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Asthma is a chronic inflammatory disease of the airways characterized by recurrent episodes of airway obstruction, hyperresponsiveness, remodeling, and eosinophilia. Phospholipase A 2 s (PLA 2 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 PLA 2 subtypes and asthma is still incomplete. Here, we show that group III-secreted PLA 2 (sPLA 2 -III) plays an ameliorating, rather than aggravating, role in asthma pathology. In both mouse and human lungs, sPLA 2 -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 (LPA 2 ) agonists suppressed thymic stromal lymphopoietin (TSLP) expression in bronchial epithelial cells and reversed airway hyperresponsiveness and eosinophilia in Pla2g3 -/- mice, suggesting that sPLA 2 -III negatively regulates allergen-induced asthma at least by producing LPA. Thus, the activation of the sPLA 2 -III-LPA pathway may be a new therapeutic target for allergic asthma., (© 2024 The Authors. The FASEB Journal published by Wiley Periodicals LLC on behalf of Federation of American Societies for Experimental Biology.)

Among the phospholipase A 2 (PLA 2 ) superfamily, which typically catalyzes the sn-2 hydrolysis of phospholipids to yield fatty acids and lysophospholipids, the secreted PLA 2 (sPLA 2 ) family contains 11 isoforms in mammals. Individual sPLA 2 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 sPLA 2 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 sPLA 2 s in given tissue microenvironments. sPLA 2 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 sPLA 2 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 sPLA 2 s in various immune responses and associated diseases., (© 2023 The Authors. Immunological Reviews published by John Wiley & Sons Ltd.)

Tissue-resident mast cells (MCs) have important roles in IgE-associated and -independent allergic reactions. Although microenvironmental alterations in MC phenotypes affect the susceptibility to allergy, understanding of the regulation of MC maturation is still incomplete. We previously reported that group III secreted phospholipase A 2 (sPLA 2 -III) released from immature MCs is functionally coupled with lipocalin-type prostaglandin D 2 (PGD 2 ) synthase in neighboring fibroblasts to supply a microenvironmental pool of PGD 2 , which in turn acts on the PGD 2 receptor DP1 on MCs to promote their proper maturation. In the present study, we reevaluated the role of sPLA 2 -III in MCs using a newly generated MC-specific Pla2g3 -deficient mouse strain. Mice lacking sPLA 2 -III specifically in MCs, like those lacking the enzyme in all tissues, had immature MCs and displayed reduced local and systemic anaphylactic responses. Furthermore, MC-specific Pla2g3 -deficient mice, as well as MC-deficient Kit W-sh mice reconstituted with MCs prepared from global Pla2g3- null mice, displayed a significant reduction in irritant contact dermatitis (ICD) and an aggravation of contact hypersensitivity (CHS). The increased CHS response by Pla2g3 deficiency depended at least partly on the reduced expression of hematopoietic PGD 2 synthase and thereby reduced production of PGD 2 due to immaturity of MCs. Overall, our present study has confirmed that MC-secreted sPLA 2 -III promotes MC maturation, thereby facilitating acute anaphylactic and ICD reactions and limiting delayed CHS response.

Among the 11 members of the secreted phospholipase A 2 (sPLA 2 ) family, group IID, IIE, IIF and III sPLA 2 s (sPLA 2 -IID, -IIE, -IIF and -III, respectively) are "new" isoforms in the history of sPLA 2 research. Relative to the better characterized sPLA 2 s (sPLA 2 -IB, -IIA, -V and -X), the enzymatic properties, distributions, and functions of these "new" sPLA 2 s have remained obscure until recently. Our current studies using knockout and transgenic mice for a nearly full set of sPLA 2 s, in combination with comprehensive lipidomics, have revealed unique and distinct roles of these "new" sPLA 2 s in specific biological events. Thus, sPLA 2 -IID is involved in immune suppression, sPLA 2 -IIE in metabolic regulation and hair follicle homeostasis, sPLA 2 -IIF in epidermal hyperplasia, and sPLA 2 -III in male reproduction, anaphylaxis, colonic diseases, and possibly atherosclerosis. In this article, we overview current understanding of the properties and functions of these sPLA 2 s and their underlying lipid pathways in vivo., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The secreted phospholipase A 2 (sPLA 2 ) family contains 10 catalytically active isoforms. Current in vitro biochemical studies have shown that individual sPLA 2 s have distinct substrate selectivity in terms of the polar head groups or sn-2 fatty acids of their substrate phospholipids. Importantly, transgenic or knockout mice for distinct sPLA 2 s display nonoverlapping phenotypes, arguing that they do act on different phospholipid substrates and mobilize unique lipid metabolites in vivo. In an effort to comprehensively understand lipid metabolism driven by individual sPLA 2 s under pathophysiological conditions, we took advantages of mass spectrometric lipidomics technology to monitor the spatiotemporal changes in phospholipids (substrates) and products (fatty acids, lysophospholipids, and their metabolites) in tissues or cells of sPLA 2 -transgenic or knockout mice. The in vivo lipidomic data were compared with the in vitro activity of recombinant sPLA 2 s toward phospholipid mixtures extracted from the target tissues, cells, or extracellular membrane components on which sPLA 2 s may intrinsically act. These approaches reveal that the overall tendency in in vitro assays using natural membranes is recapitulated in several in vivo systems, often with even more selective patterns of hydrolysis. In this chapter, we will summarize current understanding of the in vivo substrate specificity of sPLA 2 s toward natural membrane phospholipids., (© 2017 Elsevier Inc. All rights reserved.)

Within the phospholipase A 2 (PLA 2 ) family that hydrolyzes phospholipids to yield fatty acids and lysophospholipids, secreted PLA 2 (sPLA 2 ) enzymes comprise the largest group containing 11 isoforms in mammals. Individual sPLA 2 s exhibit unique tissue or cellular distributions and enzymatic properties, suggesting their distinct biological roles. Although PLA 2 enzymes, particularly cytosolic PLA 2 (cPLA 2 α), have long been implicated in inflammation by driving arachidonic acid metabolism, the precise biological roles of sPLA 2 s have remained a mystery over the last few decades. Recent studies employing mice gene-manipulated for individual sPLA 2 s, in combination with mass spectrometric lipidomics to identify their target substrates and products in vivo, have revealed their roles in diverse biological events, including immunity and associated disorders, through lipid mediator-dependent or -independent processes in given microenvironments. In this review, we summarize our current knowledge of the roles of sPLA 2 s in various immune responses and associated diseases., (© 2016 Elsevier Inc. All rights reserved.)

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., (Copyright © 2015 by the American Society for Biochemistry and Molecular Biology, Inc.)

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., (Copyright © 2014 Japanese Society of Allergology. Production and hosting by Elsevier B.V. All rights reserved.)

Within the phospholipase A2 (PLA2) superfamily, secreted PLA2 (sPLA2) enzymes comprise the largest family that contains 11 to 12 mammalian isoforms with a conserved His-Asp catalytic dyad. Individual sPLA2s exhibit unique tissue and cellular localizations and specific enzymatic properties, suggesting distinct biological roles. Individual sPLA2s are involved in diverse biological events through lipid mediator-dependent or -independent processes and act redundantly or non-redundantly in a given microenvironment. In the past few years, new biological aspects of sPLA2s have been clarified using their transgenic and knockout mouse lines in combination with mass spectrometric lipidomics to unveil their target substrates and products in vivo. In the 3rd edition of this review series, we highlight the newest understanding of the in vivo functions of sPLA2s in pathophysiological conditions in the context of immunity and metabolism. We will also describe the latest knowledge on PLA2R1, the best known sPLA2 receptor, which may serve either as a clearance or signaling receptor for sPLA2 or may even act independently of sPLA2 function., (Copyright © 2014 Elsevier B.V. and Société française de biochimie et biologie Moléculaire (SFBBM). All rights reserved.)

Phospholipase A(2) (PLA(2)) is a group of enzymes that hydrolyze the sn-2 position of glycerophospholipids to yield fatty acids and lysophospholipids. Of many PLA(2)s or related enzymes identified to date, secreted PLA(2)s (sPLA(2)s) comprise the largest family that contains 10 catalytically active isozymes. Besides arachidonic acid released from cellular membranes for eicosanoid synthesis, several if not all sPLA(2)s have recently been implicated in hydrolysis of phospholipids in lipoprotein particles. The sPLA(2)-processed low-density lipoprotein (LDL) particles contain a large amount of lysophospholipids and exhibit the property of "small-dense" or "modified" LDL, which facilitates foam cell formation from macrophages. Transgenic overexpression of these sPLA(2)s leads to development of atherosclerosis in mice. More importantly, genetic deletion or pharmacological inhibition of particular sPLA(2)s significantly attenuates atherosclerosis and aneurysm. In this article, we will give an overview of current understanding of the role of sPLA(2)s in atherosclerosis, with recent lipidomics data showing the action of a subset of sPLA(2)s on lipoprotein phospholipids.

Mammalian genomes encode genes for more than 30 phospholipase A₂s (PLA₂s) or related enzymes, which are subdivided into several classes including low-molecular-weight secreted PLA₂s (sPLA₂s), Ca²+-dependent cytosolic PLA₂s (cPLA₂s), Ca²+-independent PLA₂s (iPLA₂s), platelet-activating factor acetylhydrolases (PAF-AHs), lysosomal PLA₂s, and a recently identified adipose-specific PLA. Of these, the intracellular cPLA₂ and iPLA₂ families and the extracellular sPLA₂ family are recognized as the "big three". From a general viewpoint, cPLA₂α (the prototypic cPLA₂ plays a major role in the initiation of arachidonic acid metabolism, the iPLA₂ family contributes to membrane homeostasis and energy metabolism, and the sPLA₂ family affects various biological events by modulating the extracellular phospholipid milieus. The cPLA₂ family evolved along with eicosanoid receptors when vertebrates first appeared, whereas the diverse branching of the iPLA₂ and sPLA₂ families during earlier eukaryote development suggests that they play fundamental roles in life-related processes. During the past decade, data concerning the unexplored roles of various PLA₂ enzymes in pathophysiology have emerged on the basis of studies using knockout and transgenic mice, the use of specific inhibitors, and information obtained from analysis of human diseases caused by mutations in PLA₂ genes. This review focuses on current understanding of the emerging biological functions of PLA₂s and related enzymes., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Although perturbed lipid metabolism can often lead to skin abnormality, the role of phospholipase A(2) (PLA(2)) in skin homeostasis is poorly understood. In the present study we found that group X-secreted PLA(2) (sPLA(2)-X) was expressed in the outermost epithelium of hair follicles in synchrony with the anagen phase of hair cycling. Transgenic mice overexpressing sPLA(2)-X (PLA2G10-Tg) displayed alopecia, which was accompanied by hair follicle distortion with reduced expression of genes related to hair development, during a postnatal hair cycle. Additionally, the epidermis and sebaceous glands of PLA2G10-Tg skin were hyperplasic. Proteolytic activation of sPLA(2)-X in PLA2G10-Tg skin was accompanied by preferential hydrolysis of phosphatidylethanolamine species with polyunsaturated fatty acids as well as elevated production of some if not all eicosanoids. Importantly, the skin of Pla2g10-deficient mice had abnormal hair follicles with noticeable reduction in a subset of hair genes, a hypoplasic outer root sheath, a reduced number of melanin granules, and unexpected up-regulation of prostanoid synthesis. Collectively, our study highlights the spatiotemporal expression of sPLA(2)-X in hair follicles, the presence of skin-specific machinery leading to sPLA(2)-X activation, a functional link of sPLA(2)-X with hair follicle homeostasis, and compartmentalization of the prostanoid pathway in hair follicles and epidermis.

Although the secreted phospholipase A(2) (sPLA(2)) family has been generally thought to participate in pathologic events such as inflammation and atherosclerosis, relatively high and constitutive expression of group X sPLA(2) (sPLA(2)-X) in restricted sites such as reproductive organs, the gastrointestinal tract, and peripheral neurons raises a question as to the roles played by this enzyme in the physiology of reproduction, digestion, and the nervous system. Herein we used mice with gene disruption or transgenic overexpression of sPLA(2)-X to clarify the homeostatic functions of this enzyme at these locations. Our results suggest that sPLA(2)-X regulates 1) the fertility of spermatozoa, not oocytes, beyond the step of flagellar motility, 2) gastrointestinal phospholipid digestion, perturbation of which is eventually linked to delayed onset of a lean phenotype with reduced adiposity, decreased plasma leptin, and improved muscle insulin tolerance, and 3) neuritogenesis of dorsal root ganglia and the duration of peripheral pain nociception. Thus, besides its inflammatory action proposed previously, sPLA(2)-X participates in physiologic processes including male fertility, gastrointestinal phospholipid digestion linked to adiposity, and neuronal outgrowth and sensing.

Mammalian genomes encode genes for more than 30 phospholipase A(2)s (PLA(2)s) or related enzymes, which are subdivided into several subgroups based on their structures, catalytic mechanisms, localizations and evolutionary relationships. More than one third of the PLA(2) enzymes belong to the secreted PLA(2) (sPLA(2)) family, which consists of low-molecular-weight, Ca(2+)-requiring extracellular enzymes, with a His-Asp catalytic dyad. Individual sPLA(2) isoforms exhibit unique tissue and cellular localizations and enzymatic properties, suggesting their distinct pathophysiological roles. Recent studies using transgenic and knockout mice for several sPLA(2) isoforms, in combination with lipidomics approaches, have revealed their distinct contributions to various biological events. Herein, we will describe several examples of sPLA(2)-mediated phospholipid metabolism in vivo, as revealed by integrated analysis of sPLA(2) transgenic/knockout mice and lipid mass spectrometry. Knowledge obtained from this approach greatly contributes to expanding our understanding of the sPLA(2) biology and pathophysiology.

Among the emerging phospholipase A(2) (PLA(2)) superfamily, the secreted PLA(2) (sPLA(2)) family consists of low-molecular-mass, Ca(2+)-requiring extracellular enzymes with a His-Asp catalytic dyad. To date, more than 10 sPLA(2) enzymes have been identified in mammals. Individual sPLA(2)s exhibit unique tissue and cellular localizations and enzymatic properties, suggesting their distinct pathophysiological roles. Despite numerous enzymatic and cell biological studies on this enzyme family in the past two decades, their precise in vivo functions still remain largely obscure. Recent studies using transgenic and knockout mice for several sPLA(2) enzymes, in combination with lipidomics approaches, have opened new insights into their distinct contributions to various biological events such as food digestion, host defense, inflammation, asthma and atherosclerosis. In this article, we overview the latest understanding of the pathophysiological functions of individual sPLA(2) isoforms fueled by studies employing transgenic and knockout mice for several sPLA(2)s., (Copyright 2010 Elsevier Masson SAS. All rights reserved.)