Cutting edge:: Essential role of hypoxia inducible factor-1α in development of lipopolysaccharide-induced sepsis

Sepsis, the leading cause of death in intensive care units, reflects a detrimental host response to infection in which bacteria or LPS act as potent activators of immune cells, including monocytes and macrophages. In this report, we show that LPS raises the level of the transcriptional regulator hypoxia-inducible factor-1 alpha (HIF-1 alpha) in macrophages, increasing HIF-1 alpha and decreasingprolyl hydroxylase mRNA production in a TLR4-dependent fashion. Using murine conditional gene targeting, of HIF-1 alpha in the myeloid lineage, we demonstrate that HIF-1 alpha is a critical determinant of the sepsis phenotype. HIF-1 alpha promotes the production of inflammatory cytokines, including TNF-alpha, IL-1, IL-4, IL-6, and IL-12, that reach harmful levels in the host during early sepsis. HIF-1 alpha deletion in macrophages is protective against LPS-induced mortality and blocks the development of clinical markers including hypotension and hypothermia. Inhibition of HIF-1 alpha activity may thus represent a novel therapeutic target for LPS-induced sepsis.