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J Immunol. 2011 Jan 15;186(2):1199-208. doi: 10.4049/jimmunol.1002971. Epub 2010 Dec 10.

IL-6 trans-signaling modulates TLR4-dependent inflammatory responses via STAT3.

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1
Centre for Innate Immunity and Infectious Diseases, Monash Institute of Medical Research, Monash University, Clayton, Victoria, Australia.

Abstract

Innate immune responses triggered by the prototypical inflammatory stimulus LPS are mediated by TLR4 and involve the coordinated production of a multitude of inflammatory mediators, especially IL-6, which signals via the shared IL-6 cytokine family receptor subunit gp130. However, the exact role of IL-6, which can elicit either proinflammatory or anti-inflammatory responses, in the pathogenesis of TLR4-driven inflammatory disorders, as well as the identity of signaling pathways activated by IL-6 in a proinflammatory state, remain unclear. To define the contribution of gp130 signaling events to TLR4-driven inflammatory responses, we combined genetic and therapeutic approaches based on a series of gp130(F/F) knock-in mutant mice displaying hyperactivated IL-6-dependent JAK/STAT signaling in an experimental model of LPS/TLR4-mediated septic shock. The gp130(F/F) mice were markedly hypersensitive to LPS, which was associated with the specific upregulated production of IL-6, but not TNF-α. In gp130(F/F) mice, either genetic ablation of IL-6, Ab-mediated inhibition of IL-6R signaling or therapeutic blockade of IL-6 trans-signaling completely protected mice from LPS hypersensitivity. Furthermore, genetic reduction of STAT3 activity in gp130(F/F):Stat3(+/-) mice alleviated LPS hypersensitivity and reduced LPS-induced IL-6 production. Additional genetic approaches demonstrated that the TLR4/Mal pathway contributed to LPS hypersensitivity and increased IL-6 production in gp130(F/F) mice. Collectively, these data demonstrate for the first time, to our knowledge, that IL-6 trans-signaling via STAT3 is a critical modulator of LPS-driven proinflammatory responses through cross-talk regulation of the TLR4/Mal signaling pathway, and potentially implicate cross-talk between JAK/STAT and TLR pathways as a broader mechanism that regulates the severity of the host inflammatory response.

PMID:
21148800
DOI:
10.4049/jimmunol.1002971
[Indexed for MEDLINE]
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