HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Chwa, M. Articles by Kenney, M. C. Search for Related Content PubMed PubMed Citation Articles by Chwa, M. Articles by Kenney, M. C.

Increased Stress-Induced Generation of Reactive Oxygen Species and Apoptosis in Human Keratoconus Fibroblasts

From the Department of Ophthalmology, University of California Irvine Medical Center, Irvine, California.

PURPOSE. To determine whether keratoconus (KC) corneal fibroblast cultures have increased reactive oxygen species (ROS) production and are more susceptible to stress-related challenges.

METHODS. Normal (n = 9) and KC (n = 10) stromal fibroblast cultures were incubated in either neutral- or low-pH conditions, with or without hydrogen peroxide. Catalase activities were measured with a fluorescent substrate assay. Superoxide and ROS/reactive nitrogen species (RNS) productions were determined with an amine-reactive green-dye assay and 2',7'-dichlorodihydrofluorescein diacetate (H₂DCFDA) dye assay, respectively. Cell viability was analyzed by a dye-exclusion assay. Caspase 3 activity was measured by a fluorochrome inhibitor of caspase (FLICA) assay. A cationic (green) dye was used to measure the mitochondrial membrane potential (m).

RESULTS. KC fibroblasts had increased superoxide and ROS/RNS production (6.2-fold, P < 0.001 and 1.8-fold, P < 0.001, respectively) and catalase activity (P < 0.01) with higher concentrations of H₂O₂ compared with normal cultures (P = 0.16). After a low-pH stress challenge, KC fibroblasts maintained higher ROS/RNS levels (3.3-fold, P < 0.02), showed higher caspase-3 activity (7.5-fold, P < 0.02) and decreased m (2.6-fold, P < 0.04), and had decreased cell viability (37%, P < 0.005 vs. 20%, P < 0.27) compared with normal fibroblasts.

CONCLUSIONS. Under identical conditions, KC fibroblasts had increased basal generation of ROS/RNS and were more susceptible to stressful challenges (low-pH and/or H₂O₂ conditions) than were normal fibroblasts. In addition, the stressed KC fibroblasts possessed characteristics similar to those found in the intact KC corneas (increased catalase activity, ROS production, and apoptosis). These properties may play a role in the pathogenesis of KC.