Transient limb ischaemia remotely preconditions through a humoral mechanism acting directly on the myocardium: evidence suggesting cross-species protection

Abstract

rIPC (remote ischaemic preconditioning) is a phenomenon whereby short periods of ischaemia and reperfusion of a tissue or organ (e.g. mesentery, kidney) can protect a distant tissue or organ (e.g. heart) against subsequent, potentially lethal, ischaemia. We, and others, have shown that transient limb ischaemia can provide potent myocardial protection experimentally and clinically during cardiac surgery. Nonetheless, our understanding of the signal transduction from remote stimulus to local effect remains incomplete. The aim of the present study was to define the humoral nature of rIPC effector(s) from limb ischaemia and to study their local effects in isolated heart and cardiomyocyte models. Using a Langendorff preparation, we show that infarct size after coronary artery ligation and reperfusion was substantially reduced by rIPC in vivo, this stimulus up-regulating the MAPKs (mitogen-activating protein kinases) p42/p44, and inducing PKCepsilon (protein kinase Cepsilon) subcellular redistribution. Pre-treatment with the plasma and dialysate of plasma (obtained using 15 kDa cut-off dialysis membrane) from donor rabbits subjected to rIPC similarly protected against infarction. The effectiveness of the rIPC dialysate was abrogated by passage through a C18 hydrophobic column, but eluate from this column provided the same level of protection. The dialysate of rIPC plasma from rabbits and humans was also tested in an isolated fresh cardiomyocyte model of simulated ischaemia and reperfusion. Necrosis in cardiomyocytes treated with rIPC dialysate was substantially reduced compared with control, and was similar to cells pre-treated by 'classical' preconditioning. This effect, by rabbit rIPC dialysate, was blocked by pre-treatment with the opiate receptor blocker naloxone. In conclusion, in vivo transient limb ischaemia releases a low-molecular-mass (<15 kDa) hydrophobic circulating factor(s) which induce(s) a potent protection against myocardial ischaemia/reperfusion injury in Langendorff-perfused hearts and isolated cardiomyocytes in the same species. This cardioprotection is transferable across species, independent of local neurogenic activity, and requires opioid receptor activation.

Serum from Patients Undergoing Remote Ischemic Preconditioning Protects Cultured Human Intestinal Cells from Hypoxia-Induced Damage: Involvement of Matrixmetalloproteinase-2 and -9

“…Other ex vivo and in vitro studies also support the idea of humoral factors as mediators of RIPC effects (33,34). Shimizu et al (34) showed that in vivo transient limb ischemia releases a circulating factor(s) that induces protection against myocardial I/R injury in Langendorff-perfused hearts and isolated cardiomyocytes.…”

“…Shimizu et al (34) showed that in vivo transient limb ischemia releases a circulating factor(s) that induces protection against myocardial I/R injury in Langendorff-perfused hearts and isolated cardiomyocytes. Although the mentioned studies and our data strongly point toward the involvement of humoral factors in RIPC-mediated effects in vitro and ex vivo, we cannot exclude that neuronal pathways may also play a role in RIPCmediated organ protection in vivo.…”

Cardioprotection Techniques: Preconditioning, Postconditioning and Remote Con-ditioning (Basic Science)

“…Furthermore, the interplay between the cardioprotective factor(s) and the neural pathway remains unclear. Interestingly, it has been recently shown that the plasma from remote limb preconditioned human volunteers protected rabbit cardiomyocytes from simulated IRI, suggesting cross-species cardioprotection [180].…”

“…To summarize, these studies have suggested that the cardioprotective factor(s) are probably thermo-labile hydrophobic substances (probably peptides) between 3.5 to 8 kDa in size which have been demonstrated to act via the opioid receptor, PKC, and the PI3K-Akt pathway [177][178][179][180][181]. Whether the same protective factor(s) is released by different remotely conditioned organs or tissues is unknown as is whether the factor(s) have similar protective effects depending on the target organ or tissue.…”

“…MESSAGE RELAYED TO HEART THROUGH UNKNOWN MECHANISM protective factor(s) in remote preconditioned effluent or plasma using biochemical (chromatography) and mass spectrometry techniques but the identity of the protective factor(s) remains elusive [177][178][179][180]. To summarize, these studies have suggested that the cardioprotective factor(s) are probably thermo-labile hydrophobic substances (probably peptides) between 3.5 to 8 kDa in size which have been demonstrated to act via the opioid receptor, PKC, and the PI3K-Akt pathway [177][178][179][180][181].…”