Demonstration of mitochondrial oestrogen receptor β and oestrogen-induced attenuation of cytochrome c oxidase subunit I expression in human periodontal ligament cells

ObjectivePeriodontal ligament (PDL) cells express oestrogen receptor β (ERβ) protein, but cellular functions regulated by ERβ in these cells have not been identified. In this study we determine if ERβ is localised to mitochondria and if oestrogen regulates mitochondrial function in human PDL cells obtained from teeth extracted for orthodontic reasons.DesignSubcellular distribution of ERβ was determined by confocal microscopy of cells co-stained with ERβ antibody and the mitochondrion-selective probe MitoTracker and by immunogold electron microscopy. Expression of the mitochondrial enzyme cytochrome c oxidase subunit I, involved in oxidative phosphorylation, was determined by Western blotting in cells treated with or without physiological concentrations of the endogenous oestrogen 17β-oestradiol.ResultsERβ immunoreactivity was observed both in the nuclei and the cytoplasm. MitoTracker-labelling was observed in the cytoplasm, especially in the perinuclear region, but not in the nuclei. Co-localisation of ERβ and MitoTracker was observed in cells derived from both male and female subjects. Mitochondrial localisation of ERβ was confirmed by immunogold electron microscopy. Cells treated with or without 17β-oestradiol (100 nM) displayed an identical pattern of staining for mitochondria. Treatment with 100 nM 17β-oestradiol attenuated cytochrome c oxidase subunit I expression by about 30%, while combined treatment with 17β-oestradiol and the ER blocker ICI 182780 (10 μM) had no effect.ConclusionThis study demonstrates mitochondrial localisation of ERβ and oestrogen-induced decrease in the expression of cytochrome c oxidase subunit I in human PDL cells, suggesting that oestrogen probably via ERβ influences mitochondrial function and PDL cell energy metabolism.