Properties and regulation of cytosolic phospholipase A2

Pathogenic strategies of Pseudogymnoascus destructans during torpor and arousal of hibernating bats

Millions of hibernating bats across North America have died from white-nose syndrome (WNS), an emerging disease caused by a psychrophilic (cold-loving) fungus, Pseudogymnoascus destructans, that invades their skin. Mechanisms of P. destructans invasion of bat epidermis remain obscure. Guided by our in vivo observations, we modeled hibernation with a newly generated little brown bat (Myotis lucifugus) keratinocyte cell line. We uncovered the stealth intracellular lifestyle of P. destructans, which inhibits apoptosis of keratinocytes and spreads through the cells by two epidermal growth factor receptor (EGFR)-dependent mechanisms: active penetration during torpor and induced endocytosis during arousal. Melanin of endocytosed P. destructans blocks endolysosomal maturation, facilitating P. destructans survival and germination after return to torpor. Blockade of EGFR aborts P. destructans entry into keratinocytes.

Protective effect of arctiin against Toxoplasma gondii HSP70-induced allergic acute liver injury by disrupting the TLR4-mediated activation of cytosolic phospholipase A2 and platelet-activating factor

Toxoplasma gondii (T. gondii)-derived heat shock protein 70 (T.g.HSP70) is a toxic protein that downregulates host defense responses against T. gondii infection. T.g.HSP70 was proven to induce fatal anaphylaxis in T. gondii infected mice through cytosolic phospholipase A2 (cPLA2) activated-platelet-activating factor (PAF) production via Toll-like receptor 4 (TLR4)-mediated signaling. In this study, we investigated the effect of arctiin (ARC; a major lignan compound of Fructus arctii) on allergic liver injury using T.g.HSP70-stimulated murine liver cell line (NCTC 1469) and a mouse model of T. gondii infection. Localized surface plasmon resonance, ELISA, western blotting, co-immunoprecipitation, and immunofluorescence were used to investigate the underlying mechanisms of action of ARC on T. gondii-induced allergic acute liver injury. The results showed that ARC suppressed the T.g.HSP70-induced allergic liver injury in a dose-dependent manner. ARC could directly bind to T.g.HSP70 or TLR4, interfering with the interaction between these two factors, and inhibiting activation of the TLR4/mitogen-activated protein kinase/nuclear factor-kappa B signaling, thereby inhibiting the overproduction of cPLA2, PAF, and interferon-γ. This result suggested that ARC ameliorates T.g.HSP70-induced allergic acute liver injury by disrupting the TLR4-mediated activation of inflammatory mediators, providing a theoretical basis for ARC therapy to improve T.g.HSP70-induced allergic liver injury.

FADS2 function at the major cancer hotspot 11q13 locus alters fatty acid metabolism in cancer

Dysregulation of fatty acid metabolism and de novo lipogenesis is a key driver of several cancer types through highly unsaturated fatty acid (HUFA) signaling precursors such as arachidonic acid. The human chromosome 11q13 locus has long been established as the most frequently amplified in a variety of human cancers. The fatty acid desaturase genes (FADS1, FADS2 and FADS3) responsible for HUFA biosynthesis localize to the 11q12-13.1 region. FADS2 activity is promiscuous, catalyzing biosynthesis of several unsaturated fatty acids by Δ6, Δ8, and Δ4 desaturation. Our main aim here is to review known and putative consequences of FADS2 dysregulation due to effects on the 11q13 locus potentially driving various cancer types. FADS2 silencing causes synthesis of sciadonic acid (5Z,11Z,14Z-20:3) in MCF7 cells and breast cancer in vivo. 5Z,11Z,14Z-20:3 is structurally identical to arachidonic acid (5Z,8Z,11Z,14Z-20:4) except it lacks the internal Δ8 double bond required for prostaglandin and leukotriene synthesis, among other eicosanoids. Palmitic acid has substrate specificity for both SCD and FADS2. Melanoma, prostate, liver and lung cancer cells insensitive to SCD inhibition show increased FADS2 activity and sapienic acid biosynthesis. Elevated serum mead acid levels found in hepatocellular carcinoma patients suggest an unsatisfied demand for arachidonic acid. FADS2 circular RNAs are at high levels in colorectal and lung cancer tissues. FADS2 circular RNAs are associated with shorter overall survival in colorectal cancer patients. The evidence thusfar supports an effort for future research on the role of FADS2 as a tumor suppressor in a range of neoplastic disorders.

Identification and functional analysis of cytosolic phospholipase A2 (cPLA2) from the red swamp crayfish Procambarus clarkii: The first evidence of cPLA2 involved in immunity in invertebrates

Cytosolic phospholipase A2 (cPLA2) specifically liberates the arachidonic acids from the phospholipid substrates. In mammals, cPLA2 serves as a key control point in inflammatory responses due to its diverse downstream products. However, the role of cPLA2 in animals lower than mammals largely remains unknown. In the current research, a homolog of cPLA2 was first identified and characterized in the red swamp crayfish Procambarus clarkii. The full-length cDNA of PccPLA2 was 4432 bp in length with a 3036 bp-long open reading frame, encoding a putative protein of 1011 amino acids that contained a protein kinase C conserved region 2 and a catalytic subunit of cPLA2. PccPLA2 was ubiquitously expressed in all examined tissues with the highest expression in the hepatopancreas, and the expression in hemocytes as well as hepatopancreas was induced upon the immune challenges of WSSV and Aeromonas hydrophila. After the co-treatment of RNA interference and bacterial infection, the decline of bacteria clearance capability was observed in the hemolymph, and the expression of some antimicrobial peptides (AMPs) was significantly suppressed. Additionally, the phagocytosis of A. hydrophila by primary hemocytes decreased when treated with the specific inhibitor CAY10650 of cPLA2. These results indicated the participation of PccPLA2 in both cellular and humoral immune responses in the crayfish, which provided an insight into the role that cPLA2 played in the innate immunity of crustaceans, and even in invertebrates.

Bioactive lipid regulation of platelet function, hemostasis, and thrombosis

Platelets are small, anucleate cells in the blood that play a crucial role in the hemostatic response but are also implicated in the pathophysiology of cardiovascular disease. It is widely appreciated that polyunsaturated fatty acids (PUFAs) play an integral role in the function and regulation of platelets. PUFAs are substrates for oxygenase enzymes cyclooxygenase-1 (COX-1), 5-lipoxygenase (5-LOX), 12-lipoxygenase (12-LOX) and 15-lipoxygenase (15-LOX). These enzymes generate oxidized lipids (oxylipins) that exhibit either pro- or anti-thrombotic effects. Although the effects of certain oxylipins, such as thromboxanes and prostaglandins, have been studied for decades, only one oxylipin has been therapeutically targeted to treat cardiovascular disease. In addition to the well-known oxylipins, newer oxylipins that demonstrate activity in the platelet have been discovered, further highlighting the expansive list of bioactive lipids that can be used to develop novel therapeutics. This review outlines the known oxylipins, their activity in the platelet, and current therapeutics that target oxylipin signaling.

The Interplay among Glucocorticoid Therapy, Platelet-Activating Factor and Endocannabinoid Release Influences the Inflammatory Response to COVID-19

COVID-19 is associated with a dysregulated immune response. Currently, several medicines are licensed for the treatment of this disease. Due to their significant role in inhibiting pro-inflammatory cytokines and lipid mediators, glucocorticoids (GCs) have attracted a great deal of attention. Similarly, the endocannabinoid (eCB) system regulates various physiological processes including the immunological response. Additionally, during inflammatory and thrombotic processes, phospholipids from cell membranes are cleaved to produce platelet-activating factor (PAF), another lipid mediator. Nonetheless, the effect of GCs on this lipid pathway during COVID-19 therapy is still unknown. This is a cross-sectional study involving COVID-19 patients (n = 200) and healthy controls (n = 35). Target tandem mass spectrometry of plasma lipid mediators demonstrated that COVID-19 severity affected eCBs and PAF synthesis. This increased synthesis of eCB was adversely linked with systemic inflammatory markers IL-6 and sTREM-1 levels and neutrophil counts. The use of GCs altered these lipid pathways by reducing PAF and increasing 2-AG production. Corroborating this, transcriptome analysis of GC-treated patients blood leukocytes showed differential modulation of monoacylglycerol lipase and phospholipase A2 gene expression. Altogether, these findings offer a breakthrough in our understanding of COVID-19 pathophysiology, indicating that GCs may promote additional protective pharmacological effects by influencing the eCB and PAF pathways involved in the disease course.

Therapeutic strategy targeting host lipolysis limits infection by SARS-CoV-2 and influenza A virus

The biosynthesis of host lipids and/or lipid droplets (LDs) has been studied extensively as a putative therapeutic target in diverse viral infections. However, directly targeting the LD lipolytic catabolism in virus-infected cells has not been widely investigated. Here, we show the linkage of the LD-associated lipase activation to the breakdown of LDs for the generation of free fatty acids (FFAs) at the late stage of diverse RNA viral infections, which represents a broad-spectrum antiviral target. Dysfunction of membrane transporter systems due to virus-induced cell injury results in intracellular malnutrition at the late stage of infection, thereby making the virus more dependent on the FFAs generated from LD storage for viral morphogenesis and as a source of energy. The replication of SARS-CoV-2 and influenza A virus (IAV), which is suppressed by the treatment with LD-associated lipases inhibitors, is rescued by supplementation with FFAs. The administration of lipase inhibitors, either individually or in a combination with virus-targeting drugs, protects mice from lethal IAV infection and mitigates severe lung lesions in SARS-CoV-2-infected hamsters. Moreover, the lipase inhibitors significantly reduce proinflammatory cytokine levels in the lungs of SARS-CoV-2- and IAV-challenged animals, a cause of a cytokine storm important for the critical infection or mortality of COVID-19 and IAV patients. In conclusion, the results reveal that lipase-mediated intracellular LD lipolysis is commonly exploited to facilitate RNA virus replication and furthermore suggest that pharmacological inhibitors of LD-associated lipases could be used to curb current COVID-19- and future pandemic outbreaks of potentially troublesome RNA virus infection in humans.

miR-383 Regulates Hepatic Lipid Homeostasis and Response to Dengue Virus Infection

Recently, microRNAs (miRNAs), as endogenous noncoding RNAs that inhibit mRNA translation, have been identified to broadly possess functional roles in regulating cellular signaling and metabolic processes due to their chemical and biological properties. In addition, they have emerged to be of critical importance in modulating host-virus interactions, especially for RNA viruses. Herein, we discovered that miR-383-5p targets certain lipid and cholesterol biosynthetic pathways and restricts Dengue virus (DENV) infection in hepatic cells. Global transcriptomics analysis of Huh7 human hepatoma cells overexpressing miR-383-5p revealed enrichment of lipid and cholesterol metabolic processes. Bioinformatics analysis of genes repressed in miR-383-5p overexpressing cells divulged the repression of a key target PLA2G4A, a pro-viral host factor essential for the production of infectious DENV particles. Our study demonstrated the effectiveness of miRNA mimics as tools to study cellular signaling pathways that contribute to viral pathogenesis. Overall, our study identifies miR-383-5p as an interesting host factor during DENV propagation and highlights a potential therapeutic role in the regulation of hepatic lipid metabolism and an antiviral response to DENV.

Differential Regulation of ATP- and UTP-Evoked Prostaglandin E2 and IL-6 Production from Human Airway Epithelial Cells

The airway epithelial cells (AECs) lining the conducting passageways of the lung secrete a variety of immunomodulatory factors. Among these, PGE2 limits lung inflammation and promotes bronchodilation. By contrast, IL-6 drives intense airway inflammation, remodeling, and fibrosis. The signaling that differentiates the production of these opposing mediators is not understood. In this study, we find that the production of PGE2 and IL-6 following stimulation of human AECs by the damage-associated molecular pattern extracellular ATP shares a common requirement for Ca2+ release-activated Ca2+ (CRAC) channels. ATP-mediated synthesis of PGE2 required activation of metabotropic P2Y2 receptors and CRAC channel-mediated cytosolic phospholipase A2 signaling. By contrast, ATP-evoked synthesis of IL-6 occurred via activation of ionotropic P2X receptors and CRAC channel-mediated calcineurin/NFAT signaling. In contrast to ATP, which elicited the production of both PGE2 and IL-6, the uridine nucleotide, UTP, stimulated PGE2 but not IL-6 production. These results reveal that human AECs employ unique receptor-specific signaling mechanisms with CRAC channels as a signaling nexus to regulate release of opposing immunomodulatory mediators. Collectively, our results identify P2Y2 receptors, CRAC channels, and P2X receptors as potential intervention targets for airway diseases.

6β-Hydroxytestosterone Promotes Angiotensin II-Induced Hypertension via Enhanced Cytosolic Phospholipase A2α Activity

Supplemental Digital Content is available in the text.

This study was conducted to test the hypothesis that the CYP1B1 (cytochrome P450 1B1)-testosterone metabolite 6β-hydroxytestosterone contributes to angiotensin II-induced hypertension by promoting activation of group IV cPLA₂α (cytosolic phospholipase A₂α) and generation of prohypertensive eicosanoids in male mice. Eight-week-old male intact or orchidectomized cPLA₂α^+/+/Cyp1b1^+/+ and cPLA₂α^–/–/Cyp1b1^+/+ and intact cPLA₂α^+/+/Cyp1b1^–/– mice were infused with angiotensin II (700 ng/kg/min, subcutaneous) for 2 weeks and injected with 6β-hydroxytestosterone (15 μg/g/every third day, intraperitoneal). Systolic blood pressure was measured by tail-cuff and confirmed by radiotelemetry. Angiotensin II-induced increase in systolic blood pressure, cardiac and renal collagen deposition, and reactive oxygen species production were reduced by disruption of the cPLA₂α or Cyp1b1 genes or by administration of the arachidonic acid metabolism inhibitor 5,8,11,14-eicosatetraynoic acid to cPLA₂α^+/+/Cyp1b1^+/+ mice. 6β-hydroxytestosterone treatment restored these effects of angiotensin II in cPLA₂α^+/+/Cyp1b1^–/– mice but not in orchidectomized cPLA₂α^–/–/Cyp1b1^+/+ mice, which were lowered by 5,8,11,14-eicosatetraynoic acid in cPLA₂α^+/+/Cyp1b1^–/– mice. Antagonists of prostaglandin E₂-EP1/EP3 receptors and thromboxane A₂-TP receptors decreased the effect of 6β-hydroxytestosterone in restoring the angiotensin II-induced increase in systolic blood pressure, cardiac and renal collagen deposition, and reactive oxygen species production in cPLA₂α^+/+/Cyp1b1^–/– mice. These data suggest that 6β-hydroxytestosterone promotes angiotensin II-induced increase in systolic blood pressure and associated pathogenesis via cPLA₂α activation and generation of eicosanoids, most likely prostaglandin E₂ and thromboxane A₂ that exerts prohypertensive effects by stimulating EP1/EP3 and TP receptors, respectively. Therefore, agents that selectively block these receptors could be useful in treating testosterone exacerbated angiotensin II-induced hypertension and its pathogenesis.

A new trick for an old dog? Myocardial-specific roles for prostaglandins as mediators of ischemic injury and repair

The small lipid-derived paracrine signaling molecules known as prostaglandins have been recognized for their ability to modulate many facets of cardiovascular physiology since their initial discovery more than 85 years ago. Although the role of prostaglandins in the vasculature has gained significant attention across time, a handful of historical studies have also directly implicated the cardiomyocyte in both prostaglandin synthesis and release. Recently, our understanding of how prostaglandin receptor modulation impacts and contributes to myocardial structure and function has gained attention while leaving most other components of myocardial prostaglandin metabolism and signaling unexplored. This mini-review highlights both the key historical studies that underpin modern prostaglandin research in the heart, while concurrently presenting the latest findings related to how prostaglandin metabolism and signaling impact myocardial injury and repair.

Skeletal muscle redox signaling in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by synovitis and the presence of serum autoantibodies. In addition, skeletal muscle weakness is a common comorbidity that contributes to inability to work and reduced quality of life. Loss in muscle mass cannot alone account for the muscle weakness induced by RA, but instead intramuscular dysfunction appears as a critical factor underlying the decreased force generating capacity for patients afflicted by arthritis. Oxidative stress and associated oxidative post-translational modifications have been shown to contribute to RA-induced muscle weakness in animal models of arthritis and patients with RA. However, it is still unclear how and which sources of reactive oxygen and nitrogen species (ROS/RNS) that are involved in the oxidative stress that drives the progression toward decreased muscle function in RA. Nevertheless, mitochondria, NADPH oxidases (NOX), nitric oxide synthases (NOS) and phospholipases (PLA) have all been associated with increased ROS/RNS production in RA-induced muscle weakness. In this review, we aim to cover potential ROS sources and underlying mechanisms of oxidative stress and loss of force production in RA. We also addressed the use of antioxidants and exercise as potential tools to counteract oxidative stress and skeletal muscle weakness.

The effects of myelin on macrophage activation are phenotypic specific via cPLA2 in the context of spinal cord injury inflammation

Spinal cord injury (SCI) produces chronic, pro-inflammatory macrophage activation that impairs recovery. The mechanisms driving this chronic inflammation are not well understood. Here, we detail the effects of myelin debris on macrophage physiology and demonstrate a novel, activation state-dependent role for cytosolic phospholipase-A2 (cPLA₂) in myelin-mediated potentiation of pro-inflammatory macrophage activation. We hypothesized that cPLA₂ and myelin debris are key mediators of persistent pro-inflammatory macrophage responses after SCI. To test this, we examined spinal cord tissue 28-days after thoracic contusion SCI in 3-month-old female mice and observed both cPLA₂ activation and intracellular accumulation of lipid-rich myelin debris in macrophages. In vitro, we utilized bone marrow-derived macrophages to determine myelin's effects across a spectrum of activation states. We observed phenotype-specific responses with myelin potentiating only pro-inflammatory (LPS + INF-γ; M1) macrophage activation, whereas myelin did not induce pro-inflammatory responses in unstimulated or anti-inflammatory (IL-4; M2) macrophages. Specifically, myelin increased levels of pro-inflammatory cytokines, reactive oxygen species, and nitric oxide production in M1 macrophages as well as M1-mediated neurotoxicity. PACOCF3 (cPLA₂ inhibitor) blocked myelin's detrimental effects. Collectively, we provide novel spatiotemporal evidence that myelin and cPLA₂ play an important role in the pathophysiology of SCI inflammation and the phenotype-specific response to myelin implicate diverse roles of myelin in neuroinflammatory conditions.

Understanding the binding mechanism of succinic acid against phospholipase A2 from bee venom

Phospholipase A₂ (PLA₂ ) is responsible for the release of fatty acids from glycerophospholipids. PLA₂ is commonly found in mammalian tissues. It is also found in venom from different animals ranging from insects, arachnid, and snakes. The release of arachidonic acid in large amount results in inflammation and pain. Identification of compounds that can inhibit the activity of PLA₂ is of large scientific and medicinal interest as these compounds can act as antidotes toward snake bites and bee stings. Among the different compounds that have been tested for inhibition of PLA₂ , a secondary metabolite succinic acid is identified to inhibit PLA₂ activity. The inhibition was analyzed using an in vitro PLA₂ inhibition assay and isothermal titration calorimetry (ITC) studies. The molecular mechanism of the mode of inhibition was studied using molecular docking and simulation studies.

Involvement of phospholipase PLA2 in production of cellulase and xylanase by Penicillium oxalicum

Phospholipases play vital roles in immune and inflammatory responses in mammals and plants; however, knowledge of phospholipase functions in fungi is limited. In this study, we investigated the effects of deleting predicted phospholipase genes on cellulase and xylanase production, and morphological phenotype, in Penicillium oxalicum. Individual deletion of nine of the ten predicted phospholipase genes resulted in alteration of cellulase and xylanase production, and the morphological phenotypes, to various degrees. The mutant ∆POX07277 lost 22.5 to 82.8% of cellulase (i.e., filter paper cellulase, carboxymethylcellulase, and p-nitrophenyl-β-cellobiosidase) and xylanase production, whereas p-nitrophenyl-β-glucopyranosidase production increased by 5.8-127.8 fold. POX07277 (P. oxalicum gene No. 07277) was predicted to encode phospholipase A2 and was found to negatively affect the sporulation of P. oxalicum. Comparative transcriptomic and quantitative reverse transcription-PCR analysis indicated that POX07277 dynamically affected the expression of cellulase and xylanase genes and the regulatory genes for fungal sporulation, under micro-crystalline cellulose induction. POX07277 was required for the expression of the known regulatory gene PoxCxrB (cellulolytic and xylanolytic regulator B in P. oxalicum), which is involved in cellulase and xylanase gene expression in P. oxalicum. Conversely, POX07277 expression was regulated by PoxCxrB. These findings will aid the understanding of phospholipase functions and provide novel insights into the mechanism of fungal cellulase and xylanase gene expression. KEY POINTS : • The roles of phospholipases were investigated in Penicillium oxalicum. • POX07277 (PLA₂) is required for the expression of cellulase and xylanase genes. • PoxCxrB dynamically regulated POX07277 expression.

Eicosanoids in Cancer: New Roles in Immunoregulation

Eicosanoids represent a family of active biolipids derived from arachidonic acid primarily through the action of cytosolic phospholipase A2-α. Three major downstream pathways have been defined: the cyclooxygenase (COX) pathway which produces prostaglandins and thromboxanes; the 5-lipoxygenase pathway (5-LO), which produces leukotrienes, lipoxins and hydroxyeicosatetraenoic acids, and the cytochrome P450 pathway which produces epoxygenated fatty acids. In general, these lipid mediators are released and act in an autocrine or paracrine fashion through binding to cell surface receptors. The pattern of eicosanoid production is cell specific, and is determined by cell-specific expression of downstream synthases. Increased eicosanoid production is associated with inflammation and a panel of specific inhibitors have been developed designated non-steroidal anti-inflammatory drugs. In cancer, eicosanoids are produced both by tumor cells as well as cells of the tumor microenvironment. Earlier studies demonstrated that prostaglandin E2, produced through the action of COX-2, promoted cancer cell proliferation and metastasis in multiple cancers. This resulted in the development of COX-2 inhibitors as potential therapeutic agents. However, cardiac toxicities associated with these agents limited their use as therapeutic agents. The advent of immunotherapy, especially the use of immune checkpoint inhibitors has revolutionized cancer treatment in multiple malignancies. However, the majority of patients do not respond to these agents as monotherapy, leading to intense investigation of other pathways mediating immunosuppression in order to develop rational combination therapies. Recent data have indicated that PGE2 has immunosuppressive activity, leading to renewed interest in targeting this pathway. However, little is known regarding the role of other eicosanoids in modulating the tumor microenvironment, and regulating anti-tumor immunity. This article reviews the role of eicosanoids in cancer, with a focus on their role in modulating the tumor microenvironment. While the role of PGE2 will be discussed, data implicating other eicosanoids, especially products produced through the lipoxygenase and cytochrome P450 pathway will be examined. The existence of small molecular inhibitors and activators of eicosanoid pathways such as specific receptor blockers make them attractive candidates for therapeutic trials, especially in combination with novel immunotherapies such as immune checkpoint inhibitors.

A Thermolabile Phospholipase B from Talaromyces marneffei GD-0079: Biochemical Characterization and Structure Dynamics Study

Phospholipase B (EC 3.1.1.5) are a distinctive group of enzymes that catalyzes the hydrolysis of fatty acids esterified at the sn-1 and sn-2 positions forming free fatty acids and lysophospholipids. The structural information and catalytic mechanism of phospholipase B are still not clear. Herein, we reported a putative phospholipase B (TmPLB1) from Talaromyces marneffei GD-0079 synthesized by genome mining library. The gene (TmPlb1) was expressed and the TmPLB1 was purified using E. coli shuffle T7 expression system. The putative TmPLB1 was purified by affinity chromatography with a yield of 13.5%. The TmPLB1 showed optimum activity at 35 °C and pH 7.0. The TmPLB1 showed enzymatic activity using Lecithin (soybean > 98% pure), and the hydrolysis of TmPLB1 by ³¹P NMR showed phosphatidylcholine (PC) as a major phospholipid along with lyso-phospholipids (1-LPC and 2-LPC) and some minor phospholipids. The molecular modeling studies indicate that its active site pocket contains Ser125, Asp183 and His215 as the catalytic triad. The structure dynamics and simulations results explained the conformational changes associated with different environmental conditions. This is the first report on biochemical characterization and structure dynamics of TmPLB1 enzyme. The present study could be helpful to utilize TmPLB1 in food industry for the determination of food components containing phosphorus. Additionally, such enzyme could also be useful in Industry for the modifications of phospholipids.

Venomics and Cellular Toxicity of Thai Pit Vipers (Trimeresurus macrops and T. hageni)

The two venomous pit vipers, Trimeresurus macrops and T. hageni, are distributed throughout Thailand, although their abundance varies among different areas. No species-specific antivenom is available for their bite victims, and the only recorded treatment method is a horse antivenom raised against T. albolabris crude venom. To facilitate assessment of the cross-reactivity of heterologous antivenoms, protein profiles of T. macrops and T. hageni venoms were explored using mass-spectrometry-based proteomics. The results show that 185 and 216 proteins were identified from T. macrops and T. hageni venoms, respectively. Two major protein components in T. macrops and T. hageni venoms were snake venom serine protease and metalloproteinase. The toxicity of the venoms on human monocytes and skin fibroblasts was analyzed, and both showed a greater cytotoxic effect on fibroblasts than monocytic cells, with toxicity occurring in a dose-dependent rather than a time-dependent manner. Exploring the protein composition of snake venom leads to a better understanding of the envenoming of prey. Moreover, knowledge of pit viper venomics facilitates the selection of the optimum heterologous antivenoms for treating bite victims.

The interaction of ceramide 1-phosphate with group IVA cytosolic phospholipase A2 coordinates acute wound healing and repair

The sphingolipid ceramide 1-phosphate (C1P) directly binds to and activates group IVA cytosolic phospholipase A₂ (cPLA₂α) to stimulate the production of eicosanoids. Because eicosanoids are important in wound healing, we examined the repair of skin wounds in knockout (KO) mice lacking cPLA₂α and in knock-in (KI) mice in which endogenous cPLA₂α was replaced with a mutant form having an ablated C1P interaction site. Wound closure rate was not affected in the KO or KI mice, but wound maturation was enhanced in the KI mice compared to that in wild-type controls. Wounds in KI mice displayed increased infiltration of dermal fibroblasts into the wound environment, increased wound tensile strength, and a higher ratio of type I:type III collagen. In vitro, primary dermal fibroblasts (pDFs) from KI mice showed substantially increased collagen deposition and migration velocity compared to pDFs from wild-type and KO mice. KI mice also showed an altered eicosanoid profile of reduced proinflammatory prostaglandins (PGE₂ and TXB₂) and an increased abundance of certain hydroxyeicosatetraenoic acid (HETE) species. Specifically, an increase in 5-HETE enhanced dermal fibroblast migration and collagen deposition. This gain-of-function role for the mutant cPLA₂α was also linked to the relocalization of cPLA₂α and 5-HETE biosynthetic enzymes to the cytoplasm and cytoplasmic vesicles. These findings demonstrate the regulation of key wound-healing mechanisms in vivo by a defined protein-lipid interaction and provide insights into the roles that cPLA₂α and eicosanoids play in orchestrating wound repair.

Free-radical and biochemical reactions involving polar part of glycerophospholipids

The review summarizes and critically discusses data on biochemical and free-radical transformations of glycerophospholipids. The results presented therein demonstrate that hydroxyl-containing glycerophospholipids, such as cardiolipin, lyso-lipids and others, can undergo fragmentation upon interaction with radical agents forming the biologically active products. Hydrolysis of glycerophospholipids catalyzed by different phospholipases was shown to yield compounds, which can be involved in the free-radical fragmentation leading to significant changes in structures of original lipids.

Conceptual Evolution of Cell Signaling

During the last 100 years, cell signaling has evolved into a common mechanism for most physiological processes across systems. Although the majority of cell signaling principles were initially derived from hormonal studies, its exponential growth has been supported by interdisciplinary inputs, e.g., from physics, chemistry, mathematics, statistics, and computational fields. As a result, cell signaling has grown out of scope for any general review. Here, we review how the messages are transferred from the first messenger (the ligand) to the receptor, and then decoded with the help of cascades of second messengers (kinases, phosphatases, GTPases, ions, and small molecules such as cAMP, cGMP, diacylglycerol, etc.). The message is thus relayed from the membrane to the nucleus where gene expression ns, subsequent translations, and protein targeting to the cell membrane and other organelles are triggered. Although there are limited numbers of intracellular messengers, the specificity of the response profiles to the ligands is generated by the involvement of a combination of selected intracellular signaling intermediates. Other crucial parameters in cell signaling are its directionality and distribution of signaling strengths in different pathways that may crosstalk to adjust the amplitude and quality of the final effector output. Finally, we have reflected upon its possible developments during the coming years.

Giant Phospholipid Folds on Air-Water Surface: Structure Details, Formation Pathway, and Possible Recycle Mechanism

In vitro mimics recognized that the propensity of a negatively charged phospholipid, DPPS, monolayers to self-aggregate to three-dimensional (3D) giant folds under overcompression at an air-water interface. Time elapsing microscopical observations confirmed that such giant folds were able to float stably on the air-water interface for weeks or even longer. Ex situ atomic force microscopy (AFM) and transmission electronic microscopy (TEM) characterizations pointed out that such giant folds were composed of compactly stacked lipid layers. Phospholipase A₂ (PLA₂), a principal bactericide in human and animal tear secretion, was chosen to drive the in situ lipid giant folds disassembly on water and supported substrate surfaces, respectively. Our experimental results confirmed the layer-by-layer structures of the giant folds. It is noteworthy that the defect-rich areas of the giant lipid folds were eliminated quickly by PLA₂ while defect-free lipid zones were left untouched, suggesting that PLA₂ may serve as a highly effective and selective regenerator/cleaner of lipid aggregates in the physiological circumstance of certain organs.

Electroacupuncture for pain relief in labour inhibits spinal p38 MAPK-mediated prostaglandin E2 release and uterine prostaglandin E2 receptor expression in rats

BACKGROUND

p38 mitogen-activated protein kinase (p38 MAPK) activation involves the release of prostaglandin E2 (PGE2) and hyperalgesia. We have previously reported that electroacupuncture (EA) relieves labour pain, but the potential mechanisms remain unclear.

OBJECTIVE

To observe the effects of EA on labour pain intensity, serum PGE2 levels and the p38 MAPK signalling pathway in rats during labour.

METHODS

Female rats copulated with male rats to induce pregnancy, and then received castor oil to trigger labour. During labour, rats remained untreated (Control group, n=30) or were treated with remifentanil (n=30) or EA at Jiaji (n=30) or SP6+LI4 (n=30), respectively. The warm water tail-flick test was used to assess labour pain. Serum PGE2 levels were measured by ELISA. Protein expression of prostaglandin E2 receptor (PGER2), p38 MAPK and phospholipase A2 (PLA2) were analysed by Western blotting, and mRNA levels were measured by real-time PCR.

RESULTS

EA treatment at Jiaji or SP6+LI4 significantly relieved labour pain, decreased serum PGE2 levels and inhibited protein and gene expression of PGER2 in the myometrium. Moreover, EA reduced protein expression of PLA2 and p38 MAPK, and inhibited phosphorylation of p38 MAPK in the lumbar spinal cord but not in the cerebral grey matter. Additionally, EA markedly decreased mRNA levels of p38 MAPK in the lumbar spinal cord and significantly reduced PLA2-IV mRNA levels in both the lumbar spinal cord and cerebral grey matter.

CONCLUSIONS

This study indicates that EA relieves labour pain through, at least in part, inhibition of spinal p38 MAPK-mediated PGE2 release and uterine PGER2 expression in rats.

Biphasic Dynamics of Macrophage Immunometabolism during Mycobacterium tuberculosis Infection

Macrophages are the primary targets of Mycobacterium tuberculosis infection; the early events of macrophage interaction with M. tuberculosis define subsequent progression and outcome of infection. M. tuberculosis can alter the innate immunity of macrophages, resulting in suboptimal Th1 immunity, which contributes to the survival, persistence, and eventual dissemination of the pathogen.

Macrophages are the primary targets of Mycobacterium tuberculosis infection; the early events of macrophage interaction with M. tuberculosis define subsequent progression and outcome of infection. M. tuberculosis can alter the innate immunity of macrophages, resulting in suboptimal Th1 immunity, which contributes to the survival, persistence, and eventual dissemination of the pathogen. Recent advances in immunometabolism illuminate the intimate link between the metabolic states of immune cells and their specific functions. In this review, we describe the little-studied biphasic metabolic dynamics of the macrophage response during progression of infection by M. tuberculosis and discuss their relevance to macrophage immunity and M. tuberculosis pathogenicity. The early phase of macrophage infection, which is marked by M1 polarization, is accompanied by a metabolic switch from mitochondrial oxidative phosphorylation to hypoxia-inducible factor 1 alpha (HIF-1α)-mediated aerobic glycolysis (also known as the Warburg effect in cancer cells), as well as by an upregulation of pathways involving oxidative and antioxidative defense responses, arginine metabolism, and synthesis of bioactive lipids. These early metabolic changes are followed by a late adaptation/resolution phase in which macrophages transition from glycolysis to mitochondrial oxidative metabolism, with a consequent dampening of macrophage proinflammatory and antimicrobial responses. Importantly, the identification of upregulated metabolic pathways and/or metabolic regulatory mechanisms with immunomodulatory functions during M1 polarization has revealed novel mechanisms of M. tuberculosis pathogenicity. These advances can lead to the development of novel host-directed therapies to facilitate bacterial clearance in tuberculosis by targeting the metabolic state of immune cells.

Alisol B 23-Acetate Inhibits IgE/Ag-Mediated Mast Cell Activation and Allergic Reaction

Alisol B 23-acetate (AB23A), a natural triterpenoid, has been reported to exert hepatoprotective and antitumor activities. Aiming to investigate the anti-inflammatory activity, this study examined the effect of AB23A on mast cells and allergic reaction. AB23A inhibited the degranulation of mast cells stimulated by immunoglobulin E/antigen (IgE/Ag), and also decreased the synthesis of leukotriene C₄ (LTC₄), production of interlukin-6 (IL-6), and expression of cyclooxygenase-2 (COX-2) in a concentration-dependent manner with no significant cytotoxicity in bone marrow-derived mast cells (BMMCs). AB23A inhibited spleen tyrosine kinase (Syk) and the downstream signaling molecules including phospholipase Cγ (PLCγ), serine-threonine protein kinase/inhibitor of nuclear factor kappa-B kinase/nuclear factor kappa-B (Akt/IKK/NF-κB), and mitogen-activated protein kinases/cytosolic phospholipase A₂ (MAPK/cPLA₂). Furthermore, AB23A blocked mobilization of Ca²⁺. Similar results were obtained in other mast cell lines Rat basophilic leukemia (RBL)-2H3 cells and a human mast cell line (HMC-1). In addition, AB23A attenuated allergic responses in an acute allergy animal model, passive cutaneous anaphylaxis (PCA). Taken together, this study suggests that AB23A inhibits the activation of mast cells and ameliorates allergic reaction, and may become a lead compound for the treatment of mast cell-mediated allergic diseases.

Metabonomics analysis of kidneys in rats administered with chronic low-dose cadmium by ultra-performance liquid chromatography-mass spectrometry

This study aimed to investigate the nephrotoxicity in rats administered with chronic low-dose cadmium (Cd) by ultra-performance liquid chromatography-mass spectrometry. A total of 40 male Sprague-Dawley rats were randomly assigned to four groups, namely: control; low-dose (0.13 mg/kg·body weight [bw]); middle-dose (0.80 mg/kg·bw); and high-dose (4.89 mg/kg·bw). The rats received CdCl₂ daily via drinking water for 24 weeks. Rat kidneys were collected for metabonomics analysis. Principal components analysis and partial least-squares discriminant analysis were used to investigate the metabonomics profile changes in the kidney samples and to screen the potential biomarkers. Ten metabolites were identified in the positive and negative ion modes. Compared with the control group, the intensities of tetranor 12-HETE, uric acid, hypoxanthine, phenylacetylglycine, guanidinosuccinic acid and xanthosine significantly increased (P < 0.01), and those of imidazolelactic acid, lactose 6-phosphate, l-urobilinogen and arachidonic acid significantly decreased (P < 0.01) in the high-dose group. Results showed that exposure to Cd in rats induced oxidative stress to the kidneys and disrupted amino acid metabolism, fatty acid metabolism and energy metabolism.

S1PR2 antagonist alleviates oxidative stress-enhanced brain endothelial permeability by attenuating p38 and Erk1/2-dependent cPLA2 phosphorylation

Both sphingosine-1-phosphate receptor-2 (S1PR2) and cytosolic phospholipase A₂ (cPLA₂) are implicated in the disruption of cerebrovascular integrity in experimental stroke. However, the role of S1PR2 in induction of cPLA₂ phosphorylation during cerebral ischemia-induced endothelial dysfunction remains unknown. This study investigated the effect of S1PR2 blockade on oxidative stress-induced cerebrovascular endothelial barrier impairment and explored the possible mechanisms. In bEnd3 cells, cPLA₂ inhibitor CAY10502 as well as S1PR2 antagonist JTE013 profoundly suppressed hydrogen peroxide (H₂O₂)-induced changes of paracellular permeability and ZO-1 localization. Besides p38, extracellular signal-regulated kinase (Erk) 1/2 is required for H₂O₂-increased cPLA₂ phosphorylation and endothelial permeability. Pharmacological and genetic inhibition of S1PR2 significantly suppressed their phosphorylation in response to H₂O₂. Especially lentivirus-mediated knockdown of S1PR2 inhibited H₂O₂-induced ZO-1 redistribution and paracellular hyperpermeability. Using the permanent middle cerebral artery occlusion (pMCAO) mouse model, we found JTE013 pretreatment markedly reduced Evans blue dye (EBD) extravasation and reversed the decrease in VE-cadherin, occludin, claudin-5 and CD31 expression in infarcted hemisphere. Lentivirus-mediated S1PR2 knockdown also attenuated EBD extravasation. Furthermore, JTE013 pretreatment attenuated neurological deficit, brain edema and infarction volume. Therefore, our findings suggest the protective effect of JTE013 on brain endothelial barrier integrity is likely mediated by suppressing p38 and Erk1/2-dependent cPLA₂ phosphorylation under oxidative stress.

PDGF-BB regulates the pulmonary vascular tone: impact of prostaglandins, calcium, MAPK- and PI3K/AKT/mTOR signalling and actin polymerisation in pulmonary veins of guinea pigs

Background

Platelet-derived growth factor (PDGF)-BB and its receptor PDGFR are highly expressed in pulmonary hypertension (PH) and mediate proliferation. Recently, we showed that PDGF-BB contracts pulmonary veins (PVs) and that this contraction is prevented by inhibition of PDGFR-β (imatinib/SU6668). Here, we studied PDGF-BB-induced contraction and downstream-signalling in isolated perfused lungs (IPL) and precision-cut lung slices (PCLS) of guinea pigs (GPs).

Methods

In IPLs, PDGF-BB was perfused after or without pre-treatment with imatinib (perfused/nebulised), the effects on the pulmonary arterial pressure (P_PA), the left atrial pressure (P_LA) and the capillary pressure (P_cap) were studied and the precapillary (R_pre) and postcapillary resistance (R_post) were calculated. Perfusate samples were analysed (ELISA) to detect the PDGF-BB-induced release of prostaglandin metabolites (TXA₂/PGI₂). In PCLS, the contractile effect of PDGF-BB was evaluated in pulmonary arteries (PAs) and PVs. In PVs, PDGF-BB-induced contraction was studied after inhibition of PDGFR-α/β, L-Type Ca²⁺-channels, ROCK/PKC, prostaglandin receptors, MAP2K, p38-MAPK, PI3K-α/γ, AKT/PKB, actin polymerisation, adenyl cyclase and NO. Changes of the vascular tone were measured by videomicroscopy. In PVs, intracellular cAMP was measured by ELISA.

Results

In IPLs, PDGF-BB increased P_PA, P_cap and R_post. In contrast, PDGF-BB had no effect if lungs were pre-treated with imatinib (perfused/nebulised). In PCLS, PDGF-BB significantly contracted PVs/PAs which was blocked by the PDGFR-β antagonist SU6668. In PVs, inhibition of actin polymerisation and inhibition of L-Type Ca²⁺-channels reduced PDGF-BB-induced contraction, whereas inhibition of ROCK/PKC had no effect. Blocking of EP_1/3- and TP-receptors or inhibition of MAP2K-, p38-MAPK-, PI3K-α/γ- and AKT/PKB-signalling prevented PDGF-BB-induced contraction, whereas inhibition of EP₄ only slightly reduced it. Accordingly, PDGF-BB increased TXA₂ in the perfusate, whereas PGI₂ was increased in all groups after 120 min and inhibition of IP-receptors did not enhance PDGF-BB-induced contraction. Moreover, PDGF-BB increased cAMP in PVs and inhibition of adenyl cyclase enhanced PDGF-BB-induced contraction, whereas inhibition of NO-formation only slightly increased it.

Conclusions

PDGF-BB/PDGFR regulates the pulmonary vascular tone by the generation of prostaglandins, the increase of calcium, the activation of MAPK- or PI3K/AKT/mTOR signalling and actin remodelling. More insights in PDGF-BB downstream-signalling may contribute to develop new therapeutics for PH.

The role of the LTB4-BLT1 axis in chemotactic gradient sensing and directed leukocyte migration

Directed leukocyte migration is a hallmark of inflammatory immune responses. Leukotrienes are derived from arachidonic acid and represent a class of potent lipid mediators of leukocyte migration. In this review, we summarize the essential steps leading to the production of LTB₄ in leukocytes. We discuss the recent findings on the exosomal packaging and transport of LTB₄ in the context of chemotactic gradients formation and regulation of leukocyte recruitment. We also discuss the dynamic roles of the LTB₄ receptors, BLT1 and BLT2, in mediating chemotactic signaling in leukocytes and contrast them to other structurally related leukotrienes that bind to distinct GPCRs. Finally, we highlight the specific roles of the LTB₄-BLT1 axis in mediating signal-relay between chemotaxing neutrophils and its potential contribution to a wide variety of inflammatory conditions including tumor progression and metastasis, where LTB₄ is emerging as a key signaling component.

Phospholipase A2 activity during the replication cycle of the flavivirus West Nile virus

Positive-sense RNA virus intracellular replication is intimately associated with membrane platforms that are derived from host organelles and comprised of distinct lipid composition. For flaviviruses, such as West Nile virus strain Kunjin virus (WNV_KUN) we have observed that these membrane platforms are derived from the endoplasmic reticulum and are rich in (at least) cholesterol. To extend these studies and identify the cellular lipids critical for WNV_KUN replication we utilized a whole cell lipidomics approach and revealed an elevation in phospholipase A2 (PLA2) activity to produce lyso-phosphatidylcholine (lyso-PChol). We observed that the PLA2 enzyme family is activated in WNV_KUN-infected cells and the generated lyso-PChol lipid moieties are sequestered to the subcellular sites of viral replication. The requirement for lyso-PChol was confirmed using chemical inhibition of PLA2, where WNV_KUN replication and production of infectious virus was duly affected in the presence of the inhibitors. Importantly, we could rescue chemical-induced inhibition with the exogenous addition of lyso-PChol species. Additionally, electron microscopy results indicate that lyso-PChol appears to contribute to the formation of the WNV_KUN membranous replication complex (RC); particularly affecting the morphology and membrane curvature of vesicles comprising the RC. These results extend our current understanding of how flaviviruses manipulate lipid homeostasis to favour their own intracellular replication.

Positive-sense RNA viruses remodel the host cytoplasmic membrane architecture to induce the formation of membranous organelles termed viral replication complexes. These complexes aid the virus in providing a more efficient microenvironment for replication but additionally shield immune-stimulatory molecules from the immune response. In this report we have performed whole cell lipidomic approaches to identify a key role for the host phospholipase A2 enzyme family in generating lyso-phospholipids to remodel cellular membranes and shape the West Nile virus (WNV) replication complex. We observed elevated PLA2 activity levels in WNV-infected cell cultures from mammalian as well as arthropod origins suggesting a generic requirement of phospholipid hydrolysis for flavivirus replication. Furthermore, we found that chemical inhibition of these enzymes severely affected the ability of WNV to replicate in cells, and we could attribute this defect to an altered ultrastructural morphology of the viral replication complex. This study provides evidence for a mechanism for the biogenesis of the flavivirus replication complex and the specific utilisation of a host lipid to invoke specific membrane curvature, generating a crucial membrane organelle required for efficient virus replication.

A Lipidomics Approach to Identifying Key Lipid Species Involved in VEGF-Inhibitor Mediated Attenuation of Bleomycin-Induced Pulmonary Fibrosis

PURPOSE

Poor molecular characterization of idiopathic pulmonary fibrosis (IPF) has led to insufficient understanding of the pathogenesis of the disease, resulting in lack of effective therapies and poor prognosis. Particularly, the role of lipid imbalance due to impaired lipid metabolism in the pathogenesis of IPF has been poorly studied.

EXPERIMENTAL DESIGN

The authors have used shotgun lipidomics in a bleomycin (BLM) mouse model of pulmonary fibrosis with vascular endothelial growth factor (VEGF)-inhibitor CBO-P11 as a therapeutic measure, to identify a comprehensive set of lipids that contribute to the pathogenesis of pulmonary fibrosis.

RESULTS

The authors report that attenuation of BLM-induced fibrotic response with CBO-P11 cotreatment is accompanied by a decrease in total lipid content and specific downregulation of lipids, which are upregulated in response to BLM treatment.

CONCLUSION AND CLINICAL RELEVANCE

Dysregulated lipids identified in this study hold the potential of being future biomarkers for IPF.

Activation of protease-activated receptor 2 mediates cutaneous vasodilatation but not sweating: roles of nitric oxide synthase and cyclo-oxygenase

NEW FINDINGS

What is the central question of this study? Protease-activated receptor 2 (PAR2) is located in the endothelial cells of skin vessels and eccrine sweat glands. However, a functional role of PAR2 in the control of cutaneous blood flow and sweating remains to be assessed in humans in vivo. What is the main finding and its importance? Our results demonstrate that in normothermic resting humans in vivo, activation of PAR2 elicits cutaneous vasodilatation partly through nitric oxide synthase-dependent mechanisms, but does not mediate sweating. These results provide important new insights into the physiological significance of PAR2 in human skin. Protease-activated receptor 2 (PAR2) is present in human skin, including keratinocytes, endothelial cells of skin microvessels and eccrine sweat glands. However, whether PAR2 contributes functionally to the regulation of cutaneous blood flow and sweating remains entirely unclear in humans in vivo. We hypothesized that activation of PAR2 directly stimulates cutaneous vasodilatation and sweating via actions of nitric oxide synthase (NOS) and cyclo-oxygenase (COX). In 12 physically active young men (29 ± 5 years old), cutaneous vascular conductance (CVC) and sweat rate were measured at four intradermal microdialysis forearm skin sites that were treated with the following: (i) lactated Ringer's solution (control); (ii) 10 mm N^G -nitro-l-arginine (NOS inhibitor); (iii) 10 mm ketorolac (COX inhibitor); or (iv) a combination of both inhibitors. At all sites, a PAR2 agonist (SLIGKV-NH₂ ) was co-administered in a dose-dependent fashion (0.06, 0.18, 0.55, 1.66 and 5 mm, each for 25 min). The highest dose of SLIGKV-NH₂ (5 mm) increased CVC from baseline at the control site (P ≤ 0.05). This increase in CVC associated with PAR2 activation was attenuated by NOS inhibition regardless of the presence or absence of simultaneous COX inhibition (both P ≤ 0.05). However, COX inhibition alone did not affect the PAR2-mediated increase in CVC (P > 0.05). No increase in sweat rate was measured at any administered dose of SLIGKV-NH₂ (all P > 0.05). We show that in normothermic resting humans in vivo, PAR2 activation does not increase sweat rate, whereas it does modulate cutaneous vasodilatation through NOS-dependent mechanisms.

Antipyretic therapy: clinical pharmacology

Fever depends on a complex physiologic response to infectious agents and other conditions. To alleviate fever, many medicinal agents have been developed over a century of trying to improve upon aspirin, which was determined to work by inhibiting prostaglandin synthesis. We present the process of fever induction through prostaglandin synthesis and discuss the development of pharmaceuticals that target enzymes and receptors involved in prostaglandin-mediated signal transduction, including prostaglandin H₂ synthase (also known as cyclooxygenase), phospholipase A₂, microsomal prostaglandin E₂ synthase-1, EP receptors, and transient potential cation channel subfamily V member 1. Clinical use of established antipyretics will be discussed as well as medicinal agents under clinical trials and future research.

Augmentation of Anticancer Drug Efficacy in Murine Hepatocellular Carcinoma Cells by a Peripherally Acting Competitive N-Methyl-d-aspartate (NMDA) Receptor Antagonist

The most common solid tumors show intrinsic multidrug resistance (MDR) or inevitably acquire such when treated with anticancer drugs. In this work, we describe the discovery of a peripherally restricted, potent, competitive NMDA receptor antagonist 1l by a structure-activity study of the broad-acting ionotropic glutamate receptor antagonist 1a. Subsequently, we demonstrate that 1l augments the cytotoxic action of sorafenib in murine hepatocellular carcinoma cells. The underlying biological mechanism was shown to be interference with the lipid signaling pathway, leading to reduced expression of MDR transporters and thereby an increased accumulation of sorafenib in the cancer cells. Interference with lipid signaling pathways by NMDA receptor inhibition is a novel and promising strategy for reversing transporter-mediated chemoresistance in cancer cells.

Cytosolic Phospholipase A2α Promotes Pulmonary Inflammation and Systemic Disease during Streptococcus pneumoniae Infection

Pulmonary infection by Streptococcus pneumoniae is characterized by a robust alveolar infiltration of neutrophils (polymorphonuclear cells [PMNs]) that can promote systemic spread of the infection if not resolved. We previously showed that 12-lipoxygenase (12-LOX), which is required to generate the PMN chemoattractant hepoxilin A₃ (HXA₃) from arachidonic acid (AA), promotes acute pulmonary inflammation and systemic infection after lung challenge with S. pneumoniae As phospholipase A₂ (PLA₂) promotes the release of AA, we investigated the role of PLA₂ in local and systemic disease during S. pneumoniae infection. The group IVA cytosolic isoform of PLA₂ (cPLA₂α) was activated upon S. pneumoniae infection of cultured lung epithelial cells and was critical for AA release from membrane phospholipids. Pharmacological inhibition of this enzyme blocked S. pneumoniae-induced PMN transepithelial migration in vitro Genetic ablation of the cPLA₂ isoform cPLA₂α dramatically reduced lung inflammation in mice upon high-dose pulmonary challenge with S. pneumoniae The cPLA₂α-deficient mice also suffered no bacteremia and survived a pulmonary challenge that was lethal to wild-type mice. Our data suggest that cPLA₂α plays a crucial role in eliciting pulmonary inflammation during pneumococcal infection and is required for lethal systemic infection following S. pneumoniae lung challenge.

Platelet-Specific p38α Deficiency Improved Cardiac Function After Myocardial Infarction in Mice

OBJECTIVE

MAPKs (mitogen-activated protein kinases), especially p38, play detrimental roles in cardiac diseases and cardiac remodeling post-myocardial infarction. However, the activation and function of MAPKs in coronary thrombosis in vivo and its relationship with clinical outcomes remain poorly understood.

APPROACH AND RESULTS

Here, we showed that p38α was the major isoform expressed in human and mouse platelets. Platelet-specific p38α-deficient mice presented impaired thrombosis and hemostasis but had improved cardiac function, reduced infarct size, decreased inflammatory response, and microthrombus in a left anterior descending artery ligation model. Signaling analysis revealed that p38 activation was one of the earliest events in platelets after treatment with receptor agonists or reactive oxygen species. p38α/MAPK-activated protein kinase 2/heat shock protein 27 and p38α/cytosolic phospholipases A2 were the major pathways regulating receptor-mediated or hydrogen peroxide-induced platelet activation in an ischemic environment. Moreover, the distinct roles of ERK1/2 (extracellular signal-regulated kinase) in receptor- or reactive oxygen species-induced p38-mediated platelet activation reflected the complicated synergistic relationships among MAPKs. Analysis of clinical samples revealed that MAPKs were highly phosphorylated in platelets from preoperative patients with ST-segment-elevation myocardial infarction, and increased phosphorylation of p38 was associated with no-reflow outcomes.

CONCLUSIONS

We conclude that p38α serves as a critical regulator of platelet activation and potential indicator of highly thrombotic lesions and no-reflow, and inhibition of platelet p38α may improve clinical outcomes in subjects with ST-segment-elevation myocardial infarction.

Endocannabinoids: Effectors of glucocorticoid signaling

For decades, there has been speculation regarding the interaction of cannabinoids with glucocorticoid systems. Given the functional redundancy between many of the physiological effects of glucocorticoids and cannabinoids, it was originally speculated that the biological mechanisms of cannabinoids were mediated by direct interactions with glucocorticoid systems. With the discovery of the endocannabinoid system, additional research demonstrated that it was actually the opposite; glucocorticoids recruit endocannabinoid signaling, and that the engagement of endocannabinoid signaling mediated many of the neurobiological and physiological effects of glucocorticoids. With the development of advances in pharmacology and genetics, significant advances in this area have been made, and it is now clear that functional interactions between these systems are critical for a wide array of physiological processes. The current review acts a comprehensive summary of the contemporary state of knowledge regarding the biological interactions between glucocorticoids and endocannabinoids, and their potential role in health and disease.

Phospholipase A2 Inhibitor from Crotalus durissus terrificus rattlesnake: Effects on human peripheral blood mononuclear cells and human neutrophils cells

Crotalus Neutralizing Factor (CNF) is an inhibitor of phospholipase A₂ (PLA₂), present in the blood plasma of Crotalus durissus terrificus snake. This inhibitor neutralizes the lethal and enzymatic activity of crotoxin, the main neurotoxin from this venom. In this study, we investigated the effects of CNF on the functionality of human peripheral blood mononuclear cells (PBMCs) and human neutrophils. The following parameters were evaluated: viability and proliferation, chemotaxis, cytokines and LTB₄ production, cytosolic PLA₂s activity, myeloperoxidase (MPO) and superoxide anion (O₂^-) production. CNF showed no toxicity on PBMCs or neutrophils, and acts by stimulating the release of TNF-α and LTB₄, but neither stimulates IL-10 and IL-2 nor affects PBMCs proliferation and O₂^- release. In neutrophils, CNF induces chemotaxis but does not induce the release of both MPO and O₂^-. However, it induces LTB₄ and IL-8 production. These data show the influence of CNF on PBMCs' function by inducing TNF-α and LTB₄ production, and on neutrophils, by stimulating chemotaxis and LTB₄ production, via cytosolic PLA₂ activity, and IL-8 release. The inflammatory profile produced by CNF is shown for the first time. Our present results suggest that CNF has a role in activation of leukocytes and exert proinflammatory effects on these cell.

Bioactive lipids derived from arachidonic acid metabolism in different types of renal replacement therapy

INTRODUCTION

Metabolism and plasma concentration of lipids and lipid-derived compounds play an important role in kidney physiology and pathological processes. The component of membrane phospholipids - arachidonic acid (AA) and its active derivatives - eicosanoids are involved in the development of hypertension, diabetes, inflammation and may contribute to progression of chronic kidney disease (CKD). The purpose of the study was to determine, whether the type of renal replacement therapy has an effect on eicosanoids metabolism.

MATERIALS AND METHODS

The study included 145 patients with CKD: on conservative treatment (n=68), on peritoneal dialysis (PD) (n=23) and undergoing chronic haemodialysis (HD) (n=54). The concentrations of TXB₂, 20-HETE, 8-epi-PGF_2α in platelet poor plasma (PPP) were determined using the ELISA method and 5-HETE, 12-HETE, 15-HETE were measured using the RP-HPLC.

RESULTS

The concentrations of TXB₂ in HD group, both before (2.28±0.72ng/mL) and after (1.49±0.63ng/mL) haemodialysis treatment differed significantly from PD group (57.76±6.13ng/mL). Haemodialysis session led to the significant decrease in TXB₂ plasma concentration (p=0.046). 20-HETE concentrations in HD group (113.55±107.54pg/mL and 199.54±142.98pg/mL before and after haemodialysis, respectively) were significantly higher than in CKD 3-5 group (8.96±12.66pg/mL) and PD group (47.78±34.07pg/mL). The highest concentration of 12-HETE was obtained in PD patients (3.58±3.99ng/mL) and differed significantly from HD group after haemodialysis (0.97±0.28ng/mL) and CKD3-5 group (1.06±0.52ng/mL). The concentrations of 5-HETE, 15-HETE and 8-epi-PGF_2α-III did not differ significantly among examined groups.

CONCLUSIONS

The concentrations of active AA metabolites depend on the mode of renal replacement therapy and are associated with intensity of oxidative stress. They might be considered as potential indicators of kidney damage.

Exploring the neuroprotective effects of ginkgolides injection in a rodent model of cerebral ischemia-reperfusion injury by GC-MS based metabolomic profiling

Cerebral ischemia-reperfusion (I/R) injury usually contributes to mortality and disability after ischemic stroke. Ginkgolides injection (GIn), a standard preparation composed of ginkgo diterpene lactones extract, is clinically used for neuroprotective treatment on reconvalescents of cerebral infarction. However, the understanding about its therapeutic mechanism is still lacking. In this study, a gas chromatography-mass spectrometry (GC-MS) based metabolomic approach coupled with multivariate data analysis (MVDA) was applied to explore the neuroprotective effects of GIn in a rodent model of focal ischemic stroke induced by transient middle cerebral artery occlusion (tMCAO). Metabolomic profiling revealed a series of metabolic perturbations that underlie the cerebral I/R pathological events. GIn can reverse the I/R induced brain metabolic deviations by modulating multiple metabolic pathways, such as glycolysis, Krebs cycle, pentose phosphate pathway (PPP), γ-aminobutyrate (GABA) shunt and lipid metabolism. Moreover, the main bioactive components of GIn were distributed to brain tissue much more easily in tMCAO rats than in normal rats after an intravenous administration, suggesting that the increased cerebral exposure to ginkgolides in I/R pathological condition potentially facilitated the neuroprotective effects of GIn by directly targeting at brain. The present study provided valuable information for our understanding about metabolic changes of cerebral I/R injury and clinical application of GIn.

Mechanisms of nicotine-induced cutaneous vasodilation and sweating in young adults: roles for KCa, KATP, and KV channels, nitric oxide, and prostanoids

We evaluated the influence of K⁺ channels (i.e., Ca²⁺-activated K⁺ (K_Ca), ATP-sensitive K⁺ (K_ATP), and voltage-gated K⁺ (K_V) channels) and key enzymes (nitric oxide synthase (NOS) and cyclooxygenase (COX)) on nicotine-induced cutaneous vasodilation and sweating. Using intradermal microdialysis, we evaluated forearm cutaneous vascular conductance (CVC) and sweat rate in 2 separate protocols. In protocol 1 (n = 10), 4 separate sites were infused with (i) lactated Ringer (Control), (ii) 50 mmol·L^-1 tetraethylammonium (K_Ca channel blocker), (iii) 5 mmol·L^-1 glybenclamide (K_ATP channel blocker), and (iv) 10 mmol·L^-1 4-aminopyridine (K_V channel blocker). In protocol 2 (n = 10), 4 sites were infused with (i) lactated Ringer (Control), (ii) 10 mmol·L^-1 N^ω-nitro-l-arginine (NOS inhibitor), (iii) 10 mmol·L^-1 ketorolac (COX inhibitor), or (iv) a combination of NOS+COX inhibitors. At all sites, nicotine was infused in a dose-dependent manner (1.2, 3.6, 11, 33, and 100 mmol·L^-1; each for 25 min). Nicotine-induced increase in CVC was attenuated by the K_Ca, K_ATP, and K_V channel blockers, whereas nicotine-induced increase in sweat rate was reduced by the K_Ca and K_V channel blockers (P ≤ 0.05). COX inhibitor augmented nicotine-induced increase in CVC (P ≤ 0.05), which was absent when NOS inhibitor was co-administered (P > 0.05). In addition, our secondrary experiment (n = 7) demonstrated that muscarinic receptor blockade with 58 μmol·L^-1 atropine sulfate salt monohydrate abolished nicotine-induced increases in CVC (1.2-11 mmol·L^-1) and sweating (all doses). We show that under a normothermic resting state: (i) K_Ca, K_ATP, and K_V channels contribute to nicotinic cutaneous vasodilation, (ii) inhibition of COX augments nicotinic cutaneous vasodilation likely through NOS-dependent mechanism(s), and (iii) K_Ca and K_V channels contribute to nicotinic sweating.

Anti-inflammatory action of ethanolic extract of Ramulus mori on the BLT2-linked cascade

Mulberry tree twigs (Ramulus mori) contain large amounts of oxyresveratrols and have traditionally been used as herbal medicines because of their anti-inflammatory properties. However, the signaling mechanism by which R. mori exerts its anti-inflammatory action remains to be elucidated. In this study, we observed that R. mori ethanol extracts (RME) exerted an inhibitory effect on the lipopolysaccharide (LPS)-induced production of the pro-inflammatory cytokine interleukin-6 (IL-6) in Raw264.7 macrophage cells. Additionally, RME inhibited IL-6 production by blocking the leukotriene B₄ receptor-2 (BLT2)-dependent-NADPH oxidase 1 (NOX1)-reactive oxygen species (ROS) cascade, leading to anti-inflammatory activity. Finally, RME suppressed the production of the BLT2 ligands LTB4 and 12(S)-HETE by inhibiting the p38 kinase-cytosolic phospholipase A₂-5-/12-lipoxygenase cascade in LPS-stimulated Raw264.7 cells. Overall, our results suggest that RME inhibits the ‘BLT2 ligand-BLT2’-linked autocrine inflammatory axis, and that this BLT2-linked cascade is one of the targets of the anti-inflammatory action of R. mori. [BMB Reports 2016; 49(4): 232-237]

Polyphenols in Health and Disease

Deadly diseases, such as cardiovascular diseases and cancer, remain the major health problems worldwide. Research in cardiovascular diseases and genome-wide association studies were successful in indentifying the gene loci associated with these threatening diseases. Yet, a substantial number of casual factors remain unexplained. Over the last decade, a better understanding of molecular and biochemical mechanisms of cardiac diseases led to developing a rationale for combining various protective agents, such as polyphenols, to target multiple signaling pathways. The present review article summarizes recent advances of the use of polyphenols against diseases, such as cardiac diseases.

TNF-α-Induced cPLA2 Expression via NADPH Oxidase/Reactive Oxygen Species-Dependent NF-κB Cascade on Human Pulmonary Alveolar Epithelial Cells

Tumor necrosis factor-α (TNF-α) triggers activation of cytosolic phospholipase A₂ (cPLA₂) and then enhancing the synthesis of prostaglandin (PG) in inflammatory diseases. However, the detailed mechanisms of TNF-α induced cPLA₂ expression were not fully defined in human pulmonary alveolar epithelial cells (HPAEpiCs). We found that TNF-α-stimulated increases in cPLA₂ mRNA (5.2 folds) and protein (3.9 folds) expression, promoter activity (4.3 folds), and PGE₂ secretion (4.7 folds) in HPAEpiCs, determined by Western blot, real-time PCR, promoter activity assay and PGE₂ ELISA kit. These TNF-α-mediated responses were abrogated by the inhibitors of NADPH oxidase [apocynin (APO) and diphenyleneiodonium chloride (DPI)], ROS [N-acetyl cysteine, (NAC)], NF-κB (Bay11-7082) and transfection with siRNA of ASK1, p47 ^phox , TRAF2, NIK, IKKα, IKKβ, or p65. TNF-α markedly stimulated NADPH oxidase activation and ROS including superoxide and hydrogen peroxide production which were inhibited by pretreatment with a TNFR1 neutralizing antibody, APO, DPI or transfection with siRNA of TRAF2, ASK1, or p47 ^phox . In addition, TNF-α also stimulated p47 ^phox phosphorylation and translocation in a time-dependent manner. On the other hand, TNF-α induced TNFR1, TRAF2, ASK1, and p47 ^phox complex formation in HPAEpiCs, which were attenuated by a TNF-α neutralizing antibody. We found that pretreatment with NAC, DPI, or APO also attenuated the TNF-α-stimulated IKKα/β and NF-κB p65 phosphorylation, NF-κB (p65) translocation, and NF-κB promoter activity in HPAEpiCs. Finally, we observed that TNF-α-stimulated NADPH oxidase activation and ROS generation activates NF-κB through the NIK/IKKα/β pathway. Taken together, our results demonstrated that in HPAEpiCs, up-regulation of cPLA₂ by TNF-α is, at least in part, mediated through the cooperation of TNFR1, TRAF2, ASK1, and NADPH oxidase leading to ROS generation and ultimately activates NF-κB pathway.

Studies on Shokyo, Kanzo, and Keihi in Kakkonto Medicine on Prostaglandin E2 Production in Lipopolysaccharide-Treated Human Gingival Fibroblasts

We previously demonstrated that a kampo medicine, kakkonto, decreases lipopolysaccharide- (LPS-) induced prostaglandin E₂ (PGE₂) production by human gingival fibroblasts. In this study, we examined the herbs constituting kakkonto that exhibit this effect. Shokyo strongly and concentration dependently and kanzo and keihi moderately decreased LPS-induced PGE₂ production. Shokyo did not alter cyclooxygenase-2 (COX-2) activity, cytosolic phospholipase A₂ (cPLA₂), annexin 1 and COX-2 expression, and LPS-induced extracellular signal-regulated kinase (ERK) phosphorylation. Kanzo inhibited COX-2 activity but increased annexin 1 and COX-2 expression and did not alter LPS-induced ERK phosphorylation. Keihi inhibited COX-2 activity and LPS-induced ERK phosphorylation but slightly increased COX-2 expression and did not alter cPLA₂ and annexin 1 expression. These results suggest that the mechanism of shokyo is through the inhibition of cPLA₂ activity, and that of kanzo and keihi is through the inhibition of COX-2 activity and indirect inhibition of cPLA₂ activity. Therefore, it is possible that shokyo and kakkonto are clinically useful for the improvement of inflammatory responses.

Digital Cushion Fatty Acid Composition and Lipid Metabolism Gene Network Expression in Holstein Dairy Cows Fed a High-Energy Diet

The hoof digital cushion is a complex structure composed of adipose tissue beneath the distal phalanx, i.e. axial, middle and abaxial fat pad. The major role of these fat depots is dampening compression of the corium underneath the cushion. The study aimed to determine expression of target genes and fatty acid profiles in the hoof of non-pregnant dry Holstein cows fed low (CON) or high-energy (OVE) diets. The middle fat pad of the hoof digital cushion was collected soon after slaughter. Despite the lack of effect on expression of the transcription regulators SREBF1 and PPARG, the expression of the lipogenic enzymes ACACA, FASN, SCD, and DGAT2 was upregulated with OVE. Along with the upregulation of G6PD and IDH1, important for NADPH synthesis during lipogenesis, and the basal glucose transporter SLC2A1, these data indicated a pro-lipogenic response in the digital cushion with OVE. The expression of the lipid droplet-associated protein PLIN2 was upregulated while expression of lipolytic enzymes (ATGL, ABDH5, and LIPE) only tended to be upregulated with OVE. Therefore, OVE induced lipogenesis, lipid droplet formation, and lipolysis, albeit to different extents. Although concentration of monounsaturated fatty acids (MUFA) did not differ, among the polyunsaturated fatty acids (PUFA), the concentration of 20:5n3 was lower with OVE. Among the saturated fatty acids, 20:0 concentration was greater with OVE. Although data indicated that the hoof digital cushion metabolic transcriptome is responsive to higher-energy diets, this did not translate into marked differences in the fatty acid composition. The decrease in concentration of PUFA, which could contribute to synthesis of inflammatory molecules, in OVE-fed cows indicated that feeding higher-energy diets might be detrimental for the mediation of inflammation in digital cushion. This effect could be further exacerbated by physiologic and endocrine changes during the peripartal period that favor inflammation.