Intracortical injection of endothelin-1 induces cortical infarcts in mice: effect of neuronal expression of an adenosine transporter

Abstract

BackgroundActivation of adenosine A1 receptors has neuroprotective effects in animal stroke models. Adenosine levels are regulated by nucleoside transporters. In vitro studies showed that neuron-specific expression of human equilibrative nucleoside transporter 1 (hENT1) decreases extracellular adenosine levels and adenosine A1 receptor activity. In this study, we tested the effect of hENT1 expression on cortical infarct size following intracerebral injection of the vasoconstrictor endothelin-1 (ET-1) or saline.MethodsMice underwent stereotaxic intracortical injection of ET-1 (1 μl; 400 pmol) or saline (1 μl). Some mice received the adenosine receptor antagonist caffeine (25 mg/kg, intraperitoneal) 30 minutes prior to ET-1. Perfusion and T2-weighted magnetic resonance imaging (MRI) were used to measure cerebral blood flow (CBF) and subsequent infarct size, respectively.ResultsET-1 reduced CBF at the injection site to 7.3 ± 1.3% (n = 12) in hENT1 transgenic (Tg) and 12.5 ± 2.0% (n = 13) in wild type (Wt) mice. At 48 hours following ET-1 injection, CBF was partially restored to 35.8 ± 4.5% in Tg and to 45.2 ± 6.3% in Wt mice; infarct sizes were significantly greater in Tg (9 ± 1.1 mm3) than Wt (5.4 ± 0.8 mm3) mice. Saline-treated Tg and Wt mice had modest decreases in CBF and infarcts were less than 1 mm3. For mice treated with caffeine, CBF values and infarct sizes were not significantly different between Tg and Wt mice.ConclusionsET-1 produced greater ischemic injury in hENT1 Tg than in Wt mice. This genotype difference was not observed in mice that had received caffeine. These data indicate that hENT1 Tg mice have reduced ischemia-evoked increases in adenosine receptor activity compared to Wt mice.

Transgenic Mice Overexpressing Human Angiotensin I Receptor Gene Are Susceptible to Stroke Injury

“…Focal ischemia was induced in 3–5 months old, male C57, Hap-I and Hap-II mice by giving a ET-1 intra striatal injection using the method of Soylu et al [20]. Mice were anesthetized for a brief period in 4–5% of isoflurane in the induction chamber and then stabilized at 1–2% isoflurane using the nose cone on the stereotaxic equipment (Stoelting, Wood Dale, IL).…”

Regulation of adenosine levels during cerebral ischemia

“…This genotype difference in infarct sizes was not evident in mice that had received the adenosine receptor antagonist caffeine (25 mg/kg, ip) 30 min prior to intracerebral injection of endothelin-1, indicating that a genotype difference in ischemic adenosine levels and adenosine receptor activity was responsible for the differences in ischemic infarct sizes between wild type and hENT1 transgenic mice [33] .…”

“…Previously, it has been determined that reduction of blood flow to 20% of normal flow results in ischemic injury [32] . We found that an injection of endothelin-1 (400 pmol) into cerebral cortex produced a longlasting decrease in blood flow at the site of injection [33] . Using perfusion-weighted magnetic resonance imaging, cerebral blood flow was determined at 4 and 48 h post-injection and found to be less than 15% and 50%, respectively, relative to pre-injection values.…”

“…Interestingly, while cerebral blood flow responses were similar between wild type and hENT1 transgenic mice, cerebral infarct sizes were 60% larger, as determined by T2-weighted magnetic resonance imaging, in hENT1 transgenic mice [33] . This genotype difference in infarct sizes was not evident in mice that had received the adenosine receptor antagonist caffeine (25 mg/kg, ip) 30 min prior to intracerebral injection of endothelin-1, indicating that a genotype difference in ischemic adenosine levels and adenosine receptor activity was responsible for the differences in ischemic infarct sizes between wild type and hENT1 transgenic mice [33] .…”

CD200 restrains macrophage attack on oligodendrocyte precursors via toll-like receptor 4 downregulation

“…9 ET-1 is a potent vasoconstrictor and exhibits long-lasting actions for at least 48 h when injected into brain as a standard model for producing focally restricted ischemic injury. 10 Additionally, when injected into white matter area, ET-1 produces hallmarks of white matter injury observed in humans, such as axonal damage, demyelination, inflammation, and glial scar formation. 11 Myelin damage was detected by fluoromyelin staining (1:300, Life technologies, F34651).…”