Sympathoexcitation by bradykinin involves Ca2+-independent protein kinase C.
Bradykinin has long been known to excite sympathetic neurons via B(2) receptors, and this action is believed to be mediated by an inhibition of M-currents via phospholipase C and inositol trisphosphate-dependent increases in intracellular Ca(2+). In primary cultures of rat superior cervical ganglion neurons, bradykinin caused an accumulation of inositol trisphosphate, an inhibition of M-currents, and a stimulation of action potential-mediated transmitter release. Blockade of inositol trisphosphate-dependent signaling cascades failed to affect the bradykinin-induced release of noradrenaline, but prevented the peptide-induced inhibition of M-currents. In contrast, inhibition or downregulation of protein kinase C reduced the stimulation of transmitter release, but not the inhibition of M-currents, by bradykinin. In cultures of superior cervical ganglia, classical (alpha, betaI, betaII), novel (delta, epsilon), and atypical (zeta) protein kinase C isozymes were detected by immunoblotting. Bradykinin induced a translocation of Ca(2+)-independent protein kinase C isoforms (delta and epsilon) from the cytosol to the membrane of the neurons, but left the cellular distribution of other isoforms unchanged. This activation of Ca(2+)-independent protein kinase C enzymes was prevented by a phospholipase C inhibitor. The bradykinin-dependent stimulation of noradrenaline release was reduced by inhibitors of classical and novel protein kinase C isozymes, but not by an inhibitor selective for Ca(2+)-dependent isoforms. These results demonstrate that bradykinin B(2) receptors are linked to phospholipase C to simultaneously activate two signaling pathways: one mediates an inositol trisphosphate- and Ca(2+)-dependent inhibition of M-currents, the other one leads to an excitation of sympathetic neurons independently of changes in M-currents through an activation of Ca(2+)-insensitive protein kinase C.
Scholze
Thomas
T
Department of Pharmacology, University of Vienna, A-1090 Vienna, Austria.
Moskvina
Eugenia
E
Mayer
Martina
M
Just
Herwig
H
Kubista
Helmut
H
Boehm
Stefan
S
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels; D002478:Cells, Cultured; D020536:Enzyme Activators / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007527:Isoenzymes / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism / Q000493:pharmacokinetics; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D043782:Receptor, Bradykinin B2; D018002:Receptors, Bradykinin / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000037:antagonists & inhibitors; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D017783:Superior Cervical Ganglion; D013564:Sympathetic Nervous System / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010738:Type C Phospholipases / Q000187:drug effects / Q000378:metabolism
D015220:Calcium Channels; D020536:Enzyme Activators; D004791:Enzyme Inhibitors; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007527:Isoenzymes; D015221:Potassium Channels; D043782:Receptor, Bradykinin B2; D018002:Receptors, Bradykinin; D018160:Receptors, Cytoplasmic and Nuclear; D015544:Inositol 1,4,5-Trisphosphate; C115197:calcium-independent protein kinase C; D011493:Protein Kinase C; D010738:Type C Phospholipases; D001920:Bradykinin; D002118:Calcium; D009638:Norepinephrine