title: Ceramide induces serotonin release from RBL-2H3 mast cells through calcium mediated activation of phospholipase A2.
abstract: Ceramide has been suggested to function as a mediator of exocytosis in response to the addition of a calcium ionophore from PC12 cells. Here, we show that although cell-permeable C(6)-ceramide or a calcium ionophore alone did not increase either the degranulation of serotonin or the release of arachidonic acid (AA) from RBL-2H3 cells, their combined effect significantly stimulated these processes in a time- and dose-dependent manner. This effect was inhibited by the presence of an exogenous calcium chelator and significantly suppressed by the CERK inhibitor (K1) and phospholipase A(2) (PLA(2)) inhibitors. Moreover, cytosolic PLA(2) GIVA (cPLA(2) GIVA) siRNA-transfected RBL-2H3 cells showed a lower level of serotonin release than scramble siRNA-transfected cells. Little is known about the regulation of degranulation proximal to the activation of cytosolic phospholipase A(2) GIVA, the initial rate-limiting step in RBL-2H3 cells. In this study, we suggest that CERK, ceramide-1-phosphate, and PLA(2) are involved in degranulation in a calcium-dependent manner. Inhibition of p44/p42 mitogen-activated protein kinase partially decreased the AA release, but did not affect degranulation. Furthermore, treatment of the cells with AA (ω-6, C20:4), not linoleic acid (ω-6, C18:2) or α-linolenic acid (ω-6, C18:3), induced degranulation. Taken together, these results suggest that ceramide is involved in mast cell degranulation via the calcium-mediated activation of PLA(2).
authors.affiliation: Department of Environmental & Health Chemistry, College of Pharmacy, Chung-Ang University, 221 Huksuk-dong, Dongjak-Ku, Seoul 156-756, South Korea.
authors.forename: Jung Eun
authors.initials: JE
authors.lastname: Ji
authors.forename: Seok Kyun
authors.initials: SK
authors.lastname: Kim
authors.forename: Kyong Hoon
authors.initials: KH
authors.lastname: Ahn
authors.forename: Jong Min
authors.initials: JM
authors.lastname: Choi
authors.forename: Sung Yun
authors.initials: SY
authors.lastname: Jung
authors.forename: Kwang Mook
authors.initials: KM
authors.lastname: Jung
authors.forename: Hyung Jun
authors.initials: HJ
authors.lastname: Jeon
authors.forename: Dae Kyong
authors.initials: DK
authors.lastname: Kim
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D015550:Cell Degranulation / Q000502:physiology; D002460:Cell Line; D002518:Ceramides / Q000378:metabolism* / Q000494:pharmacology; D007476:Ionophores / Q000378:metabolism / Q000494:pharmacology; D008407:Mast Cells / Q000187:drug effects / Q000201:enzymology*; D054467:Phospholipases A2 / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D012701:Serotonin / Q000378:metabolism* / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology
chemical_list: D002518:Ceramides; D007476:Ionophores; D034741:RNA, Small Interfering; D012701:Serotonin; D054467:Phospholipases A2; D002118:Calcium