Suppression of RANKL‐dependent heme oxygenase‐1 is required for high mobility group box 1 release and osteoclastogenesis

Abstract

The differentiation of osteoclasts is regulated by several essential cytokines, such as receptor activator of nuclear factor κB ligand (RANKL) and macrophage colony-stimulating factor. Recently, high mobility group box 1 (HMGB1), a chromatin protein, also has been identified as one of these osteoclast differentiation cytokines. However, the molecular mechanisms that control HMGB1 release from osteoclast precursor cells are not known. Here, we report that RANKL-induced suppression of heme oxygenase-1 (HO-1), a heme-degrading enzyme, promotes HMGB1 release during osteoclastogenesis. In contrast, induction of HO-1 with hemin or curcumin in bone marrow-derived macrophages or RAW-D murine osteoclast precursor cells inhibited osteoclastogenesis and suppressed HMGB1 release. Since an inhibitor for p38 mitogen-activated protein kinase (MAPK) prevented the RANKL-mediated HO-1 suppression and extracellular release of HMGB1, these effects were p38 MAPK-dependent. Moreover, suppression of HO-1 in RAW-D cells by RNA interference promoted the activation of caspase-3 and HMGB1 release, whereas overexpression of HO-1 inhibited caspase-3 activation as well as HMGB1 release. Furthermore, these effects were regulated by redox conditions since antioxidant N-acetylcysteine abolished the HO-1/HMGB1/caspase-3 axis. These results suggest that RANKL-dependent HO-1 suppression leads to caspase-3 activation and HMGB1 release during osteoclastogenesis.

The Coffee Diterpene Kahweol Prevents Osteoclastogenesis via Impairment of NFATc1 Expression and Blocking of Erk Phosphorylation

“…Similarly, we have also demonstrated that OCL differentiation or survival is regulated by NAC, or the oxidation agent hydrogen peroxide, and this is accompanied by changes in the shape and sizes of the cells. Furthermore, we recently demonstrated that the RANKL-mediated suppression of anti-oxidant enzyme heme-oxigenase 1 (HO-1) promoted high mobility group box 1 (HMGB1) release and OCL differentiation (7). Therefore, the use of anti-oxidants may enable the development of therapeutic agents for bone disorders such as osteoporosis and periodontitis.…”

Fisetin Inhibits Osteoclastogenesis Through Prevention of RANKL-Induced ROS Production by Nrf2-Mediated Up-regulation of Phase II Antioxidant Enzymes

“…Bone marrow-derived macrophages (BMMs) were isolated as described previously (7). The BMMs were replated in culture plates and incubated in α-minimal essential medium (α-MEM) [Code: 135-15175, bicarbonate buffered with L-glutamine; Wako Pure Chemicals containing 10% FBS with 100 U/mL of penicillin and 100 μg/mL of streptomycin in the presence of M-CSF (50 ng/mL) and RANKL (50 ng/mL)] for 60 or 72 h until the cells differentiated into multinucleated mature OCLs.…”

“…Although over-expression of HO-1 by transient gene vector suppresses the OCL differentiation, down-regulation of HO-1 by RNA interference enhances osteoclastogenesis (7). In addition, a recent study has shown that fisetin induces HO-1 in HUVECs (17).…”

“…In addition to these signaling pathways, recent studies have also shown that generation of reactive oxygen species (ROS) is required for MAPK activation and OCL differentiation (5,6). More recently, we have reported that the RANKL-induced suppression of heme-oxygenase 1 (HO-1), a phase II antioxidant cytoprotective enzyme against oxidative stress, is essential for OCL differentiation (7 while down-regulation of HO-1 by RNA interference enhances osteoclastogenesis (7). In addition, pharmacological induction of HO-1 by curcumin or kahweol, a coffee-specific diterpene, in macrophage progenitors inhibits osteoclastogtenesis (7,8).…”

“…More recently, we have reported that the RANKL-induced suppression of heme-oxygenase 1 (HO-1), a phase II antioxidant cytoprotective enzyme against oxidative stress, is essential for OCL differentiation (7 while down-regulation of HO-1 by RNA interference enhances osteoclastogenesis (7). In addition, pharmacological induction of HO-1 by curcumin or kahweol, a coffee-specific diterpene, in macrophage progenitors inhibits osteoclastogtenesis (7,8). Therefore, regulation of HO-1 expression during osteoclastogenesis is an important factor for OCL differentiation, suggesting that HO-1 inducer could be used as new therapeutic agent against bone-lytic diseases.…”