Cytisine attenuates bone loss of ovariectomy mouse by preventing RANKL‐induced osteoclastogenesis

Abstract

Postmenopausal Osteoporosis (PMOP) is oestrogen withdrawal characterized of much production and activation by osteoclast in the elderly female. Cytisine is a quinolizidine alkaloid that comes from seeds or other plants of the Leguminosae (Fabaceae) family. Cytisine has been shown several potential pharmacological functions. However, its effects on PMOP remain unknown. This study designed to explore whether Cytisine is able to suppress RANKL‐induced osteoclastogenesis and prevent the bone loss induced by oestrogen deficiency in ovariectomized (OVX) mice. In this study, we investigated the effect of Cytisine on RAW 264.7 cells and bone marrow monocytes (BMMs) derived osteoclast culture system in vitro and observed the effect of Cytisine on ovariectomized (OVX) mice model to imitate postmenopausal osteoporosis in vivo. We found that Cytisine inhibited F‐actin ring formation and tartrate‐resistant acid phosphatase (TRAP) staining in dose‐dependent ways, as well as bone resorption by pit formation assays. For molecular mechanism, Cytisine suppressed RANK‐related trigger RANKL by phosphorylation JNK/ERK/p38‐MAPK, IκBα/p65‐NF‐κB, and PI3K/AKT axis and significantly inhibited these signalling pathways. However, the suppression of PI3K‐AKT‐NFATc1 axis was rescued by AKT activator SC79. Meanwhile, Cytisine inhibited RANKL‐induced RANK‐TRAF6 association and RANKL‐related gene and protein markers such as NFATc1, Cathepsin K, MMP‐9 and TRAP. Our study indicated that Cytisine could suppress bone loss in OVX mouse through inhibited osteoclastogenesis. All data provide the evidence that Cytisine may be a promising agent in the treatment of osteoclast‐related diseases such as osteoporosis.

Gut microbiota modulates osteoclast glutathione synthesis and mitochondrial biogenesis in mice subjected to ovariectomy

“…Operations were conducted according to our previous work. 18 All mice were sacrificed after 6 weeks, and samples were collected for further tests.…”

“…Bone marrow‐derived macrophages (BMMs) were isolated from mouse bone marrow in accordance with our previous work. 18 For cell differentiation, BMMs were cultured in α‐MEM medium containing 20 ng/ml M‐CSF and 50 ng/ml RANKL (R&D). The culture medium was replaced every 2 days until OCs formed.…”

The Pathophysiology of Osteoporosis after Spinal Cord Injury

“…Subsequently, TRAF6 recruitment initiates the activation of multiple molecules involved in signaling pathways, including JNK, p38, ERK, Akt and NF-κB [ 104 , 105 ]. The processes involved in the activation of NF-κB, p38-ERK, and JNK interact with NFATc1 in the cell nucleus, stimulating the transcription of genes crucial for osteoclastogenesis [ 106 , 107 , 108 ]. Mononucleated osteoclast progenitors fuse, and RANKL mediates reorganization of the cytoskeleton for osteocyte maturation and subsequent bone-resorbing activity ( Figure 1 ) [ 109 , 110 ].…”

Implications of enolase in the RANKL-mediated osteoclast activity following spinal cord injury

“…Successful binding of RANKL to the RANK receptor promotes osteoclast differentiation and activation through the stimulation of tumor necrosis factor receptor-associated factor (TRAF6) recruitment ( Jiang et al ., 2014 ; Liu and Zhang, 2015 ). TRAF6 recruitment initiates the activation of nuclear factor-κB (NF-κB), p38-extracellular signal-regulated kinase (ERK), and c-Jun NH(2)-terminal kinase (JNK), subsequently interacting with nuclear factor of activated T cells C1 (NFATc1) in the cell nucleus and stimulating the transcription of genes crucial for osteoclastogenesis ( Chen et al ., 2020 ; Liu et al ., 2020 ; Qian et al ., 2020 ).…”