Amyloid β1-42 (Aβ1-42) Induces the CDK2-Mediated Phosphorylation of Tau through the Activation of the mTORC1 Signaling Pathway While Promoting Neuronal Cell Death

Extracellular Vesicles from hiPSC-derived NSCs Protect Human Neurons against Aβ-42 Oligomers Induced Neurodegeneration, Mitochondrial Dysfunction and Tau Phosphorylation

Background

One of the hallmarks of Alzheimer's disease (AD) is the buildup of amyloid beta-42 (Aβ-42) in the brain, which leads to various adverse effects. Therefore, therapeutic interventions proficient in reducing Aβ-42-induced toxicity in AD are of great interest. One promising approach is to use extracellular vesicles from human induced pluripotent stem cell-derived neural stem cells (hiPSC-NSC-EVs) because they carry multiple therapeutic miRNAs and proteins capable of protecting neurons against Aβ-42-induced pathological changes. Therefore, this in vitro study investigated the proficiency of hiPSC-NSC-EVs to protect human neurons derived from two distinct hiPSC lines from Aβ-42o-induced neurodegeneration.

Methods

We isolated hiPSC-NSC-EVs using chromatographic methods and characterized their size, ultrastructure, expression of EV-specific markers and proficiency in getting incorporated into mature human neurons. Next, mature human neurons differentiated from two different hiPSC lines were exposed to 1 µM Aβ-42 oligomers (Aβ-42o) alone or with varying concentrations of hiPSC-NSC-EVs. The protective effects of hiPSC-NSC-EVs against Aβ-42o-induced neurodegeneration, increased oxidative stress, mitochondrial dysfunction, impaired autophagy, and tau phosphorylation were ascertained using multiple measures and one-way ANOVA with Newman-Keuls multiple comparisons post hoc tests.

Results

Significant neurodegeneration was observed when human neurons were exposed to Aβ-42o alone. Notably, neurodegeneration was associated with elevated levels of oxidative stress markers malondialdehyde (MDA) and protein carbonyls (PCs), increased expression of proapoptotic Bax and Bad genes and proteins, reduced expression of the antiapoptotic gene and protein Bcl-2, increased expression of genes encoding mitochondrial complex proteins, decreased expression of autophagy-related proteins Beclin-1 and microtubule-associated protein 1 light chain 3B, and increased phosphorylation of tau. However, the addition of an optimal dose of hiPSC-NSC-EVs (6 x 10 9 EVs) to human neuronal cultures exposed to Aβ-42o significantly reduced the extent of neurodegeneration, along with diminished levels of MDA and PCs, normalized expressions of Bax, Bad, and Bcl-2, and genes linked to mitochondrial complex proteins, and reduced tau phosphorylation.

Conclusions

The findings demonstrate that an optimal dose of hiPSC-NSC-EVs could significantly decrease the degeneration of human neurons induced by Aβ-42o. The results also support further research into the effectiveness of hiPSC-NSC-EVs in AD, particularly their proficiency in preserving neurons and slowing disease progression.

Natural flavonoid hesperetin blocks amyloid β-protein fibrillogenesis, depolymerizes preformed fibrils and alleviates cytotoxicity caused by amyloids

The aggregation of β-amyloid (Aβ) peptides to form amyloid plaques is one of the primary hallmarks for Alzheimer's disease (AD). Dietary flavonoid supplements containing hesperetin have an ability to decline the risk of developing AD, but the molecular mechanism is still unclear. In this work, hesperetin, a flavanone abundant in citrus fruits, has been proven to prevent the formation of Aβ aggregates and depolymerized preformed fibrils in a concentration-dependent fashion. Hesperetin inhibited the conformational conversion from the natural structure to a β-sheet-rich conformation. It was found that hesperetin significantly reduced the cytotoxicity and relieved oxidative stress eventuated by Aβ aggregates in a concentration-dependent manner. Additionally, the beneficial effects of hesperetin were confirmed in Caenorhabditis elegans, including the inhibition of the formation and deposition of Aβ aggregates and extension of their lifespan. Finally, the results of molecular dynamics simulations showed that hesperetin directly interacted with an Aβ42 pentamer mainly through strong non-polar and electrostatic interactions, which destroyed the structural stability of the preformed pentamer. To summarize, hesperetin exhibits great potential as a prospective dietary supplement for preventing and improving AD.

Uncovering Cell Cycle Dysregulations and Associated Mechanisms in Cancer and Neurodegenerative Disorders: A Glimpse of Hope for Repurposed Drugs

The cell cycle is the sequence of events orchestrated by a complex network of cell cycle proteins. Unlike normal cells, mature neurons subsist in a quiescent state of the cell cycle, and aberrant cell cycle activation triggers neuronal death accompanied by neurodegeneration. The periodicity of cell cycle events is choreographed by various mechanisms, including DNA damage repair, oxidative stress, neurotrophin activity, and ubiquitin-mediated degradation. Given the relevance of cell cycle processes in cancer and neurodegeneration, this review delineates the overlapping cell cycle events, signaling pathways, and mechanisms associated with cell cycle aberrations in cancer and the major neurodegenerative disorders. We suggest that dysregulation of some common fundamental signaling processes triggers anomalous cell cycle activation in cancer cells and neurons. We discussed the possible use of cell cycle inhibitors for neurodegenerative disorders and described the associated challenges. We propose that a greater understanding of the common mechanisms driving cell cycle aberrations in cancer and neurodegenerative disorders will open a new avenue for the development of repurposed drugs.

New spiro-indeno[1,2-b]quinoxalines clubbed with benzimidazole scaffold as CDK2 inhibitors for halting non-small cell lung cancer; stereoselective synthesis, molecular dynamics and structural insights

Despite the crucial role of CDK2 in tumorigenesis, few inhibitors reached clinical trials for managing lung cancer, the leading cause of cancer death. Herein, we report combinatorial stereoselective synthesis of rationally designed spiroindeno[1,2-b]quinoxaline-based CDK2 inhibitors for NSCLC therapy. The design relied on merging pharmacophoric motifs and biomimetic scaffold hopping into this privileged skeleton via cost-effective one-pot multicomponent [3 + 2] cycloaddition reaction. Absolute configuration was assigned by single crystal x-ray diffraction analysis and reaction mechanism was studied by Molecular Electron Density Theory. Initial MTT screening of the series against A549 cells and normal lung fibroblasts Wi-38 elected 6b as the study hit regarding potency (IC50 = 54 nM) and safety (SI = 6.64). In vitro CDK2 inhibition assay revealed that 6b (IC50 = 177 nM) was comparable to roscovitine (IC50 = 141 nM). Docking and molecular dynamic simulations suggested that 6b was stabilised into CDK2 cavity by hydrophobic interactions with key aminoacids.

APPlications of amyloid-β precursor protein metabolites in macrocephaly and autism spectrum disorder

Metabolites of the Amyloid-β precursor protein (APP) proteolysis may underlie brain overgrowth in Autism Spectrum Disorder (ASD). We have found elevated APP metabolites (total APP, secreted (s) APPα, and α-secretase adamalysins in the plasma and brain tissue of children with ASD). In this review, we highlight several lines of evidence supporting APP metabolites' potential contribution to macrocephaly in ASD. First, APP appears early in corticogenesis, placing APP in a prime position to accelerate growth in neurons and glia. APP metabolites are upregulated in neuroinflammation, another potential contributor to excessive brain growth in ASD. APP metabolites appear to directly affect translational signaling pathways, which have been linked to single gene forms of syndromic ASD (Fragile X Syndrome, PTEN, Tuberous Sclerosis Complex). Finally, APP metabolites, and microRNA, which regulates APP expression, may contribute to ASD brain overgrowth, particularly increased white matter, through ERK receptor activation on the PI3K/Akt/mTOR/Rho GTPase pathway, favoring myelination.

Cell cycle deregulation in neurodegenerative diseases

Background: Cell cycle is critical for a wide range of cellular processes such as proliferation, differentiation and apoptosis in dividing cells. Neurons are postmitotic cells which have withdrawn from the cell division cycle. Recent data show us that inappropriate activation of cell cycle regulators including cyclins, cyclin dependent kinases (CDKs) and endogenous cyclin dependent kinase inhibitors (CDKIs) may take part in the aetiology of neurodegenerative diseases. However, the mechanisms for cell cycle reentry in neurodegenerative disease remain unclear.Methods: Electronic databases such as Pubmed, Science Direct, Directory of Open Access Journals, PLOS were searched for relevant articles.Conclusion: The present work reviews basic aspects of cell cycle mechanism, as well as the evidence showing the expression of cell cycle proteins in neurodegenerative disease. We provide a brief summary of these findings and hope to highlight the interaction between the cell cycle reentry and neurodegenerative diseases. Moreover, we outline the possible signaling pathways. However more understanding of the mechanism of cell cycle is of great importance. Because these represents an alternative target for therapeutic interventions, leading to novel treatments of neurodegenerative diseases.

Inhibition of CDK4/6 regulates AD pathology, neuroinflammation and cognitive function through DYRK1A/STAT3 signaling

Repurposing approved drugs is an emerging therapeutic development strategy for Alzheimer's disease (AD). The CDK4/6 inhibitor abemaciclib mesylate is an FDA-approved drug for breast cancer treatment. However, whether abemaciclib mesylate affects Aβ/tau pathology, neuroinflammation, and Aβ/LPS-mediated cognitive impairment is unknown. In this study, we investigated the effects of abemaciclib mesylate on cognitive function and Aβ/tau pathology and found that abemaciclib mesylate improved spatial and recognition memory by regulating the dendritic spine number and neuroinflammatory responses in 5xFAD mice, an Aβ-overexpressing model of AD. Abemaciclib mesylate also inhibited Aβ accumulation by enhancing the activity and protein levels of the Aβ-degrading enzyme neprilysin and the α-secretase ADAM17 and decreasing the protein level of the γ-secretase PS-1 in young and aged 5xFAD mice. Importantly, abemaciclib mesylate suppressed tau phosphorylation in 5xFAD mice and tau-overexpressing PS19 mice by reducing DYRK1A and/or p-GSK3β levels. In wild-type (WT) mice injected with lipopolysaccharide (LPS), abemaciclib mesylate rescued spatial and recognition memory and restored dendritic spine number. In addition, abemaciclib mesylate downregulated LPS-induced microglial/astrocytic activation and proinflammatory cytokine levels in WT mice. In BV2 microglial cells and primary astrocytes, abemaciclib mesylate suppressed LPS-mediated proinflammatory cytokine levels by downregulating AKT/STAT3 signaling. Taken together, our results support repurposing the anticancer drug, CDK4/6 inhibitor abemaciclib mesylate as a multitarget therapeutic for AD pathologies.

Exploring the Role of Glycolytic Enzymes PFKFB3 and GAPDH in the Modulation of Aβ and Neurodegeneration and Their Potential of Therapeutic Targets in Alzheimer's Disease

Alzheimer's disease (AD) is presently the 6th major cause of mortality across the globe. However, it is expected to rise rapidly, following cancer and heart disease, as a leading cause of death among the elderly peoples. AD is largely characterized by metabolic changes linked to glucose metabolism and age-induced mitochondrial failure. Recent research suggests that the glycolytic pathway is required for a range of neuronal functions in the brain including synaptic transmission, energy production, and redox balance; however, alteration in glycolytic pathways may play a significant role in the development of AD. Moreover, it is hypothesized that targeting the key enzymes involved in glucose metabolism may help to prevent or reduce the risk of neurodegenerative disorders. One of the major pro-glycolytic enzyme is 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3 (PFKFB3); it is normally absent in neurons but abundant in astrocytes. Similarly, another key of glycolysis is glyceraldehyde-3-phosphate dehydrogenase (GAPDH) which catalyzes the conversion of aldolase and glyceraldehyde 3 phosphates to 1,3 bisphosphoglycerate. GAPDH has been reported to interact with various neurodegenerative disease-associated proteins, including the amyloid-β protein precursor (AβPP). These findings indicate PFKFB3 and GAPDH as a promising therapeutic target to AD. Current review highlight the contributions of PFKFB3 and GAPDH in the modulation of Aβand AD pathogenesis and further explore the potential of PFKFB3 and GAPDH as therapeutic targets in AD.

Condensed-phase signaling can expand kinase specificity and respond to macromolecular crowding

Phase separation can concentrate biomolecules and accelerate reactions. However, the mechanisms and principles connecting this mesoscale organization to signaling dynamics are difficult to dissect because of the pleiotropic effects associated with disrupting endogenous condensates. To address this limitation, we engineered new phosphorylation reactions within synthetic condensates. We generally found increased activity and broadened kinase specificity. Phosphorylation dynamics within condensates were rapid and could drive cell-cycle-dependent localization changes. High client concentration within condensates was important but not the main factor for efficient phosphorylation. Rather, the availability of many excess client-binding sites together with a flexible scaffold was crucial. Phosphorylation within condensates was also modulated by changes in macromolecular crowding. Finally, the phosphorylation of the Alzheimer's-disease-associated protein Tau by cyclin-dependent kinase 2 was accelerated within condensates. Thus, condensates enable new signaling connections and can create sensors that respond to the biophysical properties of the cytoplasm.

MicroRNA-668-3p regulates oxidative stress and cell damage induced by Aβ1-42 by targeting the OXR1/p53-p21 axis

Background

Alzheimer’s disease (AD) is the most common type of dementia in old age and has become a serious social and medical problem threatening human health. We aimed to explore the mechanisms underlying AD development by screening for microRNAs (miRNAs) that affect AD progression and examining their role in AD development.

Methods

Hematoxylin-eosin (HE) staining, immunohistochemistry, and immunofluorescence (IF) were used to analyze the characteristics of the hippocampus, neuron cell separation, and related protein expression in mice. We used Gene Expression Omnibus (GEO) data analysis to screen miRNAs and mRNAs that affect AD progression, and quantitative reverse transcription polymerase chain reaction (RT-qPCR) and western blot analysis to determine changes in miRNA and mRNA levels before and after amyloid β (Aβ)1-42 induction. In addition, we used luciferase analysis to examine miRNA and mRNA binding and the effect of miRNA/mRNA interaction on neuronal cell proliferation. Apoptosis and reactive oxygen species (ROS) levels were examined using Cell Counting Kit-8 analysis and flow cytometry (FCM), respectively. The enzyme-linked immunosorbent assay was used to analyze changes in neuronal cell-secreted oxidative stress-related protein levels through miRNA/mRNA interaction.

Results

Oxidative stress levels were significantly increased in the AD mouse model. GEO data analysis revealed 67 dysregulated miRNAs, and miR-668-3p was identified as a potential therapeutic target for AD. We found that the AD and Aβ1-42-induced models showed an increase in miR-668-3p and a decrease in oxidation resistance 1 (OXR1) expression. The luciferase analysis results revealed that miR-668-3p may play a role in AD development by targeting OXR1 and promoting intracellular oxidative stress by activating p53-p21 signaling. The final rescue experiment also confirmed that Aβ1-42-induction decreased cell proliferation, increased apoptosis, increased cell cycle arrest, and promoted oxidative stress. Tenovin-1 (TEN) enhanced the effect of Aβ1-42, and the miR-668-3p inhibitor partially alleviated it, although the effect of the miR-668-3p inhibitor was weakened by TEN.

Conclusions

MiR-668-3p negatively regulated OXR1 expression by targeting OXR1, affecting p53-p21 protein signaling, and regulating cell damage and oxidative stress induced by Aβ1-42. Therefore, miR-668-3p may be a potential therapeutic target for AD.

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

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

Novel effective small-molecule inhibitors of protein kinases related to tau pathology in Alzheimer's disease

Background: Alzheimer's disease (AD) drugs in therapy are limited to acetylcholine esterase inhibitors and memantine. Newly developed drugs against a single target structure have an insufficient effect on symptomatic AD patients. Results: Novel aromatically anellated pyridofuranes have been evaluated for inhibition of AD-relevant protein kinases cdk1, cdk2, gsk-3b and Fyn. Best activities have been found for naphthopyridofuranes with a hydroxyl function as part of the 5-substituent and a hydrogen or halogen substituent in the 8-position. Best results in nanomolar ranges were found for benzopyridofuranes with a 6-hydroxy and a 3-alkoxy substitution or an exclusive 6-alkoxy substituent. Conclusion: First lead compounds were identified inhibiting two to three kinases in nanomolar ranges to be qualified as an innovative approach for AD multitargeting.

Regulatory mechanism of cyclins and cyclin-dependent kinases in post-mitotic neuronal cell division

Neurodegenerative diseases (NDDs) are the most common life-threatening disease of the central nervous system and it cause the progressive loss of neuronal cells. The exact mechanism of the disease's progression is not clear and thus line of treatment for NDDs is a baffling issue. During the progression of NDDs, oxidative stress and DNA damage play an important regulatory function, and ultimately induces neurodegeneration. Recently, aberrant cell cycle events have been demonstrated in the progression of different NDDs. However, the pertinent role of signaling mechanism, for instance, post-translational modifications, oxidative stress, DNA damage response pathway, JNK/p38 MAPK, MEK/ERK cascade, actively participated in the aberrant cell cycle reentry induced neuronal cell death. Mounting evidence has demonstrated that aberrant cell cycle re-entry is a major contributing factor in the pathogenesis of NDDs rather than a secondary phenomenon. In the brain of AD patients with mild cognitive impairment, post miotic cell division can be seen in the early stage of the disease. However, in the brain of PD patients, response to various neurotoxic signals, the cell cycle re-entry has been observed that causes neuronal apoptosis. On contrary, the contributing factors that leads to the induction of cell cycle events in mature neurons in HD and ALS brain pathology is remain unclear. Various pharmacological drugs have been developed to reduce the pathogenesis of NDDs, but they are still not helpful in eliminating the cause of these NDDs.

Anti-Oxidative, Anti-Inflammatory and Anti-Apoptotic Effects of Flavonols: Targeting Nrf2, NF-κB and p53 Pathways in Neurodegeneration

Neurodegenerative diseases are one of the leading causes of disability and death worldwide. Intracellular transduction pathways that end in the activation of specific transcription factors are highly implicated in the onset and progression of pathological changes related to neurodegeneration, of which those related to oxidative stress (OS) and neuroinflammation are particularly important. Here, we provide a brief overview of the key concepts related to OS- and neuroinflammation-mediated neuropathological changes in neurodegeneration, together with the role of transcription factors nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor-κB (NF-κB). This review is focused on the transcription factor p53 that coordinates the cellular response to diverse genotoxic stimuli, determining neuronal death or survival. As current pharmacological options in the treatment of neurodegenerative disease are only symptomatic, many research efforts are aimed at uncovering efficient disease-modifying agents. Natural polyphenolic compounds demonstrate powerful anti-oxidative, anti-inflammatory and anti-apoptotic effects, partially acting as modulators of signaling pathways. Herein, we review the current understanding of the therapeutic potential and limitations of flavonols in neuroprotection, with emphasis on their anti-oxidative, anti-inflammatory and anti-apoptotic effects along the Nrf2, NF-κB and p53 pathways. A better understanding of cellular and molecular mechanisms of their action may pave the way toward new treatments.

Attenuation of Pb-induced Aβ generation and autophagic dysfunction via activation of SIRT1: Neuroprotective properties of resveratrol

This study examined the neuroprotective properties of resveratrol (Res) and its target sirtuin1 (SIRT1) against lead (Pb)-mediated toxicity and discovered that both resveratrol treatment and SIRT1 overexpression restored blocked autophagic flux as well as reduced β-amyloid (Aβ) contents. Four-week-old male C57BL/6 mice were employed to consumed 0.2% Pb(Ac)₂ solution or deionized water for 3 months followed by 12 months of Res (50 mg/kg BW) or vehicle gavage. In in vitro study, SH-SY5Y cells were pretreated with the SIRT1 activator SRT1720 (2 μM) or the inhibitor EX527 (2 μM) for 2 h, then 25 μM of Pb(Ac)₂ was added and incubated for 48 h. Western blotting, RT-qPCR, enzyme-linked immunosorbent assay (ELISA), and Lyso-Tracker Red Staining were next used to estimate the potential alterations of the autophagic pathway as well as BACE1-mediated amyloid processing in response to Pb exposure, respectively. Our data revealed that Res treatment or SIRT1 activation resisted the induction of autophagy by Pb exposure through inhibition of LC3 and Beclin-1 expression and promoted the degradation of Aβ and Tau phosphorylation. Besides, the SIRT1 activator (SRT1720) downregulated the expression of BACE1, the rate-limiting enzyme for Aβ production, by inhibiting the activation of nuclear factor-κB (NF-κB) in Pb-treated SH-SY5Y cells, which resulted in reduced Aβ production. Collectively, we verified the role of Res-SIRT1-autophagy as well as the SIRT1-NF-κB-BACE1 pathway in Pb-induced neuronal cell injury by in vivo or in vitro models. Our findings further elucidate the important role of SIRT1 and Res in counteracting Pb neurotoxicity, which may provide new interventions and targets for the subsequent treatment of neurodegenerative diseases.

Computational and Experimental Assessments of Magnolol as a Neuroprotective Agent and Utilization of UiO-66(Zr) as Its Drug Delivery System

The phenolic natural product magnolol exhibits neuroprotective properties through β-amyloid toxicity in PC-12 cells and ameliorative effects against cognitive deficits in a TgCRND8 transgenic mice model. Its bioavailability and blood-brain barrier crossing ability have been significantly improved using the metal-organic framework (MOF) UiO-66(Zr) as a drug delivery system (DDS). To investigate the neuroprotective effects of the Zr-based DDS, magnolol and magnolol-loaded-UiO-66(Zr) (Mag@UiO-66(Zr)) were evaluated for inhibitory activity against β-secretase and AlCl₃-induced neurotoxicity. Due to the moderate inhibition observed for magnolol in vitro, in silico binding studies were explored against β-secretase along with 11 enzymes known to affect Alzheimer's disease (AD). Favorable binding energies against CDK2, CKD5, MARK, and phosphodiesterase 3B (PDE3B) and dynamically stable complexes were noted through molecular docking and molecular dynamic simulation experiments, respectively. The magnolol-loaded DDS UiO-66(Zr) also showed enhanced neuroprotective activity against two pathological indices, namely, neutrophil infiltration and apoptotic neurons, in addition to damage reversal compared to magnolol. Thus, MOFs are promising drug delivery platforms for poorly bioavailable drugs.

Pharmacological relevance of CDK inhibitors in Alzheimer's disease

Evidence suggests that cell cycle activation plays a role in the pathophysiology of neurodegenerative diseases. Alzheimer's disease is a progressive, terminal neurodegenerative disease that affects memory and other important mental functions. Intracellular deposition of Tau protein, a hyperphosphorylated form of a microtubule-associated protein, and extracellular aggregation of Amyloid β protein, which manifests as neurofibrillary tangles (NFT) and senile plaques, respectively, characterize this condition. In recent years, however, several studies have concluded that cell cycle re-entry is one of the key causes of neuronal death in the pathogenesis of Alzheimer's disease. The eukaryotic cell cycle is well-coordinated machinery that performs critical functions in cell replenishment, such as DNA replication, cell creation, repair, and the birth of new daughter cells from the mother cell. The complex interplay between the levels of various cyclins and cyclin-dependent kinases (CDKs) at different checkpoints is needed for cell cycle synchronization. CDKIs (cyclin-dependent kinase inhibitors) prevent cyclin degradation and CDK inactivation. Different external and internal factors regulate them differently, and they have different tissue expression and developmental functions. The checkpoints ensure that the previous step is completed correctly before starting the new cell cycle phase, and they protect against the transfer of defects to the daughter cells. Due to the development of more selective and potent ATP-competitive CDK inhibitors, CDK inhibitors appear to be on the verge of having a clinical impact. This avenue is likely to yield new and effective medicines for the treatment of cancer and other neurodegenerative diseases. These new methods for recognizing CDK inhibitors may be used to create non-ATP-competitive agents that target CDK4, CDK5, and other CDKs that have been recognized as important therapeutic targets in Alzheimer's disease treatment.

Impact of Alcohol Abuse on Susceptibility to Rare Neurodegenerative Diseases

Despite the prevalence and well-recognized adverse effects of prenatal alcohol exposure and alcohol use disorder in the causation of numerous diseases, their potential roles in the etiology of neurodegenerative diseases remain poorly characterized. This is especially true of the rare neurodegenerative diseases, for which small population sizes make it difficult to conduct broad studies of specific etiological factors. Nonetheless, alcohol has potent and long-lasting effects on neurodegenerative substrates, at both the cellular and systems levels. This review highlights the general effects of alcohol in the brain that contribute to neurodegeneration across diseases, and then focuses on specific diseases in which alcohol exposure is likely to play a major role. These specific diseases include dementias (alcohol-induced, frontotemporal, and Korsakoff syndrome), ataxias (cerebellar and frontal), and Niemann-Pick disease (primarily a Type B variant and Type C). We conclude that there is ample evidence to support a role of alcohol abuse in the etiology of these diseases, but more work is needed to identify the primary mechanisms of alcohol's effects.

When Good Kinases Go Rogue: GSK3, p38 MAPK and CDKs as Therapeutic Targets for Alzheimer's and Huntington's Disease

Alzheimer's disease (AD) is a mostly sporadic brain disorder characterized by cognitive decline resulting from selective neurodegeneration in the hippocampus and cerebral cortex whereas Huntington's disease (HD) is a monogenic inherited disorder characterized by motor abnormalities and psychiatric disturbances resulting from selective neurodegeneration in the striatum. Although there have been numerous clinical trials for these diseases, they have been unsuccessful. Research conducted over the past three decades by a large number of laboratories has demonstrated that abnormal actions of common kinases play a key role in the pathogenesis of both AD and HD as well as several other neurodegenerative diseases. Prominent among these kinases are glycogen synthase kinase (GSK3), p38 mitogen-activated protein kinase (MAPK) and some of the cyclin-dependent kinases (CDKs). After a brief summary of the molecular and cell biology of AD and HD this review covers what is known about the role of these three groups of kinases in the brain and in the pathogenesis of the two neurodegenerative disorders. The potential of targeting GSK3, p38 MAPK and CDKS as effective therapeutics is also discussed as is a brief discussion on the utilization of recently developed drugs that simultaneously target two or all three of these groups of kinases. Multi-kinase inhibitors either by themselves or in combination with strategies currently being used such as immunotherapy or secretase inhibitors for AD and knockdown for HD could represent a more effective therapeutic approach for these fatal neurodegenerative diseases.

Influence of Anemia on Postoperative Cognitive Function in Patients Undergo Hysteromyoma Surgery

Cognitive dysfunction is a common disease in aging population. This study aims to compare the influence of different degrees of anemia on the cognitive function of patients undergo hysteromyoma surgery. Sixty-one patients aged 18-60 years who underwent uterine fibroid surgery in the Second Affiliated Hospital of Shantou University Medical College from March 2019 to December 2020 were selected for this study. Patients were divided into three groups: group normal (Group N, patients have no anemia), group of mild anemia (Group Mi, patients have mild anemia) and group of moderate anemia (Group Mo, patients had moderate anemia). Combined spinal and epidural anesthesia were administered. Cognitive function tests were performed 1 day before the surgery and repeated at the 5th and 30th days after surgery. Peripheral venous blood samples from patients were collected before the surgery, right after surgery and at the 24th and 72nd hours after surgery. The contents of S-100β, IL-6, TNF-α and IL-1β in serum samples were determined by ELISA. It was found that there were no significant differences in general characteristics of patients among Group N, Group Mi and Group Mo (p > 0.05). Nine patients developed postoperative cognitive dysfunction after surgery, and the incidence was 14.75% (9/61). The incidence of postoperative cognitive dysfunction (POCD) was 40% in Group Mo, which was higher than that in Group N and Group Mi. The difference was statistically significant (p < 0.05). Inflammatory factors in patients with POCD were higher in post-surgery than before-surgery (p < 0.05), while there was no statistical significance in the difference of inflammatory factors of patients without POCD before and after surgery (p > 0.05). Taken together, this study suggested that moderate anemia could be a risk factor of POCD in patients undergoing hysteromyoma surgeries. This study will help surgeons developing measures for preventing the occurrence of POCD.

Neuronal Cell Cycle Re-Entry Enhances Neuropathological Features in AppNLF Knock-In Mice

BACKGROUND

Aberrant cell cycle re-entry is a well-documented process occurring early in Alzheimer's disease (AD). This is an early feature of the disease and may contribute to disease pathogenesis.

OBJECTIVE

To assess the effect of forced neuronal cell cycle re-entry in mice expressing humanized Aβ, we crossed our neuronal cell cycle re-entry mouse model with AppNLF knock-in (KI) mice.

METHODS

Our neuronal cell cycle re-entry (NCCR) mouse model is bitransgenic mice heterozygous for both Camk2a-tTA and TRE-SV40T. The NCCR mice were crossed with AppNLF KI mice to generate NCCR-AppNLF animals. Using this tet-off system, we triggered NCCR in our animals via neuronal expression of SV40T starting at 1 month of age. The animals were examined at the following time points: 9, 12, and 18 months of age. Various neuropathological features in our mice were evaluated by image analysis and stereology on brain sections stained using either immunofluorescence or immunohistochemistry.

RESULTS

We show that neuronal cell cycle re-entry in humanized Aβ plaque producing AppNLF KI mice results in the development of additional AD-related pathologies, namely, pathological tau, neuroinflammation, brain leukocyte infiltration, DNA damage response, and neurodegeneration.

CONCLUSION

Our findings show that neuronal cell cycle re-entry enhances AD-related neuropathological features in AppNLF mice and highlight our unique AD mouse model for studying the pathogenic role of aberrant cell cycle re-entry in AD.

Synaptic Organizers in Alzheimer's Disease: A Classification Based on Amyloid-β Sensitivity

Synaptic pathology is one of the major hallmarks observed from the early stage of Alzheimer’s disease (AD), leading to cognitive and memory impairment characteristic of AD patients. Synaptic connectivity and specificity are regulated by multiple trans-bindings between pre- and post-synaptic organizers, the complex of which exerts synaptogenic activity. Neurexins (NRXs) and Leukocyte common antigen-related receptor protein tyrosine phosphatases (LAR-RPTPs) are the major presynaptic organizers promoting synaptogenesis through their distinct binding to a wide array of postsynaptic organizers. Recent studies have shown that amyloid-β oligomers (AβOs), a major detrimental molecule in AD, interact with NRXs and neuroligin-1, an NRX-binding postsynaptic organizer, to cause synaptic impairment. On the other hand, LAR-RPTPs and their postsynaptic binding partners have no interaction with AβOs, and their synaptogenic activity is maintained even in the presence of AβOs. Here, we review the current evidence regarding the involvement of synaptic organizers in AD, with a focus on Aβ synaptic pathology, to propose a new classification where NRX-based and LAR-RPTP-based synaptic organizing complexes are classified into Aβ-sensitive and Aβ-insensitive synaptic organizers, respectively. We further discuss how their different Aβ sensitivity is involved in Aβ vulnerability and tolerance of synapses for exploring potential therapeutic approaches for AD.

Cell Cycle Deficits in Neurodegenerative Disorders: Uncovering Molecular Mechanisms to Drive Innovative Therapeutic Development

Cell cycle dysregulation has been implicated in the pathogenesis of neurodegenerative disorders. Specialised function obligates neuronal cells to subsist in a quiescent state of cell cycle once differentiated and therefore the circumstances and mechanisms underlying aberrant cell cycle activation in post-mitotic neurons in physiological and disease conditions remains an intriguing area of research. There is a strict requirement of concurrence to cell cycle regulation for neurons to ensure intracellular biochemical conformity as well as interrelationship with other cells within neural tissues. This review deliberates on various mechanisms underlying cell cycle regulation in neuronal cells and underscores potential implications of their non-compliance in neural pathology. Recent research suggests that successful duplication of genetic material without subsequent induction of mitosis induces inherent molecular flaws that eventually assert as apoptotic changes. The consequences of anomalous cell cycle activation and subsequent apoptosis are demonstrated by the increased presence of molecular stress response and apoptotic markers. This review delineates cell cycle events under normal physiological conditions and deficits amalgamated by alterations in protein levels and signalling pathways associated with cell-division are analysed. Cell cycle regulators essentially, cyclins, CDKs, cip/kip family of inhibitors, caspases, bax and p53 have been identified to be involved in impaired cell cycle regulation and associated with neural pathology. The pharmacological modulators of cell cycle that are shown to impart protection in various animal models of neurological deficits are summarised. Greater understanding of the molecular mechanisms that are indispensable to cell cycle regulation in neurons in health and disease conditions will facilitate targeted drug development for neuroprotection.

Correlation of pyroglutamate amyloid β and ptau Ser202/Thr205 levels in Alzheimer's disease and related murine models

Senile plaques frequently contain Aβ-pE(3), a N-terminally truncated Aβ species that is more closely linked to AD compared to other Aβ species. Tau protein is highly phosphorylated at several residues in AD, and specifically phosphorylation at Ser202/Thr205 is known to be increased in AD. Several studies suggest that formation of plaques and tau phosphorylation might be linked to each other. To evaluate if Aβ-pE(3) and ptau Ser202/Thr205 levels correlate in human and transgenic AD mouse models, we analyzed human cortical and hippocampal brain tissue of different Braak stages as well as murine brain tissue of two transgenic mouse models for levels of Aβ-pE(3) and ptau Ser202/Thr205 and correlated the data. Our results show that Aβ-pE(3) formation is increased at early Braak stages while ptau Ser202/Thr205 mostly increases at later stages. Further analyses revealed strongest correlations between the two pathologies in the temporal, frontal, cingulate, and occipital cortex, however correlation in the hippocampus was weaker. Evaluation of murine transgenic brain tissue demonstrated a slow but steady increase of Aβ-pE(3) from 6 to 12 months of age in the cortex and hippocampus of APP_SL mice, and a very early and strong Aβ-pE(3) increase in 5xFAD mice. ptau Ser202/Thr205 levels increased at the age of 9 months in APP_SL mice and at 6 months in 5xFAD mice. Our results show that Aβ-pE(3) and ptau Ser202/Thr205 levels strongly correlate in human as well as murine tissues, suggesting that tau phosphorylation might be amplified by Aβ-pE(3).

Molecular crosstalk between cancer and neurodegenerative diseases

The progression of cancers and neurodegenerative disorders is largely defined by a set of molecular determinants that are either complementarily deregulated, or share remarkably overlapping functional pathways. A large number of such molecules have been demonstrated to be involved in the progression of both diseases. In this review, we particularly discuss our current knowledge on p53, cyclin D, cyclin E, cyclin F, Pin1 and protein phosphatase 2A, and their implications in the shared or distinct pathways that lead to cancers or neurodegenerative diseases. In addition, we focus on the inter-dependent regulation of brain cancers and neurodegeneration, mediated by intercellular communication between tumor and neuronal cells in the brain through the extracellular microenvironment. Finally, we shed light on the therapeutic perspectives for the treatment of both cancer and neurodegenerative disorders.

"Olfactory Three-Needle" Enhances Spatial Learning and Memory Ability in SAMP8 Mice

As one of the most important therapies in complementary and alternative medicine, acupuncture has been used in the treatment of Alzheimer's disease (AD). Acupuncture of “olfactory three-needle” manipulation can improve the cognitive ability of AD patients. However, the mechanism of “olfactory three-needle” in AD remains largely unknown. Here, we identified that the “olfactory three-needle” therapy and eugenol olfactory stimulation both reduced the deposition of β-amyloid (Aβ) protein and increased the expression of synaptophysin (SYP), but only the “olfactory three-needle” enhanced the spatial learning and memory ability of SAMP8. Remarkably, the “olfactory three-needle” inhibited the phosphorylation of p38MAPK and the excessive activation of microglia (MG) in the hippocampus. Our study demonstrates that the “olfactory three-needle” enhances spatial learning and memory ability by inhibiting the phosphorylation of p38MAPK and the excessive activation of MG to reduce the neuroinflammatory response and neurotoxicity of Aβ and promote synaptic regeneration, but it was not completely consistent with the stimulation of the olfactory system.

CBX4 promotes the proliferation and metastasis via regulating BMI-1 in lung cancer

Proliferation and metastasis are significantly malignant characteristics of human lung cancer, but the underlying molecular mechanisms are poorly understood. Chromobox 4 (CBX4), a member of the Polycomb group (PcG) family of epigenetic regulatory factors, enhances cellular proliferation and promotes cancer cell migration. However, the effect of CBX4 in the progression of lung cancer is not fully understood. We found that CBX4 is highly expressed in lung tumours compared with adjacent normal tissues. Overexpression of CBX4 significantly promotes cell proliferation and migration in human lung cancer cell lines. The knockdown of CBX4 obviously suppresses the cell growth and migration of human lung cancer cells in vitro. Also, the proliferation and metastasis in vivo are blocked by CBX4 knockdown. Furthermore, CBX4 knockdown effectively arrests cell cycle at the G0/G1 phase through suppressing the expression of CDK2 and Cyclin E and decreases the formation of filopodia through suppressing MMP2, MMP9 and CXCR4. Additionally, CBX4 promotes proliferation and metastasis via regulating the expression of BMI-1 which is a significant regulator of proliferation and migration in lung cancer cells. Taken together, these data suggest that CBX4 is not only a novel prognostic marker but also may be a potential therapeutic target in lung cancer.

NGF protects neuroblastoma cells against β-amyloid-induced apoptosis via the Nrf2/HO-1 pathway

As one of the main neurotrophic factors, nerve growth factor (NGF) participates in various processes related to viability, plasticity, and neuronal growth. NGF is known to protect against cell death and toxicity triggered by β‐amyloid (Aβ), but the underlying mechanism remains unclear. Here, we investigated this process in SKNSH neuroblastoma, in which NGF reduced cell death induced by Aβ25–35. Furthermore, NGF suppressed the production of reactive oxygen species (ROS) and promoted antioxidant function via Aβ25–35. Additionally, we demonstrated that NGF impaired the activation of the JNK/c‐Jun signaling pathway and significantly increased Nrf2 nuclear translocation and HO‐1 expression. Nrf2 elimination abolished the protective effect of NGF‐1 on Aβ25–35‐induced ROS generation, apoptosis, and activation of the JNK/c‐Jun pathway. The results of our study indicate that NGF protects neuroblastoma against injury triggered by Aβ25–35 via suppression of ROS–JNK/c‐Jun pathway stimulation through the Nrf2/HO‐1 pathway.

Nerve growth factor (NGF) promotes the nuclear translocation of Nrf2 and subsequently upregulates HO‐1 expression. This reduces the levels of reactive oxygen species (ROS), which attenuates the activation of JNK/c‐Jun pathway and eventually contributes to deceased cell apoptosis. The present discovery of this novel NGF/Nrf2/HO‐1 pathway and ROS–JNK/c‐Jun pathway identifies new clinical targets for therapeutic intervention of Alzheimer's disease.

Neuroprotective effects of urolithin A on H2O2-induced oxidative stress-mediated apoptosis in SK-N-MC cells

BACKGROUND/OBJECTIVES

Oxidative stress causes cell damage and death, which contribute to the pathogenesis of neurodegenerative diseases. Urolithin A (UA), a gut microbial-derived metabolite of ellagitannins and ellagic acid, has high bioavailability and various health benefits such as antioxidant and anti-inflammatory effects. However, it is unknown whether it has protective effects against oxidative stress-induced cell death. We investigated whether UA ameliorates H₂O₂-induced neuronal cell death.

MATERIALS/METHODS

We induced oxidative damage with 300 µM H₂O₂ after UA pretreatment at concentrations of 1.25, 2.5, and 5 µM in SK-N-MC cells. Cytotoxicity and cell viability were determined using the CCK-8 assay. The formation of reactive oxygen species (ROS) was measured using a 2,7-dichlorofluorescein diacetate assay. Hoechst 33342 staining was used to characterize morphological changes in apoptotic cells. The expressions of apoptosis proteins were measured using Western blotting.

RESULTS

UA significantly increased cell viability and decreased intracellular ROS production in a dose-dependent manner in SK-N-MC cells. It also decreased the Bax/Bcl-2 ratio and the expressions of cytochrome c, cleaved caspase-9, cleaved caspase-3, and cleaved PARP. In addition, it suppressed the phosphorylation of the p38 mitogen-activated protein kinase (MAPK) pathway.

CONCLUSIONS

UA attenuates oxidative stress-induced apoptosis via inhibiting the mitochondrial-related apoptosis pathway and modulating the p38 MAPK pathway, suggesting that it may be an effective neuroprotective agent.

TMP21 in Alzheimer's Disease: Molecular Mechanisms and a Potential Target

Alzheimer’s disease (AD) is the most common form of dementia in the elderly, which is characterized by progressive cognitive impairment. Neuritic plaques, neurofibrillary tangles and neuronal loss are the major neuropathological hallmarks in AD brains. TMP21 is a key molecule for protein trafficking in cells. Growing evidence indicates that TMP21 is dysregulated in AD, which plays a pivotal role in neuritic plaque formation. Therefore, we aim to review the dysregulation of TMP21 in AD, the role of TMP21 in neuritic plaque formation and underlying mechanisms. Moreover, the potential role of TMP21 in neurofibrillary tangle formation, synaptic impairment and neuronal loss is discussed. It will provide an outlook into the potential of regulating TMP21 as a therapeutic approach for AD treatment.

Primary neurons can enter M-phase

Differentiated neurons can undergo cell cycle re-entry during pathological conditions, but it remains largely accepted that M-phase is prohibited in these cells. Here we show that primary neurons at post-synaptogenesis stages of development can enter M-phase. We induced cell cycle re-entry by overexpressing a truncated Cyclin E isoform fused to Cdk2. Cyclin E/Cdk2 expression elicits canonical cell cycle checkpoints, which arrest cell cycle progression and trigger apoptosis. As in mitotic cells, checkpoint abrogation enables cell cycle progression through S and G2-phases into M-phase. Although most neurons enter M-phase, only a small subset undergo cell division. Alternatively, neurons can exit M-phase without cell division and recover the axon initial segment, a structural determinant of neuronal viability. We conclude that neurons and mitotic cells share S, G2 and M-phase regulation.

Selective Autophagy Regulates Cell Cycle in Cancer Therapy

Aberrant function of cell cycle regulators results in uncontrolled cell proliferation, making them attractive therapeutic targets in cancer treatment. Indeed, survival of many cancers exclusively relies on these proteins, and several specific inhibitors are in clinical use. Although the ubiquitin-proteasome system is responsible for the periodic quality control of cell cycle proteins during cell cycle progression, increasing evidence clearly demonstrates the intimate interaction between cell cycle regulation and selective autophagy, important homeostasis maintenance machinery. However, these studies have often led to divergent rather than unifying explanations due to complexity of the autophagy signaling network, the inconsistent functions between general autophagy and selective autophagy, and the different characteristics of autophagic substrates. In this review, we highlight current data illustrating the contradictory and important role of cell cycle proteins in regulating autophagy. We also focus on how selective autophagy acts as a central mechanism to maintain orderly DNA repair and genome integrity by degrading specific cell cycle proteins, regulating cell division, and promoting DNA damage repair. We further discuss the ways in which selective autophagy may impact the cell cycle regulators, since failure to appropriately remove these can interfere with cell death-related processes, including senescence and autophagy-related cell death. Imbalanced cell proliferation is typically utilized by cancer cells to acquire resistance. Finally, we discuss the possibility of a potent anticancer therapeutic strategy that targets selective autophagy or autophagy and cell cycle together.

Cyclin-Dependent Kinase 2 Inhibitors in Cancer Therapy: An Update

Cyclin-dependent kinase 2 (CDK2) drives the progression of cells into the S- and M-phases of the cell cycle. CDK2 activity is largely dispensable for normal development, but it is critically associated with tumor growth in multiple cancer types. Although the role of CDK2 in tumorigenesis has been controversial, emerging evidence proposes that selective CDK2 inhibition may provide a therapeutic benefit against certain tumors, and it continues to appeal as a strategy to exploit in anticancer drug development. Several small-molecule CDK2 inhibitors have progressed to the clinical trials. However, a CDK2-selective inhibitor is yet to be discovered. Here, we discuss the latest understandings of the role of CDK2 in normal and cancer cells, review the core pharmacophores used to target CDK2, and outline strategies for the rational design of CDK2 inhibitors. We attempt to provide an outlook on how CDK2-selective inhibitors may open new avenues for cancer therapy.

Momordica charantia Ethanol Extract Attenuates H₂O₂-Induced Cell Death by Its Antioxidant and Anti-Apoptotic Properties in Human Neuroblastoma SK-N-MC Cells

Oxidative stress, which is induced by reactive oxygen species (ROS), causes cellular damage which contributes to the pathogenesis of neurodegenerative diseases. Momordica charantia (MC), a traditional medicinal plant, is known to have a variety of health benefits, such as antidiabetic, anti-inflammatory, and antioxidant effects. However, it is unknown whether MC has protective effects against oxidative stress-induced neuronal cell death. The aim of this study was to investigate the potential action of MC on oxidative stress induced by H₂O₂. First, we tested whether the pretreatment of Momordica charantia ethanol extract (MCEE) attenuates H₂O₂-induced cell death in human neuroblastoma SK-N-MC cells. MCEE pretreatment significantly improved cell viability and apoptosis that deteriorated by H₂O₂. Further, MCEE ameliorated the imbalance between intracellular ROS production and removal through the enhancement of the intracellular antioxidant system. Intriguingly, the inhibition of apoptosis was followed by the blockage of mitochondria-dependent cell death cascades and suppression of the phosphorylation of the mitogen-activated protein kinase signaling (MAPKs) pathway by MCEE. Taken together, MCEE was shown to be effective in protecting against H₂O₂-induced cell death through its antioxidant and anti-apoptotic properties.

Computer-Aided Multi-Target Management of Emergent Alzheimer's Disease

Alzheimer's disease (AD) represents an enormous global health burden in terms of human suffering and economic cost. AD management requires a shift from the prevailing paradigm targeting pathogenesis to design and develop effective drugs with adequate success in clinical trials. Therefore, it is of interest to report a review on amyloid beta (Aβ) effects and other multi-targets including cholinesterase, NFTs, tau protein and TNF associated with brain cell death to be neuro-protective from AD. It should be noted that these molecules have been generated either by target-based or phenotypic methods. Hence, the use of recent advancements in nanomedicine and other natural compounds screening tools as a feasible alternative for circumventing specific liabilities is realized. We review recent developments in the design and identification of neuro-degenerative compounds against AD generated using current advancements in computational multi-target modeling algorithms reflected by theragnosis (combination of diagnostic tests and therapy) concern.

Beneficial Effects of Silibinin Against Kainic Acid-induced Neurotoxicity in the Hippocampus in vivo

Silibinin, an active constituent of silymarin extracted from milk thistle, has been previously reported to confer protection to the adult brain against neurodegeneration. However, its effects against epileptic seizures have not been examined yet. In order to investigate the effects of silibinin against epileptic seizures, we used a relevant mouse model in which seizures are manifested as status epilepticus, induced by kainic acid (KA) treatment. Silibinin was injected intraperitoneally, starting 1 day before an intrahippocampal KA injection and continued daily until analysis of each experiment. Our results indicated that silibinin-treatment could reduce seizure susceptibility and frequency of spontaneous recurrent seizures (SRS) induced by KA administration, and attenuate granule cell dispersion (GCD), a morphological alteration characteristic of the dentate gyrus (DG) in temporal lobe epilepsy (TLE). Moreover, its treatment significantly reduced the aberrant levels of apoptotic, autophagic and pro-inflammatory molecules induced by KA administration, resulting in neuroprotection in the hippocampus. Thus, these results suggest that silibinin may be a beneficial natural compound for preventing epileptic events.