UVB-elicited induction of MMP-1 expression in human ocular surface epithelial cells is mediated through the ERK1/2 MAPK-dependent pathway.
OBJECTIVE
Pterygia are common, frequently recurring ocular surface lesions characterized by tissue remodeling, cellular proliferation, angiogenesis, and inflammation. The increased incidence of pterygia in persons exposed to excessive solar radiation suggests that ultraviolet (UV) light may play a critical role in the pathogenesis of this disease. These investigations were focused on the expression of collagenase-1 (matrix metalloproteinase [MMP]-1) in pterygia and cultured pterygium epithelial cells, to determine whether the expression of this protease could be modified after exposure to UVB.


METHODS
Pterygium, conjunctival, and limbal epithelial cells were subcultured and exposed to various amounts of UVB. The conditioned medium and RNA were harvested for analysis by gelatin zymography, Western blot analysis, ELISA, and RT-PCR. Furthermore, whole pterygium specimens were irradiated to determine secreted MMP-1 levels.


RESULTS
Immunohistochemical analysis revealed enhanced MMP-1 expression in pterygia that corresponded precisely with p63-positive epithelial cells. In contrast, significantly less MMP-1 reactivity was found in normal conjunctiva, limbus, and cornea. A dose- and time-dependent increase in MMP-1 was observed when pterygium epithelial cells were exposed to UVB with no significant modulation of inhibitor activity. MMP-1 was not affected in irradiated normal conjunctival epithelial cells or in pterygium fibroblasts but was induced in limbal epithelial cells. Although the induction of MMP-1 after UVB was not mediated by an intermediate soluble factor, the extracellular signal-regulated kinase (ERK)1/2 mitogen-activated protein kinase (MAPK) intracellular pathway was involved.


CONCLUSIONS
Collectively, these data support the hypothesis of the involvement of UV light and MMPs in the development of pterygia and may assist in devising new therapeutic approaches for the treatment and prevention of pterygia.
University of New South Wales, Inflammation Research Unit, Department of Pathology, Sydney, New South Wales, Australia. n.digirolamo@unsw.edu.au
Nick
N
Di Girolamo
Minas T
MT
Coroneo
Denis
D
Wakefield
D015153:Blotting, Western; D002478:Cells, Cultured; D003228:Conjunctiva / Q000166:cytology; D004307:Dose-Response Relationship, Radiation; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000201:enzymology / Q000528:radiation effects*; D005260:Female; D005347:Fibroblasts / Q000201:enzymology / Q000528:radiation effects; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008297:Male; D020781:Matrix Metalloproteinase 1 / Q000096:biosynthesis* / Q000235:genetics; D008875:Middle Aged; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D011625:Pterygium / Q000201:enzymology / Q000532:radiotherapy*; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014466:Ultraviolet Rays
D012333:RNA, Messenger; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020781:Matrix Metalloproteinase 1