Overexpression of nitric oxide synthase by the endothelium attenuates bleomycin-induced lung fibrosis and impairs MMP-9/TIMP-1 balance.
BACKGROUND
Nitric oxide (NO) produced by endothelial NO synthase (eNOS) is thought to effect an anti-inflammatory response, but its mechanism is still unknown.


METHODS
eNOS transgenic (eNOS-TG) mice and their littermate controls (C57/BL6) were used to clarify the role of NO derived from eNOS. Bleomycin hydrochloride (1 U/body/day) or PBS was injected intraperitoneally.


RESULTS
Subpleural fibrotic changes and hydroxyproline content in the eNOS-TG mice were significantly reduced compared with those of the wild-type (WT) mice by day 56. Administration of N(omega)-nitro-L-arginine methyl ester, a potent inhibitor of NO synthase, worsened the fibrotic response in bleomycin-treated eNOS-TG mice. Gelatinolytic activity in lung homogenates, corresponding to metalloproteinase-9 (MMP-9), was significantly increased in bleomycin-injured WT mice on day 14. In contrast, the level of tissue inhibitor of metalloproteinases-1 (TIMP-1), an endogenous MMP-9 inhibitor, was increased in the bleomycin-treated eNOS-TG mice compared with WT. Immunohistochemical analysis demonstrated that MMP-9 and TIMP-1 were strongly expressed in inflammatory cells, including subpleural fibrotic lesions.


CONCLUSIONS
These data suggested that eNOS overexpression attenuates bleomycin-induced lung injury by ameliorating the MMP-9/TIMP-1 balance.
Yoshimura
Sho
S
Division of Cardiovascular and Respiratory Medicine, Department of Internal Medicine, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan.
Nishimura
Yoshihiro
Y
Nishiuma
Teruaki
T
Yamashita
Tomoya
T
Kobayashi
Kazuyuki
K
Yokoyama
Mitsuhiro
M
D000818:Animals; D001761:Bleomycin; D015153:Blotting, Western; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology; D004730:Endothelium, Vascular / Q000378:metabolism*; D005355:Fibrosis / Q000378:metabolism; D006909:Hydroxyproline / Q000378:metabolism; D007150:Immunohistochemistry; D008168:Lung / Q000378:metabolism / Q000473:pathology; D008171:Lung Diseases / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000378:metabolism*; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
D019715:Tissue Inhibitor of Metalloproteinase-1; D042461:Vascular Endothelial Growth Factor A; D001761:Bleomycin; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D020780:Matrix Metalloproteinase 9; D006909:Hydroxyproline