Tocotrienol inhibits proliferation of human Tenon’s fibroblasts in vitro: a comparative study with vitamin E forms and mitomycin C
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To evaluate the potential of the vitamin E compound α-tocotrienol as antifibrotic agent in vitro.
Using human Tenon’s capsule fibroblast cultures, the antiproliferative and cytotoxic effects of the different vitamin E forms α-tocopherol, α-tocopheryl acetate, α-tocopheryl succinate and α-tocotrienol were compared with those of mitomycin C. To mimic subconjunctival and regular oral application in vivo, exposure time of serum-stimulated and serum-restimulated fibroblasts (SF and RF, respectively) to vitamin E forms was set at 6 days. Cultures were only exposed for 5 min to mitomycin C due to its known acute toxicity and to mimic the short-time intraoperative administration. Proliferation (expressed as % of control) was determined by DNA content quantification on days 2, 4 and 6, whereas cytotoxicity was assessed by cell morphology and glucose 6-phosphate dehydrogenase (G6PD) release after 24 h.
α-Tocopherol and α-tocopheryl acetate stimulated growth of SF, but not RF. Reduction of fibroblast content by α-tocopheryl succinate was accompanied by increased G6PD release and necrosis. Contrary to α-tocopheryl succinate, 50 μM or repeatedly 20 μM of α-tocotrienol significantly inhibited proliferation without causing cellular toxicity (maximal effect: 46.8%). RF were more sensitive to this effect than SF. Mitomycin C 100–400 μg/ml showed a stronger antiproliferative effect than α-tocotrienol (maximal effect: 13.8%). Morphologic characteristics of apoptosis were more commonly found under treatment with mitomycin C.
Of the vitamin E forms tested, only α-tocotrienol significantly inhibited growth at non-toxic concentrations. In this in vitro study, antiproliferative effects of mitomycin C were stronger than those of α-tocotrienol.
KeywordsTotal Cell Lysis Tocotrienols Degenerative Cell Change
The authors thank Milko E. Iliev, MD, for helpful discussions and critical comments on the manuscript.
Financial interests: A. Meyenberg, none; D. Goldblum, none; J.-M. Zingg, none; A. Azzi, none; K. Nesaretnam, employee of the Malaysian Palm Oil Board, no proprietary interests; M. Kilchenmann, none; B. E. Frueh, none.
The authors have full control of all primary data and they agree to allow Graefe’s Archive for Clinical and Experimental Ophthalmology to review their data if requested.
- 9.Fallor MK, Silverman CA, Yoshizumi MO (1994) Ocular toxicity of experimental intravitreal vitamin E. J Toxicol 3:337–345Google Scholar
- 11.Haas AL, Boscoboinik DO, Bohnke M (1996) Inhibition of Tenon fibroblast proliferation. Comparison between tocopherol and mitomycin-C. Invest Ophthalmol Vis Sci 37(suppl):877SGoogle Scholar
- 19.Kline K, Yu W, Sanders BG (2001) Vitamin E: mechanisms of action as tumor cell growth inhibitors. J Nutr 131:161–163Google Scholar
- 27.Mietz H, Addicks K, Diestelhorst M, Kriegelstein GK (1994) Extraocular application of mitomycin C in a rabbit model: cytotoxic effects on the ciliary body and epithelium. Ophthalmic Surg 25:204–244Google Scholar
- 40.Sakamoto T, Hinton DR, Kimura H, Spee C, Gopalakrishna R, Ryan SJ (1996) Vitamin E succinate inhibits proliferation and migration of retinal pigment epithelial cells in vitro: therapeutic implication for proliferative vitreoretinopathy. Graefes Arch Clin Exp Ophthalmol 234:186–192CrossRefPubMedGoogle Scholar
- 41.Sakamoto T, Oshima Y, Ishibashi T, Inomata H (1996) Inhibitory effect of Vitamin E succinate on the proliferation of cultured bovine choroidal endothelial cells. J Jpn Ophthalmol Soci 100:777–782Google Scholar
- 45.Tasinato A, Boscoboinik D, Bartoli GM, Maroni P, Azzi A (1995) d-α-Tocopherol inhibiton of vascular smooth muscle cell proliferation occurs at physiological concentrations, correlates with protein kinase C inhibition, and is independent of its antioxidant properties. Proc Natl Acad Sci USA 92:12190–12194PubMedCrossRefGoogle Scholar