Endothelial cells retain inflammatory memory through chromatin remodeling in a two-hit model of infection-induced inflammation

Sepsis survivors face a heightened risk of secondary infections following discharge, yet the underlying mechanisms remain poorly defined. Our study identifies a novel mechanism of endothelial inflammatory memory, wherein inflammatory exposure induces durable chromatin remodeling in endothelial cells (ECs), priming them for exaggerated responses to a subsequent infection. Utilizing a clinically relevant two-hit mouse model, cecal ligation and puncture (CLP) followed by mild <i>Streptococcus pneumoniae</i> (<i>Sp</i>) infection in CLP survivors, we reveal transcriptional activation in endothelial cells (ECs) following secondary infection, marked by significantly elevated expression of proinflammatory cytokines, adhesion molecules, complement factors, and interferon-stimulated genes. Genome-wide ATAC-seq revealed that a subset of inflammatory gene loci retained increased chromatin accessibility even after cytokine withdrawal, demonstrating stable epigenetic remodeling consistent with transcriptional priming and inflammatory memory. In vitro, we uncovered a critical role for the activator protein-1 transcription factor JunB in mediating this epigenetic remodeling. JunB knockdown attenuated chromatin accessibility after an initial IL-6 challenge and subsequent transcriptional amplification upon a secondary LPS challenge, pinpointing JunB-driven chromatin modifications as central to endothelial reprogramming. Our findings offer mechanistic insights into how transient inflammation creates lasting epigenetic states within the endothelium, highlighting JunB as a potential therapeutic target to mitigate chronic endothelial dysfunction and increased susceptibility to secondary infections postsepsis.<b>NEW & NOTEWORTHY</b> We uncover that endothelial cells retain a form of inflammatory memory, driven by chromatin remodeling and sustained JunB activity. Using two-hit models in mice and human endothelial cells, we show that an initial inflammatory exposure primes the endothelium for exaggerated responses to future inflammation. This discovery reveals a new mechanism of chronic endothelial dysfunction and identifies JunB as a potential therapeutic target in postsepsis care.