High mobility group box chromosomal
protein 1 (HMGB-1) released from injured cells plays an important role in the development of
arthritis. This study investigated the anti-angiogenic effects of
cilostazol in
collagen-induced arthritis (CIA) of mice, and the underlying mechanisms involved. The expressions of HIF-1α,
VEGF, NF-κB p65 and
SIRT1 in synovial fibroblasts obtained from
rheumatoid arthritis (RA) patients were assessed by Western blotting, and in vitro and in vivo angiogenesis were analyzed. Tube formations by human microvascular endothelial cells (HMVECs) were significantly increased by direct exposure to
HMGB1 or to
conditioned medium derived from HMGB1-stimulated RA fibroblasts, and these increases were attenuated by
cilostazol, the latter of which was blocked by
sirtinol.
HMGB1 increased the expression of HIF-1α and
VEGF and concomitantly increased nuclear NF-κB p65 and
DNA binding activity, but these effects of
HMGB1 were inhibited by
cilostazol.
SIRT1 protein expression was time-dependently decreased (3-24 hr) by
HMGB1, which was recovered by pretreatment with
cilostazol (1-30 µM) or
resveratrol, accompanying with increased
SIRT1 deacetylase activity. In the tibiotarsal joint tissues of CIA mice treated with vehicle, HIF-1α- and
VEGF-positive spots and CD31 staining were markedly exaggerated, whereas
SIRT1 immunofluorescence was diminished. These variables were wholly reversed in
cilostazol (30 mg/kg/day)-treated mice. Furthermore, number of blood vessels stained by
von Willebrand factor antibody was significantly lower in
cilostazol-treated CIA mice. Summarizing,
cilostazol activated
SIRT1 and inhibited NF-κB-mediated transcription, thereby suppressing the expression of HIF-1α and
VEGF. In addition,
cilostazol caused HIF-1α deacetylation by enhancing
SIRT1 activity and reduced
VEGF production, thereby had an anti-angiogenic effect in vitro studies and in CIA murine model.