Regular ArticlePre- and Postsynaptic Neurotoxic Effects of Dopamine Demonstrated by Intrastriatal Injection
Abstract
Considerable evidence indicates that dopamine (DA) may play a neurotoxic role in brain in certain pathologic circumstances. To investigate this issue, dopamine (1000 nmol/1 μl) was directly injected into the striatum of anesthetized Sprague-Dawley rats. Control animals received equal-volume injections of γ-aminobutyric acid (GABA) or NaCl at identical concentrations (diluted in distilled H2O, pH 7.0-7.7). Brains were removed 7 to 9 days later and frozen or fixed and sectioned for histologic and autoradiographic analysis. Dopamine injection resulted in a small-volume (3.3-mm3) lesion in comparison to control GABA and NaCl injections which produced only a needle track <0.6 mm3 in volume (P < 0.01). Dose dependency of DA toxicity was demonstrated, with substantial parenchymal damage requiring an injection of 500 nmol/1 μl. Within the lesion, marked neuronal loss, macrophage invasion, and capillary and glial proliferation were present. Acetylcholinesterase staining and D1 receptor binding were markedly reduced as well. [3H]RO5-4864 binding to peripheral benzodiazepine receptors (on astrocytes) was increased in the periphery of the lesion. The binding of 1-[3H]benzo[b]cyclohexylthiophenylpiperidine to dopamine uptake sites was also reduced, but over a wider striatal area in comparison to local parenchymal damage. Prior interruption of the dopaminergic nigrostriatal pathway (by injection of 6-hydroxydopamine) appeared to potentiate the toxicity of intrastriatal dopamine injection. The findings indicate that local injection of dopamine produces both post- and presynaptic damage to nigrostriatal structures, and support the contention that dopamine may act as a low-potency neurotoxin.
References (0)
Cited by (189)
mtADENet: A novel interpretable method integrating multiple types of network-based inference approaches for prediction of adverse drug events
2024, Computers in Biology and MedicineIdentification of adverse drug events (ADEs) is crucial to reduce human health risks and accelerate drug safety assessment. ADEs are mainly caused by unintended interactions with primary or additional targets (off-targets). In this study, we proposed a novel interpretable method named mtADENet, which integrates multiple types of network-based inference approaches for ADE prediction. Different from phenotype-based methods, mtADENet introduced computational target profiles predicted by network-based methods to bridge the gap between chemical structures and ADEs, and hence can not only predict ADEs for drugs and novel compounds within or outside the drug-ADE association network, but also provide insights for the elucidation of molecular mechanisms of the ADEs caused by drugs. We constructed a series of network-based prediction models for 23 ADE categories. These models achieved high AUC values ranging from 0.865 to 0.942 in 10-fold cross validation. The best model further showed high performance on four external validation sets, which outperformed two previous network-based methods. To show the practical value of mtADENet, we performed case studies on developmental neurotoxicity and cardio-oncology, and over 50 % of predicted ADEs and targets for drugs and novel compounds were validated by literature. Moreover, mtADENet is freely available at our web server named NetInfer (http://lmmd.ecust.edu.cn/netinfer/). In summary, mtADENet would be a powerful tool for ADE prediction and drug safety assessment in drug discovery and development.
The importance of choosing a preclinical model that reflects what happens in Parkinson's disease
2019, Neurochemistry InternationalOne of the major problems in the translation of successful preclinical results to clinical studies and new therapies in Parkinson’s disease is the use of preclinical models based on exogenous neurotoxins that do not replicate what happens in the disease. The loss of dopaminergic neurons containing neuromelanin in Parkinson´s disease takes years, contrasting the very rapid degeneration induced by exogenous neurotoxins. We discuss the role of endogenous neurotoxins generated during dopamine oxidation and its possible use as new preclinical models for Parkinson´s disease.
Selective basal ganglia vulnerability to energy deprivation: Experimental and clinical evidences
2018, Progress in NeurobiologyThe basal ganglia (BG) include structures pivotal for motor and cognitive functions. Such structures are affected in neurodegenerative disorders and toxic or ischemic insults. The peculiar vulnerability of BG to toxic and ischemic damage has been the focus of preclinical research for all over the last century. This comprehensive review collects all evidences supporting a specific susceptibility of BG to energy deprivation, highlighting the pathways through which neuronal survival is jeopardized, and the consequent clinical correlates. In particular, we addressed intrinsic and extrinsic factors participating in BG neuronal vulnerability. The terminal blood supply, the main extrinsic factor, is crucial to the low threshold for hypoxic hazard. Specific, the lack of anastomoses between second and third order branches represents the frailty of an archaic terminal network, unable to guarantee collateral supply and resistance to oxygen deprivation. In addition, BG neurons survival is jeopardized by several intrinsic molecular factors. Among them, the subunit composition of ionotropic and metabotropic glutamate receptors, the impairment of mitochondria, the deficit in neurotransmitter clearance, the poor control of intracellular calcium homeostasis and the glutamatergic-dopaminergic pro-excitotoxic interplay, all play a significant role. Intrinsic and extrinsic factors represent two faces of the same coin, producing excitotoxic damage and poor ability to deal with energy deprivation. The clinical correlates of BG vulnerability are represented by ischemic lesions, such as striatocapsular infarcts and lacunar infarcts, and local toxic-induced damage, mainly associated with energy production impairment, due to carbon monoxide, cyanide and manganese.
Impact of developmental exposure to methylphenidate on rat brain's immune privilege and behavior: Control versus ADHD model
2018, Brain, Behavior, and ImmunityAttention deficit hyperactivity disorder (ADHD) is the most prevalent childhood mental disorders that often persists into adulthood. Moreover, methylphenidate (MPH) is the mainstay of medical treatment for this disorder. Yet, not much is known about the neurobiological impact of MPH on control versus ADHD conditions, which is crucial to simultaneously clarify the misuse/abuse versus therapeutic use of this psychostimulant.
In the present study, we applied biochemical and behavioral approaches to broadly explore the early-life chronic exposure of two different doses of MPH (1.5 and 5 mg/kg/day) on control and ADHD rats (Wistar Kyoto and Spontaneously Hypertensive rats, respectively). We concluded that the higher dose of MPH promoted blood-brain barrier (BBB) permeability and elicited anxiety-like behavior in both control and ADHD animals. BBB dysfunction triggered by MPH was particularly prominent in control rats, which was characterized by a marked disruption of intercellular junctions, an increase of endothelial vesicles, and an upregulation of adhesion molecules concomitantly with the infiltration of peripheral immune cells into the prefrontal cortex. Moreover, both doses of MPH induced a robust neuroinflammatory and oxidative response in control rats. Curiously, in the ADHD model, the lower dose of MPH (1.5 mg/kg/day) had a beneficial effect since it balanced both immunity and behavior relative to vehicle animals.
Overall, the contrasting effects of MPH observed between control and ADHD models support the importance of an appropriate MPH dose regimen for ADHD, and also suggest that MPH misuse negatively affects brain and behavior.
A peptide disrupting the D2R-DAT interaction protects against dopamine neurotoxicity
2017, Experimental NeurologyDopamine reuptake from extracellular space to cytosol leads to accumulation of dopamine, which triggers neurotoxicity in dopaminergic neurons. Previous studies have shown that both dopamine D2 receptor (D2R) and dopamine transporter (DAT) are involved in dopamine neurotoxicity. However, blockade of either D2R or DAT causes side effects due to antagonism of other physiological functions of these two proteins. We previously found that DAT can form a protein complex with D2R and its cell surface expression is facilitated via D2R-DAT interaction, which regulates dopamine reuptake and intracellular dopamine levels. Here we found that an interfering peptide (DAT-S1) disrupting the D2R-DAT interaction protects neurons against dopamine neurotoxicity, and this effect is mediated by inhibiting DAT cell surface expression and inhibiting both caspase-3 and PARP-1 cleavage. This study demonstrates the role of the D2R-DAT complex in dopamine neurotoxicity and investigated the potential mechanisms, which might help better understand the mechanisms of dopamine neurotoxicity. The peptide may provide some insights to improve treatments for dopamine neurotoxicity and related diseases, such as Parkinson's disease, as well as methamphetamine- and 3,4-methsylenedioxy methamphetamine-induced neurotoxicity.
Oligomerization and membrane-binding properties of covalent adducts formed by the interaction of α-synuclein with the toxic dopamine metabolite 3,4-dihydroxyphenylacetaldehyde (DOPAL)
2015, Journal of Biological ChemistryOxidative deamination of dopamine produces the highly toxic aldehyde 3,4-dihydroxyphenylacetaldehyde (DOPAL), enhanced production of which is found in post-mortem brains of Parkinson disease patients. When injected into the substantia nigra of rat brains, DOPAL causes the loss of dopaminergic neurons accompanied by the accumulation of potentially toxic oligomers of the presynaptic protein α-synuclein (aS), potentially explaining the synergistic toxicity described for dopamine metabolism and aS aggregation. In this work, we demonstrate that DOPAL interacts with aS via formation of Schiff-base and Michael-addition adducts with Lys residues, in addition to causing oxidation of Met residues to Met-sulfoxide. DOPAL modification leads to the formation of small aS oligomers that may be cross-linked by DOPAL. Both monomeric and oligomeric DOPAL adducts potently inhibit the formation of mature amyloid fibrils by unmodified aS. The binding of aS to either lipid vesicles or detergent micelles, which results in a gain of α-helix structure in its N-terminal lipid-binding domain, protects the protein against DOPAL adduct formation and, consequently, inhibits DOPAL-induced aS oligomerization. Functionally, aS-DOPAL monomer exhibits a reduced affinity for small unilamellar vesicles with lipid composition similar to synaptic vesicles, in addition to diminished membrane-induced α-helical content in comparison with the unmodified protein. These results suggest that DOPAL could compromise the functionality of aS, even in the absence of protein oligomerization, by affecting the interaction of aS with lipid membranes and hence its role in the regulation of synaptic vesicle traffic in neurons.