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IkBNS-deficiency protects mice from Listeria monocytogenes infection by blunting pro-inflammatory signature in Ly6Chigh monocytes and preventing exaggerated innate immune responses [Liver monocytes]

ABSTRACT: IkB proteins regulate the inhibition and activation of NF-kB transcription factor complexes. While classical IkB proteins keep NF-kB complexes inactive in the cytoplasm, atypical IkB proteins act on activated NF-kB complexes located in the nucleus. Most of the knowledge regarding the function of IkB proteins has been collected in vitro, while far less is known regarding their impact on activation and regulation of immune responses during in vivo infections. Combining in vivo Listeria monocytogenes (Lm) infection with comparative ex vivo transcriptional profiling of the hepatic response to the pathogen we observed that in contrast to wild type mice that mounted a robust inflammatory response, IkBNS-deficiency was generally associated with a transcriptional repression of innate immune responses. Whole tissue transcriptomics revealed a pronounced IkBNS-dependent (Nfkbid gene) reduction of myeloid cell-associated transcripts in the liver together with an exceptionally high Nfkbid promoter activity uncovered in Ly6C-high inflammatory monocytes prompted us to further characterized the specific contribution of IkBNS in the inflammatory response of monocytes to the infectious agent. Indeed, Ly6C-high monocytes primed during Lm infection in the absence of IkBNS displayed a blunted response compared to wild type-derived Ly6C-high monocytes as evidenced by the reduced early expression of hallmark transcripts of monocyte-driven inflammation such as Il-6, Nos2 and Il1-β. Strikingly, altered monocyte activation in IkBNS-deficient mice was associated with an exceptional resistance against Lm infection and protection was associated with a strong reduction in immunopathology in Lm target organs. Of note, mice lacking IkBNS exclusively in myeloid cells failed to resist Lm infection, indicating that the observed effect was not monocyte intrinsic but monocyte extrinsic. While serum cytokine-profiling did not discover obvious differences between wild type and IkBNS -/- mice for most of the analyzed mediators, IL-10 was virtually undetectable in IkBNS-deficient mice, both in the steady state and following Lm infection. Together, we show here a crucial role for IkBNS during Lm infection with IkBNS-deficient mice showing an overall blunted pro-inflammatory immune response attributed to a reduced pro-inflammatory signature in Ly6C-high monocytes. Reduced immunopathology and complete protection of mice against an otherwise lethal Lm infection identified IkBNS as molecular driver of inflammation in listeriosis.

ORGANISM(S): Mus musculus

PROVIDER: GSE220266 | GEO | 2022/12/11

REPOSITORIES: GEO

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Project description:IkB proteins regulate the inhibition and activation of NF-kB transcription factor complexes. While classical IkB proteins keep NF-kB complexes inactive in the cytoplasm, atypical IkB proteins act on activated NF-kB complexes located in the nucleus. Most of the knowledge regarding the function of IkB proteins has been collected in vitro, while far less is known regarding their impact on activation and regulation of immune responses during in vivo infections. Combining in vivo Listeria monocytogenes (Lm) infection with comparative ex vivo transcriptional profiling of the hepatic response to the pathogen we observed that in contrast to wild type mice that mounted a robust inflammatory response, IkBNS-deficiency (Nfkbid gene) was generally associated with a transcriptional repression of innate immune responses. Whole tissue transcriptomics revealed a pronounced IkBNS-dependent reduction of myeloid cell-associated transcripts in the liver together with an exceptionally high Nfkbid promoter activity uncovered in Ly6C-high inflammatory monocytes prompted us to further characterized the specific contribution of IkBNS in the inflammatory response of monocytes to the infectious agent. Indeed, Ly6C-high monocytes primed during Lm infection in the absence of IkBNS displayed a blunted response compared to wild type-derived Ly6C-high monocytes as evidenced by the reduced early expression of hallmark transcripts of monocyte-driven inflammation such as Il-6, Nos2 and Il1-β. Strikingly, altered monocyte activation in IkBNS-deficient mice was associated with an exceptional resistance against Lm infection and protection was associated with a strong reduction in immunopathology in Lm target organs. Of note, mice lacking IkBNS exclusively in myeloid cells failed to resist Lm infection, indicating that the observed effect was not monocyte intrinsic but monocyte extrinsic. While serum cytokine-profiling did not discover obvious differences between wild type and IkBNS -/- mice for most of the analyzed mediators, IL-10 was virtually undetectable in IkBNS-deficient mice, both in the steady state and following Lm infection. Together, we show here a crucial role for IkBNS during Lm infection with IkBNS-deficient mice showing an overall blunted pro-inflammatory immune response attributed to a reduced pro-inflammatory signature in Ly6C-high monocytes. Reduced immunopathology and complete protection of mice against an otherwise lethal Lm infection identified IkBNS as molecular driver of inflammation in listeriosis.

Project description:Objective: Monocytes are crucially involved in inflammatory processes. In mice, different subsets of monocytes can be distinguished by the expression of Ly6C, a surface marker that is highly expressed on inflammatory monocytes (Ly6C high) and to a lesser extent on patrolling monocytes (Ly6C low). Our previous study revealed an aggravated accumulation of inflammatory Ly6C high monocytes in atherosclerotic-prone mice bearing a deficiency in suppressor of cytokine signaling (Socs)-1. In the present study, we performed a genome-wide analysis of Socs-1-dependent gene regulation in Ly6C high and Ly6C low monocytes. Methods and Results: Monocyte subsets were isolated from socs-1+/+ rag2‒/‒ ldlr–/‒ and socs-1‒/‒ rag2‒/‒ ldlr-‒/‒ mice with subsequent identification of differential regulated genes using illumina MouseWG-6 v2.0 Expression BeadChip microarrays (45,200 transcripts). Principal component analysis illustrates a distinct separation of gene expression profiles in Ly6C high and especially Ly6C low monocytes from Socs-1 deficient mice. Additionally, microarray data revealed 46 genes to be differentially regulated in a Socs-1 dependent manner in both monocytic subsets by 2-fold or more, some of which were validated by qPCR (p<0.05, n=4-6). Among them, two principal regulators of monocyte differentiation, C-X3-C chemokine receptor 1 (Cx3cr1) and colony stimulating factor 1 receptor (Csf1r), were identified to be Socs-1 dependently regulated. Especially for Csf1r a co-expression network for correlating Socs-1 dependent gene expression and protein interaction could be compiled. Furthermore, in silico analysis of a transcription factor (TF) network correlating with Socs-1 dependent mRNA expression data revealed a cluster of TF that includes Nr4a1 as well as several ets-domain proteins that may interact and thus regulate gene expression, inter alia regression of Csf1r. Conclusion: By genome-wide analysis, we could identify Cx3cr1 and Csf1r as two essential receptors mediating monocyte differentiation that are subjected to Socs-1 dependent transcription factor regulation.