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Examination of mitochondria- and inflammasome-mediated mechanisms of clozapine-induced myocarditis using patient-derived iPSC cardiomyocytes

Abstract

Clozapine is the only approved pharmacotherapy for treatment-resistant schizophrenia. However, widespread utilization of clozapine is constrained due to the potential for severe adverse effects, including myocarditis. Multiple mechanisms have been suggested to account for the cardiotoxic effects of clozapine, yet these investigations have not used cells derived from clozapine treated patients. In this study, cardiomyocytes that were derived from induced pluripotent stem cells generated from four patients with treatment-resistant schizophrenia with (n = 2) and without (n = 2) a history of clozapine-induced myocarditis were used to assess mitochondria- and NLRP3 inflammasome-mediated mechanisms of this severe adverse drug reaction. We found treatment of cardiomyocytes with a physiologically-relevant dose (2.8 µM) of clozapine for 24 h: (1) induced cardiac dysfunction, increased cytotoxicity, and apoptosis, (2) induced oxidative stress by elevating the level of reactive oxygen species and mitochondrial fragmentation, and (3) elevated levels of proinflammatory cytokines and activated the NLRP3 inflammasome. These effects were more pronounced in cardiomyocytes derived from individuals with a history of clozapine-induced myocarditis. Furthermore, pharmacological targeting of the mitochondria (elamipretide) and inflammasome (ustekinumab) attenuated these clozapine-induced cardiotoxic effects. Collectively, these results suggest a mitochondria- and NLRP3 inflammasome-mediated mechanism in the development of myocarditis associated with clozapine and support further evaluation of therapeutics that target mitochondria and NLRP3 signaling.

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Fig. 1: Contractile characteristics of iPSC-CMs.
Fig. 2: Cytotoxcitiy and apoptosis in iPSC-CMs before and after clozapine treatment.
Fig. 3: Mitochondrial morphology of iPSC-CMs before and after clozapine treatment as visualized by TOMM20 immunostaining.
Fig. 4: NLRP3 inflammasome and pro-inflamatory cytokine levels in iPSC-CMs before and after clozapine treatment.
Fig. 5: Characterization of iPSC-derived cardiomyocytes, cytotoxicity, apoptosis, mitochondrial structure and function, protein levels of NLRP3 and GSDMD, Caspase-1 activity, and pro-inflammatory cytokines release after clozapine and elamipretide or ustekinumab treatment for 24 h.
Fig. 6: Proposed mechanisms of clozapine-induced myocarditis in cardiomyocytes.

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Data availability

The authors confirm that the data supporting the findings of this study are available within the article and its supplementary materials. All relevant data have been presented in this article. There was no data excluded from the analysis.

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Acknowledgements

This work was supported by William H. Davies Medical Research Scholarships, Calgary Chapter of the Schizophrenia Society of Alberta, Dr. S.K. Littman Graduate Award, Libin Cardiovascular Institute BRAIN CREATE Doctoral Scholarship, Maria Fotaki International Student Graduate Scholarship, and Alberta Children Hospital (ACHRI) graduate scholarship. The human iPSCs were obtained from Joseph C. Wu, MD, PhD, Stanford Cardiovascular Institute. We acknowledge the Hotchkiss Brain Institute Advanced Microscopy Platform and the Cumming School of Medicine for support and use of slide scanner microscope and Charbonneau Microscopy Facility for support and use of confocal microscope. C Pantelis was supported by a National Health and Medical Research Council (NHMRC) L3 Investigator Grant (1196508) and NHMRC Program Grant (ID: 1150083).

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NV, CAB: Writing - Original Draft; CAB, SCG, TES: Conceptualization; NV: Methodology and Formal Analysis; TES, WK, TJR, CP, NT, MJ, SCG: Review & Editing.

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Correspondence to Chad A. Bousman.

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Examination of mitochondria- and inflammasome-mediated mechanisms of clozapine-induced myocarditis using patient-derived iPSC cardiomyocytes

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Vaziri, N., Shutt, T.E., Karim, W. et al. Examination of mitochondria- and inflammasome-mediated mechanisms of clozapine-induced myocarditis using patient-derived iPSC cardiomyocytes. Mol Psychiatry 30, 3491–3501 (2025). https://doi.org/10.1038/s41380-025-02935-z

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