Bisphosphonates (BPs) are widely used for the prevention and treatment of
osteoporosis. However, there have been numerous reports of side effects of BPs, including
osteonecrosis of the jaw. In the present study, we investigated whether
hypoxia inhibits BP-induced apoptosis, and examined the mechanisms of this inhibition. The cell viability of the MG 63 human osteoblast-like cell line treated with the
nitrogen-containing (N)-BPs
alendronate,
risedronate and
zoledronate was investigated, and
hypoxia was assessed by
crystal violet staining and the MTT assay, and by observing cell morphology. The effect of N-BPs and
hypoxia on apoptotic cell signaling was evaluated using Western blotting, immunocytochemistry and the TUNEL assay. The results of
crystal violet staining and the MTT and TUNEL assays showed that the N-BPs inhibited proliferation and induced apoptosis in MG 63 cells.
Hypoxia significantly prevented N-BP-induced MG 63 cell apoptosis, and also attenuated BP-induced
c-Jun N-terminal kinase (JNK) phosphorylation and BCL-xL reduction.
Hypoxia prevented BP-induced cell damage by blocking JNK phosphorylation and by regulating the
BCL-xL protein. Thus,
hypoxia or
hypoxia-related genes, including
hypoxia-inducible factor 1α, may be a potential
therapy for BP-related side effects such as
osteonecrosis of the jaw.