Estradiol (E2)- and tamoxifen (Tmx)-bound ER-alpha (ERα) interact differentially with histone deacetylases 1 and 3 (HDACs 1 and 3)

miR-34a-5p facilitates osteogenic differentiation of bone marrow mesenchymal stem cells and modulates bone metabolism by targeting HDAC1 and promoting ER-α transcription

OBJECTIVE

Metabolism is essential for bone development. The expressions of catabolic markers in chondrocytes show association with miR-34a-5p. This study discussed the mechanism by which miR-34a-5p regulates osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) as well as bone metabolism.

METHODS

Expressions of BMSC surface markers were determined via flow cytometry. Osteogenic differentiation of BMSCs was subsequently induced. miR-34a-5p mimic, oe-HDAC1, or ER-α activator Ferutinin was introduced in BMSCs. Alkaline phosphatase activity and calcification were detected. Expressions of miR-34a-5p, HDAC1, ER-α, and osteogenic markers were determined via RT-qPCR and Western blot. The binding relationship between miR-34a-5p and HDAC1 was verified by a dual-luciferase assay. Mice at the age of 6 months and 18 months were assigned to the young group and age group for in vivo experiments, and aged mice were treated with agomiR miR-34a-5p. Expressions of serum miR-34a-5p, HDAC1, ER-α, and bone metabolism markers in mice were determined.

RESULTS

Osteogenic medium-induced BMSCs manifested increased expressions of miR-34a-5p and ER-α and decreased HDAC1 expression. miR-34a-5p overexpression promoted osteogenic differentiation of BMSCs. miR-34a-5p targeted HDAC1. HDAC1 overexpression partially counteracted the promotional action of miR-34a-5p overexpression on osteogenic differentiation of BMSCs. miR-34a-5p overexpression activated ER-α. ER-α activator Ferutinin partially nullified the regulatory function of miR-34a-5p/HDAC1 on osteogenic differentiation of BMSCs. In vivo experiments showed that miR-34a-5p overexpression enhanced the potential of bone metabolism in aged mice.

CONCLUSION

miR-34a-5p overexpression promoted osteogenic differentiation of BMSCs and enhanced bone metabolism by promoting ER-α activation via targeting HDAC1.

HDAC3-ERα Selectively Regulates TNF-α-Induced Apoptotic Cell Death in MCF-7 Human Breast Cancer Cells via the p53 Signaling Pathway

Tumor necrosis factor-α (TNF-α) plays a significant role in inflammation and cancer-related apoptosis. We identified a TNF-α-mediated epigenetic mechanism of apoptotic cell death regulation in estrogen receptor-α (ERα)-positive human breast cancer cells. To assess the apoptotic effect of TNF-α, annexin V/ propidium iodide (PI) double staining, cell viability assays, and Western blotting were performed. To elucidate this mechanism, histone deacetylase (HDAC) activity assay and immunoprecipitation (IP) were conducted; the mechanism was subsequently confirmed through chromatin IP (ChIP) assays. Finally, we assessed HDAC3-ERα-mediated apoptotic cell death after TNF-α treatment in ERα-positive human breast cancer (MCF-7) cells via the transcriptional activation of p53 target genes using luciferase assay and quantitative reverse transcription PCR. The TNF-α-induced selective apoptosis in MCF-7 cells was negatively regulated by the HDAC3-ERα complex in a caspase-7-dependent manner. HDAC3 possessed a p53-binding element, thus suppressing the transcriptional activity of its target genes. In contrast, MCF-7 cell treatment with TNF-α led to dissociation of the HDAC3-ERα complex and substitution of the occupancy on the promoter by the p53-p300 complex, thus accelerating p53 target gene expression. In this process, p53 stabilization was accompanied by its acetylation. This study showed that p53-mediated apoptosis in ERα-positive human breast cancer cells was negatively regulated by HDAC3-ERα in a caspase-7-dependent manner. Therefore, these proteins have potential application in therapeutic strategies.