MicroRNA and cytokines

Cytokines are involved in the development of cancer and chronic inflammatory lung diseases such as chronic obstructive pulmonary disease (COPD). MicroRNAs can regulate cytokine expression either by directly binding to a target sequence in a cytokine mRNA or by indirectly regulating a cluster of adenine and uridine-rich element binding proteins (ARE-BPs). Alternatively, cytokines, in particular the pro-inflammatory cytokines IL-1ß and TNF-α, can also regulate expression of miRNAs. In this regard, expression of miR-146a is dramatically increased in response to the stimulation of inflammatory cytokines in many cell types including human bronchial epithelial cells (HBECs) and human lung fibroblasts. Aberrant up-regulation of miR-146a in HBECs may provide a link between chronic inflammation and lung cancer or peri-bronchial fibrosis, while down-regulation of miR-146a in lung fibroblasts from COPD may account for deficient repair mediated by lung fibroblasts in emphysema.