The study of the protective effect of mitochondrial uncouplers during acute toxicity of the fungicide difenoconazole in different organs of mice

Pesticides represent a serious problem for agricultural workers due to their neurotoxic effects. The aim of this study was to evaluate the ability of pharmacological oxidative phosphorylation uncouplers to reduce the effect of the difenoconazole fungicide on mitochondrial DNA (mtDNA) of various organs in mice. Injections of difenoconazole caused cognitive deficits in mice, and the protonophore 2,4-dinitrophenol (2,4-DNP) and Azur I (AzI), a demethylated metabolite of methylene blue (MB), prevented the deterioration of cognitive abilities in mice induced by difenoconazole. Difenoconazole increased the rate of reactive oxygen species (ROS) production, likely through inhibition of complex I of the mitochondrial respiratory chain. After intraperitoneal administration of difenoconazole lungs, testes and midbrain were most sensitive to the accumulation of mtDNA damage. In contrast, the cerebral cortex and hippocampus were not tolerant to the effects of difenoconazole. The protonophore 2,4-DNP reduced the rate of ROS formation and significantly reduced the amount of mtDNA damage caused by difenoconazole in the midbrain, and partially, in the lungs and testes. MB, an alternative electron carrier capable of bypassing inhibited complex I, had no effect on the effect of difenoconazole on mtDNA, while its metabolite AzI, a demethylated metabolite of MB, was able to protect the mtDNA of the midbrain and testes. Thus, mitochondria-targeted therapy is a promising approach to reduce pesticide toxicity for agricultural workers.

The Ketogenic Diet but not Hydroxycitric Acid Keeps Brain Mitochondria Quality Control and mtDNA Integrity Under Focal Stroke

Mitochondrial dysfunction in the ischemic brain is one of the hallmarks of stroke. Dietary interventions such as the ketogenic diet and hydroxycitric acid supplementation (a caloric restriction mimetic) may potentially protect neurons from mitochondrial damage induced by focal stroke in mice. We showed that in control mice, the ketogenic diet and the hydroxycitric acid did not impact significantly on the mtDNA integrity and expression of genes involved in the maintenance of mitochondrial quality control in the brain, liver, and kidney. The ketogenic diet changed the bacterial composition of the gut microbiome, which via the gut-brain axis may affect the increase in anxiety behavior and reduce mice mobility. The hydroxycitric acid causes mortality and suppresses mitochondrial biogenesis in the liver. Focal stroke modelling caused a significant decrease in the mtDNA copy number in both ipsilateral and contralateral brain cortex and increased the levels of mtDNA damage in the ipsilateral hemisphere. These alterations were accompanied by a decrease in the expression of some of the genes involved in maintaining mitochondrial quality control. The ketogenic diet consumption before stroke protects mtDNA in the ipsilateral cortex, probably via activation of the Nrf2 signaling. The hydroxycitric acid, on the contrary, increased stroke-induced injury. Thus, the ketogenic diet is the most preferred variant of dietetic intervention for stroke protection compared with the hydroxycitric acid supplementation. Our data confirm some reports about hydroxycitric acid toxicity, not only for the liver but also for the brain under stroke condition.

Methylene Blue Induces Antioxidant Defense and Reparation of Mitochondrial DNA in a Nrf2-Dependent Manner during Cisplatin-Induced Renal Toxicity

Cisplatin is a platinum-based cytostatic drug that is widely used for cancer treatment. Mitochondria and mtDNA are important targets for platinum-based cytostatics, which mediates its nephrotoxicity. It is important to develop therapeutic approaches to protect the kidneys from cisplatin during chemotherapy. We showed that the exposure of mitochondria to cisplatin increased the level of lipid peroxidation products in the in vitro experiment. Cisplatin caused strong damage to renal mtDNA, both in the in vivo and in vitro experiments. Cisplatin injections induced oxidative stress by depleting renal antioxidants at the transcriptome level but did not increase the rate of H₂O₂ production in isolated mitochondria. Methylene blue, on the contrary, induced mitochondrial H₂O₂ production. We supposed that methylene blue-induced H₂O₂ production led to activation of the Nrf2/ARE signaling pathway. The consequences of activation of this signaling pathway were manifested in an increase in the expression of some antioxidant genes, which likely caused a decrease in the amount of mtDNA damage. Methylene blue treatment induced an increase in the expression of genes that were involved in the base excision repair (BER) pathway: the main pathway for mtDNA reparation. It is known that the expression of these genes can also be regulated by the Nrf2/ARE signaling pathway. We can assume that the protective effect of methylene blue is related to the activation of Nrf2/ARE signaling pathways, which can activate the expression of genes related to antioxidant defense and mtDNA reparation. Thus, the protection of kidney mitochondria from cisplatin-induced damage using methylene blue can significantly expand its application in medicine.

[Effect of methylene blue and its metabolite - azure I - on bioenergetic parameters of intact mice brain mitochondria]

Methylene blue is a phenothiazine dye that is widely used in medicine and clinical trials for the treatment of Alzheimer's disease. One of the factors of the unique therapeutic effect of methylene blue is its redox properties, allowing implementation of alternative electron transport - the dye accepts electrons from reducing equivalents in the mitochondria and transfer it them to other components of the respiratory chain or molecular oxygen. Azure I, an N-dimethylated metabolite of methylene blue, is potentially a more effective compound than methylene blue, but its ability for alternative electron transport has not been studied. We have shown that azure I, unlike methylene blue, is unable to restore the membrane potential in isolated mouse brain mitochondria, inhibited by rotenone and, therefore, is unable to perform bypass of the respiratory chain Complex I. Moreover, the addition of azure I does not affect the rate of mitochondrial respiration in contrast to methylene blue, which increases the rate of non-phosphorylation respiration. At the same time, both dyes stimulate an increase in H2O2 production. As a consequence, only methylene blue is capable of alternative electron transport, while azure I does not produce complex I bypass. This limits its therapeutic application only as a mitochondrial-targeted drug, but not as a substance with a potentially powerful antidepressant effect.

[The influence of solar and geomagnetic activity on the risk of multiple sclerosis (results of correlation and regression analysis)]

AIM

Multiple sclerosis (MS) develops as a result of an interaction between genetic and environmental factors, among them solar (SA) and geomagnetic activity (GMA) attract the particular attention. An impact of SA and GMA on intrauterine and postnatal period in MS was studied.

MATERIAL AND METHODS

The study included 358 patients with MS. Correlation (CA) and regression analysis (RA) were used to study the effects of SA and GMA during intrauterine period, the 1st year of life, a year of disease onset, a year before the onset.

RESULTS AND CONCLUSIONS

CA revealed the association between the MS onset and mean values of kp-index in the onset year and the year before the onset year, number of days with kp≥4 and kp≥5 in the onset year and the year before the onset year, mean SFU in the onset year. RA revealed the association between the MS onset and mean kp in the year before the onset year and in the onset year, number of days with kp≥7 in the onset year and the year before the onset year, mean kp during pregnancy, number of days with kp≥7 in the 1st year of life and during pregnancy. The influence of high GMA during pregnancy and in the 1st year of life increases the MS risk in the future and the high GMA predisposes to the MS onset in adults. The practical value of the study is that predicting the GMA changes we can try to prevent the onset and relapses in the risk groups.

[The role of the solar and geomagnetic activity in the etiology of multiple sclerosis: a review of the literature and prospects of research]

Despite the great progress in the study of multiple sclerosis (MS), its etiology remains unknown. It is proved that MS occurs in genetically predisposed people under the influence of environmental factors. Among these factors the solar activity (SA) and geomagnetic activity (GA) attract the particular attention. This article presents the review of studies concerning the influence of SA and GA on the incidence and course of MS.