15-HETE-substituted diglycerides selectively regulate PKC isotypes in human tracheal epithelial cells.
Human tracheal epithelial (TE) cells selectively incorporate their major lipoxygenase product, 15-hydroxyeicosatetraenoic acid (15-HETE), into the sn-2 position of phosphatidylinositol (PI) (S. E. Alpert and R. W. Walenga. Am. J. Respir. Cell Mol. Biol. 8: 273-281, 1993). Here we investigated whether 15-HETE-PI is a substrate for receptor-mediated generation of 15-HETE-substituted diglycerides (DGs) and whether these 15-HETE-DGs directly activate and/or alter conventional diacylglycerol-induced activation of protein kinase C (PKC) isotypes in these cells. Primary human TE monolayers incubated with 0.5 microM 15-[3H]-HETE or 15-[14C]HETE for 1-2 h were stimulated with 1 nM to 1 microM platelet-activating factor (PAF) for 30 s to 6 min, and the radiolabel in the medium, cellular phospholipids, and neutral lipids was assessed by high-performance liquid and thin-layer chromatography. PAF mobilized radiolabel from PI in a dose-dependent manner (22 +/- 5% decrease after 1 microM PAF) without a concomitant release of free intra- or extracellular 15-HETE. 14C-labeled DGs were present in unstimulated TE monolayers incubated with 15-[14C]HETE, and the major 14C band, identified as sn-1,2-15-[14C]HETE-DG, increased transiently in response to PAF. Western blots of freshly isolated and cultured human TE cells revealed PKC isotypes alpha, betaI, betaII, delta, epsilon, and zeta. In vitro, cell-generated sn-1, 2-15-[14C]HETE-DG selectively activated immunoprecipitated PKC-alpha and inhibited diacylglycerol-induced activation of PKC-alpha, -delta, -betaI, and -betaII. Our observations indicate that 15-HETE-DGs can modulate the activity of PKC isotypes in human TE cells and suggest an intracellular autocrine role for 15-HETE in human airway epithelia.
Alpert
S E
SE
Pediatric Pulmonary Division, Case Western Reserve University, Cleveland, Ohio 44106, USA. sealper@emory.edu
Walenga
R W
RW
Mandal
A
A
Bourbon
N
N
Kester
M
M
D002478:Cells, Cultured; D004075:Diglycerides / Q000494:pharmacology*; D015232:Dinoprostone / Q000096:biosynthesis; D004847:Epithelial Cells / Q000201:enzymology; D006801:Humans; D006893:Hydroxyeicosatetraenoic Acids / Q000493:pharmacokinetics / Q000494:pharmacology*; D007425:Intracellular Membranes / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism*; D010972:Platelet Activating Factor / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D014018:Tissue Distribution / Q000187:drug effects; D014132:Trachea / Q000166:cytology / Q000201:enzymology*
D004075:Diglycerides; D006893:Hydroxyeicosatetraenoic Acids; D007527:Isoenzymes; D010972:Platelet Activating Factor; C025984:15-hydroxy-5,8,11,13-eicosatetraenoic acid; D011493:Protein Kinase C; D015232:Dinoprostone