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Concept: GSK3B

315

The restoration of dentine lost in deep caries lesions in teeth is a routine and common treatment that involves the use of inorganic cements based on calcium or silicon-based mineral aggregates. Such cements remain in the tooth and fail to degrade and thus normal mineral volume is never completely restored. Here we describe a novel, biological approach to dentine restoration that stimulates the natural formation of reparative dentine via the mobilisation of resident stem cells in the tooth pulp. Biodegradable, clinically-approved collagen sponges are used to deliver low doses of small molecule glycogen synthase kinase (GSK-3) antagonists that promote the natural processes of reparative dentine formation to completely restore dentine. Since the carrier sponge is degraded over time, dentine replaces the degraded sponge leading to a complete, effective natural repair. This simple, rapid natural tooth repair process could thus potentially provide a new approach to clinical tooth restoration.

Concepts: Enzyme, Animal, Teeth, Tooth, Dental caries, Portland cement, GSK-3, GSK3B

2

The enzymes 5-lipoxygenase (5-LO) and glycogen synthase kinase (GSK)-3 represent promising drug targets in the treatment of inflammation. We made use of the bisindole core of indirubin, present in GSK-3 inhibitors, to innovatively target 5-LO at the ATP-binding site for the design of dual 5-LO/GSK-3 inhibitors. Evaluation of substituted indirubin derivatives led to the identification of (3Z)-6-bromo-3-[(3E)-3-hydroxyiminoindolin-2-ylidene]indolin-2-one (15) as a potent, direct, and reversible 5-LO inhibitor (IC50 = 1.5 µM), with comparable cellular effectiveness on 5-LO and GSK-3. Together, we present indirubins as novel chemotypes for the development of 5-LO inhibitors, the interference with the ATP-binding site as a novel strategy for 5-LO targeting, and dual 5-LO/GSK-3 inhibition as an unconventional and promising concept for anti-inflammatory intervention.

Concepts: Enzyme, Enzyme inhibitor, Inhibitor, Xanthine oxidase inhibitor, Enzymes, Target Corporation, GSK-3, GSK3B

0

Rhodnius prolixus is a blood-feeding insect that transmits Trypanosoma cruzi and Trypanosoma rangeli to vertebrate hosts. Rhodnius prolixus is also a classical model in insect physiology, and the recent availability of R. prolixus genome has opened new avenues on triatomine research. Glycogen synthase kinase 3 (GSK-3) is classically described as a key enzyme involved in glycogen metabolism, also acting as a downstream component of the Wnt pathway during embryogenesis. GSK-3 has been shown to be highly conserved among several organisms, mainly in the catalytic domain region. Meanwhile, the role of GSK-3 during R. prolixus embryogenesis or glycogen metabolism has not been investigated. Here we show that chemical inhibition of GSK-3 by alsterpaullone, an ATP-competitive inhibitor of GSK3, does not affect adult survival rate, though it alters oviposition and egg hatching. Specific GSK-3 gene silencing by dsRNA injection in adult females showed a similar phenotype. Furthermore, bright field and 4'-6-diamidino-2-phenylindole (DAPI) staining analysis revealed that ovaries and eggs from dsGSK-3 injected females exhibited specific morphological defects. We also demonstrate that glycogen content was inversely related to activity and transcription levels of GSK-3 during embryogenesis. Lastly, after GSK-3 knockdown, we observed changes in the expression of the Wingless (Wnt) downstream target β-catenin as well as in members of other pathways such as the receptor Notch. Taken together, our results show that GSK-3 regulation is essential for R. prolixus oogenesis and embryogenesis.

Concepts: Gene, Enzyme, RNA, Chagas disease, Glycogen, Enzyme inhibitor, GSK-3, GSK3B

0

Invasive aspergillosis (IA) is one of the most severe forms of fungi infection. IA disease is mainly due to Aspergillus fumigatus, an air-borne opportunistic pathogen. Mortality rate caused by IA is still very high (50-95%), because of difficulty in early diagnostics and reduced antifungal treatment options, thus new and efficient drugs are necessary. The aim of this work is, using Aspergillus nidulans as non-pathogen model, to develop efficient drugs to treat IA. The recent discovered role of glycogen synthase kinase-3 homologue, GskA, in A. fumigatus human infection and our previous experience on human GSK-3 inhibitors focus our attention on this kinase as a target for the development of antifungal drugs. With the aim to identify effective inhibitors of colonial growth of A. fumigatus we use A. nidulans as an accurate model for in vivo and in silico studies. Several well-known human GSK-3β inhibitors were tested for inhibition of A. nidulans colony growth. Computational tools as docking studies and binding site prediction was used to explain the different biological profile of the tested inhibitors. Three of the five tested hGSK3β inhibitors are able to reduce completely the colonial growth by covalent bind to the enzyme. Therefore these compounds may be useful in different applications to eradicate IA.

Concepts: Enzyme, Opportunistic infection, Enzyme inhibitor, Aspergillosis, Aspergillus, Aspergillus fumigatus, GSK-3, GSK3B

0

Cardiac myocyte-specific deletion of either Glycogen Synthase Kinase (GSK)3A or GSK3B leads to cardiac protection following myocardial infarction, suggesting that deletion of both isoforms may provide synergistic protection. This is an important consideration due to the fact that all GSK-3-targeted drugs including the drugs already in clinical trial target both isoforms of GSK-3 and none are isoform specific.

Concepts: Myocardial infarction, Heart, Muscle, GSK-3, GSK3B

0

1,25-dihyroxyvitamin D3 (1,25D), the biologically active form of vitamin D, is widely considered a promising therapy for acute myeloid leukemia (AML) based on its ability to drive differentiation of leukemic cells. However, clinical trials have been disappointing in part to dose-limiting hypercalcemia. Here we show how inhibiting glycogen synthase kinase-3 (GSK3) can improve the differentiation response of AML cells to 1,25D-mediated differentiation. GSK3 inhibition in AML cells enhanced the differentiating effects of low concentrations of 1,25D. Additionally, GSK3 inhibition augmented the ability of 1,25D to induce irreversible growth inhibition and slow the progression of AML in mouse models. Mechanistic studies revealed that GSK3 inhibition led to the hyperphosphorylation of the vitamin D receptor (VDR), enabling an interaction between VDR and the co-activator, SRC-3 (NCOA3), thereby increasing transcriptional activity. We also found that activation of JNK-mediated pathways in response to GSK3 inhibition contributed to the potentiation of 1,25D-induced differentiation. Taken together, our findings offer a preclinical rationale to explore the repositioning of GSK3 inhibitors to enhance differentiation-based therapy for AML treatment.

Concepts: DNA, Vitamin D, Leukemia, Acute myeloid leukemia, Inhibitor, Xanthine oxidase inhibitor, GSK-3, GSK3B

0

The HIF-1 and β-catenin protective pathways represent the two most significant cellular responses that are activated in response to acute kidney injury. We previously reported that murine Mucin 1 (Muc1) protects kidney function and morphology in a mouse model of ischemia-reperfusion injury (IRI) by stabilizing HIF-1α , enhancing HIF-1 downstream signaling and thereby preventing metabolic stress (Pastor-Soler et al. 2015 Am. J. Physiol. 308, F1452-F1462). We asked if Muc1 regulates the β-catenin protective pathway during IRI as (i) β-catenin nuclear targeting is MUC1-dependent in cultured cells, (ii) β-catenin is found in co-immunoprecipitates with human MUC1 in extracts of both cultured cells and tissues, and (iii) MUC1 prevents β-catenin phosphorylation by glycogen synthase kinase 3β (GSK3β) and thereby β-catenin degradation. Using the same mouse model of IRI, we found that levels of active GSK3β were significantly lower in kidneys of control mice compared to Muc1 KO mice. Consequently, β-catenin was significantly upregulated at 24 and 72 h recovery and appeared in the nuclear fraction at 72 h in control mouse kidneys. Both β-catenin induction and nuclear targeting were absent in Muc1 KO mice. We also found downstream induction of β-catenin pro-survival factors (activated Akt, survivin, transcription factor TCF4 and its downstream target cyclin D1) and repression of pro-apoptotic factors (p53, active Bax and cleaved caspase 3) in control mouse kidneys that were absent or aberrant in kidneys of Muc1 KO mice. Altogether, the data clearly indicate that Muc1 protection during AKI proceeds by enhancing both the HIF-1 and β-catenin protective pathways.

Concepts: Renal failure, Kidney, Enzyme, Apoptosis, Murinae, Mucin, MUC1, GSK3B

0

Novel treatments for bipolar disorders, with improved efficacy and broader spectrum of activity are urgently needed. Glycogen synthase kinase 3β (GSK-3β) has been suggested to be a key player in the pathophysiology of bipolar disorders. A series of novel GSK-3β inhibitors having the common N-[(1-alkylpiperidin-4-yl)methyl]-1H-indazole-3-carboxamide scaffold were prepared taking advantage of an X-ray co-crystal structure of compound 5 with GSK-3β. We probed different substitutions at the indazole 5-position and at the piperidine-nitrogen to obtain potent ATP-competitive GSK-3β inhibitors with good cell activity. Among the compounds assessed in the in vivo PK experiments, 14i showed, after i.p. dosing, encouraging plasma PK profile and brain exposure, as well as efficacy in a mouse model of mania. Compound 14i was selected for further in vitro/in vivo pharmacological evaluation, in order to elucidate the use of ATP-competitive GSK-3β inhibitors as new tools in the development of new treatments for mood disorders.

Concepts: Enzyme, Antidepressant, Bipolar disorder, Mania, Mood, GSK-3, Hypomania, GSK3B

0

The challenge for Glycogen Synthase Kinase-3 (GSK 3) inhibitor design lies in achieving high selectivity for one isoform over the other. The therapy of certain diseases, such as acute myeloid leukemia (AML) may require α-isoform specific targeting. The scorpion shaped GSK-3 inhibitors developed by our group achieved the highest GSK 3α selectivity reported so far, but suffered from insufficient aqueous solubility. This work presents the solubility-driven optimization of our isoform-selective inhibitors using a scorpion shaped lead. Among 15 novel compounds, compound 27 showed high activity against GSK 3α/β with the highest GSK 3α selectivity reported to date. Compound 27 was profiled for bioavailability and toxicity in a zebrafish embryo phenotype assay. Selective GSK 3α targeting in AML cell lines was achieved with compound 27, resulting in a strong differentiation phenotype and colony formation impairment, confirming the potential of GSK 3α inhibition in AML therapy.

Concepts: Leukemia, Enzyme inhibitor, Acute myeloid leukemia, Blood disorders, Inhibitor, Xanthine oxidase inhibitor, GSK-3, GSK3B

0

The mechanisms of glycogen synthase kinase-3 (GSK-3)-mediated cytoprotection during liver ischemia/reperfusion (I/R) remain controversial, particularly in older organs. This study explores the role and potential mechanisms of GSK-3 in young and aging livers.

Concepts: Glucose, Liver, Glycogen, Gallbladder, Hepatocyte, GSK-3, Glycogenesis, GSK3B