Docosahexaenoic acid induces increases in [Ca2+]i via inositol 1,4,5-triphosphate production and activates protein kinase C gamma and -delta via phosphatidylserine binding site: implication in apoptosis in U937 cells.
We investigated, in monocytic leukemia U937 cells, the effects of docosahexaenoic acid (DHA; 22:6 n-3) on calcium signaling and determined the implication of phospholipase C (PLC) and protein kinase C (PKC) in this pathway. DHA induced dose-dependent increases in [Ca2+]i, which were contributed by intracellular pool, via the production of inositol-1,4,5-triphosphate (IP3) and store-operated Ca2+ (SOC) influx, via opening of Ca2+ release-activated Ca2+ (CRAC) channels. Chemical inhibition of PLC, PKCgamma, and PKCdelta, but not of PKCbeta I/II, PKCalpha, or PKCbetaI, significantly diminished DHA-induced increases in [Ca2+]i. In vitro PKC assays revealed that DHA induced a approximately 2-fold increase in PKCgamma and -delta activities, which were temporally correlated with the DHA-induced increases in [Ca2+]i. In cell-free assays, DHA, but not other structural analogs of fatty acids, activated these PKC isoforms. Competition experiments revealed that DHA-induced activation of both the PKCs was dose-dependently inhibited by phosphatidylserine (PS). Furthermore, DHA induced apoptosis via reactive oxygen species (ROS) production, followed by caspase-3 activation. Chemical inhibition of PKCgamma/delta and of SOC/CRAC channels significantly attenuated both DHA-stimulated ROS production and caspase-3 activity. Our study suggests that DHA-induced activation of PLC/IP3 pathway and activation of PKCgamma/delta, via its action on PS binding site, may be involved in apoptosis in U937 cells.
Aires
Virginie
V
Unité Propre de Recherche et de l'Enseignement Supérieur, Equipe d'Accueil 4183-Lipides & Signalisation Cellulaire, Faculty of Life Sciences, University of Burgundy, Dijon, France.
Hichami
Aziz
A
Filomenko
Rodolphe
R
Plé
Aude
A
Rébé
Cédric
C
Bettaieb
Ali
A
Khan
Naim Akhtar
NA
D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001665:Binding Sites / Q000187:drug effects / Q000502:physiology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D004281:Docosahexaenoic Acids / Q000378:metabolism / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis* / Q000502:physiology; D007424:Intracellular Fluid / Q000378:metabolism*; D010718:Phosphatidylserines / Q000737:chemistry / Q000378:metabolism*; D011493:Protein Kinase C / Q000737:chemistry / Q000378:metabolism*; D051745:Protein Kinase C-delta / Q000737:chemistry / Q000378:metabolism*; D020298:U937 Cells
D010718:Phosphatidylserines; D004281:Docosahexaenoic Acids; D015544:Inositol 1,4,5-Trisphosphate; C087857:protein kinase C gamma; D011493:Protein Kinase C; D051745:Protein Kinase C-delta