Interleukin-10 Inhibits Lipopolysaccharide-induced Tumor Necrosis Factor-α Translation through a SHIP1-dependent Pathway

Production of the proinflammatory cytokine TNF alpha by activated macrophages is an important component of host defense. However, TNF alpha production must be tightly controlled to avoid pathological consequences. The anti-inflammatory cytokine IL-10 inhibits TNF alpha mRNA expression through activation of the STAT3 transcription factor pathway and subsequent expression of STAT3-dependent gene products. We hypothesized that IL-10 must also have more rapid mechanisms of action and show that IL-10 rapidly shifts existing TNF alpha mRNA from polyribosome-associated polysomes to monosomes. This translation suppression requires the presence of SHIP1 (SH2 domain-containing inositol 5'-phosphatase 1) and involves inhibition of Mnk1 (MAPK signal-integrating kinase 1). Furthermore, activating SHIP1 using a small-molecule agonist mimics the inhibitory effect of IL-10 on Mnk1 phosphorylation and TNF alpha translation. Our data support the existence of an alternative STAT3-independent pathway through SHIP1 for IL-10 to regulate TNF alpha translation during the anti-inflammatory response.