Methods: Expression of 84 genes related to oxidative stress was examined in cockroach allergen (CRE)-treated human primary bronchial epithelial cells (PBECs) by RT2 Profiler PCR array. The differentially expressed genes were further validated in A549 and TC-1, human and mouse lung epithelial cell lines, by qRT-PCR and in lung tissues from cockroach allergen-challenged mouse model of asthma by immunofluoresence staining. The effect of miR-155 on target gene expression and stability was also examined.
Results: Only the COX-2 gene was significantly up-regulated in CRE-treated PBECs among all examined genes. The increased COX-2 was further validated in CRE treated A549 and TC-1. COX-2 was also detected in airway epithelium of CRE-challenged mice by co-staining of COX-2 and EpCAM. Interestingly, microRNA (miR)-155 predicted to target COX-2 showed significantly increased in lung tissues from the same mouse model. miR-155 over-expression in A549 by miR-155 mimic transfection significantly enhanced COX-2 expression at the mRNA and protein levels. An increased COX-2 mRNA stability was found in miR-155 over-expressed TC-1, but not in A549.
Conclusions: These results suggest that COX-2 may be a major gene related to CRE-induced oxidative stress, and that miR-155 may play a role in regulating the COX-2-ROS axis in asthma.