1. ¹Department of Neurology, Taipei Medical University, Taipei, Taiwan
2. ²Department of Neurology, Chang Gung Memorial Hospital, Kaohsiung, Taiwan
3. ³The Institute of Neuroscience, TzuChi University, Hualien, Taiwan
4. ⁴Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
5. ⁵Department of Life Sciences, National Chung Hsing University, Taichung, Taiwan
6. ⁶Department of Molecular Virology, Immunology, and Medical Genetics, Division of Human Cancer Genetics, The Ohio State University, Columbus, Ohio, USA
7. ⁷Chi-Ching Huang Stroke Research Center, Taipei Medical University, Taipei, Taiwan

Correspondence: Dr CY Hsu, Chi-Ching Huang Stroke Research Center, Taipei Medical University, 250 Wu-Hsing Street, Taipei 110, Taiwan, Republic of China. E-mail: hsuc@tmu.edu.tw

Received 8 December 2005; Revised 6 February 2006; Accepted 6 February 2006; Published online 29 March 2006.

Abstract

Angiogenesis is induced in response to ischemia. Thrombospondin-1 (TSP-1) is a potent angiostatic factor. Silencing of TSP-1 expression may contribute to the postischemic angiogenesis. Upregulation of TSP-1, in contrast, may terminate the postischemic angiogenesis. A possible mechanism that silences TSP-1 expression is the DNA methylation of its promoter region. DNA methylation has been reported following cerebral ischemia. The present study aimed to explore whether methylation of the promoter region of TSP-1 regulates its expression after oxygen–glucose deprivation (OGD) in murine cerebral endothelial cells (CECs) in vitro. Sublethal OGD increased the extent of methylation of the promoter region of TSP-1 with a concurrent decrease in TSP-1 mRNA and protein expression in CECs. After reoxygenation, demethylation of the TSP-1 promoter region led to the restoration of TSP-1 mRNA and protein expression. The extent of methylation of the promoter region of TSP-1 was inversely correlated with the extent of TSP-1 gene expression at mRNA and protein levels after OGD. Oxygen–glucose deprivation-induced reduction in the TSP-1 mRNA level was not accompanied by a change in mRNA stability. These findings raise the possibility that OGD downregulation of TSP-1 expression is at least in part due to methylation of its promoter region.