Expression of miR-93 and IL-8 During Pseudomonas aeruginosa Mediated Induction of Pro-Inflammatory Responses

In this paper we have first analyzed the microRNA profile of cystic fibrosis (CF) bronchial epithelial IB3-1 cells infected with Pseudomonas aeruginosa by microarray and RT-qPCR, demonstrating that miR-93, which is highly expressed in basal conditions, decreases during infection in parallel with increased expression of the IL-8 gene. The down-regulation of miR-93 after P.aeruginosa infection was confirmed in other bronchial cell lines derived from both CF and non-CF individuals, namely CuFi-1 and NuLi-1 cells. Sequence analysis shows that the 3'-UTR region of the IL-8 mRNA is a potential target of miR-93 and that the consensus sequence is highly conserved throughout molecular evolution. The possible involvement of miR-93 in IL-8 gene regulation was validated using three luciferase vectors, including one carrying the complete 3'-UTR region of the IL-8 mRNA and one carrying the same region with mutated miR-93 site. Up-modulation of IL-8 following P. aeruginosa infection was counteracted in IB3-1, CuFi-1 and NuLi-1 cells by pre-miR-93 transfection. In addition, IL-8 was up-regulated in uninfected cells treated with antagomiR-93. Our results support the concept of a possible link between microRNA expression and IL-8 induction in bronchial epithelial cells infected with Pseudomonas aeruginosa. Specifically, the data presented indicate that, in addition to NF-kB dependent up-regulation of IL-8 gene transcription, IL-8 protein expression is post-transcriptionally regulated by interactions of the IL-8 mRNA with the inhibitory miR-93.