Suppression of plasminogen activator inhibitor-1 by RNA interference attenuates pulmonary fibrosis.
OBJECTIVE
There is a growing body of evidence demonstrating that plasminogen activator inhibitor-1 (PAI-1) is involved in the progression of pulmonary fibrosis. In fact, PAI-1 knockout mice are protected from bleomycin-induced pulmonary fibrosis. This study was conducted to determine whether the intrapulmonary administration of small interfering RNA (siRNA) targeting PAI-1 (PAI-1-siRNA) limits the development of bleomycin-induced pulmonary fibrosis.


METHODS
Lung biopsies from patients with idiopathic pulmonary fibrosis (IPF) were stained for PAI-1. The distribution of siRNA in the lung, the PAI-1 level in bronchoalveolar (BAL) fluid and the extent of fibrotic changes in the lung were evaluated following the intranasal administration of PAI-1-siRNA in a mouse model of bleomycin-induced pulmonary fibrosis. The effect of PAI-1-siRNA on the epithelial to mesenchymal transition (EMT) was also evaluated using a mouse lung epithelial cell line, LA-4.


RESULTS
PAI-1 was overexpressed in the hyperplastic type 2 pneumocytes lining the honeycomb lesions of patients with IPF. The single intranasal instillation of PAI-1-siRNA resulted in the diffuse uptake of siRNA into the epithelial cells lining the dense fibrotic lesions. The repeated administration of PAI-1-siRNA initiated during either the inflammatory or the fibrotic phase into bleomycin-injured mice reduced the PAI-1 level in BAL fluid and limited the accumulation of collagen in the lungs. EMT induced by transforming growth factor beta (TGFbeta) in LA-4 cells was inhibited by transfection with PAI-1-siRNA.


CONCLUSIONS
The direct suppression of PAI-1 in the lung by the intrapulmonary administration of PAI-1-siRNA attenuated the development and progression of pulmonary fibrosis. The inhibition of EMT may be, at least in part, involved in this effect.
Senoo
Tadashi
T
Department of Molecular and Internal Medicine, Graduate School of Biomedical, Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan.
Hattori
Noboru
N
Tanimoto
Takuya
T
Furonaka
Makoto
M
Ishikawa
Nobuhisa
N
Fujitaka
Kazunori
K
Haruta
Yoshinori
Y
Murai
Hiroshi
H
Yokoyama
Akihito
A
Kohno
Nobuoki
N
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001761:Bleomycin; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D049109:Cell Proliferation; D004195:Disease Models, Animal; D015316:Genetic Therapy / Q000379:methods*; D006801:Humans; D008168:Lung / Q000166:cytology; D051379:Mice; D008810:Mice, Inbred C57BL; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics* / Q000378:metabolism; D011658:Pulmonary Fibrosis / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D034622:RNA Interference; D020545:Respiratory Mucosa / Q000166:cytology; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology
D017395:Plasminogen Activator Inhibitor 1; D016212:Transforming Growth Factor beta; D001761:Bleomycin