Ultrasound stimulation induces microRNA expression changes that could be involved in sonication-induced apoptosis

Purpose The purpose of this study is to investigate the involvement of microRNAs (miRNAs) in sonicationinduced apoptosis. Methods U937 cells derived from human leukemia were sonicated with 1-MHz ultrasound at 0.4 W/cm2 and 10 % duty factor for 60 s, a condition inducing apoptosis. The total RNA was extracted from cells at various timings after sonication and subjected to microarray and real-time PCR for miRNA expression analyses. Results Expression of several miRNAs was significantly affected by sonication. For miR-424 and miR-720, whose expressions were eminently decreased by sonication, cell lines overexpressing these miRNAs were established. Conversely, for miR-663B and miR-663, whose expressions were eminently increased by sonication, cell lines inhibiting these miRNA functions were established. When these cell lines were sonicated, a cell line inhibiting miR- 663B function significantly increased sonication-induced apoptosis, suggesting this may be involved in cellular responses to sonication. Two genes that could induce apoptosis, KSR2 and CREBZF, were identified as potential target genes of miR-663B since potential target sequences on their 30 UTR mediated to decrease expression of a reporter gene. Conclusion These results suggest that miRNAs may be involved in cellular responses to ultrasound through their expression changes caused by sonication.