Anthocyanin-enriched polyphenols from Hibiscus syriacus exert anti-osteoporosis effects. - GreenMedInfo Summary
Anthocyanin-enriched polyphenols from Hibiscus syriacus L. (Malvaceae) exert anti-osteoporosis effects by inhibiting GSK-3β and subsequently activating β-catenin.
Phytomedicine. 2021 Oct ;91:153721. Epub 2021 Aug 17. PMID: 34461423
Wisurumuni Arachchilage Hasitha Maduranga Karunarathne
BACKGROUND: The bark and petal of Hibiscus syriacus L. (Malvaceae) have been used to relieve pain in traditional Korean medicine. Recently, we identified anthocyanin-enriched polyphenols from the petal of H. syriacus L. (AHs) and determined its anti-melanogenic, anti-inflammatory, and anti-oxidative properties. Nevertheless, the osteogenic potential of AHs remains unknown.
PURPOSE: This study was aimed to investigating the effect of AHs on osteoblast differentiation and osteogenesis in osteoblastic cell lines and zebrafish larvae. Furthermore, we investigated whether AHs ameliorates prednisolone (PDS)-induced osteoporosis.
STUDY DESIGN AND METHODS: Cell viability was assessed by cellular morphology, MTT assay, and flow cytometry analysis, and osteoblast differentiation was measured alizarin red staining, alkaline phosphatase (ALP) activity, and osteoblast-specific marker expression. Osteogenic and anti-osteoporotic effects of AHs were determined in zebrafish larvae.
RESULTS: AHs enhanced calcification and ALP activity concomitant with the increased expression of osterix (OSX), runt-related transcription factor 2 (RUNX2), and ALP in MC3T3-E1 preosteoblast and MG-63 osteosarcoma cells. Additionally, AHs accelerated vertebral formation and mineralization in zebrafish larvae, concurrent with the increased expression of OSX, RUNX2a, and ALP. Furthermore, PDS-induced loss of osteogenic activity and vertebral formation were restored by treatment with AHs, accompanied by a significant recovery of calcification, ALP activity, and osteogenic marker expression. Molecular docking studies showed that 16 components in AHs fit to glucagon synthase kinase-3β (GSK-3β); particularly, isovitexin-4'-O-glucoside most strongly binds to the peptide backbone of GSK-3β at GLY47(O), GLY47(N), and ASN361(O), with a binding score of -7.3. Subsequently, AHs phosphorylated GSK-3β at SER9 (an inactive form) and released β-catenin into the nucleus. Pretreatmentwith FH535, a Wnt/β-catenin inhibitor, significantly inhibited AH-induced vertebral formation in zebrafish larvae.
CONCLUSION: AHs stimulate osteogenic activities through the inhibition of GSK-3β and subsequent activation of β-catenin, leading to anti-osteoporosis effects.