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Abstract Background α5 nicotinic acetylcholine receptor (nAChR) subunits structurally stabilize functional nAChRs in many non-neuronal tissue types. The expression of α5 nAChR subunits and cell-specific markers were assessed during lung morphogenesis by co-localizing immunohistochemistry from embryonic day (E) 13.5 to post natal day (PN) 20. Transcriptional control of α5 nAChR expression by FoxA2 and GATA-6 was determined by reporter gene assays. Results Steady expression of α5 nAChR subunits was observed in distal lung epithelial cells during development while proximal lung expression significantly alternates between abundant prenatal expression, absence at PN4 and PN10, and a return to intense expression at PN20. α5 expression was most abundant on luminal edges of alveolar type (AT) I and ATII cells, non-ciliated Clara cells, and ciliated cells in the proximal lung at various periods of lung formation. Expression of α5 nAChR subunits correlated with cell differentiation and reporter gene assays suggest expression of α5 is regulated in part by FoxA2, with possible cooperation by GATA-6. Conclusions Our data reveal a highly regulated temporal-spatial pattern of α5 nAChR subunit expression during important periods of lung morphogenesis. Due to specific regulation by FoxA2 and distinct identification of α5 in alveolar epithelium and Clara cells, future studies may identify possible mechanisms of cell differentiation and lung homeostasis mediated at least in part by α5-containing nAChRs.

Abstract Background Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels comprised of five similar subunits that influence signal transduction and cell turnover. α5 is a structural subunit detected in many non-neuronal tissues; however, its function during pulmonary development is unknown. Results α5 was assessed by immunohistochemistry and RT-PCR in mouse lungs from embryonic day (E)13.5 to post-natal day (PN)20. From E13.5 to E18.5, α5 expression was primarily observed in primitive airway epithelial cells while mesenchymal expression was faint and sporadic. α5 expression was detected throughout the proximal lung at PN1 and extensively expressed in the peripheral lung at PN4, an early stage of murine alveologenesis. An interesting shift occurred wherein α5 expression was almost undetectable in the proximal lung from PN4-PN10, but significant localization was again observed at PN20. Transcriptional control of α5 was determined by assessing the activity of reporters containing 2.0-kb and 850-bp of the mouse α5 promoter. Because perinatal expression of α5 was abundant in bronchiolar and alveolar epithelium, we assessed transcriptional control of α5 in Beas2B cells, a human bronchiolar epithelial cell line, and A-549 cells, an alveolar type II cell-like human epithelial cell line. Thyroid Transcription Factor-1 (TTF-1), a key transcription regulator of pulmonary morphogenesis, significantly increased α5 transcription by acting on both the 2.0-kb and 850-bp α5 promoters. Site-directed mutagenesis revealed that TTF-1 activated α5 transcription by binding specific TTF-1 response elements. Exogenous TTF-1 also significantly induced α5 transcription. Conclusions These data demonstrate that α5 is specifically controlled in a temporal and spatial manner during pulmonary morphogenesis. Ongoing research may demonstrate that precise regulation of α5 is important during normal organogenesis and misexpression correlates with tobacco related lung disease.

Background: Galectin-3 (gal-3), a member of the β-galactoside-binding animal lectins, is involved in the recruitment, activation and removal of neutrophils. Neutrophilic asthma is characterized by a persistent elevation of airway neutrophils and impaired efferocytosis. We hypothesized that sputum gal-3 would be reduced in neutrophilic asthma and the expression of gal-3 would be associated with other markers of neutrophilic inflammation. Methods: Adults with asthma (n = 80) underwent a sputum induction following clinical assessment and blood collection. Sputum was dispersed for a differential cell count and ELISA assessment of gal-3, gal-3 binding protein (BP), interleukin (IL)-1β, IL-1 receptor antagonist (RA), IL-8 and IL-6. Gal-3 and gal-3BP immunoreactivity were assessed in mixed sputum cells. Results: Sputum gal-3 (median, (q1,q3)) was significantly reduced in neutrophilic asthma (183 ng/mL (91,287)) compared with eosinophilic (293 ng/mL (188,471), p = 0.021) and paucigranulocytic asthma (399 ng/mL (213,514), p = 0.004). The gal-3/gal-3BP ratio and IL-1RA/IL-1β ratio were significantly reduced, while gal-3BP and IL-1β were significantly elevated in neutrophilic asthma compared with eosinophilic and paucigranulocytic asthma. Conclusion: Patients with neutrophilic asthma have impairment in anti-inflammatory ratio of gal-3/gal-3BP and IL-1RA/IL-1β which provides a further framework for exploration into pathologic mechanisms of asthma phenotypes. [ABSTRACT FROM AUTHOR]

Background: α5 nicotinic acetylcholine receptor (nAChR) subunits structurally stabilize functional nAChRs in many non-neuronal tissue types. The expression of α5 nAChR subunits and cell-specific markers were assessed during lung morphogenesis by co-localizing immunohistochemistry from embryonic day (E) 13.5 to post natal day (PN) 20. Transcriptional control of α5 nAChR expression by FoxA2 and GATA-6 was determined by reporter gene assays.Results: Steady expression of α5 nAChR subunits was observed in distal lung epithelial cells during development while proximal lung expression significantly alternates between abundant prenatal expression, absence at PN4 and PN10, and a return to intense expression at PN20. α5 expression was most abundant on luminal edges of alveolar type (AT) I and ATII cells, non-ciliated Clara cells, and ciliated cells in the proximal lung at various periods of lung formation. Expression of α5 nAChR subunits correlated with cell differentiation and reporter gene assays suggest expression of α5 is regulated in part by FoxA2, with possible cooperation by GATA-6.Conclusions: Our data reveal a highly regulated temporal-spatial pattern of α5 nAChR subunit expression during important periods of lung morphogenesis. Due to specific regulation by FoxA2 and distinct identification of α5 in alveolar epithelium and Clara cells, future studies may identify possible mechanisms of cell differentiation and lung homeostasis mediated at least in part by α5-containing nAChRs. [ABSTRACT FROM AUTHOR]

Background: Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels comprised of five similar subunits that influence signal transduction and cell turnover. α5 is a structural subunit detected in many non-neuronal tissues; however, its function during pulmonary development is unknown. Results: α5 was assessed by immunohistochemistry and RT-PCR in mouse lungs from embryonic day (E)13.5 to post-natal day (PN)20. From E13.5 to E18.5, α5 expression was primarily observed in primitive airway epithelial cells while mesenchymal expression was faint and sporadic. α5 expression was detected throughout the proximal lung at PN1 and extensively expressed in the peripheral lung at PN4, an early stage of murine alveologenesis. An interesting shift occurred wherein α5 expression was almost undetectable in the proximal lung from PN4-PN10, but significant localization was again observed at PN20. Transcriptional control of α5 was determined by assessing the activity of reporters containing 2.0-kb and 850-bp of the mouse α5 promoter. Because perinatal expression of α5 was abundant in bronchiolar and alveolar epithelium, we assessed transcriptional control of α5 in Beas2B cells, a human bronchiolar epithelial cell line, and A-549 cells, an alveolar type II cell-like human epithelial cell line. Thyroid Transcription Factor-1 (TTF-1), a key transcription regulator of pulmonary morphogenesis, significantly increased α5 transcription by acting on both the 2.0-kb and 850-bp α5 promoters. Site-directed mutagenesis revealed that TTF-1 activated α5 transcription by binding specific TTF-1 response elements. Exogenous TTF-1 also significantly induced α5 transcription. Conclusions: These data demonstrate that α5 is specifically controlled in a temporal and spatial manner during pulmonary morphogenesis. Ongoing research may demonstrate that precise regulation of α5 is important during normal organogenesis and misexpression correlates with tobacco related lung disease. [ABSTRACT FROM AUTHOR]