Remembering your A, B, C's: Alzheimer's disease and ABCA1

Mechanisms of action of Fucus vesiculosus-derived fucoidan on improving dyslipidemia in New Zealand rabbits fed a high-fat diet

Dyslipidemia is a major contributor to various diseases, including atherosclerotic cardiovascular disease and obesity. Treatment strategies for dyslipidemia continue to evolve as our understanding of this metabolic disorder and potential therapeutic candidates advance. Notably, fucoidan demonstrates promising effects in ameliorating dyslipidemia in rodents, although their lipid metabolism differs significantly from humans. This study, investigates the lipid-regulatory effects of Fucus vesiculosus-derived fucoidan (FvF) and elucidates the underlying mechanisms of action using New Zealand rabbits fed a high-fat diet, whose lipid profiles closely resemble those of patients with dyslipidemia. The results demonstrate that FvF intervention ameliorates dyslipidemia and lipid deposition in a dose-dependent manner. Mechanistically, FvF intervention modulates the expression levels of multiple molecules involved in lipid transport, fatty acid synthesis and beta-oxidation, and redox balance, as revealed by quantitative reverse transcription polymerase chain reaction, western blotting, and proteomic analysis. This study is the first to report that FvF, consisting of alternating [→4)-α-L-Fucp(1 → 3)-α-L-Fucp(1→] glycosyls ameliorates dyslipidemia by directly modulating lipid metabolism and indirectly attenuating oxidative stress. These findings suggest that FvF holds significant potential as a candidate for the treatment of lipid disorder-related diseases.

New insight into the role of altered brain cholesterol metabolism in the pathogenesis of AD: A unifying cholesterol hypothesis and new therapeutic approach for AD

The dysregulation of cholesterol metabolism homeostasis has been universally suggested in the aeotiology of Alzheimer's disease (AD). Initially, studies indicate that alteration of serum cholesterol level might contribute to AD. However, because blood-brain barrier impedes entry of plasma cholesterol, brain cells are not directly influenced by plasma cholesterol. Furthermore, mounting evidences suggest a link between alteration of brain cholesterol metabolism and AD. Interestingly, Amyloid-β proteins (Aβ) can markedly inhibit cellular cholesterol biosynthesis and lower cellular cholesterol content in cultured cells. And Aβ overproduction/overload induces a significant decrease of brain cellular cholesterol content in familial AD (FAD) animals. Importantly, mutations or polymorphisms of genes related to brain cholesterol transportation, such as ApoE4, ATP binding cassette (ABC) transporters, low-density lipoprotein receptor (LDLR) family and Niemann-Pick C disease 1 or 2 (NPC1/2), obviously lead to decreased brain cholesterol transport, resulting in brain cellular cholesterol loss, which could be tightly associated with AD pathological impairments. Additionally, accumulating data show that there are reduction of brain cholesterol biosynthesis and/or disorder of brain cholesterol trafficking in a variety of sporadic AD (SAD) animals and patients. Collectively, compelling evidences indicate that FAD and SAD could share one common and overlapping neurochemical mechanism: brain neuronal/cellular cholesterol deficiency. Therefore, accumulated evidences strongly support a novel hypothesis that deficiency of brain cholesterol contributes to the onset and progression of AD. This review highlights the pivotal role of brain cholesterol deficiency in the pathogenesis of AD. The hypothesis offers valuable insights for the future development of AD treatment.

Retinoid X receptor agonist 9CDHRA mitigates retinal ganglion cell apoptosis and neuroinflammation in a mouse model of glaucoma

Glaucoma, a leading cause of irreversible blindness, is characterized by the progressive loss of retinal ganglion cells (RGCs) and optic nerve damage, often associated with elevated intraocular pressure (IOP). Retinoid X receptors (RXRs) are ligand-activated transcription factors crucial for neuroprotection, as they regulate gene expression to promote neuronal survival via several biochemical networks and reduce neuroinflammation. This study investigated the therapeutic potential of 9-cis-13,14-dihydroretinoic acid (9CDHRA), an endogenous retinoid RXR agonist, in mitigating RGC degeneration in a high-IOP-induced experimental model of glaucoma. We administered 9CDHRA to glaucomatous mice eyes via intravitreal injections and assessed its effects on endoplasmic reticulum (ER) stress markers, glial cell activation, and RGC survival. Our findings demonstrated that 9CDHRA treatment significantly protected inner retinal function and retinal laminar structure in high-IOP glaucoma. The treatment reduced ER stress markers, increased protein lysine acetylation, and diminished glial cell activation, leading to a significant decrease in apoptotic cells under glaucomatous conditions. These results suggest that 9CDHRA exerts neuroprotective effects by modulating key pathogenic pathways in glaucoma, highlighting its potential as a novel therapeutic strategy for preserving vision in glaucoma.

Liver as a new target organ in Alzheimer's disease: insight from cholesterol metabolism and its role in amyloid-beta clearance

Alzheimer's disease, the primary cause of dementia, is characterized by neuropathologies, such as amyloid plaques, synaptic and neuronal degeneration, and neurofibrillary tangles. Although amyloid plaques are the primary characteristic of Alzheimer's disease in the central nervous system and peripheral organs, targeting amyloid-beta clearance in the central nervous system has shown limited clinical efficacy in Alzheimer's disease treatment. Metabolic abnormalities are commonly observed in patients with Alzheimer's disease. The liver is the primary peripheral organ involved in amyloid-beta metabolism, playing a crucial role in the pathophysiology of Alzheimer's disease. Notably, impaired cholesterol metabolism in the liver may exacerbate the development of Alzheimer's disease. In this review, we explore the underlying causes of Alzheimer's disease and elucidate the role of the liver in amyloid-beta clearance and cholesterol metabolism. Furthermore, we propose that restoring normal cholesterol metabolism in the liver could represent a promising therapeutic strategy for addressing Alzheimer's disease.

Memantine/Rosuvastatin Therapy Abrogates Cognitive and Hippocampal Injury in an Experimental Model of Alzheimer's Disease in Rats: Role of TGF-β1/Smad Signaling Pathway and Amyloid-β Clearance

Alzheimer's disease (AD) is a multifactorial neurodegenerative disorder of complex pathogenesis and multiple interacting signaling pathways where amyloidal-β protein (Aβ) clearance plays a crucial role in cognitive decline. Herein, the current study investigated the possible modulatory effects of memantine/ rosuvastatin therapy on TGF-β1/p-Smad/p21 signaling pathway and their correlation to the blood brain barrier transporters involved in Aβ-clearance and microRNAs as a novel molecular mechanism in AD treatment. AD was induced by a single intracerebroventricular streptozotocin injection (ICV-STZ, 3 mg/kg) in rats and drug therapy was continued for 28 days after AD induction. Efficacy was monitored by applying a battery of behavioral assessments, as well as biochemical, histopathological, molecular and gene expression techniques. The upregulated TGF-β1-signaling in the untreated rats was found to be highly correlated to transporters and microRNAs governing Aβ-efflux; ABCA1/miRNA-26 and LRP1/miRNA-205 expressions, rather than RAGE/miRNA-185 controlling Aβ-influx; an effect that was opposed by the tested drugs and was found to be correlated with the abolished TGF-β1-signaling as well. Combined memantine/rosuvastatin therapy ameliorated the STZ evoked decreases in escape latency and number of crossovers in the Morris water maze test, % spontaneous alternation in the Y-maze test, and discrimination and recognition indices in the object recognition test. The evoked behavioral responses were directly related to the β-amyloid accumulation and the alteration in its clearance. Additionally, drug treatment increased brain glutathione and decreased malondialdehyde levels. These findings were histopathologically confirmed by a marked reduction of gliosis and restoration of neuronal integrity in the CA1 region of the hippocampus of the AD rats. These findings implicated that the memantine/rosuvastatin combination could offer a new therapeutic potential for AD management by abrogating the TGF-β1/p-Smad2/p21 pathway and regulating Aβ-clearance.

Targeting Lipid Metabolism in Obese Asthma: Perspectives and Therapeutic Opportunities

BACKGROUND

Obese asthma represents a unique phenotype of asthma characterized by severe symptoms, poor medication controls, increased frequency of exacerbations, and an overall diminished quality of life. Numerous factors, including the complex interactions between environment, mechanical processes, inflammatory responses, and metabolites disturbance, contribute to the onset of obese asthma.

SUMMARY

Notably, multiple metabolomics studies in the last several years have revealed the significant abnormalities in lipid metabolism among obese asthmatic patients. Several bioactive lipid messengers participate in the development of obese asthma has also been observed. Here, we present and discuss the latest advances regarding how bioactive lipid molecules contribute to the pathogenic process and mechanisms underlying obese asthma. The key roles of potentially significant effector cells and the pathways by which they respond to diverse lipid metabolites are also described. We finally summarize current lipid-related therapeutic options for the treatment of obese asthma and discuss their application prospects.

KEY MESSAGES

This review underscores the impacts of abnormal lipid metabolism in the etiopathogenesis of obese asthma and asks for further investigation to elucidate the intricate correlations among lipids, obesity, and asthma.

Nonlipogenic ABCA1 Inducers (NLAI) for Alzheimer's Disease Validated in a Mouse Model Expressing Human APOE3/APOE4

Therapeutics enhancing apolipoprotein (APOE) positive function are a priority, because APOE4 is the major genetic risk factor for Alzheimer's disease (AD). The function of APOE, the key constituent of lipoprotein particles that transport cholesterol and lipids in the brain, is dependent on lipidation by ABCA1, a cell-membrane cholesterol transporter. ABCA1 transcription is regulated by liver X receptors (LXR): agonists have been shown to increase ABCA1, often accompanied by unwanted lipogenesis and elevated triglycerides (TG). Therefore, nonlipogenic ABCA1-inducers (NLAI) are needed. Two rounds of optimization of an HTS hit, derived from a phenotypic screen, gave lead compound 39 that was validated and tested in E3/4FAD mice that express human APOE3/4 and five mutant APP and PSEN1 human transgenes. Treatment with 39 increased ABCA1 expression, enhanced APOE lipidation, and reversed multiple AD phenotypes, without increasing TG. This NLAI/LXR-agonist study is the first in a human APOE-expressing model with hallmark amyloid-β pathology.

ABCA1 Deletion Does Not Affect Aqueous Humor Outflow Function in Mice

Background

ATP binding cassette transporter A1 (ABCA1) is a candidate gene within a POAG susceptibility locus by GWAS analysis, and it is involved in IOP modulation via the Cav1/eNOS/NO signaling pathway. We aim to examine the phenotype of ABCA1 deletion in the ABCA1 gene knockout (Abca1-/-) mice.

Methods

The anterior segments of Abca1-/- eyes were imaged by slit-lamp microscopy and anterior segment OCT. IOPs were measured by rebound tonometry. By perfusing enucleated eyes at various pressures, the aqueous humor outflow facility was determined. The mRNA expressions of ABCA1, Cav1, and eNOS were measured by RT-qPCR. The protein expressions were analyzed by western blot and immunofluorescence staining.

Results

There was no significant difference in the anterior segment morphology of Abca1-/- mice. IOP and aqueous humor outflow facility did not change in Abca1-/- mice compared with wild-type mice. mRNA and protein expressions of ABCA1 were significantly lower in the outflow tissue of Abca1-/- eyes. The expressions of Cav1 and eNOS were both significantly upregulated in the outflow tissue of Abca1-/- eyes.

Conclusion

ABCA1 deletion does not affect IOP and aqueous humor outflow function but the Cav1/eNOS/NO pathway is changed in Abca1-/- mice. The function of ABCA1 in aqueous humor outflow still requires further research.

Targeting ABCA1 via Extracellular Vesicle-Encapsulated Staurosporine as a Therapeutic Strategy to Enhance Radiosensitivity

Cancer stem cells (CSCs) are essential for tumor initiation, recurrence, metastasis, and resistance. However, targeting CSCs as a therapeutic approach remains challenging. Here, a stemness signature based on 22-gene is developed to predict prognosis in esophageal squamous cell carcinoma (ESCC). Staurosporine (STS) is identified as a radioresistance suppressor by high-throughput screening of a library of 2131 natural compounds, leading to dramatically improved radiotherapy efficacy in subcutaneous tumor models. Mechanistically, STS inhibits cell proliferation through the mTOR/AKT signaling pathway and suppressed stemness by targeting ATP-binding cassette A1 (ABCA1), which is transcriptionally regulated by liver X receptor alpha (LXRα). STS can selectively bind to the nucleotide-binding domain (NBD) of ABCA1 and compete for ATP, blocking ABCA1-mediated drug efflux and facilitating intracellular accumulation of STS. Considering the cytotoxicity of STS, an extracellular vesicle-encapsulated STS system (EV-STS) is established for effective STS delivery. EV-STS shows remarkable tumor growth inhibition, even at half the dose of STS, with superior safety and efficacy. These findings indicate that ABCA1 may serve as a predictor of response to neoadjuvant chemotherapy and/or radiotherapy in ESCC patients. EV-STS has shown improved antitumor efficacy and low systemic toxicity, offering a promising therapeutic approach for ESCC.

Dysregulation of Lipid Metabolism Serves as A Link Between Alzheimer's and Cardiovascular Disease, As Witnessed in A Cross-Sectional Study

Cardiovascular risk factors and established cardiovascular disease (CVD) increase the risk of suffering dementia of the Alzheimer's type (DAT). Here, we set out to define specific molecular profiles of CVD in patients with DAT to better understand its relationship, to unravel the mechanisms underlying the high risk of developing DAT in CVD patients and to define new markers of early disease. Plasma samples from patients with DAT, with and without CVD, were analyzed through a multiomics approach, with integration of metabolomics and proteomics datasets using the OmicsNet web-based tool. Metabolomics results showed an enrichment in lipids and lipid-like molecules. Similarly, the most significant cluster identified through proteomics was formed by 5 proteins related to lipoprotein and cholesterol metabolism. After integration and functional enrichment, glycerolipid metabolism, fatty acid degradation and sphingolipid metabolism were among the most significant functions. Finally, the differential expression of ABCA1 and APOH proteins was verified, in an independent cohort also including controls and patients with CVD alone. Both proteins positively correlated with phospho-Tau (181), a classical hallmark of DAT. Different molecular profiles exist in patients with DAT, with and without CVD, with exacerbated alterations in patients in which DAT and CVD co-exist. This information may help to define biomarkers like ABCA1 and APOH that identify patients with cardiovascular dysfunction that are at high risk of developing DAT. Such markers will allow more personalized interventions to be selected, a further step towards precision medicine for individuals whose molecular profiles indicate a distinct response to the same management strategies.

Enhancing of cerebral Abeta clearance by modulation of ABC transporter expression: a review of experimental approaches

Clearance of amyloid-beta (Aβ) from the brain is impaired in both early-onset and late-onset Alzheimer's disease (AD). Mechanisms for clearing cerebral Aβ include proteolytic degradation, antibody-mediated clearance, blood brain barrier and blood cerebrospinal fluid barrier efflux, glymphatic drainage, and perivascular drainage. ATP-binding cassette (ABC) transporters are membrane efflux pumps driven by ATP hydrolysis. Their functions include maintenance of brain homeostasis by removing toxic peptides and compounds, and transport of bioactive molecules including cholesterol. Some ABC transporters contribute to lowering of cerebral Aβ. Mechanisms suggested for ABC transporter-mediated lowering of brain Aβ, in addition to exporting of Aβ across the blood brain and blood cerebrospinal fluid barriers, include apolipoprotein E lipidation, microglial activation, decreased amyloidogenic processing of amyloid precursor protein, and restricting the entrance of Aβ into the brain. The ABC transporter superfamily in humans includes 49 proteins, eight of which have been suggested to reduce cerebral Aβ levels. This review discusses experimental approaches for increasing the expression of these ABC transporters, clinical applications of these approaches, changes in the expression and/or activity of these transporters in AD and transgenic mouse models of AD, and findings in the few clinical trials which have examined the effects of these approaches in patients with AD or mild cognitive impairment. The possibility that therapeutic upregulation of ABC transporters which promote clearance of cerebral Aβ may slow the clinical progression of AD merits further consideration.

Brain cholesterol and Alzheimer's disease: challenges and opportunities in probe and drug development

Cholesterol homeostasis is impaired in Alzheimer's disease; however, attempts to modulate brain cholesterol biology have not translated into tangible clinical benefits for patients to date. Several recent milestone developments have substantially improved our understanding of how excess neuronal cholesterol contributes to the pathophysiology of Alzheimer's disease. Indeed, neuronal cholesterol was linked to the formation of amyloid-β and neurofibrillary tangles through molecular pathways that were recently delineated in mechanistic studies. Furthermore, remarkable advances in translational molecular imaging have now made it possible to probe cholesterol metabolism in the living human brain with PET, which is an important prerequisite for future clinical trials that target the brain cholesterol machinery in Alzheimer's disease patients-with the ultimate aim being to develop disease-modifying treatments. This work summarizes current concepts of how the biosynthesis, transport and clearance of brain cholesterol are affected in Alzheimer's disease. Further, current strategies to reverse these alterations by pharmacotherapy are critically discussed in the wake of emerging translational research tools that support the assessment of brain cholesterol biology not only in animal models but also in patients with Alzheimer's disease.

The ABC's of Alzheimer risk gene ABCA7

Alzheimer's disease (AD) is a growing problem worldwide. Since ABCA7's identification as a risk gene, it has been extensively researched for its role in the disease. We review its recently characterized structure and what the mechanistic insights teach us about its function. We furthermore provide an overview of identified ABCA7 mutations, their presence in different ancestries and protein domains and how they might cause AD. For ABCA7 PTC variants and a VNTR expansion, haploinsufficiency is proposed as the most likely mode-of-action, although splice events could further influence disease risk. Overall, the need to better understand expression of canonical ABCA7 and its isoforms in disease is indicated. Finally, ABCA7's potential functions in lipid metabolism, phagocytosis, amyloid deposition, and the interplay between these three, is described. To conclude, in this review, we provide a comprehensive overview and discussion about the current knowledge on ABCA7 in AD, and what research questions remain. HIGHLIGHTS: Alzheimer's risk-increasing variants in ABCA7 can be found in up to 7% of AD patients. We review the recently characterized protein structure of ABCA7. We present latest insights in genetics, expression patterns, and functions of ABCA7.

Epigenetic modifications of DNA and RNA in Alzheimer's disease

Alzheimer's disease (AD) is a complex neurodegenerative disorder and the most common form of dementia. There are two main types of AD: familial and sporadic. Familial AD is linked to mutations in amyloid precursor protein (APP), presenilin-1 (PSEN1), and presenilin-2 (PSEN2). On the other hand, sporadic AD is the more common form of the disease and has genetic, epigenetic, and environmental components that influence disease onset and progression. Investigating the epigenetic mechanisms associated with AD is essential for increasing understanding of pathology and identifying biomarkers for diagnosis and treatment. Chemical covalent modifications on DNA and RNA can epigenetically regulate gene expression at transcriptional and post-transcriptional levels and play protective or pathological roles in AD and other neurodegenerative diseases.

Gut microbiota-host lipid crosstalk in Alzheimer's disease: implications for disease progression and therapeutics

Trillions of intestinal bacteria in the human body undergo dynamic transformations in response to physiological and pathological changes. Alterations in their composition and metabolites collectively contribute to the progression of Alzheimer's disease. The role of gut microbiota in Alzheimer's disease is diverse and complex, evidence suggests lipid metabolism may be one of the potential pathways. However, the mechanisms that gut microbiota mediate lipid metabolism in Alzheimer's disease pathology remain unclear, necessitating further investigation for clarification. This review highlights the current understanding of how gut microbiota disrupts lipid metabolism and discusses the implications of these discoveries in guiding strategies for the prevention or treatment of Alzheimer's disease based on existing data.

Unraveling the Genetic Landscape of Neurological Disorders: Insights into Pathogenesis, Techniques for Variant Identification, and Therapeutic Approaches

Genetic abnormalities play a crucial role in the development of neurodegenerative disorders (NDDs). Genetic exploration has indeed contributed to unraveling the molecular complexities responsible for the etiology and progression of various NDDs. The intricate nature of rare and common variants in NDDs contributes to a limited understanding of the genetic risk factors associated with them. Advancements in next-generation sequencing have made whole-genome sequencing and whole-exome sequencing possible, allowing the identification of rare variants with substantial effects, and improving the understanding of both Mendelian and complex neurological conditions. The resurgence of gene therapy holds the promise of targeting the etiology of diseases and ensuring a sustained correction. This approach is particularly enticing for neurodegenerative diseases, where traditional pharmacological methods have fallen short. In the context of our exploration of the genetic epidemiology of the three most prevalent NDDs-amyotrophic lateral sclerosis, Alzheimer's disease, and Parkinson's disease, our primary goal is to underscore the progress made in the development of next-generation sequencing. This progress aims to enhance our understanding of the disease mechanisms and explore gene-based therapies for NDDs. Throughout this review, we focus on genetic variations, methodologies for their identification, the associated pathophysiology, and the promising potential of gene therapy. Ultimately, our objective is to provide a comprehensive and forward-looking perspective on the emerging research arena of NDDs.

Blood-brain barrier transporters: An overview of function, dysfunction in Alzheimer's disease and strategies for treatment

The blood-brain-barrier (BBB) has a major function in maintaining brain homeostasis by regulating the entry of molecules from the blood to the brain. Key players in BBB function are BBB transporters which are highly expressed in brain endothelial cells (BECs) and critical in mediating the exchange of nutrients and waste products. BBB transporters can also influence drug delivery into the brain by inhibiting or facilitating the entry of brain targeting therapeutics for the treatment of brain disorders, such as Alzheimer's disease (AD). Recent studies have shown that AD is associated with a disrupted BBB and transporter dysfunction, although their roles in the development in AD are not fully understand. Modulation of BBB transporter activity may pose a novel approach to enhance the delivery of drugs to the brain for enhanced treatment of AD. In this review, we will give an overview of key functions of BBB transporters and known changes in AD. In addition, we will discuss current strategies for transporter modulation for enhanced drug delivery into the brain.

A novel apoE-mimetic increases brain apoE levels, reduces Aβ pathology and improves memory when treated before onset of pathology in male mice that express APOE3

BACKGROUND

Alzheimer's disease (AD) is characterized by cognitive dysfunction and amyloid plaques composed of the amyloid-beta peptide (Aβ). APOE is the greatest genetic risk for AD with APOE4 increasing risk up to ~ 15-fold compared to APOE3. Evidence suggests that levels and lipidation of the apoE protein could regulate AD progression. In glia, apoE is lipidated via cholesterol efflux from intracellular pools, primarily by the ATP-binding cassette transporter A1 (ABCA1). Therefore, increasing ABCA1 activity is suggested to be a therapeutic approach for AD. CS-6253 (CS) is a novel apoE mimetic peptide that was developed to bind and stabilize ABCA1 and maintain its localization into the plasma membrane therefore promoting cholesterol efflux. The goal of this study was to determine whether CS could modulate apoE levels and lipidation, Aβ pathology, and behavior in a model that expresses human APOE and overproduce Aβ.

METHODS

In vitro, APOE3-glia or APOE4-glia were treated with CS. In vivo, male and female, E3FAD (5xFAD+/-/APOE3+/+) and E4FAD (5xFAD+/-/APOE4+/+) mice were treated with CS via intraperitoneal injection at early (from 4 to 8 months of age) and late ages (from 8 to 10 months of age). ApoE levels, ABCA1 levels and, apoE lipidation were measured by western blot and ELISA. Aβ and amyloid levels were assessed by histochemistry and ELISA. Learning and memory were tested by Morris Water Maze and synaptic proteins were measured by Western blot.

RESULTS

CS treatment increased apoE levels and cholesterol efflux in primary glial cultures. In young male E3FAD mice, CS treatment increased soluble apoE and lipid-associated apoE, reduced soluble oAβ and insoluble Aβ levels as well as Aβ and amyloid deposition, and improved memory and synaptic protein levels. CS treatment did not induce any therapeutic benefits in young female E3FAD and E4FAD mice or in any groups when treatment was started at later ages.

CONCLUSIONS

CS treatment reduced Aβ pathology and improved memory only in young male E3FAD, the cohort with the least AD pathology. Therefore, the degree of Aβ pathology or Aβ overproduction may impact the ability of targeting ABCA1 to be an effective AD therapeutic. This suggests that ABCA1-stabilizing treatment by CS-6253 works best in conditions of modest Aβ levels.

Protein Biomarkers Shared by Multiple Neurodegenerative Diseases Are Calmodulin-Binding Proteins Offering Novel and Potentially Universal Therapeutic Targets

Seven major neurodegenerative diseases and their variants share many overlapping biomarkers that are calmodulin-binding proteins: Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), frontotemporal lobar dementia (FTD), Huntington's disease (HD), Lewy body disease (LBD), multiple sclerosis (MS), and Parkinson's disease (PD). Calcium dysregulation is an early and persistent event in each of these diseases, with calmodulin serving as an initial and primary target of increased cytosolic calcium. Considering the central role of calcium dysregulation and its downstream impact on calcium signaling, calmodulin has gained interest as a major regulator of neurodegenerative events. Here, we show that calmodulin serves a critical role in neurodegenerative diseases via binding to and regulating an abundance of biomarkers, many of which are involved in multiple neurodegenerative diseases. Of special interest are the shared functions of calmodulin in the generation of protein biomarker aggregates in AD, HD, LBD, and PD, where calmodulin not only binds to amyloid beta, pTau, alpha-synuclein, and mutant huntingtin but also, via its regulation of transglutaminase 2, converts them into toxic protein aggregates. It is suggested that several calmodulin binding proteins could immediately serve as primary drug targets, while combinations of calmodulin binding proteins could provide simultaneous insight into the onset and progression of multiple neurodegenerative diseases.

International Union of Basic and Clinical Pharmacology CXIII: Nuclear Receptor Superfamily-Update 2023

The NR superfamily comprises 48 transcription factors in humans that control a plethora of gene network programs involved in a wide range of physiologic processes. This review will summarize and discuss recent progress in NR biology and drug development derived from integrating various approaches, including biophysical techniques, structural studies, and translational investigation. We also highlight how defective NR signaling results in various diseases and disorders and how NRs can be targeted for therapeutic intervention via modulation via binding to synthetic lipophilic ligands. Furthermore, we also review recent studies that improved our understanding of NR structure and signaling. SIGNIFICANCE STATEMENT: Nuclear receptors (NRs) are ligand-regulated transcription factors that are critical regulators of myriad physiological processes. NRs serve as receptors for an array of drugs, and in this review, we provide an update on recent research into the roles of these drug targets.

NOTCH3 C201R variant causes cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) that can be confused with early-onset Alzheimer's disease

BACKGROUND

NOTCH3 is the causative gene for autosomal dominant cerebral arteriopathy with subcortical infarctions and leukoencephalopathy (CADASIL) which is associated with both stroke and dementia. When CADASIL presents primarily as dementia it can be difficult to distinguish from Alzheimer's disease (AD) at both the clinical and neuropathological levels.

METHODS

We performed exome sequencing of several affected individuals from a large family affected with AD. PCR amplification and direct Sanger sequencing were used to verify variants detected by exome analysis and to screen family members at-risk to carry those variants. Neuropathologic brain evaluation by immunohistochemistry and MRI were performed for the carriers of the NOTCH3 variant.

RESULTS

In a three-generation family with AD, we found a c.601 T > C p.Cys201Arg variant in the NOTCH3 gene that caused clinical and neuropathological manifestations of CADASIL. These features included earlier onset of dementia accompanied by behavioral abnormalities in the father and son and white matter abnormalities in the asymptomatic grandson. The family is one branch of a large pedigree studied by the Alzheimer's Disease Sequencing Project (ADSP). As part of the ADSP linkage analysis and whole genome sequencing endeavor, an ABCA1 variant, p.Ala937Val, was previously found associated with AD in this pedigree.

CONCLUSIONS

Our findings, together with other reported pathogenic missense variants of the C201 codon in NOTCH3, support the role of cysteine 201 as a mutation hotspot for CADASIL and highlight the genetic complexity both clinically and pathologically of AD and related dementia.

Aerobic Exercise Facilitates the Nuclear Translocation of SREBP2 by Activating AKT/SEC24D to Contribute Cholesterol Homeostasis for Improving Cognition in APP/PS1 Mice

Impaired cholesterol synthesizing ability is considered a risk factor for the development of Alzheimer's disease (AD), as evidenced by reduced levels of key proteases in the brain that mediate cholesterol synthesis; however, cholesterol deposition has been found in neurons in tangles in the brains of AD patients. Although it has been shown that statins, which inhibit cholesterol synthesis, reduce the incidence of AD, this seems paradoxical for AD patients whose cholesterol synthesizing capacity is already impaired. In this study, we aimed to investigate the effects of aerobic exercise on cholesterol metabolism in the brains of APP/PS1 mice and to reveal the mechanisms by which aerobic exercise improves cognitive function in APP/PS1 mice. Our study demonstrates that the reduction of SEC24D protein, a component of coat protein complex II (COPII), is a key factor in the reduction of cholesterol synthesis in the brain of APP/PS1 mice. 12 weeks of aerobic exercise was able to promote the recovery of SEC24D protein levels in the brain through activation of protein kinase B (AKT), which in turn promoted the expression of mem-brane-bound sterol regulatory element-binding protein 2 (SREBP2) nuclear translocation and the expression of key proteases mediating cholesterol synthesis. Simultaneous aerobic exercise restored cholesterol transport capacity in the brain of APP/PS1 mice with the ability to efflux excess cholesterol from neurons and reduced neuronal lipid rafts, thereby reducing cleavage of the APP amyloid pathway. Our study emphasizes the potential of restoring intracerebral cholesterol homeostasis as a therapeutic strategy to alleviate cognitive impairment in AD patients.

RXR Agonists Enhance Lenalidomide Anti-Myeloma Activity and T Cell Functions while Retaining Glucose-Lowering Effect

Retinoid X receptor (RXR) heterodimerizes with the PPAR nuclear hormone receptor and regulates its downstream events. We investigated the effects of RXR agonists (LG100754, bexarotene, AGN194204, and LG101506) on lenalidomide's anti-myeloma activity, T cell functions, and the level of glucose and lipids in vivo. Genetic overexpression and CRISPR/Cas9 knockout experiments were conducted in multiple myeloma (MM) cell lines and Jurkat T cell lines to determine the roles of CRBN in RXR-agonist mediated effects. A xenograft mouse model of MM was established to determine the combination effect of LG100754 and lenalidomide. The combination of RXR agonists and lenalidomide demonstrated synergistic activity in increasing CRBN expression and killing myeloma cells. Mechanistically, the RXR agonists reduced the binding of PPARs to the CRBN promoter, thereby relieving the repressor effect of PPARs on CRBN transcription. RXR agonists downregulated the exhaustion markers and increased the activation markers of Jurkat T cells and primary human T cells. Co-administration of LG100754 and lenalidomide showed enhanced anti-tumor activity in vivo. LG100754 retained its glucose- and lipid-lowering effects. RXR agonists demonstrate potential utility in enhancing drug sensitivity and T-cell function in the treatment of myeloma.

The role of the ATP-Binding Cassette A1 (ABCA1) in neurological disorders: a mechanistic review

INTRODUCTION

Cholesterol homeostasis is critical for normal brain function. It is tightly controlled by various biological elements. ATP-binding cassette transporter A1 (ABCA1) is a membrane transporter that effluxes cholesterol from cells, particularly astrocytes, into the extracellular space. The recent studies pertaining to ABCA1's role in CNS disorders were included in this study.

AREAS COVERED

In this comprehensive literature review, preclinical and human studies showed that ABCA1 has a significant role in the following diseases or disorders: Alzheimer's disease, Parkinson's disease, Huntington's disease, multiple sclerosis, neuropathy, anxiety, depression, psychosis, epilepsy, stroke, and brain ischemia and trauma.

EXPERT OPINION

ABCA1 via modulating normal and aberrant brain functions such as apoptosis, phagocytosis, BBB leakage, neuroinflammation, amyloid β efflux, myelination, synaptogenesis, neurite outgrowth, and neurotransmission promotes beneficial effects in aforementioned diseases. ABCA1 is a key molecule in the CNS. By boosting its expression or function, some CNS disorders may be resolved. In preclinical studies, liver X receptor agonists have shown promise in treating CNS disorders via ABCA1 and apoE enhancement.

Investigation of Potential Drug Targets for Cholesterol Regulation to Treat Alzheimer's Disease

Despite extensive research and seven approved drugs, the complex interplay of genes, proteins, and pathways in Alzheimer's disease remains a challenge. This implies the intricacies of the mechanism for Alzheimer's disease, which involves the interaction of hundreds of genes, proteins, and pathways. While the major hallmarks of Alzheimer's disease are the accumulation of amyloid plaques and tau protein tangles, excessive accumulation of cholesterol is reportedly correlated with Alzheimer's disease patients. In this work, protein-protein interaction analysis was conducted based upon the genes from a clinical database to identify the top protein targets with most data-indicated involvement in Alzheimer's disease, which include ABCA1, CYP46A1, BACE1, TREM2, GSK3B, and SREBP2. The reactions and pathways associated with these genes were thoroughly studied for their roles in regulating brain cholesterol biosynthesis, amyloid beta accumulation, and tau protein tangle formation. Existing clinical trials for each protein target were also investigated. The research indicated that the inhibition of SREBP2, BACE1, or GSK3B is beneficial to reduce cholesterol and amyloid beta accumulation, while the activation of ABCA1, CYP46A1, or TREM2 has similar effects. In this study, Sterol Regulatory Element-Binding Protein 2 (SREBP2) emerged as the primary protein target. SREBP2 serves a pivotal role in maintaining cholesterol balance, acting as a transcription factor that controls the expression of several enzymes pivotal for cholesterol biosynthesis. Novel studies suggest that SREBP2 performs a multifaceted role in Alzheimer's disease. The hyperactivity of SREBP2 may lead to heightened cholesterol biosynthesis, which suggested association with the pathogenesis of Alzheimer's disease. Lowering SREBP2 levels in an Alzheimer's disease mouse model results in reduced production of amyloid-beta, a major contributor to Alzheimer's disease progression. Moreover, its thoroughly analyzed crystal structure allows for computer-aided screening of potential inhibitors; SREBP2 is thus selected as a prospective drug target. While more protein targets can be added onto the list in the future, this work provides an overview of key proteins involved in the regulation of brain cholesterol biosynthesis that may be further investigated for Alzheimer's disease intervention.

T0901317, a liver X receptor agonist, ameliorates perinatal white matter injury induced by ischemia and hypoxia in neonatal rats

Perinatal white matter injury (PWMI) can lead to permanent neurological damage in preterm infants and bring a huge economic burden to their families and society. Liver X receptors (LXRs) are transcription factors that have been confirmed to mediate the myelination process under physiological conditions and are involved in regulating neurogenesis in adult animal models of acute and chronic cerebral ischemia. However, the role of LXRs in PWMI induced by both ischemic and hypoxic stimulation in the immature brain has not been reported. Herein, we investigated the role of LXRs in a neonatal rat model of white matter loss after hypoxia-ischemia (HI) injury through intraperitoneal injection of the LXR agonist T0901317 (T09) 1 day before and 15 min postinjury. The in vivo data showed that T09 treatment significantly facilitated myelination and ameliorated neurological behavior after PWMI. Moreover, T09 enhanced the proliferation of oligodendrocyte lineage cells and reduced microgliosis and astrogliosis in the microenvironment for oligodendrocytes (OLs), maintaining a healthy microenvironment for myelinating OLs. In vitro data suggested that the expression of the myelin-related genes Plp and Cnpase was increased in OLN-93 cells after T09 intervention compared with OLN-93 cells injured by oxygen and glucose deprivation (OGD). In primary mixed astrocytes/microglia cells, T09 also reduced the expression of Il6, Cox2, Tnfa and Il10 that was induced by OGD. Mechanistically, the mRNA expression level and the protein level of ATP binding cassette subfamily A member 1 (Abca1) decreased after HI injury, and the protective effect of T09 might be related to the activation of the LXRβ-ABCA1 signaling pathway. Our study revealed the protective role of LXRs in myelination and white matter homeostasis, providing a potential therapeutic option for PWMI.

Modulation of Mitochondrial Function as a Therapeutic Strategy for Neurodegenerative Diseases

Despite recent FDA approval of anti-amyloid antibodies for Alzheimer's Disease, strategies that target early molecular mechanisms and could delay or change the disease trajectory are still needed. Mitochondria emerge as a signaling organelle that could modulate multiple molecular mechanisms to enhance cellular bioenergetics and promote neuronal survival. Approaches to enhance mitochondrial function could promote healthy aging delaying the onset of age-related diseases such as Alzheimer's Disease. Some of these strategies have been recently tested in clinical trials. Emerging evidence demonstrates that in response to mild energetic stress, mitochondria could orchestrate a robust adaptive stress response activating multiple neuroprotective mechanism. The objective of this review is to highlight recent development of mitochondria-targeting therapeutics for neurodegenerative diseases, mitochondria complex I inhibitors in particular.

HDL-like-Mediated Cell Cholesterol Trafficking in the Central Nervous System and Alzheimer's Disease Pathogenesis

The main aim of this work is to review the mechanisms via which high-density lipoprotein (HDL)-mediated cholesterol trafficking through the central nervous system (CNS) occurs in the context of Alzheimer’s disease (AD). Alzheimer’s disease is characterized by the accumulation of extracellular amyloid beta (Aβ) and abnormally hyperphosphorylated intracellular tau filaments in neurons. Cholesterol metabolism has been extensively implicated in the pathogenesis of AD through biological, epidemiological, and genetic studies, with the APOE gene being the most reproducible genetic risk factor for the development of AD. This manuscript explores how HDL-mediated cholesterol is transported in the CNS, with a special emphasis on its relationship to Aβ peptide accumulation and apolipoprotein E (ApoE)-mediated cholesterol transport. Indeed, we reviewed all existing works exploring HDL-like-mediated cholesterol efflux and cholesterol uptake in the context of AD pathogenesis. Existing data seem to point in the direction of decreased cholesterol efflux and the impaired entry of cholesterol into neurons among patients with AD, which could be related to impaired Aβ clearance and tau protein accumulation. However, most of the reviewed studies have been performed in cells that are not physiologically relevant for CNS pathology, representing a major flaw in this field. The ApoE4 genotype seems to be a disruptive element in HDL-like-mediated cholesterol transport through the brain. Overall, further investigations are needed to clarify the role of cholesterol trafficking in AD pathogenesis.

Neuroprotective Effects of Resveratrol by Modifying Cholesterol Metabolism and Aβ Processing in SAMP8 Mice

Cholesterol metabolism seems dysregulated and linked to amyloid-β (Aβ) formation in neurodegeneration, but the underlying mechanisms are poorly known. Resveratrol (RSV) is a polyphenol with antioxidant activity and neuroprotective properties. Here, we analyzed the effect of age and RSV supplementation on cholesterol metabolism in the brain and blood serum, and its potential link to Aβ processing, in SAMP8 mice—an animal model of aging and Alzheimer’s disease. In the brain, our results revealed an age-related increase in ApoE and unesterified cholesterol in the plasma membrane whereas LDL receptor, HMG-CoA reductase, HMG-CoA-C1 synthase, and ABCA1 transporter remained unaltered. Furthermore, BACE-1 and APP gene expression was decreased. This dysregulation could be involved in the amyloidogenic processing pathway of APP towards Aβ formation. In turn, RSV exhibited an age-dependent effect. While levels of unesterified cholesterol in the plasma membrane were not affected by RSV, several participants in cholesterol uptake, release, and de novo synthesis differed, depending on age. Thus, RSV supplementation exhibited a different neuroprotective effect acting on Aβ processing or cholesterol metabolism in the brain at earlier or later ages, respectively. In blood serum, HDL lipoprotein and free cholesterol were increased by age, whereas VLDL and LDL lipoproteins remained unaltered. Again, the protective effect of RSV by decreasing the LDL or increasing the HDL levels also seems to depend on the intervention’s moment. In conclusion, age is a prominent factor for cholesterol metabolism dysregulation in the brain of SAMP8 mice and influences the protective effects of RSV through cholesterol metabolism and Aβ processing.