title: Positive feedback regulation between MMP-9 and VEGF in human RPE cells.
abstract: OBJECTIVE
  The proteolytic activity of matrix metalloproteinases (MMPs) is involved in pathologic angiogenesis in the eye. However, it is unknown whether MMPs may stimulate the production of the major angiogenic factor, vascular endothelial growth factor (VEGF). The authors investigated whether MMP-2 and MMP-9 alter the expression of VEGF by retinal pigment epithelial (RPE) cells. They also sought to determine the effects of MMPs on cellular proliferation and migration and the effect of triamcinolone acetonide on MMP-9-evoked cellular responses.
  
  
  METHODS
  Human RPE cell cultures were stimulated with MMP-2 or MMP-9. The gene expression and secretion of MMP-9 and VEGF were determined by real-time RT-PCR and ELISA, respectively. Cellular proliferation was investigated with a bromodeoxyuridine immunoassay, and chemotaxis was examined with a Boyden chamber assay.
  
  
  RESULTS
  Under control conditions, RPE cells in vitro expressed a significantly higher amount of mRNA for MMP-2 than for MMP-9. Chemical hypoxia caused upregulation of the gene expression of both MMPs, whereas VEGF increased the gene expression and secretion of MMP-9. The hypoxic expression of MMP-9 was mediated by autocrine VEGF signaling. Exogenous MMP-9 increased the gene expression and secretion of VEGF, whereas MMP-2 reduced the secretion of VEGF. MMP-2 and MMP-9 did not alter the proliferation but stimulated the migration of RPE cells. Triamcinolone fully inhibited the stimulatory effect of MMP-9 on the expression of VEGF and the VEGF-evoked increase in the expression of MMP-9. However, triamcinolone had no effect on the motogenic effect of MMP-9.
  
  
  CONCLUSIONS
  There is a positive feedback regulation between MMP-9 and VEGF in RPE cells. The hypoxic expression of MMP-9 may stimulate the production and secretion of VEGF under pathologic conditions. Triamcinolone inhibits the positive feedback regulation between MMP-9 and VEGF under hypoxic conditions through inhibition of the gene expression of MMP-9 and the secretion of VEGF.
authors.affiliation: Department of Ophthalmology and Eye Clinic, University of Leipzig Faculty of Medicine, Leipzig, Germany. hollbm@medizin.uni-leipzig.de
authors.forename: Margrit
authors.initials: M
authors.lastname: Hollborn
authors.forename: Christina
authors.initials: C
authors.lastname: Stathopoulos
authors.forename: Anja
authors.initials: A
authors.lastname: Steffen
authors.forename: Peter
authors.initials: P
authors.lastname: Wiedemann
authors.forename: Leon
authors.initials: L
authors.lastname: Kohen
authors.forename: Andreas
authors.initials: A
authors.lastname: Bringmann
mesh_terms: D015687:Cell Hypoxia; D002465:Cell Movement; D049109:Cell Proliferation; D002478:Cells, Cultured; D025461:Feedback, Physiological / Q000187:drug effects / Q000502:physiology*; D005786:Gene Expression Regulation; D005938:Glucocorticoids / Q000494:pharmacology; D006801:Humans; D020778:Matrix Metalloproteinase 2 / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D020780:Matrix Metalloproteinase 9 / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D010857:Pigment Epithelium of Eye / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D014222:Triamcinolone Acetonide / Q000494:pharmacology; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism*
chemical_list: D005938:Glucocorticoids; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; C467498:vascular endothelial growth factor A, rat; C522361:MMP2 protein, human; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; D014222:Triamcinolone Acetonide