Crystallization and preliminary X-ray crystallographic studies of a Lys49-phospholipase A2 homologue from Bothrops pirajai venom complexed with rosmarinic acid

PrTX-I, a noncatalytic and myotoxic Lys49-phospholipase A(2) from Bothrops pirajai venom, was crystallized in the presence of the inhibitor rosmarinic acid (RA). This is the active compound in the methanolic extract of Cordia verbenacea, a plant that is largely used in Brazilian folk medicine. The crystals diffracted X-rays to 1.8 A resolution and the structure was solved by molecular-replacement techniques, showing electron density that corresponds to RA molecules at the entrance to the hydrophobic channel. The crystals belong to space group P2(1)2(1)2(1), indicating conformational changes in the structure after ligand binding: the crystals of all apo Lys49-phospholipase A(2) structures belong to space group P3(1)21, while the crystals of complexed structures belong to space groups P2(1) or P2(1)2(1)2(1).

Phospholipase A2 and its molecular mechanism after spinal cord injury

Phospholipases A(2) (PLA(2)s) are a diverse family of lipolytic enzymes which hydrolyze the acyl bond at the sn-2 position of glycerophospholipids to produce free fatty acids and lysophospholipids. These products are precursors of bioactive eicosanoids and platelet-activating factor which have been implicated in pathological states of numerous acute and chronic neurological disorders. To date, more than 27 isoforms of PLA(2) have been found in the mammalian system which can be classified into four major categories: secretory PLA(2), cytosolic PLA(2), Ca(2+)-independent PLA(2), and platelet-activating factor acetylhydrolases. Multiple isoforms of PLA(2) are found in the mammalian spinal cord. Under physiological conditions, PLA(2)s are involved in diverse cellular responses, including phospholipid digestion and metabolism, host defense, and signal transduction. However, under pathological situations, increased PLA(2) activity, excessive production of free fatty acids and their metabolites may lead to the loss of membrane integrity, inflammation, oxidative stress, and subsequent neuronal injury. There is emerging evidence that PLA(2) plays a key role in the secondary injury process after traumatic spinal cord injury. This review outlines the current knowledge of the PLA(2) in the spinal cord with an emphasis being placed on the possible roles of PLA(2) in mediating the secondary SCI.

[Antioxidant efficacy in the treatment of cardiac metabolism disorders during endotoxicosis]

Chronic experiments on dogs showed that antioxidant drugs (reamberin, ximedone, vitamin E) are highly effective in correcting the functional and metabolic disorders in myocardium under endogenous intoxication conditions. Recovery of the functional activity was accompanied by correction of the lipid metabolism of cardiac cell structures. One mechanism of the drug action is related to a decrease in the lipid peroxidation rate and phospholipase A2 activity in cardiac tissue structures.

Phospholipase A(2) is required for PIN-FORMED protein trafficking to the plasma membrane in the Arabidopsis root

Phospholipase A(2) (PLA(2)), which hydrolyzes a fatty acyl chain of membrane phospholipids, has been implicated in several biological processes in plants. However, its role in intracellular trafficking in plants has yet to be studied. Here, using pharmacological and genetic approaches, the root hair bioassay system, and PIN-FORMED (PIN) auxin efflux transporters as molecular markers, we demonstrate that plant PLA(2)s are required for PIN protein trafficking to the plasma membrane (PM) in the Arabidopsis thaliana root. PLA(2)alpha, a PLA(2) isoform, colocalized with the Golgi marker. Impairments of PLA(2) function by PLA(2)alpha mutation, PLA(2)-RNA interference (RNAi), or PLA(2) inhibitor treatments significantly disrupted the PM localization of PINs, causing internal PIN compartments to form. Conversely, supplementation with lysophosphatidylethanolamine (the PLA(2) hydrolytic product) restored the PM localization of PINs in the pla(2)alpha mutant and the ONO-RS-082-treated seedling. Suppression of PLA(2) activity by the inhibitor promoted accumulation of trans-Golgi network vesicles. Root hair-specific PIN overexpression (PINox) lines grew very short root hairs, most likely due to reduced auxin levels in root hair cells, but PLA(2) inhibitor treatments, PLA(2)alpha mutation, or PLA(2)-RNAi restored the root hair growth of PINox lines by disrupting the PM localization of PINs, thus reducing auxin efflux. These results suggest that PLA(2), likely acting in Golgi-related compartments, modulates the trafficking of PIN proteins.

Influence of lipid heterogeneity and phase behavior on phospholipase A2 action at the single molecule level

We monitored the action of phospholipase A(2) (PLA(2)) on L- and D-dipalmitoyl-phosphatidylcholine (DPPC) Langmuir monolayers by mounting a Langmuir-trough on a wide-field fluorescence microscope with single molecule sensitivity. This made it possible to directly visualize the activity and diffusion behavior of single PLA(2) molecules in a heterogeneous lipid environment during active hydrolysis. The experiments showed that enzyme molecules adsorbed and interacted almost exclusively with the fluid region of the DPPC monolayers. Domains of gel state L-DPPC were degraded exclusively from the gel-fluid interface where the buildup of negatively charged hydrolysis products, fatty acid salts, led to changes in the mobility of PLA(2). The mobility of individual enzymes on the monolayers was characterized by single particle tracking. Diffusion coefficients of enzymes adsorbed to the fluid interface were between 3.2 microm(2)/s on the L-DPPC and 4.9 microm(2)/s on the D-DPPC monolayers. In regions enriched with hydrolysis products, the diffusion dropped to approximately 0.2 microm(2)/s. In addition, slower normal and anomalous diffusion modes were seen at the L-DPPC gel domain boundaries where hydrolysis took place. The average residence times of the enzyme in the fluid regions of the monolayer and on the product domain were between approximately 30 and 220 ms. At the gel domains it was below the experimental time resolution, i.e., enzymes were simply reflected from the gel domains back into solution.

Activation of immune-associated phospholipase A2 is functionally linked to Toll/Imd signal pathways in the red flour beetle, Tribolium castaneum

Bacterial challenge enhances phospholipase A(2) (PLA(2)) activity, which in turn induces biosynthesis of various eicosanoids that mediate non-self recognition signal to immune effectors in insects. But, there is little information on how PLA(2) activity is controlled after the non-self recognition. A recent genome analysis of the red flour beetle, Tribolium castaneum, has annotated both Toll and Imd signal pathways that are presumably considered to specifically respond to different microbial infections to express specific antimicrobial peptides (AMPs). This study set up a hypothesis that PLA(2) activation is linked to Toll and Imd pathways in T. castaneum. Bacterial challenge to the larvae of T. castaneum induced expressions of Toll and Imd genes. Different AMP genes were induced in larvae infected with Gram-positive or -negative bacteria. RNA interference using double-stranded RNAs (dsRNAs) specific to different Toll and Imd genes showed differential inhibition of these AMP expressions, indicating that the Toll and Imd pathways play critical roles in the production of AMPs by specifically responding to various bacterial challenges in T. castaneum. These Toll and Imd immune signals are also linked to the activation of PLA(2) in T. castaneum. Activation of PLA(2) was significantly induced in response to bacterial challenge, but was inhibited by dsRNAs specific to different Toll and Imd genes. The activation of PLA(2) via Toll and Imd pathways could be explained by induction of PLA(2) gene expression because the dsRNA treatments of Toll and Imd genes suppressed the gene expression of PLA(2) in response to bacterial challenge. The functional links were further supported by an immunofluorescence assay of PLA(2) intracellular translocation. Upon bacterial challenge, hemocytes from control larvae showed intracellular translocation of their PLA(2)s near to cell membrane, but hemocytes from larvae treated with dsRNAs of the Toll and Imd genes did not show the translocation, at which the PLA(2)s appeared to be evenly spread in the cytoplasm. These results suggest that recognition of bacterial challenge initiates Toll and Imd pathways in T. castaneum, which subsequently induces the activation of immune-associated PLA(2)s as well as gene expression of various AMPs.

Distinct role of Kruppel-like factor 11 in the regulation of prostaglandin E2 biosynthesis

Kruppel-like factor (KLF) proteins are emerging as key regulators of lipid metabolism, diabetes, and the biosynthesis of immunological cytokines. However, their role in the synthesis of prostaglandins, widely known biochemical mediators that act in a myriad of cell biological processes remain poorly understood. Consequently, in this study a comprehensive investigation at the cellular, biochemical, and molecular levels reveal that KLF11 inhibits prostaglandin E(2) synthesis via transcriptional silencing of the promoter of its biosynthetic enzyme, cytosolic phospholipase A2alpha. Mechanistically, KLF11 accomplishes this function by binding to the promoter via specific GC-rich sites and recruiting the Sin3-histone deacetylase chromatin remodeling complex. Further functional characterization reveals that this function of KLF11 can be reversed by epidermal growth factor receptor-AKT-mediated post-translational modification of threonine 56, a residue within its Sin3-binding domain. This is the first evidence supporting a relevant role for any KLF protein in doing both: transcriptionally inhibiting prostaglandin biosynthesis and its reversibility by an epidermal growth factor receptor-AKT signaling-mediated posttranslational mechanisms.

Up-regulation of the expressions of phospholipase A2 inhibitors in the liver of a venomous snake by its own venom phospholipase A2

Venomous snakes such as Gloydius brevicaudus have three distinct types of phospholipase A(2) inhibitors (PLIalpha, PLIbeta, and PLIgamma) in their blood so as to protect themselves from their own venom phospholipases A(2) (PLA(2)s). Expressions of these PLIs in G. brevicaudus liver were found to be enhanced by the intramuscular injection of its own venom. The enhancement of gene expressions of PLIalpha and PLIbeta in the liver was also found to be induced by acidic PLA(2) contained in this venom. Furthermore, these effects of acidic PLA(2) on gene expression of PLIs were shown to be unrelated to its enzymatic activity. These results suggest that these venomous snakes have developed the self-protective system against their own venom, by which the venom components up-regulate the expression of anti-venom proteins in their liver.

Effect of phospholipase A2 hydrolysis products on calcium oxalate precipitation at lipid interfaces

Urinary stones are commonly composed of an inorganic component, calcium oxalate, or calcium phosphate and an organic matrix of lipids, carbohydrates, and proteinaceous matter. Of interest is the role that the organic matrix elements may play as catalysts for the heterogeneous nucleation of the calcium salts, and a number of studies have examined the role of lipids in calcium oxalate monohydrate (COM) formation. In this study, products of lipid hydrolysis from phospholipase A(2) (PLA(2)) are examined for their effect on COM formation using Langmuir monolayers as model lipid membrane assemblies. The enzyme PLA(2) hydrolyzes DPPC monolayers in the presence of a supersaturated calcium oxalate subphase, inducing the rapid and plentiful nucleation of calcium oxalate at the lipid interface. To investigate the cause of increased crystal formation in the presence of the enzyme, Langmuir monolayers modeling the hydrolysis products were investigated. Calcium oxalate crystal growth at a ternary monolayer of dipalmitoylphosphatidylcholine (DPPC), palmitic acid (PA), and a 22-carbon chain lysophospholipid (22:0 Lyso PC) dramatically increases relative to monolayers of just DPPC. Binary monolayers of DPPC with either PA or the 22:0 Lyso PC and single-component monolayers of PA were also studied. It is demonstrated that the fatty acid generated during lipid hydrolysis causes a significant increase in the extent of heterogeneous nucleation of calcium oxalate from supersaturated solutions. The results imply a possible link between increased phospholipase activity, which is associated with hyperoxaluria, and calcium oxalate precipitation.

Interfacial binding dynamics of bee venom phospholipase A2 investigated by dynamic light scattering and quartz crystal microbalance

Bee venom phospholipase A(2) (bvPLA(2)) is part of the secretory phospholipase A(2) (sPLA(2)) family whose members are active in biological processes such as signal transduction and lipid metabolism. While controlling sPLA(2) activity is of pharmaceutical interest, the relationship between their mechanistic actions and physiological functions is not well understood. Therefore, we investigated the interfacial binding process of bvPLA(2) to characterize its biophysical properties and gain insight into how membrane binding affects interfacial activation. Attention was focused on the role of membrane electrostatics in the binding process. Although dynamic light scattering experiments indicated that bvPLA(2) does not lyse lipid vesicles, a novel, nonhydrolytic activity was discovered. We employed a supported lipid bilayer platform on the quartz crystal microbalance with dissipation sensor to characterize this bilayer-disrupting behavior and determined that membrane electrostatics influence this activity. The data suggest that (1) adsorption of bvPLA(2) to model membranes is not primarily driven by electrostatic interactions; (2) lipid desorption can follow bvPLA(2) adsorption, resulting in nonhydrolytic bilayer-disruption; and (3) this desorption is driven by electrostatic interactions. Taken together, these findings provide evidence that interfacial binding of bvPLA(2) is a dynamic process, shedding light on how membrane electrostatics can modulate interfacial activation.

Niacin skin flush test: a research tool for studying schizophrenia

BACKGROUND

A body of biochemical evidence suggests that abnormal phospholipid metabolism may play a role in the etiology of schizophrenia, and possibly, other psychiatric and neurological diseases. Niacin, a B-complex vitamin, induces prostaglandin synthesis, vasodilatation, and skin flushing when applied as a solution on the skin or taken orally. In schizophrenia, diminished or absent skin response to niacin represents a robust finding.

RESULTS

Attenuated niacin skin-flush response has been analysed as a potential biochemical marker of impaired prostaglandin signaling in schizophrenia. Diminished skin redness after topical application of niacin might be caused by a reduced level of the precursor arachidonic acid in the peripheral membranes, increased activity of the enzyme phospholipase A2, abnormal expression of niacin or prostaglandin receptors, or poor vasomotor activity of cutaneous capillary walls. Heritability estimates established in several studies support niacin skin flush response as a vulnerability trait for the development of psychosis. However, the exact mechanism of a reduced skin flush, the possible influence of the long-term use of antipsychotics, and the usefulness of the test for diagnostic purpose are not clear yet.

CONCLUSIONS

Niacin skin flush test is a simple, non-invasive and easily replicable method in the research of schizophrenia. The studies investigating niacin flushing in schizophrenia are numerous but incoherent regarding methods of niacin application and evaluation of the results. New studies, controlling adequately for age, sex, drug abuse, diet, as well as genetic factors that may influence the intensity and reaction time, are necessary to clarify the usefulness of niacin testing in psychiatry.

Brain arachidonic acid uptake and turnover: implications for signaling and bipolar disorder

PURPOSE OF REVIEW

Arachidonic acid was first detected in the brain in 1922. Although earlier work examined the role of arachidonic acid in growth and development, more recent advancements have elucidated roles for arachidonic acid in brain health and disease.

RECENT FINDINGS

In this review, we summarize evidence demonstrating that unesterified arachidonic acid in the plasma pool, which is supplied in part from adipose, is readily taken up and incorporated into brain phospholipids. By labeling plasma unesterified arachidonic acid, it is possible to trace the subsequent release of arachidonic acid from brain phospholipids upon neuroreceptor-mediated release by phospholipase A2 in response to drugs and neuroinflammation in rodents. With the synthesis of 11C labeled fatty acids, brain arachidonic acid signaling can now be measured in humans with position emission tomography. Arachidonic acid signals are known to regulate important biological functions, including neuroinflammation and excitotoxicity, and we focus on how the brain arachidonic acid cascade is a common target of drugs used to treat bipolar disorder (e.g. lithium, carbamazepine and valproate).

SUMMARY

A better understanding of the regulation of arachidonic acid uptake into the brain and the brain arachidonic acid cascade could lead to new imaging techniques and the identification of novel therapeutic targets in excitotoxicity, neuroinflammation and bipolar disorder.

Increased expression and activation of cytosolic phospholipase A2 in the spinal cord of patients with sporadic amyotrophic lateral sclerosis

Compelling evidence identifies a link between cytotoxic effects of cytosolic phospholipase A2 (cPLA2) activity and neuron death in cell cultures. cPLA2 catalyzes the hydrolysis of membrane phospholipids to produce and release arachidonate, leading to plasma membrane injury, inflammatory response and subsequent cell death. To assess a role for cPLA2 in the pathomechanism of amyotrophic lateral sclerosis (ALS), we performed immunohistochemical, immunoblot, and densitometric analyses of cPLA2 and its active form phosphorylated at S505 (p-cPLA2) on spinal cords obtained at autopsy from ten sporadic ALS patients and ten age-matched controls. On sections, immunoreactivities for cPLA2 and p-cPLA2 were distinct and localized in almost all of the motor neurons, reactive astrocytes, and activated microglia in the ALS cases, while immunoreactivities were only weak or not at all observed in neurons and glia in the control cases. On immunoblots, both the cPLA2/β-actin density ratio and the p-cPLA2/cPLA2 density ratio were significantly increased in the ALS group compared to the control group. There was no significant link between the densitometric data and the clinical phenotypes, age at death or disease duration of the ALS patients. These results provide in vivo evidence for increased expression and activation of cPLA2 in motor neurons, reactive astrocytes, and activated microglia in ALS, suggesting occurrence of arachidonate cascade-induced motor neuron death via cell-autonomous and/or non-cell-autonomous mechanisms.

Annexin-II, DNA, and histones serve as factor H ligands on the surface of apoptotic cells

Apoptotic cells are opsonized by complement components such as C1q and C3b, which increases their susceptibility to phagocytosis. Soluble complement inhibitors such as factor H (fH) also recognize apoptotic cells to minimize the pro-inflammatory effects of downstream complement activation. We used four radiolabeled protein constructs that span different regions of the 20 complement control protein (CCP) modules that make up fH and found that fragments comprising CCPs 6-8, CCPs 8-15, and CCPs 19-20 but not CCPs 1-4, bound to apoptotic Jurkat T cells. There are four possible ligand types on apoptotic cells that could recruit fH: proteins, carbohydrates, lipids, and DNA. We found that CCPs 6-8 of fH bind to annexin-II, a trypsin-insensitive protein that becomes exposed on surfaces of apoptotic cells. The second ligand of fH, which interacts with CCPs 6-8 and 19-20, is DNA. Confocal microscopy showed co-localization of fH with antibodies specific for DNA. fH also binds to histones devoid of DNA, and CCPs 1-4, 6-8, and 8-15 mediate this interaction. Treatment of apoptotic cells with neuraminidase, chondroitinase, heparitinase, and heparinase did not change fH binding. Treatment of apoptotic cells with phospholipase A(2) dramatically increased both binding of fH and cell-surface DNA. We also excluded the possibility that fH interacts with lysophospholipids using surface plasmon resonance and flow cytometry with lipid-coated beads. Identification of annexin-II as one of the fH ligands on apoptotic cells together with the fact that autoantibodies against annexin-II are found in systemic lupus erythematosus provides further insight into understanding the pathogenesis of this disease.

Transglutaminase 2, a novel regulator of eicosanoid production in asthma revealed by genome-wide expression profiling of distinct asthma phenotypes

Background

A frequent manifestation of asthma, exercise-induced bronchoconstriction (EIB), occurs in 30–50% of asthmatics and is characterized by increased release of inflammatory eicosanoids. The objective of this study was to identify genes differentially expressed in EIB and to understand the function of these genes in the biology of asthma.

Methodology/Principal Findings

Genome-wide expression profiling of airway leukocytes and epithelial cells obtained by induced sputum was conducted in two groups of subjects with asthma with and without EIB (n = 7 per group), at baseline and following exercise challenge. Based on the results of the gene expression study, additional comparisons were made with a normal control group (n = 10). Localization studies were conducted on epithelial brushings and biopsies from an additional group of asthmatics with EIB (n = 3). Genes related to epithelial repair and mast cell infiltration including β-tryptase and carboxypeptidase A3 were upregulated by exercise challenge in the asthma group with EIB. A gene novel to asthma pathogenesis, transglutaminase 2 (TGM2), was the most differentially expressed at baseline between the groups. In vivo studies confirmed the increased expression of TGM2 in airway cells and airway lining fluid, and demonstrate that TGM2 is avidly expressed in the asthmatic airway epithelium. In vitro studies using recombinant human enzymes reveal that TGM2 augments the enzymatic activity of secreted phospholipase A₂ (PLA₂) group X (sPLA₂-X), an enzyme recently implicated in asthma pathogenesis.

Conclusions/Significance

This study found that TGM2, a mediator that is novel to asthma pathogenesis, is overexpressed in asthmatic airways and functions to increase sPLA₂-X enzymatic activity. Since PLA₂ serves as the first rate-limiting step leading to eicosanoid formation, these results suggest that TGM2 may be a key initiator of the airway inflammatory cascade in asthma.

Biological and biochemical characterization of two new PLA2 isoforms Cdc-9 and Cdc-10 from Crotalus durissus cumanensis snake venom

This work reports the purification, biological characterization and amino acid sequence of two new basic PLA(2) isoforms, Cdc-9 and Cdc-10, purified from the Crotalus durissus cumanensis venom by one step analytical chromatography reverse phase HPLC. The molecular masses of the PLA(2) were 14,175+/-2.7 Da for Cdc-9 and 14,228+/-3.5 Da for Cdc-10 both deduced by primary structure and confirmed by MALDI-TOF. The isoforms presented an amino acid sequence of 122 amino acid residues, being Cdc-9: SLVQFNKMIK FETRKSGLPF YAAYGCYCGW GGQRPKDATD RCCFVHDCCY GKVAKCNTKW DIYSYSLKSG YITCGKGTWC KEQICECDRV AAECLRRSLS TYKNEYMFYP DSRCREPPEY TC with pI value of 8.25 and Cdc-10: SLLQFNKMIK FETRKSGVPF YAAYGCYCGW GGRRPKDPTD RCCFVHDCCY GKLTKCNTKW DIYSYSLKSG YITCGKGTWC KEQICECDRV AAECLRRSLN TYKNEYMFYP DSRCRGPPEY TC with a pI value of 8.46, showing highly conserved Ca(2+)-binding and catalytic sites. The PLA(2) activity decreased when the isoforms Cdc-9 and Cdc-10 were incubated with 4-bromophenacyl bromide (p-BPB), anhydrous acetic acid and p-nitrobenzene sulfonyl fluoride (NBSF) when compared with the activity of both native isoforms. In mice, the PLA(2) isoforms Cdc-9 and Cdc-10 induced myonecrosis and edema. Myotoxic and edema activities were reduced after treatment of the isoforms with p-BPB; acetylation of the lysine residues and the treatment of PLA(2) with NBSF have also induced edema reduction. However, p-BPB strongly diminishes the local and systemic myotoxic effects.

Prostaglandin expression profile in hypoxic osteoblastic cells

Conditions such as fracture and unloading have been shown to be associated with tissue and cellular hypoxia in bone. The effects of hypoxia on bone cell physiology and ultimately its impact on bone tissue repair and remodeling are not well understood. In this study, we investigated the role of hypoxia on prostaglandin release from osteoblastic cells cultured in 2% (hypoxia), 5% (potentially cellular normoxia), and 21% (normoxia for standard cell culture conditions) oxygen for up to 24 h. We quantified the effects of reduced oxygen tension on the release of prostaglandin (PG)E(2), PGF(2alpha), PGD(2), and PGI(2). The mechanism by which hypoxia increases PG production was investigated by examining the various regulatory components of the PG biosynthetic pathway. Our data show that PGE(2) levels alone are significantly elevated under hypoxic conditions. Also, we show that cyclooxygenase (COX)-1 and COX-2 play an important role in hypoxia-induced PGE(2) production, possibly via a mechanism involving changes in their respective activity levels under low oxygen conditions. The effect of hypoxia on PGE(2) levels was mimicked by dimethyloxaloglycine, a known activator of the HIF pathway. In addition, we confirmed that HIF-1alpha was stabilized in osteoblastic cells under hypoxia. Taken together these data suggest a role for the HIF pathway in regulation of PGE(2) levels under hypoxic conditions. Previous studies have detected release of prostaglandins from areas of damaged bone, such as a fracture site, and our data may contribute to an understanding of how this release is regulated.

Isolevuglandins covalently modify phosphatidylethanolamines in vivo: detection and quantitative analysis of hydroxylactam adducts

Levuglandins (LGs) and isolevuglandins (isoLGs, also called "isoketals" or "isoKs") are extraordinarily reactive products of cyclooxygenase- and free radical-induced oxidation of arachidonates. We now report the detection in vivo and quantitative analysis of LG/isoLG adducts that incorporate the amino group of phosphatidylethanolamines (PEs) into LG/isoLG-hydroxylactams. Notably, LC-MS/MS detection of these hydroxylactams is achieved with samples that are an order of magnitude smaller and sample processing is much simpler and less time consuming than required for measuring protein-derived LG/isoLG-lysyl lactams. A key feature of our protocol is treatment of biological phospholipid extracts with phospholipase A(2) to generate mainly 1-palmitoyl-2-lysoPE-hydroxylactams from heterogeneous mixtures of phospholipids with a variety of acyl groups on the 2 position. Over 160% higher mean levels of LG/isoLG-PE-hydroxylactam (P<0.001) were detected in liver from chronic ethanol-fed mice (32.4+/-6.3 ng/g, n=6) compared to controls (12.1+/-1.5 ng/g, n=4), and mean levels in plasma from patients with age-related macular degeneration (5.2+/-0.4 ng/ml, n=15) were elevated approximately 53% (P<0.0001) compared to those of healthy volunteers (3.4+/-0.1 ng/ml, n=15). Just as LG/isoLG-protein adducts provide a dosimeter of oxidative injury, this study suggests that LG/isoLG-PE-hydroxylactams are potential biomarkers for assessing risk for oxidative stress-stimulated diseases.

The stimulatory effect of angiotensin II on Na(+)-ATPase activity involves sequential activation of phospholipases and sustained PKC activity

Angiotensin II (Ang II) stimulates the proximal tubule Na(+)-ATPase through the AT(1) receptor/phosphoinositide phospholipase Cbeta (PI-PLCbeta)/protein kinase C (PKC) pathway. However, this pathway alone does not explain the sustained effect of Ang II on Na(+)-ATPase activity for 30 min. The aim of the present work was to elucidate the molecular mechanisms involved in the sustained effect of Ang II on Na(+)-ATPase activity. Ang II induced fast and correlated activation of Na(+)-ATPase and PKC activities with the maximal effect (115%) observed at 1 min and sustained for 30 min, indicating a pivotal role of PKC in the modulation of Na(+)-ATPase by Ang II. We observed that the sustained activation of PKC by Ang II depended on the sequential activation of phospholipase D and Ca(2+)-insensitive phospholipase A(2), forming phosphatidic acid and lysophosphatidic acid, respectively. The results indicate that PKC could be the final target and an integrator molecule of different signaling pathways triggered by Ang II, which could explain the sustained activation of Na(+)-ATPase by Ang II.

Cross-talk between oxysterols and glucocorticoids: differential regulation of secreted phopholipase A2 and impact on oligodendrocyte death

Background

Oxysterols are oxidized forms of cholesterol. They have been shown to be implicated in cholesterol turnover, inflammation and in neurodegenerative diseases such as Alzheimer's disease and multiple sclerosis. Glial cells are targets of oxysterols: they inhibit astrocyte proliferation after brain injury, and we have previously shown that 25-hydroxycholesterol (25OH) provokes oligodendrocyte apoptosis and stimulates the expression of sPLA2 type IIA (sPLA2-IIA), which has a protective effect.

Methodology/Principal Findings

As glucocorticoids are well-known for their anti-inflammatory effects, our aim was to understand their direct effects on oxysterol-induced responses in oligodendrocytes (sPLA2-IIA stimulation and apoptosis). We demonstrate that the synthetic glucocorticoid dexamethasone (Dex) abolishes the stimulation of sPLA2-IIA by 25-hydroxycholesterol (25-OH). This inhibition is mediated by the glucocorticoid receptor (GR), which decreases the expression of the oxysterol receptor Pregnane X Receptor (PXR) and interferes with oxysterol signaling by recruiting a common limiting coactivator PGC1α. Consistent with the finding that sPLA2-IIA can partially protect oligodendrocytes against oxysterol-triggered apoptosis, we demonstrate here that the inhibition of sPLA2-IIA by Dex accelerates the apoptotic phenomenon, leading to a shift towards necrosis. We have shown by atomic force microscopy and electron microscopy that 25-OH and Dex alters oligodendrocyte shape and disorganizes the cytoplasm.

Conclusions/Significance

Our results provide a new understanding of the cross-talk between oxysterol and glucocorticoid signaling pathways and their respective roles in apoptosis and oligodendrocyte functions.

The role of negatively charged lipids in lysosomal phospholipase A2 function

Lysosomal phospholipase A2 (LPLA2) is characterized by increased activity toward zwitterionic phospholipid liposomes containing negatively charged lipids under acidic conditions. The effect of anionic lipids on LPLA2 activity was investigated. Mouse LPLA2 activity was assayed as C2-ceramide transacylation. Sulfatide incorporated into liposomes enhanced LPLA2 activity under acidic conditions and was weakened by NaCl or increased pH. Amiodarone, a cationic amphiphilic drug, reduced LPLA2 activity. LPLA2 exhibited esterase activity when p-nitro-phenylbutyrate (pNPB) was used as a substrate. Unlike the phospholipase A2 activity, the esterase activity was detected over wide pH range and not inhibited by NaCl or amiodarone. Presteady-state kinetics using pNPB were consistent with the formation of an acyl-enzyme intermediate. C2-ceramide was an acceptor for the acyl group of the acyl-enzyme but was not available as the acyl group acceptor when dispersed in liposomes containing amiodarone. Cosedimentation of LPLA2 with liposomes was enhanced in the presence of sulfatide and was reduced by raising NaCl, amiodarone, or pH in the reaction mixture. LPLA2 adsorption to negatively charged lipid membrane surfaces through an electrostatic attraction, therefore, enhances LPLA2 enzyme activity toward insoluble substrates. Thus, anionic lipids present within lipid membranes enhance the rate of phospholipid hydrolysis by LPLA2 at lipid-water interfaces.

Plant phospholipases A2: perspectives on biotechnological applications

The recent progress in knowledge on biochemical properties and functions of phospholipases A(2) in plants paved the way for approving the suitability of these enzymes for commercial use now. The secreted phospholipases A(2), representing one type of phospholipases A(2) occurring in plants, show distinct differences in substrate specificities with respect to headgroup and acyl chains of the glycerophospholipids in comparison to their counterparts from animal sources. The other type of phospholipases A(2) in plants, the patatin-related phospholipases A(2), is characterized by broad substrate specificity. Accordingly, the unique properties of the plant enzymes open new horizons to engineered biocatalysts with improved performance, e.g., for vegetable oil refinement by degumming and for targeted modification of phospholipids.

[Cardioprotective and lipid-regulating effects of etoxidol with respect to surgical endotoxinemia]

Chronic experiments on stray dogs with modeling peritonitis showed that a complex therapy involving etoxidol favors improvement of the electrophysiological and metabolic heart activity and provides correction of the lipid distress syndrome. It is established that the lipid regulating effect of etoxidol is related not only to a decrease in the intensity of lipid peroxidation (LPO), but also to the A2-phospholipasae activity of this drug.

LRP1 controls cPLA2 phosphorylation, ABCA1 expression and cellular cholesterol export

BACKGROUND

ATP-binding cassette transporter A1 mediates apolipoprotein AI-dependent efflux of cholesterol and thereby removes cholesterol from peripheral tissues. ABCA1 expression is tightly regulated and deficiency of this cholesterol transporter results in cholesterol accumulation within cells. Low-density lipoprotein receptor-related protein 1 (LRP1) participates in lipid metabolism and energy homeostasis by endocytosis of apolipoprotein E-containing lipoproteins and modulation of cellular proliferation signals.

METHODS AND PRINCIPAL FINDINGS

In the present study, we demonstrate a new role for LRP1 in reverse cholesterol transport. Absence of LRP1 expression results in increased PDGFRbeta signaling and sequential activation of the mitogen-activated protein kinase signaling pathway, which increases phosphorylation of cytosolic phospholipase A(2) (cPLA(2)). Phosphorylated and activated cPLA(2) releases arachidonic acid from the phospholipid pool. Overproduction of arachidonic acid suppresses the activation of LXR/RXR heterodimers bound to the promoter of LXR regulated genes such as ABCA1, resulting in greatly reduced ABCA1 expression.

CONCLUSIONS AND SIGNIFICANCE

LRP1 regulates LXR-mediated gene transcription and participates in reverse cholesterol transport by controlling cPLA(2) activation and ABCA1 expression. LRP1 thus functions as a physiological integrator of cellular lipid homeostasis with signals that regulate cellular proliferation and vascular wall integrity.

Food searching strategy of amoeboid cells by starvation induced run length extension

Food searching strategies of animals are key to their success in heterogeneous environments. The optimal search strategy may include specialized random walks such as Levy walks with heavy power-law tail distributions, or persistent walks with preferred movement in a similar direction. We have investigated the movement of the soil amoebae Dictyostelium searching for food. Dictyostelium cells move by extending pseudopodia, either in the direction of the previous pseudopod (persistent step) or in a different direction (turn). The analysis of ∼4000 pseudopodia reveals that step and turn pseudopodia are drawn from a probability distribution that is determined by cGMP/PLA2 signaling pathways. Starvation activates these pathways thereby suppressing turns and inducing steps. As a consequence, starved cells make very long nearly straight runs and disperse over ∼30-fold larger areas, without extending more or larger pseudopodia than vegetative cells. This ‘win-stay/lose-shift’ strategy for food searching is called Starvation Induced Run-length Extension. The SIRE walk explains very well the observed differences in search behavior between fed and starving organisms such as bumble-bees, flower bug, hoverfly and zooplankton.

Phospholipase A2 and antioxidant enzyme activities in normal and PSE pork

In order to reveal the relationship between phospholipase A(2) and antioxidant enzymes and drip loss in pork, the study was designed to examine the effects of phospholipase A(2) and antioxidant enzymes on the water-holding capacity of pork during postmortem chilling. Six PSE and RFN samples (longissimus muscle) were used to determine the activities of phospholipase A(2) (tPLA(2,) cPLA(2)+sPLA(2) and iPLA(2)), superoxide dismutase (SOD) and GSH-Px, and acid phospholipase. The results showed that pH(1 h) and pH(24 h) from PSE pork were lower (p<0.01) than for normal pork (RFN), but the L* value at 1h and 24h postmortem, TBARS content, drip loss at 48 h and 96 h, cooking loss, tPLA(2) activity and iPLA(2) were higher (p<0.01) than of normal pork. Correlation analysis indicated that drip loss at 48 h was negatively related to pH(1 h) (p<0.01) and pH(24 h) (p<0.01) but positively to T(1 h) (p<0.01) and the activities of total phospholipase A(2) (p<0.05) and calcium-independent phospholipases A(2) (p<0.01). The tPLA(2) and GSH-Px play important roles in drip loss.

In retinal vein occlusion platelet response to thrombin is increased

INTRODUCTION

Retinal vein occlusion is a major cause of ocular morbidity. The precise mechanism leading to thrombosis in retinal vein occlusion has not yet been clearly elucidated. Several risk factors have been identified, including hypertension diabetes, history of cardiovascular disease, hypercholesterolemia, hyperhomocysteinaemia, increased ocular pressure and glaucoma. Although thrombus formation in the vein plays a significant role in the onset of retinal vein occlusion, the relationship between platelet aggregation and retinal vein occlusion remains to be clarified.

MATERIALS AND METHODS

In the present study the platelet response to thrombin in a selected group of retinal vein occlusion patients was investigated. Retinal vein occlusion patients were compared to a group of healthy subjects matched for age, sex, clinical and metabolic characteristics. In resting and activated platelets of both groups of subjects total protein tyrosine phosphorylation, p38MAPK and cytosolic phospholipase A(2) phosphorylation, arachidonic acid release, intracellular calcium levels, thromboxane B(2) and superoxide anion formation were measured.

RESULTS

Results show that platelets of patients were more responsive to thrombin than healthy subjects. In resting or in thrombin stimulated platelets of patients total protein tyrosine phosphorylation, p38MAPK and cytosolic phospholipase A(2) phosphorylation were increased. Also arachidonic acid release, thromboxane B(2) and superoxide anion formation were higher in patients than in healthy subjects. In addition intracellular calcium rise induced by thrombin was increased in patients.

CONCLUSIONS

Altogether data suggest that platelet hyperaggregability inducing thrombus formation might be an important factor in the onset and/or development of retinal vein occlusion.

Differential gene expression profiles in the venom gland/sac of Orancistrocerus drewseni (Hymenoptera: Eumenidae)

To determine differential gene expression profiles in the venom gland and sac (gland/sac) of a solitary hunting wasp species, Orancistrocerus drewseni Saussure (1857), a subtractive cDNA library was constructed by suppression subtractive hybridization. A total of 498 expressed sequence tags (EST) were clustered and assembled into 205 contigs (94 multiple sequences and 111 singletons). About 65% (134) of the contigs had matched BLASTx hits (E< or =10(-4)). Among these, 115 contigs had similarity to proteins with assigned molecular function in the Gene Ontology database, and most of them (112 contigs, 83%) were homologous to genes from Hymenoptera, particularly to Apis mellifera (98 contigs). The contigs encoding hyaluronidase and phospholipase A2, known to be main components of wasp venoms, were found in high frequencies (27 and 4%, respectively, as judged by the number of ESTs) in the gene ontology category of catalytic activity. Full-length open reading frames of hyaluronidase and phospholipase A2 were characterized and their abundance in the venom gland/sac was confirmed by quantitative real-time PCR. Several contigs encoding enzymes, including zinc-metallopeptidases that are likely involved in the processing and activation of venomous proteins or peptides, were also identified from the library. Discovery of venom gland/sac-specific genes should promote further studies on biologically active components in the venom of O. drewseni.

Ligand-based gene expression profiling reveals novel roles of glucocorticoid receptor in cardiac metabolism

Recent studies have documented various roles of adrenal corticosteroid signaling in cardiac physiology and pathophysiology. It is known that glucocorticoids and aldosterone are able to bind glucocorticoid receptor (GR) and mineralocorticoid receptor, and these ligand-receptor interactions are redundant. It, therefore, has been impossible to delineate how these nuclear receptors couple with corticosteroid ligands and differentially regulate gene expression for operation of their distinct functions in the heart. Here, to particularly define the role of GR in cardiac muscle cells, we applied a ligand-based approach involving the GR-specific agonist cortivazol (CVZ) and the GR antagonist RU-486 and performed microarray analysis using rat neonatal cardiomyocytes. We indicated that glucocorticoids appear to be a major determinant of GR-mediated gene expression when compared with aldosterone. Moreover, expression profiles of these genes highlighted numerous roles of glucocorticoids in various aspects of cardiac physiology. At first, we identified that glucocorticoids, via GR, induce mRNA and protein expression of a transcription factor Kruppel-like factor 15 and its downstream target genes, including branched-chain aminotransferase 2, a key enzyme for amino acid catabolism in the muscle. CVZ treatment or overexpression of KLF15 decreased cellular branched-chain amino acid concentrations and introduction of small-interfering RNA against KLF15 cancelled these CVZ actions in cardiomyocytes. Second, glucocorticoid-GR signaling promoted gene expression of the enzymes involved in the prostaglandin biosynthesis, including cyclooxygenase-2 and phospholipase A2 in cardiomyocytes. Together, we may conclude that GR signaling should have distinct roles for maintenance of cardiac function, for example, in amino acid catabolism and prostaglandin biosynthesis in the heart.

Thematic Review Series: Proteomics. An integrated omics analysis of eicosanoid biology

Eicosanoids have been implicated in a vast number of devastating inflammatory conditions, including arthritis, atherosclerosis, pain, and cancer. Currently, over a hundred different eicosanoids have been identified, with many having potent bioactive signaling capacity. These lipid metabolites are synthesized de novo by at least 50 unique enzymes, many of which have been cloned and characterized. Due to the extensive characterization of eicosanoid biosynthetic pathways, this field provides a unique framework for integrating genomics, proteomics, and metabolomics toward the investigation of disease pathology. To facilitate a concerted systems biology approach, this review outlines the proteins implicated in eicosanoid biosynthesis and signaling in human, mouse, and rat. Applications of the extensive genomic and lipidomic research to date illustrate the questions in eicosanoid signaling that could be uniquely addressed by a thorough analysis of the entire eicosanoid proteome.

Dietary soy protein selectively reduces renal prostanoids and cyclooxygenases in polycystic kidney disease

Increasing evidence in human chronic kidney disease and in animal models indicates the potential utility of dietary soy protein in the treatment of this disorder. A model in which a beneficial soy protein effect has been consistently demonstrated is the Han:SPRD-cy rat model of polycystic kidney disease. Therefore, since dietary soy protein alters renal hemodynamics and prostanoid production, the effects of dietary soy protein on renal prostanoids and related rate-limiting enzymes were examined. Normal and diseased weanling rats were given diets containing casein or soy protein for 7 wk. At 10 wk of age, renal levels of thromboxane B(2) (TXB(2), stable metabolite of TXA(2)), prostaglandin E(2) (PGE(2)) and 6-keto PGF(1alpha) (stable metabolite of PGI(2)) and activities of cyclooxygenase 1 (COX1) and COX2 were elevated in diseased compared to normal kidneys. Soy protein feeding resulted in 49% lower in vitro steady-state levels of TXB(2), and 76% less 6-keto PGF(1alpha) produced by COX1 activity in diseased kidneys, while not altering these parameters in normal kidneys. It also resulted in 47% less TXB(2) and 36% lower 6-keto PGF(1alpha) produced by COX2 activity in diseased kidneys. The relative effect of soy protein feeding on COX2 activity was in the order of TXB(2) > 6-keto PGF(1alpha) > PGE(2). Diseased kidneys had elevated protein and mRNA levels of cytosolic phospholipase A(2) (cPLA(2)) and COX1 and lower levels of COX2. Dietary soy protein attenuated the protein levels of cPLA(2) in diseased kidneys, and reduced COX2 mRNA expression in both normal and diseased kidneys. Dietary soy protein therefore reduced the levels of specific renal prostanoids, cPLA(2) and COX enzymes in this model of polycystic kidney disease, a model in which soy protein has been demonstrated to reduce disease progression.

The ordered extension of pseudopodia by amoeboid cells in the absence of external cues

Eukaryotic cells extend pseudopodia for movement. In the absence of external cues, cells move in random directions, but with a strong element of persistence that keeps them moving in the same direction Persistence allows cells to disperse over larger areas and is instrumental to enter new environments where spatial cues can lead the cell. Here we explore cell movement by analyzing the direction, size and timing of ∼2000 pseudopodia that are extended by Dictyostelium cells. The results show that pseudpopod are extended perpendicular to the surface curvature at the place where they emerge. The location of new pseudopods is not random but highly ordered. Two types of pseudopodia may be formed: frequent splitting of an existing pseudopod, or the occasional extension of a de novo pseudopod at regions devoid of recent pseudopod activity. Split-pseudopodia are extended at ∼60 degrees relative to the previous pseudopod, mostly as alternating Right/Left/Right steps leading to relatively straight zigzag runs. De novo pseudopodia are extended in nearly random directions thereby interrupting the zigzag runs. Persistence of cell movement is based on the ratio of split versus de novo pseudopodia. We identify PLA2 and cGMP signaling pathways that modulate this ratio of splitting and de novo pseudopodia, and thereby regulate the dispersal of cells. The observed ordered extension of pseudopodia in the absence of external cues provides a fundamental insight into the coordinated movement of cells, and might form the basis for movement that is directed by internal or external cues.

Cigarette smoke extract induces cytosolic phospholipase A2 expression via NADPH oxidase, MAPKs, AP-1, and NF-kappaB in human tracheal smooth muscle cells

Up-regulation of cytosolic phospholipase A2 (cPLA2) by cigarette smoke extract (CSE) may play a critical role in airway inflammatory diseases. However, the mechanisms underlying CSE-induced cPLA2 expression in human tracheal smooth muscle cells (HTSMCs) remain unknown. CSE induced cPLA2 protein and mRNA expression, and ROS generation was attenuated by pretreatment with a reactive oxygen species (ROS) scavenger (N-acetylcysteine), or inhibitors of NADPH oxidase (diphenyleneiodonium chloride, apocynin) and transfection with p47phox siRNA, suggesting that CSE-induced cPLA2 expression was mediated through NADPH oxidase activation and ROS production in HTSMCs. Furthermore, CSE-induced cPLA2 expression was attenuated by pretreatment with the inhibitors of MEK1/2 (U0126), p38 MAPK (SB202190), and JNK (SP600125), which were further confirmed by transfection with siRNAs of JNK1, p42, and p38 to down-regulate the expression of respective proteins and reduce cPLA2 expression. Induction of cPLA2 by CSE was attenuated by selective inhibitors of NF-kappaB (helenalin) and AP-1 (curcumin). Moreover, promoter assays revealed that increases of cPLA2, NF-kappaB, and AP-1 luciferase activities stimulated by CSE were attenuated by these inhibitors. These results suggest that in HTSMCs, CSE induced NADPH oxidase activation leading to phosphorylation of p42/p44 MAPK, p38 MAPK, and JNK. These reactions induced nuclear transcription NF-kappaB and AP-1 activities which were essential for CSE-induced cPLA2 gene expression.

[Immunologic theory investigation and discussion of pain caused by lumbar intervertebral disc herniation (LDH)]

To explore the main clinical manifestation (lower back pain and ischialgia) of LDH with immunologic method and study the relationship and clinical significance of the cardinal symptom (pain) and immune comple (IC), macrophage (MP),interleukin-1 (IL-1), interleukin-6 (IL-6), tumor necrosis factor (TNF), prostaglandin E2 (PGE2), phosphatidase A2 (PLA2), nitrogen monoxidum (NO) expressing, finding a new way in order to prevention and cure of LDH. We will review immunologic theory of LDH pain.

[Controlling arachidonic acid metabolic network: from single- to multi-target inhibitors of key enzymes]

Inflammatory diseases are common medical conditions seen in disorders of human immune system. There is a great demand for anti-inflammatory drugs. There are major inflammatory mediators in arachidonic acid metabolic network. Several enzymes in this network have been used as key targets for the development of anti-inflammatory drugs. However, specific single-target inhibitors can not sufficiently control the network balance and may cause side effects at the same time. Most inflammation induced diseases come from the complicated coupling of inflammatory cascades involving multiple targets. In order to treat these complicated diseases, drugs that can intervene multi-targets at the same time attracted much attention. The goal of this review is mainly focused on the key enzymes in arachidonic acid metabolic network, such as phospholipase A2, cyclooxygenase, 5-lipoxygenase and eukotriene A4 hydrolase. Advance in single target and multi-targe inhibitors is summarized.

Recent developments in the localization of oil body-associated signaling molecules during lipolysis in oilseeds

Prior to and/or accompanying lipolytic degradation of triacylglycerols (TAGs) during seed germination in oilseeds, certain enzymatic and non-enzymatic signaling molecules are expressed on the oil body membranes. These include certain proteases, lipoxygenase, phospholipase A(2) and lipase. Although enough biochemical investigations have demonstrated their activities, recent developments in the in situ localization of these signaling molecules in germinating oilseeds, have enhanced our understanding in this field. This is evident from the temporal and spatial changes observed in the expression pattern of some of these molecules. Present review aims at providing an up-to-date account of these recent developments in the author's and other laboratories, which are largely based on fluorescence microscopic and confocal laser scanning microscopic (CLSM) imaging of the molecular changes using specific fluorescent probes. A model for the molecular events associated with oil body mobilization is also being presented.

Meloxicam and meloxicam-beta-cyclodextrin complex in model membranes: effects on the properties and enzymatic lipolysis of phospholipid monolayers in relation to anti-inflammatory activity

Meloxicam, a nonsteroidal anti-inflammatory drug (NSAID), is known as a selective cyclooxygenase-2 inhibitor. Cyclooxygenase-2 is a membrane protein, functionally coupled to an interfacial enzyme, phospholipase A2. Consequently, it may be supposed that the interactions of NSAIDs with lipid membranes play a role in the anti-inflammatory process. In order to investigate the mechanism of this process, Langmuir films formed with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-dilauroyl-sn-glycero-3-phosphocholine, 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine, or 1,2-myristoyl-sn-glycero-3-phosphoethanolamine were exposed to meloxicam and its beta-cyclodextrin inclusion complex. The monolayers were studied by measuring surface pressure, electric surface potential, Brewster angle micrographs, polarization-modulation infrared reflection-absorption spectra, and phospholipase A2 activity; the inclusion complex was studied using molecular modeling. The results obtained show that the monolayers formed in the presence of meloxicam and its complex are expanded and more liquid-like compared to pure lipids. Both compounds modify hydration of the lipid polar heads, orientation of the molecules, morphology of the domains, and the rate of lipolysis catalyzed by phospholipase A2. The latter effect may be involved in the anti-inflammatory activity of meloxicam. Importantly, the effects observed with the meloxicam-beta-cyclodextrin complex are more pronounced compared to those of the free meloxicam. This observation may be relevant for developing new meloxicam preparations with increased bioavailability.

The cyclopentenone 15-deoxy-delta 12,14-prostaglandin J(2) delays lipopolysaccharide-induced preterm delivery and reduces mortality in the newborn mouse

Intrauterine infection is a common trigger for preterm birth and is also a risk factor for the subsequent development of neurodevelopmental abnormalities in the neonate. Bacterial lipopolysaccharide (LPS) binds to toll-like receptor-4 (TLR-4) to activate proinflammatory signaling pathways, which are implicated in both preterm delivery and antenatal brain injury. The transcription factor nuclear factor-kappaB (NF-kappaB) is a key player in the orchestration of the inflammatory response and has a central role in parturition. Here we show that intrauterine administration of TLR-4-specific LPS to pregnant mice results in the activation of NF-kappaB in the maternal uterus and the fetal brain, up-regulation of proinflammatory proteins cyclooxygenase-2, chemokine ligand 1, ChemoKine (C-C motif) ligand 2, and cytosolic phospholipase A(2) in myometrium, and induction of preterm delivery. 15-Deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) is an antiinflammatory prostaglandin that plays a role in promoting the resolution of inflammation. We report that coadministration of 15d-PGJ(2) and LPS to pregnant mice delays LPS-induced preterm delivery and confers protection from LPS-induced fetal mortality. This is associated with inhibition of myometrial NF-kappaB, cytosolic phospholipase A(2), and c-Jun N-terminal kinase activation, and of inflammatory protein synthesis. Therefore 15d-PGJ(2) has anti-inflammatory effects via inhibition of multiple aspects of inflammation-driven TRL-4 signaling pathway. Thus, 15d-PGJ(2) or compounds with similar antiinflammatory functions may have potential as therapeutic agents in the management of preterm labor with the added advantage of preventing detrimental effects to the fetus that may result from infection/inflammation.

Effect of Bacillus subtilis PB6, a natural probiotic on colon mucosal inflammation and plasma cytokines levels in inflammatory bowel disease

The pathophysiology of inflammatory bowel disease (IBD) involves the production of diverse lipid mediators, namely eicosanoid, lysophospholipids, and platelet-activating factor, in which phospholipase A2 (PLA2) is the key enzyme. Thus, it has been postulated that control of lipid mediators production by inhibition of PLA2 would be useful for the treatment of IBD. This hypothesis has been tested in the present study by examining the therapeutic effect of a novel natural probitic Bacillus subtilis PB6 (ATCC- PTA 6737). B. subtilis PB6 is found to secrete surfactins (cyclic lipopeptides) which have anti-bacterial potential. These surfactins inhibit PLA2, a rate-limiting enzyme involved in the arachidonic acid associated inflammatory pathway and could downregulate the inflammatory response by regulating the eicosanoid and cytokine pathways. With this concept, an experimental animal trial has been conducted in a rat model of 2, 4, 6-trinitrobenzene sulfonic acid (TNBS)-induced colitis. The oral administration of PB6 suppresses the colitis as measured by mortality rate, changes in the weight gain, colon morphology and the levels of plasma cytokines. The animals treated orally with PB6 at 1.5 x 10(8) CFU/kg thrice daily from day 4 to 10 significantly improve gross pathology of the colon and regain the colon weight to normal (p < 0.05), compared to TNBS-induced positive control. The plasma levels of pro-inflammatory cytokines (TNF-alpha, 1L-1beta, IL-6 and IFN-gamma) are also significantly lowered (p < 0.05) and anti-inflammatory cytokine (IL-I0 and TGF-beta) significantly (p < 0.05) increased after the oral administration of PB6 on day 11. The present study supports the concept that PB6 inhibits PLA2 by the secreting surfactins. In a clinical investigation, it is found to be well tolerated by all the healthy volunteers.

Exploring the antagonistic producer Streptomyces MSI051: implications of polyketide synthase gene type II and a ubiquitous defense enzyme phospholipase A2 in the host sponge Dendrilla nigra

To explore the functional role of the antagonistic producer strain Streptomyces dendra sp. nov. MSI051 in the host sponge Dendrilla nigra, hypothetical factors including the antagonistic potential of MSI051 against biofilm bacteria and a ubiquitous defense enzyme phospholipase A2 (PLA2) in host sponge as well as in bacterial symbiont MSI051 were determined. The host sponge D. nigra and associated bacterial symbiont MSI051 contained high levels of PLA2. The host sponge showed PLA2 activity to the extent of 1032 U/L, with a specific activity of 2021 U/g, and strain MSI051 showed similar activity. The findings of the present study suggest that PLA2 in the sponge-associated bacteria might have an integrated functional role in the host defense system of marine sponges. This report may be the first on the role of PLA2 activity in sponge-associated bacteria. Isolate MSI051 was a potential antagonistic producer which showed a broad spectrum of antibacterial activity. Polyketide synthase gene type II in MSI051 ultimately evidenced the antagonistic potential. Antimicrobial activity was found to be positively skewed toward biofilm bacteria. This implies a functional role of MSI051 in the protection of host sponge against fouling processes.

Acute but not chronic donepezil increases muscarinic receptor-mediated signaling via arachidonic acid in unanesthetized rats

Donepezil, an acetylcholinesterase (AChE) inhibitor used for treating Alzheimer's disease patients, is thought to act by increasing brain extracellular acetylcholine (ACh), and ACh binding to cholinergic receptors. Muscarinic receptors are coupled to cytosolic phospholipase A2 (cPLA2) activation and arachidonic acid (AA) release from synaptic membrane phospholipid. This activation can be imaged in rodents as an AA incorporation coefficient k*, using quantitative autoradiography. Acute and chronic effects of donepezil on the AA signal, k* for AA, were measured in 81 brain regions of unanesthetized rats. Twenty min after a single oral dose (3.0 mg/kg) of donepezil, k* was increased significantly in 37 brain regions, whereas k* did not differ from control 7 h afterwards or following chronic (21 days) of donepezil. Pretreatment with atropine prevented the 20-min increments in k* following donepezil. Donepezil also increased the brain ACh concentration and reduced brain AChE activity, but did not change cPLA2 activity, regardless of administration regimen. These results show that donepezil acutely increases the brain AA signal that is mediated by ACh acting at muscarinic receptors, but that this signal is rapidly desensitized despite continued elevated brain ACh concentration. In contrast, the AA signal in response to arecoline was not altered following donepezil.

Lipid mediators and vector infection: Trypanosoma rangeli inhibits Rhodnius prolixus hemocyte phagocytosis by modulation of phospholipase A2 and PAF-acetylhydrolase activities

In this work we investigated the effects of Trypanosoma rangeli infection through a blood meal on the hemocyte phagocytosis in experiments using the 5th instar larvae of Rhodnius prolixus. Hemocyte phagocytic activity was strongly blocked by oral infection with the parasites. In contrast, hemocyte phagocytosis inhibition caused by T. rangeli infection was rescued by exogenous arachidonic acid (20 microg/insect) or platelet activating factor (PAF; 1 microg/insect) applied by hemocelic injection. Following the oral infection with the protozoan we observed significant attenuation of phospholipase A2 (PLA2) activities in R. prolixus hemocytes (cytosolic PLA2: cPLA2, secreted PLA2: sPLA2 and Ca+2-independent PLA2: iPLA2) and enhancement of sPLA2 activities in cell-free hemolymph. At the same time, the PAF-acetyl hydrolase (PAF-AH) activity in the cell-free hemolymph increased considerably. Our results suggest that T. rangeli infection depresses eicosanoid and insect PAF analogous (iPAF) pathways giving support to the role of PLA2 in the regulation of arachidonic acid and iPAF biosynthesis and of PAF-AH by reducing the concentration of iPAF in R. prolixus. This illustrates the ability of T. rangeli to modulate the immune responses of R. prolixus to favor its own multiplication in the hemolymph.

The signal molecule lysophosphatidylcholine in Eschscholzia californica is rapidly metabolized by reacylation

In cultured cells of California poppy (Eschscholzia californica), lysophosphatidylcholine (LPC) triggers a signal path that finally induces alkaloid biosynthesis. LPC is transiently generated by elicitor-activated phospholipase A(2) of the plasma membrane. Externally added LPC is rapidly acylated by a membrane-bound enzyme that shows the highest specific activity in the purified plasma membrane. The fatty acid incorporated into the sn-2 position of LPC is preferentially linoleic (18:2), which is the most abundant acyl component in the PC species of Eschscholzia cells, but a minor component of the pool of free fatty acids. The fatty acid at the sn-1 position of LPC is less important for substrate specificity. The capacity of LPC acylation by intact cells or isolated plasma membranes by far exceeds the rate of LPC generation by activated phospholipase A(2) and is not limited by the availability of acyl donors. Metabolites other than phosphatidylcholine (PC) were not significantly produced from labeled LPC within 20 min, indicating that lysophospholipases are not significantly contributing to the short-time metabolism of LPC. It is concluded that reacylation to PC is the dominating process in the detoxication of LPC and ensures the transient character of its steady state concentrations, even at maximum phospholipase A(2) activities.

The secretion and uptake of lysosomal phospholipase A2 by alveolar macrophages

Macrophages have long been known to secrete a Phospholipase A(2) with an acidic pH optimum in response to phagocytic stimuli. However, the enzyme or enzymes responsible for this activity have not been identified. We report that mouse alveolar macrophages release lysosomal phospholipase A(2) (LPLA(2)) into the medium of cultured cells following stimulation with zymosan. The release of the enzyme was detected by enzymatic activity assays as well as by Western blotting using an Ab against mouse LPLA(2). LPLA(2) is a high mannose type glycoprotein found in lysosomes, suggesting that the released enzyme might be reincorporated into alveolar macrophages via a mannose or mannose phosphate receptor. Recombinant glycosylated mouse LPLA(2) produced by HEK293 cells was applied to LPLA(2)-deficient (LPLA(2)(-/-)) mouse alveolar macrophages. The uptake of exogenous LPLA(2) into LPLA(2)(-/-) alveolar macrophages occurred in a concentration-dependent manner. The LPLA(2) taken into the alveolar macrophages colocalized with the lysosomal marker, Lamp-1. This uptake was significantly suppressed in the presence of alpha-methyl-mannoside but not in the presence of mannose 6-phosphate. Thus, the predominant pathway for uptake of exogenous LPLA(2) is via the mannose receptor, with subsequent translocation into acidic, Lamp-1-associated compartments. LPLA(2)(-/-) alveolar macrophages are characterized by marked accumulation of phosphatidylcholine and phosphatidylethanolamine. Treatment with the recombinant LPLA(2) rescued the LPLA(2)(-/-) alveolar macrophages by markedly decreasing the phospholipid accumulation. The application of a catalytically inactive LPLA(2) revealed that the enzymatic activity of LPLA(2) was required for the phospholipid reduction. These studies identify LPLA(2) as a high m.w.-secreted Phospholipase A(2).

Effects of phospholipase and lipase treatments on photosystem II core dimer from a thermophilic cyanobacterium

Lipids are important components of transmembrane protein complexes. In order to study the roles of lipids in photosystem II (PSII), we treated the PSII core dimer complex from a thermophilic cyanobacterium Thermosynechococcus vulcanus with phospholipase A(2) (PLA(2)) and lipase, and examined their effects on PSII structure and function. PLA(2)-treatment decreased the content of phospholipid, phosphatidylglycerol (PG) by 59%, leading to a decrease of oxygen evolution by 40%. On the other hand, although treatment with lipase specifically decreased the content of monogalactosyldiacylglycerol (MGDG) by 52%, it decreased oxygen evolution only by 16%. This indicates that PG plays a more important role in PSII than MGDG. Both PLA(2)- and lipase-treatments induced neither the dissociation of PSII dimer, nor any loss of polypeptides. The degradation of PG resulted in a damage to the Q(B)-binding site as demonstrated from photoreduction activity of 2,6-dichlorophenolindophenol and chlorophyll fluorescence yields in the absence or presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea, and the dependencies of oxygen evolution on various electron acceptors before and after PLA(2)- or lipase-treatments. However, there were approximately three and five molecules of PG and MGDG per PSII reaction center left in the PSII dimeric complex after the PLA(2)- and lipase-treatments. These lipids are therefore bound to the interior of the protein matrix and resistant to the lipase treatments. The resistance of these lipids against PLA(2)- and lipase-treatments may be a specific feature of PSII from the thermophilic cyanobacterium, suggesting a possible correlation between binding of lipids and thermostability of PSII.

Myotoxic phospholipases A(2) isolated from Bothrops brazili snake venom and synthetic peptides derived from their C-terminal region: cytotoxic effect on microorganism and tumor cells

This paper reports the purification and biochemical/pharmacological characterization of two myotoxic phospholipases A(2) (PLA(2)s) from Bothrops brazili venom, a native snake from Brazil. Both myotoxins (MTX-I and II) were purified by a single chromatographic step on a CM-Sepharose ion-exchange column up to a high purity level, showing M(r) approximately 14,000 for the monomer and 28,000Da for the dimer. The N-terminal and internal peptide amino acid sequences showed similarity with other myotoxic PLA(2)s from snake venoms, MTX-I belonging to Asp49 PLA(2) class, enzymatically active, and MTX-II to Lys49 PLA(2)s, catalytically inactive. Treatment of MTX-I with BPB and EDTA reduced drastically its PLA(2) and anticoagulant activities, corroborating the importance of residue His48 and Ca(2+) ions for the enzymatic catalysis. Both PLA(2)s induced myotoxic activity and dose-time dependent edema similar to other isolated snake venom toxins from Bothrops and Crotalus genus. The results also demonstrated that MTXs and cationic synthetic peptides derived from their 115-129 C-terminal region displayed cytotoxic activity on human T-cell leukemia (JURKAT) lines and microbicidal effects against Escherichia coli, Candida albicans and Leishmania sp. Thus, these PLA(2) proteins and C-terminal synthetic peptides present multifunctional properties that might be of interest in the development of therapeutic strategies against parasites, bacteria and cancer.

Identification and functional characterization of adipose-specific phospholipase A2 (AdPLA)

Phospholipases A(2) (PLA(2)s) catalyze hydrolysis of fatty acids from the sn-2 position of phospholipids. Here we report the identification and characterization of a membrane-associated intracellular calcium-dependent, adipose-specific PLA(2) that we named AdPLA (adipose-specific phospholipase A(2)). We found that AdPLA was highly expressed specifically in white adipose tissue and was induced during preadipocyte differentiation into adipocytes. Clearance of AdPLA by immunoprecipitation significantly decreased PLA activity in white adipose tissue lysates but had no effect on liver lysates, where expression was hardly detectable. In characterizing AdPLA, we employed radiochemical assays with TLC analysis of the enzyme activity of lysates from COS-7 cells overexpressing AdPLA. For kinetic studies, we produced purified recombinant AdPLA for use in a lipoxidase-coupled spectrophotometric assay. AdPLA generated free fatty acid and lysophospholipid from phosphatidylcholine with a preference for hydrolysis at the sn-2 position. Although we found low but detectable lysophospholipase activity, AdPLA showed no significant activity against a variety of other lipid substrates. Calcium was found to activate AdPLA but was not essential for activity. Studies with known phospholipase inhibitors, including bromoenolactone, methyl arachidonyl fluorophosphate, AACOCF(3), 7,7-dimethyl-5,8-eicosadienoic acid, and thioetheramide, supported that AdPLA is a phospholipase. Mutational studies showed that His-23 and Cys-113 are critical for activity of AdPLA and suggested that AdPLA is likely a His/Cys PLA(2). Overall, although AdPLA is similar to other histidine phospholipases in pH and calcium dependence, AdPLA showed different characteristics in many regards, including predicted catalytic mechanism. AdPLA may therefore represent the first member of a new group of PLA(2)s, group XVI.