Tocotrienol inhibits proliferation of human Tenon's fibroblasts in vitro: a comparative study with vitamin E forms and mitomycin C.
OBJECTIVE
To evaluate the potential of the vitamin E compound alpha-tocotrienol as antifibrotic agent in vitro.


METHODS
Using human Tenon's capsule fibroblast cultures, the antiproliferative and cytotoxic effects of the different vitamin E forms alpha-tocopherol, alpha-tocopheryl acetate, alpha-tocopheryl succinate and alpha-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.


RESULTS
alpha-Tocopherol and alpha-tocopheryl acetate stimulated growth of SF, but not RF. Reduction of fibroblast content by alpha-tocopheryl succinate was accompanied by increased G6PD release and necrosis. Contrary to alpha-tocopheryl succinate, 50 microM or repeatedly 20 microM of alpha-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 microg/ml showed a stronger antiproliferative effect than alpha-tocotrienol (maximal effect: 13.8%). Morphologic characteristics of apoptosis were more commonly found under treatment with mitomycin C.


CONCLUSIONS
Of the vitamin E forms tested, only alpha-tocotrienol significantly inhibited growth at non-toxic concentrations. In this in vitro study, antiproliferative effects of mitomycin C were stronger than those of alpha-tocotrienol.
Meyenberg
Alexander
A
Departement of Ophthalmology, University of Berne, Switzerland.
Goldblum
David
D
Zingg
Jean-Marc
JM
Azzi
Angelo
A
Nesaretnam
Kalanithi
K
Kilchenmann
Monika
M
Frueh
Beatrice E
BE
D000368:Aged; D000369:Aged, 80 and over; D000975:Antioxidants / Q000494:pharmacology*; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D003228:Conjunctiva / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D003593:Cytoplasm / Q000187:drug effects / Q000201:enzymology; D004247:DNA / Q000032:analysis; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D005954:Glucosephosphate Dehydrogenase / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D016685:Mitomycin / Q000494:pharmacology*; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology*; D024508:Tocotrienols / Q000494:pharmacology*; D014810:Vitamin E / Q000494:pharmacology
D000975:Antioxidants; D019384:Nucleic Acid Synthesis Inhibitors; D024508:Tocotrienols; D014810:Vitamin E; D016685:Mitomycin; D004247:DNA; D005954:Glucosephosphate Dehydrogenase