scholarly journals Ablation of p38α MAPK Signaling in Osteoblast Lineage Cells Protects Mice From Bone Loss Induced by Estrogen Deficiency

Endocrinology ◽  
2015 ◽  
Vol 156 (12) ◽  
pp. 4377-4387 ◽  
Author(s):  
Cyril Thouverey ◽  
Joseph Caverzasio
Keyword(s):  
Bone Loss ◽  
Nuclear Factor Κb ◽  
Mapk Signaling ◽  
Osteoclast Formation ◽  
Estrogen Deficiency ◽  
Nuclear Factor ◽  
Receptor Activator ◽  
P38α Mapk ◽  
Mapk Inhibitors ◽  
Osteoblast Lineage

Estrogen deficiency causes bone loss by increasing the number of bone-resorbing osteoclasts. Selective p38α MAPK inhibitors prevent bone-wasting effects of estrogen withdrawal but implicated mechanisms remain to be identified. Here, we show that inactivation of the p38α-encoding gene in osteoblast lineage cells with the use of an osteocalcin-cre transgene protects mice from ovariectomy-induced bone loss (a murine model of postmenopausal osteoporosis). Ovariectomy fails to induce bone loss, increase bone resorption, and stimulate receptor activator of nuclear factor κB ligand and IL-6 expression in mice lacking p38α in osteoblasts and osteocytes. Finally, TNFα or IL-1, which are osteoclastogenic cytokines overproduced in the bone marrow under estrogen deficiency, can activate p38α signaling in osteoblasts, but those cytokines cannot enhance Rankl and Il6 expressions or increase osteoclast formation in p38a-deficient osteoblast cultures. These findings demonstrate that p38α MAPK signaling in osteoblast lineage cells mediates ovariectomy-induced bone loss by up-regulating receptor activator of nuclear factor κB ligand and IL-6 production.

scholarly journals Kalkitoxin Reduces Osteoclast Formation and Resorption and Protects against Inflammatory Bone Loss

2021 ◽  
Vol 22 (5) ◽  
pp. 2303
Author(s):  
Liang Li ◽  
Ming Yang ◽  
Saroj Kumar Shrestha ◽  
Hyoungsu Kim ◽  
William H. Gerwick ◽  
...  
Keyword(s):  
Bone Loss ◽  
Transmembrane Protein ◽  
Osteoclast Differentiation ◽  
Mapk Signaling ◽  
Osteoclast Formation ◽  
Bone Diseases ◽  
Tartrate Resistant Acid Phosphatase ◽  
Nuclear Factor ◽  
Mineral Density ◽  
Multinucleated Cells

Osteoclasts, bone-specified multinucleated cells produced by monocyte/macrophage, are involved in numerous bone destructive diseases such as arthritis, osteoporosis, and inflammation-induced bone loss. The osteoclast differentiation mechanism suggests a possible strategy to treat bone diseases. In this regard, we recently examined the in vivo impact of kalkitoxin (KT), a marine product obtained from the marine cyanobacterium Moorena producens (previously Lyngbya majuscula), on the macrophage colony-stimulating factor (M-CSF) and on the receptor activator of nuclear factor κB ligand (RANKL)-stimulated in vitro osteoclastogenesis and inflammation-mediated bone loss. We have now examined the molecular mechanism of KT in greater detail. KT decreased RANKL-induced bone marrow-derived macrophages (BMMs) tartrate-resistant acid phosphatase (TRAP)-multinucleated cells at a late stage. Likewise, KT suppressed RANKL-induced pit area and actin ring formation in BMM cells. Additionally, KT inhibited several RANKL-induced genes such as cathepsin K, matrix metalloproteinase (MMP-9), TRAP, and dendritic cell-specific transmembrane protein (DC-STAMP). In line with these results, RANKL stimulated both genes and protein expression of c-Fos and nuclear factor of activated T cells (NFATc1), and this was also suppressed by KT. Moreover, KT markedly decreased RANKL-induced p-ERK1/2 and p-JNK pathways at different time points. As a result, KT prevented inflammatory bone loss in mice, such as bone mineral density (BMD) and osteoclast differentiation markers. These experiments demonstrated that KT markedly inhibited osteoclast formation and inflammatory bone loss through NFATc1 and mitogen-activated protein kinase (MAPK) signaling pathways. Therefore, KT may have potential as a treatment for destructive bone diseases.

scholarly journals Lack of NOD2 attenuates ovariectomy-induced bone loss via inhibition of osteoclasts

2017 ◽  
Vol 235 (2) ◽  
pp. 85-96 ◽  
Author(s):  
Ke Ke ◽  
Ok-Joo Sul ◽  
Soo-Wol Chung ◽  
Jae-Hee Suh ◽  
Hye-Seon Choi
Keyword(s):  
Bone Loss ◽  
Nuclear Factor Kappa B ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Nuclear Factor Κb ◽  
Innate Immune ◽  
Nuclear Factor ◽  
Oxygen Species ◽  
Receptor Activator ◽  
Recognition Receptor ◽  
Oligomerization Domain

Nucleotide-binding oligomerization domain-2 (NOD2) is a pattern recognition receptor of the innate immune system. It interacts with serine–threonine kinases to induce activation of nuclear factor κB (NF-κB), which is important for receptor activator of nuclear factor kappa-B ligand (RANKL) signaling. We tested the idea that NOD2 modulates bone metabolism via an action on osteoclasts (OCs). The absence of NOD2 reduced ovariectomy-induced bone loss in mice, and lowered the area and the activity of OCs, by impairing RANKL signaling. It also reduced the level of reactive oxygen species (ROS), as well as of NF-κB-DNA binding upon RANKL exposure. NOD2 was found to physically interact with nicotinamide adenine dinucleotide phosphate oxidase 1, and this led to increased production of ROS in OCs. Our data suggest that NOD2 contributes to bone loss in estrogen deficiency by elevating ROS levels in OCs.

scholarly journals T-cell receptor activator of nuclear factor-κB ligand/osteoprotegerin imbalance is associated with HIV-induced bone loss in patients with higher CD4+ T-cell counts

AIDS ◽  
2018 ◽  
Vol 32 (7) ◽  
pp. 885-894 ◽  
Author(s):  
Kehmia Titanji ◽  
Aswani Vunnava ◽  
Antonina Foster ◽  
Anandi N. Sheth ◽  
Jeffrey L. Lennox ◽  
...  
Keyword(s):  
T Cell ◽  
Bone Loss ◽  
T Cell Receptor ◽  
Cell Receptor ◽  
Nuclear Factor Κb ◽  
Cd4 T Cell ◽  
Nuclear Factor ◽  
Cell Counts ◽  
Receptor Activator

scholarly journals Rab11A Functions as a Negative Regulator of Osteoclastogenesis through Dictating Lysosome-Induced Proteolysis of c-fms and RANK Surface Receptors

Cells ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 2384 ◽  
Author(s):  
Yuka Okusha ◽  
Manh Tien Tran ◽  
Mami Itagaki ◽  
Chiharu Sogawa ◽  
Takanori Eguchi ◽  
...  
Keyword(s):  
Osteoclast Differentiation ◽  
Nuclear Factor Κb ◽  
Osteoclast Formation ◽  
Negative Regulator ◽  
Immunocytochemical Staining ◽  
Nuclear Factor ◽  
Lysosomal Activity ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Receptor Activator

Osteoclast differentiation and activity are controlled by two essential cytokines, macrophage colony-stimulating factor (M-CSF) and the receptor activator of nuclear factor-κB ligand (RANKL). Rab11A GTPase, belonging to Rab11 subfamily representing the largest branch of Ras superfamily of small GTPases, has been identified as one of the crucial regulators of cell surface receptor recycling. Nevertheless, the regulatory role of Rab11A in osteoclast differentiation has been completely unknown. In this study, we found that Rab11A was strongly upregulated at a late stage of osteoclast differentiation derived from bone marrow-derived macrophages (BMMs) or RAW-D murine osteoclast precursor cells. Rab11A silencing promoted osteoclast formation and significantly increased the surface levels of c-fms and receptor activator of nuclear factor-κB (RANK) while its overexpression attenuated osteoclast formation and the surface levels of c-fms and RANK. Using immunocytochemical staining for tracking Rab11A vesicular localization, we observed that Rab11A was localized in early and late endosomes, but not lysosomes. Intriguingly, Rab11A overexpression caused the enhancement of fluorescent intensity and size-based enlargement of early endosomes. Besides, Rab11A overexpression promoted lysosomal activity via elevating the endogenous levels of a specific lysosomal protein, LAMP1, and two key lysosomal enzymes, cathepsins B and D in osteoclasts. More importantly, inhibition of the lysosomal activity by chloroquine, we found that the endogenous levels of c-fms and RANK proteins were enhanced in osteoclasts. From these observations, we suggest a novel function of Rab11A as a negative regulator of osteoclastogenesis mainly through (i) abolishing the surface abundance of c-fms and RANK receptors, and (ii) upregulating lysosomal activity, subsequently augmenting the degradation of c-fms and RANK receptors, probably via the axis of early endosomes–late endosomes–lysosomes in osteoclasts.

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