Hypothermia is a very powerful temperature-dependent method to protect against clinical cardiac ischemia and reperfusion (I/R) injury. Hypothermia decreases energy utilization and preserves mechanisms to rapidly generate ATP on reperfusion. But hypothermia does not provide complete protection and has deleterious effects; cold perfusion can result in elevated cytosolic (cyt) Ca2+ and cause hyper-contracture and reduced compliance. Formation of reactive oxygen species, (ROS) and, mitochondrial (m) Ca2+ loading are major factors that cause reperfusion stunning and permanent damage after normothermic ischemia. The roles of mROS formation, m Ca2+ loading, mNADH, and other indices of mitochondrial bioenergetics during hypothermic perfusion and I/R have not been studied. Increased cellular sodium-hydrogen exchange (NHE) activity observed during I/R is an attractive candidate to link increased ROS production and m Ca2+ overload. These studies will assess hypothermic ischemia -induced effects on cyt Na+ and m Ca2+ loading, formation of ROS, KAav channels, and mitochondrial bioenergetics (NADH, ATP synthesis, O2 consumption) to determine the mechanism of protection by hypothermia and inhibition of NHE.
Major aims are: 1) To Assess the deleterious effects of hypothermia on mitochondrial function and to evaluate the cardio protective role of cardioplegia, NHE inhibition, ROS scavengers, and Kxav channel opening during and after hypothermic ischemia. 2) To determine the mechanisms of cold perfusion and I/R -induced Na+ and m Ca2+ loading on mitochondrial and myocardial dysfunction using alkalosis, ROS generators and mKAav blockers alone and together with NIIE inhibition. We will use unique on-line fluorescence techniques to assess ROS formation, redox balance, cyt [Na+], and m [Ca2+] at 37 and 27 degrees C in intact guinea pig hearts and ROS release in coronary effluent. Protection will be evidenced in intact hearts by reduced global infarct size, enzyme release, and better mechanical and metabolic function. The mechanism of hypothermic protection will be further investigated in isolated mitochondria measured for NADH, membrane potential, ATP synthesis, and 02 consumption. Emphasis will be placed on the effects of drug-induced blockade of mitochondrial ROS formation, NHE activity and KAav channel opening on cellular cation balance and mitochondrial bioenergetics.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Scientist Development Award - Research & Training (K01)
Project #
5K01HL073246-03
Application #
6931159
Study Section
Special Emphasis Panel (ZHL1-CSR-N (F1))
Program Officer
Commarato, Michael
Project Start
2003-09-01
Project End
2008-08-31
Budget Start
2005-09-01
Budget End
2006-08-31
Support Year
3
Fiscal Year
2005
Total Cost
$148,285
Indirect Cost
Name
Medical College of Wisconsin
Department
Anesthesiology
Type
Schools of Medicine
DUNS #
937639060
City
Milwaukee
State
WI
Country
United States
Zip Code
53226
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Aldakkak, Mohammed; Stowe, David F; Lesnefsky, Edward J et al. (2009) Modulation of mitochondrial bioenergetics in the isolated Guinea pig beating heart by potassium and lidocaine cardioplegia: implications for cardioprotection. J Cardiovasc Pharmacol 54:298-309
Riess, Matthias L; Camara, Amadou K S; Heinen, Andre et al. (2008) KATP channel openers have opposite effects on mitochondrial respiration under different energetic conditions. J Cardiovasc Pharmacol 51:483-91
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Aldakkak, Mohammed; Stowe, David F; Chen, Qun et al. (2008) Inhibited mitochondrial respiration by amobarbital during cardiac ischaemia improves redox state and reduces matrix Ca2+ overload and ROS release. Cardiovasc Res 77:406-15
Heinen, Andre; Aldakkak, Mohammed; Stowe, David F et al. (2007) Reverse electron flow-induced ROS production is attenuated by activation of mitochondrial Ca2+-sensitive K+ channels. Am J Physiol Heart Circ Physiol 293:H1400-7
Huang, M; Camara, A K S; Stowe, D F et al. (2007) Mitochondrial inner membrane electrophysiology assessed by rhodamine-123 transport and fluorescence. Ann Biomed Eng 35:1276-85

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