Current Pharmaceutical Design - Volume 19, Issue 36, 2013

Sporadic Alzheimer’s disease (AD) is a prevalent, complex and chronically progressive brain disease. Its course is non-linear, dynamic, adaptive to maladaptive, and compensatory to decompensatory, affecting large-scale neural networks through a plethora of mechanistic and signaling pathway alterations that converge into regional and cell type-specific neurodegeneration and, finally, into clinically overt cognitive and behavioral decline. This decline includes reductions in the activities of daily living, quality of life, independence, and life expectancy. Evolving lines of research suggest that epigenetic mechanisms may play a crucial role during AD development and progression. Epigenetics designates molecular mechanisms that alter gene expression without modifications of the genetic code. This topic includes modifications on DNA and histone proteins, the primary elements of chromatin structure. Accumulating evidence has revealed the relevant processes that mediate epigenetic modifications and has begun to elucidate how these processes are apparently dysregulated in AD. This evidence has led to the clarification of the roles of specific classes of therapeutic compounds that affect epigenetic pathways and characteristics of the epigenome. This insight is accompanied by the development of new methods for studying the global patterns of DNA methylation and chromatin alterations. In particular, high-throughput sequencing approaches, such as next-generation DNA sequencing techniques, are beginning to drive the field into the next stage of development. In parallel, genetic imaging is beginning to answer additional questions through its ability to uncover genetic variants, with or without genome-wide significance, that are related to brain structure, function and metabolism, which impact disease risk and fundamental network-based cognitive processes. Neuroimaging measures can further be used to define AD systems and endophenotypes. The integration of genetic neuroimaging methods with epigenetic markers in humans appears promising. This evolving development may lead to a new research discipline - imaging epigenetics - that will provide deeper insight into the causative pathogenetic and pathophysiological pathways through which genes and environment interrelate during life and impact human brain development, physiology, aging and disease. This knowledge may open doors for the development of novel biomarkers and preventive and disease-modifying treatments.

Introduction of diffusion tensor imaging (DTI) in 1980 and its advancement in the last three decades offered the possibility to visualize and quantify changes in white matter. DTI allows the evaluation of the structural integrity in complex neurodegenerative diseases, such as Alzheimer’s disease (AD). Progressive disintegration of functional and structural neural network coordination contributes to the cognitive dysfunction in AD. Therefore, detection of loss of cortico-cortical projections may support an early diagnosis at prodromal stages of disease which may prove essential for future preventive AD treatment trials. Moreover, structural integrity measured by DTI may help to distinguish between symptomatic and disease modifying effects of pharmacological interventions. This review gives a concise account on the physical basis of DTI acquisition and processing. We summarize DTI findings in normal aging and AD and regarding the effects of cognitive intervention and antidementive treatment on structural neural connectivity. Finally, we evaluate the promising future potential of DTI to become a surrogate endpoint in clinical AD trials.

The pathophysiological mechanisms underlying normal aging and neurodegenerative disorders represent the focus of a bulk of recent research. Physiological brain aging is characterized by a progressive dysfunction and loss of synaptic contacts and neuronal abnormal apoptosis. Neural and synaptic redundancy as well as functional and structural plastic remodeling of brain networking promote maintenance of brain activity in healthy elderly for everyday life but are not sufficient to face the pathologic scenario of excessive synaptic/ neuronal loss as in dementias. It is, then, important to implement techniques that are able to measure changes in normal aging brain and to discriminate the threshold from neurodegenerative processes. Rhythmic electromagnetic brain oscillatory activity is a hallmark of neuronal function and it contains relevant traces of neuronal assemblies cooperation across different brain functions; an integrated approach utilizing modern neurophysiological techniques, including electroencephalography (EEG), event-related potentials (ERPs), and transcranial magnetic stimulation (TMS), together with biological markers and structural and functional imaging is promising for largescale, affordable, and non-invasive intercept of at-risk populations both at a group and probably also at a single-subject level. This approach might also guarantee the possibility of studying drug-induced changes in the electrical properties of the human cortex, developing and testing models of brain connectivity and treating neuropsychiatric diseases. In this paper some neurophysiological cutting-edge techniques will be presented that provide innovative information and deal with the broad issue of the role of neurophysiology for the assessment of patho-physiological aging and dementia also providing new insight to the actions of central nervous system drugs at the cortical level.

Neuronal transmission and functional synapses require mitochondria, which are mainly involved in the generation of energy (ATP and NAD+), regulation of cell signaling and calcium homeostasis. Particularly intriguing is emerging data suggesting the relationship between mitochondria and neurotrophic factors that can act at the synaptic level promoting neuronal transmission and plasticity. On the other hand, disturbances in mitochondrial functions might contribute to impaired synaptic transmission and neuronal degeneration in Alzheimer's Disease and other chronic and acute neurodegenerative disorders. Here, we review the molecular mediators controling mitochondrial function and their impact on synaptic dysfunction associated with the pathogenesis of Alzheimer's Disease.

Schizophrenia is a major mental illness that is characterized by psychosis, apathy, social withdrawal and cognitive impairment. These abnormalities in patients results in impaired functioning in work, school, parenting, self-care, independent living, interpersonal relationships, and leisure. Although the search for the biological correlates of schizophrenia has met with limited success, new advances in genetics and pharmacology are promising. Here, we describe the symptoms, causes, diagnosis, strategies for treatment, and clinical impact of the currently available medications.

Schizophrenia is a chronic, often disabling mental illness with a lifetime prevalence of ~1% worldwide, and 2-to-3 times higher mortality rates are reported in schizophrenia patients compared to the general population. Although research has been increasingly focusing on identifying novel diagnostic and treatment resources for this illness, the diagnosis of schizophrenia is still based on clinical criteria, which are subjectively assessed and tend to vary across the course of the illness. Endophenotypes are commonly described as molecular, neuropsychological, neuro-imaging, and electrophysiological parameters that are closely associated to the genetic underpinnings of a specific disorder. Putative endophenotypes for psychiatric disorders should: 1) be associated with a specific illness in the population, 2) be heritable, 3) be present regardless of the patients clinical status, 4) co-segregate with the illness within families, and 5) be detected in non-affected family members of psychiatric patients at higher rates than in the general population. Whenever a genetic association is not present, or has not been investigated, the term biomarker is usually preferred. Endophenotypes and biomarkers are stable over time and are largely symptom independent, thus enabling an objective diagnosis of schizophrenia. Furthermore, these measures could be utilized to assess the risk of developing this disorder, and to identify novel pharmacological targets for its treatment. In this article I will present some of the most promising endophenotypes and biological markers of schizophrenia. For each of them, I will briefly describe abnormal findings in schizophrenia patients and, whenever available, in their first-degree relatives. I will then review the ability of each of these measures to identify individuals with schizophrenia (diagnostic value) and to assess the risk for schizophrenia (predictive value). Finally, I will discuss how some of these endophenotypes and biological markers could be utilized to develop novel treatment targets for schizophrenia, as well as to further the current understanding of the neurobiology of this disorder.

The term “Autism Spectrum” is often used to describe disorders that are currently classified as Pervasive Developmental Disorders. These disorders are typically characterized by social deficits, communication difficulties, stereotyped or repetitive behaviors and/or cognitive delays or mental retardation; sometimes they present high comorbidity rates with epilepsy. Although these diagnoses share some common features, individuals with these disorders are thought to be “on the spectrum” because of differences in severity across these domains. Recent advances in the genetics of autism spectrum disorders (ASDs) are offering new valuable insights into molecular and cellular mechanisms of pathology. Of particular interest are transgenic technologies that allowed the engineering of several mouse models mimicking different kinds of monogenic heritable forms of ASDs. These transgenic models provide excellent opportunities to explore in detail cellular and molecular mechanisms underlying disease pathology and to identify novel targets for therapeutic intervention. Increasing evidence suggests that the pathophysiological core of the murine model is primarily due to changes in normal synaptic transmission and plasticity. Here, we will extensively review the synaptic alterations across different animal models of ASDs and recapitulate the pharmacological strategies aimed at rescuing hippocampal plasticity phenotypes. We describe how pharmacological modulation of mGlu5 receptor, through the use of positive or negative allosteric modulators (depending on the specific disorder), may represent a promising therapeutic strategy for ASDs treatment.

Neurosteroids play essential roles in the control of central nervous system functions during physiological and pathological conditions. Increasing evidences show gender differences in the pathogenesis and clinical manifestations of several neurodevelopmental conditions, including Autism Spectrum Disorders (ASD), possibly due to the action of sex hormones during critical periods of brain development. Furthermore, it is known that neuroactive steroids contribute to neuroprotection, spinogenesis, synaptogenesis, as well as to modulation of neuronal excitability via their interaction with GABA receptors. Dysfunctions of GABAergic signaling early in development lead to a severe excitation-inhibition unbalance in neuronal circuits, which may contribute to the pathophysiology of autism. In this review, we summarize recent data concerning the functional role of neurosteroids and their relationship with the GABAergic system, focusing on GABA-mediated neurotrasmission alterations characterizing some neurodevelopmental disorders.

In the 1960s, Joseph Altman reported that the adult mammalian brain is capable of generating new neurons. Today it is understood that some of these neurons are derived from uncommitted cells in the subventricular zone lining the lateral ventricles, and the dentate gyrus of the hippocampus. The first area generates new neuroblasts which migrate to the olfactory bulb, whereas hippocampal neurogenesis seems to play roles in particular types of learning and memory. A part of these uncommitted (immature) cells is able to divide and their progeny can generate all three major cell types of the nervous system: neurons, astrocytes, and oligodendrocytes; these properties define such cells as neural stem cells. Although the roles of these cells are not yet clear, it is accepted that they affect functions including olfaction and learning/memory. Experiments with insults to the central nervous system also show that neural stem cells are quickly mobilized due to injury and in various disorders by proliferating, and migrating to injury sites. This suggests a role of endogenous neural stem cells in disease. New pools of stem cells are being discovered, suggesting an even more important role for these cells. To understand these cells and to coax them to contribute to tissue repair it would be very useful to be able to image them in the living organism. Here we discuss advances in imaging approaches as well as new concepts that emerge from stem cell biology with emphasis on the interface between imaging and stem cells.

Calix[n]arenes are macrocyclic cone-shaped compounds formed from phenolic units linked by methylene groups in the ortho position. Structural features make calix[n]arenes a versatile class of molecules that are of great interest, particularly in the pharmaceutical field. The cavity-like shape gives calix[n]arenes the ability to selectively encapsulate ions or neutral molecules, which can be used to generate carrier systems capable of increasing the solubility and diffusivity of chemical species. These resulting systems can function as deliverers of bioactive guest molecules. Host-guest molecular interactions act as the cornerstone that prompts the application of calix[n]arenes in the pharmaceutical field. Understanding their interactions in host-guest complexes is essential for the development and application of new therapeutics. In the present review, the most utilized analytical techniques for characterizing calix[n]arene inclusion complexes are discussed, and an overview of the ability of a variety of calix[n]arenes to work as host molecules for the development of chemical entities of pharmaceutical interest is also presented.

Non-covalent interactions like hydrogen bonding, hydrophobic interactions and salt bridges, have been our primary focus in designing and optimizing drugs. Recently, there is mounting evidence that non-covalent interactions involving aromatic rings are also potent forces for the recognition between small drug-like compounds and their targets. Understanding of these interactions and their physical origin is of significant interest for improving the current drug design strategy. Hence, numerous efforts have been devoted to elucidating the structural, geometrical, energetic, and thermodynamic properties of these interactions, which include π-π, cation-π and anion-πinteractions. In this review, we established a framework to systematically understand the structural basis and physicochemical properties of the aromatic interactions at the binding interface of protein-ligand complexes. Firstly, we presented an introduction including the definition, universality, energy components, geometry conformations and substituent effects of these interactions. Secondly, we retrospected the widely employed computational approaches for studying these interactions, including quantum mechanical calculations and crystallographic data mining. Finally, we illustrated with several representative protein-ligand systems to show how the aromatic interactions contribute to the design and optimization of ligand in both affinity and specificity.

The rapid increase of human infections by multidrug-resistant (MDR) Gram-negative pathogens poses a serious health threat and demands the identification of new strategies, molecular targets, and agents for the treatment of Gram-negative bacterial infections. The biosynthesis of lipid A, the membrane-anchoring portion of lipopolysaccharide (LPS), is one promising target for novel antibiotic design because lipid A is essential for LPS assembly in most Gram-negative bacteria. The first three enzymes in the biosynthesis of lipid A, UDP-N-acetylglucosamine acyltransferase (LpxA), UDP-3-O-(R-3-hydroxyacyl)-N-acetylglucosamine deacetylase (LpxC) and UDP- 3-O-(R-3-hydroxyacyl)glucosamine N-acyltransferase (LpxD), have emerged as an attractive Gram-negative antibacterial molecular target. In this article, we review recent advances in the studies on the structures and the structure-based drug designs of the three enzymes.

Ghrelin is a gut hormone that stimulates food intake. In physiological conditions, ghrelin plasma levels rise with fasting and decrease after meals. Obese individuals have low fasting ghrelin levels that rise after food restriction, which is pointed out as a reason for the difficulty in maintaining weight loss. Some bariatric surgery procedures prevent rise in ghrelin levels with weight loss and this has been hypothesised to contribute to the long-term success of the treatment. The main goal of this study was to develop a safe and effective anti-ghrelin vaccine for obesity, through the chemical conjugation of ghrelin with a virus like particle, namely NS1 protein tubules from the Bluetongue Virus (BTV) using a hetero-bifunctional cross linker. Male adult C57BL/6 mice, with a normal weight and with diet-induced obesity (DIO), were randomized into six weight matched groups (n=6/group) and each group of mice received three intra-peritoneal injections with two weeks intervals, containing either 75 μg of ghrelin- NS1 immunoconjugate, 75 μg of NS1 or PBS. Our data show that immunized animals present increasing titres of anti-ghrelin antibodies, while their cumulative food intake significantly decreased and energy expenditure was significantly enhanced, although there were no significative changes in body weight.Vaccinated DIO mice also displayed significant decrease of NPY gene expression in the basal hypothalamus reflecting a decrease in central orexigenic signals. This study suggests that this anti-ghrelin vaccine has a positive impact on energy homeostasis and may be an additional therapeutical tool to be used with diet and exercise for obesity treatment.