Differential effects of short-term ace- and AT1-receptor inhibition on postischemic injury and leukocyte adherence in vivo and in vitro.
There is recent evidence that angiotensin-converting enzyme (ACE) inhibition reduces postischemic injury and angiotensin II receptor inhibition may have similar effects. We therefore further characterized the role of ACE- vs. AT1-receptor inhibition on cell injury and temporal association of leukocyte endothelial interaction in response to ischemia-reperfusion. A combined in vivo and in vitro study comparing the ACE inhibitor enalapril and the AT1-receptor antagonist losartan was performed. The extent and temporal correlation of cellular damage (propidium-iodide staining), microvascular perfusion failure and leukocyte-endothelial interaction (leukocyte adherence) were investigated by means of intravital microscopy, after the application of hemodynamically ineffective doses of enalapril and losartan (5 mg/kg). A hamster dorsal skinfold model with a 4-h tourniquet ischemia was used. In vitro, the effect of enalapril and losartan on polymorphonuclear cell (PMN) adherence, as well as adhesion molecule expression (ICAM-1, VCAM-1), on hypoxia- or IL-1beta-stimulated endothelial cells (HUVEC) was assessed using a PMN-adhesion assay and flow cytometry, respectively. Ischemia-reperfusion responses revealed a biphasic pattern, comprised of an early phase (30 min) of acute cellular damage and microvascular perfusion failure, followed by a late increase (240 min) in leukocyte adherence in vivo. Enalapril significantly reduced early cellular damage, microvascular perfusion failure, and leukocyte adherence in response to ischemia-reperfusion. Conversely, AT1 receptor inhibition with losartan proved to be ineffective at attenuating postischemic microcirculatory disorders (leukocyte-endothelial interactions, microvascular perfusion failure) and aggravated cellular injury. In vitro, enalapril reduced PMN adherence and ICAM-1 and VCAM-1 expression, while losartan was ineffective in the same respect. Following ischemia-reperfusion injury, ACE- versus AT1-receptor inhibition induce differential effects concerning the extent and temporal association of cell injury and leukocyte-endothelial interaction. The use of enalapril combines the beneficial effects of preventing cell and vascular injury immediately after reperfusion, with a delayed inhibition of the inflammatory response. Since the AT1-receptor inhibitor losartan did not mimic effects obtained with ACE inhibition, it is conceivable that the responses in ischemia-reperfusion are mediated by a non-angiotensin II-AT1 receptor-dependent mechanism.
Guba
M
M
Department of Surgery, University of Regensburg, Germany.
Steinbauer
M
M
Büchner
M
M
Frölich
D
D
Farkas
S
S
Jauch
K W
KW
Anthuber
M
M
D057911:Angiotensin Receptor Antagonists; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology*; D000818:Animals; D002196:Capillaries / Q000187:drug effects; D002448:Cell Adhesion; D016923:Cell Death / Q000187:drug effects; D015687:Cell Hypoxia; D002460:Cell Line / Q000187:drug effects; D006224:Cricetinae; D004656:Enalapril / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects; D006439:Hemodynamics; D018056:Hemorheology; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D007962:Leukocytes / Q000166:cytology / Q000378:metabolism*; D019808:Losartan / Q000494:pharmacology; D008647:Mesocricetus; D009504:Neutrophils / Q000166:cytology / Q000187:drug effects; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism*; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin / Q000378:metabolism; D015427:Reperfusion Injury / Q000188:drug therapy / Q000378:metabolism*
D057911:Angiotensin Receptor Antagonists; D000806:Angiotensin-Converting Enzyme Inhibitors; D007375:Interleukin-1; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin; D004656:Enalapril; D007703:Peptidyl-Dipeptidase A; D019808:Losartan