Cellular and molecular dynamics in the lungs of neonatal and juvenile mice in response to E. coli.

Bacterial pneumonia in neonates can cause significant morbidity and mortality when compared to other childhood age groups. To understand the immune mechanisms that underlie these age-related differences, we employed a mouse model of Escherichia coli pneumonia to determine the dynamic cellular and molecular differences in immune responsiveness between neonates (PND 3-5) and juveniles (PND 12-18), at 24, 48, and 72 hr. Cytokine gene expression from whole lung extracts was also quantified at these time points, using quantitative RT-PCR. E. coli challenge resulted in rapid and significant increases in neutrophils, monocytes, and γδT cells, along with significant decreases in dendritic cells and alveolar macrophages in the lungs of both neonates and juveniles. E. coli-challenged juvenile lung had significant increases in interstitial macrophages and recruited monocytes that were not observed in neonatal lungs. Expression of IFNγ-responsive genes was positively correlated with the levels and dynamics of MHCII-expressing innate cells in neonatal and juvenile lungs. Several facets of immune responsiveness in the wild-type neonates were recapitulated in juvenile MHCII-/- juveniles. Employing a pre-clinical model of E. coli pneumonia, we identified significant differences in the early cellular and molecular dynamics in the lungs that likely contribute to the elevated susceptibility of neonates to bacterial pneumonia and could represent targets for intervention to improve respiratory outcomes and survivability of neonates.

DNA methyltransferase inhibition induces dynamic gene expression changes in lung CD4+ T cells of neonatal mice with E. coli pneumonia.

Bacterial pulmonary infections are a major cause of morbidity and mortality in neonates, with less severity in older children. Previous studies demonstrated that the DNA of CD4+ T cells in the mouse lung, whose primary responsibility is to coordinate the immune response to foreign pathogens, is differentially methylated in neonates compared with juveniles. Nevertheless, the effect of this differential DNA methylation on CD4+ T cell gene expression and response to infection remains unclear. Here we treated E. coli-infected neonatal (4-day-old) and juvenile (13-day-old) mice with decitabine (DAC), a DNA methyltransferase inhibitor with broad-spectrum DNA demethylating activity, and performed simultaneous genome-wide DNA methylation and transcriptional profiling on lung CD4+ T cells. We show that juvenile and neonatal mice experienced differential demethylation in response to DAC treatment, with larger methylation differences observed in neonates. By cross-filtering differentially expressed genes between juveniles and neonates with those sites that were demethylated in neonates, we find that interferon-responsive genes such as Ifit1 are the most down-regulated methylation-sensitive genes in neonatal mice. DAC treatment shifted neonatal lung CD4+ T cells toward a gene expression program similar to that of juveniles. Following lung infection with E. coli, lung CD4+ T cells in neonatal mice exhibit epigenetic repression of important host defense pathways, which are activated by inhibition of DNA methyltransferase activity to resemble a more mature profile.

DNA methylation and gene expression signatures are associated with ataxia-telangiectasia phenotype.

People with ataxia-telangiectasia (A-T) display phenotypic variability with regard to progression of immunodeficiency, sino-pulmonary disease, and neurologic decline. To determine the association between differential gene expression, epigenetic state, and phenotypic variation among people with A-T, we performed transcriptional and genome-wide DNA methylation profiling in patients with mild and classic A-T progression as well as healthy controls. RNA and genomic DNA were isolated from peripheral blood mononuclear cells for transcriptional and DNA methylation profiling with RNA-sequencing and modified reduced representation bisulfite sequencing, respectively. We identified 555 genes that were differentially expressed among the control, mild A-T, and classic A-T groups. Genome-wide DNA methylation profiling revealed differential promoter methylation in cis with 146 of these differentially expressed genes. Functional enrichment analysis identified significant enrichment in immune, growth, and apoptotic pathways among the methylation-regulated genes. Regardless of clinical phenotype, all A-T participants exhibited downregulation of critical genes involved in B cell function (PAX5, CD79A, CD22, and FCRL1) and upregulation of several genes associated with senescence and malignancy, including SERPINE1. These findings indicate that gene expression differences may be associated with phenotypic variability and suggest that DNA methylation regulates expression of critical immune response genes in people with A-T.

Inflammation and transcriptional responses of peripheral blood mononuclear cells in classic ataxia telangiectasia.

INTRODUCTION: Classic ataxia telangiectasia (A-T) is an autosomal recessive disease characterized by early onset ataxia, immune deficiency, sino-pulmonary disease, lymphoid/solid malignancies and telangiectasias. Prior studies have suggested that chronic inflammation and premature aging may contribute to the development of malignancy and pulmonary disease in people with A-T. To further examine the link between A-T and inflammation, we hypothesized that subjects with classic A-T would have greater enrichment of inflammatory pathways in peripheral blood mononuclear cells (PBMCs) compared to non A-T age-matched controls. To test this hypothesis we used RNAseq as an unsupervised approach to identify biological processes altered in people with classic A-T. METHODS: PBMCs were isolated from subjects with classic A-T and compared to non-A-T age-matched healthy controls. RNAseq with differential gene expression analyses was then performed. Selected genes were validated by RT-qPCR using cohorts of subjects consisting of classic A-T, mild A-T or non-A-T controls. Subjects with mild A-T were characterized by later onset/mild neurologic features and normal/near normal immune status. RESULTS: RNAseq revealed 310 differentially expressed genes (DEGs) including genes involved in inflammation, immune regulation, and cancer. Using gene set enrichment analysis, A-T subjects were found to have biological processes enriched for inflammatory and malignancy pathways. In examining a cohort of A-T subjects in which baseline serum IL8 and IL6 levels were measured previously, an association was found between higher serum IL8 levels and higher likelihood of developing malignancy and/or death in a subsequent 4-6 year period. CONCLUSION: RNAseq using PBMCs from subjects with classic A-T uncovered differential expression of immune response genes and biological processes associated with inflammation, immune regulation, and cancer. Follow-up of A-T subjects over a 4-6 year period revealed an association between higher baseline serum IL8 levels and malignancy/death. These findings support a role for inflammation as a contributing factor in A-T phenotypes.

Production of amphiregulin and recovery from influenza is greater in males than females.

BACKGROUND: Amphiregulin (AREG) is an epidermal growth factor that is a significant mediator of tissue repair at mucosal sites, including in the lungs during influenza A virus (IAV) infection. Previous research illustrates that males of reproductive ages experience less severe disease and recover faster than females following infection with IAV. METHODS: Whether males and females differentially produce and utilize AREG for pulmonary repair after IAV infection was investigated using murine models on a C57BL/6 background and primary mouse and human epithelial cell culture systems. RESULTS: Following sublethal infection with 2009 H1N1 IAV, adult female mice experienced greater morbidity and pulmonary inflammation during the acute phase of infection as well as worse pulmonary function during the recovery phase of infection than males, despite having similar virus clearance kinetics. As compared with females, AREG expression was greater in the lungs of male mice as well as in primary respiratory epithelial cells derived from mouse and human male donors, in response to H1N1 IAVs. Internalization of the epidermal growth factor receptor (EGFR) was also greater in respiratory epithelial cells derived from male than female mice. IAV infection of Areg knock-out (Areg-/-) mice eliminated sex differences in IAV pathogenesis, with a more significant role for AREG in infection of male compared to female mice. Deletion of Areg had no effect on virus replication kinetics in either sex. Gonadectomy and treatment of either wild-type or Areg-/- males with testosterone improved the outcome of IAV as compared with their placebo-treated conspecifics. CONCLUSIONS: Taken together, these data show that elevated levels of testosterone and AREG, either independently or in combination, improve resilience (i.e., repair and recovery of damaged tissue) and contribute to better influenza outcomes in males compared with females.

DNA methylation regulates the neonatal CD4+ T-cell response to pneumonia in mice.

Pediatric acute lung injury, usually because of pneumonia, has a mortality rate of more than 20% and an incidence that rivals that of all childhood cancers combined. CD4+ T-cells coordinate the immune response to pneumonia but fail to function robustly among the very young, who have poor outcomes from lung infection. We hypothesized that DNA methylation represses a mature CD4+ T-cell transcriptional program in neonates with pneumonia. Here, we found that neonatal mice (3-4 days old) aspirated with Escherichia coli bacteria had a higher mortality rate than juvenile mice (11-14 days old). Transcriptional profiling with an unsupervised RNA-Seq approach revealed that neonates displayed an attenuated lung CD4+ T-cell transcriptional response to pneumonia compared with juveniles. Unlike neonates, juveniles up-regulated a robust set of canonical T-cell immune response genes. DNA methylation profiling with modified reduced representation bisulfite sequencing revealed 44,119 differentially methylated CpGs, which preferentially clustered around transcriptional start sites and CpG islands. A methylation difference-filtering algorithm detected genes with a high likelihood of differential promoter methylation regulating their expression; these 731 loci encoded important immune response and tissue-protective T-cell pathway components. Disruption of DNA methylation with the hypomethylating agent decitabine induced plasticity in the lung CD4+ T-cell marker phenotype. Altogether, multidimensional profiling suggested that DNA methylation within the promoters of a core set of CD4+ T-cell pathway genes contributes to the hyporesponsive neonatal immune response to pneumonia. These findings also suggest that DNA methylation could serve as a mechanistic target for disease-modifying therapies in pediatric lung infection and injury.

The innate immune response to lower respiratory tract E. Coli infection and the role of the CCL2-CCR2 axis in neonatal mice.

Neonates have greater morbidity/mortality from lower respiratory tract infections (LRTI) compared to older children. Lack of conditioning of the pulmonary immune system due to limited environmental exposures and/or infectious challenges likely contributes to the increase susceptibility in the neonate. In this study, we sought to gain insights into the nature and dynamics of the neonatal pulmonary immune response to LRTI using a murine model. METHODS: Wildtype (WT) and Ccr2-/- C57BL/6 neonatal and juvenile mice received E. coli or PBS by direct pharyngeal aspiration. Flow cytometry was used to measure immune cell dynamics and identify cytokine-producing cells. Real-time PCR and ELISA were used to measure cytokine/chemokine expression. RESULTS: Innate immune cell recruitment in response to E. coli-induced LRTI was delayed in the neonatal lung compared to juvenile lung. Lung clearance of bacteria was also significantly delayed in the neonate. Ccr2-/- neonates, which lack an intact CCL2-CCR2 axis, had higher mortality after E. coli challenged than Ccr2+/+ neonates. A greater percentage of CD8+ T cells and monocytes from WT neonates challenged with E. coli produced TNF compared to controls. CONCLUSION: The pulmonary immune response to E. coli-induced LRTI differed significantly between neonatal and juvenile mice. Neonates were more susceptible to increasing doses of E. coli and exhibited greater mortality than juveniles. In the absence of an intact CCL2-CCR2 axis, susceptibility to LRTI-induced mortality was further increased in neonatal mice. Taken together these findings underscore the importance of age-related differences in the innate immune response to LRTI during early stages of postnatal life.

An inositolphosphorylceramide synthase is involved in regulation of plant programmed cell death associated with defense in Arabidopsis.

The Arabidopsis thaliana resistance gene RPW8 triggers the hypersensitive response (HR) to restrict powdery mildew infection via the salicylic acid-dependent signaling pathway. To further understand how RPW8 signaling is regulated, we have conducted a genetic screen to identify mutations enhancing RPW8-mediated HR-like cell death (designated erh). Here, we report the isolation and characterization of the Arabidopsis erh1 mutant, in which the At2g37940 locus is knocked out by a T-DNA insertion. Loss of function of ERH1 results in salicylic acid accumulation, enhanced transcription of RPW8 and RPW8-dependent spontaneous HR-like cell death in leaf tissues, and reduction in plant stature. Sequence analysis suggests that ERH1 may encode the long-sought Arabidopsis functional homolog of yeast and protozoan inositolphosphorylceramide synthase (IPCS), which converts ceramide to inositolphosphorylceramide. Indeed, ERH1 is able to rescue the yeast aur1 mutant, which lacks the IPCS, and the erh1 mutant plants display reduced ( approximately 53% of wild type) levels of leaf IPCS activity, indicating that ERH1 encodes a plant IPCS. Consistent with its biochemical function, the erh1 mutation causes ceramide accumulation in plants expressing RPW8. These data reinforce the concept that sphingolipid metabolism (specifically, ceramide accumulation) plays an important role in modulating plant programmed cell death associated with defense.