Glycogen synthase kinase 3 beta (GSK-3 beta) as a therapeutic target in neuroAIDS

Identification of Novel GSK-3β Hits Using Competitive Biophysical Assays

Glycogen synthase kinase 3 beta (GSK-3β) is an evolutionarily conserved serine-threonine kinase dysregulated in numerous pathologies, such as Alzheimer’s disease and cancer. Even though GSK-3β is a validated pharmacological target most of its inhibitors have two main limitations: the lack of selectivity due to the high homology that characterizes the ATP binding site of most kinases, and the toxicity that emerges from GSK-3β complete inhibition which translates into the impairment of the plethora of pathways GSK-3β is involved in. Starting from a 1D ¹⁹F NMR fragment screening, we set up several biophysical assays for the identification of GSK-3β inhibitors capable of binding protein hotspots other than the ATP binding pocket or to the ATP binding pocket, but with an affinity able of competing with a reference binder. A phosphorylation activity assay on a panel of several kinases provided selectivity data that were further rationalized and corroborated by structural information on GSK-3β in complex with the hit compounds. In this study, we identified promising fragments, inhibitors of GSK-3β, while proposing an alternative screening workflow that allows facing the flaws that characterize the most common GSK-3β inhibitors through the identification of selective inhibitors and/or inhibitors able to modulate GSK-3β activity without leading to its complete inhibition.

HIV-associated neurotoxicity and cognitive decline: Therapeutic implications

As our understanding of changes to the neurological system has improved, it has become clear that patients who have contracted human immunodeficiency virus type 1 (HIV-1) can potentially suffer from a cascade of neurological issues, including neuropathy, dementia, and declining cognitive function. The progression from mild to severe symptoms tends to affect motor function, followed by cognitive changes. Central nervous system deficits that are observed as the disease progresses have been reported as most severe in later-stage HIV infection. Examining the full spectrum of neuronal damage, generalized cortical atrophy is a common hallmark, resulting in the death of multiple classes of neurons. With antiretroviral therapy (ART), we can partially control disease progression, slowing the onset of the most severe symptoms such as, reducing viral load in the brain, and developing HIV-associated dementia (HAD). HAD is a severe and debilitating outcome from HIV-related neuropathologies. HIV neurotoxicity can be direct (action directly on the neuron) or indirect (actions off-site that affect normal neuronal function). There are two critical HIV-associated proteins, Tat and gp120, which bear responsibility for many of the neuropathologies associated with HAD and HIV-associated neurocognitive disorder (HAND). A cascade of systems is involved in HIV-related neurotoxicity, and determining a critical point where therapeutic strategies can be employed is of the utmost importance. This review will provide an overview of the existing hypotheses on HIV-neurotoxicity and the potential for the development of therapeutics to aid in the treatment of HIV-related nervous system dysfunction.

Glycogen synthase kinase (GSK)-3 and the double-strand RNA-dependent kinase, PKR: When two kinases for the common good turn bad

Glycogen synthase kinase (GSK)-3α/β and the double-stranded RNA-dependent kinase PKR are two sentinel kinases that carry-out multiple similar yet distinct functions in both the cytosol and the nucleus. While these kinases belong to separate signal transduction cascades, they demonstrate an uncanny propensity to regulate many of the same proteins either through direct phosphorylation or by altering transcription/translation, including: c-MYC, NF-κB, p53 and TAU, as well as each another. A significant number of studies centered on the GSK3 kinases have led to the identification of the GSK3 interactome and a number of substrates, which link GSK3 activity to metabolic control, translation, RNA splicing, ribosome biogenesis, cellular division, DNA repair and stress/inflammatory signaling. Interestingly, many of these same pathways and processes are controlled by PKR, but unlike the GSK3 kinases, a clear picture of proteins interacting with PKR and a complete listing of its substrates is still missing. In this review, we take a detailed look at what is known about the PKR and GSK3 kinases, how these kinases interact to influence common cellular processes (innate immunity, alternative splicing, translation, glucose metabolism) and how aberrant activation of these kinases leads to diseases such as Alzheimer's disease (AD), diabetes mellitus (DM) and cancer.

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GSK3α/β and PKR are major regulators of cellular homeostasis and the response to stress/inflammation and infection.

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GSK3α/β and PKR interact with and/or modify many of the same proteins and affect the expression of similar genes.

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A balance between AKT and PKR nuclear signaling may be responsible for regulating the activation of nuclear GSK3β.

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GSK3α/β- and PKR-dependent signaling influence major molecular mechanisms of the cell through similar intermediates.

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Aberrant activation of GSK3α/β and PKR is highly involved in cancer, metabolic disorders, and neurodegenerative diseases.

Partial Least Squares Discriminant Analysis and 3D Similarity Perspective Applied to Analyze Comprehensively the Selectivity of Glycogen Synthase Kinase 3 Inhibitors

The current work was conducted to investigate the effectiveness of two conceptually distinct in silico ligand-based tools: Partial Least Squares Discriminant Analysis (PLS-DA) and 3D similarity, including shape, physico-chemical and electrostatics to classify target-specific pharmacophores with enrichment power for selective GSK-3 inhibitors against the phylogenetically related CDK-2, CDK-4, CDK-5 and PKC. All virtual screens were performed on four data sets of targets matched pairwise, including selective and nonselective inhibitors for GSK-3. The classification method PLS-DA results revealed that all obtained models are statistically robust according to the cross-validation and response permutation tests. Regarding selective GSK-3 inhibitors differentiation in terms of selectivity (Se), specificity (Sp), and accuracy (ACC), the PLS-DA models for CDK-4/GSK-3, and PKC/GSK-3 datasets are highly efficient discriminative. 3D similarity searches for CDK-4/GSK-3, PKC/GSK-3, and CDK-2/GSK-3 datasets using the most selective reference molecules lead to highest enrichments of selective GSK-3 inhibitors. EON yields excellent early and overall enrichments for ET_ST and ET_combo for most selective query for CDK-4/GSK-3. CDK-5/GSK-3 dataset didn't show consistent statistically significant enrichments for 3D similarity virtual screening. The current methodology is reliable and could be used as a powerful tool for the detection of potentially selective molecules targeting GSK-3.

Rosmarinic Acid Derivatives' Inhibition of Glycogen Synthase Kinase-3β Is the Pharmacological Basis of Kangen-Karyu in Alzheimer's Disease

Inhibition of glycogen synthase kinase 3β (GSK-3β) is considered to be the central therapeutic approach against Alzheimer's disease (AD). In the present study, boiled water extracts of the Kangen-karyu (KK) herbal mixture and its constituents were screened for GSK-3β inhibitory activity. KK is used in traditional Kampo and Chinese medicines for improving cognitive function. The GSK-3β inhibition potential was evaluated by using the Kinase-Glo luminescent kinase assay platform. Furthermore, enzyme kinetics and in silico modeling were performed by using AutoDockTools to demonstrate the mechanism of enzyme inhibition. KK extract significantly inhibited GSK-3β in a concentration-dependent manner (IC50: 17.05 ± 1.14 μg/mL) when compared with the reference drug luteolin (IC50: 2.18 ± 0.13 μM). Among the six components of KK, extracts of Cyperi Rhizoma and Salviae Miltiorrhizae Radix significantly inhibited GSK-3β with IC50 values of 20.68 ± 2.50 and 7.77 ± 1.38 μg/mL, respectively. Among the constituents of the roots of S. miltiorrhiza water extract, rosmarinic acid, magnesium lithospermate B, salvianolic acid A, salvianolic acid B, and salvianolic acid C inhibited GSK-3β with IC50 values ranging from 6.97 to 135.5 μM. Salvianolic acid B was found to be an ATP-competitive inhibitor of GSK-3β and showed the lowest IC50 value (6.97 ± 0.96 µM). In silico modeling suggested a mechanism of action by which the hydrophobic, π⁻cation, and hydrophilic interactions of salvianolic acid B at ATP and substrate sites are critical for the observed GSK-3β inhibition. Therefore, one of the mechanisms of action of KK against AD may be the inhibition of GSK-3β and one of the active components of KK is the root of S. miltiorrhiza and its constituents: rosmarinic acid, magnesium lithospermate B, and salvianolic acids A, B, and C. Our results demonstrate the pharmacological basis for the use of KK against AD.

The role of human dopamine transporter in NeuroAIDS

HIV-associated neurocognitive disorder (HAND) remains highly prevalent in HIV infected individuals and represents a special group of neuropathological disorders, which are associated with HIV-1 viral proteins, such as transactivator of transcription (Tat) protein. Cocaine abuse increases the incidence of HAND and exacerbates its severity by enhancing viral replication. Perturbation of dopaminergic transmission has been implicated as a risk factor of HAND. The presynaptic dopamine (DA) transporter (DAT) is essential for DA homeostasis and dopaminergic modulation of the brain function including cognition. Tat and cocaine synergistically elevate synaptic DA levels by acting directly on human DAT (hDAT), ultimately leading to dysregulation of DA transmission. Through integrated computational modeling and experimental validation, key residues have been identified in hDAT that play a critical role in Tat-induced inhibition of DAT and induce transporter conformational transitions. This review presents current information regarding neurological changes in DAT-mediated dopaminergic system associated with HIV infection, DAT-mediated adaptive responses to Tat as well as allosteric modulatory effects of novel compounds on hDAT. Understanding the molecular mechanisms by which Tat induces DAT-mediated dysregulation of DA system is of great clinical interest for identifying new targets for an early therapeutic intervention for HAND.

Glycogen Synthase Kinase-3 (GSK-3)-Targeted Therapy and Imaging

Glycogen synthase kinase-3 (GSK-3) is associated with various key biological processes, including glucose regulation, apoptosis, protein synthesis, cell signaling, cellular transport, gene transcription, proliferation, and intracellular communication. Accordingly, GSK-3 has been implicated in a wide variety of diseases and specifically targeted for both therapeutic and imaging applications by a large number of academic laboratories and pharmaceutical companies. Here, we review the structure, function, expression levels, and ligand-binding properties of GSK-3 and its connection to various diseases. A selected list of highly potent GSK-3 inhibitors, with IC₅₀ <20 nM for adenosine triphosphate (ATP)-competitive inhibitors and IC₅₀ <5 μM for non-ATP-competitive inhibitors, were analyzed for structure activity relationships. Furthermore, ubiquitous expression of GSK-3 and its possible impact on therapy and imaging are also highlighted. Finally, a rational perspective and possible route to selective and effective GSK-3 inhibitors is discussed.

HIV-1-Tat Protein Inhibits SC35-mediated Tau Exon 10 Inclusion through Up-regulation of DYRK1A Kinase

The HIV-1 transactivator protein Tat is implicated in the neuronal damage that contributes to neurocognitive impairment affecting people living with HIV/AIDS. Aberrant splicing of TAU exon 10 results in tauopathies characterized by alterations in the proportion of TAU isoforms containing three (3R) or four (4R) microtubule-binding repeats. The splicing factor SC35/SRSF2 binds to nuclear RNA and facilitates the incorporation of exon 10 in the TAU molecule. Here, we utilized clinical samples, an animal model, and neuronal cell cultures and found that Tat promotes TAU 3R up-regulation through increased levels of phosphorylated SC35, which is retained in nuclear speckles. This mechanism involved Tat-mediated increased expression of DYRK1A and was prevented by DYRK1A silencing. In addition, we found that Tat associates with TAU RNA, further demonstrating that Tat interferes with host RNA metabolism in the absence of viral infection. Altogether, our data unravel a novel mechanism of Tat-mediated neuronal toxicity through dysregulation of the SC35-dependent alternative splicing of TAU exon 10. Furthermore, the increased immunostaining of DYRK1A in HIV+ brains without pathology points at dysregulation of DYRK1A as an early event in the neuronal complications of HIV infection.

Mass spectrometric phosphoproteome analysis of HIV-infected brain reveals novel phosphorylation sites and differential phosphorylation patterns

PURPOSE

To map the phosphoproteome and identify changes in the phosphorylation patterns in the HIV-infected and uninfected brain.

EXPERIMENTAL DESIGN

Parietal cortex from individuals with and without HIV infection were lysed and trypsinized. The peptides were labeled with iTRAQ reagents, combined, phospho-enriched by titanium dioxide chromatography, and analyzed by LC-MS/MS with high resolution.

RESULTS

Our phosphoproteomic workflow resulted in the identification of 112 phosphorylated proteins and 17 novel phosphorylation sites in all the samples that were analyzed. The phosphopeptide sequences were searched for kinase substrate motifs, which revealed potential kinases involved in important signaling pathways. The site-specific phosphopeptide quantification showed that peptides from neurofilament medium polypeptide, myelin basic protein, and 2'-3'-cyclic nucleotide-3' phosphodiesterase have relatively higher phosphorylation levels during HIV infection.

CONCLUSIONS AND CLINICAL RELEVANCE

This study has enriched the global phosphoproteome knowledge of the human brain by detecting novel phosphorylation sites on neuronal proteins and identifying differentially phosphorylated brain proteins during HIV infection. Kinases that lead to unusual phosphorylations could be therapeutic targets for the treatment of HIV-associated neurocognitive disorders.

Neuroprotective effects of the anti-cancer drug sunitinib in models of HIV neurotoxicity suggests potential for the treatment of neurodegenerative disorders

BACKGROUND AND PURPOSE

Anti-retrovirals have improved and extended the life expectancy of patients with HIV. However, as this population ages, the prevalence of cognitive changes is increasing. Aberrant activation of kinases, such as receptor tyrosine kinases (RTKs) and cyclin-dependent kinase 5 (CDK5), play a role in the mechanisms of HIV neurotoxicity. Inhibitors of CDK5, such as roscovitine, have neuroprotective effects; however, CNS penetration is low. Interestingly, tyrosine kinase inhibitors (TKIs) display some CDK inhibitory activity and ability to cross the blood-brain barrier.

EXPERIMENTAL APPROACH

We screened a small group of known TKIs for a candidate with additional CDK5 inhibitory activity and tested the efficacy of the candidate in in vitro and in vivo models of HIV-gp120 neurotoxicity.

KEY RESULTS

Among 12 different compounds, sunitinib inhibited CDK5 with an IC50 of 4.2 μM. In silico analysis revealed that, similarly to roscovitine, sunitinib fitted 6 of 10 features of the CDK5 pharmacophore. In a cell-based model, sunitinib reduced CDK5 phosphorylation (pCDK5), calpain-dependent p35/p25 conversion and protected neuronal cells from the toxic effects of gp120. In glial fibrillary acidic protein-gp120 transgenic (tg) mice, sunitinib reduced levels of pCDK5, p35/p25 and phosphorylated tau protein, along with amelioration of the neurodegenerative pathology.

CONCLUSIONS AND IMPLICATIONS

Compounds such as sunitinib with dual kinase inhibitory activity could ameliorate the cognitive impairment associated with chronic HIV infection of the CNS. Moreover, repositioning existing low MW compounds holds promise for the treatment of patients with neurodegenerative disorders.

Adjunctive and long-acting nanoformulated antiretroviral therapies for HIV-associated neurocognitive disorders

PURPOSE OF REVIEW

We are pleased to review current and future strategies being developed to modulate neuroinflammation while reducing residual viral burden in the central nervous system. This has been realized by targeted long-acting antiretroviral nano and adjunctive therapies being developed for HIV-infected people. Our ultimate goal is to eliminate virus from its central nervous system reservoirs and, in so doing, reverse the cognitive and motor dysfunctions.

RECENT FINDINGS

Herein, we highlight our laboratories' development of adjunctive and nanomedicine therapies for HIV-associated neurocognitive disorders. An emphasis is placed on drug-drug interactions that target both the viral life cycle and secretory proinflammatory neurotoxic factors and signaling pathways.

SUMMARY

Antiretroviral therapy has improved the quality and duration of life for people living with HIV-1. A significant long-term comorbid illness is HIV-associated neurocognitive disorders. Symptoms, although reduced in severity, are common. Disease occurs, in part, through continued low-level viral replication, inducing secondary glial neuroinflammatory activities. Our recent works and those of others have seen disease attenuated in animal models through the use of adjunctive and long-acting reservoir-targeted nanoformulated antiretroviral therapy. The translation of these inventions from animals to humans is the focus of this review.

GSK3β-activation is a point of convergence for HIV-1 and opiate-mediated interactive neurotoxicity

Infection of the CNS with HIV-1 occurs rapidly after primary peripheral infection. HIV-1 can induce a wide range of neurological deficits, collectively known as HIV-1-associated neurocognitive disorders. Our previous work has shown that the selected neurotoxic effects induced by individual viral proteins, Tat and gp120, and by HIV(+) supernatant are enhanced by co-exposure to morphine. This mimics co-morbid neurological effects observed in opiate-abusing HIV(+) patients. Although there is a correlation between opiate drug abuse and progression of HIV-1-associated neurocognitive disorders, the mechanisms underlying interactions between HIV-1 and opiates remain obscure. Previous studies have shown that HIV-1 induces neurotoxic effects through abnormal activation of GSK3β. Interestingly, expression of GSK3β has shown to be elevated in brains of young opiate abusers indicating that GSK3β is also linked to neuropathology seen with opiate-abusing patients. Thus, we hypothesize that GSK3β activation is a point of convergence for HIV- and opiate-mediated interactive neurotoxic effects. Neuronal cultures were treated with supernatant from HIV-1SF162-infected THP-1 cells, in the presence or absence of morphine and GSK3β inhibitors. Our results show that GSK3β inhibitors, including valproate and small molecule inhibitors, significantly reduce HIV-1-mediated neurotoxic outcomes, and also negate interactions with morphine that result in cell death, suggesting that GSK3β-activation is an important point of convergence and a potential therapeutic target for HIV- and opiate-mediated neurocognitive deficits.

Mechanisms of HIV-1 Tat neurotoxicity via CDK5 translocation and hyper-activation: role in HIV-associated neurocognitive disorders

The advent of more effective antiretroviral therapies has reduced the frequency of HIV dementia, however the prevalence of milder HIV associated neurocognitive disorders [HAND] is actually rising. Neurodegenerative mechanisms in HAND might include toxicity by secreted HIV-1 proteins such as Tat, gp120 and Nef that could activate neuro-inflammatory pathways, block autophagy, promote excitotoxicity, oxidative stress, mitochondrial dysfunction and dysregulation of signaling pathways. Recent studies have shown that Tat could interfere with several signal transduction mechanisms involved in cytoskeletal regulation, cell survival and cell cycle re-entry. Among them, Tat has been shown to hyper-activate cyclin-dependent kinase [CDK] 5, a member of the Ser/Thr CDKs involved in cell migration, angiogenesis, neurogenesis and synaptic plasticity. CDK5 is activated by binding to its regulatory subunit, p35 or p39. For this manuscript we review evidence showing that Tat, via calcium dysregulation, promotes calpain-1 cleavage of p35 to p25, which in turn hyper-activates CDK5 resulting in abnormal phosphorylation of downstream targets such as Tau, collapsin response mediator protein-2 [CRMP2], doublecortin [DCX] and MEF2. We also present new data showing that Tat interferes with the trafficking of CDK5 between the nucleus and cytoplasm. This results in prolonged presence of CDK5 in the cytoplasm leading to accumulation of aberrantly phosphorylated cytoplasmic targets [e.g.: Tau, CRMP2, DCX] that impair neuronal function and eventually lead to cell death. Novel therapeutic approaches with compounds that block Tat mediated hyper-activation of CDK5 might be of value in the management of HAND.

Glycogen synthase kinase-3 (GSK3): regulation, actions, and diseases

Glycogen synthase kinase-3 (GSK3) may be the busiest kinase in most cells, with over 100 known substrates to deal with. How does GSK3 maintain control to selectively phosphorylate each substrate, and why was it evolutionarily favorable for GSK3 to assume such a large responsibility? GSK3 must be particularly adaptable for incorporating new substrates into its repertoire, and we discuss the distinct properties of GSK3 that may contribute to its capacity to fulfill its roles in multiple signaling pathways. The mechanisms regulating GSK3 (predominantly post-translational modifications, substrate priming, cellular trafficking, protein complexes) have been reviewed previously, so here we focus on newly identified complexities in these mechanisms, how each of these regulatory mechanism contributes to the ability of GSK3 to select which substrates to phosphorylate, and how these mechanisms may have contributed to its adaptability as new substrates evolved. The current understanding of the mechanisms regulating GSK3 is reviewed, as are emerging topics in the actions of GSK3, particularly its interactions with receptors and receptor-coupled signal transduction events, and differential actions and regulation of the two GSK3 isoforms, GSK3α and GSK3β. Another remarkable characteristic of GSK3 is its involvement in many prevalent disorders, including psychiatric and neurological diseases, inflammatory diseases, cancer, and others. We address the feasibility of targeting GSK3 therapeutically, and provide an update of its involvement in the etiology and treatment of several disorders.

The role of tau protein in HIV-associated neurocognitive disorders

Given the increased life expectancy of human immunodeficiency virus (HIV) infected individuals treated with combination antiretroviral therapy (cART) and the ongoing inflammation observed in the brains of these patients, it is likely that premature neurodegeneration as measured by phospho-tau (p-tau) or increased total tau (t-tau) protein may become an increasing problem. This review examines the seven human studies that have occurred over the past 14 years measuring p-tau and/or t-tau in cerebrospinal fluid (CSF) or via post-mortem brain immunohistochemistry. Although not all studies are in agreement as to the changes in p-and t-tau in HIV infected patients, HIV persists in the brain despite cART. Thus is it is suggested that those maintained on long-term cART may develop tau pathology beyond the extent seen in the studies reviewed herein and overtime may then reach the threshold for clinical manifestation.

Glycogen synthase kinase-3 inhibitors: Rescuers of cognitive impairments

Impairment of cognitive processes is a devastating outcome of many diseases, injuries, and drugs affecting the central nervous system (CNS). Most often, very little can be done by available therapeutic interventions to improve cognitive functions. Here we review evidence that inhibition of glycogen synthase kinase-3 (GSK3) ameliorates cognitive deficits in a wide variety of animal models of CNS diseases, including Alzheimer's disease, Fragile X syndrome, Down syndrome, Parkinson's disease, spinocerebellar ataxia type 1, traumatic brain injury, and others. GSK3 inhibitors also improve cognition following impairments caused by therapeutic interventions, such as cranial irradiation for brain tumors. These findings demonstrate that GSK3 inhibitors are able to ameliorate cognitive impairments caused by a diverse array of diseases, injury, and treatments. The improvements in impaired cognition instilled by administration of GSK3 inhibitors appear to involve a variety of different mechanisms, such as supporting long-term potentiation and diminishing long-term depression, promotion of neurogenesis, reduction of inflammation, and increasing a number of neuroprotective mechanisms. The potential for GSK3 inhibitors to repair cognitive deficits associated with many conditions warrants further investigation of their potential for therapeutic interventions, particularly considering the current dearth of treatments available to reduce loss of cognitive functions.

Targeting platelet-derived soluble CD40 ligand: a new treatment strategy for HIV-associated neuroinflammation?

Human immunodeficiency virus type 1 (HIV) continues to be one of the most prevalent global health afflictions to date. The advent and introduction of combined antiretroviral therapy (cART) has made a significant impact on the course of infection. However, as patients are living longer, many HIV-associated illnesses are becoming prevalent among the infected population, especially those associated with chronic inflammation. Consistently, HIV-associated neuroinflammation is believed to be a major catalyst in the development of HIV-associated neurocognitive disorders (HAND), which are estimated to persist in approximately 50% of infected individuals regardless of cART. This dramatically underscores the need to develop effective adjunctive therapies capable of controlling this aspect of the disease, which are currently lacking.

We previously demonstrated that the inflammatory mediator soluble CD40 ligand (sCD40L) is elevated in both the plasma and cerebrospinal fluid of cognitively impaired infected individuals compared to their non-impaired infected counterparts. Our group, and others have recently demonstrated that there is an increasing role for this inflammatory mediator in the pathogenesis of HIV-associated neuroinflammation, thereby identifying this molecule as a potential therapeutic target for the management of HAND. Platelets are the major source of circulating sCD40L, and these small cells are increasingly implicated in a multitude of inflammatory disorders, including those common during HIV infection. Thus, antiplatelet therapies that minimize the release of platelet-derived inflammatory mediators such as sCD40L are an innovative, non-traditional approach for the treatment of HIV-associated neuroinflammation, with the potential to benefit other HIV-associated illnesses.

Improving lithium therapeutics by crystal engineering of novel ionic cocrystals

Current United States Food and Drug Administration (FDA)-approved lithium salts are plagued with a narrow therapeutic window. Recent attempts to find alternative drugs have identified new chemical entities, but lithium's polypharmacological mechanisms for treating neuropsychiatric disorders are highly debated and are not yet matched. Thus, re-engineering current lithium solid forms in order to optimize performance represents a low cost and low risk approach to the desired therapeutic outcome. In this contribution, we employed a crystal engineering strategy to synthesize the first ionic cocrystals (ICCs) of lithium salts with organic anions. We are unaware of any previous studies that have assessed the biological efficacy of any ICCs, and encouragingly we found that the new speciation did not negatively affect established bioactivities of lithium. We also observed that lithium ICCs exhibit modulated pharmacokinetics compared to lithium carbonate. Indeed, the studies detailed herein represent an important advancement in a crystal engineering approach to a new generation of lithium therapeutics.

Discovery, synthesis, and characterization of an orally bioavailable, brain penetrant inhibitor of mixed lineage kinase 3

Inhibition of mixed lineage kinase 3 (MLK3) is a potential strategy for treatment of Parkinson's disease and HIV-1 associated neurocognitive disorders (HAND), requiring an inhibitor that can achieve significant brain concentration levels. We report here URMC-099 (1) an orally bioavailable (F = 41%), potent (IC50 = 14 nM) MLK3 inhibitor with excellent brain exposure in mouse PK models and minimal interference with key human CYP450 enzymes or hERG channels. The compound inhibits LPS-induced TNFα release in microglial cells, HIV-1 Tat-induced release of cytokines in human monocytes and up-regulation of phospho-JNK in Tat-injected brains of mice. Compound 1 likely functions in HAND preclinical models by inhibiting multiple kinase pathways, including MLK3 and LRRK2 (IC50 = 11 nM). We compare the kinase specificity and BBB penetration of 1 with CEP-1347 (2). Compound 1 is well tolerated, with excellent in vivo activity in HAND models, and is under investigation for further development.

Autophagy in dementias

Dementias are a varied group of disorders typically associated with memory loss, impaired judgment and/or language and by symptoms affecting other cognitive and social abilities to a degree that interferes with daily functioning. Alzheimer's disease (AD) is the most common cause of a progressive dementia, followed by dementia with Lewy bodies (DLB), frontotemporal dementia (FTD), (VaD) and HIV-associated neurocognitive disorders (HAND). The pathogenesis of this group of disorders has been linked to the abnormal accumulation of proteins in the brains of affected individuals, which in turn has been related to deficits in protein clearance. Autophagy is a key cellular protein clearance pathway with proteolytic cleavage and degradation via the ubiquitin-proteasome pathway representing another important clearance mechanism. Alterations in the levels of autophagy and the proteins associated with the autophagocytic pathway have been reported in various types of dementias. This review will examine recent literature across these disorders and highlight a common theme of altered autophagy across the spectrum of the dementias.

Valproic acid induces hair regeneration in murine model and activates alkaline phosphatase activity in human dermal papilla cells

Background

Alopecia is the common hair loss problem that can affect many people. However, current therapies for treatment of alopecia are limited by low efficacy and potentially undesirable side effects. We have identified a new function for valproic acid (VPA), a GSK3β inhibitor that activates the Wnt/β-catenin pathway, to promote hair re-growth in vitro and in vivo.

Methodology/ Principal Findings

Topical application of VPA to male C3H mice critically stimulated hair re-growth and induced terminally differentiated epidermal markers such as filaggrin and loricrin, and the dermal papilla marker alkaline phosphatase (ALP). VPA induced ALP in human dermal papilla cells by up-regulating the Wnt/β-catenin pathway, whereas minoxidil (MNX), a drug commonly used to treat alopecia, did not significantly affect the Wnt/β-catenin pathway. VPA analogs and other GSK3β inhibitors that activate the Wnt/β-catenin pathway such as 4-phenyl butyric acid, LiCl, and BeCl₂ also exhibited hair growth-promoting activities in vivo. Importantly, VPA, but not MNX, successfully stimulate hair growth in the wounds of C3H mice.

Conclusions/ Significance

Our findings indicate that small molecules that activate the Wnt/β-catenin pathway, such as VPA, can potentially be developed as drugs to stimulate hair re-growth.

IFN-gamma mediates enhancement of HIV replication in astrocytes by inducing an antagonist of the beta-catenin pathway (DKK1) in a STAT 3-dependent manner

Typically, IFN-γ is an antiviral cytokine that inhibits the replication of many viruses, including HIV. However, in the CNS, IFN-γ induces HIV-productive replication in astrocytes. Although astrocytes in vitro are refractory to HIV replication, recent in vivo evidence demonstrated that astrocytes are infected by HIV, and their degree of infection is correlated with proximity to activated macrophages/microglia. The ability of IFN-γ to induce HIV replication in astrocytes suggests that the environmental milieu is critical in regulating the permissiveness of astrocytes to HIV infection. We evaluated the mechanism by which IFN-γ relieves restricted HIV replication in astrocytes. We demonstrate that although astrocytes have robust endogenous β-catenin signaling, a pathway that is a potent inhibitor of HIV replication, IFN-γ diminished β-catenin signaling in astrocytes by 40%, as evaluated by both active β-catenin protein expression and β-catenin-mediated T cell factor/lymphoid enhancer reporter (TOPflash) activity. Further, IFN-γ-mediated inhibition of β-catenin signaling was dependent on its ability to induce an antagonist of the β-catenin signaling pathway, Dickkopf-related protein 1, in a STAT 3-dependent manner. Inhibition of STAT3 and Dickkopf-related protein 1 abrogated the ability of IFN-γ to enhance HIV replication in astrocytes. These data demonstrated that IFN-γ induces HIV replication in astrocytes by antagonizing the β-catenin pathway. To our knowledge, this is the first report to point to an intricate cross-talk between IFN-γ signaling and β-catenin signaling that may have biologic and virologic effects on HIV outcome in the CNS, as well as on broader processes where the two pathways interface.

Deconstructing GSK-3: The Fine Regulation of Its Activity

Glycogen synthase kinase-3 (GSK-3) unique position in modulating the function of a diverse series of proteins in combination with its association with a wide variety of human disorders has attracted significant attention to the protein both as a therapeutic target and as a means to understand the molecular basis of these disorders. GSK-3 is ubiquitously expressed and, unusually, constitutively active in resting, unstimulated cells. In mammals, GSK-3α and β are each expressed widely at both the RNA and protein levels although some tissues show preferential levels of some of the two proteins. Neither gene appears to be acutely regulated at the transcriptional level, whereas the proteins are controlled posttranslationally, largely through protein-protein interactions or by posttranslational regulation. Control of GSK-3 activity thus occurs by complex mechanisms that are each dependent upon specific signalling pathways. Furthermore, GSK-3 appears to be a cellular nexus, integrating several signalling systems, including several second messengers and a wide selection of cellular stimulants. This paper will focus on the different ways to control GSK-3 activity (phosphorylation, protein complex formation, truncation, subcellular localization, etc.), the main signalling pathways involved in its control, and its pathological deregulation.

Increased CDK5 expression in HIV encephalitis contributes to neurodegeneration via tau phosphorylation and is reversed with Roscovitine

Recent treatments with highly active antiretroviral therapy (HAART) regimens have been shown to improve general clinical status in patients with human immunodeficiency virus (HIV) infection; however, the prevalence of cognitive alterations and neurodegeneration has remained the same or has increased. These deficits are more pronounced in the subset of HIV patients with the inflammatory condition known as HIV encephalitis (HIVE). Activation of signaling pathways such as GSK3β and CDK5 has been implicated in the mechanisms of HIV neurotoxicity; however, the downstream mediators of these effects are unclear. The present study investigated the involvement of CDK5 and tau phosphorylation in the mechanisms of neurodegeneration in HIVE. In the frontal cortex of patients with HIVE, increased levels of CDK5 and p35 expression were associated with abnormal tau phosphorylation. Similarly, transgenic mice engineered to express the HIV protein gp120 exhibited increased brain levels of CDK5 and p35, alterations in tau phosphorylation, and dendritic degeneration. In contrast, genetic knockdown of CDK5 or treatment with the CDK5 inhibitor roscovitine improved behavioral performance in the water maze test and reduced neurodegeneration, abnormal tau phosphorylation, and astrogliosis in gp120 transgenic mice. These findings indicate that abnormal CDK5 activation contributes to the neurodegenerative process in HIVE via abnormal tau phosphorylation; thus, reducing CDK5 might ameliorate the cognitive impairments associated with HIVE.

Histone deacetylase inhibitors suppress the expression of inflammatory and innate immune response genes in human microglia and astrocytes

Histone deacetylase inhibitors (HDACi) have been proposed as therapies for certain cancers and as an anti-reservoir therapy for HIV+ individuals with highly active anti-retroviral therapy, yet their roles in glial inflammatory and innate antiviral gene expression have not been defined. In this study, we examined the effects of two non-selective HDACi, trichostatin A and valproic acid, on antiviral and cytokine gene expression in primary human microglia and astrocytes stimulated with TLR3 or TLR4 ligand. HDACi potently suppressed the expression of innate antiviral molecules such as IFNβ, interferon-simulated genes, and proteins involved in TLR3/TLR4 signaling. HDACi also suppressed microglial and astrocytic cytokine and chemokine gene expression, but with different effects on different groups of cytokines. These results have important implications for the clinical use of HDACi.

Human immunodeficiency virus-1 Tat activates calpain proteases via the ryanodine receptor to enhance surface dopamine transporter levels and increase transporter-specific uptake and Vmax

Human immunodeficiency virus-associated neurological disease (HAND) still causes significant morbidity, despite success reducing viral loads with combination antiretroviral therapy. The dopamine (DA) system is particularly vulnerable in HAND. We hypothesize that early, "reversible" DAergic synaptic dysfunction occurs long before DAergic neuron loss. As such, aging human immunodeficiency virus (HIV)-infected individuals may be vulnerable to other age-related neurodegenerative diseases like Parkinson's disease (PD), underscoring the need to understand shared molecular targets in HAND and PD. Previously, we reported that the neurotoxic HIV-1 transactivating factor (Tat) acutely disrupts mitochondrial and endoplasmic reticulum calcium homeostasis via ryanodine receptor (RyR) activation. Here, we further report that Tat disrupts DA transporter (DAT) activity and function, resulting in increased plasma membrane (PM) DAT and increased DAT V(max), without changes in K(m) or total DAT protein. Tat also increases calpain protease activity at the PM, demonstrated by total internal reflection fluorescence microscopy of a cleavable fluorescent calpain substrate. Tat-increased PM DAT and calpain activity are blocked by the RyR antagonists ryanodine and dantrolene, the calpain inhibitor calpastatin, and by a specific inhibitor of GSK-3β. We conclude that Tat activates RyRs via a calcium- and calpain-mediated mechanism that upregulates DAT trafficking to the PM, and is independent of DAT protein synthesis, reinforcing the feasibility of RyR and GSK-3β inhibition as clinical therapeutic approaches for HAND. Finally, we provide key translational relevance for these findings by highlighting published human data of increased DAT levels in striata of HAND patients and by demonstrating similar findings in Tat-expressing transgenic mice.

Urotensin II induction of adult cardiomyocytes hypertrophy involves the Akt/GSK-3beta signaling pathway

Urotensin II (UII) a potent vasoactive peptide is upregulated in the failing heart and promotes cardiomyocytes hypertrophy, in particular through mitogen-activated protein kinases. However, the regulation by UII of GSK-3beta, a recognized pivotal signaling element of cardiac hypertrophy has not yet been documented. We therefore investigated in adult cardiomyocytes, if UII phosphorylates GSK-3beta and Akt, one of its upstream regulators and stabilizes beta-catenin, a GSK-3beta dependent nuclear transcriptional co-activator. Primary cultures of adult rat cardiomyocytes were stimulated for 48h with UII. Cell size and protein/DNA contents were determined. Phosphorylated and total forms of Akt, GSK-3beta and the total amount of beta-catenin were quantified by western blot. The responses of cardiomyocytes to UII were also evaluated after pretreatment with the chemical phosphatidyl-inositol-3-kinase inhibitor, LY294002, and urantide, a competitive UII receptor antagonist. UII increased cell size and the protein/DNA ratio, consistent with a hypertrophic response. UII also increased phosphorylation of Akt and its downstream target GSK-3beta. beta-Catenin protein levels were increased. All of these effects of UII were prevented by LY294002, and urantide. The UII-induced adult cardiomyocytes hypertrophy involves the Akt/GSK-3beta signaling pathways and is accompanied by the stabilization of the beta-catenin. All these effects are abolished by competitive inhibition of the UII receptor, consistent with new therapeutic perspectives for heart failure treatment.

Glycogen synthase kinase-3beta (GSK-3beta) inhibitors AR-A014418 and B6B3O prevent human immunodeficiency virus-mediated neurotoxicity in primary human neurons

Glycogen synthase kinase-3beta (GSK3beta) role in human immunodeficiency virus(HIV)-associated neurodegeneration has been evidenced by previous investigations. In this study, we investigated the specificity of two GSK3beta-specific inhibitors, AR-A014418 (A) and B6B30 (B) to prevent direct neurotoxicity in primary human neurons exposed to HIV (BaL). Neurons were exposed to HIV (500 pg/ml) for 12-h and 6-day periods in the presence and absence of A (1 microM, 100 nM, 10 nM) and B (50 nM, 5 nM, 500 pM) to investigate acute and ongoing mechanisms of HIV neurotoxicity. Using an lactate dehydrogenase (LDH) assay to assess cytotoxicity, we observed a significant neurotoxic effect of HIV from control values (P < .01) that was not restored via coexposures of all concentrations of A and B. Additionally, no change in LDH levels were observed after 6 days. However, activity of the acute proapoptotic markers caspases 3 and 7 using a luminescence assay were measured and found to be increased by exposure to HIV (BaL) compared to controls (P = .022). This effect was ameliorated via coexposure to all concentrations of A and 50 nM B after 12 h (P < .01) and to all concentrations of A and B after 6 days (P < .01). Overall, the results from this study provide further evidence for the ability of GSK3beta inhibition to be neuroprotective against HIV-associated neurotoxicity by reducing HIV associated procaspase induction. These data support a role for GSK3beta as a potential therapeutic target and may have important clinical implications for treatment of HIV-associated neurocognitive disorder.

Neuroprotective activities of CEP-1347 in models of neuroAIDS

When the nervous system is infected with HIV-1, it commonly results in neuroinflammation leading to overt neuronal dysfunction and subsequent cognitive and behavioral impairments. The multifaceted disease process, now referred to as HIV-1-associated neurocognitive disorders (HAND), provides a range of molecular targets for adjunctive therapies. One is CEP-1347, an inhibitor of mixed lineage kinases that elicits neuroprotective and anti-inflammatory responses in models of neurodegenerative diseases. Since HAND is associated with inflammatory encephalopathy induced by virus infection and mononuclear phagocytes (perivascular macrophages and microglia) immune activation, we investigated whether CEP-1347 could ameliorate disease in laboratory models of HAND. We now demonstrate that CEP-1347 reduces the levels of secreted proinflammatory cytokines and chemokines in HIV-1-infected human macrophages and attenuates dose-dependent neurotoxicity in rodent cortical neurons. CEP-1347-treated mice readily achieve therapeutic drug levels in peripheral blood. HIV-1 encephalitis (HIVE) mice, where human virus-infected monocyte-derived macrophages are stereotactically injected into the basal ganglia of CB17 severe combined immunodeficient mice, received daily intraperitoneal injections of CEP-1347. Here, CEP-1347 treatment of HIVE mice showed a dose-dependent reduction in microgliosis. Dendritic integrity and neuronal loss were sustained and prevented, respectively. These results demonstrate that CEP-1347 elicits anti-inflammatory and neuroprotective responses in an HIVE model of human disease and as such warrants further study as an adjunctive therapy for human disease.

Targeting protein kinases in central nervous system disorders

Protein kinases are a growing drug target class in disorders in peripheral tissues, but the development of kinase-targeted therapies for central nervous system (CNS) diseases remains a challenge, largely owing to issues associated specifically with CNS drug discovery. However, several candidate therapeutics that target CNS protein kinases are now in various stages of preclinical and clinical development. We review candidate compounds and discuss selected CNS protein kinases that are emerging as important therapeutic targets. In addition, we analyse trends in small-molecule properties that correlate with key challenges in CNS drug discovery, such as blood-brain barrier penetrance and cytochrome P450-mediated metabolism, and discuss the potential of future approaches that will integrate molecular-fragment expansion with pharmacoinformatics to address these challenges.

TLR3 and TLR4 are innate antiviral immune receptors in human microglia: role of IRF3 in modulating antiviral and inflammatory response in the CNS

In the CNS, microglia are the primary targets of HIV infection. In this study, we investigated the effect of activation of the innate antiviral receptors TLR3 and TLR4 on HIV infection of primary human microglia, as well as microglial cell signaling and gene expression. Ligands for both TLR3 and TLR4 potently inhibited HIV replication in microglia through a pathway requiring IRF3. Surprisingly, a remarkably similar pattern of cell signaling and gene expression was observed in TLR3- and TLR4-activated microglia, suggesting a relatively minor role for MyD88 following TLR4 activation in these cells. HIV did not activate IRF3 but rather decreased IRF3 protein, indicating that HIV does not activate TLR3 or RIG-like helicases in microglia. Taken together, these results indicate that activation of TLR3 or TLR4 will elicit antiviral immunity, in addition to inducing proinflammatory responses. We suggest that a balanced expression between inflammatory and innate immune genes might be achieved by IRF3 over-expression.

The ART of HIV therapies: dopaminergic deficits and future treatments for HIV pediatric encephalopathy

The concerted efforts of clinicians, scientists and caregivers of HIV-infected children have led to tremendous advances in our understanding of pediatric HIV/AIDS. Antiretroviral therapy (ART; formerly known as highly active antiretroviral therapy [HAART]) has significantly extended the longevity of HIV-infected children, but there are limitations to improvements in quality of life that may persist despite therapy. ART has remarkably reduced the incidence of neurologic deficits for the majority of infected children, but some patients do not experience these benefits and children living in poorer nations, who may not have access to antiretrovirals, are particularly at risk for developing neurologic deficits. This article reviews the neurologic symptoms of pediatric HIV infection that manifest as dopaminergic disruptions and explores potential future adjuvant therapies for HIV-related neurologic disorders in children.

Molecular pathology of neuro-AIDS (CNS-HIV)

The cognitive deficits in patients with HIV profoundly affect the quality of life of people living with this disease and have often been linked to the neuro-inflammatory condition known as HIV encephalitis (HIVE). With the advent of more effective anti-retroviral therapies, HIVE has shifted from a sub-acute to a chronic condition. The neurodegenerative process in patients with HIVE is characterized by synaptic and dendritic damage to pyramidal neurons, loss of calbindin-immunoreactive interneurons and myelin loss. The mechanisms leading to neurodegeneration in HIVE might involve a variety of pathways, and several lines of investigation have found that interference with signaling factors mediating neuroprotection might play an important role. These signaling pathways include, among others, the GSK3beta, CDK5, ERK, Pyk2, p38 and JNK cascades. Of these, GSK3beta has been a primary focus of many previous studies showing that in infected patients, HIV proteins and neurotoxins secreted by immune-activated cells in the brain abnormally activate this pathway, which is otherwise regulated by growth factors such as FGF. Interestingly, modulation of the GSK3beta signaling pathway by FGF1 or GSK3beta inhibitors (lithium, valproic acid) is protective against HIV neurotoxicity, and several pilot clinical trials have demonstrated cognitive improvements in HIV patients treated with GSK3beta inhibitors. In addition to the GSK3beta pathway, the CDK5 pathway has recently been implicated as a mediator of neurotoxicity in HIV, and HIV proteins might activate this pathway and subsequently disrupt the diverse processes that CDK5 regulates, including synapse formation and plasticity and neurogenesis. Taken together, the GSK3beta and CDK5 signaling pathways are important regulators of neurotoxicity in HIV, and modulation of these factors might have therapeutic potential in the treatment of patients suffering from HIVE. In this context, the subsequent sections will focus on reviewing the involvement of the GSK3beta and CDK5 pathways in neurodegeneration in HIV.

Mechanisms of action of the mood stabilizer valproate: a focus on GSK-3 inhibition

Valproate is the most widely prescribed antiepileptic drug worldwide, and it is also used in the treatment of bipolar affective disorder, migraine headache and cancer. However, the therapeutic mechanism of action of valproate in these illness states is not understood. This article reviews the pharmacological effects of valproate that may explain its therapeutic efficacy. It focuses on the hypothesis that inhibition of glycogen synthase kinase-3 by valproate is a crucial therapeutic mechanism of this drug in the treatment of bipolar affective disorder. Other cellular pathways and signaling molecules that are targets of valproate (such as inositol de novo biosynthesis, histone deacetylase, protein kinase C, γ-aminobutyric acid, the extracellular signal-regulated kinase pathway and others) are also discussed.

Role of psychiatric medications as adjunct therapy in the treatment of HIV associated neurocognitive disorders

Effective combination antiretroviral therapies (ART) have markedly lengthened survival among HIV infected individuals. In this long-surviving cohort, both psychiatric comorbidities and HIV-associated neurocognitive disorders (HAND) remain common. Even mild neurocognitive impairment can significantly disrupt of activities of daily living and reduce quality of life. Persistence of HAND might reflect incomplete containment of HIV within the central nervous system (CNS) due to the limited penetration of most antiretrovirals (ARVs) across the blood-brain barrier. Recent data support that certain medications used to treat psychiatric comorbidities in HIV-infected individuals may also protect the brain from toxic byproducts of HIV replication and neuroinflammation. Two drug classes in particular, glycogen synthase kinase-3 beta (GSK-3b) inhibitors and serotonin reuptake inhibitors (SRIs), may benefit individuals with HAND. Valproic acid (VPA) and lithium are potentially beneficial GSK-3b inhibitors. While the mechanism of benefit of SRIs in HAND remains unknown, evidence supports some benefit of citalopram and paroxetine. The present brief review focuses on these drugs and assesses their possible adjunct roles in the treatment of HIV-infected individuals.