ACY­1215, a HDAC6 inhibitor, decreases the dexamethasone­induced suppression of osteogenesis in MC3T3­E1 cells.

Glucocorticoid­induced osteoporosis is the commonest form of drug­induced osteoporosis. Histone deacetylase 6 (HDAC6) is involved in the differentiation from mesenchymal stem cells to osteoblasts. However, the role of ricolinostat (ACY­1215, HDAC6 inhibitor) in the dexamethasone (Dex)­induced proliferation and differentiation of preosteoblasts remains to be elucidated. The protein expression and mRNA expression levels of HDAC6, osteopontin (OPN), runt­related transcription factor 2 (Runx2), osterix (Osx), collagen I (COL1A1) and glucocorticoid receptor (GR) in MC3T3­E1 cells were analyzed by western blot analysis and reverse transcription­quantitative PCR analysis. The cell viability was detected by CCK­8 assay. The alkaline phosphatase (ALP) activity and capacity of mineralization was determined by ALP assay kit and alizarin red staining. HDAC6 expression was increased in patient serum and Dex­induced MC3T3­E1 cells at a certain concentration range; 1 µM Dex was selected for further experimentation. Cell viability was decreased after Dex induction and restored following ACY­1215 treatment. The ALP activity and capability for mineralization was decreased when MC3T3­E1 cells were induced by 1 µM Dex and was gradually improved by the treatment of ACY­1215 at 1, 5 and 10 mM. The expression of OPN, Runx2, Osx and COL1A1 was similar, with the changes of capability for mineralization. Furthermore, GR expression was increased in Dex­induced MC3T3­E1 cells. ACY­1215 promoted the GR expression in MC3T3­E1 cells from 1­5 mM while GR receptor expression was increased with 10 mM ACY­1215 treatment. In conclusion, ACY­1215 reversed the Dex­induced suppression of proliferation and differentiation of MC3T3­E1 cells.