Phloretin promotes osteoclast apoptosis in murine macrophages and inhibits estrogen deficiency-induced osteoporosis in mice. Lee Eun-Jung,Kim Jung-Lye,Kim Yun-Ho,Kang Min-Kyung,Gong Ju-Hyun,Kang Young-Hee Phytomedicine : international journal of phytotherapy and phytopharmacology Bone-remodeling imbalance induced by increased osteoclast formation and bone resorption is known to cause skeletal diseases such as osteoporosis. The reduction of estrogen levels at menopause is one of the strongest risk factors developing postmenopausal osteoporosis. This study investigated osteoprotective effects of the dihydrochalcone phloretin found in apple tree leaves on bone loss in ovariectomized (OVX) C57BL/6 female mice as a model for postmenopausal osteoporosis. OVX demoted bone mineral density (BMD) of mouse femurs, reduced serum 17β-estradiol level and enhanced serum receptor activator of NF-κB ligand (RANKL)/osteoprotegerin ratio with uterine atrophy. Oral administration of 10 mg/kg phloretin to OVX mice for 8 weeks improved such effects, compared to sham-operated mice. Phloretin attenuated TRAP activity and cellular expression of β3 integrin and carbonic anhydrase II augmented in femoral bone tissues of OVX mice. This study further examined that osteogenic activity of phloretin in RANKL-differentiated Raw 264.7 macrophages into mature osteoclasts. Phloretin at 1-20 μM stimulated Smac expression and capase-3 activation concurrently with nuclear fragmentation of multi-nucleated osteoclasts, indicating that this compound promoted osteoclast apoptosis. Consistently, phloretin enhanced bcl-2 induction but diminished bax expression. Furthermore, phloretin activated ASK-1-diverged JNK and p38 MAPK signaling pathways in mature osteoclasts, whereas it dose-dependently inhibited the RANKL-stimulated activation of ERK. Therefore, phloretin manipulated ASK-1-MAPK signal transduction leading to transcription of apoptotic genes. Phloretin was effective in preventing estrogen deficiency-induced osteoclastogenic resorption. 10.1016/j.phymed.2014.04.002

Calycosin attenuates osteoporosis and regulates the expression of OPG/RANKL in ovariectomized rats MAPK signaling. Li Ningxu,Tu Yan,Shen Yin,Qin Yanqiong,Lei Chao,Liu Xiangjie Die Pharmazie We aimed at exploring the effect of calycosin (CA) on osteoporosis in ovariectomized (OVX) rats. Sprague-Dawley (SD) rats were divided into five groups: Sham group, OVX group, OVX group treated with estradiol valerate (EV), CAL group treated with 15 mg/kg/d of CA and CAH group treated with 30 mg/kg/d of CA for 12 weeks. Bone mineral density (BMD), histopathology, body weight, parameters in serum and urine were observed. Gene expression and protein level of OPG/RANKL were also studied by real-time PCR and western blot, respectively. We further identified the effect of CA on mitogen-activated protein kinase (MAPK) signaling. In comparison with OVX rats, CAL and CAH significantly increased the BMD by 8.3% and 19.0%. Treatment with CA notably inhibited the excretion of Ca, P and Cr. CAH also significantly increased the level of alkaline phosphatase (ALP) and decreased the level of tartrate-resistant acid phosphatase (TRAP) in serum of OVX rats. CA could improve the trabecular bone area, and increased the trabecular number and the trabecular connection after 12-week. CA also increased the expression of osteoprotegerin (OPG) and decreased the Receptor Activator for Nuclear Factor-κB Ligand (RANKL) mRNA expression compared with the OVX rats. In addition, CA could effectively decrease the phosphorylation of MAPKs induced by ovariectomy. In conclusion, CA had remarkable antiosteoporotic activity and therefore can be a promising candidate for the treatment of postmenopausal osteoporosis. 10.1691/ph.2016.6627

Quercitrin attenuates osteoporosis in ovariectomized rats by regulating mitogen-activated protein kinase (MAPK) signaling pathways. Xing Li-Zhi,Ni Huai-Jun,Wang Yu-Ling Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie MAPK signaling pathways are crucial in regulating osteogenesis, a genetic disorder affecting the bones. Quercitrin, a type of flavonoid, is widely distributed in nature and involved in many pharmacological activities. But its osteoprotective functions and mechanism in osteoporosis are far from being understood clearly. In this paper, the MAPK upregulation was observed in the ovariectomy-induced bone loss. Quercitrin was found to downregulate MAPK signaling pathways and prevent the ovariectomy-induced deterioration of bone mineral density (BMD), trabecular microstructure, and bone mechanical characteristics. In this study, quercitrin was seen to prevent the progression of the postmenopausal osteoporosis among the rats, which may be mediated by the downregulated MAPK signaling pathways. 10.1016/j.biopha.2017.02.073

Effect of lncRNA AK125437 on postmenopausal osteoporosis rats via MAPK pathway. Wang H,Li Y-K,Cui M,Liu L-H,Zhao L-M,Wang X-M European review for medical and pharmacological sciences OBJECTIVE:The aim of this study was to explore the effect of long non-coding ribonucleic acid (lncRNA) AK125437 on rats with postmenopausal osteoporosis via the mitogen-activated protein kinase (MAPK) pathway. MATERIALS AND METHODS:A total of 36 Sprague-Dawley rats were randomly divided into three groups, including normal group, model group, and an inhibitor group, with 12 rats in each group. Only ovaries were exposed in normal group. The postmenopausal osteoporosis model was established in model group. Meanwhile, the intervention was performed with inhibitor for 3 months after modeling in inhibitor group, followed by sampling. The expression of receptor activator of nuclear factor kappa-B ligand (RANKL) was detected via immunohistochemistry. The protein expression level of phosphorylated p38 (p-p38) MAPK was determined via Western blotting (WB). Furthermore, the expression level of lncRNA AK125437 and the content of serum estradiol were determined via quantitative Polymerase Chain Reaction (qPCR) and enzyme-linked immunosorbent assay (ELISA), respectively. In addition, bone mineral density was measured using dual-energy X-ray bone mineral absorptiometer. RESULTS:Immunohistochemistry results indicated that model group and inhibitor group had notably up-regulated positive expression level of RANKL than normal group (p<0.05), which was remarkably lower in inhibitor group than model group (p<0.05). Western blot results showed that compared with normal group, the protein expression level of p-p38 MAPK was substantially elevated in model and inhibitor groups (p<0.05). Meanwhile, the protein expression level of p-p38 MAPK was markedly lower in inhibitor group than that in model group (p<0.05). According to qPCR results, the expression level of lncRNA AK125437 was significantly up-regulated in both model group and inhibitor group compared with normal group, showing statistically significant differences (p<0.05). However, no significant differences were observed between model group and inhibitor group (p>0.05). ELISA results revealed that model group and inhibitor group had markedly lower estradiol content than normal group (p<0.05). There was no statistically significant difference in the content of estradiol between the two groups (p>0.05). According to the measurement results of bone mineral density, compared with normal group, bone mineral density was notably lower in model group and inhibitor group (p<0.05). Furthermore, it was markedly higher in inhibitor group than that of model group (p<0.05). CONCLUSIONS:LncRNA AK125437 affects the bone mineral density of rats with postmenopausal osteoporosis by activating the MAPK pathway. 10.26355/eurrev_202003_20482