Pharmacologic preconditioning (PPC) is an approach to limit ischemia reperfusion (IR) injury that does not require prior brief ischemia or the presence of the drug once ischemia occurs. KATP channel agonists, per se, induce PPC via memory pathways that lead to cardioprotection assessed by better tissue perfusion, improved metabolic and mechanical function, fewer dysrhythmias and reduced infarct size. Limits to our understanding of features and mechanisms of PPC have impeded optimal utilization of this potent phenomenon to protect against cardiac IR injury. Particularly lacking is an understanding of the role of the mitochondrion in PPC. Big (B) conductance Ca2+ -sensitive K+ channels (BKCa) are also present in cardiac cell inner mitochondrial membrane (IMM) and appear to mediate cardioprotection. We have evidence of protection also by small conductance (S) KCa channels in the IMM. We propose that drug -induced K+ entry into the mitochondrial (m) matrix alters bioenergetics in a way that increases electron leak to induce an increase in reactive oxygen species (ROS) required to trigger downstream protective effects. Preliminary results indicate that protective effects of mKCa channel opening are blocked by dismutation of the superoxide radical. A unifying hypothesis for the initiating mechanism of PPC may be a matrix K+ influx -induced ROS generation. We will a) examine in guinea pig isolated cardiac mitochondria the bioenergetic mechanisms initiated by matrix K+ influx that lead to ROS generation and b) determine the specific ROS responsible for triggering PPC in guinea pig isolated hearts. In addition we will c) identify these channels by Western blots, 2D gel electrophoresis and MALDI- TOF and LIT SNCE mass spectrometry and characterize these channels in artificial lipid bilayers. We will use the best techniques, measures (mitochondrial respiration, cytosolic and mCa2+, NADH, mFAD, mpH, IMM potential, and several ROS) and drugs available to search for the factors, the sequence of events, and the specific ROS that initiate PPC.
These studies will result in a better understanding of the regulation of mitochondrial bioenergetic function by Ca2+, K+, and ROS, and selection of the mitochondrion as a target for pharmacologic manipulation. This research should lead to the practical application of mitochondrial-targeted drugs to prophylactically treat patients with coronary artery disease using novel approaches.
|Yang, MeiYing; Camara, Amadou K S; Aldakkak, Mohammed et al. (2017) Identity and function of a cardiac mitochondrial small conductance Ca2+-activated K+ channel splice variant. Biochim Biophys Acta 1858:442-458|
|Agarwal, Bhawana; Dash, Ranjan K; Stowe, David F et al. (2014) Isoflurane modulates cardiac mitochondrial bioenergetics by selectively attenuating respiratory complexes. Biochim Biophys Acta 1837:354-65|
|Yang, Meiying; Stowe, David F; Udoh, Kenechukwu B et al. (2014) Reversible blockade of complex I or inhibition of PKC? reduces activation and mitochondria translocation of p66Shc to preserve cardiac function after ischemia. PLoS One 9:e113534|
|Nabbi, Raha; Gadicherla, Ashish K; Kersten, Judy R et al. (2014) Genetically determined mitochondrial preservation and cardioprotection against myocardial ischemia-reperfusion injury in a consomic rat model. Physiol Genomics 46:169-76|
|Aldakkak, Mohammed; Stowe, David F; Dash, Ranjan K et al. (2013) Mitochondrial handling of excess Ca2+ is substrate-dependent with implications for reactive oxygen species generation. Free Radic Biol Med 56:193-203|
|Boelens, Age D; Pradhan, Ranjan K; Blomeyer, Christoph A et al. (2013) Extra-matrix Mg2+ limits Ca2+ uptake and modulates Ca2+ uptake-independent respiration and redox state in cardiac isolated mitochondria. J Bioenerg Biomembr 45:203-18|
|Blomeyer, Christoph A; Bazil, Jason N; Stowe, David F et al. (2013) Dynamic buffering of mitochondrial Ca2+ during Ca2+ uptake and Na+-induced Ca2+ release. J Bioenerg Biomembr 45:189-202|
|Aldakkak, Mohammed; Stowe, David F; Camara, Amadou K S (2013) Safety and Efficacy of Ranolazine for the Treatment of Chronic Angina Pectoris. Clin Med Insights Ther 2013:1-14|
|Stowe, David F; Gadicherla, Ashish K; Zhou, Yifan et al. (2013) Protection against cardiac injury by small Ca(2+)-sensitive K(+) channels identified in guinea pig cardiac inner mitochondrial membrane. Biochim Biophys Acta 1828:427-42|
|Rhodes, Samhita S; Camara, Amadou K S; Heisner, James S et al. (2012) Reduced mitochondrial Ca2+ loading and improved functional recovery after ischemia-reperfusion injury in old vs. young guinea pig hearts. Am J Physiol Heart Circ Physiol 302:H855-63|
Showing the most recent 10 out of 21 publications