Substantia Nigra Of Mouse Research Articles

Exposure to PM2.5 aggravates Parkinson’s disease via inhibition of autophagy and mitophagy pathway

Extensive health studies had declared that exposure to particulate matter (PM) was closely associated with neurodegenerative diseases, i.e. Parkinson’s disease (PD). Our aim was to clarify the potential molecular mechanism by which PM2.5 aggravated PD symptoms using in vitro and in vivo PD models. In this study, PC12 cells treated with rotenone (1 μM) and/or PM2.5 (50 μg/mL) for 4 days was used as the in vitro model. C57BL/6 J mice expored to PM2.5 (inhalation, 2.5 mg/kg) and rotenone (intraperitoneal injection, 30 mg/kg) for 28 days was used as the in vivo model. Rapamycin was used to promote the level of autophagy. The results showed that after exposure to PM2.5, the apoptosis of rotenone-treated PC12 cells were increased by increasing the ROS levels and decreasing the levels of mitochondrial membrane potential. In rotenone-treated PC12 cells, exposure to PM2.5 could decrease the expression levels of LC3II and Atg5, and increase the expression level of mTOR, suggesting that PM2.5 exposure inhibited autophagy. Furthermore, the mitophagy related genes, including PINK1 and Parkin, were decreased. At the same time, inhalation of PM2.5 could relieve the behavioral abnormalities of PD mouse induced by rotenone. The levels of inflammatory factors (TNF-α, IL-1β, and IL-6) were significantly increased. Inhalation of PM2.5 could induce the oxidative stress and apoptosis in the substantia nigra of PD mouse, as well as the key markers of autophagy and mitophagy were also changed, which was consistent with the cell model. Besides, rapamycin would relieve the damaging effect of PM2.5 by triggering autophagy and mitophagy in rotenone-induced PD models. These results indicated that exposure to PM2.5 aggravated the behavioral abnormalities of PD symptoms through increasing oxidative stress, decreasing autophagy and mitophagy, and inducing mitochondria-mediated neuronal apoptosis. These findings not only revealed the effects and mechanism of PM2.5 exposure on PD, but also provided fundamental data that can be exploited to develop environmental safety policies.

17β-Estradiol/N-acetylcysteine interaction enhances the neuroprotective effect on dopaminergic neurons in the weaver model of dopamine deficiency

The weaver mouse, is a phenocopy of Parkinson’s disease (PD) in which dopaminergic neurons degenerate gradually during development, reaching at P21 a neurodegeneration of 55%. Thus, the weaver mouse constitutes an appropriate in vivo PD model for investigating the effect of neuroprotective agents. In the present study, long-term treatment (from P1 to P21) with 17β-estradiol (17β-estradiol) significantly protected the dopaminergic neurons in the substantia nigra (SN) of weaver mouse by 54%, as was detected by immunohistochemical experiments, using the specific antibody against tyrosine hydroxylase (TH). This dopaminergic neuroprotection is in line with our biochemical results showing that 17β-estradiol treatment significantly decreased the high lipid peroxidation levels seen in the SN of weaver mouse, indicating high oxidative stress. Interestingly, co-administration of 17β-estradiol with N-acetylcysteine (NAC, precursor molecule of glutathione (GSH)) further significantly increased the survival of dopaminergic neurons in the SN (by 85%), with a parallel further decrease of lipid peroxidation to normal levels. Our results show the in vivo neuroprotective effect of 17β-estradiol, which is strongly enhanced by co administration of NAC, indicating a strong synergistic effect of the two drugs. Furthermore, the main mechanism underlying this neuroprotective action seems to be the reversal of the oxidative stress shown by the high peroxidation levels. These results could be of clinical relevance since both drugs are already used separately in the clinic, 17β-estradiol for treatment of PD and NAC as a mucolytic agent and for the treatment of several disorders.

Region specific expression of the defense enzymes MTH1, OGG1 and MUTYH against oxidative damage in nucleic acids in the substantia nigra of mouse

Region specific expression of the defense enzymes MTH1, OGG1 and MUTYH against oxidative damage in nucleic acids in the substantia nigra of mouse

Elevation of oxidized DJ-1 in the brain and erythrocytes of Parkinson disease model animals

DJ-1, the causative gene of a familial form of Parkinson's disease (PD), has been reported undergo oxidation preferentially at the 106th cysteine residue (Cys-106) under oxidative stress. Recently, it has been found that the levels of oxidized DJ-1 in erythrocytes of unmedicated PD patients are markedly higher than those in medicated PD patients and healthy subjects. In the present study, we examined the changes in oxidized DJ-1 levels in the brain and erythrocytes of PD animal models using specific antibodies against Cys-106-oxidized DJ-1. Treatment with PD model compounds such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine significantly elevated the levels of oxidized DJ-1 in erythrocytes. Immunohistochemical analysis also revealed that the number of oxidized DJ-1 antibody-positive cells in the substantia nigra of MPTP-treated mouse increased in a dose-dependent manner. These results suggest that the oxidative modification of DJ-1 in the brain and erythrocytes is involved in the pathogenesis of PD in animal models.

Abnormal expression of the G‐protein‐activated inwardly rectifying potassium channel 2 (GIRK2) in hippocampus, frontal cortex, and substantia nigra of Ts65Dn mouse: A model of Down syndrome

Ts65Dn, a mouse model of Down syndrome (DS), demonstrates abnormal hippocampal synaptic plasticity and behavioral abnormalities related to spatial learning and memory. The molecular mechanisms leading to these impairments have not been identified. In this study, we focused on the G-protein-activated inwardly rectifying potassium channel 2 (GIRK2) gene that is highly expressed in the hippocampus region. We studied the expression pattern of GIRK subunits in Ts65Dn and found that GIRK2 was overexpressed in all analyzed Ts65Dn brain regions. Interestingly, elevated levels of GIRK2 protein in the Ts65Dn hippocampus and frontal cortex correlated with elevated levels of GIRK1 protein. This suggests that heteromeric GIRK1-GIRK2 channels are overexpressed in Ts65Dn hippocampus and frontal cortex, which could impair excitatory input and modulate spike frequency and synaptic kinetics in the affected regions. All GIRK2 splicing isoforms examined were expressed at higher levels in the Ts65Dn in comparison to the diploid hippocampus. The pattern of GIRK2 expression in the Ts65Dn mouse brain revealed by in situ hybridization and immunohistochemistry was similar to that previously reported in the rodent brain. However, in the Ts65Dn mouse a strong immunofluorescent staining of GIRK2 was detected in the lacunosum molecular layer of the CA3 area of the hippocampus. In addition, tyrosine hydroxylase containing dopaminergic neurons that coexpress GIRK2 were more numerous in the substantia nigra compacta and ventral tegmental area in the Ts65Dn compared to diploid controls. In summary, the regional localization and the increased brain levels coupled with known function of the GIRK channel may suggest an important contribution of GIRK2 containing channels to Ts65Dn and thus to DS neurophysiological phenotypes.

γ-Aminobutyric acid B autoreceptors in substantia nigra and neostriatum of the weaver mutant mouse

The weaver mutation causes cell loss in the center of the substantia nigra, pars compacta. We compared the depression of γ-aminobutyric acid (GABA) A synaptic currents by the GABA B agonist R-baclofen in pars compacta neurons of weaver mice which were largely spared from cell degeneration and of wild-type mice. In weaver neurons the suppression of GABA A synaptic currents by R-baclofen was reduced compared to wild-type neurons. The EC 50 of R-baclofen was 6.3 times higher in weaver than in wild-type mice. In the neostriatum, which is not a target of the mutation, such a difference did not exist. We conclude that in the pars compacta the weaver mutation leads to a reduced presynaptic autoinhibition through GABA B receptors which may promote survival of a subset of weaver neurons in the pars compacta.

Neurons exhibiting dopamine d 2 receptor immunoreactivity in the substantia nigra of the mutant weaver mouse

Neurons exhibiting D 2 receptor-like immunoreactivity were investigated in the substantia nigra pars compacta of weaver mice at the light and electron microscope levels using immunocytochemical techniques. At the light microscope level, there was significant loss of D 2-like immunoreactive cells in weaver mice and the remaining labeled cells exhibited less intense immunoreactivity. At the ultrastructural level, there was a decrease in the number of immunoreactive profiles and fewer synapses were observed abutting labeled dendritic profiles. In addition, degenerative changes were noted in some of the D 2 receptor-like immunoreactive profiles. Double labeling with D 2 and tyrosine hydroxylase indicated that the majority of the labeled profiles were double labeled. Eight-week-old homozygous weavers were paired with wild-type littermates as controls and perfused with a buffered solution of acrolein/paraformadehyde. Midbrain sections were reacted immunocytochemically either with an antiserum to D 2 or with antisera to D 2 and tyrosine hydroxylase, using a double-labeling technique. Sections were processed for light and electron microscopy by standard methods. The results of this study confirm the autoreceptor-like activity of D 2 receptors on nigral dopamine neurons. The cell degeneration, down-regulation of D2 receptors, and decreased dendritic and synaptic components in the neuropil suggest that the synaptic integrity of the substantia nigra has been compromised, which in turn would affect the functional efficacy of the basal ganglia circuitry. This altered circuity is expressed in the Parkinson-like symptoms displayed by this mutant mouse.

Is there a significant somatodendritic uptake of dopamine in the substantia nigra? Evidence from the weaver mutant mouse

Slices of the substantia nigra from normal mice and from mice with the weaver gene were used to study somatodendritic uptake of dopamine. The substantia nigra of the homozygous weaver mouse is deficient in both cell bodies and dendrites whereas the substantia nigra of the heterozygous weaver mouse is deficient only in dendrites. Accumulation of [ 3H]dopamine by nigral slices obtained from each genotype was not different from that observed in slices obtained from control mice. The observed accumulation of [ 3H]dopamine was apparently taking place predominantly into serotonergic and noradrenergic elements since significant reductions were obtained by both fluoxetine and desipramine at concentrations that were selective for the serotonin and norepinephrine carriers, respectively. In the absence, as well as in the presence of fluoxetine and desipramine, dopamine accumulation in the substantia nigra was only slightly attenuated by the known dopamine uptake blocker GBR 12909. These data argue against a significant presence of somatodendritic uptake systems for dopamine in the substantia nigra and suggest that caution be used in the interpretation of results from studies on dopamine release from nigral slices when [ 3H]dopamine has been used to preload the tissue. Under such experimental conditions, it is likely that a large proportion of the released tritium might come from neurons other than those which contain endogenous neurotransmitter dopamine.

Electron microscopic observations in the substantia nigra of mouse during reserpine administration.

Reserpin bewirkte an den Zellen der Substantia nigra der Maus Verschwinden der Katecholamin-haltigen Granula und Anschwellen des endoplasmatischen Retikulums. Das Hauptmerkmal von normalen Kontrollzellen bildeten elektronenoptisch dichte Korper im Cytoplasma.