Ibrutinib Decreases Mitochondrial Oxidative Phosphorylation and Metabolic Gene Expression in Atrial-Like Engineered Heart Tissue

Introduction: Ibrutinib is a Bruton kinase inhibitor which treats many hematological malignancies, but also precipitates atrial fibrillation (AF). The precise mechanism(s) remain to be elucidated. Hypothesis: We hypothesized ibrutinib treatment would decrease mitochondrial function and metabolic gene expression in human inducible pluripotent stem cell-derived atrial cardiomyocytes grown as atrial-like engineered heart tissues (aEHTs). Methods: aEHTs were treated with vehicle or 1 μM ibrutinib daily, for 72 hours. Oxidative phosphorylation was assessed (n=5/group) using an Oroboros Oxygraph. Gene expression was evaluated by RNAseq (n=3/group). Results: Oxidative phosphorylation in the presence of complex I and complex II substrates, and maximal oxidative capacity, was decreased in ibrutinib-treated aEHTs compared to vehicle (Panel A). Subunit expression of complex I (NDUFA6, NDUFA9, NDUFS1, NDUFS2, NDUFS4, ND3, ND4, ND5, ND4L), complex II (SDHA, SDHB, SDHD), complex III (UQCR10, UQCRB, UQCRC1, UQCRC2, UQCRFS1), and complex IV (CO2, COX10, COX7A2, CYCS) was decreased. Ingenuity Pathway Analysis of genes differentially expressed identified TCA Cycle and Glycolysis I (Panel B), pathways that provide reducing equivalents to the electron transport chain, as pathways that were decreased by ibrutinib. These changes were accompanied by decreased AMPK Signaling, including key metabolic regulators (PRKAA2, PRKAB2, PRKAG2, SIRT1, and PPARGC1A), and Calcium Signaling. Tumor protein (TP53), nuclear protein 1 (NUPR1), and erb-B2 receptor tyrosine kinase (ERBB2) were identified as top upstream regulators. Conclusions: Ibrutinib treatment decreased oxidative phosphorylation and gene expression of electron transport chain subunits and key modulators of atrial metabolism. Together, these data identify metabolic pathways that are altered by ibrutinib in aEHTs and metabolic regulators that could be targeted for AF therapeutic intervention.