Vol 89, No 10 (2024)

Maternal hyperhomocysteinemia (HHcy) is a risk factor for the development of intrauterine growth restriction, a proposed mechanism of which is a decrease in transplacental nutrient transport. In this study, we have investigated the effect of experimental HHcy caused by daily methionine administration to pregnant rats on the free amino acid content in the mother and fetal blood. The morphological and biochemical parameters on which amino acid transport through the placenta depends have also been studied. Under the influence of HHcy on the 20th day of pregnancy, an increase in the levels of most free amino acids was observed in the mother blood, while some amino acid concentrations in the fetal blood were decreased. Under conditions of HHcy in the placental labyrinth, which is an exchange site between mother and fetal circulations, the maternal sinusoids narrowed, being accompanied by blood stagnation and red blood cell aggregation. In the labyrinth zone, we also observed an increase in the protein level of neutral amino acid transporters (LAT1, SNAT2) and an activation of the downstream effector of the mTORC1 complex, 4E-BP1, which is a positive regulator of the placental transporter expression. Maternal HHcy caused an increase in the placental barrier permeability, as evidenced by an intensification in the mother to fetus transfer of the Evans blue dye. The imbalance of the free amino acid levels in the mother and fetal blood under conditions of HHcy may be due to the competition of homocysteine with other amino acids for their common transporters, as well as a decreased exchange zone area and reduced blood flow in the placental labyrinth. An increase in the amino acid transporter expression in the labyrinth zone may be a compensatory response to an insufficient intrauterine amino acid supply and a fetal growth decrease.

Glutamine plays an important role in tumor metabolism. It is known that the core region of the solid tumors is deprived of glutamine which affects tumor growth and spread. Here we investigated the effect of glutamine deprivation on cellular metabolism and sensitivity of human glioblastoma cells U87MG and T98G to drugs of various origin: alkylating cytostatic agent temozolomide; cytokine TRAIL DR5-B – agonist of the DR5 receptor; and GMX1778 – a targeted inhibitor of the enzyme nicotinamide phosphoribosyltransferase (NAMPT), limiting NAD biosynthesis. Bioinformatics analysis of the cell transcriptomes showed that U87MG cells have a more differentiated phenotype than T98G, and also differ in the expression profile of genes associated with glutamine metabolism. Upon glutamine deprivation, the growth rate of U87MG and T98G cells decreased. Analysis of cellular metabolism by FLIM microscopy of NADH as well as assessment of the lactate content in the medium showed that glutamine deprivation shifted the metabolic status of U87MG cells towards glycolysis. This was accompanied by an increase in the expression of the stemness marker CD133, which collectively may indicate the de-differentiation of these cells. At the same time, we observed an increase in both the expression of DR5 receptor and the sensitivity of U87MG cells to DR5-B. On the contrary, glutamine deprivation of T98G cells induced a metabolic shift towards oxidative phosphorylation, a decrease in DR5 expression and resistance to DR5-B. The effects of NAMPT inhibition also differed across two cell lines and were opposite to those of DR5-B: upon glutamine deprivation, U87MG cells acquired resistance, while T98G cells were sensitized to GMX1778. Thus, phenotypic and metabolic differences between two human glioblastoma cell lines resulted in divergent metabolic changes and contrasting responses to different targeted drugs during glutamine deprivation. These data should be considered when developing treatment strategies for glioblastoma via drug deprivation of amino acids, as well as when exploring novel therapeutic targets.

This review focuses on the recently discovered specific action of two classical endocannabinoids (EC), 2-arachidonoylglycerol (2-AG) and arachidonoylethanolamide (AEA), in the case of their synthesis and degradation in skeletal muscles, in other words this review is dedicated to the properties and action of the myoendocannabinoid (myoEC) pool. The influence of this pool is considered at three different levels: at the level of skeletal muscles, motor synapses, and also at the level of the whole organism, including the central nervous system. Special attention is paid to the still significantly underestimated and intriguing ability of ECs to have a positive effect on energy exchange and contractile activity of muscle fibers, as well as on transmitter secretion in motor synapses. The role of muscle contractions in the regulation of the activity balance of synthesis and degradation enzymes for myoECs and therefore in the release of myoECs and the exertion of their specific effects is thoroughly considered. Increasingly popular hypotheses about the prominent role of myoECs (AEA and/or 2-AG) in the rise of the overall level of ECs in the blood during muscle exercise and the development of “runner’s high” and about the role of myoECs in the correction of a number of psychophysiological conditions (pain syndrome, stress, etc.) are discussed here. Thus, this review presents information about the myoEC pool from a totally new viewpoint, underlining its possible independent and non-trivial regulatory role in the body, in contrast to the traditional and well-known activity of neurogenic ECs.

Previously, we found that in the reaction center (RC) of the purple bacterium Cereibacter sphaeroides, the formation of a heterodimeric primary electron donor (P), caused by the substitution of His-L173 by Leu, was compensated by a second mutation Ile-L177 – His. Significant changes in the spectral properties, pigment composition and redox potential of P, observed in the H(L173)L RC, are restored to the corresponding characteristics of the native RC in the RC H(L173)L/I(L177)H, with the difference that the energy of the long-wavelength Q_Y optical transition of P increases significantly (by ~75 meV). In this work, using light-induced FTIR difference spectroscopy, it was shown that in the RC with double mutation, the homodimeric structure of P is preserved with partially altered electronic properties: the electronic coupling in the radical-cation of the P+ dimer is weakened and the localization of the positive charge on one of its halves increases. The results of the study of the triple mutant H(L173)L/I(L177)H/F(M197)H are consistent with the assumption that the observed changes in the P+ electronic structure, as well as considerable blue shift of Q_Y P absorption band in the RC H(L173)L/ I(L177)H, are associated with a modification of the spatial position and/or geometry of P. Using femtosecond absorption difference spectroscopy, it was shown that the mutant H(L173)L/I(L177)H RC retains a sequence of reactions P* → P+B_A− → P+H_A− → P+Q_A− with electron transfer rates and the quantum yield of the final state P+Q_A− close to those observed in the wild-type RC (P* is the singlet-excited state of P; B_A, H_A, and Q_A are molecules of bacteriochlorophyll, bacteriopheophytin, and ubiquinone in the active A-branch of cofactors, respectively). The obtained results, together with previously published data for the RC with a symmetrical double mutation H(M202)L/I(M206)H, demonstrate that by introducing additional point amino acid substitutions, the photochemical activity of the isolated RC from C. sphaeroides can be maintained at a high level even in the absence of important structural elements – axial histidine ligands to the primary electron donor P.

Changes in the intracellular concentrations of Na⁺ and K⁺ are shown to alter gene expression. Another monovalent cation, Li⁺, is well known as medicine for the treatment of psychiatric disorders but mechanism of its action is obscure. Thus, it is important to evaluate an effect of Li⁺ on gene expression in endothelial cells. Here we studied the influence of increased intracellular Na⁺ or Li⁺ concentrations on the transcription of Na⁺_i/K⁺_i-sensitive genes. A treatment of human endothelial cells (HUVEC) with LiCl for 1.5 h caused an accumulation of Li⁺ in the cells. This was followed by an increase in FOS and EGR1 mRNA and a decrease in JUN and MYC mRNA levels. Treatment of HUVEC with monensin led to an accumulation of Na⁺ and a loss of K⁺ ions. However, Na⁺-ionophore monensin had no significant effect on gene expression. Incubation of HUVEC with elevated extracellular NaCl concentration increased intracellular K⁺ concentration and ATF3 transcription and decreased JUN transcription. These results indicate that Na⁺ and Li⁺ ions have different effects on the cellular gene expression profile that apparently due to various actions on the intracellular monovalent cations ratio.