Triamcinolone acetonide inhibits IL-6- and VEGF-induced angiogenesis downstream of the IL-6 and VEGF receptors.
OBJECTIVE
To test whether triamcinolone acetonide (TA) inhibits angiogenesis induced by IL-6 or VEGF and whether this inhibition is through antagonism of the IL-6 or the VEGF receptor 2.


METHODS
A rat cornea micropocket assay was used to initiate IL-6- and VEGF-mediated angiogenesis. The ability of TA or neutralizing VEGF antibody to inhibit IL-6- or VEGF-mediated neovascularization was analyzed by measuring vessel length, vessel extension, and vessel area. The phosphorylation of signal transduction activator 3 (STAT3), VEGF receptor, and extracellular signal-regulated kinase 1/2 (ERK1/2) was determined by Western blot in human umbilical vein endothelial cell (HUVEC) lysates after stimulus with IL-6 or VEGF, with and without TA pretreatment. The effect of IL-6 or TA on STAT3 expression in cornea was determined by Western blot.


RESULTS
IL-6 induced corneal angiogenesis in a dose-dependent manner, with 350 ng producing a peak at day 6. VEGF antibodies and TA blocked IL-6-mediated limbal neovascularization. TA also directly inhibited angiogenesis stimulated by a VEGF pellet; the glucocorticoid receptor antagonist mifepristone neutralized TA inhibition of angiogenesis. TA did not inhibit IL-6-induced STAT3 phosphorylation and did not inhibit VEGF-induced phosphorylation of the VEGF receptor 2 or of ERK1/2 in endothelial cells, but TA decreased IL-6-induced STAT3 expression in cornea.


CONCLUSIONS
IL-6- and VEGF-mediated corneal neovascularization are blocked by TA through the mifepristone-sensitive steroid receptor. TA inhibits IL-6-induced STAT3 expression in cornea, but it does not inhibit activation of the IL-6 or the VEGF receptor in cultured human endothelial cells. This finding has two implications. The fact that TA directly inhibits VEGF action implies that other factors may be critical to angiogenesis and sensitive to glucocorticoids.
Ebrahem
Quteba
Q
Cole Eye Institute, Cleveland Clinic Foundation, Cleveland, OH 44195, USA.
Minamoto
Atsushi
A
Hoppe
George
G
Anand-Apte
Bela
B
Sears
Jonathan E
JE
D000818:Animals; D015153:Blotting, Western; D049033:Chorioallantoic Membrane / Q000098:blood supply; D016510:Corneal Neovascularization / Q000139:chemically induced / Q000188:drug therapy* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism; D005260:Female; D005938:Glucocorticoids / Q000494:pharmacology*; D015850:Interleukin-6 / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010766:Phosphorylation; D051381:Rats; D011916:Rats, Inbred F344; D019947:Receptors, Interleukin-6 / Q000378:metabolism*; D040262:Receptors, Vascular Endothelial Growth Factor / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000378:metabolism; D014222:Triamcinolone Acetonide / Q000494:pharmacology*; D014471:Umbilical Veins / Q000166:cytology; D042461:Vascular Endothelial Growth Factor A / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D000093242:Interleukin-6 Inhibitors
D005938:Glucocorticoids; D015850:Interleukin-6; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D019947:Receptors, Interleukin-6; D040262:Receptors, Vascular Endothelial Growth Factor; D050796:STAT3 Transcription Factor; D014222:Triamcinolone Acetonide; D042461:Vascular Endothelial Growth Factor A; D000093242:Interleukin-6 Inhibitors; C494088:Stat3 protein, rat; C467498:vascular endothelial growth factor A, rat