Urine metabolic profile in rats with arterial hypertension of different genesis.

The diversity of pathogenetic mechanisms underlying arterial hypertension leads to the necessity to devise a personalized approach to the diagnosis and treatment of the disease. Metabolomics is one of the promising methods for personalized medicine, as it provides a comprehensive understanding of the physiological processes occurring in the body. The metabolome is a set of low-molecular substances available for detection in a sample and representing intermediate and final products of cell metabolism. Changes in the content and ratio of metabolites in the sample mark the corresponding pathogenetic mechanisms by highlighting them, which is especially important for such a multifactorial disease as arterial hypertension. To identify metabolomic markers for hypertensive conditions of different origins, three forms of arterial hypertension (AH) were studied: rats with hereditary AH (ISIAH rat strain); rats with AH induced by L-NAME administration (a model of endothelial dysfunction with impaired NO production); rats with AH caused by the administration of deoxycorticosterone in combination with salt loading (hormone-dependent form - DOCA-salt AH). WAG rats were used as normotensive controls. 24-hour urine samples were collected from all animals and analyzed by quantitative NMR spectroscopy for metabolic profiling. Then, potential metabolomic markers for the studied forms of hypertensive conditions were identified using multivariate statistics. Analysis of the data obtained showed that hereditary stress-induced arterial hypertension in ISIAH rats was characterized by a decrease in the following urine metabolites: nicotinamide and 1-methylnicotinamide (markers of inflammatory processes), N- acetylglutamate (nitric oxide cycle), isobutyrate and methyl acetoacetate (gut microbiota). Pharmacologically induced forms of hypertension (the L-NAME and DOCA+NaCl groups) do not share metabolomic markers with hereditary AH. They are differentiated by N,N-dimethylglycine (both groups), choline (the L-NAME group) and 1-methylnicotinamide (the group of rats with DOCA-salt hypertension).

Metabolic profile of blood serum in experimental arterial hypertension.

The etiology of essential hypertension is intricate, since it employs simultaneously various body systems related to the regulation of blood pressure in one way or another: the sympathetic nervous system, renin-angiotensin-aldosterone and hypothalamic-pituitary-adrenal systems, renal and endothelial mechanisms. The pathogenesis of hypertension is influenced by a variety of both genetic and environmental factors, which determines the heterogeneity of the disease in human population. Hence, there is a need to perform research on experimental models - inbred animal strains, one of them being ISIAH rat strain, which is designed to simulate inherited stress-induced arterial hypertension as close as possible to primary (or essential) hypertension in humans. To determine specific markers of diseases, various omics technologies are applied, including metabolomics, which makes it possible to evaluate the content of low-molecular compounds - amino acids, lipids, carbohydrates, nucleic acids fragments - in biological samples available for clinical analysis (blood and urine). We analyzed the metabolic profile of the blood serum of male ISIAH rats with a genetic stress-dependent form of arterial hypertension in comparison with the normotensive WAG rats. Using the method of nuclear magnetic resonance spectroscopy (NMR spectroscopy), 56 metabolites in blood serum samples were identified, 18 of which were shown to have significant interstrain differences in serum concentrations. Statistical analysis of the data obtained showed that the hypertensive status of ISIAH rats is characterized by increased concentrations of leucine, isoleucine, valine, myo-inositol, isobutyrate, glutamate, glutamine, ornithine and creatine phosphate, and reduced concentrations of 2-hydroxyisobutyrate, betaine, tyrosine and tryptophan. Such a ratio of the metabolite concentrations is associated with changes in the regulation of glucose metabolism (metabolic markers - leucine, isoleucine, valine, myo-inositol), of nitric oxide synthesis (ornithine) and catecholamine pathway (tyrosine), and with inflammatory processes (metabolic markers - betaine, tryptophan), all of these changes being typical for hypertensive status. Thus, metabolic profiling of the stress-dependent form of arterial hypertension seems to be an important result for a personalized approach to the prevention and treatment of hypertensive disease.

Aggregation of α-crystallins in kynurenic acid-sensitized UVA photolysis under anaerobic conditions.

The reactions of photoexcited kynurenic acid (KNA) with bovine α-crystallins under anaerobic conditions proceed via the electron transfer from tryptophan (Trp) and tyrosine (Tyr) residues to the triplet KNA molecules. The subsequent radical reactions lead to the protein aggregation and insolubilization. The absorption of the photolyzed proteins at 335 nm as well as their total fluorescence significantly increases, while the tryptophan-related fluorescence decreases. It has been established that the alterations of the protein optical properties are related to the modifications of Trp residues. Intrinsic lens antioxidants ascorbate (Asc) and glutathione (GSH) that are present in the human lens at the millimolar level effectively block the formation of the observed light-induced protein modifications. The protective effect of Asc was attributed to its ability to quench highly reactive triplet states, while the role of GSH, most likely, corresponds to the reduction of photochemically formed radicals into a diamagnetic state. The results obtained disclose the possible mechanism of UVA-induced modifications of the lens crystallins, leading to the formation of cataract, and the role of major lens antioxidants Asc and GSH in the protection of the lens proteins.

Effect of SkQ1 eye drops on the rat lens metabolomic composition and the chaperone activity of α-crystallin.

The ability of SkQ1 eye drops to slow down the cataract development is demonstrated on the senescence-accelerated OXYS rats: the SkQ1 treatment leads to the considerable improvement of the lens condition as compared to the control group. The comparison of the chaperone activities of α-crystallins isolated from the rat lenses did not reveal significant difference between SkQ1-treated and control rats. The contents of major metabolites (23 compounds) in lenses of SkQ1-treated and untreated rats are also very similar, though the concentration of reduced glutathione (GSH) in lenses of SkQ1-treated rats is 12% lower. This difference may be attributed to the reduction of the oxidative stress under action of SkQ1 eye drops, and to the decreased requirement to produce high amounts of this antioxidant.

The therapeutic effect of mitochondria-targeted antioxidant SkQ1 and Cistanche deserticola is associated with increased levels of tryptophan and kynurenine in the rat lens.

Supplementation of senescence-accelerated OXYS rats with the mitochondria-targeted antioxidant SkQ1 and with the powder from Cistanche deserticola results in the deceleration of the cataract development and even in the improvement of lens transparency. The therapeutic effect of these preparations correlates with a significant elevation of tryptophan and kynurenine levels in the lens. This finding is attributed to a deceleration of the tryptophan and kynurenine oxidation due to antioxidant-assisted reduction of oxidative stress in the lens.

Photoactivity of kynurenine-derived UV filters.

Quantum yields of photodecomposition and triplet state formation under aerobic and anaerobic conditions are determined for kynurenine (KN), 3-hydroxykynurenine (3OHKN), xanthurenic acid (XAN), and kynurenine adducts of glutathione (GSH-KN), cysteine (Cys-KN), histidine (His-KN), and lysine (Lys-KN) in aqueous solutions. The highest yields of anaerobic photodecomposition were obtained for GSH-KN and His-KN adducts, which correlates with the highest triplet yields for these compounds. In aerobic conditions, the photodecomposition yields for all compounds under study increase; the highest decomposition rates were observed for His-KN and 3OHKN. The fast decomposition of the latter is attributed to the dark autoxidation of the starting compound.

Competition between ultrafast relaxation and photoionization in excited prefluorescent states of tryptophan and indole.

The quantum yield of photoionization of TrpH and IndH from the nonrelaxed prefluorescent state S* increases with the temperature decrease. This effect is attributed to the competition between temperature independent ionization and ultrafast thermal relaxation S* --> S1. The rate constant of the relaxation does not depend on the solvent and on the presence of the amino acid side chain: the temperature dependences of photoionization quantum yield, obtained for TrpH and IndH in different solvents, practically coincide. The activation energy for the relaxation rate constant Er approximately 4.5 kJ/mol probably corresponds to intramolecular process or to the formation of the vibronically excited transient complex between photoexcited molecule and solvent molecules.

Mechanisms of reactions of flavin mononucleotide triplet with aromatic amino acids.

Chemical reactions between the photoexcited triplet state of flavin mononucleotide and the aromatic amino acids, N-acetyl tryptophan (TrpH), N-acetyl tyrosine (TyrOH), and N-acetyl histidine (HisH) in aqueous solution have been studied in the pH range 2-12. Across the whole pH range, the principal mechanism of reaction of both TrpH and TyrOH is shown to be electron transfer. For HisH, the mechanism and rate of the reaction depend on the protonation state of the reactants. In acidic conditions (pH < 4), reaction does not occur. At 4 < pH < 11, the reaction proceeds via hydrogen atom abstraction with a rate constant varying from 3.0 x 10(6) to 2.5 x 10(8) M(-1) s(-1). In extremely basic solution (pH > 12) the mechanism switches to electron transfer.

Effects of surfactants on the photosensitized production of tyrosine radicals studied by photo-CIDNP.

The influence of the surfactants sodium dodecyl sulphate, cetyltrimethyl-ammonium bromide and triton X-100 on the photochemically induced dynamic nuclear polarization (CIDNP) of N-acetyl tyrosine has been investigated. Three photosensitizers were used to generate polarization: thionin, eosin Y and flavin mononucleotide. 600 MHz 1H photo-CIDNP experiments, supported by laser flash photolysis transient absorption measurements, indicate that the neutral triton surfactant has no influence on the nuclear polarization, but that the other two, charged, amphiphiles affect the photochemistry in a variety of ways, depending on the surfactant concentration and the identity of the sensitizer.