Remote ischemic conditioning-induced shift from a vulnerable to a tolerant penumbra: A proteomic perspective

The concept of the ischaemic penumbra - stroke tissue with the potential to survive - has opened the door to a wide range of experimental strategies that could benefit the recovery of patients after a stroke. In this study, we used proteomic analysis to examine how remote ischaemic postconditioning (RIPC) mediates a shift from a vulnerable to a tolerant penumbra. We identified 450 differentially abundant proteins between the control group and the groups subjected to ischaemia via middle cerebral artery occlusion with or without RIPC during infarct expansion. The majority of proteins were downregulated following RIPC. Based on Gene Ontology enrichment analysis, we uncovered 24 gene sets significantly influenced during the reprogramming from a vulnerable to a tolerant penumbra. RIPC treatment positively impacted the synthesis of proteins enriched in the cytosol (GO:0005829) but inhibited the abundance of proteins belonging to the cytoskeleton (GO:0005874 microtubule) and the glutamatergic synapse (GO:0098978). The shift to a tolerant phenotype involved overexpression of aminopeptidases (GO:0004177) related to proteolysis (GO:0006508). RIPC also downregulated proteins involved in the tricarboxylic acid cycle (GO:0006099), adenosine triphosphate (ATP) binding (GO:0005524), and ATP hydrolysis (GO:0016887). We validated our proteomic findings by selecting two candidate genes (Map2 and Tubb3) for immunofluorescence. We identified the low-molecular-weight Map2 isoform as a potential marker of the shift from a vulnerable to a tolerant penumbra. In summary, our findings have revealed novel avenues for multimodal investigation of reprogramming the penumbra as part of recovery from stroke.