Systematic dissection of ORMDL3 function in vitro and in vivo

ORMDL3 on human chromosome 17q21 is a major genetic influence for childhood asthma, severe asthma and asthma exacerbations. To understand further the functional roles of ORMDL3, we established both human airway epithelial models and a recombineering-generated murine Ormdl3 knockout model. The influences of ORMDL3 on inflammatory responses in vitro and in vivo were investigated. We performed gene silencing using siRNA for two days in airway epithelium cells (A549, Beas2B and NHBE cells) after which cells were stimulated with IL1B. ORMDL3 knockdown-epithelial cells released much less IL6 and IL8 at 10 hours after stimulation (P < 0.01 respectively). Over-expression of ORMDL3 in epithelial cells resulted in a significant increase in release of IL6 and IL8 shortly after stimulation. Serine-palmitoyl transferase (SPT) is the key enzyme of sphingolipid metabolism. Treatment of epithelial cells with the SPT inhibitor myriocin resulted in an increase in release of IL6 and IL8 after stimulation, mirroring the results seen with the overexpression model. A systemic metabolic screening of the ORMDL3 knockdown epithelial cells revealed ORMDL3 to be involved not only in regulating sphingolipid metabolism but also lysophospholipids metabolism and the regulation of glycolysis. Parallel global gene expression profiling of the same cells identified key transcripts involved in regulating the inflammatory response. The lung function of Ormdl3 knockout mice also exhibited a reduced response after Alternaria alternata challenge. Our findings indicate ORMDL3 is a key molecule involved in the regulation of the inflammation response through multiple pathways and is a potential therapeutic target for asthma