Paired immunoglobulin-like receptor-B inhibits pulmonary fibrosis by suppressing profibrogenic properties of alveolar macrophages.

Rationale: Macrophages are lung-resident cells that play key roles in fibrosis. Surprisingly, pathways that inhibit macrophage functions, especially in idiopathic pulmonary fibrosis (IPF), received little attention. The cell-surface molecule paired immunoglobulin-like receptor B (PIR-B) can suppress macrophage activation. Yet, its role in pulmonary fibrosis is unknown. Objective: To define the role of PIR-B in IPF. Methods: The expression of PIR-B was assessed (qPCR, flow cytometry) following bleomycin treatment. Differential cell counts, histopathology and profibrogenic-mediator expression (e.g. Collagen, α-SMA, Relm-α, MMP-12, TIMP-1) were determined (ELISA, qPCR, flow cytometry) in the lungs of wild type and Pirb-/- mice following bleomycin or IL-4 treatment. Bone marrow-derived wild-type and Pirb-/- macrophages were stimulated with IL-4 and assessed for Relm-α and MMP-12 expression. Measurements and Main Results: PIR-B was upregulated in lung myeloid cells following bleomycin administration. Bleomycin-treated Pirb-/- mice displayed increased lung histopathology, increased collagen expression and of the IL-4-associated profibrogenic markers Relm-α, MMP-12, TIMP-1 and osteopontin, which were localized to alveolar macrophages. Increased profibrogenic mediator expression in Pirb-/- mice was not due to increased IL-4/IL-13 levels, suggesting that PIR-B negatively regulates IL-4-induced macrophage activation. Indeed, IL-4 treated Pirb-/- mice displayed increased Relm-α expression and Relm-α+ macrophage levels. IL-4-activated Pirb-/- macrophages displayed increased Relm-α and MMP-12 induction. Finally, LILRB3/ILT-5, the human PIR-B ortholog was expressed and upregulated in lung biopsies from IPF patients. Conclusions: Our results establish a key role for PIR-B in IPF, likely via regulation of macrophage activation. Therefore, PIR-B/LILRB3 may be a possible target for suppressing macrophage profibrogenic activity in IPF

A protective role for IL-13 receptor α 1 in bleomycin-induced pulmonary injury and repair.

Molecular mechanisms that regulate lung repair vs. progressive scarring in pulmonary fibrosis remain elusive. Interleukin (IL)-4 and IL-13 are pro-fibrotic cytokines that share common receptor chains including IL-13 receptor (R) α1 and are key pharmacological targets in fibrotic diseases. However, the roles of IL-13Rα1 in mediating lung injury/repair are unclear. We report dysregulated levels of IL-13 receptors in the lungs of bleomycin-treated mice and to some extent in idiopathic pulmonary fibrosis patients. Transcriptional profiling demonstrated an epithelial cell-associated gene signature that was homeostatically dependent on IL-13Rα1 expression. IL-13Rα1 regulated a striking array of genes in the lung following bleomycin administration and Il13ra1 deficiency resulted in exacerbated bleomycin-induced disease. Increased pathology in bleomycin-treated Il13ra1(-/-) mice was due to IL-13Rα1 expression in structural and hematopoietic cells but not due to increased responsiveness to IL-17, IL-4, IL-13, increased IL-13Rα2 or type 1 IL-4R signaling. These data highlight underappreciated protective roles for IL-13Rα1 in lung injury and homeostasis

Too much, too little or just enough:a Goldilocks effect for IL-13 and skin barrier regulation?

The mechanistic relationship between IL-4/IL-13 and skin barrier function has been of interest since the filaggrin discovery and the subsequent in vitro demonstration that IL-4 and IL-13 downregulate filaggrin expression in cultured keratinocytes. Hönzke and colleagues explore these interactions further. The effects of IL-4/ll-13 may be context dependent, with differing roles in homeostasis and in disease

Natural Killer Receptor 1 Dampens the Development of Allergic Eosinophilic Airway Inflammation

<div><p>The function of NCR1 was studied in a model of experimental asthma, classified as a type 1 hypersensitivity reaction, in mice. IgE levels were significantly increased in the serum of OVA immunized NCR1 deficient (<i>NCR1</i>^{<i>gfp/gfp</i>}) mice in comparison to OVA immunized wild type <i>(NCR1</i>^<i>+/+</i>) and adjuvant immunized mice. Histological analysis of OVA immunized <i>NCR1</i>^{<i>gfp/gfp</i>} mice revealed no preservation of the lung structure and overwhelming peribronchial and perivascular granulocytes together with mononuclear cells infiltration. OVA immunized <i>NCR</i>^<i>+/+</i> mice demonstrated preserved lung structure and peribronchial and perivascular immune cell infiltration to a lower extent than that in <i>NCR1</i>^{<i>gfp/gfp</i>} mice. Adjuvant immunized mice demonstrated lung structure preservation and no immune cell infiltration. OVA immunization caused an increase in PAS production independently of NCR1 presence. Bronchoalveolar lavage (BAL) revealed NCR1 dependent decreased percentages of eosinophils and increased percentages of lymphocytes and macrophages following OVA immunization. In the OVA immunized <i>NCR1</i>^{<i>gfp/</i>gfp} mice the protein levels of eosinophils’ (CCL24) and Th2 CD4⁺ T-cells’ chemoattractants (CCL17, and CCL24) in the BAL are increased in comparison with OVA immunized <i>NCR</i>^<i>+/+</i> mice. In the presence of NCR1, OVA immunization caused an increase in NK cells numbers and decreased NCR1 ligand expression on CD11c⁺GR1⁺ cells and decreased NCR1 mRNA expression in the BAL. OVA immunization resulted in significantly increased IL-13, IL-4 and CCL17 mRNA expression in <i>NCR1</i>^<i>+/+</i> and <i>NCR1</i>^{<i>gfp/</i>gfp} mice. IL-17 and TNFα expression increased only in OVA-immunized <i>NCR1</i>^<i>+/+</i>mice. IL-6 mRNA increased only in OVA immunized <i>NCR1</i>^{<i>gfp/gfp</i>} mice. Collectively, it is demonstrated that NCR1 dampens allergic eosinophilic airway inflammation.</p></div

Increased inflammation in the lungs of <i>NCR1</i>^{<i>gfp/gfp</i>} mice compared to <i>NCR1</i>^<i>+/+</i> mice (H&E+PAS x340).

<p>Mice were immunized and samples were process as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0160779#pone.0160779.g002" target="_blank">Fig 2</a>. (A) OVA immunized <i>NCR</i>^{<i>gfp/gfp</i>} (H&E+PAS x340). (B) OVA/Alum immunized <i>NCR</i>^<i>+/+</i> (H&E+PAS x340). A thick arrow with a short tail identifies mononuclear cells and thin arrow with a long tail identifies polymorphonuclear cells.</p

A decrease in NCR1 mRNA expression and increase of NCR1 ligand expression in the BAL of OVA immunized mice.

<p><i>NCR</i>^<i>+/+</i> and <i>NCR</i>^{<i>gfp/gfp</i>} mice were immunized with either adjuvant alone or with OVA/alum as described in the Material and Methods section. The mice were euthanized and the lung tissue was dissociated into single cells. (A) Total number of live immune cell. (B) NK cell number as determined by anti NK1.1 antibody. (C) qRT PCR performed with <i>NCR1</i> appropriate primers (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0160779#pone.0160779.s006" target="_blank">S1 Table</a>). (D) Five populations of cells carrying or lacking CD11c or GR1 were determined and stained with LY94-Ig fusion protein. *p > 0.05.</p

NCR1 is involved in eosinophil and macrophage infiltration to the lung.

<p><i>NCR1</i>^<i>+/+</i> (Adjuvant n = 8, OVA n = 10) and <i>NCR1</i>^{<i>gfp/gfp</i>} (adjuvant n = 10, OVA n = 11) mice were immunized with either OVA or adjuvant as described in the Materials and Methods section. (A) The BAL was lavaged from each mouse, stained with PI and analyzed by flow cytometry for live cell count. The bar graph represents normalized number to the adjuvant immunized <i>NCR1</i>^<i>+/+</i> group whose average was considered as 1 of live cells in the BAL. (B-E) The bar graph represents an average percentage of eosinophils (B), macrophages (C), lymphocytes (D), and neutrophils (E) in the lung BAL (percentage of cells ± SEM; two-tailed Student <i>t</i>-test). These are the combined results of 2 experiments performed at different time points. * p < 0.05, **p < 0.01 *** p < 0.001.</p

Increased inflammation in the lungs of <i>NCR1</i>^{<i>gfp/gfp</i>} mice H&E+PAS x180).

<p><i>NCR1</i>^{<i>gfp/gfp</i>} C57Bl/6 mice were intraperitoneally (i.p) immunized with either OVA/alum or adjuvant only on days 0 and 14. Ten days after the second immunization mice were challenged twice intranasally with OVA at days 24 and 27. Twenty-four hours following the second immunization mice were euthanized and the left lungs were harvested for histology and RT-PCR. Representative Hematoxylin& Eosin (H&E) and PAS stained sections from each group are shown. Inflammation severity was assessed blindly by the pathologist. (A) OVA/alum immunized <i>NCR</i>^{<i>gfp/gfp</i>} (H&E+PAS x180). (B) Alum immunized <i>NCR</i>^{<i>gfp/gfp</i>} (H&E+PAS x180).</p