The phospholipase A2 superfamily and its group numbering system

Mechanistic Perspectives of Maslinic Acid in Targeting Inflammation

Chronic inflammation drives the development of various pathological diseases such as rheumatoid arthritis, atherosclerosis, multiple sclerosis, and cancer. The arachidonic acid pathway represents one of the major mechanisms for inflammation. Prostaglandins (PGs) are lipid products generated from arachidonic acid by the action of cyclooxygenase (COX) enzymes and their activity is blocked by nonsteroidal anti-inflammatory drugs (NSAIDS). The use of natural compounds in regulation of COX activity/prostaglandins production is receiving increasing attention. In Mediterranean diet, olive oil and table olives contain significant dietary sources of maslinic acid. Maslinic acid is arising as a safe and novel natural pentacyclic triterpene which has protective effects against chronic inflammatory diseases in various in vivo and in vitro experimental models. Understanding the anti-inflammatory mechanism of maslinic acid is crucial for its development as a potential dietary nutraceutical. This review focuses on the mechanistic action of maslinic acid in regulating the inflammation pathways through modulation of the arachidonic acid metabolism including the nuclear factor-kappa B (NF-κB)/COX-2 expression, upstream protein kinase signaling, and phospholipase A₂ enzyme activity. Further investigations may provide insight into the mechanism of maslinic acid in regulating the molecular targets and their associated pathways in response to specific inflammatory stimuli.

Interaction kinetics of serum proteins with liposomes and their effect on phospholipase-induced liposomal drug release

We used surface plasmon resonance (SPR) to measure the affinity and kinetics of the interaction between serum proteins and both conventional and PEGylated liposomes. The effect of the interactions on secretory phospholipase A2 (sPLA2)-induced release of a model drug from liposomes was also assessed. SPR analysis of 12 serum proteins revealed that the mode of interaction between serum proteins and liposomes greatly varies depending on the type of protein. For example, albumin bound to liposomes at slower association/dissociation rates with higher affinity and prevented sPLA2-induced drug release from PEGylated liposomes. Conversely, fibronectin bound at faster association/dissociation rates with lower affinity and demonstrated little impact on the drug release. These results indicate that the effect of serum proteins on sPLA2 phospholipid hydrolysis varies with the mode of interaction between proteins and liposomes. Understanding how the proteins interact with liposomes and impact sPLA2 phospholipid hydrolysis should aid the rational design of therapeutic liposomal formulations.

Darapladib for the treatment of cardiovascular disease

Elevated levels of phospholipase A2 have been linked to atherosclerotic plaque progression, instability via promoting inflammation and subsequent acute coronary events. Epidemiological studies have demonstrated the correlation between elevated levels associated phospholipase A2 and cardiovascular events. Therefore, specific inhibition of lipoprotein-associated phospholipase A2 with darapladib has been tested as a therapeutic option for atherosclerosis. The aim of this profile is to review the physiologic aspects of lipoprotein-associated phospholipase A2 and to revisit the clinical evidence of darapladib as therapeutic option for atherosclerosis.

Phospholipase A2-dependent Release of Inflammatory Cytokines by Superantigen-Stimulated Nasal Polyps of Patients with Chronic Rhinosinusitis

Background

Chronic rhinosinusitis (CRS) is an inflammatory/allergic disease with unclear pathophysiology, but it has been linked to an imbalance in the production of eicosanoids, which are metabolites of arachidonic acid, and results from phospholipids hydrolysis by phospholipase A2 (PLA2). As of yet, the role of PLA2 in CRS has hardly been studied, except for a report that group II PLA2 expression is elevated in interleukin (IL) 1β or tumor necrosis factor α-stimulated CRS nasal tissues with and without polyps. The PLA2 families include extracellular (secretory) and intracellular isoforms, which are involved in the regulation of inflammatory processes in different ways. Here we comprehensively investigated the expression of PLA2s, particularly those reported to be involved in respiratory disorders, in superantigen (SAE)-stimulated nasal polyps from patients with CRS with polyps, and determined their role in inflammatory cytokine production by inhibition of PLA2 expression.

Methods

The release of IL-5, IL-13, IL-17, and interferon γ by nasal polyps dispersed cells (NPDC) was determined concomitantly with PLA2 messenger RNA expression, under SAE stimulation, with or without dexamethasone, as a regulator of PLA2 expression.

Results

Stimulation of NPDCs by SAE-induced cytokine secretion with enhanced expression of several secretory PLA2 and Ca2+-independent PLA2, while suppressing cytosolic PLA2 expression. All these were reverted to the level of unstimulated NPDCs on treatment with dexamethasone.

Conclusion

This study further supports the key role of secretory PLA2 in the pathophysiology of respiratory disorders and presents secretory PLA2 inhibition as a therapeutic strategy for the treatment of CRS and airway pathologies in general.

Recombinant Lipases and Phospholipases and Their Use as Biocatalysts for Industrial Applications

Lipases and phospholipases are interfacial enzymes that hydrolyze hydrophobic ester linkages of triacylglycerols and phospholipids, respectively. In addition to their role as esterases, these enzymes catalyze a plethora of other reactions; indeed, lipases also catalyze esterification, transesterification and interesterification reactions, and phospholipases also show acyltransferase, transacylase and transphosphatidylation activities. Thus, lipases and phospholipases represent versatile biocatalysts that are widely used in various industrial applications, such as for biodiesels, food, nutraceuticals, oil degumming and detergents; minor applications also include bioremediation, agriculture, cosmetics, leather and paper industries. These enzymes are ubiquitous in most living organisms, across animals, plants, yeasts, fungi and bacteria. For their greater availability and their ease of production, microbial lipases and phospholipases are preferred to those derived from animals and plants. Nevertheless, traditional purification strategies from microbe cultures have a number of disadvantages, which include non-reproducibility and low yields. Moreover, native microbial enzymes are not always suitable for biocatalytic processes. The development of molecular techniques for the production of recombinant heterologous proteins in a host system has overcome these constraints, as this allows high-level protein expression and production of new redesigned enzymes with improved catalytic properties. These can meet the requirements of specific industrial process better than the native enzymes. The purpose of this review is to give an overview of the structural and functional features of lipases and phospholipases, to describe the recent advances in optimization of the production of recombinant lipases and phospholipases, and to summarize the information available relating to their major applications in industrial processes.

Hemilipin, a novel Hemiscorpius lepturus venom heterodimeric phospholipase A2, which inhibits angiogenesis in vitro and in vivo

Phospholipases A2 (PLA2) are enzymes which specifically hydrolyze the sn-2 acyl ester bond of phospholipids producing free fatty acids and lysophospholipids. The secreted PLA2 (sPLA2) are the most common types of PLA2 purified from the snake venom, mammalian pancreatic juice and other sources. They display a variety of toxic actions and biological activities, including antitumoral and antiangiogenic effects. In this study, we report the isolation, characterization and the antiangiogenic activity of Hemilipin, a novel sPLA2 extracted from Hemiscorpius lepturus venom, the most dangerous scorpion in Iran. Hemilipin was purified by HPLC and analyzed by MALDI TOF/MS. The primary structure was determined by EDMAN degradation method and the PLA2 activity by titration of fatty acids released from the egg yolk phospholipids. Its antiangiogenic activity was studied in vitro by evaluating effects on apoptosis, Matrigel angiogenesis, migration and adhesion of human umbilical vein endothelial cells (HUVECs) and human pulmonary artery endothelial cells (HPAECs) and in vivo by the chorioallantoic membrane (CAM) assay. Mass spectrometry profile showed that Hemilipin is heterodimeric and the PLA2 test demonstrated its strong hydrolytic activity. N-terminal aminoacid sequence highlighted a significant homology of Hemilipin's small and large subunits with other sPLA2 group III. Hemilipin had no effect on apoptosis, but strongly impacted angiogenesis both in vitro and in vivo. Our results demonstrate that this novel non toxic sPLA2 could be a new tool to disrupt at different steps human angiogenesis.

Structural Basis for the Inhibition of a Phospholipase A2-Like Toxin by Caffeic and Aristolochic Acids

One of the main challenges in toxicology today is to develop therapeutic alternatives for the treatment of snake venom injuries that are not efficiently neutralized by conventional serum therapy. Venom phospholipases A2 (PLA2s) and PLA2-like proteins play a fundamental role in skeletal muscle necrosis, which can result in permanent sequelae and disability. This leads to economic and social problems, especially in developing countries. In this work, we performed structural and functional studies with Piratoxin-I, a Lys49-PLA2 from Bothropspirajai venom, complexed with two compounds present in several plants used in folk medicine against snakebites. These ligands partially neutralized the myotoxic activity of PrTX-I towards binding on the two independent sites of interaction between Lys49-PLA2 and muscle membrane. Our results corroborate the previously proposed mechanism of action of PLA2s-like and provide insights for the design of structure-based inhibitors that could prevent the permanent injuries caused by these proteins in snakebite victims.

Lipid droplets in activated mast cells - a significant source of triglyceride-derived arachidonic acid for eicosanoid production

Mast cells are potent effectors of immune reactions and key players in various inflammatory diseases such as atherosclerosis, asthma, and rheumatoid arthritis. The cellular defense response of mast cells represents a unique and powerful system, where external signals can trigger cell activation resulting in a stimulus-specific and highly coordinated release of a plethora of bioactive mediators. The arsenal of mediators encompasses preformed molecules stored in cytoplasmic secretory granules, as well as newly synthesized proteinaceous and lipid mediators. The release of mediators occurs in strict chronological order and requires proper coordination between the endomembrane system and various enzymatic machineries. For the generation of lipid mediators, cytoplasmic lipid droplets have been shown to function as a major intracellular pool of arachidonic acid, the precursor for eicosanoid biosynthesis. Recent studies have revealed that not only phospholipids in mast cell membranes, but also triglycerides in mast cell lipid droplets are a substrate source for eicosanoid formation. The present review summarizes current knowledge about mast cell lipid droplet biology, and discusses expansions and challenges of traditional mechanistic models for eicosanoid production.

Synthesis and characterization of an antibacterial and non-toxic dimeric peptide derived from the C-terminal region of Bothropstoxin-I

Infectious diseases are among the leading global causes of death, increasing the search for novel antibacterial agents. Among these, biologically active peptides are an excellent research tool. Using solid-phase peptide synthesis (SPPS), this work aimed to synthesize the peptide derived from the C-terminal region of Bothropstoxin-I (BthTX-I) (p-BthTX-I, sequence: KKYRYHLKPFCKK), and its disulfide-linked dimeric form, obtained via air oxidation (p-BthTX-I)2. Two other peptides were synthesized to evaluate the dimerization effect on antimicrobial activity. In both sequences, the cysteine (Cys) residue was replaced by the serine (Ser) residue, differing, however, in their C-terminus position. The antimicrobial activity of the peptides against gram-negative (Escherichia (E.) coli) and gram-positive (Staphylococcus (S.) aureus) bacteria and yeast (Candida (C.) albicans) was evaluated. Interestingly, only peptides containing the Cys residue showed antimicrobial activity, suggesting the importance of Cys residue and its dimerization for the observed activity. Apparently, p-BthTX-I and (p-BthTX-I)2 did not promote lysis or form pores and were not able to interact with membranes. Furthermore, they neither showed antifungal activity against C. albicans nor toxicity against erythrocytes, epithelial cells, or macrophages, indicating a potential specificity against prokaryotic cells.

Auxins action on Glycine max secretory phospholipase A2 is mediated by the interfacial properties imposed by the phytohormones

Secretory phospholipase A2 (sPLA2) are soluble enzymes that catalyze the conversion of phospholipids to lysophospholipids and free fatty acids at membrane interfaces. The effect of IAA and IPA auxins over the activity of recombinant sPLA2 isoforms from Glycine max was studied using membrane model systems including mixed micelles and Langmuir lipid monolayers. Both phytohormones stimulate the activity of both plant sPLA2 using DLPC/Triton mixed micelles as substrate. To elucidate the mechanism of action of the phytohormones, we showed that both auxins are able to self-penetrate lipid monolayers and cause an increment in surface pressure and an expansion of lipid/phytohormone mixed interfaces. The stimulating effect of auxins over phospholipase A2 activity was still present when using Langmuir mixed monolayers as organized substrate regardless of sPLA2 source (plant or animal). All the data suggest that the stimulating effect of auxins over sPLA2 is due to a more favorable interfacial environment rather to a direct effect over the enzyme.

Bromoenol Lactone, an Inhibitor of Calcium-Independent Phospholipase A2, Suppresses Carrageenan-Induced Prostaglandin Production and Hyperalgesia in Rat Hind Paw

Prostaglandin (PG) E₂ and PGI₂ are essential to hyperalgesia in inflammatory tissues. These prostaglandins are produced from arachidonic acid, which is cleaved from membrane phospholipids by the action of phospholipase A₂ (PLA₂). Which isozyme of PLA₂ is responsible for the cleavage of arachidonic acid and the production of prostaglandins essential to inflammation-induced hyperalgesia is not clear. In this study, we examined the effects of two PLA₂ isozyme-specific inhibitors on carrageenan-induced production of PGE₂ and PGI₂ in rat hind paw and behavioral nociceptive response to radiant heat. Local administration of bromoenol lactone (BEL), an inhibitor of calcium-independent PLA₂ (iPLA₂), significantly reduced carrageenan-induced elevation of prostaglandins in the inflamed foot pad 3 h after injection. It also ameliorated the hyperalgesic response between 1 h and 3 h after carrageenan injection. On the other hand, AACOCF₃, an inhibitor of cytosolic PLA₂, suppressed neither prostaglandin production nor the hyperalgesic response. BEL did not suppress the mRNA levels of iPLA₂β, iPLA₂γ, cyclooxygenase-2, microsomal prostaglandin E synthase, prostaglandin I synthase, or proinflammatory cytokines in the inflamed foot pad, indicating that BEL did not suppress inflammation itself. These results suggest that iPLA₂ is involved in the production of prostaglandins and hyperalgesia at the inflammatory loci.

Group IIE secretory phospholipase A2 regulates lipolysis in adipocytes

OBJECTIVE

To examine the function of group IIE secretory phospholipase A(2) (sPLA(2) -IIE) in adipocytes and to explore the possible signaling mechanism involved.

METHODS

The expression of sPLA(2) -IIE was demonstrated using real-time PCR and Western blot analysis. Lipid accumulation was evaluated via the measurement of cellular triglycerides (TG). Lipolysis was quantified by measuring the release of free glycerol. The expressions of M-type sPLA(2) receptor (PLA(2) R1) and the genes encoding adipogenic proteins were measured using real-time PCR. The activities of the Janus kinase 2 (JAK2), extracellular regulated protein kinase (ERK), and hormone-sensitive lipase (HSL) were determined using Western blot.

RESULTS

sPLA(2) -IIE(-/-) mice gained significantly more epididymal fat than wild-type (WT) mice. When treated with adipogenic stimuli ex vivo, stromal vascular cells isolated from the adipose tissue of sPLA(2) -IIE(-/-) mice accumulated significantly more TG than those from WT mice. Conversely, a significant reduction in lipid accumulation and an increase of free glycerol were observed in OP9 cells overexpressing sPLA(2) -IIE and in 3T3-L1 cells treated with sPLA(2) -IIE protein. Moreover, sPLA(2) -IIE significantly induced adipocyte glycerol release and HSL activity, which was inhibited by PD98059, an ERK inhibitor.

CONCLUSIONS

sPLA(2) -IIE regulates lipolysis in adipocytes, likely through the ERK/HSL signaling pathway.

Deficiency of spermatogenesis and reduced expression of spermatogenesis-related genes in prefoldin 5-mutant mice

MM-1α is a c-Myc-binding protein and acts as a transcriptional co-repressor in the nucleus. MM-1α is also PDF5, a subunit of prefoldin that is chaperon comprised of six subunits and prevents misfolding of newly synthesized nascent polypeptides. Prefoldin also plays a role in quality control against protein aggregation. It has been reported that mice harboring the missense mutation L110R of MM-1α/PFD5 exhibit neurodegeneration in the cerebellum and also male infertility, but the phenotype of infertility has not been fully characterized. In this study, we first analyzed morphology of the testis and epididymis of L110R of MM-1α mice. During differentiation of spermatogenesis, spermatogonia, spermatocytes and round spermatids were formed, but formation of elongated spermatids was compromised in L110R MM-1α mice. Furthermore, reduced number/concentration of sperm in the epididymis was observed. MM-1α was strongly expressed in the round spermatids and sperms with round spermatids, suggesting that MM-1α affects the differentiation and maturation of germ cells. Changes in expression levels of spermatogenesis-related genes in mice testes were then examined. The fatty-acid-binding protein (fabp4) gene was up-regulated and three genes, including sperm-associated glutamate (E)-rich protein 4d (speer-4d), phospholipase A2-Group 3 (pla2g3) and phospholipase A2-Group 10 (pla2g10), were down-regulated in L110R MM-1α mice. L110R MM-1α and wild-type MM-1α bound to regions of up-regulated and down-regulated genes, respectively. Since these gene products are known to play a role in maturation and motility of sperm, a defect of at least MM-1α transcriptional activity is thought to induce expressional changes of these genes, resulting in male infertility.

Novel acidic phospholipase A2 from Porthidium hyoprora causes inflammation with mast cell rich infiltrate

Phospholipases A₂ (PLA₂) are a group of enzymes that hydrolyze phospholipids at the sn-2 position, being present in all nature. In venomous animals, these proteins assume a special role, being able to exert diverse pharmacological effects. In this work, authors identified a new isoform of PLA₂ in the venom of Porthidium hyoprora, which was isolated through sequential chromatographic steps and named PhTX-III. The enzyme was characterized biochemically and structurally. Structural studies using mass spectrometry confirmed an acidic secretory PLA₂, family IIA, with molecular mass of 13,620.9 Da and identification of 86% of its primary sequence. PhTX-III did not exhibit myotoxic, anticoagulant or antibacterial effects, often present in this class of enzymes. Although, it was capable of initiate inflammatory response, with local edema and release of cytokines IL-1α, IL-6 and TNF-α, probably due to mast cell degranulation.

Oligomeric state regulated trafficking of human platelet-activating factor acetylhydrolase type-II

The intracellular enzyme platelet-activating factor acetylhydrolase type-II (PAFAH-II) hydrolyzes platelet-activating factor and oxidatively fragmented phospholipids. PAFAH-II in its resting state is mainly cytoplasmic, and it responds to oxidative stress by becoming increasingly bound to endoplasmic reticulum and Golgi membranes. Numerous studies have indicated that this enzyme is essential for protecting cells from oxidative stress induced apoptosis. However, the regulatory mechanism of the oxidative stress response by PAFAH-II has not been fully resolved. Here, changes to the oligomeric state of human PAFAH-II were investigated as a potential regulatory mechanism toward enzyme trafficking. Native PAGE analysis in vitro and photon counting histogram within live cells showed that PAFAH-II is both monomeric and dimeric. A Gly-2-Ala site-directed mutation of PAFAH-II demonstrated that the N-terminal myristoyl group is required for homodimerization. Additionally, the distribution of oligomeric PAFAH-II is distinct within the cell; homodimers of PAFAH-II were localized to the cytoplasm while monomers were associated to the membranes of the endoplasmic reticulum and Golgi. We propose that the oligomeric state of PAFAH-II drives functional protein trafficking. PAFAH-II localization to the membrane is critical for substrate acquisition and effective oxidative stress protection. It is hypothesized that the balance between monomer and dimer serves as a regulatory mechanism of a PAFAH-II oxidative stress response.

Reduced activities of phospholipases A2 in platelets of drug-naïve bipolar disorder patients

OBJECTIVE

Phospholipases A2 (PLA2 ) comprise a family of hydrolytic enzymes that cleave membrane phospholipids and play a key role in cellular homeostasis. Alterations in enzymatic activity have been hypothesized in bipolar disorder (BD). Recent studies suggest that PLA2 activity in platelets may reflect PLA2 activity in the brain. The aim of this study was to determine PLA2 activity in platelets of BD patients.

METHODS

We determined the activity of PLA2 subtypes [extracellular, calcium-dependent PLA2 (sPLA2 ), intracellular, calcium-dependent PLA2 (cPLA2 ), and intracellular, calcium-independent PLA2 (iPLA2 )] by a radioenzymatic method in platelets from 20 patients with BD (15 drug-naïve and five drug-free) and from 16 age- and gender-matched healthy controls.

RESULTS

We found that iPLA2 , cPLA2 , and sPLA2 activities were lower in drug-naïve patients with BD when compared to the control group (p = 0.017, p < 0.001, and p < 0.001, respectively).

CONCLUSIONS

Reduced PLA2 activity at the early stage of BD may disrupt brain function and increase the risk for the disease. Moreover, epidemiological studies show that patients with BD have a fivefold increased risk for developing Alzheimer's disease. Because patients with Alzheimer's disease also have reduced PLA2 activity, the present finding of reduced PLA2 in the BD group may be related to the risk factor for these individuals developing Alzheimer's disease in advanced age.

Genetic variants of PLA2G6 are associated with Type 2 diabetes mellitus and triglyceride levels in a Chinese population

AIM

To test the association of PLA2G6 variants with Type 2 diabetes and clinical characteristics in large Chinese population-based samples.

METHODS

A total of 6822 people were recruited. In the first stage, 15 single nucleotide polymorphisms within the PLA2G6 region were selected and genotyped in 3700 Chinese Han people. In the second stage, the single nucleotide polymorphisms that showed a significant association were genotyped in an additional 3122 samples for replication. Genotype-phenotype association studies and meta-analyses were performed after combining data from the two stages.

RESULTS

In the first stage, we detected rs132984 and rs2284060 as significantly associated with Type 2 diabetes with odds ratios of 1.247 (95% CI 1.074-1.449, P = 0.004, empirical P = 0.047) and 1.173 (95% CI 1.059-1.299, P = 0.002, empirical P = 0.029), respectively. In the second stage, a similar effect of rs132984 on Type 2 diabetes was observed (odds ratio 1.280, 95% CI 1.094-1.497, P = 0.002). The meta-analysis showed a significant effect of the two single nucleotide polymorphisms on Type 2 diabetes (odds ratio 1.254, 95% CI 1.104-1.451, P = 4.85 × 10⁻⁵ for rs132984; odds ratio 1.120, 95% CI 1.046-1.195, P = 0.003 for rs2284060). Moreover, genotype-phenotype association analysis showed that rs132984 was associated with triglyceride levels (P = 0.022, empirical P = 0.044) and area under the curve for glucose (P = 0.015, empirical P = 0.030).

CONCLUSIONS

Our data imply that common single nucleotide polymorphisms within the PLA2G6 region are associated with Type 2 diabetes and triglyceride levels in the Chinese population.

The role of leukotrienes in allergic diseases

Leukotrienes (LTs), both LTB4 and the cysteinyl LTs (CysLTs) LTC4, LTD4 and LTE4, are implicated in a wide variety of inflammatory disorders. These lipid mediators are generated from arachidonic acid via multistep enzymatic reactions through which arachidonic acid is liberated from membrane phospholipids through the action of phospholipase A2. LTB4 and CysLTs exert their biological effects by binding to cognate receptors, which belong to the G protein-coupled receptor superfamily. LTB4 is widely considered to be a potent chemoattractant for most subsets of leukocytes, whereas CysLTs are potent bronchoconstrictors that have effects on airway remodeling. LTs play a central role in the pathogenesis of asthma and many other inflammatory diseases. This review will provide an update on the synthesis, biological function, and relevance of LTs to the pathobiology of allergic diseases, and examine the current and future therapeutic prospects of LT modifiers.

Inhibition of nicotinic acetylcholine receptors, a novel facet in the pleiotropic activities of snake venom phospholipases A2

Phospholipases A2 represent the most abundant family of snake venom proteins. They manifest an array of biological activities, which is constantly expanding. We have recently shown that a protein bitanarin, isolated from the venom of the puff adder Bitis arietans and possessing high phospholipolytic activity, interacts with different types of nicotinic acetylcholine receptors and with the acetylcholine-binding protein. To check if this property is characteristic to all venom phospholipases A2, we have studied the capability of these enzymes from other snakes to block the responses of Lymnaea stagnalis neurons to acetylcholine or cytisine and to inhibit α-bungarotoxin binding to nicotinic acetylcholine receptors and acetylcholine-binding proteins. Here we present the evidence that phospholipases A2 from venoms of vipers Vipera ursinii and V. nikolskii, cobra Naja kaouthia, and krait Bungarus fasciatus from different snake families suppress the acetylcholine- or cytisine-elicited currents in L. stagnalis neurons and compete with α-bungarotoxin for binding to muscle- and neuronal α7-types of nicotinic acetylcholine receptor, as well as to acetylcholine-binding proteins. As the phospholipase A2 content in venoms is quite high, under some conditions the activity found may contribute to the deleterious venom effects. The results obtained suggest that the ability to interact with nicotinic acetylcholine receptors may be a general property of snake venom phospholipases A2, which add a new target to the numerous activities of these enzymes.

Bee venom phospholipase A2 protects against acetaminophen-induced acute liver injury by modulating regulatory T cells and IL-10 in mice

The aim of this study was to investigate the protective effects of phospholipase A2 (PLA2) from bee venom against acetaminophen-induced hepatotoxicity through CD4⁺CD25⁺Foxp3⁺ T cells (Treg) in mice. Acetaminophen (APAP) is a widely used antipyretic and analgesic, but an acute or cumulative overdose of acetaminophen can cause severe hepatic failure. Tregs have been reported to possess protective effects in various liver diseases and kidney toxicity. We previously found that bee venom strongly increased the Treg population in splenocytes and subsequently suppressed immune disorders. More recently, we found that the effective component of bee venom is PLA2. Thus, we hypothesized that PLA2 could protect against liver injury induced by acetaminophen. To evaluate the hepatoprotective effects of PLA2, C57BL/6 mice or interleukin-10-deficient (IL-10^−/−) mice were injected with PLA2 once a day for five days and sacrificed 24 h (h) after acetaminophen injection. The blood sera were collected 0, 6, and 24 h after acetaminophen injection for the analysis of aspartate aminotransferase (AST) and alanine aminotransferase (ALT). PLA2-injected mice showed reduced levels of serum AST, ALT, proinflammatory cytokines, and nitric oxide (NO) compared with the PBS-injected control mice. However, IL-10 was significantly increased in the PLA2-injected mice. These hepatic protective effects were abolished in Treg-depleted mice by antibody treatment and in IL-10^−/− mice. Based on these findings, it can be concluded that the protective effects of PLA2 against acetaminophen-induced hepatotoxicity can be mediated by modulating the Treg and IL-10 production.

Novel metabolic biomarkers of cardiovascular disease

Coronary heart disease (CHD) accounts for one in every six deaths in US individuals. Great advances have been made in identifying important risk factors for CHD, such as hypertension, diabetes mellitus, smoking and hypercholesterolaemia, which have led to major developments in therapy. In particular, statins represent one of the greatest successes in the prevention of CHD. While these standard risk factors are important, an obvious opportunity exists to take advantage of ongoing scientific research to better risk-stratify individuals and to identify new treatment targets. In this Review, we summarize ongoing scientific research in a number of metabolic molecules or features, including lipoproteins, homocysteine, calcium metabolism and glycaemic markers. We evaluate the current state of the research and the strength of evidence supporting each emerging biomarker. We also discuss whether the associations with CHD are strong and consistent enough to improve current risk stratification metrics, and whether these markers enhance our understanding of the underlying biology of CHD and thus point towards new treatment options.

Treating coronary disease and the impact of endothelial dysfunction

Ischemic heart disease is the leading cause of morbidity and mortality throughout the world. Many clinical trials have suggested that lifestyle and pharmacologic interventions are effective in attenuating atherosclerotic disease progression and events development. However, an individualized approach with careful consideration to comprehensive vascular health is necessary to perform successful intervention strategies. Endothelial dysfunction plays a pivotal role in the early stage of atherosclerosis and is also associated with plaque progression and occurrence of atherosclerotic complications. The assessment of endothelial function provides us with important information about individual patient risk, progress and vulnerability of disease, and guidance of therapy. Thus, the application of endothelial function assessment might enable clinicians to innovate ideal individualized medicine. In this review, we summarize the current knowledge on the impact of pharmacological therapies for atherosclerotic cardiovascular disease on endothelial dysfunction, and argue for the utility of non-invasive assessment of endothelial function aiming at individualized medicine.

The fish oil ingredient, docosahexaenoic acid, activates cytosolic phospholipase A₂ via GPR120 receptor to produce prostaglandin E₂ and plays an anti-inflammatory role in macrophages

Docosahexaenoic acid (DHA) is one of the major ingredients of fish oil and has been reported to have anti-inflammatory properties mediated through the GPR120 receptor. Whether cytosolic phospholipase A2 (cPLA2 ) and lipid mediators produced from cPLA2 activation are involved in the anti-inflammatory role of DHA in macrophages has not been reported. We report here that DHA and the GPR120 agonist, GW9508, activate cPLA2 and cyclooxygenase 2 (COX-2), and cause prostaglandin E2 (PGE2) release in a murine macrophage cell line RAW264.7 and in human primary monocyte-derived macrophages. DHA and GW9508 activate cPLA2 via GPR120 receptor, G protein Gαq and scaffold protein β-arrestin 2. Extracellular signal-regulated kinase 1/2 activation is involved in DHA- and GW9508-induced cPLA2 activation, but not p38 mitogen-activated protein kinase. The anti-inflammatory role of DHA and GW9508 is in part via activation of cPLA2 , COX-2 and production of PGE2 as a cPLA2 inhibitor or a COX-2 inhibitor partially reverses the DHA- and GW9508-induced inhibition of lipopolysaccharide-induced interleukin-6 secretion. The cPLA2 product arachidonic acid and PGE2 also play an anti-inflammatory role. This effect of PGE2 is partially through inhibition of the nuclear factor-κB signalling pathway and through the EP4 receptor of PGE2 because an EP4 inhibitor or knock-down of EP4 partially reverses DHA inhibition of lipopolysaccharide-induced interleukin-6 secretion. Hence, DHA has an anti-inflammatory effect partially through induction of PGE2.

Phospholipase A(2)-catalyzed acylation of lysophospholipids analyzed by experimental design

The catalytic potential of phospholipase A2 (PLA2) for the synthesis of phospholipids with defined fatty acid structure in the sn-2 position has been underestimated hitherto because of very low conversion in most organic solvents. One of the most suitable solvents for PLA2-catalyzed phospholipid synthesis is glycerol. With the aim to analyze the effect of several interacting reaction parameters on the product yield, we studied the conversion of 1-palmitoyl-2-lyso-sn-glycero-3-phosphocholine (lyso-PC) with oleic acid as model reaction in mixtures of glycerol and methanol or ethanol by methods of experimental design. PLA2 from porcine pancreas (ppPLA2) and from bee venom (bvPLA2) were compared as catalysts. For each of the four systems, nine variables were evaluated using Plackett-Burman designs. The most significant four variables were used for subsequent modified D-optimal designs with 30 runs, yielding regression equations for describing the formation of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine as a function of the variables. In both solvent systems ppPLA2 was more appropriate for the acylation reaction than bvPLA2. Methanol proved to be more convenient as co-solvent than ethanol. The catalysis by ppPLA2 was more sensitive toward the variables temperature and concentration of Tris-HCl, whereas the reaction time and enzyme activity were more important in the acylation by bvPLA2. Conversion up to 87 (ppPLA2) and 50% (bvPLA2) can be anticipated.

Heterologous expression and biochemical and functional characterization of a recombinant alpha-type myotoxin inhibitor from Bothrops alternatus snake

Venomous and non-venomous snakes possess phospholipase A2 (PLA2) inhibitory proteins (PLIs) in their blood serum. This study shows the expression and biochemical and functional characterization of a recombinant alpha inhibitor from Bothrops alternatus snake, named rBaltMIP. Its expression was performed in Pichia pastoris heterologous system, resulting in an active recombinant protein. The expressed inhibitor was tested regarding its ability to inhibit the phospholipase activity of different PLA2s, showing slight inhibitions especially at the molar ratios of 1:1 and 1:3 (PLA2:PLI). rBaltMIP was also effective in decreasing the myotoxic activity of the tested toxins at molar ratios greater than 1:0.4 (myotoxin:PLI). The inhibition of the myotoxic activity of different Asp49 (BthTX-II and PrTX-III) and Lys49 (BthTX-I and PrTX-I) myotoxins was also performed without the prior incubation of myotoxins/inhibitor in order to analyze the real possibility of using snake plasma inhibitors or recombinant inhibitors as therapeutic agents for treating envenomations. As a result, rBaltMIP was able to significantly inhibit the myotoxicity of Lys49 myotoxins. Histopathological analysis of the gastrocnemius muscles of mice showed that the myotoxins are able to induce severe damage to the muscle fibers of experimental animals by recruiting a large number of leukocyte infiltrates, besides forming an intense accumulation of intercellular fluid, leading to local edema. When those myotoxins were incubated with rBaltMIP, a reduction of the damage site could be observed. Furthermore, the cytotoxic activity of Asp49 PLA2s and Lys49 PLA2-like enzymes on C2C12 cell lines was decreased, as shown by the higher cell viabilities after preincubation with rBaltMIP. Heterologous expression would enable large-scale obtainment of rBaltMIP, thus allowing further investigations for the elucidation of possible mechanisms of inhibition of snake PLA2s, which have not yet been fully clarified.

Are ticks venomous animals?

INTRODUCTION

As an ecological adaptation venoms have evolved independently in several species of Metazoa. As haematophagous arthropods ticks are mainly considered as ectoparasites due to directly feeding on the skin of animal hosts. Ticks are of major importance since they serve as vectors for several diseases affecting humans and livestock animals. Ticks are rarely considered as venomous animals despite that tick saliva contains several protein families present in venomous taxa and that many Ixodida genera can induce paralysis and other types of toxicoses. Tick saliva was previously proposed as a special kind of venom since tick venom is used for blood feeding that counteracts host defense mechanisms. As a result, the present study provides evidence to reconsider the venomous properties of tick saliva.

RESULTS

Based on our extensive literature mining and in silico research, we demonstrate that ticks share several similarities with other venomous taxa. Many tick salivary protein families and their previously described functions are homologous to proteins found in scorpion, spider, snake, platypus and bee venoms. This infers that there is a structural and functional convergence between several molecular components in tick saliva and the venoms from other recognized venomous taxa. We also highlight the fact that the immune response against tick saliva and venoms (from recognized venomous taxa) are both dominated by an allergic immunity background. Furthermore, by comparing the major molecular components of human saliva, as an example of a non-venomous animal, with that of ticks we find evidence that ticks resemble more venomous than non-venomous animals. Finally, we introduce our considerations regarding the evolution of venoms in Arachnida.

CONCLUSIONS

Taking into account the composition of tick saliva, the venomous functions that ticks have while interacting with their hosts, and the distinguishable differences between human (non-venomous) and tick salivary proteins, we consider that ticks should be referred to as venomous ectoparasites.

Platelets, a reliable source for peripheral Alzheimer's disease biomarkers?

Peripheral biomarkers play an indispensable role in quick and reliable diagnoses of any kind of disease. With the population ageing, the number of people suffering from age-related diseases is expected to rise dramatically over the coming decades. In particular, all types of cognitive deficits, such as Alzheimer's disease, will increase. Alzheimer's disease is characterised mainly by coexistence of amyloid plaques and neurofibrillary tangles in brain. Reliable identification of such molecular characteristics antemortem, however, is problematic due to restricted availability of appropriate sample material and definitive diagnosis is only possible postmortem. Currently, the best molecular biomarkers available for antemortem diagnosis originate from cerebrospinal fluid. Though, this is not convenient for routine diagnosis because of the required invasive lumbar puncture. As a consequence, there is a growing demand for additional peripheral biomarkers in a more readily accessible sample material. Blood platelets, due to shared biochemical properties with neurons, can constitute an attractive alternative as discussed here. This review summarises potential platelet Alzheimer's disease biomarkers, their role, implication, and alteration in the disease. For easy comparison of their performance, the Hedge effect size was calculated whenever data were available.

Peptidophospholipids: synthesis, phospholipase A2 catalyzed hydrolysis, and application to development of phospholipid prodrugs

New phospholipid analogues incorporating sn-2-peptide substituents have been prepared to probe the fundamental structural requirements for phospholipase A2 catalyzed hydrolysis of PLA2-directed synthetic substrates. Two structurally different antiviral oligopeptides with C-terminal glycine were introduced separately at the sn-2-carboxylic ester position of phospholipids to assess the role of the α-methylene group adjacent to the ester carbonyl in allowing hydrolytic cleavage by the enzyme. The oligopeptide-carrying phospholipid derivatives were readily incorporated into mixed micelles consisting of natural phospholipid (dipalmitoyl phosphatidylcholine, DPPC) and Triton X-100 as surfactant. Hydrolytic cleavage of the synthetic peptidophospholipids by the phospholipase A2 occurred slower, but within the same order of magnitude as the natural substrate alone. The results provide useful information toward better understanding the mechanism of action of the enzyme, and to improve the design and synthesis of phospholipid prodrugs targeted at secretory PLA2 enzymes.

Alkylation of histidine residues of Bothrops jararacussu venom proteins and isolated phospholipases A2: a biotechnological tool to improve the production of antibodies

Crude venom of Bothrops jararacussu and isolated phospholipases A₂ (PLA₂) of this toxin (BthTX-I and BthTX-II) were chemically modified (alkylation) by p-bromophenacyl bromide (BPB) in order to study antibody production capacity in function of the structure-function relationship of these substances (crude venom and PLA₂ native and alkylated). BthTX-II showed enzymatic activity, while BthTX-I did not. Alkylation reduced BthTX-II activity by 50% while this process abolished the catalytic and myotoxic activities of BthTX-I, while reducing its edema-inducing activity by about 50%. Antibody production against the native and alkylated forms of BthTX-I and -II and the cross-reactivity of antibodies to native and alkylated toxins did not show any apparent differences and these observations were reinforced by surface plasmon resonance (SPR) data. Histopathological analysis of mouse gastrocnemius muscle sections after injection of PBS, BthTX-I, BthTX-II, or both myotoxins previously incubated with neutralizing antibody showed inhibition of the toxin-induced myotoxicity. These results reveal that the chemical modification of the phospholipases A₂ (PLA₂) diminished their toxicity but did not alter their antigenicity. This observation indicates that the modified PLA₂ may provide a biotechnological tool to attenuate the toxicity of the crude venom, by improving the production of antibodies and decreasing the local toxic effects of this poisonous substance in animals used to produce antivenom.

Synthesis of phospholipids on a glyceric acid scaffold: design and preparation of phospholipase A2 specific substrates

Synthesis of a new series of phospholipid analogues to serve as activity-based probes of secretory phospholipase A₂ enzymes is reported. The synthesis is based upon 1) preparation of long-chain esters and amides of glyceric acid, followed by 2) regioselective derivatization of the diol function of the molecule to achieve phosphorylation at the primary hydroxyl group, and to introduce the incipient sn-2-ester group of the target compounds. The sequence has been shown to allow incorporation of fluorescent, paramagnetic, and redox-active reporter groups, leading to phospholipid analogues applicable to detect and measure enzyme activity, to develop highly specific, real-time spectroscopic assay of phospholipase A₂ enzymes, as well as to track the metabolic fate of the hydrolysis products. The synthetic method has a great deal of flexibility to open the way to the design and synthesis of activity-probes for other phospholipid metabolizing enzymes as well.

Critical role of TLR2 and MyD88 for functional response of macrophages to a group IIA-secreted phospholipase A2 from snake venom

The snake venom MT-III is a group IIA secreted phospholipase A₂ (sPLA₂) enzyme with functional and structural similarities with mammalian pro-inflammatory sPLA₂s of the same group. Previously, we demonstrated that MT-III directly activates the innate inflammatory response of macrophages, including release of inflammatory mediators and formation of lipid droplets (LDs). However, the mechanisms coordinating these processes remain unclear. In the present study, by using TLR2^−/− or MyD88^−/− or C57BL/6 (WT) male mice, we report that TLR2 and MyD88 signaling have a critical role in MT-III-induced inflammatory response in macrophages. MT-III caused a marked release of PGE₂, PGD₂, PGJ₂, IL-1β and IL-10 and increased the number of LDs in WT macrophages. In MT-III-stimulated TLR2^−/− macrophages, formation of LDs and release of eicosanoids and cytokines were abrogated. In MyD88^−/− macrophages, MT-III-induced release of PGE₂, IL-1β and IL-10 was abrogated, but release of PGD₂ and PGJ₂ was maintained. In addition, COX-2 protein expression seen in MT-III-stimulated WT macrophages was abolished in both TLR2^−/− and MyD88^−/− cells, while perilipin 2 expression was abolished only in MyD88^−/− cells. We further demonstrated a reduction of saturated, monounsaturated and polyunsaturated fatty acids and a release of the TLR2 agonists palmitic and oleic acid from MT-III-stimulated WT macrophages compared with WT control cells, thus suggesting these fatty acids as major messengers for MT-III-induced engagement of TLR2/MyD88 signaling. Collectively, our findings identify for the first time a TLR2 and MyD88-dependent mechanism that underlies group IIA sPLA₂-induced inflammatory response in macrophages.

An Asp49 phospholipase A2 from snake venom induces cyclooxygenase-2 expression and prostaglandin E2 production via activation of NF-κB, p38MAPK, and PKC in macrophages

Phospholipases A2 (PLA2) are key enzymes for production of lipid mediators. We previously demonstrated that a snake venom sPLA2 named MT-III leads to prostaglandin (PG)E2 biosynthesis in macrophages by inducing the expression of cyclooxygenase-2 (COX-2). Herein, we explored the molecular mechanisms and signaling pathways leading to these MT-III-induced effects. Results demonstrated that MT-III induced activation of the transcription factor NF-κB in isolated macrophages. By using NF-κB selective inhibitors, the involvement of this factor in MT-III-induced COX-2 expression and PGE2 production was demonstrated. Moreover, MT-III-induced COX-2 protein expression and PGE2 release were attenuated by pretreatment of macrophages with SB202190, and Ly294002, and H-7-dihydro compounds, indicating the involvement of p38MAPK, PI3K, and PKC pathways, respectively. Consistent with this, MT-III triggered early phosphorylation of p38MAPK, PI3K, and PKC. Furthermore, SB202190, H-7-dihydro, but not Ly294002 treatment, abrogated activation of NF-κB induced by MT-III. Altogether, these results show for the first time that the induction of COX-2 protein expression and PGE2 release, which occur via NF-κB activation induced by the sPLA2-MT-III in macrophages, are modulated by p38MAPK and PKC, but not by PI3K signaling proteins.

Regulation of sPLA2-IID in Human Decidua: Insights Into the Complexity of the Prostaglandin Pathway in Labor

Prostaglandins are implicated in the labor process, yet the precise role and regulation of the prostaglandin pathway remains to be elucidated. The first step in the pathway is cleavage of membrane phospholipids by phospholipase A₂ (PLA₂). Previous work demonstrated upregulation of secretory PLA₂ (sPLA₂)-IIA with labor in human myometrium, and recent evidence shows that there are numerous PLA₂ isoforms. The present study investigates the potential of additional sPLA₂ isoforms during pregnancy and labor. Real-time reverse transcriptase-polymerase chain reaction (RT-PCR), Western blotting, and immunohistochemistry were used to determine sPLA₂ expression and localization. Results show the presence of sPLA₂-IID in amnion, chorion, placenta, decidua, and myometrium. Expression of sPLA₂-IID in decidua was significantly decreased in term labor compared to nonlabor patients, whereas no significant labor-associated changes were observed in other gestational tissues. Secretory PLA₂-IID was localized within chorion fibroblasts, placenta trophoblasts, decidual cells, and in myometrial smooth muscle cells. In primary decidual cell cultures, interleukin (IL) 10 (IL-10) increased sPLA₂-IID messenger RNA (mRNA) expression, while IL-1β had no effect on sPLA₂-IID mRNA expression. In conclusion, decreased expression of sPLA₂-IID in the decidua at labor indicates that it is unlikely to contribute to increased prostaglandin production during labor. However, increased expression of sPLA₂-IID, induced by IL-10, suggests that sPLA₂-IID may play an important anti-inflammatory role at the maternal-fetal interface. Nevertheless, precise functions of sPLA₂-IID within the human uterus remain to be determined.

Cytosolic phospholipase A₂ε drives recycling through the clathrin-independent endocytic route

Previous studies have demonstrated that membrane tubule-mediated transport events in biosynthetic and endocytic routes require phospholipase A2 (PLA2) activity. Here, we show that cytosolic phospholipase A2ε (cPLA2ε, also known as PLA2G4E) is targeted to the membrane compartments of the clathrin-independent endocytic route through a C-terminal stretch of positively charged amino acids, which allows the enzyme to interact with phosphoinositide lipids [especially PI(4,5)P2] that are enriched in clathrin-independent endosomes. Ablation of cPLA2ε suppressed the formation of tubular elements that carry internalized clathrin-independent cargoes, such as MHC-I, CD147 and CD55, back to the cell surface and, therefore, caused their intracellular retention. The ability of cPLA2ε to support recycling through tubule formation relies on the catalytic activity of the enzyme, because the inactive cPLA2ε(S420A) mutant was not able to recover either tubule growth or transport from clathrin-independent endosomes. Taken together, our findings indicate that cPLA2ε is a new important regulator of trafficking processes within the clathrin-independent endocytic and recycling route. The affinity of cPLA2ε for this pathway supports a new hypothesis that different PLA2 enzymes use selective targeting mechanisms to regulate tubule formation locally during specific trafficking steps in the secretory and/or endocytic systems.

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

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Micromolar changes in lysophosphatidylcholine concentration cause minor effects on mitochondrial permeability but major alterations in function

Mice deficient in group 1b phospholipase A2 have decreased plasma lysophosphatidylcholine and increased hepatic oxidation that is inhibited by intraperitoneal lysophosphatidylcholine injection. This study sought to identify a mechanism for lysophosphatidylcholine-mediated inhibition of hepatic oxidative function. Results showed that in vitro incubation of isolated mitochondria with 40-200μM lysophosphatidylcholine caused cyclosporine A-resistant swelling in a concentration-dependent manner. However, when mitochondria were challenged with 220μM CaCl2, cyclosporine A protected against permeability transition induced by 40μM, but not 80μM lysophosphatidylcholine. Incubation with 40-120μM lysophosphatidylcholine also increased mitochondrial permeability to 75μM CaCl2 in a concentration-dependent manner. Interestingly, despite incubation with 80μM lysophosphatidylcholine, the mitochondrial membrane potential was steady in the presence of succinate, and oxidation rates and respiratory control indices were similar to controls in the presence of succinate, glutamate/malate, and palmitoyl-carnitine. However, mitochondrial oxidation rates were inhibited by 30-50% at 100μM lysophosphatidylcholine. Finally, while 40μM lysophosphatidylcholine has no effect on fatty acid oxidation and mitochondria remained impermeable in intact hepatocytes, 100μM lysophosphatidylcholine inhibited fatty acid stimulated oxidation and caused intracellular mitochondrial permeability. Taken together, these present data demonstrated that LPC concentration dependently modulates mitochondrial microenvironment, with low micromolar concentrations of lysophosphatidylcholine sufficient to change hepatic oxidation rate whereas higher concentrations are required to disrupt mitochondrial integrity.

Molecular cloning and pharmacological properties of an acidic PLA2 from Bothrops pauloensis snake venom

In this work, we describe the molecular cloning and pharmacological properties of an acidic phospholipase A(2) (PLA(2)) isolated from Bothrops pauloensis snake venom. This enzyme, denominated BpPLA(2)-TXI, was purified by four chromatographic steps and represents 2.4% of the total snake venom protein content. BpPLA(2)-TXI is a monomeric protein with a molecular mass of 13.6 kDa, as demonstrated by Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) analysis and its theoretical isoelectric point was 4.98. BpPLA(2)-TXI was catalytically active and showed some pharmacological effects such as inhibition of platelet aggregation induced by collagen or ADP and also induced edema and myotoxicity. BpPLA(2)-TXI displayed low cytotoxicity on TG-180 (CCRF S 180 II) and Ovarian Carcinoma (OVCAR-3), whereas no cytotoxicity was found in regard to MEF (Mouse Embryonic Fibroblast) and Sarcoma 180 (TIB-66). The N-terminal sequence of forty-eight amino acid residues was determined by Edman degradation. In addition, the complete primary structure of 122 amino acids was deduced by cDNA from the total RNA of the venom gland using specific primers, and it was significantly similar to other acidic D49 PLA(2)s. The phylogenetic analyses showed that BpPLA(2)-TXI forms a group with other acidic D49 PLA(2)s from the gender Bothrops, which are characterized by a catalytic activity associated with anti-platelet effects.