Isoliquiritigenin Decreases Bone Resorption and Osteoclast Differentiation

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.

A mechanistic review of chinese medicine polyphenols on bone formation and resorption

Bone reconstruction includes a steady state system of bone formation and bone absorption. This tight coupling requires subtle coordination between osteoblasts and osteoclasts. If this balance is broken, it will lead to bone mass loss, bone density reduction, and bone metabolic diseases, such as osteoporosis. Polyphenols in Chinese herbal medicines are active ingredients in plant extracts with high safety and few side effects, and they can play a role in affecting bone formation and bone resorption. Some of these have estrogen-like effects and can better target bone health in postmenopausal women. The purpose of this review is to provide comprehensive information on the mechanisms underlying the relationship between traditional Chinese medicine polyphenols and bone formation or bone resorption.