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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 mammary epithelial cell shedding.Confocal images of cultures treated with 5-HT (10−3 M) for indicated time periods showing a time–dependent induction of epithelial cell shedding by 5-HT. (A) The cultures were stained for a luminal marker (MUC1) (red) and nuclei (blue). Note the holes in the epithelium seen as areas lacking MUC1 staining (yellow arrowheads). (B) Quantification of holes in the epithelium seen upon 5-HT treatment. At least 4 different sections for each time point were analyzed. Counting was discontinued after 48 hour due to lack of resolution with respect to holes created by single cells and multiple adjacent cells. The number of holes appears to progressively increase with time of exposure to 5-HT. The data is expressed as means +/− S.E.M. (C) Shows magnified representative XY and Z sections of cultures at 0 hrs and 16 hrs after exposure to 5-HT. At 0 hrs the epithelial lining is straight and intact. By 16 Hrs the shed cells have left behind an undulating epithelial lining. The cells surrounding/lining the holes from underneath, express low to normal levels of MUC1 (blue arrows).
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pone-0017028-g003: 5-HT induces mammary epithelial cell shedding.Confocal images of cultures treated with 5-HT (10−3 M) for indicated time periods showing a time–dependent induction of epithelial cell shedding by 5-HT. (A) The cultures were stained for a luminal marker (MUC1) (red) and nuclei (blue). Note the holes in the epithelium seen as areas lacking MUC1 staining (yellow arrowheads). (B) Quantification of holes in the epithelium seen upon 5-HT treatment. At least 4 different sections for each time point were analyzed. Counting was discontinued after 48 hour due to lack of resolution with respect to holes created by single cells and multiple adjacent cells. The number of holes appears to progressively increase with time of exposure to 5-HT. The data is expressed as means +/− S.E.M. (C) Shows magnified representative XY and Z sections of cultures at 0 hrs and 16 hrs after exposure to 5-HT. At 0 hrs the epithelial lining is straight and intact. By 16 Hrs the shed cells have left behind an undulating epithelial lining. The cells surrounding/lining the holes from underneath, express low to normal levels of MUC1 (blue arrows).

Mentions: In order to determine 5-HT's effect on cell shedding we treated cultures with 5-HT for various time periods and then visualized the luminal layer using MUC1 stain. Holes in the MUC1+ epithelium were generated by the shedding of cells (Figure 3). In untreated cultures shedding was relatively rare, with 1–2 holes per 4–5 sections (Figure 3A and B). However, as early as 4 hours after 5-HT treatment we observed frequent holes in the epithelium (Figure 3A yellow arrowheads). The number of holes increased with the time of exposure to 5-HT (Figure 3B). In the magnified Z-section image at 16 hours after 5-HT treatment (Figure 3Cand S3) the undulating nature of the epithelium left behind by the shed cells was obvious. In addition, at the site of holes left behind by the shed cells, the underlying cells began to show MUC1 expression (Figure 3C Arrows). This observation suggests a replacement of the shed cells from the suprabasal cell layer. This conclusion is further supported by the observation that although increased cell shedding was observed in response to 5-HT beginning 4 hours, the barrier functions as measured by transepithelial electrical resistance (TEER), is not substantially compromised until 48 hours (Figure 4).


Multiple cellular responses to serotonin contribute to epithelial homeostasis.

Pai VP, Horseman ND - PLoS ONE (2011)

5-HT induces mammary epithelial cell shedding.Confocal images of cultures treated with 5-HT (10−3 M) for indicated time periods showing a time–dependent induction of epithelial cell shedding by 5-HT. (A) The cultures were stained for a luminal marker (MUC1) (red) and nuclei (blue). Note the holes in the epithelium seen as areas lacking MUC1 staining (yellow arrowheads). (B) Quantification of holes in the epithelium seen upon 5-HT treatment. At least 4 different sections for each time point were analyzed. Counting was discontinued after 48 hour due to lack of resolution with respect to holes created by single cells and multiple adjacent cells. The number of holes appears to progressively increase with time of exposure to 5-HT. The data is expressed as means +/− S.E.M. (C) Shows magnified representative XY and Z sections of cultures at 0 hrs and 16 hrs after exposure to 5-HT. At 0 hrs the epithelial lining is straight and intact. By 16 Hrs the shed cells have left behind an undulating epithelial lining. The cells surrounding/lining the holes from underneath, express low to normal levels of MUC1 (blue arrows).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3044750&req=5

pone-0017028-g003: 5-HT induces mammary epithelial cell shedding.Confocal images of cultures treated with 5-HT (10−3 M) for indicated time periods showing a time–dependent induction of epithelial cell shedding by 5-HT. (A) The cultures were stained for a luminal marker (MUC1) (red) and nuclei (blue). Note the holes in the epithelium seen as areas lacking MUC1 staining (yellow arrowheads). (B) Quantification of holes in the epithelium seen upon 5-HT treatment. At least 4 different sections for each time point were analyzed. Counting was discontinued after 48 hour due to lack of resolution with respect to holes created by single cells and multiple adjacent cells. The number of holes appears to progressively increase with time of exposure to 5-HT. The data is expressed as means +/− S.E.M. (C) Shows magnified representative XY and Z sections of cultures at 0 hrs and 16 hrs after exposure to 5-HT. At 0 hrs the epithelial lining is straight and intact. By 16 Hrs the shed cells have left behind an undulating epithelial lining. The cells surrounding/lining the holes from underneath, express low to normal levels of MUC1 (blue arrows).
Mentions: In order to determine 5-HT's effect on cell shedding we treated cultures with 5-HT for various time periods and then visualized the luminal layer using MUC1 stain. Holes in the MUC1+ epithelium were generated by the shedding of cells (Figure 3). In untreated cultures shedding was relatively rare, with 1–2 holes per 4–5 sections (Figure 3A and B). However, as early as 4 hours after 5-HT treatment we observed frequent holes in the epithelium (Figure 3A yellow arrowheads). The number of holes increased with the time of exposure to 5-HT (Figure 3B). In the magnified Z-section image at 16 hours after 5-HT treatment (Figure 3Cand S3) the undulating nature of the epithelium left behind by the shed cells was obvious. In addition, at the site of holes left behind by the shed cells, the underlying cells began to show MUC1 expression (Figure 3C Arrows). This observation suggests a replacement of the shed cells from the suprabasal cell layer. This conclusion is further supported by the observation that although increased cell shedding was observed in response to 5-HT beginning 4 hours, the barrier functions as measured by transepithelial electrical resistance (TEER), is not substantially compromised until 48 hours (Figure 4).

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