O status epilepticus (SE) é caracterizado por uma crise epiléptica com duração maior que 30 minutos ou crises sucessivas nas quais os níveis de consciência do paciente não são recuperados entre elas. O SE, quando ocorrido durante a infância, pode induzir morte neuronal e levar a alterações comportamentais e cognitivas na idade adulta. O dano cerebral induzido pelo SE têm sido frequentemente relacionado à excitotoxicidade glutamatérgica, principalmente através da hiperestimulação de receptores do tipo NMDA (NMDAR), levando a um excessivo influxo de íons Ca+2 no neurônio, podendo causar morte celular. No presente estudo, investigamos os efeitos de antagonistas de NMDAR sobre a morte neuronal e as alterações comportamentais em animais submetidos ao modelo de SE induzido por LiCl-pilocarpina durante períodos iniciais do desenvolvimento cerebral. Ratos Wistar de 16 dias de vida (P16) receberam uma injeção de pilocarpina (60 mg/kg i.p.) 12-18 h após terem recebido LiCl (3 mEq/kg i.p.). Animais controle receberam salina 0,9%. Na primeira parte deste trabalho, nós investigamos o efeito do antagonista não competitivo e não seletivo de NMDAR, cetamina, administrado após o início das crises, sobre a morte neuronal e as alterações comportamentais induzidas pelo SE. Neste trabalho, observou-se que o SE induzido no início da vida leva a uma expressiva perda neuronal na região CA1 do hipocampo, na habenula, na amigdala e no tálamo 24 após a convulsão. O tratamento com cetamina foi capaz de interromper as convulsões, prevenindo, também, a neurodegeneração. Além disso, o SE induzido em P16 causou aumento nos níveis de ansiedade durante o período adulto, e a intervenção com cetamina foi capaz de reduzir o efeito ansiogênico do SE. Além disso, observou-se um efeito ansiogênico da administração de cetamina per se em animais que não foram submetidos ao SE. Na segunda parte deste estudo, após identificar que o bloqueio de NMDAR é capaz de prevenir os danos a curto e longo prazo induzidos pelo SE, investigamos qual o papel dos NMDAR contendo a subunidade GluN2B na neurodegeneração induzida pelo SE. Neste trabalho, observamos que, diferentemente do bloqueio dos NMDAR através do uso da cetamina, a administração dos antagonistas específicos de NMDAR contendo a subunidade GluN2B, CP-101606 (taxoprodil) e CI-1041 (besonprodil), não foi capaz de terminar as crises convulsivas do SE. No entanto foi eficaz na redução da mortalidade em comparação com os animais SE. Observou-se ainda que diferentemente da cetamina, o bloqueio de NMDAR contendo a subunidade GluN2B não foi capaz de reverter totalmente o dano cerebral induzido pelo SE. Animais que sofreram SE e receberam CI-1041 durante as convulsões apresentaram uma redução na neurodegeneração somente em algumas regiões como hipocampo e amígdala, indicando um efeito neuroprotetor deste composto. No entanto, animais que receberam CP-101606 durante o SE não apresentaram redução na degeneração neuronal nas regiões analisadas. Nossos resultados sugerem, portanto, que o sistema glutamatérgico é um alvo em potencial para o tratamento da neurodegeneração induzida por crises epilépticas prologadas, e que o antagonismo de NMDAR pode servir, pelo menos, como terapia farmacológica complementar em pacientes que sofrem SE durante a infância. Além disso, nossos dados sugerem existir o envolvimento de outras subunidades do NMDAR, além da GluN2B, no dano neuronal induzido pelo SE. / Status epilepticus (SE) is characterized as a prolonged seizure activity or repeated seizures lasting more than 30 min. For immature brains, SE is associated with cellular and behavioral alterations such as neuronal loss and behavioral impairment during adulthood. Brain damage induced by SE has frequently been related to glutamatergic excitotoxicity, mainly through NMDA receptors overstimulation (NMDAR), which can lead to neurodegeneration. In the present study, we investigated the effects of NMDAR antagonists on short- (neuronal death) and long-term (behavioral changes) alterations in animals subjected to SE early in life. Rat pups were injected with LiCl (3 mEq/kg i.p.) 12-18 h prior to pilocarpine (60 mg/kg i.p. - SE group) or saline (0.9%) administration on 16th postnatal day (P16). In the first part of this study, we administered the noncompetitive and non-selective NMDAR antagonist, ketamine, after SE onset to investigate the effect NMDAR blocking on neuronal death and behavioral changes induced SE. We observed that SE induced caused a significant neuronal loss in the CA1 region of the hippocampus, habenula, amygdala and thalamus 24 h after seizures. Treatment with ketamine was able to terminate seizures and to prevent neurodegeneration induced by SE. Moreover, young animal treated with LiCl-pilocarpine presented elevated levels of anxiety at adulthood. Treatment with ketamine prevented this ansiogenic effect of SE. In addition, administration of ketamine alone also induced an increase in anxiety levels in adulthood. In the second part of the study, we investigate the role of NMDAR-containing GluN2B subunit in the neurodegeneration induced by early-life SE. In this work, we found that blocking of NMDAR containing the GluN2B subunit by the compounds CP-101606 (taxoprodil) and CI-1041 (besonprodil) was unable to terminate seizures induced by SE, in contrast to that observed for ketamine treatment. However, treatment with antagonists of NMDAR-containing GluN2B subunit was effective in reducing mortality as compared to SE animals. CP-101606 and CI-1041 treatment were not able to completely reverse the brain damage induced by SE. Animals that were underwent SE and received CI-1041 during seizures presented a reduction in neurodegeneration in some regions such as the hippocampus and amygdala. However, animals that received CP-101606 during SE did not present a reduction in neuronal degeneration in all regions analyzed. Our results therefore suggest that glutamatergic system is a potential target for the treatment of SE, and that antagonism of NMDAR could be used at least as a complementary pharmacotherapy in patients suffering SE during childhood. Furthermore, our data suggest that there is involvement of other NMDAR subunits, beyond GluN2B, in neuronal damage induced by SE.

O status epilepticus (SE) é caracterizado por uma crise epiléptica com duração maior que 30 minutos ou crises sucessivas nas quais os níveis de consciência do paciente não são recuperados entre elas. O SE, quando ocorrido durante a infância, pode induzir morte neuronal e levar a alterações comportamentais e cognitivas na idade adulta. O dano cerebral induzido pelo SE têm sido frequentemente relacionado à excitotoxicidade glutamatérgica, principalmente através da hiperestimulação de receptores do tipo NMDA (NMDAR), levando a um excessivo influxo de íons Ca+2 no neurônio, podendo causar morte celular. No presente estudo, investigamos os efeitos de antagonistas de NMDAR sobre a morte neuronal e as alterações comportamentais em animais submetidos ao modelo de SE induzido por LiCl-pilocarpina durante períodos iniciais do desenvolvimento cerebral. Ratos Wistar de 16 dias de vida (P16) receberam uma injeção de pilocarpina (60 mg/kg i.p.) 12-18 h após terem recebido LiCl (3 mEq/kg i.p.). Animais controle receberam salina 0,9%. Na primeira parte deste trabalho, nós investigamos o efeito do antagonista não competitivo e não seletivo de NMDAR, cetamina, administrado após o início das crises, sobre a morte neuronal e as alterações comportamentais induzidas pelo SE. Neste trabalho, observou-se que o SE induzido no início da vida leva a uma expressiva perda neuronal na região CA1 do hipocampo, na habenula, na amigdala e no tálamo 24 após a convulsão. O tratamento com cetamina foi capaz de interromper as convulsões, prevenindo, também, a neurodegeneração. Além disso, o SE induzido em P16 causou aumento nos níveis de ansiedade durante o período adulto, e a intervenção com cetamina foi capaz de reduzir o efeito ansiogênico do SE. Além disso, observou-se um efeito ansiogênico da administração de cetamina per se em animais que não foram submetidos ao SE. Na segunda parte deste estudo, após identificar que o bloqueio de NMDAR é capaz de prevenir os danos a curto e longo prazo induzidos pelo SE, investigamos qual o papel dos NMDAR contendo a subunidade GluN2B na neurodegeneração induzida pelo SE. Neste trabalho, observamos que, diferentemente do bloqueio dos NMDAR através do uso da cetamina, a administração dos antagonistas específicos de NMDAR contendo a subunidade GluN2B, CP-101606 (taxoprodil) e CI-1041 (besonprodil), não foi capaz de terminar as crises convulsivas do SE. No entanto foi eficaz na redução da mortalidade em comparação com os animais SE. Observou-se ainda que diferentemente da cetamina, o bloqueio de NMDAR contendo a subunidade GluN2B não foi capaz de reverter totalmente o dano cerebral induzido pelo SE. Animais que sofreram SE e receberam CI-1041 durante as convulsões apresentaram uma redução na neurodegeneração somente em algumas regiões como hipocampo e amígdala, indicando um efeito neuroprotetor deste composto. No entanto, animais que receberam CP-101606 durante o SE não apresentaram redução na degeneração neuronal nas regiões analisadas. Nossos resultados sugerem, portanto, que o sistema glutamatérgico é um alvo em potencial para o tratamento da neurodegeneração induzida por crises epilépticas prologadas, e que o antagonismo de NMDAR pode servir, pelo menos, como terapia farmacológica complementar em pacientes que sofrem SE durante a infância. Além disso, nossos dados sugerem existir o envolvimento de outras subunidades do NMDAR, além da GluN2B, no dano neuronal induzido pelo SE. / Status epilepticus (SE) is characterized as a prolonged seizure activity or repeated seizures lasting more than 30 min. For immature brains, SE is associated with cellular and behavioral alterations such as neuronal loss and behavioral impairment during adulthood. Brain damage induced by SE has frequently been related to glutamatergic excitotoxicity, mainly through NMDA receptors overstimulation (NMDAR), which can lead to neurodegeneration. In the present study, we investigated the effects of NMDAR antagonists on short- (neuronal death) and long-term (behavioral changes) alterations in animals subjected to SE early in life. Rat pups were injected with LiCl (3 mEq/kg i.p.) 12-18 h prior to pilocarpine (60 mg/kg i.p. - SE group) or saline (0.9%) administration on 16th postnatal day (P16). In the first part of this study, we administered the noncompetitive and non-selective NMDAR antagonist, ketamine, after SE onset to investigate the effect NMDAR blocking on neuronal death and behavioral changes induced SE. We observed that SE induced caused a significant neuronal loss in the CA1 region of the hippocampus, habenula, amygdala and thalamus 24 h after seizures. Treatment with ketamine was able to terminate seizures and to prevent neurodegeneration induced by SE. Moreover, young animal treated with LiCl-pilocarpine presented elevated levels of anxiety at adulthood. Treatment with ketamine prevented this ansiogenic effect of SE. In addition, administration of ketamine alone also induced an increase in anxiety levels in adulthood. In the second part of the study, we investigate the role of NMDAR-containing GluN2B subunit in the neurodegeneration induced by early-life SE. In this work, we found that blocking of NMDAR containing the GluN2B subunit by the compounds CP-101606 (taxoprodil) and CI-1041 (besonprodil) was unable to terminate seizures induced by SE, in contrast to that observed for ketamine treatment. However, treatment with antagonists of NMDAR-containing GluN2B subunit was effective in reducing mortality as compared to SE animals. CP-101606 and CI-1041 treatment were not able to completely reverse the brain damage induced by SE. Animals that were underwent SE and received CI-1041 during seizures presented a reduction in neurodegeneration in some regions such as the hippocampus and amygdala. However, animals that received CP-101606 during SE did not present a reduction in neuronal degeneration in all regions analyzed. Our results therefore suggest that glutamatergic system is a potential target for the treatment of SE, and that antagonism of NMDAR could be used at least as a complementary pharmacotherapy in patients suffering SE during childhood. Furthermore, our data suggest that there is involvement of other NMDAR subunits, beyond GluN2B, in neuronal damage induced by SE.

O RAGE é um receptor transmembrana, imunoglobulina-like que existe em múltiplas isoformas e interage com um amplo repertório de ligantes extracelulares. O RAGE é expresso em níveis baixos na maioria das células, porém o aumento da presença de seus ligantes no domínio extracelular faz com que o RAGE inicie uma cascata de sinalização intracelular complexa, resultando em estresse oxidativo, ativação do fator de transcrição NF-B, aumento da expressão de citocinas, além da indução de sua própria expressão. O envolvimento do RAGE neste amplo espectro de sinalização vincula este receptor a diversas condições patológicas. Nesta tese utilizamos 3 modelos experimentais que induzem inflamação sistêmica (Leishmania amazonensis, Lipopolissacarídeo e sepse) e 1 modelo experimental que mimetiza a denervação neuronal (modelos experimentais in vivo). Além disso utilizamos diferentes abordagens de bloqueio do RAGE a fim de elucidar a função deste receptor. Com base em nossos resultados os modelos experimentais foram eficientes em induzir o aumento do RAGE e sua sinalização no sistema nervoso central, desencadeando a síntese e liberação de moléculas pró-inflamatórias e o aumento do estresse oxidativo, culminando em neuroinflamação e neurodegeneração. As intervenções de bloqueio do RAGE foram eficientes em inibir as vias de sinalização intracelular mediadas pelo receptor, comprovando a via de ação. Levando em conta nossos principais resultados concluímos que: a) RAGE atua como mediador da perda neuronal em resposta ao insulto inflamatório em diversas estruturas do SNC, b) está presente no corpo dos neurônios dopaminérgicos e envolvido na morte destes neurônios; c) o aumento do RAGE é tempo-dependente e a morte dos neurônios está vinculada a ação deste receptor. / RAGE is a transmembrane, immunoglobulin-like receptor that exists in multiple isoforms and interacts with a broad repertoire of extracellular ligands. RAGE is expressed at low levels in most cells, but the increased presence of its ligands initiates a complex intracellular signaling cascade resulting in oxidative stress, activation of transcription factor NF-B, increased expression of cytokines in addition to concomitant upregulation of RAGE itself. In this thesis we used 3 experimental models which induce systemic inflammation (Leishmania amazonensis, Lipopolysaccharide and sepsis) and 1 experimental model that mimics neuronal denervation (experimental models in vivo). In addition, different approaches to block RAGE were used to elucidate the function of this receptor. Based on our results the experimental models were efficient in inducing the increase of RAGE and its signaling in the central nervous system, triggering the synthesis and release of proinflammatory molecules and the increase of oxidative stress, culminating in neuroinflammation and neurodegeneration. The RAGE blocking interventions were effective in inhibiting receptor-mediated signaling, proving the signaling pathway. Considering our main results, we conclude that: a) RAGE acts as a mediator of neuronal loss triggered by inflammatory insults in various CNS structures; b) RAGE is present in the body of dopaminergic neurons and is involved in the death of these neurons; c) the increase of RAGE is time-dependent, and the neuronal death is dependent on the action of this receptor.

O status epilepticus (SE) é caracterizado por uma crise epiléptica com duração maior que 30 minutos ou crises sucessivas nas quais os níveis de consciência do paciente não são recuperados entre elas. O SE, quando ocorrido durante a infância, pode induzir morte neuronal e levar a alterações comportamentais e cognitivas na idade adulta. O dano cerebral induzido pelo SE têm sido frequentemente relacionado à excitotoxicidade glutamatérgica, principalmente através da hiperestimulação de receptores do tipo NMDA (NMDAR), levando a um excessivo influxo de íons Ca+2 no neurônio, podendo causar morte celular. No presente estudo, investigamos os efeitos de antagonistas de NMDAR sobre a morte neuronal e as alterações comportamentais em animais submetidos ao modelo de SE induzido por LiCl-pilocarpina durante períodos iniciais do desenvolvimento cerebral. Ratos Wistar de 16 dias de vida (P16) receberam uma injeção de pilocarpina (60 mg/kg i.p.) 12-18 h após terem recebido LiCl (3 mEq/kg i.p.). Animais controle receberam salina 0,9%. Na primeira parte deste trabalho, nós investigamos o efeito do antagonista não competitivo e não seletivo de NMDAR, cetamina, administrado após o início das crises, sobre a morte neuronal e as alterações comportamentais induzidas pelo SE. Neste trabalho, observou-se que o SE induzido no início da vida leva a uma expressiva perda neuronal na região CA1 do hipocampo, na habenula, na amigdala e no tálamo 24 após a convulsão. O tratamento com cetamina foi capaz de interromper as convulsões, prevenindo, também, a neurodegeneração. Além disso, o SE induzido em P16 causou aumento nos níveis de ansiedade durante o período adulto, e a intervenção com cetamina foi capaz de reduzir o efeito ansiogênico do SE. Além disso, observou-se um efeito ansiogênico da administração de cetamina per se em animais que não foram submetidos ao SE. Na segunda parte deste estudo, após identificar que o bloqueio de NMDAR é capaz de prevenir os danos a curto e longo prazo induzidos pelo SE, investigamos qual o papel dos NMDAR contendo a subunidade GluN2B na neurodegeneração induzida pelo SE. Neste trabalho, observamos que, diferentemente do bloqueio dos NMDAR através do uso da cetamina, a administração dos antagonistas específicos de NMDAR contendo a subunidade GluN2B, CP-101606 (taxoprodil) e CI-1041 (besonprodil), não foi capaz de terminar as crises convulsivas do SE. No entanto foi eficaz na redução da mortalidade em comparação com os animais SE. Observou-se ainda que diferentemente da cetamina, o bloqueio de NMDAR contendo a subunidade GluN2B não foi capaz de reverter totalmente o dano cerebral induzido pelo SE. Animais que sofreram SE e receberam CI-1041 durante as convulsões apresentaram uma redução na neurodegeneração somente em algumas regiões como hipocampo e amígdala, indicando um efeito neuroprotetor deste composto. No entanto, animais que receberam CP-101606 durante o SE não apresentaram redução na degeneração neuronal nas regiões analisadas. Nossos resultados sugerem, portanto, que o sistema glutamatérgico é um alvo em potencial para o tratamento da neurodegeneração induzida por crises epilépticas prologadas, e que o antagonismo de NMDAR pode servir, pelo menos, como terapia farmacológica complementar em pacientes que sofrem SE durante a infância. Além disso, nossos dados sugerem existir o envolvimento de outras subunidades do NMDAR, além da GluN2B, no dano neuronal induzido pelo SE. / Status epilepticus (SE) is characterized as a prolonged seizure activity or repeated seizures lasting more than 30 min. For immature brains, SE is associated with cellular and behavioral alterations such as neuronal loss and behavioral impairment during adulthood. Brain damage induced by SE has frequently been related to glutamatergic excitotoxicity, mainly through NMDA receptors overstimulation (NMDAR), which can lead to neurodegeneration. In the present study, we investigated the effects of NMDAR antagonists on short- (neuronal death) and long-term (behavioral changes) alterations in animals subjected to SE early in life. Rat pups were injected with LiCl (3 mEq/kg i.p.) 12-18 h prior to pilocarpine (60 mg/kg i.p. - SE group) or saline (0.9%) administration on 16th postnatal day (P16). In the first part of this study, we administered the noncompetitive and non-selective NMDAR antagonist, ketamine, after SE onset to investigate the effect NMDAR blocking on neuronal death and behavioral changes induced SE. We observed that SE induced caused a significant neuronal loss in the CA1 region of the hippocampus, habenula, amygdala and thalamus 24 h after seizures. Treatment with ketamine was able to terminate seizures and to prevent neurodegeneration induced by SE. Moreover, young animal treated with LiCl-pilocarpine presented elevated levels of anxiety at adulthood. Treatment with ketamine prevented this ansiogenic effect of SE. In addition, administration of ketamine alone also induced an increase in anxiety levels in adulthood. In the second part of the study, we investigate the role of NMDAR-containing GluN2B subunit in the neurodegeneration induced by early-life SE. In this work, we found that blocking of NMDAR containing the GluN2B subunit by the compounds CP-101606 (taxoprodil) and CI-1041 (besonprodil) was unable to terminate seizures induced by SE, in contrast to that observed for ketamine treatment. However, treatment with antagonists of NMDAR-containing GluN2B subunit was effective in reducing mortality as compared to SE animals. CP-101606 and CI-1041 treatment were not able to completely reverse the brain damage induced by SE. Animals that were underwent SE and received CI-1041 during seizures presented a reduction in neurodegeneration in some regions such as the hippocampus and amygdala. However, animals that received CP-101606 during SE did not present a reduction in neuronal degeneration in all regions analyzed. Our results therefore suggest that glutamatergic system is a potential target for the treatment of SE, and that antagonism of NMDAR could be used at least as a complementary pharmacotherapy in patients suffering SE during childhood. Furthermore, our data suggest that there is involvement of other NMDAR subunits, beyond GluN2B, in neuronal damage induced by SE.

O RAGE é um receptor transmembrana, imunoglobulina-like que existe em múltiplas isoformas e interage com um amplo repertório de ligantes extracelulares. O RAGE é expresso em níveis baixos na maioria das células, porém o aumento da presença de seus ligantes no domínio extracelular faz com que o RAGE inicie uma cascata de sinalização intracelular complexa, resultando em estresse oxidativo, ativação do fator de transcrição NF-B, aumento da expressão de citocinas, além da indução de sua própria expressão. O envolvimento do RAGE neste amplo espectro de sinalização vincula este receptor a diversas condições patológicas. Nesta tese utilizamos 3 modelos experimentais que induzem inflamação sistêmica (Leishmania amazonensis, Lipopolissacarídeo e sepse) e 1 modelo experimental que mimetiza a denervação neuronal (modelos experimentais in vivo). Além disso utilizamos diferentes abordagens de bloqueio do RAGE a fim de elucidar a função deste receptor. Com base em nossos resultados os modelos experimentais foram eficientes em induzir o aumento do RAGE e sua sinalização no sistema nervoso central, desencadeando a síntese e liberação de moléculas pró-inflamatórias e o aumento do estresse oxidativo, culminando em neuroinflamação e neurodegeneração. As intervenções de bloqueio do RAGE foram eficientes em inibir as vias de sinalização intracelular mediadas pelo receptor, comprovando a via de ação. Levando em conta nossos principais resultados concluímos que: a) RAGE atua como mediador da perda neuronal em resposta ao insulto inflamatório em diversas estruturas do SNC, b) está presente no corpo dos neurônios dopaminérgicos e envolvido na morte destes neurônios; c) o aumento do RAGE é tempo-dependente e a morte dos neurônios está vinculada a ação deste receptor. / RAGE is a transmembrane, immunoglobulin-like receptor that exists in multiple isoforms and interacts with a broad repertoire of extracellular ligands. RAGE is expressed at low levels in most cells, but the increased presence of its ligands initiates a complex intracellular signaling cascade resulting in oxidative stress, activation of transcription factor NF-B, increased expression of cytokines in addition to concomitant upregulation of RAGE itself. In this thesis we used 3 experimental models which induce systemic inflammation (Leishmania amazonensis, Lipopolysaccharide and sepsis) and 1 experimental model that mimics neuronal denervation (experimental models in vivo). In addition, different approaches to block RAGE were used to elucidate the function of this receptor. Based on our results the experimental models were efficient in inducing the increase of RAGE and its signaling in the central nervous system, triggering the synthesis and release of proinflammatory molecules and the increase of oxidative stress, culminating in neuroinflammation and neurodegeneration. The RAGE blocking interventions were effective in inhibiting receptor-mediated signaling, proving the signaling pathway. Considering our main results, we conclude that: a) RAGE acts as a mediator of neuronal loss triggered by inflammatory insults in various CNS structures; b) RAGE is present in the body of dopaminergic neurons and is involved in the death of these neurons; c) the increase of RAGE is time-dependent, and the neuronal death is dependent on the action of this receptor.

The dopaminergic neurodegeneration in the substantia nigra pars compacta (SNpc) is responsible for the marked motor impairment observed in Parkinson's disease (PD). However, the molecular mechanisms underlying this are not completely understood. Since by the time of diagnosis, 50-70% of the dopaminergic neurons of the nigrostriatal pathway have already been degenerated, it is difficult to investigate the early-stage events of disease pathogenesis. Due to inaccessibility of the human brain to study initial pathogenic mechanisms of the disease, experimental models have been developed in an attempt to elucidate PD etiology and its progression. Nevertheless, PD models are a controversial issue in neuroscience research since it is challenging to mimic human neuronal complexity. Therefore, the lack of optimal models that recreate disease pathology is one of the causes of failure of clinical trials that have attempted to find new/better PD therapies. Taking this in consideration, the development of more suitable models is necessary to improve our knowledge regarding PD etiological mechanisms. Additionally, the understanding of the advantages and disadvantages of models already established would also be beneficial for PD research, which our group addressed by reviewing this subject. Considering this, we chose SH-SY5Y cells as a PD model for our studies. To investigate the initial stages of PD-induced neurodegeneration, our work focused in the role of cofilin-1, a protein involved in mitochondrial dysfunction caused by oxidant-induced-apoptosis, which are two pathogenic processes strongly related to PD. Hence, in the thesis, we aimed to validate the use of retinoic-acid-(RA)-differentiated SH-SY5Y cells as an in vitro model and use it to investigate the potential role of cofilin-1 in the initial molecular and cellular mechanisms of PD. Although SH-SY5Y cells are widely used in PD research, their major drawback is their lack of important neuronal features, such as low levels of proliferation and stellate morphology. On the other hand, SH-SY5Y cells can acquire a neuronal phenotype when treated with differentiation agents such as RA. Since several protocols have been described, the consequence of which may be the discrepancies observed among studies regarding neuronal and dopaminergic features. In Chapter I, we aimed to validate a RA-differentiation protocol for SH-SY5Y cells previously established by our research group, focusing upon characterization of neuronal features and its subsequent response to 6-hydroxydopamine (6-OHDA), a toxin widely used to induce dopaminergic degeneration. RA-differentiated SH-SY5Y cells have low proliferative rates, a pronounced neuronal morphology and high expression of genes related to synapse vesicle cycle, dopamine synthesis/degradation, and dopamine transporter (DAT). After exploring phenotypic differences between these two models, we verified that RA-differentiated cells were more sensitive to 6-OHDA toxicity than undifferentiated cells, which could be related to an increase of DAT immunocontent. Many lines of evidence have showed that DAT is responsible for 6-OHDA uptake in vivo. Once inside the neuron, 6-OHDA underwent auto-oxidation causing a significant increase in oxidative stress. However, toxin uptake is not an essential step in undifferentiated SH-SY5Y cells, as auto-oxidation occurs extracellularly. We showed here, for the first time, that RA-differentiated SH-SY5Y cells can mimic, at least in part, an important mechanism of the 6-OHDA-induced cell death found in previous in vivo studies. Hence, the cellular model established by our research group presents essential neuronal features, being a suitable model for PD research. In Chapter II, RA-differentiated SH-SY5Y cells were used as cellular model to investigate disease molecular mechanisms, focusing upon cofilin-1. Our previous data have shown that oxidation of non-phosphorylate (activated) cofilin-1 leads to mitochondrial dysfunction and cell death induced by apoptosis in tumour cells. Here we found that cofilin-1 played a role in early stages of neuronal apoptosis induced by 6-OHDA in our cellular model since cofilin-1 mitochondrial translocation precedes organelle dysfunction. Overexpression of wild type CFL1 resulted in increased sensitivity of SH-SY5Y cells to 6-OHDA-induced neuronal cell death. Furthermore, overexpression of non-oxidizable CFL1 containing Cys-to-Ala mutations (positions 39, 80 and 139) increased neuronal resistance to this toxin, suggesting that oxidation is an important step in 6-OHDA toxicity. Follow-up experiments were performed in order to evaluate clinically whether cofilin-1 pathway proteins content is altered in PD post mortem human brain. Our findings showed a significant decrease in p-cofilin-1/cofilin-1 ratio in PD patients, which indicates an increase in the amount of activated cofilin-1 available for oxidation. Moreover, through principal component analysis, the immunodetection of cofilin-1 pathway proteins were able to discriminate controls and PD individuals during the early-stage of neuropathological changings. Hence, we demonstrated, for the first time, a possible role for cofilin-1 in PD pathogenesis and its potential use as biomarker. Taken together, our data showed that RA-differentiated SH-SY5Y cells present terminally-differentiated dopaminergic neuron features, that are essential to mimic dopaminergic neurons. By using this cellular model and post mortem brain tissue, we also demonstrated a possible role for cofilin-1 in early steps of the neurodegeneration process found in PD, which it could impact drug and biomarker discovery researches.

The dopaminergic neurodegeneration in the substantia nigra pars compacta (SNpc) is responsible for the marked motor impairment observed in Parkinson's disease (PD). However, the molecular mechanisms underlying this are not completely understood. Since by the time of diagnosis, 50-70% of the dopaminergic neurons of the nigrostriatal pathway have already been degenerated, it is difficult to investigate the early-stage events of disease pathogenesis. Due to inaccessibility of the human brain to study initial pathogenic mechanisms of the disease, experimental models have been developed in an attempt to elucidate PD etiology and its progression. Nevertheless, PD models are a controversial issue in neuroscience research since it is challenging to mimic human neuronal complexity. Therefore, the lack of optimal models that recreate disease pathology is one of the causes of failure of clinical trials that have attempted to find new/better PD therapies. Taking this in consideration, the development of more suitable models is necessary to improve our knowledge regarding PD etiological mechanisms. Additionally, the understanding of the advantages and disadvantages of models already established would also be beneficial for PD research, which our group addressed by reviewing this subject. Considering this, we chose SH-SY5Y cells as a PD model for our studies. To investigate the initial stages of PD-induced neurodegeneration, our work focused in the role of cofilin-1, a protein involved in mitochondrial dysfunction caused by oxidant-induced-apoptosis, which are two pathogenic processes strongly related to PD. Hence, in the thesis, we aimed to validate the use of retinoic-acid-(RA)-differentiated SH-SY5Y cells as an in vitro model and use it to investigate the potential role of cofilin-1 in the initial molecular and cellular mechanisms of PD. Although SH-SY5Y cells are widely used in PD research, their major drawback is their lack of important neuronal features, such as low levels of proliferation and stellate morphology. On the other hand, SH-SY5Y cells can acquire a neuronal phenotype when treated with differentiation agents such as RA. Since several protocols have been described, the consequence of which may be the discrepancies observed among studies regarding neuronal and dopaminergic features. In Chapter I, we aimed to validate a RA-differentiation protocol for SH-SY5Y cells previously established by our research group, focusing upon characterization of neuronal features and its subsequent response to 6-hydroxydopamine (6-OHDA), a toxin widely used to induce dopaminergic degeneration. RA-differentiated SH-SY5Y cells have low proliferative rates, a pronounced neuronal morphology and high expression of genes related to synapse vesicle cycle, dopamine synthesis/degradation, and dopamine transporter (DAT). After exploring phenotypic differences between these two models, we verified that RA-differentiated cells were more sensitive to 6-OHDA toxicity than undifferentiated cells, which could be related to an increase of DAT immunocontent. Many lines of evidence have showed that DAT is responsible for 6-OHDA uptake in vivo. Once inside the neuron, 6-OHDA underwent auto-oxidation causing a significant increase in oxidative stress. However, toxin uptake is not an essential step in undifferentiated SH-SY5Y cells, as auto-oxidation occurs extracellularly. We showed here, for the first time, that RA-differentiated SH-SY5Y cells can mimic, at least in part, an important mechanism of the 6-OHDA-induced cell death found in previous in vivo studies. Hence, the cellular model established by our research group presents essential neuronal features, being a suitable model for PD research. In Chapter II, RA-differentiated SH-SY5Y cells were used as cellular model to investigate disease molecular mechanisms, focusing upon cofilin-1. Our previous data have shown that oxidation of non-phosphorylate (activated) cofilin-1 leads to mitochondrial dysfunction and cell death induced by apoptosis in tumour cells. Here we found that cofilin-1 played a role in early stages of neuronal apoptosis induced by 6-OHDA in our cellular model since cofilin-1 mitochondrial translocation precedes organelle dysfunction. Overexpression of wild type CFL1 resulted in increased sensitivity of SH-SY5Y cells to 6-OHDA-induced neuronal cell death. Furthermore, overexpression of non-oxidizable CFL1 containing Cys-to-Ala mutations (positions 39, 80 and 139) increased neuronal resistance to this toxin, suggesting that oxidation is an important step in 6-OHDA toxicity. Follow-up experiments were performed in order to evaluate clinically whether cofilin-1 pathway proteins content is altered in PD post mortem human brain. Our findings showed a significant decrease in p-cofilin-1/cofilin-1 ratio in PD patients, which indicates an increase in the amount of activated cofilin-1 available for oxidation. Moreover, through principal component analysis, the immunodetection of cofilin-1 pathway proteins were able to discriminate controls and PD individuals during the early-stage of neuropathological changings. Hence, we demonstrated, for the first time, a possible role for cofilin-1 in PD pathogenesis and its potential use as biomarker. Taken together, our data showed that RA-differentiated SH-SY5Y cells present terminally-differentiated dopaminergic neuron features, that are essential to mimic dopaminergic neurons. By using this cellular model and post mortem brain tissue, we also demonstrated a possible role for cofilin-1 in early steps of the neurodegeneration process found in PD, which it could impact drug and biomarker discovery researches.

The dopaminergic neurodegeneration in the substantia nigra pars compacta (SNpc) is responsible for the marked motor impairment observed in Parkinson's disease (PD). However, the molecular mechanisms underlying this are not completely understood. Since by the time of diagnosis, 50-70% of the dopaminergic neurons of the nigrostriatal pathway have already been degenerated, it is difficult to investigate the early-stage events of disease pathogenesis. Due to inaccessibility of the human brain to study initial pathogenic mechanisms of the disease, experimental models have been developed in an attempt to elucidate PD etiology and its progression. Nevertheless, PD models are a controversial issue in neuroscience research since it is challenging to mimic human neuronal complexity. Therefore, the lack of optimal models that recreate disease pathology is one of the causes of failure of clinical trials that have attempted to find new/better PD therapies. Taking this in consideration, the development of more suitable models is necessary to improve our knowledge regarding PD etiological mechanisms. Additionally, the understanding of the advantages and disadvantages of models already established would also be beneficial for PD research, which our group addressed by reviewing this subject. Considering this, we chose SH-SY5Y cells as a PD model for our studies. To investigate the initial stages of PD-induced neurodegeneration, our work focused in the role of cofilin-1, a protein involved in mitochondrial dysfunction caused by oxidant-induced-apoptosis, which are two pathogenic processes strongly related to PD. Hence, in the thesis, we aimed to validate the use of retinoic-acid-(RA)-differentiated SH-SY5Y cells as an in vitro model and use it to investigate the potential role of cofilin-1 in the initial molecular and cellular mechanisms of PD. Although SH-SY5Y cells are widely used in PD research, their major drawback is their lack of important neuronal features, such as low levels of proliferation and stellate morphology. On the other hand, SH-SY5Y cells can acquire a neuronal phenotype when treated with differentiation agents such as RA. Since several protocols have been described, the consequence of which may be the discrepancies observed among studies regarding neuronal and dopaminergic features. In Chapter I, we aimed to validate a RA-differentiation protocol for SH-SY5Y cells previously established by our research group, focusing upon characterization of neuronal features and its subsequent response to 6-hydroxydopamine (6-OHDA), a toxin widely used to induce dopaminergic degeneration. RA-differentiated SH-SY5Y cells have low proliferative rates, a pronounced neuronal morphology and high expression of genes related to synapse vesicle cycle, dopamine synthesis/degradation, and dopamine transporter (DAT). After exploring phenotypic differences between these two models, we verified that RA-differentiated cells were more sensitive to 6-OHDA toxicity than undifferentiated cells, which could be related to an increase of DAT immunocontent. Many lines of evidence have showed that DAT is responsible for 6-OHDA uptake in vivo. Once inside the neuron, 6-OHDA underwent auto-oxidation causing a significant increase in oxidative stress. However, toxin uptake is not an essential step in undifferentiated SH-SY5Y cells, as auto-oxidation occurs extracellularly. We showed here, for the first time, that RA-differentiated SH-SY5Y cells can mimic, at least in part, an important mechanism of the 6-OHDA-induced cell death found in previous in vivo studies. Hence, the cellular model established by our research group presents essential neuronal features, being a suitable model for PD research. In Chapter II, RA-differentiated SH-SY5Y cells were used as cellular model to investigate disease molecular mechanisms, focusing upon cofilin-1. Our previous data have shown that oxidation of non-phosphorylate (activated) cofilin-1 leads to mitochondrial dysfunction and cell death induced by apoptosis in tumour cells. Here we found that cofilin-1 played a role in early stages of neuronal apoptosis induced by 6-OHDA in our cellular model since cofilin-1 mitochondrial translocation precedes organelle dysfunction. Overexpression of wild type CFL1 resulted in increased sensitivity of SH-SY5Y cells to 6-OHDA-induced neuronal cell death. Furthermore, overexpression of non-oxidizable CFL1 containing Cys-to-Ala mutations (positions 39, 80 and 139) increased neuronal resistance to this toxin, suggesting that oxidation is an important step in 6-OHDA toxicity. Follow-up experiments were performed in order to evaluate clinically whether cofilin-1 pathway proteins content is altered in PD post mortem human brain. Our findings showed a significant decrease in p-cofilin-1/cofilin-1 ratio in PD patients, which indicates an increase in the amount of activated cofilin-1 available for oxidation. Moreover, through principal component analysis, the immunodetection of cofilin-1 pathway proteins were able to discriminate controls and PD individuals during the early-stage of neuropathological changings. Hence, we demonstrated, for the first time, a possible role for cofilin-1 in PD pathogenesis and its potential use as biomarker. Taken together, our data showed that RA-differentiated SH-SY5Y cells present terminally-differentiated dopaminergic neuron features, that are essential to mimic dopaminergic neurons. By using this cellular model and post mortem brain tissue, we also demonstrated a possible role for cofilin-1 in early steps of the neurodegeneration process found in PD, which it could impact drug and biomarker discovery researches.