Abstract
Cr-LAAO, an l-amino acid oxidase isolated from Calloselasma rhodosthoma snake venom, has been demonstrated as a potent stimulus for neutrophil activation and inflammatory mediator production. However, the mechanisms involved in Cr-LAAO induced neutrophil activation has not been well characterized. Here we investigated the mechanisms involved in Cr-LAAO-induced lipid body (also known as lipid droplet) biogenesis and eicosanoid formation in human neutrophils. Using microarray analysis, we show for the first time that Cr-LAAO plays a role in the up-regulation of the expression of genes involved in lipid signalling and metabolism. Those include different members of phospholipase A2, mostly cytosolic phospholipase A2-α (cPLA2-α); and enzymes involved in prostaglandin synthesis including cyclooxygenases 2 (COX-2), and prostaglandin E synthase (PTGES). In addition, genes involved in lipid droplet formation, including perilipin 2 and 3 (PLIN 2 and 3) and diacylglycerol acyltransferase 1 (DGAT1), were also upregulated. Furthermore, increased phosphorylation of cPLA2-α, lipid droplet biogenesis and PGE2 synthesis were observed in human neutrophils stimulated with Cr-LAAO. Treatment with cPLA2-α inhibitor (CAY10650) or DGAT-1 inhibitor (A922500) suppressed lipid droplets formation and PGE2 secretion. In conclusion, we demonstrate for the first time the effects of Cr-LAAO to regulate neutrophil lipid metabolism and signalling.
Highlights
Cr-LAAO, an l-amino acid oxidase isolated from Calloselasma rhodosthoma snake venom, has been demonstrated as a potent stimulus for neutrophil activation and inflammatory mediator production
The data were expressed in a heatmap as up-regulation when the expression was higher in CrLAAO-stimulated neutrophils versus the negative control, and as down-regulation when the expression was higher in the negative control than in the stimulated neutrophils. PLA2s-expressed genes were divided into cytosolic and secreted forms
COX-1 (PTGS1), cyclooxygenases 2 (COX-2) (PTGS2), prostaglandin reductase 2 (PTGR2), prostaglandin E synthase 1 (PTGES) and 2 (PTGES2), and prostaglandin E receptor subtype EP4 (PTGER4) genes were up-regulated in all samples stimulated with CrLAAO
Summary
Cr-LAAO, an l-amino acid oxidase isolated from Calloselasma rhodosthoma snake venom, has been demonstrated as a potent stimulus for neutrophil activation and inflammatory mediator production. We investigated the mechanisms involved in Cr-LAAO-induced lipid body ( known as lipid droplet) biogenesis and eicosanoid formation in human neutrophils. We show for the first time that Cr-LAAO plays a role in the up-regulation of the expression of genes involved in lipid signalling and metabolism. Those include different members of phospholipase A2, mostly cytosolic phospholipase A2-α (cPLA2-α); and enzymes involved in prostaglandin synthesis including cyclooxygenases 2 (COX-2), and prostaglandin E synthase (PTGES). Lipid bodies (LBs; known as lipid droplets) are dynamic and well regulated organelles that have their formation up-regulated in activated leukocytes and play roles during inflammation[11,12]. Accumulating evidence have indicated that LBs act as platforms for the synthesis of inflammatory lipid mediators by compartmentalizing the substrate AA as well as a large number of proteins involved in eicosanoid synthesis, such as PLA2s, COX, PTGES, and 5- and 15-lipoxygenases (5-LO and 15-LO)[18,19,20,21,22]
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