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Multiple cellular responses to serotonin contribute to epithelial homeostasis.

Pai VP, Horseman ND - PLoS ONE (2011)

Bottom Line: Specifically, serotonin's roles in regulating cell shedding, apoptosis and barrier function of the epithelium.However, upon sustained exposure, serotonin induces apoptosis in the replenishing cell population, causing irreversible changes to the epithelial membrane.The staggered nature of these events induced by serotonin slowly shifts the balance in the epithelium from reversible to irreversible.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cellular Physiology, University of Cincinnati, Cincinnati, Ohio, United States of America.

ABSTRACT
Epithelial homeostasis incorporates the paradoxical concept of internal change (epithelial turnover) enabling the maintenance of anatomical status quo. Epithelial cell differentiation and cell loss (cell shedding and apoptosis) form important components of epithelial turnover. Although the mechanisms of cell loss are being uncovered the crucial triggers that modulate epithelial turnover through regulation of cell loss remain undetermined. Serotonin is emerging as a common autocrine-paracine regulator in epithelia of multiple organs, including the breast. Here we address whether serotonin affects epithelial turnover. Specifically, serotonin's roles in regulating cell shedding, apoptosis and barrier function of the epithelium. Using in vivo studies in mouse and a robust model of differentiated human mammary duct epithelium (MCF10A), we show that serotonin induces mammary epithelial cell shedding and disrupts tight junctions in a reversible manner. However, upon sustained exposure, serotonin induces apoptosis in the replenishing cell population, causing irreversible changes to the epithelial membrane. The staggered nature of these events induced by serotonin slowly shifts the balance in the epithelium from reversible to irreversible. These finding have very important implications towards our ability to control epithelial regeneration and thus address pathologies of aberrant epithelial turnover, which range from degenerative disorders (e.g.; pancreatitis and thyrioditis) to proliferative disorders (e.g.; mastitis, ductal ectasia, cholangiopathies and epithelial cancers).

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5-HT induces delayed intra-epithelial apoptosis in MCF10A Transwell® cultures.(A) Representative confocal XY images of cultures after 5-HT treatment for the indicated time periods showing 5-HT–induced apoptosis. The sections were stained for MUC1 (red), and apoptosis (cleaved caspase 3, green). Nuclei were stained blue. (B) Quantification of cells staining positive for cleaved caspase 3. Cells from at least four independent sections were counted for each time-point. The data are expressed as mean +/− S.E.M. **p<0.01 (One way Anova). Significant induction of apoptosis is not seen until 72 hrs of 5-HT treatment. (C) Representative confocal Z-section images of cultures after 5-HT treatment for indicated time-points. The sections were stained for luminal epithelial marker (MUC1) (red) and apoptosis marker (cleaved caspase 3) (green). Nuclei were stained blue. Note that the caspase positive cells are located mainly in the suprabasal cell layer. Also certain cells from the suprabasal layer stain positive for MUC1 (yellow arrowheads).
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pone-0017028-g005: 5-HT induces delayed intra-epithelial apoptosis in MCF10A Transwell® cultures.(A) Representative confocal XY images of cultures after 5-HT treatment for the indicated time periods showing 5-HT–induced apoptosis. The sections were stained for MUC1 (red), and apoptosis (cleaved caspase 3, green). Nuclei were stained blue. (B) Quantification of cells staining positive for cleaved caspase 3. Cells from at least four independent sections were counted for each time-point. The data are expressed as mean +/− S.E.M. **p<0.01 (One way Anova). Significant induction of apoptosis is not seen until 72 hrs of 5-HT treatment. (C) Representative confocal Z-section images of cultures after 5-HT treatment for indicated time-points. The sections were stained for luminal epithelial marker (MUC1) (red) and apoptosis marker (cleaved caspase 3) (green). Nuclei were stained blue. Note that the caspase positive cells are located mainly in the suprabasal cell layer. Also certain cells from the suprabasal layer stain positive for MUC1 (yellow arrowheads).

Mentions: Since apoptosis is an important contributor to epithelial turnover, one way 5-HT could affect the epithelium is through induction of apoptosis. To understand 5-HT action on apoptosis we treated the cultures with 5-HT and stained for cleaved caspase3 (apoptosis marker). As seen in figure 5A, 5-HT induced apoptosis in the epithelium, but this effect of 5-HT was significantly delayed, with the increase in apoptosis not observed until 72 hours (Figure 5B). Notice the highly undulating membrane (due to cell shedding) as observed in the Z-sections of the cultures (Figure 5C). The apoptosis induced by 5-HT was mainly observed in the suprabasal layer of cells, which are responsible for replenishing the lost luminal cells (Figure 5C). Very few apoptotic cells were observed in the basal cells, which largely remained refractory to the apoptotic effect of 5-HT (Figure S4). Certain cells from the suprabasal layer which were not yet undergoing apoptosis expressed MUC1. However, this may not be enough to keep up with the increased cell loss. Thus, 5-HT, first through induction of luminal cell shedding and then through induction of apoptosis, shifts the balance towards cell loss, resulting in regression of the epithelium.


Multiple cellular responses to serotonin contribute to epithelial homeostasis.

Pai VP, Horseman ND - PLoS ONE (2011)

5-HT induces delayed intra-epithelial apoptosis in MCF10A Transwell® cultures.(A) Representative confocal XY images of cultures after 5-HT treatment for the indicated time periods showing 5-HT–induced apoptosis. The sections were stained for MUC1 (red), and apoptosis (cleaved caspase 3, green). Nuclei were stained blue. (B) Quantification of cells staining positive for cleaved caspase 3. Cells from at least four independent sections were counted for each time-point. The data are expressed as mean +/− S.E.M. **p<0.01 (One way Anova). Significant induction of apoptosis is not seen until 72 hrs of 5-HT treatment. (C) Representative confocal Z-section images of cultures after 5-HT treatment for indicated time-points. The sections were stained for luminal epithelial marker (MUC1) (red) and apoptosis marker (cleaved caspase 3) (green). Nuclei were stained blue. Note that the caspase positive cells are located mainly in the suprabasal cell layer. Also certain cells from the suprabasal layer stain positive for MUC1 (yellow arrowheads).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3044750&req=5

pone-0017028-g005: 5-HT induces delayed intra-epithelial apoptosis in MCF10A Transwell® cultures.(A) Representative confocal XY images of cultures after 5-HT treatment for the indicated time periods showing 5-HT–induced apoptosis. The sections were stained for MUC1 (red), and apoptosis (cleaved caspase 3, green). Nuclei were stained blue. (B) Quantification of cells staining positive for cleaved caspase 3. Cells from at least four independent sections were counted for each time-point. The data are expressed as mean +/− S.E.M. **p<0.01 (One way Anova). Significant induction of apoptosis is not seen until 72 hrs of 5-HT treatment. (C) Representative confocal Z-section images of cultures after 5-HT treatment for indicated time-points. The sections were stained for luminal epithelial marker (MUC1) (red) and apoptosis marker (cleaved caspase 3) (green). Nuclei were stained blue. Note that the caspase positive cells are located mainly in the suprabasal cell layer. Also certain cells from the suprabasal layer stain positive for MUC1 (yellow arrowheads).
Mentions: Since apoptosis is an important contributor to epithelial turnover, one way 5-HT could affect the epithelium is through induction of apoptosis. To understand 5-HT action on apoptosis we treated the cultures with 5-HT and stained for cleaved caspase3 (apoptosis marker). As seen in figure 5A, 5-HT induced apoptosis in the epithelium, but this effect of 5-HT was significantly delayed, with the increase in apoptosis not observed until 72 hours (Figure 5B). Notice the highly undulating membrane (due to cell shedding) as observed in the Z-sections of the cultures (Figure 5C). The apoptosis induced by 5-HT was mainly observed in the suprabasal layer of cells, which are responsible for replenishing the lost luminal cells (Figure 5C). Very few apoptotic cells were observed in the basal cells, which largely remained refractory to the apoptotic effect of 5-HT (Figure S4). Certain cells from the suprabasal layer which were not yet undergoing apoptosis expressed MUC1. However, this may not be enough to keep up with the increased cell loss. Thus, 5-HT, first through induction of luminal cell shedding and then through induction of apoptosis, shifts the balance towards cell loss, resulting in regression of the epithelium.

Bottom Line: Specifically, serotonin's roles in regulating cell shedding, apoptosis and barrier function of the epithelium.However, upon sustained exposure, serotonin induces apoptosis in the replenishing cell population, causing irreversible changes to the epithelial membrane.The staggered nature of these events induced by serotonin slowly shifts the balance in the epithelium from reversible to irreversible.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cellular Physiology, University of Cincinnati, Cincinnati, Ohio, United States of America.

ABSTRACT
Epithelial homeostasis incorporates the paradoxical concept of internal change (epithelial turnover) enabling the maintenance of anatomical status quo. Epithelial cell differentiation and cell loss (cell shedding and apoptosis) form important components of epithelial turnover. Although the mechanisms of cell loss are being uncovered the crucial triggers that modulate epithelial turnover through regulation of cell loss remain undetermined. Serotonin is emerging as a common autocrine-paracine regulator in epithelia of multiple organs, including the breast. Here we address whether serotonin affects epithelial turnover. Specifically, serotonin's roles in regulating cell shedding, apoptosis and barrier function of the epithelium. Using in vivo studies in mouse and a robust model of differentiated human mammary duct epithelium (MCF10A), we show that serotonin induces mammary epithelial cell shedding and disrupts tight junctions in a reversible manner. However, upon sustained exposure, serotonin induces apoptosis in the replenishing cell population, causing irreversible changes to the epithelial membrane. The staggered nature of these events induced by serotonin slowly shifts the balance in the epithelium from reversible to irreversible. These finding have very important implications towards our ability to control epithelial regeneration and thus address pathologies of aberrant epithelial turnover, which range from degenerative disorders (e.g.; pancreatitis and thyrioditis) to proliferative disorders (e.g.; mastitis, ductal ectasia, cholangiopathies and epithelial cancers).

Show MeSH
Related in: MedlinePlus