microRNA-29b mediates Th17/Treg imbalance in chronic obstructive pulmonary disease by targeting IL-22

Chronic obstructive pulmonary disease (COPD) represents a chronic inflammatory disorder of the airways induced mainly by cigarette smoking. In the current study, cigarette smoke extract (CSE) was used to develop an in vitro COPD model using human bronchial epithelium (HBE) cells to expound the possible role of microRNA-29b (miR-29b) in COPD. Firstly, miR-29b and interleukin (IL)-22 expression was assessed in serum of 20 healthy non-smokers, 20 healthy smokers and 20 COPD patients as well as CSE-treated HBE cells. Then, miR-29b and IL-22 expression was altered to evaluate their functions in Th17/Treg ratio. miR-29b inhibited Th17/Treg ratio and levels of IL-22; whereas overexpression of IL-22 reversed these trends. Moreover, rescue experiments found that IL-22 neutralized the repressive effects of miR-29b on Th17/Treg ratio and inflammatory response. Finally, we found that miR-29b blocked the JAK/STAT3 pathway in CSE-treated HBE cells. These data highlighted that miR-29bs modulated Th17/Treg imbalance in CSE-induced experimental COPD through inhibition of IL-22-dependent JAK/STAT3 pathway.