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Relationship: 2472

Title

The title of the KER should clearly define the two KEs being considered and the sequential relationship between them (i.e., which is upstream and which is downstream). Consequently all KER titles take the form “upstream KE leads to downstream KE”.  More help

Goblet cell hyperplasia leads to Chronic, Mucus hypersecretion

Upstream event
Upstream event in the Key Event Relationship. On the KER page, clicking on the Event name under Upstream Relationship will bring the user to that individual KE page. More help
Downstream event
Downstream event in the Key Event Relationship. On the KER page, clicking on the Event name under Upstream Relationship will bring the user to that individual KE page. More help

Key Event Relationship Overview

The utility of AOPs for regulatory application is defined, to a large extent, by the confidence and precision with which they facilitate extrapolation of data measured at low levels of biological organisation to predicted outcomes at higher levels of organisation and the extent to which they can link biological effect measurements to their specific causes. Within the AOP framework, the predictive relationships that facilitate extrapolation are represented by the KERs. Consequently, the overall WoE for an AOP is a reflection in part, of the level of confidence in the underlying series of KERs it encompasses. Therefore, describing the KERs in an AOP involves assembling and organising the types of information and evidence that defines the scientific basis for inferring the probable change in, or state of, a downstream KE from the known or measured state of an upstream KE. More help

AOPs Referencing Relationship

This table is automatically generated upon addition of a KER to an AOP. All of the AOPs that are linked to this KER will automatically be listed in this subsection. Clicking on the name of the AOP in the table will bring you to the individual page for that AOP. More help
AOP Name Adjacency Weight of Evidence Quantitative Understanding Point of Contact Author Status OECD Status
EGFR Activation Leading to Decreased Lung Function adjacent Moderate Moderate Karsta Luettich (send email) Under development: Not open for comment. Do not cite Under Development

Taxonomic Applicability

Select one or more structured terms that help to define the biological applicability domain of the KER. In general, this will be dictated by the more restrictive of the two KEs being linked together by the KER. Authors can indicate the relevant taxa for this KER in this subsection. The process is similar to what is described for KEs (see pages 30-31 and 37-38 of User Handbook) More help
Term Scientific Term Evidence Link
human Homo sapiens High NCBI
mouse Mus musculus Moderate NCBI
rat Rattus norvegicus Low NCBI
ferret Mustela putorius furo Low NCBI

Sex Applicability

Authors can indicate the relevant sex for this KER in this subsection. The process is similar to what is described for KEs (see pages 31-32 of the User Handbook). More help
Sex Evidence
Mixed Moderate

Life Stage Applicability

Authors can indicate the relevant life stage for this KER in this subsection. The process is similar to what is described for KEs (see pages 31-32 of User Handbook). More help
Term Evidence
All life stages Moderate

Key Event Relationship Description

Provide a brief, descriptive summation of the KER. While the title itself is fairly descriptive, this section can provide details that aren’t inherent in the description of the KEs themselves (see page 39 of the User Handbook). This description section can be viewed as providing the increased specificity in the nature of upstream perturbation (KEupstream) that leads to a particular downstream perturbation (KEdownstream), while allowing the KE descriptions to remain generalised so they can be linked to different AOPs. The description is also intended to provide a concise overview for readers who may want a brief summation, without needing to read through the detailed support for the relationship (covered below). Careful attention should be taken to avoid reference to other KEs that are not part of this KER, other KERs or other AOPs. This will ensure that the KER is modular and can be used by other AOPs. More help

Goblet cell hyperplasia refers to the increase in goblet cell numbers and is a common feature of airway epithelia in asthma and other respiratory diseases. It can arise from sustained proliferation of this cell population following airway injury by, for example, exposure to allergens, pathogens, cigarette smoke and other inhalation exposures (Miyabara et al., 1998; Nagao et al., 2003; Saetta et al., 2000; van Hove et al., 2009; Walter et al., 2002; Hao et al., 2014; Lukacs et al., 2010; Hao et al., 2013; Yageta et al., 2014; Nie et al., 2012; Hegab et al., 2007; Kim et al., 2016). Since goblet cells are mucin-producing cells, an increase in goblet cell numbers consequently equates to an increase (from basal levels) in mucin production. Chronic mucus hypersecretion is also a main feature of chronic lung diseases, and the presence of goblet cell hyperplasia or goblet cell metaplasia in the lungs of chronic obstructive pulmonary disease, asthma and cystic fibrosis patients has been inferred as cause for sustained mucus production (Rose and Voynow, 2006; Munkholm and Mortensen, 2014).  

Evidence Supporting this KER

Assembly and description of the scientific evidence supporting KERs in an AOP is an important step in the AOP development process that sets the stage for overall assessment of the AOP (see pages 49-56 of the User Handbook). To do this, biological plausibility, empirical support, and the current quantitative understanding of the KER are evaluated with regard to the predictive relationships/associations between defined pairs of KEs as a basis for considering WoE (page 55 of User Handbook). In addition, uncertainties and inconsistencies are considered. More help

This KER is inferred. However, there is indirect evidence demonstrating an increase in mucin production, which is frequently equated with increased MUC5AC mRNA and protein expression, in the presence of goblet cell hyperplasia as judged by histopathological examination and/or an increase in Alcian Blue/periodic acid Schiff (AB/PAS) and/or MUC5AC-positive antibody staining in airway epithelia following inhalation exposures (Hegab et al., 2007; An et al., 2013; Zhou et al., 2016). Goblet cell hyperplasia and mucin overproduction were also linked experimentally through genetic modification: For example, conditional deletion of Foxa2 in respiratory epithelial cells of the developing mouse lung results in goblet cell hyperplasia in bronchi and bronchioles at post-natal day 16 and later (evidenced by histology), which was accompanied by extensive AB/PAS and MUC5AC staining (Wan et al., 2004). Similarly, conditional expression of Spdef in Clara cells of the conducting airways in mice resulted in goblet cell hyperplasia in the trachea and bronchi and in peripheral airways, including smaller bronchioles that normally lack goblet cells, as shown by AB/PAS and Muc5ac staining (Park et al., 2007). 

Biological Plausibility
Define, in free text, the biological rationale for a connection between KEupstream and KEdownstream. What are the structural or functional relationships between the KEs? For example, there is a functional relationship between an enzyme’s activity and the product of a reaction it catalyses. Supporting references should be included. However, it is recognised that there may be cases where the biological relationship between two KEs is very well established, to the extent that it is widely accepted and consistently supported by so much literature that it is unnecessary and impractical to cite the relevant primary literature. Citation of review articles or other secondary sources, like text books, may be reasonable in such cases. The primary intent is to provide scientifically credible support for the structural and/or functional relationship between the pair of KEs if one is known. The description of biological plausibility can also incorporate additional mechanistic details that help inform the relationship between KEs, this is useful when it is not practical/pragmatic to represent these details as separate KEs due to the difficulty or relative infrequency with which it is likely to be measured (see page 40 of the User Handbook for further information).   More help

This KER is inferred. However, that an increase in goblet cell numbers also increases mucin production is highly plausible. Studies in human cells, mice and rats demonstrate that mucin content or MUC5AC mRNA and protein expression increase in the presence of histologically confirmed goblet cell hyperplasia. Because both events are measured in parallel and causal evidence is missing, our confidence is moderate.  

Uncertainties and Inconsistencies
In addition to outlining the evidence supporting a particular linkage, it is also important to identify inconsistencies or uncertainties in the relationship. Additionally, while there are expected patterns of concordance that support a causal linkage between the KEs in the pair, it is also helpful to identify experimental details that may explain apparent deviations from the expected patterns of concordance. Identification of uncertainties and inconsistencies contribute to evaluation of the overall WoE supporting the AOPs that contain a given KER and to the identification of research gaps that warrant investigation (seep pages 41-42 of the User Handbook).Given that AOPs are intended to support regulatory applications, AOP developers should focus on those inconsistencies or gaps that would have a direct bearing or impact on the confidence in the KER and its use as a basis for inference or extrapolation in a regulatory setting. Uncertainties that may be of academic interest but would have little impact on regulatory application don’t need to be described. In general, this section details evidence that may raise questions regarding the overall validity and predictive utility of the KER (including consideration of both biological plausibility and empirical support). It also contributes along with several other elements to the overall evaluation of the WoE for the KER (see Section 4 of the User Handbook).  More help

In some cases, it appears that authors use the terms "goblet cell hyperplasia" and "goblet cell metaplasia" interchangeably, making the evaluation of the available evidence difficult.  

Because goblet cell metaplasia is also a feature of epithelial cell remodeling in the context of wound healing, its appearance can be transient. At least one study indicates that goblet cell hyperplasia is also found in healthy non-smokers (never- and former smokers), where it appears as isolated foci—as opposed to the more extensive involvement of the airway epithelium seen in e.g. COPD patients (Polosukhin et al., 2011).  

Response-response Relationship
This subsection should be used to define sources of data that define the response-response relationships between the KEs. In particular, information regarding the general form of the relationship (e.g., linear, exponential, sigmoidal, threshold, etc.) should be captured if possible. If there are specific mathematical functions or computational models relevant to the KER in question that have been defined, those should also be cited and/or described where possible, along with information concerning the approximate range of certainty with which the state of the KEdownstream can be predicted based on the measured state of the KEupstream (i.e., can it be predicted within a factor of two, or within three orders of magnitude?). For example, a regression equation may reasonably describe the response-response relationship between the two KERs, but that relationship may have only been validated/tested in a single species under steady state exposure conditions. Those types of details would be useful to capture.  More help

In male Sprague-Dawley rats that were whole body exposed to cigarette smoke of 10 unfiltered cigarettes (containing 1.0 mg nicotine and 14 mg tar in each cigarette) for 30 min, twice daily, 6 days/week for 4 weeks, the % AB/PAS-stained epithelium increased by ca. 12% (vs ca. 1% in air-exposed animals), Muc5ac mRNA expression increased more than 2-fold, and the % Muc5ac-stained epithelium increased from ca. 1.5% to approx. 6% relative to control (An et al., 2013).

In Sprague-Dawley rats that were whole-body exposed to 4% (v/v air) cigarette smoke for 1 h daily, for 56 days, the number of goblet cells in the bronchial epithelium significantly increased (ca. 10 cells/mm epithelium in air controls vs 60 cells/mm), and the number of Muc5ac-positive cells increased from ca. 20 cells/mm to ca. 80 cells/mm (Liang et al., 2017).

In Sprague-Dawley rats that were whole-body exposed to cigarette smoke from 5 unfiltered cigarettes for 30 min, twice daily for 4 weeks, the proportion of AB/PAS-positive airway epithelium increased from 7.7 ± 62.11% (air controls) to 42.04 ± 5.40%, Muc5ac mRNA expression levels Ninincreased by about 5-fold and Muc5ac protein expression levels increased approx. 8-fold over controls (Ning et al., 2013).

There was a prominent increase in the numbers of goblet cells along the airway surface epithelium of Balb/c mice that were whole body exposed to cigarette smoke from 5 cigarettes (1.1 mg nicotine and 11 mg tar per cigarette) for 30 min twice daily, 6 days per week, for 4 weeks. Consistent with the AB/PAS staining results, the percentage of bronchial epithelial surface area positively stained by anti-Muc5ac monoclonal antibody markedly increased after 24 days of exposure (Xu et al., 2015).

The large airways of mice that were whole body exposed to cigarette smoke of 10 cigarettes (160–180 mg/m3 TPM; TE-10, Teague Enterprises) for 2 h a day, 5 days a week, for up to 12 weeks, exhibited goblet cell hyperplasia and increased mucus production, evidenced by histology and increases in the numbers of PAS-positive goblet cells (approx. 15% compared to control) and Muc5ac-positive cells (approx. 50% compared to control)(Zhou et al., 2016).

Forty-eight h after intra-tracheal administration 300 mg/kg LPS (E. coli strain 0111:B4), Sprague-Dawley rat lungs exhibited goblet cell hyperplasia, evidenced by ca. 2-fold increases in the numbers of UEA-1 (wheat agglutinin)-, MUC5AC-, and PAS-positive goblet cells compared with PBS controls (Silva et al., 2012).

Male C57BL/6 mice—sensitized subcutaneously with 100 mg of Freund adjuvant–emulsified house dust mite (HDM; 1 mg/mL) in abdomen and groins on days 0 and 14 and challenged intranasally with 50 mg of HDM extract dissolved in PBS (1mg/mL), starting on day 21, daily for 14 d—developed goblet cell hyperplasia (histology), with significant increases in PAS-positive area (ca. 8-fold) and Muc5ac protein expression (ca. 30-fold) (Shi et al., 2017).

Ferrets that were exposed to smoke from 3R4F research cigarettes for 1 h, twice daily for 6 months (SCIREQ, InExpose model) developed goblet cell hyperplasia in medium and small airways, evidenced by histopathological examination of AB/PAS-stained lung tissues. Mucus expression measured by PAS-positive goblet cell area, normalized by the size of the airway lumen to account for cell variation due to airway diameter, was 60% (0.042% ± 0.025% smoke vs. 0.025% ± 0.013% air control; P = 0.06) higher in smoke-exposed airways than in control airways. Muc5b and Muc5ac staining was greater in smoke-exposed ferrets, but patchy staining made quantification impossible (Raju et al., 2016).

In primary human bronchial epithelial cells differentiated at the air-liquid interface, basolateral treatment with 10 ng/mL IL-13 increased the number of goblet cells from 0.2 ± 0.1 to 15.9 ± 1.1, the number of PAS-positive cells from 2.5 ± 1.5 to 28.2 ± 0.7, and the number of MUC5AC-positive cells from 0.1 ± 0.1 to 25.7 ± 1.0 (Tanabe et al., 2011). Similarly, treatment of 3D bronchial organotypic cultures with 5 ng/mL IL-13 for 14 days caused goblet cell hyperplasia (histology), significantly increasing MUC5AC protein concentration (ca. 1.5-fold) in the supernatant and MUC5AC mRNA expression (ca. 10-fold) compared with vehicle (DMSO) (Mishina et al., 2015).

IL-13, added to primary human bronchial epithelial cells at the first day of air-liquid interface culture, dose-dependently increased goblet cell density (AB staining, manual counting) and MUC5AC protein expression (antibody staining, semi-automated counting). Treatment with 1 ng/mL IL-13 resulted in the largest increase in goblet cell density, independent of the counting method, with one donor showing a 5.47 ± 0.92-fold increase and the other a 10.86 ± 1.25-fold increase. The highest concentration of IL-13 studied (10 ng/mL) significantly reduced the goblet cell density in both donors. Results with IL-4 treatment were similar to those with IL-13; maximal increase in goblet cell density was achieved with 1 ng/mL, and goblet cell density decreased at 10 ng/mL (Atherton et al., 2003).

Morphometric analysis of endobronchial biopsies from patients with mild and moderate asthma showed that stored mucin in goblet cells, expressed as the volume density of mucin in the airway epithelium, was three times higher in asthmatics than in healthy subjects. Although the goblet cell size was similar in both groups, the goblet cell number was significantly increased in the subjects with asthma (41,959 ± 9,230 in controls vs 93,043 ± 15,824), indicating that the increase in stored mucin in goblet cells was secondary to goblet cell hyperplasia. MUC5AC was the most frequently expressed mucin gene in both groups, and MUC5AC gene expression was increased in the subjects with asthma, but not significantly so (Ordonez et al., 2001).

In nasal polyp tissues from 8 patients with nasal polyposis, hyperplastic epithelium occupied a mean of 75% (range, 44%-100%). Approx. 55% of the polyp epithelium exhibited positive AB/PAS staining and positive MUC5AC staining, which were significantly higher proportions of goblet cell markers than seen in the pseudostratified epithelium from controls (Burgel et al., 2000). Similarly, goblet cell hyperplasia was seen in nasal polyp tissues from 25 patients but not healthy controls, as evidenced by more PAS-positive epithelial cells (PAS staining index 1.9 [1.3, 2.2] vs 0.7 [0.4, 1.2] in controls). This was accompanied by increased MUC5AC staining, with a mean staining score of 2.2 [1.7, 3.0] in polyp tissues vs 0.6 [0.4, 1.1] in normal controls, and increased MUC5AC gene expression, with levels of 4.4 2.3, 6.3] in polyp tissues vs 1.2 [0.4, 2.2] in normal controls (Xia et al., 2014).

AB/PAS staining of lung tissues revealed a higher number of goblet cells (goblet cell rate 0.20 ± 0.10% vs 0.13 ± 0.06%) as well as higher MUC5AC expression (0.27 ± 0.09% vs 0.20 ± 0.10%) in COPD patients than in healthy controls (Ma et al., 2005).

Healthy smokers (9.80±3.49 cells/mm) had a greater goblet cell density than nonsmokers (2.31±1.81 cells/mm). Healthy smokers (26.35±10.96 μL/mm2) also had a greater mucin volume density than nonsmokers (5.77±4.34 μL/mm2). There was a significant correlation between pack-year history of smoking with goblet cell density (Kim et al., 2015).

Time-scale
This sub-section should be used to provide information regarding the approximate time-scale of the changes in KEdownstream relative to changes in KEupstream (i.e., do effects on KEdownstream lag those on KEupstream by seconds, minutes, hours, or days?). This can be useful information both in terms of modelling the KER, as well as for analyzing the critical or dominant paths through an AOP network (e.g., identification of an AO that could kill an organism in a matter of hours will generally be of higher priority than other potential AOs that take weeks or months to develop). Identification of time-scale can also aid the assessment of temporal concordance. For example, for a KER that operates on a time-scale of days, measurement of both KEs after just hours of exposure in a short-term experiment could lead to incorrect conclusions regarding dose-response or temporal concordance if the time-scale of the upstream to downstream transition was not considered. More help

Brown–Norway rats were sensitized by an intraperitoneal injection with 1 mg ovalbumin (OVA) and 200 mg Al(OH)3 in 1mL of sterile saline on days 0 and 7. The rats were then exposed to aerosolized 1% (w/v) OVA or sterile saline for 30 min on days 14–16. Marked goblet cell hyperplasia (evidenced by AB/PAS staining) was observed in the epithelium throughout the airways of the OVA-sensitized and -challenged rats 24 h after the final OVA challenge (on day 17), and the goblet cell hyperplasia progressed further on day 24. The area of AB/PAS-positive staining of the airway epithelium on day 24 revealed a 7-fold increase in the OVA-sensitized and -challenged rats relative to the OVA-sensitized and saline-treated controls (Takeyama et al., 2008).

In rats exposed to 400 ppm SO2 for 3 h a day, 5 days a week, for up to 6 weeks, the number of goblet cells in the trachea and main bronchi initially decreased. After 3 weeks, goblet cell numbers and size increased from day 4 onward, and goblet cells started appearing also in distal airways (where they are normally not present). With continuing exposure (at 6 weeks), goblet cell numbers keep increasing in the trachea (ca. 1.5-fold), proximal (ca. 2-fold) and distal airways (ca. 30-fold) (Lamb and Reid, 1968).

Intratracheal instillation of agarose plugs (0.7- to 0.8-mm diameter; 4% agarose type II) in male Fischer 344 rats caused goblet cell hyperplasia, evidenced by histology and AB/PAS staining. In the airways containing the plugs, goblet cell numbers increased from 0 cells/mm basal lamina to 13.1±5.6, 25.7±15.0, and 51.5±9.0 cells/mm basal lamina after 24, 48, and 72 h, respectively. The percentage of the total length of epithelium staining positively with AB/PAS increased from 0.1 ± 0.1% in control animals to 4.7 ± 1.4, 13.3 ± 0.7, and to 19.1 ± 0.7% at 24, 48, and 72 h, respectively. Muc5ac gene expression was found preferentially in cells that were AB/PAS-positive and increased in a time-dependent manner (Lee et al., 2000).  

Known modulating factors
This sub-section presents information regarding modulating factors/variables known to alter the shape of the response-response function that describes the quantitative relationship between the two KEs (for example, an iodine deficient diet causes a significant increase in the slope of the relationship; a particular genotype doubles the sensitivity of KEdownstream to changes in KEupstream). Information on these known modulating factors should be listed in this subsection, along with relevant information regarding the manner in which the modulating factor can be expected to alter the relationship (if known). Note, this section should focus on those modulating factors for which solid evidence supported by relevant data and literature is available. It should NOT list all possible/plausible modulating factors. In this regard, it is useful to bear in mind that many risk assessments conducted through conventional apical guideline testing-based approaches generally consider few if any modulating factors. More help

Unknown

Known Feedforward/Feedback loops influencing this KER
This subsection should define whether there are known positive or negative feedback mechanisms involved and what is understood about their time-course and homeostatic limits? In some cases where feedback processes are measurable and causally linked to the outcome, they should be represented as KEs. However, in most cases these features are expected to predominantly influence the shape of the response-response, time-course, behaviours between selected KEs. For example, if a feedback loop acts as compensatory mechanism that aims to restore homeostasis following initial perturbation of a KE, the feedback loop will directly shape the response-response relationship between the KERs. Given interest in formally identifying these positive or negative feedback, it is recommended that a graphical annotation (page 44) indicating a positive or negative feedback loop is involved in a particular upstream to downstream KE transition (KER) be added to the graphical representation, and that details be provided in this subsection of the KER description (see pages 44-45 of the User Handbook).  More help

Unknown

Domain of Applicability

As for the KEs, there is also a free-text section of the KER description that the developer can use to explain his/her rationale for the structured terms selected with regard to taxonomic, life stage, or sex applicability, or provide a more generalizable or nuanced description of the applicability domain than may be feasible using standardized terms. More help

Goblet cell hyperplasia is a common feature in the airways of humans, mice, rats and guinea pigs following exposure to noxious agents such as cigarette smoke.  

References

List of the literature that was cited for this KER description using the appropriate format. Ideally, the list of references should conform, to the extent possible, with the OECD Style Guide (OECD, 2015). More help

An, J., Li, J.-Q., Wang, T., Li, X.-O., Guo, L.-L., Wan, C., et al. (2013). Blocking of thromboxane A2 receptor attenuates airway mucus hyperproduction induced by cigarette smoke. Eur. J. Pharmacol. 703, 11-17.

Atherton, H. C., G. Jones and H. Danahay (2003). IL-13-induced changes in the goblet cell density of human bronchial epithelial cell cultures: MAP kinase and phosphatidylinositol 3-kinase regulation. Am. J. Physiol. Lung Cell. Mol. Physiol. 285, L730-L739.

Burgel, P.-R., Escudier, E., Coste, A., Dao-Pick, T., Ueki, I.F., Takeyama, K., et al. (2000). Relation of epidermal growth factor receptor expression to goblet cell hyperplasia in nasal polyps. J. Allergy Clin. Immunol. 106, 705-712.

Hao, Y., Kuang, Z., Jing, J., Miao, J., Mei, L.Y., Lee, R.J., Kim, S., Choe, S., Krause, D.C., and Lau, G.W. (2014). Mycoplasma pneumoniae Modulates STAT3-STAT6/EGFR-FOXA2 Signaling To Induce Overexpression of Airway Mucins. Infect. Immun. 82, 5246–5255.

Hao, Y., Kuang, Z., Xu, Y., Walling, B.E., and Lau, G.W. (2013). Pyocyanin-induced mucin production is associated with redox modification of FOXA2. Respir. Res. 14, 82-82.

Hegab, A.E., Sakamoto, T., Nomura, A., Ishii, Y., Morishima, Y., Iizuka, T., Kiwamoto, T., Matsuno, Y., Homma, S., and Sekizawa, K. (2007). Niflumic acid and AG-1478 reduce cigarette smoke-induced mucin synthesis: The role of hCLCA1. Chest 131, 1149-1156.

Kim, B.-G., Lee, P.-H., Lee, S.-H., Kim, Y.-E., Shin, M.-Y., Kang, Y., Bae, S.-H., Kim, M.-J., Rhim, T., Park, C.-S., et al. (2016). Long-Term Effects of Diesel Exhaust Particles on Airway Inflammation and Remodeling in a Mouse Model. Allergy Asthma Immunol. Res. 8, 246-256.

Kim, V., Oros, M., Durra, H., Kelsen, S., Aksoy, M., Cornwell, W.D., et al. (2015). Chronic Bronchitis and Current Smoking Are Associated with More Goblet Cells in Moderate to Severe COPD and Smokers without Airflow Obstruction. PLoS ONE 10, e0116108. 

Lamb, D. and Reid, L. (1968). Mitotic rates, goblet cell increase and histochemical changes in mucus in rat bronchial epithelium during exposure to sulphur dioxide. J. Pathol. Bacteriol. 96, 97-111.

Lee, H.-M., Takeyama, K., Dabbagh, K., Lausier, J.A., Ueki, I.F., and Nadel, J.A. (2000). Agarose plug instillation causes goblet cell metaplasia by activating EGF receptors in rat airways. Am. J. Physiol. Lung Cell. Mol. Physiol. 278, L185-L192.

Liang, Y., Liu, K.W., Yeung, S.C., Li, X., Ip, M.S. and Mak, J.C. (2017). (-)-Epigallocatechin-3-gallate reduces cigarette smoke-induced airway neutrophilic inflammation and mucin hypersecretion in rats. Front. Pharmacol. 8, 618.

Lukacs, N.W., Smit, J.J., Nunez, G., and Lindell, D.M. (2010). Respiratory Virus-induced TLR7 activation controls IL-17 associated Increase in mucus via IL-23 regulation: Respiratory virus induced immune environment relies on TLR7-mediated pathways to preserve a non-pathogenic response and regulates IL-17 production. J. Immunol. 185, 2231-2239.

Ma, R., Wang, Y., Cheng, G., Zhang, H., Wan, H., and Huang, S. (2005). MUC5AC expression up-regulation goblet cell hyperplasia in the airway of patients with chronic obstructive pulmonary disease. Chin. Med. Sci. J. 20, 181-184.

Mishina, K., Shinkai, M., Shimokawaji, T., Nagashima, A., Hashimoto, Y., Inoue, Y., et al. (2015). HO-1 inhibits IL-13-induced goblet cell hyperplasia associated with CLCA1 suppression in normal human bronchial epithelial cells. Int. Immunopharmacol. 29, 448-453.

Miyabara, Y., Ichinose, T., Takano, H., Lim, H. B., & Sagai, M. (1998). Effects of diesel exhaust on allergic airway inflammation in mice. J. Allergy Clin. Immunol. 102, 805-812.

Munkholm, M., and Mortensen, J. (2014). Mucociliary clearance: pathophysiological aspects. Clin. Physiol. Funct. Imaging 34, 171-177.

Nagao, K., Tanaka, H., Komai, M., Masuda, T., Narumiya, S., and Nagai, H. (2003). Role of Prostaglandin I2 in Airway Remodeling Induced by Repeated Allergen Challenge in Mice. Am. J. Respir. Cell Mol. Biol. 29, 314-320.

Nie, Y.-C., Wu, H., Li, P.-B., Luo, Y.-L., Zhang, C.-C., Shen, J.-G., and Su, W.-W. (2012). Characteristic comparison of three rat models induced by cigarette smoke or combined with LPS: to establish a suitable model for study of airway mucus hypersecretion in chronic obstructive pulmonary disease. Pulm. Pharmacol. Ther. 25, 349-356.

Ning, Y., Shang, Y., Huang, H., Zhang, J., Dong, Y., Xu, W., et al. (2013). Attenuation of cigarette smoke-induced airway mucus production by hydrogen-rich saline in rats. PLoS One. 8, e83429.

Ordoñez, C.L., Khashayar, R., Wong, H.H., Ferrando, R., Wu, R., Hyde, D.M., et al. (2001). Mild and moderate asthma is associated with airway goblet cell hyperplasia and abnormalities in mucin gene expression. Am. J. Respir. Crit. Care Med. 163, 517-523.

Park, K.-S., T. R. Korfhagen, M. D. Bruno, J. A. Kitzmiller, H. Wan, S. E. Wert, G. K. K. Hershey, G. Chen and J. A. Whitsett (2007). SPDEF regulates goblet cell hyperplasia in the airway epithelium. J. Clin. Invest. 117, 978-988.

Polosukhin, V.V., Cates, J.M., Lawson, W.E., Milstone, A.P., Matafonov, A.G., Massion, P.P., et al., (2011). Hypoxia‐inducible factor‐1 signalling promotes goblet cell hyperplasia in airway epithelium. J. Pathol. 224, 203-211.

Raju, S.V., Kim, H., Byzek, S.A., Tang, L.P., Trombley, J.E., Jackson, P., et al. (2016). A ferret model of COPD-related chronic bronchitis. JCI insight 1, e87536.

Rose, M.C., and Voynow, J.A. (2006). Respiratory tract mucin genes and mucin glycoproteins in health and disease. Physiol. Rev. 86, 245-278.

Saetta, M., Turato, G., Baraldo, S., Zanin, A., Braccioni, F., Mapp, C.E., Maestrelli, P., Cavallesco, G., Papi, A., and Fabri, L.M. (2000). Goblet Cell Hyperplasia and Epithelial Inflammation in Peripheral Airways of Smokers with Both Symptoms of Chronic Bronchitis and Chronic Airflow Limitation. Am. J. Respir. Crit. Care Med. 161, 1016-1021.

Shi, N., Zhang, J., and Chen, S.Y. (2017). Runx2, a novel regulator for goblet cell differentiation and asthma development. FASEB J. 31, 412-420.

Takeyama, K., Tamaoki, J., Kondo, M., Isono, K. and Nagai, A. (2008). Role of epidermal growth factor receptor in maintaining airway goblet cell hyperplasia in rats sensitized to allergen. Clin. Exp. Allergy 38, 857-865.

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