ABSTRACT
Parkinson's disease is a neurodegenerative disorder with motor symptoms linked to the loss of dopaminergic neurons in the substantia nigra compacta. Although the mechanisms that trigger the loss of dopaminergic neurons are unclear, mitochondrial dysfunction and inflammation are thought to have key roles1,2. An early-onset form of Parkinson's disease is associated with mutations in the PINK1 kinase and PRKN ubiquitin ligase genes3. PINK1 and Parkin (encoded by PRKN) are involved in the clearance of damaged mitochondria in cultured cells4, but recent evidence obtained using knockout and knockin mouse models have led to contradictory results regarding the contributions of PINK1 and Parkin to mitophagy in vivo5-8. It has previously been shown that PINK1 and Parkin have a key role in adaptive immunity by repressing presentation of mitochondrial antigens9, which suggests that autoimmune mechanisms participate in the aetiology of Parkinson's disease. Here we show that intestinal infection with Gram-negative bacteria in Pink1-/- mice engages mitochondrial antigen presentation and autoimmune mechanisms that elicit the establishment of cytotoxic mitochondria-specific CD8+ T cells in the periphery and in the brain. Notably, these mice show a sharp decrease in the density of dopaminergic axonal varicosities in the striatum and are affected by motor impairment that is reversed after treatment with L-DOPA. These data support the idea that PINK1 is a repressor of the immune system, and provide a pathophysiological model in which intestinal infection acts as a triggering event in Parkinson's disease, which highlights the relevance of the gut-brain axis in the disease10.
Subject(s)
Enterobacteriaceae Infections/microbiology , Enterobacteriaceae Infections/physiopathology , Intestines/microbiology , Parkinson Disease/genetics , Parkinson Disease/microbiology , Protein Kinases/deficiency , Protein Kinases/genetics , Animals , Antigen Presentation/immunology , Autoantigens/immunology , Axons/pathology , CD8-Positive T-Lymphocytes/immunology , CD8-Positive T-Lymphocytes/pathology , Citrobacter rodentium/immunology , Citrobacter rodentium/pathogenicity , Disease Models, Animal , Dopaminergic Neurons/immunology , Dopaminergic Neurons/pathology , Enterobacteriaceae Infections/immunology , Enterobacteriaceae Infections/pathology , Female , Intestines/immunology , Intestines/pathology , Levodopa/therapeutic use , Male , Mice , Mitochondria/immunology , Mitochondria/pathology , Neostriatum/immunology , Neostriatum/microbiology , Neostriatum/pathology , Neostriatum/physiopathology , Parkinson Disease/drug therapy , Parkinson Disease/physiopathology , Protein Kinases/immunology , Ubiquitin-Protein Ligases/deficiency , Ubiquitin-Protein Ligases/genetics , Ubiquitin-Protein Ligases/immunologyABSTRACT
To determine the effect of nerve growth factor (NGF) on the neurotoxicity of herpes simplex virus type 1 (HSV-1) in vivo, direct intrastriatal injection of HSV-1 in rats was followed by continuous intracerebral infusion of NGF or vehicle solution for 7 days. The mean volume of HSV-1-mediated brain tissue destruction in NGF-treated animals was significantly smaller than that in vehicle-treated animals at 1 week. Immunohistochemical staining for HSV-1 confirmed the presence of cells harboring the virus at the primary site of injection and at secondary sites of distant spread, with no significant difference in HSV-1 distribution between NGF- and vehicle-treated animals. We conclude that intrastriatal infusion of NGF locally protects against HSV-1-mediated neurolysis, but does not affect HSV-1 dissemination in the brain.