Melatonin Inhibits Osteoclastogenesis and Bone Loss in Ovariectomized Mice by Regulating PRMT1-Mediated Signaling

Abstract

Melatonin, a pineal gland hormone, has been suggested to treat postmenopausal osteoporosis due to its inhibitory effect on osteoclast differentiation. We previously reported that protein arginine methyltransferase 1 (PRMT1) was an important mediator of receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis. However, the relationship between melatonin and PRMT1 in osteoclast differentiation and estrogen deficiency-induced osteoporosis is unclear. In this study, we investigated the inhibitory mechanisms of melatonin in vitro and in vivo by focusing on PRMT1. Melatonin treatment effectively blocked RANKL-induced osteoclastogenesis by inhibiting PRMT1 and asymmetric dimethylarginine (ADMA) expression. RANKL-induced tumor necrosis factor receptor-associated factor 6 (TRAF6) and the phosphorylation of JNK were also suppressed by melatonin, and TRAF6 siRNA attenuated RANKL-induced p-JNK and PRMT1 production. Melatonin inhibited the transcriptional activity of NF-κB by interfering with the binding of PRMT1 and NF-κB subunit p65 in RANKL-treated BMDMs. Our results also revealed that melatonin inhibits RANKL-induced PRMT1 expression through receptors-independent pathway. Thus, the anti-osteoclastogenic effect of melatonin was mediated by a cascade of inhibition of RANKL-induced TRAF6, JNK, PRMT1, and NF-κB signaling in melatonin receptors-independent pathway. In vivo, ovariectomy caused significant decreases in bone mineral density, but melatonin treatment alleviated the ovariectomized (OVX)-induced bone loss by inhibiting bone resorption. Furthermore, the expression PRMT1 and TRAP mRNA was upregulated in OVX-femurs, but effectively suppressed by melatonin injection. These findings suggest that melatonin inhibited osteoclast differentiation and estrogen deficiency-induced osteoporosis by suppressing RANKL-induced TRAF6, JNK, PRMT1, and NF-κB signaling cascades in melatonin receptors-independent pathway.

The lncRNA H19/miR-541-3p/Wnt/β-catenin axis plays a vital role in melatonin-mediated osteogenic differentiation of bone marrow mesenchymal stem cells

“…Emerging reports have manifested that MT facilitates osteoblast differentiation [ 29 – 31 ]. In the present research, we confirmed the molecular mechanism of MT on osteogenic and adipogenic differentiation of BMSCs in vitro and in vivo .…”

Melatonin Inhibits Osteoclastogenesis and Osteolytic Bone Metastasis: Implications for Osteoporosis

“…Preclinical evidence has shown that one way in which melatonin promotes osteoblast differentiation is by enhancing the expression of the osteogenic marker, Osterix, apparently through the protein kinase A (PKA) and PKC signaling pathways [17]. In ovariectomized (OVX) mice, melatonin reportedly suppressed osteoclastogenesis by inhibiting receptor activator of nuclear factor-kappa B ligand (RANKL)-induced tumor necrosis factor receptor-associated factor 6 (TRAF6), c-Jun N-terminal kinase (JNK), protein arginine methyltransferase 1 (PRMT1), and NF-κB signaling through a receptor-independent pathway [18]. In bone marrow monocytes (BMMs) isolated from the femurs and tibias of C57BL/6 mice, pharmacological concentrations (1 to 100 µM) of melatonin dose-dependently suppressed osteoclast differentiation and decreased numbers of tartrate-resistant acid phosphatase (TRAP)-positive cells as well as the gene expression of osteoclast-specific markers, via a reactive oxygen species (ROS)-mediated independent pathway [19].…”

Melatonin Attenuates RANKL-Induced Osteoclastogenesis via Inhibition of Atp6v0d2 and DC-STAMP through MAPK and NFATc1 Signaling Pathways

“…Several recent studies have reported the effect of melatonin on the differentiation of osteoclasts. These studies revealed that melatonin inhibits osteoclast differentiation through downregulation of the NF-κB pathway, along with reduction of RANKL-induced TRAF6, JNK, PRMT1 and NFATc1 transcription factor induction [6,27,28].…”

“…Melatonin controls the overall remodeling process through the dual action of osteoblast bone formation and osteoclast bone resorption [4,5]. In addition, in vitro and in vivo studies provide evidence that melatonin treatment contributes to the prevention of bone loss [6]. Specifically, it regulates the balance of osteoclasts and osteoblasts through signaling transduction, including the Wnt, NFκB, and MAPK pathways, to improve bone quality [7][8][9].…”

“…Specifically, it regulates the balance of osteoclasts and osteoblasts through signaling transduction, including the Wnt, NFκB, and MAPK pathways, to improve bone quality [7][8][9]. Older people tend to have decreased melatonin secretion, which is of interest to researchers studying osteoporosis because it is associated with an increased risk of osteoporosis [1,6]. Accordingly, melatonin intake may be an alternative therapy for improving bone health [10].…”