CYSTAMINE PROTECTS APOPTOSIS OF RETINAL PIGMENT EPITHELIUM BY INHIBITION OF CASPASE–3

Abstract

Abstract: : Purpose:The pathophysiology of age related macular degeneration (AMD) is characterized by loss of retinal pigment epithelium (RPE) cells induced by apoptosis. It is discussed that this effect is mainly triggered by oxidative stress. Previous studies have shown that apoptotic cell death of cultured RPE cells is triggered by oxidative stress. This requires the activation of caspase–3. Recently, an antiapoptotic effect of cystamine by inhibition of caspase–3 activation has been reported. The present study was to investigate the protective effect of cystamine in oxidative stress induced apoptosis. Methods:In vitro, human RPE cells of five human donors were incubated with cystamine (500 µM) prior to treatment with apoptotic stressors. RPE cultures were stressed with the proteosome inhibitor MG132 and hydrogen peroxide of different concentrations. Caspase–3 activity and glutathione levels were determined by observing the cleavage of a colorimetric peptide substrate. Expression of poly (ADP–ribose) polymerase (PARP), an early target of proteolytic cleavage by the caspase–family, was demonstrated by Western blot analysis. Cell viability was characterized with live–dead–staining. Results:Induction of cell–injury in RPE cells with MG132 (0–500 nM) and hydrogen peroxide (1–1,5 mM) resulted in apoptotic cell death. Caspase–3 activity was measured in these cells. Preincubation with cystamine significantly decreased caspase–3 activity. In conclusion, PARP was demonstrated in RPE cells after oxidative–mediated injury. The treatment with cystamine resulted in an increase of glutathione levels. Conclusions:The findings demonstrate that cystamine inhibits caspase–3 acivity and increases the level of antioxidants such as glutathione. These characteristics implicate the antiapoptotic and cytprotective effects of cystamine. Finally, treatment with cystamine may protect RPE from oxidative stress induced cell death. This may delay the development of AMD.

Keywords: age–related macular degeneration • cell death/apoptosis • antioxidants