ABSTRACT
Parkinson's disease (PD) is characterized by loss of A9 dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc). An association has been reported between PD and exposure to mitochondrial toxins, including environmental pesticides paraquat, maneb, and rotenone. Here, using a robust, patient-derived stem cell model of PD allowing comparison of A53T α-synuclein (α-syn) mutant cells and isogenic mutation-corrected controls, we identify mitochondrial toxin-induced perturbations in A53T α-syn A9 DA neurons (hNs). We report a pathway whereby basal and toxin-induced nitrosative/oxidative stress results in S-nitrosylation of transcription factor MEF2C in A53T hNs compared to corrected controls. This redox reaction inhibits the MEF2C-PGC1α transcriptional network, contributing to mitochondrial dysfunction and apoptotic cell death. Our data provide mechanistic insight into gene-environmental interaction (GxE) in the pathogenesis of PD. Furthermore, using small-molecule high-throughput screening, we identify the MEF2C-PGC1α pathway as a therapeutic target to combat PD.
Subject(s)
Gene-Environment Interaction , Mitochondria/drug effects , Paraquat/toxicity , Parkinson Disease/genetics , Parkinson Disease/pathology , Humans , Induced Pluripotent Stem Cells/metabolism , MEF2 Transcription Factors , Mutation/drug effects , Neurons/metabolism , Oxidative Stress , Parkinson Disease/metabolism , Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha , Reactive Nitrogen Species/metabolism , Substantia Nigra/metabolism , Transcription Factors/metabolism , Transcription, Genetic , alpha-Synuclein/genetics , alpha-Synuclein/metabolismABSTRACT
The transcription factor NR4A3 (also known as NOR-1) is a member of the Nr4a family of nuclear receptors and is expressed in myeloid and lymphoid cells. Here, we have shown that Nr4a3 is essential for the migration of CD103+ dendritic cells (DCs) to lymph nodes (LNs). Nr4a3-deficient mice had very few CD103+ migratory DCs (mDCs) present in LNs, and mixed-chimera studies revealed that this migratory defect was cell intrinsic. We further found that CD103+ DCs from Nr4a3-deficient mice displayed a marked loss of surface expression of the chemokine CCR7. This defect in CCR7 expression was confined to CD103+ DCs, as CCR7 expression on T lymphocytes was unaffected. Moreover, CCR7 was not induced on CD103+ DCs from Nr4a3-deficient mice in response to either administration of the TLR7 agonist R848 or infection with Citrobacter rodentium in vivo. The transcription factor FOXO1 has been shown to regulate CCR7 expression. We found that FOXO1 protein was reduced in Nr4a3-deficient DCs through an AKT-dependent mechanism. Further, we found a requirement for NR4A3 in the maintenance of homeostatic mitochondrial function in CD103+ DCs, although this is likely independent of the NR4A3/FOXO1/CCR7 axis in the regulation of DC migration. Thus, NR4A3 plays an important role in the regulation of CD103+ mDCs by regulating CCR7-dependent cell migration.
Subject(s)
Antigens, CD/immunology , Cell Movement/immunology , DNA-Binding Proteins/immunology , Dendritic Cells/immunology , Integrin alpha Chains/immunology , Nerve Tissue Proteins/immunology , Receptors, Steroid/immunology , Receptors, Thyroid Hormone/immunology , Signal Transduction/immunology , Animals , Antigens, CD/genetics , Cell Movement/drug effects , Cell Movement/genetics , Citrobacter rodentium/immunology , DNA-Binding Proteins/genetics , Enterobacteriaceae Infections/genetics , Enterobacteriaceae Infections/immunology , Forkhead Box Protein O1/genetics , Forkhead Box Protein O1/immunology , Gene Expression Regulation/drug effects , Gene Expression Regulation/immunology , Imidazoles/pharmacology , Integrin alpha Chains/genetics , Mice , Mice, Knockout , Nerve Tissue Proteins/genetics , Receptors, CCR7/genetics , Receptors, CCR7/immunology , Receptors, Steroid/genetics , Receptors, Thyroid Hormone/genetics , Signal Transduction/drug effects , Signal Transduction/genetics , T-Lymphocytes/immunologyABSTRACT
BACKGROUND: Targeting the mitochondria during ischemia/reperfusion (IR) can confer cardioprotection leading to improved clinical outcomes. The cardioprotective potential of (-)-epicatechin (EPI) during IR via modulation of mitochondrial function was evaluated. METHODS AND RESULTS: Ischemia was induced in rats via a 45 min occlusion of the left anterior descending coronary artery followed by 1 h, 48 h, or 3 week reperfusion. EPI (10 mg/kg) was administered IV 15 min prior to reperfusion for the single dose group and again 12 h later for the double dose group. Controls received water. Experiments also utilized cultured neonatal rat ventricular myocytes (NRVM) and myoblasts. A single dose of EPI reduced infarct size by 27% at 48 h and 28% at 3 week. Double dose treatment further decreased infarct size by 80% at 48 h, and 52% by 3 weeks. The protective effect of EPI on mitochondrial function was evident after 1h of reperfusion when mitochondria demonstrated less respiratory inhibition, lower mitochondrial Ca2+ load, and a preserved pool of NADH that correlated with higher tissue ATP levels. Mechanistic studies in NRVM revealed that EPI acutely stimulated maximal rates of respiration, an effect that was blocked by inhibitors of the mitochondrial pyruvate carrier, nitric oxide synthase, or soluble guanylyl cyclase. In myoblasts, knockdown of components of the mitochondrial pyruvate carrier blocked EPI-induced respiratory stimulation. CONCLUSIONS: IV EPI confers cardioprotection via preservation of mitochondrial function potentially through enhanced substrate provision. These provocative results document a novel mechanism of a natural product with potential clinical utility.