Effects of spontaneous or induced brain ischemia on vessel reactivity: The role of inducible nitric oxide synthase

• Published in: Life sciences (1973) Vol. 71; no. 6; pp. 679 - 692
• Main Authors: Tokuno, Shinichi, Chen, Fei, Pernow, John, Jiang, Jiahua, Valen, Guro
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 28.06.2002
• Subjects: Acetylcholine - pharmacology; Animals; Aorta, Thoracic - drug effects; Aorta, Thoracic - physiology; Aorta, Thoracic - physiopathology; Brain Ischemia - enzymology; Brain Ischemia - physiopathology; Dinoprost - pharmacology; Disease Models, Animal; Endothelial function; In Vitro Techniques; Ischemia; Ischemic Attack, Transient - enzymology; Ischemic Attack, Transient - physiopathology; Medicin och hälsovetenskap; Mice; Mice, Inbred C57BL; Mice, Knockout; Muscle Contraction - drug effects; Muscle Relaxation - drug effects; Muscle, Smooth, Vascular - drug effects; Muscle, Smooth, Vascular - physiology; Muscle, Smooth, Vascular - physiopathology; Myocardial Ischemia - physiopathology; Nitric oxide; Nitric Oxide Synthase - deficiency; Nitric Oxide Synthase - genetics; Nitric Oxide Synthase - metabolism; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Phenylephrine - pharmacology; Preconditioning; Reference Values; Endothelial function; Ischemia; Preconditioning; Nitric oxide
• ISSN: 0024-3205; 1879-0631
• DOI: 10.1016/S0024-3205(02)01711-3

Short episodes of ischemia and reperfusion in various organs may protect the organ itself, and the heart both as an immediate and a delayed effect. The present study investigates whether a systemic protection of vascular function occurs during adaption to ischemia. Brain ischemia was induced by bilateral ligation of the internal carotid arteries in C57BL6 mice, and 24–36 hours later rings of the thoracic aorta were mounted to study in vitro relaxation and contraction, or proteins were extracted for immunoblotting for endothelial nitric oxide synthase (eNOS) or inducible NOS (iNOS). eNOS decreased, while iNOS increased in the aortic wall after carotid artery ligation. In vitro contraction to increasing concentrations of prostaglandin F 2α (PGF 2α) was attenuated, while relaxation to acetylcholine (ACh) was enhanced. The latter was abolished by the iNOS-inhibitor aminoguanidine. When brain ischemia was induced in iNOS deficient mice, an increase of aortic eNOS was found 24 hours later. The ischemia-induced attenuated relaxation to PGF 2α and enhanced relaxation to ACh were abolished. Aortic rings from mice with severe atherosclerosis (apolipoprotein E and low density lipoprotein receptor double knockout (ApoE/LDLr KO) mice) and spontaneous ischemic events in the heart or brain in vivo were also studied. Spontanous ischemic events in ApoE/LDLr KO animals did not influence iNOS and eNOS in the vessel wall. A reduced contraction to PGF 2α was observed, but relaxation to ACh was unchanged. These findings suggest that induced brain ischemia as a model of delayed, remote preconditioning protects vessel reactivity, and this protection is mediated by iNOS.