Impact of gender on upregulation of antioxidant defence mechanisms in Alzheimer's disease brain

Since oxidative stress plays an important role in the pathogenesis of Alzheimer's disease (AD) and since the age-adjusted incidence of AD is higher in females than males, we examined a possible influence of gender on antioxidant metabolism in brains from male and female AD patients and age-matched controls. Activities of copper/zinc-dependent superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione-disulfide reductase (GR) were elevated in AD samples compared to controls. Upon in vitro stimulation, levels of malondialdehyde formation were significantly lower in AD samples, probably due to the increased antioxidant capacity. Overall, our results indicate that antioxidant metabolism is functionally still intact but increased in AD implying that oxidative damage is caused rather by overproduction than by insufficient detoxification of ROS. Among AD patients, a gender-specific partial upregulation of antioxidant defence was present: activities of SOD and GPx were even further increased in female patients, and levels of 4-hydroxynonenal, a marker of oxidative damage, were higher than in male patients. Importantly, our results are in line with epidemiological studies indicating a higher risk for AD in females. Thus, gender differences in oxidative stress parameters might be related to the higher prevalence of AD in females.

Specific modulation of sigma binding sites by the anxiolytic drug opipramol

The atypical anxiolytic and antidepressive drug opipramol binds with high affinity to sigma1 and somewhat lower affinity to sigma2 sites. After subchronic treatment, opipramol significantly down-regulated sigma2 but not sigma1 sites. This effect was not seen for imipramine, citalopram, and reboxetine under similar conditions. On the other hand, only imipramine reduced the number of sigma1 sites. It is suggested that effects at sigma2 sites are involved in the anxiolytic properties of opipramol.

Abuse and dependence potential for the non-benzodiazepine hypnotics zolpidem and zopiclone: a review of case reports and epidemiological data

AIMS

The non-benzodiazepine hypnotics zolpidem and zopiclone, which are indicated for short-term treatment of insomnia, were considered originally by physicians as almost devoid of abuse and dependence potential. Several recent publications, however, have suggested that both agents carry a significant risk of abuse. To substantiate and re-evaluate this situation, the world literature was reviewed for cases of dependence of both agents; these cases were analysed in order to identify certain underlying patterns, if evident.

METHODS

A systematic review based on a Medline literature search was conducted including the years 1966-2002 to assemble all available clinical case reports that were analysed for typical features of abuse and dependence according to prespecified criteria. Only case reports were of interest, and clinical studies were excluded. No limitations as to language or publication year were applied. The terms 'zolpidem', 'zopiclone' and 'abuse', 'dependence', 'addiction', 'withdrawal' and 'intoxication' were used to identify relevant publications. Potentially relevant citations were retrieved and assessed for inclusion independently by two authors.

RESULTS

A total of 36 cases for zolpidem were identified, most of them reported in recent years, and 22 cases for zopiclone. Both sexes were involved to a similar extent; and cases were reported in all age groups. In extreme cases, dose increases reached a factor of 30-120 above the recommended doses. The majority of patients had a history of former drug or alcohol abuse and/or other psychiatric conditions.

CONCLUSION

On the basis of world-wide prescription numbers, which are approximately twofold higher for zolpidem (1,338,774,000 tablets from June 2001 to June 2002 in Europe, Japan and United States) than for zopiclone (664,897,000 tablets during the same period in Europe and Japan), the relative incidence of reported dependence similar for both drugs and remarkably lower than that of benzodiazepines used for the treatment of disturbed sleep. The findings offer the conclusion that zolpidem and zopiclone are relatively safe drugs. However, as both drugs are psychotropic drugs, patients with a history of abuse or dependence and those with psychiatric diseases seem to be at increased risk of abuse of these agents.

Brain Cholesterol, Statins and Alzheimer’s Disease

Growing evidence suggests that cellular cholesterol homeostasis is causally involved in different steps leading to pathological events in the brain of Alzheimer's Disease (AD) patients. It was previously demonstrated that the processing of the amyloid beta-peptide precursor protein (APP) is modulated by pronounced alterations in cellular cholesterol levels using statins or cholesterol extracting agents. However, a cholesterol-rich diet was found to enhance amyloid beta-peptide (Abeta) burden in the brain of transgenic mice without clearly affecting total brain cholesterol levels. Recent retrospective epidemiological studies have reported that the use of statins potentially suppresses the development of AD. Although some HMG-CoA reductase inhibitors seem to influence the central cholesterol pool in vivo, the above epidemiological findings are probably not linked to statin-induced changes in brain membrane cholesterol levels per se since not all statins active in preventing AD enter the central nervous system (CNS). Recently, we reported that different statins, regardless of their brain availability, induce alterations in cellular cholesterol distribution in the brain. Such pleiotropic, cholesterol-synthesis independent statin effects might be indirect and are possibly mediated at the blood-brain barrier (BBB) via nitric oxide (NO) or apolipoprotein E (ApoE).

Brain-membrane cholesterol in Alzheimer's disease

Cholesterol represents an important determinant of the physical state of biological membranes. Growing evidence indicate that changes in brain cholesterol and variations in neuronal membrane structure are involved in the development of Alzheimer's disease (AD). Cholesterol modulates the cleavage of the amyloid precursor protein and thus affect cellular production of beta-amyloid peptides (Ab). On the other hand, cholesterol seems to be protective against the neurotoxic and membrane disordering properties of Ab. Present review summarizes reports focusing on brain membrane changes in AD and the effects of Ab on these structures. Since it has been shown that these Ab effects are cholesterol dependent, recent findings are presented indicating that the modulation of membrane cholesterol refers to different cholesterol pools within the membranes. Further, consequences thereof for possible pharmacological strategies are discussed.

Effects of EGb 761 Ginkgo biloba extract on mitochondrial function and oxidative stress

As major sources of reactive oxygen species (ROS), mitochondrial structures are exposed to high concentrations of ROS and may therefore be particularly susceptible to oxidative damage. Mitochondrial damage could play a pivotal role in the cell death decision. A decrease in mitochondrial energy charge and redox state, loss of transmembrane potential (depolarization), mitochondrial respiratory chain impairment, and release of substances such as calcium and cytochrome c all contribute to apoptosis. These mitochondrial abnormalities may constitute a part of the spectrum of chronic oxidative stress in Alzheimer's disease. Accumulation of amyloid beta (Abeta) in form of senile plaques is also thought to play a central role in the pathogenesis of Alzheimer's disease mediated by oxidative stress. In addition, increasing evidence shows that Abeta generates free radicals in vitro, which mediate the toxicity of this peptide. In our study, PC12 cells were used to examine the protective features of EGb 761(definition see editorial) on mitochondria stressed with hydrogen peroxide and antimycin, an inhibitor of complex III. In addition, we investigated the efficacy of EGb 761 in Abeta-induced MTT reduction in PC12 cells. Moreover, we examined the effects of EGb 761 on ROS levels and ROS-induced apoptosis in lymphocytes from aged mice after in vivo administration. Here, we will report that EGb 761 was able to protect mitochondria from the attack of hydrogen peroxide, antimycin and Abeta. Furthermore, EGb 761 reduced ROS levels and ROS-induced apoptosis in lymphocytes from aged mice treated orally with EGb 761 for 2 weeks. Our data further emphasize neuroprotective properties of EGb 761, such as protection against Abeta-toxicity, and antiapoptotic properties, which are probably due to its preventive effects on mitochondria.

Cognitive and other behavioral effects of EGb 761 in animal models

Extensive pre-clinical and clinical studies conducted over more than three decades have established that EGb 761 (definition see editorial) represents a polyvalent therapeutic principle that is useful in the therapy of mildly to moderately severe dementia and other cognitive disorders. Besides cognition, other emotional and affective aspects of brain function also seem to benefit from EGb 761 treatment. Extensive behavioural studies in experimental animals are generally in line with clinical data since cognition improvement, stress protection, and antidepressive effects have been identified with this extract in proper animal models. While individual effects in all areas have been reported for adult animals and acute dosing, more pronounced effects are usually seen in aged animals and after subchronic treatment. Specifically, for the cognition improving properties pronounced beneficial effects are mainly present in those situations where cognition was impaired by aging or other noxious stimuli. Since all these conditions are associated with mitochondrial dysfunction, the stabilizing or even protecting effect of EGb 761 on mitochondrial function seems to be a major mechanism associated with many of EGb 761's behavioural effects. Bilobalide is most important in this respect. Moreover, bilobalide and the ginkgolides have recently been shown to affect chloride conductance by interfering with the function of membrane proteins related to receptor-gated chloride channels. These mechanisms are probably associated with behavioural effects requiring acute changes of neuronal activity, but might indirectly also improve mitochondrial function.

Anseculin improves passive avoidance learning of aged mice

Anseculin is a new coumarine derivative with promising cognition improving properties. We investigated its possible effects on passive avoidance learning in young and aged mice and the possible relationship to its alpha(1)-antagonistic properties.A single dose of anseculin did not affect long-term memory of young and aged mice. Moreover, in young mice, subchronic treatment with anseculin had no effect on cognitive functions, whereas aged, cognitively impaired mice clearly showed improved long-term memory with no effects on short-term memory. Further biochemical studies of aged control mice showed in comparison to the young mice a significant decrease of central alpha(1)-adrenoceptors density, but unchanged alpha(1)-adrenoceptor-mediated IP hydrolysis. Subchronic treatment with anseculin had no effect on the density of central alpha(1)-adrenoceptors in young adult mice and only a small although not significant effect on the density of cognitively-impaired aged mice. Furthermore, anseculin has no effects on alpha(1)-adrenoceptor-mediated IP hydrolysis.

Influence of pharmaceutical quality on the bioavailability of active components from Ginkgo biloba preparations

To be effective, herbal medicinal products are expected to meet comparable standards concerning the assessment of efficacy, safety and biopharmaceutical quality as chemically defined synthetic drugs as food supplements. However, these requirements are often not fulfilled, particularly regarding the characterization of biopharmaceutical properties such as in-vitro dissolution and in-vivo bioavailability. With respect to the relevance of biopharmaceutical quality of herbal medicinal products, two different Ginkgo biloba brands (test product: Ginkgo biloba capsules; reference product: Ginkgold) were analysed for dissolution rates and bioavailability of the most relevant active ingredients. Dissolution rates at pH 1 and 4.5 were determined according to the USP 23. The relative bioavailability of ginkgolide A, ginkgolide B and bilobalide was investigated after single oral administration of 120 mg Ginkgo biloba extract as tablets or capsules. Bioavailability data (area under the curve and peak concentration in plasma) were clearly different and did not show bioequivalence of test and reference products. The slow in-vitro dissolution of the test product resulted in a large decrease in bioavailability. These results indicate for the first time that the pharmaceutical properties of a herbal medicinal product have a significant impact on the rate and extent of drug absorption, and very likely on efficacy in humans.

ROS generation, lipid peroxidation and antioxidant enzyme activities in the aging brain

The objective of this study was to determine the specific relationship between brain aging and changes in the level of oxidative stress, lipid peroxidation (LPO) and in the activities of antioxidant enzymes. We used four different age groups (2-3 months, 10-11 months, 16-17 months and 20-21 months) which represented young adults, adults, beginning senescence and senescence, respectively. Basal levels of LPO products measured as malondialdehyde increased gradually with age in mouse brain homogenate. The extent of stimulated LPO products, however, was clearly decreased in the brain of adult mice compared to young mice but increased again in the brain of senescent mice. We could not detect any appreciable age-related changes in the basal as well as in stimulated levels of ROS measured with the fluorescent dyes dichlorofluorescein and dihydrorhodamine123. Nevertheless, there was a significant delay in the time course of ROS-generation in brain cells from old mice. The activities of the antioxidant enzymes CuZn-superoxide dismutase and glutathione reductase increased with age whereas glutathione peroxidase remained unchanged. On the basis of our present findings, we envisage a potential model that integrates several divergent findings described in the literature about the role of oxidative stress in brain aging.

Effects of aging and beta-amyloid on the properties of brain synaptic and mitochondrial membranes

The effects of aging and of different amyloid beta-peptides (A beta) on the properties of purified synaptosomal plasma and mitochondrial membranes were studied using different fluorescent dyes. Aging led to opposite membrane alterations in both mouse brain fractions. Cholesterol levels were significantly enhanced in synaptosomal plasma membranes (SPM) from aged mice only. Flexibility of membrane fatty acids was decreased in synaptosomal plasma and mitochondrial membranes, mobility of pyrene was enhanced, but in SPM only. With regard to acyl chain flexibility in aged brain membranes, both membrane preparations were less sensitive to A beta. By contrast, effects of A beta on the mobility of pyrene were not reduced for aged synaptic membranes, but even seemed to be enhanced in the case of aged mitochondrial membranes. The data presented significantly enhance our understanding of the mechanism of the A beta's disordering effects on synaptosomal membranes that are also detectable for mitochondrial membranes and show for the first time that A beta effects are modified by brain aging. This is of special interest since membrane alterations and in particular modifications of membrane cholesterol were recently linked to Alzheimer's Disease.

Age-related increase of oxidative stress-induced apoptosis in mice prevention by Ginkgo biloba extract (EGb761)

Enhanced apoptosis and elevated levels of reactive oxygen species (ROS) play a major role in aging. In addition, several neurodegenerative diseases are associated with increased oxidative stress and apoptosis in neuronal tissue. Antioxidative treatment has neuro-protective effects. The aim of the present study was to evaluate changes of susceptibility to apoptotic cell death by oxidative stress in aging and its inhibition by the antioxidant Ginkgo biloba extract EGb761. We investigated basal and ROS-induced levels of apoptotic lymphocytes derived from the spleen in young (3 months) and old (24 months) mice. ROS were induced by 2-deoxy-D-ribose (dRib) that depletes the intracellular pool of reduced glutathione. Lymphocytes from aged mice accumulate apoptotic cells to a significantly higher extent under basal conditions compared to cells from young mice. Treatment with dRib enhanced this difference, implicating a higher sensitivity to ROS in aging. Apoptosis can be reduced in vitro by treatment with EGb761. In addition, mice were treated daily with 100 mg/kg EGb761 per os over a period of two weeks. ROS-induced apoptosis was significantly reduced in the EGb761 group. Interestingly, this effect seemed to be more pronounced in old mice.

Pharmaceutical quality of different Ginkgo biloba brands

Ginkgo biloba-containing brands are one of the top sellers within the growing market for herbal remedies in many European countries as well as in the USA. In the consumers' interest, these brands should feature a certain quality and should be transparent in quality claims. In this investigation, a variety of products on the USA market was studied with respect to pharmaceutical quality, such as quantity of constituents and in-vitro dissolution. In terms of the content of active substances, flavone glycosides ranged from 24% to 36% and terpene lactones from 4% to 11%. With ginkgolic acids, there was a very large range, from < 500 ppm to about 90000 ppm. Comparing the dissolution rates of terpene lactones and flavone glycosides within the single products, most were approximately the same. Thus, terpene lactones and flavone glycosides were released from these products and dissolved at the same rate in most cases. Furthermore, most of the products investigated released more than the required 75% of the content of both components within 30 min. However, several products showed clear and relevant differences in dissolution rates to the rest (e.g. < 75% within 30 min or even less than 25% after 60 min in one case, indicating much poorer pharmaceutical quality). Beside the comparability respectively standardisation of the extracts used, the in-vitro dissolution of the relevant constituents should be similar to other drugs to guarantee comparable in-vivo performance of herbal products. An important step in standardising pharmaceutical quality is the pharmacopoeial monograph for Ginkgo biloba extract in Germany, standardising the content of pharmacologically relevant substances (flavone glycosides 22-27% and terpenlactones 5-7%, 2.8-3.4% ginkgolides A, B, C and 2.6-3.2% bilobalide thereof). Many of the investigated products, which refer to the German Commission E (of the Federal Institute for Drugs and Medicinal Devices) monograph, are not in accordance with this specification. Thus, they can not be considered to be pharmaceutically equivalent.

Immunomodulatory effect of gold sodium thiomalate on murine acquired immunodeficiency syndrome

Induction of IL-2 production and increased expression of CD25 were observed in C57BL/10 mice after weekly treatment with gold sodium thiomalate (GST). LP-BM5 murine leukemia virus (MuLV) infected mice treated with GST survived longer, had less cervical lymph node swelling, lower spleen weight, and fewer abnormalities in the expression of the cell surface markers, CD4, CD8a and CD45R/B220 on spleen cells than those that were not treated with GST. Thus, GST treatment may be beneficial through a decrease in disease progression via IL-2 induction in MuLV infected mice. This may have application in human immunodeficiency virus-infected individuals.

Induction of apoptosis in the blue mussel Mytilus galloprovincialis by tri-n-butyltin chloride

Induction of apoptosis by tri-n-butyltin (TBT) in gill tissue of the mussel Mytilus galloprovincialis was investigated. The terminal dUTP nick-end labeling technique (TUNEL) was used to detect cells displaying DNA fragmentation within gill structures. Genomic DNA fragmentation was detected as characteristically ladder-like pattern of DNA fragments induced by single injection of different doses of TBT (1-5 microg/g) below the mantle, directly into the pallial fluid, after 24 h of incubation. DNA degradation of higher order DNA structure, as well as reduced G(0)/G(1) cell cycle region (the sub-G(1) region) was detectable after 1.5 h of TBT incubation. Presence of apoptotic cells in mussels' gills was indicated by the selective loss of G(2)/M cells concomitant with the appearance of cells with decreased DNA content in S and G(0)/G(1) cell cycle regions. The effect of the TBT on cell cycle in a mussel gill was a dose related and exposure time depending. The possible mechanism of induction of apoptosis in vivo in gill tissue of mussel treated with TBT is discussed.

Contribution of sponge genes to unravel the genome of the hypothetical ancestor of Metazoa (Urmetazoa)

Recently the term Urmetazoa, as the hypothetical metazoan ancestor, was introduced to highlight the finding that all metazoan phyla including the Porifera (sponges) are derived from one common ancestor. Sponges as the evolutionarily oldest, still extant phylum, are provided with a complex network of structural and functional molecules. Analyses of sponge genomes from Demospongiae (Suberites domuncula and Geodia cydonium), Calcarea (Sycon raphanus) and Hexactinellida (Aphrocallistes vastus) have contributed also to the reconstruction of the evolutionary position of Metazoa with respect to Fungi. Furthermore, these analyses have provided evidence that the characteristic evolutionary novelties of Metazoa, such as the extracellular matrix molecules, the cell surface receptors, the nervous signal transduction molecules as well as the immune molecule existing in Porifera, share high sequence and in some aspects also functional similarities to related polypeptides found in other metazoan phyla. During the transition to Metazoa new domains occurred; as one example, the formation of the death domain from the ankyrin is outlined. In parallel, domanial proteins have been formed, such as the receptor tyrosine kinases. The metazoan essentials have been defined by analyzing and comparing the sponge sequences with the related sequences from the metazoans Homo sapiens, Caenorhabditis elegans and Drosophila melanogaster, the fungus Saccharomyces cerevisiae and the plant Arabidopsis thaliana. The data revealed that those sponge molecules grouped to cell adhesion cell recognition proteins are predominantly found in Protostomia and Deuterostomia while they are missing in Fungi and Viridiplantae. Moreover, evidence is presented allowing the conclusion that the sponge molecules are more closely related to the corresponding molecules from H. sapiens than to those of C. elegans or D. melanogaster. Especially surprising was the finding that the Demospongiae are provided with elements of adaptive immunity.

Molecular evolution of the metazoan extracellular matrix: cloning and expression of structural proteins from the demosponges Suberites domuncula and Geodia cydonium

One crucial event during evolution to multicellularity was the development of either direct cell-cell contact or indirect interaction via extracellular matrix (ECM) molecules. The identification of those polypeptides provides conclusive data on the phylogenetic relationship of metazoan phyla and helps us to understand the position of the Metazoa among the other kingdoms. Recently it became evident that the ECM of sponges is amazingly complex; it is composed of fibrous molecules, e.g., collagen, and their corresponding receptors, which are highly similar to those existing in other metazoan phyla. While these data already support the view of monophyly of Metazoa, additional studies are required to understand whether these molecules, which are similar in their primary sequence, also have the same function throughout the metazoan kingdom. In the present study we identified the ligand for one of the autopomorphic characters of Metazoa, the single-transmembrane receptor protein with the receptor tyrosine kinase (RTK) from G. cydonium, as an example: the putative mucus-like protein from G. cydonium. This protein was upregulated during autograft fusion in the homologous system with kinetics similar to those of the RTK. Additionally, a cDNA was isolated from S. domuncula whose deduced polypeptide displays a high sequence similarity to dermatopontin, an ECM molecule found exclusively in Metazoa. Furthermore, it is documented that expression of the fibrous ECM molecule collagen is regulated by the characteristic metazoan morphogens myotrophin and endothelial monocyte-activating polypeptide. These data indicate that the ECM of sponges is not an unstructured ground substance but provides the basis for integrated cell communication.

Specific detection of cyclobutane pyrimidine dimers in phytoplankton DNA by a non-radioactive assay based on T4-endonuclease V digestion

The effect of artificial and natural UV irradiation on DNA in marine phytoplankton Isochrysis galbana monoculture was investigated. The presence of cyclobutane pyrimidine dimers (CPDs) in unlabelled I. galbana DNA was detected by a non-radiometric alkaline filter elution assay after T4-endonuclease V digestion. The quantity of CPDs was estimated by alkaline agarose gel electrophoresis. Precise determination of the amount of DNA in the presence of I. galbana pigments was achieved by oxazole yellow homodimer (YOYO) dye. T4-endonuclease V-sensitive sites frequency (ESS/kb), measured after exposure to 2-40 kJ m(-2) of artificial UV light, increased in a dose-dependent manner. Twelve hours after irradiation cell culture growth was disrupted, and 50% of initial DNA damage in the cells was observed. After 1 h of sunlight exposure, the incidence of CPDs increase significantly. Prolonged exposition to sunlight decrease CPDs incidence due to efficiency of I. galbana DNA repair mechanisms. The presence of water-soluble crude oil fraction (WSOF) affected DNA repair efficiency resulting in accumulation of CPDs in I. galbana DNA.

Sponge Bcl-2 homologous protein (BHP2-GC) confers distinct stress resistance to human HEK-293 cells

It is established that sponges, the phylogenetically oldest still extant phylum of Metazoa, possess key molecules of the apoptotic pathways, that is members from the Bcl-2 family and a pro-apoptotic molecule with death domains. Here we report on transfection studies of human cells with a sponge gene, GCBHP2. Sponge tissue was exposed to heat shock and tributyltin, which caused an upregulation of gene expression of GCBHP2. The cDNA GCBHP2 was introduced into human HEK-293 cells and mouse NIH-3T3 cells; the stable transfection was confirmed by the identification of the transcripts, by Western blotting as well as by immunofluorescence using antibodies raised against the recombinant polypeptide. HEK-293 cells, transfected with GCBHP2, showed high resistance to serum starvation and tributyltin treatment, compared to mock-transfected cells. In contrast to mock-transfected cells, GCBHP2-transfected cells activated caspase-3 to a lower extent. Thus, sponges contain gene(s) involved in apoptotic pathway(s) displaying their function also in human cells.