Platelet-activating Factor Acetylhydrolase Research Articles

Cigarette smoke increases PAF accumulation, cell motility and EMT in triple negative breast cancer cells (58.8)

Most cancer deaths are a result of metastasis rather than the primary tumor. Although cigarette smoking has been determined as a risk factor for several cancers, its role in metastasis has not been studied in great detail. We propose that cigarette smoking plays a role in increased metastasis via inhibition of endothelial cell platelet‐activating factor acetylhydrolase (PAF‐AH) inhibition, resulting in PAF accumulation and recruitment of circulating tumor cells to secondary sites. We exposed mammary epithelial cells (MCF‐10A) and breast cancer cell lines (MCF‐7, MDA‐MB‐231, and MDA‐MB‐468) to CSE for up to 48 hours. CSE inhibited PAF‐AH activity, increased PAF accumulation, and increased cell motility in the metastatic triple negative breast cancer cell line MDA‐MB‐231. Metastatic triple negative breast cancer cells exposed to CSE showed an increase in epithelial‐mesenchymal transition (EMT) as measured by the disappearance of the epithelial marker E‐cadherin and increased expression of the mesenchymal markers Snail and Slug. Thus, PAF may be a therapeutic target to manage metastatic disease, particularly in triple negative breast cancer patients who smoke.

Recruitment of inflammatory cells to the bladder endothelium exposed to cigarette smoke extract (669.1)

Interstitial cystitis/painful bladder syndrome (IC/PBS) is a debilitating disease of unknown etiology. Several risk factors are associated with IC/PBS including smoking, weight and diet. Platelet activating factor (PAF) plays a role in inflammatory cell recruitment to the endothelium and we have shown that PAF metabolism by PAF‐acetylhydrolase (PAF‐AH) is inhibited by cigarette smoke. We propose that cigarette smoking inhibits bladder endothelial PAF‐AH activity and contributes directly to inflammatory cell recruitment in the bladder wall. Incubation of human bladder microvascular endothelial cells (HBMEC) with cigarette smoke extract (CSE, 20 µg/mL) resulted in a significant inhibition of PAF‐AH activity with increased PAF accumulation and polymorphonuclear leukocyte (PMN) adherence. Pretreatment of HBMEC with (S)‐bromoenol lactone to inhibit calcium‐independent phospholipase A2β and PAF production prior to CSE incubation lead to a significant reduction in PMN adherence to the bladder endothelium. Similarly, pretreatment of PMN with PAF receptor antagonists (WEB 4086 or Ginkgo biloba) prior to CSE caused a significant reduction in PMN adherence. We propose that targeting endothelial cell PAF production or blocking the PAF receptor may represent novel therapies for management of IC/PBS patients, particularly smokers.Grant Funding Source: Supported by a President's Research Fund, Saint Louis University grant

PMN recruitment to small airway epithelial cells in response to cigarette smoke extract (694.8)

Cigarette smoke causes airway inflammation and recruitment of inflammatory cells, requiring migration across the endothelial and epithelial cell barriers. We propose that increased platelet‐activating factor (PAF) production in the airways of smokers enhances inflammatory cell recruitment. Human small airway epithelial cells (HSAEC) incubated with cigarette smoke extract (CSE) demonstrated increased PAF accumulation that was inhibited when cells were pretreated with (S)‐bromoenol lactone ((S)‐BEL, inhibits calcium‐independent phospholipase A2β (iPLA2β). HSAEC incubated with CSE also showed a significant inhibition of PAF acetyl hydrolase (PAF‐AH, degrades PAF). This suggests that increased PAF accumulation is a combination of increased synthesis (iPLA2β activation) and decreased degradation (PAF‐AH inhibition). 舲舲Polymorphonuclear leukocyte (PMN) adherence to HSAEC was increased with CSE and inhibited when HSAEC were pretreated with (S)‐BEL or PMN were pretreated with Ginkgolide B to block the PAF receptor. CSE also increased PMN transmigration across HSAEC in a basolateral to apical direction.舲舲 Taken together, our data demonstrate that PMN accumulation in the airways of smokers depends on increased PAF accumulation in HSAEC and suggest that Ginkgo biloba is a potential therapy to manage airway inflammation.

Lipoxin A4 and Platelet Activating Factor Are Involved in E. coli or LPS-Induced Lung Inflammation in CFTR-Deficient Mice

CFTR (cystic fibrosis transmembrane conductance regulator) is expressed by both neutrophils and platelets. Lack of functional CFTR could lead to severe lung infection and inflammation. Here, we found that mutation of CFTR (F508del) or inhibition of CFTR in mice led to more severe thrombocytopenia, alveolar neutrocytosis and bacteriosis, and lower lipoxin A4/MIP-2 (macrophage inhibitory protein-2) or lipoxin A4/neutrophil ratios in the BAL (bronchoalveolar lavage) during acute E. coli pneumonia. In vitro, inhibition of CFTR promotes MIP-2 production in LPS-stimulated neutrophils; however, lipoxin A4 could dose-dependently suppress this effect. In LPS-induced acute lung inflammation, blockade of PSGL-1 (P-selectin glycoprotein ligand-1) or P-selectin, antagonism of PAF by WEB2086, or correction of mutated CFTR trafficking by KM11060 could significantly increase plasma lipoxin A4 levels in F508del relevant to wildtype mice. Concurrently, F508del mice had higher plasma platelet activating factor (PAF) levels and PAF-AH activity compared to wildtype under LPS challenge. Inhibiting hydrolysis of PAF by a specific PAF-AH (PAF-acetylhydrolase) inhibitor, MAFP, could worsen LPS-induced lung inflammation in F508del mice compared to vehicle treated F508del group. Particularly, depletion of platelets in F508del mice could significantly decrease plasma lipoxin A4 and PAF-AH activity and deteriorate LPS-induced lung inflammation compared to control F508del mice. Taken together, lipoxin A4 and PAF are involved in E. coli or LPS-induced lung inflammation in CFTR-deficient mice, suggesting that lipoxin A4 and PAF might be therapeutic targets for ameliorating CFTR-deficiency deteriorated lung inflammation.

The relation of diet with PAF and its metabolic enzymes in healthy volunteers

Platelet-activating factor (PAF), a potent inflammatory mediator, is implicated in atherosclerosis. Its key biosynthetic enzymes are lyso-PAF acetyltransferases (lyso-PAF-AT), responsible for PAF synthesis through the remodeling route and a specific CDP-choline:1-alkyl-2-acetyl-sn-glycerol cholinephosphotransferase (PAF-CPT), responsible for its de novo biosynthesis. PAF acetylhydrolase (PAF-AH) and its extracellular isoform lipoprotein-associated phospholipase A₂ catabolize PAF. The impact of diet on PAF metabolism is ill-defined. The aim was to investigate associations between PAF, its enzymes and dietary factors. One-hundred and six (n = 106) healthy volunteers were recruited. Food-frequency questionnaires, dietary recalls, lifestyle and biochemical variables were collected. Food groups, macronutrient intake, a priori (MedDietScore) and a posteriori defined food patterns with PCA analysis, dietary antioxidant capacity (DAC), glycemic index (GI) and glycemic load were assessed. PAF was inversely correlated with antioxidant-rich foods (herbal drinks and coffee), the DAC as well as a dietary pattern characterized by legumes, vegetables, poultry and fish (all Ps < 0.05). PAF was positively correlated to % fat intake. Lyso-PAF-AT was also negatively associated with healthy patterns (fruits, nuts and herbal drinks, and a pattern rich in olive oil and whole-wheat products), as well as the DAC and % monounsaturated fatty acids. PAF-CPT was negatively associated with GI and coffee intake and positively with dietary cholesterol. PAF-AH was negatively associated with coffee and positively associated with alcohol consumption (all Ps < 0.05). In conclusion, the DAC and healthy dietary patterns were inversely associated with PAF or its biosynthetic enzymes, suggesting potential new mechanisms of the diet-disease associations.

Time course-changes in phosphatidylcholine profile during oxidative modification of low-density lipoprotein

BackgroundOxidized phosphatidylcholines (oxPC) and lysophosphatidylcholine (lysoPC) generated during the formation of oxidized low-density lipoprotein (oxLDL) are involved in atherosclerotic lesion development. We investigated the time course-changes in phosphatidylcholine (PC) molecular species during oxidation of LDL to determine how those atherogenic PCs are produced.MethodsHuman and rabbit LDLs were pretreated with or without a selective platelet-activating factor acetylhydrolase (PAF-AH) inhibitor. LDL was oxidized by incubation with copper sulfate, and PC profiles were analyzed by liquid chromatography-tandem mass spectrometry.ResultsWhen human LDL was oxidized, the peak areas for polyunsaturated fatty acid (PUFA)-containing PC species dramatically decreased after a short lag period, concomitantly lysoPC species increased sharply. Although a variety of oxPC species containing oxidized fatty acyl groups or cleaved acyl chains are formed during LDL oxidation, only a few oxPC products accumulated in oxLDL: 1-palmitoyl-2-(9-oxo-nonanoyl) PC and long-chain oxPC with two double bonds. Pretreatment of LDL with the PAF-AH inhibitor greatly reduced lysoPC production while it had no effect on lipid peroxidation reactions and oxPC profiles. Rabbit LDL, which has a different composition of PC molecular species and needs a longer time to reach achieve full oxidation than human LDL, also accumulated lysoPC during oxidation. The increase in lysoPC in rabbit oxLDL was suppressed by pretreatment with the PAF-AH inhibitor. The major oxPC species formed in rabbit oxLDL were almost the same as human oxLDL.ConclusionsThese results suggest that lysoPC species are the major products and PAF-AH activity is crucial for lysoPC generation during oxidation of LDL. The oxPC species accumulated are limited when LDL is oxidized with copper ion in vitro.

Association between seven single nucleotide polymorphisms involved in inflammation and proteolysis and abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) formation involves an inflammatory and proteolytic process. Previous studies suggest that AAA is a multifactorial disease with a strong genetic background. This study evaluated the role of seven important functional single nucleotide polymorphisms (SNPs) in AAA. This was a case-control study of two independent populations: 397 AAA patients (mean aortic diameter, 6.2 ± 1.4 cm) and 393 controls (mean diameter, 2.4 ± .2 cm) recruited from Greece (the main cohort), and 400 patients (mean diameter: 5.4 ± 1 cm) and 400 controls (mean diameter, 2.4 ± .6 cm) recruited from the United Kingdom (replication cohort). The functional SNPs analyzed were rs3025058, rs3918242, rs2276109, rs1801133, rs1799752, rs1799983, and rs16874954. These regulate the following enzymes: matrix metalloproteinases (MMPs), angiotensin-converting enzyme, endothelial nitric oxide synthase, methylenetetrahydrofolate reductase (MTHFR), and platelet-activating factor acetylhydrolase or lipoprotein-associated phospholipase A2. Genotype distributions (univariate analyses) did not differ significantly between cases and controls in the main or the replication cohort, with the exception of the MMP-3 rs3025058 SNP, where differences were borderline significant (odds ratio [OR], 1.42; 95% confidence interval [CI], 1.02-1.97; P = .04) in the replication cohort. Adjusted analyses for age, sex, smoking, hypertension, and hypercholesterolemia disclosed no differences in either cohort. For SNPs that had previously been associated with AAA presence, meta-analysis of currently available data together with the two study cohorts disclosed positive associations for the MMP-3 rs3025058 (OR, 1.15; 95% CI, 1.06-1.25; P = .0009) and MTHFR rs1801133 (OR, 1.07; 95% CI, 1.02-1.12; P = .0088). The SNPs included in this analysis were not associated with AAA presence in either study population. However, meta-analysis of the currently available data disclosed a positive association for MMP-3 rs3025058 and MTHFR rs1801133.

Platelet-activating Factor Contributes to Bacillus anthracis Lethal Toxin-associated Damage

The lethal toxin (LeTx) of Bacillus anthracis plays a central role in the pathogenesis of anthrax-associated shock. Platelet-activating factor (PAF) is a potent lipid mediator that has been implicated in endotoxin-associated shock. In this study, we examined the contribution of PAF to the manifestations of lethal toxin challenge in WT mice. LeTx challenge resulted in transient increase in serum PAF levels and a concurrent decrease in PAF acetylhydrolase activity. Inhibition of PAF activity using PAF antagonists or toxin challenge of PAF receptor negative mice reversed or ameliorated many of the pathologic features of LeTx-induced damage, including changes in vascular permeability, hepatic necrosis, and cellular apoptosis. In contrast, PAF inhibition had minimal effects on cytokine levels. Findings from these studies support the continued study of PAF antagonists as potential adjunctive agents in the treatment of anthrax-associated shock.

Enhanced Proinflammatory State and Autoimmune Activation: a Breakthrough to Understanding Chronic Diseases

Insight is provided herein into the novel mechanisms of cardiometabolic risk. Previous reports, including the epidemiological work of the Turkish Adult Risk Factor study, indicated that proinflammatory state and oxidative stress are crucial for evaluating cardiometabolic risk. Autoimmune pathways in the course of oxidative stress are major determinants of cardiorenal and metabolic risk. The latter encompasses metabolic syndrome, type 2 diabetes, coronary heart disease, and chronic kidney disease (CKD). Along with platelet-activating factor acetylhydrolase, creatinine, thyroid stimulating hormone, acylation-stimulating protein, asymmetric dimethylarginine, and serum lipoprotein[Lp](a) are triggers of systemic low-grade inflammation and enhanced autoimmune reactions. Related studies are analyzed in the current review. Lp(a) plays a crucial role by taking part in the immune activation, thereby accelerating the course of diabetes, CKD, and other chronic disorders. Populations prone to impaired glucose tolerance, and particularly peri- and postmenopausal women, are at high risk of developing related vascular complications.

Computational Investigation of Darapladib and Rilapladib Binding to Platelet Activating Factor Receptor. A Possible Mechanism of Their Involvement in Atherosclerosis

Platelet Activating Factor (PAF), the most potent inflammatory mediator, is involved in a wide range of pathophysiological actions. PAF signal transduction is mediated through PAF receptors (PAFR) that are coupled with several isoforms of G-proteins. PAF hydrolysis is mediated through specific enzymes clustered as PAF acetylhydrolases (PAF-AH). The plasma isoform is known as lipoprotein-associated PLA2 (Lp-PLA2), and is considered a marker, or a mediator in the mechanism of atherosclerosis. Darapladib and rilapladib are selective Lp-PLA2 inhibitors. They are, thus, proposed as a novel therapeutic approach for cardiovascular disease (CVD). The data derived from the computational methods used in this paper suggest that darapladib and rilapladib are potential PAFR antagonists, predicted to bind inside the PAF-binding site with a comparable binding affinity to the endogenous agonist (?G = –11.1 Kcal mol–1). Darapladib (?G = –10.6 Kcal mol–1) exhibited a higher affinity than rilapladib (?G = –8.2 Kcal mol–1). The fact that darapladib down-regulates PAFR expression, while PAFR inhibitors down-regulate the expression of CD36, could be the biochemical explanation in the observed necrotic core reduction, both in animals and humans. The reported results in conjunction with bibliographical data lead to the hypothesis that the involvement of darapladib and rilapladib in atherosclerosis could be through direct inhibition of PAF activity as well as modification of PAF metabolism.

Interaction Of Platelet Activating Factor Acetyl Hydrolase (Paf Ah) Enzyme In Gln281 To Arg281 Mutation Toward Paf And Its Molecular Dynamic

Platelet Activating Factor Acetyl Hydrolase (PAF AH) or LpPLA2 is key enzyme in myocardial infarction catalyzes the sn-2 acetyl group of Platelet Activating Factor (PAF) into lyso PAF and acetate as non-potent inflammatory molecules. PAF AH plays a critical role in arterial plaque development of Coronary Artery Disease (CAD). A crystal structure of PAF AH complexes with other ligand and effects of amino acid alteration to protein plasma consequence have also been reported. Here we report on the result of molecular docking and Molecular dynamic (MD) simulation carried out for PAF AH wild type (WT)/PAF and mutant Q281R/PAF complexes. Docking result shown that amino acid residues on active site of Q281 PAF AH mutant have not recognized on PAF AH. Eelectrostatics and hydrophobic bonds significantly reduced in Q281R than wild type. In the 7500 ps MD simulation Q281R showed less dynamics than WT but enzymatic machinary of mutant Q281R was not interrupted during MD simulation as well as PAF AH wildtype. These findings clearly indicated the importance effect of mutant Q281R in PAF AH recognition to its substrate

Insulin-Regulated Protein Palmitoylation Impacts Endothelial Cell Function

Defects in insulin signaling are associated with abnormal endothelial cell function, which occurs commonly in cardiovascular disease. Targets of insulin signaling in endothelial cells are incompletely understood. Protein S-palmitoylation, the reversible modification of proteins by the lipid palmitate, is a post-translational process relevant to cell signaling, but little is known about the role of insulin in protein palmitoylation. To test the hypothesis that insulin alters protein palmitoylation in endothelial cells, we combined acyl-biotin exchange chemistry with stable isotope labeling by amino acids in cell culture to perform quantitative proteomic profiling of human endothelial cells. We identified ≈380 putative palmitoylated proteins, of which >200 were not known to be palmitoylated; ≈10% of the putative palmitoylated proteins were induced or suppressed by insulin. Of those potentially affected by insulin, <10 have been implicated in vascular function. For one, platelet-activating factor acetylhydrolase IB subunit gamma (PAFAH1b3; not previously known to be palmitoylated), we confirmed that insulin stimulated palmitoylation without affecting PAFAH1b3 protein abundance. Chemical inhibition of palmitoylation prevented insulin-induced angiogenesis in vitro; knockdown of PAFAH1b3 had the same effect. PAFAH1b3 knockdown also disrupted cell migration. Mutagenesis of cysteines at residues 56 and 206 prevented palmitoylation of PAFAH1b3, abolished its capacity to stimulate cell migration, and inhibited its association with detergent-resistant membranes, which are implicated in cell signaling. Insulin promoted the association of wild-type PAFAH1b3 with detergent-resistant membranes. These findings provide proof of principle for using proteomics to identify novel insulin-inducible palmitoylation targets relevant to endothelial function.

The 15-deoxy-δ12,14-prostaglandin J2 inhibits LPS-stimulated inflammation via enhancement of the platelet-activating factor acetylhydrolase activity in human retinal pigment epithelial cells

A well-recognized natural ligand of PPARγ, 15-deoxy-δ(12,14)-prostaglandin J(2) (15d-PGJ(2)) possesses immunomodulatory properties. The aim of this study was to elucidate whether 15d-PGJ(2) was able to attenuate lipopolysaccharide (LPS)-induced inflammatory responses in human retinal pigment epithelial (RPE) cells, which are involved in ocular immune responses. In addition, we examined whether the platelet activating factor (PAF) is associated with the anti-inflammatory activity of 15d-PGJ(2). ARPE19 cells treated with varying concentrations of 15d-PGJ(2) and a PAF antagonist (CV3988) were used in this study. The activity of PAF-acetylhydrolase (PAF-AH) was assayed by treatment with 15d-PGJ(2) and CV3988 in the presence of LPS. 15d-PGJ(2) and CV3988 inhibited the LPS-induced mRNA expression and protein production of interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), and intercellular adhesion molecule-1 (ICAM-1) in ARPE19 cells. These effects resulting from 15d-PGJ(2) were not abrogated by the PPARγ antagonist, indicating that the actions were PPARγ-independent. Furthermore, 15d-PGJ(2) and CV3988 enhanced the PAF-AH activity. Additionally, 15d-PGJ(2) inhibited the phosphorylation of the extracellular signal-regulated kinase (ERK) and the activation of nuclear transcription factor-κB (NF-κB). These results demonstrated that 15d-PGJ(2) reduced LPS-stimulated inflammatory responses in ARPE19 cells by enhancing the PAH-AH activity. These results suggest that 15d-PGJ(2) may have potent anti-inflammatory activity against ocular inflammation.

Neuroprotection by platelet-activating factor acetylhydrolase in a mouse model of transient cerebral ischemia

Neuronal damage after transient cerebral ischemia is exacerbated by signaling pathways involving activated platelet-activating factor (PAF) and ameliorated by PAF-acetylhydrolase (PAF-AH); but whether cerebral neurons can be rescued by human recombinant PAF-AH (rPAF-AH) remains unknown. Adult male mice underwent a 60min middle cerebral artery occlusion (MCAO) and reperfusion for 24h. Then, the mice received intravenous tail injections with different drugs. Neurological behavioral function was evaluated by Bederson's test, and cerebral infarction volume was assessed with tetrazolium chloride (TTC) staining. mRNA and protein expression levels of matrix metalloproteinase-2 (MMP-2, collagenase-1), MMP-9 (gelatinase-B), and vascular endothelial growth factor (VEGF) were determined by quantitative real-time PCR (RT-PCR) and western blot analysis, respectively. Compared with the vehicle group, rPAF-AH significantly improved sensorimotor function (42%, P=0.0001). The volume of non-infarcted brain tissue was increased by the rPAF-AH treatment (16.3±4.6% vs. 46.0±10.3%, respectively). rPAF-AH significantly reduced mRNA and protein levels of MMP-2 and MMP-9, but increased the mRNA (P<0.001) and protein levels (P<0.01) of VEGF. These results demonstrate that rPAF-AH provides neuroprotection against ischemic injury. Neuroprotection might be induced not only by decrease in MMP-2 and MMP-9 expression, but also by increased VEGF expression.

Development of a seaweed derived platelet activating factor acetylhydrolase (PAF-AH) inhibitory hydrolysate, synthesis of inhibitory peptides and assessment of their toxicity using the Zebrafish larvae assay

The vascular inflammatory role of platelet activating factor acetylhydrolase (PAF-AH) is thought to be due to the formation of lysophosphatidyl choline and oxidized non-esterified fatty acids. This enzyme is considered a promising therapeutic target for the prevention of atherosclerosis and there is a need to expand the available chemical templates of PAF-AH inhibitors. This study demonstrated how natural PAF-AH inhibitory peptides were isolated and characterized from the red macroalga Palmaria palmata. The dried powdered alga was hydrolyzed using the food grade enzyme papain, and the resultant peptide containing fraction generated using RP-HPLC. Several oligopeptides were identified as potential PAF-AH inhibitors following bio-guided fractionation, and the amino acid sequences of these oligopeptides were confirmed by Q-TOF-MS and microwave-assisted solid phase de novo synthesis. The most promising PAF-AH inhibitory peptide had the amino acid sequence NIGK and a PAF-AH IC50 value of 2.32mM. This peptide may constitute a valid drug template for PAF-AH inhibitors. Furthermore the P. palmata hydrolysate was nontoxic when assayed using the Zebrafish toxicity model at a concentration of 1mg/ml.

Global proteomic characterization of uterine histotroph recovered from beef heifers yielding good quality and degenerate day 7 embryos

The objective was to analyze the proteomic composition of uterine flushes collected from beef heifers on day 7 after insemination. Estrus was synchronized in crossbred beef heifers by using a protocol with a controlled intravaginal drug releasing device. Heifers detected in standing estrus (within 24–48 h after removal of controlled intravaginal drug releasing device) were inseminated (estrus = day 0) with frozen-thawed semen from a single ejaculate of a bull with proven fertility. Heifers from which an embryo was recovered (after slaughter on day 7) were classified as either having a viable embryo (morula/blastocyst stage) or a degenerate embryo (arrested at the 2- to 16-cell stage). The overall recovery rate (viable and degenerate combined) was 64%. Global liquid chromatography coupled to tandem mass spectrometry proteomic analysis of the histotroph collected identified 40 high-confidence proteins present on day 7; 26 proteins in the viable group, 10 in the degenerate group, and 4 shared between both groups. Five proteins (platelet-activating factor acetylhydrolase IB subunit γ [PAFAH1B3], tubulin α-1D chain, tubulin β-4A chain, cytochrome C, and dihydropyrimidinase-related protein-2) were unique or more abundant in the histotroph collected from animals with a viable embryo, and 1 protein (S100-A4) was more abundant in the histotroph collected from animals with a degenerate embryo. Of interest, PAFAH1B3, detected only in histotroph from the group yielding viable embryos, belongs to the group of platelet-activating factors that are known to be important for the development of the pre-implantation embryo in other species. To our knowledge this is the first report of PAFAH1B3 in relation to bovine early embryonic development.

Bacterial Clearance Is Improved in Septic Mice by Platelet-Activating Factor-Acetylhydrolase (PAF-AH) Administration

Current evidence indicates that dysregulation of the host inflammatory response to infectious agents is central to the mortality of patients with sepsis. Strategies to block inflammatory mediators such as PAF have been investigated as adjuvant therapies for sepsis. PAF-AH, the enzyme responsible for PAF degradation, showed positive results in pre-clinical studies and phase II clinical trials, but the results of a phase III study were disappointing. In this study, we investigated the potential protective mechanism of PAF-AH in sepsis using the murine model of cecal ligation and puncture (CLP). Treatment with rPAF-AH increased peritoneal fluid levels of the anti-inflammatory mediators MCP-1/CCL2 after CLP. The numbers of bacteria (CFU) in the peritoneal cavity were decreased in the rPAF-AH-treated group, indicating more efficient bacterial clearance after rPAF-AH treatment. Interestingly, we observed increased levels of nitric oxide (NO) after PAF-AH administration, and rPAF-AH treatment did not decrease CFU numbers either in iNOS-deficient mice or in CCR2-deficient mice. We concluded that administration of exogenous rPAF-AH reduced inflammatory injury, altered cytokine levels and favored bacterial clearance with a clear impact on mortality through modulation of MCP-1/CCL2 and NO levels in a clinically relevant sepsis model.

Anaphylaxis: Clinical patterns, mediator release, and severity

Prospective human studies of anaphylaxis and its mechanisms have been limited, with few severe cases or examining only 1 or 2 mediators. We wanted to define the clinical patterns of anaphylaxis and relationships between mediators and severity. Data were collected during treatment and before discharge. Serial blood samples were taken for assays of mast cell tryptase, histamine, anaphylatoxins (C3a, C4a, C5a), cytokines (IL-2, IL-6, IL-10), soluble tumor necrosis factor receptor I, and platelet activating factor acetyl hydrolase. Principal component analysis defined mediator patterns, and logistic regression identified risk factors and mediator patterns associated with reaction severity and delayed reactions. Of 412 reactions in 402 people, 315 met the definition for anaphylaxis by the National Institute of Allergy and Infectious Diseases/Food Allergy and Anaphylaxis Network. Of 97 severe reactions 45 (46%) were hypotensive, 23 (24%) were hypoxemic, and 29 (30%) were mixed. One patient died. Severe reactions were associated with older age, pre-existing lung disease, and drug causation. Delayed deteriorations treated with epinephrine occurred in 29 of 315 anaphylaxis cases (9.2%) and were more common after hypotensive reactions and with pre-existing lung disease. Twenty-two of the 29 delayed deteriorations (76%) occurred within 4 hours of initial epinephrine treatment. Of the remaining 7 cases, 2 were severe and occurred after initially severe reactions, within 10 hours. All mediators were associated with severity, and 1 group (mast cell tryptase, histamine, IL-6, IL-10, and tumor necrosis factor receptor I) was also associated with delayed deteriorations. Low platelet activating factor acetyl hydrolase activity was associated with severe reactions. The results suggest that multiple inflammatory pathways drive reaction severity and support recommendations for safe observation periods after initial treatment.

The prevalence of platelet activating factor acetylhydrolase single nucleotide polymorphisms in relationship to necrotizing enterocolitis in Northwest Louisiana infants

PurposeStudies documented that platelet activating factor (PAF) and the enzyme platelet activating factor acetylhydrolase (PAFAH) play a very important role in the pathogenesis of neonatal necrotizing enterocolitis (NEC). In this retrospective, case-controlled pilot study, the authors investigated the prevalence of single nucleotide polymorphisms (Ile198Thr and Ala379Val) of the PAFAH gene.Subjects and methodsWe screened 570 blood samples from both Caucasian and African-American preterm infants in the Northwest Louisiana population for the above mentioned PAFAH gene polymorphisms. Out of 570 infants, 36 had stage I or II NEC based on diagnostic coding, the International Classification of Diseases, 9th revision, Clinical Modification, 2009 (ICD-9-CM). The remaining infants without an ICD-9-CM diagnosis of NEC were recruited as control population. The DNA was isolated and restriction fragment length polymorphism microplate polymerase chain reaction assay was performed.ResultsVariants of the PAFAH gene polymorphism (Ile198Thr and Ala379Val) frequencies were not significantly different between the infants with NEC and the control group (P value of 0.26 by either multiple logistic regression analysis or the Cochran-Mantel-Haenszel test).ConclusionsThis is the first study of its kind in exploring the relationship between NEC and single nucleotide polymorphisms in the coding genes of the enzyme PAFAH. Our preliminary data demonstrated that adjusted for the effect of race, PAFAH polymorphisms (Ile198Thr and Ala379Val) have no significant effect on NEC.

Characterization of Streptococcal Platelet-Activating Factor Acetylhydrolase Variants That Are Involved in Innate Immune Evasion

Human pathogen group A streptococcus (GAS) has developed mechanisms to subvert innate immunity. We recently reported that the secreted esterase produced by serotype M1 GAS (SsE(M1)) reduces neutrophil recruitment by targeting platelet-activating factor (PAF). SsE(M1) and SsE produced by serotype M28 GAS (SsE(M28)) have a 37% sequence difference. This study aims at determining whether SsE(M28) is also a PAF acetylhydrolase and participates in innate immune evasion. We also examined whether SsE evolved to target PAF by characterizing the PAF acetylhydrolase (PAF-AH) activity and substrate specificity of SsE(M1), SsE(M28), SeE, the SsE homologue in Streptococcus equi, and human plasma PAF-AH (hpPAF-AH). PAF incubated with SsE(M28) or SeE was converted into lyso-PAF. SsE(M1) and SsE(M28) had kcat values of 373 s(-1) and 467 s(-1), respectively, that were ≥ 30-fold greater than that of hpPAF-AH (12 s(-1)). The comparison of SsE(M1), SsE(M28), and hpPAF-AH in kcat and Km in hydrolyzing triglycerides, acetyl esters, and PAF indicates that the SsE proteins are more potent hydrolases against PAF and have high affinity for PAF. SsE(M28) possesses much lower esterase activities against triglycerides and other esters than SsE(M1) but have similar potency with SsE(M1) in PAF hydrolysis. Deletion of sse(M28) in a covS deletion mutant of GAS increased neutrophil recruitment and reduced skin infection, whereas in trans expression of SsE(M28) in GAS reduced neutrophil infiltration and increased skin invasion in subcutaneous infection of mice. These results suggest that the SsE proteins evolved to target PAF for enhancing innate immune evasion and skin invasion.