6,7,4'-Trihydroxyflavone inhibits osteoclast formation and bone resorption in vitro and in vivo

Methanolic extract of O.umbellata L. exhibits anti-osteoporotic effect via promoting osteoblast proliferation in MG-63 cells and inhibiting osteoclastogenesis in RANKL-stimulated RAW 264.7 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Oldenlandia umbellataL., belonging to the Rubiaceae family, is an annual plant possessing anti-inflammatory and antipyretic, anti-nociceptive, anti-bacterial, anti-helminthic, antioxidant and hepatoprotective activities and used in traditional medicine to treat inflammation and respiratory diseases.

AIM OF THE STUDY

The present study aims to evaluate the anti-osteoporotic effect of Methanolic extract of O.umbellata in MG-63 cells and RANKL-stimulated RAW 264.7 cells.

MATERIALS AND METHODS

The methanolic extract from the aerial parts of O.umbellata was subjected to metabolite profiling. The anti-osteoporotic effect of MOU was assessed in MG-63 cells and RANKL-stimulated RAW 264.7 cells. In MG-63 cells, the proliferative effect of MOU was evaluated using MTT assay, ALP assay, Alizarin red staining, ELISA and western blot. Similarly, the anti-osteoclastogenic effect of MOU was assessed in RANKL-stimulated RAW 264.7 cells via MTT, TRAP staining and western blot.

RESULTS

LC-MS metabolite profiling showed the presence of 59 phytoconstituents including scandoside, scandoside methyl ester, deacetylasperuloside, asperulosidic acid, and cedrelopsin in MOU. In MG-63 cells, MOU has increased the proliferation of osteoblast cells and ALP activity, thereby increasing bone mineralization. ELISA results showed increased levels of osteogenic markers such as osteocalcin and osteopontin in the culture media. Western blot analysis showed inhibition of GSK3β protein expression and increased the expression levels of β-catenin, Runx-2, col 1 and osterix, promoting osteoblast differentiation. In RANKL-stimulated RAW 264.7 cells, MOU did not elicit any significant cytotoxicity; instead, it suppressed the osteoclastogenesis reducing the osteoclast number. MOU has reduced TRAP activity in a dose-dependent manner. MOU inhibited the TRAF6, NFATc1, c-Jun, C-fos and cathepsin K expression, thereby inhibiting osteoclast formation.

CONCLUSION

In conclusion, MOU promoted osteoblast differentiation via inhibiting GSK3β and activating Wnt/β catenin signalling and its transcription factors, including β catenin, Runx2 and Osterix. Similarly, MOU inhibited osteoclast formation by inhibiting the expression of TRAF6, NFATc1, c-Jun, C-fos and cathepsin K in RANK-RANKL signalling. Finally, it can be emphasised that O.umbellata is a potential source of therapeutic leads for the treatment of osteoporosis.

Flavonoids from Dalbergia cochinchinensis: Impact on osteoclastogenesis

Background/purpose

Dalbergia cochinchinensi has been widely used in traditional medicine because of its flavonoids. This study examined which components in D. cochinchinensis were capable of reducing or even stimulating the formation of bone-resorbing osteoclasts.

Materials and methods

We have isolated subfamilies of chalcones (isoliquiritigenin, butein), flavones (7-hydroxy-6-methoxyflavone) and neoflavanoids (5-methoxylatifolin), and performed an in vitro bioassay on osteoclastogenesis. The flavonoids were tested for their potential to change the expression of tartrate-resistant acid phosphatase (TRAP) and cathepsin K (CTSK) in murine bone marrow cultures being exposed to RANKL, M-CSF and TGF-β1 using RT-PCR, histochemistry and immunoassay.

Results

We could confirm that isoliquiritigenin and butein significantly lower the expression of TRAP and CTSK in this setting. Moreover, histochemistry supported the decrease of TRAP by the chalcones. We further observed a trend towards an increase of osteoclastogenesis in the presence of 5-methoxylatifolin and 7-hydroxy-6-methoxyflavone, particular in bone marrow cultures being exposed to RANKL and M-CSF. Consistently, the anti-inflammatory activity was restricted to isoliquiritigenin and butein in murine RAW 264.7 inflammatory macrophages stimulated by lipopolysaccharide (LPS). With respect to osteoblastogenesis, neither of the flavonoids but butyrate, a short chain fatty acid, increased the osteogenic differentiation marker alkaline phosphatase activity in ST2 murine mesenchymal cells.

Conclusion

We have identified two flavonoids from D. cochinchinensis with a potential pro-osteoclastogenic activity and confirm the anti-osteoclastogenic activity of isoliquiritigenin and butein.

Lipopolysaccharide-Induced Bone Loss in Rodent Models: A Systematic Review and Meta-Analysis

Osteoporosis has traditionally been characterized by underlying endocrine mechanisms, though evidence indicates a role of inflammation in its pathophysiology. Lipopolysaccharide (LPS), a component of gram-negative bacteria that reside in the intestines, can be released into circulation and stimulate the immune system, upregulating bone resorption. Exogenous LPS is used in rodent models to study the effect of systemic inflammation on bone, and to date a variety of different doses, routes, and durations of LPS administration have been used. The study objective was to determine whether systemic administration of LPS induced inflammatory bone loss in rodent models. A systematic search of Medline and four other databases resulted in a total of 110 studies that met the inclusion criteria. Pooled standardized mean differences (SMDs) and corresponding 95% confidence intervals (CI) with a random-effects meta-analyses were used for bone volume fraction (BV/TV) and volumetric bone mineral density (vBMD). Heterogeneity was quantified using the I² statistic. Shorter-term (<2 weeks) and longer-term (>2 weeks) LPS interventions were analyzed separately because of intractable study design differences. BV/TV was significantly reduced in both shorter-term (SMD = -3.79%, 95% CI [-4.20, -3.38], I² 62%; p < 0.01) and longer-term (SMD = -1.50%, 95% CI [-2.00, -1.00], I² 78%; p < 0.01) studies. vBMD was also reduced in both shorter-term (SMD = -3.11%, 95% CI [-3.78, -2.44]; I² 72%; p < 0.01) and longer-term (SMD = -3.49%, 95% CI [-4.94, -2.04], I² 82%; p < 0.01) studies. In both groups, regardless of duration, LPS negatively impacted trabecular bone structure but not cortical bone structure, and an upregulation in bone resorption demonstrated by bone cell staining and serum biomarkers was reported. This suggests systemically delivered exogenous LPS in rodents is a viable model for studying inflammatory bone loss, particularly in trabecular bone. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Molecular action of larvicidal flavonoids on ecdysteroidogenic glutathione S-transferase Noppera-bo in Aedes aegypti

Background

Mosquito control is a crucial global issue for protecting the human community from mosquito-borne diseases. There is an urgent need for the development of selective and safe reagents for mosquito control. Flavonoids, a group of chemical substances with variable phenolic structures, such as daidzein, have been suggested as potential mosquito larvicides with less risk to the environment. However, the mode of mosquito larvicidal action of flavonoids has not been elucidated.

Results

Here, we report that several flavonoids, including daidzein, inhibit the activity of glutathione S-transferase Noppera-bo (Nobo), an enzyme used for the biosynthesis of the insect steroid hormone ecdysone, in the yellow fever mosquito Aedes aegypti. The crystal structure of the Nobo protein of Ae. aegypti (AeNobo) complexed with the flavonoids and its molecular dynamics simulation revealed that Glu113 forms a hydrogen bond with the flavonoid inhibitors. Consistent with this observation, substitution of Glu113 with Ala drastically reduced the inhibitory activity of the flavonoids against AeNobo. Among the identified flavonoid-type inhibitors, desmethylglycitein (4′,6,7-trihydroxyisoflavone) exhibited the highest inhibitory activity in vitro. Moreover, the inhibitory activities of the flavonoids correlated with the larvicidal activity, as desmethylglycitein suppressed Ae. aegypti larval development more efficiently than daidzein.

Conclusion

Our study demonstrates the mode of action of flavonoids on the Ae. aegypti Nobo protein at the atomic, enzymatic, and organismal levels.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-022-01233-2.

Heartwood of Dalbergia cochinchinensis: 4,7,2'-Trihydroxy-4'-methoxyisoflavanol and 6,4'-Dihydroxy-7-methoxyflavane Reduce Cytokine and Chemokine Expression In Vitro

Dalbergia cochinchinensis has been widely used in traditional medicine because of its flavonoids; however, the impact of the flavonoids to modulate the inflammatory response to oral cells remains to be described. For this aim, we isolated 4,7,2'-trihydroxy-4'-methoxyisoflavanol (472T4MIF) and 6,4'-dihydroxy-7-methoxyflavane (64D7MF) from the heartwood of D. cochinchinensis and confirmed the chemical structure by nuclear magnetic resonance. We show here that both flavonoids are inhibitors of an inflammatory response of murine RAW 264.7 inflammatory macrophages stimulated by LPS. This is indicated by interleukin (IL)1, IL6, and chemokine CCL2 production besides the phosphorylation of p65. Consistently, in primary murine macrophages, both flavonoids decreased the inflammatory response by lowering LPS-induced IL1 and IL6 expression. To introduce oral cells, we have used human gingival fibroblasts and provoked the inflammatory response by exposing them to IL1β and TNFα. Under these conditions, 472T4MIF, but not 64D7MF, reduced the expression of chemokines CXCL1 and CXCL2. Taken together, we identified two flavonoids that can reduce the expression of cytokines and chemokines in macrophages and fibroblastic cells.

The Hypolipidemic Effect of Dalbergia odorifera T. C. Chen Leaf Extract on Hyperlipidemic Rats and Its Mechanism Investigation Based on Network Pharmacology

Objective

The aim of this study was to explore the hypolipidemic effect and mechanism of Dalbergia odorifera T. C. Chen leaf extract.

Methods

The hypolipidemic effect of D. odorifera leaf extract was investigated using a hyperlipidemic rat model. Then, its mechanism was predicted using network pharmacology methods and verified using western blotting.

Results

Compared with the levels in the model group, the serum levels of triglyceride (TG), total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C) decreased significantly, whereas the serum level of high-density lipoprotein cholesterol (HDL-C) increased dramatically after treatment with the extract. The degrees of hepatocyte steatosis and inflammatory infiltration were markedly attenuated in vivo. Then, its hyperlipidemic mechanism was predicted using network pharmacology-based analysis. Thirty-five key targets, including sterol regulatory element-binding protein cleavage-activating protein (SCAP), sterol regulatory element-binding protein-2 (SREBP-2), 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR), low-density lipoprotein receptor (LDLR), and ten signaling pathways, were associated with hyperlipidemia. Finally, it was verified that the extract downregulated the protein levels of SCAP, SREBP-2, and HMGCR, and upregulated protein levels of LDLR.

Conclusion

These findings provided additional evidence of the hypolipidemic effect of D. odorifera leaf extract.

6,7,4'-Trihydroxyflavanone Mitigates Methamphetamine-Induced Neurotoxicity in SH-SY5y Cells via Nrf2/heme Oxyganase-1 and PI3K/Akt/mTOR Signaling Pathways

Methamphetamine (METH) is a synthetic psychostimulant drug that has detrimental effects on the health of its users. Although it has been investigated as a cause of neurodegenerative disease due to its neurotoxicity, whether small molecules derived from natural products attenuate these side effects remains elusive. 6,7,4'-trihydroxyflavanone (THF) is a flavanone family that possesses various pharmacological activities, including anti-rheumatic, anti-ischemic, anti-inflammatory, anti-osteoclastogenic, and protective effects against METH-induced deactivation of T cells. However, little is known about whether THF protects neuronal cells from METH-induced neurotoxicity. Here, we investigated the protective effects of THF on neurotoxicity induced by METH exposure by enhancing the Nrf2/HO-1 and PI3K/Akt/mTOR signaling pathways in SH-SY5y cells. Treatment with THF did not lead to cytotoxicity, but attenuated METH-induced neurotoxicity by modulating the expression of apoptosis-related proteins, METH-induced oxidative stress, and PI3K/Akt/mTOR phosphorylation in METH-exposed SH-SY5y cells. Moreover, we found THF induced Nrf2 nuclear translocation and HO-1 expression. An inhibitor assay confirmed that the induction of HO-1 by THF attenuates METH-induced neurotoxicity. Therefore, we suggest that THF preserves neuronal cells from METH-induced neurotoxicity by upregulating HO-1 expression through the Nrf2 and PI3K/Akt/mTOR signaling pathways. Thus, THF has therapeutic potential for use in the treatment of METH-addicts suffering from neurodegenerative diseases.

(-)-Epigallocatechin-3-gallate inhibits osteoclastogenesis by blocking RANKL-RANK interaction and suppressing NF-κB and MAPK signaling pathways

Consuming green tea has many health benefits, including regulating bone metabolism and ameliorating osteoporosis, mainly in older and postmenopausal women. This osteoprotective effect has been attributed to the biologically active polyphenol (-)-epigallocatechin-3-gallate (EGCG). Although EGCG inhibits osteoclastogenesis, its underlying molecular mechanism remains to be elucidated. Interaction between receptor activator of nuclear factor (NF)-κB ligand (RANKL) and RANK plays critical roles in the differentiation and activation of osteoclasts and is therefore considered a therapeutic target for osteoclast-related diseases such as osteoporosis. In the present study, we found that EGCG can bind directly to RANK and RANKL and interfere with their interaction, thereby suppressing RANKL-induced phosphorylation of IKKα/β, IκBα, p65, JNK, ERK1/2, and p38 and key downstream regulatory factors, including nuclear factor of activated T cell c1 (NFATc1), c-Fos, tartrate-resistant acid phosphatase (TRAP), c-Src, and cathepsin K, in osteoclast precursors. This can ultimately inhibit osteoclastogenesis. Taken together, our results show that EGCG can bind directly to RANK and RANKL and block their interaction and that, by inhibiting NF-κB and mitogen-activated protein kinase (MAPK) signaling pathways, it negatively regulates RANKL-induced osteoclastogenesis in RAW 264.7 cells. Thus, regular consumption of EGCG in green tea can inhibit the development and progression of osteoclast-related diseases.

Protective Effects of 6,7,4'-Trihydroxyflavanone on Hypoxia-Induced Neurotoxicity by Enhancement of HO-1 through Nrf2 Signaling Pathway

Since hypoxia-induced neurotoxicity is one of the major causes of neurodegenerative disorders, including the Alzheimer’s disease, continuous efforts to find a novel antioxidant from natural products are required for public health. 6,7,4′-trihydroxyflavanone (THF), isolated from Dalbergia odorifera, has been shown to inhibit osteoclast formation and have an antibacterial activity. However, no evidence has reported whether THF has a protective role against hypoxia-induced neurotoxicity. In this study, we found that THF is not cytotoxic, but pre-treatment with THF has a cytoprotective effect on CoCl₂-induced hypoxia by restoring the expression of anti-apoptotic proteins in SH-SY5y cells. In addition, pre-treatment with THF suppressed CoCl₂-induced hypoxia-related genes including HIF1α, p53, VEGF, and GLUT1 at the mRNA and protein levels. Pre-treatment with THF also attenuated the oxidative stress occurred by CoCl₂-induced hypoxia by preserving antioxidant proteins, including SOD and CAT. We revealed that treatment with THF promotes HO-1 expression through Nrf2 nuclear translocation. An inhibitor assay using tin protoporphyrin IX (SnPP) confirmed that the enhancement of HO-1 by pre-treatment with THF protects SH-SY5y cells from CoCl₂-induced neurotoxicity under hypoxic conditions. Our results demonstrate the advantageous effects of THF against hypoxia-induced neurotoxicity through the HO-1/Nrf2 signaling pathway and provide a therapeutic insight for neurodegenerative disorders.

6,7,4'-Trihydroxyflavanone Protects against Dextran Sulfate Sodium-Induced Colitis by Regulating the Activity of T Cells and Colon Cells In Vivo

Colitis is a multifactorial disorder that mostly occurs in the gastrointestinal tract. Despite improvements in mucosal inflammation research, little is known regarding the small bioactive molecules that are beneficial for regulating T cells and colon cell activity. 6,7,4'-trihydroxyflavanone (THF) is a flavanone that possesses anti-osteoclastogenesis activity and exerts protective effects against methamphetamine-induced immunotoxicity. Whether THF mitigates intestinal inflammation by regulating T cells and colon cell activity remains unknown. In the present study, Jurkat and HT-29 cells were used for in vitro experiments, and dextran sulfate sodium (DSS)-induced colitis model in mice was used for in vivo experiment. We observed that THF did not have a negative effect on the viability of Jurkat and HT-29 cells. Quantitative PCR and Western blot analysis revealed that THF regulates the activity of Jurkat cells and HT-29 cells via the NFκB and MAPK pathways under stimulated conditions. In the DSS-induced colitis model, oral administration of THF attenuated the manifestations of DSS-induced colitis, including a reduction in body weight, shrinkage of the colon, and enhanced expression of pro-inflammatory cytokines in the colon and mesenteric lymph nodes. These data suggest that THF alleviates DSS-induced colitis by modulating the activity of T cells and colon cells in vivo.

6,7,4[Formula: see text]-Trihydroxyflavanone Prevents Methamphetamine-Induced T Cell Deactivation by Protecting the Activated T Cells from Apoptosis

Methamphetamine (METH) is an extremely addictive drug that has raised serious public health concerns recently. METH addiction not only results in neuronal cytotoxicity, but it also affects immune cell activity, including T lymphocytes. 6,4,7[Formula: see text]-trihydroxyflavanone (THF), isolated from Dalbergia odorifera, has been studied for its antibacterial activity, but evidence for whether THF has an anti-cytotoxic and protective effect on T cell activation exposed to METH is lacking. In this study, results showed that treatment with THF was not cytotoxic to Jurkat T cells but dose-dependently mitigated the cytotoxicity induced by exposure to METH. The Western blot results demonstrating pre-treatment with THF maintained the expression of anti-apoptotic proteins and phosphorylation of PI3K/Akt/mTOR downregulated by treatment with METH. Furthermore, we found that decreased expression of IL-2 and CD69 by METH exposure was partially restored, and viability was significantly prevented by pre-treatment with THF in activated T cells. These findings were involved in re-elevated expression of anti-apoptotic proteins as well as recovered pathways including MAPK/PI3K/Akt/mTOR in activated T cells pre-exposed to METH. Our results suggest beneficial effects of THF against the cytotoxic and immune-modulating effect of METH on T cells and therapeutic potential of THF for patients with immunodeficiency caused by METH addiction.

Liraglutide, a glucagon-like peptide-1 receptor agonist, suppresses osteoclastogenesis through the inhibition of NF-κB and MAPK pathways via GLP-1R

Bone disorders such as osteoporosis, Paget's disease of the bone, osteogenesis imperfecta, are caused by the uncoordinated action of osteoclasts and osteoblasts. Inhibiting osteoclastogenesis and suppressing the resorptive function of osteoclasts might become a gold standard strategy for treating this kind of disease. Glucagon-like peptide-1 (GLP-1) and its receptor agonist have been reported to have protective effects on bone. Little is known about the effect of GLP-1 on osteoclasts. Therefore, we investigated the effects of liraglutide, a GLP-1 receptor agonist, on murine bone marrow-derived macrophage (BMM) and RAW264.7 preosteoclast differentiation and explored the potential cellular basis of its action. In this study, we confirmed the presence of GLP-1 receptor (GLP-1R) on BMMs and RAW264.7 cells and demonstrated that GLP-1R might be important for osteoclastogenesis by increasing the expression of osteoclastogenic biomarkers after GLP-1R knockdown. In addition, we found that liraglutide treatment of both BMMs and RAW264.7 cells could inhibit osteoclast formation and bone resorption. Mechanistically, Western blotting and RT-PCR showed that liraglutide inhibited the NF-κB and MAPK signalling pathways, ultimately inhibiting the expression of nuclear factor of activated T cells (NFATc1). In addition, knocking down GLP-1R reversed the inhibitory effect of liraglutide on NF-κB/MAPK-NFATc1. Overall, these results indicated a potential therapeutic effect of liraglutide on bone disorders.

Thermosensitive nanoparticle of mPEG-PTMC for oligopeptide delivery into osteoclast precursors

Transmembrane delivery of biomolecules through nanoparticles plays an important role in targeted therapy. Here, we designed a simple nanoparticle for the delivery of model peptide drug into primary osteoclast precursor cells (bone marrow macrophages) by thermosensitive and biodegradable diblock copolymer monomethoxy poly(ethylene glycol)-block-poly(trimethylene carbonate). The model peptide drug was encapsulated into the nanoparticle by dropping the drug carrier dissolved in dimethylsulfoxide solvent into water containing poly(vinyl alcohol) to achieve temperature response nanoparticles. Through size analysis, we found that the nanoparticles possessed a temperature-sensitive property between 30°C and 40°C. Moreover, flow cytometry and spectrofluorimetry analysis indicated that nanoparticle systems underwent significant cellular uptake. In addition, the evaluation of cell biology showed that nanoparticles have excellent biocompatibility. Thus, the results indicated that the temperature-sensitive nanoparticles have potential application value for targeted delivery of oligopeptide in the treatment process of osteoarthritis.