Functional analysis of the impact of ORMDL3 expression on inflammation and activation of the unfolded protein response in human airway epithelial cells

Background: The gene ORMDL3 was shown to be associated with early-onset asthma susceptibility in multiple independent genome-wide and candidate-gene association studies. Asthmatic patients have elevated expression levels of this gene. ORMDL3 encodes a transmembrane protein localized in the endoplasmic reticulum (ER) that may be involved in ER stress and inflammation. It is essential to validate the genetic associations linking ORMDL3 with asthma through functional studies that confirm the biological relevance of this gene in disease. We investigated the effects of manipulating ORMDL3 expression levels in vitro in airway cells on innate immune inflammatory responses, ER stress and activation of the unfolded protein response (UPR). Methods: ORMDL3 expression levels were manipulated in airway cells using an overexpression plasmid and siRNA technologies. Successful modulation of ORMDL3 was confirmed at both the gene and protein level. The functional impact of modulation of ORMDL3 expression levels on inflammatory responses and activation of the UPR were quantified using complementary cellular and molecular immunology techniques. Results: Cells with altered ORMDL3 levels responded equally well to innate immune stimuli and produced similar levels of pro-inflammatory cytokines compared to wild-type cells. Treatment with ER stress inducers, thapsigargin and tunicamycin, resulted in activation of the unfolded protein response (UPR). However, we observed no difference in UPR activation in cells with ORMDL3 knockdown compared to cells with normal ORMDL3 levels. Conclusions: Our results suggest that ORMDL3 variation in the airway epithelium is unlikely to play a significant role in modulating innate immune responses and the UPR in the lung.