Objective To investigate the effect of temperature on cell proliferation and osteogenic differentiation inhibition of preosteoblast induced by hydrogen peroxide(H2 O2).Methods The MC3T3-E1 cells in the logarithmic phase were randomly divided into 0,450,500,550,600,650 μmol·L-1 H2O2 intervention groups and incubated with 0,450,500,550,600,650 μmol·L-1 H2O2 for 2 h,respectively.Other MC3T3-E1 cells in the logarithmic phase were selected and randomly divided into the control group,model group,low-temperature group,and high-temperature group.Cells in the control group were cul-tured in an incubator with 5％CO2 for 24 h at 37 ℃;cells in the model group were incubated with H2O2 for 2 h and cultured in an incubator with 5％CO2 for 24 h at 37 ℃;cells in the low-temperature group were incubated with H2O2 for 2 h and cultured in an incubator with 5％CO2 for 24 h at 32 ℃;cells in the high-temperature group were incubated with H2O2 for 2 h and cultured in an incubator with 5％CO2 for 24 h at 40 ℃.The cell proliferation in all groups was detected by cell counting kit-8.The expression levels of Runt-related transcription factor 2(RUNX2),osteopontin(OPN)and osteocalcin(OC)mRNA were detected by real-time fluorescence quantitave polymerase chain reaction;and the expression levels of RUNX2,OPN and OC protein were detected by Western blot.Results There was no statistically significant difference in cell proliferation among the 0,450 and 500 μmol·L-1 H2O2 intervention groups(P＞0.05);the cell proliferation rate in the 550,600 and 650 μmol·L-1 H2O2 intervention groups was significantly lower than that in the 0,450 and 500 μmol·L-1 H2O2 intervention groups,showing a significant decrease in cell proliferation with the increase of H2O2 concentrations(P＜0.05).In order to ensure that there were enough cells to perform the following experiments,550 μmol·L-1 H2 O2 was chosen.The cell proliferation rate in the model group and the low-temperature group was significantly lower than that in the control group and high-temperature group(P＜0.05);there was no significant difference in the cell proliferation rate between the control group and high-temperature group(P＞0.05).The relative expression of RUNX2 mRNA in the model group and high-temperature group were significantly higher than that in the control group and low-temperature group(P＜0.05);the relative expression of RUNX2 mRNA in the low-temperature group was significantly lower than that in the control group(P＜0.05);there was no significant difference in the relative expression of RUNX2 mRNA between the model group and high-temperature group(P＞0.05).The relative expression of OPN mRNA in the model group,low-temperature group and high-temperature group was significantly higher than that in the control group(P＜0.05);the relative expression of OPN mRNA in the low-temperature group and high-temperature group was significantly higher than that in the model group(P＜0.05);the relative expression of OPN mRNA in the low-tem-perature group was significantly higher than that in the high-temperature group(P＜0.05).The relative expression of OC mRNA in the model group,low-temperature group and high-temperature group was significantly than that in the control group(P＜0.05);the relative expression of OC mRNA in the low-temperature group and high-temperature group was significantly higher than that in the model group(P＜0.05);there was no significant difference in the relative expression of OC mRNA between the low-temperature group and high-temperature group(P＞0.05).The relative expressions of RUNX2,OPN and OC protein the model group,low-temperature group and high-temperature group were significantly lower than those in the control group(P＜0.05);the relative expressions of RUNX2 and OPN protein in the low-temperature group were significantly lower than those in the model group and high-temperature group(P＜0.05);the relative expression of OC protein was significantly lower than that in the high-temperature group(P＜0.05);and there was no siqnificantly difference in the relatiwe experesson of OC protein between the low-temperature group and model group(P＞0.05);the relative expressions of RUNX2,OPN and OC protein in the high-temperature group were significantly higher than those in the model group(P＜0.05).Conclusion The inhibitory effects of H2O2 on cell proliferation and osteogenic differentiation are observed in MC3T3-E1 cells;low-tempera-ture incubation can enhance the inhibition of H2O2 on cell proliferation and osteogenic differentiation in MC3T3-E1 cells,while high-temperature incubation can relieve its inhibitory effect on cell proliferation and osteogenic differentiation.RUNX2,OPN and OC protein might play an important role in cell proliferation and osteogenic differentiation mediated by temperature.

Ferroptosis (FPT), a novel form of programmed cell death, is characterized by overwhelming iron/reactive oxygen species (ROS)-dependent accumulation of lipid peroxidation (LPO). However, the insufficiency of endogenous iron and ROS level limited the FPT therapeutic efficacy to a large extent. To overcome this obstacle, the bromodomain-containing protein 4 (BRD₄)-inhibitor (+)-JQ1 (JQ1) and iron-supplement ferric ammonium citrate (FAC)-loaded gold nanorods (GNRs) are encapsulated into the zeolitic imidazolate framework-8 (ZIF-8) to form matchbox-like GNRs@JF/ZIF-8 for the amplified FPT therapy. The existence of matchbox (ZIF-8) is stable in physiologically neutral conditions but degradable in acidic environment, which could prevent the loaded agents from prematurely reacting. Moreover, GNRs as the drug-carriers induce the photothermal therapy (PTT) effect under the irradiation of near-infrared II (NIR-II) light owing to the absorption by localized surface plasmon resonance (LSPR), while the hyperthermia also boosts the JQ1 and FAC releasing in the tumor microenvironment (TME). On one hand, the FAC-induced Fenton/Fenton-like reactions in TME can simultaneously generate iron (Fe³⁺/Fe²⁺) and ROS to initiate the FPT treatment by LPO elevation. On the other hand, JQ1 as a small molecule inhibitor of BRD₄ protein can amplify FPT through downregulating the expression of glutathione peroxidase 4 (GPX4), thus inhibiting the ROS elimination and leading to the LPO accumulation. Both in vitro and in vivo studies reveal that this pH-sensitive nano-matchbox achieves obvious suppression of tumor growth with good biosafety and biocompatibility. As a result, our study points out a PTT combined iron-based/BRD₄-downregulated strategy for amplified ferrotherapy which also opens the door of future exploitation of ferrotherapy systems.