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Myeloid-Specific Gene Deletion of Protein Phosphatase 2A Magnifies MyD88- and TRIF-Dependent Inflammation following Endotoxin Challenge.

ABSTRACT: Protein phosphatase 2A (PP2A) is a member of the intracellular serine/threonine phosphatases. Innate immune cell activation triggered by pathogen-associated molecular patterns is mediated by various protein kinases, and PP2A plays a counter-regulatory role by deactivating these kinases. In this study, we generated a conditional knockout of the ? isoform of the catalytic subunit of PP2A (PP2AC?). After crossing with myeloid-specific cre-expressing mice, effective gene knockout was achieved in various myeloid cells. The myeloid-specific knockout mice (lyM-PP2Afl/fl) showed higher mortality in response to endotoxin challenge and bacterial infection. Upon LPS challenge, serum levels of TNF-?, KC, IL-6, and IL-10 were significantly increased in lyM-PP2Afl/fl mice, and increased phosphorylation was observed in MAPK pathways (p38, ERK, JNK) and the NF-?B pathway (IKK?/?, NF-?B p65) in bone marrow-derived macrophages (BMDMs) from knockout mice. Heightened NF-?B activation was not associated with degradation of I?B?; instead, enhanced phosphorylation of the NF-?B p65 subunit and p38 phosphorylation-mediated TNF-? mRNA stabilization appear to contribute to the increased TNF-? expression. In addition, increased IL-10 expression appears to be due to PP2AC?-knockout-induced IKK?/? hyperactivation. Microarray experiments indicated that the Toll/IL-1R domain-containing adaptor inducing IFN-?/ TNFR-associated factor 3 pathway was highly upregulated in LPS-treated PP2AC?-knockout BMDMs, and knockout BMDMs had elevated IFN-?/? production compared with control BMDMs. Serum IFN-? levels from PP2AC?-knockout mice treated with LPS were also greater than those in controls. Thus, we demonstrate that PP2A plays an important role in regulating inflammation and survival in the setting of septic insult by targeting MyD88- and Toll/IL-1R domain-containing adaptor inducing IFN-?-dependent pathways.

SUBMITTER: Sun L

PROVIDER: S-EPMC5173401 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature

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Myeloid-Specific Gene Deletion of Protein Phosphatase 2A Magnifies MyD88- and TRIF-Dependent Inflammation following Endotoxin Challenge.

Sun Lei L Pham Tiffany T TT Cornell Timothy T TT McDonough Kelli L KL McHugh Walker M WM Blatt Neal B NB Dahmer Mary K MK Shanley Thomas P TP

Journal of immunology (Baltimore, Md. : 1950) 20161121 1

Protein phosphatase 2A (PP2A) is a member of the intracellular serine/threonine phosphatases. Innate immune cell activation triggered by pathogen-associated molecular patterns is mediated by various protein kinases, and PP2A plays a counter-regulatory role by deactivating these kinases. In this study, we generated a conditional knockout of the α isoform of the catalytic subunit of PP2A (PP2ACα). After crossing with myeloid-specific cre-expressing mice, effective gene knockout was achieved in var ...[more]

PMID: 27872207

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Project description:BackgroundMyeloid differentiation factor 88 (MyD88) is an adaptor molecule critical for host innate immunity. Studies have shown that signaling via MyD88 contributes to cytokine storm, cardiac dysfunction, and high mortality during endotoxin shock.However, the specific contribution of MyD88 signaling of immune and cardiac origins to endotoxin shock remains unknown.MethodsTissue-specific MyD88 deletion models: Cre-recombinase transgenic mice with α-myosin heavy chain (α-MHC) or lysozyme M promoters were cross-bred with MyD88-loxP (MyD88fl/fl) mice, respectively, to generate cardiomyocyte- (α-MHCMyD88−/−) or myeloid-specific (Lyz-MyD88−/−) MyD88 deletion models and their respective MyD88fl/fl littermates. Endotoxin shock model: Mice were subjected to 15 mg/kg lipopolysaccharide (intraperitoneal injection). Cardiac function was measured by echocardiography and cytokines by multiplex assay and quantitative reverse transcription-polymerase chain reaction.Resultsα-MHC-MyD88−/− mice had 61 and 87% reduction in MyD88 gene and protein expression in cardiomyocytes,respectively, whereas Lyz-MyD88−/− had 73 and 67% decrease, respectively, in macrophages (n=3 per group). After lipopolysaccharide treatment, the two groups of MyD88fl/fl littermates had 46% (n=10) and 60% (n=15) of mortality, respectively.Both α-MHC-MyD88−/− and Lyz-MyD88−/− mice had markedly improved survival. Compared with the MyD88fl/fl littermates, Lyz-MyD88−/− mice had warmer body temperature, attenuated systemic and cardiac inflammatory cytokine production,and significantly improved cardiac function, whereas α-MHC-MyD88−/− mice had decreased myocardial inducible nitricoxide synthase induction and modestly preserved cardiac function.ConclusionsBoth cardiomyocyte- and myeloid-MyD88 signaling play a role in cardiac dysfunction and mortality during endotoxin shock. Myeloid-MyD88 signaling plays a predominant role in systemic and cardiac inflammation after endotoxin challenge.

Dataset Information

Myeloid-Specific Gene Deletion of Protein Phosphatase 2A Magnifies MyD88- and TRIF-Dependent Inflammation following Endotoxin Challenge.

Publications

Myeloid-Specific Gene Deletion of Protein Phosphatase 2A Magnifies MyD88- and TRIF-Dependent Inflammation following Endotoxin Challenge.

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