Epigallocatechin gallate activates miR-193a-3p and protects mice against glucocorticoid-induced osteoporosis by targeting NFATC1 expression

Purpose: To investigate the effect of epigallocatechin gallate (EGCG) on microRNAs in a mouse model of glucocorticoid-induced osteoporosis (GIOP), and the mechanism involved. Methods: Osteoclast-specific marker mRNA expressions, receptor activator of nuclear factor kappa-B ligand (RANKL), receptor activator of nuclear factor κ B (RANK), and miRNA expressions were determined using reverse transcription polymerase chain reaction (RT-qPCR) analysis. Western blotting was used to assay protein expressions, while miRNA and 3’UTR interaction studies were carried out with reporter assay. Results: Treatment with EGCG resulted in downregulation of glucocorticoid-induced expressions of RANKL, RANK and osteoclast-specific markers i.e. tumor necrosis factor receptor-associated factor 6, (TRAF6), nuclear factor of activated T cells 1 (NFATc1), cathepsin K, matrix metallopeptidase 9 (MMP9) and tartrate-resistant acid phosphatase (TRAP). Furthermore, EGCG treatment significantly reduced reactive oxygen species (ROS) levels and inflammatory cytokine expressions in GIOP mice. The expression of miRNA-targeting osteoclast marker mmu-mir-193-3p was significantly down-regulated in GIOP mice. However, EGCG treatment increased mmu-mir-193-3p expression and had specific interaction with NFATc1 3’UTR (3’-untranslated region). In vitro results showed that mmu-mir-193-3p mimics downregulated dexamethasone (DXM)-induced osteoclast-specific marker expressions. Conclusion: These results show that EGCG exerts a protective role against GIOP by upregulating miR- 193a-3p expressions. Keywords: Epigallocatechin gallate, Glucocorticoids, RANKL, Osteoporosis