Yanming F. Wang

Mice deficient in fractalkine are less susceptible to cerebral ischemia-reperfusion injury

Fractalkine (FKN), also known as neurotactin, is a CX(3)C chemokine that exists in both secreted and neuronal membrane-bound forms and is upregulated during brain inflammation. There is accumulating evidence that FKN induces chemotaxis by binding to its receptor CX(3)CR1 on leukocytes and microglia. We generated FKN-deficient mice to study the role of FKN in postischemic brain injury. After transient focal cerebral ischemia, FKN-deficient mice had a 28% reduction in infarction size and lower mortality rate, when compared to wild-type littermates. The findings of this study indicate a possible role for FKN in augmenting postischemic injury and mortality after transient focal cerebral ischemia.

Mice Deficient in Mac-1 (CD11b/CD18) Are Less Susceptible to Cerebral Ischemia/Reperfusion Injury

BACKGROUND AND PURPOSEnMacrophage-1 antigen (Mac-1) (CD11b/CD18), a leukocyte beta2 integrin, facilitates neutrophil adhesion, transendothelial migration, phagocytosis, and respiratory burst, all of which may mediate reperfusion-induced injury to ischemic brain tissue in conditions such as stroke. To determine the role of Mac-1 during ischemia and reperfusion in the brain, we analyzed the effect of transient focal cerebral ischemia in mice genetically engineered with a specific deficiency in Mac-1.nnnMETHODSnTransient focal ischemia/reperfusion was induced by occluding the left middle cerebral artery for 3 hours followed by a 21-hour reperfusion period in Mac-1-deficient (n=12) and wild-type (n=11) mice. Regional cerebral blood flow was determined with a laser-Doppler flowmeter. Brain sections were stained with 2% 2,3,5-triphenyltetrazolium chloride to determine the infarct volume. Neutrophil accumulation was determined by staining the brain sections with dichloroacetate esterase to identify neutrophils.nnnRESULTSnCompared with the wild-type cohort, Mac-1-deficient mice had a 26% reduction in infarction volume (P<0.05). This was associated with a 50%, but statistically insignificant, reduction in the number of extravasated neutrophils in the infarcted areas of the brains in the mutant mice. There were no differences in regional cerebral blood flow between the 2 groups.nnnCONCLUSIONSnMac-1 deficiency reduces neutrophil infiltration and cerebral cell death after transient focal cerebral ischemia. This finding may be related to a reduction in neutrophil extravasation in Mac-1-deficient mice.

P- and E-selectin-deficient mice are susceptible to cerebral ischemia-reperfusion injury.

We examined brain sections from P- and E-selectin-deficient mice (-/-) and their nontransgenic littermates (+/+) after focal cerebral ischemia and reperfusion (I/R) tissue injury. There was no difference in the subsequent infarct volume after 3 h of ischemia and 21 h of reperfusion. These data indicate that selectin-independent mechanisms mediate tissue injury after a prolonged period of transient focal ischemia.

Cerebrospinal fluid may mediate CNS ischemic injury

BackgroundThe central nervous system (CNS) is extremely vulnerable to ischemic injury. The details underlying this susceptibility are not completely understood. Since the CNS is surrounded by cerebrospinal fluid (CSF) that contains a low concentration of plasma protein, we examined the effect of changing the CSF in the evolution of CNS injury during ischemic insult.MethodsLumbar spinal cord ischemia was induced in rabbits by cross-clamping the descending abdominal aorta for 1 h, 2 h or 3 h followed by 7 d of reperfusion. Prior to ischemia, rabbits were subjected to the following procedures; 1) CSF depletion, 2) CSF replenishment at 0 mmHg intracranial pressure (ICP), and 3) replacement of CSF with 8% albumin- or 1% gelatin-modified artificial CSF, respectively. Motor function of the hind limbs and histopathological changes of the spinal cord were scored. Post-ischemic microcirculation of the spinal cord was visualized by fluorescein isothiocyanate (FITC) albumin.ResultsThe severity of histopathological damage paralleled the neurological deficit scores. Paraplegia and associated histopathological changes were accompanied by a clear post-ischemic deficit in blood perfusion.Spinal cord ischemia for 1 h resulted in permanent paraplegia in the control group. Depletion of the CSF significantly prevented paraplegia. CSF replenishment with the ICP reduced to 0 mmHg, did not prevent paraplegia. Replacement of CSF with albumin- or gelatin-modified artificial CSF prevented paraplegia in rabbits even when the ICP was maintained at 10–15 mmHg.ConclusionWe conclude that the presence of normal CSF may contribute to the vulnerability of the spinal cord to ischemic injury. Depletion of the CSF or replacement of the CSF with an albumin- or gelatin-modified artificial CSF can be neuroprotective.

ICAM-1 dependent pathway is not involved in the development of neuronal apoptosis after transient focal cerebral ischemia.

We examined brain sections from ICAM-1 deficient mice (-/-) and their nontransgenic littermates (+/+) after focal cerebral ischemia and reperfusion (I/R) for the presence of apoptosis. Despite the reduction in necrosis, the -/- mice had apoptotic cells in the ischemic hemisphere as shown by terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end-labeling (TUNEL) staining and DNA laddering. ICAM-1 deficiency minimizes necrosis but not apoptosis after temporary MCAO in mice, thereby leaving the potential for delayed neuronal cell death despite ICAM-1 inactivation.