Modulation of immunity by the secreted phospholipase A2 family

Causal relationships between plasma proteins and Alzheimer's disease using bidirectional Mendelian randomization

BackgroundAlzheimer's disease (AD) is influenced by a complex interplay of genetic, immune, and metabolic factors. Identifying plasma proteins causally linked to AD could help clarify these pathways and uncover potential therapeutic targets.ObjectiveThis study aims to investigate the causal relationships between AD and plasma proteins.MethodsWe conducted a two-stage, two-sample Mendelian randomization (MR) analysis to explore the causal relationships between plasma protein levels and AD risk. In both stages, we used non-overlapping genome-wide association study datasets for exposures (plasma protein levels) and outcome (AD) to ensure robust and independent analyses. We examined both forward (from plasma proteins to AD risk) and reverse (from AD to plasma protein expression) causal effects to elucidate potential bidirectional relationships.ResultsOur MR analysis identified 25 plasma proteins with causal associations to AD, with many implicated in immune and lipid metabolic pathways. These findings reinforce the roles of inflammation and lipid metabolism in AD pathogenesis and offer novel insights into specific proteins that may serve as biomarkers or therapeutic targets.ConclusionsThis study provides further support for the relationship between immune and lipid metabolic dysregulation and AD, advancing our understanding of the molecular mechanisms underlying disease progression and highlighting key proteins for future research and therapeutic development.

Periodic dietary restriction of animal products induces metabolic reprogramming in humans with effects on cardiometabolic health

Dietary interventions constitute powerful approaches for disease prevention and treatment. However, the molecular mechanisms through which diet affects health remain underexplored in humans. Here, we compare plasma metabolomic and proteomic profiles between dietary states for a unique group of individuals who alternate between omnivory and restriction of animal products for religious reasons. We find that short-term restriction drives reductions in levels of lipid classes and of branched-chain amino acids, not detected in a control group of individuals, and results in metabolic profiles associated with decreased risk for all-cause mortality. We show that 23% of proteins whose levels are affected by dietary restriction are druggable targets and reveal that pro-longevity hormone FGF21 and seven additional proteins (FOLR2, SUMF2, HAVCR1, PLA2G1B, OXT, SPP1, HPGDS) display the greatest magnitude of change. Through Mendelian randomization we demonstrate potentially causal effects of FGF21 and HAVCR1 on risk for type 2 diabetes, of HPGDS on BMI, and of OXT on risk for lacunar stroke. Collectively, we find that restriction-associated reprogramming improves metabolic health and emphasise high-value targets for pharmacological intervention.

Intestinal overexpression of Pla2g10 alters the composition, diversity and function of gut microbiota in mice

The intestinal microbiota is important for the health of the host and recent studies have shown that some genes of the host regulated the composition of the intestinal microbiota. Group 10 phospholipase A2 (PLA2G10) is a member of the lipolytic enzyme family PLA2, which hydrolyze the ester bond at the sn-2 position of phospholipids to produce free fatty acids and lysophospholipids. PLA2G10 is secreted into the intestinal lumen, but its impact on the gut microbiota remains unclear. In this study, we generated intestine-specific Pla2g10 knock-in mice, and used 16S RNA sequencing to compare their gut microbiota with that of their wild-type (WT) littermates. Results showed that gut-specific Pla2g10 knock-in induced both PLA2G10 mRNA and protein levels in the colon. Moreover, intestinal Pla2g10 overexpression reduced the α-diversity of the gut microbiota relative to that of WT mice. The abundance of Bacteroidetes was lower in the Pla2g10 knock-in mice than that in the control mice, while the ratio of Firmicutes/Bacteroidetes was higher. Furthermore, the abundance of the genus Allobaculum was reduced, whereas the abundance of beneficial bacteria genera, including Enterorhabdus, Dubosiella, and Lactobacillus, was increased by host intestinal Pla2g10 overexpression. In summary, intestinal Pla2g10 overexpression increased the proportions of beneficial bacterial in the colonic chyme of mice, providing a potential therapeutic target for future improvement of the gut microbiota.

Dissecting the causal effects of smoking, alcohol consumption, and related DNA methylation markers on electrocardiographic indices

BACKGROUND

Tobacco and alcohol are recognized risk factors for heart disease, yet their causal effects on electrocardiogram (ECG) signaling and mechanisms remain unclear. Previous studies may be susceptible to confounding or bias, and this study dissected the genetic architecture linking tobacco and alcohol consumption with P-wave duration, PR interval, and QT interval.

METHODS

Utilizing genetic instruments for tobacco and alcohol consumption, associated methylation quantitative trait locus (mQTL), and summary-level GWAS data for ECG indices, we assessed heritability and genetic causal associations using linkage disequilibrium score regression and Mendelian randomization (MR) analysis. Fine mapping was performed via colocalization analysis and summary-data-based MR (SMR) to identify potential shared genetic variants.

RESULTS

A positive causal relationship was found between drinks per week (DrnkWk) and QT interval [β (95%CI): 1.06 (0.91, 5.05), P = 0.005], with causality substantiated through multiple robust MR models. Multivariable MR confirmed independence from smoking phenotypes. In epigenetic MR analyses, two alcohol-related CpG loci (cg03345232 and cg04605617) were causally associated with QT interval changes, with cg04605617 mapping to PLA2G2C gene significantly prolonging QT. The mQTL rs10916683 at cg04605617 is a strong eQTL for PLA2G2C. Additionally, cg03345232 shared a causal variant (rs12881206) with QT interval predisposition through colocalization analysis. SMR analysis did not identify shared putative functional genes passing the HEIDI test between DrnkWk and the QT interval.

CONCLUSIONS

There is a causal relationship between DrnkWk and QT interval prolongation, and targeting specific DNA methylation sites like cg04605617 mapped to PLA2G2C may provide novel targets for preventing QT interval prolongation.

Metabolomics and proteomics: synergistic tools for understanding snake venom inhibition

Snake envenomation presents a significant global health challenge, especially in rural areas of tropical and subtropical regions. Traditional antivenom therapies face limitations related to efficacy, availability, and specificity, prompting a need for novel approaches. Recent advancements in omics technologies, particularly metabolomics and proteomics, have enhanced our understanding of snake venom composition, toxicity, and potential therapeutic strategies. Metabolomics allows for the study of metabolic changes induced by venom, providing insights into disrupted pathways and possible inhibitors. Proteomics facilitates the identification and characterization of venom proteins, unveiling their interactions with therapeutic agents. Integrative databases such as the Snake Venom Database (SVDB) and STAB Profiles enhance this research by cataloging venom components and aiding in the analysis of venom-antivenom interactions. The combined application of metabolomics and proteomics has led to the identification of crucial metabolic pathways and protein targets essential for effective venom inhibition. This review explores current advances in these fields, emphasizing the role of omics in identifying novel inhibitors and developing next-generation antivenoms. The integrated approach of metabolomics and proteomics offers a comprehensive understanding of snake venom biology, paving the way for more effective and tailored therapeutic solutions for envenomation.

A review on NLRP3 inflammasome modulation by animal venom proteins/peptides: mechanisms and therapeutic insights

The venom peptides from terrestrial as well as aquatic species have demonstrated potential in regulating the NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome, a sophisticated assemblage present in immune cells responsible for detecting and responding to external mediators. The NLRP3 inflammasome plays a role in several pathological conditions such as type 2 diabetes, hyperglycemia, Alzheimer's disease, obesity, autoimmune disorders, and cardiovascular disorders. Venom peptides derived from animal venoms have been discovered to selectively induce certain signalling pathways, such as the NLRP3 inflammasome, mitogen-activated protein kinase (MAPK), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Experimental evidence has demonstrated that venom peptides can regulate the expression and activation of the NLRP3 inflammasome, resulting in the secretion of pro-inflammatory cytokines including interleukin (IL)-1β and IL-18. Furthermore, these peptides have been discovered to impede the activation of the NLRP3 inflammasome, therefore diminishing inflammation and tissue injury. The functional properties of venom proteins and peptides obtained from snakes, bees, wasps, and scorpions have been thoroughly investigated, specifically targeting the NLRP3 inflammasome pathway, venom proteins and peptides have shown promise as therapeutic agents for the treatment of certain inflammatory disorders. This review discusses the pathophysiology of NLRP3 inflammasome in the onset of various diseases, role of venom as therapeutics. Further, various venom components and their role in the modulation of NLRP3 inflammasome are discoursed. A substantial number of venomous animals and their toxins are yet unexplored, and to comprehensively grasp the mechanisms of action of them and their potential as therapeutic agents, additional research is required which can lead to the development of novel therapeutics.

Bee venom: Yesterday's enemy becomes modern medicine for skin cancer

Malignant melanoma is one of the most lethal human malignancies, particularly when it spreads from its initial site in the skin to distant locations with few therapeutic options. While a range of treatment approaches exist, such as chemotherapy, radiation, immunotherapy, and targeted therapy, they typically fail to treat skin cancer, particularly in its late stages. The complex cellular and molecular mechanisms that drive melanoma growth and metastatic dissemination are both varied and complicated, posing significant challenges to the development of effective treatment approaches. As the incidence and burden of this malignancy increase, there is an urgent need for innovative therapeutic techniques. Therefore, it is vital to research alternate therapy options. Several research undertaken in recent years have found that bee venom influences a variety of cancers. The more research into using bee venom to cure skin cancer, the less attention it receives. In this context, the purpose of this proposal is to review a comprehensive assessment of the clinical impact of bee venom against skin cancer, as well as to highlight challenges and excitement down the road.

Bioactive lipid signaling and lipidomics in macrophage polarization: Impact on inflammation and immune regulation

Macrophages, crucial innate immune cells, defend against pathogens and resolve inflammation, maintaining tissue balance. They perform phagocytosis, present antigens to T cells, and bond innate and adaptive immunity through various activation states. Classical activation is associated with Th1 responses and interferon γ production, while alternative activation, induced by interleukin 4, is characterized by increased endocytosis, reduced secretion of pro-inflammatory cytokines, and roles in immunoregulation and tissue remodeling. Although these represent opposite extremes observed in vitro, the remarkable plasticity of macrophages allows for a wide spectrum of activation phenotypes that are complex to characterize experimentally. While the application of omics techniques has resulted in significant advances in the characterization of macrophage polarization, lipidomic studies have received lesser attention. Beyond their role as structural components and energy sources, lipids function as signaling molecules that regulate macrophage activation and polarization, thereby shaping immune responses. This work reviews the interaction between lipid signaling and macrophage polarization, exploring how lipid metabolism influences macrophage phenotype and function. These insights offer potential therapeutic strategies for immune-mediated diseases and inflammation-related disorders, including inflammaging.

Lipid metabolism of apoptotic vesicles accelerates cutaneous wound healing by modulating macrophage function

The application of apoptotic extracellular vesicles (ApoEVs) derived from stem cell in skin wound healing has garnered significant attention. In recent decades, scholars have shown that extracellular vesicles (EVs) established intercellular communication by carrying proteins or microRNAs, the role of lipids in EVs in wound healing has yet to be clarified. Here, we focus on the key role of group X secretory phospholipase A2 (sPLA2-X) in lipid metabolism. Specifically, sPLA2-X significantly increased the production of the anti-inflammatory lipid mediators, resolvin D5 (RvD5), by hydrolyzing phospholipids in ApoEVs. This change not only promoted the uptake of ApoEVs by macrophages, but also effectively inhibited the expression of tumor necrosis factor-alpha (TNF-α) in macrophages, promoting the healing of skin wounds. In summary, this study contributes to our understanding of the mechanisms by which ApoEVs support skin defect repair and offers a potential theoretical approach for using ApoEVs in skin wound treatment. With further research and optimization, it is expected that more efficient and secure ApoEVs-based treatment strategies will be developed, bringing new breakthroughs in clinical treatment of skin injuries and related diseases.

A recombinant sPLA2 protein promotes gut mucosal barrier against bacterial infection in fish

Secreted phospholipase A2 family protein (sPLA2) is associated with immune response and plays a critical role in the regulation of gut homeostasis. However, whether sPLA2 is involved in innate immunity in teleost is essentially unknown. For this purpose, we reported the identification of a classical sPLA2 in grass carp (CisPLA2) and elucidated its role in the antibacterial immunity in this study. The result of bioinformatics analysis showed that mammalian sPLA2-IIA is the most similar homologue to CisPLA2. CisPLA2 is expressed in a variety of tissues, including liver and gut, and is significantly upregulated in response to Aeromonas hydrophila infection. Recombinant CisPLA2 protein (rCisPLA2) showed significant antibacterial activity against A. hydrophila by enhancing the phagocytosis of host phagocytes in vitro. Moreover, rCisPLA2 induces significant expression of the antimicrobial molecules and tight junctions in the gut during bacterial infection. Fish administered with rCisPLA2 significantly alleviates the gut permeability and apoptosis. In addition, rCisPLA2 preserves the morphology of the gut mucosa and limits the colonization of A. hydrophila in systemic immune organs. These results indicate that CisPLA2 plays a crucial role in the regulation of gut mucosal barrier, and thus has a potential application for antimicrobial immunity in fish.

Drug-phospholipid conjugate nano-assembly for drug delivery

Phospholipid-based liposomes are among the most successful nanodrug delivery systems in clinical use. However, these conventional liposomes present significant challenges including low drug-loading capacity and issues with drug leakage. Drug-phospholipid conjugates (DPCs) and their assemblies offer a promising strategy for addressing these limitations. In this review, we summarize recent advances in the design, synthesis, and application of DPCs for drug delivery. We begin by discussing the chemical backbone structures and various design strategies such as phosphate head embedding and mono-/bis-embedding in the sn-1/sn-2 positions. Furthermore, we highlight stimulus-responsive designs of DPCs and their applications in treating diseases such as cancer, inflammation, and malaria. Lastly, we explore future directions for DPCs development and their potential applications in drug delivery.

Up-regulation of IL-1β and sPLA2-III in the medial prefrontal cortex contributes to orofacial and somatic hyperalgesia induced by malocclusion via glial-neuron crosstalk

The medial prefrontal cortex (mPFC) has been identified as a key brain region involved in the modulation of chronic pain. Our recent study demonstrated that unilateral anterior crossbite (UAC) developed the comorbidity model of temporomandibular disorders (TMD) and fibromyalgia syndrome (FMS), which was characterized by both orofacial and somatic hyperalgesia. In the present study, UAC rats exhibited significant changes in gene expression in the mPFC. Enrichment analysis revealed that the significantly involved pathways were cytokines-cytokine receptor interaction and immune response. The expression of group III secretory phospholipase A2 (sPLA2-III) was significantly increased in the mPFC of UAC rats. Silencing sPLA2-III expression in the mPFC blocked the orofacial and somatic hyperalgesia. Immunofluorescence showed that sPLA2-III was mainly localized in neurons. The expression of interleukin-1β (IL-1β) in the mPFC significantly increased after UAC. Injection of IL-1β antibody into the mPFC blocked orofacial and somatic hyperalgesia. IL-1β was mainly localized in microglia cells. Furthermore, injection of IL-1β antibody significantly reduced the expression of sPLA2-III. These results indicate that neuroinflammatory cascade responses induced by glial-neuron crosstalk in the mPFC may contribute to the development of TMD and FMS comorbidity, and IL-1β and sPLA2-III are identified as novel potential therapeutic targets for the treatment of chronic pain in the comorbidity of TMD and FMS.

Synthesis and diverse biological activities of substituted indole β-carbolines: a review

β-Carboline bearing indole is one of the heterocyclic compounds that play a vital role in medicinal chemistry with various pharmacological effects such as anticancer, anti-acetylcholinesterase, anti-inflammation, antimalarial, antibacterial, anti-diabetic, and antioxidant. Over the last two decades, many studies on the synthesis and biological activity of indole β-carboline compounds have been conducted yet there is no appropriate data summary has been presented. Thus, the goal of this review was to highlight the synthesis pathway and bioactivity of substituted indole β-carboline reported from 2005 to date. In addition, this will encourage further investigation into the synthesis and evaluation of new indole β-carboline, in the hope of contributing to the development of potentially new medications for the treatment of various ailments.

Group X phospholipase A2 links colonic lipid homeostasis to systemic metabolism via host-microbiota interaction

The gut microbiota influences physiological functions of the host, ranging from the maintenance of local gut homeostasis to systemic immunity and metabolism. Secreted phospholipase A2 group X (sPLA2-X) is abundantly expressed in colonic epithelial cells but is barely detectable in metabolic and immune tissues. Despite this distribution, sPLA2-X-deficient (Pla2g10-/-) mice displayed variable obesity-related phenotypes that were abrogated after treatment with antibiotics or cohousing with Pla2g10+/+ mice, suggesting the involvement of the gut microbiota. Under housing conditions where Pla2g10-/- mice showed aggravation of diet-induced obesity and insulin resistance, they displayed increased colonic inflammation and epithelial damage, reduced production of polyunsaturated fatty acids (PUFAs) and lysophospholipids, decreased abundance of several Clostridium species, and reduced levels of short-chain fatty acids (SCFAs). These obesity-related phenotypes in Pla2g10-/- mice were reversed by dietary supplementation with ω3 PUFAs or SCFAs. Thus, colonic sPLA2-X orchestrates ω3 PUFA-SCFA interplay via modulation of the gut microbiota, thereby secondarily affecting systemic metabolism.

Analyzing how SiMiao Wan regulates ferroptosis to prevent RA-ILD using metabolomics and cyberpharmacology

BACKGROUND

Interstitial lung disease (ILD) is a common complication of rheumatoid arthritis (RA) that plays a significant role in the morbidity and mortality of individuals with this condition. In clinical settings, Si Miao Wan (SMW), a traditional Chinese medicine, is often utilized for the management of RA, as it is believed to possess properties that aid in reducing inflammation, eliminating excess moisture, and alleviating joint pain.

PURPOSE

The primary objective of this investigation was to elucidate the potential mechanism of RA-ILD prevention from the perspective of ferroptosis mediated by SMW.

METHODS

UPLC-Q-TOF/MS and network pharmacology were employed to forecast the potential targets of SMW for the early prevention of RA-ILD. Following this, HE staining, metabolomics, and RT-PCR were utilized to investigate the mechanism by which SMW prevents RA-ILD at an early stage.

RESULTS

Following six weeks of continuous administration of SMW extract at a dosage of 2.16 g/kg/day, it was observed that SMW exhibited early preventive effects against RA-ILD. Metabolomics analysis revealed seven potential biomarkers linked to the pharmacological efficacy of SMW in the early prevention of RA-ILD. Additionally, network pharmacology analysis suggested that SMW may exert its therapeutic effects on RA-ILD by modulating signaling pathways associated with lipid metabolism, atherosclerosis, TNF, and IL-17. Ultimately, through the integration of metabolomics and network pharmacology analysis, along with subsequent verification, it was determined that the early prevention of rheumatoid arthritis-associated interstitial lung disease (RA-ILD) by Shenmai injection (SMW) is associated with the ferroptosis pathway.

CONCLUSION

This research offers preliminary insights into the potential mechanism by which traditional Chinese medicine Shen Mai Wan (SMW) may mitigate the early onset of Rheumatoid Arthritis-Interstitial Lung Disease (RA-ILD) via the process of ferroptosis. Furthermore, it establishes a theoretical framework for the development of innovative SMW-based pharmaceuticals for the management of RA-ILD. The signal proteins implicated in this process are anticipated to emerge as crucial targets for the prevention of RA-ILD.

Differentiating human phospholipase A2's activity toward phosphatidylinositol, phosphatidylinositol phosphate and phosphatidylinositol bisphosphate

Phospholipase A2's (PLA2's) constitute a superfamily of enzymes that hydrolyze the sn-2 fatty acyl chain on glycerophospholipids. We have previously reported that each PLA2 Type shows a unique substrate specificity for the molecular species it hydrolyzes, especially the acyl chain that is cleaved from the sn-2 position and to some extent the polar group. However, phosphatidylinositol (PI) and PI phosphates (PIPs) have not been as well studied as substrates as other phospholipids because the PIPs require adaptation of the standard analysis methods, but they are important in vivo. We determined the in vitro activity of the three major types of human PLA2's, namely the cytosolic (c), calcium-independent (i), and secreted (s) PLA2's toward PI, PI-4-phosphate (PI(4)P), and PI-4,5-bisphosphate (PI(4,5)P2). The in vitro assay revealed that Group IVA cPLA2 (GIVA cPLA2) showed relatively high activity toward PI and PI(4)P among the tested PLA2's; nevertheless, the highly hydrophilic headgroup disrupted the interaction between the lipid surface and the enzyme. GIVA cPLA2 and GVIA iPLA2 showed detectable activity toward PI(4,5)P2, but it appeared to be a poorer substrate for all of the PLA2's tested. Furthermore, molecular dynamics (MD) simulations demonstrated that Thr416 and Glu418 of GIVA cPLA2 contribute significantly to accommodating the hydrophilic head groups of PI and PI(4)P, which could explain some selectivity for PI and PI(4)P. These results indicated that GIVA cPLA2 can accommodate PI and PI(4)P in its active site and hydrolyze them, suggesting that the GIVA cPLA2 may best account for the PI and PIP hydrolysis in living cells.

Extracellular vesicles as a hydrolytic platform of secreted phospholipase A2

Extracellular vesicles (EVs) represent small vesicles secreted from cells, including exosomes (40-150 nm in diameter), which are released via the multivesicular endosomal pathway, and microvesicles and ectosomes (100-1000 nm), which are produced by plasma membrane budding. Broadly, EVs also include vesicles generated from dying cells, such as apoptotic bodies (5-10 μm), as well as exomeres (< 50 nm), which are very small, non-membranous nanoparticles. EVs play important roles in cell-to-cell signaling in various aspects of cancer, immunity, metabolism, and so on by transferring proteins, microRNAs (miRNAs), and metabolites as cargos from donor cells to recipient cells. Although lipids are one of the major components of EVs, they have long been recognized as merely the "wall" that partitions the lumen of the vesicle from the outside. However, it has recently become obvious that lipid composition of EVs influences their properties and functions, that EVs act as a carrier of a variety of lipid mediators, and that lipid mediators are produced in EV membranes by the hydrolytic action of secreted phospholipase A2s (sPLA2s). In this article, we will make an overview of the roles of lipids in EVs, with a particular focus on sPLA2-driven mobilization of lipid mediators from EVs and its biological significance.

Plasma proteomics and lipidomics facilitate elucidation of the link between Alzheimer's disease development and vessel wall fragility

Proximity Extension Assay (PEA) and mass spectrometry (MS) methodologies were utilized for the proteomic and lipidomic characterization of plasma specimens from patients who developed Alzheimer's disease. Proteomics was performed by both PEA and Liquid Chromatography (LC)/MS in this study, but all the more because LC/MS generally tends to be biased towards proteins with high expression and high variability, generating hypotheses proved challenging. Consequently, attempt was made to interpret the results from the PEA data. There were 150 significantly variable proteins and 68 lipids among 1000 proteins and 400 lipids. Pathway analysis was performed for both total and variable proteins measured to reduce bias, and it appeared that vascular fragility was related to AD. Furthermore, a multitude of lipid-associated proteins exhibited statistical changes. In certain instances, the function of individual proteins affected the factors associated with them, whereas others demonstrated trends contrary to anticipated outcomes. These trends seem indicative of diverse feedback mechanisms that provide homeostatic equilibrium. The degree of unsaturation of fatty acids, correlated with cardiovascular risk, warrants specific attention. Certain bile acids exhibited the potential to cause vascular endothelial damage. Contemplating these discoveries in tandem with previously documented phenomena, subtle shifts in homeostatic functions seem to be linked to the fragility of vascular endothelial cells. This is evidenced by the slow and chronic evolution of Alzheimer's disease from preclinical stages to its manifestation.

Lipid metabolism associated crosstalk: the bidirectional interaction between cancer cells and immune/stromal cells within the tumor microenvironment for prognostic insight

Cancer is closely related to lipid metabolism, with the tumor microenvironment (TME) containing numerous lipid metabolic interactions. Cancer cells can bidirectionally interact with immune and stromal cells, the major components of the TME. This interaction is primarily mediated by fatty acids (FAs), cholesterol, and phospholipids. These interactions can lead to various physiological changes, including immune suppression, cancer cell proliferation, dissemination, and anti-apoptotic effects on cancer cells. The physiological modulation resulting from this lipid metabolism-associated crosstalk between cancer cells and immune/stromal cells provides valuable insights into cancer prognosis. A comprehensive literature review was conducted to examine the function of the bidirectional lipid metabolism interactions between cancer cells and immune/stromal cells within the TME, particularly how these interactions influence cancer prognosis. A novel autophagy-extracellular vesicle (EV) pathway has been proposed as a mediator of lipid metabolism interactions between cancer cells and immune cells/stromal cells, impacting cancer prognosis. As a result, different forms of lipid metabolism interactions have been described as being linked to cancer prognosis, including those mediated by the autophagy-EV pathway. In conclusion, understanding the bidirectional lipid metabolism interactions between cancer cells and stromal/immune cells in the TME can help develop more advanced prognostic approaches for cancer patients.

Ectodomain shedding of PLA2R1 is mediated by the metalloproteases ADAM10 and ADAM17

Phospholipase A2 receptor 1 (PLA2R1) is a 180-kDa transmembrane protein that plays a role in inflammation and cancer and is the major autoantigen in membranous nephropathy, a rare but severe autoimmune kidney disease. A soluble form of PLA2R1 has been detected in mouse and human serum. It is likely produced by proteolytic shedding of membrane-bound PLA2R1 but the mechanism is unknown. Here, we show that human PLA2R1 is cleaved by A Disintegrin And Metalloprotease 10 (ADAM10) and ADAM17 in HEK293 cells, mouse embryonic fibroblasts, and human podocytes. By combining site-directed mutagenesis and sequencing, we determined the exact cleavage site within the extracellular juxtamembrane stalk of human PLA2R1. Orthologs and paralogs of PLA2R1 are also shed. By using pharmacological inhibitors and genetic approaches with RNA interference and knock-out cellular models, we identified a major role of ADAM10 in the constitutive shedding of PLA2R1 and a dual role of ADAM10 and ADAM17 in the stimulated shedding. We did not observe evidence for cleavage by β- or γ-secretase, suggesting that PLA2R1 may not be a substrate for regulated intramembrane proteolysis. PLA2R1 shedding occurs constitutively and can be triggered by the calcium ionophore ionomycin, the protein kinase C activator PMA, cytokines, and lipopolysaccharides, in vitro and in vivo. Altogether, our results show that PLA2R1 is a novel substrate for ADAM10 and ADAM17, producing a soluble form that is increased in inflammatory conditions and likely exerts various functions in physiological and pathophysiological conditions including inflammation, cancer, and membranous nephropathy.

Secreted phospholipase PLA2G2E contributes to regulation of T cell immune response against influenza virus infection

The involvement of secreted phospholipase A2s in respiratory diseases, such as asthma and respiratory viral infections, is well-established. However, the specific role of secreted phospholipase A2 group IIE (PLA2G2E) during influenza virus infection remains unexplored. Here, we investigated the role of PLA2G2E during H1N1 influenza virus infection using a targeted mouse model lacking Pla2g2e gene (Pla2g2e-/-). Our findings demonstrated that Pla2g2e-/- mice had significantly lower survival rates and higher viral loads in lungs compared to wild-type mice following influenza virus infection. While Pla2g2e-/- mice displayed comparable innate and humoral immune responses to influenza virus challenge, the animals showed impaired influenza-specific cellular immunity and reduced T cell-mediated cytotoxicity. This indicates that PLA2G2E is involved in regulating specific T cell responses during influenza virus infection. Furthermore, transgenic mice expressing the human PLA2G2E gene exhibited resistance to influenza virus infection along with enhanced influenza-specific cellular immunity and T cell-mediated cytotoxicity. Pla2g2e deficiency resulted in perturbation of lipid mediators in the lung and T cells, potentially contributing to its impact on the anti-influenza immune response. Taken together, these findings suggest that targeting PLA2G2E could hold potential as a therapeutic strategy for managing influenza virus infections.IMPORTANCEThe influenza virus is a highly transmissible respiratory pathogen that continues to pose a significant public health concern. It effectively evades humoral immune protection conferred by vaccines and natural infection due to its continuous viral evolution through the genetic processes of antigenic drift and shift. Recognition of conserved non-mutable viral epitopes by T cells may provide broad immunity against influenza virus. In this study, we have demonstrated that phospholipase A2 group IIE (PLA2G2E) plays a crucial role in protecting against influenza virus infection through the regulation of T cell responses, while not affecting innate and humoral immune responses. Targeting PLA2G2E could therefore represent a potential therapeutic strategy for managing influenza virus infection.

1-L Transcription of SARS-CoV-2 Spike Protein S1 Subunit

The COVID-19 pandemic prompted rapid research on SARS-CoV-2 pathogenicity. Consequently, new data can be used to advance the molecular understanding of SARS-CoV-2 infection. The present bioinformatics study discusses the "spikeopathy" at the molecular level and focuses on the possible post-transcriptional regulation of the SARS-CoV-2 spike protein S1 subunit in the host cell/tissue. A theoretical protein-RNA recognition code was used to check the compatibility of the SARS-CoV-2 spike protein S1 subunit with mRNAs in the human transcriptome (1-L transcription). The principle for this method is elucidated on the defined RNA binding protein GEMIN5 (gem nuclear organelle-associated protein 5) and RNU2-1 (U2 spliceosomal RNA). Using the method described here, it was shown that 45% of the genes/proteins identified by 1-L transcription of the SARS-CoV-2 spike protein S1 subunit are directly linked to COVID-19, 39% are indirectly linked to COVID-19, and 16% cannot currently be associated with COVID-19. The identified genes/proteins are associated with stroke, diabetes, and cardiac injury.

Modulation of Phospholipase A2 Membrane Activity by Anti-inflammatory Drugs

The phospholipase A2 (PLA2) superfamily consists of lipolytic enzymes that hydrolyze specific cell membrane phospholipids and have long been considered a central hub of biosynthetic pathways, where their lipid metabolites exert a variety of physiological roles. A misregulated PLA2 activity is associated with mainly inflammatory-derived pathologies and thus has shown relevant therapeutic potential. Many natural and synthetic anti-inflammatory drugs (AIDs) have been proposed as direct modulators of PLA2 activity. However, despite the specific chemical properties that these drugs share in common, little is known about the indirect modulation able to finely tune membrane structural changes at the precise lipid-binding site. Here, we use a novel experimental strategy based on differential scanning calorimetry to systematically study the structural properties of lipid membrane systems during PLA2 cleavage and under the influence of several AIDs. For a better understanding of the AIDs-membrane interaction, we present a comprehensive and comparative set of molecular dynamics (MD) simulations. Our thermodynamic results clearly demonstrate that PLA2 cleavage is hindered by those AIDs that significantly reduce the lipid membrane cooperativity, while the rest of the AIDs oppositely tend to catalyze PLA2 activity to different extents. On the other hand, our MD simulations support experimental results by providing atomistic details on the binding, insertion, and dynamics of each AID on a pure lipid system; the drug efficacy to impact membrane cooperativity is related to the lipid order perturbation. This work suggests a membrane-based mechanism of action for diverse AIDs against PLA2 activity and provides relevant clues that must be considered in its modulation.

Balancing Act of the Intestinal Antimicrobial Proteins on Gut Microbiota and Health

The human gut houses a diverse and dynamic microbiome critical for digestion, metabolism, and immune development, exerting profound effects on human health. However, these microorganisms pose a potential threat by breaching the gut barrier, entering host tissues, and triggering infections, uncontrolled inflammation, and even sepsis. The intestinal epithelial cells form the primary defense, acting as a frontline barrier against microbial invasion. Antimicrobial proteins (AMPs), produced by these cells, serve as innate immune effectors that regulate the gut microbiome by directly killing or inhibiting microbes. Abnormal AMP production, whether insufficient or excessive, can disturb the microbiome equilibrium, contributing to various intestinal diseases. This review delves into the complex interactions between AMPs and the gut microbiota and sheds light on the role of AMPs in governing host-microbiota interactions. We discuss the function and mechanisms of action of AMPs, their regulation by the gut microbiota, microbial evasion strategies, and the consequences of AMP dysregulation in disease. Understanding these complex interactions between AMPs and the gut microbiota is crucial for developing strategies to enhance immune responses and combat infections within the gut microbiota. Ongoing research continues to uncover novel aspects of this intricate relationship, deepening our understanding of the factors shaping gut health. This knowledge has the potential to revolutionize therapeutic interventions, offering enhanced treatments for a wide range of gut-related diseases.

Group III secreted phospholipase A2 -driven lysophospholipid pathway protects against allergic asthma

Asthma is a chronic inflammatory disease of the airways characterized by recurrent episodes of airway obstruction, hyperresponsiveness, remodeling, and eosinophilia. Phospholipase A2 s (PLA2 s), which release fatty acids and lysophospholipids from membrane phospholipids, have been implicated in exacerbating asthma by generating pro-asthmatic lipid mediators, but an understanding of the association between individual PLA2 subtypes and asthma is still incomplete. Here, we show that group III-secreted PLA2 (sPLA2 -III) plays an ameliorating, rather than aggravating, role in asthma pathology. In both mouse and human lungs, sPLA2 -III was expressed in bronchial epithelial cells and decreased during the asthmatic response. In an ovalbumin (OVA)-induced asthma model, Pla2g3-/- mice exhibited enhanced airway hyperresponsiveness, eosinophilia, OVA-specific IgE production, and type 2 cytokine expression as compared to Pla2g3+/+ mice. Lipidomics analysis showed that the pulmonary levels of several lysophospholipids, including lysophosphatidylcholine, lysophosphatidylethanolamine, and lysophosphatidic acid (LPA), were decreased in OVA-challenged Pla2g3-/- mice relative to Pla2g3+/+ mice. LPA receptor 2 (LPA2 ) agonists suppressed thymic stromal lymphopoietin (TSLP) expression in bronchial epithelial cells and reversed airway hyperresponsiveness and eosinophilia in Pla2g3-/- mice, suggesting that sPLA2 -III negatively regulates allergen-induced asthma at least by producing LPA. Thus, the activation of the sPLA2 -III-LPA pathway may be a new therapeutic target for allergic asthma.

Lysolipids are prominent in subretinal drusenoid deposits, a high-risk phenotype in age-related macular degeneration

Introduction

Age related macular degeneration (AMD) causes legal blindness worldwide, with few therapeutic targets in early disease and no treatments for 80% of cases. Extracellular deposits, including drusen and subretinal drusenoid deposits (SDD; also called reticular pseudodrusen), disrupt cone and rod photoreceptor functions and strongly confer risk for advanced disease. Due to the differential cholesterol composition of drusen and SDD, lipid transfer and cycling between photoreceptors and support cells are candidate dysregulated pathways leading to deposit formation. The current study explores this hypothesis through a comprehensive lipid compositional analysis of SDD.

Methods

Histology and transmission electron microscopy were used to characterize the morphology of SDD. Highly sensitive tools of imaging mass spectrometry (IMS) and nano liquid chromatography tandem mass spectrometry (nLC-MS/MS) in positive and negative ion modes were used to spatially map and identify SDD lipids, respectively. An interpretable supervised machine learning approach was utilized to compare the lipid composition of SDD to regions of uninvolved retina across 1873 IMS features and to automatically discern candidate markers for SDD. Immunohistochemistry (IHC) was used to localize secretory phospholipase A2 group 5 (PLA2G5).

Results

Among the 1873 detected features in IMS data, three lipid classes, including lysophosphatidylcholine (LysoPC), lysophosphatidylethanolamine (LysoPE) and lysophosphatidic acid (LysoPA) were observed nearly exclusively in SDD while presumed precursors, including phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidic acid (PA) lipids were detected in SDD and adjacent photoreceptor outer segments. Molecular signals specific to SDD were found in central retina and elsewhere. IHC results indicated abundant PLA2G5 in photoreceptors and retinal pigment epithelium (RPE).

Discussion

The abundance of lysolipids in SDD implicates lipid remodeling or degradation in deposit formation, consistent with ultrastructural evidence of electron dense lipid-containing structures distinct from photoreceptor outer segment disks and immunolocalization of secretory PLA2G5 in photoreceptors and RPE. Further studies are required to understand the role of lipid signals observed in and around SDD.