RESUMO
BACKGROUND: Consumer and research activity monitors have become popular because of their ability to quantify energy expenditure (EE) in free-living conditions. However, the accuracy of activity trackers in determining EE in people with Huntington's Disease (HD) is unknown. RESEARCH QUESTION: Can the ActiGraph wGT3X-B or the Fitbit Charge 4 accurately measure energy expenditure during physical activity, in people with HD compared to Indirect Calorimetry (IC) (Medisoft Ergo Card)? METHODS: We conducted a cross-sectional, observational study with fourteen participants with mild-moderate HD (mean age 55.7 ± 11.4 years). All participants wore an ActiGraph and Fitbit during an incremental test, running on a treadmill at 3.2 km/h and 5.2 km/h for three minutes at each speed. We analysed and compared the accuracy of EE estimates obtained by Fitbit and ActiGraph against the EE estimates obtained by a metabolic cart, using with Intra-class correlation (ICC), Bland-Altman analysis and correlation tests. RESULTS: A significant correlation and a moderate reliability was found between ActiGraph and IC for the incremental test (r = 0.667)(ICC=0.633). There was a significant correlation between Fitbit and IC during the incremental test (r = 0.701), but the reliability was poor at all tested speeds in the treadmill walk. Fitbit significantly overestimated EE, and ActiGraph underestimated EE compared to IC, but ActiGraph estimates were more accurate than Fitbit in all tests. SIGNIFICANCE: Compared to IC, Fitbit Charge 4 and ActiGraph wGT3X-BT have reduced accuracy in estimating EE at slower walking speeds. These findings highlight the need for population-specific algorithms and validation of activity trackers.
Assuntos
Monitores de Aptidão Física , Doença de Huntington , Humanos , Adulto , Pessoa de Meia-Idade , Idoso , Reprodutibilidade dos Testes , Estudos Transversais , Acelerometria , Monitorização Ambulatorial , Metabolismo EnergéticoRESUMO
Chronic myelogenous leukemia (CML) is a myeloproliferative disorder characterized at the molecular level by the expression of Bcr-Abl, a chimeric protein with deregulated tyrosine kinase activity. The protein-tyrosine phosphatase 1B (PTP1B) is up-regulated in Bcr-Abl-expressing cells, suggesting a regulatory link between the two proteins. To investigate the interplay between these two proteins, we inhibited the activity of PTP1B in Bcr-Abl-expressing TonB.210 cells by either pharmacological or siRNA means and examined the effects of such inhibition on Bcr-Abl expression and function. Herein we describe a novel mechanism by which the phosphatase activity of PTP1B is required for Bcr-Abl protein stability. Inhibition of PTP1B elicits tyrosine phosphorylation of Bcr-Abl that triggers the degradation of Bcr-Abl through ubiquitination via the lysosomal pathway. The degradation of Bcr-Abl consequently inhibits tyrosine phosphorylation of Bcr-Abl substrates and the downstream production of intracellular reactive oxygen species. Furthermore, PTP1B inhibition reduces cell viability and the IC(50) of the Bcr-Abl inhibitor imatinib mesylate. Degradation of Bcr-Abl via PTP1B inhibition is also observed in human CML cell lines K562 and LAMA-84. These results suggest that inhibition of PTP1B may be a useful strategy to explore in the development of novel therapeutic agents for the treatment of CML, particularly because host drugs currently used in CML such as imatinib focus on inhibiting the kinase activity of Bcr-Abl.
Assuntos
Proteínas de Fusão bcr-abl/metabolismo , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Regulação Leucêmica da Expressão Gênica/efeitos dos fármacos , Leucemia Mielogênica Crônica BCR-ABL Positiva/enzimologia , Proteína Tirosina Fosfatase não Receptora Tipo 1/metabolismo , RNA Interferente Pequeno/farmacologia , Ubiquitinação/efeitos dos fármacos , Benzamidas , Proteínas de Fusão bcr-abl/genética , Regulação Enzimológica da Expressão Gênica/genética , Regulação Leucêmica da Expressão Gênica/genética , Humanos , Mesilato de Imatinib , Células K562 , Leucemia Mielogênica Crônica BCR-ABL Positiva/tratamento farmacológico , Leucemia Mielogênica Crônica BCR-ABL Positiva/genética , Lisossomos/genética , Lisossomos/metabolismo , Piperazinas/farmacologia , Inibidores de Proteínas Quinases/farmacologia , Estabilidade Proteica/efeitos dos fármacos , Proteína Tirosina Fosfatase não Receptora Tipo 1/antagonistas & inibidores , Proteína Tirosina Fosfatase não Receptora Tipo 1/genética , Pirimidinas/farmacologia , RNA Interferente Pequeno/genética , Espécies Reativas de Oxigênio/metabolismo , Ubiquitinação/genéticaRESUMO
In the present study we demonstrated that neurotoxin MPP(+)-induced DNA damage is followed by ataxia telangiectasia muted (ATM) activation either in cerebellar granule cells (CGC) or in B65 cell line. In CGC, the selective ATM inhibitor KU-55933 showed neuroprotective effects against MPP(+)-induced neuronal cell loss and apoptosis, lending support to the key role of ATM in experimental models of Parkinson's disease. Likewise, we showed that knockdown of ATM levels in neuroblastoma B65 cells using an ATM-specific siRNA attenuates the phosphorylation of retinoblastoma protein without affecting other cell-cycle proteins involved in the G(0)/G(1) cell-cycle phase. Moreover, we demonstrated DNA damage, in human brain samples of PD patients. These findings support a model in which MPP(+) leads to ATM activation with a subsequent DNA damage response and activation of pRb. Therefore, this study demonstrates a new link between DNA damage by MPP(+) and cell-cycle re-entry through retinoblastoma protein phosphorylation.
Assuntos
1-Metil-4-Fenil-1,2,3,6-Tetra-Hidropiridina/metabolismo , Proteínas de Ciclo Celular/metabolismo , Cerebelo/citologia , Dano ao DNA/efeitos dos fármacos , Proteínas de Ligação a DNA/metabolismo , Neurotoxinas/farmacologia , Doença de Parkinson/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Supressoras de Tumor/metabolismo , Idoso , Idoso de 80 Anos ou mais , Animais , Apoptose/efeitos dos fármacos , Proteínas Mutadas de Ataxia Telangiectasia , Encéfalo/patologia , Ciclo Celular , Linhagem Celular , Células Cultivadas , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Morfolinas/farmacologia , Pironas/farmacologia , Ratos , Ratos Sprague-DawleyRESUMO
Cytoskeletal alteration is a key factor in neurodegenerative processes like Alzheimer's or Parkinson's disease. Colchicine is a microtubule-disrupting agent that binds to tubuline, inhibiting microtubule assembly, and which triggers apoptosis. The present research describes the transcriptional activation of molecules related to alternative forms of apoptosis, in an acute colchicine model of apoptosis in rat cerebellar granule neurons (CGNs). Treatment with colchicine up-regulated significantly the activity of genes related to oxidative stress: glutathione peroxidase 1 and catalase; altered significantly genes related to cell cycle control (cyclin D1 and cyclin-dependent kinase 2), genes related to classical apoptosis pathway (caspase 3) and a neuronal cell-related gene (pentraxin 1). Colchicine treatment also down-regulated the gene expression of calpain 1. In conclusion, our experiments demonstrate that the cell damage caused by exposure to colchicine activates the classical apoptosis pathway, but also promotes the up-regulation of several genes related to oxidative stress and cell cycle control. Present data may help to a better understanding of the molecular mechanisms involved in cytoskeletal degradation-induced apoptosis in neurons.
Assuntos
Cerebelo/efeitos dos fármacos , Colchicina/toxicidade , Perfilação da Expressão Gênica/métodos , Neurônios/efeitos dos fármacos , Análise de Sequência com Séries de Oligonucleotídeos , Ativação Transcricional/efeitos dos fármacos , Moduladores de Tubulina/toxicidade , Animais , Animais Recém-Nascidos , Apoptose/efeitos dos fármacos , Apoptose/genética , Cálcio/metabolismo , Ciclo Celular/efeitos dos fármacos , Ciclo Celular/genética , Células Cultivadas , Cerebelo/metabolismo , Cerebelo/patologia , Relação Dose-Resposta a Droga , Neurônios/metabolismo , Neurônios/patologia , Estresse Oxidativo/efeitos dos fármacos , Estresse Oxidativo/genética , Ratos , Ratos Sprague-DawleyRESUMO
The mechanisms involved in neuronal loss in Parkinson's disease (PD) are not known, although recent studies performed in PD experimental models suggest that cdk5/p25 plays a predominant role. In the present study, we examined the gyrus cinguli of cases with PD and compared them with age-matched controls, and we demonstrated an activation of the calpain/cdk5 pathway. We found an increase in the p25/p35 immunoreactivity ratio and in the expression of transcription factor E2F-1. Our results implicate the cdk5/p25 pathway and re-entry into the cell cycle in the process of neuronal loss in patients with PD.
Assuntos
Calpaína/metabolismo , Quinase 5 Dependente de Ciclina/metabolismo , Giro do Cíngulo/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Doença de Parkinson/patologia , Transdução de Sinais/fisiologia , Idoso , Idoso de 80 Anos ou mais , Estudos de Casos e Controles , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Doença de Parkinson/metabolismoRESUMO
Whole genome amplification (WGA) has become an invaluable method for preserving limited samples of precious stock material and has been used during the past years as an alternative tool to increase the amount of DNA before library preparation for next-generation sequencing. Myelodysplastic syndromes (MDS) are a group of clonal hematopoietic stem cell disorders characterized by presenting somatic mutations in several myeloid-related genes. In this work, targeted deep sequencing has been performed on four paired fresh DNA and WGA DNA samples from bone marrow of MDS patients, to assess the feasibility of using WGA DNA for detecting somatic mutations. The results of this study highlighted that, in general, the sequencing and alignment statistics of fresh DNA and WGA DNA samples were similar. However, after variant calling and when considering variants detected at all frequencies, there was a high level of discordance between fresh DNA and WGA DNA (overall, a higher number of variants was detected in WGA DNA). After proper filtering, a total of three somatic mutations were detected in the cohort. All somatic mutations detected in fresh DNA were also identified in WGA DNA and validated by whole exome sequencing.
Assuntos
Análise Mutacional de DNA/métodos , DNA/normas , Sequenciamento de Nucleotídeos em Larga Escala/normas , Mutação/genética , Síndromes Mielodisplásicas/genética , Análise de Sequência de DNA/normas , DNA/química , DNA/genética , Análise Mutacional de DNA/normas , HumanosRESUMO
The pharmacological use of new therapeutics is often limited by a safe and effective drug-delivery system. In this sense, new chemical CDK inhibitors are not an exception. Nanotechnology may be able to solve some of the main problems limiting cancer treatments such as more specific delivery of therapeutics and reduction of toxic secondary effects. It provides new delivery systems able to specifically target cancer cells and release the active molecules in a controlled fashion. Specifically, silica mesoporous supports (SMPS) have emerged as an alternative for more classical drug delivery systems based on polymers. In this chapter, we describe the synthesis of a SMPS containing the CDK inhibitor roscovitine as cargo molecule and the protocols for confirmation of the proper cargo release of the nanoparticles in cell culture employing cell viability, cellular internalization, and cell death induction studies.
Assuntos
Quinases Ciclina-Dependentes/antagonistas & inibidores , Sistemas de Liberação de Medicamentos , Inibidores de Proteínas Quinases/administração & dosagem , Purinas/administração & dosagem , Morte Celular , Sobrevivência Celular , Química Farmacêutica/métodos , Avaliação Pré-Clínica de Medicamentos , Células HeLa , Humanos , Cinética , Lisossomos/metabolismo , Teste de Materiais , Nanomedicina/métodos , Nanopartículas/química , Polímeros/química , Roscovitina , Dióxido de Silício/química , TensoativosRESUMO
Experimental data implicate calpain activation in the pathways involved in neuronal apoptosis. Indeed, calpain inhibitors confer neuroprotection in response to various neurotoxic stimuli. However, the pathways involved in calpain activation-induced apoptosis are not well known. We demonstrate that apoptosis (40%) induced by serum/potassium (S/K) withdrawal on cerebellar granule cells (CGNs) is inhibited by selective calpain inhibitors PD150606 (up to 15%) and PD151746 (up to 29%), but not PD145305 in CGNs. zVAD-fmk, a broad spectrum inhibitor of caspases, attenuates apoptosis (up to 20%) mediated by S/K deprivation and protects against cell death, as measured by MTT ([3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium]) assay. PD150606 and PD151746 prevented apoptosis mediated by S/K withdrawal through inhibition of calpain. Furthermore, PD151746 was able to inhibit caspase-3 activity. After S/K withdrawal, we observed an increase in cdk5/p25 formation and MEF2 phosphorylation that was prevented by 40 microM PD150606 and PD151746. This indicates that calpain inhibition may be an upstream molecular target that prevents neuronal apoptosis in vitro. Taken together, these data suggest an apoptotic route in S/K withdrawal in CGNs mediated by calpain activation, cdk5/p25 formation and MEF2 inhibition. Calpain inhibitors may attenuate S/K withdrawal-induced apoptosis and may provide a potential therapeutic target for drug treatment in a neurodegenerative process.
Assuntos
Apoptose/efeitos dos fármacos , Calpaína/antagonistas & inibidores , Cerebelo/citologia , Fatores de Regulação Miogênica/antagonistas & inibidores , Neurônios/efeitos dos fármacos , Animais , Animais Recém-Nascidos , Técnicas de Cultura de Células , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Meios de Cultura , Inibidores Enzimáticos/farmacologia , Fatores de Transcrição MEF2 , Neurônios/metabolismo , Neurônios/patologia , Ratos , Ratos Sprague-DawleyRESUMO
Serum and potassium (S/K) deprivation is a well-known apoptotic model in cerebellar granule neurons (CGNs), used to study the efficacy of potential neuroprotective drugs. The objective of this study was to determine the pathways involved in the neuroprotective role of flavopiridol, a pan-inhibitor of cyclin-dependent kinases (CDKs), upon S/K withdrawal-induced apoptosis in CGNs. Cell death in primary cultures of rat CGNs was accompanied by chromatin condensation and activation of caspases-3, -6, and -9. Caspase-3 activity was also evaluated by cleavage of 120-kDa alpha-spectrin. Flavopiridol (1 microM) prevented caspase activation and abolished apoptotic features mediated by S/K withdrawal. Re-entry in the cell cycle is also involved in apoptotic neuronal cell death. Flavopiridol (1 microM) inhibited DNA synthesis as measured by BrdU incorporation, thus enhancing proliferating cell nuclear antigen expression. Serum/potassium (S/K) deprivation induced apoptotic cell death mediated by the activation of several kinases such as glycogen synthase kinase-3beta and CDK5, as well as the breakdown of p35 in the neurotoxic fragment p25; inactivation of myocyte enhancer factor-2 (MEF2) was also found. Pretreatment with flavopiridol prevented these biochemical and molecular alterations. Taken together, these findings suggest an apoptotic route in CGNs after S/K withdrawal mediated by the activation of several kinases involved in cell cycle deregulation and MEF2 inactivation. We propose that the antiapoptotic properties of flavopiridol are mediated through kinase pathway inhibition.
Assuntos
Apoptose/fisiologia , Cerebelo/fisiologia , Flavonoides/farmacologia , Neurônios/fisiologia , Piperidinas/farmacologia , Potássio/farmacologia , Inibidores de Proteínas Quinases/farmacologia , Animais , Animais Recém-Nascidos , Apoptose/efeitos dos fármacos , Ciclo Celular/efeitos dos fármacos , Quinases Ciclina-Dependentes/antagonistas & inibidores , Citometria de Fluxo , Modelos Neurológicos , Neurônios/citologia , Neurônios/efeitos dos fármacos , Ratos , Ratos Sprague-DawleyRESUMO
Caspase-3 is a key protein involved in the classical apoptosis mechanism in neurons, as in many other cells types. In the present research, we describe the transcriptional activity of caspase-3 gene as a marker of acute toxicity in a primary culture model of rat cerebellar granule neurons (CGNs). CGNs were incubated for 16h in complete medium containing the chemicals at three concentrations (10, 100microM and 1mM). A total of 48 different compounds were tested. Gene transcriptional activity was determined by low-density array assays, and by single Taqman caspase-3 assays. Results from the PCR arrays showed that the caspase-3 gene was up-regulated when CGNs were exposed to neurotoxic chemicals. Significative correlations were found between the transcriptional activity of caspase-3 and the activity of some other genes related to apoptosis, cell-cycle and ROS detoxification. In our experiments, acute exposure of CGNs to well-documented pro-apoptotic xenobiotics modulated significantly caspase-3 gene expression, whereas chemicals not related to apoptosis did not modify caspase-3 gene expression. In conclusion, acute exposure of CGNs to neurotoxic compounds modulates the transcriptional activity of genes involved in the classical apoptotic pathway, oxidative stress and cell-cycle control. Transcriptional activity of caspase-3 correlates significantly with these changes and it could be a good indicator of acute neurotoxicity.
Assuntos
Caspase 3/metabolismo , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Neurotoxinas/toxicidade , Transcrição Gênica/efeitos dos fármacos , Animais , Biomarcadores , Caspase 3/genética , Cerebelo/citologia , Relação Dose-Resposta a Droga , Ratos , Ratos Sprague-DawleyRESUMO
In the present study the role of JAK/STAT and Akt in apoptosis was evaluated in cerebellar granule cells after treatment with the mitochondrial toxin MPP(+). Firstly, we evaluated the role of the prosurvival Akt pathway in MPP(+)-induced apoptosis and found that MPP(+) rapidly reduced the phosphorylation of Akt at Ser473. Since PTEN is an upstream regulator of Akt, its inhibition with bpV(pic) (1-30 µM) should activate Akt, however, it did not attenuate CGC cell death mediated by MPP(+) but protected CGC from apoptosis mediated by S/K deprivation. We also demonstrated that after the treatment with the complex I inhibitor, the expression levels of STAT1 increased and the levels of STAT3 decreased at the time points tested (0.5-8h). Meanwhile, pharmacological inhibition of the JAK/STAT pathway with AG490 (10-40 µM) was neuroprotective, probably due to its antioxidant properties, the Jak2-inhibitor-II potentiated MPP(+) neurotoxicity. Collectively, our data indicate that the treatment of CGC with the neurotoxin MPP(+) decreased two prosurvival pathways: STAT3 and Akt. Meanwhile Akt activation, using a PTEN inhibitor, did not play a prominent role in neuroprotection; loss of STAT3 could be a signal pathway involved in neuroprotection against the Parkinsonian neurotoxin MPP(+).
Assuntos
1-Metil-4-fenilpiridínio/toxicidade , Apoptose/fisiologia , Janus Quinase 2/fisiologia , Neurônios/enzimologia , Proteínas Proto-Oncogênicas c-akt/fisiologia , Transdução de Sinais/fisiologia , Animais , Animais Recém-Nascidos , Apoptose/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/fisiologia , Células Cultivadas , Cerebelo/efeitos dos fármacos , Cerebelo/enzimologia , Janus Quinase 2/antagonistas & inibidores , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/fisiologia , Neurônios/efeitos dos fármacos , Transtornos Parkinsonianos/metabolismo , Transtornos Parkinsonianos/patologia , Ratos , Ratos Sprague-Dawley , Fator de Transcrição STAT1/fisiologia , Fator de Transcrição STAT3/fisiologia , Transdução de Sinais/efeitos dos fármacosRESUMO
Pentachlorophenol (PCP) (C(6)HCl(5)O) is a synthetic toxic organochloride fungicide for humans which exhibit neurotoxic properties. In the present research, we describe the potential pathways implicated in PCP-induced apoptosis in an acute model of toxicity in rat cerebellar granule neurons (CGNs). In our experiments, acute exposure of CGNs to micromolar concentrations of PCP induced the transcriptional activity of genes related to the classical apoptosis pathway (caspase 3, caspase 8, Bad), oxidative stress and glutathione metabolism (glutathione peroxidase-1, catalase, glutathione-S-transferase-3 and superoxide dismutase-1), and mitogenic response (cyclin D1, cdk2, cdk4, cdkn2b). Results from Western blot also shown significative increases in the expression of cyclins D1, E and A and cdk4. The mitogenic response was also related to a significative increase in the phosphorylation of retinoblastoma protein (Rb). PCP would cause apoptosis up-regulating the transcriptional activity of p53 gene and also increasing their activation by phosphorylation, concomitant with a decrease in the sirtuin 1 content. In conclusion, acute exposure of CGNs to PCP induces the classical p53 apoptotic pathway, promotes the up-regulation of several genes related to oxidative stress and the over-expression of molecules involved in the cell cycle control.
Assuntos
Apoptose/fisiologia , Cerebelo/efeitos dos fármacos , Cerebelo/metabolismo , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Pentaclorofenol/toxicidade , Animais , Técnicas de Cultura de Células , Proteínas de Ciclo Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Regulação para Baixo/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Espécies Reativas de Oxigênio/metabolismo , Regulação para Cima/efeitos dos fármacosRESUMO
The aim of the present study was to evaluate the neuroprotective effects of caffeine, an inhibitor of ataxia telangiectasia mutated (ATM) enzyme and an antagonist of adenosine receptors, in two models of apoptosis in cerebellar granule neurons (CGNs): the inhibition of mitochondrial complex I by the neurotoxin MPP(+) and serum and potassium deprivation. We used cerebellar granule neurons because of low glial contamination. Cell viability was measured by the MTT method, and apoptosis was evaluated by assessing DNA fragmentation with flow cytometry or quantification of nuclear condensation. Our data indicate that the neuroprotective effects of caffeine in the MPP+ model of apoptosis are mediated through activation of the ATM/p53 pathway. In addition, caffeine decreased the expression of cyclin D and the transcription factor E2F-1, a regulator of apoptosis in neurons. Caffeine-mediated neuroprotection was not mediated through blockade of adenosine receptors because DPCPX and CGS-15943, two antagonists of these receptors, failed to attenuate apoptosis produced by MPP+ treatment. In addition, caffeine did not exert neuroprotective effects after serum and potassium withdrawal, a p53-independent model of apoptosis. Taken together, our findings indicate that DNA damage/ATM activation is a key component of MPP+-induced apoptosis in CGNs through activation of p53 and reentry into the cell cycle, specifically expression of the transcription factor E2F-1.
Assuntos
Apoptose/efeitos dos fármacos , Cafeína/farmacologia , Cerebelo/citologia , Complexo I de Transporte de Elétrons/metabolismo , Neurônios/efeitos dos fármacos , Fármacos Neuroprotetores/farmacologia , Transdução de Sinais/efeitos dos fármacos , Análise de Variância , Animais , Animais Recém-Nascidos , Proteínas Mutadas de Ataxia Telangiectasia , Proteínas de Ciclo Celular/metabolismo , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Proteínas de Ligação a DNA/metabolismo , Relação Dose-Resposta a Droga , Fator de Transcrição E2F1/metabolismo , Inibidores Enzimáticos/farmacologia , Citometria de Fluxo/métodos , Inibição Neural/efeitos dos fármacos , Proteínas Serina-Treonina Quinases/metabolismo , Ratos , Proteína Supressora de Tumor p53/metabolismo , Proteínas Supressoras de Tumor/metabolismoRESUMO
In this study, the effects of melatonin on MPP+ -treated cerebellar granule neurons (CGNs) in culture were investigated. Results showed that MPP+ treatment significantly decreased cell viability and increased the apoptotic cell population at 24 and 48 hr. Calpain and caspase-3 activation was also determined, with results showing a strong increase in calpain (74%) and caspase 3 activity (70%), as measured by alpha-spectrin cleavage and fluorometric and colorimetric analysis, respectively. There are several studies suggesting that the activation of the cdk5/p35 pathway at its cleavage to cdk5/p25 may play a role in neuronal cell death in neurodegenerative diseases. Moreover, these studies indicate that this cleavage is mediated by calpains, and that MPP+ prompted an increase in cdk5 expression, as well as the cleavage of p35-p25, in a time-dependent manner. 1 mm Melatonin not only reduced the neurotoxic effects of MPP+ on cell viability, but also prevented apoptosis mediated by this Parkinsonian toxin in CGNs. 1 mm Melatonin reduced cdk5 expression, as well as the cleavage of p35-p25. These data indicate that melatonin possesses some neuro-protective properties against MPP+ -induced apoptosis. Moreover, these data suggest that the calpain/cdk5 signaling cascade has a potential role in the MPP+ -mediated apoptotic process in CGNs.