NF-κB/c-Rel deficiency causes Parkinson’s disease-like prodromal symptoms and progressive pathology in mice

Background:Parkinson’s disease(PD),the most common neurodegenerative movement disorder,is characterized by dopaminergic nigrostriatal neuron loss and brain accumulation of Lewy bodies,protein aggregates mainly composed ofα-synuclein.We reported that mice deficient for NF-κB/c-Rel(c-rel^(-/-))develop a late-onset parkinsonism.At 18 months of age,c-rel^(-/-)mice showed nigrostriatal degeneration and accumulation ofα-synuclein aggregates associated with a motor impairment responsive to L-DOPA administration.Being c-Rel protein a transcriptional regulator for mitochondrial anti-oxidant and antiapoptotic factors,it has been inferred that its deficiency may affect the resilience of“energy demanding”nigral dopaminergic neurons to the aging process.PD patients manifest a prodromal syndrome that includes olfactory and gastrointestinal dysfunctions years before the frank degeneration of nigrostriatal neurons and appearance of motor symptoms.According to the Braak staging,the onset of non-motor and motor symptoms relates to progressive ascendant diffusion ofα-synuclein pathology in the brain.The aim of this study was to identify whether c-rel^(-/-)deficiency is associated with the onset of premotor signs of PD and spatio-temporal progression of cerebralα-synuclein deposition.Methods:Intestinal and olfactory functions,intestine and brainα-synuclein deposition as well as striatal alterations,were assessed in c-rel^(-/-)and control mice from 2 to 18 months of age.Results:From 2 months of age,c-rel^(-/-)mice displayed intestinal constipation and increasing olfactory impairment.At 2 months,c-rel^(-/-)mice exhibited a mildα-synuclein accumulation in the distal colon.Moreover,they developed an agedependent deposition of fibrillaryα-synuclein that,starting at 5 months from the olfactory bulbs,dorsal motor nucleus of vagus and locus coeruleus,reached the substantia nigra at 12 months.At this age,theα-synuclein pathology associated with a drop of dopamine transporter in the striatum that anticipated by 6 months the axonal degeneration.From 12 months onwards oxidative/nitrosative stress developed in the striatum in parallel with altered expression of mitochondrial homeostasis regulators in the substantia nigra.Conclusions:In c-rel^(-/-)mice,reproducing a parkinsonian progressive pathology with non-motor and motor symptoms,a Braak-like pattern of brain ascendingα-synuclein deposition occurs.The peculiar phenotype of c-rel^(-/-)mice envisages a potential contribution of c-Rel dysregulation to the pathogenesis of PD.

Considerations on the role of environmental toxins in idiopathic Parkinson’s disease pathophysiology

Neurodegenerative diseases are characterized by a progressive dysfunction of the nervous system.Often associated with atrophy of the affected central or peripheral nervous structures,they include diseases such as Parkinson’s Disease(PD),Alzheimer’s Disease and other dementias,Genetic Brain Disorders,Amyotrophic Lateral Sclerosis(ALS or Lou Gehrig’s Disease),Huntington’s Disease,Prion Diseases,and others.The prevalence of neurodegenerative diseases has increased over the last years.This has had a major impact both on patients and their families and has exponentially increased the medical bill by hundreds of billions of Euros.Therefore,understanding the role of environmental and genetic factors in the pathogenesis of PD is crucial to develop preventive strategies.While some authors believe that PD is mainly genetic and that the aging of the society is the principal cause for this increase,different studies suggest that PD may be due to an increased exposure to environmental toxins.In this article we review epidemiological,sociological and experimental studies to determine which hypothesis is more plausible.Our conclusion is that,at least in idiopathic PD(iPD),the exposure to toxic environmental substances could play an important role in its aetiology.