Ultrasound stimulation induces microRNA expression changes that could be involved in sonication-induced apoptosis.
OBJECTIVE
The purpose of this study is to investigate the involvement of microRNAs (miRNAs) in sonication-induced apoptosis.


METHODS
U937 cells derived from human leukemia were sonicated with 1-MHz ultrasound at 0.4 W/cm(2) 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 3' UTR mediated to decrease expression of a reporter gene.


CONCLUSIONS
These results suggest that miRNAs may be involved in cellular responses to ultrasound through their expression changes caused by sonication.
Department of Radiological Sciences, Graduate School of Medicine and Pharmaceutical Sciences for Research, University of Toyama, 2630 Sugitani, Toyama, 930-0194, Japan. ogawa@med.u-toyama.ac.jp.
Ryohei
R
Ogawa
Department of Urology, Graduate School of Medicine and Pharmaceutical Sciences for Research, University of Toyama, Toyama, Japan.
Akihiro
A
Morii
Department of Urology, Graduate School of Medicine and Pharmaceutical Sciences for Research, University of Toyama, Toyama, Japan.
Akihiko
A
Watanabe
Apoptosis; Expression; MicroRNA; Microarray