NAADP/SERCA3-Dependent Ca2+ Stores Pathway Specifically Controls Early Autocrine ADP Secretion Potentiating Platelet Activation

RATIONALE

Ca²⁺ signaling is a key and ubiquitous actor of cell organization and its modulation controls many cellular responses. SERCAs (sarco-endoplasmic reticulum Ca²⁺-ATPases) pump Ca²⁺ into internal stores that play a major role in the cytosolic Ca²⁺ concentration rise upon cell activation. Platelets exhibit 2 types of SERCAs, SERCA2b and SERCA3 (SERCA3 deficient mice), which may exert specific roles, yet ill-defined. We have recently shown that Ca²⁺ mobilization from SERCA3-dependent stores was required for full platelet activation in weak stimulation conditions.

OBJECTIVE

To uncover the signaling mechanisms associated with Ca²⁺ mobilization from SERCA3-dependent stores leading to ADP secretion.

METHODS AND RESULTS

Using platelets from wild-type or Serca3-deficient mice, we demonstrated that an early (within 5-10 s following stimulation) secretion of ADP specifically dependent on SERCA3 stored Ca²⁺ is exclusively mobilized by nicotinic acid adenosine dinucleotide-phosphate (NAADP): both Ca²⁺ mobilization from SERCA3-dependent stores and primary ADP secretion are blocked by the NAADP receptor antagonist Ned-19, and reciprocally both are stimulated by permeant NAADP. In contrast, Ca²⁺ mobilization from SERCA3-dependent stores and primary ADP secretion were unaffected by inhibition of the production of IP3 (inositol-1,4,5-trisphosphate) by phospholipase-C and accordingly were not stimulated by permeant IP3.

CONCLUSIONS

Upon activation, an NAADP/SERCA3 Ca²⁺ mobilization pathway initiates an early ADP secretion, potentiating platelet activation, and a secondary wave of ADP secretion driven by both an IP3/SERCA2b-dependent Ca²⁺ stores pathway and the NAADP/SERCA3 pathway. This does not exclude that Ca²⁺ mobilized from SERCA3 stores may also enhance platelet global reactivity to agonists. Because of its modulating effect on platelet activation, this NAADP-SERCA3 pathway may be a relevant target for anti-thrombotic therapy. Graphic Abstract: A graphic abstract is available for this article.

Spectrophotometric assays for measuring redox biomarkers in blood and tissues: the NADPH network

Nicotinamide adenine dinucleotide (NAD+/NADH) along with its phosphorylated form (NADP+/NADPH) are two molecules ubiquitously present in all organisms, and they play key roles as cofactors in fundamental catabolic and anabolic processes, respectively. The oxidation of NADPH to NADP+ initiates a cascade of reactions, where a network of molecules is implicated. The molecules of this cascade form a network with eminent translational potential in redox metabolism. A special point of interest is that spectrophotometric assays have been developed both for NADH/NADPH and the molecules directly regulated by them. Therefore, crucial molecules of the NADPH-dependent redox network can be measured, and the results can be used to assess the bioenergetic and/or oxidative stress status. The main aim of this review is to collectively present the NADPH-related molecules, namely NADPH, NADH, NAD+ kinase, NADPH oxidase, peroxiredoxin, thioredoxin, thioredoxin reductase, and nitric oxide synthase, that can be measured in blood and tissues with the use of a spectrophotometer, which is probably the most simple, inexpensive and widely used tool in biochemistry. We are providing the researchers with reliable and valid spectrophotometric assays for the measurement of the most important biomarkers of the NADPH network in blood and other tissues, thus allowing the opportunity to follow the redox changes in response to a stimulus.

Whole Blood Metabolomics by 1H NMR Spectroscopy Provides a New Opportunity To Evaluate Coenzymes and Antioxidants

Conventional human blood metabolomics employs serum or plasma and provides a wealth of metabolic information therein. However, this approach lacks the ability to measure and evaluate important metabolites such as coenzymes and antioxidants that are present at high concentrations in red blood cells. As an important alternative to serum/plasma metabolomics, we show here that a simple 1H NMR experiment can simultaneously measure coenzymes and antioxidants in extracts of whole human blood, in addition to the nearly 70 metabolites that were shown to be quantitated in serum/plasma recently [ Anal. Chem. 2015 , 87 , 706 - 715 ]. Coenzymes of redox reactions: oxidized/reduced nicotinamide adenine dinucleotide (NAD+ and NADH) and nicotinamide adenine dinucleotide phosphate (NADP+ and NADPH); coenzymes of energy including adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP); and antioxidants, the sum of oxidized and reduced glutathione (GSSG and GSH) can be measured with essentially no additional effort. A new method was developed for detecting many of these unstable species without affecting other blood/blood plasma metabolites. The identities of coenzymes and antioxidants in blood NMR spectra were established combining 1D/2D NMR techniques, chemical shift databases, pH measurements and, finally, spiking with authentic compounds. This is the first study to report identification of major coenzymes and antioxidants and quantify them, simultaneously, with the large pool of other metabolites in human blood using NMR spectroscopy. Considering that the levels of coenzymes and antioxidants represent a sensitive measure of cellular functions in health and numerous diseases, the NMR method presented here potentially opens a new chapter in the metabolomics of blood.

[DIAGNOSTIC MARKERS AS PREDICTORS OF NECESSITY FOR THE OPERATIVE INTERVENTIONS PERFORMANCE IN PATIENTS FOR CORRECTION OF OXIDATIVE STRESS IN AN ACUTE PANCREATITIS]

In the investigation 70 patients were included, treated for necrotic acute pancreatitis. On the 7th day from an acute pancreatitis occurrence a state of oxidative system was studied in the patients. Raising of the blood serum concentration of malonic dialdehyde higher than 3.68 mcmol/l, reduction of the glutationperoxidase activity lower than 8.49 mcmol NADFН(2) h/mg protein and glutationreductase — lower than 5.18 mcmol NADFН(2) h/mg of protein before 7 days of treatment of an acute pancreatitis was accompanied by raising of the pancreas infectioning risk, what have had demanded the operative intervention performance.

Middle-aged rats orally supplemented with gel-encapsulated catechin favorably increases blood cytosolic NADPH levels

Green tea catechins are primarily known to function as free radical scavengers and have several beneficial uses. Orally supplemented catechin (OSC) was previously shown to increase mitochondrial heme and catalase levels in rat heart blood, however, its effect in the cytosol has not been elucidated. Here, we determined the effects of OSC in the rat heart blood cytosol. We used middle-aged (40 week-old) and young (4 week-old) rats throughout the study. We isolated blood cytosol, verified its purity, and determined heme, hydrogen peroxide (H2O2) levels, catalase (CAT) activities, gp91(phox) amounts, NADP and NAD pools, sirtuin 1 (SIRT1) and glutathione reductase (GR) activities, and free fatty acids (FFA). We established that OSC is associated with decreased heme-dependent H2O2 amounts while increasing heme-independent CAT activity. Moreover, we found that OSC-related decrease in NAD(+) amounts among middle-aged rats is associated to increased NADPH levels and SIRT1 activity. In contrast, we associated OSC-related decrease in NAD(+) amounts among young rats to decreased NADPH levels and increased SIRT1 activity. This highlights a major difference between catechin-treated middle-aged and young rats. Furthermore, we observed that cytosolic FFA and GR levels were significantly increased only among OSC-treated middle-aged rats which we hypothesize are related to increased NADPH levels. This insinuates that OSC treatment allows higher catechin amounts to enter the bloodstream of middle-aged rats. We propose that this would favorably increase NADPH amounts and lead to the simultaneous decrease in NADPH-related pro-oxidant activity and increase in NADPH-related biomolecules and anti-oxidant activities.

The assessment of the energy metabolism in patients with chronic fatigue syndrome by serum fluorescence emission

CONTEXT

Chronic fatigue syndrome (CFS) is a debilitating fatigue illness that has unknown etiology and lacks an objective diagnostic marker.

OBJECTIVE

To examine the metabolic component of CFS to determine if practitioners can use serum NAD(P)H concentration measurements to monitor metabolism and fatigue status in patients with CFS.

DESIGN

The research team conducted a case-control study, comparing a group of patients who were diagnosed with CFS with a control group of healthy subjects. The team obtained venous blood samples from fasting patients to examine the serum NAD(P)H concentrations.

SETTING

The study occurred at the Riordan Clinic in Witchita, Kansas.

PARTICIPANTS

The study included 44 CFS patients at the Riordan Clinic and 30 healthy control participants. The CFS patients presented a spectrum of symptoms that had existed for at least 6 months: new, unexplained, persistent, or relapsing chronic fatigue that bed rest did not resolve and that was severe enough to reduce daily activity significantly by 50% in conjunction with headache, muscle pain, pain in multiple joints, and unrefreshing sleep. In the control group, the research team enrolled subjects without diagnosis of disease or injury.

OUTCOME MEASURES

The research team determined levels of serum reduced nicotinamide adenine dinucleotides (NADH and NAD[P]H) by measuring serum fluorescence emission at 450 nm. The team then conducted sensitivity and specificity analyses. Results NAD(P)H concentrations in serum of CFS participants averaged 8.0 ± 1.4 (standard deviation [SD]) nmol/mL, while those in the healthy controls averaged 10.8 ± 0.8 (SD) nmol/mL, a statistically significant difference. Using a cut-off concentration of 9.5 nmol/mL, the research team attained a sensitivity of 0.73 and a specificity of 1.0. An analysis of receiver-operator characteristics yielded an area under the curve of 0.9. The research team compared serum NAD(P)H to several endocrine and metabolic lab parameters. Serum NAD(P)H was directly correlated with serum CoQ10 levels and inversely correlated with urine hydroxyhemopyrrolin-2-one levels.

CONCLUSIONS

Based on these findings, the research team proposed using serum NAD(P)H, measured as an intrinsic serum-fluorescence emission, to monitor metabolism and fatigue status in patients with CFS. Following patients NAD(P)H levels over time may aid in selecting therapeutic strategies and monitoring treatment outcomes.

Monitoring the intracellular store Ca2+ concentration in agonist-stimulated, intact human platelets by using Fluo-5N

BACKGROUND

Most Ca(2+) signaling research in platelets has relied solely on monitoring the cytosolic Ca(2+) concentration ([Ca(2+)](cyt)). Changes in [Ca(2+)](cyt) constitute the net effect of Ca(2+) fluxes into the cytosol across the plasma membrane (PM) and from intracellular stores, and Ca(2+) sequestration into the stores and Ca(2+) removal across the PM. This makes interpretation of the effects of pharmacologic or genetic interventions on Ca(2+) signaling difficult and subject to error.

OBJECTIVES

To validate the use of the low-affinity Ca(2+) indicator Fluo-5N to monitor the concentration of Ca(2+) in the intracellular stores ([Ca(2+)](st)) of human platelets as a first step in developing assays for a systems-level analysis of platelet Ca(2+) signaling.

METHODS

Fluo-5N-loaded and Fura-2-loaded human platelets were used to observe the effects of agonist stimulation and other manipulations on [Ca(2+)](cyt) and [Ca(2+)](st).

RESULTS

Fluo-5N fluorescence changed appropriately in response to compounds that induce passive depletion of intracellular Ca(2+) stores and to physiologic agonists. Ca(2+) reuptake inhibitors and blockers of Ca(2+) release channels had the expected effects on Fura-2 and Fluo-5N fluorescence. Agonist-evoked Ca(2+) release was reversed by Ca(2+) addition to the medium, and required intact Ca(2+) reuptake mechanisms. Store refilling was observed in the presence of sarcoplasmic/endoplasmic reticulum Ca(2+) -ATPase (SERCA) inhibitors and ionomycin, suggesting the presence of a non-SERCA Ca(2+) reuptake mechanism. Evidence for a role for Ca(2+) -induced Ca(2+) release in agonist-evoked responses was obtained.

CONCLUSIONS

Our data provide a validation of the use of Fluo-5N as a method for monitoring changes in [Ca(2+)](st) in human platelets.

Elevated peroxidative glutathione redox status in atherosclerotic patients with increased thickness of carotid intima media

BACKGROUND

Atherosclerosis is a chronic inflammatory disease. Accumulated evidences suggest a deep involvement of oxidative damage in the development of atherosclerosis, but little is discussed over the relationship between plasma glutathione redox status as the most important intrinsic antioxidant defensive mechanism and the atherosclerosis.

METHODS

A total of 132 patients suspected with atherosclerosis were assigned to three groups by high frequency ultrasonic examination of the carotid artery. With the thickness of intima of the carotid artery as an index of degree of atherosclerosis progression, 56 were included in plaque-forming group (A), 42 in carotid artery intima-thickening group (B), and 34 in normal carotid artery intima-thickness group (C). All patients were subjected to the measurement of plasma glutathione (GSH) (reduced form GSH and oxidized form GSSG), nicotinamide adenine dinucleotide phosphate (NADP) (reduced form NADPH and oxidized form NADP(+)), oxidized low density lipoprotein (oxLDL), and malondialdehyde (MDA). The GSH/GSSG and NADPH/NADP(+) redox potentials were calculated according to the Nernst equation, and their correlation with intima thickness and oxLDL was analyzed.

RESULTS

With the thickening of artery intima (from group C to A), GSH concentration and the ratio of GSH/GSSG gradually reduced, and GSSG and GSH/GSSG redox potential gradually increased (more positive) (P < 0.05). The NADPH and NADPH/NADP(+) redox status also showed similar but milder changes. The products of oxidative stress oxLDL and MDA increased significantly along with the thickening of artery intima (P < 0.05). The analysis of the relationship between GSH/GSSG redox potential, intima thickness, and oxLDL showed positive correlations (P < 0.05). The plasma GSH/GSSG redox status was positively correlated with the intima thickness of the carotid artery and the oxidized injury of LDL. The redox status shifted to oxidizing direction along with the intima thickening and plaque-forming.

CONCLUSION

Elevated peroxidative glutathione redox status was deeply implicated in atherosclerosis progressing, and it may be a sensitive and reliable index for monitoring oxidative status in atherosclerosis.

Whole blood NAD and NADP concentrations are not depressed in subjects with clinical pellagra

Population surveys for niacin deficiency are normally based on clinical signs or on biochemical measurements of urinary niacin metabolites. Status may also be determined by measurement of whole blood NAD and NADP concentrations. To compare these methods, whole blood samples and spot urine samples were collected from healthy subjects (n = 2) consuming a western diet, from patients (n = 34) diagnosed with pellagra and attending a pellagra clinic in Kuito (central Angola, where niacin deficiency is endemic), and from female community control subjects (n = 107) who had no clinical signs of pellagra. Whole blood NAD and NADP concentrations were measured by microtiter plate-based enzymatic assays and the niacin urinary metabolites 1-methyl-2-pyridone-5-carboxamide (2-PYR) and 1-methylnicotinamide (1-MN) by HPLC. In healthy volunteers, inter- and intra-day variations for NAD and NADP concentrations were much lower than for the urinary metabolites, suggesting a more stable measure of status. However, whole blood concentrations of NAD and NADP or the NAD:NADP ratio were not significantly depressed in clinical pellagra. In contrast, the concentrations of 2-PYR and 1-MN, expressed relative to either creatinine or osmolality, were lower in pellagra patients and markedly higher following treatment. The use of the combined cut-offs (2-PYR <3.0 micromol/mmol creatinine and 1-MN <1.3 micromol/mmol creatinine) gave a sensitivity of 91% and specificity of 72%. In conclusion, whole blood NAD and NADP concentrations gave an erroneously low estimate of niacin deficiency. In contrast, spot urine sample 2-PYR and 1-MN concentrations, relative to creatinine, were a sensitive and specific measure of deficiency.

Highly sensitive spectrofluorimetric determination of trace amounts NADP using Europium ion-doxycycline complex probe

A new spectrofluorimetric method was developed for determination of trace amount of Coenzyme II (NADP). Using europium ion-doxycycline (DC) as a fluorescent probe, in the buffer solution of pH 8.44, NADP can remarkably enhance the fluorescence intensity of the Eu(3+)-DC complex at lambda=612 nm and the enhanced fluorescence intensity is in proportion to the concentration of NADP. Optimum conditions for the determination of NADP were also investigated. The dynamic range for the determination of NADP is 3.3 x 10(-7) to 6.1 x 10(-6) mol l(-1) with detection limit of 6.8 x 10(-8) mol l(-1). This method is simple, practical and relatively free interference from coexisting substances and can be successfully applied to determination of NADP in synthetic water samples and in serum samples. Moreover, the enhancement mechanisms of the fluorescence intensity in the Eu(3+)-DC system and the Eu(3+)-DC-NADP system have been also discussed.

[The relationship between oxidized form glutathione, coenzyme II and carotid artery atherosclerosis]

OBJECTIVE

To explore the relationship between plasma redox status and atherosclerosis.

METHODS

IVUS was performed in common carotid in the neck of 167 patients with heart diseases. Patients were divided into three groups: plaque-forming group (A, n = 79), intima-thickening group (B, n = 52) and control group (C, n = 36). Plasma glutathione (reduced form GSH and oxidized form GSSG), nicotinamide adenine dinucleotide phosphate (reduced form NADPH and oxidized form NADP(+)), oxidized low density lipoprotein (ox-LDL) and malondialdehyde (MDA) were measured in all patients. The GSH/GSSG and NADPH/NADP(+) redox potential were calculated according to Nernst equation, and correlation analysis performed.

RESULTS

GSH and GSH/GSSG gradually reduced and GSH/GSSG redox potential gradually increased in proportion to the thickening of artery intima (from Group C to Group A, P < 0.05). Similar but milder results were shown for NADPH and NADPH/NADP(+) redox status. The products of oxidative stress ox-LDL and MDA also increased significantly (P < 0.05) in proportion to the thickening of artery intima. GSH/GSSG redox potential is positively correlated to ox-LDL (P < 0.05). The redox status shifted to oxidizing direction in proportion to the intima thickness.

CONCLUSION

The imbalance of plasma redox status deviating to oxidation might be implicated in oxidized injury of lipid, intima thickening and atherosclerosis progress.

Antioxidant profiles in full term and preterm neonates

BACKGROUND

Free radical damage has been recognized to be a common pathogenic mechanism of many neonatal diseases associated with oxygen toxicity.

METHODS

A set of antioxidant measurements were used to investigate differences in levels between full term and premature infants after birth. Four groups of full term and preterm infants were enrolled, including full term appropriate-for-age (FT-AGA), full term small-for-age (FT-SGA), larger preterm (LPT) and smaller preterm infants (SPT). After birth, seven antioxidants, including superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), nicotinamide-adenine dinucleotide phosphate (NADP) represented by the NADPH ratio (NADPH, the reduced form of NADP)/(NADPNADPH), glucose-6-phosphate dehydrogenase (G6PD), and vitamins A and E were measured.

RESULTS

FT-SGA infants had significantly lower levels of GSH, NADPH ratio and vitamin A than the FT-AGA infants but higher CAT, G6PD and vitamin E levels. LPT infants had lower levels of CAT, GSH, NADPH ratio and vitamin A but higher G6PD activity than the FT-AGA infants. SPT infants showed the same pattern of differences in various antioxidants as those of the LPT infants when compared to FT-AGA infants. Vitamin E levels did not statistically differ between SPT and LPT infants. SPT infants had significantly lower levels of GSH and NADPH ratio than the LPT infants.

CONCLUSIONS

Intrauterine growth retardation and prematurity may influence antioxidant imbalance and free radical damage. In addition, such data for healthy full term and preterm infants may be used as reference data when evaluating antioxidant deficiency in high-risk neonates.

A streamlined method to predict hepatic clearance using human liver microsomes in the presence of human plasma

INTRODUCTION

Human liver microsomal incubations are often used to predict the metabolic lability of new chemical entities. The clearance values are scaled-up from in vitro data and mathematically corrected for plasma protein binding, or in some cases the free fraction ratio of plasma to microsomes, using well-established scaling methods such as the well-stirred model. This can be time consuming for multiple compounds since it requires separate experiments to determine in vitro lability, and free fraction.

METHODS

We attempted to streamline clearance predictions by combining experiments into one. Firstly, we combined the free fraction experiments into one free fraction ratio by measuring the partitioning of compound between plasma and microsomes, and by applying this experimental ratio to clearance predictions found that it performed at least as well as free fractions determined separately. We also incubated compounds with plasma added to the incubation mixture and compared the predicted clearances to values determined using traditional mathematical protein binding corrections.

RESULTS

Consistently, incubations with added plasma resulted in CL predictions closer to literature values than incubations only mathematically corrected for protein binding. For example, incorporating plasma into a ketamine incubation resulted in a CL value of 15.1 mL/min/kg, compared with a value of 10.2 using mathematical binding corrections. The literature value is 16.4 mL/min/kg.

DISCUSSION

This work characterizes this new method and compares it to the traditional microsomal incubation method using several literature compounds, and suggests that streamlining the methods may generate quality data faster and with less resource investment.

Conversion ratio of tryptophan to niacin in Japanese women fed a purified diet conforming to the Japanese Dietary Reference Intakes

In order to establish the human requirements of niacin, it is first important to know how much tryptophan is converted to niacin in the human body. In a general, 60 mg of tryptophan is equivalent to 1 mg of niacin, whereas the conversion ratio of tryptophan to niacin is yet to be confirmed. The aim of this study was to know the conversion ratio of tryptophan to niacin in Japanese females fed a purified diet, which followed the Japanese Dietary Reference Intakes. Ten young Japanese females were housed in the same facility and given the same daily living activity schedule for 7 d. The composition of their purified diet was conformed to the Dietary Reference Intakes in Japan. The diet was niacin free. In order to investigate the conversion ratio, daily urinary outputs were collected. Tryptophan-niacin metabolites in the urine were measured and the conversion ratio of tryptophan to niacin calculated. The conversion ratio was calculated by comparing the dietary intake of tryptophan and the sum of the niacin catabolites such as N1-methylnicotinamide, N1-methyl-2-pyridone-5-carboxamide, and N1-methyl-4-pyridone-3-carboxamide, which were derived only from the dietary intake of tryptophan. The ratio was calculated as 1.5 +/- 0.1 (mean +/-SE for 10 women; in molar basis) on the last day of the experiment. It was calculated that if the excretory percentage of niacin metabolites in the urine were 60%, of the tryptophan ingested, the conversion factor would be a value of 67, meaning that is 67 mg of tryptophan is equal to 1 mg of niacin.

Purine nucleotides and their metabolites in erythrocytes of streptozotocin diabetic rats

OBJECTIVES

In the present study it was tried to obtain a complete overview of purine nucleotide metabolism in erythrocytes of streptozotocin (STZ) induced diabetes mellitus rats.

METHODS

Erythrocyte levels of the main nucleotides (ATP, ADP, AMP, GTP, GDP, GMP, IMP, NAD+, NADP+), nucleosides (Ado, Guo, Ino) and the base Hyp were measured using the HPLC method. The parameters that can be deduced from their concentrations: TAN, TGN and AEC, GEC expressed by the ratio of high/low energy nucleoside phosphates were calculated. The effects of streptozotocin-induced diabetes on the concentration and metabolism of rat erythrocyte purine and pyridine nucleotides and the activity of Na+, K+-ATPase as well as Ca2+-ATPase were investigated.

RESULTS

Increased dephosphorylation of adenine nucleotides (found as the increased concentration of Ado and Hyp and the decrease in AEC value) and the decrease in ATP and TAN and the changes in the concentrations of NAD+ and NADP+ suggest serious purine and pyridine metabolism disruptions in diabetic erythrocytes and decrease in ATPases activity.

CONCLUSION

The observations suggest that purine nucleotide degradation is markedly accelerated in erythrocytes of STZ diabetic rats.

Effects of excess nicotinamide administration on the urinary excretion of nicotinamide N-oxide and nicotinuric acid by rats

We investigated a useful chemical index for an excessive nicotinamide intake and how this excessive nicotinamide intake affects the tryptophan-nicotinamide metabolism in rats. Weaning rats were fed on a tryptophan-limited and nicotinic acid-free diet containing no, 0.003%, 0.1%, 0.2%, or 0.3% nicotinamide for 21 days. Urine samples were collected on the last day and analyzed the intermediates and metabolites on the tryptophan-nicotinamide pathway. Nicotinamide N-oxide, nicotinic acid and nicotinuric acid, metabolites of nicotinamide, were detected when nicotinamide at more than 0.1% had been taken. An intake of nicotinamide of more than 0.1% increased the urinary excretion of quinolinic acid, an intermediate on the pathway. Nicotinamide N-oxide and nicotinuric acid increased with increasing dietary concentration of nicotinamide. These results show that the measurements of nicotinamide N-oxide and nicotinuric acid in urine would be useful indices for an excessive nicotinamide intake.

Hematological responses of the Neotropical teleost matrinxã (Brycon cephalus) to environmental nitrite

Environmental increase in nitrite impairs the function of several aquatic species, including fishes. Nitrite reacts with hemoglobin yielding the non-functional methemoglobin (metHb), and many physiological disturbances can arise. The physiological mechanisms to cope with nitrite are still unclear in fish. Hematological parameters, the role of NADH-methemoglobin reductase system and the electrolytic balance were studied in the freshwater teleost Brycon cephalus (matrinxã) exposed to 0.2, 0.4 and 0.6 mg/L of nitrite N-NO(2) for 24 and 96 h. Hematocrit, total hemoglobin and the red blood cell (RBC) number decreased. Methemoglobin content increased from 1% to 69% for 24 h of exposure and drastically from 5-6% to 90% for 96 h. The activity of NADH-methemoglobin reductase system displayed a tendency of increase in response to nitrite concentration or time of exposure. In the plasma, nitrite was accumulated to values 30-fold higher than the environmental concentration. The plasma K(+) concentration increased only in fish exposed to NO(2) for 24 h. No changes in plasma protein and Na(+) were observed during nitrite exposure but Cl-presented a punctual increase at 0.2 mg/L N-NO(2)-96 h. The hematological data suggest that nitrite caused functional and hemolytic anemia. Furthermore, the electrolytic balance was relatively undisturbed, and the nitrite clearance in matrinxã is likely depending on other factors than NADH-methemoglobin reductase system.

Effect of lead ions on rat erythrocyte purine content

The influence of short-term exposure to lead on the energetic status of erythrocytes in rats is reported in this study. The male Wistar rats selected for this study drank water containing 1% lead(II) acetate and/or intraperitoneal injections of 1 or 2 mg/kg body wt every 4 d starting on the eighth of the experiment, over a period of 1 mo. The whole-blood lead concentration measured after 4 wk was 1.51-35.31 microg/dL. The concentrations of adenosine, adenosine triphosphates, diphosphates, and monophosphates (ATP, ADP, and AMP), guanine triphosphates, diphosphates and monophosphates (GTP, GDP, and GMP), guanosine (Guo), inosine (Ino), inosine monophosphate (IMP), hypoxantine (Hyp), and nicotinamide dinucleotide and its phosphate (NAD(+) and NADP(+)) were determined by high-performance liquid chromatography (HPLC). The mean concentrations of ATP, GTP, NAD(+), and NADP(+) and those of adenylate (AEC) and guanylate (GEC) were significantly reduced in erythrocytes from the animals exposed to lead when compared to untreated controls. These results suggest that a lead ion disrupts the erythrocyte energy pathways. The decreases of NAD(+) and ATP could be used as an indicator of the extent of exposure to low levels of lead.

Methemoglobinemia and eccentrocytosis in equine erythrocyte flavin adenine dinucleotide deficiency

This report describes erythrocyte biochemical findings in an adult Spanish mustang mare that exhibited persistent methemoglobinemia, eccentrocytosis, and pyknocytosis that were not related to the consumption or administration of an exogenous oxidant. The methemoglobinemia was attributed to a deficiency in cytochrome-b5 reductase (Cb5R) activity, and the eccentrocytes and pyknocytes were attributed to a marked deficiency in reduced nicotinamide adenine dinucleotide phosphate-dependent glutathione reductase (GR) activity that resulted in decreased reduced glutathione concentration within erythrocytes. The GR activity increased to a near-normal value after addition of flavin adenine dinucleotide (FAD) to the enzyme assay, indicating a deficiency of FAD in erythrocytes. The methemoglobinemia, eccentrocytosis, and pyknocytosis were attributed to deficiency of FAD in erythrocytes because the GR and Cb5R enzymes use FAD as a cofactor. This deficiency in FAD results from a defect in erythrocyte riboflavin metabolism, which has not been documented previously in animals.

Alpha-tocopherol and NADPH in the erythrocytes and plasma of multiple sclerosis patients. Effect of interferon-beta-1b treatment

OBJECTIVES

To investigate the influence of interferon-beta-1b (INF-beta-1b) therapy on blood antioxidants (alpha-tocopherol and NADPH) in multiple sclerosis (MS).

PATIENTS AND METHODS

Patients with relapsing-remitting MS (n = 14) have been studied during 6 months of INF-beta-1b therapy. alpha-Tocopherol was determined by HPLC and UV or electrochemical detection; NADPH was quantified spectrophotometrically.

RESULTS

The erythrocyte alpha-tocopherol level was reduced (p < 0.001) before treatment, but had regained the control level by 6 months of therapy. The plasma alpha-tocopherol/lipid ratios were constant during therapy. Plasma triglyceride levels were transiently increased (p = 0.0270) after 1 month of treatment. INF-beta-1b had also induced a transient decrease in NADPH after 1 month, but thereafter the level returned to approximately the initial value (p = 0.0248).

CONCLUSION

INF-beta-1b seems to exert a sparing effect toward the erythrocyte alpha-tocopherol content. The fall in NADPH in parallel to the rise in plasma triglycerides suggests stimulation of fatty acid synthesis by INF-beta-1b.

Quantitative evolutionary design of glucose 6-phosphate dehydrogenase expression in human erythrocytes

Why do the activities of some enzymes greatly exceed the flux capacity of the embedding pathways? This is a puzzling open problem in quantitative evolutionary design. In this work we investigate reasons for high expression of a thoroughly characterized enzyme: glucose 6-phosphate dehydrogenase (G6PD) in human erythrocytes. G6PD catalyses the first step of the pathway that supplies NADPH for antioxidant defense mechanisms. Normal G6PD activity far exceeds the capacity of human erythrocytes for a steady NADPH supply, which is limited upstream of G6PD. However, the distribution of erythrocyte G6PD activity in human populations reveals a selective pressure for maintaining high activity. To clarify the nature of this selective pressure, we studied how G6PD activity and other parameters in a model of the NADPH redox cycle affect metabolic performance. Our analysis indicates that normal G6PD activity is sufficient but not superfluous to avoid NADPH depletion and ensure timely adaptation of the NADPH supply during pulses of oxidative load such as those that occur during adherence of erythrocytes to phagocytes. These results suggest that large excess capacities found in some biochemical and physiological systems, rather than representing large safety factors, may reflect a close match of system design to unscrutinized performance requirements. Understanding quantitative evolutionary design thus calls for careful consideration of the various performance specifications that biological components/processes must meet in order for the organism to be fit. The biochemical systems framework used in this paper is generally applicable for such a detailed examination of the quantitative evolutionary design of gene expression levels in other systems.

[Pathomechanism of hyperlipoproteinemia in chronic renal failure]

Lipid disorders are one of the known metabolic changes associated with chronic renal failure (CRF) [1, 2]. They are present as: hypertriglyceridemia--existed in 60% of CRF patients and hypercholesterolemia observed in 20-30% of people with this syndrome. These disorders, what was shown also in our own studies, are existing in different intensity in patients treated with maintenance haemodialysis [3], peritoneal dialysis [4] and after renal transplantation as well [5]. Mechanism of hypertriglyceridemia, despite over thirty years of studies, is still not finally elucidated. The opinion that it is a result of impaired triglyceride removal (due to decreased activities of both lipoprotein and hepatic lipases) is well documented, however the role of lipogenesis in its development is obscure [6, 7]. The reports concerning this problem contain contradictory data. In our studies performed several years ago we have shown that lipogenesis rate in white adipose tissue of uremic rats is significantly augmented [8, 9, 10] due to activation of free fatty acid synthase. Therefore, recently we paid once again our attention on the activity of this lipogenesis rate limiting enzyme responsible for the long term regulation. We measured its activity, protein abundance and mRNA level in liver and epididymal white adipose tissue of rats with surgically induced renal failure (two-stage subtotal nephrectomy). The results support the thesis that lipogenesis takes a part in a hypertriglyceridemia found in renal failure. There have been observed a significant increase in plasma triglyceride and VLDL concentrations in uremic animals and it was associated with the increase of FAS activity, FAS protein abundance and FAS mRNA. The results were similar in both studied tissues. Moreover, there have been also observed the increased activities of malic enzyme, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. All these enzymes participate in NADPH production, which is a necessary substrate for fatty acid biosynthesis [11, 12, 13]. Concluding, it appears that the rise in plasma triglyceride and VLDL concentrations observed in CRF rats is not only the result of increased liver and white adipose tissue lipogenesis rate. One has to remember, that these date are strictly original and enabling to elucidation further pathogenesis of hyperlipidemia in CRF. In the second set of experiments performed also in rats with experimentally induced CRF we have found that hypercholesterolemia observed in those animals is dependent on the significant activation of cholesterol synthase, induced by increased production of this enzyme (increment of protein abundance and synthase mRNA [14, 15]. Simultaneously, we have performed original studies on the diurnal rhythm of cholesterologenesis, showing that activity of this process is significantly augmented during whole twenty four hours [15]. Summarizing, one have to underline that our observations have important impact to the elucidation of lipid disturbances pathomechanism. Nevertheless further studies are necessary to establish how experimental data are corresponding with human pathology.

Hexose monophosphate shunt activities in human erythrocytes during oxidative damage induced by hydrogen peroxide

Human red blood cells (HRBCs) were exposed to H(2)O(2) either as bolus or as a flux generated by a glucose-glucose oxidase system. H(2)O(2) concentrations were in the range 10(-5)-10(-3) M and exposure times to the oxidative stress were 10 min and 60 min. The production of NADPH by the hexose monophosphate shunt (HMPS) was accurately measured by gas chromatography-isotope ratio mass spectrometry as the production of (13)CO(2) from [1-(13)C]glucose. Depending on the duration of exposure and H(2)O(2) concentration, the production of (13)CO(2) by HRBCs under a flux of H(2)O(2) was increased two- to eight-fold in comparison with that obtained under a bolus of H(2)O(2). Under flux stimulation, spectral data show the formation of compound I, and a red shift caused by the presence of compounds II and III, whereas under a bolus stress no obvious spectra changes were observed. Inhibition of catalase by 3-amino-1,2,4-triazole (3-AT) or by sodium azide, followed by a bolus of H(2)O(2) led to a two- to five-fold increases in (13)CO(2) production compared with controls, depending on H(2)O(2) concentration. In contrast, 3-AT-inhibited HRBCs exposed to a flux of H(2)O(2) did not present an increase in (13)CO(2) production. The present paper emphasizes the importance and role of NADPH production following a bolus or a flux stimulation of H(2)O(2). The difference between responses in HMPS activities under the two types of stress could be related to a different balance of activity between 'catalatic' and 'peroxidatic' modes of catalase following H(2)O(2) exposure.

[Integral evaluation of redox metabolism in erythrocytes from patients with various anemias]

The potentiometric determination method (Vmax NADP.H) was made use of to make an integral evaluation of the status of the oxidant-restorative metabolism of erythrocytes; the method facilitates essentially the diagnostics in certain hemolytic processes like G-6-PD-insufficiency, toxic hemolytic anemia and auto-immune hemlytic anemia. Essential differences of the oxidant-restorative potential of erythrocytes (Vmax NADP.H) at congenital and acquired hemolytic anemias were detected, which can be used in the hematological practice alongside with other laboratory tests in the differentiated diagnostics of hemolytic anemias of unclear etiologies.

Pyridine nucleotide redox potential in erythrocytes of saudi subjects with sickle cell disease

Key antioxidant defense reactions in RBCs are linked to nicotinamide adenine dinucleotide (NAD(+)) and nicotinamide adenine dinucleotide phosphate (NADP(+)). The ratio of reduced (NAD(P)H) to total pyridine nucleotide pool [(NAD(P)(T) i.e. NAD(P)H plus NAD(P)(+)], which is known as redox potential, reflects the redox status of erythrocytes. Through the utilization of a spectrophotometric cycling assay, the NAD(+) and NADP(+) redox potentials were determined in erythrocytes from normal Saudi subjects and those with sickle cell disease (SCD). The sickle erythrocytes NADH/NAD(T) ratio (0.386) was reduced compared to the normal ratio (0.464). This reduction appears to be due to a significant increase in oxidized NAD(+) in sickle RBCs. However, the value of the redox potential of erythrocytes in Saudi subjects with SCD is slightly higher than that reported for comparable African Americans. Although the high fetal hemoglobin is the main factor in the amelioration of the clinical course exhibited by Saudi sickle cell patients, it is assumed that the slight improvement in the redox potential may play a part in this process. This is supported by a relatively uninhibited glycolytic pathway in the erythrocytes of Saudi subjects with SCD with a higher level of NADH than their African American counterparts.

Decreased redox state in red blood cells from patients with sarcoidosis

BACKGROUND AND AIM OF THE WORK

The glutathione system has a key role in the defence against oxidative stress. To function properly, this system needs NADPH to maintain glutathione (GSH) in its reduced form. We hypothesized that the clinical problems associated with sarcoidosis might be related to a decreased anti-oxidant defence and we therefore measured the activity of the NADPH-generating enzyme glucose-6-phosphate dehydrogenase (G6PD), the GSH-regenerating enzyme glutathione reductase (GR) and indirectly the level of NADPH in red blood cells from patients with sarcoidosis.

METHODS

In a population of sarcoidosis (n = 88) patients, G6PD, GR and GR activity after incubation with chromate (GR-Cr) were measured in erythrocytes. A decreased concentration of NADPH was revealed by an increased GR-Cr (> 0.6 IU/g Hb). To exclude a mutation in the G6PD gene, sequencing was performed in cases with an abnormal GR-Cr. Sarcoidosis pulmonary disease severity was evaluated by means of laboratory data, radiographic staging, HRCT scoring, pulmonary function and exercise capacity testing.

RESULTS

Fourteen (29.2%) females and one (2.5%) male demonstrated an increased GR-Cr test, indicative of a decreased NADPH level. Patients with an abnormal test result demonstrated also significantly increased ACE and GR values (p < 0.05). Only one female case (of 6 tested) appeared to have a mutation in the G6PD gene.

CONCLUSION

In a considerable percentage of female patients with sarcoidosis, a decreased level of NADPH in the erythrocytes was found.

Effects of fatty liver induced by niacin-free diet with orotic acid on the metabolism of tryptophan to niacin in rats

The effects of dietary orotic acid on the metabolism of tryptophan to niacin in weaning rats was investigated. The rats were fed with a niacin-free, 20% casein diet containing 0% (control diet) or 1% orotic acid diet (test diet) for 29 d. Retardation of growth, development of fatty liver, and enlargement of liver were observed in the test group in comparison with the control group. The concentrations of NAD and NADP in liver significantly decreased, while these in blood did not decrease compared to the control group. The formation of the upper metabolites of tryptophan to niacin such as anthranilic acid, kynurenic acid, and 3-hydroxyanthranilic acid were not affected, but the quinolinic acid and beyond, such as nicotinamide, N1-methylnicotinamide, N1-methyl-2-pyridone-5-carboxamide, and N1-methyl-4-pyridone-3-carboxamide, were significantly reduced by the administration of orotic acid. Therefore, the conversion ratio of tryptophan to niacin significantly decreased in the test group in comparison with the control group.

Efficacy of turmeric on blood sugar and polyol pathway in diabetic albino rats

In the traditional system of medicine, Ayurveda, several spices and herbs are thought to possess medicinal properties. Among the spices, turmeric rhizomes (Curcuma longa. Linn.) are used as flavoring and coloring agents in the Indian diet everyday. In this research, we studied the effect of turmeric and its active principle, curcumin, on diabetes mellitus in a rat model. Alloxan was used to induce diabetes. Administration of turmeric or curcumin to diabetic rats reduced the blood sugar, Hb and glycosylated hemoglobin levels significantly. Turmeric and curcumin supplementation also reduced the oxidative stress encountered by the diabetic rats. This was demonstrated by the lower levels of TBARS (thiobarbituric acid reactive substances), which may have been due to the decreased influx of glucose into the polyol pathway leading to an increased NADPH/NADP ratio and elevated activity of the potent antioxdiant enzyme GPx. Moreover, the activity of SDH (sorbitol dehydrogenase), which catalyzes the conversion of sorbitol to fructose, was lowered significantly on treatment with turmeric or curcumin. These results also appeared to reveal that curcumin was more effective in attenuating diabetes mellitus related changes than turmeric.

[A simple and reliable spectrophotometric method for quantification of pyridine nucleotides in serum]

Pyridine nucleotides plays an important role in the maintenance of cellular homeostasis and its disturbance also involves in many perturbance of metabolism, so a simple and reliable assay for determination of oxidized and reduced pyridine nucleotides in serum would be significantly necessary in understanding the redox status of body. A novel modified method, which is based on Nisselbam and making use of a cycling enzymatic reaction and spectrophotometric assay to measure the pyridine nucleotides in serum, showed good results. The standard curve has fine linear relationship; the recovery of added standard samples is almost perfect. Twenty-seven samples from 27 normal subjects were examined by the method. The results were: NADPH 8.385 +/- 1.516 nmol/ml, NADP+ 3.624 +/- 0.985 nmol/ml, and NADPH/NADP+ 2.3612 +/- 0.8057; no significant difference in the variables was found between the male and female. This is a sensitive, simple, reliable and easy-practicing method for oxidized and reduced pyridine nucleotides assay.

Effects of dietary pyrazinamide, an antituberculosis agent, on the metabolism of tryptophan to niacin and of tryptophan to serotonin in rats

The effects of pyrazinamide on the metabolism of tryptophan to niacin and of tryptophan to serotonin were investigated to elucidate the mechanism for pyrazinamide action against tuberculosis. Weanling rats were fed with a diet with or without 0.25% pyrazinamide for 61 days. Urine samples were periodically collected for measuring the tryptophan metabolites. The administration of pyrazinamide significantly increased the metabolites, 3-hydroxyanthranilic acid and beyond, especially quinolinic acid, nicotinamide, N'-methylnicotinamide, and N1-methyl-4-pyridone-3-carboxamide, and therefore significantly increased the conversion ratio of tryptophan to niacin and the blood NAD level . However, no difference in the upper metabolites of the tryptophan to niacin pathway such as anthranilic acid, kynurenic acid and xanthurenic acid was apparent between the two groups. No difference in the concentrations of trytptophan and serotonin in the blood were apparent either. It is suggested from these results that the action of pyrazinamide against tuberculosis is linked to the increase in turnover of NAD and to the increased content of NAD in the host cells.

Elevation of blood NAD level after moderate exercise in young women and mice

We previously reported that the blood NAD levels are decreased by severe exercise, and administration of nicotinamide, a precursor of NAD, improves the endurance capacity of mice. In the present study, we determined whether moderate exercise changes the blood NAD levels in humans and mice. College female students exercised moderately with bike-ergometers. The blood NAD levels elevated after moderate exercise. Mice were forced to swim in a running water pool for 5 min as a moderate exercise, 15 min as a strong exercise, and until exhaustion as a severe exercise (average swimming time was 28.7 min). A 5 min swim gave a result similar to that of moderate exercise by human subjects. However, the blood NAD levels decreased after all-out exercise. The changes in whole blood tryptophan (a precursor of pyridine nucleotides) levels were similar to that in NAD. The glucose levels in whole blood and the non-esterified fatty acid levels in serum decreased according to exercising time. These data are the first demonstration of moderate exercise raising the blood NAD levels in human and mice. Elevation of the blood NAD levels may reflect changes in niacin metabolism that occur in response to exercise.

Interferon-gamma and sinusoidal electric fields signal by modulating NAD(P)H oscillations in polarized neutrophils

Metabolic activity in eukaryotic cells is known to naturally oscillate. We have recently observed a 20-s period NAD(P)H oscillation in neutrophils and other polarized cells. Here we show that when polarized human neutrophils are exposed to interferon-gamma or to ultra-low-frequency electric fields with periods double that of the NAD(P)H oscillation, the amplitude of the NAD(P)H oscillations increases. Furthermore, increases in NAD(P)H amplitude, whether mediated by interferon-gamma or by an oscillating electric field, signals increased production of reactive oxygen metabolites. Hence, amplitude modulation of NAD(P)H oscillations suggests a novel signaling mechanism in polarized cells.

Reduction of hydroxamic acids to the corresponding amides catalyzed by rabbit blood

1. The hydroxamic acids N-hydroxyphenacetin and N-hydroxy-2-acetylaminofluorene were reduced to the corresponding amides, phenacetin and 2-acetylaminofluorene respectively by rabbit blood supplemented with both NAD(P)H and FAD. These reducing activities were found in erythrocytes but not in plasma, and were sensitive to inhibition by carbon monoxide and oxygen. When blood or erythrocytes were boiled, these activities were not abolished. 2. Haemoproteins such as haemoglobin and catalase exhibited the reductase activity in the presence of both NAD(P)H and FAD under anaerobic conditions. The activity was not abolished when the haemoproteins were boiled. 3. Haematin showed a significant reducing activity in the presence of these cofactors. The activity of haematin was also observed with the photochemically reduced form of FAD. 4. The reduction system in blood was composed of NAD(P)H, FAD and haemoglobin. Reduction appears to proceed in two steps, i.e. the reduction of FAD by NADH or NADPH, followed by the non-enzymatic reduction of the hydroxamic acids to the amides by reduced FAD, catalyzed by the haem group of haemoglobin in rabbit erythrocytes.

Crystallization and preliminary structural results of catalase from human erythrocytes

Catalase (hydrogen peroxide:hydrogen peroxide oxidoreductase, E.C. 1. 11.1.6) is present in most aerobic prokaryotic and eukaryotic cells. Despite a large number of studies on catalases, the only mammalian catalase structure available is that from beef liver, in which about 50% of the haem groups are degraded to bile pigments. Three different crystal forms of human erythrocyte catalase were obtained by the hanging-drop vapour-diffusion technique using PEG as precipitant. Monoclinic crystals, with space group P21 and unit-cell parameters a = 102.9, b = 140.0, c = 173.6 A and beta = 103.2 degrees, require NADP(H) in the crystallization solution. Two types of hexagonal packing, with unit-cell parameters of either a = b = 86. 9, c = 255.5 A or a = b = 90.0, c = 521.2 A, were obtained under identical crystallization conditions in the absence of NADP(H). Only one diffraction data set could be collected: this was obtained from the hexagonal crystals with the smaller c axis using synchrotron radiation, with resolution to 2.65 A. A molecular-replacement solution, determined using a modified beef-liver catalase model as a search structure, corresponds to space group P6422 and contains a single subunit in the asymmetric unit, with an estimated solvent volume of about 50%. The packing determined suggests how minor rearrangements might allow the transition between both hexagonal crystal forms and provides an explanation for the anisotropic character of the corresponding diffractions.

Polyol pathway activation and glutathione redox status in non-insulin-dependent diabetic patients

The current study aimed to evaluate whether nicotinamide adenine dinucleotide phosphate (NADPH) alteration in erythrocytes from patients with non-insulin-dependent diabetes mellitus (NIDDM) is responsible for the impaired glutathione (GSH) redox status, and to assess if short-term inhibition of the polyol pathway normalizes NADPH levels and GSH redox status via an amelioration of the NADPH/total NADP (tNADP) ratio. For this purpose, erythrocyte NADPH and GSH levels were measured in 18 NIDDM patients at baseline and then after 1 week of random double-blind assignment to treatment with either tolrestat (an aldose reductase inhibitor, 200 mg daily) (n = 12) or placebo (n = 6). A group of 16 healthy volunteers served as the control. In the basal condition, mean GSH (P < .0001) and NADPH (P < .0001) levels and NADPH/tNADP (P < .0001) and GSH/ glutathione disulfide (GSSG) (P < .005) ratios were lower in NIDDM patients than in control subjects. Tolrestat treatment increased GSH levels (P < .05 v placebo and baseline) and the NADPH/tNADP ratio (P < .05 v placebo and baseline). Interestingly, tolrestat-induced changes in GSH and NADPH levels and in GSH/GSSG and NADPH/tNADP ratios were significant only in patients who showed a decreased NADPH/tNADP ratio at baseline (n = 8). In these latter patients, we also found a direct correlation between percentage increments in GSH levels and NADPH/tNADP ratios after tolrestat treatment (r = .71, P < .05). In conclusion, our findings support the hypothesis that polyol pathway activation decreases NADPH and GSH levels. Accordingly, short-term inhibition of this enzymatic route increased both the GSH level and the NADPH/tNADP ratio. These changes were observable only in the subgroup of patients with an abnormal NADPH/tNADP ratio at baseline. Polyol pathway inhibition could be useful for decreasing oxidative stress in NIDDM.

Elevated expression of p47phox and p67phox proteins in neutrophils from burned rats

The molecular control of neutrophil respiratory burst in burn injury was investigated through quantitation of protein factors, p47phox and p67phox, which are required for the activation of the phagocyte plasma membrane NADPH-oxidase. Circulating neutrophils were isolated from rats with 30% body surface area covered with full thickness burns. Neutrophil O2- generation, and p47phox and p67phox expressions, respectively, were determined using spectrophotometric and immunoblot techniques. Formylmethionyl-leucyl-phenylalanine stimulated superoxide anion generation was approximately 50% higher in neutrophils from rats 24 and 72 h after burns compared with that in sham control rats. The level of superoxide production was .47 +/- .05 nanomoles per minute per 10(6) cells (mean +/- SE, n = 6) at 24 h and .45 +/- .05 (n = 6) at 72 h postburn, whereas in sham control animals it was .32 +/- .02 (n = 8). Compared with the sham group p47phox levels, p47phox expression was 5.7-fold, 4.4-fold, and 4.5-fold higher, respectively, at 24, 36 and 72 h postburn. The levels of p67phox in burned animals were 2-fold higher than in the sham group, (p < .05) at 24 h postburn, and approximately 50% higher than sham at 36 h after the burn. The p67phox levels in rats 72 h after the burn were not significantly different from the sham values. These data support the occurrence of an up-regulation of p47phox and p67phox expressions accompanying the enhanced neutrophil respiratory burst activity during the early stages of burn injury. The up-regulation of p47phox and p67phox could be responsible for the priming of neutrophil O2- production leading to host tissue injury.

[The role of NADPH in the development of neonatal jaundice with G6PD deficiency]

OBJECTIVE

To investigate the role of NADPH in the development of neonatal jaundice with G6PD deficiency.

METHODS

The enzyme activities of G6PD, catalse (Cat) and glutathione peroxidase (GSH-px) were measured by quantitative determination of enzyme activity. The level of MDA was analyzed with alpha-thiobarbituric acid and the level of NADPH was determined with modified Nisselbaum JS's. Comparisons of these markers between G6PD normal and deficient erythrocytes were made before and during the incubation of the erythrocytes with H2O2.

RESULTS

The level of MDA, which was 36 +/- 8n-mol.L-1.gHb-1, was increased and that of NADPH, which was 1792 +/- 106mumol.L-1.gHb-1, was decreased in jaundiced neonates with G6PD deficiency compared with those with normal G6PD activity. When the cells were incubated with H2O2, the level of NADPH and the activities of Cat and GSHpx in erythrocytes with normal G6PD activity increased at first, and then turned to decrease as the incubation lasted longer than 30 minutes. But in G6PD-deficient erythrocytes all these markers decreased continuously as the cells were incubated with H2O2.

CONCLUSIONS

The diminished capability of generation of NADPH in G6PD-deficient erythrocytes may contribute directly to the more extensive peroxidation of the cells. The defect capacity of generation of NADPH, which resulted in the weakened capability of antiperoxidation and finally the lysis of erythrocytes, was one of the important mechanisms in the development of jaundice in G6PD-deficient neonates.

Active involvement of catalase during hemolytic crises of favism

The endemic occurrence of favism in certain Mediterranean regions provided an investigative opportunity for testing in vivo the validity of claims as to the role of catalase in protecting human erythrocytes against peroxidative injury. Reduced activity of catalase was found in the erythrocytes of six boys who were deficient in erythrocytic glucose-6-phosphate dehydrogenase (G6PD) and who were studied while suffering hemolysis after ingesting fava beans. Activity of catalase was further reduced when their red blood cells were incubated with aminotriazole. In contrast, minimal reduction of catalase activity was found, both with and without incubation with aminotriazole, in erythrocytes of a G6PD-deficient boy who had ingested fava beans 7 days earlier and in erythrocytes of seven G6PD-deficient men with a past history of favism. These results confirmed earlier studies in vitro indicating that catalase is a major disposer of hydrogen peroxide in human erythrocytes and, like the glutathione peroxidase/reductase pathway, is dependent on the availability of reduced nicotinamide adenine dinucleotide phosphate (NADPH). The effect of divicine on purified catalase and on the catalase of intact G6PD-deficient erythrocytes was similar to the previously demonstrated effect on catalase of a known system for generating hydrogen peroxide. This effect of divicine strengthens earlier arguments that divicine is the toxic peroxidative component of fava beans.

Redox state, antioxidative activity and lipid peroxidation in erythrocytes and plasma of chronic ambulatory peritoneal dialysis patients

Red blood cells and plasma reduced and oxidized glutathione levels, glutathione peroxidase (GSH-Px) activity, thiobarbituric acid reactants (TBAR) of both chronic ambulatory peritoneal dialysis (CAPD) patients and a matched control group were investigated in this study. Oxidized and reduced pyridinic nucleotides in red blood cells (RBC), in which NADPH is a direct expression of hexose monophosphate shunt function, were also studied. The results obtained indicate that RBC and plasma are exposed to oxidative stress in CAPD. This condition is characterized by a decreased GSH/GSSG ratio, particularly evident in RBC as a consequence of the GSSG accumulation. Lipid peroxidation is increased, as indicated by raised TBAR levels, and reduced pyridinic nucleotides are decreased. Increased GSH-Px levels and unmodified or slightly increased GSH content were observed in the RBC but not in plasma, which showed decreased GSH and unmodified peroxidase activity. Peroxidase correlated positively with TBAR levels in the RBC lysates. In a subgroup of patients treated with erythropoietin (vs. untreated patients and controls) no differences were observed in the glutathione-related parameters studied. These data suggest that a mechanism for adaptation to oxidative conditions may be present in CAPD and its effects on RBC integrity are discussed in comparison with the hemodialysis conditions previously studied.

Single extraction method for the spectrophotometric quantification of oxidized and reduced pyridine nucleotides in erythrocytes

A simplified and reliable assay for the determination of erythrocyte pyridine nucleotide (NAD and NADP) concentrations, as well as the ratio of the reduced [NADH/NADPH] to oxidized [NAD+/NADP+] nucleotide, is important in understanding both normal and abnormal red blood cells (RBC). However, previously published methods for quantitating pyridine nucleotides are inappropriate for RBC, difficult to use, or inaccurate. The method described within this paper provides for both improved reliability and ease of use. In addition, we have documented that significant pools of NADPH and NADH are tightly bound to proteins (e.g., catalase) and not detectable by many of the assay systems previously used. This results in a significant change in not only total RBC pyridine nucleotide content but also in the ratio of reduced to nonreduced nucleotide.

Carbonyl reductase activity for acetohexamide in human erythrocytes

Acetohexamide is an oral antidiabetic agent and is metabolized by the reductive conversion of the acetoxy group to a secondary alcohol metabolite. In vivo, many drugs are metabolized by reductase enzymes; however, the characteristics of the enzymes that reduce carbonyl compounds need to be clarified. We tested whether reductase activity for acetohexamide can be found in human erythrocytes. Enzyme activity was monitored by formation of hydroxyhexamide using HPLC methods. In human erythrocytes, reductase activity (6.10 +/- 1.20 nmol/min/g hemoglobin) (mean +/- SD) was indeed observed, when 0.5 mM acetohexamide was used as a substrate. KM values and Vmax at the physiologically important pH 7.4 were 0.70 +/- 0.13 mM and 9.19 +/- 0.88 nmol/min/g hemoglobin, respectively. Separation of protein by gel filtration gave one major peak fraction with reductase activity whose molecular weight was estimated to be 31,000. Known substrates of carbonyl reductase such as menadione, daunorubicin, and ethacrynic acid inhibited the acetohexamide reduction. The acetohexamide reductase in erythrocyte showed characteristics of carbonyl reductase. Furthermore, acetohexamide reductase activity in erythrocyte was approximately 30% activity of that of human liver (0.17 +/- 0.05 nmol/min/mg cytosolic protein). The pattern of inhibitors in human liver was essentially the same as that in erythrocytes. It is plausible that the activity in erythrocytes may predict the activity in the liver. It was concluded that carbonyl reductase in human erythrocyte plays an important role in acetohexamide metabolism.

Activation of respiratory burst oxidase is accompanied by desensitization of p47phox in nucleoside-triphosphate binding along with its translocation to cell membrane

A cytosolic component of human neutrophils, p47phox, potentiates respiratory burst oxidase translocating from cytosol to membrane upon cell stimulation. In this study, the nucleotide-binding ability of p47phox was examined using [32P]GTP dialdehyde (oGTP), [32P]oATP, and [32P]oNADPH. p47phox showed affinities for both oGTP and oATP that were 14 times higher than that for oNADPH, suggesting that it is a nucleoside triphosphate (NTP)-binding protein rather than an NADPH-binding protein. Binding analysis of p47phox using either [32P]oGTP or [32P]oATP revealed an apparent binding constant for each individual NTP analogue and the same maximum binding value, which suggests that both NTPs share a common specific binding site. Stimulation of neutrophils with phorbol myristate acetate (PMA) resulted in enhancement of the oxidase activity to generate O2- anion and was accompanied by substantial translocation of p47phox to membrane. However, p47phox derived from the stimulated cell membrane had lost its NTP-binding ability, unlike that from the resting cytosol. These results suggest that the binding of NTP to p47phox may be involved in the process that activates the oxidase and is desensitized in translocated p47phox.

Erythrocyte redox state in uremic anemia: effects of hemodialysis and relevance of glutathione metabolism

Reduced and oxidized glutathione and pyridine coenzymes, glutathione-related enzymes and Cu,Zn-superoxide dismutase (Cu,Zn-SOD) were investigated in the RBC of patients with chronic renal failure (CRF) and in age- and sex-matched controls. The effects of hemodialysis (HD) were also studied. A defective RBC redox state was shown in the CRF group based on a decreased GSH/GSSG ratio and NADPH levels. Increased activities of glutathione transferase (GSH-S-T) and Cu,Zn-SOD were observed before HD. Dialysis apparently restores the levels of antioxidant enzymes and at the same time strongly affects the redox state. Thus we can speculate that HD can generate severe redox impairment inducing damage in RBC and plasma antioxidant enzymes. Increased erythrocyte GSSG and GSM-S-T levels coupled with a reduced hexose monophosphate shunt (HMPS) function may be useful indexes of oxidative stress in uremic anemia.

Variations of adenine nucleotide levels in normal and pathologic human erythrocytes exposed to oxidative stress

Normal human erythrocytes suspended in isotonic saline at 0.5 haematocrit displayed, after 30 min exposure to 1 mM tert-butylhydroperoxide at 37 degrees C, a marked increase of NADPH, while the concentration of the other adenine nucleotides was almost unchanged. Hereditary Spherocytosis and glucose-6-phosphate dehydrogenase-deficient red blood cells exhibited, under basal conditions, higher levels of most of the nucleotides assayed and significant amounts of hypoxanthine. Treatment with tert-butylhydroperoxide caused, in glucose-6-phosphate dehydrogenase-deficient erythrocytes, a pronounced decrease of ADP and of AMP levels, a substantial invariance of other adenine nucleotides and a considerable raise of hypoxanthine. On the contrary, Hereditary Spherocytosis erythrocytes exhibited, after oxidative stress, increased levels of ADP and of AMP, a slight decrease of ATP and an accumulation of hypoxanthine similar to that found in enzyme-deficient red cells. In both the pathologic erythrocytes the addition of phosphate during the oxidative treatment resulted in a lower formation of hypoxanthine, while the presence of 10 mM glucose, fully prevented its appearance.

HPLC determination of oxidized and reduced pyridine coenzymes in human erythrocytes

The nucleotide concentrations in acid and alkaline erythrocyte extracts have been measured by RP-HPLC in healthy controls and in patients bearing different inherited disorders, with altered erythrocyte NAD(P) levels. The objective was the simultaneous determination of the nucleotide profile and of the oxidative state of pyridine coenzymes by the most suitable extraction method. Both alkaline and acid extractions were necessary to obtain the complete pattern, due to defective recovery of the oxidized or reduced coenzymes, respectively, during the extraction procedures. Purine nucleotide quantification seemed to be reliable by all methods. High NADP+ levels were confirmed in two glucose-6-phosphate dehydrogenase deficient patients, coupled with raised NAD levels, lowered NADPH/NADP+ ratio and increased NADH/NAD+ ratio. Higher NAD+ and normal or lower NADH/NAD+ ratios were found in two hypoxanthine-phosphoribosyltransferase deficient patients, while a patient with superactive phosphoribosylpyrophosphate synthetase showed a decreased NADH level in addition to the low NAD+ level previously found.

Niacin deficiency and cancer in women

A new interest in the relationship between niacin and cancer has evolved from the discovery that the principal form of this vitamin, NAD, is consumed as a substrate in ADP-ribose transfer reactions. Poly(ADP-ribose) polymerase, an enzyme activated by DNA strand breaks, is the ADP-ribosyltransferase of greatest interest with regard to effects on the niacin status of cells since its Km for NAD is high, and its activity can deplete NAD. Studies of the consequences of DNA damage in cultured mouse and human cells as a function of niacin status have supported the hypothesis that niacin may be a protective factor that limits carcinogenic events. To test this hypothesis in humans, we used a biochemical method based on the observation that as niacin nutriture decreases, NAD readily declines and NADP remains relatively constant. This has been demonstrated in both fibroblasts and in whole blood from humans. Thus, we use "niacin number," (NAD/NAD+NADP) x 100% from whole blood, as a measure of niacin status. Healthy control subjects showed a mean niacin number of 62.8 +/- 3.0 compared to 64.0 for individuals on a niacin-controlled diet. Analyses of women in the Malmö Diet and Cancer Study showed a mean niacin number of 60.4 with a range of 44 to 75. The distribution of niacin status in this population was nongaussian, with an unpredictably large number of individuals having low values.

[Respiratory reactivity and parameters of nonspecific immunity in workers of the Chernobyl nuclear power plant during adaptation to mountain climate]

The quantitative composition of the peripheral blood, enzymatic activity of neutrophils and hypoxic ventilatory drive were determined in people working at the Chernobyl NPP during sojourn for 28 days in the Caucasus mountains at 220 m altitude with a periodical climbing up to 4200 m. At the initial state we found neutropenia, lymphocytosis, an increase in the number of prolymphocytes and big hairy lymphocytes, a decrease in the number of small lymphocytes, fall in activity of enzymes responsible for oxygen-dependent and oxygen-independent mechanisms of bactericidity. The indices of sensitivity to the hypoxic respiration stimulus did not essentially differ from the norm. Staying at altitude promoted normalization of the number of segmento-nuclear neutrophils, lymphocytes (their small population, in particular), an increase in the number of eosinophiles of the peripheral blood. Changes in the activity of myeloperoxidase, NADP-oxidase and cationic proteins in the neutrophils were observed. A considerable increase of the ventilatory drive to the hypoxic respiration stimulus was determined. Accentuation of fermentative transformations proved to be closely related to the ventilatory response to hypoxia: weak activation of NADP-oxidase and a decrease of myeloperoxidase activity were observed in people with initially low respiration reactivity, while a considerable increase in activity of these enzymes and in content of cationic proteins was observed in people with high respiration reactivity. Individual peculiarities of the reaction to staying at altitude should be taken into account when developing particular methods of immune correction.