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The risk for suffering immune checkpoint inhibitors (ICIs)‐associated myocarditis increases in patients with pre‐existing conditions and the mechanisms remain to be clarified. Spatial transcriptomics, single‐cell RNA sequencing, and flow cytometry are used to decipher how anti‐cytotoxic T lymphocyte antigen‐4 m2a antibody (anti‐CTLA‐4 m2a antibody) aggravated cardiac injury in experimental autoimmune myocarditis (EAM) mice. It is found that anti‐CTLA‐4 m2a antibody increases cardiac fibroblast‐derived C‐X‐C motif chemokine ligand 1 (Cxcl1), which promots neutrophil infiltration to the myocarditic zones (MZs) of EAM mice via enhanced Cxcl1‐Cxcr2 chemotaxis. It is identified that the C–C motif chemokine ligand 5 (Ccl5)‐neutrophil subpopulation is responsible for high activity of cytokine production, adaptive immune response, NF‐κB signaling, and cellular response to interferon‐gamma and that the Ccl5‐neutrophil subpopulation and its‐associated proinflammatory cytokines/chemokines promoted macrophage (Mφ) polarization to M1 Mφ. These altered infiltrating landscape and phenotypic switch of immune cells, and proinflammatory factors synergistically aggravated anti‐CTLA‐4 m2a antibody‐induced cardiac injury in EAM mice. Neutralizing neutrophils, Cxcl1, and applying Cxcr2 antagonist dramatically alleviates anti‐CTLA‐4 m2a antibody‐induced leukocyte infiltration, cardiac fibrosis, and dysfunction. It is suggested that Ccl5‐neutrophil subpopulation plays a critical role in aggravating anti‐CTLA‐4 m2a antibody‐induced cardiac injury in EAM mice. This data may provide a strategic rational for preventing/curing ICIs‐associated myocarditis. [ABSTRACT FROM AUTHOR]

Targeting cytotoxic T‐lymphocyte‐associated antigen‐4 (CTLA‐4) with specific antibody offers long‐term benefits for cancer immunotherapy but can cause severe adverse effects in the heart. This study aimed to investigate the role of anti‐CTLA‐4 antibody in pressure overload‐induced cardiac remodeling and dysfunction. Transverse aortic constriction (TAC) was used to induce cardiac hypertrophy and heart failure in mice. Two weeks after the TAC treatment, mice received anti‐CTLA‐4 antibody injection twice a week at a dose of 10 mg/kg body weight. The administration of anti‐CTLA‐4 antibody exacerbated TAC‐induced decline in cardiac function, intensifying myocardial hypertrophy and fibrosis. Further investigation revealed that anti‐CTLA‐4 antibody significantly elevated systemic inflammatory factors levels and facilitated the differentiation of T helper 17 (Th17) cells in the peripheral blood of TAC‐treated mice. Importantly, anti‐CTLA‐4 mediated differentiation of Th17 cells and hypertrophic phenotype in TAC mice were dramatically alleviated by the inhibition of interleukin‐17A (IL‐17A) by an anti‐IL‐17A antibody. Furthermore, the C‐X‐C motif chemokine receptor 4 (CXCR4) antagonist AMD3100, also reversed anti‐CTLA‐4‐mediated cardiotoxicity in TAC mice. Overall, these results suggest that the administration of anti‐CTLA‐4 antibody exacerbates pressure overload‐induced heart failure by activating and promoting the differentiation of Th17 cells. Targeting the CXCR4/Th17/IL‐17A axis could be a potential therapeutic strategy for mitigating immune checkpoint inhibitors‐induced cardiotoxicity. [ABSTRACT FROM AUTHOR]