Annexin A5 Scintigraphy of Forearm as a Novel In Vivo Model of Skeletal Muscle Preconditioning in Humans

Abstract

Background-Nonlethal ischemia and reperfusion reduce ischemia-reperfusion-induced cell death, a phenomenon called ischemic preconditioning. In animal models, this potent endogenous protection is mimicked in vivo by administration of adenosine. In humans, exploitation of ischemic preconditioning is hindered by the lack of an appropriate in vivo model to study this phenomenon. To solve this problem, we aimed to set up an easy-to-use human in vivo model to study ischemic or pharmacological preconditioning. Methods and Results-Healthy male volunteers performed unilateral ischemic handgrip. At reperfusion, we intravenously injected technetium-99m-labeled Annexin A5, a presumed marker of ischemic injury, and we imaged both forearms and hands simultaneously with a gamma camera. Region of interest analysis (counts per pixel) and subsequent calculation of the percentage difference in radioactivity between experimental and control hands (thenar muscle; meanϮSE) revealed significant uptake to the ischemically exercised tissue (26Ϯ3% at 4 hours after reperfusion; PϽ0.05). This selective localization of Annexin A5 was reduced by ischemic preconditioning (10 minutes of ischemia plus reperfusion before ischemic exercise) or by infusion of adenosine into the brachial artery to 6Ϯ1% and 10Ϯ3%, respectively (PϽ0.05 versus ischemic exercise alone), resembling observations in animal models with infarct size as an end point.Appropriate control experiments supported our conclusion. Conclusions-Annexin

Atorvastatin does not Affect Ischaemia-Induced Phosphatidylserine Exposition in Humans in-vivo

“…One and four hours after this administration both hands were scanned simultaneously by use of a gamma camera (Orbiter camera equipped with low-energy high-resolution collimators; Siemens, Hoffman Estates, Ill, USA) as previously described 28) . Caffeine plasma concentrations were determined using reversed-phase HPLC with UV detection set at 273 nm 37) .…”

“…Based on previous studies, a between subject SD of 10% was predicted [28][29][30] . Conservatively assuming a correlation coefficient of 0.5 between first and second paired observation, we calculated that with an alpha of 0.05 and a power of 90%, using 24 subjects allows us to find a difference in annexin A5 targeting of 7%.…”

“…We have developed an experimental model to study PS exposure after IR in healthy volunteers. Our model uses radiolabeled recombinant annexin A5 to visualise PS-exposition that occurs after 10 minutes of forearm ischemia combined with isometric exercise 28) . Interventions that have been shown in preclinical and clinical research to modulate myocardial infarct size (ischaemic preconditioning, and administration of adenosine, dipyridamole, and caffeine) similarly modulate annexin A5 targeting in our forearm model, further supporting a role for PS-exposure in IRinjury [28][29][30] .…”

The changes of technetium-99m-labeled annexin-V in delayed anesthetic preconditioning during myocardial ischemia/reperfusion

“…When it is bound to the phosphatidylserine it can be used to detect the apoptosis in vivo. Technetium-99m-labeled annexin-V is a promising method for assessing the degree of apoptosis [15][16][17]. In this study we used this technology to measure myocardial apoptosis with great success.…”

“…Annexin-V is an endogenous protein that has a high affinity for binding to phosphatidylserine. Technetium99m-labeled annexin-V is a promising method to assess the degrees of apoptosis [15][16][17]. By using 3 different technologies, real-time imaging of technetium-99m-labeled annexin-V, transferase dUTP nick end labeling (TUNEL) assay, and caspase-3, we test the hypothesis that delayed APC with sevoflurane can attenuate myocardial apoptosis during I/R.…”