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.

Abstract

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.

• Authors: M Cristina Kenney, Marilyn Chwa, Shari R Atilano, Annie Tran, Marilee Carballo, Mehrnoosh Saghizadeh, Vasilis Vasiliou, Wakako Adachi, Donald J Brown
• Journal: Investigative ophthalmology & visual science (Invest Ophthalmol Vis Sci) Vol. 46 Issue 3 Pg. 823-32 (Mar 2005) ISSN: 0146-0404 [Print] United States
• PMID: 15728537 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• RNA, Messenger
• Tissue Inhibitor of Metalloproteinase-1
• Catalase
• Superoxide Dismutase
• Aldehyde Dehydrogenase
• Glutathione Reductase
• Glutathione Transferase
• Cathepsins
• Cysteine Endopeptidases
• CTSV protein, human
• Matrix Metalloproteinases

Topics

• Aldehyde Dehydrogenase (genetics, metabolism)
• Blotting, Western
• Catalase (genetics, metabolism)
• Cathepsins (genetics, metabolism)
• Cornea (enzymology)
• Cysteine Endopeptidases (genetics, metabolism)
• Fluorescent Antibody Technique, Indirect
• Gene Expression Regulation, Enzymologic (physiology)
• Glutathione Reductase (genetics, metabolism)
• Glutathione Transferase (genetics, metabolism)
• Humans
• Keratoconus (enzymology, genetics)
• Matrix Metalloproteinases (genetics, metabolism)
• Oxidative Stress (physiology)
• RNA, Messenger (metabolism)
• Reverse Transcriptase Polymerase Chain Reaction
• Superoxide Dismutase (genetics, metabolism)
• Tissue Inhibitor of Metalloproteinase-1 (genetics, metabolism)