A74-09 Differentiation Expression and Regulation of Wnt5a Isoforms in Different Lung Disease Models

Abstract Rationale WNT5a is essential in many aspects of lung biology. Dysregulated WNT5a has been observed in multiple lung diseases including idiopathic pulmonary fibrosis (IPF), acute respiratory syndrome (ARDS), bronchopulmonary dysplasia (BPD), pulmonary arterial hypertension (PAH), chronic obstructive pulmonary disease (COPD), and lung cancer. Most interpretations on WNT5a’s roles in lung diseases are based on the assumption that WNT5a molecules represent a uniform population. However, it has been shown that there are two isoforms of WNT5a in other tissues, which differentially regulate cell proliferation and are conserved across mouse and human. This study characterized WNT5a isoform expression in two lung disease models: bleomycin-induced pulmonary fibrosis and Pseudomonas aeruginosa (PA)-induced acute lung injury (ALI)/ARDS. Potential mechanisms that regulate Wnt5a isoform expression were investigated by targeting key intracellular pathways involved in both injuries. Methods Adult mice (2 to 3 months of age) were treated with bleomycin, PA, or vehicle via intratracheal instillation. Lungs of bleomycin-treated mice were collected and analyzed within 21 days after injury, while PA-treated lungs were collected at 24 hours post infection. Since Wnt5a is predominantly expressed in fibroblasts of the lung, we used lung fibroblast cultures to further assess the effects of the injury stimuli. Relative expression levels of long and short forms of Wnt5a, Wnt5a-L and Wnt5a-S, respectively, in lung tissues and fibroblasts were analyzed by qRT-PCR. For potential mechanisms that modulate expression of Wnt5a isoforms, the cells were treated with inhibitors of the ERK and AKT pathways, which are known to be activated in both injury responses. Results Both Wnt5a isoforms were upregulated by bleomycin injury. Remarkably, Wnt5a-L was selectively downregulated in both PA-infected lungs and PA-infected fibroblasts, while Wnt5a-S remained unaltered. Mechanistically, ERK pathway mediates activation of both isoforms while AKT pathway selectively represses Wnt5a-L expression. Conclusions Wnt5a isoforms are differentially regulated under distinct disease conditions, suggesting that they may contribute differently to pathogenesis of lung diseases. Interactions of key intracellular pathways such as ERK and AKT may play important roles in differential regulation of WNT5a isoform expression. Supported by NIH and the Hastings foundation. This abstract is funded by: Supported by NIH and the Hastings foundation