[Vitamin D3 availability and functional activity of peripheral blood phagocytes in experimental type 1 diabetes].

The study was devoted to identifying the relation between vitamin D3 availability (assessed by the level of circulatory 25OHD3), content of vitamin D3 25-hydroxylase isozymes CYP27A1 and CYP2R1 in hepatic tissue and functional activity of peripheral blood phagocytes in mice with experimental type 1 diabetes. It has been shown that diabetes is accompanied by the development of vitamin D3-deficiency which is characterized by decreased 25OHD3 content in blood serum and determined by changes in tissue expression of the major isoforms of vitamin D3 25-hydroxylase. The level of hepatic CYP27A1 was revealed to be markedly reduced with a concurrent significant augmentation of CYP2R1. Cholecalciferol administration resulted in normalization of tissue levels of both isoforms of vitamin D3 25-hydroxylase and blood serum 25OHD3 content. Diabetes-associated vitamin D3 deficiency correlated with a decrease in phagocytic activity of granulocytes and monocytes, and their ability to produce antibacterial biooxidants such as reactive oxygen and nitrogen forms. Vitamin D3 efficacy to attenuate these abnormalities of immune function was established, indicating an important immunoregulatory role of cholecalciferol in the phagocytic mechanism of antigens elimination implemented by granulocytes and monocytes.

[The ROS-generating and antioxidant systems in the liver of rats treated with prednisolone and vitamin D3].

The mechanisms of glucocorticoid-induced disturbances of liver function is currently not fully clarified. Vitamin D3 was previously shown to play an important role in the regulation of impaired oxidative metabolism and detoxification function of the liver associated with the effects of hepatotoxic compounds. The study was undertaken to define the intensity of oxidative metabolism in the rat liver and survival of hepatocytes after prolonged prednisolone administration and to assess whether vitamin D3 is capable to counter glucocorticoid-induced changes. It has been shown that prednisolone (0.5 mg per animal for 30 days) leads to 1.6-fold increase in the percentage of necrotic cells among isolated hepatocytes as compared with the control. The glucocorticoid-induced impairment of hepatocellular function was accompanied by enhanced generation of reactive oxygen species (ROS), accumulation of TBA-active products and carbonylated proteins but reduced levels of free SH-groups of low molecular weight compounds. It was demonstrated a decrease in the activities of key enzymes of antioxidant system (SOD, catalase, glutathione peroxidase), whereas the activities of pro-oxidant enzymes NAD(P)H-quinone oxidoreductase and semicarbazide-sensitive amine oxidase were shown to be increased. Vitamin D3 (and to greater extent in combination with α-tocopherol) administration (100 IU) on the background of glucocorticoid therapy caused normalizing effects on the level of ROS formation, oxidative modification of biomolecules and activity of antioxidant enzymes resulting in better survival of hepatocytes. These data suggest a potential role of vitamin D3 in the regulation of oxidative metabolism alterations related to hepatotoxic action of glucocorticoids.

[Immunomodulatory effects of vitamin D3 and bisphosphonates in nutritional osteoporosis in rats].

The aim of this study was to determine the effectiveness of separate and combined administration of vitamin D3 and different forms of bisphosphonate (disodium salt of methylenbisphosphonic acid dihydrate and alendronate) on the function of immune cells in rats with nutritional osteoporosis. It was shown that D-hypovitaminosis leads to reduced 25OHD3, which is a biomarker for vitamin D3 and disturbances of metabolic processes in bone tissue that correlated with osteoporosis manifestation. Immunologic disorders related to nutritional osteoporosis were accompanied by the decrease in phagocytic activity of granulocytes and impaired ability to produce bactericidal oxidants. Inhibition of B-cell immunity also occurred in patholgy. Thus, the present study revealed more pronounced immunomodulatory effects of vitamin D3 on phagocytic immunity, whereas bisphosphonates were effective in improving the humoral immune protection.

[Role of PARP and protein poly-ADP-ribosylation process in regulation of cell functions].

This review focuses on the biological role of enzymes involved in posttranslational modification of proteins by their poly-ADP-ribosylation, a NAD-consuming process with an emerging key role in providing fundamental cell functions. To this end, detailed analysis of structural organization in relation to basic functions of the poly(ADP-ribose) polymerase-1 (PARP-1), the founding member of the PARP family, and other poly(ADP-ribose) polymerase isoforms is presented here. These include the current views on the role of PARP family enzymes and processes of poly-ADP-ribosylation of proteins in chromatin structure remodeling, DNA damage repair, regulation of gene expression, and integration of cellular signaling pathways. Considerable attention is paid to the involvement of PARP in cellular functions, particularly in cell division, intracellular transport of macromolcules, proteasomal protein degradation, immune response and caspase-independent necrotic pathways defined as necroptosis (programmed necrosis). In the light of the remarkable successes that have been reported for treating inflammatory disorders and cancer with different classes of PARPs inhibitors, we discuss the prospects of targeting PARPs with therapeutic purposes.

[Noncoenzyme function of vitamin PP and its biologically active derivatives: the current state of the problem].

This review is devoted to the current state of investigations of vitamin PP and nicotinamide dinucleotides noncoenzyme functions. Particular attention has been focused on the role of these compounds in post-translation modification of proteins (mono- and poly-ADP-ribosylation), in regulation of gene activity, calcium homeostasis and Ca2+ signalling as well as in modulation of synaptic transmission. Biological significance of these processes in cell function was elicited. The role of deregulation of vitamin PP mediated signalling mechanisms involved in control over the cell function under conditions of different diseases was emphasized.

[Mechanisms of diabetes-induced impairements of serotonin release from rat brain synaptosomes: effect of nicotinamide].

It has been previously shown that diabetes-associated central nervous system abnormalities are characterized by progressive alterations of neurotransmission. In particular, recent studies from our group have demonstrated that more early diabetes is accompanied by the increased spontaneous serotonin release from isolated synaptic endings; however the mechanism is still not clear. The current study was undertaken to estimate the relative importance of membrane potential and extracellular Ca2+ in the serotonin secretion process in diabetes. With the premise that increased phosphorylation of target proteins may be responsible for the increase in transmitter release we tested whether cAMP/PKA-mediated phosphorylations as well as mono-ADP-ribosylation of effector proteins were implicated in diabetes-associated brain failures. In addition, the effects of nicotinamide, a multiple-action compound, were examined. It was shown that diabetes caused a significant increase in spontaneous release of [2-(14)C]serotonin that was accompanied by synaptic membranes depolarization. Omission of Ca2+ from the incubation medium largely inhibited serotonin release only in untreated diabetes. Exposure of diabetic synaptosomes to cAMP-dependent protein kinase inhibitor H89, similar to Ca2+ -free medium, downregulated serotonin release. The level of constitutively mono-ADP-ribosylated proteins of diabetic synaptosomes was elevated vs control. Protein mono-ADP-ribosylation induced by cholera toxin (CTX), activator of Gs-protein-coupled adenylyl cyclase, resulted in excessive 1.2-fold enhancement over basal level but to the less extent in diabetes as compared with that of control. Nevertheless, CTX as well as forskolin exerted more strong stimulating effect on serotonin release from diabetic synaptosomes as compared to control. H89 counteracted CTX-related action on this variable strongly suggesting that impaired serotonin release is, at least, dependent on Gs-protein-mediated phosphorylation. Nicotinamide treatment virtually normalized both protein mono-ADP-ribosylation and serotonin release as well as synaptosomal response to all stimuli used. The data suggest that alterations in protein mono-ADP-ribosylation may be involved as a possible mechanism responsible for the impaired neurotransmission in diabetes and nicotinamide may efficiently protect against ADP-ribosylationmediated abnormalities in brain function.

[State of GABA-benzodiazepine receptor complex in diabetic neuropathy: effect of nicotinamide and nicotinoyl-GABA]. / Stan HAMK-benzodiazepinovoho retseptornoho kompleksu za diabetychnoï neiropatiï: efekt nikotynamidu ta nikotynoïl-HAMK.

An increase in GABA uptake by isolated rat brain synaptic endings as well as a decrease of pharmacologically active GABA analogue muscimol specific binding have indicated a physiologically drastic failure in realization of GABA-mediated inhibitory effects in CNS induced by diabetic encephalopathy. In spite of the impairment of inhibitory function of GABAergic transmission in diabetes a crucial activation of benzodiazepine receptors was determined, as it is tested by the increase in specific binding of flunitrazepam by synaptic membranes. This increase may play an important role in endogenous control of neural activity associated with the factors undefined so far. Using the approach that GABA, and several synthetic GABA agonists, appear to increase the affinity of the benzodiazepine recognition sites for such ligands, presumably by some allosteric mechanism, the findings concerning the in vitro binding assay technique confirm at least some of the functional characteristics observed between GABA and benzodiazepine receptors in vivo under pathological conditions. Indeed, the absence of activating effect on the affinity of flunitrazepam specific binding in the presence of micromolar concentrations of exogenous GABA implicate diabetes-induced alterations in coupling GABA- and benzodiazepine receptors that might be linked to changes in conformantial state of this membrane-bound complex and could partially explain diabetes-induced impairments of GABAergic transmission evaluated in the present study. Our study suggests that nicotinamide and especially GABA play an important role in improving the functioning of brain GABA-benzodiazepine complex impaired in diabetes through specific ligand-mediated mechanism and can be useful in the management of diabetes-associated brain failures.

[Oxidative stress correction by nicotinamide and nicotynol-GABA in diabetic neuropathy]. / Korektsiia nikotynamidom ta nikotynoïl-HAMK oksydatyvnoho stresu za diabetychnoï neiropatiï.

Concentration of lipid peroxidation products and antioxidant enzyme activities in rat brain and erythrocytes and the effects of nicotinamide and nicotinoyl-GABA administration on these parameters were estimated on 21st day of streptozotocin-induced diabetes. It was demonstrated more then two-fold diabetes-induced accumulation of conjugated dienes and malondialdehyde in tissues studied. Superoxide dismutase and glutathione reductase activities of both brain homogenate and erythrocytes as well as catalase and glutathione peroxidase activities of brain homogenate were shown to decrease significantly in diabetic rats, meanwhile, catalase activity of erythrocytes was increased and glutathione peroxidase unchanged. So the correlation between changes in enzymatic antioxidant system in brain and erythocytes failed to be found. Alterations observed were virtually prevented by the course of nicotinamide and nicotinoyl-GABA treatment. The results suggested that the suppression of antioxidant system could be primary biochemical disturbance in diabetic neuropathy progression. It was shown that the antioxidant efficacy of nicotinoyl-GABA is lower than that of nicotinamide. It was suggested that the mechanism of antioxidant action of nicotinamide and its structural analogue consists of both scavenging of lipid peroxides and NAD biosynthesis that leads to activation and normalization of altered energy and lipid metabolism.