PPAR is known for its anti-inflammatory actions in macrophages. However, which macrophage populations express PPAR in vivo and how it regulates tissue homeostasis in the steady state and during inflammation is not completely understood. We show that lung and spleen macrophages constitutively expressed PPAR, while other macrophage populations did not. Recruitment of monocytes to sites of inflammation was associated with induction of PPAR as they differentiated to macrophages. Its absence in these macrophages led to failed resolution of inflammation, characterized by persistent, low-level recruitment of leukocytes. Conversely, PPAR agonists supported an earlier cessation in leukocyte recruitment during resolution of acute inflammation and likewise suppressed monocyte recruitment to chronically inflamed atherosclerotic vessels. In the steady state, PPAR deficiency in macrophages had no obvious impact in the spleen but profoundly altered cellular lipid homeostasis in lung macrophages. Reminiscent of pulmonary alveolar proteinosis, LysM-Cre x PPARflox/flox mice displayed mild leukocytic inflammation in the steady-state lung and succumbed faster to mortality upon infection with S. pneumoniae. Surprisingly, this mortality was not due to overly exuberant inflammation, but instead to impaired bacterial clearance. Thus, in addition to its anti-inflammatory role in promoting resolution of inflammation, PPAR sustains functionality in lung macrophages and thereby has a pivotal role in supporting pulmonary host defense.
Systemic analysis of PPARγ in mouse macrophage populations reveals marked diversity in expression with critical roles in resolution of inflammation and airway immunity.
Sex, Treatment
View SamplesHuman and mouse blood each contain two monocyte subsets. Here, we investigated the extent of their similarity using a microarray approach. Approximately 300 genes in human and 550 genes in mouse were differentially expressed between subsets. More than 130 of these gene expression differences were conserved between mouse and human monocyte subsets. We confirmed numerous differences at the cell surface protein level. Despite overall conservation, some molecules were conversely expressed between the two species subsets, including CD36, CD9, and TREM-1. Furthermore, other differences existed, including a prominent PPAR signature in mouse monocytes absent in human. Overall, human and mouse monocyte subsets are far more broadly conserved than currently recognized. Thus, studies in mice may indeed yield relevant information regarding the biology of human monocyte subsets. However, differences between the species deserve consideration in models of human disease studied in the mouse.
Comparison of gene expression profiles between human and mouse monocyte subsets.
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View SamplesHuman and mouse blood each contain two monocyte subsets. Here, we investigated the extent of their similarity using a microarray approach. Approximately 300 genes in human and 550 genes in mouse were differentially expressed between subsets. More than 130 of these gene expression differences were conserved between mouse and human monocyte subsets. We confirmed numerous differences at the cell surface protein level. Despite overall conservation, some molecules were conversely expressed between the two species subsets, including CD36, CD9, and TREM-1. Furthermore, other differences existed, including a prominent PPAR signature in mouse monocytes absent in human. Overall, human and mouse monocyte subsets are far more broadly conserved than currently recognized. Thus, studies in mice may indeed yield relevant information regarding the biology of human monocyte subsets. However, differences between the species deserve consideration in models of human disease studied in the mouse.
Comparison of gene expression profiles between human and mouse monocyte subsets.
No sample metadata fields
View SamplesMouse aorta smooth muscle cells (SMCs) express TNF receptor superfamily member 1A (TNFR1) and lymphotoxin receptor (LTR). Circumstantial evidence has linked the SMC LTR to tertiary lymphoid organogenesis in diseased aortae of hyperlipidemic mice. Here, we explored potential roles of TNFR1 and LTR activation in cultured SMCs. TNFR1 signaling by TNF activated the classical RelA NF-B pathway, whereas LTR signaling by agonistic anti LTR antibody activated both the classical RelA and alternative RelB NF-B pathways. Addition of both agonists synergized to enhance p100 inhibitor processing to the p52 subunit of NF-B and promoted its nuclear translocation suggesting RelA-RelB cross-talk in transcription regulation. Correspondingly, microarrays showed that simultaneous TNFR1 and LTR activation when compared to activation of single receptors was followed by markedly elevated levels of mRNAs encoding leukocyte homeostatic chemokines CCL2, CCL5, CXCL1, and CX3CL1. Furthermore, SMCs acquired prototypical features of mesenchymal cells known as lymphoid tissue organizers (LTOs), which control tertiary lymphoid organogenesis in autoimmune diseases, through hyperinduction of CCL7, CCL9, CXCL13, CCL19, CXCL16, VCAM-1, and ICAM-1. Experiments with ltbr-/- SMCs suggested that the LTR-RelB activation component of NF-B signaling was obligatory to generate the LTO phenotype. TNFR1-LTR crosstalk also resulted in augmented synthesis and prolonged secretion of lymphorganogenic chemokine proteins into the culture medium. Thus, combined TNFR1-LTR signaling triggers SMC transdifferentiation into a phenotype that strikingly resembles LTOs. LTO-like SMCs may adopt a thus far unrecognized role in diseased arteries, i.e. to coordinate tertiary lymphoid organogenesis in atherosclerosis, aortic aneurysm, and transplant vasculopathy.
Mouse aorta smooth muscle cells differentiate into lymphoid tissue organizer-like cells on combined tumor necrosis factor receptor-1/lymphotoxin beta-receptor NF-kappaB signaling.
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View SamplesCultured mouse aorta endothelial cells (from 8-12 weeks old C57BL/6J mice, passage 2-3) were exposed to phosphate buffered saline (control) or a combination of TNFalpha plus agonistic alpha-LTR antibody for 24 hours as described in Ltzer et al. 2009. Arterioscler. Thromb. Vasc. Biol., in press. Total RNA was extracted and microarrays were prepared.
Mouse aorta smooth muscle cells differentiate into lymphoid tissue organizer-like cells on combined tumor necrosis factor receptor-1/lymphotoxin beta-receptor NF-kappaB signaling.
Specimen part
View SamplesWe previously observed that formation of aorta and innominate artery atherosclerotic lesions in the intima of hyperlipidemic apoE-deficient mice but not wild-type mice was accompanied by a marked age-dependent adventitial T cell infiltration. As the mice aged, adventitial T cells formed T/T cell-, T/B cell-, and T/B/dendritic cell aggregates adjacent to atherosclerotic lesions. Some of the adventitial infiltrates formed large clusters of various immune cells including T cells, B cells (centrocytes, follicular mantle cells), dendritic cells, follicular dendritic cells, and plasma cells with preferential formation in the suprarenal portion of the abdominal aorta. These data demonstrated that the immune lineage cell composition of atherosclerotic lesions and adventitia were distinct: The macrophage-foam cell-, T cell-, and SMC-dominated cell composition of atherosclerosis lesions versus the presence of immune cells capable of carrying out antigen-dependent T cell-driven humoral immune responses in the adventitia also indicated that immune reactions carried out in lesions or the adventitia are fundamentaly different. To distinguish between immunity-regulating genes in atherosclerosis lesions versus the adventitia, a combination of microarray profiling and laser capture microdissection was used. Stringent filters revealed 1163 differentially up-regulated probesets in apoE-/- mouse aortae at 78 weeks (w) versus 6 w. A fuzzy c-means cluster algorythm identified 2 clusters that significantly differed in their slope angles between time points: An apparent atherosclerosis cluster consisted of 771 probesets and an apparent adventitia cluster consisted of 392 probesets. Up-regulated genes at 32 w mirrored the influx of monocyte/macrophages into intima lesions whereas genes up-regulated between 32-78 w mirrored adventitial inflammation. To segregate both clusters into separate gene ontology (GO) molecular function groups, we determined statistically significant up-regulation (unpaired Student t-test; p < 0.05) between 6-32 w for the atherosclerosis cluster and between 32-78 w for the adventitia cluster. Among others, GO molecular function terms cytokine activity, cytokine binding, and immunoglobulin binding in the atherosclerosis cluster and cytokine activity, chemokine receptor activity, and antigen binding in the ATLO cluster suggested candidate genes in relation to inflammation triggered by macrophages or adventitia infiltration, respectively. Among other prototype atherosclerosis genes such as Itgax (complement receptor 4), Cd68, Lysz (lysozyme), Vcam1, and Icam1, the atherosclerosis cluster showed markedly overrepresented prototype macrophage/foam cell genes regulating inflammation in cytokine activity (GO: 0005125): Spp1 (osteopontin) and Il6; in cytokine binding (GO: 0019955) Cd74, Il10rb, Ccr2, and Ccr5; and in immunoglobulin binding (GO: 00119865) the proinflammatory galactose-binding lectin Lgals3, as well as genes in scavenger receptor activity and lipid transporter activity. By contrast, the adventitia cluster showed overrepresented genes regulating B cell recruitment, B cell maturation, germinal center formation, and autoimmunity in cytokine activity including Cxcl13, Ccl21, and Ltb, in CXC chemokine receptor activity the secondary lymphoid organ counterreceptor of CXCL13 Blr1 (also known as Cxcr5), Cxcr3, and Cxcr6; and in antigen binding several histocompatibility-2 loci and various markedly expressed immunoglobulin genes. As embryonic lymph node development and tertiary lymphoid organ neogenesis share common features signal intensities of genes specifying the GO molecular function term lymph node development (GO: 0048535) were examined in arrays prepared from wild-type and apoE-/- aortae. These results showed that Id2, Nfkb1, and Ltbr were constitutively expressed at significant levels in aortae of both mouse genotypes whereas other genes including Lta, Ltb, Glycam1, and the two lymphorganogenic genes Cxcl13 and Ccl21 were induced at 78 w in apoE-deficient aortae only. Thus, genes expressed by macrophage-foam cells and genes regulating ATLO neogenesis, embryonic lymph node development, or B cell maturation were constitutively expressed in the arterial wall in both genotypes or emerged in a stepwise fashion at 32 w and 78 w. To verify microarray signal intensity data, separate aortae extracts were examined by quantitative RT-PCR (QRT-PCR) analyses of wild-type and apoE-deficient mice at 32 and 78 w. These data showed that array signal values accurately reflected gene transcripts. Cell lineage analyses of the adventitial infiltrate and kinetic aorta microarray- and QRT-PCR analyses thus provided circumstantial evidence that immune responses in atherosclerosis intima lesions and the adventitia were distinct. To examine this possibility further, we selected areas of the abdominal aorta burdened with advanced lesions and separated lesions and corresponding adventitial infiltrates of 78 w old apoE-deficient mice by laser dissection microscopy. In addition, adventitiae of aorta segments that were not associated with adjacent lesions and adventitiae of wild-type mice were prepared. Consistent with the lack of a major adventitial leukocyte infiltration, wild-type adventitiae showed gene expression levels that were similar to lesion-free adventitiae of apoE-deficient mice indicating that atherosclerotic lesions directly affected adventitial inflammation in a segmental fashion. Stringent filter criteria identified genes that were differentially expressed in adventitiae and atherosclerotic lesions. Statistical analyses of overrepresented genes in GO molecular function or biological process groups were particularly instructive in cytokine activity, cytokine binding, antigen processing and presentation as well as in lymph node development. Thus, adventitiae in aorta segments with associated atherosclerotic lesions in cytokine activity showed overrepresentation of genes known to be associated with tertiary lymphoid organ formation including Cxcl13, Ccl21, and Ltb, whereas atherosclerotic lesions showed overrepresentation of prototype atherosclerosis-associated genes Ssp1 (osteopontin), Bmp4 (bone morphogenic protein 4), and Cxc3cl1 (fractalkine); in cytokine binding adventitiae showed overrepresentation of receptors implicated in B cell immunity and autoimmunity including Brl1 (counterreceptor for CXCL13), Ccr7, Tnfrsf4, and Cxcr3 whereas lesions showed overrepresentation of inflammatory mediator receptors including Tnfrs1b, Tgfbr1, and Il7r; moreover, in antigen processing and presentation, adventitiae showed overrepresentation of several histocompatibility loci; additional adventitial gene expression overrepresentations were observed in lymph node development (Fas, SpiB, Ltb, Flt3) whereas lesions showed expression of prototype macrophage genes including Tlr4, Tgfb1, and Tgfb2. These data provide comprehensive topographical transcriptome information in adventitial tissue adjacent to atherosclerotic lesions versus lesions and are expected to form the basis for future cell lineage expression analyses using single cell detection methodology including ISH.
Lymphotoxin beta receptor signaling promotes tertiary lymphoid organogenesis in the aorta adventitia of aged ApoE-/- mice.
Sex, Age, Specimen part
View SamplesThe activation of endothelium by tumor cells is one of the main steps by tumor metastasis. The role of the blood components (platelets and leukocytes) in this process remain unclear.
Selectin-mediated activation of endothelial cells induces expression of CCL5 and promotes metastasis through recruitment of monocytes.
Specimen part
View SamplesIn response to UVB irradiation, human keratinocytes transiently block cell cycle progression to allow ample time for DNA repair and cell fate determination. These cellular processes are important for evading the initiation of carcinogenesis in skin. We previously showed that repression of mRNA translation initiation through phosphorylation of eIF2a (eIF2a-P) protects keratinocytes from UVB-induced apoptosis. In this study, we elucidate the mechanism of eIF2a-P cytoprotection in response to UVB. Loss of eIF2a-P induced by UVB diminished G1 arrest, DNA repair rate, and cellular senescence coincident with enhanced cell death in human keratinocytes. Genome-wide translation analyses revealed that the mechanism for these critical changes directed by eIF2a-P involved induced expression of CDKN1A encoding p21 protein. p21 is a major regulator of the cell cycle, and we show that human CDKN1A mRNA splice variant 4 is preferentially translated by eIF2a-P during stress in a mechanism mediated in part by upstream ORFs situated in the 5'-leader of CDKN1A mRNA. We conclude that eIF2a-P is cytoprotective in response to UVB by a mechanism featuring translation of a specific splice variant of CDKN1A that facilitates G1 arrest and subsequent DNA repair. Overall design: Untreated and irradiated N-TERT keratinocytes are split into 3 groups: monosome fraction, polysome fraction, and whole cell lysate. N=3.
Translational control of a human <i>CDKN1A</i> mRNA splice variant regulates the fate of UVB-irradiated human keratinocytes.
Specimen part, Cell line, Treatment, Subject
View SamplesUnderstanding the structure and interplay of cellular signalling pathways is one of the great challenges in molecular biology. Boolean Networks can infer signalling networks from observations of protein activation. In situations where it is difficult to assess protein activation directly, Nested Effect Models are an alternative. They derive the network structure indirectly from downstream effects of pathway perturbations. To date, Nested Effect Models cannot resolve signalling details like the formation of signalling complexes or the activation of proteins by multiple alternative input signals. Here we introduce Boolean Nested Effect Models (B-NEM). B-NEMs combine the use of downstream effects with the higher resolution of signalling pathway structures in Boolean Networks. We show that B-NEMs accurately reconstruct signal flows in simulated data. Using B-NEM we then resolve BCR signalling via PI3K and TAK1 kinases in BL2 lymphoma cell lines.
Analyzing synergistic and non-synergistic interactions in signalling pathways using Boolean Nested Effect Models.
Specimen part, Cell line, Treatment
View SamplesIdentification of genes up or down regulated in LPS stimulated samples in comparison to control samples.
Genomic data integration using guided clustering.
Specimen part, Cell line, Treatment
View Samples