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Pamela Gasse, Caroline Mary, Isabelle Guenon, Nicolas Noulin, Sabine Charron, Silvia Schnyder-Candrian, Bruno Schnyder, Shizuo Akira, Valérie F.J. Quesniaux, Vincent Lagente, Bernhard Ryffel, Isabelle Couillin
Published in Volume 117, Issue 12
J Clin Invest. 2007; 117(12):3786–3799 doi:10.1172/JCI32285
Abstract | Full text | PDF | Supplemental material
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Figure 10
Schematic diagram illustrating the signaling pathways, cellular sources and the specific cascade after BLM-induced lung injury.

(i) BLM induces pulmonary cell injury. (ii) Danger/stress signals generated by dying cells are sensed by the inflammasome rather than TLRs in antigen-presenting cells (alveolar macrophages, dendritic cells, and/or epithelial cells). (iii) Danger signals induce membrane signals, leading probably to the activation of a NALP protein and to the recruitment and activation of the adaptor ASC and caspase-1, known to interact via PYR-PYR and CARD-CARD homotypic interactions. (iv) Inflammasome activation results in the processing and maturation of pro-IL-1β into its biologically active form IL-1, and to IL-1β secretion. The production of pro-IL-1β seems independent of TLRs and could be attributed to sensing by other NACHT-LRRs. (v) IL-1β then activates the IL-1R1 complex in tissue-resident cells (probably pulmonary epithelial cells), leading to the recruitment of MyD88 via TIR-TIR homotypic interactions. Triggering of the IL-1R1/MyD88 pathway results in the activation of transcription factors such as NF-κB, which will turn on the transcription of neutrophil-attracting chemokines such as KC, lymphocyte-attracting chemokines such as TARC, and the transcription of inflammatory cytokines such as IL-6, resulting in lung inflammation (vi). IL-1R1/MyD88-dependent IL-1β production by tissue-resident cells may contribute to an autocrine/paracrine amplification loop. IL-1R1 blockade with IL-1Ra (anakinra) attenuates lung inflammation induced by BLM. IL-1β will also activate the IL-1R1/MyD88 pathway in fibroblasts, leading to metalloproteinase/TIMP-1 imbalance in favor of TIMP-1 and to fibroblast proliferation, resulting in collagen deposition and pulmonary fibrosis (vii).