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Natale G.,University of Pisa | Pasquali L.,University of Pisa | Paparelli A.,University of Pisa | Fornai F.,University of Pisa | Fornai F.,Laboratory of Neurobiology of Movement Disorders
Neurogastroenterology and Motility | Year: 2011

Background Neurodegenerative diseases may extend outside the central nervous system (CNS) and involve the gastrointestinal (GI) tract. The gut would appear to be a pathological marker for neurodegeneration, as well as a site for studying the pathophysiology of neurodegeneration. In fact, both in the ENS and CNS, misfolded proteins are likely to initiate a process of neurodegeneration. For example, the very same protein aggregates can be detected both in the ENS and CNS. In both systems, misfolded proteins are likely to share common cell-to-cell diffusion mechanisms, which may occur through a parallel prion-like diffusion process. Independently from the enteric or central origin, misfolded proteins may proceed along the following steps, they: (i) form aggregates; (ii) are expressed on plasma membrane; (iii) are secreted extracellularly; (iv) are glycated to form advanced glycation end-products (AGEs); (v) are internalized through specific receptors placed on neighboring cells (RAGEs); (vi) are cleared by autophagy; and (vii) are neurotoxic. These features are common for a-synuclein (in Parkinson's disease and other synucleinopathies), β-amyloid and tau (in degenerative dementia), SOD-1 and TDP43 (in amyotrophic lateral sclerosis), and PrPsc (in prion diseases). While in some diseases these features are common to both ENS and CNS, in others this remains a working hypothesis. Purpose This review analyzes GI alterations from a pathological perspective to assess whether the enteric nervous system (ENS) mirrors the neuropathology described in the CNS. We discuss the potential mechanisms that lead to the onset and spread of neurodegeneration within the gut, from the gut to the brain, and vice versa. © 2011 Blackwell Publishing Ltd. Source

Lenzi P.,University of Pisa | Marongiu R.,CSS Mendel Institute | Marongiu R.,New York Medical College | Falleni A.,University of Pisa | And 8 more authors.
Archives Italiennes de Biologie | Year: 2012

Mutations in the PTEN-induced putative kinase1 (PINK1) represent the second most frequent cause of autosomal recessive Parkinson's disease. The PINK1 protein mainly localizes to mitochondria and interacts with a variety of proteins, including the pro-autophagy protein beclin1 and the ubiquitin-ligase parkin. Upon stress conditions, PINK1 is known to recruit parkin at the surface of dysfunctional mitochondria and to activate the mitophagy cascade. Aim of this study was to use a simple and highly reproducible catecholamine cell model and transmission electron microscopy to characterize whether PINK1 could affect mitochondrial homeostasis, the recruitment of specific proteins at mitochondria, mitophagy and apoptosis. Samples were analyzed both in baseline conditions and following treatment with methamphetamine (METH), a neurotoxic compound which strongly activates autophagy and produces mitochondrial damage. Our data provide robust sub-cellular evidence that the modulation of PINK1 levels dramatically affects the morphology and number of mitochondria and the amount of cell death. In particular, especially upon METH exposure, PINK1 is able to increase the total number of mitochondria, concurrently recruit beclin1, parkin and ubiquitin and enhance the clearance of damaged mitochondria. In the absence of functional PINK1 and upon autophagy stress, we observe a failure of the autophagy system at large, with marked accumulation of dysfunctional mitochondria and dramatic increase of apoptotic cell death. These findings highlight the strong neuroprotective role of PINK1 as a key protein in the surveillance and regulation of mitochondrial homeostasis. Source

Natale G.,University of Pisa | Kastsiushenka O.,University of Pisa | Fulceri F.,University of Pisa | Ruggieri S.,Laboratory of Neurobiology of Movement Disorders | And 3 more authors.
Brain Research | Year: 2010

Gastrointestinal (GI) dysfunction occurs frequently in early Parkinson's disease (PD) and it is supposed to anticipate motor symptoms. About 80% of PD patients suffer from constipation before the onset of movement disorders. Despite such a high prevalence of gut impairment in PD, the molecular mechanisms remain poorly investigated. This is also due to the scarcity of experimental studies. In the present work, we tried to reproduce digestive abnormalities observed in PD patients by administering the parkinsonism-inducing neurotoxin 1-methyl-4-phenyl-1,2,3,6,-tetrahydropyridine (MPTP) to C57BL mice. We show that in these mice, MPTP (20 mg/kg × 3) while producing the classic striatal dopamine (DA) denervation, persistently delays colonic motility, produces constipation, and reduces the number of enteric TH-positive neurons. The loss of TH-positive cells in the gut is selectively due to the disappearance of DA neurons within both myenteric and mostly submucosal plexus in the intestine, while no change is detected in the esophagus and stomach. In contrast, norepinephrine (NE) neurons are not affected. These data were confirmed by immunohistochemistry and by HPLC showing the significant loss of DA levels while NE and 5-HT content was not affected. Dopamine cell loss was associated with increased α-synuclein levels. These functional, biochemical, and morphological findings extend the PD-mimicking effects of MPTP to GI dysfunctions and provide a useful experimental model to understand gut dysfunction in PD and to find effective treatments for digestive symptoms. © 2010 Elsevier B.V. All rights reserved. Source

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