Extracellular CIRP decreases Siglec-G expression on B-1a cells skewing them towards a pro-inflammatory phenotype in sepsis.

Abstract

BACKGROUND:

Sepsis is a life-threatening disease syndrome caused by a dysregulated host response to infection and injury. Extracellular cold-inducible RNA-binding protein (eCIRP) acts as a damage-associated molecular pattern. Peritoneal cavity (PerC) B-1a cells attenuate inflammation and tissue injury by spontaneous releasing natural IgM and IL-10. Sialic acid-binding immunoglobulin-type lectin-G (Siglec-G) is a CD33-related receptor highly expressed in B-1a cells to serve critical immunoregulatory functions. In sepsis, B-1a cell numbers in PerC are decreased. We hypothesized that eCIRP causes the reduction of PerC B-1a cells and alters their function during sepsis.

METHODS:

Sepsis was induced in WT and CIRP-/- mice by cecal ligation and puncture (CLP). PerC washout cells were collected and B-1a cells and Siglec-G were assessed by flow cytometry. Mice were i.p. injected with recombinant murine (rm) CIRP and after 20 h, Siglec-G expression in PerC B-1a cells were assessed. PerC B-1a cells were treated with rmCIRP for 4 h and Siglec-G expression was assessed. PerC B-1a cells were pre-treated with anti-Siglec-G Ab and then after stimulated with rmCIRP for 24 h, IL-6 levels in the culture supernatants were assessed.

RESULTS:

eCIRP levels in the PerC were elevated in septic mice. In WT mice, the frequencies and numbers of total and Siglec-G+ B-1a cells in the PerC were significantly decreased in the CLP group compared to sham group, whereas in CIRP-/- mice, their frequencies and numbers in sepsis were significantly rescued compared to WT septic mice. Mice injected with rmCIRP showed decreased frequencies and numbers of total and Siglec-G+ PerC B-1a cells compared to PBS-injected mice. In vitro treatment of PerC B-1a cells with rmCIRP demonstrated significant reduction in Siglec-G mRNA and protein compared to PBS group. PerC B-1a cells treated with anti-Siglec-G Ab had significantly higher production of IL-6 in response to rmCIRP compared to IgG control. Anti-Siglec-G Ab treated B-1a cells co-cultured with macrophages produced significantly higher levels of IL-6, and TNF-α, and lower levels of IL-10 compared to IgG-treated B-1a cells and macrophage co-cultures stimulated with rmCIRP.

CONCLUSION:

eCIRP reduces PerC B-1a cell pool and skews them to a pro-inflammatory phenotype by downregulating Siglec-G expression. Targeting eCIRP will retain Siglec-G expressing B-1a cells in the PerC and preserve their anti-inflammatory function in sepsis.

• Authors: William Royster, Hui Jin, Ping Wang, Monowar Aziz
• Journal: Molecular medicine (Cambridge, Mass.) (Mol Med) Vol. 27 Issue 1 Pg. 55 (05 31 2021) ISSN: 1528-3658 [Electronic] England
• PMID: 34058975 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Biomarkers
• Cirbp protein, mouse
• Cytokines
• Inflammation Mediators
• RNA-Binding Proteins
• Receptors, Antigen, B-Cell
• Sialic Acid Binding Immunoglobulin-like Lectins
• Siglecg protein, mouse
• Toll-Like Receptor 4

Topics

• Animals
• Ascitic Fluid (metabolism)
• Biomarkers
• Cytokines (blood, genetics, metabolism)
• Disease Models, Animal
• Extracellular Space (metabolism)
• Gene Expression Regulation
• Immunophenotyping
• Inflammation Mediators (metabolism)
• Macrophages (immunology, metabolism)
• Male
• Mice
• Mice, Knockout
• Phenotype
• RNA-Binding Proteins (genetics, metabolism)
• Receptors, Antigen, B-Cell (genetics, metabolism)
• Sepsis (diagnosis, etiology, metabolism)
• Sialic Acid Binding Immunoglobulin-like Lectins (genetics, metabolism)
• Toll-Like Receptor 4 (metabolism)