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Chemical Science Jun 2024Secreted phospholipase A2 (sPLA2) is a Ca-dependent, widely distributed enzyme superfamily in almost all mammalian tissues and bacteria. It is also a critical component...
Secreted phospholipase A2 (sPLA2) is a Ca-dependent, widely distributed enzyme superfamily in almost all mammalian tissues and bacteria. It is also a critical component of the venom of nearly all snakes, as well as many invertebrate species. In non-venomous contexts, sPLA2 assumes significance in cellular signaling pathways by binding cell membranes and catalyzing ester bond hydrolysis at the sn-2 position of phospholipids. Elevated levels of GIIA sPLA2 have been detected in the synovial fluid of arthritis patients, where it exhibits a pro-inflammatory function. Consequently, identifying sPLA2 inhibitors holds promise for creating highly effective pharmaceutical treatments. Beyond arthritis, the similarities among GIIA sPLA2s offer an opportunity for developing treatments against snakebite envenoming, the deadliest neglected tropical disease. Despite decades of study, the details of PLA2 membrane-binding, substrate-binding, and reaction mechanism remain elusive, demanding a comprehensive understanding of the sPLA2 catalytic mechanism. This study explores two reaction mechanism hypotheses, involving one or two water molecules, and distinct roles for the Ca cofactor. Our research focuses on the human synovial sPLA2 enzyme bound to lipid bilayers of varying phospholipid compositions, and employing adiabatic QM/MM and QM/MM MD umbrella sampling methods to energetically and geometrically characterize the structures found along both reaction pathways. Our studies demonstrate the higher frequency of productive conformations within the single-water pathway, also revealing a lower free energy barrier for hydrolyzing POPC. Furthermore, we observe that the TS of this concerted one-step reaction closely resembles transition state geometries observed in X-ray crystallography complexes featuring high-affinity transition state analogue inhibitors.
PubMed: 38939148
DOI: 10.1039/d4sc02315c -
Frontiers in Aging Neuroscience 2024At least one-third of the identified risk alleles from Genome-Wide Association Studies (GWAS) of Alzheimer's disease (AD) are involved in lipid metabolism, lipid...
INTRODUCTION
At least one-third of the identified risk alleles from Genome-Wide Association Studies (GWAS) of Alzheimer's disease (AD) are involved in lipid metabolism, lipid transport, or direct lipid binding. In fact, a common genetic variant (ε4) in a cholesterol and phospholipid transporter, Apolipoprotein E (), is the primary genetic risk factor for late-onset AD. In addition to genetic variants, lipidomic studies have reported severe metabolic dysregulation in human autopsy brain tissue, cerebrospinal fluid, blood, and multiple mouse models of AD.
METHODS
We aimed to identify an overarching metabolic pathway in lipid metabolism by integrating analyses of lipidomics and transcriptomics from the Religious Order Study and Rush Memory Aging Project (ROSMAP) using differential analysis and network correlation analysis.
RESULTS
Coordinated differences in lipids were found to be dysregulated in association with both mild cognitive impairment (MCI) and carriers. Interestingly, these correlations were weakened when adjusting for education. Indeed, the cognitively non-impaired carriers have higher education levels in the ROSMAP cohort, suggesting that this lipid signature may be associated with a resilience phenotype. Network correlation analysis identified multiple differential lipids within a single module that are substrates and products in the Lands Cycle for acyl chain remodeling. In addition, our analyses identified multiple genes in the Lands Cycle acyl chain remodeling pathway, which were associated with cognitive decline independent of amyloid-β (Aβ) load and tau tangle pathologies.
DISCUSSION
Our studies highlight the critical differences in acyl chain remodeling in brain tissue from carriers and individual non-carriers with MCI. A coordinated lipid profile shift in dorsolateral prefrontal cortex from both carriers and MCI suggests differences in lipid metabolism occur early in disease stage and highlights lipid homeostasis as a tractable target for early disease modifying intervention.
PubMed: 38938596
DOI: 10.3389/fnagi.2024.1419253 -
Bioscience, Biotechnology, and... Jun 2024We synthesized a phenolic hydroxy group-bearing version (1) of a simplified analog of aplysiatoxin comprising a carvone-based conformation-controlling unit. Thereafter,...
We synthesized a phenolic hydroxy group-bearing version (1) of a simplified analog of aplysiatoxin comprising a carvone-based conformation-controlling unit. Thereafter, we evaluated its antiproliferative activity against human cancer cell lines and its binding affinity to protein kinase C (PKC) isozymes. The antiproliferative activity and PKC-binding ability increased with the introduction of the phenolic hydroxy group. The results of molecular dynamics simulations and subsequent relative binding free-energy calculations conducted using an alchemical transformation procedure showed that the phenolic hydroxy group in 1 could form a hydrogen bond with a phospholipid and the PKC. The former hydrogen bonding formation facilitated the partitioning of the compound from water to the phospholipid membrane and the latter compensated for the loss of hydrogen bond with the phospholipid upon binding to the PKC. This information may facilitate the development of rational design methods for PKC ligands with additional hydrogen bonding groups.
PubMed: 38936828
DOI: 10.1093/bbb/zbae091 -
Langmuir : the ACS Journal of Surfaces... Jun 2024In spite of the widespread use of alkanols as penetration enhancers, their effect on vesicular formulations remains largely unexplored. These can affect the stability...
In spite of the widespread use of alkanols as penetration enhancers, their effect on vesicular formulations remains largely unexplored. These can affect the stability and integrity of the phospholipid bilayers. In this study, we have investigated the interaction of linear (ethanol, butanol, hexanol, octanol) and branched alkanols (t-amylol and t-butanol) with three phospholipids (soya lecithin, SL; soy L-α-phosphatidylcholine, SPC; and 1,2-dipalmitoyl--glycero-3-phosphocholine, DPPC). Thermodynamic and structural aspects of these interactions were studied as a function of the alkanol concentration and chain length. Our interpretations are based on isothermal titration calorimetry (ITC) and dynamic light scattering (DLS) experiments. We observed one-site interactions wherein hydroxyl and acyl groups interacted with the polar and nonpolar regions of the phospholipid, respectively. The stability and structural integrity of bilayers appeared to be dependent upon (a) the hydrocarbon chain length and concentration of alcohols, and (b) the degree of unsaturation in the phospholipid molecule. We found that these interactions triggered a reduction in the enthalpy which was compensated by increased entropy, keeping free energy negative. Drop in enthalpy indicates reversible disordering of the bilayer which enables the diffusion of alcohol without triggering destabilization. Ethanol engaged predominantly with the interface, and it resulted in higher enthalpic changes. Interactions became increasingly unfavorable with longer alcohols - a cutoff point was recorded with hexanol. The overall sequence of membrane disordering capability was recorded as follows: ethanol < butanol < octanol < hexanol. Octanol's larger size restricted its penetration in the bilayer, and hence it caused less enthalpic changes relative to hexanol. This could also be verified from the trends in the area ratio of these vesicles obtained from the DLS data. Branched alkanols displayed a lower binding affinity with the phospholipids relative to their linear counterparts. These data are useful while contemplating the inclusion of short-chain alcohols as penetration enhancers in phospholipid vesicles.
PubMed: 38935825
DOI: 10.1021/acs.langmuir.4c01499 -
Molecules (Basel, Switzerland) Jun 2024This study investigated the mechanism by which fucoxanthin acts as a novel ferroptosis inducer to inhibit tongue cancer. The MTT assay was used to detect the inhibitory...
This study investigated the mechanism by which fucoxanthin acts as a novel ferroptosis inducer to inhibit tongue cancer. The MTT assay was used to detect the inhibitory effects of fucoxanthin on SCC-25 human tongue squamous carcinoma cells. The levels of reactive oxygen species (ROS), mitochondrial membrane potential (MMP), glutathione (GSH), superoxide dismutase (SOD), malondialdehyde (MDA), and total iron were measured. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blotting were used to assess glutathione peroxidase 4 (GPX4), nuclear factor erythroid 2-related factor 2 (Nrf2), Keap1, solute carrier family 7 member 11 (SLC7A11), transferrin receptor protein 1 (TFR1), p53, and heme oxygenase 1 (HO-1) expression. Molecular docking was performed to validate interactions. Compared with the control group, the activity of fucoxanthin-treated SCC-25 cells significantly decreased in a dose- and time-dependent manner. The levels of MMP, GSH, and SOD significantly decreased in fucoxanthin-treated SCC-25 cells; the levels of ROS, MDA, and total iron significantly increased. mRNA and protein expression levels of Keap1, GPX4, Nrf2, and HO-1 in fucoxanthin-treated cells were significantly decreased, whereas levels of TFR1 and p53 were significantly increased, in a concentration-dependent manner. Molecular docking analysis revealed that binding free energies of fucoxanthin with p53, SLC7A11, GPX4, Nrf2, Keap1, HO-1, and TFR1 were below -5 kcal/mol, primarily based on active site hydrogen bonding. Our findings suggest that fucoxanthin can induce ferroptosis in SCC-25 cells, highlighting its potential as a treatment for tongue cancer.
Topics: Humans; NF-E2-Related Factor 2; Ferroptosis; Xanthophylls; Heme Oxygenase-1; Cell Line, Tumor; Phospholipid Hydroperoxide Glutathione Peroxidase; Molecular Docking Simulation; Reactive Oxygen Species; Signal Transduction; Tongue Neoplasms; Receptors, Transferrin; Membrane Potential, Mitochondrial; Kelch-Like ECH-Associated Protein 1; Gene Expression Regulation, Neoplastic; Amino Acid Transport System y+; Superoxide Dismutase; Down-Regulation; Antigens, CD
PubMed: 38930897
DOI: 10.3390/molecules29122832 -
Molecules (Basel, Switzerland) Jun 2024Miniaturized weak affinity chromatography is emerging as an interesting alternative to conventional biophysical tools for performing fragment-screening studies in the...
Miniaturized weak affinity chromatography is emerging as an interesting alternative to conventional biophysical tools for performing fragment-screening studies in the context of fragment-based drug discovery. In order to push back the analytical limits, it is necessary not only to control non-specific interactions with chromatographic support, but also to adapt this methodology by comparing the results obtained on an affinity column to a control column. The work presented in this study focused on fragment screening that targets a model membrane protein, the adenosine A2A receptor, embedded in nanodiscs (NDs) as biomimetic membranes. By studying the retention behavior of test fragment mixtures on supports modified with different types of NDs, we were able to determine the contribution of ND-related non-specific interactions, in particular the electrostatic effect of anionic phospholipids and the hydrophobic effect of neutral phospholipids. Different strategies for the preparation of control columns (empty NDs, orthosteric site blocking) were investigated and are presented for the first time. With these two types of control columns, the screening enabled the identification of two new fragments of AAR, which were confirmed by competition experiments and whose K values, estimated directly during the screening or after the competition experiments in frontal mode, were in good agreement.
Topics: Ligands; Chromatography, Affinity; Nanostructures; Receptor, Adenosine A2A; Membrane Proteins; Protein Binding; Humans; Phospholipids; Hydrophobic and Hydrophilic Interactions; Drug Discovery
PubMed: 38930880
DOI: 10.3390/molecules29122814 -
Antioxidants (Basel, Switzerland) Jun 2024(SH) is widely consumed as a healthy seaweed food in the Asia-Pacific region. However, the bioactive components contributing to its biological activity remain unknown....
(SH) is widely consumed as a healthy seaweed food in the Asia-Pacific region. However, the bioactive components contributing to its biological activity remain unknown. Herein, we optimized multifrequency ultrasonic-assisted extraction conditions to achieve higher antioxidant activity using a response surface methodology and an artificial neural network. High-resolution mass spectrometry (HRMS; negative mode) was used to tentatively identify the secondary metabolites in the optimized SH extract, which were further tested against oxidative stress in RAW264.7 cells. Additionally, the identified compounds were analyzed in silico to determine their binding energies with the Keap1 protein (4L7B). We identified 89 compounds using HRMS, among which 19 metabolites (8 polyphenolics, 2 flavonoids, 2 lignans, 2 terpenes, 2 tannins, 2 sulfolipids, and 1 phospholipid) were putatively reported for the first time in SH. The in vitro results revealed that optimized SH extract inhibited oxidative stress via the Nrf2/MAPKs/HO-1 pathway in a dose-dependent manner. This result was validated by performing in silico simulation, indicating that sargaquinoic acid and glycitein-7--glucuronide had the highest binding energies (-9.20 and -9.52 Kcal/mol, respectively) toward Keap1 (4L7B). This study offers a unique approach for the scientific community to identify potential bioactive compounds by optimizing the multivariant extraction processing conditions, which could be used to develop functional and nutraceutical foods.
PubMed: 38929129
DOI: 10.3390/antiox13060690 -
International Journal of Molecular... Jun 2024Our study aimed to investigate the role of ferroptosis in sevoflurane-induced hearing impairment and explore the mechanism of the microRNA-182-5p...
Our study aimed to investigate the role of ferroptosis in sevoflurane-induced hearing impairment and explore the mechanism of the microRNA-182-5p (miR-182-5p)/Glutathione Peroxidase 4 (GPX4) pathway in sevoflurane-induced ototoxicity. Immunofluorescence staining was performed using myosin 7a and CtBP2. Cell viability was assessed using the CCK-8 kit. Fe concentration was measured using FerroOrange and Mi-to-FerroGreen fluorescent probes. The lipid peroxide level was assessed using BODIPY 581/591 C11 and MitoSOX fluorescent probes. The auditory brainstem response (ABR) test was conducted to evaluate the hearing status. Bioinformatics tools and dual luciferase gene reporter analysis were used to confirm the direct targeting of miR-182-5p on GPX4 mRNA. GPX4 and miR-182-5p expression in cells was assessed by qRT-PCR and Western blot. Ferrostatin-1 (Fer-1) pretreatment significantly improved hearing impairment and damage to ribbon synapses in mice caused by sevoflurane exposure. Immunofluorescence staining revealed that Fer-1 pretreatment reduced intracellular and mitochondrial iron overload, as well as lipid peroxide accumulation. Our findings indicated that miR-182-5p was upregulated in sevoflurane-exposed HEI-OC1 cells, and miR-182-5p regulated GPX4 expression by binding to the 3'UTR of GPX4 mRNA. The inhibition of miR-182-5p attenuated sevoflurane-induced iron overload and lipid peroxide accumulation. Our study elucidated that the miR-182-5p/GPX4 pathway was implicated in sevoflurane-induced ototoxicity by promoting ferroptosis.
Topics: Ferroptosis; MicroRNAs; Sevoflurane; Phospholipid Hydroperoxide Glutathione Peroxidase; Animals; Mice; Ototoxicity; Signal Transduction; Cell Line; Male; Hearing Loss; Mice, Inbred C57BL; Phenylenediamines; Cyclohexylamines
PubMed: 38928480
DOI: 10.3390/ijms25126774 -
International Journal of Molecular... Jun 2024Human corneal fibrosis can lead to opacity and ultimately partial or complete vision loss. Currently, corneal transplantation is the only treatment for severe corneal...
Human corneal fibrosis can lead to opacity and ultimately partial or complete vision loss. Currently, corneal transplantation is the only treatment for severe corneal fibrosis and comes with the risk of rejection and donor shortages. Sphingolipids (SPLs) are known to modulate fibrosis in various tissues and organs, including the cornea. We previously reported that SPLs are tightly related to both, transforming growth factor beta (TGF-β) signaling and corneal fibrogenesis. The aim of this study was to investigate the effects of sphingosine-1-phosphate (S1P) and S1P inhibition on specific TGF-β and SPL family members in corneal fibrosis. Healthy human corneal fibroblasts (HCFs) were isolated and cultured in EMEM + FBS + VitC (construct medium) on 3D transwells for 4 weeks. The following treatments were prepared in a construct medium: 0.1 ng/mL TGF-β1 (β1), 1 μM sphingosine-1-phosphate (S1P), and 5 μM Sphingosine kinase inhibitor 2 (I). Five groups were tested: (1) control (no treatment); rescue groups; (2) β1/S1P; (3) β1/I; prevention groups; (4) S1P/β1; and (5) I/β1. Each treatment was administered for 2 weeks with one treatment and switched to another for 2 weeks. Using Western blot analysis, the 3D constructs were examined for the expression of fibrotic markers, SPL, and TGF-β signaling pathway members. Scratch assays from 2D cultures were also utilized to evaluate cell migration We observed reduced fibrotic expression and inactivation of latent TGF-β binding proteins (LTBPs), TGF-β receptors, Suppressor of Mothers Against Decapentaplegic homologs (SMADs), and SPL signaling following treatment with I prevention and rescue compared to S1P prevention and rescue, respectively. Furthermore, we observed increased cell migration following stimulation with I prevention and rescue groups, with decreased cell migration following stimulation with S1P prevention and rescue groups after 12 h and 18 h post-scratch. We have demonstrated that I treatment reduced fibrosis and modulated the inactivation of LTBPs, TGF-β receptors, SPLs, and the canonical downstream SMAD pathway. Further investigations are warranted in order to fully uncover the potential of utilizing SphK I as a novel therapy for corneal fibrosis.
Topics: Humans; Sphingosine; Lysophospholipids; Fibrosis; Cornea; Signal Transduction; Transforming Growth Factor beta; Fibroblasts; Cells, Cultured; Sphingolipids; Phosphotransferases (Alcohol Group Acceptor); Corneal Diseases
PubMed: 38928268
DOI: 10.3390/ijms25126560 -
International Journal of Molecular... Jun 2024LPA receptors were expressed in TREx HEK 293 cells, and their signaling and phosphorylation were studied. The agonist, lysophosphatidic acid (LPA), increased...
LPA receptors were expressed in TREx HEK 293 cells, and their signaling and phosphorylation were studied. The agonist, lysophosphatidic acid (LPA), increased intracellular calcium and ERK phosphorylation through pertussis toxin-insensitive processes. Phorbol myristate acetate, but not LPA, desensitizes LPA-mediated calcium signaling, the agonists, and the phorbol ester-induced LPA internalization. Pitstop 2 (clathrin heavy chain inhibitor) markedly reduced LPA-induced receptor internalization; in contrast, phorbol ester-induced internalization was only delayed. LPA induced rapid β-arrestin-LPA receptor association. The agonist and the phorbol ester-induced marked LPA receptor phosphorylation, and phosphorylation sites were detected using mass spectrometry. Phosphorylated residues were detected in the intracellular loop 3 (S221, T224, S225, and S229) and in the carboxyl terminus (S321, S325, S331, T333, S335, Y337, and S343). Interestingly, phosphorylation sites are within sequences predicted to constitute β-arrestin binding sites. These data provide insight into LPA receptor signaling and regulation.
Topics: Humans; Receptors, Lysophosphatidic Acid; Phosphorylation; HEK293 Cells; Signal Transduction; Lysophospholipids; beta-Arrestins; Binding Sites; Calcium Signaling
PubMed: 38928196
DOI: 10.3390/ijms25126491