Group IIA secretory phospholipase A 2 is a unique 12/15-lipoxygenase-regulated gene in cytokine-stimulated rat fibroblastic 3Y1 cells

Abstract

We have proposed previously that the expression of group IIA secretory phospholipase A 2 (sPLA 2-IIA), an enzyme implicated in inflammation, is under the control of group IVA cytosolic phospholipase A 2 (cPLA 2) and 12/15-lipoxygense (12/15-LOX) in cytokine-stimulated rat fibroblastic 3Y1 cells. Here, we show that the reduction of cytokine-stimulated sPLA 2-IIA induction by the cPLA 2 inhibitor arachidonyl trifluoromethyl ketone (AACOCF 3) is partially overcome by the addition of various lysophospholipids, such as lysophosphatidylcholine (LysoPC). Furthermore, this lysophospholipid effect was enhanced by further addition of 12/15-LOX products, such as 12( S)- or 15( S)-hydroxyeicosatetraenoic acid (HETE) and 13( S)-hydroxyoctadecadienoic acid (HODE), thus substantiating the hypothesis that the expression of sPLA 2-IIA is selectively regulated by lipid products of the cPLA 2–12/15-LOX pathway. In an attempt to identify a set of 12/15-LOX-regulated genes, the cDNA subtraction technique, followed by Northern blotting, was performed to screen particular clones, the expression of which was suppressed by the LOX inhibitor nordihydroguaiaretic acid (NDGA). NDGA-sensitive clones identified thus far included sPLA 2-IIA, cytoplasmic signaling intermediates, several oxygenases, extracellular matrices, secretory proteins, and other cellular proteins. Of these genes, however, only the expression of sPLA 2-IIA and 14-3-3η was enhanced by 12/15-LOX expression. Taken together, our data suggest that sPLA 2-IIA represents a particular group of genes, the transcription of which is up-regulated by 12/15-LOX metabolites.