miRNA-221-3p Enhances the Secretion of Interleukin-4 in Mast Cells through the Phosphatase and Tensin Homolog/p38/Nuclear Factor-kappaB Pathway.

Mast cells play a central role in asthma. Moreover, serum miRNA-221-3p (miR-221) has been shown to be markedly increased in children with asthma. In the current study, we aimed to examine miR-221 expression in an asthma model and elucidate the mechanisms regulating interleukin (IL)-4 secretion in mast cells. Using polymerase chain reaction, we found that miR-221 was upregulated in a murine asthma model and in P815 mast cells after lipopolysaccharide (LPS) stimulation. Moreover, miR-221 upregulated IL-4 secretion from P815 cells, as shown by enzyme-linked immunosorbent assays. Bioinformatics analysis, luciferase reporter gene assays, and western blotting showed that phosphatase and tensin homolog (PTEN) was a target of miR-221 and could block IL-4 secretion stimulated by miR-221. The phosphorylation of p38 (protein) and activity of nuclear factor-kappaB (NF-κB) were increased after overexpression of miR-221, as shown by electrophoretic mobility shift assays. Finally, treatment with specific inhibitors could block IL-4 secretion. In conclusion, miR-221, which was overexpressed in a murine asthma model, stimulated IL-4 secretion in mast cells through a pathway involving PTEN, p38, and NF-κB.