Pharmacogenomics of neurodegenerative diseases

Genetic markers in biological fluids for aging-related major neurocognitive disorder

Aging-related major neurocognitive disorder (NCD), formerly named dementia, comprises of the different acquired diseases whose primary deficit is impairment in cognitive functions such as complex attention, executive function, learning and memory, language, perceptual/motor skills, and social cognition, and that are related to specific brain regions and/or networks. According to its etiology, the most common subtypes of major NCDs are due to Alzheimer' s disease (AD), vascular disease (VaD), Lewy body disease (LBD), and frontotemporal lobar degeneration (FTLD). These pathologies are frequently present in mixed forms, i.e., AD plus VaD or AD plus LBD, thus diagnosed as due to multiple etiologies. In this paper, the definitions, criteria, pathologies, subtypes and genetic markers for the most common age-related major NCD subtypes are summarized. The current diagnostic criteria consider cognitive decline leading to major NCD or dementia as a progressive degenerative process with an underlying neuropathology that begins before the manifestation of symptoms. Biomarkers associated with this asymptomatic phase are being developed as accurate risk factor and biomarker assessments are fundamental to provide timely treatment since no treatments to prevent or cure NCD yet exist. Biological fluid assessment represents a safer, cheaper and less invasive method compared to contrast imaging studies to predict NCD appearance. Genetic factors particularly have a key role not only in predicting development of the disease but also the age of onset as well as the presentation of comorbidities that may contribute to the disease pathology and trigger synergistic mechanisms which may, in turn, accelerate the neurodegenerative process and its resultant behavioral and functional disorders.

Lack of association between nuclear factor erythroid-derived 2-like 2 promoter gene polymorphisms and oxidative stress biomarkers in amyotrophic lateral sclerosis patients

Oxidative stress involvement has been strongly hypothesized among the possible pathogenic mechanisms of motor neuron degeneration in amyotrophic lateral sclerosis (ALS). The intracellular redox balance is finely modulated by numerous complex mechanisms critical for cellular functions, among which the nuclear factor erythroid-derived 2-like 2 (NFE2L2/Nrf2) pathways. We genotyped, in a cohort of ALS patients (n = 145) and healthy controls (n = 168), three SNPs in Nrf2 gene promoter: −653 A/G, −651 G/A, and −617 C/A and evaluated, in a subset (n = 73) of patients, advanced oxidation protein products (AOPP), iron-reducing ability of plasma (FRAP), and plasma thiols (-SH) as oxidative damage peripheral biomarkers. Nrf2 polymorphisms were not different among patients and controls. Increased levels of AOPP (P < 0.05) and decreased levels of FRAP (P < 0.001) have been observed in ALS patients compared with controls, but no difference in -SH values was found. Furthermore, no association was found between biochemical markers of redox balance and Nrf2 polymorphisms. These data confirm an altered redox balance in ALS and indicate that, while being abnormally modified compared to controls, the oxidative stress biomarkers assessed in this study are independent from the −653 A/G, −651 G/A, and −617 C/A Nrf2 SNPs in ALS patients.

Nullity of GSTT1/GSTM1 related to pesticides is associated with Parkinson's disease

Genetic and environmental factors affect the pathogenesis of Parkinson's disease (PD). Genetic variants of the enzyme glutathione S-transferases (GST) may be related to the disease. This study aimed to evaluate the influence of genetic variants of GST (GSTT1/GSTM1) and their association with the exposure to environmental toxins in PD patients. We studied 254 patients with PD and 169 controls. The GSTM1/GSTT1 variants were analyzed by polymerase chain reaction. We applied the Fisher's exact test and the χ2 test for statistical analysis (p<0.05). The present and absence for GSTT1 and GSTM1 were similar in patients and controls. The null for GSTT1 and GSTM1 (0/0) and exposure to pesticides prevailed in patients (18%) compared to controls (13%, p=0.014). This study suggests the association between PD and previous exposure to pesticides, whose effect may be enhanced in combination with null for GSTT1/GSTM1.

A synopsis on the role of tyrosine hydroxylase in Parkinson's disease

Parkinson's disease (PD) is a common chronic progressive neurodegenerative disorder in elderly people. A consistent neurochemical abnormality in PD is degeneration of dopaminergic neurons in substantia nigra pars compacta, leading to a reduction of striatal dopamine (DA) levels. As tyrosine hydroxylase (TH) catalyses the formation of L-dihydroxyphenylalanine (L-DOPA), the rate-limiting step in the biosynthesis of DA, the disease can be considered as a TH-deficiency syndrome of the striatum. Problems related to PD usually build up when vesicular storage of DA is altered by the presence of either α-synuclein protofibrils or oxidative stress. Phosphorylation of three physiologically-regulated specific sites of N-terminal domain of TH is vital in regulating its kinetic and protein interaction. The concept of physiological significance of TH isoforms is another interesting aspect to be explored further for a comprehensive understanding of its role in PD. Thus, a logical and efficient strategy for PD treatment is based on correcting or bypassing the enzyme deficiency by the treatment with L-DOPA, DA agonists, inhibitors of DA metabolism or brain grafts with cells expressing a high level of TH. Neurotrophic factors are also attracting the attention of neuroscientists because they provide the essential neuroprotective and neurorestorative properties to the nigrostriatal DA system. PPAR-γ, a key regulator of immune responses, is likewise a promising target for the treatment of PD, which can be achieved by the use of agonists with the potential to impact the expression of pro- and anti-inflammatory cytokines at the transcriptional level in immune cells via expression of TH. Herein, we review the primary biochemical and pathological features of PD, and describe both classical and developing approaches aimed to ameliorate disease symptoms and its progression.

The X-Linked Adrenoleukodystrophy (X-ALD) and Oxidative Stress

Most of the studies indicate that there is as yet no complete cure for X-ALD. However, methods of the treatment seem to slow rather than treat the disease. One method is the use of Lorenzo's oil in conjunction with a low fat diet, which may help in cerebral X-ALD. X-ALD is in very close resemblance to another neurodegenerative disease, amyotrophic lateral sclerosis (ALS). One of the believed pathomechanisms of ALS is oxidative stress; therefore, this article's emphasis on the role of reactive oxygen species in X-ALD. The aim of the present study was to review the literature concerning the advances in the treatment of X-adrenoleukodystrophy (X-ALD, OMIM # 300100) in the last two decades and to shed more light on the link between oxidative stress and X-ALD. This review article may point to a deficit in reactive oxygen species (ROS) scavenging and/or ROS overproduction being involved in the aetiopathology of these neurodegenerative diseases. Consequently, one of the useful neuronal rescue strategies could be the treatment with antioxidant agents.

MDR1 gene polymorphisms and clinical relevance

In vivo and in vitro studies have demonstrated that P-glycoprotein (P-gp) plays a very significant role in the ADME processes (absorption, distribution, metabolism, excretion) and drug-drug interaction (DDI) of drugs in humans. P-gp is the product of multidrug resistance gene (MDR1/ABCB1). Pharmacogenomics and pharmacogenetics studies have revealed that genetic polymorphisms of MDR1 are associated with alteration in P-gp expression and function in different ethnicities and subjects. By now, 50 single nucleotide polymorphisms (SNPs) and 3 insertion/deletion polymorphisms have been found in the MDR1 gene. Some of them, such as C3435T, have been identified to be a risk factor for numerous diseases. It is believed that further understanding of the physiology and biochemistry of P-gp with respect to its genetic variations may be important for individualized pharmacotherapy. Therefore, based on the latest public information and our studies, this review focuses on the following four aspects: 1) the impact of P-gp on pharmacokinetics; 2) MDR1 genetic polymorphisms and their impacts on pharmacogenetics; 3) relationship between altered P-gp expression and function and the MDR1(C3435T) SNP, and 4) relevance of MDR1 polymorphisms to certain human diseases.

Pharmacogenomics and treatment for dementia induced by Alzheimer’s disease

Pharmacogenomics is the study of interindividual genetic variability, which plays a significant role in defining drug response and toxicity. As research has graduated from studying single candidate genes to whole-genome scans, pharmacogenomics is beginning to make its impact on the therapeutics of complex CNS disorders, such as schizophrenia, Parkinson’s disease and Alzheimer’s disease. Alzheimer’s disease is a progressive complex disorder, where genetic predisposition interacts with environmental factors. With conventional therapeutics only providing symptomatic treatment, the current focus of the pharmaceutical industry is on novel strategies with an etiopathogenic orientation. In this review, we have summarized the current knowledge of pathogenetic mechanisms of Alzheimer’s disease, with a focus on the known relevant molecules and the potential of pharmacogenomics in translating this knowledge of human genome variability into efficacious and safer therapeutics.

Polymorphism in environment responsive genes and association with Parkinson disease

Attempts were made in the present case-control study to investigate the association of polymorphism in the genes encoding proteins involved in toxication-detoxication and dopaminergic pathways and susceptibility to Parkinson's disease (PD). Seventy patients suffering from PD and one hundred healthy controls belonging to the same geographical location and same ethnicity were included in the study. PCR-RFLP and allele-specific PCR-based methodology were used to identify the genotypes. Multivariate logistic regression analysis revealed that heterozygous genotypes of cytochrome P4502D6*4(CYP2D6*4), CYP2E1*5B (RsaI) polymorphism and homozygous mutant genotypes of CYP2E1*6 (Dra1) were found to be overrepresented in PD cases when compared to the controls. Risk was also found to be increased in patients carrying glutathione S-transferase T1 (GSTT1) null or homozygous variant genotypes of GSTP1. Significant association was observed for monoamine oxidase-B(MAO-B) variant allele G and PD, whereas no difference in genotype and allele frequencies was observed for manganese-superoxide dismutase (MnSOD), dopamine receptor-D2(DRD2), and dopamine transporter (DAT) genes between controls and PD cases. Genotype combinations characterized by the presence of two variant genotypes on their corresponding loci revealed that four combinations of GSTT1 null and MnSOD(-9Val) or GST null and MAOB-G or CYP2E1*5B and MAO-B-AG or CYP2E1*5B and DRD2 (Taq1A-het) genotypes in the patients exhibited severalfold higher and significant association with risk to PD. Our data suggest that polymorphism in the genes involved in detoxification and dopamine regulation may modulate the susceptibility to PD and could be important risk factors in the pathogenesis of PD.

Age-related inflammatory diseases: role of genetics and gender in the pathophysiology of Alzheimer's disease

Alzheimer's disease (AD) is a heterogeneous and progressive neurodegenerative disease which in Western societies mainly accounts for clinical dementia. A high proportion of women are affected by this disease, especially at a very advanced age, which might to a large extent be associated with the fact that women live longer. However, some studies suggest that incidence rates may be really increased in women. For this reason the influence of estrogens on the brain and the decrease of it during menopause are of special interest. After menopause, circulating levels of estrogens markedly decline, influencing several brain processes predicted to influence AD risk. The control of estrogens on oxidative stress, inflammation, and the cerebral vasculature might also be expected to increase AD risk. During the Women's Health Initiative Memory Study--a randomized, placebo-controlled trial of women 65-79 years of age--oral estrogen plus progestin was seen to double the rate of developing dementia, with risk appearing soon after the treatment was initiated. On the basis of current evidence, hormone therapy (HT) is thus not indicated for the prevention of AD. Inflammation clearly occurs in pathologically vulnerable regions of the AD brain and the search for genetic factors influencing the pathogenesis of AD has led to the identification of numerous gene polymorphisms that act as susceptibility modifiers. Accordingly, several reports have indicated that the risk of AD is substantially influenced by several genetic polymorphisms in the promoter region, or other untranslated regions, of genes encoding inflammatory mediators. Here we review several data suggesting that inflammatory genetic variation may contribute to higher AD susceptibility in women too. All together this information may represent the basis both for future recognition of individuals at risk as well as for a pharmacogenomic approach in achieving drug responsiveness.

Treatment of Alzheimer's disease: From pharmacology to a better understanding of disease pathophysiology

Alzheimer's disease (AD) is the most common cause of cognitive impairment in older patients and is expected to increase greatly in prevalence in the next future. It is characterized by the development of senile plaques and neurofibrillary tangles, which are associated with neuronal loss affecting to a greater extent cholinergic neurons. A cascade of pathophysiological events is triggered in AD that ultimately involves common cellular signalling pathways and leads to cellular and neural networks dysfunction, failure of neurotransmission, cell death and a common clinical outcome. The process is asynchronous and viable neurons remain an important target for therapeutic intervention at each stage of disease evolution. At present symptomatic drugs inhibiting the degradation of acetylcholine within synapses and more recently glutamate receptor antagonists represent the mainstay of therapy. However, interventions able to halt or slow disease progression (i.e., disease-modifying agents) are necessary. Although much progress has been made in this area, there are currently no clinically approved interventions for AD classed as disease modifying or neuroprotective. This paper reviews the main symptomatic strategies available for treating AD and future strategies for improving our therapeutic approach to AD.

Influência genética na degeneração do disco intervertebral

As doenças que afetam o sistema músculo-esquelético acometem centenas de milhões de pessoas no mundo e estão entre as causas mais comuns de invalidez e sofrimento crônico. A doença vertebral degenerativa constitui uma exacerbação do processo de envelhecimento, podendo estar envolvidos os fatores genéticos, ambientais ou lesões traumáticas, deformidades e doenças preexistentes. Muito se tem discutido sobre os múltiplos fatores envolvidos na degeneração discal, mas sua etiologia permanece indeterminada. Contudo, atualmente a participação da genética parece muito mais forte do que se suspeitava anteriormente. Neste artigo, é abordada a participação de alguns genes no processo discogênico, bem como o que isso representa para o melhor entendimento da etiopatogênese da doença e na melhora de seu tratamento.

Inflammation in central nervous system injury

Inflammation is a key component of host defence responses to peripheral inflammation and injury, but it is now also recognized as a major contributor to diverse, acute and chronic central nervous system (CNS) disorders. Expression of inflammatory mediators including complement, adhesion molecules, cyclooxygenase enzymes and their products and cytokines is increased in experimental and clinical neurodegenerative disease, and intervention studies in experimental animals suggest that several of these factors contribute directly to neuronal injury. Most notably, specific cytokines, such as interleukin-1 (IL-1), have been implicated heavily in acute neurodegeneration, such as stroke and head injury. In spite of their diverse presentation, common inflammatory mechanisms may contribute to many neurodegenerative disorders and in some (e.g. multiple sclerosis) inflammatory modulators are in clinical use. Inflammation may have beneficial as well as detrimental actions in the CNS, particularly in repair and recovery. Nevertheless, several anti-inflammatory targets have been identified as putative treatments for CNS disorders, initially in acute conditions, but which may also be appropriate to chronic neurodegenerative conditions.

Genetic polymorphisms of the human MDR1 drug transporter

P-glycoprotein is an ATP-dependent efflux pump that contributes to the protection of the body from environmental toxins. It transports a huge variety of structurally diverse compounds. P-glycoprotein is involved in limiting absorption of xenobiotics from the gut lumen, in protection of sensitive tissues (brain, fetus, testis), and in biliary and urinary excretion of its substrates. P-glycoprotein can be inhibited or induced by xenobiotics, thereby contributing to variable drug disposition and drug interactions. Recently, several SNPs have been identified in the MDR1 gene, some of which can affect P-glycoprotein expression and function. Potential implications of MDR1 polymorphisms for drug disposition, drug effects, and disease risk are discussed.

Using cDNA microarray to assess Parkinson's disease models and the effects of neuroprotective drugs

The remarkable progress made by molecular biology and molecular genetics during the past decade, and the advent of the novel tools of genomics and proteomics, are expected to reveal differential expression profiles of thousands of genes and proteins involved in the degeneration of dopamine-containing cells in Parkinson's disease and allow more focused treatments according to individual genotypes. Of particular interest is the application of microarrays in drug discovery and design to identify 'fingerprints' as potential candidate targets for drug intervention. The major microarray findings relevant to Parkinson's disease and its neurotoxin-induced animal and cell models will be discussed, with particular reference to the neuroprotective therapeutic potential that could arise from the development of drugs 'a la carte'.

Genetic and environmental factors in cancer and neurodegenerative diseases

The aim of this review is to summarise the recent findings in the fields of carcinogenesis and neurodegenerative diseases, the both disorders are characterised by the contribution of different factors including the inheritance of mutated genes, and the exposure to endogenous or exogenous agents during the life. We first analysed the causative genes until now discovered in both processes, then we focused our attention on the role of environmental exposure, susceptibility factors, oxidative stress, apoptosis and aging to the development of such disorders. The genotype at a particular locus may account for an inter-individual susceptibility that can both increase or decrease the risk to develop the pathology especially after the exposure to environmental agents. The mechanism of apoptosis, that is an excellent strategy in order to eliminate damaged cells, seems to be lost during carcinogenesis, while it seems to be involved in the neuronal death in a lot of neurodegenerative disorders. Oxidative stress can both lead to DNA mutations or to the formation of damaged proteins, so being an important risk factor for the initiation and the progression of a disease: in fact it may be one of the causes or can arise as a consequence of a damage caused by other factors increasing then the first damage. It is well established that carcinogenesis is a multi-step process caused by series of successive mutations occurring into a cell and conferring to this cell a growth advantage, so that age is the largest risk factor for cancer in humans. Pathophysiology of neurodegenerative diseases is complex and likely involves multiple overlapping and perhaps redundant pathways of neuronal damage, characterised by the generation of anomalous proteins, often due to mutations in the corresponding gene, and by their subsequent accumulation into or outside specific areas of the brain.

Neuroplasticity in Alzheimer's disease

Ramon y Cajal proclaimed in 1928 that "once development was ended, the founts of growth and regeneration of the axons and dendrites dried up irrevocably. In the adult centers the nerve paths are something fixed, ended and immutable. Everything must die, nothing may be regenerated. It is for the science of the future to change, if possible, this harsh decree." (Ramon y Cajal, 1928). In large part, despite the extensive knowledge gained since then, the latter directive has not yet been achieved by 'modern' science. Although we know now that Ramon y Cajal's observation on CNS plasticity is largely true (for lower brain and primary cortical structures), there are mechanisms for recovery from CNS injury. These mechanisms, however, may contribute to the vulnerability to neurodegenerative disease. They may also be exploited therapeutically to help alleviate the suffering from neurodegenerative conditions.

Early and late gene changes in MPTP mice model of Parkinson's disease employing cDNA microarray

Recently, we reported specific brain gene expression changes in the chronic MPTP model inthe late stage of degeneration, employing cDNA expression array, which indicate a "domino" cascade of events involved in neuronal cell death. In an attempt to elucidate early gene expression profile in the region of the substantia nigra (SN) and the striatum of acute MPTP-treated mice (3-24 h), we elected a restricted number of genes affected by the long-term MPTP treatment, and their expression was examined. Specifically, we detected alterations in the expression of genes implicated in oxidative-stress, inflammatory processes, signal transduction and glutamate toxicity. These pro-toxic genes appear to be compensated by the elevated expression in trophic factors and antioxidant defenses, which are also activated by short exposure to MPTP. The time course of these gene expression changes indicates the importance of investigating the early gene cascade of events occurring prior to late nigrostriatal dopamine neuronal cell death.

Proteomic profiling and neurodegeneration in Alzheimer's disease

Quantitative proteome analysis of Alzheimer's disease (AD) brains was performed using 2-D gels to identify disease specific changes in protein expression. The task of characterizing the proteome and its components is now practically achievable because of the development and integration of four important tools: protein, EST, and complete genome sequence databases, mass spectrometry, matching software for protein sequences and protein separation technology. Mass spectrometry (MS) instrumentation has undergone a tremendous change over the past decade, culminating in the development of highly sensitive, robust instruments that can reliably analyze biomolecules, particularly proteins and peptides; we identified 35 proteins from over 100 protein spots on a 2-D gel. Using this current technology, protein-expression profiling, which is actually a specialized form of mining, is an important principal application of proteomics. The information obtained has tremendous potential as a means of determining the pathogenesis, and detecting disease markers and potential targets for drug therapy in AD.

Expression polymorphism of the blood-brain barrier component P-glycoprotein (MDR1) in relation to Parkinson's disease

Because drug transporters such as P-glycoprotein, the product of the multidrug resistance (MDR1 ) gene, contribute to the function of the blood-brain barrier, we hypothesized that differences in their expression could affect the uptake of neurotoxic xenobiotics, thereby modulating interindividual susceptibility for neurological disorders such as Parkinson's disease. In a pilot case-control study comprising 95 Parkinson's disease patients (25 early-onset patients with onset age < or = 45 years) and 106 controls we analysed the three common polymorphisms, 3435C >T in exon 26, 2677G > T,A in exon 21, and -129T > C in exon 1b. There were no statistically significant associations between any of these polymorphisms and Parkinson's disease. However, a distribution pattern consistent with our hypothesis was observed in that the frequency of the 3435T/T genotype, which had previously been associated with decreased P-glycoprotein expression and function, was highest in the early-onset Parkinson's disease group (36.0%), second-highest in the late-onset Parkinson's disease group (22.9%), and lowest in the control group (18.9%). Furthermore, we confirmed that the MDR1 exon 21 and exon 26 polymorphisms are in significant linkage disequilibrium since the [2677G, 3435C] and [2677T, 3435T] haplotypes were far more frequently observed than expected. In conclusion, MDR1 and other drug transporters represent plausible candidates as Parkinson's disease risk genes. Larger studies are required to confirm this role in the etiology of Parkinson's disease.

Pharmaceutical education in the wake of genomic technologies for drug development and personalized medicine

The development of safe and effective new therapeutics is a long, difficult, and expensive process. Over the last 20-30 years, recombinant DNA (rDNA) technology has provided a multiple of new methods, molecular targets and DNA-based diagnostics to pharmaceutical research that can be utilized in assays for screening and developing potential biopharmaceutical drugs. In parallel, new innovative approaches to drug delivery systems were discovered and reached the market. Pharmaceutical biotechnology, pharmacogenomics, combinatorial chemistry, in close relation to high-throughput screening technologies, and bioinformatics are major advances that give a new direction to pharmaceutical sciences. To meet with the needs of this new dynamic era of pharmaceutical research and health care environment, pharmaceutical education has to set new priorities to keep pace with the challenges related to genomic technologies. The development of new initiative education programs, for both undergraduate and graduate curricula, in pharmacy has to be focused on preparing pharmacists oriented for both pharmacy practice and drug research and development. This can be achieved by providing future pharmacists with knowledge, skills and attitudes to be more competitive in the health care system, pharmacy practice-related fields, pharmaceutical industry and drug research and development areas, or finally in academia. Educators and pharmacy school members have the responsibility of deciding how, to what extent, by which methods, and/or in which way these changes and new directions in the education programs should be developed.

Using meta-analysis to explain the diversity of results in genetic studies of late-onset Alzheimer's disease and to identify high-risk subgroups

In late-onset Alzheimer's disease, there is a puzzling inconsistency between the findings of case-control studies of most proposed risk genes, except apolipoprotein E epsilon4. This inconsistency may stem from the failure to define the genetic and non-genetic interactions that affect the disease association of each particular susceptibility gene. Such interactions will limit the influence of the gene to a 'relevant subset' of vulnerable people. The relevant subsets for many risk genes will be narrow, compared to that of apolipoprotein E epsilon4. Studies may therefore miss the association or even suggest that a risk gene is protective. In these circumstances, the precise composition of a cohort is critical and defining the relevant subset is crucial. We illustrate how such definition may be achieved through meta-analysis. We take as an example the butyrylcholinesterase K variant, whose association with Alzheimer's disease may now be provisionally defined. This analysis leads to the identification of a potentially high-risk group: over 75 year old male carriers of both apolipoprotein E epsilon4 and butyrylcholinesterase K variant.

Comparative genome analysis and pathway reconstruction

Pathway reconstruction builds on genome and biochemical data with the aim of reconstructing higher level interactions between identified enzymes in a specific genome, in particular the different enzyme pathways (species or individual/patient). Metabolite flow in a pathway is analyzed by different tools, such as elementary mode analysis. This reveals key enzymes and pharmacological targets in the enzyme network. An overview of bioinformatic tools and algorithms for these tasks, application examples and recent results from these techniques are presented. Target selection, drug development and optimization can all be sped up using these approaches.