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 PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Hyun, H. J. Articles by Yoon, Y. H. Search for Related Content PubMed PubMed Citation Articles by Hyun, H. J. Articles by Yoon, Y. H.

Depletion of Intracellular Zinc and Copper with TPEN Results in Apoptosis of Cultured Human Retinal Pigment Epithelial Cells

¹ From the National Creative Research Initiative Center for the Study of CNS Zinc; the ² Departments of Ophthalmology and ³ Neurology, University of Ulsan College of Medicine, Seoul, Korea; and the ⁴ Department of Molecular Biology, Seoul National University, Korea.

PURPOSE. Although zinc deficiency may contribute to the pathogenesis of age-related macular degeneration, how it leads to retinal pigment epithelium (RPE) degeneration is unknown. To investigate this, cultured human RPE cells were rendered zinc depleted with a membrane-permeant metal chelator, N,N,N',N-tetrakis(2-pyridylmethyl) ethylenediamine (TPEN), and the resultant cytopathic changes were examined.

METHODS. RPE cell degeneration was examined with light microscopy, TdT-mediated dUTP nick end labeling (TUNEL) staining, Hoechst dye staining, and electron microscopy and quantified with cell counting or lactate dehydrogenase release assay. The effect of sublethal zinc depletion on the vulnerability of RPE cells to UV irradiation or hydrogen peroxide (H₂O₂) exposure, was studied in cultures without or with pretreatment with low-concentration TPEN.

RESULTS. Exposure to 1 to 4 µM TPEN for 48 hours induced RPE cell death in a concentration-dependent manner. Features of apoptosis such as membrane blebbing, chromatin condensation, nuclear fragmentation, and caspase-3 activation, accompanied the TPEN-induced cell death. Addition of equimolar zinc or copper completely reversed TPEN-induced apoptosis, whereas addition of iron had no effect. As in apoptosis of several other cell types including neurons, a protein synthesis inhibitor as well as caspase inhibitors blocked TPEN-induced apoptosis. On the contrary, at sublethal concentrations, TPEN increased the vulnerability of RPE cells to subsequent UV irradiation but not to H₂O₂ exposure.

CONCLUSIONS. The present results suggest that depletion of intracellular zinc and copper, but not copper alone, may be harmful to RPE cells, directly inducing apoptosis or indirectly increasing vulnerability of RPE cells to UV injury. The present culture model may be useful for gaining insights into the mechanisms of zinc depletion-associated RPE cell degeneration.

This article has been cited by other articles:

				L. Mecklenburg and U. Schraermeyer An Overview on the Toxic Morphological Changes in the Retinal Pigment Epithelium after Systemic Compound Administration Toxicol Pathol, February 1, 2007; 35(2): 252 - 267. [Abstract] [Full Text] [PDF]

				T. K. Sigdel, J. A. Easton, and M. W. Crowder Transcriptional Response of Escherichia coli to TPEN. J. Bacteriol., September 1, 2006; 188(18): 6709 - 6713. [Abstract] [Full Text] [PDF]

				J.-H. Yang, W.-D. Le, S. F. Basinger, S. M. Wu, and C.-y. Yang Mechanisms of Apoptosis in Human Retinal Pigment Epithelium Induced by TNF-{alpha} in Conditions of Heavy Metal Ion Deficiency Invest. Ophthalmol. Vis. Sci., March 1, 2005; 46(3): 1039 - 1046. [Abstract] [Full Text] [PDF]

				C. Zhang, J. Baffi, S. W. Cousins, and K. G. Csaky Oxidant-induced cell death in retinal pigment epithelium cells mediated through the release of apoptosis-inducing factor J. Cell Sci., May 15, 2003; 116(10): 1915 - 1923. [Abstract] [Full Text] [PDF]