Pharmacological activity of Costus spicatus in experimental Bothrops atrox envenomation

CONTEXT

Medicinal plants encompass a rich source of active compounds that can neutralize snake venoms or toxins. Costus spicatus (Jacq.) Sw. (Costaceae) is used by the Amazonian population to treat inflammation, pain and other pathological manifestations.

OBJECTIVE

To evaluate the influence of C. spicatus aqueous extract on edema, peritonitis, nociception, coagulation, haemorrhage and indirect haemolytic activity induced by Bothrops atrox venom (BAV).

MATERIALS AND METHODS

Dried and pulverized leaves were extracted with distilled water. Envenoming was induced by administration of B. atrox snake venom in Swiss Webster mice. The experimental groups consisted of BAV (at the minimum dose to induce measurable biological responses) and C. spicatus extract (CSE, 1.25, 2.5, 5.0, 7.5 and 10 mg/kg/25 μl phosphate-buffered saline) administered individually and in combination (BAVCSE). PBS was used as a control. In vitro assays were also conducted in order to evaluate phospholipase A2 coagulant activities (indirect haemolytic method).

RESULTS

CSE significantly reduced the venom-induced edema and nociception at all concentrations tested and inhibited migration of inflammatory cells at the three least concentrations (5.0, 7.5 and 10 mg/kg/25 μl PBS). CSE was not effective in inhibiting coagulant, haemorrhagic and indirect haemolytic activities of the venom.

DISCUSSION AND CONCLUSION

The data suggest that CSE could exhibit a central mechanism for pain inhibition, and may also inhibit prostaglandin synthesis. These findings corroborate the traditional administration of C. spicatus decoction to treat inflammatory disorders, including those caused by B. atrox envenomation.

Modulatory effect of cadmium on the expression of phospholipase A2 and proinflammatory genes in rat testis

Cadmium (Cd) is a toxic metal that is hazardous to health, and its exposure showed a significant reduction in mitochondrial phospholipid function in the rat testes. Cd induction enhanced phospholipases (PLA2 s) activities, specifically the secretory PLA2 and cytosolic PLA2 . There was a reduction in mitochondrial membrane potential and significant decline in the respiratory complexes, which was confirmed by 2D blue native gel. The mRNA expression of cyclooxygenase and proinflammatory cytokine genes interleukin (IL)-1, IL-6, tumor necrosis factor-α, inducible nitric oxide synthase, and interferon-γ increased and that of anti-inflammatory cytokine IL-10 reduced with Cd exposure in a time-dependent manner. The gene expression of the proapoptotic factor Bax was elevated, and in parallel, the antiapoptotic factor Bcl2 was down-regulated. Hence, this study explored the testes under Cd toxicity and observed alterations in PLA2 s and mitochondrial membrane composition/function and further explored the impact of these alterations on proinflammation and apoptosis. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1176-1184, 2016.

Anti-inflammatory and anti-proliferative activities of the wild edible cruciferous: Diplotaxis simplex

Context The present study deals with new biological properties of the wild edible Diplotaxis simplex (Viv.) Spreng (Brassicaceae). Objectives The current study evaluates the antioxidant, the anti-inflammatory and the anti-cancer properties of ethyl acetate and ethanol extracts from D. simplex flowers. Materials and methods The anti-proliferative activity of the extracts (10-70 μg/mL) was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) against human colon cancer cell line Caco-2. The anti-inflammatory potential was evaluated by the inhibitory effect of the extracts (1.5-7.5 mg/mL) on phospholipase A2 activity as well as on carrageenan-induced paw oedema in mice. Extracts (200 mg/kg) or indomethacin (50 mg/kg) as positive control were injected intraperitoneally for albino mice prior to the induction of the oedema by carrageenan. Antioxidant activities were investigated using various complementary methods. Results Flower extracts contained a high level of polyphenolics (17.10-52.70 mg GAE/g) and flavonoids (74.20-100.60 mg QE/g), which correlate with its appreciable antioxidant potential in β-carotene peroxidation (IC50 value: 12.50-27.10 μg/mL), DPPH(•) radical-scavenging (IC50 value: 0.20-0.40 mg/mL), Fe(3+ )reducing (EC50 value: 0.10-0.14 mg/mL) and Fe(2+ )chelating (IC50 value: 0.20-0.60 mg/mL) assays. These extracts were effective in inhibiting cancer cell growth (IC50 value: 62.0-63.25 μg/mL). Besides, the ethyl acetate extract inhibited phospholipase A2 activity (IC50 value: 2.97 mg/mL) and reduced the paw oedema in mice (from 0.38 ± 0.01 to 0.24 ± 0.01 cm), 4 h post-carrageenan challenge. Conclusion These data suggest that D. simplex may be useful as a candidate in the treatment of inflammation and the colon cancer.

Cytosolic and Calcium-Independent Phospholipases A2 Activation and Prostaglandins E2 Are Associated with Escherichia coli-Induced Reduction of Insulin Secretion in INS-1E Cells

It is suspected that microbial infections take part in the pathogenesis of diabetes mellitus type 1 (T1DM). Glucose-induced insulin secretion is accompanied by the release of free arachidonic acid (AA) mainly by cytosolic- and calcium independent phospholipases A₂ (cPLA₂ and iPLA₂). Insulinoma cell line (INS-1E) was infected with E. coli isolated from the blood culture of a patient with sepsis. Invasion assay, Scanning Electron Microscopy and Transmission Electron Microscopy demonstrated the capacity of E. coli to enter cells, which was reduced by PLA₂ inhibitors. Glucose-induced insulin secretion was significantly increased after acute infection (8h) but significantly decreased after chronic infection (72h). PLA₂ activities, cPLA₂, iPLA₂, phospho-cPLA₂, and COX-2 expressions were increased after acute and, even more, after chronic E. coli infection. The silencing of the two isoforms of PLA₂s, with specific cPLA₂- or iPLA₂-siRNAs, reduced insulin secretion after acute infection and determined a rise in insulin release after chronic infection. Prostaglandins E₂ (PGE₂) production was significantly elevated in INS-1E after long-term E. coli infection and the restored insulin secretion in presence of L798106, a specific EP3 antagonist, and NS-398, a COX-2 inhibitor, and the reduction of insulin secretion in presence of sulprostone, a specific EP3 agonist, revealed their involvement in the effects triggered by bacterial infection. The results obtained demonstrated that cPLA₂ and iPLA₂ play a key role in insulin secretion process after E. coli infection. The high concentration of AA released is transformed into PGE₂, which could be responsible for the reduced insulin secretion.

Varespladib (LY315920) Appears to Be a Potent, Broad-Spectrum, Inhibitor of Snake Venom Phospholipase A2 and a Possible Pre-Referral Treatment for Envenomation

Snakebite remains a neglected medical problem of the developing world with up to 125,000 deaths each year despite more than a century of calls to improve snakebite prevention and care. An estimated 75% of fatalities from snakebite occur outside the hospital setting. Because phospholipase A2 (PLA2) activity is an important component of venom toxicity, we sought candidate PLA2 inhibitors by directly testing drugs. Surprisingly, varespladib and its orally bioavailable prodrug, methyl-varespladib showed high-level secretory PLA2 (sPLA2) inhibition at nanomolar and picomolar concentrations against 28 medically important snake venoms from six continents. In vivo proof-of-concept studies with varespladib had striking survival benefit against lethal doses of Micrurus fulvius and Vipera berus venom, and suppressed venom-induced sPLA2 activity in rats challenged with 100% lethal doses of M. fulvius venom. Rapid development and deployment of a broad-spectrum PLA2 inhibitor alone or in combination with other small molecule inhibitors of snake toxins (e.g., metalloproteases) could fill the critical therapeutic gap spanning pre-referral and hospital setting. Lower barriers for clinical testing of safety tested, repurposed small molecule therapeutics are a potentially economical and effective path forward to fill the pre-referral gap in the setting of snakebite.

Peroxiredoxin 6 (Prdx6) supports NADPH oxidase1 (Nox1)-based superoxide generation and cell migration

Nox1 is an abundant source of reactive oxygen species (ROS) in colon epithelium recently shown to function in wound healing and epithelial homeostasis. We identified Peroxiredoxin 6 (Prdx6) as a novel binding partner of Nox activator 1 (Noxa1) in yeast two-hybrid screening experiments using the Noxa1 SH3 domain as bait. Prdx6 is a unique member of the Prdx antioxidant enzyme family exhibiting both glutathione peroxidase and phospholipase A2 activities. We confirmed this interaction in cells overexpressing both proteins, showing Prdx6 binds to and stabilizes wild type Noxa1, but not the SH3 domain mutant form, Noxa1 W436R. We demonstrated in several cell models that Prdx6 knockdown suppresses Nox1 activity, whereas enhanced Prdx6 expression supports higher Nox1-derived superoxide production. Both peroxidase- and lipase-deficient mutant forms of Prdx6 (Prdx6 C47S and S32A, respectively) failed to bind to or stabilize Nox1 components or support Nox1-mediated superoxide generation. Furthermore, the transition-state substrate analogue inhibitor of Prdx6 phospholipase A2 activity (MJ-33) was shown to suppress Nox1 activity, suggesting Nox1 activity is regulated by the phospholipase activity of Prdx6. Finally, wild type Prdx6, but not lipase or peroxidase mutant forms, supports Nox1-mediated cell migration in the HCT-116 colon epithelial cell model of wound closure. These findings highlight a novel pathway in which this antioxidant enzyme positively regulates an oxidant-generating system to support cell migration and wound healing.

Connarus favosus Planch.: An inhibitor of the hemorrhagic activity of Bothrops atrox venom and a potential antioxidant and antibacterial agent

ETHNOPHARMACOLOGICAL RELEVANCE

The plant species Connarus favosus is used in folk medicine in the west of Pará state, Brazil, to treat snakebites.

AIM OF THE STUDY

To investigate the potential of the aqueous extract of Connarus favosus (AECf) to inhibit hemorrhagic and phospholipase A2 activities induced by Bothrops atrox venom (BaV) and to determine the antioxidant and antimicrobial potentials of the extract.

MATERIALS AND METHODS

AECf was analyzed phytochemically for phenolics (condensed tannins and hydrolyzable tannins) by colorimetry. Antioxidant activity was evaluated by quantitative assays using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and Fe(3+)/phenanthroline. Antimicrobial activity was evaluated by the minimal inhibitory concentration test, and cytotoxicity was evaluated using human fibroblast cells (MRC-5). Inhibition of BaV-induced hemorrhagic activity was assessed after oral administration of the extract using pre-treatment, post-treatment and combined (BA plus AECf) treatment protocols. Inhibition of indirect hemolysis caused by phospholipase A2 (PLA2) was investigated in vitro. Interaction between AECf and BaV was investigated by SDS-PAGE electrophoresis, Western blot (Wb) and zymography.

RESULTS

The phytochemical profile of AECf revealed ten secondary metabolite classes, and colorimetry showed high total phenolic and total (condensed and hydrolyzable) tannin content. AECf exhibited high antioxidant and antimicrobial potentials. The IC50 for the cytotoxic effect was 51.91 (46.86-57.50)µg/mL. Inhibition of BaV-induced hemorrhagic activity was significant in all the protocols, and inhibition of PLA2 activity was significant with the two highest concentrations. The BaV/AECf mixture produced the same bands as BaV by itself in SDS-PAGE and Wb although the bands were much fainter. Zymography confirmed the proteolytic activity of BaV, but when the venom was pre-incubated with AECf this activity was blocked.

CONCLUSION

AECf was effective in reducing BaV-induced hemorrhagic activity when administered by the same route as that used in folk medicine and exhibited antioxidant and antimicrobial potentials.

High-Density Lipoprotein Function in Exudative Age-Related Macular Degeneration

Purpose

High-density lipoproteins (HDL) have long been implicated in the pathogenesis of age-related macular degeneration (AMD). However, conflicting results have been reported with regard to the associations of AMD with HDL-cholesterol levels. The present study is the first to assess HDL composition and metrics of HDL function in patients with exudative AMD and control patients.

Methods

Blood samples were collected from 29 patients with exudative AMD and 26 age-matched control patients. Major HDL associated apolipoproteins were determined in apoB-depleted serum by immunoturbidimetry or ELISA, HDL-associated lipids were quantified enzymatically. To get an integrated measure of HDL quantity and quality, we assessed several metrics of HDL function, including cholesterol efflux capacity, anti-oxidative and anti-inflammatory activities using apoB-depleted serum from study participants.

Results

In our study, we observed that the HDL associated acute phase protein serum amyloid A (SAA) was significantly increased in AMD patients (p<0.01), whereas all other assessed apolipoproteins including ApoA-I, apoA-II, apoC-II, apoC-III and apoE as well as major HDL associated lipids were not altered. HDL efflux capacity, anti-oxidative capacity and arylesterase activity were not different in AMD patients when compared with the control group. The ability of apoB-depleted serum to inhibit monocyte NF-κB expression was significantly improved in AMD patients (mean difference (MD) -5.6, p<0.01). Moreover, lipoprotein-associated phospholipase A2 activity, a marker of vascular inflammation, was decreased in AMD subjects (MD -24.1, p<0.01).

Conclusions

The investigated metrics of HDL composition and HDL function were not associated with exudative AMD in this study, despite an increased content of HDL associated SAA in AMD patients. Unexpectedly, anti-inflammatory activity of apoB-depleted serum was even increased in our study. Our data suggest that the investigated parameters of serum HDL function showed no significant association with exudative AMD. However, we cannot exclude that alterations in locally produced HDL may be part of the AMD pathogenesis.

Peroxiredoxin 6 homodimerization and heterodimerization with glutathione S-transferase pi are required for its peroxidase but not phospholipase A2 activity

Peroxiredoxin 6 (Prdx6) is a unique 1-Cys member of the peroxiredoxin family with both GSH peroxidase and phospholipase A2 (PLA2) activities. It is highly expressed in the lung where it plays an important role in antioxidant defense and lung surfactant metabolism. Glutathionylation of Prdx6 mediated by its heterodimerization with GSH S-transferase π (πGST) is required for its peroxidatic catalytic cycle. Recombinant human Prdx6 crystallizes as a homodimer and sedimentation equilibrium analysis confirmed that this protein exists as a high affinity dimer in solution. Based on measurement of molecular mass, dimeric Prdx6 that was oxidized to the sulfenic acid formed a sulfenylamide during storage. After examination of the dimer interface in the crystal structure, we postulated that the hydrophobic amino acids L145 and L148 play an important role in homodimerization of Prdx6 as well as in its heterodimerization with πGST. Oxidation of Prdx6 also was required for its heterodimerization. Sedimentation equilibrium analysis and the Duolink proximity ligation assay following mutation of the L145 and L148 residues of Prdx6 to Glu indicated greatly decreased dimerization propensity reflecting the loss of hydrophobic interactions between the protein monomers. Peroxidase activity was markedly reduced by mutation at either of the Leu sites and was essentially abolished by the double mutation, while PLA2 activity was unaffected. Decreased peroxidase activity following mutation of the interfacial leucines presumably is mediated via impaired heterodimerization of Prdx6 with πGST that is required for reduction and re-activation of the oxidized enzyme.

Transformable DNA nanocarriers for plasma membrane targeted delivery of cytokine

Direct delivery of cytokines using nanocarriers holds great promise for cancer therapy. However, the nanometric scale of the vehicles made them susceptible to size-dependent endocytosis, reducing the plasma membrane-associated apoptosis signaling. Herein, we report a tumor microenvironment-responsive and transformable nanocarrier for cell membrane targeted delivery of cytokine. This formulation is comprised of a phospholipase A2 (PLA2) degradable liposome as a shell, and complementary DNA nanostructures (designated as nanoclews) decorated with cytokines as the cores. Utilizing the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) as a model cytokine, we demonstrate that the TRAIL loaded DNA nanoclews are capable of transforming into nanofibers after PLA2 activation. The nanofibers with micro-scaled lengths efficiently present the loaded TRAIL to death receptors on the cancer cell membrane and amplified the apoptotic signaling with reduced TRAIL internalization.

Quantifying Demyelination in NK venom treated nerve using its electric circuit model

Reduction of myelin in peripheral nerve causes critical demyelinating diseases such as chronic inflammatory demyelinating polyneuropathy, Guillain-Barre syndrome, etc. Clinical monitoring of these diseases requires rapid and non-invasive quantification of demyelination. Here we have developed formulation of nerve conduction velocity (NCV) in terms of demyelination considering electric circuit model of a nerve having bundle of axons for its quantification from NCV measurements. This approach has been validated and demonstrated with toad nerve model treated with crude Naja kaouthia (NK) venom and also shows the effect of Phospholipase A2 and three finger neurotoxin from NK-venom on peripheral nerve. This opens future scope for non-invasive clinical measurement of demyelination.

Exposure to p,p'-DDE Alters Macrophage Reactivity and Increases Macrophage Numbers in Adipose Stromal Vascular Fraction

Exposure to p,p'-DDE (DDE), the main bioaccumulative metabolite of the organochlorine insecticide p,p'-DDT, is associated with a higher prevalence of obesity, dyslipidemia, insulin resistance, metabolic syndrome, and immunomodulation. The present study was carried out to determine whether DDE perturbs adipose tissue homeostasis through modulation of macrophage function. Treatment with DDE or a cyclooxygenase-2 inhibitor prior to lipopolysaccharide exposure significantly decreased production of prostaglandins (PG) from J774a.1 macrophages in vitro. Similarly, J774A.1 cell lysates incubated with DDE or a specific cyclooxygenase-2 inhibitor (NS-398) produced significantly less PGE2 and PGF2α. Macrophage polarization studies revealed a pattern of DDE effects that were not fully consistent with a purely pro- or purely anti- M1 or M2 effect. However, DDE suppressed expression of two M1 markers (induced by an M1 stimulus) and enhanced expression of an M2 marker (induced by an M2 stimulus). Further studies including assessment of macrophage function are needed to fully characterize the effects of DDE on macrophage polarization. Obesity is characterized by an increase in the number of resident adipose tissue macrophages. To assess monocyte/macrophage recruitment to the adipose tissue in vivo, male C57Bl/6H mice were treated with 2 mg/kg DDE or corn oil vehicle for 5 days by gavage. Epididymal fat pads were digested and macrophage populations were analyzed by flow cytometry. In DDE-treated animals, there was a significant increase (37%) in F4/80(+)CD11b(+) macrophages/g of epididymal adipose over vehicle (P < .05). Together, these results suggest a role for DDE in the enhancement of adipose tissue macrophage recruitment and/or proliferation, as well as modulation of immune cell function that may contribute to the etiology of metabolic diseases associated with organochlorine exposure.

Lipoprotein X Causes Renal Disease in LCAT Deficiency

Human familial lecithin:cholesterol acyltransferase (LCAT) deficiency (FLD) is characterized by low HDL, accumulation of an abnormal cholesterol-rich multilamellar particle called lipoprotein-X (LpX) in plasma, and renal disease. The aim of our study was to determine if LpX is nephrotoxic and to gain insight into the pathogenesis of FLD renal disease. We administered a synthetic LpX, nearly identical to endogenous LpX in its physical, chemical and biologic characteristics, to wild-type and Lcat-/- mice. Our in vitro and in vivo studies demonstrated an apoA-I and LCAT-dependent pathway for LpX conversion to HDL-like particles, which likely mediates normal plasma clearance of LpX. Plasma clearance of exogenous LpX was markedly delayed in Lcat-/- mice, which have low HDL, but only minimal amounts of endogenous LpX and do not spontaneously develop renal disease. Chronically administered exogenous LpX deposited in all renal glomerular cellular and matrical compartments of Lcat-/- mice, and induced proteinuria and nephrotoxic gene changes, as well as all of the hallmarks of FLD renal disease as assessed by histological, TEM, and SEM analyses. Extensive in vivo EM studies revealed LpX uptake by macropinocytosis into mouse glomerular endothelial cells, podocytes, and mesangial cells and delivery to lysosomes where it was degraded. Endocytosed LpX appeared to be degraded by both human podocyte and mesangial cell lysosomal PLA2 and induced podocyte secretion of pro-inflammatory IL-6 in vitro and renal Cxl10 expression in Lcat-/- mice. In conclusion, LpX is a nephrotoxic particle that in the absence of Lcat induces all of the histological and functional hallmarks of FLD and hence may serve as a biomarker for monitoring recombinant LCAT therapy. In addition, our studies suggest that LpX-induced loss of endothelial barrier function and release of cytokines by renal glomerular cells likely plays a role in the initiation and progression of FLD nephrosis.

Phospholipase A2-Induced Remodeling Processes on Liquid-Ordered/Liquid-Disordered Membranes Containing Docosahexaenoic or Oleic Acid: A Comparison Study

Vesicle cycling, which is an important biological event, involves the interplay between membrane lipids and proteins, among which the enzyme phospholipase A2 (PLA2) plays a critical role. The capacity of PLA2 to trigger the budding and fission of liquid-ordered (L(o)) domains has been examined in palmitoyl-docosahexaenoylphosphatidylcholine (PDPC) and palmitoyl-oleoylphosphatidylcholine (POPC)/sphingomyelin/cholesterol membranes. They both exhibited a L(o)/liquid-disordered (L(d)) phase separation. We demonstrated that PLA2 was able to trigger budding in PDPC-containing vesicles but not POPC ones. The enzymatic activity, line tension, and elasticity of the membrane surrounding the L(o) domains are critical for budding. The higher line tension of Lo domains in PDPC mixtures was assigned to the greater difference in order parameters of the coexisting phases. The higher amount of lysophosphatidylcholine generated by PLA2 in the PDPC-containing mixtures led to a less-rigid membrane, compared to POPC. The more elastic L(d) membranes in PDPC mixtures exert a lower counteracting force against the L(o) domain bending.

Bee Venom Phospholipase A2: Yesterday's Enemy Becomes Today's Friend

Bee venom therapy has been used to treat immune-related diseases such as arthritis for a long time. Recently, it has revealed that group III secretory phospholipase A₂ from bee venom (bee venom group III sPLA₂) has in vitro and in vivo immunomodulatory effects. A growing number of reports have demonstrated the therapeutic effects of bee venom group III sPLA₂. Notably, new experimental data have shown protective immune responses of bee venom group III sPLA₂ against a wide range of diseases including asthma, Parkinson’s disease, and drug-induced organ inflammation. It is critical to evaluate the beneficial and adverse effects of bee venom group III sPLA₂ because this enzyme is known to be the major allergen of bee venom that can cause anaphylactic shock. For many decades, efforts have been made to avoid its adverse effects. At high concentrations, exposure to bee venom group III sPLA₂ can result in damage to cellular membranes and necrotic cell death. In this review, we summarized the current knowledge about the therapeutic effects of bee venom group III sPLA₂ on several immunological diseases and described the detailed mechanisms of bee venom group III sPLA₂ in regulating various immune responses and physiopathological changes.

Niacin Skin Sensitivity Is Increased in Adolescents at Ultra-High Risk for Psychosis

Background

Most studies provide evidence that the skin flush response to nicotinic acid (niacin) stimulation is impaired in schizophrenia. However, only little is known about niacin sensitivity in the ultra-high risk (UHR) phase of psychotic disorders.

Methods

We compared visual ratings of niacin sensitivity between adolescents at UHR for psychosis according to the one year transition outcome (UHR-T n = 11; UHR-NT n = 55) with healthy controls (HC n = 25) and first episode schizophrenia patients (FEP n = 25) treated with atypical antipsychotics.

Results

Contrary to our hypothesis niacin sensitivity of the entire UHR group was not attenuated, but significantly increased compared to the HC group, whereas no difference could be found between the UHR-T and UHR-NT groups. As expected, niacin sensitivity of FEP was attenuated compared to HC group. In UHR individuals niacin sensitivity was inversely correlated with omega-6 and -9 fatty acids (FA), but positively correlated with phospholipase A₂ (inPLA₂) activity, a marker of membrane lipid repair/remodelling.

Conclusions

Increased niacin sensitivity in UHR states likely indicates an impaired balance of eicosanoids and omega-6/-9 FA at a membrane level. Our findings suggest that the emergence of psychosis is associated with an increased mobilisation of eicosanoids prior to the transition to psychosis possibly reflecting a “pro-inflammatory state”, whereas thereafter eicosanoid mobilisation seems to be attenuated. Potential treatment implications for the UHR state should be further investigated.

Decrease of small dense LDL and lipoprotein-associated phospholipase A2 due to human growth hormone treatment in short children with growth hormone deficiency and small for gestational age status

BACKGROUND

Growth hormone deficiency (GHD) and small for gestational age (SGA) status are associated with cardiovascular risks. We therefore, investigated antiatherogenic effects of growth hormone (GH).

METHODS

Subfractions of low-density lipoprotein (LDL) and high-density lipoprotein (HDL), lipoprotein-associated phospholipase A2 (Lp-PLA2), and high-sensitivity C-reactive protein (hsCRP) were measured at baseline, after 8 and 52 weeks of GH treatment in 51 short children born SGA (n=33) or with GHD (n=18).

RESULTS

The overall group showed post-treatment reductions of LDL cholesterol (LDL-C) (p=0.016), small-dense LDL cholesterol (sdLDL-C, p<0.001), Lp-PLA2 (p<0.001), and hsCRP (p=0.005), but increase of HDL2a cholesterol (HDL2a-C, p=0.025). SGA children revealed significant correlations between Lp-PLA2 and LDL-C and sdLDL-C both before and after GH, significant reductions of sdLDL-C, Lp-PLA2, hsCRP, and an increase of HDL2a-C. GHD children showed the same lipid responses, though not significantly.

CONCLUSIONS

Children with GHD or born SGA may benefit from GH by growth acceleration and reduction of cardiovascular long-term risks.

The oxytocin receptor antagonist, Atosiban, activates pro-inflammatory pathways in human amnion via G(αi) signalling

Oxytocin (OT) plays an important role in the onset of human labour by stimulating uterine contractions and promoting prostaglandin/inflammatory cytokine synthesis in amnion via oxytocin receptor (OTR) coupling. The OTR-antagonist, Atosiban, is widely used as a tocolytic for the management of acute preterm labour. We found that in primary human amniocytes, Atosiban (10 μM) signals via PTX-sensitive Gαi to activate transcription factor NF-κB p65, ERK1/2, and p38 which subsequently drives upregulation of the prostaglandin synthesis enzymes, COX-2 and phospho-cPLA2 and excretion of prostaglandins (PGE2) (n = 6; p < 0.05, ANOVA). Moreover, Atosiban treatment increased expression and excretion of the inflammatory cytokines, IL-6 and CCL5. We also showed that OT-simulated activation of NF-κB, ERK1/2, and p38 and subsequent prostaglandin and inflammatory cytokine synthesis is via Gαi-2 and Gαi-3 but not Gαq, and is not inhibited by Atosiban. Activation or exacerbation of inflammation is not a desirable effect of tocolytics. Therefore therapeutic modulation of the OT/OTR system for clinical management of term/preterm labour should consider the effects of differential G-protein coupling of the OTR and the role of OT or selective OTR agonists/antagonists in activating proinflammatory pathways.

Phospholipase A2 as a Molecular Determinant of Store-Operated Calcium Entry

Activation of phospholipases A2 (PLA2) leads to the generation of biologically active lipid products that can affect numerous cellular events. Ca(2+)-independent PLA2 (iPLA2), also called group VI phospholipase A2, is one of the main types forming the superfamily of PLA2. Beside of its role in phospholipid remodeling, iPLA2 has been involved in intracellular Ca(2+) homeostasis regulation. Several studies proposed iPLA2 as an essential molecular player of store operated Ca(2+) entry (SOCE) in a large number of excitable and non-excitable cells. iPLA2 activation releases lysophosphatidyl products, which were suggested as agonists of store operated calcium channels (SOCC) and other TRP channels. Herein, we will review the important role of iPLA2 on the intracellular Ca(2+) handling focusing on its role in SOCE regulation and its implication in physiological and/or pathological processes.

Effect of firocoxib on cyclooxygenase 2, microsomal prostaglandin E2 synthase 1, and cytosolic phospholipase A2 gene expression in equine mononuclear cells

OBJECTIVE

To validate primer sets for use in reverse transcription quantitative PCR assays to measure gene expression of cytosolic phospholipase A2 (cPLA2) and microsomal prostaglandin E2 synthase 1 (mPGES1) in equine mononuclear cells and determine the effects of firocoxib, a selective cyclooxygenase 2 (COX-2) inhibitor, on COX-2, cPLA2, and mPGES1 gene expression following incubation of mononuclear cells with lipopolysaccharide (LPS).

ANIMALS

8 healthy adult horses.

PROCEDURES

Peripheral blood mononuclear cells were isolated by density gradient centrifugation and incubated at 37°C with medium alone, firocoxib (100 ng/mL), LPS (1 ng/mL or 1 μg/mL), or combinations of firocoxib and both LPS concentrations. After 4 hours, supernatants were collected and tested for prostaglandin E2 (PGE2) concentration with an enzyme inhibition assay, and gene expression in cell lysates was measured with PCR assays.

RESULTS

Primer pairs for cPLA2 and mPGES1 yielded single products on dissociation curve analyses, with mean assay efficiencies of 102% and 100%, respectively. Incubation with firocoxib and LPS significantly decreased PGE2 supernatant concentrations and significantly reduced COX-2 and mPGES1 gene expression, compared with values following incubation with LPS alone.

CONCLUSIONS AND CLINICAL RELEVANCE

Primer sets for mPGES1 and cPLA2 gene expression in equine mononuclear cells were successfully validated. Firocoxib significantly decreased LPS-induced COX-2 and mPGES1 expression, suggesting that it may be useful in the control of diseases in which expression of these genes is upregulated.

Critical role of peroxiredoxin 6 in the repair of peroxidized cell membranes following oxidative stress

Phospholipids are a major structural component of all cell membranes; their peroxidation represents a severe threat to cellular integrity and their repair is important to prevent cell death. Peroxiredoxin 6 (Prdx6), a protein with both GSH peroxidase and phospholipase A(2) (PLA(2)) activity, plays a critical role in antioxidant defense of the lung and other organs. We investigated the role of Prdx6 in the repair of peroxidized cell membranes in pulmonary microvascular endothelial cells (PMVEC) and isolated mouse lungs treated with tert-butyl hydroperoxide and lungs from mice exposed to hyperoxia (100% O(2)). Lipid peroxidation was evaluated by measurement of thiobarbituric acid reactive substances, oxidation of diphenyl-1-pyrenylphosphine, or ferrous xylenol orange assay. The exposure dose was varied to give a similar degree of lipid peroxidation at the end of exposure in the different models. Values for lipid peroxidation returned to control levels within 2 h after oxidant removal in wild-type PMVEC and perfused lungs but were unchanged in Pxdx6 null preparations. An intermediate degree of repair was observed with PMVEC and lungs that expressed only C47S or D140A mutant Prdx6; the former mutant does not have peroxidase activity, while the latter loses its PLA(2) activity. Prdx6 null mice showed markedly delayed recovery from lipid peroxidation during 20 h observation following exposure to hyperoxia. Thus, Prdx6 plays a critical role in the repair of peroxidized phospholipids in cell membranes and the recovery of lung cells from peroxidative stress; the peroxidase and PLA(2) activity each contribute to the recovery process.

H-rev107 Regulates Cytochrome P450 Reductase Activity and Increases Lipid Accumulation

H-rev107 is a member of the HREV107 type II tumor suppressor gene family and acts as a phospholipase to catalyze the release of fatty acids from glycerophospholipid. H-rev107 has been shown to play an important role in fat metabolism in adipocytes through the PGE2/cAMP pathway, but the detailed molecular mechanism underlying H-rev107-mediated lipid degradation has not been studied. In this study, the interaction between H-rev107 and cytochrome P450 reductase (POR), which is involved in hepatic lipid content regulation, was determined by yeast two-hybrid screen and confirmed by using in vitro pull down assays and immunofluorescent staining. The expression of POR in H-rev107-expressing cells enhanced the H-rev107-mediated release of arachidonic acid. However, H-rev107 inhibited POR activity and relieved POR-mediated decreased triglyceride content in HtTA and HeLa cervical cells. The inhibitory effect of H-rev107 will be abolished when POR-expressing cells transfected with PLA₂-lacking pH-rev107 or treated with PLA₂ inhibitor. Silencing of H-rev107 using siRNA resulted in increased glycerol production and reversion of free fatty acid-mediated growth suppression in Huh7 hepatic cells. In summary, our results revealed that H-rev107 is also involved in lipid accumulation in liver cells through the POR pathway via its PLA₂ activity.

PLA2-responsive and SPIO-loaded phospholipid micelles

PLA2-responsive and superparamagnetic iron oxide (SPIO) nanoparticle-loaded phospholipid micelles were developed. The release of a phospholipid-conjugated dye from these micelles was triggered due to phospholipid degradation by phospholipase A2. The high relaxivity of the encapsulated SPIO could enable non-invasive magnetic resonance imaging.

Anti-inflammatory activity studies on the stems and roots of Jasminum lanceolarium Roxb

Jasminum lanceolarium Roxb is an important traditional Chinese medicine. Its stems and roots have been used for the treatment of rheumatism and fever while the leaves are used as an anti-inflammatory agent to relieve pain. In order to support its traditional Chinese medicinal uses, five animal models were designed and the anti-inflammatory and analgesic properties of the 70% EtOH-H2O extracts of J. lanceolarium (EJL) were investigated. Meanwhile, biochemical parameters such as cyclooxygenase-2 (COX-2), 5-lipoxygenase (5-LOX) in blood serum of rats exposed to acute (carrageenan) inflammation model were evaluated. At doses of 400 mg/kg, EJL exhibited higher anti-inflammation effect than that of indomethacin and better analgesic activity than that of aspirin (P<0.001). Furthermore, eleven isolated compounds including six lignanoids (1, 2, 6, 7, 8, and 11) and five iridoids (3, 4, 5, 9, and 10) were isolated from the active extracts and showed significant anti-inflammatory activities with the IC50 values of 1.76-5.22 mg/mL, respectively, when testing their inhibitory effects on phospholipase A2 in vitro. The results demonstrated that the possible anti-inflammatory mechanisms might be attributed to inhibit the hydrolysis of membrane phospholipids, production on both COX-2 and 5-LOX, and then finally inhibit the release of prostaglandins (PGs), which suggested that EJL had a non-selective inhibitory effect on the release or actions of these mediators, and might be a dual LOX-COX inhibitor for the treatment of inflammation from the natural resource. The studies on the animals and the inflammatory mediators, along with the bioactive compounds presumed that the existences of iridoids and lignanoids could be response for their bioactivities of the whole plants.

Partial Characterization of Venom from the Colombian Spider Phoneutria Boliviensis (Aranae:Ctenidae)

We report on the first studies on the characterization of venom from Phoneutria boliviensis (Aranae:Ctenidae) (F. O. Pickard-Cambridge, 1897), done with Colombian species. After the electrostimulation extraction process, the venom showed physicochemical properties corresponding to a colorless and water-soluble liquid with a density of 0.86 mg/mL and 87% aqueous content. P. boliviensis venom and RP-HPLC fractions showed hemolytic activity and hydrolyzed the synthetic substrate 4-nitro-3-octanoyloxy-benzoic acid, indicating the presence of phospholipases A₂ enzymes. The electrophoretic profile showed an important protein content with molecular masses below 14 kDa, and differences between male and female protein content were also revealed. The RP-HPLC venom profile exposes differences between males and female content consistent with the electrophoretic profile. Five fractions collected from the RP-HPLC displayed significant larvicidal activity. Mass analysis indicates the presence of peptides ranging from 1047.71 to 3278.07 Da. Two peptides, Ctenitoxin-Pb48 and Ctenitoxin-Pb53, were partially identified using HPLC-nESI-MS/MS, which showed a high homology with other Ctenitoxins (family Tx3) from Phoneutria nigriventer, Phoneutria keyserlingi and Phoneutria reidyi affecting voltage-gated calcium receptors (Cav 1, 2.1, 2.2 and 2.3) and NMDA-glutamate receptors.

Periodontal microbiota and phospholipases: the Oral Infections and Vascular Disease Epidemiology Study (INVEST)

OBJECTIVE

Periodontal infections have been linked to cardiovascular disease, including atherosclerosis, and systemic inflammation has been proposed as a possible mediator. Secretory phospholipase A2 (s-PLA2) and Lipoprotein-associated PLA2 (Lp-PLA2) are inflammatory enzymes associated with atherosclerosis. No data are available on the association between oral microbiota and PLA2s. We studied whether a relationship exists between periodontal microbiota and the activities of these enzymes.

METHODS

The Oral Infection and Vascular Disease Epidemiology Study (INVEST) collected subgingival biofilms and serum samples from 593 dentate men and women (age 68.7 ± 8.6 years). 4561 biofilm samples were collected in the two most posterior teeth of each quadrant (average 7/participant) for quantitative assessment of 11 bacterial species using DNA-DNA checkerboard hybridization. Mean concentration of s-PLA2 and activities of s-PLA2 and Lp-PLA2 were regressed on tertiles of etiologic dominance (ED). ED is defined as the level of presumed periodontopathic species/combined level of all eleven species measured, and represents the relative abundance of periodontopathic organisms. Analyses were adjusted for age, sex, race/ethnicity, education, smoking, BMI, diabetes, LDL cholesterol and HDL cholesterol, and systolic blood pressure.

RESULTS

Higher levels of s-PLA2 activity were observed across increasing tertiles of etiologic dominance (0.66 ± 0.04 nmol ml(-1) min(-1), 0.73 ± 0.04 nmol ml(-1) min(-1), 0.89 ± 0.04 nmol ml-1 min-1; p < 0.001), with also a trend of association between Lp-PLA2 activity and ED (p = 0.07), while s-PLA2 concentration was unrelated to ED.

CONCLUSION

Increasingly greater s-PLA2 activity at higher tertiles of etiologic dominance may provide a mechanistic explanatory link of the relationship between periodontal microbiota and vascular diseases. Additional studies investigating the role of s-PLA2 are needed.

The Calcium Goes Meow: Effects of Ions and Glycosylation on Fel d 1, the Major Cat Allergen

The major cat allergen, Fel d 1, is a structurally complex protein with two N-glycosylation sites that may be filled by different glycoforms. In addition, the protein contains three putative Ca²⁺ binding sites. Since the impact of these Fel d 1 structure modifications on the protein dynamics, physiology and pathology are not well established, the present work employed computational biology techniques to tackle these issues. While conformational effects brought upon by glycosylation were identified, potentially involved in cavity volume regulation, our results indicate that only the central Ca²⁺ ion remains coordinated to Fel d 1 in biological solutions, impairing its proposed role in modulating phospholipase A₂ activity. As these results increase our understanding of Fel d 1 structural biology, they may offer new support for understanding its physiological role and impact into cat-promoted allergy.

Sulfated Galactan from Palisada flagellifera Inhibits Toxic Effects of Lachesis muta Snake Venom

In Brazil, snakebites are a public health problem and accidents caused by Lachesis muta have the highest mortality index. Envenomation by L. muta is characterized by systemic (hypotension, bleeding and renal failure) and local effects (necrosis, pain and edema). The treatment to reverse the evolution of all the toxic effects is performed by injection of antivenom. However, such therapy does not effectively neutralize tissue damage or any other local effect, since in most cases victims delay seeking appropriate medical care. In this way, alternative therapies are in demand, and molecules from natural sources have been exhaustively tested. In this paper, we analyzed the inhibitory effect of a sulfated galactan obtained from the red seaweed Palisada flagellifera against some toxic activities of L. muta venom. Incubation of sulfated galactan with venom resulted in inhibition of hemolysis, coagulation, proteolysis, edema and hemorrhage. Neutralization of hemorrhage was also observed when the galactan was administered after or before the venom injection; thus mimicking a real in vivo situation. Moreover, the galactan blocked the edema caused by a phospholipase A₂ isolated from the same venom. Therefore, the galactan from P. flagellifera may represent a promising tool to treat envenomation by L. muta as a coadjuvant for the conventional antivenom.

Cytoplasmic phospholipase A₂ modulation of adolescent rat ethanol-induced protein kinase C translocation and behavior

Ethanol consumption typically begins during adolescence, a developmental period which exhibits many age-dependent differences in ethanol behavioral sensitivity. Protein kinase C (PKC) activity is largely implicated in ethanol-behaviors, and our previous work indicates that regulation of novel PKC isoforms likely contributes to decreased high-dose ethanol sensitivity during adolescence. The cytoplasmic Phospholipase A2 (cPLA2) signaling cascade selectivity modulates novel and atypical PKC isoform activity, as well as adolescent ethanol hypnotic sensitivity. Therefore, the current study was designed to ascertain adolescent cPLA2 activity both basally and in response to ethanol, as well as it's involvement in ethanol-induced PKC isoform translocation patterns. cPLA2 expression was elevated during adolescence, and activity was increased only in adolescents following high-dose ethanol administration. Novel, but not atypical PKC isoforms translocate to cytosolic regions following high-dose ethanol administration. Inhibiting cPLA2 with AACOCF3 blocked ethanol-induced PKC cytosolic translocation. Finally, inhibition of novel, but not atypical, PKC isoforms when cPLA2 activity was elevated, modulated adolescent high-dose ethanol-sensitivity. These data suggest that the cPLA2/PKC pathway contributes to the acute behavioral effects of ethanol during adolescence.

Privileged frameworks from snake venom

Venom as a form of chemical prey capture is a key innovation that has underpinned the explosive radiation of the advanced snakes (Caenophidia). Small venom proteins are often rich in disulfide bonds thus facilitating stable molecular scaffolds that present key functional residues on the protein surface. New toxin types are initially developed through the venom gland over-expression of normal body proteins, their subsequent gene duplication and diversification that leads to neofunctionalisation as random mutations modify their structure and function. This process has led to preferentially selected (privileged) cysteine-rich scaffolds that enable the snake to build arrays of toxins many of which may lead to therapeutic products and research tools. This review focuses on cysteine-rich small proteins and peptides found in snake venoms spanning natriuretic peptides to phospholipase enzymes, while highlighting their three-dimensional structures and biological functions as well as their potential as therapeutic agents or research tools.

Phospholipase A2 regulation of lipid droplet formation

The classical regard of lipid droplets as mere static energy-storage organelles has evolved dramatically. Nowadays these organelles are known to participate in key processes of cell homeostasis, and their abnormal regulation is linked to several disorders including metabolic diseases (diabetes, obesity, atherosclerosis or hepatic steatosis), inflammatory responses in leukocytes, cancer development and neurodegenerative diseases. Hence, the importance of unraveling the cell mechanisms controlling lipid droplet biosynthesis, homeostasis and degradation seems evident Phospholipase A2s, a family of enzymes whose common feature is to hydrolyze the fatty acid present at the sn-2 position of phospholipids, play pivotal roles in cell signaling and inflammation. These enzymes have recently emerged as key regulators of lipid droplet homeostasis, regulating their formation at different levels. This review summarizes recent results on the roles that various phospholipase A2 forms play in the regulation of lipid droplet biogenesis under different conditions. These roles expand the already wide range of functions that these enzymes play in cell physiology and pathophysiology.

The role of lipoprotein-associated phospholipase A2 in a murine model of experimental autoimmune uveoretinitis

Macrophage activation is, in part, regulated via hydrolysis of oxidised low density lipoproteins by Lipoprotein-Associated phospholipase A₂ (Lp-PLA₂), resulting in increased macrophage migration, pro-inflammatory cytokine release and chemokine expression. In uveitis, tissue damage is mediated as a result of macrophage activation; hence inhibition of Lp-PLA₂ may limit macrophage activation and protect the tissue. Utilising Lp-PLA₂ gene-deficient (KO) mice and a pharmacological inhibitor of Lp-PLA₂ (SB-435495) we aimed to determine the effect of Lp-PLA₂ suppression in mediating retinal protection in a model of autoimmune retinal inflammation, experimental autoimmune uveoretinitis (EAU). Following immunisation with RBP-3 (IRBP) 1–20 or 161–180 peptides, clinical disease was monitored and severity assessed, infiltrating leukocytes were enumerated by flow cytometry and tissue destruction quantified by histology. Despite ablation of Lp-PLA₂ enzyme activity in Lp-PLA₂ KO mice or wild-type mice treated with SB-435495, the number of infiltrating CD45⁺ cells in the retina was equivalent to control EAU animals, and there was no reduction in disease severity. Thus, despite the reported beneficial effects of therapeutic Lp-PLA₂ depletion in a variety of vascular inflammatory conditions, we were unable to attenuate disease, show delayed disease onset or prevent progression of EAU in Lp-PLA₂ KO mice. Although EAU exhibits inflammatory vasculopathy there is no overt defect in lipid metabolism and given the lack of effect following Lp-PLA₂ suppression, these data support the hypothesis that sub-acute autoimmune inflammatory disease progresses independently of Lp-PLA₂ activity.

Polyunsaturated fatty acid-phospholipid remodeling and inflammation

PURPOSE OF REVIEW

To highlight some of the recent advances related to the control of polyunsaturated fatty acid (PUFA) incorporation and remodeling in membrane glycerophospholipids in inflammatory cells.

RECENT FINDINGS

Several enzymes have recently been identified that are associated with the control of PUFA incorporation and remodeling into membrane phospholipids and their release. The functional roles of the different enzyme isotypes in the control of PUFA availability for lipid mediator biosynthesis and cell signaling are only now being established. The expression of specific acyl-CoA synthetase, lysophospholipid acyltransferase and phospholipase A2 isotypes has recently been shown to have an impact on membrane PUFA content, on the production of lipid mediators and on inflammation.

SUMMARY

A better understanding of the complex processes associated with the control PUFA remodeling in membrane phospholipids may lead to the discovery of new therapeutic targets for the treatment of inflammatory diseases.

Structures and binding studies of the complexes of phospholipase A2 with five inhibitors

Phospholipase A2 (PLA2) catalyzes the hydrolysis of phospholipids into arachidonic acid and lysophospholipids. Arachidonic acid is used as a substrate in the next step of the multistep pathway leading to the production of eicosanoids. The eicosanoids, in extremely low concentrations, are required in a number of physiological processes. However, the increase in their concentrations above the essential physiological requirements leads to various inflammatory conditions. In order to prevent the unwanted rise in the concentrations of eicosanoids, the actions of PLA2 and other enzymes of the pathway need to be blocked. We report here the structures of five complexes of group IIA PLA2 from Daboia russelli pulchella with tightly binding inhibitors, (i) p-coumaric acid, (ii) resveratrol, (iii) spermidine, (iv) corticosterone and (v) gramine derivative. The binding studies using fluorescence spectroscopy and surface plasmon resonance techniques for the interactions of PLA2 with the above five compounds showed high binding affinities with values of dissociation constants (KD) ranging from 3.7×10(-8) M to 2.1×10(-9) M. The structure determinations of the complexes of PLA2 with the above five compounds showed that all the compounds bound to PLA2 in the substrate binding cleft. The protein residues that contributed to the interactions with these compounds included Leu2, Leu3, Phe5, Gly6, Ile9, Ala18, Ile19, Trp22, Ser23, Cys29, Gly30, Cys45, His48, Asp49 and Phe106. The positions of side chains of several residues including Leu2, Leu3, Ile19, Trp31, Lys69, Ser70 and Arg72 got significantly shifted while the positions of active site residues, His48, Asp49, Tyr52 and Asp99 were unperturbed.

Multivalent nanoparticle networks enable point-of-care detection of human phospholipase-A2 in serum

A rapid and highly sensitive point-of-care (PoC) lateral flow assay for phospholipase A2 (PLA2) is demonstrated in serum through the enzyme-triggered release of a new class of biotinylated multiarmed polymers from a liposome substrate. Signal from the enzyme activity is generated by the adhesion of polystreptavidin-coated gold nanoparticle networks to the lateral flow device, which leads to the appearance of a red test line due to the localized surface plasmon resonance effect of the gold. The use of a liposome as the enzyme substrate and multivalent linkers to link the nanoparticles leads to amplification of the signal, as the cleavage of a small amount of lipids is able to release a large amount of polymer linker and adhesion of an even larger amount of gold nanoparticles. By optimizing the molecular weight and multivalency of these biotinylated polymer linkers, the sensitivity of the device can be tuned to enable naked-eye detection of 1 nM human PLA2 in serum within 10 min. This high sensitivity enabled the correct diagnosis of pancreatitis in diseased clinical samples against a set of healthy controls using PLA2 activity in a point-of-care device for the first time.

Enzyme-specific sensors via aggregation of charged p-phenylene ethynylenes

Chemical and biological sensors are sought for their ability to detect enzymes as biomarkers for symptoms of various disorders, or the presence of chemical pollutants or poisons. p-Phenylene ethynylene oligomers with pendant charged groups have been recently shown to have ideal photophysical properties for sensing. In this study, one anionic and one cationic oligomer are combined with substrates that are susceptible to enzymatic degradation by phospholipases or acetylcholinesterases. The photophysical properties of the J-aggregated oligomers with the substrate are ideal for sensing, with fluorescence quantum yields of the sensors enhanced between 30 and 66 times compared to the oligomers without substrate. The phospholipase sensor was used to monitor the activity of phospholipase A1 and A2 and obtain kinetic information, though phospholipase C did not degrade the sensor. The acetylcholinesterase sensor was used to monitor enzyme activity and was also used to detect the inhibition of acetylcholinesterase by three different inhibitors. Phospholipase A2 is a biomarker for heart and circulatory disease, and acetylcholinesterase is a biomarker for Alzheimer's, and indicative of exposure to certain pesticides and nerve agents. This work shows that phenylene ethynylene oligomers can be tailored to enzyme-specific sensors by careful selection of substrates that induce formation of a molecular aggregate, and that the sensing of enzymes can be extended to enzyme kinetics and detection of inhibition. Furthermore, the aggregates were studied through all-atom molecular dynamics, providing a molecular-level view of the formation of the molecular aggregates and their structure.

Membrane-mediated actions of 1,25-dihydroxy vitamin D3: a review of the roles of phospholipase A2 activating protein and Ca(2+)/calmodulin-dependent protein kinase II

The secosteroid 1α,25-dihydroxy vitamin D3 [1α,25(OH)2D3] acts on cells via classical steroid hormone receptor-mediated gene transcription and by initiating rapid membrane-mediated signaling pathways. In its membrane-initiated pathway, after 1α,25(OH)2D3 interacts with protein disulfide isomerase, family A, member 3 (Pdia3) in caveolae, phospholipase A2 (PLA2) and protein kinase C (PKC) are activated. Recent efforts to determine the signaling proteins involved in the 1α,25(OH)2D3 signal from Pdia3 to PLA2 have indicated that phospholipase A2 activating protein (PLAA) and Ca(2+)/calmodulin-dependent kinase II (CaMKII) are required. PLAA is located in caveolae, where it interacts with Pdia3 and caveolin-1 (Cav-1) to initiate rapid signaling via CaMKII, activating PLA2, leading to activation of protein kinase C (PKC) and PKC-dependent responses.

Membranes serve as allosteric activators of phospholipase A2, enabling it to extract, bind, and hydrolyze phospholipid substrates

Defining the molecular details and consequences of the association of water-soluble proteins with membranes is fundamental to understanding protein-lipid interactions and membrane functioning. Phospholipase A2 (PLA2) enzymes, which catalyze the hydrolysis of phospholipid substrates that compose the membrane bilayers, provide the ideal system for studying protein-lipid interactions. Our study focuses on understanding the catalytic cycle of two different human PLA2s: the cytosolic Group IVA cPLA2 and calcium-independent Group VIA iPLA2. Computer-aided techniques guided by deuterium exchange mass spectrometry data, were used to create structural complexes of each enzyme with a single phospholipid substrate molecule, whereas the substrate extraction process was studied using steered molecular dynamics simulations. Molecular dynamic simulations of the enzyme-substrate-membrane systems revealed important information about the mechanisms by which these enzymes associate with the membrane and then extract and bind their phospholipid substrate. Our data support the hypothesis that the membrane acts as an allosteric ligand that binds at the allosteric site of the enzyme's interfacial surface, shifting its conformation from a closed (inactive) state in water to an open (active) state at the membrane interface.

"Self" and "non-self" in the control of phytoalexin biosynthesis: plant phospholipases A2 with alkaloid-specific molecular fingerprints

The overproduction of specialized metabolites requires plants to manage the inherent burdens, including the risk of self-intoxication. We present a control mechanism that stops the expression of phytoalexin biosynthetic enzymes by blocking the antecedent signal transduction cascade. Cultured cells of Eschscholzia californica (Papaveraceae) and Catharanthus roseus (Apocynaceae) overproduce benzophenanthridine alkaloids and monoterpenoid indole alkaloids, respectively, in response to microbial elicitors. In both plants, an elicitor-responsive phospholipase A2 (PLA2) at the plasma membrane generates signal molecules that initiate the induction of biosynthetic enzymes. The final alkaloids produced in the respective plant inhibit the respective PLA, a negative feedback that prevents continuous overexpression. The selective inhibition by alkaloids from the class produced in the "self" plant could be transferred to leaves of Nicotiana benthamiana via recombinant expression of PLA2. The 3D homology model of each PLA2 displays a binding pocket that specifically accommodates alkaloids of the class produced by the same plant, but not of the other class; for example, C. roseus PLA2 only accommodates C. roseus alkaloids. The interaction energies of docked alkaloids correlate with their selective inhibition of PLA2 activity. The existence in two evolutionary distant plants of phospholipases A2 that discriminate "self-made" from "foreign" alkaloids reveals molecular fingerprints left in signal enzymes during the evolution of species-specific, cytotoxic phytoalexins.

[The Progress of Research About Pancreatic Lipase]

During the digestive procedure, pancreatic lipase is known as the main enzyme in vivo for digestion and absorption of dietary fat, consisting of pancreatic triglyceride lipase, pancreatic lipase related proteins 1 and 2, bile salt - stimulated Lipase and phospholipase A2. The changes of the development pattern of pancreatic lipase have confirmed associations with metabolic diseases such as obesity, not only because age is connected with the development of pancreatic lipase, but also pancreatic lipase itself is regulated by the dietary structure and endocrine hormone.

Membrane actions of 1α,25(OH)2D3 are mediated by Ca(2+)/calmodulin-dependent protein kinase II in bone and cartilage cells

1α,25(OH)2D3 regulates osteoblasts and chondrocytes via its membrane-associated receptor, protein disulfide isomerase A3 (Pdia3) in caveolae. 1α,25(OH)2D3 binding to Pdia3 leads to phospholipase-A2 (PLA2)-activating protein (PLAA) activation, stimulating cytosolic PLA2 and resulting in prostaglandin E2 (PGE2) release and PKCα activation, subsequently stimulating differentiation. However, how PLAA transmits the signal to cPLA2 is unknown. Ca(2+)/calmodulin (CaM)-dependent protein kinase II (CaMKII) activation is required for PLA2 activation in vascular smooth muscle cells, suggesting a similar role in 1α,25(OH)2D3-dependent signaling. The aim of the present study is to evaluate the roles of CaM and CaMKII as mediators of 1α,25(OH)2D3-stimulated PLAA-dependent activation of cPLA2 and PKCα, and downstream biological effects. The results indicated that 1α,25(OH)2D3 and PLAA-peptide increased CaMKII activity within 9 min. Silencing Cav-1, Pdia3 or Plaa in osteoblasts suppressed this effect. Similarly, antibodies against Plaa or Pdia3 blocked 1α,25(OH)2D3-dependent CaMKII. Caveolae disruption abolished activation of CaMKII by 1α,25(OH)2D3 or PLAA. CaMKII-specific and CaM-specific inhibitors reduced cPLA2 and PKC activities, PGE2 release and osteoblast maturation markers in response to 1α,25(OH)2D3. Camk2a-silenced but not Camk2b-silenced osteoblasts showed comparable effects. Immunoprecipitation showed increased interaction of CaM and PLAA in response to 1α,25(OH)2D3. The results indicate that membrane actions of 1α,25(OH)2D3 via Pdia3 triggered the interaction between PLAA and CaM, leading to dissociation of CaM from caveolae, activation of CaMKII, and downstream PLA2 activation, and suggest that CaMKII plays a major role in membrane-mediated actions of 1α,25(OH)2D3.

Peroxidative metabolism of arachidonic acid in the course of Lyme arthritis

OBJECTIVE

The objective of the study was measurement of serum arachidonic acid level as well as the product of its peroxidation - 8-isoPGF2α, and the activity of phospholipase A2 and PAF-acetylhydrolase that participate in releasing 8-isoPGF2α from glycerol skeleton, and the potential designation of their role in the pathomechanism of Lyme disease (LD).

MATERIAL AND METHODS

Changes in the phospholipid arachidonic acid level and the level of 8-isoPGF2α were determined in the plasma and urine of patients with LA (n=57) and of healthy controls (n=41). The activity of phospholipase A2 and PAF acetylhydrolase were assayed. All examined parameters were also measured in the plasma of some LA patients (n=13) after antibiotics treatment.

RESULTS

An almost 3-fold higher level of the total plasma 8-isoPGF2α was observed in LA patients compared to the controls, while in the urine it increased over 5-fold. The plasma PLA2 activity was more than 3-fold higher in LA patients than in the healthy subjects, while PAF acetylhydrolase activity was observed to be modestly, but not significantly lower. The total 8-isoPGF2α level in the plasma and urine of LA patients was significantly lower after antibiotics treatment. The plasma activity of PAF-AH in the LA patients was increased, while the cPLA2 activity decreased after antibiotics treatment.

CONCLUSIONS

It may be suggested that in the course of LA, the level of binding 8-isoPGF2α is significantly enhanced, and it may also be suggested that uncontrolled changes in the lipid status of some patients may make their Lyme arthritis unresponsive to antibiotics.

Prostaglandin pathways in duodenal chemosensing

Acid-sensing pathways, which trigger mucosal defense mechanisms in response to luminal acid, involve the rapid afferent-mediated "capsaicin pathway" and the sustained "prostaglandin (PG) pathway." Luminal acid quickly increases protective PG synthesis and release from epithelia, although the mechanism by which luminal acid induces PG synthesis is still mostly unknown. Acid exposure augments purinergic ATP-P2Y signaling by inhibition of intestinal alkaline phosphatase activity. Since P2Y activation increases intracellular Ca2+, we further hypothesized that ATP-P2Y signals increase the generation of H2O2 derived from dual oxidase, a member of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase family activated by Ca2+. Our recent studies suggest that acid exposure increases H2O2 output, followed by phospholipase A2 and cyclooxygenase activation, increasing PG synthesis. Released prostaglandin E2 augments protective HCO3- and mucus secretion via EP4 receptor activation. Thus, the PG pathway as a component of duodenal acid sensing consists of acid-related intestinal alkaline phosphatase inhibition, ATP-P2Y signals, dual oxidase 2-derived H2O2 production, phospholipase A2 activation, prostaglandin E2 synthesis, and EP4 receptor activation. The PG pathway is also involved in luminal bacterial sensing in the duodenum via activation of pattern recognition receptors, including Toll-like receptors and nucleotide-binding oligomerization domain 2. The presence of acute mucosal responses to luminal bacteria suggests that the duodenum is important for host defenses and may reduce bacterial loading to the hindgut using H2O2, complementing gastric acidity and anti-bacterial bile acids.

Phospholipase A2 isolated from the venom of Crotalus durissus terrificus inactivates dengue virus and other enveloped viruses by disrupting the viral envelope

The Flaviviridae family includes several virus pathogens associated with human diseases worldwide. Within this family, Dengue virus is the most serious threat to public health, especially in tropical and sub-tropical regions of the world. Currently, there are no vaccines or specific antiviral drugs against Dengue virus or against most of the viruses of this family. Therefore, the development of vaccines and the discovery of therapeutic compounds against the medically most important flaviviruses remain a global public health priority. We previously showed that phospholipase A₂ isolated from the venom of Crotalus durissus terrificus was able to inhibit Dengue virus and Yellow fever virus infection in Vero cells. Here, we present evidence that phospholipase A₂ has a direct effect on Dengue virus particles, inducing a partial exposure of genomic RNA, which strongly suggests inhibition via the cleavage of glycerophospholipids at the virus lipid bilayer envelope. This cleavage might induce a disruption of the lipid bilayer that causes a destabilization of the E proteins on the virus surface, resulting in inactivation. We show by computational analysis that phospholipase A₂ might gain access to the Dengue virus lipid bilayer through the pores found on each of the twenty 3-fold vertices of the E protein shell on the virus surface. In addition, phospholipase A₂ is able to inactivate other enveloped viruses, highlighting its potential as a natural product lead for developing broad-spectrum antiviral drugs.

The role of arachidonic acid in the regulation of nitric oxide synthase isoforms by HIV gp120 protein in astroglial cells

HIV-associated neurocognitive disorder (HAND) is a common cognitive impairment in AIDS that affects 15 to 50% of adults infected with human immunodeficiency virus (HIV). Excessive amounts of nitric oxide (NO), as produced by inducible NO synthase (iNOS) upon exposure of activated microglia and astrocytes to cytokines and/or viral proteins (e.g., HIV tat and gp120), are assumed to contribute to neuronal abnormalities in HAND. Evidence exists supporting the notion that iNOS induction takes place after an early decline in physiological NO levels (i.e., NO released by constitutive NOS). Here, we demonstrate that HIV-1 gp120 is able to inhibit neuronal NOS through a cytosolic phospholipase A2 (cPLA2)-dependent arachidonic acid (AA) production, this response being critical for allowing activation of the transcriptional factor NF-κB and subsequent iNOS and interleukin-1β transcription in astroglial cells. In this context, AA seems to act as an upstream proinflammatory effector. In view of the pathogenic role of cPLA2 in HAND, a deeper insight into the molecular and cellular mechanisms of its modulation may be helpful in finding new drugs to manage cognitive impairment in HIV-1 patients.

In vitro exposure of tobacco specific nitrosamines decreases the rat lung phospholipids by enhanced phospholipase A2 activity

Tobacco-specific nitrosamines (TSNA) have implications in the pathogenesis of various lung diseases and conditions are prevalent even in non-smokers. N-nitrosonornicotine (NNN) and 4-(methyl nitrosamino)-1-(3-pyridyl)-1-butanone (NNK) are potent pulmonary carcinogens present in tobacco product and are mainly responsible for lung cancer. TSNA reacts with pulmonary surfactants, and alters the surfactant phospholipid. The present study was undertaken to investigate the in vitro exposure of rat lung tissue slices to NNK or NNN and to monitor the phospholipid alteration by [(32)P]orthophosphate labeling. Phospholipid content decreased significantly in the presence of either NNK or NNN with concentration and time dependent manner. Phosphatidylcholine (PC) is the main phospholipid of lung and significant reduction was observed in PC ∼61%, followed by phosphatidylglycerol (PG) with 100μM of NNK, whereas NNN treated tissues showed a reduction in phosphatidylserine (PS) ∼60% and PC at 250μM concentration. The phospholipase A2 assays and expression studies reveal that both compounds enhanced phospholipid hydrolysis, thereby reducing the phospholipid content. Collectively, our data demonstrated that both NNK and NNN significantly influenced the surfactant phospholipid level by enhanced phospholipase A2 activity.

Piperine inhibits the activities of platelet cytosolic phospholipase A2 and thromboxane A2 synthase without affecting cyclooxygenase-1 activity: different mechanisms of action are involved in the inhibition of platelet aggregation and macrophage inflammatory response

PURPOSE: Piperine, a major alkaloid of black pepper (Piper nigrum) and long pepper (Piper longum), was shown to have anti-inflammatory activity through the suppression of cyclooxygenase (COX)-2 gene expression and enzyme activity. It is also reported to exhibit anti-platelet activity, but the mechanism underlying this action remains unknown. In this study, we investigated a putative anti-platelet aggregation mechanism involving arachidonic acid (AA) metabolism and how this compares with the mechanism by which it inhibits macrophage inflammatory responses; METHODS: Rabbit platelets and murine macrophage RAW264.7 cells were treated with piperine, and the effect of piperine on the activity of AA-metabolizing enzymes, including cytosolic phospholipase A₂ (cPLA₂), COX-1, COX-2, and thromboxane A₂ (TXA₂) synthase, as well as its effect on AA liberation from the plasma membrane components, were assessed using isotopic labeling methods and enzyme immunoassay kit; RESULTS: Piperine significantly suppressed AA liberation by attenuating cPLA₂ activity in collagen-stimulated platelets. It also significantly inhibited the activity of TXA₂ synthase, but not of COX-1, in platelets. These results suggest that piperine inhibits platelet aggregation by attenuating cPLA₂ and TXA₂ synthase activities, rather than through the inhibition of COX-1 activity. On the other hand, piperine significantly inhibited lipopolysaccharide-induced generation of prostaglandin (PG)E₂ and PGD₂ in RAW264.7 cells by suppressing the activity of COX-2, without effect on cPLA₂; CONCLUSION: Our findings indicate that piperine inhibits platelet aggregation and macrophage inflammatory response by different mechanisms.

Lysophosphatidylcholine enhances susceptibility in signaling pathway against pathogen infection through biphasic production of reactive oxygen species and ethylene in tobacco plants

It was previously reported that the amounts of lysophosphatidylcholines (lysoPCs), which are naturally occurring bioactive lipid molecules, significantly increase following pathogen inoculation, as determined using ultraperformance liquid chromatography-quadrupole-time of flight/mass spectrometry analyses. Here, real-time quantitative RT-PCR was performed for the phospholipase A2 (PLA2) genes, Nt1PLA2 and Nt2PLA2, which are responsible for LysoPCs generation. The transcription level of Nt2PLA2 in pathogen-infected tobacco plants transiently peaked at 1h and 36 h, whereas induction of Nt1PLA2 transcription peaked at 36 h. A prominent biphasic ROS accumulation in lysoPC (C18:1(9Z))-treated tobacco leaves was also observed. Transcription of NtRbohD, a gene member of NADPH oxidase, showed biphasic kinetics upon lysoPC 18:1 treatment, as evidenced by an early transient peak in phase I at 1h and a massive peak in phase II at 12h. Each increase in NtACS2 and NtACS4 transcription, gene members of the ACC synthase family, was followed by biphasic peaks of ethylene production after lysoPC 18:1 treatment. This suggested that lysoPC (C18:1)-induced ethylene production was regulated at the transcriptional level of time-dependent gene members. LysoPC 18:1 treatment also rapidly induced cell damage. LysoPC 18:1-induced cell death was almost completely abrogated in ROS generation-impaired transgenic plants (rbohD-as and rbohF-as), ethylene production-impaired transgenic plants (CAS-AS and CAO-AS), and ethylene signaling-impaired transgenic plants (Ein3-AS), respectively. Taken together, pathogen-induced lysoPCs enhance pathogen susceptibility accompanied by ROS and ethylene biosynthesis, resulting in chlorophyll degradation and cell death. Expression of PR genes (PR1-a, PR-3, and PR-4b) and LOX3 was strongly induced in lysoPC 18:1-treated leaves, indicating the involvement of lysoPC 18:1 in the defense response. However, lysoPC 18:1 treatment eventually resulted in cell death, as evidenced by metacaspase gene expression. Therefore, a hypothesis is proposed that the antipathogenic potential of lysoPC 18:1 is dependent on how quickly it is removed from cells for avoidance of lysoPC toxicity.