Attenuation of temporary focal cerebral ischemic injury in the mouse following transfection with interleukin-1 receptor antagonist.

The proinflammatory cytokine interleukin-1 beta (IL-1beta) is thought to play an important role in the stimulation of the inflammatory response following ischemia and reperfusion. This study investigated the inflammatory effect of IL-1beta during transient focal cerebral ischemia and reperfusion in the mouse transduced with the interleukin-1 receptor antagonist (IL-1ra) gene. An adenoviral vector encoding, either the human IL-1ra gene (AdRSVIL-1ra) or the LacZ gene (AdRSVlacZ) or normal saline, were injected into the right lateral ventricles of adult CD-1 mice (n=96). Five days later, the mice received 1 h temporary middle cerebral artery occlusion (tMACAO) followed by 23 h reperfusion. Cerebral blood flow (CBF), infarct volume, blood-brain barrier (BBB) permeability, and the number of intracellular adhesion molecule-1 positive vessels were measured to determine the effect of IL-1beta during postischemic reperfusion. Infarct volume in the AdRSVIL-1ra-transduced mice was markedly reduced compared to the AdRSVlacZ-transduced and saline-injected mice (36.0+/-5.3 mm(3) vs. 60.0+/-6.2 mm(3), 69. 5+/-6.3 mm(3), after 23 h of reperfusion, n=6-8 per group, p<0.05). BBB disruption and intracellular adhesion molecule-1 expression (135+/-23 vs. 311+/-40 and 357+/-51, n=6-8 per group, p<0.05) in the AdRSVIL-1ra-transduced mice were also less than that of the AdRSVlacZ-transduced and saline-injected mice. Our studies demonstrated that overexpression of IL-1ra in the mouse brain can downregulate intracellular adhesion molecule-1 expression both in the cortex and basal ganglia, which suggests that IL-1beta may play an important role in the activation of the inflammatory response during focal cerebral ischemia by promoting leukocyte adhesion to endothelial cells. The decrease of BBB disruption in AdRSVIL-1ra-transduced mice suggests that the endothelial cells may be a target for IL-1beta during postischemic reperfusion.

Comparison of cerebral blood flow and injury following intracerebral and subdural hematoma in the rat.

Subdural hematomas (SDH) can induce ischemia and neuronal damage in the underlying cortex. However, the extent to which intracerebral hematomas (ICH) produce reductions in cerebral blood flow (CBF) sufficient to cause ischemic damage is uncertain. Intracranial hemorrhage was induced by the injection of 100 or 200 microl of blood into the subdural space (SDH) or into the caudate nucleus (ICH) of the rat. CBF was measured using [14C]-iodoantipyrine autoradiography at 4 h. Brain damage was measured using 2,3, 5-triphenyl tetrazolium chloride (TTC) staining at 24 h and brain edema was measured using the wet/dry weight method. Brain ion contents were measured at 24 h using a flame photometer and chloridometer. In the CBF studies, the volume of tissue perfused below the ischemic threshold (<20 ml/100 g/min) for SDH was 122+/-35 mm3 (sham: 3.3+/-1.7 mm3). Following ICH, there was a small volume of tissue perfused below the ischemic threshold 50+/-11 mm3 (sham: 3. 3+/-2.5 mm3) but this volume corresponded closely to the volume of clot (71+/-5 mm3). The extent of brain damage, measured by TTC staining, in the cerebral cortex correlated with the increasing volume of the subdural blood clot (sham: 9+/-3 mm3; 200 microl: 81+/-19 mm3; P<0.01). Conversely, minimal brain damage was detected following ICH. The injection of blood into the subdural space or into the brain parenchyma induced blood volume-dependent increases in brain water content at 24 h. Increases in brain water content after SDH, were confined to the cerebral cortex (sham: 0.1+/-0.1 g/g dry weight; 200 microl: 0.8+/-0.3 g/g dry weight; P<0.001). In contrast, increases in brain water content after ICH were predominantly in the subcortical region (sham: 0.1+/-0.1 g/g dry weight; 200 microl: 0.4+/-0.2 g/g dry weight; P<0.01). The present investigations demonstrate differences in CBF, brain injury and edema formation following SDH and ICH indicating that these conditions may require different therapeutic interventions.

Tumor necrosis factor alpha expression produces increased blood-brain barrier permeability following temporary focal cerebral ischemia in mice.

Alteration of blood-brain barrier (BBB) function occurs in both permanent and temporary cerebral ischemia. Studies in vivo and in vitro have shown that tumor necrosis factor-alpha (TNFalpha) is involved in changes of BBB permeability. However, the relationship between TNFalpha expression and BBB disruption during reperfusion is unclear. The aim of this study is to find the cell source of TNFalpha and to determine the relationship between TNFalpha expression and BBB disruption following temporary focal cerebral ischemia in mice. Adult CD-1 mice received 1 h middle cerebral artery occlusion (MCAO) followed by 2 h, 6 h, 12 h, 24 h, and 48 h of reperfusion. MCAO was achieved using an intraluminal suture technique and reperfusion was performed by the suture withdrawal. Neutralizing monoclonal anti-mouse TNFalpha antibody was administrated intraventricularly immediately after reperfusion. TNFalpha expression was determined by double labeling immunohistochemistry. BBB permeability was determined by albumin immunostaining. TNFalpha immunoreactivity (IR) was observed in the ipsilateral hemisphere from 1 h MCAO with 2 h reperfusion. TNFalpha positive cells included neurons, astrocytes, and ependymal cells. BBB disruption was detected beginning at 6 h reperfusion but was not present at 2 h of reperfusion. The areas of BBB disruption were significantly enlarged at 12 h reperfusion and plateaued at 24 h to 48 h reperfusion. BBB disruptions were significantly attenuated in the anti-TNFalpha antibody treated mice (p<0.05). Our results demonstrate that TNFalpha IR existed in neurons, astrocytes, and ependymal cells during reperfusion. TNFalpha IR following temporary focal cerebral ischemia precedes increased BBB permeability. Treatment with TNFalpha antibody reduces BBB disruption, suggesting TNFalpha may be an important mediator in altering BBB permeability during reperfusion.

Blood-brain barrier mechanisms involved in brain calcium and potassium homeostasis.

This study examined the potential roles of the plasma membrane Ca2+-ATPase (PMCA) at the blood-CSF and blood-brain barriers in brain Ca2+ homeostasis and blood-brain barrier Na+/K+-ATPase subunits in brain K+ homeostasis. During dietary-induced hypo- and hypercalcemia (0.59+/-0.06 and 1.58+/-0.12 mM [Ca2+]) there was no significant change in choroid plexus PMCA (Western Blots) compared to normocalcemic rats (plasma [Ca2+]: 1.06+/-0.11 mM). In contrast, PMCA in cerebral microvessels isolated from hypocalcemic rats was 150% greater than that in controls (p<0.001). Comparison of the alpha3 subunit of Na+/K+-ATPase from cerebral microvessels isolated from hypo-, normo- and hyperkalemic rats (2.3+/-0.1, 3.9+/-0.1 and 7. 2+/-0.6 mM [K+]) showed a 75% reduction in the amount of this isoform during hyperkalemia. None of the other Na+/K+-ATPase isoforms varied with plasma [K+]. These results suggest that both PMCA and the alpha3 subunit of Na+/K+-ATPase at the blood-brain barrier play a role in maintaining a constant brain microenvironment during fluctuations in plasma composition.