Mitochondrial Protection and Against Glutamate Neurotoxicity via Shh/Ptch1 Signaling Pathway to Ameliorate Cognitive Dysfunction by Kaixin San in Multi-Infarct Dementia Rats.

Multi-infarct dementia (MID), a prominent subtype of vascular dementia (VD), is responsible for at least 15 to 20 percent of dementia in the elderly. Mitochondrial dysfunctions and glutamate neurotoxicity due to chronic hypoperfusion and oxidative stress were regarded as the major risk factors in the pathogenesis. Kaixin San (KXS), a classic prescription of Beiji Qianjin Yaofang, was applied to treatment for "amnesia" and has been demonstrated to alleviate the cognitive deficit in a variety of dementias, including MID. However, little is known whether mitochondria and glutamate are associated with the protection of KXS in MID treatment. The aim of this study was to investigate the role of KXS in improving the cognitive function of MID rats through strengthening mitochondrial functions and antagonizing glutamate neurotoxicity via the Shh/Ptch1 signaling pathway. Our data showed that KXS significantly ameliorated memory impairment and hippocampal neuron damage in MID rats. Moreover, KXS improved hippocampal mitochondrial functions by reducing the degree of mitochondrial swelling, increasing the mitochondrial membrane potential (MMP), and elevating the energy charge (EC) and ATP content in MID rats. As expected, the concentration of glutamate and the expression of p-NMDAR1 were significantly reduced by KXS in the brain tissue of MID rats. Furthermore, our results showed that KXS noticeably activated the Shh/Ptch1 signaling pathway which was demonstrated by remarkable elevations of Ptch1, Smo, and Gli1 protein levels in the brain tissue of MID rats. Intriguingly, the inhibition of the Shh signaling pathway with cyclopamine significantly inhibited the protective effects of KXS on glutamate-induced neurotoxicity in PC12 cells. To sum up, these findings suggested that KXS protected MID rats from memory loss by rescuing mitochondrial functions as well as against glutamate neurotoxicity through activating Shh/Ptch1 signaling pathway.

[Effects of Tongluo Xingnao effervescent tablets on blood rheology, iNOS, VEGF and LDH-5 in MID rats].

The study was to explore effects of Tongluo Xingnao effervescent tablets on the blood rheology, iNOS, VEGF and LDH-5 in multi-infarct dementia(MID) model rats. Establish MID model rats were induced by microthrombosis, from which 50 successful model rats were randomly divided into five groups, such as the model control group, the dihydroergotoxine mesylate tablets(hydergine) group(0.7 mg•kg⁻¹), Tongluo Xingnao effervescent tablets high-dose, medium-dose and low-dose groups(7.56, 3.78, 1.89 g•kg⁻¹). Another ten rats in the sham group were randomly selected as the parallel control group. Each group was orally administered with drugs for 90 days. The learning and memory ability was evaluated with the Morris water maze test, while the whole blood viscosity and the erythrocyte aggregation index derived from abdominal aorta were measured in different shear rates. In addition, the levels of VEGF and iNOS in the serum were determined by ELISA kits. The expression of LDH-5 in hippocampus of rats was measured with immunohistochemistry and image quantitative analysis. The result showed that Tongluo Xingnao effervescent tablets notably decreased the escape latency of MID model rats, increased times of entering into the escape platform and prolonged retention time in medium ring, meanwhile the whole blood viscosity in MID model rats was also notably reduced in four shear rates, i.e. 1, 5, 30, 200 S⁻¹, erythrocyte aggregation index, serum VEGF and iNOS, and average optical density value of LDH-5, with a statistically significant differences compared with the model control group (P<0.05). In conclusion, Tongluo Xingnao effervescent tablets could improve the ability of learning and memory of MID model rats and the blood rheology, reduce the level of iNOS, VEGF and the expression of LDH-5, and then improved the brain energy supply.

Effects of acupuncture on declined cerebral blood flow, impaired mitochondrial respiratory function and oxidative stress in multi-infarct dementia rats.

Brain energy disorders and oxidative stress due to chronic hypoperfusion were considered to be the major risk factors in the pathogenesis of dementia. In previous studies, we have demonstrated that acupuncture treatment improved cognitive function of VaD patients and multi-infarct dementia (MID) rats. Acupuncture therapy also increased the activities of glycometabolic enzymes in the brain. But it is not clear whether acupuncture treatment compensates neuronal energy deficit after cerebral ischemic through enhancing the activities of glucose metabolic enzymes and preserving mitochondrial function, and whether acupuncture neuroprotective effect is associated with activations of mitochondrial antioxidative defense system. So, the effect of acupuncture therapy on cognitive function, cerebral blood flow (CBF), mitochondrial respiratory function and oxidative stress in the brain of MID rats was investigated in this study. The results showed that acupuncture treatment significantly improved cognitive abilities and increased regional CBF of MID rats. Acupuncture elevated the activities of total SOD, CuZnSOD and MnSOD, decreased the level of malondialdehyde (MDA) and superoxide anion, regulated the ratio of reduced glutathione (GSH) and oxidized glutathione (GSSG) in mitochondria, and raised the level of the respiratory control index (RCI) and P/O ratio and the activities of mitochondrial respiratory enzymes of MID rats. These results indicated that acupuncture treatment improved cognitive function of MID rats; and this improvement might be due to increased CBF, which ameliorated mitochondrial dysfunction induced by ischemia and endogenous oxidative stress system of brain.

[Effect of sailuotong capsule on intervening cognitive dysfunction of multi-infarct dementia in rats].

OBJECTIVE: To study the effect of Sailuotong capsule (Sailuotong) on learning and memory functions of multi-infarct dementia (MID) rats and its mechanism. METHOD: All SD rats were divided into five groups, namely the sham operation group, the model group, the positive group, the low dosage Sailuotong-treated group and the high dosage Sailuotong-treated group. The multi-infarct dementia model was established by injecting the micro-sphere vascular occlusive agent. On the 10th day after the successful operation, the rats were administered intragastrically with distilled water, memantine hydrochloride (20 mg x kg(-1)) and Sailuotong (16.5 mg x kg(-1) and 33.0 mg x kg(-1)) once a day for 60 days respectively, in order to detect the effect of Sailuotong in different doses on the latent period and route length in Morris water maze and the activities of choline acetyltransferase (ChAT) and acetylcholinesterase (AchE) in brain tissues. RESULT: Compared with the sham operation rats, it had been observed that the latent period and route length of MID rats in Morris water maze were significantly increased (P < 0.05 or P < 0.01), and the activity of ChAT in brain tissues was significantly decreased (P < 0.05). After the intervention with Sailuotong for sixty days, the latent period and route length of MID rats in Morris water maze significantly shrank (P < 0.05 or P < 0.01). Additionally, Sailuotong decreased AchE activity, while increasing ChAT activity in brain tissues of MID rats (P < 0.05 or P < 0.01). CONCLUSION: Sailuotong capsule can improve cognitive dysfunction of MID rats to some extent. Its mechanism may be related to its different regulation of activities of ChAT and AchE in brain tissues.

Increased binding to 5-HT1A and 5-HT2A receptors is associated with large vessel infarction and relative preservation of cognition.

Vascular dementia accounts for approximately 15-20% of all dementias. In addition, a significant subset of people with Alzheimer's disease have concurrent cerebrovascular disease. Vascular dementia is caused by different cerebrovascular morphological abnormalities including large artery territory infarction (multi-infarct vascular dementia) and sub-cortical ischaemic vascular dementia. Despite this distinction, there is a lack of studies examining the neurochemistry of individual vascular dementia subtypes. Serotonin is believed to play an important role in cognition, and serotonin receptors may provide a novel target for future anti-dementia therapeutics. This study aimed to determine levels of two serotonin receptors in subtypes of vascular dementia and relate any changes to cognition. We have determined, using saturation radioligand binding, the binding parameters (affinity and maximal binding) of ((3)H)-WAY 100635 binding to 5-HT(1A) receptors and ((3)H)-ketanserin binding to 5-HT(2A) receptors in post-mortem tissue from the frontal and temporal cortices of patients with either multi-infarct vascular dementia, sub-cortical ischaemic vascular dementia, mixed Alzheimer's disease/vascular dementia or stroke no dementia (SND). 5-HT(1A) and 5-HT(2A) receptor binding was significantly increased in the temporal cortex of patients with either multi-infarct vascular dementia or SND, compared to age-matched controls. 5-HT(1A) receptor maximal binding in the temporal cortex was also positively correlated with cognition as determined by Mini-Mental State Examination (MMSE) and Cambridge Assessment of Mental Health for the Elderly scores (CAMCOG). These results reveal an important distinction between the neurochemistry of multi-infarct vascular dementia/SND and sub-cortical ischaemic vascular dementia, suggesting that pharmacological manipulation of serotonin offers the possibility to develop novel therapies for stroke and multi-infarct vascular dementia patients. The results also highlight the importance of the cortical 5-HT(1A) receptor in mediating cognition.

Lateralization of hippocampal nitric oxide mediator system in people with Alzheimer disease, multi-infarct dementia and schizophrenia.

There is evidence that brain lateralization underlying hemispheric specialization can be observed also at biochemical level. However, hemispheric differences in nitric oxide mediator system have not yet been evaluated. The hippocampus and planum temporale are highly asymmetrical regions but the degree of their laterality is altered in demented or psychotic people. In the study, l-glutamate/l-arginine/l-citrulline concentrations, nitric oxide synthase activities/expressions and nitrites/nitrates levels were estimated in autoptic hippocampi. Right/left laterality in endothelial synthase activity and in nitrites/nitrates was observed in controls. Lateral changes were estimated in patients with Alzheimer disease (a marked increase in activities of constitutive synthases and in expression of inducible enzyme in the left side) and schizophrenia (an increase in activities of all enzymes especially in the right side). Significant shifts from positive to negative correlations were found between laterality of some components of nitric oxide pathway and of planum temporale volumetry under pathological conditions. The hippocampal nitric oxide system appears to be globally right/left lateralized, especially via actions of highly asymmetrical endothelial synthase. The results suggest a specific involvement of all synthases in the development of selected diseases and show that lateral analyses are of sufficient sensitivity to reveal subtle links. The volumetric asymmetry of the planum temporale as a marker of handedness is not probably simply linked to brain laterality at biochemical level but reflects alterations due to pathological processes.

Protective effects of Nicotiflorin on reducing memory dysfunction, energy metabolism failure and oxidative stress in multi-infarct dementia model rats.

The present study aimed to determine whether Nicotiflorin, a natural flavonoid extracted from coronal of Carthamus tinctorius, has a protective effect on cerebral multi-infarct dementia in rats. The multi-infarct dementia model rats were prepared by injecting man-made micro-thrombi into the right hemisphere. The administration groups were treated once daily with 30, 60 and 120 mg/kg Nicotiflorin (i.g.) from 5 days before ischemia operation to 3 days after the operation for biochemical examination, 10 days for Morris water maze study and morphological observations and 20 days for eight-arm radial maze task. 2,3,5-triphenyltetrazolium chloride (TTC) staining showed that infarct volume of each Nicotiflorin administration group was much smaller than that of vehicle-treated multi-infarct dementia group, and hematoxylin and eosin (HE) staining showed that histopathological abnormalities of each Nicotiflorin group were also much lighter than that of vehicle-treated multi-infarct dementia group. Each Nicotiflorin group showed much better spatial memory performance in Morris water maze tests and eight-arm radial maze task compared with the vehicle-treated multi-infarct dementia group, significantly attenuated the elevation of lactic acid and malondialdehyde (MDA) contents and the decrease in lactate dehydrogenase (LDH), Na(+)K(+)ATPase, Ca(2+)Mg(2+)ATPase and superoxide dismutase (SOD) activity in the brain tissue which was composed of striatum, cortex and hippocampus of the ischemia hemisphere at day 3 after ischemia operation. These results suggest that Nicotiflorin has protective effects on reducing memory dysfunction, energy metabolism failure and oxidative stress in multi-infarct dementia model rats.

Hereditary multi-infarct dementia of the Swedish type is a novel disorder different from NOTCH3 causing CADASIL.

Several hereditary small vessel diseases (SVDs) of the brain have been reported in recent years. In 1977, Sourander and Wålinder described hereditary multi-infarct dementia (MID) in a Swedish family. In the same year, Stevens and colleagues reported chronic familial vascular encephalopathy in an English family bearing a similar phenotype. These disorders have invariably been suggested to be cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL) but their genetic identities remain unknown. We used molecular, radiological and neuropathological methods to characterize these disorders. Direct DNA sequencing unexpectedly confirmed that affected members of the English family carried the R141C mutation in the NOTCH3 gene diagnostic of CADASIL. However, we did not detect any pathogenic mutations in the entire 8091 bp reading frame of NOTCH3 or find clear evidence for NOTCH3 gene linkage in the Swedish DNA. This was consistent with the lack of hyperintense signals in the anterior temporal pole and external capsule in Swedish subjects upon magnetic resonance imaging. We further found no evidence for granular osmiophilic material in skin biopsy or post-mortem brain samples of affected members in the Swedish family. In addition, there was distinct lack of NOTCH3 N-terminal fragments in the cerebral microvasculature of the Swedish hereditary MID subjects compared to the intense accumulation in the English family afflicted with CADASIL. Several differences in arteriosclerotic changes in both the grey and white matter were also noted between the disorders. The sclerotic index values, density of collagen IV immunoreactivity in the microvasculature and number of perivascular macrophages were greater in the English CADASIL samples compared to those from the Swedish brains. Multiple approaches suggest that the Swedish family with hereditary MID suspected to be CADASIL has a different novel disorder with dissimilar pathological features and belongs to the growing number of genetically uncharacterized familial SVDs.

Ki67 and doublecortin positive cells in the human prefrontal cortices of normal aging and vascular dementia.

Immunohistochemical localizing of the proliferation of Ki67 nuclei and doublecortin positive cells were performed in the prefrontal cortex of normal aged and vascular dementia (multiple infarct dementia) patients. Positive Ki67 nuclei and doublecortin positive cells were observed in both groups, with slightly higher density in the prefrontal cortex of vascular dementia. When the Ki67 sites were superimposed with the neuronal specific enolase localizations, only about 5% of the cells was doubly labeled, indicating few proliferating cells were neurons. This percentage did not vary between specimens of normal aging and those of vascular dementia.

N-methyl-D-aspartate receptor and apoptosis in Alzheimer's disease and multiinfarct dementia.

This study investigates the role of excitotoxicity in Alzheimer's disease and in multiinfarct dementia by examining, via immunohistochemical methods, the number of cells that are positive for N-methyl-D-aspartate (NMDA) receptor and the degree of colocalization between NMDA receptor and apoptosis markers such as TUNEL or activated caspase-3 in the frontal cortex of individuals with these two conditions, comparing the results with those from subjects who died of normal aging. We showed an increased number of NMDA receptor-positive cells and an increased number of TUNEL-labeled cells in the frontal cortex of subjects with Alzheimer's disease, especially in the deeper layers of the cortex. However, only about 10% of cells showed colocalization of NMDA receptor with the apoptosis markers studied, suggesting that NMDA-mediated excitotoxicity does not play a major role in neuronal apoptosis in Alzheimer's disease or in multiinfarct dementia.

Positron emission tomography examination of cerebral blood flow and glucose metabolism in young CADASIL patients.

BACKGROUND AND PURPOSE: CADASIL causes repeated ischemic strokes leading to subcortical vascular dementia. The purpose of this study was to assess whether cerebral blood flow (CBF) and regional cerebral metabolic rates of glucose (rCMR(gluc)) in CADASIL patients are affected in early adulthood. METHODS: CBF and rCMR(gluc) were examined with positron emission tomography in correlation with magnetic resonance imaging (MRI) in 14 adult (19 to 41 years) CADASIL patients with the Notch3 R133C mutation. Seven patients had experienced transient ischemic attack and 3 had experienced > or =1 strokes. RESULTS: The mean CBF in the CADASIL patients was significantly lower in both frontal (P=0.019) and occipital (P=0.009) white matter (WM) than those in the controls. CBF decreased significantly with increased severity of the disease. The patients had lower mean rCMR(gluc) values than the controls, although differences were not statistically significant. Sum scores of semiquantitative MRI rating scale (Scheltens) correlated significantly with WM CBF but not with rCMR(gluc). CONCLUSIONS: In CADASIL, there is an early and significant decrease in the CBF of WM associated with simultaneous MRI changes. These are obviously caused by the arteriopathy in long penetrating arteries and indicate early tissue damage, also expressed as impaired rCMR(gluc) in the WM.

Hypothalamic digoxin, hemispheric chemical dominance and syndrome X with multiple lacunar state. A hypothesis.

This study assessed the changes in digoxin and some other metabolites of the isoprenoid pathway in metabolic syndrome X presenting with multiple lacunar state. The isoprenoid pathway and digoxin status was also studied for comparison in individuals of differing hemispheric dominance to find out the role of cerebral dominance in the genesis of syndrome X. There was an increase in plasma HMG CoA reductase activity with a consequent increase in serum digoxin, which caused a reduction in RBC membrane Na(+)-K+ ATPase activity. There was an increase in serum tryptophan and its metabolites and a decrease in tyrosine and its metabolites. Serum magnesium was decreased with consequent alteration in the metabolism of glycosaminoglycans and glycolipids. Increase in dolichol, another product of the isoprenoid pathway, resulted in alteration in glycoprotein metabolism. Changes in the composition of membrane glycosaminoglycans, glycoproteins and cholesterol: phospholipid ratio were also observed in this disorder leading to decreased lysosomal stability. Decrease in ubiquinone, another isoprenoid metabolite, resulted in alteration in the free radical generation. Membrane Na(+)-K+ ATPase inhibition due to digoxin, altered membrane structure, increased tryptophan catabolites and decreased tyrosine catabolites can lead to increased intracellular calcium and reduced intracellular magnesium which can account for the symptoms of syndrome X. The biochemical patterns including hyperdigoxinemia observed in syndrome X correlated with those obtained in right hemispheric chemical dominance. Right hemispheric chemical dominance is a predisposing factor for syndrome X with multiple lacunar state.

Cortical hypometabolism and crossed cerebellar diaschisis suggest subcortically induced disconnection in CADASIL: an 18F-FDG PET study.

UNLABELLED: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited small-vessel disease caused by mutations in the NOTCH3 gene. As in sporadic small-vessel disease, ischemic lesions are largely confined to subcortical structures, whereas the cortex is spared. CADASIL, therefore, may serve as a model to study subcortically induced remote effects. The purpose of this study was to evaluate with (18)F-FDG PET whether regional cerebral metabolic rate of glucose (rCMRglc) is altered in CADASIL patients and, if so, whether there is evidence of subcortically induced disconnection. METHODS: Eleven CADASIL patients (7 women, 4 men; mean age, 55.8 +/- 6.7 y) without cortical lesions on brain MR images underwent PET after intravenous injection of 120 MBq (18)F-FDG, with calculation of rCMRglc according to a previously published method. For further processing, patient studies were registered to a template of a healthy control group and region-of-interest-based and voxelwise comparisons were performed. RESULTS: In CADASIL patients, mean rCMRglc was significantly reduced in all cortical and subcortical structures, compared with the values in healthy volunteers. In the subcortical gray matter, metabolic rates, given as the percentage of the mean of healthy volunteers, were 49.7%, 65.3%, and 51.6% in the caudate, putamen, and thalamus, respectively. Among cortical structures, the values were 66.9%, 67.9%, 67.2%, and 76.5% for the frontal, parietal, temporal, and occipital lobes, respectively. On an individual level, most patients showed marked asymmetry and inhomogeneities of cortical glucose metabolism. In 6 (55%) CADASIL patients, there was evidence of crossed cerebellar diaschisis. CONCLUSION: This study showed that cortical glucose metabolism is significantly lower in CADASIL patients than in healthy volunteers. The observed decrease in rCMRglc may in part be explained by a reduction of cerebral blood flow and neuronal loss. In addition, our data provide evidence of remote effects secondary to the functional disruption of subcortical fiber tracts in this particular type of small-vessel disease.

Evaluation of diagnostic NOTCH3 immunostaining in CADASIL.

CADASIL is caused by mutations in the NOTCH3 gene. Although increasingly recognized as a disease entity, the diagnostic confirmation can be lengthy or inconclusive. Recently, NOTCH3 immunostaining of skin biopsy specimens has been introduced as a new diagnostic test. The aim of this study was to independently assess the diagnostic value of NOTCH3 immunostaining, and determine whether the degree of immunostaining correlates with other disease parameters. We determined NOTCH3 mutation carrier status in 62 symptomatic and asymptomatic individuals from 15 CADASIL families. Skin biopsy specimens of these individuals, as well as of a disease control group, were immunostained with NOTCH3 antibody and blindly analyzed by two independent observers to determine sensitivity and specificity. A semiquantitative NOTCH3 immunostaining score was correlated with clinical, genetic and MRI parameters. The sensitivity was 90.2% and 85.4%, respectively, for the two observers, the specificity 95.2% and 100%; both lower than previously reported. Certain NOTCH3 mutations may underlie false-negative results. False-positive results were found in a non-mutated control, and also in one disease control. There was no difference in immunostaining between symptomatic and asymptomatic NOTCH3 mutated individuals. Furthermore, the NOTCH3 immunostaining score did not correlate with clinical or MRI parameters. NOTCH3 immunostaining is a supportive, but not definitive, CADASIL diagnostic test, and should be interpreted in the context of clinical and radiological data. Confirmation by DNA analysis is requisite for positive results, and when there exists high clinical suspicion, also for negative results.

Applications of diffusion-weighted and diffusion tensor MRI to white matter diseases - a review.

This paper reviews the current applications of diffusion-weighted and diffusion tensor MRI in diseases of the brain white matter. The contribution that diffusion-weighted imaging has made to our understanding of white matter diseases is critically appraised. The quantitative nature of diffusion MRI is one of its major attractions; however, this is offset by the more advanced hardware required to collect diffusion-weighted images reliably, and the more complex processing to produce quantitative parametric diffusion images. With the now common availability of scanners equipped to perform echo-planar imaging, the acquisition of diffusion tensor images is sure to become more widespread and routine.

Mouse Notch 3 expression in the pre- and postnatal brain: relationship to the stroke and dementia syndrome CADASIL.

Mutations in the human Notch 3 gene cause the vascular stroke and dementia syndrome CADASIL (Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy) characterized by degeneration of vascular smooth muscle cells and multiple small infarcts in the white and deep gray matter of the brain. Here we have analyzed the expression pattern of the Notch 3 gene in the pre- and postnatal mouse brain. Prenatal Notch 3 expression is restricted to a scattered population of cells within the vessel wall of all major blood vessels in the developing embryo, including those that form the perineural vascular plexus. Expression in the postnatal brain is confined to a scattered cell population within the vessel wall of small to medium-sized penetrating arteries, which are the vessel type primarily affected in CADASIL patients. In contrast, no expression was observed in capillaries and veins. Notch 3 is most likely expressed in a subset of vascular smooth muscle cells, and the expression pattern of one of the Notch ligands, Serrate 1, was very similar to that observed for Notch 3. The Notch 3 expressing pattern was not significantly altered in platelet-derived growth factor B- (PDGF-B) deficient mouse embryos, demonstrating that Notch 3 expression is not under direct control of PDGF-B. These data show that Notch 3 expression is conserved between mouse and human and suggest that the mouse is a valid system for analysis of CADASIL.

CADASIL Notch3 mutant proteins localize to the cell surface and bind ligand.

Cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a vascular dementia arising from abnormal arteriolar vascular smooth muscle cells. CADASIL results from mutations in Notch3 that alter the number of cysteine residues in the extracellular epidermal growth factor-like repeats, important for ligand binding. It is not known whether CADASIL mutations lead to loss or gain of Notch3 receptor function. To examine the functional consequences of CADASIL mutations, we engineered 4 CADASIL-like mutations into rat Notch3 and have shown that the presence of an unpaired cysteine does not impair cell-surface expression or ligand binding.

Aberrant expression of the glutamate transporter excitatory amino acid transporter 1 (EAAT1) in Alzheimer's disease.

Glutamate-mediated toxicity has been implicated in the neurodegeneration observed in Alzheimer's disease. In particular, glutamate transport dysfunction may increase susceptibility to glutamate toxicity, thereby contributing to neuronal cell injury and death. In this study, we examined the cellular localization of the glial glutamate transporter excitatory amino acid transporter 1 (EAAT1) in the cerebral cortex of control, Alzheimer's disease, and non-Alzheimer dementia cases. We found that EAAT1 was strongly expressed in a subset of cortical pyramidal neurons in dementia cases showing Alzheimer-type pathology. In addition, tau (which is a marker of neurofibrillary pathology) colocalized to those same pyramidal cells that expressed EAAT1. These findings suggest that EAAT1 changes are related to tau expression (and hence neurofibrillary tangle formation) in dementia cases showing Alzheimer-type pathology. This study implicates aberrant glutamate transporter expression as a mechanism involved in neurodegeneration in Alzheimer's disease.

Mitochondrial dysfunction associated with a mutation in the Notch3 gene in a CADASIL family.

BACKGROUND: Cerebral autosomal arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is characterized by recurrent subcortical ischemic strokes and dementia caused by mutations in the Notch3 gene. In Drosophila melanogaster, Notch signaling has a pleiotropic effect, affecting most tissues of the organism during development. OBJECTIVE: To characterize a potential mitochondrial dysfunction associated with mutations in the Notch3 gene. METHODS: Biochemical, histochemical, molecular, and genetic analyses were performed on muscle biopsy specimens and fibroblasts obtained from patients of a Spanish family with CADASIL. Additional biochemical and molecular analyses of the N(55e11) mutant of D. melanogaster were performed. RESULTS: In muscle biopsy specimens, a significant decrease was found in the activity of complex I (NADH [reduced form of nicotinamide adenine dinucleotide] dehydrogenase), and in one patient, histochemical analysis showed the presence of ragged-red fibers with abnormal cytochrome c oxidase staining. Reduced fibroblast activity of complex V (ATP synthase) was found. Supporting data on patients with CADASIL, it was found that the mutation N(55e11) in Drosophila decreases the activity of mitochondrial respiratory complexes I and V. CONCLUSIONS: Mitochondrial respiratory chain activity responds, directly or indirectly, to the Notch signaling pathway. Mitochondrial dysfunction in patients with CADASIL may be an epiphenomenon, but results of this study suggest that the pathophysiology of the disease could include a defect in oxidative phosphorylation.

Altered white and gray matter metabolism in CADASIL: a proton MR spectroscopy and 1H-MRSI study.

OBJECTIVE: Subcortical white matter hyperintensities (WMH) and small cystic lesions are the radiologic hallmark of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a hereditary angiopathy causing stroke in young adults. To further characterize the cerebral pathology in vivo we analyzed metabolite concentrations in normal and abnormal appearing brain tissue using single and multiple voxel proton MR spectroscopy (1H-MRS and 1H-MRSI). METHODS: Twenty patients with CADASIL and 21 age-matched controls were studied with 1H-MRSI at the level of the centrum semiovale; short echo time 1H-MRS was performed in six patients (WMH) and 10 controls. LCModel fits were used to estimate absolute and relative concentrations of N:-acetylaspartate (NAA), choline-containing compounds (Cho), total creatine (Cr) within WMH, normal appearing white matter (NAWM), and cortical gray matter (GM) as well as myo-inositol (mI) and lactate in WMH. RESULTS: 1H-MRSI-Patients with CADASIL showed significantly reduced NAA, Cho, Cr, and total metabolite content (Met(tot)) in WMH and NAWM. Normalization to Met(tot) revealed that NAA/Met(tot) was reduced in all regions, whereas Cho and Cr were relatively elevated in WMH. Short echo time 1H-MRS showed decreased NAA, Cr, Met(tot), and NAA/Met(tot) and elevated mI/Met(tot) and lactate in WMH. Metabolite changes were larger in severely affected subjects. Rankin scores correlated negatively with NAA/Met(tot) (all regions) and NAA/Cho (WMH), and positively with Cho/Met(tot) (WMH) and Cr/Met(tot) (NAWM). CONCLUSION: Marked metabolic abnormalities were observed in abnormal and normal appearing white matter in patients with CADASIL. The findings suggest axonal injury, enlarged extracellular spaces, myelin loss, and gliosis. The cortical abnormalities may reflect structural damage or functional neuronal impairment secondary to white matter pathology. NAA reductions were correlated with clinical disability emphasizing the clinicopathologic relevance of axonal injury in CADASIL.