Endotoxic shock inAUF1knockout mice mediated by failure to degrade proinflammatory cytokine mRNAs

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Abstract
Excessive production of proinflammatory cytokines, particularly tumor necrosis factor-α (TNFα) and interleukin-1β (IL-1β), plays a critical role in septic shock induced by bacterial endotoxin (endotoxemia). Precise control of cytokine expression depends on rapid degradation of cytokine mRNAs, mediated by an AU-rich element (ARE) in the 3′ noncoding region and by interacting ARE-binding proteins, which control the systemic inflammatory response. To understand the function of the ARE-binding protein AUF1, we developed anAUF1knockout mouse. We show that AUF1 normally functions to protect against the lethal progression of endotoxemia. Upon endotoxin challenge,AUF1knockout mice display symptoms of severe endotoxic shock, including vascular hemorrhage, intravascular coagulation, and high mortality, resulting from overproduction of TNFα and IL-1β. Overexpression of these two cytokines is specific, and shown to result from an inability to rapidly degrade these mRNAs in macrophages following induction. Neutralizing antibodies to TNFα and IL-1β protectAUF1knockout mice against lethal endotoxic shock. These and other data describe a novel post-transcriptional mechanism whereby AUF1 acts as a crucial attenuator of the inflammatory response, promoting the rapid decay of selective proinflammatory cytokine mRNAs following endotoxin activation. Defects in the AUF1 post-transcriptionally controlled pathway may be involved in human inflammatory disease.