The immune checkpoint TIM-3/HMGB-1 axis in myocardial infarction

Immune checkpoints are understudied in cardiovascular disease. We investigated the TIM-3 pathway in human serum, peripheral blood mononuclear cells (PBMCs) and cardiac tissue following myocardial infarction (MI). First, TIM-3 ligands in serum, galectin-9 and HMGB-1, were associated with cardiac remodelling 4 months post-MI (n = 357). Next, post-hoc single-cell RNA-sequencing of PBMCs from MI patients (n = 38) and controls (n = 38) revealed acute downregulation of TIM-3 in lymphocytes 24 h post-MI, which occurred after 8 weeks in myeloid cells. In the heart, single-nucleus RNA-sequencing and spatial transcriptomics of MI tissue demonstrated cardiomyocyte HMGB-1 upregulation which could communicate with myeloid TIM-3. Pro-inflammatory macrophages specifically showed significant TIM-3 expression and NLRP3 inflammasome activity. On the protein level, HMGB-1 was also upregulated in the infarcted heart and actively translocated throughout the cells. Finally, in vitro macrophage stimulation with HMGB-1 induced pro-inflammatory polarization (e.g. NLRP3 pathway activation), which was prevented by blocking TIM-3. Thus, TIM-3/HMGB-1 interaction presents as a target in cardiac inflammation following MI.