Regulatory role of heme oxygenase 1 in inflammation of rheumatoid arthritis.
OBJECTIVE
To examine the expression and pathogenetic roles of heme oxygenase 1 (HO-1), an inducible heme-degrading enzyme with antiinflammatory properties, in rheumatoid arthritis (RA).


METHODS
HO-1 expression in synovial tissue from patients with RA, patients with osteoarthritis, and patients with noninflammatory joint diseases was determined by immunoblotting and immunohistochemistry. Effects of various agents, such as hemin (a chemical inducer of HO-1), small interfering RNA (siRNA) specific for HO-1, HO-1 expression vector, and antirheumatic agents, on HO-1 expression in RA synovial cell lines were analyzed by real-time reverse transcription-polymerase chain reaction (PCR) and immunoblotting. Cytokine synthesis was evaluated by real-time PCR and enzyme-linked immunosorbent assay.


RESULTS
HO-1 was expressed more abundantly in the lesions of synovial tissue from patients with RA than in those from the other patient groups. Hemin, auranofin, and HO-1 expression vector induced HO-1 and reduced expression of tumor necrosis factor alpha (TNFalpha) messenger RNA, lipopolysaccharide (LPS)-induced secretion of interleukin-6 (IL-6) and IL-8, and expression of cyclooxygenase 2 in the synovial cell lines. Treatment with HO-1-specific siRNA augmented the synthesis of TNFalpha, IL-6, and IL-8 and canceled the suppressive effects of auranofin on TNFalpha secretion. When hemoglobin, as a scavenger of carbon monoxide, was added to auranofin-treated synovial cell lines, LPS-dependent production of IL-6 and IL-8 was increased.


CONCLUSIONS
Our data demonstrate that HO-1 is expressed in RA synovial tissues and plays a regulatory role in the development of inflammation. The pharmacologic effects of auranofin depend, in part, on the levels of HO-1, suggesting that HO-1 induction is a novel therapeutic strategy for RA.
Department of Internal Medicine and Clinical Immunology, Yokohama City University Graduate School of Medicine, Yokohama, Japan.
Hideo
H
Kobayashi
Mitsuhiro
M
Takeno
Tomoyuki
T
Saito
Yukiko
Y
Takeda
Yohei
Y
Kirino
Koji
K
Noyori
Takeshi
T
Hayashi
Atsuhisa
A
Ueda
Yoshiaki
Y
Ishigatsubo
D001172:Arthritis, Rheumatoid / Q000201:enzymology / Q000276:immunology*; D002460:Cell Line; D005260:Female; D051547:Heme Oxygenase-1 / Q000096:biosynthesis / Q000502:physiology*; D006801:Humans; D007249:Inflammation / Q000201:enzymology; D008875:Middle Aged; D013583:Synovial Membrane / Q000166:cytology / Q000201:enzymology
D051547:Heme Oxygenase-1