Dicarbonyl-Modified Low-Density Lipoproteins Are Key Inducers of LOX-1 and NOX1 Gene Expression in the Cultured Human Umbilical Vein Endotheliocytes

Expression of LOX-1 and NOX1 genes in the human umbilical vein endotheliocytes (HUVECs) cultured in the presence of low-density lipoproteins (LDL) modified with various natural dicarbonyls was investigated for the first time. It was found that among the investigated dicarbonyl-modified LDLs (malondialdehyde (MDA)-modified LDLs, glyoxal-modified LDLs, and methylglyoxal-modified LDLs), the MDA-modified LDLs caused the greatest induction of the LOX-1 and NOX1 genes, as well as of the genes of antioxidant enzymes and genes of proapoptotic factors in HUVECs. Key role of the dicarbonyl-modified LDLs in the molecular mechanisms of vascular wall damage and endothelial dysfunction is discussed.

The Role of Phospholipase Activity of Peroxiredoxin 6 in Its Transmembrane Transport and Protective Properties

Peroxiredoxin 6 (Prdx6) is a multifunctional eukaryotic antioxidant enzyme. Mammalian Prdx6 possesses peroxidase activity against a wide range of organic and inorganic hydroperoxides, as well as exhibits phospholipase A2 (aiPLA2) activity, which plays an important role in the reduction of oxidized phospholipids and cell membrane remodeling. Exogenous Prdx6 has recently been shown to be able to penetrate inside the cell. We hypothesized that this entry may be due to the phospholipase activity of Prdx6. Experiments using exogenous Prdx6 in three cell lines (3T3, A549, RAW 264.7) demonstrated that it is the phospholipase activity that promotes its penetration into the cell. Overoxidation of Prdx6 led to a suppression of the peroxidase activity and a 3-to-4-fold growth of aiPLA2, which enhanced the efficiency of its transmembrane transport into the cells by up to 15 times. A mutant form of Prdx6-S32A with an inactivated phospholipase center turned out to be unable to enter the cells in both the reduced and oxidized state of the peroxidase active center. Previously, we have shown that exogenous Prdx6 has a significant radioprotective action. However, the role of phospholipase activity in the radioprotective effects of Prdx6 remained unstudied. Trials with the mutant Prdx6-S32A form, with the use of a total irradiation model in mice, showed a nearly 50% reduction of the radioprotective effect upon aiPLA2 loss. Such a significant decrease in the radioprotective action may be due to the inability of Prdx6-S32A to penetrate animal cells, which prevents its reduction by the natural intracellular reducing agent glutathione S-transferase (πGST) and lowers the efficiency of elimination of peroxides formed from the effect of ionizing radiation. Thus, phospholipase activity may play an important role in the reduction of oxidized Prdx6 and manifestation of its antioxidant properties.

Role of Glutathione Peroxidases and Peroxiredoxins in Free Radical-Induced Pathologies

In this review, we discuss the pathogenesis of some socially significant diseases associated with the development of oxidative stress, such as atherosclerosis, diabetes, and radiation sickness, as well as the possibilities of the therapeutic application of low-molecular-weight natural and synthetic antioxidants for the correction of free radical-induced pathologies. The main focus of this review is the role of two phylogenetically close families of hydroperoxide-reducing antioxidant enzymes peroxiredoxins and glutathione peroxidases - in counteracting oxidative stress. We also present examples of the application of exogenous recombinant antioxidant enzymes as therapeutic agents in the treatment of pathologies associated with free-radical processes and discuss the prospects of the therapeutic use of exogenous antioxidant enzymes, as well as the ways to improve their therapeutic properties.

Thymulin and peroxiredoxin 6 have protective effects against streptozotocin-induced type 1 diabetes in mice

Protective effects of peroxiredoxin 6 (PRDX6) in RIN-m5F β-cells and of thymulin in mice with alloxan-induced diabetes were recently reported. The present work was aimed at studying the efficiency of thymulin and PRDX6 in a type 1 diabetes mellitus model induced by streptozotocin in mice. Effects of prolonged treatment with PRDX6 or thymic peptide thymulin on diabetes development were evaluated. We assessed the effects of the drugs on the physiological status of diabetic mice by measuring blood glucose, body weight, and cell counts in several organs, as well as effects of thymulin and PRDX6 on the immune status of diabetic mice measuring concentrations of pro-inflammatory cytokines in blood plasma (TNF-α, interleukin-5 and 17, and interferon-γ), activity of NF-κB and JNK pathways, and Hsp90α expression in immune cells. Both thymulin and PRDX6 reduced the physiological impairments in diabetic mice at various levels. Thymulin and PRDX6 provide beneficial effects in the model of diabetes via very different mechanisms. Taken together, the results of our study indicated that the thymic peptide and the antioxidant enzyme have anti-inflammatory functions. As increasing evidences show diabetes mellitus as a distinct comorbidity leading to acute respiratory distress syndrome and increased mortality in patients with COVID-19 having cytokine storm, thymulin, and PRDX6 might serve as a supporting anti-inflammatory treatment in the therapy of COVID 19 in diabetic patients.

Peroxiredoxin 6 Attenuates Alloxan-Induced Type 1 Diabetes Mellitus in Mice and Cytokine-Induced Cytotoxicity in RIN-m5F Beta Cells

Type 1 diabetes is associated with the destruction of pancreatic beta cells, which is mediated via an autoimmune mechanism and consequent inflammatory processes. In this article, we describe a beneficial effect of peroxiredoxin 6 (PRDX6) in a type 1 diabetes mouse model. The main idea of this study was based on the well-known data that oxidative stress plays an important role in pathogenesis of diabetes and its associated complications. We hypothesised that PRDX6, which is well known for its various biological functions, including antioxidant activity, may provide an antidiabetic effect. It was shown that PRDX6 prevented hyperglycemia, lowered the mortality rate, restored the plasma cytokine profile, reversed the splenic cell apoptosis, and reduced the β cell destruction in Langerhans islets in mice with a severe form of alloxan-induced diabetes. In addition, PRDX6 protected rat insulinoma RIN-m5F β cells, cultured with TNF-α and IL-1β, against the cytokine-induced cytotoxicity and reduced the apoptotic cell death and production of ROS. Signal transduction studies showed that PRDX6 prevented the activation of NF-κB and c-Jun N-terminal kinase signaling cascades in RIN-m5F β cells cultured with cytokines. In conclusion, there is a prospect for therapeutic application of PRDX6 to delay or even prevent β cell apoptosis in type 1 diabetes.

Catalytic and Signaling Role of Peroxiredoxins in Carcinogenesis

Cancer cells experience strong oxidative stress caused by disorders in cell metabolism and action of external factors. For survival, cancer cells have developed a highly efficient system of antioxidant defense, some of the most important elements of which are peroxiredoxins (Prxs). Prxs are an evolutionarily ancient family of selenium-independent peroxidases that reduce a wide range of organic and inorganic hydroperoxides in the cell and the extracellular space. In addition, some Prxs exhibit chaperone and phospholipase activities. Prxs play an important role in the maintenance of the cell redox homeostasis; they prevent oxidation and aggregation of regulatory proteins, thereby affecting many cell signaling pathways. Prxs are involved in the regulation of cell growth, differentiation, and apoptosis. Due to their versatility and wide representation in all tissues and organs, Prxs participate in the development/suppression of many pathological conditions, among which cancer occupies a special place. This review focuses on the role of Prxs in the development of various forms of cancer. Understanding molecular mechanisms of Prx involvement in these processes will allow to develop new approaches to the prevention and treatment of cancer.

Protective Effect of Peroxiredoxin 6 Against Toxic Effects of Glucose and Cytokines in Pancreatic RIN-m5F β-Cells

Taking into account a special role of pancreatic β-cells in the development of diabetes mellitus, the effects of peroxiredoxin 6 (Prx6) on the viability and functional activity of rat insulinoma RIN-m5F β-cells were studied under diabetes-simulating conditions. For this purpose, the cells were cultured at elevated glucose concentrations or in the presence of pro-inflammatory cytokines (TNF-α and IL-1) known for their special role in the cytotoxic autoimmune response in diabetes. It was found that the increased glucose concentration of 23-43 mM caused death of 20-60% β-cells. Prx6 added to cells significantly reduced the level of reactive oxygen species and protected the RIN-m5F β-cells from hyperglycemia, reducing the death of these cells by several fold. A measurement of insulin secretion by the RIN-m5F β-cells showed a significant stimulatory effect of Prx6 on the insulin-producing activity of pancreatic β-cells. It should be noted that the stimulatory activity of Prx6 was detected during culturing the cells under both normal and unfavorable conditions. The regulation of the NF-κB signaling cascade could be one of the mechanisms of Prx6 action on β-cells, in particular, through activation of RelA/p65 phosphorylation at Ser536.

Natural Dicarbonyls Inhibit Peroxidase Activity of Peroxiredoxins

It was established that recombinant human peroxiredoxins (Prx1, Prx2, Prx4, and Prx6) inhibit natural dicarbonyls formed during free radical peroxidation of unsaturated lipids (malonic dialdehyde) and oxidative transformations of glucose (glyoxal and methylglyoxal). A possible role of the decrease in the activity of peroxiredoxins under oxidative and carbonyl stress is discussed as an important factor that triggers the molecular mechanisms of vascular wall damage in atherosclerosis and diabetes mellitus.

Protective and adaptogenic role of peroxiredoxin 2 (Prx2) in neutralization of oxidative stress induced by ionizing radiation

A radioprotective effect of exogenous recombinant peroxiredoxin 2 (Prx2) was revealed and characterized using an animal model of whole body X-ray irradiation at sublethal and lethal doses. Prx2 belongs to an evolutionarily ancient family of peroxidases that are involved in enzymatic degradation of a wide variety of organic and inorganic hydroperoxides. Apart from that, the oxidized form of Prx2 also exhibits chaperone activity, thereby preventing protein misfolding and aggregation under oxidative stress. Intravenous administration of Prx2 in animals at a concentration of 20 µg/g 15 min before exposure to ionizing radiation contributes to a significantly higher survival rate, suppresses the development of leucopenia and thrombocytopenia, as well as protects the bone marrow cells from genome DNA damage. Moreover, injection of Prx2 leads to suppression of apoptosis, stimulates cell proliferation and results in a more rapid recovery of the cell redox state. Exogenous Prx2 neutralizes the effect of the priming dose on the second irradiation of the cells. The radioprotective properties of exogenous Prx2 are stipulated by its broad substrate peroxidase activity, chaperone activity in the oxidized state, and are also due to the signal-regulatory function of Prx2 mediated by the regulation of the level of hydroperoxides as well as via interaction with redox-sensitive regulatory proteins.

Radioprotective Role of Peroxiredoxin 6

Peroxiredoxin 6 (Prdx6) is a member of an evolutionary ancient family of peroxidase enzymes with diverse functions in the cell. Prdx6 is an important enzymatic antioxidant. It reduces a wide range of peroxide substrates in the cell, thus playing a leading role in the maintenance of the redox homeostasis in mammalian cells. Beside peroxidase activity, Prdx6 has been shown to possess an activity of phospholipase A2, an enzyme playing an important role in membrane phospholipid metabolism. Moreover, Prdx6 takes part in intercellular and intracellular signal transduction due to its peroxidase and phospholipase activity, thus facilitating the initiation of regenerative processes in the cell, suppression of apoptosis, and activation of cell proliferation. Being an effective and important antioxidant enzyme, Prdx6 plays an essential role in neutralizing oxidative stress caused by various factors, including action of ionizing radiation. Endogenous Prdx6 has been shown to possess a significant radioprotective potential in cellular and animal models. Moreover, intravenous infusion of recombinant Prdx6 to animals before irradiation at lethal or sublethal doses has shown its high radioprotective effect. Exogenous Prdx6 effectively alleviates the severeness of radiation lesions, providing normalization of the functional state of radiosensitive organs and tissues, and leads to a significant elevation of the survival rate of animals. Prdx6 can be considered as a potent and promising radioprotective agent for reducing the pathological effect of ionizing radiation on mammalian organisms. The radioprotective properties and mechanisms of radioprotective action of Prdx6 are discussed in the current review.

[Effect of conditioned medium from mesenchymal stem cells on regeneration of endothelium at HCl-induced damage trachea in rats]

The purpose. Respiratory epithelium regeneration is studied in rats with tracheal damage induced by inhaling hydrochloric acid vapor. Method. Regeneration process after the chemical burn was activated by intratracheal administration of preparations obtained from the same-species mesenchymal stem cells (MSC). Results. Tracheal epithelium is shown to recover almost completely on day 3-7 after applying MSC compositions (MSCs). Closed structures containing ciliated cells similar to ciliated cells of the respiratory epithelium lining the trachea are formed in the submucosal epithelium during regeneration. These structures migrate towards epithelium and get incorporated into the damaged epithelium. This phenomenon is apparently indicative of the special mechanism of respiratory epithelium regeneration after HCl-induced injury. Conclusion. It is demonstrated in this study that cell-free MSCs instilled intratracheally promote the recovery of normal submucosal epithelium by either preventing or reducing necrosis and inflammation. Such topical MSCs administration significantly accelerates migration of ciliated cell towards the surface and de novo formation of the ciliary epithelium.

Vascular Pathology of Ischemia/Reperfusion Injury of Rat Small Intestine

Ischemia/reperfusion (I/R) injury of the small intestine caused by occlusion of the superior mesenteric artery affects the intestinal tissue as well as components of the blood circulatory system from the microvasculature to mesenteric vessels. The aim of this work was to study the correlation between the dynamics of destruction development in the intestinal tissue, microvasculature, and mesenteric vessels in I/R of the small intestine. The microvasculature was analyzed by whole-organ continuous monitoring of the intestinal mucosal blood perfusion by laser Doppler flowmetry during the entire I/R. Real-time RT-PCR was used to assess gene expression of NF-κB, caspase-3, Ki67, and TNF-α in blood vessels. At the start of reperfusion, the first targets to be disrupted are microvessels in the apical villi. Injury of the apical part of the microcirculatory bloodstream correlates with the reduction in intestinal mucosal blood perfusion, which occurred simultaneously with apical villous destruction. By the end of the reperfusion period, the low intestinal mucosal blood perfusion is mirrored by the destruction of the microvasculature and mucosal structures in the entire organ. The development of mesenteric vessel injury is characterized by a change in NO metabolism and damaged endothelial cells concomitant with an alteration in the expression of genes encoding NF-κB, caspase-3, and Ki67 by the end of the reperfusion period. In I/R injury, detrimental effects on the intestinal tissue, microvasculature, and mesenteric vessels develop and exhibit common mechanisms of function, which show strong correlations.

Construction of a Fusion Enzyme Exhibiting Superoxide Dismutase and Peroxidase Activity

A chimeric gene construct encoding human peroxiredoxin 6 and Mn-superoxide dismutase from Escherichia coli was developed. Conditions for expression of the fusion protein in E. coli cell were optimized. Fusing of the enzymes into a single polypeptide chain with peroxiredoxin 6 at the N-terminus (PSH) did not affect their activities. On the contrary, the chimeric protein with reverse order of enzymes (SPH) was not obtained in a water-soluble active form. The active chimeric protein (PSH) exhibiting both peroxidase and superoxide dismutase activities was prepared and its physicochemical properties were characterized.

Cardioprotective Effect of Modified Peroxiredoxins in Retrograde Perfusion of Isolated Rat Heart under Conditions of Oxidative Stress

Antioxidant properties of recombinant peroxiredoxin-6 and chimeric protein PSH combining peroxidase and superoxide dismutase activities were studied on the model of retrograde perfusion of isolated rat heart under conditions of H2O2-induced oxidative stress. The exogenous antioxidant proteins exhibited cardioprotective properties manifested in heart rate normalization, maintenance of contractile activity of the myocardium, and prevention of H2O2-induced LPO in oxidative stress. Localization of peroxiredoxin-6 and PSH in the cardiac tissue was determined and myocardial structures most effectively protected by the antioxidant enzymes from ischemia/reperfusion-induced damages were identified. The results suggest that modified peroxiredoxins are promising components of perfusion media for preservation of isolated organs.

[Xenopus laevis peroxiredoxins: Gene expression during development and characterization of the enzymes]

Reactive oxygen species (ROS) are produced via catabolic and anabolic processes during normal embryonic development, and ROS content in the cell is maintained at a certain level. Peroxiredoxins are a family of selenium-independent peroxidases and play a key role in maintaining redox homeostasis of the cell. In addition to regulating the ROS level, peroxiredoxins are involved in intracellular and intercellular signaling, cell differentiation, and tissue development. The time course of peroxiredoxin gene (prx1-6) expression was studied in Xenopus laevis during early ontogeny (Nieuwkoop and Faber stages 10-63). The highest expression level was observed for prx1 at these developmental stages. The prx1, prx3, and prx4 expression level changed most dramatically in response to oxidative stress artificially induced in X. laevis embryos. In X. laevis adults, prx1-6 were all intensely expressed in all organs examined, the prx1 expression level being the highest. The X. laevis prx1-6 genes were cloned and expressed in Escherichia coli, and physico-chemical characteristics were compared for the recombinant enzymes. The highest peroxidase activity and thermal stability were observed for Prx1 and Prx2. It was assumed that Prx1 plays a leading role in X. laevis early development.

Protective Effect of Peroxiredoxin 6 in Ischemia/Reperfusion-Induced Damage of Small Intestine

BACKGROUND

Strong oxidative stress starting in the epithelium upon restoration of blood cell circulation is a major cause of necrosis of the intestinal epithelium in ischemia/reperfusion-induced damage.

AIM

The purpose of this study was to investigate the tissue-protective effect of exogenous peroxiredoxin 6 (Prx6) in ischemia/reperfusion-induced damage of small intestine.

METHODS

The research was carried out using a model of acute superior mesenteric artery occlusion in Wistar male rats. Exogenous Prx6 was administrated intravenously 15 min prior to small intestine ischemia. The distribution of endogenous Prx6 in the small intestine was determined by immunohistochemical analysis. The expression level of antioxidant enzymes was evaluated by RT-PCR in real time.

RESULTS

Exogenous Prx6 injected to animals intravenously was detected in blood vessel lumens, and its diffuse distribution was subsequently confirmed in the intestinal epithelium. Expression analysis of genes coding for major antioxidant enzymes demonstrated a significant activation of SOD 1, SOD 3, Prx6, GPx2, GPx7 expression during I/R-induced damage of the small intestine. Injection of exogenous Prx6 prior to induced ischemia resulted in minimization of oxidative injury by reducing necrosis and apoptosis, by normalization of gene activity of antioxidant enzyme. It eventually led to a reduction of epithelium destruction in the small intestine. By contrast, administration of a purified mutant form of Prx6 (Prx6C47S) without peroxidase activity had no protective effect.

CONCLUSION

The application of exogenous Prx6 enables normalization of the antioxidant status of the small intestine and reduction of cell destruction upon I/R-induced organ damage.

[cDNA cloning, expression and determination of substrate specificity of mice selenocysteine-containing protein SelV (Selenoprotein V)]

To date various bioinformatics tools allowed to identify 25 selenocysteine-containing mammalian proteins. The name of these proteins assumes that they contain the amino acid selenocysteine (Sec). Functionally characterized selenocysteine-containing proteins are oxidoreductases with various functions, including glutathione peroxidases, thioredoxin reductases, deiodinases etc. However, the functions of more than half of identified proteins are still unclear, and mammalian selenoprotein SeIV is among them. We studied the selV in all stages of postnatal development with the maximum level of mRNA expression during puberty, whereas in adult mice (8-18 months) we observed a gradual decrease of expression. In order to get closer to the functional role of Selenoprotein V, we have carried out experiments on the substrate specificity and enzymatic activity measurement of this selenocysteine-containing protein. It was shown that SelV posseses glutathionperoxidase and thioredoxinreductase activities.

[Potential-dependent Cation Selective Ion Channels Formed by Peroxiredoxin 6 in the Lipid Bilayer]

The antioxidant enzyme peroxiredoxin 6 forms cation selective ion cluster-type channels in the lipid bilayer. Channel clustering as oligomeric structure consists of three or more subunits--channels with conductance of about 350 pS in the 200 mM KCl. Mean dwell time of the channel's open states decreases with increasing membrane voltage. A possible molecular mechanism of the observed potential-dependent inactivation of the channel cluster is discussed.

[Peroxyredoxins as multifunctional enzymes]

Peroxiredoxins are evolutionarily ancient, but relatively recently discovered group of seleniumindependent peroxidases. Peroxiredoxins protect cells from various peroxides and play an important role in maintaining the oxidation-reduction homeostasis. Moreover, they are involved in many cellular processes that are not related to peroxidase activity. Here, recent data on the structure and function of peroxiredoxins, regulation of gene expression and activity of different peroxiredoxins are considered.

[Characterization of some thiol oxidoreductase family members]

There are no doubt about the important role of free radicals and reactive oxygen species in the processes of cell activity. The disturbances of intracellular redox processes are often accompanied with the development of such common pathologies as diabetes, myocardial infarction, neurodegeneration, broncho-pulmonary diseases, cancer, etc. To date, there are a large number of antioxidant enzymes related to different redox biology systems, the key role among them is played by enzymes belong to the thiol oxidoreductases superfamily, which consists of thioredoxin, glutaredoxin, peroxiredoxin, protein disulfidizomeraz, glutathione peroxidase families, and a number of other proteins. In addition to the antioxidant function, thiol oxidoreductases display the ability to recycle of hydroperoxide to form specific disulfide bonds within and between proteins that significantly extends the range of their functionality. Therefore, biochemical characterization and elucidation of functional mechanisms of the superfamily proteins is a highly actual problem of redox biology.

[Biosyinthesis and mechanism of selenocysteine incorporation into synthesized proteins]

Universal genetic code provides the ability to encode only twenty "canonical" amino acids, whereas the twenty first amino acid--selenocysteine (Sec), is encoded by one of three well-known stop codon (UGA). In terms of molecular biology, selenocysteine is of exceptional interest, the mechanism of its incorporation into synthesized polypeptide chains is very different from that of the other typical 20 amino acids. This process involves some cis- and trans-active factors, such as the SECIS element (Selenocystein insertion sequence), a structure located in the 3'-untranslated region of eukaryotic mRNA, and in the open reading frame immediately after the UGA-selenocysteine codon in bacteria, which, in turn, leads to differences in the mechanism of selenocysteine incorporation in these domains of life. The trans-factors include Sec-tRNA([Ser]Sec) that has a unique system of biosynthesis, Sec-specific elongation factor EFsec and SBP2--Sec binding protein. Thus, for realization of the selenocysteine incorporation process during translation a large number of additional molecules must be synthesized in the cell, this fact makes the selenocysteine containing proteins rather "expensive" and emphasizes their crucial role in metabolism.

[The search of partners of a new mammalian selenium-containing protein V (SelV) and expression it's mRNA during ontogenesis and spermatogenesis]

Selenium is a biologically active trace elements, which is part of several proteins, and thus linked with the activity of many organs, tissues and systems of organism. There are 25 mammalian selenoproteins at present, one of which is SelV (Selenoprotein V). Since this protein has thioredoxin-like folding and a conserved motif (CXXU, where C is cysteine, U-selenocysteine) in its catalytic center, it belongs to the family of redox proteins, whose members are involved in redox reactions. In this paper, we show that the redox protein SelV can interact with O-linked N-acetylglucosamine transferase (OGT) and proteins belonging to the family of ASB: Asb-17, and Asb-9. The specificity of interactions SelV with OGT and Asb-9, but not with Asb-17 is confirmed by coimmunopretsipitation. In addition, expression of SelV mRNA in the later stages spermatogenesis, as well as in puberty and reproductive periods of rats is shown.

[Two peroxiredoxins 6 of Xenopus laevis]

Two different genes of peroxiredoxin 6 are encoded in the genome of Xenopus laevis: xen1 (Acc.no. EMBL Data Bank - BCO54278) and xen2 (Acc.no. EMBL Data Bank - BC540309). Both genes were cloned and expressed in Escherichi coil. Proteins were purified and analyzed. The amino acid sequences of the enzymes Xen1 and Xen2 are 95% identical with the same peroxidase activity, pH and temperature optimums, as well as thermostability, being approximately equal. The expression of peroxiredoxin 6 genes significantly differ during ontogenesis of X. laevis. The expression of xen1 starts on a later stage of development 47-48, while the gene xen2 is expressed on all stages of development with the same increase starting from stage 0-5. The level of xen2 expression in embryos increased after incubation in presence of hydrogen peroxide. The comparison of amino acid sequences of proteins Xen1 and Xen2 shows that only the enzyme Xen2 may have phospholipase activity, since it has residues of phospholipase A2 active center: Ser31, His25, Asp139.

[Modified peroxiredoxins as prototypes of drugs a powerful antioxidant]

The possibility of using modified peroxyredoxins as powerful antioxidant agents has been considered. Peroxyredoxins immobilized on perfluorocarbon emulsions and PTD-modified peroxyredoxins have been studied. It has been shown that peroxyredoxins efficiently bind to particles of perfluorocarbon emulsions, while maintaining their antioxidant properties. A panel of PTD-modified peroxyredoxins has been created and peroxyredoxins most effective both in antioxidant properties and the ability to penetrate cells have been selected. The modified peroxyredoxins obtained may serve as the basis for the design of drug with powerful antioxidant action.

[Peroxiredoxins, a new family of antioxidant proteins]

Current ideas are discussed about the structures and mechanisms of action of proteins that have been united at present into a family of thiol-specific antioxidants or peroxiredoxins, which protect the cells of different organisms from the action of hydrogen peroxide. Peroxiredoxins fulfill the same function as antioxidant enzymes such as catalases and glutathione-dependent peroxidases; however, their catalytic activity is lower than that of these enzymes. The level of expression of genes of peroxiredoxins is increased in many pathological states accompanied by oxidative stress, and today there is direct evidence for the important role of peroxiredoxins in the vital activity of cells.

[Effect of negative air ions on respiratory organs and blood]

The effect of negatively charged ions on respiratory organs and blood of rats has been studied. It was shown that the inhaling of negative air ions (NAI) for 60 min with a concentration of NAI at the place of location of animals 320-350 000 ions/cm2 activated the secretion of goblet cells without damaging the mucosa of the trachea and changed the spectrum of proteins of bronchopulmonary lavage. It was also found that the spontaneous production of reactive oxygen species (ROS) by cells of nonfractionated blood after the exposure to NAI increased in both males and females; the intensity of ROS generation induced by opsonized zymosan increased only in females. Different sensitivity of the antioxidant enzymes superoxide dismutase and glutathione reductase of blood to NAI in females and males was revealed. These results enable one to consider the effect of NAI as priming and a weak activation of the respiratory organs through the direct action on the mucosa of the primary target organs of the respiratory tract and then on the blood.

[Study of the quaternary structure of rat 1-Cys peroxiredoxin]

Peroxiredoxins (Prx) are a family of antioxidant proteins with peroxidase activity. The ability of 1-Cys Prx to self-associate was studied with the use of native PAGE and Western blotting. Two protein bands corresponding to monomeric and dimeric forms were detected in the preparation of the recombinant 1-Cys Prx subjected to native PAGE, with dimers being more abundant. The third band corresponding to the oligomeric form was detected after incubation of the recombinant 1-Cys Prx with DTT, although monomers and dimers were also observed. These results indicate that monomeric, dimeric, and oligomeric states of the protein are likely to be interchangeable. Native PAGE in combination with Western blot analysis revealed that self-association of 1-Cys Prx also occurred at physiologically relevant concentrations in vivo. The native 1-Cys Prx existed in the monomeric and dimeric forms in rat olfactory epithelium, with monomers being more common. The structural sensitivity of the recombinant 1-Cys Prx to imidazole was shown.

The novel approach to the protein design: active truncated forms of human 1-CYS peroxiredoxin

The object of the present study is the verification of a new approach to the design of the active truncated forms of enzymes. The method is based on a new way of investigating the protein sequences--the ANalysis of Informational Structure (ANIS). The analysis of informational structure allows to determine the hierarchically organized structures (IDIC-trees) formed by the sites with the Increased Degree of Informational Coordination between residues. The proposed approach involves the consequent removal of the fragments corresponding to the individual IDIC-trees from the wild-type enzyme sequences. The described procedure was applied to the design of the active truncated form of human 1-CYS peroxiredoxin (PrxVI). Two variants of the PrxVI truncated sequences were proposed according to ANIS method. These truncated forms of the enzyme were expressed in E. coli and purified. The respective antioxidant activities were measured. It was shown that one of the truncated recombinant proteins retains more than 90% of the wild-type PrxVI enzymatic activity. According to the results of our study we can assume that ANIS method can be an effective tool for the design of the active truncated forms of the enzymes or the chimeric proteins which combine the enzymatic activities of their wild-type prototypes.

Peroxiredoxin VI in human respiratory system

Peroxiredoxins (Prxs) constitute a novel family of antioxidant proteins, which specifically prevent enzymes from metal-catalyzed oxidation. The localization of a member of the mono-cystein subfamily of Prxs, Prx VI in human respiratory system and its antioxidant properties were investigated. By immunoblotting, the Prx VI was found to be present in human respiratory epithelium. Immunostaining with rabbit polyclonal antibody raised against the Prx VI revealed that the said protein was present in apical areas and mucus of all respiratory airways from trachea to bronchioles. Immunodepletion of the Prx VI profoundly decreased the antioxidant activity of the respiratory epithelium extract.

[Comparative effectiveness of antioxidants in protecting the bacterial plasmatic membrane from the active froms of oxygen]

The effect of hydroxyl radicals OH. generated by the decomposition of H2O2 by Fe2+ ions (Fenton reaction) on the barrier properties of plasma membranes of Escherichia coli cells K-12 was studied by electroorientation spectroscopy. It was found that the administration of hydrogen peroxide led to the disturbance of the barrier properties of plasma membranes only when the cells were preincubated with Fe2+ ions and their constant concentration in the system was maintained by ascorbate or dithiotreitol (150-500 microM). The extent of the toxic action on plasma membranes depended on the concentration of reacting elements and the substance used as a reducer Fe2+. The efficiency of protection of antioxidants of different classes (enzymic, SH-containing, and phenolic compounds) against the toxic action of hydroxyl radicals on plasmatic membranes was shown.

Localization of 28-kDa peroxiredoxin in rat epithelial tissues and its antioxidant properties

Peroxiredoxins are a novel family of antioxidant proteins that specifically prevent enzymes from metal-catalyzed oxidation. The localization of a member of the mono-cystein subfamily of peroxiredoxins, the 28-kDa protein, in different rat tissues and its antioxidant properties were investigated. By immunoblotting, the 28-kDa peroxiredoxin was found to be most highly concentrated in olfactory epithelium and present in all tissues tested (skin, lung, trachea, kidney, womb, and brain). Immunostaining with rabbit polyclonal antibody raised against the 28-kDa peroxiredoxin revealed the particularly high level of the 28-kDa peroxiredoxin immunoreactivity in air-contacting areas (apical regions and mucus of the olfactory and respiratory epithelium and skin epidermis), which are continually exposed to numerous air-borne reactive oxygen species. In the apical regions of the olfactory and respiratory epithelium, the 28-kDa-peroxiredoxin immunogold labeling outlined microvilli and cilia and was mainly located in sustentacular cells and in respiratory and goblet cells, as electron-microscopic analysis revealed. In skin epidermis, the 28-kDa peroxiredoxin immunoreactivity was confined to the granular layer and specifically concentrated in sebaceous glands of hair follicle. In situ hybridization with 33P-labeled antisense RNA probe revealed the expression of the 28-kDa peroxiredoxin mRNA in tissues with a high level of the 28-kDa peroxiredoxin immunoreactivity. Immunodepletion of the 28-kDa peroxiredoxin profoundly decreased the antioxidant activity of the olfactory tissue extract.

[Protective activity of 28-kDa 1-Cys peroxiredoxin determines its peroxidase activity]

The 28 kDa peroxiredoxin from rat exhibited peroxidase activity only in the presence of dithiothreitol. Both organic and nonorganic peroxidases were found to be substrates for the 28-kDa peroxiredoxin activity. Analysis of the protective antioxidant activity of the 28-kDa peroxiredoxin revealed that it is accounted for by its peroxidase activity.

A novel 45 kDa secretory protein from rat olfactory epithelium: primary structure and localisation

cDNA clones encoding the 45 kDa protein were isolated from a rat olfactory epithelium cDNA library and their inserts were sequenced. The reconstructed protein sequence comprises 400 amino acids with a calculated molecular mass of 46,026 Da. A homology was revealed between the amino acid sequence of the 45 kDa protein and the proteins involved in the transfer of hydrophobic ligands. Using in situ hybridisation, the 45 kDa protein mRNA expression was detected in the layer of supportive cells of olfactory epithelium, apical region of trachea, surface layer of the ciliated bronchial epithelium in lung and in skin epidermis.

[Study of structure of secretory 28 kDa protein from the rat olfactory epithelium]

Clone lambda a26.1 isolated from rat olfactory epithelium contains a full-length 28-kDa protein cDNA (1414 b.p.). The reconstructed protein sequence comprises 223 aa with a calculated molecular mass of 24,630 Da. A substantial homology was revealed between the amino acid sequence of the 28-kDa protein and those of thiol-specific antioxidants (peroxiredoxines). The 28-kDa protein belongs to the 1 Cys-subfamily of peroxiredoxines and is the first member of peroxiredoxines identified in the olfactory epithelium.

Identification of a 28 kDa secretory protein from rat olfactory epithelium as a thiol-specific antioxidant

The 28 kDa secretory protein is one of the abundant water-soluble proteins in olfactory epithelium of mammals. Analysis of partial amino acid sequence of the 28 kDa protein strongly suggested that it belongs to a new family of highly conserved antioxidant proteins requiring thiol for their antioxidant activity (TSA/AhpC family). In the present study, we found the 28 kDa protein to have thiol-dependent antioxidant activity, thereby protecting radical-sensitive proteins such as glutamine synthetase and hemoglobin from oxidative modification caused by thiol-dependent metal ion-catalyzed oxidation system. The purified 28 kDa protein did not possess catalase or glutathione peroxidase activities, and required thiols to exhibit its antioxidant activity. The 28 kDa protein is the first member of the family of thiol-specific antioxidants identified in olfactory epithelium and the first secretory protein shown to be thiol-specific antioxidant.

[Properties of the catalytic center of a secretory 28kDa protein (1-cys peroxiredoxin) from rat olfactory epithelium]

The secretory 28 kD protein, an abundant water-soluble protein from rat olfactory epithelium, belongs to the 1-Cys subfamily of thiol-specific antioxidants (peroxiredoxins). The 28 kD protein contains a single cysteine residue at the position 46 which accounts for the antioxidant activity. Here we studied the effects of N-ethyilmaleimide and t-butyl hydroperoxide on the antioxidant activity of the 28 kD protein and that of the 23 kD protein from rat erythrocyte which is a member of 2-Cys subfamily of peroxiredoxines. N-ethylmaleimide, modifier for cysteine residues, had no effect on antioxidant activity of the dithiothreitol-treated 28 kD protein but irreversibly inhibited activity of the 23 kD protein under reducing conditions. The 28 kD protein was sensitive to treatment with peroxides: t-butyl hydroperoxide at micromolar concentrations was shown to irreversibly inactivate 28 kD protein. In the presence of dithiothreitol, the lower level of peroxide concentrations was required to inhibit 28 kD protein activity. The mechanism of this effect may be mediated through conversion of sulfhydryl group of 46Cys to oxidized states (46Cys-SO2H and 46Cys-SO3H). Antioxidant property of 23 kD protein was impaired by t-butyl hydroperoxide only in the presence of dithiothreitol. The concentrations of t-butyl hydroperoxide needed to affect the 23 kD protein were at least one order of magnitude higher than were required for the 28 kD protein inhibition. The given results suggest the essential differences between catalytic site of 28 kD protein and that of 2-Cys peroxiredoxins.

[Electron microscopic analysis of the effect of modulated microwave radiation on isolated rat olfactory mucosa]

Isolated olfactory neuroepithelium and neighbouring respiratory epithelium of 6 Wistar rats after exposure to high frequency irradiation (the microwave carrier frequency was 0.9 GHz; the rectangular pulse modulation was 16 pulses per second; the pulse duration was 50%; the microwave power density in exposure glass chamber was 15 W/kg; the exposure time was 15 min) were studied using high resolution transmission electron microscopy. Ultrathin sections of both epithelia showed the drastic changes in ultrastructure of mucosa. Knobs of primary olfactory neurons and apical parts of supporting (sustacle) cells of the neuroepithelium showed strong vacuolization due to stimulating effect of the microwave irradiation on mucus secretion. The fusion of neighbouring cilia of respiratory cells was revealed. Such "giant cilia" contained more than 5-10 axonemes with basal bodies. In one case the mucus contained paracrystalline structures which were formed by microvilli and nonidentified filamentous protein (10 nm in dia). Degeneration of primary olfactory neuron axons was revealed.

45-kDa GTP-binding protein from rat olfactory epithelium: purification, characterization and localization

The rat olfactory epithelium contains a specific water-soluble 45-kDa protein. This protein is recognized by anti-peptide antibodies which react with alpha-subunits of the known G-proteins. The 45-kDa protein has been isolated using DEAE-chromatography and gel-exclusion chromatography. The content of 45-kDa protein is about 2% of the total soluble proteins of the olfactory mucosa and it is located at the mucociliary surface. According to photo-affinity labeling, the 45-kDa protein possesses a high affinity to GTP and exhibits low GTP hydrolytic activity. The functions of the 45-kDa protein are discussed.

Novel 28-kDa secretory protein from rat olfactory epithelium

We have isolated a novel secretory 28-kDa protein which is an abundant component of the rat olfactory mucosa. The partial sequence of the 28-kDa protein has been determined. The amino acid sequence of the 28-kDa protein is similar to that of non-selenium glutathione peroxidase from bovine ciliary body. The 28-kDa protein catalyzed decomposition of the hydrogen peroxide as well as organic hydroperoxides by reduced glutathione and seems to be a member of the glutathion peroxidase family.

Water-soluble GTP-binding protein from rat olfactory epithelium

Rat olfactory epithelium and ciliar cytosol of olfactory cells contained the water-soluble 45 kDa protein which was revealed by antibodies against a peptide fragment of the alpha-subunits common to the G-proteins. No analogous proteins were found in other rat tissues. According to the photo-affinity labeling, the 45 kDa protein possessed a high affinity to GTP; it also exhibited a low GTP hydrolytic activity.

Influence of microwaves on different types of receptors and the role of peroxidation of lipids on receptor-protein shedding

The effects of a continuous wave or pulse-modulated, 900 MHz microwave field were studied by in vitro assays of rat chemoreceptors. The pulsed field was modulated as rectangular waves at rates of 1, 6, 16, 32, 75, or 100 pps. The pulse-period to pulse-duration ratio was 5 in all cases, and specific absorption rates (SARs) ranged from 0.5 to 18 W/kg. Binding of ligands to cell membranes was differentially affected by exposure to microwaves. For example, binding of H3-glutamic acid to hippocampal cells was not altered by a 15 min exposure to a continuous wave field at 1 W/kg, but binding of H3-dihydroalprenolol to liver-cell membranes of neonates underwent a fivefold decrease under the same field conditions. This effect was not dependent on modulation or on a change in the constant of stimulus-receptor binding but depended on a shedding of the membrane's receptor elements into solution. The magnitude of inhibition correlated with the oxygen concentration in the exposed suspension. Antioxidants (dithiothreitol and ionol) inhibited the shedding of receptor elements. The microwave exposure did not cause an accumulation of products from the peroxidation of lipids (POL). Ascorbate-dependent or non-enzymatic POL was not responsible for the inhibition, and POL was not found in other model systems. However, enzymatic POL mechanisms in localized areas of receptor binding remain a possibility.

GTP-binding protein associated with amino acid binding proteins from olfactory epithelium of skate, Dasyatis pastinaca

Amino acid binding protein (98 kDa) from olfactory epithelium of skate, Dasyatis pastinaca, form a stable complex with the 56 kDa protein. This complex dissociates in the presence of 10 microM GTP gamma S and 2 mM MgCl2. The 56 kDa protein has a steady-state GTPase activity (15 nmol/min per mg). Binding of amino acids to the 98 kDa protein specifically stimulates GTPase activity of the 56 kDa protein; half-maximal stimulation of GTPase activity is observed at 0.1 microM amino acid.

Properties of odour-binding glycoproteins from rat olfactory epithelium

The specific membrane glycoproteins with high affinity for camphor and decanal were isolated from rat olfactory epithelium. Antibodies to these glycoproteins inhibited both the electroolfactogram and the binding of odorants. The enzyme immunoassay has shown these glycoproteins to be present in the olfactory epithelium of rat, mouse, guinea-pig and hamster but not in that of frog and carp. The molecular mass of the odour-binding glycoproteins from rat olfactory epithelium solubilized by Triton X-100 was approx. 140 kDa. They consisted of two subunits (88 and 55 kDa). The 88 kDa subunit was capable of binding odorants. The data obtained suggest that the glycoproteins isolated have some properties that make them plausible candidates for olfactory receptor molecules.

Microwave effect on camphor binding to rat olfactory epithelium

Microwave radiation decreased specific camphor binding to a membrane fraction of rat epithelium but not to a Triton X-100 extract of this fraction. Inhibition of the ligand binding did not depend on the modulation frequency of the microwave field in the region 1-100 Hz and was not a linear function of specific absorption rate (SAR). The decreased ligand binding was due to a shedding or release of the specific camphor-binding protein from the membrane into solution. It is highly probable that several other membrane proteins may be shed into solution during microwave exposure.

The subunits of specific odor-binding glycoproteins from rat olfactory epithelium

The specific odor-binding glycoproteins have been isolated from rat olfactory epithelium. They consist of two subunits, gp88 and gp55. Subunit gp88 is capable of odorant binding.

[Development of olfactory epithelial grafts in the anterior chamber of the eye]

Olfactory epithelium of newborn rats was transplanted into the anterior eye chamber of the adult rat. Within 6-8 weeks the transplants increased in weight by a factor of 20-50. Morphological analysis has shown the cells similar to olfactory sensory neurones in the grafts. Electroolfactograms obtained with n-amyl acetate and camphor had the amplitude of about three times less and the duration of about 8-10 times more than those from the normal olfactory epithelium at the same concentration of stimuli. Within six hours after 3H-beta-alanine had been introduced into the anterior eye chamber, 72% of the label were present in the carnosine fraction. The data obtained suggest that olfactory sensory neurones appear in the olfactory epithelium grafts into the anterior eye chamber.

Molecular mechanisms of olfactory reception. VI. Kinetic characteristics of camphor interaction with binding sites of rat olfactory epithelium

Camphor binding to a possible receptor of rat olfactory epithelium has been studied within the ligand concentration range 10(-11)-10(-6) M. At these concentrations camphor is bound by a set of receptors. They are distinguished by both the affinity to the ligand (K1 = 5 X 10(-10) M, K2 = 3.5 X 10(-8) M, K3 approximately equal to 10(-6) M) and their amount in the epithelium. The differences in the affinities are due to different values of the association rate constant of camphor (k1), which varies from 10(6) M-1 X s-1 for the receptors with high affinity up to 2 X 10(2) M-1 X s-1 for those with low affinity. These data are discussed in terms of equilibrium and kinetic models of the receptor-stimulus interaction.