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Mako Endo, Naoki Okumura, Theofilos Tourtas, Ursula Schlotzer-Schrehardt, Friedrich E Kruse, Noriko Koizumi; Feasibility of caspase inhibitor to treat Fuchs endothelial corneal dystrophy. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1436.
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© ARVO (1962-2015); The Authors (2016-present)
Fuchs endothelial corneal dystrophy (FECD) causes apoptosis of corneal endothelial cells (CECs) and is a major cause of corneal endothelial dysfunction. Though the pathophysiology of FECD has yet to be clarified, the involvement of transforming growth factor beta (TGF-β) signaling, endoplasmic reticulum (ER) stress, and apoptosis has been posited. To date, the only therapeutic modality is corneal transplantation, and no pharmaceutical treatment exists. In this study, we investigated the feasibility of caspase inhibitor as a possible treatment candidate for FECD.
Cell damage was induced as FECD mimic in vitro models; i.e., 1) immortalized FECD cells (iFECD) treated with TGF-β2 (10 ng/mL), 2) immortalized human CECs (iHCECs) treated with ER-stress-inducer thapsigargin (TG, 10 μM), and 3) iHCECs treated with ultraviolet (UV, 100 J/m2) irradiation. Caspase inhibitors (Z-VD-FMK or Emricasan) were used to evaluate the anti-apoptotic effect. Cell damage was examined by phase-contrast microscopy. The cleavage of caspase 3 and poly (ADP-ribose) polymerase (PARP) was determined by western blotting. Apoptotic cell population was determined with Annexin V-positive cells using flow cytometry.
Phase contrast images showed that cells were damaged and the existence of floating cells among the TGF-β2-treated iFECD, TG-treated iHCECs, and UV-treated iHCECs. On the other hand, caspase inhibitors suppressed the number of floating cells in those three cell damage models. Western blotting showed that cleavage of caspase 3 and PARP was induced in all three models, but caspase inhibitors suppressed the cleavage of those apoptotic proteins. Flow cytometry demonstrated that Annexin V-positive apoptotic cells were increased in iFECD with stimulation of TGF-β2 (20.4±0.5%), but Z-VD-FMK significantly suppressed Annexin V-positive cell numbers (8.9±0.5%) (p<0.01). Similarly, Annexin V-positive cells in TG-treated iHCECs and UV-treated iHCECs were downregulated by Z-VD-FMK (from 27.2±1.2% to 4.8±0.3% and from 17.3±1.4% to 1.2±0.3%, respectively) (p<0.01).
Our findings indicate that caspase inhibitor suppresses apoptosis in in vitro FECD mimicking models; i.e., TGF-β signaling activation, ER stress, and UV irradiation. We propose that caspase is a therapeutic target, and that caspase inhibitors might be clinically applicable pharmaceutical agents for treating FECD.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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