Group V secreted phospholipase A2 plays a protective role against aortic dissection.

Aortic dissection is a life-threatening aortopathy involving separation of the aortic wall, whose underlying mechanisms are still incompletely understood. Epidemiological evidence suggests that unsaturated fatty acids improve cardiovascular health. Here, using quantitative RT-PCR, histological analyses, magnetic cell sorting and flow cytometry assays, and MS-based lipidomics, we show that the activity of a lipid-metabolizing enzyme, secreted phospholipase A2 group V (sPLA2-V), protects against aortic dissection by endogenously mobilizing vasoprotective lipids. Global and endothelial cell-specific sPLA2-V-deficient mice frequently developed aortic dissection shortly after infusion of angiotensin II (AT-II). We observed that in the AT-II-treated aorta, endothelial sPLA2-V mobilized oleic and linoleic acids, which attenuated endoplasmic reticulum stress, increased the expression of lysyl oxidase, and thereby stabilized the extracellular matrix in the aorta. Of note, dietary supplementation with oleic or linoleic acid reversed the increased susceptibility of sPLA2-V-deficient mice to aortic dissection. These findings reveal an unexplored functional link between sPLA2-driven phospholipid metabolism and aortic stability, possibly contributing to the development of improved diagnostic and/or therapeutic strategies for preventing aortic dissection.

Expression of sPLA2-V, estrogen and its target protein in myocardium tissue.

In this study, we examined the effects of Prostaglandin E1 and tea polysaccharides (TP) on serum estrogen and FSH levels, myocardium sPLA2-V positive levels, and sPLA2-V protein expression in the rats fed on hypercholesterolemic diet. Hyperlipidemic rats were treated with Prostaglandin E1 and TP. Serum estrogen and FSH levels were significantly enhanced by Prostaglandin E1 and TP, whereas myocardium sPLA2-V positive rate and protein expression levels were decreased compared to the HCD group. Our results suggest that Prostaglandin E1 and TP exert strong heart-protective effects and therefore can be used to reduce the risk of heart disorders.

Quantitative structure-activity relationship (QSAR) analysis of a series of indole analogues as inhibitor for human group V secretory phospholipase A2.

Phospholipase A2s (PLA2) are a class of enzymes, which catalyze the hydrolysis of membrane phospholipids at the sn-2 position to release fatty acids and lysophospholipids. When the fatty acid is arachidonic acid (AA), a complementary metabolism leads to pro-inflammatory mediators collectively known as eicosanoids. Thus, inhibiting PLA2 activity remains a prime target for the development of new drugs for the treatment of inflammation-related diseases. More than one type of PLA2s plays a major role in inflammatory disease conditions. In the present study, quantitative structure-activity relationship (QSAR) study was performed for a series of 48 Me-indoxam derivatives as human group V PLA, (hVPLA2) inhibitors, using molecular operating environment (MOE) software. The hVPLA2 is a secretory PLA2 (sPLA2), involved in eicosanoid formation in inflammatory cells such as macrophages and mast cells. These studies have come out with three good predictive models (r = 0.82-0.84), which are cross-validated (rcv = 0.68-0.70) by leave-out-one method (Loo). The positive correlation of spatial descriptor Pmiz with inhibitory activity shows that proper orientation of the substitution at R position towards Z-axis is necessary to facilitate the possible interactions of the indole core with active site residues of the PLA2 enzyme. The negative contribution of b_rotN (atom and bond count-type descriptor) suggests that increasing flexibility conferred by the R substitution is detrimental for the activity. In addition to the hVPLA2 inhibitory activity is found to be highly influenced by molecular size, energy and polarity of the Me-indoxam derivatives.

PGE2 release is independent of upregulation of Group V phospholipase A2 during long-term stimulation of P388D1 cells with LPS.

P388D1 cells release arachidonic acid (AA) and produce prostaglandin E2 (PGE2) upon long-term stimulation with lipopolysaccharide (LPS). The cytosolic Group IVA (GIVA) phospholipase A2 (PLA2) has been implicated in this pathway. LPS stimulation also results in increased expression and secretion of a secretory PLA2, specifically GV PLA2. To test whether GV PLA2 contributes to PGE2 production and whether GIVA PLA2 activation increases the expression of GV PLA2, we utilized the specific GIVA PLA2 inhibitor pyrrophenone and second generation antisense oligonucleotides (AS-ONs) designed to specifically inhibit expression and activity of GV PLA2. Treatment of P388D1 cells with antisense caused a marked decrease in basal GV PLA2 mRNA and prevented the LPS-induced increase in GV PLA2 mRNA. LPS-stimulated cells release active GV PLA2 into the medium, which is inhibited to background levels by antisense treatment. However, LPS-induced PGE2 release by antisense-treated cells and by control cells are not significantly different. Collectively, the results suggest that the upregulation of GV PLA2 during long-term LPS stimulation is not required for PGE2 production by P388D1 cells. Experiments employing pyrrophenone suggested that GIVA PLA2 is the dominant player involved in AA release, but it appears not to be involved in the regulation of LPS-induced expression of GV PLA2 or cyclooxygenase-2.

Groups IV, V, and X phospholipases A2s in human neutrophils: role in eicosanoid production and gram-negative bacterial phospholipid hydrolysis.

The bacterial tripeptide formyl-Met-Leu-Phe (fMLP) induces the secretion of enzyme(s) with phospholipase A(2) (PLA(2)) activity from human neutrophils. We show that circulating human neutrophils express groups V and X sPLA(2) (GV and GX sPLA(2)) mRNA and contain GV and GX sPLA(2) proteins, whereas GIB, GIIA, GIID, GIIE, GIIF, GIII, and GXII sPLA(2)s are undetectable. GV sPLA(2) is a component of both azurophilic and specific granules, whereas GX sPLA(2) is confined to azurophilic granules. Exposure to fMLP or opsonized zymosan results in the release of GV but not GX sPLA(2) and most, if not all, of the PLA(2) activity in the extracellular fluid of fMLP-stimulated neutrophils is due to GV sPLA(2). GV sPLA(2) does not contribute to fMLP-stimulated leukotriene B(4) production but may support the anti-bacterial properties of the neutrophil, because 10-100 ng per ml concentrations of this enzyme lead to Gram-negative bacterial membrane phospholipid hydrolysis in the presence of human serum. By use of a recently described and specific inhibitor of cytosolic PLA(2)-alpha (group IV PLA(2)alpha), we show that this enzyme produces virtually all of the arachidonic acid used for the biosynthesis of leukotriene B(4) in fMLP- and opsonized zymosan-stimulated neutrophils, the major eicosanoid produced by these pro-inflammatory cells.