Hypoxia-stimulated vascular endothelial growth factor production in human nasal polyp fibroblasts: effect of epigallocatechin-3-gallate on hypoxia-inducible factor-1 alpha synthesis.
OBJECTIVE
To verify the inhibitory effects of epigallocatechin-3-gallate (EGCG) on the synthesis of hypoxia-induced vascular endothelial growth factor (VEGF) in nasal polyp fibroblasts (NPFs).


METHODS
Eight primary cultures of NPFs were established from nasal polyps. Effects of EGCG on the production of hypoxia-inducible factor (HIF)-1 alpha (the most potent VEGF stimulant) and VEGF by NPFs under hypoxic conditions were measured by Western blot analysis. Immunohistochemical staining was used to examine the in vivo expressions of HIF-1 alpha and VEGF in 20 sections of nasal polyps.


RESULTS
Western blot analysis showed that cobalt chloride induced HIF-1 alpha and VEGF synthesis in NPFs in a time-dependent manner, reaching a plateau at 4 and 8 hours, respectively, following treatment. Epigallocatechin-3-gallate attenuated the level of HIF-1 alpha induced by cobalt chloride and also reduced cobalt chloride-stimulated VEGF production by suppressing HIF-1 alpha synthesis. Furthermore, oligomycin (a specific HIF-1 alpha inhibitor) combined with EGCG resulted in a more profound inhibition of VEGF synthesis compared with oligomycin or EGCG treatment alone. Nevertheless, the synergistic effect seemed smaller than the sum of their individual actions. Immunohistochemical analysis revealed the presence of HIF-1 alpha and VEGF in NPFs and mononuclear round cells. Intimate alignment of VEGF-positive fibroblasts and proliferating small capillaries was frequently found.


CONCLUSIONS
Nasal polyp fibroblasts contribute to the pathogenesis of nasal polyps by producing VEGF to promote angiogenesis under hypoxic conditions. Epigallocatechin-3-gallate substantially diminishes HIF-1 alpha and VEGF synthesis in NPFs.
Lin
Sze-Kwan
SK
Department of Dentistry, National Taiwan University Hospital, 1 Chang-Teh St, Taipei, Taiwan.
Shun
Chia-Tung
CT
Kok
Sang-Heng
SH
Wang
Chih-Chiang
CC
Hsiao
Tzu-Yu
TY
Liu
Chia-Ming
CM
D000975:Antioxidants / Q000494:pharmacology*; D028241:Camellia sinensis; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D015687:Cell Hypoxia; D002478:Cells, Cultured; D003035:Cobalt; D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D009298:Nasal Polyps / Q000503:physiopathology*; D009389:Neovascularization, Pathologic; D010936:Plant Extracts; D042461:Vascular Endothelial Growth Factor A / Q000037:antagonists & inhibitors* / Q000096:biosynthesis
D000975:Antioxidants; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D010936:Plant Extracts; D042461:Vascular Endothelial Growth Factor A; D003035:Cobalt; D002392:Catechin; C045651:epigallocatechin gallate; C018021:cobaltous chloride