IRF3 Signaling within the Mouse Stroma Influences Sepsis Pathogenesis

Abstract

IFN regulatory factor 3 (IRF3) is a transcription factor that is activated by multiple pattern-recognition receptors. We demonstrated previously that IRF3 plays a detrimental role in a severe mouse model of sepsis, induced by cecal ligation and puncture. In this study, we found that IRF3-knockout (KO) mice were greatly protected from sepsis in a clinically relevant version of the cecal ligation and puncture model incorporating crystalloid fluids and antibiotics, exhibiting improved survival, reduced disease score, lower levels of serum cytokines, and improved phagocytic function relative to wild-type (WT) mice. Computational modeling revealed that the overall complexity of the systemic inflammatory/immune network was similar in IRF3-KO versus WT septic mice, although the tempo of connectivity differed. Furthermore, the mediators driving the network differed: TNF-a, IL-1b, and IL-6 predominated in WT mice, whereas MCP-1 and IL-6 predominated in IRF3-KO mice. Network analysis also suggested differential IL-6-related inflammatory programs in WT versus IRF3-KO mice. We created bone marrow chimeras to test the role of IRF3 within leukocytes versus stroma. Surprisingly, chimeras with IRF3-KO bone marrow showed little protection from sepsis, whereas chimeras with IRF3-KO stroma showed a substantial degree of protection. We found that WT and IRF3-KO macrophages had a similar capacity to produce IL-6 and phagocytose bacteria in vitro. Adoptive transfer experiments demonstrated that the genotype of the host environment affected the capacity of monocytes to produce IL-6 during sepsis. Thus, IRF3 acts principally within the stromal compartment to exacerbate sepsis pathogenesis via differential impacts on IL-6-related inflammatory programs.

Aged IRF3-KO Mice are Protected from Sepsis

“…Previous reports from our lab showed that young adult IRF3-KO mice are significantly protected from sepsis induced by CLP in the absence 19 or presence 20 of clinical treatments. Absence of IRF3 was also found to protect mice from the systemic inflammatory response induced by liposome:DNA.…”

“…CLP surgeries were performed per our prior reports. 20 , 24 Briefly, mice were anesthetized with isoflurane (2–2.5%) using a precision vaporizer. Buprenorphine-SR (1mg/kg; Zoopharm, Windsor, CO) was given s.c. prior to the surgery for pain management.…”

“…We selected the 0h (baseline), 6h and 18h time points because our prior experiments indicate that serum cytokines are substantially elevated at 6h and 18h post-sepsis. 19 , 20 , 24 , 28 IL-6 and IL-12/23p40, and MCP-1 were quantified in the serum using BD OptEIA ELISA kits (Becton Dickinson, Franklin Lakes, NJ). The CK and Alanine Aminotransferase (ALT) enzymes were measured in serum samples using the CK Liquid Reagent Set, and ALT Liquid Reagent Set (both from Pointe Scientific Inc. MI, USA), per the manufacturer’s protocol.…”

“…In the present study, we hypothesized that IRF3 also contributes to sepsis pathogenesis in the context of aging. 19 , 20 To study this, we utilized a clinically relevant model of sepsis induced by CLP, incorporating crystalloid fluids and antibiotics. We found that aged IRF3-KO mice are protected from sepsis in comparison to their WT counterparts.…”

IRF3 Knockout Results in Partial or Complete Rejection of Murine Mesothelioma

“…Supporting this observation, recent evidence has also shown that IRF3 acts principally within the stromal compartment to drive the networks TNF-α, IL-1β, and IL-6 in WT mice, whereas MCP-1 and IL-6 predominated in IRF3-KO mice. These studies show that IRF3KO affects macrophages by changing their capacity to produce IL-6 and MCP-1 [ 46 ]. Their results could explain our findings.…”