Mitochondria mass is low in mouse substantia nigra dopamine neurons: implications for Parkinson’s disease. Exp Neurol
Department of Psychiatry, University of Texas, Southwestern Medical School, 5323 Harry Hines Blvd., Dallas, TX 75390-9070, USA.Experimental Neurology (Impact Factor: 4.7). 02/2007; 203(2):370-80. DOI: 10.1016/j.expneurol.2006.08.015
In Parkinson's disease (PD) there is a selective loss of certain midbrain dopaminergic (DA) neurons. The most vulnerable neurons reside in the substantia nigra zona compacta (SNC), whereas the DA neurons in the ventral tegmental area (VTA) and interfascicular (IF) nucleus are less vulnerable to degeneration. Many sporadic PD patients have a defect in mitochondria respiration, and some of the genes that cause PD are mitochondrial-related (e.g., PINK1, Parkin, DJ1). The present study sought to determine whether mitochondria mass is different in SNC neurons compared to other midbrain DA neurons and to non-DA neurons in the mouse. At the electron microscopic level, mitochondria in the SN DA neurons occupy 40% less of the soma and dendritic area than in the SN non-DA neurons. The area occupied by mitochondria in the SN DA neurons is also lower than in the VTA neurons, although not different from the IF neurons. The red nucleus somata have the largest percentage of the somata occupied by mitochondria (12%). Mitochondria size is related to somata size; the largest mitochondria are found in the red nucleus neurons and the smallest mitochondria are found in the IF neurons. At the light microscopic level, SNC, VTA and IF DA neurons have <50% of the cytoplasm immunostained with the mitochondrial antibody 1D6, whereas non-DA neurons in the same midbrain regions contain mitochondria areas up to >65% of the cytoplasm area. These data indicate that mitochondria size and mass are not the same for all neurons, and the SNC DA neurons have relatively low mitochondria mass. The low mitochondria mass in SNC DA neurons may contribute to the selective vulnerability of these neurons in certain rodent models of PD.
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- "The range of possible morphologies for mitochondria is wide and dependent on cell-type, particularly for neurons and especially for the dopaminergic (DA) neurons implicated in Parkinson's disease (PD). Mitochondria in these highly-specialized neurons are smaller and have a lower total mass compared to mitochondria in other neurons (Liang et al., 2007;Perier and Vila, 2012), and are selectively vulnerable to oxidative stress (Surmeier and Schumacker, 2013;Wiemerslage et al., 2013). In general, "
ABSTRACT: Background: Studies of mitochondrial morphology vary in techniques. Most use one morphological parameter while others describe mitochondria qualitatively. Because mitochondria are so dynamic, a single parameter does not capture the true state of the network and may lead to erroneous conclusions. Thus, a gestalt method of analysis is warranted. New method: This work describes a method combining immunofluorescence assays with computerized image analysis to measure the mitochondrial morphology within neuritic projections of a specific population of neurons. Six parameters of mitochondrial morphology were examined utilizing ImageJ to analyze colocalized signals. Results: Using primary neuronal cultures from Drosophila, we tested mitochondrial morphology in neurites of dopaminergic (DA) neurons. We validate our model using mutants with known defects in mitochondrial morphology. Furthermore, we show a difference in mitochondrial morphology between cells treated as control or with a neurotoxin inducing PD (Parkinson's Disease in humans)-like pathology. We also show interactions between morphological parameters and experimental treatment. Comparison with existing methods: Our method is a significant improvement of previously described methods. Six morphometric parameters are quantified, providing a gestalt analysis of mitochondrial morphology. Also it can target specific populations of mitochondria using immunofluorescence assay and image analysis. Conclusions: We found that our method adequately detects differences in mitochondrial morphology between treatment groups. We conclude that some parameters may be unique to a mutation or a disease state, and the relationship between parameters is altered by experimental treatment. We suggest at least four variables should be considered when using mitochondrial structure as an experimental endpoint.
- "The latter can react with nitrogen reactive species producing peroxynitrite (Meiser et al., 2013). Evidence in mouse has also indicated that lower mitochondria content is found in dopaminergic compared to other nondopaminergic cell populations present in the substantia nigra or in other midbrain dopaminergic nuclei such as VTA and interfascicular nucleus (Liang et al., 2007). Other studies have shown a redox modulation on the activity and expression of the tyrosine hydroxylase (TH), which represents the rate-limiting enzyme in the biosynthesis of DA (Di Giovanni et al., 2012). "
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- "The mishandling of DA via reduced VMAT2, associated to an increased striatal DOPAC/DA (Fig. 4a), and GSSG/GSH ratios (Fig. 4b), might be sufficient to cause DA-mediated toxicity and neurodegeneration in the nigrostriatal DA system (Mooslehner et al. 2001; Caudle et al. 2007; Chen et al. 2008b; for review, see Taylor et al. 2011). The specific vulnerability of nigrostriatal DA neurons might be explained because they have a higher ROS formation than those DA neurons in limbic system (Surmeier et al. 2011) and also these A9 DA neurons are specially prone to ROS attack, that is, the scarce proportion of glial cells surrounding DA neurons in the substantia nigra (for review, Mena et al. 2002), the presence of neuromelanin pigment in subpopulations of DA-containing mesencephalic neurons (Hirsch et al. 1988) and the low content of mitochondria in DA neurons of the substantia nigra pars compacta (Liang et al. 2007) might be mentioned between other characteristics. The results demonstrate that AGC1-MAS deficiency in mice targets monoaminergic brain systems in striatum. "
ABSTRACT: The mitochondrial transporter of aspartate-glutamate Aralar/AGC1 is a regulatory component of the malate-aspartate shuttle. Aralar-deficiency in mouse and human causes a shutdown of brain shuttle activity and global cerebral hypomyelination. A lack of neurofilament-labelled processes is detected in the cerebral cortex, but whether different types of neurons are differentially affected by Aralar-deficiency is still unknown. We have now found that Aralar-knockout (Aralar-KO) postnatal mice show hyperactivity, anxiety-like behaviour and hyperreactivity with a decrease of dopamine (DA) in terminal-rich regions. The striatum is the brain region most affected in terms of size, amino acid and monoamine content. We find a decline in vesicular monoamine transporter-2 (VMAT2) levels associated with increased DA metabolism through MAO activity (DOPAC/DA ratio) in Aralar-KO striatum. However, no decrease in DA or in the number of nigral tyrosine hydroxylase-positive cells was detected in Aralar-KO brainstem. Adult Aralar-hemizygous mice presented also increased DOPAC/DA ratio in striatum and enhanced sensitivity to amphetamine. Our results suggest that Aralar-deficiency causes a fall in GSH/GSSG ratio and VMAT2 in striatum that might be related to a failure to produce mitochondrial NADH and to an increase of ROS in the cytosol. The results indicate that the nigrostriatal dopaminergic system is a target of Aralar-deficiency. ©2012 International Society for Neurochemistry, J. Neurochem. (2012) 10.1111/jnc.12096.