Goblet cell metaplasia, associated with increased mucus production, is a key pathogenic feature of chronic airway disorders, such as asthma, COPD and cystic fibrosis, all of which contribute to significant morbidity and mortality worldwide. Pharmacological targeting of goblet cell metaplasia represents a significant clinical challenge. Therefore, identification of new molecular mechanisms in airway epithelial differentiation will provide novel therapeutic targets for treatment of chronic airway disorders. Our grant proposal focuses on novel molecular mechanisms in goblet cell differentiation that are regulated by FoxM1, a transcription factor from the Forkhead box (FOX) family. While FoxM1 plays an important role in embryonic development and pathogenesis of various cancers, the role of FoxM1 in chronic airway diseases is unknown. In our preliminary data, FoxM1 was induced in airway epithelial cells of mice with asthma-like diseases caused by OVA, IL-13 and house dust mite extract (HDM). FoxM1 was also induced in airway epithelial cells of human patients with asthma and COPD. Genetic deletion of the Foxm1 gene (CCSP-Cre) or pharmacological inhibition of the FoxM1 protein (ARF peptide) in HDM-challenged airway epithelium effectively diminished goblet cell metaplasia, reduced lung inflammation and decreased airway hyper-responsiveness to methacholine. While these data suggest that FoxM1 plays a key role in asthma pathogenesis, molecular mechanisms regulated by FoxM1 remain uncharacterized. We propose to test the hypothesis that FoxM1 acts downstream of the IL-13/Stat6 pathway to induce expression of goblet cell-specific genes in airway epithelial cells.
In Aim I, we will use transgenic mice with FoxM1 "gain-of-function" and "loss-of-function" in airway Clara cells to identify downstream FoxM1 target genes critical for allergen-mediated differentiation of Clara cells into goblet cells. Furthermore, we provide preliminary data demonstrating that IL-13 induces FoxM1 expression in cultured human airway epithelial cells and airway epithelium of transgenic mice. Knockdown of FoxM1 in vitro inhibited differentiation of airway epithelial cells toward goblet cell phenotype in response to IL-13 stimulation.
In Aim II, we will determine if FoxM1 is required for IL-13/Stat6 signaling to induce goblet cell differentiation in vivo. The IL-13/Stat6 signaling pathway will be activated using intratracheal administration of IL-13 and a Doxycycline-inducible IL-13 transgene. FoxM1 inhibition will be achieved by a genetic approach (IL-13/ CCSP- Cre/ Foxm1-/- mice) and a pharmacological approach (ARF peptide and novel small molecule FoxM1 inhibitors). These experiments will determine whether inactivation of FoxM1 will prevent or decrease IL- 13/Stat6 signaling in airway epithelial cells in vivo. Altogether, these studies will identify molecular mechanisms regulated by FoxM1 in airway epithelial cells and determine the therapeutic benefit of FoxM1 inhibitors in mouse asthma models.
Our grant proposal focuses on novel molecular mechanisms in goblet cell differentiation regulated by FoxM1, a transcription factor from the Forkhead box (FOX) family. We will use transgenic mouse models and novel FoxM1 inhibitors to identify upstream regulators and downstream target genes of FoxM1 during allergen-mediated differentiation of airway Clara cells into goblet cells.