Model of redox regulation of hyper- or hypothyreoidism

Since the triiodothyronine (T3) shifts the tissue metabolism to oxidative direction, one should await that in hyperthyreoidism caused by T3 an oxidosis will be formed, whilst in hypothyreoidism called forth by subtotal thyreoidectomy, redosis will be emerged. However, according to our experiments these interrelationships proved to be inverse. These "paradoxal" changes of redox-state are the consequences of the flowing redox compensations elicited by the tissue redox-buffer capacity (RBC). The pathomechanism can be modelled with differential equation (computer analysis). The redox-state changes are characteristics in each tissues. Between the RBC of the tissue and the shift of redox-state potential (E'0) there is a negative correlation. As an autoregulatory mechanims, the redosis formed in hyperthyreoidism will increase the hormone synthesis in the thyroid gland, while the oxidosis after hypothyreoidism will decrease the synthesis. In other words, these processes strengthen each other. Changes of the heart frequency show correlation with the E'0, and can be described by differential equation. Our theoretical model for the redox regulation might answer also the question of the reversibility-irreversibility range of the autoregulation in the pathomechanism.     

Correlations between the actual redox-state potential (E0') of biophase and heart activity in vivo

In CFY rats the tissue redox-state potential (E0') in heart, m. vastus medialis and in the liver, and the heart frequency and QRS amplitudes were measured parallel. It was observed that following compensatory redosis caused by konakion both the autorhythmic heart frequency and QRS amplitudes increased, while after compensatory oxidosis induced by urea occurred the opposite. Following compensatory redosis caused by konakion acetylcholine decreased, but adrenaline increased the heart frequency and QRS amplitudes more intensively than at normal E0' values. After compensatory oxidosis caused by urea, acetylcholine decreased the heart frequency and QRS amplitudes significantly less. Adrenaline decreased the heart frequency in such milieu. On the basis of these data the following conclusions are proposed; For the realization of autorhythmic activity, for negative type acetylcholine and for positive type adrenaline effects in heart, a relatively low primordial tissue E0' value is an essential back-ground element. Among the mechanisms controlling autorhythmicity and sympathetic/parasympathetic effects the actual and permanently changing tissue E0' value is also an important modifying, or through biochemical redox feed-back mechanisms even a regulatory factor of heart activity.     

Might the cell damaging effect of alcohol be prevented by redox agents?

It was found that alcohol caused pathological and irreversible decrements of the redox-state potential (redosis) in the pancreas and the liver. On giving reducing agents, a compensatory oxidosis developed, and this could prevent the cell damaging effect of alcohol. This effect was most marked in the reversible phase, while it could be effective also in the irreversible phase. By measuring the redox buffer capacity in the tissues it is possible to determine the measure of reversibility of the injury caused by alcohol.     

Influence of 3-methylcholanthrene on the redox-state of liver and red muscles in vivo

It was observed, that following an injection of 3-methylcholanthrene (MC), the tissue redox-state potential is modified expressively both in liver and in red muscles. In the liver in the first day an oxidosis develops, which is followed by redosis, but in the muscle a redosis can be observed already in the first day. It is a meaningful fact, that MC influences biochemical processes in the early phase of its effect not only in the liver but also in the red muscle. By reason of this data the possibility of a prevention of the MC influence by adequate redox agents might also be arised.     

Changes in autorhythmic heart frequency elicited by redox agents

In isolated frog heart it was established that methylene-blue (MB, an oxidizing agent) decreased, while ascorbate (ASC, a reducing agent) increased the frequency of autorhythmic heart contractions. After MB treatment, in parallel with this phenomenon, the extracellular K+ concentration [K+]o showed a slow increase, but following ASC application a slow decrease occurred. Since these correlations are in good accordance with the idea that the pacemaking ability of heart, among other properties, depends on the voltage and time-dependent decrease in potassium conductance following the spike, changes in [K+]o might be one mechanism by which oxidizing and reducing agents modulate heart frequencies. On the basis of the effect of insulin (INS) and K-strophantoside (STR) on these modulatory influences, it is presumed that the changes in slow delta [K+]o transients might result, at least partly, from the effect of redox agents on the active transport system. In light of the increase in passive K+ fluxes after oxidant treatment and the decrease in this parameter following reductant treatment an effect of redox agents on the characteristics of the K+-channel is also postulated.     

Correlations between positive and negative aeroions, tissue redox-state potential and heart frequency in rats

It was observed in rats that following positive aeroionization the redox-state potential (E'0) in skeletal muscles and liver was decreased, and the heart frequency increased. After negative ionization these interrelationships took place inversely. It was also established that upon adding an oxidant (menadione) i.v., the E'0 was decreased (compensatorily) in the organs mentioned above, parallel with the increment of heart frequency. Following injection of reductants (cysteine, thiamine) a reverse image was observed. Applying simultaneously positive ionization and reducing agents, the E'0 change and the heart frequency alteration failed to appear. The phenomenon was the same after simultaneous application of negative ionization and oxidant (menadione) injection. Because the heart effect of positive and negative ionization could readily be prevented by a respective redox agent, it seemed that actions of aeroions are exerted through shifts in tissue E'0. The most probable site of action of E'0, is the pacemaker mechanism, but an action on serotonin liberation may also be assumed.     

Analysis of the influence of aeroions on ECG and correlation between this action and tissue redox-state potential

It was observed in rats, that following negative aeroionization heart frequency and the altitude of P-waves increased. After positive ionization these interrelationships took place inversely. As between these effects and the tendency of tissue redox-state potential changes correlation was seen, the results were grouped also on redox basis, independently on whether the increase or decrease of redox-state potential was caused by negative or positive aeroions. The results of this grouping showed, that following an elevation of tissue redox-state potential (+delta E'0) heart frequency dropped, and the altitude of T-waves increased. After a decrease of tissue redox-state potential (-delta E'0) these interrelationships were realized inversely. After -delta E'0 the positive chronotropic influence of noradrenaline increased, but consequent to +delta E'0 the classical positive chronotropic effect of this catecholamine was reversed. These results corroborate our earlier notion, that aeroions exert their action on heart through changing tissue redox-state potential.     

Correlations between the tissue redox-state and K(+)-contractures

Analyzing the mechanisms of redox-modulation of the excitatory-contractory process, recently the amplitude of K(+)-contractures, tissue redox-state potential and electrical burst activity were simultaneously measured in the rectus abdominis muscle of the frog (Rana esculenta) following oxidant (thionine) and reductant (ascorbate) treatments. Pretreatment with oxidant in parallel with the increment of redox-state potential increased, while pretreatment with reductant, parallel with the decrement of redox-state potential decreased significantly both the amplitudes of K(+)-contractures and the electrical burst activity. The main mechanisms of action of this phenomenon, at least of the phasic portion, in all probability is the increase of intracellular quotient of the ionized/bound calcium after oxidizing, but a decrease of this quotient following reducing shifts. In the case of tonic portion an increase of Ca2(+)-influx through the Na(+)-Ca2(+)-exchange diffusion mechanisms seems feasible. Other mechanisms are also discussed. Hence, the mechanism of K(+)-contractures is under the control of tissue redox-state potential as well.     

Redox-state of intactNitella cells: dependency on intracellular pH and photosynthesis

Summary The present paper describes the construction and properties of a Pt/Ir-semi-microelectrode and its application as a redoxsensitive electrode in intact cells of the giant algaNitella. For compartmental analysis of the stationary redox-state voltage (E_RED), a value reflecting the interaction of the dominant redox couples with a Pt/Ir-electrode, the redox-sensitive electrode was inserted into the vacuole of leaf cells or cytoplasm enriched fragments (CEF) fromNitella internodal cells. After correction for the membrane voltage, measured with a second, conventional voltage electrode, E_RED values of+237±93mVand+419±51 mV with respect to a normal H⁺-electrode were obtained for cytoplasm and vacuole, respectively. The redox-state of the cell culture medium was+604 mV. The steady state E_RED in the cytoplasm can be perturbed by experimental treatments: indirect acidification of the cytoplasm by an external pH jump from 7.5 to 5.8 and direct acidification, by acid loading with 5 mM butyrate, both resulted in a positive shift of E_RED, i.e., to an increase in cytoplasmic oxidation. At the same time the membrane depolarized electrically following the external pH jump, but hyperpolarized in response to acid loading. The data demonstrate the direct dependence of cytoplasmic redox state on intracellular pH, probably due to enhanced oxidation of protonated redox couples favoured by mass action. The electrical membrane voltage changes were not correlated with the shift in cytoplasmic E_RED. This demonstrated that redox energy does not determine the electrical membrane voltage. Cytoplasmic E_RED was also affected by photosynthesis. When CEFs were transferred from light to dark, or exposed to 10M 3-(3,4-dichlorophenyl)-1,l-dimethylurea (DCMU), E_RED shifted negatively (more reduced) by 6.4±4.5mV or 4.2±2mV, respectively. These data compare favourably with biochemical estimates of cytoplasmic pyridin nucleotides which also show an increase in cytoplasmic reduction in the dark. Therefore, it is unlikely that diffusable reducing equivalents are supplied to the cytoplasm from photosynthetically-active chloroplasts to act as secondary messengers.Abbreviations E_M transmembrane voltage - E_RED redox-state voltage - E₀ midpoint-redox-voltage - APW artificial pond water - CEF cytoplasm enriched fragment     

Opposite effects of methylene blue and ascorbate on lipid peroxidation in muscles. Correlation with the redox state. I. Experiments on satisfied frogs

Homogenates of heart, stomach and rectus abdominis muscles of the frog have shown different degrees of malondialdehyde (MDA) formation. MDA content was highest in heart, and lowest in stomach musculature. The resultant tissue redox-state potential (RSP) and redox potential (E'0) in homogenates determined potentiometrically also showed differences with opposite signs in relation to MDA levels. An electron acceptor, methylene blue (MB), decreased but an electron donor, ascorbate (Asc), increased the MDA level in each of the muscles. These effects were dependent upon the concentration of MB and Asc and proportional to the control MDA content in each muscle. Thus an inverse interdependence between MDA level and redox state existed even when a positive change in redox potentials was induced by MB, and also when a negative change was induced by Asc. Since there was a close negative correlation between the changes of MDA concentration and redox potential in the homogenates, it is strongly suggested that the changes of redox state in muscle are implicated in the processes leading to lipid peroxidation (LP).     

Purification and characterization of ZmRIP1, a novel reductant-inhibited protein tyrosine phosphatase from maize

Protein tyrosine phosphatases (PTPases) have long been thought to be activated by reductants and deactivated by oxidants, owing to the presence of a crucial sulfhydryl group in their catalytic centers. In this article, we report the purification and characterization of Reductant-Inhibited PTPase1 (ZmRIP1) from maize (Zea mays) coleoptiles, and show that this PTPase has a unique mode of redox regulation and signaling. Surprisingly, ZmRIP1 was found to be deactivated by a reductant. A cysteine (Cys) residue (Cys-181) near the active center was found to regulate this unique mode of redox regulation, as mutation of Cys-181 to arginine-181 allowed ZmRIP1 to be activated by a reductant. In response to oxidant treatment, ZmRIP1 was translocated from the chloroplast to the nucleus. Expression of ZmRIP1 in Arabidopsis (Arabidopsis thaliana) plants and maize protoplasts altered the expression of genes encoding enzymes involved in antioxidant catabolism, such as At1g02950, which encodes a glutathione transferase. Thus, the novel PTPase identified in this study is predicted to function in redox signaling in maize.     

Role of cellular redox state and glutathione in adenylate cyclase activity in rat adipocytes.

Adenylate cyclase in rat adipocyte membranes was inactivated as a result of treatment with sulfhydryl oxidants or with p-chloromercuribenzoate as well as by S-alkylating agents. The inhibition of the basal and isoproterenol- or glucagon-stimulated enzyme activity by the oxidants or the mercurial could be reversed by adding thiols to the isolated membranes. The activity of the enzyme paralleled the cellular glutathione (GSH) content. Lowering of intracellular glutathione by incubating the cells with specific reactants resulted in the inhibition of both basal and hormone-stimulated adenylate cyclase activity in the isolated membranes. Activity could be partly restored by supplying glucose to the incubation medium of intact cells. The fluoride-stimulated adenylate cyclase was also inhibited by the oxidants or the sulfhydryl inhibitors. The results suggest that adenylate cyclase may be partly regulated by oxidation-reduction. Thus, a direct relationship between both basal and hormone-stimulated adenylate cyclase activity and the cellular redox potential, determined by the cellular level of reduced glutathione, may be ascribed to the protection of the catalytic -SH groups of the enzyme from oxidative or peroxidative reactions and maintenance of the redox optimum for the reaction.     

Redox and spectroscopic properties of oxidized MoFe protein from Azotobacter vinelandii

The MoFe protein from Azotobacter vinelandii undergoes a six-electron oxidation by various organic dye oxidants with full retention of initial activity. Reduction of the oxidized protein by S2O42- and by controlled potential electrolysis indicates the presence of two reduction regions at -290 and -480 mV, each requiring three electrons for complete reaction. Control of the oxidation conditions provides a means for preparing two distinct MoFe protein species selectively oxidized by three electrons. Selective reduction of the redox region at -290 mV causes development of the EPR signal associated with fully reduced MoFe protein while reduction at -480 mV produces a change in the visible spectrum but has no effect on the EPR signal intensity. Kinetic differences for reduction of the two redox regions indicate that the cofactor region undergoes a more rapid reaction with reductant than the other metal redox sites.     

The role of superoxide anions in regulation of coronary vessel tone and myocardial contractile function in changed redox-state of the myocardium

The study relates to the character of tirone effect (chemical trap of superoxide--anions) on regulation of coronary vessel tone and myocardial contractile function in normal and changed cell redox-state of coronary and cardiac vessels. The experiments were performed in 64 female Wistar rats (180-320 g). The coronary blood flow and myocardial contractile junction were studied in isolated heart preparations. To determine the role of superoxide-anions in regulation of coronary vessel tone, tirone was added to the perfusion solution (4,5-dihydroxy-1,3-benzene disulfonic acid, 10 mm, Sigma USA). Preliminary injection of N-acetyl-L-cysteine evoked a 16 % increase, whereas injection of L-buthionine-(S,R)-sulfoximine reduced concentration of nonprotein thiol group in the myocardium and erythrocytes of experimental animals by 37%. The influence of superoxide anions on the cardiac vessel tone and myocardial contractile function was due to nitric monoxide participation the concentration of which increased in binding of superoxide anions and was directly dependent on concentration of sulfhydrilis groups in the cardiac cells. The oxygen active forms and cellular redox-state seem to play an important role in the regulation mechanisms of the coronary vessel tone and myocardial contractile function.     

Oxidative stress and redox regulation of phospholipase D in myocardial disease

Oxidative stress may be viewed as an imbalance between reactive oxygen species (ROS) and oxidant production and the state of glutathione redox buffer and antioxidant defense system. Recently, a new paradigm of redox signaling has emerged whereby ROS and oxidants can function as intracellular signaling molecules, where ROS- and oxidant-induced death signal is converted into a survival signal. It is now known that oxidative stress is involved in cardiac hypertrophy and in the pathogenesis of cardiomyopathies, ischemic heart disease and congestive heart failure. Phospholipase D (PLD) is an important signaling enzyme in mammalian cells, including cardiomyocytes. PLD catalyzes the hydrolysis of phosphatidylcholine to produce phosphatidic acid (PA). Two mammalian PLD isozymes, PLD1 and PLD2 have been identified, characterized and cloned. The importance of PA in heart function is evident from its ability to stimulate cardiac sarcolemmal membrane and sarcoplasmic reticular Ca2+-related transport systems and to increase the intracellular concentration of free Ca2+ in adult cardiomyocytes and augment cardiac contractile activity of the normal heart. In addition, PA is also considered an important signal transducer in cardiac hypertrophy. Accordingly, this review discusses a role for redox signaling mediated via PLD in ischemic preconditioning and examines how oxidative stress affects PLD in normal hearts and during different myocardial diseases. In addition, the review provides a comparative account on the regulation of PLD activities in vascular smooth muscle cells under conditions of oxidative stress.     

Neurotoxic effects evoked by cyanobacterial extracts suggest multiple receptors involved in electrophysiological responses of molluscan (CNS, heart) models

The responses of the snail central neurons (Helix pomatia, Lymnaea stagnalis) and the isolated Helix heart were characterized evoked by cyanobacterial extracts (Cylindrospermopsis raciborskii ACT strains) isolated from Lake Balaton (Hungary). The nicotinergic acetylcholine (ACh) receptors in the CNS (both excitatory and inhibitory) were blocked by the extracts of ACT 9502 and ACT 9505 strains and the anatoxin- a (homoanatoxin-a) producing reference strain of Oscillatoria sp. (PCC 6506), similar to the inhibitory effects of the pure anatoxin-a. The enhancement of the ACh responses by the ACT 9504 extract suggests additional, probably acetylcholine esterase inhibitory mechanisms. On the isolated Helix heart the crude ACT 9505 and PCC 6506 extracts evoked frequency increase and transient twitch contraction, opposite to the ACh evoked heart relaxation. Anatoxin-a similarly contracted the heart but did not increase its contration frequency. These data suggest the involvement of some non-cholinergic mechanisms, acting very likely by direct modulation of the electrical or contractile system of the isolated heart. Diversity of the effects evoked by the cyanobacterial extracts in the CNS and heart suggest pharmacologically different neuroactive components among the secondary metabolites of the cyanobacteria acting on both (anatoxin-a like) cholinergic and (unidentified) non-cholinergic receptors.     

The role of oxygen free radicals in the development of chronic renal failure.

This study examined whether there is increased production of oxygen free radicals during chronic renal failure. Rats subjected to 3/4 nephrectomy and sham operated controls were killed after 3 weeks. Lipid extracts of plasma and renal tissue were examined by HPLC and kidney specimens were also analyzed by EPR spectroscopy. The redox capacity of blood was assessed using nitroblue tetrazolium and plasma ascorbate levels were measured with HPLC. There was no detectable renal production of oxygen free radicals in rats with chronic renal failure. Kidney parenchymal content of other oxidants and the oxidant:reductant ratio were similar in control and uremic animals. The plasma redox capacity and ascorbate levels were elevated in uremic rats. We conclude that early in the course of chronic renal failure, there is not excessive production of oxygen free radicals. There is accumulation of reductants, primarily ascorbate, in the plasma of uremic animals.     

Redox agents modulate a(K+)0 changes evoked by acetylcholine and adrenaline in frog heart

It was observed earlier, that in the presence of oxidizing agents the acetylcholine exerted a positive ino- and chronotropic effect, while the positive ino- and chronotropic action of adrenaline was decreased. In the presence of reducing agents both the negative inotropic effect of acetylcholine and the positive inotropic action of adrenaline was increased. Analyzing the ionic mechanism background of these correlations, the changes of extracellular K(+)-activity (a(K+)0) were followed and it was established that; In relation to slow transient changes (in min time ranges) an oxidant decreased the a(K+)0 following acetylcholine, while it increased the a(K+)0 after adrenaline application. A reductant increased the a(K+)0 with acetylcholine, but decreased a(K+)0 in the presence of adrenaline. Because of the inverse character of redox modulation on a(K+)0 levels, a reverse change in a(K+)0 should be (at least one of) the site of action of the opposite effects of oxidants or reductants exerted on ino- and chronotropism of acetylcholine or adrenaline.     

Is calcineurin a peroxide-specific sensor in T-lymphocytes?

Calcineurin activity in T-lymphocytes has been shown to be sensitive to H(2)O(2). In this report, we investigate the effects of H(2)O(2)and other physiological oxidants on calcineurin activity both in vivo and in vitro. Intracellular calcineurin activity, as determined by NF-AT phosphorylation state and activity, is inhibited by H(2)O(2) but is insensitive to superoxide and NaOCl. Similarly, treatment of T-lymphocytes with NaOCl and paraquat does not drastically alter the activity of calcineurin in crude cell lysate, while H(2)O(2) causes significant inhibition. Sensitivity to H(2)O(2) and NaOCl in vivo correlates with the half-life of each species in cell medium. The intracellular redox potential is unaffected by H(2)O(2) (100 micro M) or NaOCl (600 micro M), indicating that H(2)O(2) inhibits calcineurin via a direct mechanism that does not involve a change in the cytosolic redox potential. In contrast, calcineurin activity in cell lysate is inhibited by all three oxidants. H(2)O(2) inactivation of calcineurin is rapid, with inactivation occurring in 相似文献