Inhibition of tau phosphorylation: a new therapeutic strategy for the treatment of Alzheimer’s disease and other neurodegenerative disorders

1,3,5-Triazine as a promising scaffold in the development of therapeutic agents against breast cancer

1,3,5-Triazine scaffold has garnered considerable interest due to its wide-ranging pharmacological properties, particularly in the field of cancer research. Breast cancer is the most commonly diagnosed cancer among women. Approximately one in eight women will receive a diagnosis of invasive breast cancer during their lifetime. The five-year survival rate for invasive breast cancer is less than 30 %, indicating a need to develop a more effective therapeutic agent targeting breast cancer. This review discusses bioactive 1,3,5-triazines targeting breast cancer cells by the inhibition of different enzymes, which include PI3K, mTOR, EGFR, VEGFR, FAK, CDK, DHFR, DNA topoisomerase, ubiquitin-conjugating enzyme, carbonic anhydrase, and matrix metalloproteinase. The anticancer agent search in some drug discovery programs is based on compound screening for antiproliferative activity. Often, multiple targets contribute to the anticancer effect of 1,3,5-triazines and this approach allows identification of active molecules prior to identification of their targets.

Structure-activity relationship (SAR) studies of synthetic glycogen synthase kinase-3β inhibitors: A critical review

Glycogen Synthase Kinase-3 (GSK-3) is a constitutively dynamic, omnipresent serine/threonine protein kinase regularly called as a "multitasking kinase" due to its pliable function in diverse signaling pathways. It exists in two isoforms i.e., GSK-3α and GSK-3β. Inhibition of GSK-3 may be useful in curing various diseases such as Alzheimer's disease, type II diabetes, mood disorders, cancers, chronic inflammatory agents, stroke, bipolar disorders and so on, but the approach poses significant challenges. Lithium was the first GSK-3β inhibitor to be used for therapeutic outcome and has been effectively used for many years. In recent years, a large number of structurally diverse potent GSK-3β inhibitors are reported. The present review focuses on the recent developments in the area of medicinal chemistry to explore the diverse chemical structures of potent GSK-3β inhibitors and also describes its structure-activity relationships (SAR) and molecular binding interactions of favorable applicability in various diseases.

Design, synthesis and anti-Alzheimer's activity of novel 1,2,3-triazole-chromenone carboxamide derivatives

Alzheimer's disease (AD) is a well-known neurodegenerative disorder affecting millions of old people worldwide and the corresponding epidemiological data highlights the significance of the disease. As AD is a multifactorial illness, various single-target directed drugs that have reached clinical trials have failed. Therefore, various factors associated with outset of AD have been considered in targeted drug discovery and development. In this work, a wide range of 1,2,3-triazole-chromenone carboxamides were designed, synthesized, and evaluated for their cholinesterase inhibitory activity. Among them, N-(1-benzylpiperidin-4-yl)-7-((1-(3,4-dimethylbenzyl)-1H-1,2,3-triazol-4-yl)methoxy)-2-oxo-2H-chromene-3-carboxamide (11b) showed the best acetylcholinesterase inhibitory activity (IC₅₀ = 1.80 µM), however, it was inactive toward butyrylcholinesterase. It should be noted that compound 11b was evaluated for its BACE1 inhibitory activity and calculated IC₅₀ = 21.13 µM confirmed desired inhibitory activity. Also, this compound revealed satisfactory neuroprotective effect against H₂O₂-induced cell death in PC12 neurons at 50 µM as well as metal chelating ability toward Fe²⁺, Cu²⁺, and Zn²⁺ ions.

A novel GSK-3β inhibitor YQ138 prevents neuronal injury induced by glutamate and brain ischemia through activation of the Nrf2 signaling pathway

AIM

To discover neuroprotective compounds and to characterize the discovered active compound YQ138 as a novel GSK-3β inhibitor.

METHODS

Primary rat cerebellar granule cells (CGCs) were treated with glutamate, and cell viability was analyzed with MTT assay, which was used as in vitro model for screening neuroprotective compounds. Active compound was further tested in OGD- or serum deprivation-induced neuronal injury models. The expression levels of GSK-3β downstream proteins (Nrf2, HO-1, NQO1, Tau and β-catenin) were detected with Western blotting. For evaluating the neuroprotective effects in vivo, adult male rats were subjected to transient middle cerebral artery occlusion (tMCAO), then treated with YQ138 (10 mg/kg, iv) at 2, 4 and 6 h after ischemia onset.

RESULTS

From a compound library consisting of about 2000 potential kinase inhibitors, YQ138 was found to exert neuroprotective effects: pretreatment with YQ138 (0.1-40 μmol/L) dose-dependently inhibited glutamate-induced neuronal death. Furthermore, pretreatment with YQ138 (10 μmol/L) significantly inhibited OGD- or serum deprivation-induced neuronal death. Among a panel of seven kinases tested, YQ138 selectively inhibited the activity of GSK-3β (IC50=0.52 nmol/L). Furthermore, YQ138 dose-dependently increased the expression of β-catenin, and decreased the phosphorylation of Tau in CGCs. Moreover, YQ138 significantly increased the expression of GSK-3β downstream antioxidative proteins Nrf2, HO-1, NQO1, GSH and SOD in CGCs. In rats with tMCAO, administration of YQ138 significantly decreased infarct volume, improved the neurological deficit, and increased the expression of Nrf2 and HO-1 and the activities of SOD and GSH in the cerebral cortex.

CONCLUSION

A novel GSK-3β inhibitor YQ138 effectively suppresses brain ischemic injury in vitro and in vivo.

Synthesis and biological evaluation of 3-([1,2,4]triazolo[4,3-a]pyridin-3-yl)-4-(indol-3-yl)-maleimides as potent, selective GSK-3β inhibitors and neuroprotective agents

A series of novel 3-([1,2,4]triazolo[4,3-a]pyridin-3-yl)-4-(indol-3-yl)-maleimides were designed, prepared and evaluated for their GSK-3β inhibitory activities. Most compounds showed high potency to GSK-3β inhibition with high selectivity. Among them, compounds 7c, 7f, 7h, 7l and 7m significantly reduced GSK-3β substrate Tau phosphorylation at Ser396 in primary neurons, showing the inhibition of cellular GSK-3β. In the in vitro neuronal injury models, compounds 7c, 7f, 7h, 7l and 7m prevented neuronal death against glutamate, oxygen-glucose deprivation and nutrient serum deprivation which are associated with cerebral ischemic stroke. In the in vivo cerebral ischemia animal model, compound 7f reduced infarct size by 15% and improved the neurological deficit following focal cerebral ischemia. These findings may provide new insights into the development of novel GSK-3β inhibitors with potential neuroprotective activity.

Design, synthesis and evaluation of 7-azaindazolyl-indolyl-maleimides as glycogen synthase kinase-3β (GSK-3β) inhibitors

A series of 7-azaindazolyl-indolyl-maleimides were designed, synthesized and evaluated for their GSK-3β inhibitory activity. Most compounds exhibited potent activity against GSK-3β. Among them, compounds 17a, 17b, 17g, 17i, 29a and 30 significantly reduced Aβ-induced Tau hyperphosphorylation, showin;g the inhibition of GSK-3β at the cell level. Preliminary structure-activity relationships were discussed based on the experimental data obtained.

Synthesis and biological evaluation of 3-benzisoxazolyl-4-indolylmaleimides as potent, selective inhibitors of glycogen synthase kinase-3β

A series of novel 3-benzisoxazolyl-4-indolyl-maleimides were synthesized and evaluated for their GSK-3β inhibitory activity. Most compounds exhibited high inhibitory potency towards GSK-3β. Among them, compound 7j with an IC₅₀ value of 0.73 nM was the most promising GSK-3β inhibitor. Preliminary structure-activity relationships were examined and showed that different substituents on the indole ring and N¹-position of the indole ring had varying degrees of influence on the GSK-3β inhibitory potency. Compounds 7c, 7f, 7j-l and 7o-q could obviously reduce Aβ-induced Tau hyperphosphorylation by inhibiting GSK-3β in a cell-based functional assay.

Switching reversibility to irreversibility in glycogen synthase kinase 3 inhibitors: clues for specific design of new compounds

Development of kinase-targeted therapies for central nervous system (CNS) diseases is a great challenge. Glycogen synthase kinase 3 (GSK-3) offers a great potential for severe CNS unmet diseases, being one of the inhibitors on clinical trials for different tauopathies. Following our hypothesis based on the enhanced reactivity of residue Cys199 in the binding site of GSK-3, we examine here the suitability of phenylhalomethylketones as irreversible inhibitors. Our data confirm that the halomethylketone unit is essential for the inhibitory activity. Moreover, addition of the halomethylketone moiety to reversible inhibitors turned them into irreversible inhibitors with IC(50) values in the nanomolar range. Overall, the results point out that these compounds might be useful pharmacological tools to explore physiological and pathological processes related to signaling pathways regulated by GSK-3 opening new avenues for the discovery of novel GSK-3 inhibitors.

Insights from investigating the interactions of adamantane-based drugs with the M2 proton channel from the H1N1 swine virus

The M2 proton channel is one of indispensable components for the influenza A virus that plays a vital role in its life cycle and hence is an important target for drug design against the virus. In view of this, the three-dimensional structure of the H1N1-M2 channel was developed based on the primary sequence taken from a patient recently infected by the H1N1 (swine flu) virus. With an explicit water-membrane environment, molecular docking studies were performed for amantadine and rimantadine, the two commercial drugs generally used to treat influenza A infection. It was found that their binding affinity to the H1N1-M2 channel is significantly lower than that to the H5N1-M2 channel, fully consistent with the recent report that the H1N1 swine virus was resistant to the two drugs. The findings and the relevant analysis reported here might provide useful structural insights for developing effective drugs against the new swine flu virus.

Synthesis and biological evaluation of novel 4-azaindolyl-indolyl-maleimides as glycogen synthase kinase-3beta (GSK-3beta) inhibitors

A series of novel 4-azaindolyl-indolyl-maleimides were synthesized and evaluated for their GSK-3beta inhibitory activity. Most compounds exhibited high potency to GSK-3beta. Among them, compound 7c was the most promising GSK-3beta inhibitor. Preliminary structure-activity relationships were discussed based on the experimental data obtained and showed that different substituents on the indole ring and side chains at 1-position of indole had varying degrees of influence on the GSK-3beta inhibitory potency. In a cell-based functional assay, compounds 7c and 15a significantly reduced Abeta-induced Tau hyperphosphorylation by inhibiting GSK-3beta.

Looking for novel ways to treat the hallmarks of Alzheimer's disease

Alzheimer's disease (AD) represents an increasing public health issue as demographic changes and generally improved medical care result in a larger aged population. Although significant advances have been made in the diagnosis and treatment of AD, the unmet medical need remains and few treatment options are available. This review focuses on emerging therapies that aim to treat the underlying causes of the disease rather than the symptoms. Such disease-modifying treatments, focused on the two main hallmarks of the disease (plaques and tangles), include new and old targets which have significant potential in the field and are on the cusp of providing new treatment paradigms within the coming years.

3D-QSAR and molecular docking study on bisarylmaleimide series as glycogen synthase kinase 3, cyclin dependent kinase 2 and cyclin dependent kinase 4 inhibitors: An insight into the criteria for selectivity

Selective glycogen synthase kinase 3 (GSK3) inhibition over cyclin dependent kinases such as cyclin dependent kinase 2 (CDK2) and cyclin dependent kinase 4 (CDK4) is an important requirement for improved therapeutic profile of GSK3 inhibitors. The concepts of selectivity and additivity fields have been employed in developing selective CoMFA models for these related kinases. Initially, sets of three individual CoMFA models were developed, using 36 compounds of bisarylmaleimide series to correlate with the GSK3, CDK2 and CDK4 inhibitory potencies. These models showed a satisfactory statistical significance: CoMFA-GSK3 (r(2)(con), r(2)(cv): 0.931, 0.519), CoMFA-CDK2 (0.937, 0.563), and CoMFA-CDK4 (0.892, 0.725). Three different selective CoMFA models were then developed using differences in pIC(50) values. These three models showed a superior statistical significance: (i) CoMFA-Selective1 (r(2)(con), r(2)(cv): 0.969, 0.768), (ii) CoMFA-Selective 2 (0.974, 0.835) and (iii) CoMFA-Selective3 (0.963, 0.776). The selective models were found to outperform the individual models in terms of the quality of correlation and were found to be more informative in pinpointing the structural basis for the observed quantitative differences of kinase inhibition. An in-depth comparative investigation was carried out between the individual and selective models to gain an insight into the selectivity criterion. To further validate this approach, a set of new compounds were designed which show selectivity and were docked into the active site of GSK3, using FlexX based incremental construction algorithm.

Identification of potential glycogen kinase-3 inhibitors by structure based virtual screening

Glycogen synthase kinase-3 (GSK3) is a serine/threonine kinase that has attracted much drug discovery attention in recent years. Structural crystallography of the kinase has produced several high resolution inhibitor-GSK3 complexes and this is offering valuable information about the important pharmacophoric features present in the inhibitor, the protein target and the bioactive conformation. The availability of several GSK3-inhibitor co-crystals was successfully exploited to derive a pharmacophore query which retains the all important inhibitor-GSK3 interaction chemistry. A hypothesis containing three features: two hydrogen bond donors and one hydrogen acceptor was found to explain much of the inhibitor-GSK3 interaction. Subsequently, the query has been submitted to three databases for electronic screening. The hits obtained were docked into glycogen synthase kinase-3beta active site. A total of 21 novel potential leads were proposed after thorough examination by a combination of methods: (i) visual examination of how well they dock into the glycogen synthase kinase-3beta binding site, (ii) detailed analysis of their FlexX, G_Score, PMF_Score, ChemScore and D_Score values, (iii) comparative investigation of the docking scores of the hits with that of the thus far reported inhibitors (iv) determination of the binding mode and examination of how the hits retain interactions with the important amino acid residues of the kinase binding site. The hydrophobic heterocycles identified in this investigation are expected to be important additions to the armamentarium of GSK3 hyperactivity antagonism. Further more, the present work may further our current knowledge of the molecular basis of activation, inhibition and regulation of this pharmaceutically important kinase.

Insights from modeling the 3D structure of NAD(P)H-dependent D-xylose reductase of Pichia stipitis and its binding interactions with NAD and NADP

NAD(P)H-dependent d-xylose reductase is a homodimeric oxidoreductase that belongs to the aldo-keto reductase superfamily. The enzyme has the special function to catalyze the first step in the assimilation of xylose into yeast metabolic pathways. Performing this function via reducing the open chain xylose to xylitol, the xylose reductase of Pichia stipitis is one of the most important enzymes that can be used to construct recombinant Saccharomyces cerevisiae strain for utilizing xylose and producing alcohol. To investigate into the interaction mechanism of the enzyme with its ligand NAD and NADP, the 3D structure was developed for the NAD(P)H-dependent d-xylose reductase from P. stipitis. With the 3D structure, the molecular docking operations were conducted to find the most stable bindings of the enzyme with NAD and NADP, respectively. Based on these results, the binding pockets of the enzyme for NAD and NADP have been explicitly defined. It has been found that the residues in forming the binding pockets for both NAD and NADP are almost the same and mainly hydrophilic. These findings may be used to guide mutagenesis studies, providing useful clues to modify the enzyme to improve the utilization of xylose for producing alcohol. Also, because human aldose reductases have the function to reduce the open chain form of glucose to sorbitol, a process physiologically significant for diabetic patients at the time that their blood glucose levels are elevated, the information gained through this study may also stimulate the development of new strategies for therapeutic treatment of diabetes.

Investigation of Potential Glycogen Synthase Kinase 3 Inhibitors Using Pharmacophore Mapping and Virtual Screening

Glycogen synthase kinase-3 is a serine/threonine kinase that has attracted significant drug discovery attention in recent years. To investigate the identification of new potential glycogen synthase kinase-3 inhibitors, a pharmacophore mapping study was carried out using a set of 21 structurally diverse glycogen synthase kinase-3 inhibitors. A hypothesis containing four features: two hydrophobic, one hydrogen bond donor and another hydrogen bond acceptor was found to be the best from the 10 common feature hypotheses produced by HipHop module of Catalyst. The best hypothesis has a high cost of 156.592 and higher best fit values were obtained for the 21 inhibitors using this best hypothesis than the other HipHop hypotheses. The best hypothesis was then used to screen electronically the NCI2000 database. The hits obtained were docked into glycogen synthase kinase-3beta active site. A total of five novel potential leads were proposed after: (i) visual examination of how well they dock into the glycogen synthase kinase-3beta-binding site, (ii) comparative analysis of their FlexX, G-Score, PMF-Score, ChemScore and D-Scores values, (iii) comparison of their best fit value with the known inhibitors and (iv) examination of the how the hits retain interactions with the important amino acid residues of glycogen synthase kinase-3beta-binding site.

Neuroprotection and neurodegenerative diseases: from biology to clinical practice

Neurodegenerative diseases and, in particular, Alzheimer disease, are characterized by progressive neuronal loss correlated in time with the symptoms of the disease considered. Whereas the symptoms of those incapacitating diseases are beginning to be managed with a relative efficacy, the ultimate objective of therapy nonetheless remains preventing cell (neuronal and/or astrocytic) death in a neurocytoprotective approach. In biologic terms, in the light of progress at basic research level, three strategies may be envisaged: (1) antagonizing the cytotoxic causal events (excess intracellular calcium, accumulation of abnormal proteins, excitotoxic effects of amino acids, oxidative stress, processes related to inflammation, etc.); (2) stimulating the endogenous protective processes (anti-free radical or DNA repair systems, production of neurotrophic factors, potential cytoprotective action of steroids, etc.); (3) promoting damaged structure repair strategies (grafts) or deep brain or cortical neurostimulation with a view to triggering (beyond the symptomatic actions) potential 'protective' cell mechanisms. The clinical transition of the various strategies whose efficacy is being tested in animal and/or cell models, experimental analogs of the diseases, and thus the objective demonstration in humans of pharmacological and/or surgical neurocytoprotection, is currently the subject of considerable methodological debate (What are the right psychometric assessment criteria? What are the most pertinent laboratory or neuroradiological markers, etc.?). A number of clinical trials have been completed or are ongoing with drugs that are reputed to be neuroprotective. Thus, elements of the response are beginning to be generated with a view to determining whether it will soon be possible to effectively slow or even stop the neurodegenerative process whose etiology, in most cases, remains obscure.

Pharmacology of Alzheimer's disease: appraisal and prospects

Ten years after the introduction of the first drug, tacrine, in the treatment of Alzheimer's disease, it seems appropriate to re-appraise the pharmacological processes of innovation in the research field of dementia. The aim of this review is to pinpoint concrete improvements achieved in this field, regarding experimental methods and clinical evaluation of the compounds, as well as the neurochemistry of the disease and cellular targets to consider in priority. This review deals with this objective in three parts: (1) assessment of current therapeutics, (2) discussion of the experimental models and clinical practices and (3) prospective drugs of the future. The implementation of considered strategies will require the involvement and close cooperation between political decisions, pharmaceutical companies and the scientific community.

Pharmacologie de la maladie d’Alzheimer : vision du futur

Ten years after the introduction of the first drug for the treatment of Alzheimer's disease, tacrine, it seems appropriate to reappraise the pharmacological processes of innovation in the field of research in dementia. The aim of this review is to pinpoint concrete improvements achieved in this field, in terms of experimental methods and clinical evaluation of the compounds, as well as the neurochemistry of the disease and cellular targets deserving of initial consideration. * The article first considers the use of animal models of Alzheimer's disease, which are classified according to two categories: animals with lesions of some neuronal pathways specifically implicated in clinical symptoms (i.e. lesions of the nucleus basalis of Meynert, the origin of cholinergic projections to the cortex underlying memory processes); and transgenic models, which are intended to reproduce some of the neuropathological hallmarks of Alzheimer's disease. Drugs can be tested in animals with such alterations for their effect on neuropathology, neurochemistry and behavioural disturbances. More recently, in silico models have been developed, which offer the possibility of simulating the pharmacodynamic effects of drugs in specific areas of the brain. These experiments are helpful in distinguishing purely symptomatic effects from disease-modifying effects, the latter being the ultimate goal of the modern pharmacology of dementia. * The second breakthrough considered in this article is the codification and standardisation of clinical methods for obtaining a more accurate and earlier diagnosis (the recent introduction of the concept of "Mild Cognitive Impairment", which includes patients who will later develop a true clinical dementia syndrome). In that respect, the determination of the biological markers of Alzheimer's disease (apolipoprotein E, amyloid substance, protein-tau, isoprostane) as well as progress in neuroimaging (functional positron emission tomography [fPET]-scan, single photon emission-computed tomography [SPECT], functional nuclear magnetic resonance [fNMR]) are discussed in terms of their potential as new tools in the early stages of drug development (surrogate markers). The methods used during the comparative clinical trials (phase III) have been elaborated and internationally standardised during the assessment of the different acetylcholinesterase inhibitors (AChE-I), with the knowledge that, since 1994, four of these have been officially approved: tacrine, donepezil, rivastigmine and galantamine; the same methods have been used for developing memantine, a recently-launched modulator of glutamatergic neurotransmission. The validated scales now take into consideration not only the cognitive dimensions of Alzheimer's disease but also the behavioural symptoms, with the introduction of the concept of BPSD (behavioural psychological symptoms of dementia). Some proposals to improve this clinical assessment of anti-dementia drugs are presented here. * The section of this article dealing with prospective issues considers the main pathways of interest in drug innovation and the elucidation of new targets for the future compounds. As well as their symptomatic effects on the different components of cognition, drugs should be neuroprotective and limit the lesions documented in Alzheimer's disease, with the aim of progressing far beyond the amyloid hypothesis (immunisation, beta-sheet breakers, secretase inhibitors). The field of excitotoxicity (which is mainly glutamate dependent) appears fruitful, because of the possibility of pharmacological intervention at the different steps in the excitotoxic process. All the new directions presented in this article support the concept of true disease-modifying agents. In conclusion, this prospective review should be considered as a guide in fostering drug innovation in Alzheimer's disease and related disorders and should help to decrease the gap existing between neuroscience and therapeutics.

Application of graph theory: prediction of glycogen synthase kinase-3 β inhibitory activity of thiadiazolidinones as potential drugs for the treatment of Alzheimer's disease

The relationship of Wiener's index, a distance-based topological descriptor; Zagreb group parameter, M(1), an adjacency-based topological descriptor and eccentric connectivity index,an adjacency-cum-distance based topological descriptor with the glycogen synthase kinase-3 beta inhibitory activity of thiadiazolidinones has been investigated. A training set comprising 28 analogues of substituted thiadiazolidinones was selected for the present investigations. The values of the Wiener's index, Zagreb group parameter, and eccentric connectivity index for each of 28 analogues comprising the data set were computed. Resulting data was analyzed and suitable models developed after identification of active ranges. Subsequently, biological activity was predicted for each analogue involved in the data set using these models, which was then compared with the reported glycogen synthase kinase-3 beta inhibitory activities. Accuracy of prediction was found to vary from a minimum of approximately 83% for model based on Zagreb group parameter to a maximum of approximately 87% for model based on Wiener's index.

Design, synthesis, and biological evaluation of novel 7-azaindolyl-heteroaryl-maleimides as potent and selective glycogen synthase kinase-3beta (GSK-3beta) inhibitors

Two approaches were developed to synthesize the novel 7-azaindolyl-heteroarylmaleimides. The first approach was based upon the palladium-catalyzed Suzuki cross-coupling or Stille cross-coupling of 2-chloro-maleimide 5 with various arylboronic acids or arylstannanes. The second approach was based upon the condensation of ethyl 7-azaindolyl-3-glyoxylate 12 with various acetamides. The hydroxypropyl-substituted 7-azaindolylmaleimide template was first used to screen different heteroaryls attached to the maleimide. Replacement of hydroxypropyl with different chain lengths and different functional groups were studied next. Many compounds synthesized were demonstrated to have high potency at GSK-3beta, good GS activity in HEK293 cells and good to excellent metabolic stability in human liver microsomes. Three representative compounds (21, 33, and 34) were demonstrated to have good selectivity against a panel of 80 kinase assays. Among them, compound 33 exhibited very weak inhibitions at the other 79 kinase assays, and behaved as a highly selective GSK-3beta inhibitor.

Synthesis and biological evaluation of novel macrocyclic bis-7-azaindolylmaleimides as potent and highly selective glycogen synthase kinase-3 beta (GSK-3 beta) inhibitors

Palladium catalyzed cross-coupling reactions were used to synthesize two key intermediates 3 and 5 that resulted in the synthesis of novel series of macrocyclic bis-7-azaindolylmaleimides. Among the three series of macrocycles, the oxygen atom and thiophene containing linkers yielded molecules with higher inhibitory potency at GSK-3 beta (K(i)=0.011-0.079 microM) while the nitrogen atom containing linkers yielded molecules with lower potency (K(i)=0.150->1 microM). Compound 33 and 36 displayed 1-2 orders of magnitude selectivity at GSK-3 beta against CDK2, PKC beta II, Rsk3 and little or no inhibitions to the other 62 protein kinases. Compound 46 was at least 100-fold more selective towards GSK-3 beta than PKC beta II, and it had little or no activity against a panel of 65 protein kinases, almost behaved as a GSK-3 beta 'specific inhibitor'. All three compounds showed good potency in GS assay. Molecular docking studies were conducted in an attempt to rationalize the GSK-3 beta selectivity of azaindolylmaleimides. The high selectivity, inhibitory potency and cellular activities of these non-crown-ether typed molecules may provide them as a valuable pharmacological tools in elucidating the complex roles of GSK-3 beta in cell signaling pathways and the potential usage for the treatment of elevated level of GSK-3 beta involved diseases.

Glycogen synthase kinase 3 (GSK-3) inhibitors as new promising drugs for diabetes, neurodegeneration, cancer, and inflammation

Glycogen synthase kinase 3 (GSK-3) was initially described as a key enzyme involved in glycogen metabolism, but is now known to regulate a diverse array of cell functions. Two forms of the enzyme, GSK-3alpha and GSK-3beta, have been previously identified. Small molecules inhibitors of GSK-3 may, therefore, have several therapeutic uses, including the treatment of neurodegenerative diseases, diabetes type II, bipolar disorders, stroke, cancer, and chronic inflammatory disease. As there is lot of recent literature dealing with the involvement of GSK-3 in the molecular pathways of different diseases, this review is mainly focused on the new GSK-3 inhibitors discovered or specifically developed for this enzyme, their chemical structure, synthesis, and structure-activity relationships, with the aim to provide some clues for the future optimization of these promising drugs.

The multifaceted roles of glycogen synthase kinase 3beta in cellular signaling

Glycogen synthase kinase-3beta (GSK3beta) is a fascinating enzyme with an astoundingly diverse number of actions in intracellular signaling systems. GSK3beta activity is regulated by serine (inhibitory) and tyrosine (stimulatory) phosphorylation, by protein complex formation, and by its intracellular localization. GSK3beta phosphorylates and thereby regulates the functions of many metabolic, signaling, and structural proteins. Notable among the signaling proteins regulated by GSK3beta are the many transcription factors, including activator protein-1, cyclic AMP response element binding protein, heat shock factor-1, nuclear factor of activated T cells, Myc, beta-catenin, CCAAT/enhancer binding protein, and NFkappaB. Lithium, the primary therapeutic agent for bipolar mood disorder, is a selective inhibitor of GSK3beta. This raises the possibility that dysregulation of GSK3beta and its inhibition by lithium may contribute to the disorder and its treatment, respectively. GSK3beta has been linked to all of the primary abnormalities associated with Alzheimer's disease. These include interactions between GSK3beta and components of the plaque-producing amyloid system, the participation of GSK3beta in phosphorylating the microtubule-binding protein tau that may contribute to the formation of neurofibrillary tangles, and interactions of GSK3beta with presenilin and other Alzheimer's disease-associated proteins. GSK3beta also regulates cell survival, as it facilitates a variety of apoptotic mechanisms, and lithium provides protection from many insults. Thus, GSK3beta has a central role regulating neuronal plasticity, gene expression, and cell survival, and may be a key component of certain psychiatric and neurodegenerative diseases.