ИСТИНА

Background: Neuronal homeostasis and neurotransmission are critically dependent on the function and regulation of mitochondrial 2-oxo acid dehydrogenases [1]. Developing tools to regulate these enzymes is of pivotal importance. Recently we have proposed synthetic mimics of pyruvate, 2-oxoglutarate and 2-oxoadipate as highly specific inhibitors of the cognate dehydrogenases in vitro and in situ [2, 3]. In these compounds, the carboxyl group of 2-oxo acids is substituted with the phosphonate one, causing a tight binding to the corresponding 2-oxo acid dehydrogenases. Application of these inhibitors to cell cultures showed cell-specific roles of each of the 2-oxo acid dehydrogenases for metabolism and physiology, providing a basis for assessing the effects of the phosphonates as regulators of the 2-oxo acid dehydrogenases in vivo. Objective: To characterize metabolic, physiological and behavioural outcomes of the inhibition of the pyruvate, 2-oxoglutarate or 2-oxoadipate dehydrogenases by the phosphonate analogues of the respective 2-oxo acids in vivo. Methods: Membrane-permeable precursors of the synthetic phosphonate analogues of pyruvate, 2-oxoglutarate or 2-oxoadipate were administered to Wistar male rats intranasally at 0.02 mmol/kg dosage. Effects of the in vivo inhibition of the enzymes on the brain cortex metabolism, animal behaviour and ECG were characterized 24 hours after the drug administration. To reveal the phosphonates-induced changes in the brain metabolism, activities of the target and metabolically associated enzymes, as well as amino acid profiles were assessed as described earlier [4]. The Open Field test was used to determine the accompanying behavioural changes. Relative contributions of the sympathetic and parasympathetic components to the heart rate regulation were assessed using ECG with subcutaneous electrode implantation. One-way ANOVA with Tukey’s post-hoc test or Mann-Whitney test were employed to determine statistically significant differences between the animal groups (p≤0.05) and trends (0.05≤p≤0.1). Results: The inhibitor of pyruvate dehydrogenase decreased the brain levels of amino acids, including excitatory neurotransmitters glutamate and aspartate, concomitant with an elevation of glutamine synthase activity. The biochemical changes were associated with a shift towards the sympathetic control of the heart activity, indicated by a two-fold increase in heart rate variability-based “stress index” (p=0.08). Administration of the inhibitor of 2-oxoglutarate dehydrogenase resulted in a significant rearrangement of the amino acid pool and an altered redox metabolism, expressed as two-fold decreases in the levels of cystine and glutathione. On the physiological level, the 2-oxoglutarate dehydrogenase inhibitor increased anxiety indicators, such as duration of grooming and defecation. Treatment with the inhibitor of 2-oxoadipate dehydrogenase elevated the brain levels of aspartate and glutamate, accompanied by a two-fold increase in locomotion. Conclusion: Specific inhibition of essential mitochondrial dehydrogenases linked to the neurotransmitter production, by synthetic analogues of 2-oxo acids may be useful for correcting neurological and/or mental disorders through directed regulation of the brain metabolism and related physiological processes. The study is supported by Russian Science Foundation, grant 18-14-00116 to V. I. Bunik.