Temporal proteomic and phosphoproteomic profiling of the left ventricle in a novel rat model of ischemia/reperfusion with or without ischemic preconditioning
Authors: Hussain S , Kakaei Y , Shekka Espinosa A , Elmahdy A , Sevastianova V , Zulfaj E , Jha A , Al-Awar A , Jha S , Pylova T , Krasnikova M , Andersson E A , Andersson E A , Silva V R R , Redfors B 
Published: November 2023

Abstract

Background
The relationship between ischemic preconditioning (IPC) and myocardial stunning is incompletely understood. Preconditioning has been shown to protect against ischemic injury, whereas myocardial stunning, i.e. transient contractile dysfunction in the setting of ischemia, can lead to severe heart failure and has been considered a deleterious process. To understand this relationship, we recently developed a novel rat model of ischemia-reperfusion (I/R) injury in the presence or absence of IPC. In the presence of IPC (2 cycles of 5 min of I/R followed by 13.5 min of ischemia), we observe a profound myocardial stunning at 4h of reperfusion which completely resolves at 48h. In the absence of IPC, we observe necrosis at 4h of reperfusion and sustained injury at 48h. Despite extensive studies on IPC and myocardial stunning in the setting of I/R, the molecular basis of the relationship between these phenomena are still unknown.

Purpose
To investigate alterations in protein expression after IPC and myocardial stunning in a novel rat model of I/R injury.

Methods
We utilized tandem mass tags and mass spectrometry to identify temporal changes in the proteomic- and phosphoproteomic-profiles in left ventricular (LV) tissue from rat hearts following 13.5 min of ischemia and 4h of reperfusion in the presence of absence of IPC.

Results
Proteomics analysis of the LV tissues collected at baseline showed that 115 proteins were differentially expressed between IPC and non-IPC groups. We observed abundant changes in sarcoplasmic proteins, sarcoplasmic reticulum-related proteins, and actin-based cell projection proteins. Most of these proteins are implicated in arylesterase activity, haemoglobin binding, and nitrogen metabolism. At 4h, differentially expressed proteins were predominantly related to wound healing, coagulation, and lipase activity. Phosphoproteomic analysis at baseline showed that 686 phosphosites were differentially regulated between IPC and non-IPC groups. Aberrant phosphorylation patterns mostly occurred in sarcomere proteins, Z-disc, I-band, contractile fiber associated with actin binding, and the thyroid hormone signalling pathway. At 4h, 520 phosphosites differed between IPC and non-IPC rats; these phosphosites were abundant in contractile fiber proteins, myofibril proteins, and sarcomere proteins associated with calcium signalling and cardiomyopathies.

Conclusions
This study demonstrates marked changes in proteins and phosphosites related to lipase activity, haemoglobin binding, calcium signalling, and the cardiac contractile apparatus in IPC versus non-IPC groups. This extensive catalogue of novel proteins and phosphosites associated with IPC and myocardial stunning in the setting of I/R injury sets the stage for future manipulation of myocardial stunning and preconditioning in both experimental and clinical settings.