A Pharmacological Overview and Recent Patent of Triazine Scaffold in Drug Development: A Review

The triazine moiety holds a special and very important position in the field of medicinal chemistry owing to its enormous biological and pharmacological potential. Over eras, triazine scaffolds have been investigated for synthesizing novel molecules that may be used for the treatment of different types of pathological conditions, such as infections, cancer, inflammation etc. A vast number of lead molecules have been established from the triazine moiety. The triazine fused with numerous heterocyclic rings, such as pyrrole, benzimidazole, indole, imidazole, carbazole, etc., have formed various bicyclic with pharmacological actions. The triazines display a wide range of activities, and synthesizing various marketable medicines that hold triazine moiety has made the attention of chemists worldwide grow over the years in the moiety. In this review article, the commercially available compound containing triazine has been presented, and an attempt has been made to collect the works reported, mostly in the past decade, by numerous scientists, related to the structural differences amongst the triazine analogues giving antitumor, and antimicrobial and other activities. The objective of this review article was to outline the current information on triazines and their derivatives with respect to their biological potential and various pharmacological activities. The summary of this review article would be helpful and describe the function and activity of the moiety to bring up-to-date the scientists working in the direction of designing and synthesising novel lead molecules for the treatment of different types of disease with the current molecules that have been synthesized from the triazine scaffold.

Capturing biomarkers associated with Alzheimer disease subtypes using data distribution characteristics

Late-onset Alzheimer disease (AD) is a highly complex disease with multiple subtypes, as demonstrated by its disparate risk factors, pathological manifestations, and clinical traits. Discovery of biomarkers to diagnose specific AD subtypes is a key step towards understanding biological mechanisms underlying this enigmatic disease, generating candidate drug targets, and selecting participants for drug trials. Popular statistical methods for evaluating candidate biomarkers, fold change (FC) and area under the receiver operating characteristic curve (AUC), were designed for homogeneous data and we demonstrate the inherent weaknesses of these approaches when used to evaluate subtypes representing less than half of the diseased cases. We introduce a unique evaluation metric that is based on the distribution of the values, rather than the magnitude of the values, to identify analytes that are associated with a subset of the diseased cases, thereby revealing potential biomarkers for subtypes. Our approach, Bimodality Coefficient Difference (BCD), computes the difference between the degrees of bimodality for the cases and controls. We demonstrate the effectiveness of our approach with large-scale synthetic data trials containing nearly perfect subtypes. In order to reveal novel AD biomarkers for heterogeneous subtypes, we applied BCD to gene expression data for 8,650 genes for 176 AD cases and 187 controls. Our results confirm the utility of BCD for identifying subtypes of heterogeneous diseases.

In-vitro Evaluation of Triazine Scaffold for Anticancer Drug Development: A Review

INTRODUCTION

The widespread importance of the synthesis and modification of anticancer agents has given rise to many numbers of medicinal chemistry programs. In this regard, triazine derivatives have attracted attention due to their remarkable activity against a wide range of cancer cells. This evaluation covers work reports to define the anticancer activity, the most active synthesized compound for the target, the SAR and, when described, the probable MOA besides similarly considered to deliver complete and target-pointed data for the development of types of anti-tumour medicines of triazine derivatives. Triazine scaffold for the development of anticancer analogues. Triazine can also relate to numerous beneficial targets, and their analogues have auspicious in-vitro and in-vivo anti-tumour activity. Fused molecules can improve efficacy, and drug resistance and diminish side effects, and numerous hybrid molecules are beneath diverse stages of clinical trials, so hybrid derivatives of triazine may offer valuable therapeutic involvement for the dealing of tumours.

OBJECTIVE

The objective of the recent review was to summarize the recent reports on triazine as well as its analogues with respect to its anticancer therapeutic potential.

CONCLUSION

The content of the review would be helpful to update the researchers working towards the synthesis and designing of new molecules for the treatment of various types of cancer disease with the recent molecules that have been produced from the triazine scaffold. Triazine scaffolds based on 1,3,5-triazine considerably boost molecular diversity levels and enable covering chemical space in key medicinal chemistry fields.

Mechanisms underlying large-leaf yellow tea mediated inhibition of cognitive impairment in the 5xFAD model of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is the most common cause of dementia and is characterized by amyloid-β (Aβ) peptides and hyperphosphorylated Tau proteins. Evidence indicates that AD and type 2 diabetes mellitus (T2DM) share pathophysiological characteristics, including impaired insulin sensitivity. Large-leaf yellow tea (LYT) has been widely recognized for its health benefits, and we previously found that LYT can improve peripheral insulin resistance.

PURPOSE

This study aimed to investigate the protective effects and underlying mechanisms of LYT in the 5xFAD mouse model of AD.

METHODS

HPLC and spectrophotometric methods determined the chemical composition of the LYT extract. 5xFAD mice were treated with LYT supplementation (2 and 4 mg/ml) in drinking water for six months. Barnes and Y mazes were used to evaluate cognitive function, and the open field test assessed anxiety-like behavior. Immunofluorescence, silver, and Nissl staining were used to evaluate the pathological effects of LYT extract. A FRET-based assay assessed β-site APP cleavage enzyme 1 (BACE1) activity, ELISA measured Aβ levels in the brain, and Western blot analyses explored protein expression levels.

RESULTS

Our results revealed that LYT significantly attenuated memory impairment and anxiety levels and alleviated cerebral neural damage. A reduction of senile plaques was also observed in both the cortex and hippocampus. LYT significantly inhibited the activity of BACE1, which resulted in a lower Aβ protein level. In addition, LYT enhanced insulin receptor substrate 1 (IRS-1)-mediated phosphorylation of phosphoinositide 3-kinase (PI3K) and protein kinase B (AKT), further suppressed glycogen synthase kinase-3β (GSK3β), and ultimately inhibited hyperphosphorylation of the protein Tau. The inhibitory effect of the LYT extract on the phosphorylation of Tau and BACE1 activity was dose-dependent.

CONCLUSION

LYT improves cognitive ability and reduces Aβ production by inhibiting BACE1 activity. Decreases of Tau protein hyperphosphorylation upon LYT treatment appear to be associated with the regulation of the IRS-1/PI3K/AKT/GSK3β axis. Thus, the findings of this study also provide new evidence that LYT regulates insulin signaling pathways within the central nervous system.

A review on cyclin-dependent kinase 5: An emerging drug target for neurodegenerative diseases

Cyclin-dependent kinase 5 (CDK5) is the serine/threonine-directed kinase mainly found in the brain and plays a significant role in developing the central nervous system. Recent evidence suggests that CDK5 is activated by specific cyclins regulating its expression and activity. P35 and p39 activate CDK5, and their proteolytic degradation produces p25 and p29, which are stable products involved in the hyperphosphorylation of tau protein, a significant hallmark of various neurological diseases. Numerous high-affinity inhibitors of CDK5 have been designed, and some are marketed drugs. Roscovitine, like other drugs, is being used to minimize neurological symptoms. Here, we performed an extensive literature analysis to highlight the role of CDK5 in neurons, synaptic plasticity, DNA damage repair, cell cycle, etc. We have investigated the structural features of CDK5, and their binding mode with the designed inhibitors is discussed in detail to develop attractive strategies in the therapeutic targeting of CDK5 for neurodegenerative diseases. This review provides deeper mechanistic insights into the therapeutic potential of CDK5 inhibitors and their implications in the clinical management of neurodegenerative diseases.

Tau, tau kinases, and tauopathies: An updated overview

Tau is a macrotubule-associated protein primarily involved in the stabilization of the cytoskeleton. Under normal conditions, phosphorylation reduces the affinity of tau for tubulin, allowing the protein to detach from microtubules and ensuring the system dynamics in neuronal cells. However, hyperphosphorylated tau aggregates into paired helical filaments, the main constituents of neurofibrillary tangles found in the brains of patients with Alzheimer's disease and other tauopathies. In this review, we provide an overview of the structure of tau and the pathophysiological roles of tau phosphorylation. We also evaluate the major protein kinases involved and discuss the progress made in the development of drug therapies aimed at inhibiting tau kinases.

CEND1 deficiency induces mitochondrial dysfunction and cognitive impairment in Alzheimer's disease

Alzheimer's disease (AD) is the most common form of neurodegenerative disease featured with memory loss and cognitive function impairments. Chronic mitochondrial stress is a vital pathogenic factor for AD and finally leads to massive neuronal death. However, the underlying mechanism is unclear. By proteomic analysis, we identified a new mitochondrial protein, cell-cycle exit and neuronal differentiation 1 (CEND1), which was decreased significantly in the brain of 5xFAD mice. CEND1 is a neuronal specific protein and locates in the presynaptic mitochondria. Depletion of CEND1 leads to increased mitochondrial fission mediated by upregulation of dynamin related protein 1 (Drp1), resulting in abnormal mitochondrial functions. CEND1 deficiency leads to cognitive impairments in mice. Overexpression of CEND1 in the hippocampus of 5xFAD mice rescued cognitive deficits. Moreover, we identified that CDK5/p25 interacted with and phosphorylated CEND1 which promoted its degradation. Our study provides new mechanistic insights in mitochondrial function regulations by CEND1 in Alzheimer's disease.

Glucose metabolism and AD: evidence for a potential diabetes type 3

BACKGROUND

Alzheimer's disease is the most prevalent cause of dementia in the elderly. Neuronal death and synaptic dysfunctions are considered the main hallmarks of this disease. The latter could be directly associated to an impaired metabolism. In particular, glucose metabolism impairment has demonstrated to be a key regulatory element in the onset and progression of AD, which is why nowadays AD is considered the type 3 diabetes.

METHODS

We provide a thread regarding the influence of glucose metabolism in AD from three different perspectives: (i) as a regulator of the energy source, (ii) through several metabolic alterations, such as insulin resistance, that modify peripheral signaling pathways that influence activation of the immune system (e.g., insulin resistance, diabetes, etc.), and (iii) as modulators of various key post-translational modifications for protein aggregation, for example, influence on tau hyperphosphorylation and other important modifications, which determine its self-aggregating behavior and hence Alzheimer's pathogenesis.

CONCLUSIONS

In this revision, we observed a 3 edge-action in which glucose metabolism impairment is acting in the progression of AD: as blockade of energy source (e.g., mitochondrial dysfunction), through metabolic dysregulation and post-translational modifications in key proteins, such as tau. Therefore, the latter would sustain the current hypothesis that AD is, in fact, the novel diabetes type 3.

Alzheimer’s Disease and Tau Self-Assembly: In the Search of the Missing Link

Alzheimer’s disease (AD) is a multifactorial neurodegenerative disease characterized by progressive cognitive impairment, apathy, and neuropsychiatric disorders. Two main pathological hallmarks have been described: neurofibrillary tangles, consisting of tau oligomers (hyperphosphorylated tau) and Aβ plaques. The influence of protein kinases and phosphatases on the hyperphosphorylation of tau is already known. Hyperphosphorylated tau undergoes conformational changes that promote its self-assembly. However, the process involving these mechanisms is yet to be elucidated. In vitro recombinant tau can be aggregated by the action of polyanions, such as heparin, arachidonic acid, and more recently, the action of polyphosphates. However, how that process occurs in vivo is yet to be understood. In this review, searching the most accurate and updated literature on the matter, we focus on the precise molecular events linking tau modifications, its misfolding and the initiation of its pathological self-assembly. Among these, we can identify challenges regarding tau phosphorylation, the link between tau heteroarylations and the onset of its self-assembly, as well as the possible metabolic pathways involving natural polyphosphates, that may play a role in tau self-assembly.

The Atypical Cyclin-Dependent Kinase 5 (Cdk5) Guards Podocytes from Apoptosis in Glomerular Disease While Being Dispensable for Podocyte Development

Cyclin-dependent kinase 5 (Cdk5) is expressed in terminally differentiated cells, where it drives development, morphogenesis, and survival. Temporal and spatial kinase activity is regulated by specific activators of Cdk5, dependent on the cell type and environmental factors. In the kidney, Cdk5 is exclusively expressed in terminally differentiated glomerular epithelial cells called podocytes. In glomerular disease, signaling mechanisms via Cdk5 have been addressed by single or combined conventional knockout of known specific activators of Cdk5. A protective, anti-apoptotic role has been ascribed to Cdk5 but not a developmental phenotype, as in terminally differentiated neurons. The effector kinase itself has never been addressed in animal models of glomerular disease. In the present study, conditional and inducible knockout models of Cdk5 were analyzed to investigate the role of Cdk5 in podocyte development and glomerular disease. While mice with podocyte-specific knockout of Cdk5 had no developmental defects and regular lifespan, loss of Cdk5 in podocytes increased susceptibility to glomerular damage in the nephrotoxic nephritis model. Glomerular damage was associated with reduced anti-apoptotic signals in Cdk5-deficient mice. In summary, Cdk5 acts primarily as master regulator of podocyte survival during glomerular disease and—in contrast to neurons—does not impact on glomerular development or maintenance.

Inflammation: A Major Target for Compounds to Control Alzheimer's Disease

Several hypotheses have been postulated to explain how Alzheimer's disease is triggered, but none of them provide a unified view of its pathogenesis. The dominant hypothesis based on build-ups of the amyloid-β peptide has been around for longer than three decades; however, up to today, numerous clinical trials based on the amyloid postulates have been attempted, but all of them have failed. Clearly, the revisited tau hypothesis provides a better explanation of the clinical observations of patients, but it needs to integrate the cumulative observations on the onset of this disease. In this context, the neuroimmuno modulation theory, based on the involvement of inflammatory events in the central nervous system, accounts for all these observations. In this review we intend to emphasize the idea that neuroinflammation is a main target for the search of new therapeutic strategies to control Alzheimer's disease. Beyond mono-targeting approaches using synthetic drugs that control only specific pathophysiological events, emerging therapeutics views based on multi targeting compounds appear to provide a new pathway for Alzheimer's disease treatment.

Impact of Tau on Neurovascular Pathology in Alzheimer's Disease

Alzheimer's disease (AD) is a chronic neurodegenerative disorder and the most prevalent cause of dementia. The main cerebral histological hallmarks are represented by parenchymal insoluble deposits of amyloid beta (Aβ plaques) and neurofibrillary tangles (NFT), intracellular filamentous inclusions of tau, a microtubule-associated protein. It is well-established that cerebrovascular dysfunction is an early feature of AD pathology, but the detrimental mechanisms leading to blood vessel impairment and the associated neurovascular deregulation are not fully understood. In 90% of AD cases, Aβ deposition around the brain vasculature, known as cerebral amyloid angiopathy (CAA), alters blood brain barrier (BBB) essential functions. While the effects of vascular Aβ accumulation are better documented, the scientific community has only recently started to consider the impact of tau on neurovascular pathology in AD. Emerging compelling evidence points to transmission of neuronal tau to different brain cells, including astrocytes, as well as to the release of tau into brain interstitial fluids, which may lead to perivascular neurofibrillar tau accumulation and toxicity, affecting vessel architecture, cerebral blood flow (CBF), and vascular permeability. BBB integrity and functionality may therefore be impacted by pathological tau, consequentially accelerating the progression of the disease. Tau aggregates have also been shown to induce mitochondrial damage: it is known that tau impairs mitochondrial localization, distribution and dynamics, alters ATP and reactive oxygen species production, and compromises oxidative phosphorylation systems. In light of this previous knowledge, we postulate that tau can initiate neurovascular pathology in AD through mitochondrial dysregulation. In this review, we will explore the literature investigating tau pathology contribution to the malfunction of the brain vasculature and neurovascular unit, and its association with mitochondrial alterations and caspase activation, in cellular, animal, and human studies of AD and tauopathies.

Epigenetic Effects Induced by Methamphetamine and Methamphetamine-Dependent Oxidative Stress

Methamphetamine is a widely abused drug, which possesses neurotoxic activity and powerful addictive effects. Understanding methamphetamine toxicity is key beyond the field of drug abuse since it allows getting an insight into the molecular mechanisms which operate in a variety of neuropsychiatric disorders. In fact, key alterations produced by methamphetamine involve dopamine neurotransmission in a way, which is reminiscent of spontaneous neurodegeneration and psychiatric schizophrenia. Thus, understanding the molecular mechanisms operated by methamphetamine represents a wide window to understand both the addicted brain and a variety of neuropsychiatric disorders. This overlapping, which is already present when looking at the molecular and cellular events promoted immediately after methamphetamine intake, becomes impressive when plastic changes induced in the brain of methamphetamine-addicted patients are considered. Thus, the present manuscript is an attempt to encompass all the molecular events starting at the presynaptic dopamine terminals to reach the nucleus of postsynaptic neurons to explain how specific neurotransmitters and signaling cascades produce persistent genetic modifications, which shift neuronal phenotype and induce behavioral alterations. A special emphasis is posed on disclosing those early and delayed molecular events, which translate an altered neurotransmitter function into epigenetic events, which are derived from the translation of postsynaptic noncanonical signaling into altered gene regulation. All epigenetic effects are considered in light of their persistent changes induced in the postsynaptic neurons including sensitization and desensitization, priming, and shift of neuronal phenotype.

Contribution of Tau Pathology to Mitochondrial Impairment in Neurodegeneration

Tau is an essential protein that physiologically promotes the assembly and stabilization of microtubules, and participates in neuronal development, axonal transport, and neuronal polarity. However, in a number of neurodegenerative diseases, including Alzheimer’s disease (AD), tau undergoes pathological modifications in which soluble tau assembles into insoluble filaments, leading to synaptic failure and neurodegeneration. Mitochondria are responsible for energy supply, detoxification, and communication in brain cells, and important evidence suggests that mitochondrial failure could have a pivotal role in the pathogenesis of AD. In this context, our group and others investigated the negative effects of tau pathology on specific neuronal functions. In particular, we observed that the presence of these tau forms could affect mitochondrial function at three different levels: (i) mitochondrial transport, (ii) morphology, and (iii) bioenergetics. Therefore, mitochondrial dysfunction mediated by anomalous tau modifications represents a novel mechanism by which these forms contribute to the pathogenesis of AD. In this review, we will discuss the main results reported on pathological tau modifications and their effects on mitochondrial function and their importance for the synaptic communication and neurodegeneration.

Reduction of ciliary length through pharmacologic or genetic inhibition of CDK5 attenuates polycystic kidney disease in a model of nephronophthisis

Polycystic kidney diseases (PKDs) comprise a subgroup of ciliopathies characterized by the formation of fluid-filled kidney cysts and progression to end-stage renal disease. A mechanistic understanding of cystogenesis is crucial for the development of viable therapeutic options. Here, we identify CDK5, a kinase active in post mitotic cells, as a new and important mediator of PKD progression. We show that long-lasting attenuation of PKD in the juvenile cystic kidneys (jck) mouse model of nephronophthisis by pharmacological inhibition of CDK5 using either R-roscovitine or S-CR8 is accompanied by sustained shortening of cilia and a more normal epithelial phenotype, suggesting this treatment results in a reprogramming of cellular differentiation. Also, a knock down of Cdk5 in jck cells using small interfering RNA results in significant shortening of ciliary length, similar to what we observed with R-roscovitine. Finally, conditional inactivation of Cdk5 in the jck mice significantly attenuates cystic disease progression and is associated with shortening of ciliary length as well as restoration of cellular differentiation. Our results suggest that CDK5 may regulate ciliary length by affecting tubulin dynamics via its substrate collapsin response mediator protein 2. Taken together, our data support therapeutic approaches aimed at restoration of ciliogenesis and cellular differentiation as a promising strategy for the treatment of renal cystic diseases.

The Ever-Changing Morphology of Hippocampal Granule Neurons in Physiology and Pathology

Newborn neurons are continuously added to the hippocampal dentate gyrus throughout adulthood. In this review, we analyze the maturational stages that newborn granule neurons go through, with a focus on their unique morphological features during each stage under both physiological and pathological circumstances. In addition, the influence of deleterious (such as schizophrenia, stress, Alzheimer's disease, seizures, stroke, inflammation, dietary deficiencies, or the consumption of drugs of abuse or toxic substances) and neuroprotective (physical exercise and environmental enrichment) stimuli on the maturation of these cells will be examined. Finally, the regulation of this process by proteins involved in neurodegenerative and neurological disorders such as Glycogen synthase kinase 3β, Disrupted in Schizophrenia 1 (DISC-1), Glucocorticoid receptor, pro-inflammatory mediators, Presenilin-1, Amyloid precursor protein, Cyclin-dependent kinase 5 (CDK5), among others, will be evaluated. Given the recently acquired relevance of the dendritic branch as a functional synaptic unit required for memory storage, a full understanding of the morphological alterations observed in newborn neurons may have important consequences for the prevention and treatment of the cognitive and affective alterations that evolve in conjunction with impaired adult hippocampal neurogenesis.

Effect of the inhaled anesthetics isoflurane, sevoflurane and desflurane on the neuropathogenesis of Alzheimer's disease (review)

The incidence of Alzheimer's disease (AD) in individuals >65 years of age is 13% and ~66 million individuals in this age group undergo surgery annually under anesthesia. It is therefore important to determine whether commonly used inhaled anesthetics induce cytotoxicity, which may lead to neurodegeneration. Findings from several studies suggest that the anesthetics, isoflurane, sevoflurane and desflurane, may activate caspases, increase the synthesis and accumulation of β-amyloid (Aβ) protein, and induce hyperphosphorylation of tau proteins, all of which are cellular responses consistent with the neuropathogenesis of AD. Other studies have arrived at different and occasionally contradictory conclusions. The present review attempts to resolve this discrepancy by reviewing previous studies, which have investigated the effects of commonly used inhaled anesthetics on the synthesis and accumulation of Aβ, tau pathology and cognitive function. The possible underlying mechanism was also reviewed. However, several aspects of this phenomenon remain to be elucidated. Further studies are required to fully examine anesthesia-induced neurotoxicity and elucidate the effect of inhaled anesthetics on the onset and progression of AD.

Purkinje Cell Pathology and Loss in Multiple Sclerosis Cerebellum

Cerebellar ataxia commonly occurs in multiple sclerosis, particularly in chronic progressive disease. Previous reports have highlighted both white matter and grey matter pathological changes within the cerebellum; and demyelination and inflammatory cell infiltrates appear commonly. As Purkinje cell axons are the sole output of the cerebellar cortex, understanding pathologic processes within these cells is crucial to develop strategies to prevent their loss and thus reduce ataxia. We studied pathologic changes occurring within Purkinje cells of the cerebellum. Using immunohistochemic techniques, we found changes in neurofilament phosphorylation states within Purkinje cells, including loss of dephosphorylated neurofilament and increased phosphorylated and hyperphosphorylated neurofilament. We also found Purkinje axonal spheroids and Purkinje cell loss, both of which occurred predominantly within areas of leucocortical demyelination within the cerebellar cortex. These changes have important implications for the study of cerebellar involvement in multiple sclerosis and may help design therapies to reduce the burden of ataxia in the condition.

Cyclin I and p35 determine the subcellular distribution of Cdk5

The atypical cyclin-dependent kinase 5 (Cdk5) serves an array of different functions in cell biology. Among these are axonal guidance, regulation of intercellular contacts, cell differentiation, and prosurvival signaling. The variance of these functions suggests that Cdk5 activation comes to pass in different cellular compartments. The kinase activity, half-life, and substrate specificity of Cdk5 largely depend on specific activators, such as p25, p35, p39, and cyclin I. We hypothesized that the subcellular distribution of Cdk5 activators also determines the localization of the Cdk5 protein and sets the stage for targeted kinase activity within distinct cellular compartments to suit the varying roles of Cdk5. Cdk5 localization was analyzed in murine kidney and brain slices of wild-type and cyclin I- and/or p35-null mice by immunohistochemistry and in cultured mouse podocytes using immunofluorescence labeling, as well as cell fractionation experiments. The predominance of cyclin I mediates the nuclear localization of Cdk5, whereas the predominance of p35 results in a membranous localization of Cdk5. These findings were further substantiated by overexpression of cyclin I and p35 with altered targeting characteristics in human embryonic kidney 293T cells. These studies reveal that the subcellular localization of Cdk5 is determined by its specific activators. This results in the directed Cdk5 kinase activity in specific cellular compartments dependent on the activator present and allows Cdk5 to serve multiple independent roles.

Discovery of thienoquinolone derivatives as selective and ATP non-competitive CDK5/p25 inhibitors by structure-based virtual screening

Calpain mediated cleavage of CDK5 natural precursor p35 causes a stable complex formation of CDK5/p25, which leads to hyperphosphorylation of tau. Thus inhibition of this complex is a viable target for numerous acute and chronic neurodegenerative diseases involving tau protein, including Alzheimer's disease. Since CDK5 has the highest sequence homology with its mitotic counterpart CDK2, our primary goal was to design selective CDK5/p25 inhibitors targeting neurodegeneration. A novel structure-based virtual screening protocol comprised of e-pharmacophore models and virtual screening workflow was used to identify nine compounds from a commercial database containing 2.84 million compounds. An ATP non-competitive and selective thieno[3,2-c]quinolin-4(5H)-one inhibitor (10) with ligand efficiency (LE) of 0.3 was identified as the lead molecule. Further SAR optimization led to the discovery of several low micromolar inhibitors with good selectivity. The research represents a new class of potent ATP non-competitive CDK5/p25 inhibitors with good CDK2/E selectivity.

Divergent and convergent roles for kinases and phosphatases in neurofilament dynamics

C-terminal neurofilament phosphorylation mediates cation-dependent self-association leading to neurofilament incorporation into the stationary axonal cytoskeleton. Multiple kinases phosphorylate the C-terminal domains of the heavy neurofilament subunit (NF-H), including cyclin-dependent protein kinase 5 (CDK5), mitogen-activated protein kinases (MAPKs), casein kinase 1 and 2 (CK1 and CK2) and glycogen synthase kinase 3β (GSK3β). The respective contributions of these kinases have been confounded because they phosphorylate multiple substrates in addition to neurofilaments and display extensive interaction. Herein, differentiated NB2a/d1 cells were transfected with constructs expressing GFP-tagged NF-H, isolated NF-H sidearms and NF-H lacking the distal-most 187 amino acids. Cultures were treated with roscovitine, PD98059, Li(+), D4476, tetrabromobenzotriazole and calyculin, which are active against CDK5, MKK1 (also known as MAP2K1), GSK3β, CK1, CK2 and protein phosphatase 1 (PP1), respectively. Sequential phosphorylation by CDK5 and GSK3β mediated the neurofilament-neurofilament associations. The MAPK pathway (i.e. MKK1 to ERK1/2) was found to downregulate GSK3β, and CK1 activated PP1, both of which promoted axonal transport and restricted neurofilament-neurofilament associations to axonal neurites. The MAPK pathway and CDK5, but not CK1 and GSK3β, inhibited neurofilament proteolysis. These findings indicate that phosphorylation of neurofilaments by the proline-directed MAPK pathway and CDK5 counterbalance the impact of phosphorylation of neurofilaments by the non-proline-directed CK1 and GSK3β.

Linking pathways in the developing and aging brain with neurodegeneration

The molecular and cellular mechanisms, which coordinate the critical stages of brain development to reach a normal structural organization with appropriate networks, are progressively being elucidated. Experimental and clinical studies provide evidence of the occurrence of developmental alterations induced by genetic or environmental factors leading to the formation of aberrant networks associated with learning disabilities. Moreover, evidence is accumulating that suggests that also late-onset neurological disorders, even Alzheimer's disease, might be considered disorders of aberrant neural development with pathological changes that are set up at early stages of development before the appearance of the symptoms. Thus, evaluating proteins and pathways that are important in age-related neurodegeneration in the developing brain together with the characterization of mechanisms important during brain development with relevance to brain aging are of crucial importance. In the present review we focus on (1) aspects of neurogenesis with relevance to aging; (2) neurodegenerative disease (NDD)-associated proteins/pathways in the developing brain; and (3) further pathways of the developing or neurodegenerating brains that show commonalities. Elucidation of complex pathogenetic routes characterizing the earliest stage of the detrimental processes that result in pathological aging represents an essential first step toward a therapeutic intervention which is able to reverse these pathological processes and prevent the onset of the disease. Based on the shared features between pathways, we conclude that prevention of NDDs of the elderly might begin during the fetal and childhood life by providing the mothers and their children a healthy environment for the fetal and childhood development.

Regulation of Sox6 by cyclin dependent kinase 5 in brain

Cyclin dependent kinase 5 (Cdk5) is a proline-directed Ser/Thr kinase involved in various biological functions during normal brain development and neurodegeneration. In brain, Cdk5 activity is specific to post-mitotic neurons, due to neuronal specific expression of its activator p35. The biological functions of Cdk5 have been ascribed to its cytoplasmic substrates, however not much is known in nucleus. Here, we show that nuclear transcription factor Sox6 is a direct nuclear target of Cdk5. Sox6 is expressed in Tuj1 positive neurons, suggesting that Sox6 is expressed in differentiating neurons. The expression of Sox6 is high in mitotic nuclei during embryonic day 12 (E12) and gradually decreases during development into adult. On the other hand, Cdk5 expression gradually increases during its development. We show that Sox6 is expressed in mitotic nuclei in embryonic day 12 (E12) and in migrating neurons of E16. Sox6 is phosphorylated in vivo. Sox6 was detected by phospho-Ser/Thr and phospho-Ser/Thr-Pro and MPM-2 (Mitotic protein #2) antibodies in brain. Furthermore, calf intestinal alkaline phosphatase (CIAP) digestion resulted in faster migration of Sox6 band. The GST-Sox6 was phosphorylated by Cdk5/p35. The mass spectrometry analysis revealed that Sox6 is phosphorylated at T119PER motif. We show that Sox6 steady state levels are regulated by Cdk5. Cdk5 knockout mice die in utero and Sox6 protein expression is remarkably high in Cdk5-/- brain, however, there is no change in mRNA expression, suggesting a post-translational regulation of Sox6 by Cdk5. Transfection of primary cortical neurons with WT Cdk5 reduced Sox6 levels, while dominant negative (DN) Cdk5 and p35 increased Sox6 levels. Thus, our results indicate that Cdk5 regulates Sox6 steady state protein level that has an important role in brain development and function.

Activation of cyclin-dependent kinase 5 mediates orofacial mechanical hyperalgesia

Background

Cyclin-dependent kinase 5 (Cdk5) is a unique member of the serine/threonine kinase family. This kinase plays an important role in neuronal development, and deregulation of its activity leads to neurodegenerative disorders. Cdk5 also serves an important function in the regulation of nociceptive signaling. Our previous studies revealed that the expression of Cdk5 and its activator, p35, is upregulated in nociceptive neurons during peripheral inflammation. The aim of the present study was to characterize the involvement of Cdk5 in orofacial pain. Since mechanical hyperalgesia is the distinctive sign of many orofacial pain conditions, we adapted an existing orofacial stimulation test to assess the behavioral responses to mechanical stimulation in the trigeminal region of the transgenic mice with either reduced or increased Cdk5 activity.

Results

Mice overexpressing or lacking p35, an activator of Cdk5, showed altered phenotype in response to noxious mechanical stimulation in the trigeminal area. Mice with increased Cdk5 activity displayed aversive behavior to mechanical stimulation as indicated by a significant decrease in reward licking events and licking time. The number of reward licking/facial contact events was significantly decreased in these mice as the mechanical intensity increased. By contrast, mice deficient in Cdk5 activity displayed mechanical hypoalgesia.

Conclusions

Collectively, our findings demonstrate for the first time the important role of Cdk5 in orofacial mechanical nociception. Modulation of Cdk5 activity in primary sensory neurons makes it an attractive potential target for the development of novel analgesics that could be used to treat multiple orofacial pain conditions.

Genetic and biochemical evidence for a functional role of BACE1 in the regulation of insulin mRNA expression

OBJECTIVE

Beta-site amyloid precursor protein cleaving enzyme (BACE1) is highly expressed in pancreatic β-cells. The BACE1 gene is located in a region associated with a high diabetes risk in PIMA Indians.

DESIGN AND METHODS

INS-1E cells were used to study the impact of siRNA-mediated BACE1 knockdown and glucose metabolism was characterized in Bace1(-/-) mice. BACE1 gene was sequenced in DNA samples from 48 subjects and 13 representative single nucleotide polymorphisms (SNPs) were then genotyped for association studies in 1,527 Caucasians.

RESULTS

Reduction of Bace1 expression results in a significant decrease in insulin mRNA expression in INS-1E cells. Bace1(-/-) mice display significantly lower body weight, lower plasma insulin concentrations, but normal glucose tolerance and insulin sensitivity. In a case-control study including 538 healthy controls and 989 patients with type 2 diabetes (T2D), one SNP (rs535860) was significantly associated with T2D (P < 3.5 × 10(-5) , adjusted for age, sex, and BMI).

CONCLUSIONS

Reduced Bace1 expression causes impaired insulin expression in pancreatic β-cells of Bace1(-/-) mice, suggesting that BACE1 plays a role in the regulation of insulin biogenesis. The functionally relevant rs535860 SNP may decrease BACE1 expression by creating a new miR-661 binding site and could therefore contribute to T2D development.

Anesthesia and tau pathology

Alzheimer's disease (AD) is the most common form of dementia and remains a growing worldwide health problem. As life expectancy continues to increase, the number of AD patients presenting for surgery and anesthesia will steadily rise. The etiology of sporadic AD is thought to be multifactorial, with environmental, biological and genetic factors interacting together to influence AD pathogenesis. Recent reports suggest that general anesthetics may be such a factor and may contribute to the development and exacerbation of this neurodegenerative disorder. Intra-neuronal neurofibrillary tangles (NFT), composed of hyperphosphorylated and aggregated tau protein are one of the main neuropathological hallmarks of AD. Tau pathology is important in AD as it correlates very well with cognitive dysfunction. Lately, several studies have begun to elucidate the mechanisms by which anesthetic exposure might affect the phosphorylation, aggregation and function of this microtubule-associated protein. Here, we specifically review the literature detailing the impact of anesthetic administration on aberrant tau hyperphosphorylation as well as the subsequent development of neurofibrillary pathology and degeneration.

Proteomic identification of proteins suggestive of immune-mediated response or neuronal degeneration in serum of achalasia patients

Background/Aims

The primary pathophysiologic abnormality in achalasia is known to be a loss of inhibitory myenteric ganglion cells, which may result from an immune-mediated response or neuronal degeneration. The aim of this study was to identify proteins suggestive of an immune-mediated response or neuronal degeneration in the serum of achalasia patients using a proteomic analysis.

Methods

Blood samples were collected from five symptomatic achalasia patients and five sex- and age-matched healthy controls. Serum proteomic analysis was conducted, and the protein spots were identified using matrix-assisted laser desorption ionization/time-of-flight and a proteomics analyzer. The serum level of C3 was measured by enzyme-linked immunosorbent assay in nine patients with achalasia and 18 sex- and age-matched healthy controls.

Results

Of the 658 matched protein spots, 28 spots were up-regulated over 2-fold in the serum from achalasia patients compared with that from controls. The up-regulated proteins included complement C4B5, complement C3, cyclin-dependent kinase 5, transthyretin, and alpha 2 macroglobulin. The serum levels of C3 in achalasia patients were significantly higher than those of controls.

Conclusions

The serum proteomic analysis of achalasia patients suggests an immune-mediated response or neuronal degeneration. Further validation studies in larger samples and the esophageal tissue of achalasia patients are required.

Neural restrictive silencer factor and choline acetyltransferase expression in cerebral tissue of Alzheimer's Disease patients: A pilot study

Decreased Choline Acetyltransferase (ChAT) brain level is one of the main biochemical disorders in Alzheimer’s Disease (AD). In rodents, recent data show that the CHAT gene can be regulated by a neural restrictive silencer factor (NRSF). The aim of the present work was to evaluate the gene and protein expression of CHAT and NRSF in frontal, temporal, entorhinal and parietal cortices of AD patient brains. Four brains from patients with AD and four brains from subjects without dementia were studied. Cerebral tissues were obtained and processed by the guanidine isothiocyanate method for RNA extraction. CHAT and NRSF gene and protein expression were determined by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting. CHAT gene expression levels were 39% lower in AD patients as compared to the control group (p < 0.05, U test). ChAT protein levels were reduced by 17% (p = 0.02, U test). NRSF gene expression levels were 86% higher in the AD group (p = 0.001, U test) as compared to the control group. In the AD subjects, the NRSF protein levels were 57% higher (p > 0.05, U test) than in the control subjects. These findings suggest for the first time that in the brain of AD patients high NRSF protein levels are related to low CHAT gene expression levels.

Hyperphosphorylation of tau by GSK-3β in Alzheimer’s disease: The interaction of Aβ and sphingolipid mediators as a therapeutic target

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder characterized by the extracellular deposits of β amyloid peptides (Aβ) in senile plaques, and intracellular aggregates of hyperphosphorylated tau in neurofibrillary tangles (NFT). Although accumulation of Aβ has been long considered a leading hypothesis in the disease pathology, it is increasingly evident that the role hyperphosphorylation of tau in destabilization of microtubule assembly and disturbance of axonal transport is equally detrimental in the neurodegenerative process. The main kinase involved in phosphorylation of tau is glycogen-synthase kinase 3-beta (GSK-3β). Intracellular accumulation of Aβ also likely induces increase in hyperphosphorylated tau by a mechanism dependent on GSK-3β. In addition, Aβ affects production of ceramides, the major sphingolipids in mammalian cells, by acting on sphingomyelinases, enzymes responsible for the catabolic formation of ceramides from the sphingomyelin. Generated ceramides in turn increase production of Aβ by acting on β-secretase, a key enzyme in the proteolytic processing of the amyloid precursor protein (APP), altogether leading to a ceramide-Aβ-hyperphosphorylated tau cascade that ends in neuronal death. Modulators and inhibitors acting on members of this devastating cascade are considered as potential targets for AD therapy. There is still no adequate treatment for AD patients. Novel therapeutic strategies increasingly consider the combination of multiple targets and interactions among the key members of implicated molecular pathways. This review summarizes recent findings and therapeutic perspectives in the pathology and treatment of AD, with the emphasis on the interplay between hyperphosphorylated tau, amyloid β, and sphingolipid mediators.

A truncated peptide from p35, a Cdk5 activator, prevents Alzheimer's disease phenotypes in model mice

Alzheimer's disease (AD), one of the leading neurodegenerative disorders of older adults, which causes major socioeconomic burdens globally, lacks effective therapeutics without significant side effects. Besides the hallmark pathology of amyloid plaques and neurofibrillary tangles (NFTs), it has been reported that cyclin-dependent kinase 5 (Cdk5), a critical neuronal kinase, is hyperactivated in AD brains and is, in part, responsible for the above pathology. Here we show that a modified truncated 24-aa peptide (TFP5), derived from the Cdk5 activator p35, penetrates the blood-brain barrier after intraperitoneal injections, inhibits abnormal Cdk5 hyperactivity, and significantly rescues AD pathology (up to 70-80%) in 5XFAD AD model mice. The mutant mice, injected with TFP5 exhibit behavioral rescue, whereas no rescue was observed in mutant mice injected with either saline or scrambled peptide. However, TFP5 does not inhibit cell cycle Cdks or normal Cdk5/p35 activity, and thereby has no toxic side effects (even at 200 mg/kg), a common problem in most current therapeutics for AD. In addition, treated mice displayed decreased inflammation, amyloid plaques, NFTs, cell death, and an extended life by 2 mo. These results suggest TFP5 as a potential therapeutic, toxicity-free candidate for AD.

Hypothermia-induced hyperphosphorylation: a new model to study tau kinase inhibitors

Tau hyperphosphorylation is one hallmark of Alzheimer's disease (AD) pathology. Pharmaceutical companies have thus developed kinase inhibitors aiming to reduce tau hyperphosphorylation. One obstacle in screening for tau kinase inhibitors is the low phosphorylation levels of AD-related phospho-epitopes in normal adult mice and cultured cells. We have shown that hypothermia induces tau hyperphosphorylation in vitro and in vivo. Here, we hypothesized that hypothermia could be used to assess tau kinase inhibitors efficacy. Hypothermia applied to models of biological gradual complexity such as neuronal-like cells, ex vivo brain slices and adult non-transgenic mice leads to tau hyperphosphorylation at multiple AD-related phospho-epitopes. We show that Glycogen Synthase Kinase-3 inhibitors LiCl and AR-A014418, as well as roscovitine, a cyclin-dependent kinase 5 inhibitor, decrease hypothermia-induced tau hyperphosphorylation, leading to different tau phosphorylation profiles. Therefore, we propose hypothermia-induced hyperphosphorylation as a reliable, fast, convenient and inexpensive tool to screen for tau kinase inhibitors.

Metformin attenuates Alzheimer's disease-like neuropathology in obese, leptin-resistant mice

Diabetes increases the risk of Alzheimer's disease (AD). The pathological hallmarks for AD brains are extracellular amyloid plaques formed by β-amyloid peptide (Aβ) and intracellular neurofibrillary tangles consisting of hyperphosphorylated tau protein. This study was designed to determine AD-like brain changes in mice modeling for type 2 diabetes. The effects of metformin on these changes also were studied. Seven-week old male db/db mice received intraperitoneal injection of 200 mg kg⁻¹ d⁻¹ metformin for 18 weeks. They were subjected to Barnes maze at an age of 21 weeks and fear conditioning at an age of 24 weeks to assess their cognitive functions. Hippocampus was harvested after these tests for biochemical evaluation. The db/db mice had more tau phosphorylated at S396 and total tau in their hippocampi than their non-diabetic control db+mice. Activated/phosphorylated c-jun N-terminal kinase (JNK), a tau kinase, was increased in the db/db mouse hippocampus. Metformin attenuated the increase of total tau, phospho-tau and activated JNK. The db/db mice had increased Aβ levels. Metformin attenuated the reduction of synaptophysin, a synaptic protein, in the db/db mouse hippocampus. Metformin did not attenuate the impairments of spatial learning and memory as well as long-term hyperglycemia in the db/db mice. Our results suggest that the db/db mice have multiple AD-like brain changes including impaired cognitive functions, increased phospho-tau and Aβ as well as decreased synaptic proteins. Activation of JNK may contribute to the increased phospho-tau in the db/db mice. Metformin attenuates AD-like biochemical changes in the brain of these mice.

Modulation of ultra-low-molecular-weight heparin on [Ca²⁺]i in nervous cells

Heparin is an effective competitive antagonist of inositol 1,4,5-trisphosphate receptors (IP(3)Rs). It binds to IP(3)Rs and affects calcium homeostasis. Ultra-low-molecular-weight heparin (ULMWH) is heparin's derivative, the present study was designed to test the effects of ULMWH on intracellular calcium concentration ([Ca(2+)]i) in primary cultured neurons. [Ca(2+)]i was measured by Multilabel Counter Victor-1420 using Fura-2/AM as the calcium fluorescent probe. The results indicated that ULMWH decreased the resting [Ca(2+)]i with or without extracellular Ca(2+). They had no effects on high K(+)-induced elevation of intracellular Ca(2+) level indicating that ULMWH had no effect on external Ca(2+) influx mediated by voltage-dependent calcium channels. However, they partially reduced the increase in [Ca(2+)]i induced by glutamate. Furthermore, ULMWH significantly inhibited the inositol 1,4,5-trisphosphate (IP(3))-induced increase in [Ca(2+)]i both in cellular and subcellular level. These results suggest that ULMWH may reduce [Ca(2+)]i in neurons through suppressing Ca(2+) release from IP(3)-sensitive stores.

Propofol directly increases tau phosphorylation

In Alzheimer's disease (AD) and other tauopathies, the microtubule-associated protein tau can undergo aberrant hyperphosphorylation potentially leading to the development of neurofibrillary pathology. Anesthetics have been previously shown to induce tau hyperphosphorylation through a mechanism involving hypothermia-induced inhibition of protein phosphatase 2A (PP2A) activity. However, the effects of propofol, a common clinically used intravenous anesthetic, on tau phosphorylation under normothermic conditions are unknown. We investigated the effects of a general anesthetic dose of propofol on levels of phosphorylated tau in the mouse hippocampus and cortex under normothermic conditions. Thirty min following the administration of propofol 250 mg/kg i.p., significant increases in tau phosphorylation were observed at the AT8, CP13, and PHF-1 phosphoepitopes in the hippocampus, as well as at AT8, PHF-1, MC6, pS262, and pS422 epitopes in the cortex. However, we did not detect somatodendritic relocalization of tau. In both brain regions, tau hyperphosphorylation persisted at the AT8 epitope 2 h following propofol, although the sedative effects of the drug were no longer evident at this time point. By 6 h following propofol, levels of phosphorylated tau at AT8 returned to control levels. An initial decrease in the activity and expression of PP2A were observed, suggesting that PP2A inhibition is at least partly responsible for the hyperphosphorylation of tau at multiple sites following 30 min of propofol exposure. We also examined tau phosphorylation in SH-SY5Y cells transfected to overexpress human tau. A 1 h exposure to a clinically relevant concentration of propofol in vitro was also associated with tau hyperphosphorylation. These findings suggest that propofol increases tau phosphorylation both in vivo and in vitro under normothermic conditions, and further studies are warranted to determine the impact of this anesthetic on the acceleration of neurofibrillary pathology.

The revitalized tau hypothesis on Alzheimer's disease

Many hypotheses have been raised regarding the pathophysiology of Alzheimer's disease (AD). Because amyloid beta peptide (Abeta) deposition in senile plaques appears as a late, nonspecific event, recent evidence points to tau phosphorylation and aggregation as the final common pathway in this multifactorial disease. Current approaches that provide evidence in favor of neuroimmunomodulation in AD and the roles of tau pathological modifications and aggregation into oligomers and filamentous forms are presented. We propose an integrative model on the pathogenesis of AD that includes several damage signals such as Abeta oligomers, oxygen free radicals, iron overload, homocysteine, cholesterol and LDL species. These activate microglia cells, releasing proinflammatory cytokines and producing neuronal degeneration and tau pathological modifications. Altered and aggregated forms of tau appear to act as a toxic stimuli contributing to neurodegeneration. Recent findings provide further support to the central role of tau in the pathogenesis of AD, so this protein has turned into a diagnostic and therapeutic target for this disease.

A 24-residue peptide (p5), derived from p35, the Cdk5 neuronal activator, specifically inhibits Cdk5-p25 hyperactivity and tau hyperphosphorylation

The activity of Cdk5-p35 is tightly regulated in the developing and mature nervous system. Stress-induced cleavage of the activator p35 to p25 and a p10 N-terminal domain induces deregulated Cdk5 hyperactivity and perikaryal aggregations of hyperphosphorylated Tau and neurofilaments, pathogenic hallmarks in neurodegenerative diseases, such as Alzheimer disease and amyotrophic lateral sclerosis, respectively. Previously, we identified a 125-residue truncated fragment of p35 called CIP that effectively and specifically inhibited Cdk5-p25 activity and Tau hyperphosphorylation induced by Aβ peptides in vitro, in HEK293 cells, and in neuronal cells. Although these results offer a possible therapeutic approach to those neurodegenerative diseases assumed to derive from Cdk5-p25 hyperactivity and/or Aβ induced pathology, CIP is too large for successful therapeutic regimens. To identify a smaller, more effective peptide, in this study we prepared a 24-residue peptide, p5, spanning CIP residues Lys(245)-Ala(277). p5 more effectively inhibited Cdk5-p25 activity than did CIP in vitro. In neuron cells, p5 inhibited deregulated Cdk5-p25 activity but had no effect on the activity of endogenous Cdk5-p35 or on any related endogenous cyclin-dependent kinases in HEK293 cells. Specificity of p5 inhibition in cortical neurons may depend on the p10 domain in p35, which is absent in p25. Furthermore, we have demonstrated that p5 reduced Aβ(1-42)-induced Tau hyperphosphorylation and apoptosis in cortical neurons. These results suggest that p5 peptide may be a unique and useful candidate for therapeutic studies of certain neurodegenerative diseases.

Synaptotoxicity of Alzheimer beta amyloid can be explained by its membrane perforating property

The mechanisms that induce Alzheimer's disease (AD) are largely unknown thereby deterring the development of disease-modifying therapies. One working hypothesis of AD is that Aβ excess disrupts membranes causing pore formation leading to alterations in ionic homeostasis. However, it is largely unknown if this also occurs in native brain neuronal membranes. Here we show that similar to other pore forming toxins, Aβ induces perforation of neuronal membranes causing an increase in membrane conductance, intracellular calcium and ethidium bromide influx. These data reveal that the target of Aβ is not another membrane protein, but that Aβ itself is the cellular target thereby explaining the failure of current therapies to interfere with the course of AD. We propose that this novel effect of Aβ could be useful for the discovery of anti AD drugs capable of blocking these “Aβ perforates”. In addition, we demonstrate that peptides that block Aβ neurotoxicity also slow or prevent the membrane-perforating action of Aβ.

CDK5 phosphorylates eNOS at Ser-113 and regulates NO production

Phosphorylation of endothelial nitric oxide synthase (eNOS) is key mechanism in response to various forms of cellular stimulation. Through protein nitration by peroxynitrite, eNOS is believed to be responsible for the major abnormalities in several important neurodegenerative diseases including Alzheimer's (AD) and Parkinson's diseases (PD). Recent studies provide important in vivo evidence that hyperactivation of Cdk5 by p25 plays an essential role in the cell death of neurons in experimental models of AD and PD. This study focuses on the functional regulation of eNOS by Cdk5/p35 complex in a phosphorylation dependent manner. Our results showed that Cdk5 can phosphorylate eNOS both in vitro and in vivo. In vitro kinase assay together with the bioinformatic analysis and site direct mutagenesis revealed that Ser-113 is the major phosphorylation site for Cdk5. Most interestingly, the nitrite production was significantly reduced in eNOS and Cdk5/p35 co-transfected SH-SY5Y cells when compared with co-transfection of Cdk5/p35 and S113A. Together, our data suggest that Cdk5 can phosphorylate eNOS at the Ser-113 site and down-regulate eNOS-derived NO levels.

Roles of cholesterol and lipids in the etiopathogenesis of Alzheimer's disease

Alzheimer's disease is the principal cause of dementia throughout the world and the fourth cause of death in developed economies.This brain disorder is characterized by the formation of brain protein aggregates, namely, the paired helical filaments and senile plaques. Oxidative stress during life, neuroinflamamtion, and alterations in neuron-glia interaction patterns have been also involved in the etiopathogenesis of this disease. In recent years, cumulative evidence has been gained on the involvement of alteration in neuronal lipoproteins activity, as well as on the role of cholesterol and other lipids in the pathogenesis of this neurodegenerative disorder. In this review, we analyze the links between changes in cholesterol homeostasis, and the changes of lipids of major importance for neuronal activity and Alheimer's disease. The investigation on the fine molecular mechanisms underlying the lipids influence in the etiopathogenesis of Alzheimer's disease may shed light into its treatment and medical management.

Targeting mitochondrial dysfunction in neurodegenerative disease: Part II

IMPORTANCE OF THE FIELD

With improvements in life expectancy over the past decades, the incidence of neurodegenerative disease has dramatically increased and new therapeutic strategies are urgently needed. One possible approach is to target mitochondrial dysfunction, which has been implicated in the pathogenesis of numerous neurodegenerative disorders.

AREAS COVERED IN THIS REVIEW

This review examines the role of mitochondrial dysfunction in neurodegeneration, drawing examples from common diseases such as Alzheimer's disease and rarer familial disorders such as Charcot-Marie-Tooth. The review is provided in two parts. In part I we discussed the mitochondrial defects which have been most extensively researched (oxidative stress, bioenergetic dysfunction, calcium mishandling). We focus now on those defects which have more recently been implicated in neurodegeneration; in mitochondrial fusion/fission, protein import, protein quality control, kinase signalling and opening of the permeability transition pore.

WHAT THE READER WILL GAIN

An examination of mitochondrial defects observed in neurodegeneration, and existing and possible future therapies to target these defects.

TAKE HOME MESSAGE

The mitochondrially-targeted therapeutics that have reached clinical trials so far have produced encouraging but largely inconclusive results. Increasing understanding of mitochondrial dysfunction has, however, led to preclinical work focusing on novel approaches, which has generated exciting preliminary data.