Extracellular CIRP as an endogenous TREM-1 ligand to fuel inflammation in sepsis
Naomi-Liza Denning, Monowar Aziz, Atsushi Murao, Steven D. Gurien, Mahendar Ochani, Jose M. Prince, Ping Wang
Naomi-Liza Denning, Monowar Aziz, Atsushi Murao, Steven D. Gurien, Mahendar Ochani, Jose M. Prince, Ping Wang
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Research Article Immunology Inflammation

Extracellular CIRP as an endogenous TREM-1 ligand to fuel inflammation in sepsis

Abstract

Extracellular cold-inducible RNA-binding protein (eCIRP) is a recently discovered damage-associated molecular pattern. Understanding the precise mechanism by which it exacerbates inflammation is essential. Here we identified that eCIRP is a new biologically active endogenous ligand of triggering receptor expressed on myeloid cells-1 (TREM-1), fueling inflammation in sepsis. Surface plasmon resonance revealed a strong binding affinity between eCIRP and TREM-1, and fluorescence resonance energy transfer assay confirmed eCIRP’s interaction with TREM-1 in macrophages. Targeting TREM-1 by its siRNA or a decoy peptide, LP17, or by using TREM-1–/– mice dramatically reduced eCIRP-induced inflammation. We developed a potentially novel 7-aa peptide derived from human eCIRP, M3, which blocked the interaction of TREM-1 and eCIRP. M3 suppressed inflammation induced by eCIRP or agonist TREM-1 antibody cross-linking in murine macrophages or human peripheral blood monocytes. M3 also inhibited eCIRP-induced systemic inflammation and tissue injury. Treatment with M3 further protected mice from sepsis, improved acute lung injury, and increased survival. Thus, we have discovered a potentially novel TREM-1 ligand and developed a new peptide, M3, to block eCIRP–TREM-1 interaction and improve outcomes in sepsis.

Authors

Naomi-Liza Denning, Monowar Aziz, Atsushi Murao, Steven D. Gurien, Mahendar Ochani, Jose M. Prince, Ping Wang

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Figure 5

M3 inhibits eCIRP- and LPS-mediated inflammation.

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M3 inhibits eCIRP- and LPS-mediated inflammation. Adult C57BL/6 mice wer...
Adult C57BL/6 mice were randomly assigned to sham, vehicle (PBS), or treatment group. rmCIRP at a dose of 5 mg/kg BW or equivalent volume normal saline was administered. M3 at a dose of 10 mg/kg BW or vehicle was given i.p. at the time of rmCIRP injection. At 5 hours after rmCIRP injection, mice were euthanized, and blood and tissue were collected for analysis. Lung mRNA and protein levels of (A and B) TNF-α, (E and F) IL-1β, and (I and J) IL-6 were measured by RT-PCR and ELISA. Serum levels of (C) IL-6 and (D) IL-1β were measured by ELISA. Data are expressed as mean ± SEM. The groups were compared by 1-way ANOVA and Tukey’s method (*P < 0.05 vs. sham, and #P < 0.05 vs. vehicle mice). Adult C57BL/6 mice were i.p. injected with LPS at a dose of 15 mg/kg BW or equivalent volume normal saline (sham). M3 at a dose of 10 mg/kg BW or vehicle (PBS) was given simultaneously. After 90 minutes, serum was collected, and ELISA was used to measure (G) IL-6 and (H) TNF-α. Data are expressed as mean ± SEM. n = 4–5 mice/group. The groups were compared by 1-way ANOVA and Tukey’s method (*P < 0.05 vs. sham, and #P < 0.05 vs. vehicle-treated mice). C57BL/6 mice were injected i.p. with 15 mg/kg BW LPS and simultaneously given M3 i.p. at a dose of 10 mg/kg BW or equivalent volume vehicle (PBS). (K) Mice were monitored for survival for 7 days. n = 20 mice/group; *P < 0.05 vs. LPS + vehicle (PBS), log-rank (Mantel-Cox) test.