Plasticity of Hopx+ type I alveolar cells to regenerate type II cells in the lung

It is well established that hyperoxia injures and kills alveolar endothelial and type I epithelial cells of the lung. Although type II epithelial cells remain morphologically intact, it remains unclear whether they are also damaged. DNA integrity was investigated in adult mice whose type II cells were identified by their endogenous expression of pro-surfactant protein C or transgenic expression of enhanced green fluorescent protein. In mice exposed to room air, punctate perinuclear 8-oxoguanine staining was detected in ∼4% of all alveolar cells and in 30% of type II cells. After 48 or 72 h of hyperoxia, 8-oxoguanine was detected in 11% of all alveolar cells and in >60% of type II cells. 8-Oxoguanine colocalized by confocal microscopy with the mitochondrial transmembrane protein cytochrome oxidase subunit 1. Type II cells isolated from hyperoxic lungs exhibited nuclear DNA strand breaks by comet assay even though they were viable and morphologically indistinguishable from cells isolated from lungs exposed to room air. These data reveal that type II cells exposed to in vivo hyperoxia have oxidized and fragmented DNA. Because type II cells are essential for lung remodeling, our findings raise the possibility that they are proficient in DNA repair.

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Integrin mediation of type II cell adherence to provisional matrix proteins

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1996.271.2.l277 ◽

1996 ◽

Vol 271 (2) ◽

pp. L277-L286 ◽

Cited By ~ 6

Author(s):

H. J. Kim ◽

D. H. Ingbar ◽

C. A. Henke

Keyword(s):

Cell Adhesion ◽

Matrix Proteins ◽

Alveolar Type ◽

Type I ◽

Type Ii Cells ◽

Type Ii ◽

Alveolar Cells ◽

Type Ii Cell ◽

Type Ii Alveolar Cells ◽

Alpha V Beta 3

Lung injury causes alveolar type I epithelial cell death, basement membrane denudation, and alveolar flooding with serum fibronectin and fibrinogen. For successful restoration of normal architecture, the epithelium must be regenerated from progenitor type II alveolar cells. Using adhesion assays, we examined whether type II alveolar cells adhere to the provisional matrix proteins fibronectin, fibrinogen, and fibrin, and whether integrins mediate this adherence. Rat type II cells adhered to fibronectin, vitronectin, fibrinogen, and fibrin. Synthetic RGD (arginine-glycine-aspartic acid) peptide blocked this adhesion. Flow cytometry and Western analysis indicated that type II cells expressed beta 1- and alpha v beta 3-integrins. Anti-beta 1-and anti-alpha v beta 3-integrin antibodies blocked type II cell adhesion to fibronectin and to fibronectin and fibrinogen, respectively. In summary, type II cells adhered to fibronectin, fibrinogen, and fibrin, and adhesion was partially mediated by integrins. This study provides the first evidence of type II cell adhesion to fibrin gels and vitronectin, beta 1- and alpha v beta 3-integrin mediation of type II cell adhesion, and the presence of the alpha v beta 3-integrin on type II epithelial cells.

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[Ca2+]i oscillations regulate type II cell exocytosis in the pulmonary alveolus

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.2000.279.1.l5 ◽

2000 ◽

Vol 279 (1) ◽

pp. L5-L13 ◽

Cited By ~ 105

Author(s):

Yugo Ashino ◽

Xiaoyou Ying ◽

Leland G. Dobbs ◽

Jahar Bhattacharya

Keyword(s):

Type I ◽

Type Ii Cells ◽

Type Ii ◽

Alveolar Cells ◽

Lung Inflation ◽

Type I Cells ◽

Lung Expansion ◽

Type Ii Cell ◽

I Cells

Pulmonary surfactant, a critical determinant of alveolar stability, is secreted by alveolar type II cells by exocytosis of lamellar bodies (LBs). To determine exocytosis mechanisms in situ, we imaged single alveolar cells from the isolated blood-perfused rat lung. We quantified cytosolic Ca2+ concentration ([Ca2+]i) by the fura 2 method and LB exocytosis as the loss of cell fluorescence of LysoTracker Green. We identified alveolar cell type by immunofluorescence in situ. A 15-s lung expansion induced synchronous [Ca2+]i oscillations in all alveolar cells and LB exocytosis in type II cells. The exocytosis rate correlated with the frequency of [Ca2+]i oscillations. Fluorescence of the lipidophilic dye FM1-43 indicated multiple exocytosis sites per cell. Intracellular Ca2+ chelation and gap junctional inhibition each blocked [Ca2+]i oscillations and exocytosis in type II cells. We demonstrated the feasibility of real-time quantifications in alveolar cells in situ. We conclude that in lung expansion, type II cell exocytosis is modulated by the frequency of intercellularly communicated [Ca2+]i oscillations that are likely to be initiated in type I cells. Thus during lung inflation, type I cells may act as alveolar mechanotransducers that regulate type II cell secretion.

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Respiratory Failure Due to Differentiation Arrest and Expansion of Alveolar Cells following Lung-Specific Loss of the Transcription Factor C/EBPα in Mice

Molecular and Cellular Biology ◽

10.1128/mcb.26.3.1109-1123.2006 ◽

2006 ◽

Vol 26 (3) ◽

pp. 1109-1123 ◽

Cited By ~ 45

Author(s):

Daniela S. Bassères ◽

Elena Levantini ◽

Hongbin Ji ◽

Stefano Monti ◽

Shannon Elf ◽

...

Keyword(s):

Transcription Factor ◽

Cell Differentiation ◽

Respiratory Failure ◽

Leucine Zipper ◽

Type I ◽

Type Ii ◽

Alveolar Cells ◽

Proliferating Cells ◽

Therapeutic Benefits ◽

Factor C

ABSTRACT The leucine zipper family transcription factor CCAAT enhancer binding protein alpha (C/EBPα) inhibits proliferation and promotes differentiation in various cell types. In this study, we show, using a lung-specific conditional mouse model of C/EBPα deletion, that loss of C/EBPα in the respiratory epithelium leads to respiratory failure at birth due to an arrest in the type II alveolar cell differentiation program. This differentiation arrest results in the lack of type I alveolar cells and differentiated surfactant-secreting type II alveolar cells. In addition to showing a block in type II cell differentiation, the neonatal lungs display increased numbers of proliferating cells and decreased numbers of apoptotic cells, leading to epithelial expansion and loss of airspace. Consistent with the phenotype observed, genes associated with alveolar maturation, survival, and proliferation were differentially expressed. Taken together, these results identify C/EBPα as a master regulator of airway epithelial maturation and suggest that the loss of C/EBPα could also be an important event in the multistep process of lung tumorigenesis. Furthermore, this study indicates that exploring the C/EBPα pathway might have therapeutic benefits for patients with respiratory distress syndromes.

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CD95 death-inducing signaling complex formation and internalization occur in lipid rafts of type I and type II cells

European Journal of Immunology ◽

10.1002/eji.200324786 ◽

2004 ◽

Vol 34 (7) ◽

pp. 1930-1940 ◽

Cited By ~ 77

Author(s):

Adriana Eramo ◽

Massimo Sargiacomo ◽

Lucia Ricci-Vitiani ◽

Matilde Todaro ◽

Giorgio Stassi ◽

...

Keyword(s):

Complex Formation ◽

Lipid Rafts ◽

Type I ◽

Type Ii Cells ◽

Type Ii ◽

Signaling Complex

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The Roles Potassium Currents Play in Regulating the Electrical Activity of Ventral Cochlear Nucleus Neurons

Journal of Neurophysiology ◽

10.1152/jn.00127.2002 ◽

2003 ◽

Vol 89 (6) ◽

pp. 3097-3113 ◽

Cited By ~ 180

Author(s):

Jason S. Rothman ◽

Paul B. Manis

Keyword(s):

Cochlear Nucleus ◽

Auditory Nerve ◽

Threshold Current ◽

Repetitive Firing ◽

Resting Membrane Potential ◽

Type I ◽

Type Ii Cells ◽

Type Ii ◽

Ventral Cochlear Nucleus ◽

Discharge Patterns

Using kinetic data from three different K+ currents in acutely isolated neurons, a single electrical compartment representing the soma of a ventral cochlear nucleus (VCN) neuron was created. The K+ currents include a fast transient current ( IA), a slow-inactivating low-threshold current ( ILT), and a noninactivating high-threshold current ( IHT). The model also includes a fast-inactivating Na+ current, a hyperpolarization-activated cation current ( Ih), and 1–50 auditory nerve synapses. With this model, the role IA, ILT, and IHT play in shaping the discharge patterns of VCN cells is explored. Simulation results indicate that IHT mainly functions to repolarize the membrane during an action potential, and IA functions to modulate the rate of repetitive firing. ILT is found to be responsible for the phasic discharge pattern observed in Type II cells (bushy cells). However, by adjusting the strength of ILT, both phasic and regular discharge patterns are observed, demonstrating that a critical level of ILT is necessary to produce the Type II response. Simulated Type II cells have a significantly faster membrane time constant in comparison to Type I cells (stellate cells) and are therefore better suited to preserve temporal information in their auditory nerve inputs by acting as precise coincidence detectors and having a short refractory period. Finally, we demonstrate that modulation of Ih, which changes the resting membrane potential, is a more effective means of modulating the activation level of ILT than simply modulating ILT itself. This result may explain why ILT and Ih are often coexpressed throughout the nervous system.

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Disparate cytokine regulation of ICAM-1 in rat alveolar epithelial cells and pulmonary endothelial cells in vitro

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1995.269.1.l127 ◽

1995 ◽

Vol 269 (1) ◽

pp. L127-L135 ◽

Cited By ~ 5

Author(s):

W. W. Barton ◽

S. Wilcoxen ◽

P. J. Christensen ◽

R. Paine

Keyword(s):

Endothelial Cells ◽

Epithelial Cells ◽

Inflammatory Cytokines ◽

Alveolar Epithelial Cells ◽

Normal Lung ◽

Type I ◽

Type Ii Cells ◽

Type Ii ◽

Alveolar Epithelial

Intercellular adhesion molecule-1 (ICAM-1) is expressed at high levels on type I alveolar epithelial cells in the normal lung and is induced in vitro as type II cells spread in primary culture. In contrast, in most nonhematopoetic cells ICAM-1 expression is induced in response to inflammatory cytokines. We have formed the hypothesis that the signals that control ICAM-1 expression in alveolar epithelial cells are fundamentally different from those controlling expression in most other cells. To test this hypothesis, we have investigated the influence of inflammatory cytokines on ICAM-1 expression in isolated type II cells that have spread in culture and compared this response to that of rat pulmonary artery endothelial cells (RPAEC). ICAM-1 protein, determined both by a cell-based enzyme-linked immunosorbent assay and by Western blot analysis, and mRNA were minimally expressed in unstimulated RPAEC but were significantly induced in a time- and dose-dependent manner by treatment with tumor necrosis factor-alpha, interleukin-1 beta, or interferon-gamma. In contrast, these cytokines did not influence the constitutive high level ICAM-1 protein expression in alveolar epithelial cells and only minimally affected steady-state mRNA levels. ICAM-1 mRNA half-life, measured in the presence of actinomycin D, was relatively long at 7 h in alveolar epithelial cells and 4 h in RPAEC. The striking lack of response of ICAM-1 expression by alveolar epithelial cells to inflammatory cytokines is in contrast to virtually all other epithelial cells studied to date and supports the hypothesis that ICAM-1 expression by these cells is a function of cellular differentiation.(ABSTRACT TRUNCATED AT 250 WORDS)

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Sulfation of extracellular matrices modifies responses of alveolar type II cells to fibroblast growth factors

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1996.271.5.l688 ◽

1996 ◽

Vol 271 (5) ◽

pp. L688-L697 ◽

Cited By ~ 9

Author(s):

P. L. Sannes ◽

J. Khosla ◽

P. W. Cheng

Keyword(s):

Growth Factors ◽

Biological Significance ◽

Alveolar Type ◽

Type I ◽

Type Ii Cells ◽

Type Ii ◽

Fibroblast Growth ◽

Alveolar Type Ii Cells ◽

Proliferation And Differentiation ◽

Type Ii Cell

The pulmonary alveolar basement membrane (BM) associated with alveolar type II cells has been shown to be significantly less sulfated than that of type I cells. To examine the biological significance of this observation, we measured the incorporation of 5-bromodeoxyuridine (BrdU) as an indicator of DNA synthesis in isolated rat type II cells cultured for 72-120 h on substrata that were naturally sulfated, not sulfated, or chemically desulfated in serum-free, hormonally defined media, with and without selected growth factors. The percentage of cells incorporating BrdU was significantly elevated by desulfated chondroitin sulfate in the presence of fibroblast growth factor-2 (FGF-2 or basic FGF) and depressed by heparin in the presence of either FGF-1 or acidic FGF or FGF-2. This depressive effect was lost by removing sulfate from the heparin. Some responses were dependent on the period of time in culture and concentration and molecular weight of the substrata. These observations support the notion that sulfation per se of certain components of BM is a key determinant of type II cell responses to select growth factors that may define patterns of proliferation and differentiation.

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