MicroRNA-146a and microRNA-155 expression in induced sputum of allergic asthmatics

Background: MicroRNAs (miRs) are potent regulators of cellular functions during immune responses by their ability to function as posttranscriptional regulators. We have previously demonstrated that microRNA-155 (miR-155) deficient mice failed to develop a proper Th2 response upon ovalbumin (OVA) challenge in a mouse model of allergic airway inflammation. miR-155 seems to enhance a pro-inflammatory response while miR-146a is suggested to be inhibitory. This study aimed to adress whether miR-155 as well as miR-146 expression is altered in allergic asthmatic individuals (AA). Methods: Induced sputum and blood samples were obtained from stable AA and healthy volunteers (HV) from the epidemiological cohort the West Sweden Asthma Study. As an acute model we isolated peripheral blood mononuclear cells (PBMCs) and performed in vitro stimulation with anti-CD3/CD28 or as a control with PBS. Expression of miR-155 and miR-146a in sputum supernatants, PBMCs and PBMC supernatants was determined by qPCR. Results: MiR-155 was significantly down regulated in sputum supernatants from stable AA in comparison to HV (P in vitro stimulation by anti-CD3/CD28, and similar results were obtained in PBMC supernatants. Conclusion: Differential expression of miR-155 in AA compared to HV indicate a regulatory role in the airways of allergic asthma possibly reflecting the ongoing immune response. If a strong non-specific anti-CD3/CD28 activation in vitro reflect the fine tuning properties of microRNAs in vivo remains to be investigated.