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Kenney, M.C. et al.

Kenney, Chwa, Atilano, Tran, Carballo, Saghizadeh, Vasiliou, Adachi, Brown,

Increased levels of catalase and cathepsin V/ L2 but decreased TIMP-1 in keratoconus corneas: evidence that oxidative stress plays a role in this disorder.

PURPOSE: The mRNA levels of antioxidant enzymes, matrix metalloproteinases, cathepsin V/ L2, and tissue inhibitor of matrix metalloproteinases (TIMPs) were determined in keratoconus and normal corneas. Protein levels or enzyme activities were analyzed when RNA levels were different. METHODS: A total of 25 physiologic (normal) and 32 keratoconus corneas were studied. mRNAs were analyzed by semiquantitative reverse transcription-polymerase chain reaction and Southern blot analysis. Proteins were assessed by immunohistochemistry and/or Western blot analysis. Catalase activity was measured in corneal extracts. Antioxidant enzymes examined were catalase, superoxide dismutase (SOD)-1, SOD3, glutathione reductase, glutathione S-transferase and aldehyde dehydrogenase 3A1. Degradative enzymes examined were cathepsin V/ L2 and matrix metalloproteinase (MMP)-1, -2, -7, -9, and -14. Tissue inhibitor of matrix metalloproteinase (TIMP)-1, -2, and -3 were also examined. RESULTS: Keratoconus corneas exhibited a 2.2-fold increase of catalase mRNA level (P < 0.01) and 1.8-fold of enzyme activity (P < 0.03); a 1.5-fold increase of cathepsin V/ L2 mRNA (P < 0.03) and abnormal protein distribution; and a 1.8-fold decrease of TIMP-1 mRNA (P < 0.05) and 2.8-fold decrease of protein (P < 0.0001) compared with normal (physiologic) corneas. RNA levels for other antioxidant and degradative enzymes were similar between normal and keratoconus corneas. CONCLUSIONS: Keratoconus corneas have elevated levels of cathepsins V/ L2, -B, and -G, which can stimulate hydrogen peroxide production, which, in turn, can upregulate catalase, an antioxidant enzyme. In addition, decreased TIMP-1 and increased cathepsin V/ L2 levels may play a role in the matrix degradation that is a hallmark of keratoconus corneas. The findings support the hypothesis that keratoconus corneas undergo oxidative stress and tissue degradation.[1]

References

Increased levels of catalase and cathepsin V/L2 but decreased TIMP-1 in keratoconus corneas: evidence that oxidative stress plays a role in this disorder. Kenney, M.C., Chwa, M., Atilano, S.R., Tran, A., Carballo, M., Saghizadeh, M., Vasiliou, V., Adachi, W., Brown, D.J. Invest. Ophthalmol. Vis. Sci. (2005) [Pubmed]

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