title: Studies on a mechanism by which cytosolic phospholipase A2 regulates the expression and function of type IIA secretory phospholipase A2.
abstract: Although it has been proposed that arachidonate release by several secretory phospholipase A2 (sPLA2) isozymes is modulated by cytosolic PLA2 (cPLA2), the cellular component(s) that intermediates between these two signaling PLA2s remains unknown. Here we provide evidence that 12- or 15-lipoxygenase (12/15-LOX), which lies downstream of cPLA2, plays a pivotal role in cytokine-induced gene expression and function of sPLA2-IIA. The sPLA2-IIA expression and associated PGE2 generation induced by cytokines in rat fibroblastic 3Y1 cells were markedly attenuated by antioxidants that possess 12/15-LOX inhibitory activity. 3Y1 cells expressed 12/15-LOX endogenously, and forcible overexpression of 12/15-LOX in these cells greatly enhanced cytokine-induced expression of sPLA2-IIA, with a concomitant increase in delayed PG generation. Moreover, studies using 293 cells stably transfected with sPLA2-IIA revealed that stimulus-dependent hydrolysis of membrane phospholipids by sPLA2-IIA was enhanced by overexpression of 12/15-LOX. These results indicate that the product(s) generated by the cPLA2-12/15-LOX pathway following cell activation may play two roles: enhancement of sPLA2-IIA gene expression and membrane sensitization that leads to accelerated sPLA2-IIA-mediated hydrolysis.
authors.affiliation: Department of Health Chemistry, Showa University School of Pharmaceutical Sciences, Tokyo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kuwata
authors.forename: S
authors.initials: S
authors.lastname: Yamamoto
authors.forename: Y
authors.initials: Y
authors.lastname: Miyazaki
authors.forename: S
authors.initials: S
authors.lastname: Shimbara
authors.forename: Y
authors.initials: Y
authors.lastname: Nakatani
authors.forename: H
authors.initials: H
authors.lastname: Suzuki
authors.forename: N
authors.initials: N
authors.lastname: Ueda
authors.forename: S
authors.initials: S
authors.lastname: Yamamoto
authors.forename: M
authors.initials: M
authors.lastname: Murakami
authors.forename: I
authors.initials: I
authors.lastname: Kudo
mesh_terms: D000818:Animals; D001092:Arachidonate 12-Lipoxygenase / Q000502:physiology; D001093:Arachidonate 15-Lipoxygenase / Q000502:physiology; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology* / Q000502:physiology; D004789:Enzyme Activation / Q000502:physiology; D004790:Enzyme Induction / Q000502:physiology; D054501:Group II Phospholipases A2; D006801:Humans; D006868:Hydrolysis; D007527:Isoenzymes / Q000096:biosynthesis / Q000502:physiology; D051379:Mice; D010741:Phospholipases A / Q000096:biosynthesis* / Q000502:physiology; D054467:Phospholipases A2; D010743:Phospholipids / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000502:physiology
chemical_list: D007527:Isoenzymes; D010743:Phospholipids; D001092:Arachidonate 12-Lipoxygenase; D001093:Arachidonate 15-Lipoxygenase; D010741:Phospholipases A; D054501:Group II Phospholipases A2; D054467:Phospholipases A2