Activation of MDL-1 (CLEC5A) on immature myeloid cells triggers lethal shock in mice
Ricky Cheung, … , Paul G. Heyworth, Robert H. Pierce
Ricky Cheung, … , Paul G. Heyworth, Robert H. Pierce
Published October 17, 2011
Citation Information: J Clin Invest. 2011;121(11):4446-4461. https://doi.org/10.1172/JCI57682.
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Research Article

Activation of MDL-1 (CLEC5A) on immature myeloid cells triggers lethal shock in mice

Abstract

Systemic inflammatory response syndrome (SIRS) is a potentially lethal condition, as it can progress to shock, multi-organ failure, and death. It can be triggered by infection, tissue damage, or hemorrhage. The role of tissue injury in the progression from SIRS to shock is incompletely understood. Here, we show that treatment of mice with concanavalin A (ConA) to induce liver injury triggered a G-CSF–dependent hepatic infiltration of CD11b+Gr-1+Ly6G+Ly6C+ immature myeloid cells that expressed the orphan receptor myeloid DAP12–associated lectin–1 (MDL-1; also known as CLEC5A). Activation of MDL-1 using dengue virus or an agonist MDL-1–specific antibody in the ConA-treated mice resulted in shock. The MDL-1+ cells were pathogenic, and in vivo depletion of MDL-1+ cells provided protection. Triggering MDL-1 on these cells induced production of NO and TNF-α, which were found to be elevated in the serum of treated mice and required for MDL-1–induced shock. Surprisingly, MDL-1–induced NO and TNF-α production required eNOS but not iNOS. Activation of DAP12, DAP10, Syk, PI3K, and Akt was critical for MDL-1–induced shock. In addition, Akt physically interacted with and activated eNOS. Therefore, triggering of MDL-1 on immature myeloid cells and production of NO and TNF-α may play a critical role in the pathogenesis of shock. Targeting the MDL-1/Syk/PI3K/Akt/eNOS pathway represents a potential new therapeutic strategy to prevent the progression of SIRS to shock.

Authors

Ricky Cheung, Fran Shen, Joseph H. Phillips, Mandy J. McGeachy, Daniel J. Cua, Paul G. Heyworth, Robert H. Pierce

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Figure 3

MDL-1+ cells are CD11b+Ly6G+Ly6C+, with ring-shaped nuclei.

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MDL-1+ cells are CD11b+Ly6G+Ly6C+, with ring-shaped nuclei. (A) Leuk...
(A) Leukocytes isolated from livers of ConA-treated mice were purified using CD45 microbeads and analyzed by flow cytometry for expression of CD11b, Gr-1, Ly6G, Ly6C, and MDL-1 gated on CD45+ cells. Background signal was established in the same population by staining with the matched isotype controls. Numbers indicate the percentages of Ly6G+Ly6Clo (red ellipsoid), Ly6G–Ly6Chi (green ellipsoid), and Ly6G–Ly6Clo (blue ellipsoid) cell populations. The individual population was analyzed for MDL-1 expression (dotted line indicates isotype control). (B) Quantitation of MDL-1+Ly6G+Ly6Clo cells isolated from livers of naive and ConA-treated mice by flow cytometry. *P < 0.05, **P < 0.01 compared with naive cells. (C) Morphologic analysis of Diff-Quik–stained Cytospin preparations of Gr-1+ cells isolated from livers of naive and ConA-treated mice. Note the increased number of cells with ring-shaped nuclei (indicated by arrowheads) with ConA treatment. Scale bar: 10 μm. (D) Representative micrographs of H&E-stained liver sections from naive and ConA-treated mice. ConA treatment increased the number of cells with ring-shaped nuclei as indicated by arrowheads. Scale bar: 10 μm. (E) Representative micrographs of immunostained Cytospin preparations of Gr-1+ cells isolated from livers of naive and ConA-treated mice. Cells were stained with antibodies against CD11b (green) and MDL-1 (red). Nuclei were counterstained with DAPI (blue). Scale bar: 10 μm.