Dipyridamole increases oxygen-glucose deprivation-induced injury in cortical cell culture.

Abstract

Background and Purpose Adenosine transport inhibitors attenuate ischemic central neuronal damage in vivo, but the locus of this protective action is presently unknown. To help address the question of whether adenosine transport inhibitors have a protective effect directly on brain parenchyma, we tested the effect of the adenosine transport inhibitor dipyridamole on neuronal loss induced by oxygen-glucose deprivation in vitro.Methods Murine cortical cultures were exposed to combined oxygen and glucose deprivation, iV-methyl-D-aspartate, or kainate. The extracellular concentrations of glutamate and adenosine were measured by high-performance liquid chromatography; neuronal cell death was assessed by morphological examination and measurement of lactate dehydrogenase release.Results Cultures exposed to oxygen-glucose deprivation for 30 to 75 minutes exhibited an insult-dependent increase in extracellular adenosine, followed shortly by an increase in E xtracellular adenosine levels have been shown to increase during reduced energy conditions both in vivo 1 -2 and in vitro. 3 However, the source of the extracellular adenosine is not known. In vivo studies have shown that inhibition of the adenosine transporter increases extracellular adenosine 45 and attenuates ischemic damage.6 ' 8 These results are consistent with the possibility that adenosine is formed extracellularly (by the breakdown of ATP and other adenine nucleotides released during the ischemic period), and the adenosine transporter serves to remove extracellular adenosine.However, adenosine transport inhibitors are known to have multiple effects. Specifically, dipyridamole has been shown to potentiate hypoxic pial arteriolar vasodilation 9 and increase cerebral blood flow during anoxia.10 Thus, the protective effects of adenosine transport inhibitors could be primarily due to effects on blood flow. Furthermore, in vitro studies using neurons 11 Addition of the Al receptor antagonist 8-cyclopentyltheophylline during oxygen-glucose deprivation enhanced both glutamate release and neuronal damage. Addition of 10 ^.mol/L dipyridamole decreased extracellular adenosine and also enhanced extracellular glutamate and neuronal death. In contrast, dipyridamole increased the levels of extracellular adenosine stimulated by Af-methyl-D-aspartate or kainate.Conclusions These results are consistent with the idea that endogenous adenosine has a neuroprotective effect directly on cortical cells exposed to oxygen-glucose deprivation. However, inhibition of adenosine transport with dipyridamole was surprisingly not an effective strategy for enhancing this protective effect. The beneficial effects of adenosine transport inhibitors observed in vivo may be mediated indirectly-for example, by effects on the vasculature. To help address the question of whether adenosine transport inhibitors have a protective effect directly on brain parenchyma, we tested the effect of dipyridamole on the neuronal loss induced by oxygen-glucose deprivation in murine cortical cell cultures. Material...

A1 adenosine receptors mediate hypoglycemia-induced neuronal injury

“…We present data that suggest that glucose deprivation promotes neuronal injury that is mediated by A 1 ARs. In contrast, direct A 1 AR antagonism, using 8-cyclopentyltheophylline, has been shown to increase neuronal death following exposure of mixed neuron-glia cultures to combined hypoxia/hypoglycemia (Lobner & Choi 1994). However, in the same study, the adenosine uptake inhibitor, dipyridamole, also enhanced hypoxia/hypoglycemia-induced neuronal death.…”

Neuronal Gap Junction Coupling Is Regulated by Glutamate and Plays Critical Role in Cell Death during Neuronal Injury

“…To determine changes during neuronal injury in neuronal gap junction coupling and expression of Cx36, we used OGD (see Materials and Methods), that is considered an in vitro model of ischemia (Lobner and Choi, 1994). Tests were done in wild-type mouse neuronal somatosensory cortical cultures after their maturation (Fig.…”

System xc−Activity and Astrocytes Are Necessary for Interleukin-1β-Mediated Hypoxic Neuronal Injury

“…After confirming absence of LDH leakage, which assessed for cell damage and hence nonspecific leakage of glutamate from dying cells, samples were stored at Ϫ20°C until analyzed. Two hundred microliters were assayed for glutamate via phenylisothiocyanate derivatization, HPLC (1100 series; Agilent, Palo Alto, CA) separation using a Hypersil-ODS reversephase column and ultraviolet detection at a wavelength of 254 nm, as described previously (Lobner and Choi, 1994;Hewett et al, 1996). Before the HPLC run, the samples were reconstituted in solvent consisting of 0.14 M sodium acetate, 0.05% tetraethylammonium, and 6% acetonitrile and brought to pH 6.4 with glacial acetic acid.…”