The inhibitory effects of roflumilast on lipopolysaccharide-induced nitric oxide production in RAW264.7 cells are mediated by heme oxygenase-1 and its product carbon monoxide.
OBJECTIVE
Heme oxygenase-1 (HO-1) is an enzyme that degrades heme into biliverdin, free iron, and carbon monoxide (CO). This enzyme is known to have cytoprotective and anti-inflammatory effects. In this study, we investigated whether roflumilast, a newly developed specific phosphodiesterase 4 (PDE4) inhibitor, mediates some of its anti-inflammatory effects by blocking nitric oxide (NO) and tumor necrosis factor alpha (TNF-alpha) via the induction of HO-1 expression in macrophages.


METHODS
The expression of iNOS and HO-1 was analyzed by western blot analysis. The production of NO and TNF-alpha was assayed by Greiss and ELISA, respectively.


RESULTS
Roflumilast markedly suppressed LPS-induced NO and TNF-alpha production and these phenomena were correlated with the induction of HO-1 protein levels. Moreover, the inhibitory effects of roflumilast on NO production were abrogated by a HO-1 inhibitor and a CO scavenger. Tricarbonyldichlrororuthenium(II) dimer, a CO releasing molecule significantly suppressed NO production.


CONCLUSIONS
These results suggested that roflumilast exerts its anti-inflammatory effects in macrophages through a novel mechanism that involves the action of HO-1 and its product, CO.
Kwak
H J
HJ
Laboratory of Molecular Pharmacology and Physiology, Medicinal Science Division, Korea Research Institute of Chemical Technology, 100 Jang-Dong, Yusung, Taejon, 305-343.
Song
J S
JS
No
Z S
ZS
Song
J H
JH
Yang
S D
SD
Cheon
H G
HG
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors; D000631:Aminopyridines / Q000494:pharmacology*; D000818:Animals; D001549:Benzamides / Q000494:pharmacology*; D015153:Blotting, Western; D002248:Carbon Monoxide / Q000378:metabolism; D002460:Cell Line; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D003521:Cyclopropanes / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D006419:Heme Oxygenase (Decyclizing) / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism*; D009942:Organometallic Compounds / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D000631:Aminopyridines; D001549:Benzamides; D003521:Cyclopropanes; D008070:Lipopolysaccharides; D009942:Organometallic Compounds; D014409:Tumor Necrosis Factor-alpha; C447082:tricarbonyldichlororuthenium (II) dimer; C424423:Roflumilast; D009569:Nitric Oxide; D002248:Carbon Monoxide; D006419:Heme Oxygenase (Decyclizing); D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4