Transgenic mice overexpressing endothelin-1 in astrocytes display greater infarct size and more severe neurological deficit after transient focal cerebral ischemia

Abstract

Our preliminary studies demonstrated that endothelin-1 (ET-1) mRNA expression is increased in astrocyte-like and endothelial cells in experimentally induced hypoxia/ischemia. Therefore, we developed a transgenic mouse model to study the role of astrocytic ET-1 in cerebral injury by microinjection of a modified GFAP genomic cassette containing the mouse ET-1 cDNA. A total of 5 lines were generated. All embryos appeared to develop to full term since the number of animals being born followed Mendelian distribution. Two lines of mice, 3804 and 3808, show brain-specific transgene expression as revealed by both rt-PCR and Northern analyses. In line 3804, the brain ET-1 peptide level was increased by two folds. No obvious abnormalities were observed in the gross anatomy of the brain and cerebrovasculature of these transgenic mice. GFAP ICC also revealed no differences in the number of positively-stained astrocytes and their cellular distribution. Therefore, it appears that over-expression of ET-1 in the brain did not affect the development of the mouse embryo and the brain. However, upon focal cerebral ischemia induced by transient filament occlusion of the middle cerebral artery, transgenic mouse brains displayed an increase in infarct area and infarct volume percentages. A higher number of transgenic mice showed more severe neurological deficit when compared to their wildtype littermates. The present data suggested that overexpression of ET-1 in astrocytes may have adverse effects on the brain during cerebral ischemic injury. Supported by Research Grants Council Hong Kong