Faculty Bibliography

Inflammatory mechanisms are involved in the pathogenesis of Alzheimer's disease (AD). It is postulated that cytokine synthesis is altered in AD patients compared with nondemented subjects. Glucocorticoids play an important role in cytokine synthesis. We assessed the release of tumor necrosis factor-alpha (TNF-alpha), interleukin-10 (IL-10) and interleukin-12 (IL-12) and its regulation by dexamethasone in AD patients in vitro. Cytokine levels were measured using the ELISA method in unstimulated, LPS-stimulated or whole-blood samples incubated with LPS and dexamethasone from 18 AD patients and 12 controls. The cytokine levels spontaneously produced by blood cells after incubation with LPS or LPS and dexamethasone did not differ significantly between groups. Dexamathasone inhibited TNF-alpha synthesis by LPS-stimulated blood cells more effectively in AD patients than in controls. These results suggest that cytokine synthesis in AD patients could be regulated by glucocorticoids in a different way than in nondemented subjects

A significant percentage of Alzheimer's disease (AD) patients exhibit concomitant vascular pathology. Epidemiological evidence suggest that vascular disease may not only add to global cognitive impairment but also exacerbate the course of AD pathology. The goal of this study was to analyze the impact of global ischemia on the cellular and amyloid-beta pathology in AD murine transgenic (Tg) models. Seven month old double Tg mice, expressing Swedish amyloid precursor protein (APP) and M146L presenilin 1 (PS1) mutations and single Tg mice (PS1 mutation alone) were subjected to 45 minutes bilateral common carotid artery occlusion or sham surgery. Behavioral testing performed two weeks after the surgery showed impaired learning and memory retention on Morris water maze and Hebb-Williams tests in both single PS1 and double PS1/APP Tg mice which underwent ischemia comparing to sham operated animals (p<0.05). Double Tg mice scored worse than single Tg mice. Animals were sacrificed two months after ischemia. The total brain volume was decreased by 6.5% and 5% and the ventricular volume was increased by 33.7% and 46.4% in single and double operated Tg mice, respectively comparing to sham animals. Unbiased stereological analysis demonstrated a 23% neuronal dropout in the CA1 sector of the cornu Ammonis after ischemia. Increased Abetaburden and plaque density was also observed in APP/PS1 animals which underwent ischemia comparing to sham operated ones. Overall, this data indicate that global ischemia exacerbate both neuronal and Abetarelated pathology in AD Tg animal models

Deposition of amyloid-beta (Abeta) in form of the senile plaques and in vessel walls is a hallmark of Alzheimer's disease (AD). Apolipoprotein E (apoE) is known to act as a pathological chaperone by increasing the beta-sheet content of Abeta, promoting its fibrillization, toxicity, and deposition in the brain. ApoE binds to residues 12-28 of Abeta. We report in vitro and in vivo data on the blocking of the apoE/Abeta interaction by a synthetic peptide homologues to residues 12-28 of Abeta. To eliminate any residual toxicity and fibrillogenic potential the peptide sequence was altered by replacing a valine in position 18 by a proline (Abeta12-28P). On ELISA Abeta12-28P demonstrates high affinity binding to apoE and in competitive binding experiments inhibits the binding of apoE to Abeta42. Abeta12-28P also reduces the toxicity of Abeta in cell culture, as well as blocking the enhanced fibril formation of Abeta in the presence of apoE4, measured by the Thioflavin-T assay. The in vivo effect of Abeta12-28P was assessed in double transgenic (Tg) APP/PS1 AD mice which received 1mg of Abeta12-28P or placebo three times a week for four weeks. There was an approximately five fold reduction of the total and fibrillar Abeta in treated mice comparing to control (p<0.05). Also, Abeta40 and Abeta42 levels in the brain demonstrated a 40-60% reduction of both species in the total Abeta fraction and in the soluble Abeta fraction in treated mice comparing to controls. No significant titer of anti-Abeta antibodies in treated animals was detected, indicating that the effect of Abeta12-28P on Abeta deposition observed in vivo is not immune mediated. Overall, compounds blocking the interaction between Abeta and its pathological chaperones such as apoE (or alpha1anti-chymotrypsin, perlecan etc.) can be considered as an alternative approach for the treatment of beta-amyloidosis in AD

Presenilin 1 (PS1) mutations have been identified in many pedigrees with early-onset familial Alzheimer's disease (FAD). PS1 mutants are known to influence gamma-secretase action and increase amyloid-beta (Abeta) 1-42 production, but there is also evidence suggesting direct involvement of PS1 in the neuronal pathology of AD. Transgenic (Tg) mice expressing the M146L PS1 mutation, associated with FAD symptom onset in the forties, demonstrate no difference in the total number of neurons (fractionator method) in the CA1 sector of the cornu Ammonis comparing with wild type (wt) animals at two months of age. At the age of 9 months and 22 months PS1 M146L Tg mice demonstrated 20% and 29% neuronal dropout comparing to age-matched controls, respectively (p<0.05). Between 2 months and 22 months old wt animals did not show any significant neuronal loss; however, 22 month old M146L PS1 mice showed a 41% neuronal decline compared to 2 month old controls. PS1 M146L Tg animals also exhibited impaired performance of both learning and retention on the Morris water maze test (p<0.05), but not on locomotor testing comparing to wt mice. We have also analyzed another line of Tg mice expressing a P117L PS1 mutation associated with an onset of disease as early as 23 years. These mice at the age of 6 months demonstrate a 17.9% reduction in the total number of CA1 neurons comparing to wt mice and a 26.5% reduction comparing to mice expressing the wt form of human PS1 (p<0.05). Overall, this data suggest that PS1 mutations are directly involved in neuronal pathology which is age-dependant. This process is unrelated to Abeta deposition since PS1 Tg mice do not develop amyloid plaques

Hypercortisolemia is thought to be a marker of the stress response following stroke. The aim of this study was to investigate the prevalence and prognostic significance of hypercortisolemia. The circadian variation of cortisol level and the relationship between serum cortisol levels and other stress, inflammatory, and haemostatic markers were also investigated. Seventy consecutive patients with their first ischemic stroke and 24 age- and sex-matched controls were included in the study. Serum cortisol levels (at 6:00 AM, 10:00 AM, 6:00 PM, and 10:00 PM), 24-h urine catecholamine excretion, beta-thromboglobulin levels, and other standard biochemical and haematological parameters were measured on the first day of hospitalisation and in control subjects. Outcome measures used the Barthel Index at Day 30, as well as 30- and 90-day mortality rates. Hypercortisolemia, defined as at least two of the four measurements above the normal range of serum cortisol levels (i.e. >618 nmol/l from the morning samples and >460 nmol/l from the evening samples) was found in 25 (35.7%) of the acute stroke patients and in 3 (12.5%) of the controls (p<0.05). Hypercortisolemia was associated with older age, greater severity of neurological deficit, larger ischemic lesions on CT, and worse prognoses (p<0.05). The study did not find a correlation between serum cortisol levels and other markers of the stress response such as catecholamines excretion and glucose levels. A significant correlation between serum cortisol levels and some markers of the inflammatory response, such as fever, fibrinogen level, white blood cell (WBC) count, and beta-thromboglobulin level, was established in stroke patients. Prognostic significance of hypercortisolemia in acute stroke patients seems to be related to the inflammatory response rather than to the stress response

The role of the lipid abnormalities as a risk factor for stroke remains controversial; very likely because only the standard lipid fractions are measured and because different causes of stroke are not considered. LDL phenotype B promotes atherogenesis and is recognized as a risk factor for ischemic heart disease, but its prevalence in ischemic stroke of distinct causes is unknown. Therefore we designed the study to investigate the prevalence of LDL phenotype B in stroke survivors with large vessel disease (LVD) or small vessel disease (SVD) and to establish the relationship between LDL phenotypes and basic lipid fractions in this group of patients. 59 patients (24 patients with LVD and 35 patients with SVD) being at least 3 months after ischemic stroke were included into the study. 30 sex- and age-matched subject served as controls. The concentrations of total cholesterol, HDL- and LDL-cholesterol, as well as triglycerides were measured and the LDL phenotype was determined using the potassium bromide density gradient ultracentrifugation. The LDL phenotype B was more frequent in patients with LVD (67%, p < 0.05) compared to patients with SVD and with controls. LDL phenotype B was also more frequent in patients with SVD (40%) and in all stroke survivors combined (51%), when compared with control group (17%, p < 0.05; chi-square test). Among stroke survivors, controls and studied subjects as a whole, those with LDL phenotype B revealed the lower concentration of HDL-cholesterol (1.19 +/- 0.33 vs. 1.46 +/- 0.42; 1.16 +/- 0.29 vs. 1.53 +/- 0.3 and 1.19 +/- 0.32 vs. 1.49 +/- 0.37, respectively; p < 0.05, Student t-test) when compared with carriers of LDL A phenotype. The LDL phenotype B is more frequent in ischemic stroke survivors compared to controls, and within the group of stroke survivors, LDL B is more prevalent in patients with LVD. The LDL phenotype B is associated with lower concentration of HDL-cholesterol