREB knockdown also decreased the efficacy of BSO on ERK1/2 activation. BSO facilitated dynamin-related protein 1 (DRP1)-mediated mitochondrial fission in CA1 neurons, which abrogated by GPx1 knockdown and U0126. CREB knockdown blunted BSO-induced DRP1 upregulation without affecting DRP1 S616 phosphorylation ratio. Following status epilepticus (SE), GPx1 expression was reduced in CA1 neurons and DGC. SE also decreased CREB activity CA1 neurons, but not DGC. SE degenerated CA1 neurons, but not DGC, accompanied by mitochondrial elongation. These post-SE events were ameliorated by N-acetylcysteine (NAC, an antioxidant), but deteriorated by GPx1 knockdown. These findings indicate that a transient GPx1-ERK1/2-CREB activation may be a defense mechanism to protect hippocampal neurons against oxidative stress via maintenance of proper mitochondrial dynamics.

Mitochondrial Dynamics in Brain Cells During Normal and Pathological Aging

Mitochondrial dynamics significantly play a major role in the pathogenesis of neurodegenerative diseases, such as Parkinson's disease and Alzheimer's disease. The dysregulation of mitochondrial biogenesis and function, characterized by impaired fission and fusion processes mediated by a number of proteins, in particular, Drp1, Mfn1, Mfn2, Opa1, and PGC-1α, contributes to neuronal vulnerability and degeneration. Insufficient mitophagy and disrupted mitochondrial transport exacerbate oxidative stress and neurotoxicity. Emerging therapeutic strategies that target mitochondrial dynamics, including various pharmacological agents, demonstrate potential for restoring mitochondrial balance and enhancing neuroprotection. This growing body of research underscores the importance of mitochondrial health in developing effective interventions for neurodegenerative conditions. This review highlights well-established links between the disruption of mitochondrial dynamics and the development of neurodegenerative processes. We also discuss different therapeutic strategies that target mitochondrial function in neurons that have been proposed as perspective neuroprotective treatments.

Single-nucleus RNA sequencing-based construction of a hippocampal neuron atlas in mice with epileptic cognitive impairment

The hippocampus plays a critical role in learning and memory, and mice with epileptic cognitive impairment exhibit hippocampal atrophy. However, there is still a lack of research on the hippocampal cell atlas related to these disorders. Here, we utilized snRNA-seq to characterize the transcriptomic changes in hippocampal neurons of drug-resistant epilepsy (DRE) cognitive-impaired mice. The intercellular heterogeneity of 20 subpopulations of neurons was analyzed, focusing on aspects such as cell communication, gene expressions, GO and KEGG enrichment analysis, and module gene set analysis. Based on the degree of relevance to synaptic biological functions, the subpopulations associated with cognitive impairment (ExN1, 3, 8 and InN1, 6) were preliminarily identified. We also identified some key biomarkers in DRE cognitive-impaired mice, such as Ptprz1 and Calb1. Finally, we integrate and validate our dataset using identified well-annotated marker genes in the hippocampal region, further supporting the functional annotation of neuronal subpopulations.

Contrasting Effects of an Atherogenic Diet and High-Protein/Unsaturated Fatty Acids Diet on the Accelerated Aging Mouse Model SAMP8 Phenotype

Background/Objectives: Aging has been extensively studied, with a growing interest in memory impairment by a neurobiological approach. Mitochondrial dysfunction is a hallmark of aging, contributing to the aging phenotype; therefore, mitochondrial interventions seem fundamental. The diet is a physiological approximation for modifying mitochondria, which could impact the age-related phenotype. Methods: We studied two diets with low-carbohydrate and high-fat compositions, differing in the amount of protein and the fat type disposable-the atherogenic diet Cocoa (high protein/high saturated fat/high cholesterol) and the South Beach diet (very high-protein/high-unsaturated fat)-on oxidative stress, mitochondrial state, and hippocampus-dependent memory in 3-month-old Senescence-Accelerated Mouse Model (SAMP8) seed over 3 months to determine their pro- or anti-aging effects. Results: Despite its bad reputation, the Cocoa diet reduces the reactive oxygen species (ROS) content without impacting the energy state and hippocampus-dependent spatial acuity. In contrast to the beneficial impact proposed for the South Beach diet, it induced a pro-aging phenotype, increasing oxidative damage and the levels of NR2B subunit of the NMDA, impairing energy and spatial acuity. Surprisingly, despite the negative changes observed with both diets, this led to subtle memory impairment, suggesting the activation of compensatory mechanisms preventing more severe cognitive decline. Conclusions: Our results demonstrated that diets usually considered good could be detrimental to the onset of aging. Also, probably due to the brain plasticity of non-aged animals, they compensate for the damage, preventing a more aggravated phenotype. Nevertheless, these silent changes could predispose or increase the risk of suffering pathologies at advanced age.

Regulatory Role of NF-κB on HDAC2 and Tau Hyperphosphorylation in Diabetic Encephalopathy and the Therapeutic Potential of Luteolin

Diabetic encephalopathy (DE) is a severe complication of the central nervous system associated with diabetes. In this study, we investigated the regulatory role of mammalian target of rapamycin (mTOR) on nuclear factor κB (NF-κB) in mice with DE, and the neuroprotective effect and therapeutic mechanisms of luteolin, a natural flavonoid compound with anti-inflammatory, antioxidant, and neuroprotective properties. The results indicated that treatment with luteolin improved the degree of cognitive impairment in mice with DE. It also decreased the levels of phosphorylated mTOR, phosphorylated NF-κB, and histone deacetylase 2 (HDAC2) and increased the expression of brain-derived neurotrophic factor and synaptic-related proteins. Furthermore, protein-protein interaction and the Gene Ontology analysis revealed that luteolin was involved in the regulatory network of HDAC2 expression through the mTOR/NF-κB signaling cascade. Our bioinformatics and molecular docking results indicated that luteolin may also directly target HDAC2, as an HDAC2 inhibitor, to alleviate DE, complementing mTOR/NF-κB signaling inhibition. Analysis of luteolin's target proteins and their interactions suggest an effect on HDAC2 and cognition. In conclusion, HDAC2 and tau hyperphosphorylation are regulated by the mTOR/NF-κB signaling cascade in DE, and luteolin is found to reverse these effects, demonstrating its protective role in DE.

ARTICLE HIGHLIGHTS

SIRT6 prevent chronic cerebral hypoperfusion induced cognitive impairment by remodeling mitochondrial dynamics in a STAT5-PGAM5-Drp1 dependent manner

Vascular dementia (VaD) is a prevalent form of dementia resulting from chronic cerebral hypoperfusion (CCH). However, the pathogenic mechanisms of VaD and corresponding therapeutic strategies are not well understood. Sirtuin 6 (SIRT6) has been implicated in various biological processes, including cellular metabolism, DNA repair, redox homeostasis, and aging. Nevertheless, its functional relevance in VaD remains unexplored. In this study, we utilized a bilateral common carotid artery stenosis (BCAS) mouse model of VaD to investigate the role of SIRT6. We detected a significant decrease in neuronal SIRT6 protein expression following CCH. Intriguingly, neuron-specific ablation of Sirt6 in mice exacerbated neuronal damage and cognitive deficits after CCH. Conversely, treatment with MDL-800, an agonist of SIRT6, effectively mitigated neuronal loss and facilitated neurological recovery. Mechanistically, SIRT6 inhibited excessive mitochondrial fission by suppressing the CCH-induced STAT5-PGAM5-Drp1 signaling cascade. Additionally, the gene expression of monocyte SIRT6 in patients with asymptomatic carotid stenosis showed a correlation with cognitive outcomes, suggesting translational implications in human subjects. Our findings provide the first evidence that SIRT6 prevents cognitive impairment induced by CCH, and mechanistically, this protection is achieved through the remodeling of mitochondrial dynamics in a STAT5-PGAM5-Drp1-dependent manner.

Combination of RNA-seq and proteomics reveals the mechanism of DL0410 treatment in APP/PS1 transgenic mouse model of Alzheimer's disease

There is a lack of a systematic understanding of the specific mechanism of action of DL0410 in AD treatment. In this study, the combination of RNA-seq and proteomics was firstly employed to uncover the mechanism of action of DL0410 in APP/PS1 transgenic mice. The results of behavioral tests showed that oral administration of DL0410 for 8 weeks improved memory and cognition of APP/PS1 mice. DL0410 significantly reduced β-amyloid deposition and resulted in significant upregulation of synaptophysin, PSD95 and NMDAR/ CaMKⅡ signaling pathway in the hippocampus and cortex, indicating that DL0410 improved synaptic plasticity in APP/PS1 mice, which agrees with the results of RNA-seq and proteomics. Furthermore, the enrichment results of differentially expressed genes identified by RNA-seq and proteomics demonstrate the potential protective effects of DL0410 against oxidative stress and mitochondrial dysfunction. As expected, DL0410 dose-dependently ameliorated oxidative damage and markedly increased the expression of PGC-1α, TFAM, SOD1 and SOD2. Mitochondrial high-resolution respirometry results revealed that mitochondrial respiratory function was significantly improved in APP/PS1 mice administered with DL0410. In addition, DL0410 treatment reduced oxidative damage, strengthened antioxidant system and improved mitochondrial function in Aβ-induced HT22 cells. Altogether, our findings suggest the potential of DL0410 as a novel candidate for AD treatment.

More than a number: Incorporating the aged phenotype to improve in vitro and in vivo modeling of neurodegenerative disease

Age is the number one risk factor for developing a neurodegenerative disease (ND), such as Alzheimer's disease (AD) or Parkinson's disease (PD). With our rapidly ageing world population, there will be an increased burden of ND and need for disease-modifying treatments. Currently, however, translation of research from bench to bedside in NDs is poor. This may be due, at least in part, to the failure to account for the potential effect of ageing in preclinical modelling of NDs. While ageing can impact upon physiological response in multiple ways, only a limited number of preclinical studies of ND have incorporated ageing as a factor of interest. Here, we evaluate the aged phenotype and highlight the critical, but unmet, need to incorporate aspects of this phenotype into both the in vitro and in vivo models used in ND research. Given technological advances in the field over the past several years, we discuss how these could be harnessed to create novel models of ND that more readily incorporate aspects of the aged phenotype. This includes a recently described in vitro panel of ageing markers, which could help lead to more standardised models and improve reproducibility across studies. Importantly, we cannot assume that young cells or animals yield the same responses as seen in the context of ageing; thus, an improved understanding of the biology of ageing, and how to appropriately incorporate this into the modelling of ND, will ensure the best chance for successful translation of new therapies to the aged patient.

METTL3 confers protection against mitochondrial dysfunction and cognitive impairment in an Alzheimer disease mouse model by upregulating Mfn2 via N6-methyladenosine modification

Mitofusin 2 (MFN2) has been found to be downregulated in patients with Alzheimer disease (AD) but little is known about its roles in the pathogenesis of AD. We explored the mechanism of N6-methyladenosine (m6A) methylation of Mfn2 in hippocampal mitochondrial dysfunction in an AD mouse model. APP/PS1 transgenic mice underwent stereotaxic injection of adeno-associated viruses and their behaviors were assessed. METTL3 and MFN2 expressions were measured by qRT-PCR and Western blot, accompanied by assessment of mitochondrial morphology, ATP, mitochondrial membrane potential, and amyloid-β content. Binding between METTL3 and MFN2, the total amount of m6A, and the m6A modification of Mfn2 were also determined. METTL3 and MFN2 were downregulated in hippocampal tissues of the AD model mice; METTL3 enhanced MFN2 expression via m6A modification. Overexpression of METTL3 or MFN2 ameliorated mitochondrial dysfunction indicated by fewer damaged mitochondria, increased ATP and JC-1 levels, and reduced Aβ content; improved cognitive impairment in the mice was indicated by the novel object discrimination index and Morris water maze tests. Effects of METTL3 overexpression were abrogated by further knockdown of MFN2. Thus, METTL3 ameliorated mitochondrial dysfunction and cognitive impairment in the AD model mice by increasing MFN2 expression via m6A modification.

CREB: A Promising Therapeutic Target for Treating Psychiatric Disorders

Psychiatric disorders are complex, multifactorial illnesses. It is challenging for us to understand the underlying mechanism of psychiatric disorders. In recent years, the morbidity of psychiatric disorders has increased yearly, causing huge economic losses to the society. Although some progress, such as psychotherapy drugs and electroconvulsive therapy, has been made in the treatment of psychiatric disorders, including depression, anxiety, bipolar disorder, obsessive-compulsive and autism spectrum disorders, antidepressants and psychotropic drugs have the characteristics of negative effects and high rate of relapse. Therefore, researchers continue to seek suitable interventions. cAMP response element binding protein (CREB) belongs to a protein family and is widely distributed in the majority of brain cells that function as a transcription factor. It has been demonstrated that CREB plays an important role in neurogenesis, synaptic plasticity, and neuronal growth. This review provides a 10-year update of the 2013 systematic review on the multidimensional roles of CREB-mediated transcriptional signaling in psychiatric disorders. We also summarize the classification of psychiatric disorders and elucidate the involvement of CREB and related downstream signalling pathways in psychiatric disorders. Importantly, we analyse the CREB-related signal pathways involving antidepressants and antipsychotics to relieve the pathological process of psychiatric disorders. This review emphasizes that CREB signalling may have a vast potential to treat psychiatric disorders like depression. Furthermore, it would be helpful for the development of potential medicine to make up for the imperfection of current antidepressants and antipsychotics.

Mitochondrial protein prohibitin promotes learning memory recovery in mice following intracerebral hemorrhage via CAMKII/CRMP signaling pathway

Prohibitin (PHB) is a mitochondrial inner membrane protein with neuroprotective, antioxidant, and apoptosis-reducing effects. This study aimed to explore the role of PHB in pathological symptoms, behavioral deficits, and cognitive impairment in a collagenase-IV-induced intracerebral hemorrhage (ICH) murine model. In this study, mice that received collagenase IV injection were pretreated with PHB or saline 21 days prior to modeling. The role of PHB in memory and learning ability was monitored using the Morris water maze, Y-maze, and rotarod, social, startle, and nest-building tests. The effect of PHB on depression-like symptoms was examined using the forced swimming, tail suspension, and sucrose preference tests. Subsequently, mouse samples were analyzed using immunohistochemistry, western blotting, Perls staining, Nissl staining, and gene sequencing. Results showed that collagenase IV significantly induced behavioral deficits, brain edema, cognitive impairment, and depressive symptoms. PHB overexpression effectively alleviated memory, learning, and motor deficits in mice with ICH. PHB markedly inhibited the number of terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling-positive cells and protein levels of ionized calcium-binding adapter molecule 1, glial fibrillary acidic protein, and interleukin-1β in the perihematomal region of ICH mice. PHB overexpression also remarkably promoted production of neurologin1 (NLGL1), and upregulated levels of Ca2+-calmodulin-dependent kinase II (CaMKII) and collapsin response mediator protein-1 (CRMP1) proteins. In conclusion, PHB overexpression can effectively alleviate the neurological deficits and neurodegeneration around the hematoma region. This may play a protective role by upregulating the expression of NLGL1 and promoting expression of CaMKII and CRMP1.

Fermented soybean foods (natto) ameliorate age-related cognitive decline by hippocampal TAAR1-mediated activation of the CaMKII/CREB/BDNF signaling pathway in senescence-accelerated mouse prone 8 (SAMP8)

Natto is a traditional fermented soybean-based food that has been an integral part of Japanese cuisine for several centuries. Although there have been extensive studies on the cognitive benefits of soybeans, only limited studies have examined the effects of natto on cognitive function. This study investigated the potential cognitive benefits of natto in senescence-accelerated mouse-prone 8 (SAMP8) mice. After 12 weeks of oral administering natto fermented for 18 h, the spatial learning and memory performance were improved compared with those in SAMP8 control mice. Furthermore, activation of the brain-derived neurotrophic factor (BDNF)/tropomyosin receptor kinase B (TrkB)/cAMP response element-binding protein (CREB) signaling and N-methyl-D-aspartate receptor (NMDAR)-calcium/calmodulin-dependent protein kinase II (CaMKII) cascade was observed in the hippocampus of SAMP8 mice that were fed natto. Additionally, natto administration upregulated trace amine-associated receptor 1 (TAAR1) as a modulator of NMDAR. These findings suggest that natto ameliorates cognitive decline by activating the TAAR1-mediated CaMKII/CREB/BDNF signaling pathway in the hippocampus of SAMP8 mice.

1,5-anhydro-D-fructose induces anti-aging effects on aging-associated brain diseases by increasing 5'-adenosine monophosphate-activated protein kinase activity via the peroxisome proliferator-activated receptor-γ co-activator-1α/brain-derived neurotrophic factor pathway

5'-Adenosine monophosphate-activated protein kinase (AMPK) is a metabolic sensor that serves as a cellular housekeeper; it also controls energy homeostasis and stress resistance. Thus, correct regulation of this factor can enhance health and survival. AMPK signaling may have a critical role in aging-associated brain diseases. Some in vitro studies have shown that 1,5-anhydro-D-fructose (1,5-AF) induces AMPK activation. In the present study, we experimentally evaluated the effects of 1,5-AF on aging-associated brain diseases in vivo using an animal model of acute ischemic stroke (AIS), stroke-prone spontaneously hypertensive rats (SHRSPs), and the spontaneous senescence-accelerated mouse-prone 8 (SAMP8) model. In the AIS model, intraperitoneal injection of 1,5-AF reduced cerebral infarct volume, neurological deficits, and mortality. In SHRSPs, oral administration of 1,5-AF reduced blood pressure and prolonged survival. In the SAMP8 model, oral administration of 1,5-AF alleviated aging-related decline in motor cognitive function. Although aging reduced the expression levels of peroxisome proliferator-activated receptor-γ co-activator-1α (PGC-1α) and brain-derived neurotrophic factor (BDNF), we found that 1,5-AF activated AMPK, which led to upregulation of the PGC-1α/BDNF pathway. Our results suggest that 1,5-AF can induce endogenous neurovascular protection, potentially preventing aging-associated brain diseases. Clinical studies are needed to determine whether 1,5-AF can prevent aging-associated brain diseases.

Hyaluronic Acid Conjugated with 17β-Estradiol Effectively Alleviates Estropause-Induced Cognitive Deficits in Rats

Women are at a higher risk of cognitive impairments and Alzheimer's disease (AD), particularly after the menopause, when the estrous cycle becomes irregular and diminishes. Numerous studies have shown that estrogen deficiency, especially estradiol (E2) deficiency, plays a key role in this phenomenon. Recently, a novel polymeric drug, hyaluronic acid-17β-estradiol conjugate (HA-E2), has been introduced for the delivery of E2 to brain tissues. Studies have indicated that HA-E2 crosses the blood-brain barrier (BBB) and facilitates a prolonged E2 release profile while lowering the risk of estrogen-supplement-related side effects. In this study, we used ovariohysterectomy (OHE) rats, a postmenopausal cognitive deficit model, to explore the effect of a 2-week HA-E2 treatment (210 ng/kg body weight, twice a week) on the cholinergic septo-hippocampal innervation system, synaptic transmission in hippocampal pyramidal neurons and cognitive improvements. Our study revealed an 11% rise in choline acetyltransferase (ChAT) expression in both the medial septal nucleus (MS nucleus) and the hippocampus, along with a 14-18% increase in dendritic spine density in hippocampal pyramidal neurons, following HA-E2 treatment in OHE rats. These enhancements prompted the recovery of cognitive functions such as spatial learning and memory. These findings suggest that HA-E2 may prevent and improve estrogen-deficiency-induced cognitive impairment and AD.

Isoflurane-induced reduction in neurogenesis derived from the tertiary dentate matrix

Anesthetics-induced disruption of dentate neurogenesis in the young brain is strongly suggested to contribute to delayed neurocognitive deficit. In postnatal rodents, the neurogenesis of the dentate gyrus (DG) is sequentially derived from the secondary dentate matrix, tertiary dentate matrix and subgranular zone (SGZ). However, the effects of anesthetics on the dentate neurogenesis derived from specific sites are poorly understood. To trace the new cells generated from the postnatal secondary dentate matrix, peak stage of the tertiary dentate matrix and early stage of the SGZ after isoflurane exposure, mice at postnatal day 1 (P1), P7 and P31 were injected with BrdU at 12 h before the exposure. We found that isoflurane exposure significantly reduced the numbers of proliferating cells (1 day old), immature granule cells (21 days old) or mature granule cells (42 days old) derived from the peak stage of the tertiary dentate matrix and postnatal secondary dentate matrix, but not from the SGZ. Quantitative assessment of BrdU-/BrdU+NeuN-positive cells and cleaved caspase-3 level in the DG indicated that the reduction was correlated with cell loss rather than neuronal differentiation. Mechanistically, we demonstrated that the PI3K/Akt/GSK-3β pathway enriched by mRNA-sequencing is a requirement for the isoflurane-induced loss of 1-day-old proliferating cells generated from the tertiary dentate matrix. In addition, this study demonstrated that P1 and P7 mice, but not P31 mice exposure to isoflurane resulted in subsequent deficits in performance of the tasks of the Morris Water Maze.

Novel Phenylethanoid Glycosides Improve Hippocampal Synaptic Plasticity via the Cyclic Adenosine Monophosphate-CREB-Brain-Derived Neurotrophic Growth Factor Pathway in APP/PS1 Transgenic Mice

INTRODUCTION

Alzheimer's disease (AD) is a major public health concern worldwide, but there are still no drugs available that treat it effectively. Previous studies have shown that phenylethanoid glycosides have pharmacological effects, which include anti-AD properties, but the underlying mechanisms by which they ameliorate AD symptoms remain unknown.

METHODS

In this study, we used an APP/PS1 AD mouse model to explore the function and mechanisms underlying savatiside A (SA) and torenoside B (TB) in the treatment of AD. SA or TB (100 mg·kg-1·d-1) was orally administered to 7-month-old APP/PS1 mice for 4 weeks. Cognitive and memory functions were measured using behavioral experiments (including the Morris water maze test and the Y-maze spontaneous alternation test). Molecular biology experiments (including Western blotting, immunofluorescence, and enzyme-linked immunosorbent assays) were used to detect any corresponding changes in signaling pathways.

RESULTS

The results showed that SA or TB treatment could significantly reduce cognitive impairment in APP/PS1 mice. We also showed that chronic treatment with SA/TB could prevent spine loss, synaptophysin immunoreactivity, and neuronal loss in mice, thereby improving synaptic plasticity and moderating learning and memory deficits. SA/TB administration also promoted the expression of synaptic proteins in APP/PS1 mouse brains and upregulated phosphorylation of proteins in the cyclic adenosine monophosphate (cAMP)/CREB/brain-derived neurotrophic growth factor (BDNF) pathway that are responsible for synaptic plasticity. Additionally, chronic SA/TB treatment increased the levels of BDNF and nerve growth factor (NGF) in the brains of APP/PS1 mice. Both astrocyte and microglia volumes, as well as the generation of amyloid β, were also decreased in SA/TB-treated APP/PS1 mice compared to control APP/PS1 mice.

CONCLUSION

In summary, SA/TB treatment was associated with activation of the cAMP/CREB/BDNF pathway and increased BDNF and NGF expression, indicating that SA/TB improves cognitive functioning via nerve regeneration. SA/TB is a promising candidate drug for the treatment of AD.

Effect of gastrodin against cognitive impairment and neurodegeneration in APP/PS1 mice via regulating gut microbiota-gut-brain axis

Gastrodin (Gas) has exhibited protective activity in neurological disorders. Here, we investigated the neuroprotective effect and potential mechanisms of Gas against cognitive impairment via regulating gut microbiota. APPswe/PSEN1dE9 transgenic (APP/PS1) mice were treated intragastrically with Gas for 4 weeks, and then cognitive deficits, deposits of amyloid-β (Aβ) and phosphorylation of tau were analyzed. The expression levels of insulin-like growth factor-1 (IGF-1) pathway-related proteins, such as cAMP response element-binding protein (CREB), were detected. Meanwhile, gut microbiota composition was evaluated. Our results showed that Gas treatment significantly improved cognitive deficits and Aβ deposition in APP/PS1 mice. Moreover, Gas treatment increased the level of Bcl-2 and decreased level of Bax and ultimately inhibited neuronal apoptosis. Gas treatment markedly increased the expression levels of IGF-1 and CREB in APP/PS1 mice. Moreover, Gas treatment improved abnormal composition and structure of gut microbiota in APP/PS1 mice. These findings revealed that Gas actively participated in regulating the IGF-1 pathway to inhibit neuronal apoptosis via the gut-brain axis and that it can be considered a new therapeutic strategy against Alzheimer's disease.

Mitochondrial Bioenergetics, Redox Balance, and Calcium Homeostasis Dysfunction with Defective Ultrastructure and Quality Control in the Hippocampus of Aged Female C57BL/6J Mice

Aging is a physiological process that generates progressive decline in many cellular functions. There are many theories of aging, and one of great importance in recent years is the mitochondrial theory of aging, in which mitochondrial dysfunction that occurs at advanced age could be responsible for the aged phenotype. In this context, there is diverse information about mitochondrial dysfunction in aging, in different models and different organs. Specifically, in the brain, different studies have shown mitochondrial dysfunction mainly in the cortex; however, until now, no study has shown all the defects in hippocampal mitochondria in aged female C57BL/6J mice. We performed a complete analysis of mitochondrial function in 3-month-old and 20-month-old (mo) female C57BL/6J mice, specifically in the hippocampus of these animals. We observed an impairment in bioenergetic function, indicated by a decrease in mitochondrial membrane potential, O2 consumption, and mitochondrial ATP production. Additionally, there was an increase in ROS production in the aged hippocampus, leading to the activation of antioxidant signaling, specifically the Nrf2 pathway. It was also observed that aged animals had deregulation of calcium homeostasis, with more sensitive mitochondria to calcium overload and deregulation of proteins related to mitochondrial dynamics and quality control processes. Finally, we observed a decrease in mitochondrial biogenesis with a decrease in mitochondrial mass and deregulation of mitophagy. These results show that during the aging process, damaged mitochondria accumulate, which could contribute to or be responsible for the aging phenotype and age-related disabilities.

Carnosic Acid Attenuates AβOs-Induced Apoptosis and Synaptic Impairment via Regulating NMDAR2B and Its Downstream Cascades in SH-SY5Y Cells

Neuronal death and synaptic loss are principal pathological features of Alzheimer's disease (AD). Amyloid beta oligomers (AβOs) constitute the main neurotoxin underscoring AD pathology. AβOs interact with N-methyl-D-aspartate receptors (NMDARs), resulting in neurotoxic events, including activation of apoptosis and synaptic impairment. Carnosic acid (CA), extracted from Salvia rosmarinus, has been verified its neuroprotective effects in AD. However, the precise mechanisms by which CA induces synaptic protection remain unclear. In this study, we established an in vitro AD model using SH-SY5Y human neuroblastoma cells. We observed that CA improved neuronal survival by suppressing apoptosis. Moreover, CA restored synaptic impairments by increasing expression levels of brain-derived neurotrophic factor (BDNF), postsynaptic density protein-95 (PSD-95), and synaptophysin (Syn). Furthermore, we found these protective effects were dependent on inhibiting the phosphorylation of NMDAR subtype 2B (NMDAR2B), which further suppressed calcium overload and promoted activation of the extracellular signal-regulated kinase (ERK)-cAMP response element-binding protein (CREB) pathway. Administration of N-methyl-D-aspartic acid (NMDA), an agonist of NMDARs, abolished these effects of CA. Our findings demonstrate that CA exerts neuroprotective effects in an in vitro model of AD by regulating NMDAR2B and its downstream cascades, highlighting the therapeutic potential of CA as a NMDARs-targeted candidate in the treatment of AD.

Acupuncture Interventions for Alzheimer’s Disease and Vascular Cognitive Disorders: A Review of Mechanisms

Cognitive impairment (CI) related to Alzheimer's disease (AD) and vascular cognitive disorders (VCDs) has become a key problem worldwide. Importantly, CI is a neuropsychiatric abnormality mainly characterized by learning and memory impairments. The hippocampus is an important brain region controlling learning and memory. Recent studies have highlighted the effects of acupuncture on memory deficits in AD and VCDs. By reviewing the literature published on this topic in the past five years, the present study intends to summarize the effects of acupuncture on memory impairment in AD and VCDs. Focusing on hippocampal synaptic plasticity, we reviewed the mechanisms underlying the effects of acupuncture on memory impairments through regulation of synaptic proteins, AD characteristic proteins, intestinal microbiota, neuroinflammation, microRNA expression, orexin system, energy metabolism, etc., suggesting that hippocampal synaptic plasticity may be the common as well as the core link underlying the above mechanisms. We also discussed the potential strategies to improve the effect of acupuncture. Additionally, the effects of acupuncture on synaptic plasticity through the regulation of vascular–glia–neuron unit were further discussed.

Patchouli alcohol as a selective estrogen receptor β agonist ameliorates AD-like pathology of APP/PS1 model mice

Clinical evidence shows that postmenpausal women are almost twice as likely to develop Alzheimer's disease (AD) as men of the same age, and estrogen is closely related to the occurrence of AD. Estrogen receptor (ER) α is mainly expressed in the mammary gland and other reproductive organs like uterus while ERβ is largely distributed in the hippocampus and cardiovascular system, suggesting that ERβ selective agonist is a valuable drug against neurodegenerative diseases with low tendency in inducing cancers of breast and other reproductive organs. In this study we identified a natural product patchouli alcohol (PTA) as a selective ERβ agonist which improved the cognitive defects in female APP/PS1 mice, and explore the underlying mechanisms. Six-month-old female APP/PS1 mice were administered PTA (20, 40 mg · kg-1 · d-1, i.g.) for 90 days. We first demonstrated that PTA bound to ERβ with a dissociation constant (KD) of 288.9 ± 35.14 nM in microscale thermophoresis. Then we showed that PTA administration dose-dependently ameliorated cognitive defects evaluated in Morris water maze and Y-maze testes. Furthermore, PTA administration reduced amyloid plaque deposition in the hippocampus by promoting microglial phagocytosis; PTA administration improved synaptic integrity through enhancing BDNF/TrkB/CREB signaling, ameliorated oxidative stress by Catalase level, and regulated Bcl-2 family proteins in the hippocampus. The therapeutic effects of PTA were also observed in vitro: PTA (5, 10, 20 μM) dose-dependently increased phagocytosis of o-FAM-Aβ42 in primary microglia and BV2 cells through enhancing ERβ/TLR4 signaling; PTA treatment ameliorated o-Aβ25-35-induced reduction of synapse-related proteins VAMP2 and PSD95 in primary neurons through enhancing ERβ/BDNF/TrkB/CREB pathways; PTA treatment alleviated o-Aβ25-35-induced oxidative stress in primary neurons through targeting ERβ and increasing Catalase expression. Together, this study has addressed the efficacy of selective ERβ agonist in the amelioration of AD and highlighted the potential of PTA as a drug lead compound against the disease.

Combined exposure of lead and high-fat diet enhanced cognitive decline via interacting with CREB-BDNF signaling in male rats

The health risks to populations induced by lead (Pb) and high-fat diets (HFD) have become a global public health problem. Pb and HFD often co-exist and are co-occurring risk factors for cognitive impairment. This study investigates effect of combined Pb and HFD on cognitive function, and explores the underlying mechanisms in terms of regulatory components of synaptic plasticity and insulin signaling pathway. We showed that the co-exposure of Pb and HFD further increased blood Pb levels, caused body weight loss and dyslipidemia. The results from Morris water maze (MWM) test and Nissl staining disclosed that Pb and HFD each contributed to cognitive deficits and neuronal damage and combined exposure enhanced this toxic injury. Pb and HFD decreased the levels of synapsin-1, GAP-43 and PSD-95 protein related to synaptic properties and SIRT1, NMDARs, phosphorylated CREB and BDNF related to synaptic plasticity regulatory, and these decreases was greater when combined exposure. Additionally, we revealed that Pb and HFD promoted IRS-1 phosphorylation and subsequently reduced downstream PI3K-Akt kinases phosphorylation in hippocampus and cortex of rats, and this process was aggravated when co-exposure. Collectively, our data suggested that combined exposure of Pb and HFD enhanced cognitive deficits, pointing to additive effects in rats than the individual stress effects related to multiple signaling pathways with CREB-BDNF signaling as the hub. This study emphasizes the need to evaluate the effects of mixed exposures on brain function in realistic environment and to better inform prevention of neurological disorders via modulating central pathway, such as CREB/BDNF signaling.

Electroacupuncture Enhances Neuroplasticity by Regulating the Orexin A-Mediated cAMP/PKA/CREB Signaling Pathway in Senescence-Accelerated Mouse Prone 8 (SAMP8) Mice

Learning and memory disorders and decreased neuroplasticity are the main clinical manifestations of age-induced cognitive dysfunction. Orexin A (OxA) has been reported to show abnormally elevated expression in the cerebrospinal fluid (CSF) of patients with Alzheimer's disease (AD) and to be associated with cognitive impairment. Here, we further assessed whether the excitatory neurotransmitter OxA is involved in neuroplasticity and cognitive function in senescence-accelerated mouse prone 8 (SAMP8) mice. In this study, we investigated the mechanism of OxA by using behavioral tests, CSF microdialysis, immunofluorescence, toluidine blue staining, gene silencing, transmission electron microscopy, and Western blotting. The results showed that 10 Hz electroacupuncture (EA) effectively alleviated learning and memory impairment in 7-month-old SAMP8 mice, reduced OxA levels in the CSF, increased the level of the neurotransmitter glutamate, alleviated pathological damage to hippocampal tissue, improved the synaptic structure, enhanced synaptic transmission, and regulated the expression of cAMP/PKA/CREB signaling pathway-related proteins. These results suggest that EA enhances neuroplasticity in SAMP8 mice by regulating the OxA-mediated cAMP/PKA/CREB signaling pathway, thus improving cognitive function. These findings suggest that EA may be beneficial for the prevention and treatment of age-induced cognitive impairment.

Roles of N-Methyl-D-Aspartate Receptors (NMDARs) in Epilepsy

Epilepsy is one of the most common neurological disorders characterized by recurrent seizures. The mechanism of epilepsy remains unclear and previous studies suggest that N-methyl-D-aspartate receptors (NMDARs) play an important role in abnormal discharges, nerve conduction, neuron injury and inflammation, thereby they may participate in epileptogenesis. NMDARs belong to a family of ionotropic glutamate receptors that play essential roles in excitatory neurotransmission and synaptic plasticity in the mammalian CNS. Despite numerous studies focusing on the role of NMDAR in epilepsy, the relationship appeared to be elusive. In this article, we reviewed the regulation of NMDAR and possible mechanisms of NMDAR in epilepsy and in respect of onset, development, and treatment, trying to provide more evidence for future studies.

Ganoderic acid improves 5-fluorouracil-induced cognitive dysfunction in mice

5-Fluorouracil (5-FU) is a chemotherapeutic drug with a good anti-cancer effect on various types of cancers, such as colorectal cancer and breast cancer. However, previous studies have found that 5-FU could induce cognitive deficit in clinics. As ganoderic acid, isolated from Ganoderma lucidum, has a protective effect on neurons, this study investigated the effects of ganoderic acid (GA) against 5-FU-induced cognitive dysfunction with a series of behavioral tests and related indicators. Experimental results showed that GA significantly prevented the reduction of spatial and non-spatial memory in 5-FU-treated mice. In addition, GA not only ameliorated the damage to hippocampal neurons and mitochondrial structure, but also significantly improved abnormal protein expression of mitochondrial biogenesis related marker PGC-1α, and mitochondrial dynamics related markers MFN2, DRP1 and FIS1 in the hippocampi of 5-FU-treated mice. Moreover, GA could up-regulate the expression of neuronal survival and growth-related proteins, such as BDNF, p-ERK, p-CREB, p-Akt, p-GSK3β, Nrf2, p-mTOR, and p-S6, in the hippocampi of 5-FU-treated mice. These results suggest that GA could prevent cognitive dysfunction in mice treated with 5-FU via preventing mitochondrial impairment and enhancing neuronal survival and growth, which provide evidence for GA as a promising adjunctive therapy for chemotherapy related cognitive impairment in clinics.

Effects of Naodesheng tablets on amyloid beta-induced dysfunction: A traditional Chinese herbal formula with novel therapeutic potential in Alzheimer's disease revealed by systems pharmacology

Naodesheng (NDS) tablets have been widely used to treat ischemic stroke clinically. NDS relieves neurological function impairment and improve learning and memory in rats with focal cerebral ischemia, suggesting that NDS has potential for Alzheimer's disease (AD) treatment. However, there are no studies about its effective material basis and possible mechanisms. In this study, a systems pharmacology method was applied to reveal the potential molecular mechanism of NDS in the treatment of AD. First, we obtained 360 NDS candidate constituents through ADMET filter analysis. Then, 115 AD-related targets were uncovered by pharmacophore model prediction via mapping the predicted targets against AD-related proteins. In addition, compound-target and target-function networks were established to suggest potential synergistic effects among the candidate constituents. Furthermore, potential targets regulated by NDS were integrated into AD-related pathways to demonstrate the therapeutic mechanism of NDS in AD treatment. Subsequently, a validation experiment proved the therapeutic effect of NDS on cognitive dysfunction in rats with intracerebroventricular injection of Aβ. We found that administration of NDS tablets regulates β-amyloid metabolism, improves synaptic plasticity, inhibits neuroinflammation and improves learning and memory function. In conclusion, this is the first study to provide a comprehensive systems pharmacology approach to elucidate the potential therapeutic mechanism of NDS tablets for AD treatment. We suggest that the protective effects of NDS in neurodegenerative conditions could be partly attributed to its role in improving synaptic plasticity and inhibiting neuroinflammation via NF-κB signaling pathway inhibition and cAMP/PKA/CREB signaling pathway activation.

Isoflurane post-conditioning attenuates cerebral ischemia/reperfusion injury by reducing apoptotic through activating the BMP7/SMAD signaling pathway in rats

The expressions of different temporal patterns of bone morphogenetic proteins (BMPs) have changed after ischemic strokes, and ischemic preconditioning-induced neuroprotection was attenuated when BMP7 was inhibited. In the previous study, the neuroprotection of isoflurane postconditioning (ISPOC) against cerebral ischemia-reperfusion (I/R) injury has been addressed, with particular relevance to the role of BMP7. Consequently, in the present study, we continued to explore the mechanisms involved in the BMP7 signal mediated the neuroprotection of ISPOC. A rat model of the middle cerebral artery occlusion was used in this study. Rats were administered 1.5 % isoflurane, 60 min after 90 min of ischemia, followed by a 24 h reperfusion period. The 1.5 % ISPOC significantly ameliorated the cerebral infarct volumes, neurologic deficit scores, damaged neurons, and apoptotic neurons. Moreover, ISPOC unregulated the expressions of BMP7, p-Smad1/5/9, and p-p38. Whereas, the neuroprotective effect was weakened by LDN-193189 and SB203580, respectively, a BMP7/Smad1/5/9 and p38MAPK signaling pathway inhibitor. Furthermore, LDN-193189 downregulated the expression of p-p38. The present results of this study indicated that the neuroprotection of 1.5 % isoflurane postconditioning to cerebral ischemia-reperfusion injury is related to the activating of BMP7/Smad1/5/9 and p38MAPK signal pathway.