In Vitro and In Vivo Transglutaminase 2 Expression in Asthma and COPD

Rationale: Tissue transglutaminase 2 (TG2) is over-expressed in a variety of inflammatory diseases including allergic asthma. Both bronchial asthma and chronic obstructive pulmonary disease (COPD) are characterized by chronic persistent inflammatory process, but the nature of the inflammation is different markedly. However, in real practice, both may occur concurrently in some patients, and such conditions have been defined as asthma-COPD overlap syndrome (ACOS). Therefore, we purposed to evaluate the expression of TG2 in asthma, and COPD in vitro, and in vivo studies. 

Methods: Cigarette smoke extracts (CSE) were withdrawn into a polypropylene syringe (50mL) at a rate of one puff/min (5 times) and then bubbled slowly. For in vitro study, we used NCI-H292 cell lines, stimulated by IL-13 (10ng/mL), TNF-α (20ng/mL) and cigarette smoking extracts (CSE). TG2 expression was measured by immunoassay. To induce allergic asthma, ovalbumin sensitization and challenge was done in senescence accelerated mouse (SAM). For smoking group, mice were exposed to five cigarettes a day for 5 days/week for 8weeks. 

Results: Co-treatment of IL-13 and TNF-α increased TG2 expression in NCI-H292 cells (P<0.05). CSE treatment also increased TG2 expression in cells (P<0.05). Treatment with IL-13, TNF-α and CSE showed decreased TG2 expression than single treatment. In vivo study, TG2 expression was significantly increased in OVA and smoking group, however, it was decreased in co-treated group (OVA and smoking, P<0.05). 

Conclusions: TG2 expression was increased in both asthma and COPD model. In ACOS model, TG2 expression was decreased compared to single asthma and COPD.