Generation and Characterization of Mice Expressing a Conditional Allele of the Interleukin-1 Receptor Type 1

Abstract

The cytokines IL-1α and IL-1β exert powerful pro-inflammatory actions throughout the body, mediated primarily by the intracellular signaling capacity of the interleukin-1 receptor (IL-1R1). Although Il1r1 knockout mice have been informative with respect to a requirement for IL-1R1 signaling in inflammatory events, the constitutive nature of gene elimination has limited their utility in the assessment of temporal and spatial patterns of cytokine action. To pursue such questions, we have generated C57Bl/6J mice containing a floxed Il1r1 gene (Il1r1loxP/loxP), with loxP sites positioned to flank exons 3 and 4 and thereby the ability to spatially and temporally eliminate Il1r1 expression and signaling. We found that Il1r1loxP/loxP mice breed normally and exhibit no gross physical or behavioral phenotypes. Moreover, Il1r1loxP/loxP mice exhibit normal IL-1R1 receptor expression in brain and spleen, as well as normal IL-1R1-dependent increases in serum IL-6 following IL-1α injections. Breeding of Il1r1loxP/loxP mice to animals expressing a cytomegalovirus (CMV)-driven Cre recombinase afforded efficient excision at the Il1r1 locus. The Il1r1loxP/loxP line should be a valuable tool for the assessment of contributions made by IL-1R1 signaling in diverse cell types across development.

Interleukin-1β signaling in fenestrated capillaries is sufficient to trigger sickness responses in mice

“…To generate Cx3cr1 Δ Myd88 mice, it was necessary to breed compound heterozygous mice ( Cx3cr1 -Cre +/− Myd88 fl/WT ) until spontaneous genetic recombination was detected. While breeding was ongoing, a line of mice carrying a conditional allele of interleukin 1 receptor 1 ( Il1r1 fl/fl ) became available, allowing disruption of IL-1β signaling in microglia independent of Myd88 ( Cx3cr1 Δ Il1r1 ) [ 29 ]. NF-κB IR in brain sections from IL-1β-treated control ( Cx3cr1 -CreERT2/YFP +/− , Myd88 / Il1r1 WT/WT ; Cx3cr1 +/WT ), Cx3cr1 Δ Myd88 , and Cx3cr1 Δ Il1r1 animals confirms that both Cx3cr1 -CreERT2 knockout lines eliminated the response to IL-1β in almost all microglia (Additional file 6 : Figure S6).…”

“…For this series of experiments, the following animal strains were used: C57BL/6J (Jackson Laboratory, Bar Harbor, Maine; stock #000664), Myd88 knockout ( Myd88 KO; Jackson Laboratory stock #009088), Tek -Cre (Jackson Laboratory stock #004128), conditional Myd88 ( Myd88 fl/fl ; Jackson Laboratory stock #008888), Rosa26-flox-stop-TdTomato (Jackson Laboratory stock #007908), Slco1c1 -CreERT2 (provided by Dr. Marcus Schwaninger) [ 17 ], Cx3cr1 -CreERT2 (provided by Dr. Wen-Biao Gan) [ 28 ], and conditional IL-1 receptor ( Il1r1 fl/fl provided by Dr. Randy D. Blakely) [ 29 ]. Each of the Cre strains was backcrossed onto the Myd88 fl/fl background for at least three generations with the Cre allele carried by the paternal line (father was Cre +/−: Myd88 fl/fl , and mother was Cre −/−: Myd88 fl/fl ).…”

New Insights into the Role of IL-1β in Experimental Autoimmune Encephalomyelitis and Multiple Sclerosis

“…Collectively, these studies suggest the possibility that hematopoietic non-T H cells, radioresistant microglia, and/or radioresistant non-hematopoietic cells all may respond to IL-1β to enhance neuroinflammation during EAE. Future studies using Il1r1 fl/fl mice (34, 86–88) crossed to additional Cre-expressing strains should be useful to dissect the roles of the aforementioned cell types.…”

Contributions of Interleukin-1 Receptor Signaling in Traumatic Brain Injury

“…We posit here that further work in the preclinical and clinical arenas is warranted, as each will provide crucial information required to further the potential use of pharmacotherapies targeting IL-1-mediated signaling. We also believe that recently developed molecular tools aimed at delineating the roles of IL-1 signaling, such as IL-1R1 loxP/loxP mice and IL-1R1 Restore mice, will prove useful for determining the specific cell types and timelines critical for targeting IL-1 signaling post-TBI, similar to efforts in preclinical models for ischemia (Liu et al, 2015;Robson et al, 2016;Wong et al, 2019). Although IL-1-targeted therapies have been shown to be safe in clinical populations post-injury, the temporal requirements for targeting IL-1 signaling are important, and the optimization of timing post-injury should be analyzed thoroughly for studies moving forward.…”