HDAC1 modulates sepsis-induced immunosuppression by driving the exhaustion of CD8+ T cells.

Sepsis, a systemic inflammatory response to infection, remains a leading cause of mortality in intensive care units, with sepsis-induced immunosuppression being a critical pathophysiological process. In this study, we investigated the role of histone deacetylase 1 (HDAC1) in sepsis-induced CD8+ T cell exhaustion, a key driver of immunosuppression. Clinical analyses of patients with sepsis revealed that reduced peripheral blood lymphocyte levels, particularly CD8+ T cell depletion, strongly correlated with worsened outcomes. In a murine sepsis model, single-cell RNA-Seq revealed a significant decrease in the proportion of CD8+ T cells and an increase in the proportion of exhausted CD8+ T cells in mouse lungs. Adoptive transfer of CD8+ T cells effectively reduced sepsis mortality by preserving organ function. We further demonstrated that HDAC1 expression was significantly upregulated in CD8+ T cells from patients with sepsis. In vitro studies showed that HDAC1 inhibition preserved CD8+ T cell function by maintaining T cell activity and reducing the expression of inhibitory molecules such as PD-1. Pharmacological inhibition of HDAC1 reduced mortality and reversed CD8+ T cell exhaustion by restoring the balance between activator protein-1 (AP-1) and nuclear factor of activated T cells (NFAT). Additionally, we found that HDAC1 directly interacted with NFAT1, promoting its nuclear translocation and further enhancing the expression of inhibitory molecules. Our findings highlight HDAC1 as a potential therapeutic target for sepsis-induced immunosuppression. By elucidating the molecular mechanisms underlying HDAC1-mediated immunosuppression, we have provided potential strategies for developing immunomodulatory therapies for the treatment of sepsis.