Objective To investigate the improvement effect of Necrostatin-1 (Nec-1) on mouse models with immune checkpoint inhibitor (ICI) -associated myocarditis (ICIAM) and potential mechanism.

Methods Ten male BALB/c mice aged 6-8 weeks were selected to construct the ICIAM models. The echocardiography and serum myocardial injury markers were used to assess cardiac function of mice. The levels of inflammatory markers including tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were detected by enzyme-linked immunosorbent assay (ELISA) and quantitative real-time polymerase chain reaction (qRT-PCR), respectively. Hematoxylin-eosin (HE) staining was used to evaluate myocardial inflammation, and Masson staining was used to evaluate myocardial fibrosis. The expressions of myocardial necroptosis proteins including receptor-interacting protein kinase 1 (RIP1), RIP3, mixed lineage kinase domain-like protein (MLKL) and their phosphorylated forms were detected by Western blotting. The spleen lymphocytes were extracted and co-cultured with HL-1 cell line. Cell viability was measured by cell counting kit-8 (CCK-8). The release of reactive oxygen species (ROS) and changes of mitochondrial membrane potential were observed. RIP1, RIP3, MLKL and their phosphorylated forms were determined. The levels of markers of oxidative stress, including malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), were measured.

Results Nec-1 significantly improved the cardiac function injury of mice induced by ICI, and inhibited the release of TNF-α and IL-1β in plasma of ICIAM mice (P＜0.001); inhibited expressions of phosphorylated RIP1, RIP3 and MLKL (P＜0.05); decreased MDA activity, and increased SOD and GSH-Px activity (P＜0.001). In HL-1 cells, Nec-1 intervention inhibited the RIP1-RIP3-MLKL pathway (P＜0.05), improved decrease of the cell viability induced by lymphocytes (P＜0.001), decreased ROS release, increased mitochondrial membrane potential, inhibited MDA activity, and increased SOD and GSH-Px activities (P＜0.001).

Conclusions Necroptosis plays an important role in the occurrence and development of ICIAM, but Nec-1 could alleviate the progression of ICIAM by inhibiting necroptosis induced by oxidative stress in cardiomyocytes; RIP1 maybe a new target in treatment of ICIAM.