Imatinib Mesylate Induces Necroptotic Cell Death and Impairs Autophagic Flux in Human Cardiac Progenitor Cells

The receptor tyrosine kinase inhibitor imatinib improves patient cancer survival but is linked to cardiotoxicity. This study investigated imatinib's effects on cell viability, apoptosis, autophagy, and necroptosis in human cardiac progenitor cells in vitro. Imatinib reduced cell viability (75.9 +/- 2.7% vs. 100.0 +/- 0.0%) at concentrations comparable to peak plasma levels (10 mu M). Imatinib reduced cells' TMRM fluorescence (74.6 +/- 6.5% vs. 100.0 +/- 0.0%), consistent with mitochondrial depolarisation. Imatinib increased lysosome and autophagosome content as indicated by LAMP2 expression (2.4 +/- 0.3-fold) and acridine orange fluorescence (46.0 +/- 5.4% vs. 9.0 +/- 3.0), respectively. Although imatinib increased expression of autophagy-associated proteins and also impaired autophagic flux, shown by proximity ligation assay staining for LAMP2 and LC3II (autophagosome marker): 48 h of imatinib treatment reduced visible puncta to 2.7 +/- 0.7/cell from 11.3 +/- 2.1 puncta/cell in the control. Cell viability was partially recovered by autophagosome inhibition by wortmannin, with the viability increasing 91.8 +/- 8.2% after imatinib-wortmannin co-treatment (84 +/- 1.5% after imatinib). Imatinib-induced necroptosis was associated with an 8.5 +/- 2.5-fold increase in mixed lineage kinase domain-like pseudokinase activation. Imatinib-induced toxicity was rescued by RIP1 inhibition: 88.6 +/- 3.0% vs. 100.0 +/- 0.0% in the control. Imatinib applied to human cardiac progenitor cells depolarises mitochondria and induces cell death through necroptosis, recoverable by RIP1 inhibition, with a partial role for autophagy.