Abstract
The effect of chronic ozone exposure to ischemia reperfusion (I/R) injury in isolated perfused rat hearts was previously demonstrated. The present study tested our hypothesis that chronic ozone exposure led to attenuation of polyamines in the heart, which may limit sensitivity to I/R. Sprague Dawley rats were continuously exposed for 8 hrs/day for 28 days to filtered air or 0.8 ppm ozone. Isolated hearts were previously subjected to 0.5 hour of global ischemia followed by 1 hour of reperfusion after which global polyamine content was examined between the two groups. Spermidine production was significantly increased in the experimental group compared to control group (of I/R hearts). These results suggest that ozone-induced sensitivity to chronic I/R injury activates myocardial polyamine stress response characterized by increased enzymatic activities and accumulation of spermidine. Collectively, these results suggest that I/R possibly disturbs polyamine metabolism, and increased oxidative stress and concomitant reduced myocardial cell viability.
Highlights
Cardiovascular disease is one of the leading causes of mortality in the United States with 81 million reported cases from cardiovascular disease (CVD) in 2006 [1]
These results suggest that ozone-induced sensitivity to chronic ischemia reperfusion (I/R) injury activates myocardial polyamine stress response characterized by increased enzymatic activities and accumulation of spermidine
The chromatographs from experimental group were compared with standards to identify specific polyamines (Figures 5-6 of chromatograms corresponding to experimental group) which were identified and quantified
Summary
Cardiovascular disease is one of the leading causes of mortality in the United States with 81 million reported cases from cardiovascular disease (CVD) in 2006 [1]. The effect of chronic exposure of ozone on CVD was previously investigated and shown to be related to changes in cardiac function after I/R injury. This approach measured left ventricular end diastolic pressure (LVEDP) which decreased whereas myocardial tumor necrosis factor-alpha (TNF alpha) and lipid peroxidation levels increased. Polyamines (such as spermidine, cadaverine and putrescine) are linear polycations with one or more amine groups and are involved in cell synthesis of DNA and protein These metabolites are catalyzed by catabolic enzymes such as ornithine decarboxylase and spermidine-N1-acetyltransferase which aid synthesis and breakdown respectively. In our study the focus was measurement of changes in the other polyamines such as cadaverine, putrescine, and spermidine, from which we observed an increase of spermidine in the experimental-to-control ratio; tentatively indicate that a number of triggers are necessary for the appropriate response
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