Inhibition of HMGB1-Induced Angiogenesis by Cilostazol via SIRT1 Activation in Synovial Fibroblasts from Rheumatoid Arthritis

Abstract

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.

Glycyrrhizin, an HMGB1 inhibitor, exhibits neuroprotective effects in rats after lithium-pilocarpine-induced status epilepticus

“…HMGB1 is a ubiquitous non‐histone DNA‐binding protein, extracellularly it serves as a signalling molecule involved in acute and chronic inflammation, including pneumonia and arthritis . GL is the specific inhibitor of HMGB1.…”

Suppression of RANKL-induced osteoclast differentiation by cilostazol via SIRT1-induced RANK inhibition

“…Furthermore, synovial inflammation and bone erosion were significantly inhibited by cilostazol treatment in a murine CIA model. Recently, it was found that cilostazol like resveratrol (a known SIRT1 activator) elevated HMGB1-induced decreased SIRT1 protein expression and activity, whereas HMGB1-stimulated NF-κB activation was strongly inhibited by cilostazol [18]. Shakibaei et al [19] reported that RANKL up-regulated p300 (a histone acetyltransferase) expression, which, in turn, promoted NF-κB acetylation.…”

Regulation and function of SIRT1 in rheumatoid arthritis synovial fibroblasts

“…Down regulation of SIRT1 or inhibition of sirtuin activities in synovial cells of RA patients was found to reduce the expression of inflammatory mediators [13,14], and overexpression of SIRT1 increased production of pro-inflammatory cytokines in rheumatoid arthritis synovial fibroblasts (RASF) and monocytes from healthy persons [13]. In contrast, levels of SIRT1 were diminished in joint tissues of mice with collagen-induced arthritis [15]. Moreover, deletion of SIRT1 aggravated inflammatory arthritis in serum transfer arthritis model and increased production of pro-inflammatory cytokines in macrophages [16].…”