Expression of tissue inhibitors of matrix metalloproteinases 1 and 2 in corneal epithelium after UV irradiation

Abstract

Abstract Purpose Tissue inhibitors of metalloproteinases (TIMPs) are capable of inhibiting the activities of all known matrix metalloproteinases (MMPs) and therefore they play a key role in maintaining the balance between synthesis and degradation of basic extracellular matrix components (collagens, glycosaminoglycans) in the normal cornea. However, under pathological conditions, disruption of this balance may appear due to the increased expression of MMPs or decreased expression of TIMPs. Purpose of this study was to investigate whether changes in expression of TIMPs might contribute to increased proteolytic activity of MMPs in corneas irradiated by UV rays. Methods In the first group of rabbits the corneas were irradiated with UVA lamp (365 nm, once a day during 4 days, a dose per day 1.01 J/cm2), in the second group with UVB lamp (312 nm, once a day during 4 days, a dose per day 1.01 J/cm2). Normal corneas served as controls. TIMP‐1 and TIMP‐2 were examined in cryostat sections immunohistochemically using mouse monoclonal anti‐TIMP‐1 and anti‐TIMP‐2 antibodies. Results Immunohistochemical examination showed that UVA rays did not change the expression of TIMPs studied in the corneal epithelium. In contrast, UVB rays induced the decreased expression of TIMPs in corneal epithelial cells. From both enzymes investigated in UVB irradiated corneas the decrease of TIMP‐1 expression was more significant than expression of TIMP‐2. Conclusion Even if further studies are necessary, our results point to the suggestions that insufficient inhibition of MMPs due to the decreased presence of TIMPs in corneas irradiated by UVB rays may lead to corneal damage from excessive proteolytic degradation of corneal proteins.