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.
"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). "
"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. "
"There are also other reported differences in these two dopaminergic neuron populations. Liand and colleagues found that A9 neurons have a signifi cantly smaller area of the cytoplasm occupied by mitochondria compared to the neighboring nondopaminergic neurons (Liang et al. , 2007 ). It was also noticeable that histochemistry studies with [ 3 H]dihydrorotenone, which binds Complex I, showed that the SN was one of the sites with relatively lower signals, inferring decreased activity (Talpade et al. , 2000 ). "
[Show abstract][Hide abstract] ABSTRACT: Mitochondrial dysfunctions are very common features of age-related neurological diseases such as Parkinson ' s, Alzheimer ' s and Huntington ' s disease. Several studies have shown that bioenergetic impairments have a major role in the degeneration of the central nervous system (CNS) in these patients. Accordingly, one of the main symptoms in many mitochondrial diseases is severe encephalopathy. The het-erogeneity of the brain in terms of anatomic structures, cell composition, regional functions and biochemical properties makes the analysis on this organ very complex and diffi cult to interpret. Humans, in addition to animal models, exposed to toxins that affect mitochondrial function, in particular oxidative phosphorylation, exhibit degeneration of specifi c regions within the brain. Moreover, mutations in ubiquitously expressed genes that are involved in mitochondrial function also induce regional-specifi c cell death in the CNS. In this review, we will discuss some current hypotheses to explain the regional susceptibilities to mitochondrial dysfunctions in the CNS.
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.