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 ISI Web of Science 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 ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Ho, J. H.-C. Articles by Su, Y. Search for Related Content PubMed PubMed Citation Articles by Ho, J. H.-C. Articles by Su, Y.

Internalization Is Essential for the Antiapoptotic Effects of Exogenous Thymosin ß-4 on Human Corneal Epithelial Cells

¹From the Institute of Biopharmaceutical Science, National Yang-Ming University, Taipei, Taiwan; the ²Department of Ophthalmology, Buddhist Tzu Chi General Hospital-Taipei, Taiwan; and the ³Department of Medical Research and Education, Taipei Veterans General Hospital and School of Medicine, National Yang-Ming University, Taipei, Taiwan.

PURPOSE. Exogenous thymosin ß-4 (Tß₄) has been shown to inhibit the apoptosis in nontransformed human corneal epithelial cells that is triggered by ethanol. The purpose of this study is to examine whether exogenous Tß₄ protects SV40-immortalized human corneal epithelial T (HCE-T) cells against the toxic effects of Fas ligand (FasL) and hydrogen peroxide (H₂O₂) and to elucidate its mechanism of action.

METHODS. HCE-T cells were incubated without or with the recombinant histidine-tagged Tß₄ produced by Escherichia coli before the addition of FasL or H₂O₂. Cell viability was determined by MTT or MTS assay, and activation of caspase-8, -9, and -3 was examined by colorimetric and fluorescent substrate cleavage assays. The internalization of exogenous Tß₄ in HCE-T cells was analyzed by immunofluorescence staining. Cytochalasin D, an actin depolymerization agent, was added to examine whether the actin cytoskeleton is involved in Tß₄ entry and whether the internalization of this peptide is crucial for its cytoprotection.

RESULTS. The death of HCE-T cells induced by both FasL and H₂O₂ was dramatically reduced by the recombinant Tß₄ pretreatment. Moreover, FasL-mediated activation of caspases-8 and -3 as well as H₂O₂-triggered stimulation of caspases-9 and -3 in these cells was abolished by preincubating them with the exogenous Tß₄. Of note, internalization of this G-actin-sequestering peptide into HCE-T cells was found to be essential in cell death prevention, in that disruption of the cellular entry of Tß₄ by cytochalasin D abrogated its cytoprotective effects.

CONCLUSIONS. This is the first report to demonstrate that the internalization of exogenous Tß₄ is essential for its antiapoptotic activity in human corneal epithelial cells.

This article has been cited by other articles:

				J H-C Ho, K-C Tseng, W-H Ma, K-H Chen, O K-S Lee, and Y Su Thymosin beta-4 upregulates anti-oxidative enzymes and protects human cornea epithelial cells against oxidative damage Br. J. Ophthalmol., July 1, 2008; 92(7): 992 - 997. [Abstract] [Full Text] [PDF]

				G. SOSNE, P. QIU, and M. KURPAKUS-WHEATER Thymosin beta-4 and the Eye: I Can See Clearly Now the Pain Is Gone Ann. N.Y. Acad. Sci., September 1, 2007; 1112(1): 114 - 122. [Abstract] [Full Text] [PDF]

				L.-I. LARSSON and S. HOLCK Localization of Thymosin beta-4 in Tumors Ann. N.Y. Acad. Sci., September 1, 2007; 1112(1): 317 - 325. [Abstract] [Full Text] [PDF]