Early Effects of Alpha-Synuclein Depletion by Pan-Neuronal Inactivation of Encoding Gene on Electroencephalogram Coherence between Different Brain Regions in Mice

Inactivation of the Snca gene in young mice by chronic injections of tamoxifen (TAM), a selective estrogen receptor modifier, has been shown to decrease the level of alpha-synuclein, a key peptide in the pathogenesis of Parkinson's disease. In young mice, different time courses of the effect were observed in different brain areas, meaning associated disturbances in the intracerebral relations, namely in brain function after TAM-induced synucleinopathy.

METHODS

We analyzed electroencephalogram (EEG) coherence ("functional connectivity") between the cortex (MC), putamen (Pt), and dopamine-producing brain regions (ventral tegmental area, VTA, and substantia nigra, SN) in two groups of two-month-old male mice. We compared EEG coherences in the conditional knockout Sncaflox/flox mice with those in their genetic background (C57Bl6J) one, two, and three months after chronic (for five days) intraperitoneal injections of TAM or the vehicle (corn oil). The EEG coherences in the TAM-treated group were compared with those in the alpha-synuclein knockout mice.

RESULTS

A significant suppression of EEG coherence in the TAM-treated mice versus the vehicle group was observed in all inter-structural relations, with the exception of MC-VTA at one and three months and VTA-SN at two months after the injections. Suppressive changes in EEG coherence were observed in the alpha-synuclein knockout mice as well; the changes were similar to those in TAM-treated mice three months after treatment.

CONCLUSION

our data demonstrate a combined time-dependent suppressive effect induced by TAM on intracerebral EEG coherence.

В6.А-DYSFPRMD/GENEJ MICE AS A GENETIC MODEL OF DYSFERLINOPATHY

The aim of the work was behavioral and pathomorphological phenotyping of the mice knockout for the DYSF gene, which plays an important role in the development and progression of dysferlinopathy.

Materials and methods. A B6.A-Dysfprmd/GeneJ (Bla/J) mice subline was used in the work. During the study, a muscle activity was determined basing on the following tests: “Inverted grid”, “Grip strength”, “Wire Hanging”, “Weight-loaded swimming”, Vertical Pole”. Histological and immunofluorescent examinations of skeletal muscles (m. gastrocnemius, m. tibialis) were performed. The presence and distribution of the dysferlin protein was assessed, and general histological changes in the skeletal muscle characteristics of mice at the age of 12 and 24 weeks, were described. A morphometric analysis with the determination of the following parameters was performed: the proportion of necrotic muscle fibers; the proportion of fibers with centrally located nuclei; the mean muscle fiber diameter.

Results. The “Grip strength” test and the “Weight-loaded swimming” test revealed a decrease in the strength of the forelimbs and endurance in the studied mice of the Bla/J subline compared to the control line. The safety of physical performance was checked using the “Wire Hanging” test and the “Vertical Pole” test, which showed a statistically significant difference between the studied mice and control. The coordination of movements and muscle strength of the limbs examined in the “Inverted Grid” test did not change in these age marks. Decreased grip strength of the forelimbs, decreased physical endurance with age, reflects the progression of the underlying muscular disease. Histological methods in the skeletal muscles revealed signs of a myopathic damage pattern: necrotic muscle fibers, moderate lympho-macrophage infiltration, an increase in the proportion of fibers with centrally located nuclei, and an increase in the average fiber diameter compared to the control. The dysferlin protein was not found out in the muscle tissues.

Conclusion. Taking into account the results of the tests performed, it was shown that the absence of Dysf-/- gene expression

in Bla/J subline mice led to muscular dystrophy with the onset of the development of phenotypic disease manifestations at the age of 12 weeks and their peak at 24 weeks. Histopathological phenotypic manifestations of the disease are generally nonspecific and corresponded to the data of intravital pathoanatomical examination in diferlinopathy patients. The mice of the studied subline Bla/J are a representative model of dysferlinopathy and can be used to evaluate new therapeutic agents for the treatment of this disease.

Synuclein Proteins in MPTP-Induced Death of Substantia Nigra Pars Compacta Dopaminergic Neurons

Parkinson’s disease (PD) is one of the key neurodegenerative disorders caused by a dopamine deficiency in the striatum due to the death of dopaminergic (DA) neurons of the substantia nigra pars compacta. The initially discovered A53T mutation in the alpha-synuclein gene was linked to the formation of cytotoxic aggregates: Lewy bodies in the DA neurons of PD patients. Further research has contributed to the discovery of beta- and gamma-synucleins, which presumably compensate for the functional loss of either member of the synuclein family. Here, we review research from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) toxicity models and various synuclein-knockout animals. We conclude that the differences in the sensitivity of the synuclein-knockout animals compared with the MPTP neurotoxin are due to the ontogenetic selection of early neurons followed by a compensatory effect of beta-synuclein, which optimizes dopamine capture in the synapses. Triple-knockout synuclein studies have confirmed the higher sensitivity of DA neurons to the toxic effects of MPTP. Nonetheless, beta-synuclein could modulate the alpha-synuclein function, preventing its aggregation and loss of function. Overall, the use of knockout animals has helped to solve the riddle of synuclein functions, and these proteins could be promising molecular targets for the development of therapies that are aimed at optimizing the synaptic function of dopaminergic neurons.

A novel curcumin oil solution can better alleviate the motor activity defects and neuropathological damage of a Parkinson’s disease mouse model

Curcumin has been reported to improve or prevent movement disorders in Parkinson’s disease (PD); however, its low bioavailability is the biggest obstacle to its application. To optimize the limited efficacy of curcumin and to improve its protective effects against PD, we prepared and tested a novel curcumin oil solution. In vivo imaging was used to confirm that the curcumin oil solution has higher bioavailability than curcumin alone. To test its motor effects on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced movement disorders, behavioral tests, including the open-field test, pole test, rotarod test, and automated gait analysis were used. Finally, pathological evaluation using immunohistochemistry and western blotting analysis was done. Encouragingly, the behavioral test findings exhibited a better protective effect against MPTP-induced movement disorders. In addition, it had a greater protective effect on dopaminergic neurons in the compact part of the substantia nigra along with the PD process according to pathological evaluation. This novel curcumin oil solution may provide a new choice for PD prevention as a dietary supplement or clinically assisted treatment based on its better bioavailability and efficiency.