Comparative proteome analysis of the tear samples in patients with low-grade keratoconus
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To elucidate the metabolic processes playing roles in the formation of keratoconus (KC).
Tears samples were collected using capillary glass tubes without stimulation and without prior anesthesia from 17 patients and 16 controls. Proteomic analysis by fluorescent 2D gel electrophoresis (DIGE) coupled with MALDI-TOF/TOF was performed. The identified proteins that were differentially regulated were subjected to Ingenuity Pathway Analysis (IPA). Corneal topography analyses with Sirius topography system (Costruzioni Strumenti Oftalmici, Florence, Italy) were performed on all participants. The steepest keratometry index was lower than 50 diopters in all keratoconus patients.
DIGE analysis showed changes in abundance of nine proteins. Six of these proteins, namely serum albumin, Keratin Type II Cytoskeletal 1, IgG gamma chain-1, GAPDH, alpha-1 antitrypsin and ApoA-I, were down-regulated in the KC samples in comparison with the controls. In addition, we detected up-regulation of lysozyme C, keratin type I cytoskeletal 10 and lipocalin. The subsequent IPA predicted that NADH repair pathway is activated in the KC patients. This pathway involves generation of NADHX as a by-product via catalysis by GAPDH. NADHX is an inhibitor of several dehydrogenases and must be removed.
The involvement of NADHX repair pathway in KC should be investigated, since preliminary clues obtained in this study point to that direction. In particular, showing the presence of ATP-dependent NAD(P)H-hydrate dehydratase that eliminates NADHX would strengthen our findings and would be a major step toward understanding KC.
KeywordsTear proteome Keratoconus DIGE MALDI-TOF/TOF
This study was supported by Kocaeli University Scientific Research Project Coordination Unit (KOU-BAP: Project Number: 2014/052).
Compliance with ethical standards
Conflict of interest
Author Fatih Yenihayat declares that he has no conflict of interest. Author Özgül Altıntaş declares that she has no conflict of interest. Author Murat Kasap declares that he has no conflict of interest. Author Gürler Akpınar declares that he has no conflict of interest. Author Nil Güzel declares that she has no conflict of interest. Author Onur Sinan Çelik declares that he has no conflict of interest.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional ethical committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
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