(2 R ,3 S )-Pinobanksin-3-cinnamate promotes osteoblast differentiation through cAMP and cGMP pathways

Flavones have the potential of being used as a dietary supplement for bone health promotion beyond calcium and vitamin D. Recent studies have showed that flavones enhanced bone formation and inhibited bone resorption by affecting osteoblast and osteoclast differentiation through various cell signaling pathways. In this study, we investigated the effects of a new flavone (2R,3S)-pinobanksin-3-cinnamate, isolated from the metabolites of the endophytic fungus Penicillium sp. FJ-1 of Acanthus ilicifolius L., Acanthaceae, on osteoblast differentiation by using MC3T3-E1 cells. It was observed that (2R,3S)-pinobanksin-3-cinnamate promoted osteoblast differentiation, as evidenced by increased mineralization process and alkaline phosphatase activity, as well as expression of genes encoding the bone differentiation. Moreover (2R,3S)-pinobanksin-3-cinnamate treatment upregulated the gene expression of wingless-type MMTV integration site family, bone morphogenetic protein and runt-related transcription factor 2, and protein expression of phosphor-Smad1/5/8, β-catenin and runt-related transcription factor 2 in MC3T3-E1 cells. The osteoblast differentiation effects induced by (2R,3S)-pinobanksin-3-cinnamate were attenuated by the bone morphogenetic protein antagonist Noggin, and wingless-type MMTV integration site family signaling pathway inhibitors Dickkopf-1. Co-treatment with adenosine 30,50-cyclic monophosphate and guanosine 30,50-cyclic monophosphate pathway inhibitors, H89 and KT5823, respectively, reversed the (2R,3S)-pinobanksin-3-cinnamate-induced activations of p-Smad1/5/8, β-catenin, and runt-related transcription factor 2. Our data demonstrated that (2R,3S)-pinobanksin-3-cinnamate promoted the osteoblast differentiation of MC3T3-E1 cells, at least partially through the adenosine 30,50-cyclic monophosphate and guanosine 30,50-cyclic monophosphate signaling pathways, providing the scientific rational to develop (2R,3S)-pinobanksin-3-cinnamate against bone loss-associated diseases. Keywords: (2R ;3S)-pinobanksin-3-cinnamate, Osteoblast differentiation, MC3T3-E1 cells, cAMP, cGMP