Oxidative Stress in Mononuclear Cells Plays a Dominant Role in Their Adhesion to Mouse Femoral Artery After Injury

Abstract

Abstract-Leukocyte recruitment plays a pivotal role during inflammation after vascular injury. The importance of oxidative stress in vascular injury and its modulation by angiotensin II receptor blockers (olmesartan) have been demonstrated. We examined the contribution of leukocyte-associated oxidative stress in acute-phase leukocyte recruitment and its modulation by olmesartan. Male mice were treated with olmesartan (5 mg/kg per day) or vehicle for 7 days before the transluminal wire injury of the femoral artery. Intravital microscopy of the artery revealed that the mechanical injury increased adherent leukocytes at both 24 hours and 7 days after the injury, which was significantly reduced by olmesartan treatment. Dihydroethidium-associated fluorescence intensity observed in vehicle-treated mice was significantly diminished under olmesartan treatment. Apocynin, a nicotinamide-adenine dinucleotide phosphate oxidase inhibitor, showed a similar inhibitory effect on the leukocyte adhesion. Adoptive transfer of mononuclear cells, harvested from mice after wire injury, but not from those without wire injury, exhibited adhesion to the recipient injured artery. Furthermore, olmesartan treatment of mononuclear cells, but not of injured vasculature, reduced their recruitment to the injured artery. These data indicate that leukocyte recruitment to the mechanically injured artery is mediated by oxidative stress in leukocytes but not in vasculatures. Treatment with olmesartan blocked leukocyte recruitment by antagonizing mononuclear cells-associated oxidative stress. Key Words: angiotensin receptors Ⅲ imaging Ⅲ inflammation Ⅲ oxidant stress Ⅲ leukocytes V ascular injury, including an angioplasty of coronary artery, has been shown to induce oxidative stress through activation of the renin-angiotensin system. 1,2 Angiotensin (Ang) II is known to induce oxidative stress and leukocyte adhesion in the vascular wall, 3,4 whereas the local renin-angiotensin system in the vasculature plays an important role in the development of injury-induced inflammation. 5,6 Recent studies suggest an efficacy of Ang II type 1 receptor blocker (ARB) in reducing intimal hyperplasia after mechanical injury in animal models. 7,8 However, the role of ARB in the modulation of vascular inflammation at the early phase of the injury has not been fully investigated. The importance of Ang II and Ang II type 1 receptor in the development of atherosclerosis has been proposed on hypercholesterolemic mice. 9,10 The anti-inflammatory effect of ARB has been demonstrated in the microvasculature of the same mouse model. 11 Later, Petnehazy et al 12 reported that, in the atherosclerosis model, the leukocyte-associated but not vasculature-associated Ang II signal plays a dominant role in leukocyte recruitment in the microvasculature, indicating a previously unrecognized role of Ang II-dependent oxidative stress in leukocytes during atherosclerosis. In contrast, limited information is available regarding the role of leukocytes in their recruitment to the mechanically...

Combination of amlodipine and atorvastatin synergistically reduces leukocyte recruitment to mechanically injured mouse femoral artery

“…We recently developed a novel intravital microscopic system to directly monitor leukocyte recruitment in athero-prone arteries in vivo. 17,18 Using our technique, we have found that oxidative stress has an important role in leukocyte recruitment after luminal injury and documented the anti-inflammatory potential of compounds related to cardiovascular diseases. 18 In the present study, we examined the effects of atorvastatin and amlodipine on the recruitment of leukocytes to the site of vascular injury.…”

“…C-SF-1515, Cook, Bloomington, IN, USA), as previously described. 17,18 Briefly, the femoral artery was exposed, and upstream and downstream areas of the arterial branch were clamped. Then, a guide wire was inserted into the femoral artery and removed from the vessel, followed by branch ligation.…”

“…17,18 Briefly, the mice were anesthetized with pentobarbital and mechanically ventilated so as to maintain a normal acid-base balance. Rectal temperature was kept at 36.0-37.0 1C with a heating pad and an infrared heat lamp.…”

“…All images were analyzed using an image analysis program (MetaMorph; Molecular Devices, Sunnyvale, CA, USA) in accordance with the manufacturer's protocol, as previously described. 17,18 Briefly, the number of adherent cells during the 1-min recording period was counted in a region of interest, a 100-mmÂ100-mm rectangle segment of the vessel, and expressed as the number of adherent cells per 10 4 mm 2 on the vessel surface.…”

“…18 To examine whether atorvastatin and amlodipine have anti-oxidative properties, we monitored oxidative stress in the injured arteries using DHE, a fluorescence probe for superoxide, to visualize oxidative stress in situ. As shown in Figure 3a, oxidative stress in the vasculature was significantly increased by vascular injury, which was subsequently reduced by low-dose atorvastatin or amlodipine.…”