Apoptotic epithelial cell death: a prerequisite for palatal fusion. An in vivo study in rabbits

Abstract Thrombocytopenia is associated with worse outcomes in patients with acute respiratory distress syndrome, which is most commonly caused by infection and marked by alveolar–capillary barrier disruption. However, the mechanisms by which platelets protect the lung alveolar–capillary barrier during infectious injury remain unclear. We found that natively thrombocytopenic Mpl−/− mice deficient in the thrombopoietin receptor sustain severe lung injury marked by alveolar barrier disruption and hemorrhagic pneumonia with early mortality following acute intrapulmonary Pseudomonas aeruginosa (PA) infection; barrier disruption was attenuated by platelet reconstitution. Although PA infection was associated with a brisk neutrophil influx, depletion of airspace neutrophils failed to substantially mitigate PA-triggered alveolar barrier disruption in Mpl−/− mice. Rather, PA cell-free supernatant was sufficient to induce lung epithelial cell apoptosis in vitro and in vivo and alveolar barrier disruption in both platelet-depleted mice and Mpl−/− mice in vivo. Cell-free supernatant from PA with genetic deletion of the type 2 secretion system, but not the type 3 secretion system, mitigated lung epithelial cell death in vitro and lung injury in Mpl−/− mice. Moreover, platelet releasates reduced poly (ADP ribose) polymerase cleavage and lung injury in Mpl−/− mice, and boiling of platelet releasates, but not apyrase treatment, abrogated PA supernatant–induced lung epithelial cell cytotoxicity in vitro. These findings indicate that while neutrophil airspace influx does not potentiate infectious lung injury in the thrombocytopenic host, platelets and their factors protect against severe pulmonary complications from pathogen-secreted virulence factors that promote host cell death even in the absence of overt infection.

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Inhibition of epithelial cell death in the secondary palate in vitro by alteration of lysosome function.

Journal of Histochemistry & Cytochemistry ◽

10.1177/26.12.569675 ◽

1978 ◽

Vol 26 (12) ◽

pp. 1109-1114 ◽

Cited By ~ 21

Author(s):

R M Greene ◽

R M Pratt

Keyword(s):

Cell Death ◽

Acid Phosphatase ◽

Epithelial Cell ◽

Lysosomal Enzymes ◽

Developmental Age ◽

Secondary Palate ◽

Epithelial Cell Death ◽

Histochemical Examination

The secondary palate in vivo and in vitro exhibits selective cell death at its medialedge epithelium (MEE) at a precise developmental age. This epithelial degeneration is mediated, in part, by MEE lysosomes. Previous studies in vitro (27) showed that the glutamine analogue, diazo-oxo-norleucine (DON), prevented MEE cell death by inhibiting glucosamine synthesis and thereby the glycosylation of proteins without affecting either the synthesis or activity of palatal lysosomal enzymes. In the present study, histochemical examination of MEE from DON treated day-15 rat palates demonstrated that acid phosphatase activity was restricted to Golgi saccules and associated vesicles as well as to lysosomes. Control MEE had reaction product in these structures and distributed diffusely throughout the cytoplasm of degenerating cells. DON treatment therefore appears to alter the intracellular distribution of lysosomal enzymes. Since DON treatment appears to have prevented MEE cell death by inhibiting glycosylation of proteins, glycosylation of lysosomal membranes or lysosomal enzymes may be essential for its role in programmed cell death.

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Alveolar epithelial cell death adjacent to underlying myofibroblasts in advanced fibrotic human lung

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1998.275.6.l1192 ◽

1998 ◽

Vol 275 (6) ◽

pp. L1192-L1199 ◽

Cited By ~ 67

Author(s):

Bruce D. Uhal ◽

Iravati Joshi ◽

W. Frank Hughes ◽

Carlos Ramos ◽

Annie Pardo ◽

...

Keyword(s):

Cell Death ◽

Epithelial Cell ◽

Human Lung ◽

Alveolar Epithelial Cell ◽

Cell Loss ◽

Alveolar Epithelial ◽

Picrosirius Red ◽

Epithelial Cell Death

Earlier work from this laboratory showed that abnormal fibroblast phenotypes isolated from fibrotic human lung produce factor(s) capable of inducing apoptosis and necrosis of alveolar epithelial cells in vitro [B. D. Uhal, I. Joshi, A. True, S. Mundle, A. Raza, A. Pardo, and M. Selman. Am. J. Physiol. 269 ( Lung Cell. Mol. Physiol. 13): L819–L828, 1995]. To determine whether epithelial cell death is associated with proximity to abnormal fibroblasts in vivo, the spatial distribution of epithelial cell loss, DNA fragmentation, and myofibroblasts was examined in the same tissue specimens used previously for fibroblast isolation. Paraffin sections of normal and fibrotic human lung were subjected to in situ end labeling (ISEL) of fragmented DNA and simultaneous immunolabeling of α-smooth muscle actin (α-SMA); replicate samples were subjected to electron microscopy and detection of collagens by the picrosirius red technique. Normal human lung exhibited very little labeling except for positive α-SMA immunoreactivity of smooth muscle surrounding bronchi and vessels. In contrast, fibrotic human lung exhibited moderate to heavy ISEL of interstitial, cuboidal epithelial, and free alveolar cells. ISEL of the alveolar epithelium was not distributed uniformly but was most intense immediately adjacent to underlying foci of α-SMA-positive fibroblast-like interstitial cells. Both electron microscopy and picrosirius red confirmed epithelial cell apoptosis, necrosis, and cell loss adjacent to foci of collagen accumulation surrounding fibroblast-like cells. These results demonstrate that the cuboidal epithelium of the fibrotic lung contains dying as well as proliferating cells and support the hypothesis that alveolar epithelial cell death is induced by abnormal lung fibroblasts in vivo as it is in vitro.

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Polyhexamethylene Guanidine Phosphate Induces Apoptosis through Endoplasmic Reticulum Stress in Lung Epithelial Cells

International Journal of Molecular Sciences ◽

10.3390/ijms22031215 ◽

2021 ◽

Vol 22 (3) ◽

pp. 1215

Author(s):

Mi Ho Jeong ◽

Mi Seon Jeon ◽

Ga Eun Kim ◽

Ha Ryong Kim

Keyword(s):

Endoplasmic Reticulum ◽

Cell Death ◽

Epithelial Cell ◽

Er Stress ◽

Lung Fibrosis ◽

A549 Cells ◽

Polyhexamethylene Guanidine ◽

Lung Epithelial ◽

Epithelial Cell Death ◽

Guanidine Phosphate

Airway epithelial cell death contributes to the pathogenesis of lung fibrosis. Polyhexamethylene guanidine phosphate (PHMG-p), commonly used as a disinfectant, has been shown to be strongly associated with lung fibrosis in epidemiological and toxicological studies. However, the molecular mechanism underlying PHMG-p-induced epithelial cell death is currently unclear. We synthesized a PHMG-p–fluorescein isothiocyanate (FITC) conjugate and assessed its uptake into lung epithelial A549 cells. To examine intracellular localization, the cells were treated with PHMG-p–FITC; then, the cytoplasmic organelles were counterstained and observed with confocal microscopy. Additionally, the organelle-specific cell death pathway was investigated in cells treated with PHMG-p. PHMG-p–FITC co-localized with the endoplasmic reticulum (ER), and PHMG-p induced ER stress in A549 cells and mice. The ER stress inhibitor tauroursodeoxycholic acid (TUDCA) was used as a pre-treatment to verify the role of ER stress in PHMG-p-induced cytotoxicity. The cells treated with PHMG-p showed apoptosis, which was inhibited by TUDCA. Our results indicate that PHMG-p is rapidly located in the ER and causes ER-stress-mediated apoptosis, which is an initial step in PHMG-p-induced lung fibrosis.

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