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Eur J Nutr. 2019 Jul 6. doi: 10.1007/s00394-019-02047-9. [Epub ahead of print]

Beneficial effects of δ-tocotrienol against oxidative stress in osteoblastic cells: studies on the mechanisms of action.

Author information

1
Department of Medical Biotechnology and Translational Medicine, Università degli Studi di Milano, Via Vanvitelli, 32, 20129, Milan, Italy.
2
Department of Pharmacological and Biomolecular Sciences, Università degli Studi di Milano, 20133, Milan, Italy.
3
Department of Health, Animal Science and Food Safety, Università degli Studi di Milano, 20133, Milan, Italy.
4
Department of Medical Biotechnology and Translational Medicine, Università degli Studi di Milano, Via Vanvitelli, 32, 20129, Milan, Italy. valeria.sibilia@unimi.it.

Abstract

PURPOSE:

Natural antioxidants are considered as promising compounds in the prevention/treatment of osteoporosis. We studied the ability of purified δ-tocotrienol (δ-TT) isolated from a commercial palm oil (Elaeis guineensis) fraction to protect osteoblast MC3T3-E1 and osteocyte MLO-Y4 cells against tert-butyl hydroperoxide (t-BHP)-induced oxidative damage and the mechanisms involved in its protective action in MC3T3-E1.

METHODS:

MC3T3-E1 and MLO-Y4 cells were treated with δ-TT (1.25-20 µg/ml for 2 h) followed by t-BHP at 250 µM or 125 µM for 3 h, respectively. MTT test was used to measure cell viability. Apoptotic cells were stained with Hoechst-33258 dye. Intracellular ROS levels were measured by dichlorofluorescein CM-DCFA. The OPT fluorimetric assay was used to detect the reduced glutathione to oxidized glutathione ratio (GSH/GSSG) contents.

RESULTS:

δ-TT significantly prevented the effects of t-BHP on cell viability and apoptosis reaching a maximum protective activity at 10 and 5 µg/ml in MC3T3-E1 and MLO-Y4 cells, respectively. This protective effect was due to a reduction of intracellular ROS levels and an increase in the defense systems shown by the increase in the GSH/GSSG. GSH loss induced by an inhibitor of GSH synthesis significantly reduced the δ-TT-positive effect on ROS levels. δ-TT prevention of oxidative damage was completely removed by combined treatment with the specific inhibitors of PI3K/AKT (LY294002) and Nrf2 (ML385).

CONCLUSIONS:

The δ-TT protective effect against oxidative damage in MC3T3-E1 cells is due to a reduction of intracellular ROS levels and an increase of the GSH/GSSG ratio, and involves an interaction between the PI3K/Akt-Nrf2 signaling pathways.

KEYWORDS:

MC3T3-E1 cells; MLO-Y4 cells; Oxidative stress; Signaling pathways; Tocotrienol

PMID:
31280345
DOI:
10.1007/s00394-019-02047-9

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