Glucocorticoid-induced
osteoporosis is a common form of secondary
osteoporosis.
Glucocorticoids affect both bone formation and resorption, and prolonged
glucocorticoid exposure can suppress osteoblast activities.
beta-Ecdysone, found in many plants, is involved in
protein synthesis,
carbohydrate and lipid metabolism, and immunologic modulation. Here, we evaluated the effects of
beta-ecdysone on osteoblast viability by assessing apoptosis following treatment with excess
glucocorticoids. Mouse bone marrow stromal cells were induced to differentiate and grow into osteoblasts, and then treated with 10 µM
glucocorticoid and 10, 1, or 0.1 µM
beta-ecdysone. The expression levels of osteoblast growth and differentiation factors (runt-related
transcription factor 2,
osteogenic protein-1, and
alkaline phosphatase), apoptosis-related genes (transformation-related
protein 53,
ataxia telangiectasia mutated
protein,
caspase-3, and
caspase-8), and Akt1 and phospho-Akt (Thr308) were then assessed via
alkaline phosphatase staining,
acridine orange-
propidium iodide staining,
annexin V/PI apoptosis assay, real-time RT-PCR, and Western blot analyses. Notably, treatment with 10 µM
glucocorticoid resulted in reduced osteoblast viability and the specific activity of
alkaline phosphatase as well as reduced runt-related
transcription factor 2,
osteogenic protein-1, and
alkaline phosphatase mRNA expression in vitro, indicating that
glucocorticoid inhibited osteogenic differentiation. Moreover,
glucocorticoid treatment yielded increased transformation-related
protein 53,
ataxia telangiectasia mutated
protein,
caspase-3, and
caspase-8 expression and decreased Akt1 and phospho-Akt levels, indicating
glucocorticoid-induced apoptosis. Meanwhile,
beta-ecdysone inhibited
glucocorticoid function, preserving the expression of Akt1 and phospho-Akt and reducing the expression of transformation-related
protein 53,
ataxia telangiectasia mutated
protein,
caspase-3, and
caspase-8. Thus,
beta-ecdysone prevented
glucocorticoid-induced osteoblast apoptosis in vitro. These data highlight the potential for
beta-ecdysone as a treatment for preventing the effects of
glucocorticoid on bone growth.