Cardiac Survival Signalling, Oxidative Stress & Reperfusion Injury during Postnatal Development

Abstract

Cardiac vulnerability to injury following ischemia/reperfusion (I/R) during postnatal development displays a biphasic pattern in rats, with 14-day olds being least vulnerable. The underlying cause for this change is not currently known. We hypothesise that developmental differences in survival signalling pathways (e.g. Reperfusion Injury Salvage Kinase (RISK) & Survivor Activating Factor Enhancement (SAFE)) contribute to these biphasic changes. The work presented therefore looked to identify any changes in the expression of relevant proteins over the course of postnatal development, as well as to examine the effects of targeted inhibition of these proteins on cardiac injury, and to assess the morphology and abundance of cardiac ultrastructures related to survival signalling and the response to I/R.
Hearts from 7-day old, 14-day old, 28-day old and adult male Wistar rats were extracted and processed for measurements of protein expression, cardiomyocyte viability, cardiac injury, and cardiac structural/ultrastructural differences. This was done using a range of techniques, including proteomics, Langendorff perfusion, cardiomyocyte isolation, western blotting, histology and electron microscopy.
Several key survival signalling proteins, including AKT, PKCε, and AMPK, showed a biphasic profile of expression that parallels the biphasic profile of cardiac vulnerability to I/R. Inhibition of these proteins reduced cardiomyocyte viability and increased cardiac infarct size in 14-day olds, but not in adults. Mitochondria, which are important endpoints for survival signalling, displayed changes in morphology indicative of less injury and disruption in 14-day old than adult hearts following I/R. Ultrastructures associated with cardioprotection (e.g. caveolae and exosome containing MVBs) were also more abundant in 14-day old hearts in comparison with adults. In conclusion, these data show that the least vulnerable age group (14-day olds) has an abundance of pro-survival proteins and that their inhibition rendered them more vulnerable to I/R, which was supported by ultrastructural changes.

Date of Award	7 May 2019
Original language	English
Awarding Institution	University of Bristol
Supervisor	Saadeh Suleiman (Supervisor) & Massimo Caputo (Supervisor)