Disruption Of Epithelial Integrity Research Articles

Cortical Neural Precursors Inhibit Their Own Differentiation via N-Cadherin Maintenance of β-Catenin Signaling

Little is known about the architecture of cellular microenvironments that support stem and precursor cells during tissue development. Although adult stem cell niches are organized by specialized supporting cells, in the developing cerebral cortex, neural stem/precursor cells reside in a neurogenic niche lacking distinct supporting cells. Here, we find that neural precursors themselves comprise the niche and regulate their own development. Precursor-precursor contact regulates beta-catenin signaling and cell fate. In vivo knockdown of N-cadherin reduces beta-catenin signaling, migration from the niche, and neuronal differentiation in vivo. N-cadherin engagement activates beta-catenin signaling via Akt, suggesting a mechanism through which cells in tissues can regulate their development. These results suggest that neural precursor cell interactions can generate a self-supportive niche to regulate their own number.

Does activation of the FcγRIIa play a role in the pathogenesis of the acute lung injury/acute respiratory distress syndrome?

ALI (acute lung injury) and its more severe form ARDS (acute respiratory distress syndrome) are inflammatory diseases of the lung characterized by hypoxaemia and diffuse bilateral infiltrates. Disruption of epithelial integrity and injury to endothelium are contributing factors of the development of ALI/ARDS, and alveolar damage is the most pronounced feature of ALI/ARDS. The resulting increase in lung microvascular permeability promotes influx of inflammatory cells to the alveolar spaces. Oedema fluid contains pro-nflammatory mediators and plasma proteins, including Igs (immunoglobulins). Moreover, several reports describe the presence of autoantibodies and immune complexes [anti-IL-8 (interleukin-8) autoantibody/IL-8 complexes] in lung fluids (oedema and bronchoalveolar lavage fluids) from patients with ALI/ARDS. These immune complexes associate with FcγRIIa (Fcγ IIa receptor) in lungs of patients with ARDS. Furthermore, the expression of FcγRIIa is substantially elevated in lungs of these patients. FcγRIIa appears on virtually all myeloid cells, platelets and endothelial cells. It is a low-affinity receptor for IgG that preferentially binds aggregated immunoglobulins and immune complexes. FcγRs regulate phagocytosis and cell-mediated cytotoxicity, and initiate the release of inflammatory mediators. It should be noted that immune complexes formed between either anti-neutrophil autoantibodies and their specific antigens or anti-HLA (human leucocyte antigen) antibodies and target antigens are implicated in the pathogenesis of TRALI (transfusion-related acute lung injury), and importantly, animal studies indicate that FcγRs are essential for these complexes to cause damage to the lungs. Therefore, we hypothesize that FcγRs such as FcγRIIa could contribute to the pathogenesis of ALI/ARDS.

The Drosophila Metastasis Suppressor Gene Nm23 Homolog, awd, Regulates Epithelial Integrity during Oogenesis

The expression levels of the metastasis suppressor gene Nm23 have been shown to correlate positively or inversely with prognosis in different cancer cohorts. This indicates that Nm23 may be needed at different expression levels and may function differently in various tissues. Here we report a novel epithelial function of the Drosophila melanogaster homolog of human Nm23, abnormal wing discs (awd). We show a dynamic expression pattern of the Awd protein during morphogenesis of the Drosophila follicle cells during oogenesis. Loss-of-function awd mutant cells result in the accumulation and spreading of adherens junction components, such as Drosophila E-cadherin, beta-catenin/Armadillo, and alpha-spectrin, and the disruption of epithelial integrity, including breaking up of the epithelial sheet and piling up of follicle cells. In contrast, overexpression of awd diminishes adherens junction components and induces a mesenchymal-cell-like cell shape change. The gain-of-function phenotype is consistent with a potential oncogenic function of this metastasis suppressor gene. Interestingly, we demonstrate that the epithelial function of awd is mediated by Rab5 and show that the Rab5 expression level is downregulated in awd mutant cells. Therefore, awd modulates the level and localization of adherens junction components via endocytosis. This is the first demonstration of an in vivo function of Nm23 family genes in regulating epithelial morphogenesis.

Internalization of Non-Clustered Desmoglein 1 without Depletion of Desmoglein 1 from Adhesion Complexes in An Experimental Model of the Autoimmune Disease Pemphigus Foliaceus

Serum antibodies against desmoglein 1 (Dsg1) are known to induce the clinical and histological manifestations of pemphigus foliaceus (PF), autoimmune bullous disease targeting skin. The basic pathophysiological phenomenon of PF blistering is the disruption of epithelial integrity in the granular layer of the epidermis due to separation of keratinocytes from one another, or acantholysis. In this report we investigate the changes in subcellular distribution of Dsg1 in response to serum of patients with PF by using an in vitro model of PF. Immunofluorescence analysis on HaCaT cells indicates that non-clustered Dsg1 is markedly internalized after exposure to serum. However, binding of PF IgG to Dsg1-rich adhesion complexes (desmosomes) does not cause disruption of such structures nor depletion of clustered Dsg1, as revealed by colocalization of PF IgG and Dsg1 in a punctate staining on cell membrane 24 hours after treatment. Furthermore, morphological studies demonstrate that the dramatic alterations induced by PF sera are not the result of apoptotic programs. Taken together, our data strongly suggest that anti-Dsg1 antibodies from PF serum could cause the internalization of non-clustered Dsg1 and perturb the formation of new desmosomes but not directly disrupt Dsg1-containing junctions when stable contacts are already formed.

The Impact of Mechanical Ventilation on Immature Airway Smooth Muscle: Functional, Structural, Histological, and Molecular Correlates

Preterm infants exposed to mechanical ventilation often develop airway dysfunction and bronchopulmonary dysplasia. The mechanisms of mechanical ventilation-induced airway injury are currently unknown. This study correlates the age-related effects of mechanical ventilation on airway function with structural alterations at the tissue, cellular, ultrastructural, and molecular levels. Mechanically ventilated and nonventilated tracheal rings were obtained from premature and newborn lambs. In tissue baths, the passive and active length-tension relationships and dose-response characteristics of the tracheal rings were determined. Fixed tracheal rings were digested and the resulting isolated smooth muscle cells measured. Rings were analyzed by light and electron microscopy. Additionally, protein was extracted from the tracheal smooth muscle and myosin heavy chain isoforms were separated by SDS-polyacrylamide gel electrophoresis and analyzed by densitometry. Mechanical ventilation resulted in a significant decrease of both the slope of the passive length-stress relationship and of maximal force generation, with both effects being most pronounced in the newborn age group. These age-related functional alterations correlated with a decrease in smooth muscle cell length and a disruption of ultrastructural architecture, which were also most pronounced in the older groups. Furthermore, mechanical ventilation resulted in epithelial denudation at all ages. There were no acute statistically significant effects of mechanical ventilation on myosin heavy chain isoform expression. This study demonstrates age-related effects of mechanical ventilation on the passive and active characteristics of tracheal function and provides a structural analysis of potential mechanisms. The mechanisms behind these functional differences involve ultrastructural changes in cell length, tissue matrix, and disruption of epithelial integrity. These findings help elucidate the pathogenesis of ventilator-induced airway injury.

Bves is expressed in the epithelial components of the retina, lens, and cornea.

To demonstrate the expression pattern and subcellular localization of Bves/Pop1a protein, a newly identified cell adhesion molecule, during eye development and corneal regeneration. Staged embryonic and adult eyes were assayed using fluorescence immunohistochemistry to detect the Bves protein. A human corneal epithelial (HCE) cell line was used as a model to examine Bves localization during corneal growth and regeneration, with and without antisense morpholino treatment. The data detail the expression and localization of Bves protein before, during, and after differentiation of the eye. In these analyses, Bves was localized to an apical-lateral position in the initial epithelial primordia of the eye. Later, Bves became localized to specific cell types and subcellular domains in the retina, lens, and cornea, indicating changes in Bves expression in the differentiated eye. Finally, an in vitro model of corneal wound healing showed that Bves staining was missing at the epithelial surface during cellular migration across the wound, but it reappeared at points of cell contact during the reinitiation of epithelial continuity. When epithelial sheets were treated with Bves antisense morpholinos to inhibit Bves function, disruption of epithelial integrity was observed. After injury, similar treatment resulted in an acceleration of cell movement at the wound surface but regeneration of an intact epithelium was ultimately impeded. Taken together, these studies suggest that Bves is expressed in epithelial elements of the developing eye and may have a role in corneal epithelial growth and regeneration.

Subinhibitory concentrations of erythromycin reduce pneumococcal adherence to respiratory epithelial cells in vitro.

We have investigated the influence of subinhibitory concentrations of erythromycin on the interaction between Streptococcus pneumoniae and human respiratory epithelial cells. Confluent in vitro cell cultures were inoculated with erythromycin-resistant S. pneumoniae and incubated for 24 h. Erythromycin significantly reduced adherence of the pneumococci after 4 h and 24 h: 4.0% +/- 0.7% (mean +/- S.E.M. ) of the pneumococci adhered to the epithelial cells in medium with erythromycin, compared with 7.7% +/- 0.8% in medium without erythromycin (P: = 0.002) after 4 h, and the corresponding values after 24 h were 24.2% +/- 5.3% and 38.4% +/- 5.0%, respectively (P: = 0.038). Disruption of epithelial integrity by S. pneumoniae, measured as the decrease in transepithelial electrical resistance, was delayed in the presence of erythromycin. Neither addition of erythromycin to the culture medium nor infection of the cell cultures with pneumococci significantly affected secretion of interleukin-8 by the epithelial cells. Addition of erythromycin to a pneumococcal suspension in cell culture medium without respiratory epithelial cells almost completely prevented the release of pneumolysin. We conclude that erythromycin at subinhibitory concentrations reduces the adherence to and disruption of respiratory epithelial cells by S. pneumoniae, possibly by interfering with pneumolysin release.

DC Electric Fields Induce Rapid Directional Migration in Cultured Human Corneal Epithelial Cells

After an epithelium is wounded, multiple soluble and extracellular matrix-associated signals induce a repair response. An often-overlooked signal is the endogenous electrical field established in the vicinity of the wound immediately upon disruption of epithelial integrity. Previous studies have detected lateral electric fields of approximately 42mVmm−1near bovine corneal wounds. In addition, electric fields on the order of 100–200mVmm−1have been measured lateral to wounds in mammalian epidermis. Here we report the migratory response of human corneal epithelial cells to DC electric fields of similar, physiologic magnitude. Our findings demonstrate that in a 100mVmm−1DC field, corneal epithelial cells demonstrate directed migration towards the cathode. The migratory speed and distances traversed by cultured human corneal epithelial cells is remarkably similar to those of cultured skin-derived keratinocytes under similar conditions; however, corneal epithelial cells demonstrate a more rapid directional response to the field than keratinocytes. These findings suggest that endogenous, wound-induced electric fields present in the cornea play an important role in human corneal wound healing, by orienting the directional response of migratory cells so that they efficiently re-epithelialize the wounded area.

Inflammation in Prostate Biopsies of Men without Prostatic Malignancy or Clinical Prostatitis

Objective: Inflammation is a frequent histological finding in prostate biopsies, performed on men without prostatic malignancy or clinical prostatitis. We investigated the relationship between morphological parameters of inflammation in prostatic tissue and total serum prostate–specific antigen (PSA) and prostate–specific antigen density (PSAD) levels to determine if subclinical inflammation can cause elevation of PSA and PSAD.Methods: We reviewed 268 prostate biopsies, performed on 238 men with elevated PSA and/or abnormal digital rectal examination of the prostate. All premalignant and malignant biopsies and cases of clinical prostatitis were excluded. The inflammation in the remaining 145 prostate biopsies was scored for extent of inflammation and aggressiveness of inflammation, using the four–point scale designed by Irani and co–workers. In this prostatic inflammation scoring system, extent of inflammation is graded from 0 up to 3 according to the degree of invasion of inflammatory cells in prostatic tissue. Aggressiveness of inflammation is graded from 0 up to 3 according to the degree of contact or disruption of prostatic glandular epithelium by inflammatory cells.Results: Each of the studied biopsies showed inflammatory cells. Median PSA levels in grades 1, 2 and 3 of extent of inflammation were, respectively, 5.7, 6.8 and 13.0. Median PSAD levels in these groups were 0.13, 0.16 and 0.33. There was no significant difference between these grades for PSA nor for PSAD. Median PSA levels in grades 0, 1 and 2 of aggressiveness of inflammation were, respectively, 3.9, 5.9 and 8.9. Median PSAD levels in these groups were 0.12, 0.18 and 0.17. For both parameters, there was a significant difference between grades (respectively, p = 0.0028 and p = 0.0330).Conclusion: Inflammation of the prostate is a histological finding in almost every set of prostate biopsies, even when there are no signs of clinical prostatitis. This subclinical inflammation can cause PSA elevation. Not the extent of inflammation is of importance, but the disruption of epithelial integrity caused by the inflammatory infiltrate. When confronted with a patient with an elevated PSA level whose prostate biopsies reveal no malignancy but only inflammation, this concept can help in determining the need for quick repeat biopsies.

Airway epithelial cells: functional roles in airway disease.

"Airway Epithelial Cells: Functional Roles in Airway Disease." American Journal of Respiratory and Critical Care Medicine, 150(5_pt_2), pp. S27–S30

Intestinal cytokines in inflammatory bowel disease and invasive diarrhoea

In the intestine large numbers of bacteria and their products are separated by a single epithelial layer from resident inflammatory cells (macrophages and lymphocytes). Many of these bacterial products, such as lipopolysaccharides and peptidoglycans, are potent stimulators of free radical and inflammatory cytokine production by macrophages. This can occur in vivo in response to mucosal invasion by enteropathogenic bacteria or because of inappropriate activation of these cells, as in chronic inflammatory bowel disease. In this review we present evidence for production of cytokines in normal intestine and in intestinal inflammatory conditions. The adverse effects of cytokine production upon intestinal homeostasis, in particular disruption of epithelial integrity and prothrombotic changes in the vascular endothelium, are also discussed.

In Vivo Measurement of Gastric Mucus pH in Canines: Effect of High Luminal Acidity and Prostaglandin E2

We measured gastric mucus pH in vivo in a canine chambered stomach preparation using glass pH microelectrodes. The average maximum mucus pH was 6.52 at a luminal pH of 3.0, declining gradually as luminal pH was lowered; the mucus pH gradient was obliterated completely when luminal pH reached 1.1. At a luminal pH of 1.0, the average maximum mucus pH increased to 6.03, whereas transmural potential dropped from -50.3 to -31.8 mV. Prostaglandin E2 pretreatment (10 μg/ml) prevented epithelial injury during exposure to 100 mM HCl, but mucus pH was unchanged as compared with the acid-only group (4.77 vs. 4.72, p = 0.92). Histology on stomachs exposed to a luminal pH of 1.0 revealed characteristic changes of superficial epithelial injury without affecting the deeper gastric glands or disrupting the basal lamina. Prostaglandin E2 pretreatment prevented these histologic changes. These results indicate that although the mucus pH gradient can be overwhelmed by high luminal acidity, a newly formed mucus pH gradient may develop after disruption of epithelial integrity, possibly providing protection for the mucosa during the period of epithelial repair. The high mucus pH (4.77) accompanying normal histology and unchanged potential suggests that prostaglandin E2 may protect the surface epithelium by the stimulation of bicarbonate secretion.