Nitrosative Stress, Mitochondrial Peptides, and Ferroptosis Markers in Corneal Epithelial Cells from Keratoconus Patients

Purpose To investigate the possible contribution of nitrosative stress, mitochondrial peptide levels (humanin and mitochondrial open-reading frame of the 12S rRNA-c), and ferroptosis parameters in corneal epithelial cells obtained from patients with keratoconus. Methods This prospective study was conducted on corneal epithelial cell samples taken from 75 adult patients with keratoconus and 25 age-matched postmortem controls. The Amsler-Krumeich classification was used for staging the keratoconus. All parameters, except nitric oxide, were measured by ELISA, and nitric oxide levels were determined by the chemiluminescence method. Results Humanin levels in keratoconus corneal epithelial cells were increased in stage 3 (p < .05), while mitochondrial open-reading frame of the 12S rRNA-c (p < .01) levels were diminished in all stages. Significant increases in nitric oxide (p < .001) and 3-nitrotyrosine (p < .05) levels were detected in the keratoconus group, indicating the involvement of nitrosative stress. In stage 3, glutathione peroxidase 4 levels were shown to be decreased (p < .01), while long-chain fatty acid CoA ligase 4 (p < .05) and malondialdehyde (p < .05) levels were increased. Conclusion This is the first study to show that humanin and mitochondrial open-reading frame of the 12S rRNA-c can participate in the pathophysiology of keratoconus. In addition to the mitochondrial peptides, our data suggest that increased nitrosative stress and ferroptosis may contribute to the pathophysiology of keratoconus.