Exploring the Human Plasma Proteome for Humoral Mediators of Remote Ischemic Preconditioning - A Word of Caution

Abstract

Despite major advances in early revascularization techniques, cardiovascular diseases are still the leading cause of death worldwide, and myocardial infarctions contribute heavily to this. Over the past decades, it has become apparent that reperfusion of blood to a previously ischemic area of the heart causes damage in and of itself, and that this ischemia reperfusion induced injury can be reduced by up to 50% by mechanical manipulation of the blood flow to the heart. The recent discovery of remote ischemic preconditioning (RIPC) provides a non-invasive approach of inducing this cardioprotection at a distance. Finding its endogenous mediators and their operative mode is an important step toward increasing the ischemic tolerance. The release of humoral factor(s) upon RIPC was recently demonstrated and several candidate proteins were published as possible mediators of the cardioprotection. Before clinical applicability, these potential biomarkers and their efficiency must be validated, a task made challenging by the large heterogeneity in reported data and results. Here, in an attempt to reproduce and provide more experimental data on these mediators, we conducted an unbiased in-depth analysis of the human plasma proteome before and after RIPC. From the 68 protein markers reported in the literature, only 28 could be mapped to manually reviewed (Swiss-Prot) protein sequences. 23 of them were monitored in our untargeted experiment. However, their significant regulation could not be reproducibly estimated. In fact, among the 394 plasma proteins we accurately quantified, no significant regulation could be confidently and reproducibly assessed. This indicates that it is difficult to both monitor and reproduce published data from experiments exploring for RIPC induced plasma proteomic regulations, and suggests that further work should be directed towards small humoral factors. To simplify this task, we made our proteomic dataset available via ProteomeXchange, where scientists can mine for novel potential targets.

Remote Ischemic Conditioning Alters Methylation and Expression of Cell Cycle Genes in Aneurysmal Subarachnoid Hemorrhage

“…41 This is consistent with our finding of over a two-fold increase of CRISP3 gene expression in blood followed by RIC (Supplemental table I), suggesting its role as a humoral RIC mediator and surrogate marker. CRISP-3 is a glycoprotein present in exocrine secretions, bone marrow, secretory granules of neutrophils, and in plasma bound to a1B-glycoprotein.…”

Across-Species Transfer of Protection by Remote Ischemic Preconditioning With Species-Specific Myocardial Signal Transduction by Reperfusion Injury Salvage Kinase and Survival Activating Factor Enhancement Pathways

“…More systematic studies using proteomic approaches to identify the protective humoral transfer factor in plasma have also failed. [19][20][21] Apart from the transfer signal, the recruited cardioprotective signaling pathways within the target myocardium are unclear in detail. To what extent RIPC shares established cardioprotective signaling pathways, such as the reperfusion injury salvage kinase (RISK) pathway 22 or the survival activating factor enhancement (SAFE) pathway, 23 with other conditioning strategies remains still to be clarified.…”

Remote ischemic conditioning: a promising therapeutic intervention for multi-organ protection

“…The results showed that transferring plasma and dialysate (with 15 kDa dialysis membrane) harvested from donor rabbits undergoing limb-RIC conferred protection to non-preconditioned animals; nonetheless, this phenomenon vanished in subjects who were pretreated with naloxone, implying the possible participation of the opioid receptor pathway. Afterwards, experimental studies, specifically those adopting Langendorff bioassays, proposed that this protection was attributed to unidentified hydrophobic, thermolabile circulating proteins with molecular weights ranging from 3.5 to 15-30 kDa [ 49 , 50 ]. Notably, the presence of protective factors after RIC has also been explored in humans, denoting the results as follows: plasma dialysate from diabetic patients without periphery neuropathy who underwent RIC could confer a cardioprotective effect to rabbit hearts suffering IRI, whereas, this effect was suppressed in hearts immersed with RIC dialysate from diabetic patients concurrent with peripheral neuropathy [ 51 ].…”