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Differential effects of short-term ace- and AT1-receptor inhibition on postischemic injury and leukocyte adherence in vivo and in vitro.

Abstract
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.
AuthorsM Guba, M Steinbauer, M Büchner, D Frölich, S Farkas, K W Jauch, M Anthuber
JournalShock (Augusta, Ga.) (Shock) Vol. 13 Issue 3 Pg. 190-6 (Mar 2000) ISSN: 1073-2322 [Print] UNITED STATES
PMID10718375 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References
  • Angiotensin Receptor Antagonists
  • Angiotensin-Converting Enzyme Inhibitors
  • Interleukin-1
  • Receptor, Angiotensin, Type 1
  • Receptor, Angiotensin, Type 2
  • Receptors, Angiotensin
  • Enalapril
  • Peptidyl-Dipeptidase A
  • Losartan
Topics
  • Angiotensin Receptor Antagonists
  • Angiotensin-Converting Enzyme Inhibitors (pharmacology)
  • Animals
  • Capillaries (drug effects)
  • Cell Adhesion
  • Cell Death (drug effects)
  • Cell Hypoxia
  • Cell Line (drug effects)
  • Cricetinae
  • Enalapril (pharmacology)
  • Endothelium, Vascular (cytology, drug effects)
  • Hemodynamics
  • Hemorheology
  • Humans
  • Interleukin-1 (pharmacology)
  • Leukocytes (cytology, metabolism)
  • Losartan (pharmacology)
  • Mesocricetus
  • Neutrophils (cytology, drug effects)
  • Peptidyl-Dipeptidase A (metabolism)
  • Receptor, Angiotensin, Type 1
  • Receptor, Angiotensin, Type 2
  • Receptors, Angiotensin (metabolism)
  • Reperfusion Injury (drug therapy, metabolism)

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