Abstract TP109: Impact of ATP-Induced Mild Hypothermia on Focal Cerebral Ischemia in Rats
Brain ischemia is a devastating disorder without effective therapies. One of the most promising approaches to attenuate ischemic brain injury is mild hypothermia. Recent studies show that adenosine nucleotides can induce hypothermia in mice. The purpose of the present study was to test the hypothesis that ATP, a common form of energy currency, induces mild hypothermia in rats and reduces brain injury following focal cerebral ischemia. ATP solution was dissolved in water and intraperitoneally injected; and focal stroke was induced by a suture model of middle cerebral artery occlusion and ischemic outcomes were evaluated within 24 hr. We found that injections of ATP lowered core body temperature in a dose-dependent manner; the dose appropriate for subsequent experiments was 2 g/kg as it reduced temperature to the range of mild hypothermia for approximately 7 hours. While intravenous injection of ATP was less effective in lowering body temperature. However, when ATP-induced hypothermia was applied to stroke, a neuroprotective effect was not observed. In contrast, the infarct volume grew even larger in ATP-treated rats. Not surprisingly, this was accompanied by an increased rate of seizure events, hemorrhagic transformation, and higher mortality. Continuous monitoring of physiological parameters revealed that ATP severely reduced heartbeat rate and blood pressure. ATP also raised blood glucose to dangerous levels and this was accompanied by severe acidosis and hypocalcemia. Western blotting showed that ATP treatment decreased levels of both phospho-Akt and total-Akt in the ischemic cortex. Our results reveal that, despite inducing hypothermia, ATP is not appropriate for protecting the brain against stroke, as it is associated with exaggerated ischemic outcomes and dangerous systemic side effects.
- © 2012 by American Heart Association, Inc.