Long-term Reprogramming and Altered Ontogeny of Classical Monocytes Mediates Enhanced Lung Injury in Sepsis Survivor Mice.

Prior infection elicits durable reprogramming in myeloid cells and their progenitors; however, the long-term consequences of this reprogramming are not well understood. We previously established a murine model of sepsis survival induced by cecal ligation and puncture which results in enhanced lung injury responses to lipopolysaccharide. In this model, classical monocytes from post-sepsis mice display persistently enhanced cytokine expression after lipopolysaccharide. To test the hypothesis that inflammatory reprogramming of monocytes mediates enhanced lung injury in post-sepsis mice, depletion and/or adoptive transfer was performed three weeks and three months after sepsis. Transcriptomic and epigenomic pathways associated with monocyte reprogramming and shifts in novel monocyte subsets were determined after sepsis in mice and humans. Monocytes from post-sepsis mice mediated enhanced LPS-induced lung injury and promoted neutrophil degranulation. Prior sepsis enhanced JAK-STAT signaling and AP-1 binding in monocytes, shifting toward the neutrophil-like monocyte subset and their progenitors. Similar neutrophil-like monocyte shifts were observed in adult sepsis patients and monocyte counts were predictive of 90-day mortality. We conclude that sepsis induces inflammatory memory affecting bone marrow progenitors and monocyte subsets predisposing to lung injury. These observations serve as a foundation for future investigations on neutrophil-like monocytes and inflammatory program interaction in tissue injury responses.