Hydroxytyrosol induces epigenetic changes in chondrocyte response to oxidative stress.

OBJECTIVE: To our knowledge, no relationship has been revealed between nutraceutical compounds and microRNA (miR) network in OA models, so far.  Here, we investigated whether and how a miR is implicated in hydroxytyrosol (HT)-mediated chondroprotection following H2O2-promoted oxidative stress through the post-transcriptional modulation of sirtuin-1. METHODOLOGY: Human primary chondrocytes and C-28/I2 cell line were treated with 100µM HT 30 minutes before 100µM H2O2 addition. In silico analysis were exploited to select putative miR candidates able to target sirtuin-1 mRNA. Transient transfection approach was performed to examine the effects after modulation of miR levels. RESULTS: MiR-9 was identified as a putative regulator of sirtuin-1 and confirmed after luciferase-based gene reporter assay. Moreover, tuning of miR-9 levels is responsible for both cell death induced by H2O2 partly through down-regulation of sirtuin-1 and the protective effect of HT, as observed by trypan blue exclusion and caspase activity assays following transfection of miR-9 inhibitor and mimic. CONCLUSION: The molecular dissection of how bioactive compounds exert beneficial effects through induction of epigenetic changes, may disclose an interesting therapeutic tool and represents a research topic that deserves further investigation.