The medium was changed every 3 d. Cell NVP-BGJ398 mouse viability was assessed by the MTT assay.
Briefly, MC3T3-E1 cells were incubated in 96-well plates and maintained in the growth media for 24 h at 37°C. At 80% confluence, cells were treated with different concentrations of KRG and Dex for 48 h. Then, 10 μL of MTT solution (5 mg/mL) was added to each well, and the cells were incubated for another 4 h at 37°C. After the formation of formazan crystals, the MTT medium was aspirated and replaced with 150 μL of dimethyl sulfoxide (DMSO) for dissolving the formazan crystals. Then, the plates were shaken for 5 min. The absorbance of each well was recorded at 570 nm with a microplate spectrophotometer (Molecular Devices, Sunnyvale, CA, USA). Relative cellular growth was determined by calculating the ratio of the average absorbance in treatment cells to Adriamycin that in control cells. Cell viability was expressed as the ratio of optical densities. To measure alkaline phosphatase (ALP) activity, cells were washed with phosphate-buffered saline twice and sonicated in lysis
buffer consisting of 10mM Tris-HCl (pH 7.5), 0.5mM MgCl2, and 0.1% Triton X-100. After centrifugation at 10,000 × g for 20 min at 4°C, ALP activity in the supernatant was indicated in triplicate with the LabAssay ALP kit (Wako Pure Chemicals Industries, Chuo-ku, Osaka, Japan). Protein concentration was analyzed with a bicinchoninic acid protein assay kit (Thermo Pierce, Rockford, IL). Total RNA was isolated with the RNAisol PLUS reagent (Takara Bio Inc.), according Protein kinase N1 to the manufacturer’s protocol. The concentration of total RNA was calculated from its absorbance at 260 nm and 280 nm, each with an ND1000 spectrophotometer (Thermo, USA). First-strand cDNA was synthesized with 1 μg of total RNA according to the manufacturer’s protocol (Takara Bio Inc.). SYBR-Green-based quantitative real-time
PCR was performed using SYBR Primix Ex Taq (Takara Bio Inc.) with the appropriate sense and antisense primers. The primer sets used in this study are shown in Table 1. All reactions were carried out in triplicate and data were analyzed by the 2–ΔΔCT method. Beta-actin was used as an internal standard gene. Treated cells were washed twice with ice-cold phosphate-buffered saline and then solubilized in 100 μL of lysis buffer [20mM Tris-HCl (pH 7.5), 150mM NaCl, 1mM ethylenediamine tetra-acetic acid, 1mM Ethylene glycol tetraacetic acid (EGTA), 1% Triton X-100, 2.5mM sodium pyrophosphate, 1mM β-glycerophosphate, 1mM Na3VO4, 50mM NaF, and 1 μg/mL leupeptin). After a freeze–thaw cycle and vortexing for 1 h at 4°C, the lysate was clarified by centrifugation at 12,000 × g at 4°C for 5 min. The extracts were separated by sodium dodecyl sulfate–polyacrylamide gel electrophoresis and then electroblotted onto a nitrocellulose membrane.