Leukocyte Accumulation and Hemodynamic Changes in the Cerebral Microcirculation During Early Reperfusion After Stroke

Abstract

Background and Purpose-Leukocytes contribute to cerebral ischemia-reperfusion injury. However, few experimental models examine both in vivo behavior of leukocytes and microvascular rheology after stroke. The purpose of the present study was to characterize patterns of leukocyte accumulation in the cerebral microcirculation and to examine the relationship between leukocyte accumulation and microcirculatory hemodynamics after middle cerebral artery occlusion and reperfusion (MCAO-R). Methods-Male rats (250 to 350 g) were anesthetized and ventilated. Tail catheters were inserted for measurement of arterial blood gases and administration of drugs. Body temperature was maintained at 37°C. Animals were subjected to 2 hours of MCAO by the filament method. A cranial-window preparation was performed, and the brain was superfused with warm, aerated artificial cerebrospinal fluid. Reperfusion was initiated by withdrawing the filament, and the pial microcirculation was observed by use of intravital fluorescence microscopy. Leukocyte accumulation in venules, arterioles, and capillaries; leukocyte rolling in venules; and leukocyte venular shear rate were assessed during 1 hour of reperfusion. Results-We found significant leukocyte adhesion in cerebral venules during 1 hour of reperfusion after 2 hours of MCAO.Leukocyte trapping in capillaries and adhesion to arterioles after MCAO-R tended to increase compared with controls, but the increase was not significant. We also found that shear rate was significantly reduced in venules during early reperfusion after MCAO. Conclusions-A model using the filament method of stroke and fluorescence microscopy was used to examine white-cell behavior and hemodynamics in the cerebral microcirculation after MCAO-R. We observed a significant increase in leukocyte rolling and adhesion in venules and a significant decrease in blood shear rate in the microcirculation of the brain during early reperfusion. Leukocytes may activate and damage the blood vessels and surrounding brain cells, which contributes to an exaggerated inflammatory component to reperfusion. The model described can be used to examine precisely blood cell-endothelium interactions and hemodynamic changes in the microcirculation during postischemic reperfusion. Information from these and similar experiments may contribute to our understanding of the early inflammatory response in the brain during reperfusion after stroke.

Platelet–Leukocyte–Endothelial Cell Interactions after Middle Cerebral Artery Occlusion and Reperfusion

“…Leukocyte-endothelial cell interactions have been previously described in porcine (Gidday et al, 1997), gerbil (Uhl et al, 2000), rat (Dirnagl et al, 1994), and murine (Ishikawa et al, 2003) models of global I/R, and after focal I/R in the rat (Ishikawa et al, 1999;Ritter et al, 2000). The present study represents the first attempt to systematically evaluate the effects of focal I/R on the…”

Systemic Inflammatory Stimulus Potentiates the Acute Phase and CXC Chemokine Responses to Experimental Stroke and Exacerbates Brain Damage via Interleukin-1- and Neutrophil-Dependent Mechanisms

“…Alternatively, more abundant cortical expression of mediators required for neutrophil extravasation (selectins, chemokines, adhesion molecules) could determine the relative predominance of cortical neutrophil accumulation. Neutrophils may promote the conversion of vulnerable yet viable cortical tissue to infarction through microvessel obstruction/thrombosis that compromises reperfusion (del Zoppo et al, 1991;Ritter et al, 2000), production of reactive oxygen species (ROS) causing oxidative stress (Aizawa et al, 2006), and release of matrix metalloproteinases that degrade components of the vascular basement membrane and extracellular matrix (Asahi et al, 2001;Gidday et al, 2005). This may account for the markedly greater BBB permeability and aggravated cerebral edema we observed in response to IL-1␤ challenge.…”

Gene Expression in Blood Changes Rapidly in Neutrophils and Monocytes after Ischemic Stroke in Humans: A Microarray Study

“…After experimental strokes, there is adhesion of leukocytes to venules within 1 h in a rat model (Ritter et al, 2000) and within the first 2 h in a pig model (Gidday et al, 1997). An antibody to the CD18 adhesion molecule blocked the leukocyte adherence to the vessel walls (Gidday et al, 1997).…”