Pinoresinol promotes MC3T3-E1 cell proliferation and differentiation via the cyclic AMP/protein kinase A signaling pathway

Estradiol (E2) is a first-line drug for osteoporosis (OP) treatment via promotion of osteoblastic proliferation and differentiation. However, a long-term use of E2 would produce side effects thus, it is imperative to discover safer and more effective drugs. Pinoresinol (PINO) has a similar chemical structure to E2. The present study aimed to investigate whether PINO could promote osteoblastic proliferation and differentiation and the potential mechanisms. After treatment with 0.1 µg/l PINO for 2 days, MC3T3-E1 cell migration was assessed by wound healing assay. Estrogen (E2) treatment served as a positive control. RT-qPCR and western blotting were used for mRNA and protein expression analyses. Alkaline phosphatase (ALP) activity assay and Alizarin red staining were performed to investigate the calcification and mineralization, and the cyclic AMP (cAMP) level was detected by enzyme-linked immunosorbent assay (ELISA). H89, an inhibitor of protein kinase A (PKA), was introduced to verify the role of cAMP/PKA in the effect of PINO on MC3T3-E1 cells. Cell viability was the highest under 48 h of 0.1 µg/l PINO treatment. After treatment with PINO, a significant increase was observed in the migration rate and the expression of collagen type I (Col-I), ALP, osteopontin (OPN), runt-related transcription factor 2 (Runx2) and bone morphogenetic protein-2 (BMP-2) (P<0.01). The ALP activity and Alizarin red size in PINO and E2 groups were notably increased. The increased cAMP, PKA and phosphorylated cAMP response element-binding protein (CREB) levels were also observed in the PINO group. Furthermore, H89 co-treatment abolished the positive effects of PINO on cell viability and migration. PINO had similar effects to E2 on the osteoblastic proliferation and differentiation, and these positive effects may be attributed to the regulation of the cAMP/PKA signaling pathway.