Down-regulation of miR-133a contributes to up-regulation of Rhoa in bronchial smooth muscle cells.
BACKGROUND
Augmented bronchial smooth muscle (BSM) contraction is one of the causes of bronchial hyperresponsiveness. The protein RhoA and its downstream pathways have now been proposed as a new target for asthma therapy. MicroRNAs (miRNAs) play important roles in normal and diseased cell functions, and a contribution of miR-133 to RhoA expression has been suggested in cardiomyocytes.


OBJECTIVE
To make clear the mechanism(s) of up-regulation of RhoA observed in the BSMs of experimental asthma, the role of miR-133a in RhoA expression was tested.


METHODS
Total proteins and RNAs (containing miRNAs) were extracted from cultured human BSM cells (hBSMCs) that were treated with antagomirs and/or IL-13, and bronchial tissues of BALB/c mice that were sensitized and repeatedly challenged with ovalbumin. RhoA protein and miR-133a were detected by immunoblotting and quantified real-time reverse transcriptase-polymerase chain reaction, respectively.


RESULTS
In hBSMCs, an up-regulation of RhoA was observed when the function of endogenous miR-133a was inhibited by its antagomir. Treatment of hBSMCs with IL-13 caused an up-regulation of RhoA and a down-regulation of miR-133a. In bronchial tissues of the repeatedly ovalbumin-challenged mice, a significant increase in RhoA was observed. Interestingly, the level of miR-133a was significantly decreased in BSMs of the challenged mice.


CONCLUSIONS
These findings suggest that RhoA expression is negatively regulated by miR-133a in BSMs. IL-13 might, at least in part, contribute to the reduction of miR-133a.
Chiba
Yoshihiko
Y
Department of Pharmacology, School of Pharmacy, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan. chiba@hoshi.ac.jp
Tanabe
Miki
M
Goto
Kumiko
K
Sakai
Hiroyasu
H
Misawa
Miwa
M
D000818:Animals; D001249:Asthma / Q000235:genetics / Q000378:metabolism*; D001980:Bronchi / Q000166:cytology / Q000378:metabolism*; D016535:Bronchial Hyperreactivity / Q000235:genetics / Q000378:metabolism*; D001985:Bronchial Provocation Tests; D002478:Cells, Cultured; D004195:Disease Models, Animal; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D015854:Up-Regulation; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
D035683:MicroRNAs; D020742:rhoA GTP-Binding Protein