Endoplasmic reticulum-mitochondrial dysfunctions induced by inhibition of protein phosphatase 2A and the astrocytic role in neuroprotection in neurodegenerative diseases

As doenças neurodegenerativas constituem um grupo de doenças marcadas pela progressiva morte neuronal e consequente disfunção cognitiva. A prevalência dessas patologias tem aumentado rapidamente com o crescimento da expectativa de vida da população, fazendo do desenvolvimento de tratamentos efetivos e métodos de diagnóstico precoce uma questão de saúde pública a nível global. Entretanto, a evolução dessas pesquisas aparece como um grande desafio, visto a grande variedade de apresentações clínicas e distintos achados neuropatológicos presentes nessas doenças, tornando ainda mais difícil a compreensão dos mecanismos envolvidos na patogênese e evolução de seus processos neurodegenerativos. Alguns achados comuns à maior parte desses distúrbios e ainda pouco esclarecidos são a redução no metabolismo energético celular e disfunções na proteostase celular que levam ao acúmulo de diferentes proteínas patológicas. Na presente tese, avançamos na elucidação das alterações presentes nos circuitos de sinalização desses mecanismos e no entendimento da associação destes com outro achado frequente nas doenças neurodegenerativas: a redução da atividade da proteína fosfatase 2A (PP2A). Além disso, também ampliamos o entendimento sobre possíveis mecanismos neuroprotetores para esses distúrbios, demonstrando a necessidade de modular a interação astrócito-neurônio para a ação preventiva alcançada no tratamento com memantina em nosso modelo de inibição da atividade da PP2A. Dessa forma, buscamos progredir no contexto da busca por um diagnóstico precoce e por tratamentos eficazes para as doenças neurodegenerativas.Neurodegenerative diseases are a group of disorders marked by progressive neuronal death and consequent cognitive dysfunction. The prevalence of these pathologies has raised rapidly with the increase in the life expectancy of the population, making the development of effective treatments and methods of early diagnosis a public health issue at a global level. However, the evolution of these researches presents a challenge, considering the great variety of clinical presentations and different neuropathological findings present in these diseases, making it even more difficult to understand the mechanisms involved in the pathogenesis and evolution of their neurodegenerative processes. Some findings common to most of these disorders and still unclear are the reduction in cellular energy metabolism and dysfunctions in the cellular proteostase that lead to the accumulation of different pathological proteins. In the present thesis, we advanced the elucidation of the alterations present in the signaling circuits of these mechanisms and in the understanding of the association of these with another frequent finding in the neurodegenerative diseases: the reduced activity of protein phosphatase 2A (PP2A). In addition, we also broadened our understanding of possible neuroprotective mechanisms for these disorders, demonstrating the need to modulate the neuron-astrocyte interaction for the preventive action achieved in the treatment with memantine in our model of inhibition of PP2A activity. Thus, we seek to progress in the context of the search for an early diagnosis and effective treatments for neurodegenerative diseases

Peripheral oxidative stress biomarkers in spinocerebellar ataxia type 3/Machado–Joseph disease

Objectives: Spinocerebellar ataxia type 3/Machado–Joseph disease (SCA3/MJD) is a polyglutamine disorder with no current disease-modifying treatment. Conformational changes in mutant ataxin-3 trigger different pathogenic cascades, including reactive oxygen species (ROS) generation; however, the clinical relevance of oxidative stress elements as peripheral biomarkers of SCA3/MJD remains unknown. We aimed to evaluate ROS production and antioxidant defense capacity in symptomatic and presymptomatic SCA3/MJD individuals and correlate these markers with clinical and molecular data with the goal of assessing their properties as disease biomarkers. Methods: Molecularly confirmed SCA3/MJD carriers and controls were included in an exploratory case–control study. Serum ROS, measured by 2′,7′-dichlorofluorescein diacetate (DCFH-DA) as well as superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) antioxidant enzyme activities, levels were assessed. Results: Fifty-eight early/moderate stage symptomatic SCA3/MJD, 12 presymptomatic SCA3/MJD, and 47 control individuals were assessed. The DCFH-DA levels in the symptomatic group were 152.82 nmol/mg of protein [95% confidence interval (CI), 82.57–223.08, p < 0.001] higher than in the control and 243.80 nmol/mg of protein (95% CI, 130.64–356.96, p < 0.001) higher than in the presymptomatic group. The SOD activity in the symptomatic group was 3 U/mg of protein (95% CI, 0.015–6.00, p = 0.048) lower than in the presymptomatic group. The GSH-Px activity in the symptomatic group was 13.96 U/mg of protein (95% CI, 5.90–22.03, p < 0.001) lower than in the control group and 20.52 U/mg of protein (95% CI, 6.79–34.24, p < 0.001) lower than in the presymptomatic group and was inversely correlated with the neurological examination score for spinocerebellar ataxias (R = −0.309, p = 0.049). Conclusion: Early/moderate stage SCA3/MJD patients presented a decreased antioxidant capacity and increased ROS generation. GSH-Px activity was the most promising oxidative stress disease biomarker in SCA3/MJD. Further longitudinal studies are necessary to identify both the roles of redox parameters in SCA3/MJD pathophysiology and as surrogate outcomes for clinical trials

Peripheral Oxidative Stress Biomarkers in Spinocerebellar Ataxia Type 3/Machado–Joseph Disease

Objectives: Spinocerebellar ataxia type 3/Machado–Joseph disease (SCA3/MJD) is a polyglutamine disorder with no current disease-modifying treatment. Conformational changes in mutant ataxin-3 trigger different pathogenic cascades, including reactive oxygen species (ROS) generation; however, the clinical relevance of oxidative stress elements as peripheral biomarkers of SCA3/MJD remains unknown. We aimed to evaluate ROS production and antioxidant defense capacity in symptomatic and presymptomatic SCA3/MJD individuals and correlate these markers with clinical and molecular data with the goal of assessing their properties as disease biomarkers. Methods: Molecularly confirmed SCA3/MJD carriers and controls were included in an exploratory case–control study. Serum ROS, measured by 2′,7′-dichlorofluorescein diacetate (DCFH-DA) as well as superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) antioxidant enzyme activities, levels were assessed. Results: Fifty-eight early/moderate stage symptomatic SCA3/MJD, 12 presymptomatic SCA3/MJD, and 47 control individuals were assessed. The DCFH-DA levels in the symptomatic group were 152.82 nmol/mg of protein [95% confidence interval (CI), 82.57–223.08, p < 0.001] higher than in the control and 243.80 nmol/mg of protein (95% CI, 130.64–356.96, p < 0.001) higher than in the presymptomatic group. The SOD activity in the symptomatic group was 3 U/mg of protein (95% CI, 0.015–6.00, p = 0.048) lower than in the presymptomatic group. The GSH-Px activity in the symptomatic group was 13.96 U/mg of protein (95% CI, 5.90–22.03, p < 0.001) lower than in the control group and 20.52 U/mg of protein (95% CI, 6.79–34.24, p < 0.001) lower than in the presymptomatic group and was inversely correlated with the neurological examination score for spinocerebellar ataxias (R = −0.309, p = 0.049). Conclusion: Early/moderate stage SCA3/MJD patients presented a decreased antioxidant capacity and increased ROS generation. GSH-Px activity was the most promising oxidative stress disease biomarker in SCA3/MJD. Further longitudinal studies are necessary to identify both the roles of redox parameters in SCA3/MJD pathophysiology and as surrogate outcomes for clinical trials

Peripheral oxidative stress biomarkers in spinocerebellar ataxia type 3/Machado–Joseph disease

Objectives: Spinocerebellar ataxia type 3/Machado–Joseph disease (SCA3/MJD) is a polyglutamine disorder with no current disease-modifying treatment. Conformational changes in mutant ataxin-3 trigger different pathogenic cascades, including reactive oxygen species (ROS) generation; however, the clinical relevance of oxidative stress elements as peripheral biomarkers of SCA3/MJD remains unknown. We aimed to evaluate ROS production and antioxidant defense capacity in symptomatic and presymptomatic SCA3/MJD individuals and correlate these markers with clinical and molecular data with the goal of assessing their properties as disease biomarkers. Methods: Molecularly confirmed SCA3/MJD carriers and controls were included in an exploratory case–control study. Serum ROS, measured by 2′,7′-dichlorofluorescein diacetate (DCFH-DA) as well as superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) antioxidant enzyme activities, levels were assessed. Results: Fifty-eight early/moderate stage symptomatic SCA3/MJD, 12 presymptomatic SCA3/MJD, and 47 control individuals were assessed. The DCFH-DA levels in the symptomatic group were 152.82 nmol/mg of protein [95% confidence interval (CI), 82.57–223.08, p < 0.001] higher than in the control and 243.80 nmol/mg of protein (95% CI, 130.64–356.96, p < 0.001) higher than in the presymptomatic group. The SOD activity in the symptomatic group was 3 U/mg of protein (95% CI, 0.015–6.00, p = 0.048) lower than in the presymptomatic group. The GSH-Px activity in the symptomatic group was 13.96 U/mg of protein (95% CI, 5.90–22.03, p < 0.001) lower than in the control group and 20.52 U/mg of protein (95% CI, 6.79–34.24, p < 0.001) lower than in the presymptomatic group and was inversely correlated with the neurological examination score for spinocerebellar ataxias (R = −0.309, p = 0.049). Conclusion: Early/moderate stage SCA3/MJD patients presented a decreased antioxidant capacity and increased ROS generation. GSH-Px activity was the most promising oxidative stress disease biomarker in SCA3/MJD. Further longitudinal studies are necessary to identify both the roles of redox parameters in SCA3/MJD pathophysiology and as surrogate outcomes for clinical trials