Interleukin-4 Aggravates LPS-Induced Striatal Neurodegeneration In Vivo via Oxidative Stress and Polarization of Microglia/Macrophages.

The present study investigated the effects of interleukin (IL)-4 on striatal neurons in lipopolysaccharide (LPS)-injected rat striatum in vivo. Either LPS or PBS as a control was unilaterally injected into the striatum, and brain tissues were processed for immunohistochemical and Nissl staining or for hydroethidine histochemistry at the indicated time points after LPS injection. Analysis by NeuN and Nissl immunohistochemical staining showed a significant loss of striatal neurons at 1, 3, and 7 days post LPS. In parallel, IL-4 immunoreactivity was upregulated as early as 1 day, reached a peak at 3 days, and was sustained up to 7 days post LPS. Increased levels of IL-4 immunoreactivity were exclusively detected in microglia/macrophages, but not in neurons nor astrocytes. The neutralizing antibody (NA) for IL-4 significantly protects striatal neurons against LPS-induced neurotoxicity in vivo. Accompanying neuroprotection, IL-4NA inhibited activation of microglia/macrophages, production of reactive oxygen species (ROS), ROS-derived oxidative damage and nitrosative stress, and produced polarization of microglia/macrophages shifted from M1 to M2. These results suggest that endogenous IL-4 expressed in LPS-activated microglia/macrophages contributes to striatal neurodegeneration in which oxidative/nitrosative stress and M1/M2 polarization are implicated.

Progression of subcortical atrophy and iron deposition in multiple system atrophy: a comparison between clinical subtypes.

Magnetic resonance imaging (MRI) can be useful not only for the diagnosis of multiple system atrophy (MSA) itself, but also to distinguish between different clinical subtypes. This study aimed to investigate whether there are differences in the progression of subcortical atrophy and iron deposition between two variants of MSA. Two serial MRIs at baseline and follow-up were analyzed in eight patients with the parkinsonian variant MSA (MSA-P), nine patients with cerebellar variant MSA (MSA-C), and fifteen patients with Parkinson's disease (PD). The R2* values and volumes were calculated for the selected subcortical structures (caudate nucleus, putamen, globus pallidus, and thalamus) using an automated region-based analysis. In both volume and R2*, a higher rate of progression was identified in MSA-P patients. Volumetric analysis showed significantly more rapid progression of putamen and caudate nucleus in MSA-P than in MSA-C. With regard to R2* changes, a significant increase at follow-up and a higher rate of progression were identified in the putamen of MSA-P group compared to MSA-C and PD groups. This longitudinal study revealed different progression rates of MRI markers between MSA-P and MSA-C. Iron-related degeneration in the putamen may be more specific for MSA-P.

A rat model of striatonigral degeneration generated by simultaneous injection of 6-hydroxydopamine into the medial forebrain bundle and quinolinic acid into the striatum.

A double toxin-double lesion strategy is well-known to generate a rat model of striatonigral degeneration (SND) such as multiple system atrophy-parkinsonian type. However, with this model it is difficult to distinguish SND from Parkinson's disease (PD). In this study, we propose a new rat model of SND, which is generated by simultaneous injection of 6-hydroxydopamine into the medial forebrain bundle and quinolinic acid into the striatum. Stepping tests performed 30 min after intraperitoneal L-dopa administration at 6 weeks post-surgery revealed an L-dopa response in the PD group but not the SND group. Apomorphine-induced rotation tests revealed no rotational bias in the SND group, which persisted for 2 months, but contralateral rotations in the PD group. MicroPET scans revealed glucose hypometabolism and dopamine transporter impairment on the lesioned striatum in the SND group. Tyrosine hydroxylase immunostaining in the SND group revealed that 74.7% of nigral cells on the lesioned side were lost after lesion surgery. These results suggest that the proposed simultaneous double toxin-double lesion method successfully created a rat model of SND that had behavioral outcomes, multitracer microPET evaluation, and histological aspects consistent with SND pathology. This model will be useful for future study of SND.

Sirtuin 2 (SIRT2) enhances 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced nigrostriatal damage via deacetylating forkhead box O3a (Foxo3a) and activating Bim protein.

Sirtuins are NAD-dependent protein deacetylases that were shown to have beneficial effects against age-related diseases. SIRT2 is a strong deacetylase that is highly expressed in brain. It has been associated with neurodegenerative diseases. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a dopaminergic neurotoxin that replicates most of the clinical features of Parkinson disease (PD) and produces a reliable and reproducible lesion of the nigrostriatal dopaminergic pathway and neurodegeneration after its systemic administration. Chronic administration of MPTP induces lesion via apoptosis. We show here that SIRT2 deacetylates Foxo3a, increases RNA and protein levels of Bim, and as a result, enhances apoptosis in the MPTP model of PD. We also show that neurodegeneration induced by chronic MPTP regimen is prevented by genetic deletion of SIRT2 in mouse. Deletion of SIRT2 leads to the reduction of apoptosis due to an increase in acetylation of Foxo3a and a decrease in Bim levels. We demonstrate that SIRT2 deacetylates Foxo3a, activates Bim, and induces apoptosis only in 1-methyl-4-phenylpyridinium-treated cells. Therefore, designing SIRT2 inhibitors might be helpful to develop effective treatments for PD.

Peripheral inflammation increases the deleterious effect of CNS inflammation on the nigrostriatal dopaminergic system.

Evidence supports the role of inflammation in the development of neurodegenerative diseases. In this work, we are interested in inflammation as a risk factor by itself and not only as a factor contributing to neurodegeneration. We tested the influence of a mild to moderate peripheral inflammation (injection of carrageenan into the paws of rats) on the degeneration of dopaminergic neurons in an animal model based on the intranigral injection of lipopolysaccharide (LPS), a potent inflammatory agent. Overall, the treatment with carrageenan increased the effect of the intranigral injection of LPS on the loss of dopaminergic neurons in the SN along with all the other parameters studied, including: serum levels of the inflammatory markers TNF-α, IL-1ß, IL-6 and C-reactive protein; activation of microglia, expression of proinflammatory cytokines, the adhesion molecule ICAM and the enzyme iNOS, loss of astrocytes and damage to the blood brain barrier (BBB). The possible implication of BBB rupture in the increased loss of dopaminergic neurons has been studied using another Parkinson's disease animal model based on the intraperitoneal injection of rotenone. In this experiment, loss of dopaminergic neurons was also strengthened by carrageenan, without affecting the BBB. In conclusion, our data show that a mild to moderate peripheral inflammation can exacerbate the degeneration of dopaminergic neurons caused by a harmful stimulus.

Evaluation of a multiple system atrophy model in rats using multitracer microPET.

BACKGROUND: A double toxin-double lesion strategy is appropriate for mimicking of striatonigral degeneration. Because knowledge of human pathology is limited, animal models must be well characterized prior to testing of therapeutic approaches to treat multiple system atrophy. In double-toxin animal models, however, reduced contralateral rotation after apomorphine injection is restored within a few weeks via an unknown mechanism; the animals thus revert to PD status. We assessed this phenomenon using multitracer microPET and tissue staining. METHODS: Five adult male Wistar rats received injections of 6-hydroxydopamine (6-OHDA) into the right medial forebrain bundle (MFB), followed 3 weeks later by injections of quinolinic acid (QA) into the ipsilateral striatum. Apomorphine-induced rotation tests were performed 1 week after each injection, and 6 and 10 weeks after QA injection. Rotarod tests were performed weekly after 6-OHDA injection. MSA-p status was characterized by microPET 5 and 10 weeks after QA injection using the tracers 2-deoxy-2-[(18)F]-fluoro-D-glucose ([(18)F]-FDG) and [(18)F]-N-(3-fluoropropyl)-2-carbomethoxy-3-(4-iodophenyl)nortropane ([(18)F]-FP-CIT). Histological changes were evaluated by tyrosine hydroxylase (TH) and cresyl violet staining. RESULTS: The numbers of apomorphine-induced rotations increased contralaterally after 6-OHDA lesions were created, but decreased significantly after QA administration (p = 0.007). Five weeks after QA injection, however, contralateral rotation again increased and persisted for 1 month. Rotarod rotation differed significantly between the intact and PD states (p < 0.05), but not between the PD and MSA-p states. MicroPET revealed glucose hypometabolism and dopamine transporter (DAT) impairment on the lesioned side of the striatum 1 and 2 months after QA lesion surgery. Loss of nigral cells was confirmed by TH immunostaining, and striatal atrophy was observed upon cresyl violet staining. CONCLUSION: Pathological changes consistent with MSA-p can be generated by the double toxin-double lesion method and persist during follow-up. Behavioral tests, such as drug-induced rotation and rotarod tests, are not appropriate for long-term follow-up in the MSA-p model, suggesting the need for development of more appropriate behavioral tests.

Elevation of striatal interleukin-6 and serum corticosterone contents in MPTP-treated mice.

1. Changes in the content of striatal interleukins (IL-1 beta and IL-6) and serum corticosterone in relation to deterioration of the dopaminergic system induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP; a dopaminergic neurotoxin; 20 mg/kg i.p., four administrations/12 h) in C57BL/6J mice were investigated. 2. Striatal dopamine, IL-1 beta, IL-6 and serum corticosterone were measured on days 1 and 7 post-MPTP. 3. Dopamine depletion was more severe on day 7 than on day 1 post-treatment. 4. Increases in IL-6 were observed on days 1 and 7 post-MPTP. The increase in striatal IL-6 content varied with the extent of dopamine depletion, although the IL-1 beta concentration remained unchanged compared with control values on days 1 and 7 post-treatment. 5. Serum corticosterone was not different from control on day 1 post-MPTP. However, marked increases in the serum corticosterone were observed on day 7 post-treatment. 6. These results suggest that changes in striatal IL-6 and serum corticosterone are closely associated with the severity of MPTP-induced dopaminergic degeneration.