N-methyl pyrrolidone (NMP) ameliorates the hypoxia-reduced osteoblast differentiation via inhibiting the NF-κB signaling

Abstract

Ischemic-hypoxic condition for local osteoblasts and bone mesenchymal stem cells during bone fracture inhibits bone repairing. N-methyl pyrrolidone (NMP) has been approved as a safe and biologically inactive small chemical molecule, and might be useful for bone fracture repairing. In the present study, we investigated the effect of NMP on the hypoxia-reduced cellular viability and the expression of differentiation-associated markers, such as bone morphogenetic protein 2 (BMP-2), propeptide of type I procollagen I (PINP), alkaline phosphatase (ALP) or runt-related transcription factor 2 (Runx2) in the osteoblasts, and then we examined the molecular mechanism underlining such effect in the human osteoblastic hFOB 1.19 cells. Our results demonstrated that NMP significantly blocked the hypoxia-induced cell viability reduction and inhibited the hypoxia-caused expression downregulation of BMP-2, PINP, ALP and Runx2 in hFOB 1.19 cells. Then we confirmed the involvement of nuclear factor κB (NF-κB) pathway in the regulation by NMP on the hypoxia-mediated the reduction of osteoblast differentiation. The upregulated expression and transcriptional activity of NF-κB, while the downregulated inhibitory κB expression by the hypoxia treatment was reversed by the treatment with 10 mM NMP. In conclusion, our study found a protective role of NMP in osteoblast differentiation in response to hypoxia, and such protection was through inhibiting the NF-κB signaling. This suggests that NMP might be a protective agent in bone fracture repairing.