Structure and Properties of a Human Non-pancreatic Phospholipase A2

Revisiting the reaction pathways for phospholipid hydrolysis catalyzed by phospholipase A2 with QM/MM methods

Secreted phospholipase A2 (sPLA2) is a Ca2+-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 Ca2+ 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.

Four phospholipase A2 genes encoded in the western flower thrips genome and their functional differentiation in mediating development and immunity

Eicosanoids are synthesized from phospholipids by the catalytic activity of phospholipase A2 (PLA2). Even though several PLA2s are encoded in the genome of different insect species, their physiological functions are not clearly discriminated. This study identified four PLA2 genes encoded in the western flower thrips, Frankliniella occidentalis. Two PLA2s (Fo-PLA2C and Fo-PLA2D) are predicted to be secretory while the other two PLA2s (Fo-PLA2A and Fo-PLA2B) are intracellular. All four PLA2 genes were expressed in all developmental stages, of which Fo-PLA2B and Fo-PLA2C were highly expressed in larvae while Fo-PLA2A and Fo-PLA2D were highly expressed in adults. Their expressions in different tissues were also detected by fluorescence in situ hybridization. All four PLA2s were detected in the larval and adult intestines and the ovary. Feeding double-stranded RNAs specific to the PLA2 genes specifically suppressed the target transcript levels. Individual RNA interference (RNAi) treatments led to significant developmental retardation, especially in the treatments specific to Fo-PLA2B and Fo-PLA2D. The RNAi treatments also showed that Fo-PLA2B and Fo-PLA2C expressions were required for the induction of immune-associated genes, while Fo-PLA2A and Fo-PLA2D expressions were required for ovary development. These results suggest that four PLA2s are associated with different physiological processes by their unique catalytic activities and expression patterns.

Screening of insect immune suppressors using a recombinant phospholipase A2 of a lepidopteran insect

Phospholipase A2 (PLA2 ) catalyzes phospholipids at the sn-2 position to release free fatty acids, including arachidonic acid (AA) or its precursor. The free AA is then oxygenated into different eicosanoids, which mediate the diverse physiological processes in insects. Any inhibition of the PLA2 catalysis would give rise to serious malfunctioning in insect growth and development. An onion moth, Acrolepiopsis sapporensis, encodes four different PLA2 genes (As-PLA2 A-As-PLA2 D), in which As-PLA2 A is dominantly expressed at all developmental stages and in different larval tissues. RNA interference of the As-PLA2 A expression significantly reduced the PLA2 activity of A. sapporensis, which suffered from immunosuppression. A recombinant As-PLA2 A protein was purified from a bacterial expression system, which exhibited a typical Michaelis-Menten kinetics and hence susceptible to a specific inhibitor to sPLA2 and dithiothreitol. A total of 19 bacterial metabolites derived from Xenorhabdus and Photorhabdus were screened against the recombinant As-PLA2 A. Five potent metabolites were highly inhibitory and followed a competitive enzyme inhibition. These five inhibitors suppressed the immune responses of A. sapporensis by inhibiting hemocyte-spreading behavior and phenoloxidase activity. However, an addition of AA could significantly rescue the immunosuppression induced by the selected inhibitors. These studies suggest that the recombinant As-PLA2 A protein can be applied for high-throughput screening of insect immunosuppressive compounds.

Modulation of immunity by the secreted phospholipase A2 family

Among the phospholipase A2 (PLA2 ) superfamily, which typically catalyzes the sn-2 hydrolysis of phospholipids to yield fatty acids and lysophospholipids, the secreted PLA2 (sPLA2 ) family contains 11 isoforms in mammals. Individual sPLA2 s have unique enzymatic specificity toward fatty acids and polar heads of phospholipid substrates and display distinct tissue/cellular distributions, suggesting their distinct physiological functions. Recent studies using knockout and/or transgenic mice for a full set of sPLA2 s have revealed their roles in modulation of immunity and related disorders. Application of mass spectrometric lipidomics to these mice has enabled to identify target substrates and products of individual sPLA2 s in given tissue microenvironments. sPLA2 s hydrolyze not only phospholipids in the plasma membrane of activated, damaged or dying mammalian cells, but also extracellular phospholipids such as those in extracellular vesicles, microbe membranes, lipoproteins, surfactants, and dietary phospholipids, thereby exacerbating or ameliorating various diseases. The actions of sPLA2 s are dependent on, or independent of, the generation of fatty acid- or lysophospholipid-derived lipid mediators according to the pathophysiological contexts. In this review, we make an overview of our current understanding of the roles of individual sPLA2 s in various immune responses and associated diseases.

scTenifoldXct: A semi-supervised method for predicting cell-cell interactions and mapping cellular communication graphs

We present scTenifoldXct, a semi-supervised computational tool for detecting ligand-receptor (LR)-mediated cell-cell interactions and mapping cellular communication graphs. Our method is based on manifold alignment, using LR pairs as inter-data correspondences to embed ligand and receptor genes expressed in interacting cells into a unified latent space. Neural networks are employed to minimize the distance between corresponding genes while preserving the structure of gene regression networks. We apply scTenifoldXct to real datasets for testing and demonstrate that our method detects interactions with high consistency compared with other methods. More importantly, scTenifoldXct uncovers weak but biologically relevant interactions overlooked by other methods. We also demonstrate how scTenifoldXct can be used to compare different samples, such as healthy vs. diseased and wild type vs. knockout, to identify differential interactions, thereby revealing functional implications associated with changes in cellular communication status.

The Roles of sPLA2s in Skin Homeostasis and Disease

Among the phospholipase A₂ (PLA₂) family, the secreted PLA₂ (sPLA₂) family in mammals contains 11 members that exhibit unique tissue or cellular distributions and enzymatic properties. Current studies using knockout and/or transgenic mice for a nearly full set of sPLA₂s, in combination with comprehensive lipidomics, have revealed the diverse pathophysiological roles of sPLA₂s in various biological events. Individual sPLA₂s exert specific functions within tissue microenvironments, likely through the hydrolysis of extracellular phospholipids. Lipids are an essential biological component for skin homeostasis, and disturbance of lipid metabolism by deletion or overexpression of lipid-metabolizing enzymes or lipid-sensing receptors often leads to skin abnormalities that are easily visible on the outside. Over the past decades, our studies using knockout and transgenic mice for various sPLA₂s have uncovered several new aspects of these enzymes as modulators of skin homeostasis and disease. This article summarizes the roles of several sPLA₂s in skin pathophysiology, providing additional insight into the research fields of sPLA₂s, lipids, and skin biology.

PLA2G2A+ cancer-associated fibroblasts mediate pancreatic cancer immune escape via impeding antitumor immune response of CD8+ cytotoxic T cells

Our previous research defined a novel metabolic cancer associated fibroblasts subset (meCAFs) enriched in loose-type pancreatic ductal adenocarcinoma (PDAC) and related to CD8⁺ T cells accumulation. Consistently, the abundance of meCAFs was associated with poor prognosis but better immunotherapy responses in PDAC patients. However, the metabolic characteristic of meCAFs and its cross-talk with CD8⁺ T cells remain to be elucidated. In this study, we identified PLA2G2A as a marker of meCAFs. In particular, the abundance of PLA2G2A⁺ meCAFs was positively related to the accumulation of total CD8⁺ T cells and negatively correlated with clinical outcomes of PDAC patients and infiltration of intratumoral CD8⁺ T cells. We demonstrated that PLA2G2A⁺ meCAFs substantially attenuated the antitumor ability of tumor infiltrating CD8⁺ T cells and facilitated tumor immune escape in PDAC. Mechanistically, PLA2G2A regulated the function of CD8⁺ T cells as a pivotal soluble mediator via MAPK/Erk and NF-κB signaling pathways. In conclusion, our study identified the unrecognized role of PLA2G2A⁺ meCAFs in promoting tumor immune escape by impeding the antitumor immune function of CD8⁺ T cells, and strongly suggested PLA2G2A as a promising biomarker and therapeutic target for immunotherapy in PDAC.

Pla2g2a promotes innate Th2-type immunity lymphocytes to increase B1a cells

Newborns require early generation of effective innate immunity as a primary physiological mechanism for survival. The neonatal Lin28⁺Let7^– developmental pathway allows increased generation of Th2-type cells and B1a (B-1 B) cells compared to adult cells and long-term maintenance of these initially generated innate cells. For initial B1a cell growth from the neonatal to adult stage, Th2-type IL-5 production from ILC2s and NKT2 cells is important to increase B1a cells. The Th17 increase is dependent on extracellular bacteria, and increased bacteria leads to lower Th2-type generation. Secreted group IIA-phospholipase A2 (sPLA2-IIA) from the Pla2g2a gene can bind to gram-positive bacteria and degrade bacterial membranes, controlling microbiota in the intestine. BALB/c mice are Pla2g2a⁺, and express high numbers of Th2-type cells and B1a cells. C57BL/6 mice are Pla2g2a-deficient and distinct from the SLAM family, and exhibit fewer NKT2 cells and fewer B1a cells from the neonatal to adult stage. We found that loss of Pla2g2a in the BALB/c background decreased IL-5 from Th2-type ILC2s and NKT2s but increased bacterial-reactive NKT17 cells and MAIT cells, and decreased the number of early-generated B1a cells and MZ B cells and the CD4/CD8 T cell ratio. Low IL-5 by decreased Th2-type cells in Pla2g2a loss led to low early-generated B1a cell growth from the neonatal to adult stage. In anti-thymocyte/Thy-1 autoreactive μκ transgenic (ATAμκ Tg) Pla2g2a⁺ BALB/c background C.B17 mice generated NKT2 cells that continuously control CD1d⁺ B1 B cells through old aging and lost CD1d in B1 B cells generating strong B1 ATA B cell leukemia/lymphoma. Pla2g2a-deficient ATAμκTg C57BL/6 mice suppressed the initial B1a cell increase, with low/negative spontaneous leukemia/lymphoma generation. These data confirmed that the presence of Pla2g2a to control bacteria is important to allow the neonatal to adult stage. Pla2g2a promotes innate Th2-type immunity lymphocytes to increase early generated B1a cells.

Biochemical, Kinetic and Biological Properties of Group V Phospholipase A2 from Dromedary

Secretory group V phospholipase A2 (PLA₂-V) is known to be involved in inflammatory processes in cellular studies, nevertheless, the biochemical and the enzymatic characteristics of this important enzyme have been unclear yet. We reported, as a first step towards understanding the biochemical properties, catalytic characteristics, antimicrobial and cytotoxic effects of this PLA₂, the production of PLA₂-V from dromedary. The obtained DrPLA₂-V has an absolute requirement for Ca²⁺ and NaTDC for enzymatic activity with an optimum pH of 9 and temperature of 45 °C with phosphatidylethanolamine as a substrate. Kinetic parameters showed that K_cat/Km_app is 2.6 ± 0.02 mM⁻¹ s⁻¹. The enzyme was found to display potent Gram-positive bactericidal activity (with IC50 values of about 5 µg/mL) and antifungal activity (with IC50 values of about 25 µg/mL)in vitro. However, the purified enzyme did not display a cytotoxic effect against cancer cells.

The interaction of secreted phospholipase A2-IIA with the microbiota alters its lipidome and promotes inflammation

Secreted phospholipase A₂-IIA (sPLA₂-IIA) hydrolyzes phospholipids to liberate lysophospholipids and fatty acids. Given its poor activity toward eukaryotic cell membranes, its role in the generation of proinflammatory lipid mediators is unclear. Conversely, sPLA₂-IIA efficiently hydrolyzes bacterial membranes. Here, we show that sPLA₂-IIA affects the immune system by acting on the intestinal microbial flora. Using mice overexpressing transgene-driven human sPLA₂-IIA, we found that the intestinal microbiota was critical for both induction of an immune phenotype and promotion of inflammatory arthritis. The expression of sPLA₂-IIA led to alterations of the intestinal microbiota composition, but housing in a more stringent pathogen-free facility revealed that its expression could affect the immune system in the absence of changes to the composition of this flora. In contrast, untargeted lipidomic analysis focusing on bacteria-derived lipid mediators revealed that sPLA₂-IIA could profoundly alter the fecal lipidome. The data suggest that a singular protein, sPLA₂-IIA, produces systemic effects on the immune system through its activity on the microbiota and its lipidome.

Evaluation of the Impact of Esterases and Lipases from the Circulatory System against Substrates of Different Lipophilicity

Esterases and lipases can process amphiphilic esters used as drugs and prodrugs and impact their pharmacokinetics and biodistribution. These hydrolases can also process ester components of drug delivery systems (DDSs), thus triggering DDSs destabilization with premature cargo release. In this study we tested and optimized assays that allowed us to quantify and compare individual esterase contributions to the degradation of substrates of increased lipophilicity and to establish limitations in terms of substrates that can be processed by a specific esterase/lipase. We have studied the impact of carbonic anhydrase; phospholipases A1, A2, C and D; lipoprotein lipase; and standard lipase on the hydrolysis of 4-nitrophenyl acetate, 4-nitrophenyl palmitate, DGGR and POPC liposomes, drawing structure–property relationships. We found that the enzymatic activity of these proteins was highly dependent on the lipophilicity of the substrate used to assess them, as expected. The activity observed for classical esterases was diminished when lipophilicity of the substrate increased, while activity observed for lipases generally increased, following the interfacial activation model, and was highly dependent on the type of lipase and its structure. The assays developed allowed us to determine the most sensitive methods for quantifying enzymatic activity against substrates of particular types and lipophilicity.

Isolation and Characterization of A2-EPTX-Nsm1a, a Secretory Phospholipase A2 from Malaysian Spitting Cobra (Naja sumatrana) Venom

Phospholipase A₂ (PLA₂) toxins are one of the main toxin families found in snake venom. PLA₂ toxins are associated with various detrimental effects, including neurotoxicity, myotoxicity, hemostatic disturbances, nephrotoxicity, edema, and inflammation. Although Naja sumatrana venom contains substantial quantities of PLA₂ components_, there is limited information on the function and activities of PLA₂ toxins from the venom. In this study, a secretory PLA₂ from the venom of Malaysian N. sumatrana, subsequently named A2-EPTX-Nsm1a, was isolated, purified, and characterized. A2-EPTX-Nsm1a was purified using a mass spectrometry-guided approach and multiple chromatography steps. Based on LC-MSMS, A2-EPTX-Nsm1a was found to show high sequence similarity with PLA₂ from venoms of other Naja species. The PLA₂ activity of A2-EPTX-Nsm1 was inhibited by 4-BPB and EDTA. A2-EPTX-Nsm1a was significantly less cytotoxic in a neuroblastoma cell line (SH-SY5Y) compared to crude venom and did not show a concentration-dependent cytotoxic activity. To our knowledge, this is the first study that characterizes and investigates the cytotoxicity of an Asp49 PLA₂ isolated from Malaysian N. sumatrana venom in a human neuroblastoma cell line.

Human Group IIA Phospholipase A2-Three Decades on from Its Discovery

Phospholipase A₂ (PLA₂) enzymes were first recognized as an enzyme activity class in 1961. The secreted (sPLA₂) enzymes were the first of the five major classes of human PLA₂s to be identified and now number nine catalytically-active structurally homologous proteins. The best-studied of these, group IIA sPLA₂, has a clear role in the physiological response to infection and minor injury and acts as an amplifier of pathological inflammation. The enzyme has been a target for anti-inflammatory drug development in multiple disorders where chronic inflammation is a driver of pathology since its cloning in 1989. Despite intensive effort, no clinically approved medicines targeting the enzyme activity have yet been developed. This review catalogues the major discoveries in the human group IIA sPLA₂ field, focusing on features of enzyme function that may explain this lack of success and discusses future research that may assist in realizing the potential benefit of targeting this enzyme. Functionally-selective inhibitors together with isoform-selective inhibitors are necessary to limit the apparent toxicity of previous drugs. There is also a need to define the relevance of the catalytic function of hGIIA to human inflammatory pathology relative to its recently-discovered catalysis-independent function.

Sex-Biased Expression of Pharmacogenes across Human Tissues

Individual response to drugs is highly variable and largely influenced by genetic variants and gene-expression profiles. In addition, it has been shown that response to drugs is strongly sex-dependent, both in terms of efficacy and toxicity. To expand current knowledge on sex differences in the expression of genes relevant for drug response, we generated a catalogue of differentially expressed human transcripts encoded by 289 genes in 41 human tissues from 838 adult individuals of the Genotype-Tissue Expression project (GTEx, v8 release) and focused our analysis on relevant transcripts implicated in drug response. We detected significant sex-differentiated expression of 99 transcripts encoded by 59 genes in the tissues most relevant for human pharmacology (liver, lung, kidney, small intestine terminal ileum, skin not sun-exposed, and whole blood). Among them, as expected, we confirmed significant differences in the expression of transcripts encoded by the cytochromes in the liver, CYP2B6, CYP3A7, CYP3A5, and CYP1A1. Our systematic investigation on differences between male and female in the expression of drug response-related genes, reinforce the need to overcome the sex bias of clinical trials.

Role of human group IIA secreted phospholipase A2 in malaria pathophysiology: Insights from a transgenic mouse model

We previously showed that injection of recombinant human group IIA secreted phospholipase A₂ (hGIIA sPLA₂) to Plasmodium chabaudi-infected mice lowers parasitaemia by 20%. Here, we show that transgenic (TG) mice overexpressing hGIIA sPLA₂ have a peak of parasitaemia about 30% lower than WT littermates. During infection, levels of circulating sPLA₂, enzymatic activity and plasma lipid peroxidation were maximal at day-14, the peak of parasitaemia. Levels of hGIIA mRNA increased in liver but not in spleen and blood cells, suggesting that liver may contribute as a source of circulating hGIIA sPLA₂. Before infection, baseline levels of leukocytes and pro-inflammatory cytokines were higher in TG mice than WT littermates. Upon infection, the number of neutrophils, lymphocytes and monocytes increased and were maximal at the peak of parasitaemia in both WT and TG mice, but were higher in TG mice. Similarly, levels of the Th1 cytokines IFN-γ and IL-2 increased in WT and TG mice, but were 7.7- and 1.7-fold higher in TG mice. The characteristic shift towards Th2 cytokines was observed during infection in both WT and TG mice, with increased levels of IL-10 and IL-4 at day-14. The current data are in accordance with our previous in vitro findings showing that hGIIA kills parasites by releasing toxic lipids from oxidized lipoproteins. They further show that hGIIA sPLA₂ is induced during mouse experimental malaria and has a protective in vivo role, lowering parasitaemia by likely releasing toxic lipids from oxidized lipoproteins but also indirectly by promoting a more sustained innate immune response.

Reorganization of Metabolism during Cardiomyogenesis Implies Time-Specific Signaling Pathway Regulation

Understanding the cell differentiation process involves the characterization of signaling and regulatory pathways. The coordinated action involved in multilevel regulation determines the commitment of stem cells and their differentiation into a specific cell lineage. Cellular metabolism plays a relevant role in modulating the expression of genes, which act as sensors of the extra-and intracellular environment. In this work, we analyzed mRNAs associated with polysomes by focusing on the expression profile of metabolism-related genes during the cardiac differentiation of human embryonic stem cells (hESCs). We compared different time points during cardiac differentiation (pluripotency, embryoid body aggregation, cardiac mesoderm, cardiac progenitor and cardiomyocyte) and showed the immature cell profile of energy metabolism. Highly regulated canonical pathways are thoroughly discussed, such as those involved in metabolic signaling and lipid homeostasis. We reveal the critical relevance of retinoic X receptor (RXR) heterodimers in upstream retinoic acid metabolism and their relationship with thyroid hormone signaling. Additionally, we highlight the importance of lipid homeostasis and extracellular matrix component biosynthesis during cardiomyogenesis, providing new insights into how hESCs reorganize their metabolism during in vitro cardiac differentiation.

Mann T, Bastard K, F. Scott K, Church WB. Structural and Functional Aspects of Targeting the Secreted Human Group IIA Phospholipase A2

Human group IIA secretory phospholipase A₂ (hGIIA) promotes the proliferation of cancer cells, making it a compelling therapeutic target, but it is also significant in other inflammatory conditions. Consequently, suitable inhibitors of hGIIA have always been sought. The activation of phospholipases A₂ and the catalysis of glycerophospholipid substrates generally leads to the release of fatty acids such as arachidonic acid (AA) and lysophospholipid, which are then converted to mediator compounds, including prostaglandins, leukotrienes, and the platelet-activating factor. However, this ability of hGIIA to provide AA is not a complete explanation of its biological role in inflammation, as it has now been shown that it also exerts proinflammatory effects by a catalysis-independent mechanism. This mechanism is likely to be highly dependent on key specific molecular interactions, and the full mechanistic descriptions of this remain elusive. The current candidates for the protein partners that may mediate this catalysis-independent mechanism are also introduced in this review. A key discovery has been that selective inhibition of the catalysis-independent activity of hGIIA is achieved with cyclised derivatives of a pentapeptide, FLSYK, derived from the primary sequence of hGIIA. The effects of hGIIA on cell function appear to vary depending on the pathology studied, and so its mechanism of action is complex and context-dependent. This review is comprehensive and covers the most recent developments in the understanding of the many facets of hGIIA function and inhibition and the insight they provide into their clinical application for disease treatment. A cyclic analogue of FLSYK, c2, the most potent analogue known, has now been taken into clinical trials targeting advanced prostate cancer.

Polymorphism of Secretary PLA2G2A Gene Associated with Its Serum Level in Type2 Diabetes Mellitus Patients in Northern Iran

BACKGROUND

Inflammation may occur in Type2 diabetes mellitus. sPLA2 is among the factors that contribute to the activation of pathways involved in inflammation. Several agents affect serum sPLA2 level, one of which is genetic diversity.

OBJECTIVE

The current study was performed to determine whether there is a relationship between sPLA2 gene (-763C > G) polymorphism and circulating sPLA2 level in patients with Type 2 diabetes.

METHODS

DNA was extracted from blood samples and used for the amplification of sPLA2 gene using ARMS-PCR.

RESULTS

A statistical analysis using SPSS (version 16) revealed a significant correlation between -763C > G sPLA2 gene polymorphisms and the disease incidence in patients with T2DM. Among the three possible genotypes (GG, CC, and CG), CG genotype was found to have a higher frequency(53%) in T2DM patients. GG and CC genotypes frequencies were 20 and 27%, respectively. In healthy individuals, the frequencies of CC, GG, and GC genotypes were 77, 9.8% and 13.2%, respectively). Patients with genotype GG had the highest level of sPLA2. We showed that C>G polymorphism at position- 763 is associated with a high level of sPLA2 in both T2DM patients and healthy individuals. The average of sPLA2 circulating level was (170.48± 84.90), (106.62 ± 74.31), in patients and normal individuals, respectively.

CONCLUSION

Our findings show that sPLA2 serum level is significantly higher in patients with T2DM disease than that in healthy individuals.

Overcoming Resistance to Therapies Targeting the MAPK Pathway in BRAF-Mutated Tumours

Overactivation of the mitogen-activated protein kinase (MAPK) pathway is an important driver of many human cancers. First line, FDA-approved therapies targeting MAPK signalling, which include BRAF and MEK inhibitors, have variable success across cancers, and a significant number of patients quickly develop resistance. In recent years, a number of preclinical studies have reported alternative methods of overcoming resistance, which include promoting apoptosis, modulating autophagy, and targeting mitochondrial metabolism. This review summarizes mechanisms of resistance to approved MAPK-targeted therapies in BRAF-mutated cancers and discusses novel preclinical approaches to overcoming resistance.

A Potential Role of Phospholipase 2 Group IIA (PLA2-IIA) in P. gingivalis-Induced Oral Dysbiosis

Porphyromonas gingivalis is an oral pathogen with the ability to induce oral dysbiosis and periodontal disease. Nevertheless, the mechanisms by which P. gingivalis could abrogate the host-microbe symbiotic relationship leading to oral dysbiosis remain unclear. We have recently demonstrated that P. gingivalis specifically increased the antimicrobial properties of oral epithelial cells, through a strong induction of the expression of PLA₂-IIA in a mechanism that involves activation of the Notch-1 receptor. Moreover, gingival expression of PLA₂-IIA was significantly increased during initiation and progression of periodontal disease in non-human primates and interestingly, those PLA₂-IIA expression changes were concurrent with oral dysbiosis. In this chapter, we present an innovative hypothesis of a potential mechanism involved in P. gingivalis-induced oral dysbiosis and inflammation based on our previous observations and a robust body of literature that supports the antimicrobial and proinflammatory properties of PLA₂-IIA as well as its role in other chronic inflammatory diseases.

Interactions of the effector ExoU from Pseudomonas aeruginosa with short-chain phosphatidylinositides provide insights into ExoU targeting to host membranes

Pseudomonas aeruginosa is an opportunistic multidrug-resistant pathogen and a common cause of infection in cystic fibrosis and ventilator-associated pneumonia and in burn and wound patients. P. aeruginosa uses its type III secretion system to secrete various effector proteins directly into mammalian host cells. ExoU is a potent type III secretion system effector that, after secretion, localizes to the inner cytoplasmic membrane of eukaryotic cells, where it exerts its phospholipase A2 activity upon interacting with ubiquitin and/or ubiquitinated proteins. In this study, we used site-directed spin-labeling electron paramagnetic resonance spectroscopy to examine the interaction of ExoU with soluble analogs of phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P₂). We found that dioctanoyl PI(4,5)P₂ binds to and induces conformational changes in a C-terminal four-helix bundle (4HB) domain of ExoU implicated previously in membrane binding. Other soluble phosphoinositides also interacted with the 4HB but less effectively. Molecular modeling and ligand docking studies indicated the potential for numerous hydrogen bond interactions within and between interhelical loops of the 4HB and suggested several potential interaction sites for PI(4,5)P₂ Site-directed mutagenesis experiments confirmed that the side chains of Gln-623 and Arg-661 play important roles in mediating PI(4,5)P₂-induced conformational changes in ExoU. These results support a mechanism in which direct interactions with phosphatidylinositol-containing lipids play an essential role in targeting ExoU to host membrane bilayers. Molecules or peptides that block this interaction may prove useful in preventing the cytotoxic effects of ExoU to mitigate the virulence of P. aeruginosa strains that express this potent phospholipase toxin.

Secretory Phospholipases A2 in Plants

Secreted phospholipases (sPLA2s) in plants are a growing group of enzymes that catalyze the hydrolysis of sn-2 glycerophospholipids to lysophospholipids and free fatty acids. Until today, around only 20 sPLA2s were reported from plants. This review discusses the newly acquired information on plant sPLA2s including molecular, biochemical, catalytic, and functional aspects. The comparative analysis also includes phylogenetic, evolutionary, and tridimensional structure. The observations with emphasis in Glycine max sPLA2 are compared with the available data reported for all plants sPLA2s and with those described for animals (mainly from pancreatic juice and venoms sources).

Prostaglandins and Other Eicosanoids in Insects: Biosynthesis and Biological Actions

This essay reviews the discoveries, synthesis, and biological significance of prostaglandins (PGs) and other eicosanoids in insect biology. It presents the most current - and growing - understanding of the insect mechanism of PG biosynthesis, provides an updated treatment of known insect phospholipase A2 (PLA2), and details contemporary findings on the biological roles of PGs and other eicosanoids in insect physiology, including reproduction, fluid secretion, hormone actions in fat body, immunity and eicosanoid signaling and cross-talk in immunity. It completes the essay with a prospectus meant to illuminate research opportunities for interested readers. In more detail, cellular and secretory types of PLA2, similar to those known on the biomedical background, have been identified in insects and their roles in eicosanoid biosynthesis documented. It highlights recent findings showing that eicosanoid biosynthetic pathway in insects is not identical to the solidly established biomedical picture. The relatively low concentrations of arachidonic acid (AA) present in insect phospholipids (PLs) (< 0.1% in some species) indicate that PLA2 may hydrolyze linoleic acid (LA) as a precursor of eicosanoid biosynthesis. The free LA is desaturated and elongated into AA. Unlike vertebrates, AA is not oxidized by cyclooxygenase, but by a specific peroxidase called peroxinectin to produce PGH2, which is then isomerized into cell-specific PGs. In particular, PGE2 synthase recently identified converts PGH2 into PGE2. In the cross-talks with other immune mediators, eicosanoids act as downstream signals because any inhibition of eicosanoid signaling leads to significant immunosuppression. Because host immunosuppression favors pathogens and parasitoids, some entomopathogens evolved a PLA2 inhibitory strategy activity to express their virulence.

Phospholipid Remodeling in Physiology and Disease

Phospholipids are major constituents of biological membranes. The fatty acyl chain composition of phospholipids determines the biophysical properties of membranes and thereby affects their impact on biological processes. The composition of fatty acyl chains is also actively regulated through a deacylation and reacylation pathway called Lands' cycle. Recent studies of mouse genetic models have demonstrated that lysophosphatidylcholine acyltransferases (LPCATs), which catalyze the incorporation of fatty acyl chains into the sn-2 site of phosphatidylcholine, play important roles in pathophysiology. Two LPCAT family members, LPCAT1 and LPCAT3, have been particularly well studied. LPCAT1 is crucial for proper lung function due to its role in pulmonary surfactant biosynthesis. LPCAT3 maintains systemic lipid homeostasis by regulating lipid absorption in intestine, lipoprotein secretion, and de novo lipogenesis in liver. Mounting evidence also suggests that changes in LPCAT activity may be potentially involved in pathological conditions, including nonalcoholic fatty liver disease, atherosclerosis, viral infections, and cancer. Pharmacological manipulation of LPCAT activity and membrane phospholipid composition may provide new therapeutic options for these conditions.

Roles of secreted phospholipase A2 group IIA in inflammation and host defense

Among all members of the secreted phospholipase A₂ (sPLA₂) family, group IIA sPLA₂ (sPLA₂-IIA) is possibly the most studied enzyme. Since its discovery, many names have been associated with sPLA₂-IIA, such as "non-pancreatic", "synovial", "platelet-type", "inflammatory", and "bactericidal" sPLA_2. Whereas the different designations indicate comprehensive functions or sources proposed for this enzyme, the identification of the precise roles of sPLA₂-IIA has remained a challenge. This can be attributed to: the expression of the enzyme by various cells of different lineages, its limited activity towards the membranes of immune cells despite its expression following common inflammatory stimuli, its ability to interact with certain proteins independently of its catalytic activity, and its absence from multiple commonly used mouse models. Nevertheless, elevated levels of the enzyme during inflammatory processes and associated consistent release of arachidonic acid from the membrane of extracellular vesicles suggest that sPLA₂-IIA may contribute to inflammation by using endogenous substrates in the extracellular milieu. Moreover, the remarkable potency of sPLA₂-IIA towards bacterial membranes and its induced expression during the course of infections point to a role for this enzyme in the defense of the host against invading pathogens. In this review, we present current knowledge related to mammalian sPLA₂-IIA and its roles in sterile inflammation and host defense.

Group IID, IIE, IIF and III secreted phospholipase A2s

Among the 11 members of the secreted phospholipase A₂ (sPLA₂) family, group IID, IIE, IIF and III sPLA₂s (sPLA₂-IID, -IIE, -IIF and -III, respectively) are “new” isoforms in the history of sPLA₂ research. Relative to the better characterized sPLA₂s (sPLA₂-IB, -IIA, -V and -X), the enzymatic properties, distributions, and functions of these “new” sPLA₂s have remained obscure until recently. Our current studies using knockout and transgenic mice for a nearly full set of sPLA₂s, in combination with comprehensive lipidomics, have revealed unique and distinct roles of these “new” sPLA₂s in specific biological events. Thus, sPLA₂-IID is involved in immune suppression, sPLA₂-IIE in metabolic regulation and hair follicle homeostasis, sPLA₂-IIF in epidermal hyperplasia, and sPLA₂-III in male reproduction, anaphylaxis, colonic diseases, and possibly atherosclerosis. In this article, we overview current understanding of the properties and functions of these sPLA₂s and their underlying lipid pathways in vivo.

In silico investigation of the molecular effects caused by R123H variant in secretory phospholipase A2-IIA associated with ARDS

Phospholipase A2-IIA catalyzes the hydrolysis of the sn-2 ester of glycerophospholipids. A rare c.428G > A (p.Arg143His) variant in PLA2G2A gene was found in two infants affected by acute respiratory distress syndrome (ARDS) by whole coding region and exon/intron boundaries sequencing. To obtain insights into the possible molecular effects of the rare R123H mutation in secretory PLA2-IIA (sPLA2-IIA), molecular modelling, molecular dynamics (MD) using principal component analysis (PCA) and continuum electrostatic calculations were conducted on the crystal structure of the wild type protein and on a generated model structure of the R123H mutant. Analysis of MD trajectories indicate that the overall stability of the protein is not affected by this mutation but nevertheless the catalytically crucial H-bond between Tyr51 and Asp91 as well as main electrostatic interactions in the region close to the mutation site are altered. PCA results indicate that the R123H replacement alter the internal molecular motions of the enzyme and that collective motions are increased. Electrostatic surface potential studies suggest that after mutation the interfacial binding to anionic phospholipid membranes and anionic proteins may be changed. The strengthening of electrostatic interactions may be propagated into the active site region thus potentially affecting the substrate recognition and enzymatic activity. Our findings provide the basis for further investigation and advances our understanding of the effects of mutations on sPLA2 structure and function.

Review of four major distinct types of human phospholipase A2

The phospholipase A2 superfamily of enzymes plays a significant role in the development and progression of numerous inflammatory diseases. Through their catalytic action on membrane phospholipids, phospholipases are the upstream regulators of the eicosanoid pathway releasing free fatty acids for cyclooxygenases, lipoxygenases, and cytochrome P450 enzymes which produce various well-known inflammatory mediators including leukotrienes, thromboxanes and prostaglandins. Elucidating the association of phospholipases A2 with the membrane, the extraction and binding of phospholipid substrates, and their interactions with small-molecule inhibitors is crucial for the development of new anti-inflammatory therapeutics. Studying phospholipases has been challenging because they act on the surface of cellular membranes and micelles. Multidisciplinary approaches including hydrogen/deuterium exchange mass spectrometry, molecular dynamics simulations, and other computer-aided drug design techniques have been successfully employed by our laboratory to study interactions of phospholipases with membranes, phospholipid substrates and inhibitors. This review summarizes the application of these techniques to study four human recombinant phospholipases A2.

Molecular dynamics simulations reveal structural insights into inhibitor binding modes and functionality in human Group IIA phospholipase A2

Human Group IIA phospholipase A₂ (hGIIA) promotes inflammation in immune-mediated pathologies by regulating the arachidonic acid pathway through both catalysis-dependent and -independent mechanisms. The hGIIA crystal structure, both alone and inhibitor-bound, together with structures of closely related snake-venom-derived secreted phospholipase enzymes has been well described. However, differentiation of biological and nonbiological contacts and the relevance of structures determined from snake venom enzymes to human enzymes are not clear. We employed molecular dynamics (MD) and docking approaches to understand the binding of inhibitors that selectively or nonselectively block the catalysis-independent mechanism of hGIIA. Our results indicate that hGIIA behaves as a monomer in the solution environment rather than a dimer arrangement that is in the asymmetric unit of some crystal structures. The binding mode of a nonselective inhibitor, KH064, was validated by a combination of the experimental electron density and MD simulations. The binding mode of the selective pentapeptide inhibitor FLSYK to hGIIA was stipulated to be different to that of the snake venom phospholipases A₂ of Daboia russelli pulchella (svPLA₂ ). Our data suggest that the application of MD approaches to crystal structure data is beneficial in evaluating the robustness of conclusions drawn based on crystal structure data alone. Proteins 2017; 85:827-842. © 2016 Wiley Periodicals, Inc.

Protective effect of quinacrine against glycerol-induced acute kidney injury in rats

BACKGROUND

Acute kidney injury (AKI) is a serious clinical problem with high rate of mortality and morbidity. Currently used prophylactic and therapeutic strategies to address AKI are limited and warrant further studies. In the present study an attempt was made to investigate the effect of quinacrine, a phospholipase A2 inhibitor against glycerol induced AKI in rats.

METHODS

Adult female Wistar rats were divided in to five groups. After 24 h of water deprivation rats in groups 3, 4 and 5 received an intraperitoneal injection of quinacrine (3 mg/kg, 10 mg/kg and 30 mg/kg of body weight respectively). Thirty minutes after the first injection of quinacrine animals in groups 3, 4 and 5 received an intramuscular injection of 25% glycerol (10 ml/kg of body weight). The animals in group 2 received 25% glycerol (10 ml/kg of body weight) only whereas rats in group 1 served as control . The quinacrine administration was continued once daily for three days, on the fourth day animals were sacrificed, blood and kidney were collected for various biochemical and histopathological studies.

RESULTS

Glycerol treatment produced significant renal structural abnormalities and functional impairment (increased urea and creatinine). Increase in myeloperoxidase (MPO) and malondialdehyde (MDA) clearly suggested the involvement of oxidative stress and neutrophilic activity following glycerol administration. Quinacrine dose dependently attenuated glycerol induced structural and functional changes in kidney.

CONCLUSION

The reversal of glycerol induced AKI by quinacrine points towards a role of phospholipase A2 (PLA2) in the pathogenesis of renal injury. The result of this study suggests that quinacrine may offer an alternative mode of treatment for AKI.

Preparation of the Full Set of Recombinant Mouse- and Human-Secreted Phospholipases A2

A family of 14-20kDa, disulfide-rich, calcium-dependent secreted phospholipases A₂ (sPLA₂s) that release fatty acids from the sn-2 position of glycerophospholipids can be found in mammals. They have a diverse array of tissue distribution and biological functions. In this chapter we provide detailed protocols for production of nearly all of the mouse and human sPLA₂s mainly by expression in bacteria and in vitro refolding or by expression in insect cells. High-resolution mass spectrometry and enzymatic assays were, respectively, used to show that all disulfides are formed and that the enzymes are active, strongly suggesting that each sPLA₂ was prepared in the structurally native form. The availability of these proteins has allowed kinetic studies to be carried out, to prepare highly selective antisera, to screen for selective inhibitors, to study receptor binding, and to study the action of each enzyme on mammalian cell membranes and their in vivo biological roles.

A new era of secreted phospholipase A₂

Among more than 30 members of the phospholipase A2 (PLA2) superfamily, secreted PLA2 (sPLA2) enzymes represent the largest family, being Ca(2+)-dependent low-molecular-weight enzymes with a His-Asp catalytic dyad. Individual sPLA2s exhibit unique tissue and cellular distributions and enzymatic properties, suggesting their distinct biological roles. Recent studies using transgenic and knockout mice for nearly a full set of sPLA2 subtypes, in combination with sophisticated lipidomics as well as biochemical and cell biological studies, have revealed distinct contributions of individual sPLA2s to various pathophysiological events, including production of pro- and anti-inflammatory lipid mediators, regulation of membrane remodeling, degradation of foreign phospholipids in microbes or food, or modification of extracellular noncellular lipid components. In this review, we highlight the current understanding of the in vivo functions of sPLA2s and the underlying lipid pathways as revealed by a series of studies over the last decade.

Kinetic characterization, optimum conditions for catalysis and substrate preference of secretory phospholipase A2 from Glycine max in model membrane systems

Two secretory phospholipase A2 (sPLA2s) from Glycine max, GmsPLA2-IXA-1 and GmsPLA2-XIB-2, have been purified as recombinant proteins and the activity was evaluated in order to obtain the optimum conditions for catalysis using mixed micelles and lipid monolayers as substrate. Both sPLA2s showed a maximum enzyme activity at pH 7 and a requirement of Ca(2+) in the micromolar range. These parameters were similar to those found for animal sPLA2s but a surprising optimum temperature for catalysis at 60 °C was observed. The effect of negative interfacial charges on the hydrolysis of organized substrates was evaluated through initial rate measurements using short chain phospholipids with different head groups. The enzymes showed subtle differences in the specificity for phospholipids with different head groups (DLPC, DLPG, DLPE, DLPA) in presence or absence of NaCl. Both recombinant enzymes showed lower activity toward anionic phospholipids and a preference for the zwitterionic ones. The values of the apparent kinetic parameters (Vmax and KM) demonstrated that these enzymes have more affinity for phosphatidylcholine compared with phosphatidylglycerol, in contrast with the results observed for pancreatic sPLA2. A hopping mode of catalysis was proposed for the action of these sPLA2 on mixed phospholipid/triton micelles. On the other hand, Langmuir-monolayers assays indicated an optimum lateral surface pressure for activity in between 13 and 16 mN/m for both recombinant enzymes.

Secreted phospholipase A2 and mast cells

Phospholipase A2s (PLA2s) are a group of enzymes that hydrolyze the sn-2 position of phospholipids to release (typically unsaturated) fatty acids and lysophospholipids, which serve as precursors for a variety of bioactive lipid mediators. Among the PLA2 superfamily, secreted PLA2 (sPLA2) enzymes comprise the largest subfamily that includes 11 isoforms with a conserved His-Asp catalytic dyad. Individual sPLA2 enzymes exhibit unique tissue and cellular localizations and specific enzymatic properties, suggesting their distinct biological roles. Recent studies using transgenic and knockout mice for individual sPLA2 isofoms have revealed their involvement in various pathophysiological events. Here, we overview the current state of knowledge about sPLA2s, specifically their roles in mast cells (MCs) in the context of allergology. In particular, we highlight group III sPLA2 (PLA2G3) as an "anaphylactic sPLA2" that promotes MC maturation and thereby anaphylaxis through a previously unrecognized lipid-orchestrated circuit.

Epithelium specific ETS transcription factor, ESE-3, of Protobothrops flavoviridis snake venom gland transactivates the promoters of venom phospholipase A2 isozyme genes

Protobothrops flavoviridis (habu) (Crotalinae, Viperidae) is a Japanese venomous snake, and its venom contains the enzymes with a variety of physiological activities. The phospholipases A2 (PLA2s) are the major components and exert various toxic effects. They are expressed abundantly in the venom gland. It is thought that the venom gland-specific transcription factors play a key role for activation of PLA2 genes specifically expressed in the venom gland. Thus, the full-length cDNA library for P. flavoviridis venom gland after milking of the venom was made to explore the transcription factors therein. As a result, three cDNAs encoding epithelium-specific ETS transcription factors (ESE)-1, -2, and -3 were obtained. Among them, ESE-3 was specifically expressed in the venom gland and activated the proximal promoters of venom PLA2 genes, which are possibly regarded as the representatives of the venom gland-specific protein genes in P. flavoviridis. Interestingly, the binding specificity of ESE-3 to the ETS binding motif located near TATA box is well correlated with transcriptional activities for the venom PLA2 genes. This is the first report that venom gland-specific transcription factor could actually activate the promoters of the venom protein genes.

Platelets release mitochondria serving as substrate for bactericidal group IIA-secreted phospholipase A2 to promote inflammation

Mitochondrial DNA (mtDNA) is a highly potent inflammatory trigger and is reportedly found outside the cells in blood in various pathologies. Platelets are abundant in blood where they promote hemostasis. Although lacking a nucleus, platelets contain functional mitochondria. On activation, platelets produce extracellular vesicles known as microparticles. We hypothesized that activated platelets could also release their mitochondria. We show that activated platelets release respiratory-competent mitochondria, both within membrane-encapsulated microparticles and as free organelles. Extracellular mitochondria are found in platelet concentrates used for transfusion and are present at higher levels in those that induced acute reactions (febrile nonhemolytic reactions, skin manifestations, and cardiovascular events) in transfused patients. We establish that the mitochondrion is an endogenous substrate of secreted phospholipase A2 IIA (sPLA2-IIA), a phospholipase otherwise specific for bacteria, likely reflecting the ancestral proteobacteria origin of mitochondria. The hydrolysis of the mitochondrial membrane by sPLA2-IIA yields inflammatory mediators (ie, lysophospholipids, fatty acids, and mtDNA) that promote leukocyte activation. Two-photon microscopy in live transfused animals revealed that extracellular mitochondria interact with neutrophils in vivo, triggering neutrophil adhesion to the endothelial wall. Our findings identify extracellular mitochondria, produced by platelets, at the midpoint of a potent mechanism leading to inflammatory responses.

Serum Phospholipase A2-IIA, hs-CRP, and Lipids in Women With Subclinical Hypothyroidism

BACKGROUND

Subclinical hypothyroidism (SCH) is a metabolic disorder characterized by elevated TSH level but normal T4 level. Some previous studies suggest that SCH is associated with inflammation.

OBJECTIVES

The present study aimed to compare lipid serum levels in SCH patients and normal participants, also explore possible association between SCH and the two inflammatory markers hs-CRP and PLA2-IIA.

PATIENTS AND METHODS

This study was performed on 77 women aged 20-45 (39 with SCH and 38 in the control group). TSH and T4 levels were measured by electrochemiluminescenceassay. Lipid profiles were analyzed using enzymatic-colorimetric methods. Hs-CRP and PLA2-IIA were determined using the ELISA method. IBM SPSS 19.0 was used for statistical analysis.

RESULTS

Serum levels of TG, cholesterol, and LDL were higher in the SCH group than the control group. However, there was no significant difference between the two groups for HDL level. Likewise, no difference was observed for the serum level of hs-CRP. PLA2-IIA mean value was higher in the SCH group.

CONCLUSIONS

SCH is associated with increased level of PLA2-IIA, which is independent of BMI. The stronger association of SCH with PLA2-IIA than with hs-CRP indicates that PLA2-IIA is an inducer of inflammation while hs-CRP is not.

Secreted phospholipase A2 is increased in meconium-stained amniotic fluid of term gestations: potential implications for the genesis of meconium aspiration syndrome

BACKGROUND

Meconium-stained amniotic fluid (MSAF) represents the passage of fetal colonic content into the amniotic cavity. Meconium aspiration syndrome (MAS) is a complication that occurs in a subset of infants with MSAF. Secreted phospholipase A2 (sPLA2) is detected in meconium and is implicated in the development of MAS. The purpose of this study was to determine if sPLA2 concentrations are increased in the amniotic fluid of women in spontaneous labor at term with MSAF.

MATERIALS AND METHODS

This was a cross-sectional study of patients in spontaneous term labor who underwent amniocentesis (n = 101). The patients were divided into two study groups: (1) MSAF (n = 61) and (2) clear fluid (n = 40). The presence of bacteria and endotoxin as well as interleukin-6 (IL-6) and sPLA2 concentrations in the amniotic fluid were determined. Statistical analyses were performed to test for normality and bivariate analysis. The Spearman correlation coefficient was used to study the relationship between sPLA2 and IL-6 concentrations in the amniotic fluid.

RESULTS

Patients with MSAF have a higher median sPLA2 concentration (ng/mL) in amniotic fluid than those with clear fluid [1.7 (0.98-2.89) versus 0.3 (0-0.6), p < 0.001]. Among patients with MSAF, those with either microbial invasion of the amniotic cavity (MIAC, defined as presence of bacteria in the amniotic cavity), or bacterial endotoxin had a significantly higher median sPLA2 concentration (ng/mL) in amniotic fluid than those without MIAC or endotoxin [2.4 (1.7-6.0) versus 1.7 (1.3-2.5), p < 0.05]. There was a positive correlation between sPLA2 and IL-6 concentrations in the amniotic fluid (Spearman Rho = 0.3, p < 0.05).

CONCLUSION

MSAF that contains bacteria or endotoxin has a higher concentration of sPLA2, and this may contribute to induce lung inflammation when meconium is aspirated before birth.

Inhibition of sPLA₂-IIA prevents LPS-induced neuroinflammation by suppressing ERK1/2-cPLA₂α pathway in mice cerebral cortex

Neuroinflammation is involved in various central nervous system (CNS) disorders, including brain infections, ischemia, trauma, stroke, and degenerative CNS diseases. In the CNS inflammation, secretory phospholipase A₂-IIA (sPLA₂-IIA) acts as a mediator, resulting in the generation of the precursors of pro-inflammatory lipid mediators, such as prostaglandins (PGs) and leukotrienes (LTs). However, the role of sPLA₂-IIA in neuroinflammation is more complicated and remains unclear yet. In the present study, we investigated the effect of sPLA₂-IIA inhibition by specific inhibitor SC-215 on the inflammation in LPS-induced mice cerebral cortex and primary astrocytes. Our results showed that the inhibition of sPLA₂-IIA alleviated the release of PGE₂ by suppressing the activation of ERK1/2, cPLA₂α, COX-2 and mPGES-1. These findings demonstrated that sPLA₂-IIA showed the potential to regulate the neuroinflammation in vivo and in vitro, indicating that sPLA₂-IIA might be a novel target for the treatment of acute neuroinflammation.