Basal Mitophagy Occurs Independently of PINK1 in Mouse Tissues of High Metabolic Demand

Dysregulated mitophagy has been linked to Parkinson’s disease (PD) due to the role of PTEN-induced kinase 1 (PINK1) in mediating depolarization-induced mitophagy in vitro. Elegant mouse reporters have revealed the pervasive nature of basal mitophagy in vivo, yet the role of PINK1 and tissue metabolic context remains unknown. Using mito-QC, we investigated the contribution of PINK1 to mitophagy in metabolically active tissues. We observed a high degree of mitophagy in neural cells, including PDrelevant mesencephalic dopaminergic neurons and microglia. In all tissues apart from pancreatic islets, loss of Pink1 did not influence basal mitophagy, despite disrupting depolarization-induced Parkin activation. Our findings provide the first in vivo evidence that PINK1 is detectable at basal levels and that basal mammalian mitophagy occurs independently of PINK1. This suggests multiple, yet-tobe- discovered pathways orchestrating mammalian mitochondrial integrity in a context-dependent fashion, and this has profound implications for our molecular understanding of vertebrate mitophagy

Estudi de la neurodegeneració i les alteracions de la barrera hematoencefàlica en rates tractades amb àcid 3-nitropropiònic

[cat] L’àcid 3-nitropropiònic (3NP) és una toxina d’origen vegetal la ingesta de la qual produeix, en humans, una síndrome neurològica que presenta una simptomatologia similar a la de la malaltia de Huntington (MH). Injectada a rosegadors o primats, la toxina s’ha utilitzat per desenvolupar models animals de la MH, ja que els produeix lesions similars a les observades a l’esmentada malaltia, consistents en una afectació específica del cos estriat del seus cervells. A nivell bioquímic, aquesta molècula inhibeix de forma irreversible la succinat deshidrogenasa mitocondrial, i per tant el complex II de la cadena respiratòria. Això provoca una disminució a la producció d’ATP, punt de posada en marxa dels mecanismes d’excitotoxicitat secundària i de producció d’espècies reactives d’oxigen i per tant, de l’estrès oxidatiu, que porten a l’activació de diferents vies metabòliques de la neurona responsables de la seva mort, com són la necrosi o l’apoptosi mediades per l’activació de calpaïnes i caspases respectivament. Pel que fa a l’apoptosi, es pensa que la reactivació del cicle cel•lular podria estar involucrada en la seva activació. Reforçant aquesta idea, nombrosos estudis han detectat activació de diferents proteïnes reguladores del cicle cel•lular en teixit post mortem de pacients afectats de malalties neurodegeneratives. Per altra banda, el 3NP produeix alteracions a la permeabilitat de la barrera hematoencefàlica (BHE) dels rosegadors tractats i, recentment, s’ha vist que un dels mecanismes que pot estar implicat en aquest fet és la digestió per part de la gelatinasa MMP-9. Així, els objectius d’aquesta tesi consisteixen en estudiar la possible participació de la reactivació del cicle cel•lular en la neurodegeneració induïda en rates per l’administració del 3NP, i per altra banda caracteritzar les alteracions de la permeabilitat de la BHE i el paper que les gelatinases MMP-2 i MMP-9 i altres tipus cel•lulars com astròcits i micròglia hi poden jugar. Pel que fa al primer objectiu, s’ha vist que, tot i que s’ha detectat l’activació d’elements del cicle cel•lular a la lesió dels animals tractats, la reactivació del cicle cel•lular no intervé en la posada en marxa de la neurodegeneració provocada per la toxina, i s’ha arribat a la conclusió que l’expressió d’aquests elements pot estar relacionada amb una resposta tardana encaminada a la supervivència cel•lular. A partir d’aquí, s’han estudiat diferents proteïnes que poden estar relacionades amb la mort neuronal, com ATM, p53, Akt i GSK3beta. Els resultats que s'han obtingut en aquest cas indiquen que la pèrdua de la forma activa de l’Akt i la inhibició de la GSK3beta poden estar relacionades amb la neurodegeneració induïda pel 3NP. Pel que fa a l’estudi de les alteracions de la BHE, s’ha observat que, a la zona lesionada dels animals tractats amb 3NP, hi ha una gran alteració dels seus components com són les cèl•lules endotelials, la proteïna de les unions estretes ZO-1 i la laminina, component bàsic de la membrana basal dels vasos. Finalment, s’ha comprovat que la MMP-9 i la micròglia reactiva juguen un paper destacat a la degradació de la microvasculatura cerebral afectada per l’administració del 3NP.[eng] 3-nitropropionic acid (3-NPA) is a natural toxin that provokes, in humans, a neurological symptomatology which is similar to that observed in Huntington’s disease (HD). When injected to rodents or primates, it produces cerebral lesions, mainly located in their striata, which are similar to those observed in the brains of HD patients. 3-NPA irreversibly inhibits mitochondrial succinate dehidrogenase, which in turn causes a decrease in ATP production that triggers secondary excitotoxicity and reactive oxygen species production. These events lead neurons to their death by necrosis or apoptosis. It has been suggested that cell cycle re-entry may be involved in the activation of the apoptotic cascade. Reinforcing this, the activation of different cell cycle elements has been detected in post mortem brains of pacients affected by neurodegenerative diseases. Furthermore, blood brain barrier (BBB) disfunction has been detected in rodents administrated with 3-NPA, and it has been recently proposed that matrix metalloproteinase-9 (MMP-9) is involved in this process. The main objectives of this work were to study the role of cell cycle re-entry in the striatal neurodegeneration induced by 3-NPA and to characterize the alterations of BBB permeability. Regarding BBB impairment, the role of MMP-2 and MMP 9 and other cellular types such as astrocytes and microglia was considered. Although activation of G1 phase cell cycle elements was detected in the striatal lesion of 3-NPA treated rats, it was concluded that cell cycle re-entry was not involved in the activation of the neurodegenerative process, but it might be related to a late survival response. Moreover, it was shown that the loss of the active form of Akt and the inhibition of GSK3beta might be linked to the striatal neurodegeneration induced by 3-NPA. Furthermore, severe alterations in the permeability of the BBB and in the staining pattern of some of its components such as endothelial cells, tight junctions and basement membrane were detected in the striatal lesion of treated rats. Finally, gelatinolytic activity, which was mainly attributed to MMP-9, and reactive microglia were profusely detected around the injured vessels in the striatal lesion of 3-NPA, indicating that they might play a determinant role in BBB disruption in this mode

Erratum: Cerebral Amyloid Angiopathy, Blood-Brain Barrier Disruption and Amyloid Accumulation in SAMP8 Mice

Cerebrovascular dysfunction and β-amyloid peptide deposition on the walls of cerebral blood vessels might be an early event in the development of Alzheimer’s disease. Here we studied the time course of amyloid deposition in blood vessels and blood-brain barrier (BBB) disruption in the CA1 subzone of the hippocampus of SAMP8 mice and the association between these two variables. We also studied the association between the amyloid deposition in blood vessels and the recently described amyloid clusters in the parenchyma, as well as the association of these clusters with vessels in which the BBB is disrupted. SAMP8 mice showed greater amyloid deposition in blood vessels than age-matched ICR-CD1 control mice. Moreover, at 12 months of age the number of vessels with a disrupted BBB had increased in both strains, especially SAMP8 animals. At this age, all the vessels with amyloid deposition showed BBB disruption, but several capillaries with an altered BBB showed no amyloid on their walls. Moreover, amyloid clusters showed no spatial association with vessels with amyloid deposition, nor with vessels in which the BBB had been disrupted. Finally, we can conclude that vascular amyloid deposition seems to induce BBB alterations, but BBB disruption may also be due to other factors

Effect of Lycopersicon esculentum extract on apoptosis in the rat cerebellum, following prenatal and postnatal exposure to an electromagnetic field

The expansion of mobile phone technology has raised concerns regarding the effect of 900-MHz electromagnetic field (EMF) exposure on the central nervous system. At present, the developing human brain is regularly exposed to mobile telephones, pre- and postnatally. Several studies have demonstrated the acute effects of EMF exposure during pre- or postnatal periods; however, the chronic effects of EMF exposure are less understood. Thus, the aim of the present study was to determine the chronic effects of EMF on the pre- and postnatal rat cerebellum. The control group was maintained in the same conditions as the experimental groups, without the exposure to EMF. In the EMF1 group, the rats were exposed to EMF during pre- and postnatal periods (until postnatal day 80). In the EMF2 group, the rats were also exposed to EMF pre- and postnatally; in addition, however, they were provided with a daily oral supplementation of Lycopersicon esculentum extract (∼2 g/kg). The number of caspase-3-labeled Purkinje neurons and granule cells present in the rats in the control and experimental groups were then counted. The neurodegenerative changes were studied using cresyl violet staining, and these changes were evaluated. In comparison with the control animals, the EMF1 group demonstrated a significant increase in the number of caspase-3-labeled Purkinje neurons and granule cells present in the cerebellum (P<0.001). However, in comparison with the EMF1 group, the EMF2 group exhibited significantly fewer caspase-3-labeled Purkinje neurons and granule cells in the cerebellum. In the EMF1 group, the Purkinje neurons were revealed to have undergone dark neuron degenerative changes. However, the presence of dark Purkinje neurons was reduced in the EMF2 group, compared with the EMF1 group. The results indicated that apoptosis and neurodegeneration in rats exposed to EMF during pre- and postnatal periods may be reduced with Lycopersicon esculentum extract therapy