Eicosanoid signaling in neuroinflammation associated with Alzheimer's disease

A Lipidomic Approach to Studying the Downregulation of Free Fatty Acids by Cytosolic Phospholipase A2 Inhibitors

Inhibitors of cytosolic phospholipase A2 (GIVA cPLA2) have received great attention, since this enzyme is involved in a number of inflammatory diseases, including cancer and auto-immune and neurodegenerative diseases. Traditionally, the effects of GIVA cPLA2 inhibitors in cells have been studied by determining the inhibition of arachidonic acid release. However, although to a lesser extent, GIVA cPLA2 may also hydrolyze glycerophospholipids, releasing other free fatty acids (FFAs), such as linoleic acid or oleic acid. In the present work, we applied a liquid chromatography-high-resolution mass spectrometry method to study the levels of intracellular FFAs, after treating cells with selected GIVA cPLA2 inhibitors. Six inhibitors belonging to different chemical classes were studied, using SH-SY5Y neuroblastoma cells as a model. This lipidomic approach revealed that treatment with each inhibitor created a distinct intracellular FFA profile, suggesting not only inhibitory potency against GIVA cPLA2, but also other parameters affecting the outcome. Potent inhibitors were found to reduce not only arachidonic acid, but also other long-chain FAs, such as adrenic or linoleic acid, even medium-chain FAs, such as caproic or caprylic acid, suggesting that GIVA cPLA2 inhibitors may affect FA metabolic pathways in general. The downregulation of intracellular FFAs may have implications in reprogramming FA metabolism in neurodegenerative diseases and cancer.

Omega-3 EPA Supplementation Shapes the Gut Microbiota Composition and Reduces Major Histocompatibility Complex Class II in Aged Wild-Type and APP/PS1 Alzheimer's Mice: A Pilot Experimental Study

Background/Objectives: Neuroinflammation, a hallmark of Alzheimer's disease (AD), is characterized by elevated levels of inflammatory signaling molecules, including cytokines and eicosanoids, as well as increased microglial reactivity, and is augmented by gut microbiota dysbiosis via the gut-brain axis. We conducted a pilot experiment to elucidate the anti-inflammatory effects of dietary omega-3 polyunsaturated fatty acid (ω-3 PUFA) eicosapentaenoic acid (EPA) on the gut microbiota and neuroinflammation. Methods: Female APP/PS1 mice (TG) and non-transgenic littermates (WT), 13-14 months old, were fed a diet supplemented with 0.3% EPA or control chow for 3 weeks. The gut microbiota composition, hippocampal and plasma eicosanoids levels, platelet activation, and microglial phagocytosis, as well as the brain and retinal genes and protein expression, were analyzed. Results: EPA supplementation decreased the percentage of Bacteroidetes and increased bacteria of the phylum Firmicutes in APP/PS1 and WT mice. Inflammatory lipid mediators were elevated in the hippocampus of the TG mice, accompanied by a reduction in the endocannabinoid docosahexaenoyl ethanolamide (DHEA). Dietary EPA did not affect hippocampal lipid mediators, but reduced the levels of arachidonic-derived 5-HETE and N-arachidonoylethanolamine (AEA) in WT plasma. Moreover, EPA supplementation decreased major histocompatibility complex class II (MHCII) gene expression in the retina in both genotypes, and MHCII+ cells in the hippocampus of TG mice. Conclusions: This pilot study showed that short-term EPA supplementation shaped the gut microbiota by increasing butyrate-producing bacteria of the Firmicutes phylum and decreasing Gram-negative LPS-producing bacteria of the Bacteroidetes phylum, and downregulated the inflammatory microglial marker MHCII in two distinct regions of the central nervous system (CNS). Further investigation is needed to determine whether EPA-mediated effects on the microbiome and microglial MHCII have beneficial long-term effects on AD pathology and cognition.

Memantine and amantadine KLVFF peptide conjugates: Synthesis, structure determination, amyloid-β interaction and effects on recognition memory in mice

BACKGROUND

Adamantane derivatives, such as memantine (Mem) and amantadine (Ada), have distinct mechanisms and therapeutic applications. Ada is primarily utilized as an antiviral and anti-Parkinson drug without significant pro-cognitive effects, Mem is effective in various clinical conditions characterized by cognitive deficits, including Alzheimer's disease. Recent evidence highlights a neuroprotective role for Aβ monomers, suggesting that preventing their aggregation into toxic oligomers could be a promising therapeutic strategy. Based on the observation that the Lys-Leu-Val-Phe-Phe (KLVFF) peptide, can block the transition of randomly coiled Aβ monomers into toxic β-sheet aggregates, two KLVFF conjugates, the Mem-Succ-KLVFF and Ada-Succ-KLVFF were investigated.

METHODS

Peptides were synthesized by Microwave-Assisted Solid Phase Peptide Synthesis (MW-SPPS). Circular Dichroism (CD), Th-T fluorescence and Gel-Electrophoresis techniques were used to assess the inhibitory effect on Aβ42 fibrillogenesis. The formation of inclusion complexes with β-Cyclodextrin (β-CyD) was demonstrated by NMR Spectroscopy. The Novel Object Recognition (NOR) test, followed by double-blind analysis, was applied for in vivo response to compounds administration. In vitro effects on neurons were studied by MTT assay and WB analysis, whereas HR ESI-MS allowed the molecular detection on brain homogenates.

RESULTS

These compounds differently affect Aβ42 aggregation. Mem-Succ-KLVFF, and Succ-KLVFF affect pCREB levels in differentiated SH-SY5Y, a signaling pathway involved in memory processes. In the NOR test, both Mem and KLVFF exhibited pro-cognitive effects individually and synergistically when co-administered.

CONCLUSION

Structure-activity relationships are discussed, integrating in vivo results, memory-related cellular pathways, and HR-ESI-MS analyses. These findings support the therapeutic potential of these compounds in preserving cognitive function.

Genome-wide pleiotropy analysis of longitudinal blood pressure and harmonized cognitive performance measures

Background

Genome-wide association studies (GWAS) have identified over 1,000 blood pressure (BP) loci and over 80 loci for Alzheimer's disease (AD). Considering BP is an AD risk factor, identifying pleiotropy in BP and cognitive performance measures may indicate mechanistic links between BP and AD.

Methods

Genome-wide scans for pleiotropy in BP variables-systolic (SBP), diastolic (DBP), mean arterial (MAP), and pulse pressure (PP)-and co-calibrated scores for cognitive domains (executive function, language, and memory) were performed using generalized linear mixed models and 116,075 longitudinal measures from 25,726 participants of clinic-based and prospective cohorts. GWAS was conducted using PLACO to estimate each SNP's main effect and interaction with age, and their joint effect on pleiotropy. Effects of genome-wide significant (GWS) pleiotropic SNPs on cognition as direct or mediated through BP were evaluated using Mendelian randomization. Potential contribution of genes in top-ranked pleiotropic loci to cognitive resilience was assessed by comparing their expression in brain tissue from pathologically confirmed AD cases with and without clinical symptoms.

Results

Pleiotropy GWAS identified GWS associations with APOE and 11 novel loci. In the total sample, pleiotropy was identified for SBP and language with JPH2 ( P Joint =6.09×10 -9 ) and GATA3 ( P G×Age =1.42×10 -8 ), MAP and executive function with PAX2 ( P G×Age =4.22×10 -8 ), MAP and language with LOC105371656 ( P G×Age =1.75×10 -8 ), and DBP and language with SUFU ( P G =2.10×10 -8 ). In prospective cohorts, pleiotropy was found for SBP and language with RTN4 ( P G×Age =1.49×10 -8 ), DBP and executive function with ULK2 ( P Joint =2.85×10 -8 ), PP and memory with SORBS2 ( P G =2.33×10 -8 ), and DBP and memory with LOC100128993 ( P G×Age =2.81×10 -8 ). In clinic-based cohorts, pleiotropy was observed for PP and language with ADAMTS3 ( P G =2.37×10 -8 ) and SBP and memory with LINC02946 ( P G×Age =3.47×10 -8 ). Five GWS pleiotropic loci influence cognition directly, and genes at six pleiotropic loci were differentially expressed between pathologically confirmed AD cases with and without clinical symptoms.

Conclusion

Our results provide insight into the underlying mechanisms of high BP and AD. Ongoing efforts to harmonize BP and cognitive measures across several cohorts will improve the power of discovering, replicating, and generalizing novel associations with pleiotropic loci.

The emerging role of 12/15-lipoxygenase in ischemic stroke

The arachidonic acid metabolic pathway is a classic inflammatory pathway. 12/15-lipoxygenase (LOX), a member of the lipoxygenase family that metabolizes arachidonic acid, has been implicated in the pathogenesis of numerous central nervous system (CNS) diseases. Ischemic stroke is a devastating disease in which the occlusion of cerebral arteries leads to a series of pathophysiological changes in brain tissue, triggering an inflammatory cascade within the brain that results in neuroinflammation. Prior research has shown that 12/15-LOX levels in the brain are elevated following stroke. In this review, we elaborate on the key pathological mechanisms that unfold following ischemic stroke, including neuroinflammation, oxidative stress, neuronal apoptosis, and blood-brain barrier disruption, and present evidence demonstrating that 12/15-LOX inhibition could be used to treat ischemic stroke through various avenues. Furthermore, we list currently available inhibitors of 12/15-LOX and the preclinical or clinical applications, offering novel insights for the early diagnosis, prognosis evaluation, and targeted therapy in neurological diseases.

Recent advances in potential enzymes and their therapeutic inhibitors for the treatment of Alzheimer's disease

Alzheimer's disease (AD), a chronic neurodegenerative disease, is clinically characterized by loss of memory and learning ability among other neurological deficits. Amyloid plaques, hyperphosphorylated tau protein, and neurofibrillary tangles involve in AD etiology. Meanwhile, enzymes and their inhibitors have become the focus of research in AD treatment. In this review, the molecular mechanisms involved in the pathogenesis of AD were overviewed and various enzymes such as acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), β-secretase, γ-secretase, monoamine oxidase (MAO), and receptor of advanced glycation end products (RAGE) were highlighted as potential targets for AD treatment. Several hybrid molecules with essential substructures derived from various chemotypes have demonstrated desired pharmacological activity. It is envisioned that the development of new drugs that inhibit enzymes involved in AD is a future trend in the management of the disease.