Irradiation Effect on Osteoblast and Osteoclast in vitro with Metalloporphyrin

Objective: The worst long-term complication of head and neck cancer radiotherapy is osteoradionecrosis. The cellular and molecular mechanisms involved in osteoradionecrosis are caused by dysregulation of bone healing, such as deficient osteoblasts and osteoclasts, amplified by a cascade of cytokine activities via chronic oxidative stress, leading to abnormal reactive oxygen species (ROS). Metalloporphyrins (MnTE-2-PyP) have emerged as being especially promising due to their distinct antioxidant properties. The aim of this study was to investigate the irradiation effect on osteoblast and osteoclast in vitro with administration of metalloporphyrin antioxidants.

Method: Osteoblast (MC3T3-E1) and osteoclast (RAW264.7) cell lines were used. MnTE-2-PyP was added (10 μg/ml) into the cell cultures 1 hr before irradiation. MC3T3-E1 and RAW cells were then exposed to gamma-ray irradiation at total doses of 0, 2, 4, 6, 8 and 10 Gy. Cell viability and caspase 3/7 activation (apoptosis) were tested by ApoLive-Glo™ Multiplex Assay (Promega). The GSH-Glo™ Glutathione Assay (Promega) was used for the quantification of glutathione (GSH) as an indicator of toxicological responses or oxidative stress. Cell assays were performed 48h post-irradiation to test the effect of MnTE-2-PyP with and without radiation on cells.

Result: For cell viability, MnTE-2-PyP significantly decreased radiation damage on MC3T3-E1 and RAW cells at all doses (P<0.05). On the contrary, caspase3/7 apoptosis levels were significantly decreased in irradiated cells treated with MnTE-2-PyP than their counterparts without MnTE-2-PyP (P<0.05). In addition, the oxidative stress indicated by GSH level were significantly lowered in MnTE-2-PyP -treated cells at all the radiation doses (P<0.05).

Conclusion: MnTE-2-PyP might protect osteoblast and osteoclast during radiotherapy via decreasing the oxidative stress and apoptosis in vital cell organelles.