A unifying hypothesis of Alzheimer's disease. III. Risk factors

The Role of Cortisol in Chronic Stress, Neurodegenerative Diseases, and Psychological Disorders

Cortisol, a critical glucocorticoid hormone produced by the adrenal glands, plays a pivotal role in various physiological processes. Its release is finely orchestrated by the suprachiasmatic nucleus, governing the circadian rhythm and activating the intricate hypothalamic-pituitary-adrenal (HPA) axis, a vital neuroendocrine system responsible for stress response and maintaining homeostasis. Disruptions in cortisol regulation due to chronic stress, disease, and aging have profound implications for multiple bodily systems. Animal models have been instrumental in elucidating these complex cortisol dynamics during stress, shedding light on the interplay between physiological, neuroendocrine, and immune factors in the stress response. These models have also revealed the impact of various stressors, including social hierarchies, highlighting the role of social factors in cortisol regulation. Moreover, chronic stress is closely linked to the progression of neurodegenerative diseases, like Alzheimer's and Parkinson's, driven by excessive cortisol production and HPA axis dysregulation, along with neuroinflammation in the central nervous system. The relationship between cortisol dysregulation and major depressive disorder is complex, characterized by HPA axis hyperactivity and chronic inflammation. Lastly, chronic pain is associated with abnormal cortisol patterns that heighten pain sensitivity and susceptibility. Understanding these multifaceted mechanisms and their effects is essential, as they offer insights into potential interventions to mitigate the detrimental consequences of chronic stress and cortisol dysregulation in these conditions.

Association between aluminum in drinking water and incident Alzheimer's disease in the Canadian Study of Health and Aging cohort

Epidemiological evidence linking aluminum in drinking water and Alzheimer's disease (AD) has been inconsistent, with previous studies often limited by small sample sizes. The present study addresses this issue using data from the Canadian Study of Health and Aging (CSHA), a prospective cohort of 10,263 subjects followed-up from 1991-1992 through 2001-2002. Participants' residential histories were linked to municipal drinking water sources in 35 Canadian municipalities to obtain ecologic pH, aluminum, fluoride, iron and silica concentrations in drinking water. Cox proportional hazards models were used to examine associations between aluminum and incident AD [Hazard Ratios (HRs), 95% confidence intervals (CIs)], adjusting for age, gender, history of stroke, education, and high blood pressure. A total of 240 incident AD cases were identified during follow-up of 3, 638 subjects derived from the CSHA cohort with complete data on all covariates. With categorical aluminum measurements, there was an increasing, but not statistically significant, exposure-response relationship (HR = 1.34, 95% CI 0.88-2.04, in the highest aluminum exposure category; p = 0.13 for linear trend). Similar results were observed using continuous aluminum measurements (HR=1.21, 95% CI 0.97-1.52, at the interquartile range of 333.8 μg/L; p = 0.09 for linear trend). In a subsample genotyped for ApoE-ε4, there was some evidence of an association between aluminum and AD (p = 0.03 for linear trend). Although a clear association between aluminum in drinking water and AD was not found, the linear trend observed in ApoE-ε4 subsample warrants further examination.

Central Role of Glucocorticoid Receptors in Alzheimer's Disease and Depression

Alzheimer’s disease (AD) is the principal neurodegenerative pathology in the world displaying negative impacts on both the health and social ability of patients and inducing considerable economic costs. In the case of sporadic forms of AD (more than 95% of patients), even if mechanisms are unknown, some risk factors were identified. The principal risk is aging, but there is growing evidence that lifetime events like chronic stress or stress-related disorders may increase the probability to develop AD. This mini-review reinforces the rationale to consider major depressive disorder (MDD) as an important risk factor to develop AD and points the central role played by the hypothalamic-pituitary-adrenal (HPA) axis, glucocorticoids (GC) and their receptors (GR) in the etiology of MDD and AD. Several strategies directly targeting GR were tested to neutralize the HPA axis dysregulation and GC overproduction. Given the ubiquitous expression of GR, antagonists have many undesired side effects, limiting their therapeutic potential. However, a new class of molecules was developed, highly selective and acting as modulators. They present the advantage to selectively abrogate pathogenic GR-dependent processes, while retaining beneficial aspects of GR signaling. In fact, these “selective GR modulators” induce a receptor conformation that allows activation of only a subset of downstream signaling pathways, explaining their capacity to combine agonistic and antagonistic properties. Thus, targeting GR with selective modulators, alone or in association with current strategies, becomes particularly attractive and relevant to develop novel preventive and/or therapeutic strategies to tackle disorders associated with a dysregulation of the HPA axis.

Blood Brain Barrier and Alzheimer's Disease: Similarity and Dissimilarity of Molecular Alerts

Background

Blood brain barrier and Alzheimer’s disease are interrelated. This interrelation is detected by physicochemical methods, pharmacological and electrophysiological analyses. Nature of the phenomenon is extremely complex. The description of this interrelation in mathematical terms is a very important task.

Objective

The systematization of facts, which are described in the literature and related to interaction between processes, which influence Alzheimer's disease and blood brain barrier is the subject of this work. In addition, establishing of correlations between molecular features and endpoints, which are related to the treatment of Alzheimer's disease and blood brain barrier using the CORAL software are subjects of this work.

Methods

The information on logically structured analysis is available in the literature and building up quantitative structure – activity relationships (QSARs) by the Monte Carlo method has been used to solve the task of systematization of facts related to the “treatment of Alzheimer's disease vs. blood brain barrier”.

Results

Comparison of agreements and disagreements of the available published papers together with the statistical quality of built up QSARs are results of this work.

Conclusion

The facts from published papers and technical details of QSAR built up in this study give possibility to formulate the following rules: (i) there are molecular alerts, which are promoters to increase blood brain barrier and therapeutic activity of anti-Alzheimer disease agents; (ii) there are molecular alerts, which contradict each other.

Alzheimer's Disease: From Mitochondrial Perturbations to Mitochondrial Medicine

Age-related neurodegenerative diseases such as Alzheimer's disease (AD) are distressing conditions causing countless levels of suffering for which treatment is often insufficient or inexistent. Considered to be the most common cause of dementia and an incurable, progressive neurodegenerative disorder, the intricate pathogenic mechanisms of AD continue to be revealed and, consequently, an effective treatment needs to be developed. Among the diverse hypothesis that have been proposed to explain AD pathogenesis, the one concerning mitochondrial dysfunction has raised as one of the most discussed with an actual acceptance in the field. It posits that manipulating mitochondrial function and understanding the deficits that result in mitochondrial injury may help to control and/or limit the development of AD. To achieve such goal, the concept of mitochondrial medicine places itself as a promising gathering of strategies to directly manage the major insidious disturbances of mitochondrial homeostasis as well as attempts to directly or indirectly manage its consequences in the context of AD. The aim of this review is to summarize the evolution that occurred from the establishment of mitochondrial homeostasis perturbation as masterpieces in AD pathogenesis up until the development of mitochondrial medicine. Following a brief glimpse in the past and current hypothesis regarding the triad of aging, mitochondria and AD, this manuscript will address the major mechanisms currently believed to participate in above mentioned events. Both pharmacological and lifestyle interventions will also be reviewed as AD-related mitochondrial therapeutics.

Microsomal epoxide hydrolase 1 (EPHX1): Gene, structure, function, and role in human disease

Microsomal epoxide hydrolase (EPHX1) is an evolutionarily highly conserved biotransformation enzyme for converting epoxides to diols. Notably, the enzyme is able to either detoxify or bioactivate a wide range of substrates. Mutations and polymorphic variants in the EPHX1 gene have been associated with susceptibility to several human diseases including cancer. This review summarizes the key knowledge concerning EPHX1 gene and protein structure, expression pattern and regulation, and substrate specificity. The relevance of EPHX1 for human pathology is especially discussed.

High corn oil dietary intake improves health and longevity of aging mice

Corn oil has been recommended as a replacement for saturated fats because of its high levels of poly- and mono-unsaturated fatty acids. In the present study, we tested whether very high levels of corn oil (58.6% fat-derived calories, FDC) intake improve health and longevity of aging mice. Twelve month old male C57BL/6 mice were fed a normal diet (10% FDC of corn oil, N) or a high fat diet (58.6% FDC of corn oil, HF) for 13-15 months. Our results show that a HF diet significantly increased the longevity of the aged mice (at 25 months of age, 53.8% of mice died in the N group, whereas the mortality rate was only 23.2% in the HF group). High corn oil also reversed aging-increased blood lipids including triglyceride, total cholesterol and LDL. Similarly, high corn oil intake overturned aging-raised pro-inflammatory markers including IL-1β, IL-6, and monocyte chemotactic protein-1 (MCP-1) in the blood. In addition, corn oil intake reversed aging-damaged rotarod performance and liver function. Interestingly, the HF group was significantly heavier than the N group (53.6g/mouse vs. 41.3g/mouse); however, both HF and N groups had the same calorie intake (12.48 kcal/d/mouse vs. 12.24 kcal/d/mouse). Although, the HF group's food consumption was lower than that of the N group (2.4 g/d/mouse vs. 3.4 g/d/mouse). These results suggest that if total calorie consumption stays in the normal range, very high levels of corn oil intake improve health and longevity of aging mice.

Dietary antiaging phytochemicals and mechanisms associated with prolonged survival

Aging is well-known an inevitable process that is influenced by genetic, lifestyle and environmental factors. However, the exact mechanisms underlying the aging process are not well understood. Increasing evidence shows that aging is highly associated with chronic increase in reactive oxygen species (ROS), accumulation of a low-grade proinflammatory phenotype and reduction in age-related autophagy, suggesting that these factors may play important roles in promoting aging. Indeed, reduction of ROS and low-grade inflammation and promotion of autophagy by calorie restriction or other dietary manipulation can extend lifespan in a wide spectrum of model organisms. Interestingly, recent studies show that some food-derived small molecules, also called phytochemicals, can extend lifespan in various animal species. In this paper, we review several recently identified potential antiaging phytochemicals that have been studied in cells, animals and humans and further highlight the cellular and molecular mechanisms underlying the antiaging actions by these molecules.

Molecular neuropathogenesis of Alzheimer's disease: an interaction model stressing the central role of oxidative stress

Alzheimer's disease (AD) exhibits a complex etiology that simultaneously manifests as a complex cellular, neurobiological, molecular, anatomic-physiological and clinical entity. Other significant psychiatric conditions, such as depression and schizophrenia, may also present with complex and concurrent clinical and/or molecular phenotypes. These neuropsychiatric pathologies also originate from both environmental and genetic factors. We analyzed the molecular phenotypes of AD and discuss them with respect to the classical theories, which we integrated into mechanisms that share molecular and/or anatomical connections. Based on these mechanisms, we propose an interaction model and discuss the model in light of studies that refute or support it. Given the spectrum of AD phenotypes, we limit the scope of our discussion to a few, which facilitates concrete analysis. In addition, the study of specific, individual pathogenic phenotypes may be critical to defining the complex mechanisms leading to AD, thereby improving strategies for developing novel therapies.

A pilot study of gene/gene and gene/environment interactions in Alzheimer disease

BACKGROUND

Although some genes associated with increased risk of Alzheimer Disease (AD) have been identified, few data exist related to gene/gene and gene/environment risk of AD. The purpose of this pilot study was to explore gene/gene and gene/environment associations in AD and to obtain data for sample size estimates for larger, more definitive studies of AD.

METHODS

The effect of gene/gene and gene/environment interaction related to late onset Alzheimer Disease (LOAD) was investigated in 153 subjects with LOAD and 302 gender matched controls enrolled in the Personalized Medicine Research Project, a population-based bio-repository. Genetic risk factors examined included APOE, ACE, OLR1,and CYP46 genes, and environmental factors included smoking, total cholesterol, LDL, HDL, triglycerides, C-reactive protein, blood pressure, statin use, and body mass index.

RESULTS

The mean age of the cases was 78.2 years and the mean age of the controls was 87.2 years. APOE4 was significantly associated with LOAD (OR=3.55, 95%CL=1.70, 7.45). Cases were significantly more likely to have ever smoked cigarettes during their life (49.3% versus 38.4%, p=0.03). The highest recorded blood pressure and pulse pressure measurements were significantly higher in the controls than the cases (all P<0.005). Although not statistically significant in this pilot study, the relationship of the following factors was associated in opposite directions with LOAD based on the presence of an APOE4 allele: obesity at the age of 50, ACE, OLR1, and CYP46.

CONCLUSIONS

These pilot data suggest that gene/gene and gene/environment interactions may be important in LOAD, with APOE, a known risk factor for LOAD, affecting the relationship of ACE and OLR1 to LOAD. Replication with a larger sample size and in other racial/ethnic groups is warranted and the allele and risk factor frequencies will assist in choosing an appropriate sample size for a definitive study.

The vascular contribution to Alzheimer's disease

AD (Alzheimer's disease) is a progressive neurodegenerative disease of unknown origin. Despite questions as to the underlying cause(s) of this disease, shared risk factors for both AD and atherosclerotic cardiovascular disease indicate that vascular mechanisms may critically contribute to the development and progression of both AD and atherosclerosis. An increased risk of developing AD is linked to the presence of the apoE4 (apolipoprotein E4) allele, which is also strongly associated with increased risk of developing atherosclerotic cardiovascular disease. Recent studies also indicate that cardiovascular risk factors, including elevated blood cholesterol and triacylglycerol (triglyceride), increase the likelihood of AD and vascular dementia. Lipids and lipoproteins in the circulation interact intimately with the cerebrovasculature, and may have important effects on its constituent brain microvascular endothelial cells and the adjoining astrocytes, which are components of the neurovascular unit. The present review will examine the potential mechanisms for understanding the contributions of vascular factors, including lipids, lipoproteins and cerebrovascular Abeta (amyloid beta), to AD, and suggest therapeutic strategies for the attenuation of this devastating disease process. Specifically, we will focus on the actions of apoE, TGRLs (triacylglycerol-rich lipoproteins) and TGRL lipolysis products on injury of the neurovascular unit and increases in blood-brain barrier permeability.

The GRK2 Overexpression Is a Primary Hallmark of Mitochondrial Lesions during Early Alzheimer Disease

Increasing evidence points to vascular damage as an early contributor to the development of two leading causes of age-associated dementia, namely Alzheimer disease (AD) and AD-like pathology such as stroke. This review focuses on the role of G protein-coupled receptor kinases (GRKs) as they relate to dementia and how the cardio and cerebrovasculature is involved in AD pathogenesis. The exploration of GRKs in AD pathogenesis may help bridge gaps in our understanding of the heart-brain connection in relation to neurovisceral damage and vascular complications of AD. The a priori basis for this inquiry stems from the fact that kinases of this family regulate numerous receptor functions in the brain, myocardium and elsewhere. The aim of this review is to discuss the finding of GRK2 overexpression in the context of early AD pathogenesis. Also, we consider the consequences for this overexpression as a loss of G-protein coupled receptor (GPCR) regulation, as well as suggest a potential role for GPCRs and GRKs in a unifying theory of AD pathogenesis through the cerebrovasculature. Finally, we synthesize this newer information in an attempt to put it into context with GRKs as regulators of cellular function, which makes these proteins potential diagnostic and therapeutic targets for future pharmacological intervention.

Amyloid precursor protein transgenic mouse models and Alzheimer's disease: understanding the paradigms, limitations, and contributions

Transgenic (Tg) mice that overexpress mutant familial Alzheimer's disease (AD) amyloid precursor protein (APP) genes have contributed to an understanding of dementia pathology, and support the amyloid cascade hypothesis. Although many sophisticated mice APP models exist, none recapitulates AD cellular and behavioral pathology. The morphological resemblance to AD amyloidosis is impressive, but fundamental biophysical and biochemical properties of the APP/Abeta produced in Tg mice differ substantially from those of humans. The greater resilience of Tg mice in the presence of substantial Abeta burdens suggests that levels and forms deleterious to human neurons are not as noxious in these models. Transgenic mice were widely used for testing AD therapeutic agents, and demonstrated promising results. Unfortunately, clinical trials resulted in unforeseen adverse events or negative therapeutic outcomes. The disparity between success and failure is in part attributable to evolutionary divergence between humans and rodents. These observations suggest that the pathogenesis of AD is by far more intricate than can be explained by a straightforward accumulation of Abeta.

Antibody responses, amyloid-beta peptide remnants and clinical effects of AN-1792 immunization in patients with AD in an interrupted trial

Post mortem examinations of AN-1792-vaccinated humans revealed this therapy produced focal senile plaque disruption. Despite the dispersal of substantial plaque material, vaccination did not constitute even a partial eradication of brain amyloid as water soluble amyloid-beta (Abeta) 40/42 increased in the gray matter compared to sporadic Alzheimer's disease (AD) patients and total brain Abeta levels were not decreased. Significant aspects of AD pathology were unaffected by vaccination with both vascular amyloid and hyper-phosphorylated tau deposits appeared refractory to this therapy. In addition, vaccination resulted in the consequential and drastic expansion of the white matter (WM) amyloid pool to levels without precedent in sporadic AD patients. Although vaccination disrupted amyloid plaques, this therapy did not enhance long-term cognitive function or necessarily halt neurodegeneration. The intricate involvement of vascular pathology in AD evolution and the firm recalcitrance of vessel-associated amyloid to antibody-mediated disruption suggest that immunization therapies might be more effective if administered on a prophylactic basis before vascular impairment and well ahead of any clinically evident cognitive decline. Amyloid-beta is viewed as pathological based on the postmortem correlation of senile plaques with an AD diagnosis. It remains uncertain which of the various forms of this peptide is the most toxic and whether Abeta or senile plaques themselves serve any desirable or protective functions. The long-term cognitive effects of chronic immunotherapy producing a steadily accumulating and effectively permanent pool of disrupted Abeta peptides within the human brain are unknown. In addition, the side effects of such therapy provided on a chronic basis could extend far beyond the brain. Eagerly seeking new therapies, critical knowledge gaps should prompt us to take a more wholistic perspective viewing Abeta and the amyloid cascade as aspects of complex and many-faceted physiological processes that sometimes end in AD dementia.

Survey of trace metals in drinking water supplied to rural populations in the eastern Llanos of Venezuela

To ascertain the water quality for human consumption, chemical parameters such as pH, conductivity and total dissolved calcium, magnesium, iron, aluminum, zinc, copper and manganese were measured during four sampling periods (November 2002; March, May and July 2003) in drinking water wells which supply several forest camps and rural populations located in the eastern Llanos of Venezuela. Copper levels in drinking water in November 2002 were found to be significantly higher (P<0.05) than the other assessed periods. Temporal variations of the other parameters considered were not statistically significant. Calcium and magnesium concentrations were found to be extremely low (mean concentration+/-S.D. of 0.27+/-0.25mg/l for Ca and 0.219+/-0.118 for Mg) during the four sampling periods, probably because of the carbonate bearing scarcity in the soils lithic component. The rest of the metals complied with the Venezuelan and International guidelines of quality criteria for drinking water.

Insights into cerebrovascular complications and Alzheimer disease through the selective loss of GRK2 regulation

Alzheimer disease (AD) and stroke are two leading causes of age-associated dementia. Increasing evidence points to vascular damage as an early contributor to the development of AD and AD-like pathology. In this review, we discuss the role of G protein-coupled receptor kinase 2 (GRK2) as it relates to individuals affected by AD and how the cardiovasculature plays a role in AD pathogenesis. The possible involvement of GRKs in AD pathogenesis is an interesting notion, which may help bridge the gap in our understanding of the heart–brain connection in relation to neurovisceral damage and vascular complications in AD, since kinases of this family are known to regulate numerous receptor functions both in the brain, myocardium, and elsewhere. The aim of this review is to discuss our findings of overexpression of GRK2 in the context of the early pathogenesis of AD, because increased levels of GRK2 immunoreactivity were found in vulnerable neurons of AD patients as well as in a two-vessel occlusion (2-VO) mammalian model of ischaemia. Also, we consider the consequences for this overexpression as a loss of G-protein coupled receptor (GPCR) regulation, as well as suggest a potential role for GPCRs and GRKs in a unifying theory of AD pathogenesis, particularly in the context of cerebrovascular disease. We synthesize this newer information and attempt to put it into context with GRKs as regulators of diverse physiological cellular functions that could be appropriate targets for future pharmacological intervention.

Depression and risk for Alzheimer disease: systematic review, meta-analysis, and metaregression analysis

CONTEXT

A history of depression may increase risk for developing Alzheimer disease (AD) later in life. Clarifying this relation might improve understanding of risk factors for and disease mechanisms in AD.

OBJECTIVE

To systematically review and complete a meta-analysis on the relation of depression and AD.

DATA SOURCES

We conducted electronic bibliographic searches of MEDLINE, PsychLit, EMBASE, and BIOSIS using search terms sensitive to studies of etiology combined with searches on terms related to depression and AD and reviewed reference lists of articles.

STUDY SELECTION

Studies with data contrasting depressed vs nondepressed patients who did and did not later develop AD were included. Studies that related continuous measures of depression and cognitive status were excluded.

DATA EXTRACTION

Numerical data were independently extracted by 3 reviewers. They also rated studies on a scale that assessed quality indicators for observational studies. Data on the interval between observation of depression and the diagnosis of AD were collected when available.

DATA SYNTHESIS

Meta-analytic evaluation with random-effects models resulted in pooled odds ratios of 2.03 (95% confidence interval, 1.73-2.38) for case-control and of 1.90 (95% confidence interval, 1.55-2.33) for cohort studies. Findings of increased risk were robust to sensitivity analyses. Interval between diagnoses of depression and AD was positively related to increased risk of developing AD, suggesting that rather than a prodrome, depression may be a risk factor for AD.

CONCLUSIONS

A history of depression may confer an increased risk for later developing AD. This relation may reflect an independent risk factor for the disease.

Expression of microsomal epoxide hydrolase is elevated in Alzheimer's hippocampus and induced by exogenous β-amyloid and trimethyl-tin

The brain is a potential target for drugs and environmental toxins. Microsomal epoxide hydrolase (mEH) is one of several critical biotransformation enzymes in xenobiotic metabolism and detoxification. In the present study, we report that the expression of mEH is significantly elevated in the hippocampus and associated cortex, but not in the cerebellum, in Alzheimer's disease (AD) patients. A large proportion of the mEH-positive cells are located around beta-amyloid plaques. The mEH-positive-staining cells are astrocytes and pyramidal neurons. Western blotting analysis confirmed increased expression of mEH in AD hippocampal tissues. In primary hippocampal glial culture, beta-amyloid aggregation stimulated mEH expression in the astrocytes, which displayed a patchy distribution. An environmental neurotoxic agent, trimethyl-tin, also activated mEH expression in rat hippocampus and entorhinal cortex. The present study demonstrates a significant increase in mEH expression in the AD hippocampus, a region showing abundant neuropathology in AD. The expression of mEH could also be elevated by exposure to exogenous beta-amyloid in vitro and environmental toxins in vivo. Our studies suggest that mEH may play a role in pathogenesis of neurodegeneration in response to environmental stress.

Protective effects of Ginkgo biloba leaf extract on aluminum-induced brain dysfunction in rats

This study examined the protective effects of Ginkgo biloba extract (GbE) on the learning and memory function in aluminum-treated rats and potential mechanisms. Wistar rats were given daily aluminum chloride 500 mg/kg, i.g, for one month, followed by continuous exposure via the drinking water containing 1600 ppm aluminum chloride for up to 5 months. The ability of spatial learning and memory was tested by Morris water maze. Aluminum administration significantly increased escape latency and searching distance, indicative of brain dysfunction. GbE treatment (50-200 mg/kg, i.g) significantly protected against aluminum-induced brain dysfunction, as evidenced by decreased escape latency and searching distance compared with the Al alone group. To examine the mechanisms of the protection, the expressions of amyloid precursor protein (APP) and caspase-3 in brain regions were examined by immunohistochemistry. GbE treatment reduced the contents of APP and caspase-3 in hippocampus of aluminum-treated rats in a dose-dependent manner. At the highest dose of GbE (200 mg/kg), the immunostain for APP and caspase-3 was returned to normal levels. In summary, this study demonstrates that GbE is effective in improving the ability of spatial learning and memory of aluminum-intoxicated rats. This protection appears to be due to a decreased expression of APP and caspase-3 in rat brain, resulting in a decrease in the production of insoluble fragments of Abeta-amyloid.

Modulation of mitochondrial membrane potential and reactive oxygen species production by copper in astrocytes

In monolayers of cultured rat astrocytes a number of agents that induce oxidative stress act synergistically with exposure to copper leading to rapid depolarization of the mitochondrial membrane potential (Psi m) and increased reactive oxygen species (ROS) production. Copper sensitized astrocytes to the action of menadione, an intracellular generator of superoxide anion radical, exogenous hydrogen peroxide (H2O2) and rotenone, an inhibitor of mitochondrial electron transport chain complex I. However, significant differences were observed in the ability to modulate the copper-enhanced oxidative stress depending on which stressor was used. The inhibitor of mitochondrial permeability transition cyclosporin A attenuated the effect of copper and rotenone, but had no protective action in the case of H2O2/copper and menadione/copper combinations. The H2O2 scavenger pyruvate was effective at protecting mitochondria against damage associated with the combined exposure to H2O2/copper and menadione/copper but not to the rotenone/copper combination. The antioxidant Trolox was ineffective at protecting against any of these actions and indeed had a damaging effect when combined with copper. The membrane-permeable copper chelator neocuproine combined with sensitizing concentrations of menadione caused a decrease in Psi m, mimicking the action of copper. Penicillamine, a membrane-impermeable copper chelator, was effective at reducing copper sensitization. Endogenous copper, mobilized during periods of oxidative stress, may play a role in the pathophysiology of brain injury. Our results suggest that this might be particularly dangerous in dysfunctional conditions in which the mitochondrial electron transport chain is compromised.

Alzheimer's disease: the pharmacological pathway

The current pharmacological treatment of Alzheimer's disease (AD) comes down to four marketed drugs (tacrine, donepezil, rivastigmine and galantamine) all of which are cholinesterase inhibitors, conforming to the cholinergic hypothesis. The future is clearly directed at new biological targets closely linked to the pathophysiology of the disease and more precisely, the pathological hallmark of AD which includes widespread neuronal degeneration, neuritic plaques containing beta-amyloid and tau-rich neurofibrillary tangles. For clinicians, this means that new curative drugs will have to be prescribed early in the course of the disease. This review describes the main entry pathways for drug discovery in AD: (1) supplementation therapy, (2) anti-apoptotic compounds, (3) substances with a mitochondrial impact, (4) anti-amyloid substances, (5) anti-protein aggregation and (6) lipid-lowering drugs. The rapidity at which these compounds will be at our disposal is highly dependent on the policy of the pharmaceutical companies.

Will a healthy lifestyle help prevent Alzheimer's disease?

Alzheimer's disease (AD) appears to resemble other chronic diseases, whereby a myriad of interconnected factors, including those associated with lifestyle, are involved in disease development. In this paper, we examine accepted and proposed risk factors for AD and explore health behaviors, including diet, exercise, prevention of injury, and cognitive stimulation, that may help prevent AD. Adherence to a healthy lifestyle may directly protect against AD or may prevent diseases associated with AD, such as vascular disease and diabetes. A healthy lifestyle to prevent AD may be important throughout life rather than after disease manifestation and may be particularly relevant if other factors, such as genetic predisposition, also increase risk of AD. If changes in lifestyle can help prevent AD by reducing modifiable risk factors, this knowledge can aid individuals who wish to take action to protect themselves and their families from the disease.

Neurodegenerative disorders of protein aggregation

In recent years, it has become increasingly clear that many neurodegenerative diseases involve aggregation and deposition of misfolded proteins such as amyloid beta, tau, alpha-synuclein and polyglutamine containing proteins. This abnormal deposition of misfolded proteins produce malfunctioning of a distinctive set of neurons. It may also induce oxidative and endoplasmic reticulum stress and proteosomal and mitochondrial dysfunction that ultimately leads to neuronal death. While hereditary forms of disorders are caused by genetic mutations, many sporadic cases are likely to be due to genetic and environmental factors. These disorders are progressive in nature. Therefore, treatment is difficult. However, for some diseases, a growing number of treatment options such as drugs, antioxidants, cell transplantation, surgery, rehabilitation procedures and preimplantation diagnosis is available. It should be noted that many of these treatments produce unacceptable risks or adverse effects and they are of only minimal benefit for patients. In future, an understanding of the causes of protein aggregation and genetic and environmental susceptibility factors of a specific individual (or specific individual determinants) may provide a better opportunity for an effective therapeutic intervention.