58 research outputs found
Mitochondrial Fusion/Fission, Transport and Autophagy in Parkinson's Disease: When Mitochondria Get Nasty
Understanding the molecular basis of Parkinson's disease (PD) has proven to be a major challenge in the field of neurodegenerative diseases. Although several hypotheses have been proposed to explain the molecular mechanisms underlying the pathogenesis of PD, a growing body of evidence has highlighted the role of mitochondrial dysfunction and the disruption of the mechanisms of mitochondrial dynamics in PD and other parkinsonian disorders. In this paper, we comment on the recent advances in how changes in the mitochondrial function and mitochondrial dynamics (fusion/fission, transport, and clearance) contribute to neurodegeneration, specifically focusing on PD. We also evaluate the current controversies in those issues and discuss the role of fusion/fission dynamics in the mitochondrial lifecycle and maintenance. We propose that cellular demise and neurodegeneration in PD are due to the interplay between mitochondrial dysfunction, mitochondrial trafficking disruption, and impaired autophagic clearance
Microtubule Depolymerization Potentiates Alpha-Synuclein Oligomerization
Parkinson's disease (PD) is associated with perturbed mitochondria function and alpha-synuclein fibrillization. We evaluated potential mechanistic links between mitochondrial dysfunction and alpha-synuclein aggregation. We studied a PD cytoplasmic hybrid (cybrid) cell line in which platelet mitochondria from a PD subject were transferred to NT2 neuronal cells previously depleted of endogenous mitochondrial DNA. Compared to a control cybrid cell line, the PD line showed reduced ATP levels, an increased free/polymerized tubulin ratio, and alpha-synuclein oligomer accumulation. Taxol (which stabilizes microtubules) normalized the PD tubulin ratio and reduced alpha-synuclein oligomerization. A nexus exists between mitochondrial function, cytoskeleton homeostasis, and alpha-synuclein oligomerization. In our model, mitochondrial dysfunction triggers an increased free tubulin, which destabilizes the microtubular network and promotes alpha-synuclein oligomerization
Mitochondrial Dysfunction: The Road to Alpha-Synuclein Oligomerization in PD
While the etiology of Parkinson's disease remains largely elusive, there is accumulating evidence suggesting that mitochondrial dysfunction occurs prior to the onset of symptoms in Parkinson's disease. Mitochondria are remarkably primed to play a vital role in neuronal cell survival since they are key regulators of energy metabolism (as ATP producers), of intracellular calcium homeostasis, of NAD+/NADH ratio, and of endogenous reactive oxygen species production and programmed cell death. In this paper, we focus on mitochondrial dysfunction-mediated alpha-synuclein aggregation. We highlight some of the findings that provide proof of evidence for a mitochondrial metabolism control in Parkinson's disease, namely, mitochondrial regulation of microtubule-dependent cellular traffic and autophagic lysosomal pathway. The knowledge that microtubule alterations may lead to autophagic deficiency and may compromise the cellular degradation mechanisms that culminate in the progressive accumulation of aberrant protein aggregates shields new insights to the way we address Parkinson's disease. In line with this knowledge, an innovative window for new therapeutic strategies aimed to restore microtubule network may be unlocked
AlteraçÔes micrometeorológicas em vinhedos pelo uso de coberturas de plåstico
The objective of this work was to evaluate the effects of plastic covering on the microclimate of vineyards (Vitis vinifera L., cultivar Moscato Giallo), in Serra GaĂșcha region in Rio Grande do Sul State, Brazil. The experiment was performed in Flores da Cunha, RS, during the 2005/2006 growing season. It comprised uncovered and covered rows of vines, using a 160 ”m thick plastic film. Photossinthetically active radiation (PAR), air temperature and humidity, and wind velocity were monitored: over the plastic covering; between the film and the canopy; over the uncovered canopy; and close to grapes of both treatments. Reference evapotranspiration was estimated for both treatments. From the incoming PAR, 67.5% reached the covered canopy, 16% reached the covered grapes, and 36% reached the uncovered grapes. The plastic covering increased by 3.4ÂșC the maximum air temperatures close to plants. Diurnal air relative humidity was reduced, while water vapor pressure and vapor pressure deficit were increased because of the plastic covering, which also reduced in 88% the wind velocity in comparison to open air. The reference evapotranspiration on the covered canopy was 35% lower than in open air. Although increasing diurnal air temperatures, the plastic covering may reduce the evaporative demand on vineyards, by reducing the incoming solar radiation and the wind velocity.O objetivo deste trabalho foi avaliar os efeitos da cobertura de plĂĄstico sobre alguns elementos meteorolĂłgicos que formam o microclima de vinhedos de Vitis vinifera L., cultivar Moscato Giallo, em Flores da Cunha, na Serra GaĂșcha. O experimento foi conduzido na safra 2005/2006, com os tratamentos: fileiras de plantas descobertas; e fileiras de plantas cobertas com plĂĄstico transparente tipo rĂĄfia, com 160 ”m de espessura. MediçÔes contĂnuas de radiação fotossinteticamente ativa, temperatura e umidade do ar, e velocidade do vento foram realizadas: acima da cobertura; entre a cobertura e o dossel; sobre o dossel descoberto; e junto aos cachos de ambos tratamentos. Estimou-se a evapotranspiração de referĂȘncia nos dois tratamentos. Da radiação fotossinteticamente ativa incidente, 67,5% chegou ao dossel coberto, 16% atingiu os cachos cobertos e 36% chegou aos cachos descobertos. A cobertura aumentou em 3,4°C as temperaturas mĂĄximas do ar junto Ă s plantas. A umidade relativa do ar diurna foi menor, enquanto a pressĂŁo de vapor e o deficit de saturação foram superiores debaixo da cobertura. A velocidade do vento foi reduzida pela cobertura em 88%. No ambiente coberto, a evapotranspiração de referĂȘncia foi 65% daquela do ambiente externo. Embora aumente as temperaturas diurnas, a cobertura de plĂĄstico promoveu redução na demanda evaporativa do vinhedo
Mitochondria and protein homeostasis in Parkinson's disease : from quality control pathways to an integrated network
Tese de doutoramento em CiĂȘncias da SaĂșde (CiĂȘncias BiomĂ©dicas), apresentada Ă Faculdade de Medicina da Universidade de CoimbraParkinsonâs disease (PD) is the second most prevalent neurodegenerative disorder
affecting almost 2% of people over 65 years of age. The primary neuropathological
hallmark of PD is the degeneration of the nigrostriatal dopaminergic pathway which, by
depleting dopamine in the brain, initiates abnormal motor symptoms including resting
tremor, bradykinesia, postural instability, gait difficulty and rigidity. A second relevant
hallmark is the presence of intracellular inclusion bodies, known as Lewy bodies that
mainly contain aggregated α-synuclein.
While the etiology involved in the development of PD is unknown, 90-95% of PD
cases occurs sporadically and correlates, in part, with mitochondrial dysfunction and
oxidative stress. Furthermore, the identification of single genes associated to the familial
forms of PD has revolutionized this field of research, providing unique opportunities to
pursue novel mechanisms and clues to the pathogenesis of PD. The sustained study of
the cellular functions of each PD-related gene indicates that protein misfolding and
aggregation, as well as, dysfunction of their quality control systems may play a crucial
role in the cascade of deleterious events implicated in the neurodegenerative process of
PD. Thus, clear insights into how mitochondrial dysfunction, oxidative stress and protein
homeostasis systems interconnect, overlap or converge to produce nigral neuronal
degeneration is essential to understand the pathogenesis of sporadic PD (sPD).
In this thesis, we initially addressed the potential implications of an altered
structural and functional crosstalk between mitochondria and the endoplasmic reticulum
(ER), two important metabolic organelles for the maintenance of cellular protein
homeostasis. We reported that mitochondrial dysfunction induced by an acute stimulus
of the neurotoxin MPP+ renders cells more susceptible to develop an ER stress
response. We found that MPP+ was able to evoke a sustained flux of Ca2+ from the ER to
mitochondria which subsequently triggered ER- and mitochondria-dependent apoptotic
pathways. Our findings highlight the inevitable role of ER to mitochondria Ca2+ fluxes and
their requirement for a mitochondria-dependent cell death induction, enclosing a
feedback loop whereas mitochondria signals ER and ER induces further mitochondrial
alterations, leading to the activation of cascade of signals that culminates in apoptotic
cell death.
Furthermore, we also found that ER stress response strengthens mitochondrial
stress-induced abnormalities. We demonstrated that sustained ER stress caused by
accumulation of unfolded or misfolded proteins potentiated Ca2+ overload and impairment of mitochondrial function mainly characterized by dissipation of mitochondrial membrane
potential and substantial decline in the mitochondrial respiratory chain complex I activity.
These cumulative events led to induction of apoptotic cell death.
In addition, we assessed the role of mitochondrial metabolism in the regulation of
the autophagy-lysosomal pathway, a major cellular homeostatic process that mediates
the degradation of long-lived proteins and dysfunctional or superfluous organelles in
eukaryotic cells. We demonstrated that prolonged metabolic failure due to mitochondrial
dysfunction, either in cellular models harboring sPD subjects mtDNA (sPD cybrids), cells
depleted of all mtDNA (Rho0 cells), or in MPP+-treated rat cortical neurons causes a
functional decline in the activity of the autophagic system. This defect is a consequence
of alterations in microtubules (MT) assembly that hamper mitochondria and
autophagosome transport along the MT network toward the lysosomal compartment.
Consequently, deficient autophagic turnover potentiates the accumulation of α-synuclein
oligomers and, ultimately, prompts apoptosis. Our data identify for the first time the PDassociated
defects in mitochondrial dysfunction as the basis for the selective transport
abnormalities and highly characteristic pattern of neuritic dystrophy associated to the
autophagic pathology in PD.
Finally, we dissected the molecular mechanisms by which mitochondrial
metabolism in sPD can affect MT-directed autophagic turnover that, in turn, regulates
intracellular protein homeostasis. We demonstrated that sirtuin 2 (SIRT2), a NAD+
dependent protein deacetylase, controls the functional ability of the autophagic system
by modulating the acetylation status of the MT cytoskeleton.
The studies presented here provide novel insights into the multiple mechanisms
that dictate the association between mitochondria, intracellular metabolism and
proteotoxicity in sPD, and contribute with new findings that could have important
therapeutic implications to halt or retard the progression of sPD pathology.A doença de Parkinson (DP) é a segunda doença neurodegenerativa mais comum,
afectando cerca de 2% dos indivĂduos com idade superior a 65 anos. A marca
neuropatológica primåria desta doença é a disfunção da via dopaminérgica
nigroestriatal, da qual resulta a depleção de dopamina no cérebro, conduzindo aos
principais sintomas motores que caracterizam a clĂnica da doença e que incluem tremor
de repouso, bradicinesia, instabilidade postural e rigidez muscular. Outra caracterĂstica
neuropatológica da DP é a presença de corpos de inclusão intracelulares, designados
de Corpos de Lewy, que sĂŁo maioritariamente constituĂdos por α-synucleĂna na forma
agregada.
Embora a etiologia da doença permaneça por esclarecer, sabe-se que 90-95%
dos casos de DP ocorrem de uma forma esporĂĄdica e pensa-se que, em parte, se
correlacionam com a disfunção da mitocÎndria e com o stresse oxidativo. A identificação
de genes associados Ă s formas familiares da DP revolucionou a forma de pensar dos
investigadores da ĂĄrea, proporcionando oportunidades Ășnicas para estudar novos
mecanismos envolvidos na etiopatogenia da DP. O estudo continuado das funçÔes
celulares de cada um dos genes relacionados com a DP indica que o misfolding e a
agregação proteica, bem como a disfunção dos sistemas de controlo de qualidade
proteica, desempenham um papel crucial na cascata de eventos implicada no processo
de neurodegeneração da DP. Assim, uma visão clara de como e quando a disfunção
mitocondrial, o stresse oxidativo e os mecanismos de homeostase proteica se
entrecruzam, sobrepÔem ou convergem para produzir degeneração nigorestriatal é
essencial para a compreensĂŁo da fisiopatologia da DP do tipo esporĂĄdico (sDP).
Nesta tese, abordåmos, inicialmente, as potenciais implicaçÔes das alteraçÔes na
interação estrutural e funcional entre a mitocĂŽndria e o retĂculo endoplasmĂĄtico (RE),
dois organelos importantes envolvidos na manutenção da homeostase proteica celular.
Reportamos que a disfunção mitocondrial induzida por um estĂmulo agudo da
neurotoxina MPP+ aumenta a susceptibilidade das células para o desenvolvimento de
uma resposta ao stresse do RE. VerificĂĄmos que o MPP+ foi capaz de evocar um fluxo
contĂnuo de Ca2+ entre o RE e a mitocĂŽndria, desencadeando, subsequentemente, a
activação de vias apoptóticas dependentes do RE e da mitocÎndria. Os resultados
obtidos destacam o papel inevitĂĄvel dos fluxos de Ca2+ entre o RE e a mitocĂŽndria, e a
sua relevùncia para a indução de morte celular dependente da mitocÎndria,
estabelecendo-se um ciclo de retrocontrolo em que a mitocÎndria sinaliza o RE e o RE induz alteraçÔes posteriores na mitocÎndria, conduzindo à activação de uma cascata de
sinalização que culmina na morte celular por apoptose.
Do mesmo modo, observĂĄmos que o stresse do RE potencia alteraçÔes ao nĂvel
da função mitocĂŽndrial. Demonstramos que stresse do RE prolongado devido Ă
acumulação de proteĂnas mal processadas no seu interior conduz a um fluxo excessivo
de Ca2+ para o interior mitocÎndria e a um comprometimento da função mitocondrial,
caracterizada principalmente pela dissipação do potencial de membrana e por um
decréscimo substancial da actividade da cadeia respiratória mitocondrial.
Cumulativamente, estes eventos desencadeam a indução de morte celular por
apoptose.
Por outro lado, avaliåmos o papel do metabolismo mitocondrial na regulação da
via autofågica-lisossomal, um processo homeoståtico celular que medeia a degradação
de proteĂnas de longa duração e organelos disfuncionais em cĂ©lulas eucariĂłticas.
Demonstramos que uma falĂȘncia metabĂłlica prolongada devido a disfunção mitocondrial
quer em cĂ©lulas hĂbridas portadoras de ADN mitocondrial de doentes de sDP (cĂbridos
sDP), em células depletadas do seu ADN mitocondrial (células Rho0) ou em culturas
primĂĄrias de neurĂłnios corticais de rato tratados com MPP+, provoca um declĂnio
funcional na actividade do sistema autofĂĄgico. Este defeito Ă© uma consequĂȘncia de
alteraçÔes estruturais na rede microtubular (MT), comprometendo o transporte de
mitocĂŽndrias e autofagossomas para o compartimento lisossomal, onde ocorre
degradação. Consequentemente, um ineficaz turnover autofågico potencia a
acumulação de oligĂłmeros de α-sinucleĂna e, em Ășltima anĂĄlise, desencadeia apoptose.
Assim, os dados obtidos identificam pela primeira vez os defeitos na função mitocondrial
associados Ă DP como a base para alteraçÔes especĂficas no transporte intracelular e
no padrĂŁo caracterĂstico da distrofia neurĂtica associado Ă patologia autofĂĄgica na DP.
Por fim, analisåmos os mecanismos moleculares através dos quais o metabolismo
mitocondrial em sDP pode afectar o turnover autofĂĄgico dependente da rede MT, o qual,
por sua vez, regula a homeostase proteica intracelular. Demonstramos que a sirtuina 2
(SIRT2), uma desacetilase citoplasmĂĄtica dependente do NAD+, controla a capacidade
funcional do sistema autofågico, modulando o estado de acetilação do MTs.
Os estudos apresentados fornecem novas pistas relativamente aos mĂșltiplos
mecanismos que determinam a associação entre mitocÎndria, metabolismo intracelular
e proteotoxicidade e contribuem com novas perspectivas que poderĂŁo ter importantes
implicaçÔes terapĂȘuticas no sentido impedir ou retardar a progressĂŁo da sPD.O trabalho apresentado nesta tese foi financiado pelo projecto PTDC/SAUNEU/102710/2008 concedido Ă Professora Doutora Sandra Morais Cardoso pela Fundação para a CiĂȘncia e Tecnologia (FCT-MEC, Portugal). A autora usufruiu de uma
bolsa de Doutoramento (SFRHD/BD/38743/2007) concedida pela FCT-MEC, Portuga
Manutenção do campo de golfe. A importùncia da sua gestão ambiental
Mestrado em Arquitectura Paisagista - Instituto Superior de AgronomiaThe evolution of the golf courses design has neglected the initial concept of sustainability, due to the emergence of a style that ignored the natural shape and the existing forms of the land. Such style has been considered responsible for the increase of the environmental impacts associated with maintenance activities.
The current challenge is to make golf more sustainable by applying a proper environmental management, which plays a vital role and is essential to its success, contributing to the achievement of environmental and economic goals.
In this thesis one aims to demonstrate the importance of environmental management in maintaining a golf course. ISO 14001 concepts and GEO requirements will be applied in the management of the Oeiras golf course. The use of GEO OnCourseTM standards, specific for golf courses, will allow the certification of the implemented procedures. Collectively, the use of these strategies will allow the reduction of environmental impacts, in addition to enhancing the preservation of natural areas, protection of soil and water resources, environmental awareness of golfers and the general public, and the minimization of maintenance costs
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