Relationship:965

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Key Event Relationship Overview

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Description of Relationship

Upstream Event Downstream Event/Outcome
EGFR, Activation Transdifferentiation of ciliated epithelial cells, Increase

AOPs Referencing Relationship

AOP Name Type of Relationship Weight of Evidence Quantitative Understanding
EGFR Activation Leading to Mucus Hypersecretion Directly Leads to Moderate Moderate

Taxonomic Applicability

Name Scientific Name Evidence Links

How Does This Key Event Relationship Work

EGFR can be activated by IL13 and ROS to lead to ciliated cell transdifferentiation. IL13 stimulates transdifferentiation of ciliated epithelial cells to goblet cells through EGFR activation (Tyner et al., 2006), MMP/ADAM (Yoshisue and Hasegawa 2004), p38 MAPK (Fujisawa et al., 2008) and inhibition of FOXJ1 (Gomperts et al., 2007). In addition to IL13, IL4 has been shown to act through shared receptor IL4RA to stimulate goblet cell differentiation and inhibit ciliogenesis (Laoukili et al., 2001). IL4 and IL13 but not IL5 or IL9 have been shown to induce goblet cell metaplasia in mouse trachial epiethelial cells (Fujisawa et al., 2008). IL13 can activate EGFR by shedding EGFR ligand TGFA (Yoshisue and Hasegawa, 2004) and also act through IL4RA (Laoukili et al., 2001) and IL13RA2 (Tyner et al., 2006) which could be EGFR independent. EGFR can also be activated by xanthanine oxidase ROS via hyaluronic acid depolymerization and EGFR processing by tissue kalikrein which releases EGF (Casalino-Matsuda et al., 2006).

Weight of Evidence

Biological Plausibility

Ciliated cell transdifferentiation to goblet cells is biologically plausible as a number of studies have shown this to occur in response to IL13 by a mix of features characteristic of each cell type within a cell (Tyner et al., 2006), (Laoukili et al., 2001), (Gomperts et al., 2007) or fluorescent labeling from ciliated cells detected in goblet cells after differentiation (Turner et al., 2011). One study has shown EGFR involvement via IL13-induced TGFA (Yoshisue and Hasegawa, 2004) and another study showed ROS-induced EGF and subsequent EGFR activation leading to an increase in goblet cells and decrease in ciliated cells (Casalino-Matsuda et al., 2006).

Ciliated cell transdifferentiation conflicts with the traditional dogma that ciliiated cells are terminally differentiated under normal conditions (Rawlins and Hogan, 2008), and in response to napthalene or sulfur dioxide-induced injury (Rawlins et al., 2006). However other studies showed that napthalene-induced injury can result in transdifferentiation of ciliated cells (Park et al., 2006) and there is a wide variety of responses in epithelial repair among different mouse strains (Lawson et al., 2002).

Empirical Support for Linkage

Include consideration of temporal concordance here

Studies have shown a decrease in ciliated cells with an increased dose of IL13 or EGFR activation. One study has shown both an increase in goblet cells and decrease in ciliated cells. Since there is only one study showing the inverse relationship between goblet and ciliated cells numbers indicating transdifferentiation, the empirical support for this KER is moderate.

Transdifferentiation in mouse tracheal epithelial cell cultures shown by loss of ciliated cell marker beta-tubulin decreases when inhibited by EGFR and PI3K inhibitor dose-dependently (Tyner et al., 2006).

IL-13 stimulates goblet cell differentiation and inhibits ciliogenesis in human nasal epithelium shown by decreased ciliary beat frequency with increasing IL13 dose (Laoukili et al., 2001).

IL13 induces transdifferentiation from ciliated to goblet in a 3D human airway epithelial model at a concentration of 50 or 100ng/mL IL13 for 3 days, resulting in dose-dependent decrease of ciliated cells (Gomperts et al. 2007).

In cultured human bronchial epithelial cells, goblet cells were derived from ciliated cells after 1 ng/mL IL13 treatment. Increase in goblet cells and decrease in ciliated cells occurred from 7-14 days (Turner 2011).

Uncertainties or Inconsistencies

IL13-induced goblet cell increase has been shown to be concentration-dependent in human bronchial epithelial cells with 1ng/ml inducing and 10ng/ml suppressing goblet cell increase (Atherton, et al. 2003), however multiple studies have shown that concentrations from 5-100ng/mL do induce goblet cell hyperplasia, including in human bronchial epithelial cells (Yoshisue and Hasegawa, 2004).

It has been shown that two weeks but not one week of human nasal epithelial cell differentiation and IL13 treatment showed a decrease in proportion of ciliated cells (shown by glutamylated tubulin protein expression) (Laouikili et al., 2001), however other studies showed that IL13-induced ciliated to goblet cell differentiation were observed in as little as 3-5 days cultured human airway epithelium, mouse tracheal epithelial cells and a Sendai virus mouse model (Gomperts et al., 2007), (Fujisawa et al., 2008), (Tyner et al., 2006). This difference may be due to the difference in cell types used in these experiments. Ciliated cells of pseudostratified airway epithelium do not become mucous cells after ovalbumin (OVA) challenge for 48 hours which may be due to insufficient time for OVA-induced IL13 upregulation and subsequent effects (Pardo-Saganta et al., 2013). This AOP is focused on mucus hypersecretion in the context of COPD and not asthma, which could act differently.

Quantitative Understanding of the Linkage

Is it known how much change in the first event is needed to impact the second? Are there known modulators of the response-response relationships? Are there models or extrapolation approaches that help describe those relationships?

It has been proposed that the effects of IL13 and IL4 on differentiation to goblet cells is concentration-dependent in human bronchial epithelial cells, with 1ng/ml inducing an increase in goblet cell density acting through MAPK and p38 MAPK but not EGFR and 10ng/ml inducing a reduction in goblet cell density (Atherton et al. 2003). Other studies have agreed with this finding, with 1ng/mL IL13 leading to an increase in goblet hyperplasia in human bronchial epitehlial cells (Turner 2011) and 5ng/mL having a lack of effect inducing goblet cell differentiation in nasal epithelial cells (Kim 2002). On the contrary, multiple studies have shown that concentrations from 5-100ng/mL do induce goblet cell hyperplasia in human bronchial epithelial cells, human nasal epithelial cells, cultured human differentiated airway epithelial tissue, cultured guinea pig tracheal epithelium, and mouse tracheal epithelial cells (Yoshisue 2004, Laouikili 2001, Gomperts 2007, Kondo 2002, Fujisawa 2008).

It has also been proposed that two weeks of differentiation is necessary to see the effects (Laouikili 2001) and could explain why differentiation was not observed in a two day OVA-induced murine model (Pardo-Saganta 2013) or seven day human nasal epithelial cell model (Kim 2002). On the contrary, IL13-induced goblet cell metaplasia was also observed in short term experiments of 3-5 days in cultured human airway epithelium, mouse tracheal epithelial cells and a Sendai virus mouse model (Gomperts 2007, Fujisawa 2008, Tyner 2006).

Evidence Supporting Taxonomic Applicability

There are many human studies demonstrating transdifferentiation from ciliated to goblet cells including in 3D human airway epithelial models (Gomperts et al. 2007), human bronchial or nasal epithelial cells in vitro (Yoshisue and Hasegawa 2004, Turner et al. 2011, Laoukili, et al. 2001) and in COPD patients (Tyner, et al. 2006).

Two mouse studies have demonstrated transdifferentiation and goblet metaplasia (Tyner, et al. 2006, Fujisawa, et al. 2008) while another mouse study has shown that ciliated cells of pseudostratified airway epithelium do not become mucous cells after ovalbumin challenge (Pardo-Saganta, et al. 2013), however this could be due to the short 48 hour time point which has been noted is not enough time for transdifferentiation (Laoukili, et al. 2001).

Rat studies have demonstrated IL-13 and/or EGFR involvement in goblet cell metaplasia/hyperplasia, however no rat studies have directly measured transdifferentiation of ciliated to goblet cells to our knowledge (Shim 2001, Takeyama 2008).

References