Remote Ischemic Conditioning: An Update on Mechanisms Karin Przyklenk PhD Director, Cardiovascular Research Institute Professor, Departments of Physiology & Emergency Medicine Wayne State University School of Medicine Detroit MI ICT Focus Group Meeting: 17th November, 2013 Myocardial ‘Conditioning’ classic cardioprotective paradigms: ischemic preconditioning, postconditioning • protective stimuli (brief antecedent ischemia; stuttered reflow) applied to the heart remote ischemic conditioning (RIC): protective stimulus applied at a remote site first evidence: remote preconditioning (Przyklenk et al, 1993) remote ischemia coronary occlusion reperfusion Remote Ischemic Conditioning: First Evidence Infarct Size 25 (% of Risk Region) 20 15 p<0.05 10 Control 5 1 h LAD Occl 4.5 h Reflow 0 Control Cx PC Circumflex (Cx) PC 1 h LAD Occl 4.5 h Reflow Cx Occl infarct size (% of risk region) Significant reduction of infarct size with ‘intra-cardiac’ remote ischemic preconditioning Przyklenk et al, Circulation 1993;87:893-99. Developing the Concept . . . intra-cardiac RIC inter-organ RIC ‘Inter-organ’ RIC • • • model: isolated bufferperfused rabbit PC stimulus: transfer of coronary effluent endpoint: infarct size 50 Donor: Control 30 40’ ischemia 1 h Reflow Effluent Acceptor: Control Infarct Size (% of Risk Region) 40 20 ** 10 ** 40’ ischemia 0 Donor: PC 40’ ischemia Effluent n Do Acceptor: PC ntr o C or- ol pto e c Ac l tro n o r-C PC PC r r no pto e Do c Ac 40’ ischemia infarct size **p<0.01 vs Donor-Control Dickson et al, Am J Physiol 1999;277:H2451-57. ‘Inter-Organ’ RIC • • • model: anesthetized pig PC stimulus: skeletal muscle ischemia endpoint: infarct size Control 40’ LAD Occl 2 h Reflow Hindlimb ischemia 40’ LAD Occl infarct size (% of risk region) Kharbanda et al, Circulation 1997;106:2881-83. Developing the Concept . . . intra-cardiac RIC inter-organ RIC Phase II clinical trials Phase III clinical trials Developing the Concept . . . characterize (physiology) understand (mechanisms) apply Why is this important? ~25 published Phase II clinical trials cardiac surgery; elective PCI; primary PCI in patients with STEMI stimulus: multiple (3-4) 5 min episodes of limb ischemia primary endpoint: infarct size or its surrogate outcomes have been mixed . . . . . . possibly a consequence of gaps in our understanding of the mechanisms of RPC Ovize, Thibault & Przyklenk, Circulation Research 2013;113:439-50. Mechanisms For pre-, postconditioning: trigger receptor stimulation signaling effector CARDIOPROTECTION adenosine; bradykinin, opioids G-protein coupled receptors RISK, SAFE pathways (ERK, PI3 kinase/Akt, JAK, STAT3) mitochondria (mPTP) Mechanisms For pre-, postconditioning: trigger receptor stimulation signaling effector CARDIOPROTECTION Mechanisms For pre-, postconditioning: For remote conditioning: trigger trigger receptor stimulation COMMUNICATION signaling effector CARDIOPROTECTION receptor stimulation signaling effector CARDIOPROTECTION Communication In 1993: trigger COMMUNICATION the infarct-sparing effect of remote conditioning ‘. . . may be mediated by factor(s) activated, produced, or transported throughout the heart during brief ischemia-reperfusion.’ receptor stimulation In 2013 . . . signaling effector CARDIOPROTECTION Communication: circulating humoral factor Candidates: adenosine, bradykinin, opiods by HPLC: ‘small (<15 kDa) hydrophobic molecule’ from proteomic screens: Apo-A1 • Hilbert et al, PLoS 2013;8:e77211 • Hepponstall et al, PLoS 2012;7:e48284 ‘educated guesses’: SDF1-α/CXCR4; microRNAs • Davidson et al, Basic Res Cardiol 2013;108:377 • Duan et al, Cardiology 2012;122:36-43 SDF1-α/CXCR4 Signaling Plasma SDF1- Concentration (pg/mL) 1200 p<0.01 1000 800 Infarct Size 600 (% of Risk Region) 60 400 200 40 0 Control • in vivo rat model • plasma SDF1-α concentration • ** RIC increased following RIC CXCR4 inhibitor (AMD3100) attenuated the infarct-sparing effect of RIC Davidson et al, Basic Res Cardiol 2013;108:377 20 0 ol r t n Co r r ito ito b b i i nh nh I I + + ol IC r t R n Co RIC Communication: circulating humoral factor Candidates: adenosine, bradykinin, opiods by HPLC: ‘small (<15 kDa) hydrophobic molecule’ from proteomic screens: Apo-A1 ‘educated guesses’: SDF1-α/CXCR4; microRNAs Source: myocytes, endothelial cells? Transported to heart via: blood/perfusate exosomes, microparticles/microvesicles : neuronal pathways Communication: neuronal pathways Source: activation of sensory neurons stimulation of afferent neuronal pathways CNS Transported to heart via: activation of efferent neuronal pathways ‘Remote Preconditioning Reflex’ Mastitskaya et al, Cardiovasc Res 2012;95:487-94. Gourine & Gourine, Physiology 2013: in press. Communication: neuronal pathways Source: activation of sensory neurons stimulation of afferent neuronal pathways CNS Transported to heart via: activation of efferent neuronal pathways Model-dependent? In some models: integrated (neurohumoral communication)? redundant? Summary In 1993: trigger COMMUNICATION the infarct-sparing effect of remote conditioning ‘. . . may be mediated by factor(s) activated, produced, or transported throughout the heart during brief ischemia-reperfusion.’ receptor stimulation In 2013 . . . signaling effector CARDIOPROTECTION observations, associations . . . no integrated, unifying hypothesis Collaborators Peter Whittaker, PhD Joe Wider Vishnu Undyala Eric Dickson, MD Michelle Maynard Craig Smith, MD Chad Darling, MD Dale Greiner, PhD Signaling • myocardial biopsies obtained • from patients during coronary artery bypass surgery ‘unique signaling signature of RIPC’: increased STAT5 phosphorylation in patients that received RIPC vs Controls Heusch et al, Circ Res 2012;110:111-15.