Pharmacological Inhibition of Soluble Epoxide Hydrolase as a New Therapy for Alzheimer's Disease

Novel molecular mechanism driving neuroprotection after soluble epoxide hydrolase inhibition: Insights for Alzheimer's disease therapeutics

BACKGROUND

Neuroinflammation is widely recognized as a significant hallmark of Alzheimer's disease (AD). To combat neuroinflammation, the inhibition of the soluble epoxide hydrolase (sEH) enzyme has been demonstrated crucial. Importantly, sEH inhibition could be related to other neuroprotective pathways described in AD.

AIMS

The aim of the study was to unveil new molecular pathways driving neuroprotection through sEH, we used an optimized, potent, and selective sEH inhibitor (sEHi, UB-SCG-51).

MATERIALS AND METHODS

UB-SCG-51 was tested in neuroblastoma cell line, SH-SY5Y, in primary mouse and human astrocytes cultures challenged with proinflammatory insults and in microglia cultures treated with amyloid oligomers, as well as in mice AD model (5XFAD).

RESULTS

UB-SCG-51 (10 and 30 μM) prevented neurotoxic reactive-astrocyte conversion in primary mouse astrocytes challenged with TNF-α, IL-1α, and C1q (T/I/C) combination for 24 h. Moreover, in microglial cultures, sEHi reduced inflammation and glial activity. In addition, UB-SCG-51 rescued 5XFAD cognitive impairment, reducing the number of Amyloid-β plaques and Tau hyperphosphorylation accompanied by a reduction in neuroinflammation and apoptotic markers. Notably, a transcriptional profile analysis revealed a new pathway modulated by sEHi treatment. Specifically, the eIF2α/CHOP pathway, which promoted the endoplasmic reticulum response, was increased in the 5XFAD-treated group. These findings were confirmed in human primary astrocytes by combining sEHi and eIF2α inhibitor (eIF2αi) treatment. Besides, combining both treatments resulted in increased in C3 gene expression after T/I/C compared with the group treated with sEHi alone in cultures.

DISCUSSION

Therefore, sEHi rescued cognitive impairment and neurodegeneration in AD mice model, based on the reduction of inflammation and eIF2α/CHOP signaling pathway.

CONCLUSIONS

In whole, our results support the concept that targeting neuroinflammation through sEH inhibition is a promising therapeutic strategy to fight against Alzheimer's disease with additive and/or synergistic activities targeting neuroinflammation and cell stress.

Cerebrovascular Dysfunction in Alzheimer's Disease and Transgenic Rodent Models

Alzheimer's Disease (AD) and Alzheimer's Disease-Related Dementia (ADRD) are the primary causes of dementia that has a devastating effect on the quality of life and is a tremendous economic burden on the healthcare system. The accumulation of extracellular beta-amyloid (Aβ) plaques and intracellular hyperphosphorylated tau-containing neurofibrillary tangles (NFTs) in the brain are the hallmarks of AD. They are also thought to be the underlying cause of inflammation, neurodegeneration, brain atrophy, and cognitive impairments that accompany AD. The discovery of APP, PS1, and PS2 mutations that increase Aβ production in families with early onset familial AD led to the development of numerous transgenic rodent models of AD. These models have provided new insight into the role of Aβ in AD; however, they do not fully replicate AD pathology in patients. Familial AD patients with mutations that elevate the production of Aβ represent only a small fraction of dementia patients. In contrast, those with late-onset sporadic AD constitute the majority of cases. This observation, along with the failure of previous clinical trials targeting Aβ or Tau and the modest success of recent trials using Aβ monoclonal antibodies, has led to a reappraisal of the view that Aβ accumulation is the sole factor in the pathogenesis of AD. More recent studies have established that cerebral vascular dysfunction is one of the earliest changes seen in AD, and 67% of the candidate genes linked to AD are expressed in the cerebral vasculature. Thus, there is an increasing appreciation of the vascular contribution to AD, and the National Institute on Aging (NIA) and the Alzheimer's Disease Foundation recently prioritized it as a focused research area. This review summarizes the strengths and limitations of the most commonly used transgenic AD animal models and current views about the contribution of Aβ accumulation versus cerebrovascular dysfunction in the pathogenesis of AD.

Systematic druggable genome-wide Mendelian randomisation identifies therapeutic targets for Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is the leading cause of dementia. Currently, there are no effective disease-modifying treatments for AD. Mendelian randomisation (MR) has been widely used to repurpose licensed drugs and discover novel therapeutic targets. Thus, we aimed to identify novel therapeutic targets for AD and analyse their pathophysiological mechanisms and potential side effects.

METHODS

A two-sample MR integrating the identified druggable genes was performed to estimate the causal effects of blood and brain druggable expression quantitative trait loci (eQTLs) on AD. A repeat study was conducted using different blood and brain eQTL data sources to validate the identified genes. Using AD markers with available genome-wide association studies data, we evaluated the causal relationship between established AD markers to explore possible mechanisms. Finally, the potential side effects of the druggable genes for AD treatment were assessed using a phenome-wide MR.

RESULTS

Overall, 5883 unique druggable genes were aggregated; 33 unique potential druggable genes for AD were identified in at least one dataset (brain or blood), and 5 were validated in a different dataset. Among them, three prior druggable genes (epoxide hydrolase 2 (EPHX2), SERPINB1 and SIGLEC11) reached significant levels in both blood and brain tissues. EPHX2 may mediate the pathogenesis of AD by affecting the entire hippocampal volume. Further phenome-wide MR analysis revealed no potential side effects of treatments targeting EPHX2, SERPINB1 or SIGLEC11.

CONCLUSIONS

This study provides genetic evidence supporting the potential therapeutic benefits of targeting the three druggable genes for AD treatment, which will be useful for prioritising AD drug development.

Quantitative Profiling Method for Oxylipins in Neurodegenerative Diseases by Liquid Chromatography Coupled with Tandem Mass Spectrometry

Aging is one of the major risk factors for many chronic diseases, including diabetes, neuropathy, hypertension, cancer, and neurodegenerative diseases. However, the mechanism behind aging and how aging affects a variety of disease progression remains unknown. Recent research demonstrated the cytochrome P450 (CYP)-epoxide hydrolase (EH) metabolites of polyunsaturated fatty acids (PUFAs) play a critical role in the abovementioned age-associated diseases. Therefore, aging could affect the abovementioned chronic diseases by modulating CYP-EH PUFA metabolism. Unfortunately, investigating how aging affects CYP-EH metabolism in human and mammalian models poses significant challenges. In this regard, we will use C. elegans as a model organism to investigate the aging effects on CYP-EH metabolism of PUFA, owing to its long history of being used to study aging and its associated benefits of conducting aging research. This project will develop analytical tools to measure the endogenous levels of CYP-EH PUFA metabolites in C. elegans using state-of-the-art ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS). These metabolites are very potent but present in low abundance. The dramatic increase in sensitivity in UPLC-MS/MS allows us to monitor these metabolites over the lifespan of C. elegans with minimum samples. Our results show that C. elegans produces similar CYP PUFA metabolites to mammals and humans using our SPE-UPLC-MS/MS method. We will also show that our method successfully determined the CYP-EH PUFA metabolites profile changes induced by the inhibition of C. elegans EH. The method developed from this project will significantly improve our understanding of the role of dietary PUFAs and associated metabolism on aging and neurodegeneration and will uncover new mechanisms of how aging affects neurodegeneration through the modulation of PUFA metabolic pathways.

Cytochrome P450 and Epoxide Hydrolase Metabolites in Aβ and tau-induced Neurodegeneration: Insights from Caenorhabditis elegans

This study aims to uncover potent cytochrome P450 (CYP) and epoxide hydrolase (EH) metabolites implicated in Aβ and/or tau-induced neurodegeneration, independent of neuroinflammation, by utilizing Caenorhabditis elegans (C. elegans) as a model organism. Our research reveals that Aβ and/or tau expression in C. elegans disrupts the oxylipin profile, and epoxide hydrolase inhibition alleviates the ensuing neurodegeneration, likely through elevating the epoxy-to-hydroxy ratio of various CYP-EH metabolites. In addition, our results indicated that the Aβ and tau likely affect the CYP-EH metabolism of PUFA through different mechanism. These findings emphasize the intriguing relationship between lipid metabolites and neurodegenerations, in particular, those linked to Aβ and/or tau aggregation. Furthermore, our investigation sheds light on the crucial and captivating role of CYP PUFA metabolites in C. elegans physiology, opening up possibilities for broader implications in mammalian and human contexts.

New Sight: Enzymes as Targets for Drug Development

In the dynamic realm of medical research, a resounding chord is struck by recent studies that have propelled drug discovery to new horizons across a spectrum of disciplines [...].

Dihydroxy-Metabolites of Dihomo-γ-linolenic Acid Drive Ferroptosis-Mediated Neurodegeneration

Even after decades of research, the mechanism of neurodegeneration remains understudied, hindering the discovery of effective treatments for neurodegenerative diseases. Recent reports suggest that ferroptosis could be a novel therapeutic target for neurodegenerative diseases. While polyunsaturated fatty acid (PUFA) plays an important role in neurodegeneration and ferroptosis, how PUFAs may trigger these processes remains largely unknown. PUFA metabolites from cytochrome P450 and epoxide hydrolase metabolic pathways may modulate neurodegeneration. Here, we test the hypothesis that specific PUFAs regulate neurodegeneration through the action of their downstream metabolites by affecting ferroptosis. We find that the PUFA dihomo-γ-linolenic acid (DGLA) specifically induces ferroptosis-mediated neurodegeneration in dopaminergic neurons. Using synthetic chemical probes, targeted metabolomics, and genetic mutants, we show that DGLA triggers neurodegeneration upon conversion to dihydroxyeicosadienoic acid through the action of CYP-EH (CYP, cytochrome P450; EH, epoxide hydrolase), representing a new class of lipid metabolites that induce neurodegeneration via ferroptosis.

Mendelian randomization analyses of smoking and Alzheimer's disease in Chinese and Japanese populations

Background

Previous epidemiological studies have reported controversial results on the relationship between smoking and Alzheimer's disease (AD). Therefore, we sought to assess the association using Mendelian randomization (MR) analysis.

Methods

We used single nucleotide polymorphisms (SNPs) associated with smoking quantity (cigarettes per day, CPD) from genome-wide association studies (GWAS) of Japanese population as instrumental variables, then we performed two-sample MR analysis to investigate the association between smoking and AD in a Chinese cohort (1,000 AD cases and 500 controls) and a Japanese cohort (3,962 AD cases and 4,074 controls), respectively.

Results

Genetically higher smoking quantity showed no statistical causal association with AD risk (the inverse variance weighted (IVW) estimate in the Chinese cohort: odds ratio (OR) = 0.510, 95% confidence interval (CI) = 0.149-1.744, p = 0.284; IVW estimate in the Japanese cohort: OR = 1.170, 95% confidence interval CI = 0.790-1.734, p = 0.434).

Conclusion

This MR study, for the first time in Chinese and Japanese populations, found no significant association between smoking and AD.

Vascular and Nonvascular Mechanisms of Cognitive Impairment and Dementia

Aging, familial gene mutations, and genetic, environmental, and modifiable lifestyle risk factors predispose individuals to cognitive impairment or dementia by influencing the efficacy of multiple, often interdependent cellular and molecular homeostatic pathways mediating neuronal, glial, and vascular integrity and, ultimately, cognitive status. This review summarizes data from foundational and recent breakthrough studies to highlight common and differential vascular and nonvascular pathogenic mechanisms underlying the progression of Alzheimer disease, vascular dementia, frontotemporal dementia, and dementia with Lewy bodies.

Dihydroxy-Metabolites of Dihomo-gamma-linolenic Acid Drive Ferroptosis-Mediated Neurodegeneration

Even after decades of research, the mechanism of neurodegeneration remains understudied, hindering the discovery of effective treatments for neurodegenerative diseases. Recent reports suggest that ferroptosis could be a novel therapeutic target for neurodegenerative diseases. While polyunsaturated fatty acid (PUFA) plays an important role in neurodegeneration and ferroptosis, how PUFAs may trigger these processes remains largely unknown. PUFA metabolites from cytochrome P450 and epoxide hydrolase metabolic pathways may modulate neurodegeneration. Here, we test the hypothesis that specific PUFAs regulate neurodegeneration through the action of their downstream metabolites by affecting ferroptosis. We find that the PUFA, dihomo gamma linolenic acid (DGLA), specifically induces ferroptosis-mediated neurodegeneration in dopaminergic neurons. Using synthetic chemical probes, targeted metabolomics, and genetic mutants, we show that DGLA triggers neurodegeneration upon conversion to dihydroxyeicosadienoic acid through the action of CYP-EH, representing a new class of lipid metabolite that induces neurodegeneration via ferroptosis.

Current Pharmacotherapy and Multi-Target Approaches for Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by decreased synaptic transmission and cerebral atrophy with appearance of amyloid plaques and neurofibrillary tangles. Cognitive, functional, and behavioral alterations are commonly associated with the disease. Different pathophysiological pathways of AD have been proposed, some of which interact and influence one another. Current treatment for AD mainly involves the use of therapeutic agents to alleviate the symptoms in AD patients. The conventional single-target treatment approaches do not often cause the desired effect in the disease due to its multifactorial origin. Thus, multi-target strategies have since been undertaken, which aim to simultaneously target multiple targets involved in the development of AD. In this review, we provide an overview of the pathogenesis of AD and the current drug therapies for the disease. Additionally, rationales of the multi-target approaches and examples of multi-target drugs with pharmacological actions against AD are also discussed.

Neuroprotective Epigenetic Changes Induced by Maternal Treatment with an Inhibitor of Soluble Epoxide Hydrolase Prevents Early Alzheimer's Disease Neurodegeneration

Modulation of Alzheimer's disease (AD) risk begins early in life. During embryo development and postnatal maturation, the brain receives maternal physiological influences and establishes epigenetic patterns that build its level of resilience to late-life diseases. The soluble epoxide hydrolase inhibitor N-[1-(1-oxopropyl)-4-piperidinyl]-N'-[4-(trifluoromethoxy)phenyl] urea (TPPU), reported as ant-inflammatory and neuroprotective against AD pathology in the adult 5XFAD mouse model of AD, was administered to wild-type (WT) female mice mated to heterozygous 5XFAD males during gestation and lactation. Two-month-old 5XFAD male and female offspring of vehicle-treated dams showed memory loss as expected. Remarkably, maternal treatment with TPPU fully prevented memory loss in 5XFAD. TPPU-induced brain epigenetic changes in both WT and 5XFAD mice, modulating global DNA methylation (5-mC) and hydroxymethylation (5-hmC) and reducing the gene expression of some histone deacetylase enzymes (Hdac1 and Hdac2), might be on the basis of the long-term neuroprotection against cognitive impairment and neurodegeneration. In the neuropathological analysis, both WT and 5XFAD offspring of TPPU-treated dams showed lower levels of AD biomarkers of tau hyperphosphorylation and microglia activation (Trem2) than the offspring of vehicle-treated dams. Regarding sex differences, males and females were similarly protected by maternal TPPU, but females showed higher levels of AD risk markers of gliosis and neurodegeneration. Taken together, our results reveal that maternal treatment with TPPU impacts in preventing or delaying memory loss and AD pathology by inducing long-term modifications in the epigenetic machinery and its marks.

Synthesis, In Vitro Profiling, and In Vivo Evaluation of Benzohomoadamantane-Based Ureas for Visceral Pain: A New Indication for Soluble Epoxide Hydrolase Inhibitors

The soluble epoxide hydrolase (sEH) has been suggested as a pharmacological target for the treatment of several diseases, including pain-related disorders. Herein, we report further medicinal chemistry around new benzohomoadamantane-based sEH inhibitors (sEHI) in order to improve the drug metabolism and pharmacokinetics properties of a previous hit. After an extensive in vitro screening cascade, molecular modeling, and in vivo pharmacokinetics studies, two candidates were evaluated in vivo in a murine model of capsaicin-induced allodynia. The two compounds showed an anti-allodynic effect in a dose-dependent manner. Moreover, the most potent compound presented robust analgesic efficacy in the cyclophosphamide-induced murine model of cystitis, a well-established model of visceral pain. Overall, these results suggest painful bladder syndrome as a new possible indication for sEHI, opening a new range of applications for them in the visceral pain field.

The epoxy fatty acid pathway enhances cAMP in mammalian cells through multiple mechanisms

The cellular mechanism by which epoxy fatty acids (EpFA) improves disease status is not well characterized. Previous studies suggest the involvement of cellular receptors and cyclic AMP (cAMP). Herein, the action of EpFAs derived from linoleic acid (LA), arachidonic acid (ARA), and docosahexaenoic acid on cAMP levels was studied in multiple cell types to elucidate relationships between EpFAs, receptors and cells' origin. cAMP levels were enhanced in HEK293 and LLC-PK1 cells by EpFAs from LA and ARA. Using selective antagonists, the EpFA effects on cAMP levels appear dependent on the prostaglandin E2 receptor 2 (EP2) but not 4 (EP4). Human coronary artery smooth muscle cells responded similarly to the EpFAs. However, we were not able to show the involvement of any of the receptors tested in this cell type. The results pinpointed distinct cell lines and receptor subtypes that natively respond to EpFA.

Cognitive Decline and BPSD Are Concomitant with Autophagic and Synaptic Deficits Associated with G9a Alterations in Aged SAMP8 Mice

Behavioural and psychological symptoms of dementia (BPSD) are presented in 95% of Alzheimer’s Disease (AD) patients and are also associated with neurotrophin deficits. The molecular mechanisms leading to age-related diseases are still unclear; however, emerging evidence has suggested that epigenetic modulation is a key pathophysiological basis of ageing and neurodegeneration. In particular, it has been suggested that G9a methyltransferase and its repressive histone mark (H3K9me2) are important in shaping learning and memory by modulating autophagic activity and synaptic plasticity. This work deepens our understanding of the epigenetic mechanisms underlying the loss of cognitive function and BPSD in AD. For this purpose, several tasks were performed to evaluate the parameters of sociability (three-chamber test), aggressiveness (resident intruder), anxiety (elevated plus maze and open field) and memory (novel object recognition test) in mice, followed by the evaluation of epigenetic, autophagy and synaptic plasticity markers at the molecular level. The behavioural alterations presented by senescence-accelerated mice prone 8 (SAMP8) of 12 months of age compared with their senescence-accelerated mouse resistant mice (SAMR1), the healthy control strain was accompanied by age-related cognitive deficits and alterations in epigenetic markers. Increased levels of G9a are concomitant to the dysregulation of the JNK pathway in aged SAMP8, driving a failure in autophagosome formation. Furthermore, lower expression of the genes involved in the memory-consolidation process modulated by ERK was observed in the aged male SAMP8 model, suggesting the implication of G9a. In any case, two of the most important neurotrophins, namely brain-derived neurotrophic factor (Bdnf) and neurotrophin-3 (NT3), were found to be reduced, along with a decrease in the levels of dendritic branching and spine density presented by SAMP8 mice. Thus, the present study characterizes and provides information regarding the non-cognitive and cognitive states, as well as molecular alterations, in aged SAMP8, demonstrating the AD-like symptoms presented by this model. In any case, our results indicate that higher levels of G9a are associated with autophagic deficits and alterations in synaptic plasticity, which could further explain the BPSD and cognitive decline exhibited by the model.

A Combined Chronic Low-Dose Soluble Epoxide Hydrolase and Acetylcholinesterase Pharmacological Inhibition Promotes Memory Reinstatement in Alzheimer’s Disease Mice Models

Alzheimer’s disease (AD) is a progressive neurological disorder with multifactorial and heterogeneous causes. AD involves several etiopathogenic mechanisms such as aberrant protein accumulation, neurotransmitter deficits, synaptic dysfunction and neuroinflammation, which lead to cognitive decline. Unfortunately, the currently available anti-AD drugs only alleviate the symptoms temporarily and provide a limited therapeutic effect. Thus, new therapeutic strategies, including multitarget approaches, are urgently needed. It has been demonstrated that a co-treatment of acetylcholinesterase (AChE) inhibitor with other neuroprotective agents has beneficial effects on cognition. Here, we have assessed the neuroprotective effects of chronic dual treatment with a soluble epoxide hydrolase (sEH) inhibitor (TPPU) and an AChE inhibitor (6-chlorotacrine or rivastigmine) in in vivo studies. Interestingly, we have found beneficial effects after chronic low-dose co-treatment with TPPU and 6-chlorotacrine in the senescence-accelerated mouse prone 8 (SAMP8) mouse model as well as with TPPU and rivastigmine co-treatment in the 5XFAD mouse model, in comparison with the corresponding monotherapy treatments. In the SAMP8 model, no substantial improvements in synaptic plasticity markers were found, but the co-treatment of TPPU and 6-chlorotacrine led to a significantly reduced gene expression of neuroinflammatory markers, such as interleukin 6 (Il-6), triggering receptor expressed on myeloid cell 2 (Trem2) and glial fibrillary acidic protein (Gfap). In 5XFAD mice, chronic low-dose co-treatment of TPPU and rivastigmine led to enhanced protein levels of synaptic plasticity markers, such as the phospho-cAMP response element-binding protein (p-CREB) ratio, brain-derived neurotrophic factor (BDNF) and postsynaptic density protein 95 (PSD95), and also to a reduction in neuroinflammatory gene expression. Collectively, these results support the neuroprotectant role of chronic low-dose co-treatment strategy with sEH and AChE inhibitors in AD mouse models, opening new avenues for effective AD treatment.

Advancements in the development of multi-target directed ligands for the treatment of Alzheimer's disease

Alzheimer's disease (AD) is a multifactorial irreversible neurological disorder which results in cognitive impairment, loss of cholinergic neurons in synapses of the basal forebrain and neuronal death. Exact pathology of the disease is not yet known however, many hypotheses have been proposed for its treatment. The available treatments including monotherapies and combination therapies are not able to combat the disease effectively because of its complex pathological mechanism. A multipotent drug for AD has the potential to bind or inhibit multiple targets responsible for the progression of the disease like aggregated Aβ, hyperphosphorylated tau proteins, cholinergic and adrenergic receptors, MAO enzymes, overactivated N-methyl-d-aspartate (NMDA), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor etc. The traditional approach of one disease-one target-one drug has been rationalized to one drug-multi targets for the chronic diseases like AD and cancer. Thus, over the last decade research focus has been shifted towards the development of multi target directed ligands (MTDLs) which can simultaneously inhibit multiple targets and stop or slow the progression of the disease. The MTDLs can be more effective against AD and eliminate any possibility of drug-drug interactions. Many important active pharmacophore units have been fused, merged or incorporated into different scaffolds to synthesize new potent drugs. In the current article, we have described various hypothesis for AD and effectiveness of the MTDLs treatment strategy is discussed in detail. Different chemical scaffolds and their synthetic strategies have been described and important functionalities are identified in the chemical scaffold that have the potential to bind to the multiple targets. The important leads identified in this study with MTDL characteristics have the potential to be developed as drug candidates for the effective treatment of AD.

Unveiling the Multitarget Anti-Alzheimer Drug Discovery Landscape: A Bibliometric Analysis

Multitarget anti-Alzheimer agents are the focus of very intensive research. Through a comprehensive bibliometric analysis of the publications in the period 1990-2020, we have identified trends and potential gaps that might guide future directions. We found that: (i) the number of publications boomed by 2011 and continued ascending in 2020; (ii) the linked-pharmacophore strategy was preferred over design approaches based on fusing or merging pharmacophores or privileged structures; (iii) a significant number of in vivo studies, mainly using the scopolamine-induced amnesia mouse model, have been performed, especially since 2017; (iv) China, Italy and Spain are the countries with the largest total number of publications on this topic, whereas Portugal, Spain and Italy are the countries in whose scientific communities this topic has generated greatest interest; (v) acetylcholinesterase, β-amyloid aggregation, oxidative stress, butyrylcholinesterase, and biometal chelation and the binary combinations thereof have been the most commonly pursued, while combinations based on other key targets, such as tau aggregation, glycogen synthase kinase-3β, NMDA receptors, and more than 70 other targets have been only marginally considered. These results might allow us to spot new design opportunities based on innovative target combinations to expand and diversify the repertoire of multitarget drug candidates and increase the likelihood of finding effective therapies for this devastating disease.

Discovery and In Vivo Proof of Concept of a Highly Potent Dual Inhibitor of Soluble Epoxide Hydrolase and Acetylcholinesterase for the Treatment of Alzheimer's Disease

With innumerable clinical failures of target-specific drug candidates for multifactorial diseases, such as Alzheimer's disease (AD), which remains inefficiently treated, the advent of multitarget drug discovery has brought a new breath of hope. Here, we disclose a class of 6-chlorotacrine (huprine)-TPPU hybrids as dual inhibitors of the enzymes soluble epoxide hydrolase (sEH) and acetylcholinesterase (AChE), a multitarget profile to provide cumulative effects against neuroinflammation and memory impairment. Computational studies confirmed the gorge-wide occupancy of both enzymes, from the main site to a secondary site, including a so far non-described AChE cryptic pocket. The lead compound displayed in vitro dual nanomolar potencies, adequate brain permeability, aqueous solubility, human microsomal stability, lack of neurotoxicity, and it rescued memory, synaptic plasticity, and neuroinflammation in an AD mouse model, after low dose chronic oral administration.

Unprecedented diterpenoid dimers with soluble epoxide hydrolase inhibitory effect from Euphorbia fischeriana

Biseuphoids A (1) and B (2), two unprecedented ent-abietane-type diterpenoid dimers linked by monomeric blocks through C-17-C-12' and C-17-C-11', respectively, were isolated from Euphorbia fischeriana, along with their biogenesis related diterpenoid monomers, 17-hydroxyjolkinolide B (3), caudicifolin (4), and fischeriabietane C (5). Their structures were elucidated by extensive spectroscopy assisted by quantum chemical NMR and ECD calculations. The unusual dimeric skeletons are possibly derived from the adduct of diterpenoid monomers through Michael-like reactions. The novel dimers 1 and 2 exhibited inhibitory activities on soluble epoxide hydrolase (sEH) with IC₅₀ values of 8.17 and 5.61 μM, respectively. Molecular dynamics studies illustrated that both 1 and 2 can occupy the catalytic pocket of sEH by forming stable hydrogen bonds with the key amino acid residues including Gln384, Asn378, Pro361, Ala365, Asn366, and Asn472.

Activating endogenous resolution pathways by soluble epoxide hydrolase inhibitors for the management of COVID-19

Anti-inflammatory, specialized proresolving mediators such as resolvins, protectins, maresins, and lipoxins derived from polyunsaturated acids may play a potential role in lung diseases as they protect different organs in animal disease models. Polyunsaturated fatty acids are an important resource for epoxy fatty acids (EET, EEQ, and EDP) that mediate a broad array of anti-inflammatory and proresolving mechanisms, such as mitigation of the cytokine storm. However, epoxy fatty acids are rapidly metabolized by soluble epoxide hydrolase (sEH). In animal studies, administration of sEH inhibitors (sEHIs) increases epoxy fatty acid levels, reduces lung inflammation, and improves lung function, making it a viable COVID-19 treatment approach. Thus, using sEHIs to activate endogenous resolution pathways might be a novel method to minimize organ damage in severe cases and improve outcomes in COVID-19 patients. This review focuses on the use of sEH inhibitors to activate endogenous resolution mechanisms for the treatment of COVID-19.

Use of AD Informer Set compounds to explore validity of novel targets in Alzheimer's disease pathology

Introduction

A chemogenomic set of small molecules with annotated activities and implicated roles in Alzheimer's disease (AD) called the AD Informer Set was recently developed and made available to the AD research community: https://treatad.org/data‐tools/ad‐informer‐set/.

Methods

Small subsets of AD Informer Set compounds were selected for AD‐relevant profiling. Nine compounds targeting proteins expressed by six AD‐implicated genes prioritized for study by Target Enablement to Accelerate Therapy Development for Alzheimer's Disease (TREAT‐AD) teams were selected for G‐protein coupled receptor (GPCR), amyloid beta (Aβ) and tau, and pharmacokinetic (PK) studies. Four non‐overlapping compounds were analyzed in microglial cytotoxicity and phagocytosis assays.

Results

The nine compounds targeting CAPN2, EPHX2, MDK, MerTK/FLT3, or SYK proteins were profiled in 46 to 47 primary GPCR binding assays. Human induced pluripotent stem cell (iPSC)‐derived neurons were treated with the same nine compounds and secretion of Aβ peptides (Aβ40 and Aβ42) as well as levels of phosphophorylated tau (p‐tau, Thr231) and total tau (t‐tau) peptides measured at two concentrations and two timepoints. Finally, CD1 mice were dosed intravenously to determine preliminary PK and/or brain‐specific penetrance values for these compounds. As a final cell‐based study, a non‐overlapping subset of four compounds was selected based on single‐concentration screening for analysis of both cytotoxicity and phagocytosis in murine and human microglia cells.

Discussion

We have demonstrated the utility of the AD Informer Set in the validation of novel AD hypotheses using biochemical, cellular (primary and immortalized), and in vivo studies. The selectivity for their primary targets versus essential GPCRs in the brain was established for our compounds. Statistical changes in tau, p‐tau, Aβ40, and/or Aβ42 and blood–brain barrier penetrance were observed, solidifying the utility of specific compounds for AD. Single‐concentration phagocytosis results were validated as predictive of dose–response findings. These studies established workflows, validated assays, and illuminated next steps for protein targets and compounds.

2-(Piperidin-4-yl)acetamides as Potent Inhibitors of Soluble Epoxide Hydrolase with Anti-Inflammatory Activity

The pharmacological inhibition of soluble epoxide hydrolase (sEH) has been suggested as a potential therapy for the treatment of pain and inflammatory diseases through the stabilization of endogenous epoxyeicosatrienoic acids. Numerous potent sEH inhibitors (sEHI) have been developed, however many contain highly lipophilic substituents limiting their availability. Recently, a new series of benzohomoadamantane-based ureas endowed with potent inhibitory activity for the human and murine sEH was reported. However, their very low microsomal stability prevented further development. Herein, a new series of benzohomoadamantane-based amides were synthetized, fully characterized, and evaluated as sEHI. Most of these amides were endowed with excellent inhibitory potencies. A selected compound displayed anti-inflammatory effects with higher effectiveness than the reference sEHI, TPPU.

Inhibition of Soluble Epoxide Hydrolase Is Protective against the Multiomic Effects of a High Glycemic Diet on Brain Microvascular Inflammation and Cognitive Dysfunction

Diet is a modifiable risk factor for cardiovascular disease (CVD) and dementia, yet relatively little is known about the effect of a high glycemic diet (HGD) on the brain’s microvasculature. The objective of our study was to determine the molecular effects of an HGD on hippocampal microvessels and cognitive function and determine if a soluble epoxide hydrolase (sEH) inhibitor (sEHI), known to be vasculoprotective and anti-inflammatory, modulates these effects. Wild type male mice were fed a low glycemic diet (LGD, 12% sucrose/weight) or an HGD (34% sucrose/weight) with/without the sEHI, trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (t-AUCB), for 12 weeks. Brain hippocampal microvascular gene expression was assessed by microarray and data analyzed using a multi-omic approach for differential expression of protein and non-protein-coding genes, gene networks, functional pathways, and transcription factors. Global hippocampal microvascular gene expression was fundamentally different for mice fed the HGD vs. the LGD. The HGD response was characterized by differential expression of 608 genes involved in cell signaling, neurodegeneration, metabolism, and cell adhesion/inflammation/oxidation effects reversible by t-AUCB and hence sEH inhibitor correlated with protection against Alzheimer’s dementia. Ours is the first study to demonstrate that high dietary glycemia contributes to brain hippocampal microvascular inflammation through sEH.

Association of plasma and CSF cytochrome P450, soluble epoxide hydrolase, and ethanolamide metabolism with Alzheimer's disease

BACKGROUND

Alzheimer's disease, cardiovascular disease, and other cardiometabolic disorders may share inflammatory origins. Lipid mediators, including oxylipins, endocannabinoids, bile acids, and steroids, regulate inflammation, energy metabolism, and cell proliferation with well-established involvement in cardiometabolic diseases. However, their role in Alzheimer's disease is poorly understood. Here, we describe the analysis of plasma and cerebrospinal fluid lipid mediators in a case-control comparison of ~150 individuals with Alzheimer's disease and ~135 healthy controls, to investigate this knowledge gap.

METHODS

Lipid mediators were measured using targeted quantitative mass spectrometry. Data were analyzed using the analysis of covariates, adjusting for sex, age, and ethnicity. Partial least square discriminant analysis identified plasma and cerebrospinal fluid lipid mediator discriminates of Alzheimer's disease. Alzheimer's disease predictive models were constructed using machine learning combined with stepwise logistic regression.

RESULTS

In both plasma and cerebrospinal fluid, individuals with Alzheimer's disease had elevated cytochrome P450/soluble epoxide hydrolase pathway components and decreased fatty acid ethanolamides compared to healthy controls. Circulating metabolites of soluble epoxide hydrolase and ethanolamides provide Alzheimer's disease predictors with areas under receiver operator characteristic curves ranging from 0.82 to 0.92 for cerebrospinal fluid and plasma metabolites, respectively.

CONCLUSIONS

Previous studies report Alzheimer's disease-associated soluble epoxide hydrolase upregulation in the brain and that endocannabinoid metabolism provides an adaptive response to neuroinflammation. This study supports the involvement of P450-dependent and endocannabinoid metabolism in Alzheimer's disease. The results further suggest that combined pharmacological intervention targeting both metabolic pathways may have therapeutic benefits for Alzheimer's disease.

Inhibition of sEH via stabilizing the level of EETs alleviated Alzheimer's disease through GSK3β signaling pathway

Alzheimer's disease (AD) is the most common neurodegenerative disorder characterized by dementia. Inhibition of soluble epoxide hydrolase (sEH) regulates inflammation involving in central nervous system (CNS) diseases. However, the exactly mechanism of sEH in AD is still unclear. In this study, we evaluated the vital role of sEH in amyloid beta (Aβ)-induced AD mice, and revealed a possible molecular mechanism for inhibition of sEH in the treatment of AD. The results showed that the sEH expression and activity were remarkably increased in the hippocampus of Aβ-induced AD mice. Chemical inhibition of sEH by TPPU, a selective sEH inhibitor, alleviated spatial learning and memory deficits, and elevated levels of neurotransmitters in Aβ-induced AD mice. Furthermore, inhibition of sEH could ameliorate neuroinflammation, neuronal death, and oxidative stress via stabilizing the in vivo level of epoxyeicosatrienoic acids (EETs), especially 8,9-EET and 14,15-EET, further resulting in the anti-AD effect through the regulation of GSK3β-mediated NF-κB, p53, and Nrf2 signaling pathways. These findings revealed the underlying mechanism of sEH as a potential therapeutic target in treatment of AD.

Antibody Protection against Long-Term Memory Loss Induced by Monomeric C-Reactive Protein in a Mouse Model of Dementia

Monomeric C-reactive protein (mCRP), the activated isoform of CRP, induces tissue damage in a range of inflammatory pathologies. Its detection in infarcted human brain tissue and its experimentally proven ability to promote dementia with Alzheimer’s disease (AD) traits at 4 weeks after intrahippocampal injection in mice have suggested that it may contribute to the development of AD after cerebrovascular injury. Here, we showed that a single hippocampal administration of mCRP in mice induced memory loss, lasting at least 6 months, along with neurodegenerative changes detected by increased levels of hyperphosphorylated tau protein and a decrease of the neuroplasticity marker Egr1. Furthermore, co-treatment with the monoclonal antibody 8C10 specific for mCRP showed that long-term memory loss and tau pathology were entirely avoided by early blockade of mCRP. Notably, 8C10 mitigated Egr1 decrease in the mouse hippocampus. 8C10 also protected against mCRP-induced inflammatory pathways in a microglial cell line, as shown by the prevention of increased generation of nitric oxide. Additional in vivo and in vitro neuroprotective testing with the anti-inflammatory agent TPPU, an inhibitor of the soluble epoxide hydrolase enzyme, confirmed the predominant involvement of neuroinflammatory processes in the dementia induced by mCRP. Therefore, locally deposited mCRP in the infarcted brain may be a novel biomarker for AD prognosis, and its antibody blockade opens up therapeutic opportunities for reducing post-stroke AD risk.

Dietary Spray-Dried Porcine Plasma Reduces Neuropathological Alzheimer's Disease Hallmarks in SAMP8 Mice

Alzheimer's disease (AD) is characterized by the aberrant processing of amyloid precursor protein (APP) and the accumulation of hyperphosphorylated tau, both of which are accompanied by neuroinflammation. Dietary supplementation with spray-dried porcine plasma (SDP) has anti-inflammatory effects in inflammation models. We investigated whether dietary supplementation with SDP prevents the neuropathological features of AD. The experiments were performed in 2- and 6-month-old SAMP8 mice fed a control diet, or a diet supplemented with 8% SDP, for 4 months. AD brain molecular markers were determined by Western blot and real-time PCR. Senescent mice showed reduced levels of p-GSK3β (Ser9) and an increase in p-CDK5, p-tau (Ser396), sAPPβ, and the concentration of Aβ40, (all p < 0.05). SDP prevented these effects of aging and reduced Bace1 levels (all p < 0.05). Senescence increased the expression of Mme1 and Ide1 and pro-inflammatory cytokines (Il-17 and Il-18; all p < 0.05); these changes were prevented by SDP supplementation. Moreover, SDP increased Tgf-β expression (p < 0.05). Furthermore, in aged mice, the gene expression levels of the microglial activation markers Trem2, Ym1, and Arg1 were increased, and SDP prevented these increases (all p < 0.05). Thus, dietary SDP might delay AD onset by reducing its hallmarks in senescent mice.

Natural soluble epoxide hydrolase inhibitors from Inula britanica and their potential interactions with soluble epoxide hydrolase: Insight from inhibition kinetics and molecular dynamics

Soluble epoxide hydrolase (sEH) is a potential drug target to treat inflammation and neurodegenerative diseases. In this study, we found that the extract of Inula britanica exhibited significantly inhibitory effects against sEH, therefore, we investigated its phytochemical constituents to obtain seven new compounds together with sixteen known ones (1-20), including two pairs of novel enantiomers, (2S,3S)-britanicafanin A (1a), (2R,3R)-britanicafanin A (1b), (2R,3S)-britanicafanin B (2a), and (2S,3R)-britanicafanin B (2b), and three new lignans britanicafanins C-E (3-5). Their structures were determined by HRESIMS, 1D and 2D NMR, and electronic circular dichroism (ECD) spectra as well as quantum chemical computations. All the isolates were evaluated for their inhibitory effects against sEH, compounds 1-3, 5-7, 9, 10, 13, 14, and 17-20 showed significant inhibitory effects against sEH with IC₅₀ values from 3.56 μM to 26.93 μM. The inhibition kinetics results indicated that compounds 9, 10, 13, and 19 were all uncompetitive inhibitors, and their inhibition constants (K_i) values were 7.11, 1.99, 4.06, and 8.78 μM, respectively. Their potential interactions were analyzed by molecular docking and molecular dynamics (MD), which suggested that amino acid residues Asp335 and Asn359, especially Gln384, played an important role in the inhibition of compounds 10 and 13 on sEH, and compounds 10 and 13 could be considered as the potential candidates for the development of sEH inhibitors.

An epoxide hydrolase inhibitor reduces neuroinflammation in a mouse model of Alzheimer's disease

Neuroinflammation has been increasingly recognized to play a critical role in Alzheimer's disease (AD). The epoxy fatty acids (EpFAs) are derivatives of the arachidonic acid metabolism pathway and have anti-inflammatory activities. However, their efficacy is limited because of their rapid hydrolysis by the soluble epoxide hydrolase (sEH). We report that sEH is predominantly expressed in astrocytes and is elevated in postmortem brain tissue from patients with AD and in the 5xFAD β amyloid mouse model of AD. The amount of sEH expressed in AD mouse brains correlated with a reduction in brain EpFA concentrations. Using a specific small-molecule sEH inhibitor, 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU), we report that TPPU treatment protected wild-type mice against LPS-induced inflammation in vivo. Long-term administration of TPPU to the 5xFAD mouse model via drinking water reversed microglia and astrocyte reactivity and immune pathway dysregulation. This was associated with reduced β amyloid pathology and improved synaptic integrity and cognitive function on two behavioral tests. TPPU treatment correlated with an increase in EpFA concentrations in the brains of 5xFAD mice, demonstrating brain penetration and target engagement of this small molecule. These findings support further investigation of TPPU as a potential therapeutic agent for the treatment of AD.

Natural soluble epoxide hydrolase inhibitors from Alisma orientale and their potential mechanism with soluble epoxide hydrolase

Inhibition of soluble epoxide hydrolase (sEH) is considered to be an effective treatment for inflammation-related diseases, and small molecules origin from natural products show promising activity against sEH. Two undescribed protostanes, 3β-hydroxy-25-anhydro-alisol F (1) and 3β-hydroxy-alisol G (2) were isolated from Alisma orientale and identified as new sEH inhibitors with IC₅₀ values of 10.06 and 30.45 μM, respectively. Potential lead compound 1 was determined as an uncompetitive inhibitor against sEH, which had a K_i value of 5.13 μM. In-depth molecular docking and molecular dynamics simulations revealed that amino acid residue Ser374 plays an important role in the inhibition of 1, which also provides an idea for the development of sEH inhibitors based on protostane-type triterpenoids.

Inhibition of Soluble Epoxide Hydrolase Ameliorates Phenotype and Cognitive Abilities in a Murine Model of Niemann Pick Type C Disease

Niemann-Pick type C (NPC) disease is a rare autosomal recessive inherited childhood neurodegenerative disease characterized by the accumulation of cholesterol and glycosphingolipids, involving the autophagy-lysosome system. Inhibition of soluble epoxide hydrolase (sEH), an enzyme that metabolizes epoxy fatty acids (EpFAs) to 12-diols, exerts beneficial effects in modulating inflammation and autophagy, critical features of the NPC disease. This study aims to evaluate the effects of UB-EV-52, an sEH inhibitor (sEHi), in an NPC mouse model (Npc) by administering it for 4 weeks (5 mg/kg/day). Behavioral and cognitive tests (open-field test (OF)), elevated plus maze (EPM), novel object recognition test (NORT) and object location test (OLT) demonstrated that the treatment produced an improvement in short- and long-term memory as well as in spatial memory. Furthermore, UB-EV-52 treatment increased body weight and lifespan by 25% and reduced gene expression of the inflammatory markers (i.e., Il-1β and Mcp1) and enhanced oxidative stress (OS) markers (iNOS and Hmox1) in the treated Npc mice group. As for autophagic markers, surprisingly, we found significantly reduced levels of LC3B-II/LC3B-I ratio and significantly reduced brain protein levels of lysosomal-associated membrane protein-1 (LAMP-1) in treated Npc mice group compared to untreated ones in hippocampal tissue. Lipid profile analysis showed a significant reduction of lipid storage in the liver and some slight changes in homogenated brain tissue in the treated NPC mice compared to the untreated groups. Therefore, our results suggest that pharmacological inhibition of sEH ameliorates most of the characteristic features of NPC mice, demonstrating that sEH can be considered a potential therapeutic target for this disease.

Discovery of Soluble Epoxide Hydrolase Inhibitors from Chemical Synthesis and Natural Products

Soluble epoxide hydrolase (sEH) is an α/β hydrolase fold protein and widely distributed in numerous organs including the liver, kidney, and brain. The inhibition of sEH can effectively maintain endogenous epoxyeicosatrienoic acids (EETs) levels and reduce dihydroxyeicosatrienoic acids (DHETs) levels, resulting in therapeutic potentials for cardiovascular, central nervous system, and metabolic diseases. Therefore, since the beginning of this century, the development of sEH inhibitors is a hot research topic. A variety of potent sEH inhibitors have been developed by chemical synthesis or isolated from natural sources. In this review, we mainly summarized the interconnected aspects of sEH with cardiovascular, central nervous system, and metabolic diseases and then focus on representative inhibitors, which would provide some useful guidance for the future development of potential sEH inhibitors.

Cytochrome P450 Metabolism of Polyunsaturated Fatty Acids and Neurodegeneration

Due to the aging population in the world, neurodegenerative diseases have become a serious public health issue that greatly impacts patients' quality of life and adds a huge economic burden. Even after decades of research, there is no effective curative treatment for neurodegenerative diseases. Polyunsaturated fatty acids (PUFAs) have become an emerging dietary medical intervention for health maintenance and treatment of diseases, including neurodegenerative diseases. Recent research demonstrated that the oxidized metabolites, particularly the cytochrome P450 (CYP) metabolites, of PUFAs are beneficial to several neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease; however, their mechanism(s) remains unclear. The endogenous levels of CYP metabolites are greatly affected by our diet, endogenous synthesis, and the downstream metabolism. While the activity of omega-3 (ω-3) CYP PUFA metabolites and omega-6 (ω-6) CYP PUFA metabolites largely overlap, the ω-3 CYP PUFA metabolites are more active in general. In this review, we will briefly summarize recent findings regarding the biosynthesis and metabolism of CYP PUFA metabolites. We will also discuss the potential mechanism(s) of CYP PUFA metabolites in neurodegeneration, which will ultimately improve our understanding of how PUFAs affect neurodegeneration and may identify potential drug targets for neurodegenerative diseases.

2-Oxaadamant-1-yl Ureas as Soluble Epoxide Hydrolase Inhibitors: In Vivo Evaluation in a Murine Model of Acute Pancreatitis

In vivo pharmacological inhibition of soluble epoxide hydrolase (sEH) reduces inflammatory diseases, including acute pancreatitis (AP). Adamantyl ureas are very potent sEH inhibitors, but the lipophilicity and metabolism of the adamantane group compromise their overall usefulness. Herein, we report that the replacement of a methylene unit of the adamantane group by an oxygen atom increases the solubility, permeability, and stability of three series of urea-based sEH inhibitors. Most of these oxa-analogues are nanomolar inhibitors of both the human and murine sEH. Molecular dynamics simulations rationalize the molecular basis for their activity and suggest that the presence of the oxygen atom on the adamantane scaffold results in active site rearrangements to establish a weak hydrogen bond. The 2-oxaadamantane 22, which has a good solubility, microsomal stability, and selectivity for sEH, was selected for further in vitro and in vivo studies in models of cerulein-induced AP. Both in prophylactic and treatment studies, 22 diminished the overexpression of inflammatory and endoplasmic reticulum stress markers induced by cerulein and reduced the pancreatic damage.

The UPR in Neurodegenerative Disease: Not Just an Inside Job

Neurons are highly specialized cells that continuously and extensively communicate with other neurons, as well as glia cells. During their long lifetime, the post-mitotic neurons encounter many stressful situations that can disrupt protein homeostasis (proteostasis). The importance of tight protein quality control is illustrated by neurodegenerative disorders where disturbed neuronal proteostasis causes neuronal dysfunction and loss. For their unique function, neurons require regulated and long-distance transport of membrane-bound cargo and organelles. This highlights the importance of protein quality control in the neuronal endomembrane system, to which the unfolded protein response (UPR) is instrumental. The UPR is a highly conserved stress response that is present in all eukaryotes. However, recent studies demonstrate the existence of cell-type-specific aspects of the UPR, as well as cell non-autonomous UPR signaling. Here we discuss these novel insights in view of the complex cellular architecture of the brain and the implications for neurodegenerative diseases.