Insight into adenosine receptor function using antisense and gene-knockout approaches

Mutually protective actions of kainic acid epileptic preconditioning and sublethal global ischemia on hippocampal neuronal death: involvement of adenosine A1 receptors and K(ATP) channels

Preconditioning with sublethal ischemia attenuates the detrimental effects of subsequent prolonged ischemic insults. This research elucidates potential in vivo cross-tolerance between different neuronal death-generating treatments such as kainate administration, which induces seizures and global ischemia. This study also investigates the effects of a mild epileptic insult on neuronal death in rat hippocampus after a subsequent, lethal epileptic stress using kainic acid (KA) as a model of epilepsy. Three preconditioning groups were as follows: group 1 was injected with 5 mg/kg KA before a 6-minute global ischemia; group 2 received a 3-minute global ischemia before 7.5 mg/kg KA; and group 3 was injected with a 5-mg/kg dose of KA before a 7.5-mg/kg KA injection. The interval between treatments was 3 days. Neuronal degeneration, revealed by the silver impregnation method and analysis of cresyl violet staining, was markedly reduced in rats preconditioned with a sublethal ischemia or a 5-mg/kg KA treatment. Labeling with terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'triphosphate-biotin nick-end labeling and DNA laddering confirmed the component of DNA fragmentation in the death of ischemic and epileptic neurons and its reduction in all preconditioned animals. The current study supports the existence of bidirectional cross-tolerance between KA excitotoxicity and global ischemia and suggests the involvement of adenosine A1 receptors and sulfonylurea- and ATP-sensitive K+ channels in this protective phenomenon.

Oligonucleotide-based inhibition of embryonic gene expression

We describe a technique to define gene function using antisense oligonucleotide (AS-ODN) inhibition of gene expression in mice. A single intravenous injection of an AS-ODN targeting vascular endothelial growth factor (VEGF) into pregnant mice between E7.5-8.5 resulted in a lack of primary angiogenesis. This enabled us to define the critical window required to inhibit VEGF expression and recapitulate the primary loss of function phenotype observed in VEGF (-/-) embryos. This phenotype was sequence-specific and time- and dose-dependent. Injection of an AS-ODN targeting a second gene, E-cadherin, into pregnant mice at E10 confirmed a hypothesized secondary phenotype. This is the first report of AS-ODN inhibition of gene expression in utero and provides a new strategy for target validation in functional genomics.