The 5-Lipoxygenase as modulator of Alzheimer's γ-secretase and therapeutic target

Multifaceted Biological Activities of Culinary Herb and Spice Extracts: In Vitro and In Silico Simulation Insights into Inflammation-Related Targets

Culinary herbs and spices are valued worldwide for their flavor, aroma, and medicinal benefits. They encompass diverse bioactive metabolites, such as polyphenols and terpenoids, which contribute to plant defense and offer anticarcinogenic, anti-inflammatory, antioxidant, and cognitive-enhancing effects. This study aimed to establish the volatile fingerprint of culinary herbs (lemon verbena, chives, basil, sage, coriander, and parsley) and spices (curcuma, nutmeg, cumin, black pepper, Jamaica pepper, and juniper berry) using headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME/GC-MS). The predominant volatile organic metabolites (VOMs) identified were subjected to in silico molecular docking simulations of anti-Alzheimer's (e.g., acetylcholinesterase (AChE), butyrylcholinesterase (BChE)), antioxidants (e.g., monoamine oxidase B (MAO-B), inducible nitric oxide synthase (iNOS)), and anti-inflammatory receptors (e.g., 5-lipoxygenase (5-LOX), cyclooxygenase-2 (COX-2)). The culinary herb and spice extracts were also subjected to in vitro assays to evaluate their potential as antioxidant (DPPH, ABTS, and ORAC) and anti-inflammatory (% protein denaturation) agents. A total of 121 VOMs were identified in the culinary herbs and spices, with the predominant chemical families being monoterpenoids (48.3%), sesquiterpenoids (14.0%), esters (11.9%), and carbonyl compounds (8.8%). In silico molecular docking simulations revealed that cuminaldehyde, β-caryophyllene, γ-curcumene, germacrene D, and τ-cadinol exhibited the strongest inhibitory activities against the selected receptors. Among the extracts, Jamaica pepper showed the highest antioxidant and anti-inflammatory activities, while lemon verbena exhibited the lowest ones. These findings highlight the promising potential of the studied culinary herbs and spices in the modulation of inflammatory processes related to Alzheimer's disease. However, further investigations, particularly clinical studies, are recommended to validate these results and explore their therapeutic applications.

Metabolic Alteration in Oxylipins and Endocannabinoids Point to an Important Role for Soluble Epoxide Hydrolase and Inflammation in Alzheimer's Disease - Finding from Alzheimer's Disease Neuroimaging Initiative

Mounting evidence implicates inflammation as a key factor in Alzheimer's disease (AD) development. We previously identified pro-inflammatory soluble epoxide hydrolase (sEH) metabolites to be elevated in plasma and CSF of AD patients and to be associated with lower cognition in non-AD subjects. Soluble epoxide hydrolase is a key enzyme converting anti-inflammatory epoxy fatty acids to pro-inflammatory diols, reported to be elevated in multiple cardiometabolic disorders. Here we analyzed over 700 fasting plasma samples from the baseline of Alzheimer's Disease Neuroimaging Initiative (ADNI) 2/GO study. We applied targeted mass spectrometry method to provide absolute quantifications of over 150 metabolites from oxylipin and endocannabinoids pathway, interrogating the role for inflammation/immune dysregulation and the key enzyme soluble epoxide hydrolase in AD. We provide further insights into the regulation of this pathway in different disease stages, APOE genotypes and between sexes. Additionally, we investigated in mild cognitive impaired (MCI) patients, metabolic signatures that inform about resilience to progression and conversion to AD. Key findings include I) confirmed disruption in this key central pathway of inflammation and pointed to dysregulation of sEH in AD with sex and disease stage differences; II) identified markers of disease progression and cognitive resilience using sex and ApoE genotype stratified analysis highlighting an important role for bile acids, lipid peroxidation and stress response hormone cortisol. In conclusion, we provide molecular insights into a central pathway of inflammation and links to cognitive dysfunction, suggesting novel therapeutic approaches that are based on targeting inflammation tailored for subgroups of individuals based on their sex, APOE genotype and their metabolic profile.

"A patent review on arachidonic acid lipoxygenase (LOX) inhibitors for the treatment of neurodegenerative diseases (2018-present)"

INTRODUCTION

Neuroinflammation is correlated to neurodegenerative diseases like Alzheimer's disease (AD), Amyotrophic Lateral Sclerosis (ALS), Multiple Sclerosis (MS), Huntington Disease (HD), and Parkinson's disease (PD). A lot of recent research and patents are focused on the design and synthesis of arachidonic acid lipoxygenase (ALOX) inhibitors for the treatment of neurodegenerative diseases.

AREAS COVERED

The survey covers natural products, synthesis, hybrids, and assessments of biological effects in biological studies as ALOX inhibitors. A survey of patent publications from 2018 to present, taken from Google Scholar, Espanet, Web of Science, Drugbank, Scopus, or PubMed is analyzed.

EXPERT OPINION

The authors suggest that (i) numerous areas of biology-pharmacology need to be considered: selectivity, in vivo studies, toxicity, bioavailability, and drug-likeness, the mechanism of action in different animals and humans, evaluation of more efficient and selective biological tests; (ii) synthetic method outbalance in the discovery and production of ALOX inhibitors with greater selectivity. Several ALOX inhibitors show promising results for the treatment of neurological disorders. Their clinical evaluation will be critical to assess therapeutic utility. The compounds for which the mechanism of action and their bioavailability are well defined can be used as lead compounds for the treatment of neurodegenerative diseases.

Protective effects of licofelone on scopolamine-induced spatial learning and memory impairment by enhancing parkin-dependent mitophagy and promotion of neural regeneration and in adult mice

Inhibition of COX and LOX could contribute to memory formation and prevention of neurodegeneration, by alleviation of neuroinflammation and improvement of mitochondrial homeostasis. We aimed to assess the effect of licofelone, a dual COX and 5-LOX inhibitor on memory formation, neural apoptosis, neural regeneration, and mitophagy in acute and chronic dosages, given that licofelone could regulate nitric oxide levels. Y-maze and Passive Avoidance tests were used to evaluate memory function in NMRI mice using the EthoVision setting, following scopolamine administration (1 mg/kg, i.p.) as an acute amnestic drug. Hippocampi were used to evaluate the levels of apoptosis via TUNEL assay, neural regeneration via immunohistochemistry method detecting doublecortin and nestin, and mitophagy via Western blot of mitophagy proteins Parkin and ATG5. While acute high-dose licofelone (20 mg/kg) could reverse amnestic effects of scopolamine in passive avoidance test (p = 0.0001), Chronic licofelone (10 mg/kg for 10 consecutive days) could improve performance in Y-maze (p = 0.0007). Molecular analysis revealed that the chronic form of the drug could enhance neural regeneration in CA1 and SGZ regions, reset mitophagy levels as much as the healthy state, and reduce apoptosis rate. Licofelone appears to show a desirable anti-amnestic profile in a low dose chronically; it is hence recommended for future clinical studies on the prevention of neuroinflammation and memory deficit.

Leukotriene signaling in neurodegeneration: implications for treatment strategies

Leukotrienes (LTs) are a group of substances that cause inflammation. They are produced by the enzyme 5-lipoxygenase (5-LOX) from arachidonic acid. Cysteinyl LTs are a group of lipid molecules that have a prominent role in inflammatory signaling in the allergic diseases. Although they are traditionally known for their role in allergic disease, current advancements in bio-medical research have shed light on the involvement of these inflammatory mediators in diseases such as in the inflammation related to central nervous system (CNS) disorders. Among the CNS diseases, LTs, along with 5-LOX and their receptors, have been shown to be associated with multiple sclerosis (MS), Alzheimer's disease (AD), and Parkinson's disease (PD). Through a comprehensive review of current research and experimentation, this investigation provides an insight on the biosynthesis, receptors, and biological effects of LTs in the body. Furthermore, implications of leukotriene signaling in CNS and its intricate role in neurodegeneration are also studied. Through the revelation of these insights, our aim is to establish a foundation for the development of enhanced and focused therapeutic approaches in the continuous endeavor to combat neurodegeneration. Furthermore, the pharmacological inhibition of leukotriene signaling with selective inhibitors offers promising prospects for future interventions and treatments for neurodegenerative diseases.

Discovery of a potent melatonin-based inhibitor of quinone reductase-2 with neuroprotective and neurogenic properties

5-Methoxy-3-(5-methoxyindolin-2-yl)-1H-indole (3), whose structure was unambiguously elucidated by X-ray analysis, was identified as a multi-target compound with potential application in neurodegenerative diseases. It is a low nanomolar inhibitor of QR2 (IC50 = 7.7 nM), with greater potency than melatonin and comparable efficacy to the most potent QR2 inhibitors described to date. Molecular docking studies revealed the potential binding mode of 3 to QR2, which explains its superior potency compared to melatonin. Furthermore, compound 3 inhibits hMAO-A, hMAO-B and hLOX-5 in the low micromolar range and is an excellent ROS scavenger. In phenotypic assays, compound 3 showed neuroprotective activity in a cellular model of oxidative stress damage, it was non-toxic, and was able to activate neurogenesis from neural stem-cell niches of adult mice. These excellent biological properties, together with its both good in silico and in vitro drug-like profile, highlight compound 3 as a promising drug candidate for neurodegenerative diseases.

Impact of 5-Lipoxygenase Deficiency on Dopamine-Mediated Behavioral Responses

The 5-lipoxygenase/leukotriene system has been implicated in both physiological and pathological states within the central nervous system. Understanding how this system interacts with the dopaminergic system could provide valuable insights into dopamine-related pathologies. This study focused on examining both motor and non-motor dopamine-related responses in 5-lipoxygenase/leukotriene-deficient mice. We used pharmacological agents such as amphetamine, apomorphine, and reserpine to challenge the dopaminergic system, evaluating their effects on prepulse inhibition reaction (PPI), general motor activity, and oral involuntary movements. Additionally, we analyzed striatal glial marker expression (GFAP and Iba-1) in reserpine-treated mice. The 5-lipoxygenase/leukotriene-deficient mice exhibited increased spontaneous locomotor activity, including both horizontal and vertical exploration, along with stereotyped behavior compared to wild-type mice. This hyperactivity was reduced by acute apomorphine treatment. Although basal PPI responses were unchanged, 5-lipoxygenase/leukotriene-deficient mice displayed a significant reduction in susceptibility to amphetamine-induced PPI disruption. Conversely, these mice were more vulnerable to reserpine-induced involuntary movements. There were no significant differences in the basal expression of striatal GFAP and Iba-1 positive cells between 5-lipoxygenase/leukotriene-deficient and wild-type mice. However, reserpine treatment significantly increased GFAP immunoreactivity in wild-type mice, an effect not observed in 5-lipoxygenase-deficient mice. Additionally, the percentage of activated microglia was significantly higher in reserpine-treated wild-type mice, an effect absents in 5-lipoxygenase/leukotriene-deficient mice. Our findings suggest that 5-lipoxygenase/leukotriene deficiency leads to a distinctive dopaminergic phenotype, indicating that leukotrienes may influence the modulation of dopamine-mediated responses.

Eicosanoid signaling in neuroinflammation associated with Alzheimer's disease

Alzheimer's disease (AD) is a prevalent neurodegenerative condition affecting a substantial portion of the global population. It is marked by a complex interplay of factors, including the accumulation of amyloid plaques and tau tangles within the brain, leading to neuroinflammation and neuronal damage. Recent studies have underscored the role of free lipids and their derivatives in the initiation and progression of AD. Eicosanoids, metabolites of polyunsaturated fatty acids like arachidonic acid (AA), emerge as key players in this scenario. Remarkably, eicosanoids can either promote or inhibit the development of AD, and this multifaceted role is determined by how eicosanoid signaling influences the immune responses within the brain. However, the precise molecular mechanisms dictating the dual role of eicosanoids in AD remain elusive. In this comprehensive review, we explore the intricate involvement of eicosanoids in neuronal function and dysfunction. Furthermore, we assess the therapeutic potential of targeting eicosanoid signaling pathways as a viable strategy for mitigating or halting the progression of AD.

A biomedical perspective of pyocyanin from Pseudomonas aeruginosa: its applications and challenges

Pyocyanin is a bioactive pigment produced by Pseudomonas aeruginosa. It is an important virulence factor that plays a critical role in P. aeruginosa infections as a redox-active secondary metabolite and a quorum sensing (QS) signaling molecule. Pyocyanin production from chorismic acid requires the involvement of two homologous operons, phz1 and phz2, which are activated by QS regulatory proteins. Pyocyanin inhibits the proliferation of bacterial, fungal, and mammalian cells by inducing oxidative stress due to which it acts as a potent antibacterial, antifungal, and anticancer agent. Its potential role as a neuroprotectant needs further exploration. However, pyocyanin exacerbates the damaging effects of nosocomial infections caused by P. aeruginosa in immunocompromised individuals. Further, cystic fibrosis (CF) patients are highly susceptible to persistent P. aeruginosa infections in the respiratory system. The bacterial cells form colonies and three interconnected QS networks-pqs, las, and rhl-get activated, thus stimulating the cells to produce pyocyanin which exacerbates pulmonary complications. As an opportunistic pathogen, P. aeruginosa produces pyocyanin to impede the recovery of injuries like burn wounds through its anti-proliferative activity. Moreover, pyocyanin plays a vital role in compounding P. aeruginosa infections by promoting biofilm formation. This review begins with a brief description of the characteristics of pyocyanin, its activity, and the different aspects of its production including its biosynthesis, the role of QS, and the effect of environmental factors. It then goes on to explore the potential applications of pyocyanin as a biotherapeutic molecule while also highlighting the biomedical challenges and limitations that it presents.

Montelukast as a treatment for refractory cutaneous lupus: A case series

INTRODUCTION

There are no drugs specifically approved to treat cutaneous lupus. Inflammatory cells in lupus skin lesions can produce leukotrienes (LT), which promote tissue damage. In addition to hypersensitivity reactions, LT are also associated with cardiovascular diseases and elevated serum LT levels have been linked to worse atherosclerotic disease in lupus. Targeting LT could thus be an alternative to treat lupus. We present 4 cases of cutaneous lupus successfully treated with montelukast (MLK), a Cys-LT antagonist.

METHODS

Four consecutive female systemic lupus erythematosus (SLE) patients with refractory skin lesions were treated with MLK (10 mg/d) in the Hospital Universitário Walter Cantídio of the Universidade Federal do Ceará. Skin lesions were scored using Revised Cutaneous LE Disease Area and Severity Index (RCLASI). Relative expression of the 5-lipoxigenase (ALOX5) and 15-lipoxigenase (ALOX15) genes was determined in peripheral blood cells (PBC) from lupus patients and 4 age-matched female controls.

RESULTS

All patients experienced improvement of skin lesions measured using RCLASI scores within 2-12 weeks following initiation of MLK. The response was sustained for at least 3 months follow-up and no adverse events were recorded. ALOX5 but not ALOX15 gene expression was significantly (P = 0.0425) increased in PBC from SLE patients vs controls.

CONCLUSION

This is the first report of a fast and sustained successful response of cutaneous lupus to MLK. Given its acceptable safety profile, our data encourage development of a randomized trial as an attempt to reposition MLK as a safe, affordable alternative to treat cutaneous lupus.

Structures of Leukotriene Biosynthetic Enzymes and Development of New Therapeutics

Leukotrienes are potent immune-regulating lipid mediators with patho-genic roles in inflammatory and allergic diseases, particularly asthma. These autacoids also contribute to low-grade inflammation, a hallmark of cardiovascular, neurodegenerative, metabolic, and tumor diseases. Biosynthesis of leukotrienes involves release and oxidative metabolism of arachidonic acid and proceeds via a set of cytosolic and integral membrane enzymes that are typically expressed by cells of the innate immune system. In activated cells, these enzymes traffic and assemble at the endoplasmic and perinuclear membrane, together comprising a biosynthetic complex. Here we describe recent advances in our molecular understanding of the protein components of the leukotriene-synthesizing enzyme machinery and also briefly touch upon the leukotriene receptors. Moreover, we discuss emerging opportunities for pharmacological intervention and development of new therapeutics.

Synthesis, structural characterization and study of antioxidant and anti-PrPSc properties of flavonoids and their rhenium(I)-tricarbonyl complexes

This study aims at the synthesis and initial biological evaluation of novel rhenium-tricarbonyl complexes of 3,3',4',5,7-pentahydroxyflavone (quercetin), 3,7,4΄-trihydroxyflavone (resokaempferol), 5,7-dihydroxyflavone (chrysin) and 4΄,5,7-trihydroxyflavonone (naringenin) as neuroprotective and anti-PrP agents. Resokaempferol was synthesized from 2,2΄,4-trihydroxychalcone by H₂O₂/NaOH. The rhenium-tricarbonyl complexes of the type fac-[Re(CO)₃(Fl)(sol)] were synthesized by reacting the precursor fac-[Re(CO)₃(sol)₃]⁺ with an equimolar amount of the flavonoids (Fl) quercetin, resokaempferol, chrysin and naringenin and the solvent (sol) was methanol or water. The respective Re-flavonoid complexes were purified by semi-preparative HPLC and characterized by spectroscopic methods. Furthermore, the structure of Re-chrysin was elucidated by X-ray crystallography. Initial screening of the neuroprotective properties of these compounds included the in vitro assessment of the antioxidant properties by the DPPH assay as well as the anti-lipid peroxidation of linoleic acid in the presence of AAPH and their ability to inhibit soybean lipoxygenase. From the above studies, it was concluded that the complexes' properties are mainly correlated with the structural characteristics and the presence of the flavonoids. The flavonoids and their respective Re-complexes were also tested in vitro for their ability to inhibit the formation and aggregation of the amyloid-like abnormal prion protein, PrP^Sc, by employing the real-time quaking-induced conversion assay with recombinant PrP seeded with cerebrospinal fluid from patients with Creutzfeldt-Jakob disease. All the compounds blocked de novo abnormal PrP formation and aggregation.

Recent Trends in the Management of Alzheimer's Disease: Current Therapeutic Options and Drug Repurposing Approaches

Alzheimer's disease is one of the most progressive forms of dementia, ultimately leading to death in aged populations. The major hallmarks of Alzheimer's disease include deposition of extracellular amyloid senile plaques and intracellular neurofibrillary tangles in brain neuronal cells. Although there are classical therapeutic options available for the treatment of the diseases, however, they provide only a symptomatic relief and do not modify the molecular pathophysiological course of the disease. Recent research advances in Alzheimer's disease have highlighted the potential role of anti-amyloid, anti-tau, and anti-inflammatory therapies. However, these therapies are still in different phases of pre-clinical/clinical development. In addition, drug repositioning/repurposing is another interesting and promising approach to explore rationalized options for the treatment of Alzheimer's disease. This review discusses the different aspects of the pathophysiological mechanism involved in the progression of Alzheimer's disease along with the limitations of current therapies. Furthermore, this review also highlights emerging investigational drugs along with recent drug repurposing approaches for Alzheimer's disease.

New Zileuton-Hydroxycinnamic Acid Hybrids: Synthesis and Structure-Activity Relationship towards 5-Lipoxygenase Inhibition

A novel series of zileuton-hydroxycinnamic acid hybrids were synthesized and screened as 5-lipoxygenase (5-LO) inhibitors in stimulated HEK293 cells and polymorphonuclear leukocytes (PMNL). Zileuton’s (1) benzo[b]thiophene and hydroxyurea subunits combined with hydroxycinnamic acid esters’ ester linkage and phenolic acid moieties were investigated. Compound 28, bearing zileuton’s (1) benzo[b]thiophene and sinapic acid phenethyl ester’s (2) α,β-unsaturated phenolic acid moiety 28, was shown to be equipotent to zileuton (1), the only clinically approved 5-LO inhibitor, in stimulated HEK293 cells. Compound 28 was three times as active as zileuton (1) for the inhibition of 5-LO in PMNL. Compound 37, bearing the same sinapic acid (3,5-dimethoxy-4-hydroxy substitution) moiety as 28, combined with zileuton’s (1) hydroxyurea subunit was inactive. This result shows that the zileuton’s (1) benzo[b]thiophene moiety is essential for the inhibition of 5-LO product biosynthesis with our hydrids. Unlike zileuton (1), Compound 28 formed two π–π interactions with Phe177 and Phe421 as predicted when docked into 5-LO. Compound 28 was the only docked ligand that showed a π–π interaction with Phe177 which may play a part in product specificity as reported.

Biotin, coenzyme Q10, and their combination ameliorate aluminium chloride-induced Alzheimer's disease via attenuating neuroinflammation and improving brain insulin signaling

Insulin is important for brain function and neuronal survival. Insulin signaling is initiated by the phosphorylation of insulin receptor substrate-1 (IRS-1) at tyrosine (pTyr) residue. However, IRS-1 is inhibited by phosphorylation at serine (pSer). In Alzheimer's disease (AD), oxidative stress and accumulation of amyloid beta (Aβ) induce neuroinflammation, which augments pSer-IRS-1 and reduces pTyr-IRS-1 disturbing insulin signaling pathway. Coenzyme Q10 (CoQ10) and biotin possess antioxidant and anti-inflammatory properties, and, in this study, their impact on insulin signaling is investigated in an aluminium chloride (AlCl3 ) model of AD. AD was induced by oral administration of AlCl3 (75 mg/kg) for 60 days. Biotin (2 mg/kg), CoQ10 (10 mg/kg), and their combination were supplemented concomitantly with AlCl3 for 60 days. Memory test and histological examination were performed. Brain levels of lipid peroxides, antioxidants (reduced glutathione and superoxide dismutase), inflammatory markers (tumor necrosis factor-α, interleukin-6 [IL-6], IL-1, and nuclear factor κB), and phosphorylated Akt (survival kinase) as well as protein levels of Aβ, IRS-1 (pTyr and pSer), and caspase-3 (apoptotic marker) were determined. AlCl3 resulted in impaired memory, significant increase in Aβ, lipid peroxides, inflammatory markers, caspase-3, and pSer-IRS-1, with significant reduction of the antioxidants, pTyr-IRS-1, and p-Akt reflecting Aβ-induced inflammation and defective insulin signaling. Histological examination revealed focal aggregations of inflammatory cells and neuronal degeneration. The biochemical deviations and histological changes were attenuated by the concomitant treatment with biotin and, to greater extent, with CoQ10 and the combination. In conclusion, biotin and CoQ10 could protect against AD via attenuating inflammatory response and enhancing insulin signaling.

Phosphorylation of 5-LOX: The Potential Set-point of Inflammation

Inflammation secondary to tissue injuries serves as a double-edged sword that determines the prognosis of tissue repair. As one of the most important enzymes controlling the inflammation process by producing leukotrienes, 5-lipoxygenase (5-LOX, also called 5-LO) has been one of the therapeutic targets in regulating inflammation for a long time. Although a large number of 5-LOX inhibitors have been explored, only a few of them can be applied clinically. Surprisingly, phosphorylation of 5-LOX reveals great significance in regulating the subcellular localization of 5-LOX, which has proven to be an important mechanism underlying the enzymatic activities of 5-LOX. There are at least three phosphorylation sites in 5-LOX jointly to determine the final inflammatory outcomes, and adjustment of phosphorylation of 5-LOX at different phosphorylation sites brings hope to provide an unrecognized means to regulate inflammation. The present review intends to shed more lights into the set-point-like mechanisms of phosphorylation of 5-LOX and its possible clinical application by summarizing the biological properties of 5-LOX, the relationship of 5-LOX with neurodegenerative diseases and brain injuries, the phosphorylation of 5-LOX at different sites, the regulatory effects and mechanisms of phosphorylated 5-LOX upon inflammation, as well as the potential anti-inflammatory application through balancing the phosphorylation-depended set-point.

Antagonism of cysteinyl leukotrienes and their receptors as a neuroinflammatory target in Alzheimer's disease

BACKGROUND

Alzheimer's disease is a complex multifaceted neurodegenerative disorder. It is characterized by the deposition of extracellular amyloid senile plaques and intracellular neurofibrillary tangles leading to progressive dementia and death in aged adult population. Recent emerging research has highlighted a potential pharmacological role of 5-lipoxyenase-cysteinyl leukotriene pathway in molecular pathogenesis of Alzheimer's disease.

OBJECTIVE

Although cysteinyl leukotrienes and their receptors have a major clinical role in chronic respiratory inflammation, their roles in chronic neuroinflammation in Alzheimer's disease need a detailed and careful exploration.

RESULTS AND CONCLUSION

This review article highlights a novel role of cysteinyl leukotrienes and their receptors in pathophysiology of Alzheimer's disease in order to understand the underlying molecular mechanism. In addition, it summarizes the recent advances in various pre-clinical and clinical strategies used to modulate this pathway for therapeutic targeting of Alzheimer's disease.

The Role of Eicosanoids in Alzheimer's Disease

Alzheimer's disease (AD) is one of the most common neurodegenerative disorders known. Estimates from the Alzheimer's Association suggest that there are currently 5.8 million Americans living with the disease and that this will rise to 14 million by 2050. Research over the decades has revealed that AD pathology is complex and involves a number of cellular processes. In addition to the well-studied amyloid-β and tau pathology, oxidative damage to lipids and inflammation are also intimately involved. One aspect all these processes share is eicosanoid signaling. Eicosanoids are derived from polyunsaturated fatty acids by enzymatic or non-enzymatic means and serve as short-lived autocrine or paracrine agents. Some of these eicosanoids serve to exacerbate AD pathology while others serve to remediate AD pathology. A thorough understanding of eicosanoid signaling is paramount for understanding the underlying mechanisms and developing potential treatments for AD. In this review, eicosanoid metabolism is examined in terms of in vivo production, sites of production, receptor signaling, non-AD biological functions, and known participation in AD pathology.

Inflammation: the link between comorbidities, genetics, and Alzheimer's disease

Alzheimer’s disease (AD) is a neurodegenerative disorder, most cases of which lack a clear causative event. This has made the disease difficult to characterize and, thus, diagnose. Although some cases are genetically linked, there are many diseases and lifestyle factors that can lead to an increased risk of developing AD, including traumatic brain injury, diabetes, hypertension, obesity, and other metabolic syndromes, in addition to aging. Identifying common factors and trends between these conditions could enhance our understanding of AD and lead to the development of more effective treatments. Although the immune system is one of the body’s key defense mechanisms, chronic inflammation has been increasingly linked with several age-related diseases. Moreover, it is now well accepted that chronic inflammation has an important role in the onset and progression of AD. In this review, the different inflammatory signals associated with AD and its risk factors will be outlined to demonstrate how chronic inflammation may be influencing individual susceptibility to AD. Our goal is to bring attention to potential shared signals presented by the immune system during different conditions that could lead to the development of successful treatments.

Leukotriene biosynthetic enzymes as therapeutic targets

Leukotrienes are powerful immune-regulating lipid mediators with established pathogenic roles in inflammatory allergic diseases of the respiratory tract - in particular, asthma and hay fever. More recent work indicates that these lipids also contribute to low-grade inflammation, a hallmark of cardiovascular, neurodegenerative, and metabolic diseases as well as cancer. Biosynthesis of leukotrienes involves oxidative metabolism of arachidonic acid and proceeds via a set of soluble and membrane enzymes that are primarily expressed by cells of myeloid origin. In activated immune cells, these enzymes assemble at the endoplasmic and perinuclear membrane, constituting a biosynthetic complex. This Review describes recent advances in our understanding of the components of the leukotriene-synthesizing enzyme machinery, emerging opportunities for pharmacological intervention, and the development of new medicines exploiting both antiinflammatory and pro-resolving mechanisms.

Overexpression of 5-Lipoxygenase Worsens the Phenotype of a Mouse Model of Tauopathy

Brain accumulation of increasing amount of phosphorylated microtubule associated tau protein is one the major hallmark lesions of Alzheimer's disease (AD) and related tauopathies. Consistent evidence from clinical and animal studies has shown that neuroinflammation characterizes these diseases. The 5-lipoxygenase (5LO) is an enzyme protein whose metabolic products are lipids with potent inflammatory actions. Previously, we showed that blockade of 5LO activation ameliorates the phenotype of the htau transgenic mice. Here, by employing a vector system to overexpress 5LO in the brain of the same mouse model, we investigated its role and contribution to their behavioral deficits and development of tau neuropathology. Compared with controls, 5LO gene targeted mice manifested significant impairments in their memory and learning ability. On the other hand, brain tissues of the same mice had higher 5LO protein level and activity which resulted in intense neuroinflammation and synaptic pathology. Further, the same mice had a significant elevation of tau phosphorylation, which associated with the activation of the cdk5 kinase and an accumulation of insoluble tau. The functional involvement of this kinase in the 5LO-dependent tau phosphorylation was confirmed in neuronal cells. Taken together, our findings demonstrate that neuronal 5LO is directly involved in tau phosphorylation and tau neuropathology, and for this reason, it should be considered a good therapeutic target for tauopathies.

Quantitative proteomics of acutely-isolated mouse microglia identifies novel immune Alzheimer's disease-related proteins

BACKGROUND

Microglia are innate immune cells of the brain that perform phagocytic and inflammatory functions in disease conditions. Transcriptomic studies of acutely-isolated microglia have provided novel insights into their molecular and functional diversity in homeostatic and neurodegenerative disease states. State-of-the-art mass spectrometry methods can comprehensively characterize proteomic alterations in microglia in neurodegenerative disorders, potentially providing novel functionally relevant molecular insights that are not provided by transcriptomics. However, comprehensive proteomic profiling of adult primary microglia in neurodegenerative disease conditions has not been performed.

METHODS

We performed quantitative mass spectrometry based proteomic analyses of purified CD11b⁺ acutely-isolated microglia from adult (6 mo) mice in normal, acute neuroinflammatory (LPS-treatment) and chronic neurodegenerative states (5xFAD model of Alzheimer's disease [AD]). Differential expression analyses were performed to characterize specific microglial proteomic changes in 5xFAD mice and identify overlap with LPS-induced pro-inflammatory changes. Our results were also contrasted with existing proteomic data from wild-type mouse microglia and from existing microglial transcriptomic data from wild-type and 5xFAD mice. Neuropathological validation studies of select proteins were performed in human AD and 5xFAD brains.

RESULTS

Of 4133 proteins identified, 187 microglial proteins were differentially expressed in the 5xFAD mouse model of AD pathology, including proteins with previously known (Apoe, Clu and Htra1) as well as previously unreported relevance to AD biology (Cotl1 and Hexb). Proteins upregulated in 5xFAD microglia shared significant overlap with pro-inflammatory changes observed in LPS-treated mice. Several proteins increased in human AD brain were also upregulated by 5xFAD microglia (Aβ peptide, Apoe, Htra1, Cotl1 and Clu). Cotl1 was identified as a novel microglia-specific marker with increased expression and strong association with AD neuropathology. Apoe protein was also detected within plaque-associated microglia in which Apoe and Aβ were highly co-localized, suggesting a role for Apoe in phagocytic clearance of Aβ.

CONCLUSIONS

We report a comprehensive proteomic study of adult mouse microglia derived from acute neuroinflammation and AD models, representing a valuable resource to the neuroscience research community. We highlight shared and unique microglial proteomic changes in acute neuroinflammation aging and AD mouse models and identify novel roles for microglial proteins in human neurodegeneration.

Antileukotriene therapy by reducing tau phosphorylation improves synaptic integrity and cognition of P301S transgenic mice

The 5‐lipoxygenase (5LO) is a source of inflammatory leukotrienes and is upregulated in Alzheimer's disease and related tauopathies. However, whether it directly modulates tau phosphorylation and the development of its typical neuropathology in the absence of Aβ or is a secondary event during the course of the disease pathogenesis remains to be fully elucidated. The goal of this study was to evaluate the effect that pharmacologic blockade of this inflammatory pathway has on the phenotype of a transgenic mouse model of tauopathy, the P301S mice. Starting at 3 months of age, P301S mice were randomized to receive zileuton, a specific 5LO blocker, for 7 months; then, its effect on their behavioral deficits and neuropathology was assessed. Inhibition of leukotrienes formation was associated with a reduction in tau phosphorylation and an amelioration of memory and learning as well as synaptic integrity, which were secondary to a downregulation of the cdk5 kinase pathway. Our results demonstrate that the 5LO enzyme is a key player in modulating tau phosphorylation and pathology and that blockade of its enzymatic activity represents a desirable disease‐modifying therapeutic approach for tauopathy.

Thyme essential oils from Spain: Aromatic profile ascertained by GC–MS, and their antioxidant, anti-lipoxygenase and antimicrobial activities

Six samples of red thyme (Thymus zygis) and two samples of winter thyme (Thymus hyemalis) essential oils (EOs) were obtained from plants cultivated in south-eastern Spain and extracted by steam distillation. Analysis by gas chromatography coupled with mass spectrometry detection provided the relative (%) and absolute (mM) concentrations. Thymol (30–54%), p-cymene (14–27%) and γ-terpinene (8–28%) were the most abundant components of T. zygis EO, while 1,8-Cineole (3–37%), p-cymene (1–29%), linalool (8–13%) and thymol (0–19%) were the most abundant components in the case of T. hyemalis EO. Enantioselective gas chromatography identified (−)-linalool, (−)-borneol and (+)-limonene as the main enantiomers. Several methods to evaluate antioxidant capacities were applied to the EOs, concluding that their activities were mainly due to thymol and linalool. The inhibition of lipoxygenase activity, mainly due to thymol, p-cymene and linalool, suggested their possible use as anti-inflammatories. The high antibacterial and antifungal activities determined for the EOs means that they can be used as natural preservatives. The results support the potential use of Thymus sp. EOs as natural food, cosmetic and pharmaceutical ingredients.