Reduction BACE1 expression via suppressing NF-κB mediated signaling by Tamibarotene in a mouse model of Alzheimer's disease

Associations of CSF BACE1 with amyloid pathology, neurodegeneration, and cognition in Alzheimer's disease

Β-site amyloid precursor protein (APP) cleaving enzyme (BACE1) is a crucial protease in the production of amyloid-β (Aβ) in Alzheimer's disease (AD) patients. However, the side effects observed in clinical trials of BACE1 inhibitors, including reduction in brain volume and cognitive worsening, suggest that the exact role of BACE1 in AD pathology is not fully understood. To further investigate this, we examined cerebrospinal fluid (CSF) levels of BACE1 and its cleaved product sAPPβ that reflects BACE1 activity in the China Aging and Neurodegenerative Disorder Initiative cohort. We found significant correlations between CSF BACE1 or sAPPβ levels and CSF Aβ40, Aβ42, and Aβ42/Aβ40 ratio, but not with amyloid deposition detected by 18F-Florbetapir PET. Additionally, CSF BACE1 and sAPPβ levels were positively associated with cortical thickness in multiple brain regions, and higher levels of sAPPβ were linked to increased cortical glucose metabolism in frontal and supramarginal areas. Interestingly, individuals with higher baseline levels of CSF BACE1 exhibited slower rates of brain volume reduction and cognitive worsening over time. This suggests that increased levels and activity of BACE1 may not be the determining factor for amyloid deposition, but instead, may be associated with increased neuronal activity and potentially providing protection against neurodegeneration in AD.

Targeting blood brain barrier-Remote ischemic conditioning alleviates cognitive impairment in female APP/PS1 rats

AIMS

Alzheimer's disease (AD) is a significant global health concern, and it is crucial that we find effective methods to prevent or slow down AD progression. Recent studies have highlighted the essential role of blood vessels in clearing Aβ, a protein that contributes to AD. Scientists are exploring blood biomarkers as a potential tool for future AD diagnosis. One promising method that may help prevent AD is remote ischemic conditioning (RIC). RIC involves using sub-lethal ischemic-reperfusion cycles on limbs. However, a comprehensive understanding of how RIC can prevent AD and its long-term effectiveness is still lacking. Further research is essential to fully comprehend the potential benefits of RIC in preventing AD.

METHODS

Female wild-type (WT) and APP/PS1 transgenic rats, aged 12 months, underwent ovariectomy and were subsequently assigned to WT, APP/PS1, and APP/PS1 + RIC groups. RIC was conducted five times a week for 4 weeks. The rats' depressive and cognitive behaviors were evaluated using force swimming, open-field tests, novel objective recognition, elevated plus maze, and Barnes maze tests. Evaluation of the neurovascular unit (NVU), synapses, vasculature, astrocytes, and microglia was conducted using immunofluorescence staining (IF), Western blot (WB), and transmission electron microscopy (TEM). Additionally, the cerebro-vasculature was examined using micro-CT, and cerebral blood flow (CBF) was measured using Speckle Doppler. Blood-brain barrier (BBB) permeability was determined by measuring the Evans blue leakage. Finally, Aβ levels in the rat frontal cortex were measured using WB, ELISA, or IF staining.

RESULTS

RIC enhanced memory-related protein expression and rescued depressive-like behavior and cognitive decline in APP/PS1 transgenic rats. Additionally, the intervention protected NVU in the rat frontal cortex, as evidenced by (1) increased expression of TJ (tight junction) proteins, pericyte marker PDGFRβ, and glucose transporter 1 (GLUT1), as well as decreased VCAM1; (2) mitigation of ultrastructure impairment in neuron, cerebral vascular, and astrocyte; (3) upregulation of A2 astrocyte phenotype markers and downregulation of A1 phenotype markers, indicating a shift toward a healthier phenotype. Correspondingly, RIC intervention alleviated neuroinflammation, as evidenced by the decreased Iba1 level, a microglia marker. Meanwhile, RIC intervention elevated CBF in frontal cortex of the rats. Notably, RIC intervention effectively suppressed Aβ toxicity, as demonstrated by the enhancement of α-secretase and attenuation of β-secretase (BACE1) and γ- secretase and Aβ1-42 and Aβ1-40 levels as well.

CONCLUSION

Chronic RIC intervention exerts vascular and neuroprotective roles, suggesting that RIC could be a promising therapeutic strategy targeting the BBB and NVU during AD development.

Cancer drugs with high repositioning potential for Alzheimer's disease

INTRODUCTION

Despite the recent full FDA approval of lecanemab, there is currently no disease modifying therapy (DMT) that can efficiently slow down the progression of Alzheimer's disease (AD) in the general population. This statement emphasizes the need to identify novel DMTs in the shortest time possible to prevent a global epidemic of AD cases as the world population experiences an increase in lifespan.

AREAS COVERED

Here, we review several classes of anti-cancer drugs that have been or are being investigated in Phase II/III clinical trials for AD, including immunomodulatory drugs, RXR agonists, sex hormone therapies, tyrosine kinase inhibitors, and monoclonal antibodies.

EXPERT OPINION

Given the overall course of brain pathologies during the progression of AD, we express a great enthusiasm for the repositioning of anti-cancer drugs as possible AD DMTs. We anticipate an increasing number of combinatorial therapy strategies to tackle AD symptoms and their underlying pathologies. However, we strongly encourage improvements in clinical trial study designs to better assess target engagement and possible efficacy over sufficient periods of drug exposure.

NF-κB Pathway and Its Inhibitors: A Promising Frontier in the Management of Alzheimer's Disease

The nuclear factor kappa B (NF-κB) pathway has emerged as a pivotal player in the pathogenesis of various diseases, including neurodegenerative illnesses like Alzheimer's disease (AD). The involvement of the NF-κB pathway in immune system responses, inflammation, oxidative stress, and neuronal survival highlights its significance in AD progression. We discuss the advantages of NF-κB pathway inhibition, including the potential to mitigate neuroinflammation, modulate amyloid beta (Aβ) production, and promote neuronal survival. However, we also acknowledge the limitations and challenges associated with this approach. Balancing the fine line between dampening inflammation and preserving physiological immune responses is critical to avoid unintended consequences. This review combines current knowledge on the NF-κB pathway's intricate involvement in AD pathogenesis, emphasizing its potential as a therapeutic target. By evaluating both advantages and limitations, we provide a holistic view of the feasibility and challenges of NF-κB pathway modulation in AD treatment. As the quest for effective AD therapies continues, an in-depth understanding of the NF-κB pathway's multifaceted roles will guide the development of targeted interventions with the potential to improve AD management.

The neurobiology and therapeutic potential of multi-targeting β-secretase, glycogen synthase kinase 3β and acetylcholinesterase in Alzheimer's disease

Alzheimer's Disease (AD) is the most common form of dementia, affecting almost 50 million of people around the world, characterized by a complex and age-related progressive pathology with projections to duplicate its incidence by the end of 2050. AD pathology has two major hallmarks, the amyloid beta (Aβ) peptides accumulation and tau hyperphosphorylation, alongside with several sub pathologies including neuroinflammation, oxidative stress, loss of neurogenesis and synaptic dysfunction. In recent years, extensive research pointed out several therapeutic targets which have shown promising effects on modifying the course of the disease in preclinical models of AD but with substantial failure when transposed to clinic trials, suggesting that modulating just an isolated feature of the pathology might not be sufficient to improve brain function and enhance cognition. In line with this, there is a growing consensus that an ideal disease modifying drug should address more than one feature of the pathology. Considering these evidence, β-secretase (BACE1), Glycogen synthase kinase 3β (GSK-3β) and acetylcholinesterase (AChE) has emerged as interesting therapeutic targets. BACE1 is the rate-limiting step in the Aβ production, GSK-3β is considered the main kinase responsible for Tau hyperphosphorylation, and AChE play an important role in modulating memory formation and learning. However, the effects underlying the modulation of these enzymes are not limited by its primarily functions, showing interesting effects in a wide range of impaired events secondary to AD pathology. In this sense, this review will summarize the involvement of BACE1, GSK-3β and AChE on synaptic function, neuroplasticity, neuroinflammation and oxidative stress. Additionally, we will present and discuss new perspectives on the modulation of these pathways on AD pathology and future directions on the development of drugs that concomitantly target these enzymes.

Anti-inflammatory Action of BT75, a Novel RARα Agonist, in Cultured Microglia and in an Experimental Mouse Model of Alzheimer's Disease

BT75, a boron-containing retinoid, is a novel retinoic acid receptor (RAR)α agonist synthesized by our group. Previous studies indicated that activation of retinoic acid (RA) signaling may attenuate progression of Alzheimer's disease (AD). Presently, we aimed to examine the anti-inflammatory effect of BT75 and explore the possible mechanism using cultured cells and an AD mouse model. Pretreatment with BT75 (1-25 µM) suppressed the release of nitric oxide (NO) and IL-1β in the culture medium of mouse microglial SIM-A9 cells activated by LPS. BMS195614, an RARα antagonist, partially blocked the inhibition of NO production by BT75. Moreover, BT75 attenuated phospho-Akt and phospho-NF-κB p65 expression augmented by LPS. In addition, BT75 elevated arginase 1, IL-10, and CD206, and inhibited inducible nitric oxide synthase (iNOS) and IL-6 formation in LPS-treated SIM-A9 cells, suggesting the promotion of M1-M2 microglial phenotypic polarization. C57BL/6 mice were injected intracerebroventricularly (icv) with streptozotocin (STZ) (3 mg/kg) to provide an AD-like mouse model. BT75 (5 mg/kg) or the vehicle was intraperitoneally (ip) injected to icv-STZ mice once a day for 3 weeks. Immunohistochemical analyses indicated that GFAP-positive cells and rod or amoeboid-like Iba1-positive cells, which increased in the hippocampal fimbria of icv-STZ mice, were reduced by BT75 treatment. Western blot results showed that BT75 decreased levels of neuronal nitric oxide synthase (nNOS), GFAP, and phosphorylated Tau, and increased levels of synaptophysin in the hippocampus of icv-STZ mice. BT75 may attenuate neuroinflammation by affecting the Akt/NF-κB pathway and microglial M1-M2 polarization in LPS-stimulated SIM-A9 cells. BT75 also reduced AD-like pathology including glial activation in the icv-STZ mice. Thus, BT75 may be a promising anti-inflammatory and neuroprotective agent worthy of further AD studies.

Emerging therapeutics agents and recent advances in drug repurposing for Alzheimer's disease

Alzheimer's disease (AD) is a multivariate and diversified disease and affects the most sensitive areas of the brain, the cerebral cortex, and the hippocampus. AD is a progressive age-related neurodegenerative disease most often associated with memory deficits and cognition that get more worsen over time. The central theory on the pathophysiological hallmark features of AD is characterized by the accumulation of amyloid β (Aβ) peptides, also associated with tau proteins (τ) dysfunctioning which leads to distorted microtubular structure, affects the cholinergic system, and mitochondrial biogenesis. This review emphasizes how simple it is to find novel treatments for AD and focuses on several recently developed medications through repurposing that can speed up traditional drug development.

Activation of the RARα Attenuated CSF Hypersecretion to Inhibit Hydrocephalus Development via Regulating the MAFB/MSR1 Pathway

Hydrocephalus has been observed in rats with spontaneous hypertension (SHRs). It has been demonstrated that activation of the oxidative stress related protein retinoic acid receptor alpha (RARα) has neuroprotective impacts. Our investigation aims to determine the potential role and mechanism of RARα in hydrocephalus. The RARα-specific agonist (Am80) and RARα inhibitor (AGN196996) were used to investigate the role of RARα in cerebrospinal fluid (CSF) secretion in the choroid plexus of SHRs. Evaluations of CSF secretion, ventricular volume, Western blotting, and immunofluorescent staining were performed. Hydrocephalus and CSF hypersecretion were identified in SHRs but not in Wistar-Kyoto rats, occurring at the age of 7 weeks. The RARα/MAFB/MSR1 pathway was also activated in SHRs. Therapy with Am80 beginning in week 5 decreased CSF hypersecretion, hydrocephalus development, and pathological changes in choroid plexus alterations by week 7. AGN196996 abolished the effect of Am80. In conclusion, activation of the RARα attenuated CSF hypersecretion to inhibit hydrocephalus development via regulating the MAFB/MSR1 pathway. RARα may act as a possible therapeutic target for hydrocephalus.

BACE1 Inhibitors for Alzheimer's Disease: The Past, Present and Any Future?

Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder and the most common cause of dementia in the elderly. The complexity of AD has hindered the development of either a cure or a disease-modifying therapy to halt the disease progression. Numerous hypotheses were presented in order to explain the mechanisms underlying the pathogenesis of AD. Introduced in 1992, the "Amyloid Cascade Hypothesis" had a huge impact on the field and inspired the rise of various drug candidates, especially amyloid-beta (Aβ)-directed drugs; including beta-site amyloid precursor protein cleaving enzyme 1 (BACE1) inhibitors. Adopted by a number of pharmaceutical companies, the development of BACE1 inhibitors has gained momentum in the past decade with promising results from experimental and early clinical-phase studies. Nevertheless, nearly all BACE1 inhibitors failed in later phases of clinical trials, due to safety and/or efficacy issues, and others were discontinued early in favor of second-generation small-molecule candidates. This paper aims to provide a comprehensive review of all BACE1 inhibitors to ever reach clinical trials, and we discuss the challenges and different perspectives on whether BACE1 inhibitors are to be reconsidered or revitalized in the future.

The Molecular Effects of Environmental Enrichment on Alzheimer's Disease

Environmental enrichment (EE) is an environmental paradigm encompassing sensory, cognitive, and physical stimulation at a heightened level. Previous studies have reported the beneficial effects of EE in the brain, particularly in the hippocampus. EE improves cognitive function as well as ameliorates depressive and anxiety-like behaviors, making it a potentially effective neuroprotective strategy against neurodegenerative diseases such as Alzheimer's disease (AD). Here, we summarize the current evidence for EE as a neuroprotective strategy as well as the potential molecular pathways that can explain the effects of EE from a biochemical perspective using animal models. The effectiveness of EE in enhancing brain activity against neurodegeneration is explored with a view to differences present in early and late life EE exposure, with its potential application in human being discussed. We discuss EE as one of the non pharmacological approaches in preventing or delaying the onset of AD for future research.

Drug repositioning: Progress and challenges in drug discovery for various diseases

Compared with traditional de novo drug discovery, drug repurposing has become an attractive drug discovery strategy due to its low-cost and high efficiency. Through a comprehensive analysis of the candidates that have been identified with drug repositioning potentials, it is found that although some drugs do not show obvious advantages in the original indications, they may exert more obvious effects in other diseases. In addition, some drugs have a synergistic effect to exert better clinical efficacy if used in combination. Particularly, it has been confirmed that drug repositioning has benefits and values on the current public health emergency such as the COVID-19 pandemic, which proved the great potential of drug repositioning. In this review, we systematically reviewed a series of representative drugs that have been repositioned for different diseases and illustrated successful cases in each disease. Especially, the mechanism of action for the representative drugs in new indications were explicitly explored for each disease, we hope this review can provide important insights for follow-up research.