Angiotensin-converting enzyme inhibitor ramiprilat interferes with the sequestration of the B2 kinin receptor within the plasma membrane of native endothelial cells.
BACKGROUND
ACE (kininase II) inhibitors have been shown to exert their beneficial cardiovascular effects via the inhibition of both angiotensin II formation and bradykinin breakdown. Because recent evidence suggests that ACE inhibitors may also interfere with B2 kinin receptor signaling and thus enhance the vascular response to bradykinin, we examined whether the distribution of B2 kinin receptors within the plasma membrane of native endothelial cells is affected by an ACE inhibitor.


RESULTS
Localization of the B2 kinin receptor in membranes prepared from native porcine aortic endothelial cells was evaluated by means of specific [3H]bradykinin binding and immunoprecipitation of the B2 receptor from isolated membranes. Effects of bradykinin and ramiprilat on intracellular signaling were determined by monitoring the activation of the extracellularly regulated kinases Erk1 and Erk2 as well as [Ca2+]i increases in fura 2-loaded endothelial cells. Stimulation of native endothelial cells with bradykinin 100 nmol/L resulted in the time-dependent sequestration of the B2 receptor to caveolin-rich (CR) membranes, which was maximal after 5 minutes. Pretreatment with ramiprilat 100 nmol/L for 15 minutes significantly attenuated the recovery of B2 kinin receptors in CR membranes while increasing that from membranes lacking caveolin. This effect was not due to the inhibition of bradykinin degradation, because no effect was seen in the presence of an inhibitory concentration of the synthetic ACE substrate hippuryl-L-histidyl-L-leucine. Ramiprilat also decreased [3H]bradykinin binding to CR membranes when applied either before or after bradykinin stimulation. Moreover, ramiprilat resulted in reactivation of the B2 receptor in bradykinin-stimulated cells and induced a second peak in [Ca2+]i and reactivation of Erk1/2.


CONCLUSIONS
The ACE inhibitor ramiprilat interferes with the targeting of the B2 kinin receptor to CR membrane domains in native endothelial cells. Therefore, effects other than the inhibition of kininase II may account for the effects of ramiprilat and other ACE inhibitors on the vascular system.
Benzing
T
T
Institut für Kardiovaskuläre Physiologie, Klinikum der J.W. Goethe-Universität, Frankfurt am Main, Germany.
Fleming
I
I
Blaukat
A
A
Müller-Esterl
W
W
Busse
R
R
D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology*; D000818:Animals; D001011:Aorta; D001692:Biological Transport / Q000187:drug effects; D001920:Bradykinin / Q000031:analogs & derivatives / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D017257:Ramipril / Q000031:analogs & derivatives* / Q000494:pharmacology; D043782:Receptor, Bradykinin B2; D018002:Receptors, Bradykinin / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013552:Swine
D000806:Angiotensin-Converting Enzyme Inhibitors; D008565:Membrane Proteins; D043782:Receptor, Bradykinin B2; D018002:Receptors, Bradykinin; C052549:ramiprilat; C065679:icatibant; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D017257:Ramipril; D001920:Bradykinin