Fig. 7

Blockage of NRF2 partially abolished the protective effects of psoralen on radiation-induced osteoporosis in mice. A specific chemical inhibitor of NRF2 (ML385, 30 mg/Kg) was intraperitoneally injected 1 h before psoralen treatment. The microCT images and quantitative data demonstrated that the protective effects of psoralen on bone structure were remarkably impaired in the ML385 administration groups (a and b). The results of the calcein double-labeling analysis showed that blockade of NRF2 significantly abolished psoralen-mediated new bone formation in irradiated mice (c and d). The HE staining data showed that ML385 remarkably blunted the rescue and prevented the effects of psoralen on the bone structure of irradiated mice (e). OCN staining data showed that ML385 blunted the restorative effects of psoralen on osteoblasts in irradiated mice (f and g). The serum TRAP ELISA data further validated the blunting of ML385 on the therapeutic effects of psoralen on irradiation-induced osteoporosis (h). Gene expression analysis of OCN in femur bones indicated that ML385 led to a turnover of the promotion of bone formation and suppression on bone resorption by psoralen. (i). All data are shown as the mean ± SD. **P < 0.01, *P < 0.05. The scale bars represent 2 mm (a and c), 500 μm (e), and 200 μm (f), respectively. IR: irradiation; BV/TV: bone volume per tissue volume; Tb.N: trabecular bone number; Tb.Sp: trabecular separation; Tb.Th: trabecular bone thickness; BFR: bone formation rate; MAR: mineral deposition rate; TRAP: tartrate-resistant acid phosphatase; OCN: osteocalcin; TRAF6: TNF receptor-associated factor 6; Ob.S/B.S: osteoblast surface per bone surface; Ob.N/B.Pm: number of osteoblasts per bone perimeter; Oc.S/B.S: osteoclast surface per bone surface; and Oc.N/B.Pm: number of osteoclasts per bone perimeter