Cerebrovascular White Matter Lesions Research Articles

Selective accumulation of adiponectin in the cerebral cortex under chronic cerebral hypoperfusion in the rat

Adiponectin is a plasma protein predominantly derived from adipocytes. Adiponectin has beneficial properties against diabetes, cardiovascular diseases, and cancer. In experimental acute cerebral ischemia, adiponectin accumulates on vessels in ischemic lesions and has anti-inflammatory protective effects. Chronic cerebral hypoperfusion is associated with white matter lesions and risk of dementia. Chronic cerebral hypoperfusion induced by permanent occlusion of the bilateral common carotid artery can experimentally produce cerebrovascular white matter lesions in the rat brain. Microglia are activated shortly after ischemia and correlate with the severity of white matter and hippocampal tissue damage. These data suggest that the inflammatory response selectively increases white matter and hippocampal damage during chronic cerebral hypoperfusion. However, factors protecting the cerebral cortex have not been elucidated. To clarify the role of adiponectin, we investigated possible changes in adiponectin and adiponectin receptor 1 (ADR1) in the brains of rats under chronic cerebral hypoperfusion. Adiponectin accumulated on the vessels predominantly in the cerebral cortex under chronic cerebral hypoperfusion. Adiponectin accumulation was not detected in the white matter or hippocampus. In the cerebral cortex, the number of ADR1-immunopositive vessels was increased, and adiponectin was colocalized with ADR1. It is plausible that accumulation of adiponectin may be mediated by the binding of adiponectin to ADR1, and its accumulation in the cerebral cortex may protect tissue injury by inhibiting inflammation under chronic cerebral hypoperfusion.

Soluble epoxide hydrolase inhibition Promotes White Matter Integrity and Long-Term Functional Recovery after chronic hypoperfusion in mice

Chronic cerebral hypoperfusion induced cerebrovascular white matter lesions (WMLs) are closely associated with cognitive impairment and other neurological deficits. The mechanism of demyelination in response to hypoperfusion has not yet been fully clarified. Soluble epoxide hydrolase (sEH) is an endogenous key enzyme in the metabolic conversion and degradation of P450 eicosanoids called epoxyeicosatrienoic acids. Inhibition of sEH has been suggested to represent a prototype “combination therapy” targeting multiple mechanisms of stroke injury with a single agent. However, its role in the pathological process after WMLs has not been clarified. The present study was to investigate the role of a potent sEH inhibitor, 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU), on multiple elements in white matter of mice brain after chronic hypoperfusion. Adult male C57BL/6 mice were subjected to bilateral carotid artery stenosis (BCAS) to induce WMLs. Administration of TPPU significantly inhibited microglia activation and inflammatory response, increased M2 polarization of microglial cells, enhanced oligodendrogenesis and differentiation of oligodendrocytes, promoted white matter integrity and remyelination following chronic hypoperfusion. Moreover, these cellular changes were translated into a remarkable functional restoration. The results suggest that sEH inhibition could exert multi-target protective effects and alleviate cognitive impairment after chronic hypoperfusion induced WMLs in mice.

Induction of Genes Expressed in Endothelial Cells of the Corpus Callosum in the Chronic Cerebral Hypoperfusion Rat Model

Background: Cerebrovascular white matter lesions (WMLs) are associated with cognitive impairment in patients with subcortical vascular dementia. We performed a comprehensive gene expression analysis to elucidate genes associated with WML development in a chronic cerebral hypoperfusion rat model. Methods: Brains of rats with bilateral carotid ligation (2VO, n = 10) and sham-operated rats (n = 5-10/group) were removed on days 1, 7, or 28 after surgery. Total RNA isolated from the corpus callosum was evaluated by microarray analysis and quantitative reverse transcription-polymerase chain reaction. Results: On days 7 and 28, WMLs exhibited histologic changes. On day 7, 16 genes were differentially expressed between groups. mRNA levels of Ptprb, Kcnj8, Crispld2, Bcl6b, and Gja5 were differentially expressed in 2VO rats on day 7, but then returned to normal, whereas mRNA levels of Vwf and Trappc6a were upregulated after day 7. Immunohistochemistry showed that GJA5 and vWF were detected in endothelial cells, KCNJ8 in endothelial cells and astrocytes, CRISPLD2 in neurons and astrocytes, and TRAPPC6A in neurons. Conclusion: Our findings indicate novel genes that may be associated with WML development in the chronic cerebral hypoperfusion rat model, and suggest an important role of neurovascular dysfunction in the pathophysiology.

Is endothelial dysfunction of cerebral small vessel responsible for white matter lesions after chronic cerebral hypoperfusion in rats?

Cerebral white matter (WM) lesions contribute to cognitive impairment and motor dysfunction in the elderly. Intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) are two important adhesion molecules that are upregulated during endothelial activation. Data from recent studies have suggested that ICAM-1 levels are related to progression of white matter hyperintensities (WMH) on MRI. In the present study, we hypothesized that ICAM-1 and VCAM-1 are involved in the endothelial dysfunction and the subsequent WM lesions after chronic cerebral hypoperfusion. Rats underwent bilateral common carotid artery ligation. They were divided into the lipoic acid group and the saline (vehicle) group. RT-PCR and double immunofluorescence for ICAM-1, VCAM-1, endothelial cells (staining positive for von Willebrand factor, vWF), reactive astrocytes (GFAP staining) and activated microglia/macrophages/(CD11b/c staining) were analyzed at baseline and at 1, 3, 7, 14 and 28 days after hypoperfusion. The severity of the WM lesions in the corpus callosum, internal capsule, and external capsule of both hemispheres was graded by luxol fast blue staining. RT-PCR and double immunofluorescence analysis of white matter from rats that had received lipoic acid (100 mg/kg/day) for 28 days exhibited markedly reduced expression of ICAM-1 and VCAM-1 over endothelial cells compared with that of rats receiving saline. In the rats treated with lipoic acid, the WM lesions after chronic cerebral hypoperfusion were significantly less severe, and the number of reactive astrocytes and activated microglia/macrophages (CD11b/c staining) were also significantly lower as compared with the saline-treated rats. These findings indicate that endothelial dysfunction plays a critical role in overexpression of ICAM-1 and VCAM-1, glial cell activation and WM lesions after chronic cerebral hypoperfusion and suggest the potential value of lipoic acid as a therapeutic tool in cerebrovascular WM lesions. Our results also provide support for endothelial activation being involved in early pathogenesis of WM lesions and suggest that therapies that stabilize the endothelium may have a role in preventing WM lesions progression.

Plasma globotriaosylsphingosine: Diagnostic value and relation to clinical manifestations of Fabry disease

Fabry disease is an X-linked lysosomal storage disorder due to deficiency of alpha-Galactosidase A, causing accumulation of globotriaosylceramide and elevated plasma globotriaosylsphingosine (lysoGb3). The diagnostic value and clinical relevance of plasma lysoGb3 concentration was investigated. All male and adult female patients with classical Fabry disease could be discerned by an elevated plasma lysoGb3. In young pre-symptomatic Fabry heterozygotes, lysoGb3 levels can be normal. Individuals carrying the R112H and P60L mutations, without classical Fabry symptoms, showed no elevated plasma lysoGb3. Multiple regression analysis showed that there is no correlation of plasma lysoGb3 concentration with total disease severity score in Fabry males. However, plasma lysoGb3 concentration did correlate with white matter lesions (odds ratio: 6.1 per 100 nM lysoGb3 increase (95% CI: 1.4–25.9, p=0.015). In females, plasma lysoGb3 concentration correlated with overall disease severity. Furthermore, plasma lysoGb3 level was related to left ventricular mass (19.5±5.5g increase per 10nM lysoGb3 increase; p=0.001). In addition, it was assessed whether lifetime exposure to lysoGb3 correlates with disease manifestations. Male Fabry patients with a high lysoGb3 exposure (>10,000U), were moderately or severely affected, only one mildly. Female patients with a low exposure (<1000U) were asymptomatic or mildly affected. A large proportion of the females with an exposure >1000U showed disease complications. Plasma lysoGb3 is useful for the diagnosis of Fabry disease. LysoGb3 is an independent risk factor for development of cerebrovascular white matter lesions in male patients and left ventricular hypertrophy in females. Disease severity correlates with exposure to plasma lysoGb3.

Expression of S100 protein and protective effect of arundic acid on the rat brain in chronic cerebral hypoperfusion

S100 protein is expressed primarily by astroglia in the brain, and accumulates in and around the ischemic lesions. Arundic acid, a novel astroglia-modulating agent, is neuroprotective in acute cerebral infarction, whereas the protective effects remain unknown during chronic cerebral hypoperfusion. Rats undergoing chronic cerebral hypoperfusion were subjected to a bilateral ligation of the common carotid arteries, and were allowed to survive for 3, 7 and 14 days. The animals received a daily intraperitoneal injection of 5.0, 10.0 or 20.0 mg/kg of arundic acid, or vehicle, for 14 days. Alternatively, other groups of rats received a delayed intraperitoneal injection of 20.0 mg/kg of arundic acid or vehicle, which started from 1, 3 or 7 days after ligation and continued to 14 days. The degree of white matter (WM) lesions and the numerical density of S100 protein-immunoreactive astroglia were estimated. In the WM of rats with vehicle injections, the number of S100 protein-immunoreactive astroglia increased significantly after chronic cerebral hypoperfusion as compared to the sham-operation. A dosage of 10.0 and 20.0 mg/kg of arundic acid suppressed the numerical increase in S100 protein-immunoreactive astroglia and the WM lesions. These pathological changes were suppressed with delayed treatment up to 7 days in terms of astroglial activation, and up to 3 days in terms of the WM lesions. The protective effects of arundic acid against WM lesions were demonstrated in a dose-dependent manner, and even after postischemic treatments. These results suggest the potential usefulness of arundic acid in the treatment of cerebrovascular WM lesions.

Matrix Metalloproteinase-2 Plays a Critical Role in the Pathogenesis of White Matter Lesions After Chronic Cerebral Hypoperfusion in Rodents

Cerebrovascular white matter (WM) lesions contribute to cognitive impairment and motor dysfunction in the elderly. A disruption of the blood-brain barrier (BBB) is believed to be a critical early event leading to these WM lesions. Previous studies have suggested the involvement of matrix metalloproteinase-2 (MMP-2) in BBB disruptions and the upregulation of MMP-2 after chronic cerebral hypoperfusion in a rat model. In the present study, we asked whether MMP-2 is involved in the BBB disruption and the subsequent WM lesions after chronic cerebral hypoperfusion. We compared the severity of white matter lesions in rats after chronic cerebral hypoperfusion with or without an MMP inhibitor. Then, we also induced the chronic cerebral hypoperfusion in wild-type and MMP-2-null mice. In the rats treated with a relatively selective MMP-2 inhibitor, AG3340, the WM lesions after chronic cerebral hypoperfusion were significantly less severe, and the number of activated astroglia and microglia were also significantly lower as compared with the vehicle-treated rats. Gene knockout of MMP-2 also reduced the severity of the WM lesions and the number of activated astroglia and microglia in a mice system. In both rodents, the disruption of BBB function, as assessed by IgM staining and the Evans blue extravasation test, was less severe when MMP-2 activity was attenuated. These findings indicate that MMP-2 plays a critical role in the BBB disruption, glial cell activation, and WM lesions after chronic cerebral hypoperfusion and suggest the potential value of MMP-2 inhibitors as a therapeutic tool in cerebrovascular WM lesions.

White matter lesions and glial activation in a novel mouse model of chronic cerebral hypoperfusion.

Cerebrovascular white matter (WM) lesions are closely associated with cognitive impairment and gait disorders in the elderly. We have successfully established a mouse model of chronic cerebral hypoperfusion that may provide new strategies for the molecular analysis of cerebrovascular WM lesions. Adult C57Bl/6 male mice were subjected to bilateral common carotid artery stenosis (BCAS) using external microcoils with varying inner diameters from 0.16 to 0.22 mm. Cerebral blood flow (CBF) in the frontal cortices was measured by laser-Doppler flowmetry at 2 hours and at 1, 3, 7, 14, and 30 days after BCAS. The brains were then removed and examined at 30 days with histological stains and immunohistochemistry for markers of microglia and astroglia. At 2 hours, the CBF values (ratio to the preoperative value) did not change in the 0.22 mm group but decreased significantly to 77.3+/-13.4% in the 0.20 mm group, 67.3+/-18.5% in the 0.18 mm group, and 51.4+/-11.5% in the 0.16 mm group. At day 1, the CBF began to recover in all groups but remained significantly lower until 14 days in comparison to the control group. In the 0.20 mm and 0.18 mm groups, WM lesions occurred after 14 days without any gray matter involvement. These lesions were the most intense in the corpus callosum adjacent to the lateral ventricle but were mild in the anterior commissure and optic tract. In contrast, 4 of 5 mice developed some gray matter changes in the 0.16 mm group. The proliferation of activated microglia and astroglia was observed in the WM beyond 3 days after BCAS. WM lesions were successfully induced after chronic cerebral hypoperfusion with relative preservation of the visual pathway. These features in this mouse model are appropriate for cognitive assessment and genetic analysis, and it may provide a powerful tool to understand the pathophysiology of WM lesions.

Ibudilast, a phosphodiesterase inhibitor, protects against white matter damage under chronic cerebral hypoperfusion in the rat

Cerebrovascular white matter (WM) lesions, which are frequently observed in vascular cognitive impairment and vascular dementia, can be produced in rats by clipping the common carotid arteries bilaterally. Since TNF-α is known to cause the degeneration of myelin, we examined whether these lesions can be ameliorated by ibudilast, a cyclic AMP phosphodiesterase (PDE) inhibitor that suppresses tumor necrosis factor (TNF)-α production. After the ligation of both common carotid arteries in 29 rats, 21 rats received a daily oral administration of 10, 30 or 60 mg/kg ibudilast and 8 rats received vehicle for 14 days. The pathological changes in the white matter were quantified in terms of white matter lesions and the emergence of activated microglia immunoreactive for major histocompatibility complex (MHC) antigen. In the vehicle-treated animals, white matter lesions and microglial activation occurred in the optic tract, internal capsule and corpus callosum. A low dose (10 mg/kg) of ibudilast failed to suppress the white matter lesions and microglial activation, whereas a dose of either 30 or 60 mg/kg ibudilast ameliorated these lesions ( p<0.001). Without an alterations in laboratory blood data, 60 mg/kg ibudilast exhibited percent reduction of the white matter lesions ranging between 50% and 70%, which was more effective than 30 mg/kg ibudilast ( p<0.05). The TNF-α immunoreactive glia decreased in number in the 60 mg/kg ibudilast-treated group as compared to the vehicle-treated group ( p<0.001). These results indicate a dose-dependent protective effect of ibudilast against cerebrovascular white matter lesions and suggest a potential use for ibudilast in the treatment of vascular dementia.

Chronic cerebral hypoperfusion induces white matter lesions and loss of oligodendroglia with DNA fragmentation in the rat.

Cerebrovascular white matter lesions represent an age-related neurodegenerative condition that appears as a hyperintense signal on magnetic resonance images. These lesions are frequently observed in aging, hypertension and cerebrovascular disease, and are responsible for cognitive decline and gait disorders in the elderly population. In humans, cerebrovascular white matter lesions are accompanied by apoptosis of oligodendroglia, and have been thought to be caused by chronic cerebral ischemia. In the present study, we tested whether chronic cerebral hypoperfusion induces white matter lesions and apoptosis of oligodendroglia in the rat. Doppler flow meter analysis revealed an immediate reduction of cerebral blood flow ranging from 30% to 40% of that before operation; this remained at 52-64% between 7 and 30 days after operation. Transferrin-immunoreactive oligodendroglia decreased in number and the myelin became degenerated in the medial corpus callosum at 7 days and thereafter. Using the TUNEL method, the number of cells showing DNA fragmentation increased three- to eightfold between 3 and 30 days post-surgery compared to sham-operated animals. Double labeling with TUNEL and immunohistochemistry for markers of either astroglia or oligodendroglia showed that DNA fragmentation occurred in both of these glia. Messenger RNA for caspase-3 increased approximately twofold versus the sham-operated rats between 1 and 30 days post-surgery. Immunohistochemistry revealed up-regulation of caspase-3 in the oligodendroglia of the white matter, and also in the astroglia and neurons of the gray matter. Molecules involved in apoptotic signaling such as TNF-alpha and Bax were also up-regulated in glial cells. These results indicate that chronic cerebral hypoperfusion induces white matter degeneration in association with DNA fragmentation in oligodendroglia.

Cerebral vasomotor reactivity to postural change is impaired in patients with cerebrovascular white matter lesions.

Vasomotor reactivity is decreased in terms of cerebral blood flow (CBF) response to hypercapnia in patients with cerebrovascular white matter (WM) lesions. This study evaluated whether vasomotor reactivity is altered during postural change in these patients. We examined 28 consecutive patients with cerebrovascular WM lesions, subgrouped into 19 with Schmidt scale 2 and 9 with scale 3 WM lesions. These patients were compared with 15 age-matched patients with lacunar infarction but without significant WM lesions and 6 controls without cerebrovascular disease. With blood pressure monitoring, brain SPECT scans were done in the supine and upright position using HMPAO as a tracer. The ratio of radioisotope (RI) counts in the frontal and parieto-temporal lobes to those in the cerebellar hemispheres (CBF ratio) was evaluated. In the comparison among the three groups, there were no significant differences in the changes of systemic blood pressure after rising. The baseline CBF ratio in the supine position was also not different among the three groups. After rising, the CBF ratio in each region of interest (ROI) did not change significantly in either lacunar infarction or control groups. By contrast, in patients with WM lesions, the CBF ratio in the frontal lobe decreased after rising (p < 0.0001). In the subgroup analysis, there was a significant increase in blood pressure 1, 2 and 3 min after rising (p < 0.05), with a higher tendency in the scale 3 WM lesion group as compared to the scale 2 WM lesion group. The CBF ratio was decreased in both frontal and parieto-temporal areas in the scale 2 WM lesion group, whereas this was significant only in the frontal areas in the scale 3 WM lesion group. Vasomotor reactivity is impaired in cerebrovascular WM lesions, suggesting a susceptibility to postural changes in these patients.

Blood-brain barrier disruption in white matter lesions in a rat model of chronic cerebral hypoperfusion.

Blood-brain barrier damage has been implicated in the pathogenesis of cerebrovascular white matter lesions. This type of lesion is responsible for cognitive impairment in the elderly and can be induced by permanent ligation of the bilateral common carotid arteries in the rat. Because it is unclear whether the blood-brain barrier is impaired, we examined whether vascular permeability to horseradish peroxidase is altered using this model. According to light microscopic results, the reaction product of horseradish peroxidase was most intensely localized to the paramedian part of the corpus callosum in the brain, occurring to a small degree at 3 hours, day 1, markedly on day 3, but reduced on days 7 and 14. By electron microscopic study of the same area, the reaction product of horseradish peroxidase was localized to the plasmalemmal vesicles in the endothelial cells 3 hours after ligation, but appeared in the cytoplasm on days 1 and 3, suggesting a diffuse leakage of horseradish peroxidase. In addition, the reaction product was dispersed into the cytoplasm of glial cells in the perivascular regions on day 3. The luminal surface of the endothelial cell cytoplasm appeared irregular on day 7, suggesting a conformational change of the endothelial cells. Collagen fibrils proliferated in the thickened basal lamina and mitochondria degenerated in the pericyte on days 7 and 14. Perivascular glial endfeet were swollen throughout the survival period. In sham-operated rats, the reaction product of horseradish peroxidase was not observed at any time interval, except in vesicular structures. These findings indicate that chronic cerebral hypoperfusion induces blood-brain barrier damage with subsequent morphologic changes of the vascular structures in the corpus callosum. An extravasation of macromolecules, such as proteases and immunoglobulins, may contribute to the pathogenesis of white matter lesions.

Blood-brain barrier dysfunction in Binswanger's disease; an immunohistochemical study.

Binswanger's disease is pathologically characterized by a combination of diffuse cerebrovascular white matter lesions and lacunar infarcts in the basal ganglia and white matter. Although a blood-brain barrier (BBB) dysfunction has been implicated in the pathogenesis of these white matter (WM) lesions, few authors have addressed this problem. In the present study, we describe BBB dysfunction and its regional differences in the brains of Binswanger's disease patients. Twelve brains from Binswanger's disease patients (group III) were examined and compared with those from five patients with non-neurological disease (group I) and five cortical infarct patients without significant WM lesions (group II). Immunohistochemistry was performed for glial fibrillary acidic protein and vimentin as astroglial cell markers, and for immunoglobulins, complements and fibrinogen as extravasated serum protein markers. The grading scores for IgG extravasation were significantly higher in group III as compared to group I, in both the periventricular WM and the subcortical WM (P < 0.01). In group III, the scores in the periventricular WM and subcortical WM were significantly higher than in the subcortical U fibers and cerebral cortex (P < 0.01 for the periventricular WM; P < 0.001 for the subcortical WM), respectively. Clasmatodendritic astroglia, which had swollen cell bodies and large cytoplasmic vacuoles with disintegrated processes, incorporated the serum components IgG, IgM, C3d, Clq and fibrinogen, both in the periventricular WM and subcortical WM in 5 out of 12 (42%) Binswanger's disease brains. These results indicate that WM lesions in Binswanger's disease are accompanied by BBB dysfunction, although it remains uncertain whether BBB dysfunction is secondary to either chronic cerebral ischemia or arterial hypertension.

Bundles of amyloid precursor protein-immunoreactive axons in human cerebrovascular white matter lesions.

Cerebral white matter lesions commonly observed in Binswanger's disease, multi-infarct encephalopathy and elderly people are neuropathologically characterized by diffuse incomplete demyelination and considered to be ischemic in nature. Arteriolosclerosis in the white matter is a common feature in these white matter lesions. To investigate a possible alteration of the distribution of amyloid precursor protein (APP), chromogranin A (CgA) and synaptophysin (Syn) in such white matter lesions, we examined 15 cases with white matter lesions and 5 without white matter lesions. Many bundles of axons with APP-like immunoreactivity (LI) were observed particularly in mild white matter lesions. Such bundles of axons showed similar but less intense CgA-LI and Syn-LI. They appeared to occur in areas with many ameboid or ramified microglia labeled with anti-leukocyte common antigen and few astrocytes labeled with anti-glial fibrillary acidic protein. In the center of moderate of severe white matter lesions bundles of axons with APP-LI were never observed. Since APP, CgA and Syn undergo fast axonal transport, and since following ischemic insults to central nervous system microglial reaction occurs earlier than astroglial changes, our results suggest that axonal damage, which induces disturbance of fast axonal transport, can occur even in the early stage of white matter lesions.