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The etiology and pathogenesis of Parkinson's disease (PD) are tightly linked to the gain-of-function of α-synuclein. However, gradual accumulation of α-synuclein aggregates in dopaminergic neurons of substantia nigra pars compacta (SNpc) leads to the depletion of the functional pool of soluble α-synuclein, and therefore, creates loss-of-function conditions, particularly in presynaptic terminals of these neurons. Studies of how this late-onset depletion of a protein involved in many important steps of neurotransmission contributes to PD progression and particularly, to worsening the nigrostriatal pathology at late stages of the disease are limited and obtained data, are controversial. Recently, we produced a mouse line for conditional knockout of the gene encoding α-synuclein, and here we used its tamoxifen-inducible pan-neuronal inactivation to study consequences of the adult-onset (from the age of 6 months) and late-onset (from the age of 12 months) α-synuclein depletion to the nigrostriatal system. No significant changes of animal balance/coordination, the number of dopaminergic neurons in the SNpc and the content of dopamine and its metabolites in the striatum were observed after adult-onset α-synuclein depletion, but in aging (18-month-old) late-onset depleted mice we found a significant reduction of major dopamine metabolites without changes to the content of dopamine itself. Our data suggest that this might be caused, at least partially, by reduced expression of aldehyde dehydrogenase ALDH1a1 and could lead to the accumulation of toxic intermediates of dopamine catabolism. By extrapolating our findings to a potential clinical situation, we suggest that therapeutic downregulation of α-synuclein expression in PD patients is a generally safe option as it should not cause adverse side effects on the functionality of their nigrostriatal system. However, if started in aged patients, this type of therapy might trigger slight functional changes of the nigrostriatal system with potentially unwanted additive effect to already existing pathology. • Efficient depletion of striatal α-synuclein after adult-onset inactivation of Snca. • Nigrostriatal system is not markedly affected by adult-onset depletion of α-synuclein. • Changes to striatal dopamine metabolism after α-synuclein depletion in aging animals. • Downregulation of ALDH1a1 as a possible cause of striatal dopamine metabolism changes. [ABSTRACT FROM AUTHOR]

The class of carbazoles includes compounds with high biological activities and broad spectra of action. PLX01107 and PLX01008 are xenomycins, a new subclass of antimicrobial carbazole derivatives demonstrating strong antifungal activity in vitro . We performed three tests, a bacterial reverse mutation assay (Ames test), in vitro cytokinesis-block micronucleus assay, and chromosome aberration test in mouse bone marrow cells, to investigate the possible genotoxicity of these compounds. Despite their structural similarity, the two compounds had different genotoxicity profiles. PLX01008 showed positive effects in all assays. PLX01107 showed no mutagenicity in the Ames test but demonstrated strong cytogenetic activity in vitro and in vivo . PLX01107 was also tested in the in vivo alkaline comet assay, where a weak but statistically significant increase in DNA damage was seen in liver cells 24 h after treatment. Significantly increased levels of formamidopyrimidine DNA glycosylase (FPG)-sensitive sites were found in bone marrow cells of PLX01107-treated mice (FPG-modified comet assay), suggesting induction of oxidative or alkylation damage to DNA. [ABSTRACT FROM AUTHOR]

We performed an inter-laboratory study to determine the variation of comet assay results and to identify its possible reasons. An exchange of slides between Labs in different stages of the comet assay protocol was performed. Because identical slides, durations of alkali treatment and electrophoresis, and similar electric field strengths (2.0V/cm and 2.14V/cm) were used, we concluded that the observed inter-laboratory difference in the results is directly associated with the electrophoresis step. In Lab 1, mouse bone marrow cells were exposed to methyl methanesulfonate at concentrations of 10, 25 and 50μM for 3h at 37°C. In Lab 2, cells the same as in Lab 1 were immobilized in LMA on slides and exposed to X-rays at doses of 3-8Gy. We found that the transportation of slides after lysis or electrophoresis step, as well as different dyes used for scoring did not produce any significant effect on the results. No substantial difference in the data was also revealed when various software packages were used for image analysis. The temperature of the alkaline solution was shown to increase during electrophoresis and, besides, the temperature heterogeneity of the solution took place in the area of the platform, with a maximum in the middle of the chamber. The temperature heterogeneity could affect the rate of conversion of alkali labile sites into single stranded breaks. Thus, it was clearly indicated that real temperature variations during the alkali treatment and electrophoresis were an essential factor in the variability of the results between our Labs. [ABSTRACT FROM AUTHOR]