A novel receptor-interacting protein-1 (RIP1) inhibitor (547) protects human cardiac cells from ischemia/reperfusion-triggered necroptotic cell death
Authors: Peters MC , Neef K , Markovska A , Oerlemans MIF , Chamuleau SAJ , Sluijter JPG 
Published: June 2022

Abstract

Funding Acknowledgements
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): M.M.C.P. is supported by a Netherlands Cardiovascular Research Initiative (CVON) grant (REMAIN 2014B27) and J.P.G.S is supported by Horizon2020 ERC-2016-COG-EVICARE [725229] and BRAVE (grant number 874827.

Purpose
Restoring perfusion, either by coronary angioplasty or bypass anastomosis, is performed around 2 million times per year throughout Europe to treat patients after myocardial infarction. Although this treatment is highly efficient to resolve myocardial ischemia, reperfusion is accompanied by damage through the release of reactive oxygen species (ROS). This ischemia/reperfusion (I/R) injury is manifested by cardiomyocyte death, caused to a certain extent by necroptosis. As a potential means of cardioprotection, we applied the small molecule compound 547 inhibiting RIP1-kinase, a central mediator of the necroptosis pathway, in an in vitro model of human cardiac I/R injury.

Methods
Human foetal cardiomyocyte progenitor cells (hfCPCs) were cultured and characterized for cell type defining markers before being subjected to simulated I/R damage using hydrogen peroxide (H2O2). Cardioprotective effects of 547 were assessed 24 hours after induction of damage and application of the compound. Cell viability and necroptosis pathway activation were assessed by flow cytometry, immunocytochemistry, and western blotting. Furthermore, mitochondrial damage was determined by JC-1 staining.

Results
hfCPCs expressed indicative markers SCA1, GATA4, PECAM-1, VEGF and C-KIT. Treatment with compound 547 significantly protected hfCPCs from H2O2 induced damage (viable cells: 84,3 ± 4,3% vs 1,6 ± 0,31%; P&lt;0,0001). 547 decreased the necrotic cell population (DAPI+ AnnV-) (3,0 ± 1,1% vs 10,1 ± 1,5%, P&lt;0,0001) and reduced phosphorylation of necrosome components RIP1 (1,3 ± 0,35 fold vs 3,7 ± 0,78 fold; P&lt; 0,01), RIP3 (1,0 ± 0,46 fold vs 4,3 ± 1,5 fold; P&lt; 0,05), and MLKL (1,1 ± 0,15 fold vs 5,7 ± 1,7 fold; P&lt; 0,01) without decreasing unphosphorylated protein or mRNA levels. Interestingly, 547 treatment prevented oxidative stress induced loss of nuclear RIP1 and RIP3 as measured by immunocytochemistry and western blotting of cell fractions (nuclear/cytoplasmic ratio RIP1: 0,80 ± 0,0006 [Control] vs 1,5 ± 0,17 fold [547]; P&lt; 0,01; nuclear/cytoplasmic ratio RIP3: 0,76 ± 0,10 [Control] vs 1,6 ± 0,18 fold [547]; P&lt; 0,01). Remarkably, compound 547 also decreased H2O2–induced mitochondrial depolarization (JC-1 staining/membrane depolarization index: 4,5 ± 0,85% vs 1,2 ± 0,38%; P&lt; 0,05)) and expression and activation of CAMKII (0,46 ± 0,13 fold; P&lt;0,01), a protein mediating mitochondria-dependent cell death.

Conclusions
Administration of compound 547 led to inhibition of necroptosis, increased cell viability and reduced mitochondrial damage in an in vitro human cardiac I/R injury model, emphasizing the potential of necroptosis inhibition for cardioprotection. Assessing clinical applicability will require further studies in relevant in vivo models.