Glycogen synthase kinase-3beta (GSK-3beta) has been demonstrated to play a critical role in a diverse range of cellular functions from cell fate determination to cancer development. It is also implicated to be involved in the pathogenesis of neurodegenerative diseases (e.g. Alzheimer's disease), cancers and endocrine disorders (e.g. Type II diabetes). To gain further insight into the cellular mechanisms mediated by GSK-3beta, proteomic approach to identify novel cellular targets has become popular in recent years. GSK-3beta was inhibited by treating with lithium and kenpaullone in SH-SY5Y cell model, and over-expressed in Chinese Hamster Ovary (CHO) Tet-Off cell model. To getting more reliable results, we have used both conventional 2-D approach and Difference Gel Electrophoresis (DIGE) approach for this proteomic study. In 2-D electrophoresis, samples were resolved by two-dimensional polyacrylamide gel-electrophoresis (2D-PAGE). Protein spots were excised from the gels for in-gel trypsin digestion and further subjected to protein identification using mass spectrometry (MALDI-TOF-MS or MS/MS). In the GSK-3beta inhibition approach, cofilin was found to be down-regulated and Pin1 was found to be up-regulated, these consequence events demonstrated inhibition of GSK-3beta would protect the cells from structure alteration and tau hyperphosphorylation. In the GSK-3beta activation approach, cyclin-dependent kinase 5 (CDK-5) was found to significantly up-regulated in tau and GSK-3beta/Tau over-expressed cells, confirmed by Western blotting and RT-PCR. This finding indicates there is a new pathway between GSK-3beta, tau and CDK-5. Pin1 is also identified to be up-regulated after GSK-3beta activation. This result indicated a protection mechanism in response to the accumulation of hyperphosphorylated tau proteins. Our study help to get a better understanding of the GSK-3beta mediated substrates and pathways that help us to identify novel targets for the treatment of neurodegenerative and other diseases mediated by GSK-3beta. / Mak, Ying Cheong. / "September 2007." / Source: Dissertation Abstracts International, Volume: 69-08, Section: B, page: 4588. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 157-181). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Glioblastoma is the most malignant form of brain cancer. Due to its aggressive nature, extensive research has been performed, but little progress has been made in identifying effective treatment options. Glycogen synthase kinase-3 (GSK-3) is a ubiquitous, multifaceted protein kinase. Previous studies have shown that small molecule inhibitors of GSK-3 block the migration of glioblastoma cells and may prevent spread of tumor in the brain. However, these studies were performed using non-selective GSK-3 inhibitors (LiCl and an indirubin derivative, BIO); thus, it was unclear whether GSK-3 was the most important target. In this study, we used recently generated highly selective GSK-3 inhibitors (CHIR99021, AZD1080, and AZD2858, as well as BIO) to investigate these questions. These were applied to four glioblastoma cell lines: G30, G9, U251, and U1242, in three migration assays: transwell, spheroid, and wound healing (scratch) assay to further assess the suitability of GSK-3 as a target in glioblastoma. We also utilized the ATP Luciferase reporter assay for cell viability to assess the influence of our panel of drugs on cell migration versus viability. In addition, the TOPFlash Luciferase reporter assay was performed as an indicator of the level of GSK-3 inhibition. The TOPFlash assay showed that all GSK-3 inhibitors were able to increase luciferase levels. This indicates that GSK-3 was inhibited in our cells after drug treatment. The transwell assays showed us that the GSK-3 inhibitors were able to block migration significantly in all cell lines tested in a dose-dependent manner. The effectiveness of GSK-3 inhibition in the three-dimensional collagen spheroid assays was cell line-dependent, with the non-selective GSK-3 inhibitor BIO showing the most potent effects. Cell migration was not blocked by any of the three selective GSK-3 inhibitors in the wound healing scratch assay. Thus we have found that the three distinct highly selective inhibitors of GSK-3 block glioblastoma cell migration, but only work consistently in the transwell assay. Therefore, we conclude that GSK-3 might be important in the contraction and morphological changes necessary for glioblastoma cells to migrate through the 8 micron pores in the transwell. Further investigation into this observation is necessary. Though results were variable between assays, we conclude that the inhibition of GSK-3 is a promising potential therapeutic strategy for glioblastoma treatment.

The intracellular delivery of molecules to modulate signaling pathways and gene expression is a powerful approach to control stem cell fate decision. For applications in gene therapy and regenerative medicine, the use of genetic material and viral vectors raise concerns because stem cells persist throughout life, and long-term effects of uncontrolled genetic modifications could affect the cellular progeny. An alternative is to deliver directly peptides or proteins using cell-permeable peptides (CPPs) which have the ability of crossing the plasma membrane and carrying cargos into cells. CPPs can therefore be used to deliver factors to direct stem cells proliferation, survival and differentiation. This thesis describes an approach to control stem cell fate based on the delivery of a CPP-conjugated bioactive peptide. A first significant contribution from this work is the development of a flow cytometric assay to accurately quantify the uptake of a panel of CPPs. This study revealed that HIV-transactivator of transcription (TAT) and Antennapedia (Antp) offered the highest level of translocation in different cell types. The uptake was improved by treating the cells with a single, low-voltage electrical pulse that selectively enhances the amount of TAT-conjugated peptides and proteins delivered by at least an order of magnitude, without causing cellular toxicity or apoptosis. Subsequently, flow cytometry, confocal microscopy, capillary electrophoresis and mass spectrometry were used to examine the intracellular fate of TAT-conjugated peptides in order to define the parameters that limit their bioactivity and point to specific sequence modifications that can improve their efficacy. The advances described in this thesis were applied to the development of TAT-eIF2B, a peptide-inhibitor of glycogen synthase kinase-3 (GSK-3). TAT-eIF2B was found to be specific for GSK-3 and had a significant positive effect on the formation of neurospheres in embryonic stem cell cultures and on the survival of myeloid progenitors in cytokine-starved fetal liver cell cultures. On the other hand, GSK-3 inhibition reduced the number of neurospheres generated by human olfactory neuroepithelium cells due to lower proliferation and increased neuronal differentiation. In summary, this work describes the development of a peptide-based technology to deliver bioactive cargoes in cells, and it demonstrates its utility for modulating the activity of a master regulator of stem cell fate decision.

The intracellular delivery of molecules to modulate signaling pathways and gene expression is a powerful approach to control stem cell fate decision. For applications in gene therapy and regenerative medicine, the use of genetic material and viral vectors raise concerns because stem cells persist throughout life, and long-term effects of uncontrolled genetic modifications could affect the cellular progeny. An alternative is to deliver directly peptides or proteins using cell-permeable peptides (CPPs) which have the ability of crossing the plasma membrane and carrying cargos into cells. CPPs can therefore be used to deliver factors to direct stem cells proliferation, survival and differentiation. This thesis describes an approach to control stem cell fate based on the delivery of a CPP-conjugated bioactive peptide. A first significant contribution from this work is the development of a flow cytometric assay to accurately quantify the uptake of a panel of CPPs. This study revealed that HIV-transactivator of transcription (TAT) and Antennapedia (Antp) offered the highest level of translocation in different cell types. The uptake was improved by treating the cells with a single, low-voltage electrical pulse that selectively enhances the amount of TAT-conjugated peptides and proteins delivered by at least an order of magnitude, without causing cellular toxicity or apoptosis. Subsequently, flow cytometry, confocal microscopy, capillary electrophoresis and mass spectrometry were used to examine the intracellular fate of TAT-conjugated peptides in order to define the parameters that limit their bioactivity and point to specific sequence modifications that can improve their efficacy. The advances described in this thesis were applied to the development of TAT-eIF2B, a peptide-inhibitor of glycogen synthase kinase-3 (GSK-3). TAT-eIF2B was found to be specific for GSK-3 and had a significant positive effect on the formation of neurospheres in embryonic stem cell cultures and on the survival of myeloid progenitors in cytokine-starved fetal liver cell cultures. On the other hand, GSK-3 inhibition reduced the number of neurospheres generated by human olfactory neuroepithelium cells due to lower proliferation and increased neuronal differentiation. In summary, this work describes the development of a peptide-based technology to deliver bioactive cargoes in cells, and it demonstrates its utility for modulating the activity of a master regulator of stem cell fate decision.

Spinal cord injury (SCI) results in extensive demyelination, leading to deleterious axon degeneration and inability of functional recovery. Remyelination has become a part of the fundamental strategy for SCI repair. Endogenous neural progenitor cells (NPCs) respond to SCI producing progenies and provide a possible source of regenerated oligodedrocytes for remyelination. During development of the central nervous system, glycogen synthase kinase-3 isoform beta (GSK-3β) is involved in multiple pathways that regulate oligodendrocyte differentiation and myelination, and thus may also play an important part in remyelination after SCI. This study aims to investigate (1) the role of GSK-3β in the differentiation of adult spinal cord derived-neural progenitor cells (ASC-NPCs); (2) whether AR-A014418 as a GSK-3β inhibitor, can promote oligodendroglial differentiation of ASC-NPCs; (3) the effect of LiCl, another GSK-3β inhibitor, on functional recovery after SCI; (4) the effects of LiCl on the myelin and axonal preservation after SCI. Neurosphere culture from adult mouse spinal cord was performed to test the effect of GSK-3β inhibitors, LiCl and AR-A014418, on differentiation of ASC-NPCs. Phenotyping of differentiated ASC-NPCs by immunocytochemistry (ICC) was performed to identify oligodendroglia progenitor cells (OPCs) at different stages. It was shown that LiCl (1 mM) and AR-A014418 (5 μM) promoted differentiation of OPCs as labeled by oligodendrocyte lineage-specific markers: PDGFR-α, NG2 and O4, while AR-A014418 was more potent in the OPC differentiation. Moreover, preliminary data from western blot confirmed that ARA014418 (5 μM) treatment increased the expression level of pGSK (inactive form of GSK-3) in differentiated ASC-NPCs. This suggests a possible strategy to modulate endogenous NPC response to SCI: to induce the preferential differentiation of NPCs into oligodendrocyte lineage by inhibiting GSK-3β activity and thus leading to enhanced remyelination by the differentiated oligodendrocytes. Basso Mouse Scale (BMS) open field test was used to evaluate the locomotive function of the spinal cord injured mice. The result showed that LiCl (4 mM, 200 μl) administration delivered locally at the lesion site by osmotic pump for 2 weeks improved functional recovery after SCI. Furthermore, immunohistochemistry (IHC) analyses revealed that LiCl treatment inhibited GSK-3β activity in the 〖Olig2〗^+ OPCs/oligodendrocytes, confirming LiCl as a GSK-3β inhibitor in vivo. Moreover, LiCl treatment better preserved myelin and axons detected by myelin basic protein (MBP) immunostaining and neurofilment-200 (NF-200) immunostaining respectively in the injured spinal cords. All together, the data from our in vitro and in vivo experiments suggested that LiCl treatment after spinal cord injury is beneficial for functional recovery by preventing the loss of myelin and axons after SCI and this effect is mediated via GSK-3β inhibition This study provided evidence for the involvement of GSK-3β in the regulation of OPC differentiation and the subsequent remyelination in the injured adult spinal cord. We propose GSK-3β as an important therapeutic target for SCI repair, LiCl as a potential candidate for SCI clinical treatment and the possibility to manipulate endogenous NPCs after SCI to enhance oligodendrocyte differentiation, remyelination, and ultimately better functional recovery.. / published_or_final_version / Anatomy / Master / Master of Philosophy

Glycogen synthase kinase-3 (GSK3) is a ubiquitously expressed protein kinase with key roles in controlling proliferation, differentiation and survival of a wide variety of mammalian cells. In most cells, GSK3 is active in the absence of growth factor signaling and acts to inhibit cell proliferation and induce apoptosis. In cardiomyocytes, GSK3 plays a novel role as a negative regulator of cardiac hypertrophy, and it appears that GSK3 plays a central role as an inhibitor of cardiac hypertrophy induced by a variety of stimuli. In the present study, we sought to further elucidate the role of GSK3 in cardiomyocyte hypertrophy by studying the effects of inhibition of GSK3 in the absence of other hypertrophic stimuli. By combining global expression profiling with computational predictions and experimental analysis of transcription factor binding sites, we have identified hypertrophy-related genes that are controlled directly by GSK3 and have found that CREB is a major transcriptional target of GSK3 in cardiomyocytes. In addition, we find that inhibition of GSK3 is sufficient to induce the re-expression of fetal development genes characteristic of hypertrophy, but not sufficient to induce the full hypertrophic phenotype of cardiomyocyte growth.

Heidelberg, Univ., Diss., 2007.

Thesis (M.Sc.)--York University, 2009. Graduate Programme in Higher Education. / Typescript. Includes bibliographical references (leaves 76-87). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR51589

Thesis (MScMedSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Introduction: The worldwide escalation in the incidence of obesity and its strong association with insulin resistance, type 2 diabetes and the cardiovascular complications that accompany these disease states have elicited interest in the underlying mechanisms of these pathologies. Preliminary data generated in our laboratory showed that obesity is associated with abnormalities in the insulin signalling pathway. Specifically, we found a down-regulation of protein kinase B (PKB/Akt), which is known to mediate the metabolic effects of insulin. One of the downstream targets of PKB/Akt is glycogen synthase kinase-3 (GSK-3), which is inhibited by this phosphorylation. Detrimental effects of unopposed activity of GSK-3 have recently been described. This may play a pivotal role in some of the adverse consequences of insulin resistance in the heart. Hypothesis: Chronic inhibition of GSK-3 will induce myocardial hypertrophy or exacerbate the development of existing hypertrophy in a pre-diabetic model of diet induced obesity and insulin resistance. Objectives: (1) Assess the extent of the development of myocardial hypertrophy in a rat model of diet induced obesity (DIO) and insulin resistance. (2) Assess the effect of inhibition of GSK-3 protein on the development of myocardial hypertrophy. Methods: Two groups of age-matched male Wistar rats were used. Control animals received standard rat chow, while obese animals received a high caloric diet for 20 weeks. After 12 weeks, half of the animals in both groups received GSK-3 inhibitor treatment (CHIR118637, 30mg/kg/day, Novartis). At the end of 20 weeks, three series of experiments were conducted. (i) The animals were subjected to echocardiography to determine in vivo myocardial function, and biometric, metabolic and biochemical parameters were evaluated. (ii) The ability of the cardiomyocytes to accumulate deoxy-glucose after stimulation with insulin was determined, and (iii) the localization of key proteins was monitored using fluorescence microscopy and cell size was determined using light microscopy and flow activated cell sorter analysis. Results and discussion: The high caloric diet increased body weight (p<0.005) and intraperitoneal fat mass (p<0.01) when compared to controls. Complications associated with obesity, such as impaired glucose tolerance (p<0.05), hyperinsulinemia (p<0.0005) and an increased HOMA-IR index (p<0.01) were observed. Additionally, cardiomyocytes from the DIO animals had a significantly impaired response to insulin, specifically when 10nM (p<0.05) and 100nM (p<0.05) of insulin were used as stimulus. We also found a dysregulation in PKB/Akt, indicated by a down-regulation of phosphorylated PKB/Akt (p<0.01). The diet promoted the development of myocardial hypertrophy, since the ventricular weight (p<0.05) and ventricular weight to tibia length ratio were increased (p<0.01). Echocardiography experiments showed an increase in end diastolic diameter in the DIO animals (p<0.05). Additionally, there was an increase in the cardiomyocyte cell width in the DIO rats (p<0.0001) and a tendency for peri-nuclear localization of NFATc3. GSK-3 inhibition promoted the development of insulin resistance in control animals, as indicated by an increase in the body weight (p<0.05), serum insulin levels (p<0.01) and HOMA-IR index (p<0.01). In the DIO animals, the GSK-3 inhibitor treatment improved insulin resistance, as a decrease in serum insulin concentration (p<0.05) was observed. The cardiomyocytes from the treated DIO animals also showed an increase in glucose uptake (p<0.05) when stimulated with 100nM of insulin. The GSK-3 inhibitor promoted the development of myocardial hypertrophy in the control animals, indicated by an increase in ventricular weight (p<0.05) and cardiomyocyte cell width (p<0.0001), but did not exacerbate hypertrophy in the DIO animals. Conclusion: Both the high caloric diet and the GSK-3 inhibitor promoted the development of insulin resistance and myocardial hypertrophy in the rats. In the DIO animals the GSK-3 inhibitor treatment ameliorated insulin resistance and did not promote the further development of myocardial hypertrophy. / AFRIKAANSE OPSOMMING: Inleiding: Die huidige styging in vetsugtigheid en die sterk assosiasie daarvan met insulien weerstandigheid, tipe 2 diabetes en kardiovaskulêre komplikasies soos hipertrofie, het ‘n belangstelling in die onderliggende meganismes van hierdie siektetoestande ontlok. Voorlopige data uit ons laboratorium het getoon dat vetsug geassosieerd is met abnormaliteite in die insulien seintransduksie-pad soos byvoorbeeld ‘n afregulering van miokardiale proteïen kinase B (PKB/Akt), wat bekend is om die metaboliese effekte van insulien te medieer. Een van die proteïene wat deur PKB/Akt gefosforileer en daardeur geïnhibeer word, is glikogeen sintase kinase-3 (GSK-3). Negatiewe effekte van onge-opponeerde aktiwiteit van GSK-3 is beskryf en dit mag ‘n sleutelrol speel in sommige van die nadelige gevolge van insulien weerstandigheid in die hart. Hipotese: Chroniese onderdrukking van GSK-3 sal miokardiale hipertrofie ontlok of die bestaande hipertrofie in ‘n pre-diabetiese model van dieet-geïnduseerde vetsug en insulien weerstandigheid vererger. Doelstellings: (1) Om die omvang van die ontwikkeling van miokardiale hipertrofie in ‘n rotmodel van dieet-geïnduseerde vetsug te ondersoek en (2) om die effek van inhibisie van GSK-3 op die ontwikkeling van hipertrofie te ondersoek. Metodes: Ouderdomsgepaarde manlike Wistarrotte is in hierdie studie gebruik. Die diere is vir ‘n periode van 20 weke aan verskillende diëte onderwerp, naamlik standaard kommersiële rotkos vir die kontrole diere en ‘n hoë kalorie dieet vir die eksperimenteel vet diere (DIO). Helfte van elke groep diere is vir 8 weke met ‘n GSK-3 inhibitor behandel (CHIR118637, 30mg/kg/day, Novartis). Na die 20 weke is 3 eksperimentele reekse uitgevoer: (i) Die diere is eggokardiografies ondersoek om in vivo miokardiale funksie te bepaal en biometriese, metaboliese en biochemiese parameters is evalueer. (ii) Die vermoë van kardiomiosiete om de-oksiglukose na insulien stimulasie te akkumuleer, is bepaal, en (iii) die lokalisering van sleutelproteïene is met behulp van fluoressensie mikroskopie en die selgrootte met behulp van ligmikroskopie bepaal. Resultate en bespreking: Die hoë kalorie dieet het gepaard gegaan met ‘n beduidende toename in liggaamsgewig (p<0.005) en intraperitoneale vetmassa (p<0.01) in vergelyking met diere op die kontrole dieet. Newe-effekte geassosieerd met vetsug nl. onderdrukte glucose toleransie (p<0.05), hiperinsulinemie (p<0.0005) en ‘n verhoogde HOMA-IR index (p<0.01) is ook waargeneem. Daar was ook ‘n beduidend ingekorte respons van glukose opname deur kardiomiosiete van die vet diere na stimulasie met 10nM (p<0.05) en 100nM (p<0.05) insulien. Disregulering van PKB/Akt is gevind in die vorm van ‘n afregulering van die fosforilering van die proteïen (p<0.01). Die dieet het ook gelei tot die ontwikkeling van miokardiale hipertrofie aangesien die ventrikulêre gewig (p<0.05) asook die verhouding van die ventrikulêre gewig teenoor tibia lengte beduidend toegeneem het (p<0.01). Eggokardiografie het ‘n toename in ventrikulêre end-diastoliese dimensie in die DIO diere aangetoon (p<0.05). Tesame hiermee het die breedte van kardiomiosiete van die DIO diere toegeneem (p<0.0001) en daar was ook ‘n peri-nukluêre lokalisering van NFATc3. Behandeling van kontrole diere met ‘n GSK-3 inhibitor het insulienweerstandigheid ontlok soos afgelei uit ‘n verhoging in liggaamsgewig (p<0.05), serum insulien-vlakke (p<0.01) en die HOMA-IR waarde (p<0.01). In teenstelling het behandeling van die DIO diere met die GSK-3 inhibitor tot ‘n verbetering van insulienweerstandigheid gelei aangesien ‘n verlaging in serum insulien konsentrasies gevind is (p<0.05). Kardiomiosiete vanaf die behandelde DIO diere het ook ‘n verhoogde insulien-gestimuleerde glukose opname met 100nM insulien getoon (p<0.05). Behandeling met die GSK-3 inhibitor het die ontwikkeling van miokardiale hipertrofie in die kontrole diere teweeggebring, soos aangetoon deur ‘n toename in die ventrikulêre gewig (p<0.05) en ‘n groter selwydte in kardiomiosiete terwyl dit geen invloed op die bestaande hipertrofie van die vet diere gehad het nie. Gevolgtrekking: Die huidige studie het getoon dat die betrokke dieet asook behandeling met ‘n GSK-3 inhibitor insulienweerstandigheid sowel as die ontwikkelling van miokardiale hipertrofie in rotte ontlok. In die DIO diere het die behandeling met die GSK-3 inhibitor bloedglukose en insulien-vlakke verlaag en het nie hipertrofie vererger nie.

Apesar da elevada prevalência dos transtornos depressivos em idosos, os mecanismos fisiopatológicos subjacentes a estes quadros são pouco conhecidos. Atualmente, o principal foco dos estudos sobre a fisiopatologia da depressão geriátrica são as alterações cerebrovasculares associadas a estes quadros. Outros mecanismos fisiopatológicos têm sido estudados, como as alterações em cascatas neurotróficas e inflamatórias. A enzima glicogênio sintase quinase 3 beta (GSK-3B) tem sido implicada na patogênese de diversos transtornos mentais, em especial os transtornos afetivos (i.e. depressão maior e o transtorno afetivo bipolar) e doenças neurodegenerativas (i.e. doença de Alzheimer). Entretanto, não há estudos que avaliam o papel desta enzima nos pacientes idosos com depressão maior. Desta maneira, o objetivo principal deste trabalho é avaliar a atividade da GSK-3B em pacientes idosos com depressão maior. A hipótese deste estudo é que a atividade enzimática está aumentada nos pacientes idosos deprimidos em relação a idosos saudáveis. Para este estudo, recrutamos 40 idosos com depressão maior (de acordo com os critérios diagnósticos do DSM-IV) e que não estavam em uso de antidepressivos. O grupo comparativo foi constituído por 13 idosos saudáveis, sem evidências de transtornos cognitivos ou do humor. A gravidade da sintomatologia depressiva foi avaliada pela escala de depressão de Hamilton de 21 itens (HAM-D); o desempenho cognitivo dos pacientes e controles foi avaliado pelo teste cognitivo de Cambridge (CAMCOG) e pelo mini-exame do estado mental (MEEM). A expressão da GSK-3B foi determinada em plaquetas através de ensaio imunoenzimático (EIA), sendo estabelecido os níveis totais da GSK-3B (T-GSK-3B) e de sua forma fosforilada (P-GSK-3B), inativa. A atividade enzimática foi inferida indiretamente pela razão P-GSK- 3B / T-GSK-3B. Nos pacientes idosos com depressão maior, observou-se uma redução significante dos níveis P-GSK-3B (p=0,03) e da razão da GSK- 3B (p=0,03). Os pacientes com sintomatologia depressiva mais grave (HAMD > 21) e déficits cognitivos mais intensos (CAMCOG < 86) apresentaram maior atividade enzimática (p=0,03 e teste, p=0,01, respectivamente). Os resultados deste trabalho sugerem que a atividade da GSK-3B está significantemente aumentada em pacientes idosos com depressão maior e que está alteração é mais pronunciada nos pacientes com sintomatologia depressiva e déficits cognitivos mais graves. Neste contexto, a atividade da GSK-3B pode ser considerada um marcador de estado em pacientes idosos com episódios depressivos mais graves e ser um importante alvo para o desenvolvimento de estratégias terapêuticas para estes quadros / Despite the high prevalence of depressive disorders in the elderly, its main physiopathological mechanisms are largely unknown. In the recent years, most of the research efforts focused on the association between cerebrovascular changes and geriatric depression. Nonetheless, other mechanisms have been studied, such as changes in neurotrophic and inflammatory cascades. The enzyme glycogen synthase kinase 3 beta (GSK- 3B) has been implicated in many mental disorders, in particular affective disorders (i.e. major depression and bipolar disorder) and neurodegenerative disorders (i.e. Alzheimers disease). However, there is no study so far that addressed the role of this enzyme in elderly patients with major depression. Therefore, the main objective of this study was to evaluate if GSK-3B activity is changed in elderly patients with major. The working hypothesis is that enzyme activity is significantly increased in elderly patients with major depression as compared to elderly controls. We recruited 40 elderly patients with current major depressive episode (according to the DSM-IV criteria) that was not under antidepressant treatment. The comparison group included 13 healthy elderly subjects with no evidence of cognitive impairment or major psychiatric disorder. The severity of depressive symptoms was assessed by the Hamilton Depression Scale 21 items; cognitive performance was assessed by the Cambridge Cognitive test (CAMCOG) and the Mini-mental State Examination (MMSE). The levels of total and phosphorylated GSK-3B (T-GSK-3B and P-GSK-3B, respectively) levels were determined in platelets by immunoenzymatic assay (EIA). Enzyme activity was indirectly inferred by the ratio P-GSK-3B / T-GSK-3B. Elderly patients with major depression had a significant reduction in the P-GSK-3B levels (p = 0.03) and GSK-3B ratio (p= 0.03). The patients with severe depressive episode (HAM-D scores above 21 points) and cognitive impairment (CAMCOG scores below 86 points) presented the more significant reduction of GSK-3B ratio (p = 0.03 and p = 0.01, respectively). These data altogether suggest that GSK-3B activity is significantly increased in elderly patients with major depression, in particular in those with more severe depressive episode and worse cognitive performance. In this context, the increased enzyme activity may be regarded as a state marker of severe depressive episodes and may an important target to the development of therapeutic strategies to this disorder