Reduced pCREB in Alzheimer's disease prefrontal cortex is reflected in peripheral blood mononuclear cells

Repetitive transcranial magnetic stimulation in Alzheimer's disease: effects on neural and synaptic rehabilitation

Alzheimer's disease is a neurodegenerative disease resulting from deficits in synaptic transmission and homeostasis. The Alzheimer's disease brain tends to be hyperexcitable and hypersynchronized, thereby causing neurodegeneration and ultimately disrupting the operational abilities in daily life, leaving patients incapacitated. Repetitive transcranial magnetic stimulation is a cost-effective, neuro-modulatory technique used for multiple neurological conditions. Over the past two decades, it has been widely used to predict cognitive decline; identify pathophysiological markers; promote neuroplasticity; and assess brain excitability, plasticity, and connectivity. It has also been applied to patients with dementia, because it can yield facilitatory effects on cognition and promote brain recovery after a neurological insult. However, its therapeutic effectiveness at the molecular and synaptic levels has not been elucidated because of a limited number of studies. This study aimed to characterize the neurobiological changes following repetitive transcranial magnetic stimulation treatment, evaluate its effects on synaptic plasticity, and identify the associated mechanisms. This review essentially focuses on changes in the pathology, amyloidogenesis, and clearance pathways, given that amyloid deposition is a major hypothesis in the pathogenesis of Alzheimer's disease. Apoptotic mechanisms associated with repetitive transcranial magnetic stimulation procedures and different pathways mediating gene transcription, which are closely related to the neural regeneration process, are also highlighted. Finally, we discuss the outcomes of animal studies in which neuroplasticity is modulated and assessed at the structural and functional levels by using repetitive transcranial magnetic stimulation, with the aim to highlight future directions for better clinical translations.

High-intensity training on CREB activation for improving brain health: a narrative review of possible molecular talks

Although physical exercise has obvious benefits in brain physiology, the molecular biomarkers induced by exercise protocols are inconclusive. Evidence indicates that exercise interventions are effective in shaping brain physiology. However, the potential mediator for improving brain functions is uncertain. CREB is one of the potential targets of exercise that triggers various molecular cross-talk to improve neurogenesis, long-term potentiation, and synaptogenesis. Therefore, CREB may be situated on the causal path between maintaining brain health and exercising. To support this, studies have shown that exercise-mediated CREB phosphorylation improves cognitive functions and memory. In addition, among the protocols of exercise (types, duration, and frequency), the intensity has been reported to be the most effective in triggering CREB-mediated molecular signaling. For example, HIT increases the synthesis of CREB, which may not only induce brain physiology but also induce brain pathology by higher activation of its downstream targets, such as BDNF. Therefore, this review aims to understand the effects of HIT on CREB function and how HIT can mediate the CREB-induced molecular cross-talk for maintaining brain health.

Linking activation of synaptic NMDA receptors-induced CREB signaling to brief exposure of cortical neurons to oligomeric amyloid-beta peptide

Amyloid-beta peptide oligomers (AβO) have been considered "primum movens" for a cascade of events that ultimately cause selective neuronal death in Alzheimer's disease (AD). However, initial events triggered by AβO have not been clearly defined. Synaptic (Syn) N-methyl-d-aspartate receptors (NMDAR) are known to activate cAMP response element-binding protein (CREB), a transcriptional factor involved in gene expression related to cell survival, memory formation and synaptic plasticity, whereas activation of extrasynaptic (ESyn) NMDARs was linked to excitotoxic events. In AD brain, CREB phosphorylation/activation was shown to be altered, along with dyshomeostasis of intracellular Ca2+ (Ca2+ i). Thus, in this work, we analyze acute/early and long-term AβO-mediated changes in CREB activation involving Syn or ESyn NMDARs in mature rat cortical neurons. Our findings show that acute AβO exposure produce early increase in phosphorylated CREB, reflecting CREB activity, in a process occurring through Syn NMDAR-mediated Ca2+ influx. Data also demonstrate that AβO long-term (24 h) exposure compromises synaptic function related to Ca2+-dependent CREB phosphorylation/activation and nuclear CREB levels and related target genes, namely Bdnf, Gadd45γ, and Btg2. Data suggest a dual effect of AβO following early or prolonged exposure in mature cortical neurons through the activation of the CREB signaling pathway, linked to the activation of Syn NMDARs.

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.

Early disruption of the CREB pathway drives dendritic morphological alterations in FTD/ALS cortical neurons

Synaptic loss and dendritic degeneration are common pathologies in several neurodegenerative diseases characterized by progressive cognitive and/or motor decline, such as Alzheimer's disease (AD) and frontotemporal dementia/amyotrophic lateral sclerosis (FTD/ALS). An essential regulator of neuronal health, the cAMP-dependent transcription factor CREB positively regulates synaptic growth, learning, and memory. Phosphorylation of CREB by protein kinase A (PKA) and other cellular kinases promotes neuronal survival and maturation via transcriptional activation of a wide range of downstream target genes. CREB pathway dysfunction has been strongly implicated in AD pathogenesis, and recent data suggest that impaired CREB activation may contribute to disease phenotypes in FTD/ALS as well. However, the mechanisms behind reduced CREB activity in FTD/ALS pathology are not clear. In this study, we found that cortical-like neurons derived from iPSC lines carrying the hexanucleotide repeat expansion in the C9ORF72 gene, a common genetic cause of FTD/ALS, displayed a diminished activation of CREB, resulting in decreased dendritic and synaptic health. Importantly, we determined such impairments to be mechanistically linked to an imbalance in the ratio of regulatory and catalytic subunits of the CREB activator PKA and to be conserved in C9-ALS patient's postmortem tissue. Modulation of cAMP upstream of this impairment allowed for a rescue of CREB activity and an amelioration of dendritic morphology and synaptic protein levels. Our data elucidate the mechanism behind early CREB pathway dysfunction and discern a feasible therapeutic target for the treatment of FTD/ALS and possibly other neurodegenerative diseases.

Evaluating the Role of N-Acetyl-L-Tryptophan in the Aβ 1-42-Induced Neuroinflammation and Cognitive Decline in Alzheimer's Disease

Alzheimer's disease (AD), a neurodegenerative condition previously known to affect the older population, is also now seen in younger individuals. AD is often associated with cognitive decline and neuroinflammation elevation primarily due to amyloid β (Aβ) accumulation. Multiple pathological complications in AD call for therapies with a wide range of neuroprotection. Our study aims to evaluate the effect of N-acetyl-L-tryptophan (NAT) in ameliorating the cognitive decline and neuroinflammation induced by Aβ 1-42 oligomers and to determine the therapeutic concentration of NAT in the brain. We administered Aβ 1-42 oligomers in rats via intracerebroventricular (i.c.v.) injection to induce AD-like conditions. The NAT-treated animals lowered the cognitive decline in the Morris water maze characterized by shorter escape latency and increased path efficiency and platform entries. Interestingly, the hippocampus and frontal cortex showed downregulation of tumor necrosis factor, interleukin-6, and substance P levels. NAT treatment also reduced acetylcholinesterase activity and total and phosphorylated nuclear factor kappa B and Tau levels. Lastly, we observed upregulation of cAMP response element-binding protein 1 (CREB1) signaling. Surprisingly, our HPLC method was not sensitive enough to detect the therapeutic levels of NAT in the brain, possibly due to NAT concentrations being below the lowest limit of quantification of our validated method. To summarize, the administration of NAT significantly lowered cognitive decline, neuroinflammatory pathways, and Tau protein and triggered the upregulation of CREB1 signaling, suggesting its neuroprotective role in AD-like conditions.

Deep Learning-Driven Exploration of Pyrroloquinoline Quinone Neuroprotective Activity in Alzheimer's Disease

Alzheimer's disease (AD) is a pressing concern in neurodegenerative research. To address the challenges in AD drug development, especially those targeting Aβ, this study uses deep learning and a pharmacological approach to elucidate the potential of pyrroloquinoline quinone (PQQ) as a neuroprotective agent for AD. Using deep learning for a comprehensive molecular dataset, blood-brain barrier (BBB) permeability is predicted and the anti-inflammatory and antioxidative properties of compounds are evaluated. PQQ, identified in the Mediterranean-DASH intervention for a diet that delays neurodegeneration, shows notable BBB permeability and low toxicity. In vivo tests conducted on an Aβ₁₋₄₂-induced AD mouse model verify the effectiveness of PQQ in reducing cognitive deficits. PQQ modulates genes vital for synapse and anti-neuronal death, reduces reactive oxygen species production, and influences the SIRT1 and CREB pathways, suggesting key molecular mechanisms underlying its neuroprotective effects. This study can serve as a basis for future studies on integrating deep learning with pharmacological research and drug discovery.

Alterations in Immune Responses Are Associated with Dysfunctional Intracellular Signaling in Peripheral Blood Mononuclear Cells of Men and Women with Mild Cognitive Impairment and Alzheimer's disease

Deficits in the neuroendocrine-immune network in the periphery associated with the onset and progression of mild cognitive impairment (MCI) and Alzheimer's disease (AD) have not been extensively studied. The present study correlatively examines the association between cell-mediated immune responses, stress hormones, amyloid precursor protein (APP) expression, peripheral blood mononuclear cells (PBMC), and intracellular signaling molecules in the pathophysiology of MCI and AD compared to adults. Serum APP, lymphocyte proliferation, total cholinesterase (TChE), butyrylcholinesterase (BChE) activities, cytokines (IL-2, IFN-γ, IL-6, and TNF-α), and intracellular signaling molecules (p-ERK, p-CREB, and p-Akt) were measured in the PBMCs of adult, old, MCI, and AD men and women initially and after 3 years in the same population. An age- and disease-associated decline in mini-mental state examination (MMSE) scores and lymphocyte proliferation of MCI and AD men and women were observed. An age- and disease-related increase in serum APP, cortisol levels, and TChE activity were observed in men and women. Enhanced production of Th1 cytokine, IL-2, pro-inflammatory cytokines, and suppressed intracellular transcription factors may promote the inflammatory environment in MCI and AD patients. The expression of CREB and Akt was lower in MCI and AD men, while the expression of p-ERK was higher, and p-CREB was lower in MCI and AD women after 3 years. These results suggest that changes in specific intracellular signaling pathways may influence alterations in cell-mediated immunity to promote disease progression in MCI and AD patients.

Binding mechanism of full-length Aβ40 peptide to a mixed lipid bilayer

The destructive effect of Aβ peptides on membranes is an important source of its cytotoxicity in the pathogenesis of Alzheimer's disease. We have investigated the binding mechanism between the Aβ42 peptide and bilayer in our former work. However, as another abundant form of Aβ peptides in the physiological environment, the binding mechanism between Aβ40 peptide and the lipid bilayer still remains ambiguous. Hence, we performed all-atom simulations on the Aβ40 peptides with the lipid bilayer herein using replica exchange with the solute tempering 2 method. We obtained four major binding models with the hydrophobic C-terminus as the most preferable binding region. Hydrophobic residues and positively charged residues are the principal residues involved in the peptide-bilayer interactions. Aβ40 peptides in our simulation mainly adopt a β-rich conformation in both bound and unbound states. Besides, we determined peptide-water interactions and found that bound peptides prefer forming hydrogen bonds with water molecules than unbound peptides. Our findings herein may provide new insights for the in-depth understanding of the membrane-destructive mechanism of Aβ peptides.

CREB: A multifaceted transcriptional regulator of neural and immune function in CNS tumors

Cancers of the central nervous system (CNS) are unique with respect to their tumor microenvironment. Such a status is due to immune-privilege and the cellular behaviors within a highly networked, neural-rich milieu. During tumor development in the CNS, neural, immune and cancer cells establish complex cell-to-cell communication networks which mimic physiological functions, including paracrine signaling and synapse-like formations. This crosstalk regulates diverse pathological functions contributing to tumor progression. In the CNS, regulation of physiological and pathological functions relies on various cell signaling and transcription programs. At the core of these events lies the cyclic adenosine monophosphate (cAMP) response element binding protein (CREB), a master transcriptional regulator in the CNS. CREB is a kinase inducible transcription factor which regulates many CNS functions, including neurogenesis, neuronal survival, neuronal activation and long-term memory. Here, we discuss how CREB-regulated mechanisms operating in diverse cell types, which control development and function of the CNS, are co-opted in CNS tumors.

Neuroprotective potentials of Lead phytochemicals against Alzheimer's disease with focus on oxidative stress-mediated signaling pathways: Pharmacokinetic challenges, target specificity, clinical trials and future perspectives

BACKGROUND

Alzheimer's diseases (AD) and dementia are among the highly prevalent neurological disorders characterized by deposition of beta amyloid (Aβ) plaques, dense deposits of highly phosphorylated tau proteins, insufficiency of acetylcholine (ACh) and imbalance in glutamatergic system. Patients typically experience cognitive, behavioral alterations and are unable to perform their routine activities. Evidence also suggests that inflammatory processes including excessive microglia activation, high expression of inflammatory cytokines and release of free radicals. Thus, targeting inflammatory pathways beside other targets might be the key factors to control- disease symptoms and progression.

PURPOSE

This review is aimed to highlight the mechanisms and pathways involved in the neuroprotective potentials of lead phytochemicals. Further to provide updates regarding challenges associated with their use and their progress into clinical trials as potential lead compounds.

METHODS

Most recent scientific literature on pre-clinical and clinical data published in quality journals especially on the lead phytochemicals including curcumin, catechins, quercetin, resveratrol, genistein and apigenin was collected using SciFinder, PubMed, Google Scholar, Web of Science, JSTOR, EBSCO, Scopus and other related web sources.

RESULTS

Literature review indicated that the drug discovery against AD is insufficient and only few drugs are clinically approved which have limited efficacy. Among the therapeutic options, natural products have got tremendous attraction owing to their molecular diversity, their safety and efficacy. Research suggest that natural products can delay the disease onset, reduce its progression and regenerate the damage via their anti-amyloid, anti-inflammatory and antioxidant potentials. These agents regulate the pathways involved in the release of neurotrophins which are implicated in neuronal survival and function. Highly potential lead phytochemicals including curcumin, catechins, quercetin, resveratrol, genistein and apigenin regulate neuroprotective signaling pathways implicated in neurotrophins-mediated activation of tropomyosin receptor kinase (Trk) and p75 neurotrophins receptor (p75NTR) family receptors.

CONCLUSIONS

Phytochemicals especially phenolic compounds were identified as highly potential molecules which ameliorate oxidative stress induced neurodegeneration, reduce Aβ load and inhibit vital enzymes. Yet their clinical efficacy and bioavailability are the major challenges which need further interventions for more effective therapeutic outcomes.

Death-associated protein kinase 1 as a therapeutic target for Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent form of dementia in the elderly and represents a major clinical challenge in the ageing society. Neuropathological hallmarks of AD include neurofibrillary tangles composed of hyperphosphorylated tau, senile plaques derived from the deposition of amyloid-β (Aβ) peptides, brain atrophy induced by neuronal loss, and synaptic dysfunctions. Death-associated protein kinase 1 (DAPK1) is ubiquitously expressed in the central nervous system. Dysregulation of DAPK1 has been shown to contribute to various neurological diseases including AD, ischemic stroke and Parkinson's disease (PD). We have established an upstream effect of DAPK1 on Aβ and tau pathologies and neuronal apoptosis through kinase-mediated protein phosphorylation, supporting a causal role of DAPK1 in the pathophysiology of AD. In this review, we summarize current knowledge about how DAPK1 is involved in various AD pathological changes including tau hyperphosphorylation, Aβ deposition, neuronal cell death and synaptic degeneration. The underlying molecular mechanisms of DAPK1 dysregulation in AD are discussed. We also review the recent progress regarding the development of novel DAPK1 modulators and their potential applications in AD intervention. These findings substantiate DAPK1 as a novel therapeutic target for the development of multifunctional disease-modifying treatments for AD and other neurological disorders.

Neuroprotective effect of isovaleraldehyde accompanied with upregulation of BDNF and CREB phosphorylation via the PKA pathway

Recently, the number of patients diagnosed with dementia has increased. The World Health Organization (WHO) estimates that 50 million patients suffer from dementia. Although several therapeutic strategies have been proposed, currently, there is no curative approach for treating dementia. Neurodegeneration is an irreversible process. As this disease gradually progresses over 15-20 years, a low-cost and sustainable method for preventing these diseases is desired. Cacao nib is consumed in many countries, and a recent clinical study indicated that cocoa intake upregulates brain-derived neurotrophic factor (BDNF), which plays a significant role in memory formation and neuronal cell survival. In the present study, neural cells were treated with cacao nib extract or the 17 characteristic components of cacao nib. Treatment with Cacao nib extract upregulates BDNF mRNA expression. In addition, cacao nib extract elicits the phosphorylation of cAMP-response-element-binding protein (CREB), which regulates the transcription of BDNF. Among the 17 species screened, isovaleraldehyde (IVA), also known as an aroma component of cacao nibs extract, improved BDNF mRNA expression without SH-SY5Y cell toxicity. IVA also promoted CREB phosphorylation through a cAMP-dependent protein kinase (PKA)-dependent mechanism. In conclusion, IVA could be responsible for the BDNF upregulation effect of cacao nib, and IVA upregulated BDNF expression via the PKA-CREB axis.

Sevoflurane suppresses ALG13 transcription in a CREBBP-dependent manner to induce hippocampal damage and cognitive impairment

BACKGROUND

Sevoflurane (Sev) is a common clinical anesthetic but may lead to cognitive impairment. This study aims to deconstruct the underpinning molecular mechanism involved in Sev-induced neurological damage.

METHODS

Bioinformatics analyses was conducted to investigate candidate cognitive impairment-related physiological substrates of Sev. C57BL/6 mice and SH-SY5Y cells were exposed to Sev to generate animal and cellular models, respectively. Neurological impairment in mice was evaluated by Morris water maze test, modified Longa scoring, and pathological changes and cell apoptosis in the hippocampal tissues. In vitro, viability, apoptosis, and inflammatory cytokine concentration in SH-SY5Y cells were measured. Gain- or loss-of-function studies of CREB binding protein (CREBBP) and its predicted target asparagine-linked glycosylation 13 (ALG13) were performed in mice and in SH-SY5Y cells to investigate their roles in neural damage.

RESULTS

Sev treatment induced neurological deficit in mice and damage on SH-SY5Y cells, and reduced protein level of CREBBP protein in both models. CREBBP overexpression restored learning and memory ability of mice, reduced neurological deficit score, and reduced cell apoptosis while enhancing neuronal viability in the hippocampus. In vitro, the CREBBP overexpression increased viability while suppressing apoptosis and inflammation in SH-SY5Y cells. CREBBP bound to the ALG13 promoter to increase its transcription. Further knockdown of ALG13 negated the neuro-protective functions of CREBBP in vivo and in vitro.

CONCLUSION

This study demonstrates that Sev targets CREBBP to inhibit ALG13 transcription to induce hippocampal damage and cognitive impairment.

Adipocyte-Derived Small Extracellular Vesicles from Patients with Alzheimer Disease Carry miRNAs Predicted to Target the CREB Signaling Pathway in Neurons

Alzheimer disease (AD) is characterized by amyloid-β (Aβ) plaques, neurofibrillary tangles, synaptic dysfunction, and progressive dementia. Midlife obesity increases the risk of developing AD. Adipocyte-derived small extracellular vesicles (ad-sEVs) have been implicated as a mechanism in several obesity-related diseases. We hypothesized that ad-sEVs from patients with AD would contain miRNAs predicted to downregulate pathways involved in synaptic plasticity and memory formation. We isolated ad-sEVs from the serum and cerebrospinal fluid (CSF) of patients with AD and controls and compared miRNA expression profiles. We performed weighted gene co-expression network analysis (WGCNA) on differentially expressed miRNAs to identify highly interconnected clusters correlating with clinical traits. The WGCNA identified a module of differentially expressed miRNAs, in both the serum and CSF, that was inversely correlated with the Mini-Mental State Examination scores. Within this module, miRNAs that downregulate CREB signaling in neurons were highly represented. These results demonstrate that miRNAs carried by ad-sEVs in patients with AD may downregulate CREB signaling and provide a potential mechanistic link between midlife obesity and increased risk of AD.

Exploring Rosiglitazone's Potential to Treat Alzheimer's Disease through the Modulation of Brain-Derived Neurotrophic Factor

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that debilitates over 55 million individuals worldwide. Currently, treatments manage and alleviate its symptoms; however, there is still a need to find a therapy that prevents or halts disease progression. Since AD has been labeled as "type 3 diabetes" due to its similarity in pathological hallmarks, molecular pathways, and comorbidity with type 2 diabetes mellitus (T2DM), there is growing interest in using anti-diabetic drugs for its treatment. Rosiglitazone (RSG) is a peroxisome proliferator-activated receptor-gamma agonist that reduces hyperglycemia and hyperinsulinemia and improves insulin signaling. In cellular and rodent models of T2DM-associated cognitive decline and AD, RSG has been reported to improve cognitive impairment and reverse AD-like pathology; however, results from human clinical trials remain consistently unsuccessful. RSG has also been reported to modulate the expression of brain-derived neurotrophic factor (BDNF), a protein that regulates neuroplasticity and energy homeostasis and is implicated in both AD and T2DM. The present review investigates RSG's limitations and potential therapeutic benefits in pre-clinical models of AD through its modulation of BDNF expression.

Maternal neglect alters reward-anticipatory behavior, social status stability, and reward circuit activation in adult male rats

Introduction

Adverse early life experiences affect neuronal growth and maturation of reward circuits that modify behavior under reward predicting conditions. Previous studies demonstrate that rats undergoing denial of expected reward in the form of maternal contact (DER-animal model of maternal neglect) during early post-natal life developed anhedonia, aggressive play-fight behaviors and aberrant prefrontal cortex structure and neurochemistry. Although many studies revealed social deficiency following early-life stress most reports focus on individual animal tasks. Thus, attention needs to be given on the social effects during group tasks in animals afflicted by early life adversity.

Methods

To investigate the potential impact of the DER experience on the manifestation of behavioral responses induced by natural rewards, we evaluated: 1) naïve adult male sexual preference and performance, and 2) anticipatory behavior during a group 2-phase food anticipation learning task composed of a context-dependent and a cue-dependent learning period.

Results

DER rats efficiently spent time in the vicinity of and initiated sexual intercourse with receptive females suggesting an intact sexual reward motivation and consummation. Interestingly, during the context-dependent phase of food anticipation training DER rats displayed a modified exploratory activity and lower overall reward-context association. Moreover, during the cue-dependent phase DER rats displayed a mild deficit in context-reward association while increased cue-dependent locomotion. Additionally, DER rats displayed unstable food access priority following food presentation. These abnormal behaviours were accompanied by overactivation of the ventral prefrontal cortex and nucleus accumbens, as assessed by pCREB levels.

Conclusions/discussion

Collectively, these data show that the neonatal DER experience resulted in adulthood in altered activation of the reward circuitry, interfered with the normal formation of context-reward associations, and disrupted normal reward access hierarchy formation. These findings provide additional evidence to the deleterious effects of early life adversity on reward system, social hierarchy formation, and brain function.

The action of phosphodiesterase-5 inhibitors on β-amyloid pathology and cognition in experimental Alzheimer's disease: A systematic review

Alzheimer's disease (AD) is the most frequent cause of dementia worldwide. The etiology of AD is partially explained by the deposition of β-amyloid in the brain. Despite extensive research on the pathogenesis of AD, the current treatments are ineffective. Here, we systematically reviewed studies that investigated whether phosphodiesterase 5 inhibitors (PDE5i) are efficient in reducing the β-amyloid load in hippocampi and improving cognitive decline in rodent models with β-amyloid accumulation. We identified ten original studies, which used rodent models with β-amyloid accumulation, were treated with PDE5i, and β-amyloid was measured in the hippocampi. PDE5i was efficient in reducing the β-amyloid levels, except for one study that exclusively used female rodents and the treatment did not affect β-amyloid levels. Interestingly, PDE5i prevented cognitive decline in all studies. This study supports the potential therapeutic use of PDE5i for the reduction of the β-amyloid load in hippocampi and cognitive decline. However, we highlight the importance of conducting additional experimental studies to evaluate the PDE5i-related molecular mechanisms involved in β-amyloid removal in male and female animals.

Study on correlations of BDNF, PI3K, AKT and CREB levels with depressive emotion and impulsive behaviors in drug-naïve patients with first-episode schizophrenia

BACKGROUND

The pathogenesis of schizophrenia is still unknown. Nearly a half of schizophrenic patients have depressive symptoms and even some impulsive behaviors. The definite diagnosis of schizophrenia is an immense challenge. Molecular biology plays an essential role in the research on the pathogenesis of schizophrenia.

OBJECTIVE

This study aims to analyze the correlations of serum protein factor levels with depressive emotion and impulsive behaviors in drug-naïve patients with first-episode schizophrenia.

METHODS

Seventy drug-naïve patients with first-episode schizophrenia and sixty-nine healthy volunteers from the health check center in the same period participated in this study. In both the patient group and control group, brain-derived neurotrophic factor (BDNF), phosphatidylin-ositol-3-kinase (PI3K), protein kinase B (AKT), and cAMP-response element binding protein (CREB) levels in the peripheral blood were tested by enzyme-linked immunosorbent assay (ELISA). The depressive emotion and impulsive behaviors were evaluated with Chinese versions of the Calgary Depression Scale for Schizophrenia (CDSS) and Short UPPS-P Impulsive Behavior Scale (S-UPPS-P), respectively.

RESULTS

The serum levels of BDNF, PI3K, and CREB in the patient group were lower than those in the control group, while AKT level, total CDSS score and total S-UPPS-P score were all higher. In the patient group, total CDSS score, and total S-UPPS-P score were both correlated negatively with BDNF, PI3K, and CREB levels but positively with AKT level, and the lack-of-premeditation (PR) sub-scale score was not significantly correlated with BDNF, PI3K, AKT, and CREB levels.

CONCLUSION

Our study results showed that the peripheral blood levels of BDNF, PI3K, AKT, and CREB in drug-naïve patients with first-episode schizophrenia were significantly different from those in the control group. The levels of these serum protein factors are promising biomarkers to predict schizophrenic depression and impulsive behaviors.

Traumatic MicroRNAs: Deconvolving the Signal After Severe Traumatic Brain Injury

History of traumatic brain injury (TBI) represents a significant risk factor for development of dementia and neurodegenerative disorders in later life. While histopathological sequelae and neurological diagnostics of TBI are well defined, the molecular events linking the post-TBI signaling and neurodegenerative cascades remain unknown. It is not only due to the brain's inaccessibility to direct molecular analysis but also due to the lack of well-defined and highly informative peripheral biomarkers. MicroRNAs (miRNAs) in blood are promising candidates to address this gap. Using integrative bioinformatics pipeline including miRNA:target identification, pathway enrichment, and protein-protein interactions analysis we identified set of genes, interacting proteins, and pathways that are connected to previously reported peripheral miRNAs, deregulated following severe traumatic brain injury (sTBI) in humans. This meta-analysis revealed a spectrum of genes closely related to critical biological processes, such as neuroregeneration including axon guidance and neurite outgrowth, neurotransmission, inflammation, proliferation, apoptosis, cell adhesion, and response to DNA damage. More importantly, we have identified molecular pathways associated with neurodegenerative conditions, including Alzheimer's and Parkinson's diseases, based on purely peripheral markers. The pathway signature after acute sTBI is similar to the one observed in chronic neurodegenerative conditions, which implicates a link between the post-sTBI signaling and neurodegeneration. Identified key hub interacting proteins represent a group of novel candidates for potential therapeutic targets or biomarkers.

Effects of sesamin on Aβ1-42-induced oxidative stress and LTP impairment in a rat model of Alzheimer's disease

The present study examined the protective effect of sesamin (Ses) on β-amyloid (Aβ)-induced long-term potentiation (LTP) impairment at the PP-DG synapses in male rats. Wistar rats were randomly assigned to seven groups: control, sham, Aβ; ICV Aβ_1-42 microinjection, Ses, Aβ + Ses; first, ICV Aβ injections and then receiving Ses, Ses + Aβ: four weeks of pretreatment with Ses and then Aβ injection, and Ses + Aβ + Ses: pre (four weeks) and post (four weeks) treatment with Ses. Ses-treated groups received 30 mg/kg of Ses once a day by oral gavage for four weeks. After the treatment period, the animals were positioned in a stereotaxic device for surgery and field potential recording. The population spike (PS) amplitude and slope of excitatory postsynaptic potentials (EPSP) were evaluated in the DG region. Serum oxidative stress biomarkers (total oxidant status (TOS) and total antioxidant capacity (TAC)) were measured. Aβ impaired LTP induction at the PP-DG synapses evidenced by a decrease in EPSP slope and PS amplitude of LTP. In Aβ rats, Ses increased EPSP slope and PS amplitude of LTP in the DG granular cells. Also, an increase in TOS and a reduction in TAC caused by Aβ were significantly corrected by Ses. Ses could prevent Aβ-induced LTP impairment at the PP-DG synapses in male rats, which can be due to its preventive effects on oxidative stress.

Differential dysregulation of CREB and synaptic genes in transgenic Drosophila melanogaster expressing shaggy (GSK3), TauWT, or Amyloid-beta

BACKGROUND

Tau, Amyloid-beta (Aβ₄₂), and Glycogen synthase kinase 3 (GSK3) contribute to synaptic dysfunction observed in Alzheimer's disease (AD), the most common form of dementia. In the current study, the effect of pan-neuronal expression of Tau^WT, Aβ₄₂, or shaggy (orthologue of GSK3) in Drosophila melanogaster was assessed on the locomotor function, ethanol sensitivity, synaptic genes and CREB expression. The effect of Tau^WT and Aβ₄₂ on the expression of shaggy was also determined.

METHODS AND RESULTS

Gene expression analysis was performed using quantitative real-time RT-PCR method. While syt1, SNAP25 and CREB (upstream transcription factor of syt1 and SNAP25) were upregulated in flies expressing Tau^WT or Aβ_42, a prominent decline was observed in those genes in shaggy expressing flies. Although all transgenic flies showed climbing disability and higher sensitivity to ethanol, abnormality in these features was significantly more prominent in transgenic flies expressing shaggy compared to Tau^WT or Aβ₄₂. Despite a significant upregulation of shaggy transcription in Tau^WT expressing flies, Aβ₄₂ transgenic flies witnessed no significant changes.

CONCLUSIONS

Tau^WT, Aβ₄₂, and shaggy may affect synaptic plasticity through dysregulation of synaptic genes and CREB, independently. However shaggy has more detrimental effect on synaptic genes expression, locomotor ability and sensitivity to ethanol. It is important when it comes to drug discovery. It appears that CREB is a direct effector of changes in synaptic genes expression as they showed similar pattern of alteration and it is likely to be a part of compensatory mechanisms independent of the GSK3/CREB pathway in Tau^WT or Aβ₄₂ expressing flies.

The Effect of Lidocaine on the Experimental Model of Streptozotocin-Induced Alzheimer's Disease

Introduction

Alzheimer's disease (AD) is a neurodegenerative disease caused by the accumulation of amyloid plaques in the cerebral cortex and hippocampus. In this study, the effects of local anesthetic lidocaine on neurodegeneration markers and memory were investigated for the first time in streptozotocin-induced rat AD model.

Methods

Streptozotocin (STZ) was administered intracerebroventricularly (ICV) into Wistar rats to develop AD model. For lidocaine group (n=14), lidocaine (5 mg/kg) was administered intraperitoneally (IP) in addition to STZ injection. Control group animals (n=9) were treated with saline for 21 days. Morris Water Maze (MWM) test was performed to evaluate memory after the injections were completed. Also, the serum levels of TAR DNA-binding protein-43 (TDP-43), amyloid precursor protein (APP), β-secretase 1, nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), response element binding protein (CREB), c-FOS were measured using ELISA test and compared between groups.

Results

Lidocaine group animals showed lower escape latency and time in quadrant scores in MWM inferring better memory performance. Furthermore, lidocaine administration caused a significant decline in TDP-43 levels. However, the expression of APP and β-secretase were significantly higher in AD and lidocaine groups compared to control group. Moreover, lidocaine group markedly had higher serum NGF, BDNF, CREB, and c-FOS levels compared to those in the AD group.

Conclusion

In addition to neuroprotective effects in STZ-induced AD model, Lidocaine also appears to improve memory. This effect might be associated with increased levels of several growth factors and associated intracellular molecules. The therapeutic role of lidocaine in the pathophysiology of AD should be studied in the future.

Early Diagnosis of Alzheimer's Disease with Blood Test; Tempting but Challenging

The increasing prevalence of Alzheimer's disease (AD) has led to a health crisis. According to official statistics, more than 55 million people globally have AD or other types of dementia, making it the sixth leading cause of death. It is still difficult to diagnose AD and there is no definitive diagnosis yet; post-mortem autopsy is still the only definite method. Moreover, clinical manifestations occur very late in the course of disease progression; therefore, profound irreversible changes have already occurred when the disease manifests. Studies have shown that in the preclinical stage of AD, changes in some biomarkers are measurable prior to any neurological damage or other symptoms. Hence, creating a reliable, fast, and affordable method capable of detecting AD in early stage has attracted the most attention. Seeking clinically applicable, inexpensive, less invasive, and much more easily accessible biomarkers for early diagnosis of AD, blood-based biomarkers (BBBs) seem to be an ideal option. This review is an inclusive report of BBBs that have been shown to be altered in the course of AD progression. The aim of this report is to provide comprehensive insight into the research status of early detection of AD based on BBBs.

Proteomic-Based Approach Reveals the Involvement of Apolipoprotein A-I in Related Phenotypes of Autism Spectrum Disorder in the BTBR Mouse Model

Autism spectrum disorder (ASD) is a neurodevelopmental disorder. Abnormal lipid metabolism has been suggested to contribute to its pathogenesis. Further exploration of its underlying biochemical mechanisms is needed. In a search for reliable biomarkers for the pathophysiology of ASD, hippocampal tissues from the ASD model BTBR T+ Itpr3tf/J (BTBR) mice and C57BL/6J mice were analyzed, using four-dimensional (4D) label-free proteomic analysis and bioinformatics analysis. Differentially expressed proteins were significantly enriched in lipid metabolic pathways. Among them, apolipoprotein A-I (ApoA-I) is a hub protein and its expression was significantly higher in the BTBR mice. The investigation of protein levels (using Western blotting) also confirmed this observation. Furthermore, expressions of SphK2 and S1P in the ApoA-I pathway both increased. Using the SphK inhibitor (SKI-II), ASD core phenotype and phenotype-related protein levels of P-CREB, P-CaMKII, and GAD1 were improved, as shown via behavioral and molecular biology experiments. Moreover, by using SKI-II, we found proteins related to the development and function of neuron synapses, including ERK, caspase-3, Bax, Bcl-2, CDK5 and KCNQ2 in BTBR mice, whose levels were restored to protein levels comparable to those in the controls. Elucidating the possible mechanism of ApoA-I in ASD-associated phenotypes will provide new ideas for studies on the etiology of ASD.

Nitric oxide/cGMP/CREB pathway and amyloid-beta crosstalk: From physiology to Alzheimer's disease

The nitric oxide (NO)/cGMP pathway has been extensively studied for its pivotal role in synaptic plasticity and memory processes, resulting in an increase of cAMP response element-binding (CREB) phosphorylation, and consequent synthesis of plasticity-related proteins. The NO/cGMP/CREB signaling is downregulated during aging and neurodegenerative disorders and is affected by Amyloid-β peptide (Aβ) and tau protein, whose increase and deposition is considered the key pathogenic event of Alzheimer's disease (AD). On the other hand, in physiological conditions, the crosstalk between the NO/cGMP/PKG/CREB pathway and Aβ ensures long-term potentiation and memory formation. This review summarizes the current knowledge on the interaction between the NO/cGMP/PKG/CREB pathway and Aβ in the healthy and diseased brain, offering a new perspective to shed light on AD pathophysiology. We will focus on the synaptic mechanisms underlying Aβ physiological interplay with cGMP pathway and how this balance is corrupted in AD, as high levels of Aβ interfere with NO production and cGMP molecular signaling leading to cognitive impairment. Finally, we will discuss results from preclinical and clinical studies proposing the increase of cGMP signaling as a therapeutic strategy in the treatment of AD.

A mink (Neovison vison) model of self-injury: Effects of CBP-CREB axis on neuronal damage and behavior

Objective

Self-injurious behavior (SIB) is a clinically challenging problem in the general population and several clinical disorders. However, the precise molecular mechanism of SIB is still not clear. In this paper, the systematic investigation of the genesis and development of SIB is conducted based on behavioral and pathophysiology studies in mink (Neovison vison) models.

Method

The night-vision video was used to observe the mink behavior, and the duration was a month. HE stain was performed to characterize the pathology change in the brain of a mink. IHC assay was performed to conduct the protein level detection of Iba-1, p-CREB, CBP, and p300 in the brain tissues. Elisa assay was used to examine the levels of NfL and NfH in serum and CSF of mink. The qRT-PCR assay was used to detect the expression of Bcl-2, NOR1, FoxO4, c-FOS, CBP, and p300 in brain tissues. Western blot was used to detect the protein levels of p-CREB, CBP, and p300 in brain tissues. We also used Evans Blue as a tracer to detect whether the blood-brain barrier was impaired in the brain of mink.

Result

The behavioral test, histopathological and molecular biology experiments were combined in this paper, and the results showed that CBP was related to SIB. Mechanism analysis showed that the dysregulation of CBP in brain-activated CREB signaling will result in nerve damage of the brain and SIB symptoms in minks. More importantly, the CBP-CREB interaction inhibitor might help relieve SIB and nerve damage in brain tissues.

Conclusion

Our results illustrate that the induction of CBP and the activation of CREB are novel mechanisms in the genesis of SIB. This finding indicates that the CBP-CREB axis is critical for SIB and demonstrates the efficacy of the CBP-CREB interaction inhibitor in treating these behaviors.

Cutaneous burn injury induces neuroinflammation and reactive astrocyte activation in the hippocampus of aged mice

BACKGROUND

By 2050, one in six people globally will be 65 or older. Confusion and delirium are significant complications after burn injury, especially in the elderly population. The etiology is still unknown, however complications may be driven by pro-inflammatory activation of astrocytes within the hippocampus (HPC) after burn injury. Reduced levels of phosphorylated cyclic-AMP response binding element (pCREB), caused by elevated systemic pro-inflammatory cytokines, could lead to cognitive decline and memory impairment.

METHODS

To examine the effects of remote injury on neuroinflammation in advanced age, young and aged mice were subjected to a 15 % total body surface area scald burn or sham injury, and euthanized after 24 h. Expression of ccl2 and tnfa were measured by qPCR in the whole brain and HPC. Astrocyte activation was measured by immunofluorescence within the HPC. pCREB was measured by immunohistochemistry in the dentate gyrus.

RESULTS

We saw an 80-fold increase in ccl2 and a 30-fold elevation in tnfa after injury in the whole brain of aged mice compared to young groups and aged sham mice (p < 0.05 and p < 0.05, respectively). Additionally, there was a 30-fold increase in ccl2 within isolated HPC of aged injured mice when compared to sham injured animals (p < 0.05). When investigating specific HPC regions, immunofluorescence staining showed a >20 % rise in glial fibrillary acidic protein (GFAP) positive astrocytes within the cornu ammonis 3 (CA3) of aged injured mice when compared to all other groups (p < 0.05). Lastly, we observed a >20 % decrease in pCREB staining by immunohistochemistry in the dentate gyrus of aged mice compared to young regardless of injury (p < 0.05).

CONCLUSIONS

These novel data suggest that remote injury in aged, but not young, mice is associated with neuroinflammation and astrocyte activation within the HPC. These factors, paired with an age related reduction in pCREB, could help explain the increased cognitive decline seen in burn patients of advanced age. To our knowledge, we are the first group to examine the impact of advanced age combined with burn injury on inflammation and astrocyte activation within the brain.

Focus on long non-coding RNA MALAT1: Insights into acute and chronic lung diseases

Acute lung injury (ALI) is a pulmonary illness with a high burden of morbidity and mortality around the world. Chronic lung diseases also represent life-threatening situations. Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) is a type of long non-coding RNA (lncRNA) and is highly abundant in lung tissues. MALAT1 can function as a competitive endogenous RNA (ceRNA) to impair the microRNA (miRNA) inhibition on targeted messenger RNAs (mRNAs). In this review, we summarized that MALAT1 mainly participates in pulmonary cell biology and lung inflammation. Therefore, MALAT1 can positively or negatively regulate ALI and chronic lung diseases (e.g., chronic obstructive pulmonary disease (COPD), bronchopulmonary dysplasia (BPD), pulmonary fibrosis, asthma, and pulmonary hypertension (PH)). Besides, we also found a MALAT1-miRNA-mRNA ceRNA regulatory network in acute and chronic lung diseases. Through this review, we hope to cast light on the regulatory mechanisms of MALAT1 in ALI and chronic lung disease and provide a promising approach for lung disease treatment.

Augmenting neurogenesis rescues memory impairments in Alzheimer's disease by restoring the memory-storing neurons

Hippocampal neurogenesis is impaired in Alzheimer's disease (AD) patients and familial Alzheimer's disease (FAD) mouse models. However, it is unknown whether new neurons play a causative role in memory deficits. Here, we show that immature neurons were actively recruited into the engram following a hippocampus-dependent task. However, their recruitment is severely deficient in FAD. Recruited immature neurons exhibited compromised spine density and altered transcript profile. Targeted augmentation of neurogenesis in FAD mice restored the number of new neurons in the engram, the dendritic spine density, and the transcription signature of both immature and mature neurons, ultimately leading to the rescue of memory. Chemogenetic inactivation of immature neurons following enhanced neurogenesis in AD, reversed mouse performance, and diminished memory. Notably, AD-linked App, ApoE, and Adam10 were of the top differentially expressed genes in the engram. Collectively, these observations suggest that defective neurogenesis contributes to memory failure in AD.

Glucose derived carbon nanosphere (CSP) conjugated TTK21, an activator of the histone acetyltransferases CBP/p300, ameliorates amyloid-beta 1-42 induced deficits in plasticity and associativity in hippocampal CA1 pyramidal neurons

The master epigenetic regulator lysine acetyltransferase (KAT) p300/CBP plays a pivotal role in neuroplasticity and cognitive functions. Recent evidence has shown that in several neurodegenerative diseases, including Alzheimer's disease (AD), the expression level and function of p300/CBP are severely compromised, leading to altered gene expression causing pathological conditions. Here, we show that p300/CBP activation by a small-molecule TTK21, conjugated to carbon nanosphere (CSP) ameliorates Aβ-impaired long-term potentiation (LTP) induced by high-frequency stimulation, theta burst stimulation, and synaptic tagging/capture (STC). This functional rescue was correlated with CSP-TTK21-induced changes in transcription and translation. Mechanistically, we observed that the expression of a large number of synaptic plasticity- and memory-related genes was rescued, presumably by the restoration of p300/CBP mediated acetylation. Collectively, these results suggest that small-molecule activators of p300/CBP could be a potential therapeutic molecule for neurodegenerative diseases like AD.

The neuroprotective effects of glucagon-like peptide 1 in Alzheimer's and Parkinson's disease: An in-depth review

Currently, there is no disease-modifying treatment available for Alzheimer's and Parkinson's disease (AD and PD) and that includes the highly controversial approval of the Aβ-targeting antibody aducanumab for the treatment of AD. Hence, there is still an unmet need for a neuroprotective drug treatment in both AD and PD. Type 2 diabetes is a risk factor for both AD and PD. Glucagon-like peptide 1 (GLP-1) is a peptide hormone and growth factor that has shown neuroprotective effects in preclinical studies, and the success of GLP-1 mimetics in phase II clinical trials in AD and PD has raised new hope. GLP-1 mimetics are currently on the market as treatments for type 2 diabetes. GLP-1 analogs are safe, well tolerated, resistant to desensitization and well characterized in the clinic. Herein, we review the existing evidence and illustrate the neuroprotective pathways that are induced following GLP-1R activation in neurons, microglia and astrocytes. The latter include synaptic protection, improvements in cognition, learning and motor function, amyloid pathology-ameliorating properties (Aβ, Tau, and α-synuclein), the suppression of Ca2+ deregulation and ER stress, potent anti-inflammatory effects, the blockage of oxidative stress, mitochondrial dysfunction and apoptosis pathways, enhancements in the neuronal insulin sensitivity and energy metabolism, functional improvements in autophagy and mitophagy, elevated BDNF and glial cell line-derived neurotrophic factor (GDNF) synthesis as well as neurogenesis. The many beneficial features of GLP-1R and GLP-1/GIPR dual agonists encourage the development of novel drug treatments for AD and PD.

Neurospecific Molecules Measured in Periphery in Humans: How Do They Correlate with the Brain Levels? A Systematic Review

Human brain state is usually estimated by brain-specific substances in peripheral tissues, but, for most analytes, a concordance between their content in the brain and periphery is unclear. In this systematic review, we summarized the investigated correlations in humans. PubMed was searched up to June 2022. We included studies measuring the same endogenous neurospecific analytes in the central nervous system and periphery in the same subjects. Not eligible were studies of cerebrospinal fluid, with significant blood–brain barrier disruption, of molecules with well-established blood-periphery concordance or measured in brain tumors. Seventeen studies were eligible. Four studies did not report on correlation and four revealed no significant correlation. Four molecules were examined twice. For BDNF, there was no correlation in both studies. For phenylalanine, glutamine, and glutamate, results were contradictory. Strong correlations were found for free tryptophan (r = 0.97) and translocator protein (r = 0.90). Thus, only for three molecules was there some certainty. BDNF in plasma or serum does not reflect brain content, whereas free tryptophan (in plasma) and translocator protein (in blood cells) can serve as peripheral biomarkers. We expect a breakthrough in the field with advanced in vivo metabolomic analyses, neuroimaging techniques, and blood assays for exosomes of brain origin.

Modulation of MAPK- and PI3/AKT-Dependent Autophagy Signaling by Stavudine (D4T) in PBMC of Alzheimer’s Disease Patients

Background: Aβ₄₂ deposition plays a pivotal role in AD pathogenesis by inducing the activation of microglial cells and neuroinflammation. This process is antagonized by microglia-mediated clearance of Aβ plaques. Activation of the NLRP3 inflammasome is involved in neuroinflammation and in the impairments of Aβ-plaque clearance. On the other hand, stavudine (D4T) downregulates the NLRP3 inflammasome and stimulates autophagy-mediated Aβ-clearing in a THP-1-derived macrophages. Methods: We explored the effect of D4T on Aβ autophagy in PBMC from AD patients that were primed with LPS and stimulated with Aβ oligomers in the absence/presence of D4T. We analyzed the NLRP3 activity by measuring NLRP3-ASC complex formation by AMNIS FlowSight and pro-inflammatory cytokine (IL-1β, IL-18 and Caspase-1) production by ELISA. The phosphorylation status of p38, ERK, AKT, p70, and the protein expression of CREB, LAMP2A, beclin-1, Caspase-3 and Bcl2 were analyzed by Western blot. Results: Data showed that D4T: (1) downregulates NLRP3 inflammasome activation and the production of down-stream pro-inflammatory cytokines in PBMC; (2) stimulates the phosphorylation of AKT, ERK and p70 as well as LAMP2A, beclin-1 and Bcl2 expression and reduces Caspase-3 expression, suggesting an effect of this compound on autophagy; (3) increases phospho-CREB, which is a downstream target of p-ERK and p-AKT, inducing anti-inflammatory cytokine production and resulting in a possible decrease of Aβ-mediated cytotoxicity; and (4) reduces the phosphorylation of p38, a protein involved in the production of pro-inflammatory cytokines and tau hyperphosphorylation. Conclusions: D4T reduces the activation of the NLRP3 inflammasome, and it might stimulate autophagy as well as the molecular mechanism that modulates Aβ cytotoxicity, and D4T might reduce inflammation in the cells of AD patients. It could be very interesting to check the possible beneficial effects of D4T in the clinical scenario.

Single-cell network biology characterizes cell type gene regulation for drug repurposing and phenotype prediction in Alzheimer's disease

Dysregulation of gene expression in Alzheimer's disease (AD) remains elusive, especially at the cell type level. Gene regulatory network, a key molecular mechanism linking transcription factors (TFs) and regulatory elements to govern gene expression, can change across cell types in the human brain and thus serve as a model for studying gene dysregulation in AD. However, AD-induced regulatory changes across brain cell types remains uncharted. To address this, we integrated single-cell multi-omics datasets to predict the gene regulatory networks of four major cell types, excitatory and inhibitory neurons, microglia and oligodendrocytes, in control and AD brains. Importantly, we analyzed and compared the structural and topological features of networks across cell types and examined changes in AD. Our analysis shows that hub TFs are largely common across cell types and AD-related changes are relatively more prominent in some cell types (e.g., microglia). The regulatory logics of enriched network motifs (e.g., feed-forward loops) further uncover cell type-specific TF-TF cooperativities in gene regulation. The cell type networks are also highly modular and several network modules with cell-type-specific expression changes in AD pathology are enriched with AD-risk genes. The further disease-module-drug association analysis suggests cell-type candidate drugs and their potential target genes. Finally, our network-based machine learning analysis systematically prioritized cell type risk genes likely involved in AD. Our strategy is validated using an independent dataset which showed that top ranked genes can predict clinical phenotypes (e.g., cognitive impairment) of AD with reasonable accuracy. Overall, this single-cell network biology analysis provides a comprehensive map linking genes, regulatory networks, cell types and drug targets and reveals cell-type gene dysregulation in AD.

GSK3β and mTORC1 Represent 2 Distinct Signaling Markers in Peripheral Blood Mononuclear Cells of Drug-Naive, First Episode of Psychosis Patients

BACKGROUND AND HYPOTHESIS

Schizophrenia is characterized by a complex interplay between genetic and environmental risk factors converging on prominent signaling pathways that orchestrate brain development. The Akt/GSK3β/mTORC1 pathway has long been recognized as a point of convergence and etiological mechanism, but despite evidence suggesting its hypofunction, it is still not clear if this is already established during the first episode of psychosis (FEP).

STUDY DESIGN

Here, we performed a systematic phosphorylation analysis of Akt, GSK3β, and S6, a mTORC1 downstream target, in fresh peripheral blood mononuclear cells from drug-naive FEP patients and control subjects.

STUDY RESULTS

Our results suggest 2 distinct signaling endophenotypes in FEP patients. GSK3β hypofunction exhibits a promiscuous association with psychopathology, and it is normalized after treatment, whereas mTORC1 hypofunction represents a stable state.

CONCLUSIONS

Our study provides novel insight on the peripheral hypofunction of the Akt/GSK3β/mTORC1 pathway and highlights mTORC1 activity as a prominent integrator of altered peripheral immune and metabolic states in FEP patients.

Memory related molecular signatures: The pivots for memory consolidation and Alzheimer's related memory decline

Age-related cognitive decline is the major cause of concern due to its 70% more incidence than dementia cases worldwide. Moreover, aging is also the major risk factor of Alzheimer's disease (AD), associated with progressive memory loss. Approx. 13 million people will have Alzheimer-related memory decline by 2050. Learning and memory is the fundamental process of brain functions. However, the mechanism for the same is still under investigation. Thus, it is critical to understand the process of memory consolidation in the brain and extrapolate its understanding to the memory decline mechanism. Research on learning and memory has identified several molecular signatures such as Protein kinase M zeta (PKMζ), Calcium/calmodulin-dependent protein kinase II (CaMKII), Brain-derived neurotrophic factor (BDNF), cAMP-response element binding protein (CREB) and Activity-regulated cytoskeleton-associated protein (Arc) crucial for the maintenance and stabilization of long-term memory in the brain. Interestingly, memory decline in AD has also been linked to the abnormality in expressing these memory-related molecular signatures. Hence, in the present consolidated review, we explored the role of these memory-related molecular signatures in long-term memory consolidation. Additionally, the effect of amyloid-beta toxicity on these molecular signatures is discussed in detail.

Kisspeptin-13 prevented the electrophysiological alterations induced by Amyloid-Beta pathology in rat: Possible involvement of stromal interaction molecules and pCREB

Alzheimer's disease (AD) is a progressive neurological disease that slowly causing memory impairments with no effective treatment. We have recently reported that kisspeptin-13 (KP-13) ameliorates Aβ toxicity-induced memory deficit in rats. Here, the possible cellular impact of kisspeptin receptor activation in a rat model of the early stage AD was assessed using whole-cell patch-clamp recording from CA1 pyramidal neurons and molecular approaches. Compared to neurons from the control group, cells from the Aβ-treated group displayed spontaneous and evoked hyperexcitability with lower spike frequency adaptation. These cells had also a lower sag ratio in response to hyperpolarizing prepulse current delivered before a depolarizing current injection. Neurons from the Aβ-treated group exhibited short spike onset latency, lower rheobase and short utilization time compared with those in the control group. Furthermore, phase plot analysis of action potential showed that Aβ treatment affected the action potential features. These electrophysiological changes induced by Aβ were associated with increased expression of stromal interaction molecules (STIMs), particularly (STIM2) and decreased pCREB/CREB ratio. Treatment with KP-13 following Aβ injection into the entorhinal cortex, however, prevented the excitatory effect of Aβ on spontaneous and evoked neuronal activity, increased the latency of onset, enhanced the sag ratio, increased the rheobase and utilization time, and prevented the changes induced Aβ on spike parameters. In addition, the KP-13 application after Aβ treatment reduced the expression of STIMs and increased the pCREB/CREB ratio compared to those receiving Aβ treatment alone. In summary, these results provide evidence that activation of kisspeptin receptor may be effective against pathology of Aβ.

Ginsenosides in central nervous system diseases: Pharmacological actions, mechanisms, and therapeutics

The nervous system is one of the most complex physiological systems, and central nervous system diseases (CNSDs) are serious diseases that affect human health. Ginseng (Panax L.), the root of Panax species, are famous Chinese herbs that have been used for various diseases in China, Japan, and Korea since ancient times, and remain a popular natural medicine used worldwide in modern times. Ginsenosides are the main active components of ginseng, and increasing evidence has demonstrated that ginsenosides can prevent CNSDs, including neurodegenerative diseases, memory and cognitive impairment, cerebral ischemia injury, depression, brain glioma, multiple sclerosis, which has been confirmed in numerous studies. Therefore, this review summarizes the potential pathways by which ginsenosides affect the pathogenesis of CNSDs mainly including antioxidant effects, anti-inflammatory effects, anti-apoptotic effects, and nerve protection, which provides novel ideas for the treatment of CNSDs.

Simultaneous administration of bromodomain and histone deacetylase I inhibitors alleviates cognition deficit in Alzheimer's model of rats

BACKGROUND

Histone deacetylases (HDACs) target various genes responsible for cognitive functions. However, chromatin readers, particularly bromodomain-containing protein 4 (BRD4), are capable to change the final products of genes. The objective of this study was to evaluate the simultaneous effects of inhibition of HDACs and BRD4 on spatial and aversive memories impaired by amyloid β (Aβ) in a rat model of Alzheimer's disease (AD) considering CREB and TNF-α signaling.

METHODS

Forty male Wistar rats aged 3 months were randomly divided into five groups: saline +DMSO, Aβ+saline+DMSO, Aβ+JQ1, Aβ+MS-275, Aβ+JQ1+MS-275, and received the related treatments. MS-275, is the second generation of HDACs inhibitor, and JQ1 is a potent inhibitor of the BET family of bromodomain proteins in mammals. After the treatments, cognitive function was assessed by Morris water maze (MWM) and passive avoidance learning (PAL). The hippocampal level of mRNA for CREB and TNF-α, and also phosphorylated CREB were measured using real-time PCR and western blotting respectively.

RESULTS

Administration of JQ1 and MS-275, either separately or simultaneously, improved acquisition and retrieval of spatial and aversive memories as it was evident by decreased escape latency and increased time spent in the target quadrant (TTS) in Morris water maze (MWM), together with increase in step-through latency, but reduced time spent in the dark zone time in passive avoidance learning (PAL) compared with Aβ+saline+DMSO. Furthermore, there was a significant rise in the hippocampal level of CREB mRNA and phosphorylated CREB, but a reduction in TNF-α expression in comparison with Aβ + Saline.

CONCLUSION

Simultaneous administration of JQ1 and MS-275 improves acquisition and retrieval of both spatial and aversive memories partly via CREB and TNF-α signaling with no superiority to monotherapy.

Co-Expression Network Analysis of Micro-RNAs and Proteins in the Alzheimer's Brain: A Systematic Review of Studies in the Last 10 Years

MicroRNAs (miRNAs) are small non-coding nucleic acids that can regulate post-transcriptional gene expression by binding to complementary sequences of target mRNA. Evidence showed that dysregulated miRNA expression may be associated with neurological conditions such as Alzheimer’s disease (AD). In this study, we combined the results of two independent systematic reviews aiming to unveil the co-expression network of miRNAs and proteins in brain tissues of AD patients. Twenty-eight studies including a total of 113 differentially expressed miRNAs (53 of them validated by qRT-PCR), and 26 studies including a total of 196 proteins differentially expressed in AD brains compared to healthy age matched controls were selected. Pathways analyses were performed on the results of the two reviews and 39 common pathways were identified. A further bioinformatic analysis was performed to match miRNA and protein targets with an inverse relation. This revealed 249 inverse relationships in 28 common pathways, representing new potential targets for therapeutic intervention. A meta-analysis, whenever possible, revealed miR-132-3p and miR-16 as consistently downregulated in late-stage AD across the literature. While no inverse relationships between miR-132-3p and proteins were found, miR-16′s inverse relationship with CLOCK proteins in the circadian rhythm pathway is discussed and therapeutic targets are proposed. The most significant miRNA dysregulated pathway highlighted in this review was the hippo signaling pathway with p = 1.66 × 10⁻⁹. Our study has revealed new mechanisms for AD pathogenesis and this is discussed along with opportunities to develop novel miRNA-based drugs to target these pathways.

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.

Amelioration of lipopolysaccharide-induced memory impairment in equilibrative nucleoside transporter-2 knockout mice is accompanied by the changes in glutamatergic pathways

Neuroinflammation has been implicated in cognitive deficits in neurological and neurodegenerative diseases. Lipopolysaccharide (LPS)-induced neuroinflammation and the breakdown of the blood-brain barrier can be attenuated in mice with equilibrative nucleoside transporter-2 (ENT2/Ent2) deletion. The present study was aimed to investigate the role of ENT2 in cognitive and neuronal functions under physiological and inflammatory conditions, in terms of behavioral performance and synaptic plasticity in saline- and LPS-treated Ent2 knockout (KO) mice and their wild-type (WT) littermate controls. Repeated administrations of LPS significantly impaired spatial memory formation in Morris water maze and hippocampal-dependent long-term potentiation (LTP) in WT mice. The LPS-treated WT mice exhibited significant synaptic and neuronal damage in the hippocampus. Notably, the LPS-induced impairment in spatial memory and LTP performance were attenuated in Ent2 KO mice, along with the preservation of neuronal survival. The beneficial effects were accompanied by the normalization of excessive extracellular glutamate and aberrant downstream signaling of glutamate receptor activation, including the upregulation of phosphorylated p38 mitogen-activated protein kinase and the downregulation of phosphorylated cyclic adenosine monophosphate-response element-binding protein. There was no significant difference in behavioral outcome and all tested parameters between these two genotypes under physiological condition. These results suggest that ENT2 plays an important role in regulating inflammation-associated cognitive decline and neuronal damage.

Synaptic disruption and CREB-regulated transcription are restored by K+ channel blockers in ALS

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease, which is still missing effective therapeutic strategies. Although manipulation of neuronal excitability has been tested in murine and human ALS models, it is still under debate whether neuronal activity might represent a valid target for efficient therapies. In this study, we exploited a combination of transcriptomics, proteomics, optogenetics and pharmacological approaches to investigate the activity-related pathological features of iPSC-derived C9orf72-mutant motoneurons (MN). We found that human ALSC9orf72 MN are characterized by accumulation of aberrant aggresomes, reduced expression of synaptic genes, loss of synaptic contacts and a dynamic "malactivation" of the transcription factor CREB. A similar phenotype was also found in TBK1-mutant MN and upon overexpression of poly(GA) aggregates in primary neurons, indicating a strong convergence of pathological phenotypes on synaptic dysregulation. Notably, these alterations, along with neuronal survival, could be rescued by treating ALS-related neurons with the K+ channel blockers Apamin and XE991, which, respectively, target the SK and the Kv7 channels. Thus, our study shows that restoring the activity-dependent transcriptional programme and synaptic composition exerts a neuroprotective effect on ALS disease progression.

The Pathogenesis Mechanism, Structure Properties, Potential Drugs and Therapeutic Nanoparticles against the Small Oligomers of Amyloid-β

Alzheimer's Disease (AD) is a devastating neurodegenerative disease that affects millions of people in the world. The abnormal aggregation of amyloid β protein (Aβ) is regarded as the key event in AD onset. Meanwhile, the Aβ oligomers are believed to be the most toxic species of Aβ. Recent studies show that the Aβ dimers, which are the smallest form of Aβ oligomers, also have the neurotoxicity in the absence of other oligomers in physiological conditions. In this review, we focus on the pathogenesis, structure and potential therapeutic molecules against small Aβ oligomers, as well as the nanoparticles (NPs) in the treatment of AD. In this review, we firstly focus on the pathogenic mechanism of Aβ oligomers, especially the Aβ dimers. The toxicity of Aβ dimer or oligomers, which attributes to the interactions with various receptors and the disruption of membrane or intracellular environments, were introduced. Then the structure properties of Aβ dimers and oligomers are summarized. Although some structural information such as the secondary structure content is characterized by experimental technologies, detailed structures are still absent. Following that, the small molecules targeting Aβ dimers or oligomers are collected; nevertheless, all of these ligands have failed to come into the market due to the rising controversy of the Aβ-related "amyloid cascade hypothesis". At last, the recent progress about the nanoparticles as the potential drugs or the drug delivery for the Aβ oligomers are present.

Tau seeds are subject to aberrant modifications resulting in distinct signatures

The prion-like spread of tau pathology could underlie a spectrum of clinical syndromes including Alzheimer's disease (AD). Although evidence indicates that tau is transmissible, it is unclear how pathogenic tau seeds are processed in neurons. Here, we analyze fibrillar wild-type and disease-associated P301L tau seeds by using in vitro and neuronal assays. We show that P301L seeds are uniquely modified by post-translational modifications (PTMs) within the microtubule-binding region (MTBR). Although these modifications do not alter tau seed trafficking or localization, acetylated tau variants show accelerated tau aggregation, enhanced tau PTM priming, and prion-like templating. To explain the enhanced tau seed acetylation, we demonstrate that P301L seeds undergo auto-acetylation. Moreover, tau acts generally to inhibit HDAC6 deacetylase activity by preventing HDAC6 phosphorylation, leading to increased substrate acetylation. Our study highlights complex post-translational regulation of transmissible tau seeds and provides insight into the biological properties of tau strains in AD and other tauopathies.

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

Alzheimer's disease (AD) is an age-related neurodegenerative disease, and the imbalance between production and clearance of β-amyloid (Aβ) is involved in its pathogenesis. Autophagy is an intracellular degradation pathway whereby leads to removal of aggregated proteins, up-regulation of which may be a plausible therapeutic strategy for the treatment of AD. Histamine H3 receptor (H3R) is a presynaptic autoreceptor regulating histamine release via negative feedback way. Our previous study showed that thioperamide, as an antagonist of H3R, enhances autophagy and protects against ischemic injury. However, the effect of thioperamide on autophagic function and Aβ pathology in AD remains unknown. In this study, we found that thioperamide promoted cognitive function, ameliorated neuronal loss, and Aβ pathology in APP/PS1 transgenic (Tg) mice. Interestingly, thioperamide up-regulated autophagic level and lysosomal function both in APP/PS1 Tg mice and in primary neurons under Aβ-induced injury. The neuroprotection by thioperamide against AD was reversed by 3-MA, inhibitor of autophagy, and siRNA of Atg7, key autophagic-related gene. Furthermore, inhibition of activity of CREB, H3R downstream signaling, by H89 reversed the effect of thioperamide on promoted cell viability, activated autophagic flux, and increased autophagic-lysosomal proteins expression, including Atg7, TFEB, and LAMP1, suggesting a CREB-dependent autophagic activation by thioperamide in AD. Taken together, these results suggested that H3R antagonist thioperamide improved cognitive impairment in APP/PS1 Tg mice via modulation of the CREB-mediated autophagy and lysosomal pathway, which contributed to Aβ clearance. This study uncovered a novel mechanism involving autophagic regulating behind the therapeutic effect of thioperamide in AD.

Compartmentalized Signaling in Aging and Neurodegeneration

The cyclic AMP (cAMP) signalling cascade is necessary for cell homeostasis and plays important roles in many processes. This is particularly relevant during ageing and age-related diseases, where drastic changes, generally decreases, in cAMP levels have been associated with the progressive decline in overall cell function and, eventually, the loss of cellular integrity. The functional relevance of reduced cAMP is clearly supported by the finding that increases in cAMP levels can reverse some of the effects of ageing. Nevertheless, despite these observations, the molecular mechanisms underlying the dysregulation of cAMP signalling in ageing are not well understood. Compartmentalization is widely accepted as the modality through which cAMP achieves its functional specificity; therefore, it is important to understand whether and how this mechanism is affected during ageing and to define which is its contribution to this process. Several animal models demonstrate the importance of specific cAMP signalling components in ageing, however, how age-related changes in each of these elements affect the compartmentalization of the cAMP pathway is largely unknown. In this review, we explore the connection of single components of the cAMP signalling cascade to ageing and age-related diseases whilst elaborating the literature in the context of cAMP signalling compartmentalization.