adenosine-kinase and Cerebral-Infarction

Protective mechanisms of the brain may reduce the extent of injury after focal cerebral ischemia. Here, we explored in a mouse model of focal cerebral ischemia potential synergistic neuroprotective effects of two mediators of neuroprotection: (i) neuronal or glial precursor cells and (ii) the inhibitory neuromodulator adenosine. Embryonic stem (ES) cells, engineered to release adenosine by biallelic disruption of the adenosine kinase gene, and respective wild-type cells were induced to differentiate into either neural or glial precursor cells and were injected into the striatum of mice 1 week before middle cerebral artery occlusion. All stem cell-derived graft recipients were characterized by a significant reduction in infarct volume, an effect that was augmented by the release of adenosine. Neuroprotection was strongest in adenosine-releasing glial precursor cell recipients, which were characterized by an 85% reduction of the infarct area. Graft-mediated neuroprotection correlated with a significant improvement of general and focal neurologic scores. Histologic analysis before and after ischemia revealed clusters of implanted cells within the striatum of all treated mice. We conclude that ES cell derived adenosine-releasing brain implants provide neuroprotection by synergism of endogenous precursor cell-mediated effects and paracrine adenosine release.

Topics: Adenosine; Adenosine Kinase; Alleles; Animals; Brain Ischemia; Cerebral Infarction; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Nervous System Diseases; Neurons; Stem Cell Transplantation

Brain ischemia is associated with a marked increase in extracellular adenosine levels. This results in activation of cell surface adenosine receptors and some degree of neuroprotection. Adenosine kinase is a key enzyme controlling adenosine metabolism. Inhibition of this enzyme enhances the levels of endogenous brain adenosine already elevated as a result of the ischemic episode. We studied a novel adenosine kinase inhibitor (AKI), GP683, in a rat focal ischemia model.. Four groups of 10 adult Sprague-Dawley rats were exposed to 90 minutes of temporary middle cerebral artery (MCA) occlusion. Animals were injected intraperitoneally with vehicle, 0.5 mg/kg, 1.0 mg/kg, or 2.0 mg/kg of GP683 30, 150, and 270 minutes after the induction of ischemia by a researcher blinded to treatment group. The animals were euthanatized 24 hours after MCA occlusion, and brains were stained with 2,3,5-triphenyltetrazolium chloride. We measured brain temperatures in a separate group of 6 rats before and after administration of 1.0 mg/kg GP683.. All treated groups showed a reduction in infarct volumes, but a significant effect was observed only in the 1.0 mg/kg-dose group (44% reduction, P=0.0077). Body weight, physiological parameters, neurological scores, and mortality did not differ among the 4 groups. No apparent behavioral side effects were observed. Brain temperatures did not change after drug injection.. Our results indicate that the use of AKIs offers therapeutic potential and may represent a novel approach to the treatment of acute brain ischemia. The therapeutic effect observed was not caused by a decrease in brain temperature.

Topics: Adenosine Kinase; Animals; Arterial Occlusive Diseases; Body Temperature; Brain; Cerebral Infarction; Disease Models, Animal; Ischemic Attack, Transient; Male; Neuroprotective Agents; Pyrimidines; Rats; Rats, Sprague-Dawley; Time Factors

Endogenous adenosine released locally during cerebral ischemia is neuroprotective, and agents which decrease adenosine inactivation may potentiate its protective effects. The effects of 5'-deoxy-5-iodotubercidin (5'd-5IT), an inhibitor of the adenosine-catabolizing enzyme, adenosine kinase, were studied in male Wistar rats subjected to 2 h of transient middle cerebral artery occlusion. 5'd-5IT or the vehicle (10% DMSO in saline) was administered i.p. 30 min before, and 2 h and 6 h after the induction of middle cerebral artery occlusion. The infarct volume was determine using 2,3,5-triphenyltetrazolium chloride staining 48 h after middle cerebral artery occlusion. The infarct volume was significantly reduced in rats treated with 1.85 mg/kg x 3 (57% reduction, P < 0.001) or 1.0 mg/kg x 3 (34% reduction, P < 0.05), but not 0.3 mg/kg x 3 5'd-5IT compared to vehicle-treated rats. The reduction of infarct volume was accompanied by a significant improvement in behavioral measures of neurological deficit. These data further support a role of adenosine in neuroprotection and suggest that adenosine kinase inhibition may be a useful approach to the treatment of focal cerebral ischemia.

Topics: Adenosine Kinase; Animals; Arterial Occlusive Diseases; Body Temperature; Body Weight; Brain; Cerebral Infarction; Enzyme Inhibitors; Ischemic Attack, Transient; Male; Neuroprotective Agents; Rats; Rats, Wistar; Tubercidin

The adenosine kinase inhibitor, 5'-deoxyiodotubercidin (5dITU), was examined in a rat focal stoke model with temporary (105 min) middle cerebral artery occlusion (MCAO) followed by a 24 h recovery period. Inhibition of this adenosine metabolizing enzyme indirectly enhances the actions of endogenous adenosine without inducing cardiovascular side effects. Such effects could limit the potential clinical application of any approach targeting adenosine receptor activation. MCAO was accomplished with a transluminal 4-0 nylon suture inserted through the common carotid artery to block blood flow at the origin of the MCA. Treatment with 5dITU 30 min prior to and 5 h after MCAO resulted in a dose dependent (0.1-0.5 mg/kg, i.p.) reduction in infarct volume. A significant (P = 0.02) 44% reduction (control, 265 +/- 35 mm3; treated, 149 +/- 30 mm3) was observed at 0.5 mg/kg. However, at the highest dose examined (1.0 mg/kg) infarct volume was unaffected. To assess the potential for acute (i.e. post-occlusion) treatment, 5dITU was administered (0.33 mg/kg, i.v.) successively at each of 0.5, 1.75 and 3.5 h after MCAO. Post-occlusion treatment resulted in a significant (P = 0.037) 32% reduction in infarct volume (control, 314 +/- 34 mm3; treated, 212 +/- 28 mm3). At this dose there were no apparent changes in a number of physiological parameters monitored over the period of MCAO. The present study shows that intervention with an adenosine kinase inhibitor in an ischemic brain injury model is neuroprotective whether treatment is begun prior to or just after MCAO.

Topics: Adenosine Kinase; Animals; Cerebral Arteries; Cerebral Infarction; Cerebrovascular Disorders; Constriction, Pathologic; Male; Rats; Tubercidin