ACCEPTED MANUSCRIPT Plasma Levels of Oxidative stress-Responsive Apoptosis Inducing Protein (ORAIP) in Rats Subjected to Physicochemical Oxidative Stresses

�Oxidative stress is known to play a pivotal role in the pathogenesis of various disorders including atherosclerosis, aging, and especially ischemia/reperfusion injury. It causes cell damage that leads to apoptosis. However the precise mechanism has been uncertain. Recently, we identified an apoptosis-inducing humoral factor in a hypoxia/reoxygenated medium of cardiac myocytes. We named this novel post-translationally modified secreted form of eukaryotic translation initiation factor 5A as Oxidative stress-Responsive Apoptosis Inducing Protein (ORAIP). We developed a sandwich enzyme-linked immunosorbent assay and confirmed that myocardial ischemia/reperfusion markedly increased plasma levels of ORAIP. To investigate whether the role of ORAIP is common to various types of oxidative stress, we measured plasma ORAIP levels in rats subjected to three physicochemical models of oxidative stress including N2/O2 inhalation, cold/warm-stress (heat shock), and blood acidification. In all three models, plasma ORAIP levels significantly increased and reached a peak level at 10 to 30 min after stimulation, then decreased within 60 min. The (mean ± SE) plasma ORAIP levels before and after (peak) stimulation were (16.4 ± 9.6) and (55.2 ± 34.2) ng/ml in N2/O2 inhalation, (14.1 ± 12.4) and (34.3 ± 14.6) ng/ml in cold/warm-stress, and (18.9 ± 14.3) and (134.0 ± 67.2) ng/ml in blood acidification study. These data strongly suggest that secretion of ORAIP in response to oxidative 3 stress is universal mechanism and plays an essential role. ORAIP will be an important novel biomarker as well as a specific therapeutic target of these oxidative stress-induced cell injury.