Role of the membrane in the formation of heme degradation products in red blood cells

Membrane-Bound Ferric Hemoglobin in Nucleated Erythrocytes of the Black Scorpionfish Scorpaena porcus, Linnaeus 1758

The content of membrane-bound methemoglobin (MtHb) in nucleated erythrocytes was studied in the black scorpionfish Scorpaena porcus (Linnaeus, 1758) in vitro. Spectral characteristics were determined for a whole hemolysate, a hemolysate obtained by stroma precipitation (a clarified hemolysate), and a resuspended stroma. The MtHb proportion in the erythrocyte stroma was found to exceed 80% (6.20 ± 0.59 µM). Clarified hemolysates were nearly free of MtHb (0.5 ± 0.2 µM). Membrane-bound ferric hemoglobin did not affect the erythrocyte resistance to osmotic shock. The osmotic fragility range was determined using a LaSca-TM laser microparticle analyzer (BioMedSystems, Russia) to be 102-136 mOsm/kg, much the same as in other bony fish species. A nitrite load (10 mg/L) significantly increased the MtHb content in the blood. However, the membrane-bound ferric hemoglobin content did not change significantly, amounting to 6.34 ± 1.09 µM (approximately 95%). The finding suggested a functional importance for MtHb present in the plasma membrane of nucleated erythrocytes. Membrane-bound MtHb was assumed to neutralize the external oxidative load and the toxic effect of hydrogen sulfide in bottom water layers, where the species lives.

Co-administration of angiotensin II and simvastatin triggers kidney injury upon heme oxygenase-1 deficiency

Kidneys are pivotal organ in iron redistribution and can be severely damaged in the course of hemolysis. In our previous studies, we observed that induction of hypertension with angiotensin II (Ang II) combined with simvastatin administration results in a high mortality rate or the appearance of signs of kidney failure in heme oxygenase-1 knockout (HO-1 KO) mice. Here, we aimed to address the mechanisms underlying this effect, focusing on heme and iron metabolism. We show that HO-1 deficiency leads to iron accumulation in the renal cortex. Higher mortality of Ang II and simvastatin-treated HO-1 KO mice coincides with increased iron accumulation and the upregulation of mucin-1 in the proximal convoluted tubules. In vitro studies showed that mucin-1 hampers heme- and iron-related oxidative stress through the sialic acid residues. In parallel, knock-down of HO-1 induces the glutathione pathway in an NRF2-depedent manner, which likely protects against heme-induced toxicity. To sum up, we showed that heme degradation during heme overload is not solely dependent on HO-1 enzymatic activity, but can be modulated by the glutathione pathway. We also identified mucin-1 as a novel redox regulator. The results suggest that hypertensive patients with less active HMOX1 alleles may be at higher risk of kidney injury after statin treatment.

Synthesis of new coumarin[1,3]oxazine derivatives of 7-hydroxy-6-isobornyl-4-methylcoumarin and their antioxidant activity

In this work, we synthesized a series of new 9,10-dihydro-2H,8H-chromeno[8,7e][1,3]oxazine-2-on derivatives which incorporate isobornylcoumarin and 1,3-oxazine moieties. A structure-antioxidant activity relationship was analyzed. A comparative evaluation of their radical scavenging activity, antioxidant and membrane-protective properties was carried out in test with DPPH, as well as on the models of Fe²⁺ /ascorbate-initiated lipid peroxidation and oxidative hemolysis of mammalian red blood cells. The results suggest that all the obtained coumarin[1,3]oxazine derivatives of 7-hydroxy-6-isobornyl-4-methylcoumarin are capable of exhibiting antioxidant activity in various model systems. Compound 7 with a phenyl fragment, combining high radical scavenging activity and the ability to inhibit Fe²⁺ /ascorbate-initiated peroxidation of animal lipids in a heterogeneous environment, also proved to be the most effective membrane protector and antioxidant in the model of H₂ O₂ -induced erythrocyte hemolysis.

Honeysuckle extract (Lonicera pallasii L.) exerts antioxidant properties and extends the lifespan and healthspan of Drosophila melanogaster

Honeysuckle Lonicera pallasii (Lonicera caerulea L.) is an excellent source of anthocyanins which have a number of health-promoting properties mainly associated with antioxidant and anti-inflammatory activities. Cyanidin-3-O-glucoside (C3G) is one of the most common anthocyanins naturally found in honeysuckle. The goal of the present study was to investigate antioxidant and anti-aging properties of Lonicera pallasii (Lonicera caerulea L.) extract (LE) and C3G using red blood cells (RBC) and Drosophila melanogaster models. LE and C3G treatment at a concentration of 100 μM induced enhancement of median and maximum lifespan up to 8%. LE and C3G supplementation at a concentration of 100 μM increased stress resistance up to 10%. The locomotor activity decreased during LE and C3G treatment in 4 and 6 weeks up to 52% in females. The integrity of the intestinal barrier was increased by 4% after LE treatment. These effects were accompanied by increased expression of Hif1 (pro-longevity gene) in response to C3G treatment and decreased expression of Keap1 (anti-longevity gene) after C3G and LE supplementation. RNA interference-mediated knockdown of Sirt6 completely abolished the positive effect obtained of LE and C3G supplementation in males which indicates that lifespan-extending effect is associated with Sirt6 activation. The experiments on the various in-vitro models (including radical scavenging activity and oxidative hemolysis of RBC demonstrated antioxidant and membrane-protective activities of LE and C3G. The present study indicates that Lonicera extract can prolong the lifespan and improve the healthspan of Drosophila model through biological and antioxidant activities.

Factors influencing the antioxidant effect of phospholipase A2 against lipid oxidation promoted by trout hemoglobin and hemin in washed muscle

The antioxidant effect of porcine pancreatic phospholipase A2 (PLA2) was previously demonstrated. Understanding how PLA2 inhibits lipid oxidation promoted by hemoglobin (Hb) is important for its applications in muscle foods. Effects of enzyme dose, pH, and calcium ion on the ability of PLA2 to inhibit trout hemoglobin-mediated lipid oxidation were investigated in washed cod muscle (WCM). Results indicated that PLA2 required calcium ion for both the hydrolyzing activity and the antioxidant effect. The abilities of PLA2 to inhibit lipid oxidation and suppress oxidation of Hb to form methemoglobin and ferryl hemoglobin were pH-dependent. The lag phase before lipid oxidation enters the exponential phase reciprocally shortened as more hemin was bound to the insoluble matrix of WCM. However, PLA2 was able to inhibit lipid oxidation without preventing the interaction between hemin and the insoluble matrix of the washed muscle.

Fluorescent Heme Degradation Products Are Biomarkers of Oxidative Stress and Linked to Impaired Membrane Integrity in Avian Red Blood Cells

Oxidative stress is generally understood to be an important mediator of life-history traits, yet the specific relationships between oxidative stress and life-history traits have been difficult to describe because there is often a lack of covariation among biomarkers of oxidative stress. For instance, although oxidative damage to red blood cell (RBC) membranes can lead to pathological conditions (i.e., anemia), in some cases there is not a clear relationship between lipid oxidation and RBC membrane resistance to pro-oxidants. Alternatively, oxidative damage to hemoglobin may be an indirect mechanism contributing to RBC membrane damage. To better understand the mechanisms contributing to oxidative damage and probe new approaches to measuring oxidative stress, we used a series of in vitro and in vivo procedures in zebra finches (Taeniopygia guttata) to explore (1) whether avian RBCs exposed to a pro-oxidant generate fluorescent heme degradation products (HDPs), (2) whether HDPs interact with RBC membranes, and (3) whether HDPs are linked to impaired RBC integrity. We found that finch RBCs exposed in vitro to hydrogen peroxide produced fluorescent HDPs and HDPs associated with RBC membranes. Exposure to hydrogen peroxide also caused a reduction in hemoglobin and an increase in percent methemoglobin (a hemoglobin oxidation product), further indicating hemoglobin degradation. Moreover, HDP fluorescence correlated with impaired membrane integrity and erythrocyte osmotic fragility in vivo. This study suggests that reactive oxygen species may indirectly impair RBC membrane integrity via hemoglobin degradation products that associate with RBC membranes and that HDPs may be an inexpensive and logistically simple tool for measuring oxidative stress.

Red Blood Cells and Hemoglobin in Human Atherosclerosis and Related Arterial Diseases

As the main particulate component of the circulating blood, RBCs play major roles in physiological hemodynamics and impact all arterial wall pathologies. RBCs are the main determinant of blood viscosity, defining the frictional forces exerted by the blood on the arterial wall. This function is used in phylogeny and ontogeny of the cardiovascular (CV) system, allowing the acquisition of vasomotricity adapted to local metabolic demands, and systemic arterial pressure after birth. In pathology, RBCs collide with the arterial wall, inducing both local retention of their membranous lipids and local hemolysis, releasing heme-Fe⁺⁺ with a high toxicity for arterial cells: endothelial and smooth muscle cells (SMCs) cardiomyocytes, neurons, etc. Specifically, overloading of cells by Fe⁺⁺ promotes cell death. This local hemolysis is an event associated with early and advanced stages of human atherosclerosis. Similarly, the permanent renewal of mural RBC clotting is the major support of oxidation in abdominal aortic aneurysm. In parallel, calcifications promote intramural hemorrhages, and hemorrhages promote an osteoblastic phenotypic shift of arterial wall cells. Different plasma or tissue systems are able, at least in part, to limit this injury by acting at the different levels of this system.

Thiram-induced cytotoxicity and oxidative stress in human erythrocytes: an in vitro study

Tetramethylthiuram disulfide, commonly known as thiram, is an organosulfur compound which is used as a bactericide, fungicide and ectoparasiticide to prevent disease in seeds and crops. Being a fungicide there is a high probability of human occupational exposure to thiram and also via consumption of contaminated food. In this work, the cytotoxicity of thiram was studied under in vitro conditions using human erythrocytes as the cellular model. Erythrocytes were incubated with different concentrations of thiram (25-500 μM) for 4 h at 37 °C. Control cells (thiram untreated) were similarly incubated at 37 °C. Whole cells and hemolysates were analyzed for various biochemical parameters. Treatment of erythrocytes with thiram increased protein and lipid oxidation and hydrogen peroxide level in hemolysates but decreased glutathione and total sulfhydryl group content. This was accompanied by hemoglobin oxidation, heme degradation and release of free iron. Activities of all major antioxidant enzymes were inhibited. The antioxidant power of thiram treated erythrocytes was lowered resulting in decreased metal reducing and free radical quenching ability. These results suggest that thiram enhances the generation of reactive species that cause oxidative modification of cell components. This was confirmed by experiments that showed enhanced generation of reactive oxygen and nitrogen species in thiram treated erythrocytes. Activities of marker enzymes of glucose metabolism and erythrocyte membrane were also inhibited. All effects were seen in a thiram concentration-dependent manner. Electron microscopy further supported the damaging effect of thiram on erythrocytes. Thus thiram induces oxidative stress condition in human erythrocytes and causes oxidative modification of cell components.

Hemoglobin-derived peptides and mood regulation

Evidence accumulated over the past decades has revealed that red blood cells and hemoglobin (Hb) in the blood play important roles in modulating moods and emotions. The number of red blood cells affects the mood. Hb is the principal content in the red blood cells besides water. Denatured Hb is hydrolyzed to produce bioactive peptides. RVD-hemopressin α (RVD-Hpα), which is a fragment of α-chain (95-103) in Hb, functions as a negative allosteric modulator of cannabinoid receptor 1 and a positive allosteric modulator of cannabinoid receptor 2. Hemorphins, which are fragments of β-chain in Hb, exert their effects on opioid receptors. Two hemorphins, namely, LVV-hemorphin-6 and LVV-hemorphin-7, could induce anxiolytic-like effects. The use of Hb-derived bioactive peptides for the treatment of mood disorders is desirable due to cannabinoid-opioid cross modulation and the critical roles of the two systems in physiological processes, such as memory, mood and emotion.

On the Effects of Reactive Oxygen Species and Nitric Oxide on Red Blood Cell Deformability

The main function of red blood cells (RBCs) is the transport of respiratory gases along the vascular tree. To fulfill their task, RBCs are able to elastically deform in response to mechanical forces and, pass through the narrow vessels of the microcirculation. Decreased RBC deformability was observed in pathological conditions linked to increased oxidative stress or decreased nitric oxide (NO) bioavailability, like hypertension. Treatments with oxidants and with NO were shown to affect RBC deformability ex vivo, but the mechanisms underpinning these effects are unknown. In this study we investigate whether changes in intracellular redox status/oxidative stress or nitrosation reactions induced by reactive oxygen species (ROS) or NO may affect RBC deformability. In a case-control study comparing RBCs from healthy and hypertensive participants, we found that RBC deformability was decreased, and levels of ROS were increased in RBCs from hypertensive patients as compared to RBCs from aged-matched healthy controls, while NO levels in RBCs were not significantly different. To study the effects of oxidants on RBC redox state and deformability, RBCs from healthy volunteers were treated with increasing concentrations of tert-butylhydroperoxide (t-BuOOH). We found that high concentrations of t-BuOOH (≥ 1 mM) significantly decreased the GSH/GSSG ratio in RBCs, decreased RBC deformability and increased blood bulk viscosity. Moreover, RBCs from Nrf2 knockout (KO) mice, a strain genetically deficient in a number of antioxidant/reducing enzymes, were more susceptible to t-BuOOH-induced impairment in RBC deformability as compared to wild type (WT) mice. To study the role of NO in RBC deformability we treated RBC suspensions from human volunteers with NO donors and nitrosothiols and analyzed deformability of RBCs from mice lacking the endothelial NO synthase (eNOS). We found that NO donors induced S-nitrosation of the cytoskeletal protein spectrin, but did not affect human RBC deformability or blood bulk viscosity; moreover, under unstressed conditions RBCs from eNOS KO mice showed fully preserved RBC deformability as compared to WT mice. Pre-treatment of human RBCs with nitrosothiols rescued t-BuOOH-mediated loss of RBC deformability. Taken together, these findings suggest that NO does not affect RBC deformability per se, but preserves RBC deformability in conditions of oxidative stress.

Understanding quasi-apoptosis of the most numerous enucleated components of blood needs detailed molecular autopsy

Erythrocytes are the most numerous cells in human body and their function of oxygen transport is pivotal to human physiology. However, being enucleated, they are often referred to as a sac of molecules and their cellularity is challenged. Interestingly, their programmed death stands a testimony to their cell-hood. They are capable of self-execution after a defined life span by both cell-specific mechanism and that resembling the cytoplasmic events in apoptosis of nucleated cells. Since the execution process lacks the nuclear and mitochondrial events in apoptosis, it has been referred to as quasi-apoptosis or eryptosis. Several studies on molecular mechanisms underlying death of erythrocytes have been reported. The data has generated a non-cohesive sketch of the process. The lacunae in the present knowledge need to be filled to gain deeper insight into the mechanism of physiological ageing and death of erythrocytes, as well as the effect of age of organism on RBCs survival. This would entail how the most numerous cells in the human body die and enable a better understanding of signaling mechanisms of their senescence and premature eryptosis observed in individuals of advanced age.

Using Raman spectroscopy to assess hemoglobin oxygenation in red blood cell concentrate: an objective proxy for morphological index to gauge the quality of stored blood?

A relationship has been found between hemoglobin oxygenation of stored red blood cells (measured using Raman spectroscopy) and a morphological index.

The Effect of Polymeric Nanoparticles on Biocompatibility of Carrier Red Blood Cells

Red blood cells (RBCs) can be used for vascular delivery of encapsulated or surface-bound drugs and carriers. Coupling to RBC prolongs circulation of nanoparticles (NP, 200 nm spheres, a conventional model of polymeric drug delivery carrier) enabling their transfer to the pulmonary vasculature without provoking overt RBC elimination. However, little is known about more subtle and potentially harmful effects of drugs and drug carriers on RBCs. Here we devised high-throughput in vitro assays to determine the sensitivity of loaded RBCs to osmotic stress and other damaging insults that they may encounter in vivo (e.g. mechanical, oxidative and complement insults). Sensitivity of these tests is inversely proportional to RBC concentration in suspension and our results suggest that mouse RBCs are more sensitive to damaging factors than human RBCs. Loading RBCs by NP at 1:50 ratio did not affect RBCs, while 10–50 fold higher NP load accentuated RBC damage by mechanical, osmotic and oxidative stress. This extensive loading of RBC by NP also leads to RBCs agglutination in buffer; however, addition of albumin diminished this effect. These results provide a template for analyses of the effects of diverse cargoes loaded on carrier RBCs and indicate that: i) RBCs can tolerate carriage of NP at doses providing loading of millions of nanoparticles per microliter of blood; ii) tests using protein-free buffers and mouse RBCs may overestimate adversity that may be encountered in humans.

Oxidative stress and rheologic properties of stored red blood cells before and after transfusion to surgical patients

BACKGROUND

The loss of structural and functional integrity of red blood cells (RBCs) during storage, collectively referred to as "storage lesion," has been implicated in reduced oxygen delivery after transfusion. RBCs are highly susceptible to oxidative damage from generation of reactive oxygen species by autoxidation of hemoglobin. Therefore, we examined whether increased oxidative stress (OS) in stored RBCs is associated with impaired cell membrane deformability before or after transfusion.

STUDY DESIGN AND METHODS

Thirty-four patients undergoing multilevel spine fusion surgery were enrolled. OS in RBCs was assessed by the presence of fluorescent heme degradation products and methemoglobin, which were measured with fluorimetric and spectrophotometric methods, respectively. Deformability and aggregation were determined by ektacytometry in stored RBCs, autologous salvaged RBCs, and posttransfusion blood samples.

RESULTS

OS in stored RBCs was significantly increased with longer storage (R = 0.54, p = 0.032) and significantly higher than that in fresh RBCs (9.1 ± 1.3 fluorescent arbitrary units vs. 7.7 ± 0.9 fluorescent arbitrary units, p < 0.001). Deformability decreased (R = -0.60, p = 0.009) with increasing storage duration. OS was elevated (p < 0.05) and deformability was decreased (p < 0.05) in postoperative blood from patients who had undergone moderate (≥4 RBC units) but not minimal or no transfusion. Neither the decrease in deformability of RBCs nor the aggregation changes were correlated with OS.

CONCLUSIONS

Although stored RBCs show signs of increased OS and loss of cell membrane deformability, these changes were not directly correlated and were only evident after moderate but not lower dose transfusion in postoperative surgical patients. These findings suggest that factors other than OS may contribute to impaired rheology with stored RBCs in the clinical setting.

Serum pantetheinase/vanin levels regulate erythrocyte homeostasis and severity of malaria

Tissue pantetheinase, encoded by the VNN1 gene, regulates response to stress, and previous studies have shown that VNN genes contribute to the susceptibility to malaria. Herein, we evaluated the role of pantetheinase on erythrocyte homeostasis and on the development of malaria in patients and in a new mouse model of pantetheinase insufficiency. Patients with cerebral malaria have significantly reduced levels of serum pantetheinase activity (PA). In mouse, we show that a reduction in serum PA predisposes to severe malaria, including cerebral malaria and severe anemia. Therefore, scoring pantetheinase in serum may serve as a severity marker in malaria infection. This disease triggers an acute stress in erythrocytes, which enhances cytoadherence and hemolysis. We speculated that serum pantetheinase might contribute to erythrocyte resistance to stress under homeostatic conditions. We show that mutant mice with a reduced serum PA are anemic and prone to phenylhydrazine-induced anemia. A cytofluorometric and spectroscopic analysis documented an increased frequency of erythrocytes with an autofluorescent aging phenotype. This is associated with an enhanced oxidative stress and shear stress-induced hemolysis. Red blood cell transfer and bone marrow chimera experiments show that the aging phenotype is not cell intrinsic but conferred by the environment, leading to a shortening of red blood cell half-life. Therefore, serum pantetheinase level regulates erythrocyte life span and modulates the risk of developing complicated malaria.

Peroxiredoxin 2, glutathione peroxidase, and catalase in the cytosol and membrane of erythrocytes under H2O2-induced oxidative stress

Erythrocytes are continuously exposed to risk of oxidative injury due to oxidant oxygen species. To prevent damage, they have antioxidant agents namely, catalase (Cat), glutathione peroxidase (GPx), and peroxiredoxin 2 (Prx2). Our aim was to contribute to a better understanding of the interplay between Prx2, Cat, and GPx under H2O2-induced oxidative stress, by studying their changes in the red blood cell cytosol and membrane, in different conditions. These three enzymes were quantified by immunoblotting. Malondialdehyde, that is, lipoperoxidation (LPO) in the erythrocyte membrane, and membrane-bound hemoglobin (MBH) were evaluated, as markers of oxidative stress. We also studied the erythrocyte membrane protein profile, to estimate how oxidative stress affects the membrane protein structure. We showed that under increasing H2O2 concentrations, inhibition of the three enzymes with or without metHb formation lead to the binding of Prx2 and GPx (but not Cat) to the erythrocyte membrane. Prx2 was detected mainly in its oxidized form and the linkage of metHb to the membrane seems to compete with the binding of Prx2. Catalase played a major role in protecting erythrocytes from high exogenous flux of H2O2, since whenever Cat was active there were no significant changes in any of the studied parameters. When only Cat was inhibited, Prx2 and GPx were unable to prevent H2O2-induced oxidative stress resulting in increasing MBH and membrane LPO. Additionally, the inhibition of one or more of these enzymes induced changes in the anchor/linker proteins of the junctional complexes of the membrane cytoskeleton-lipid bilayer, which might lead to membrane destabilization.

Hydrogen peroxide sensitive hemoglobin-capped gold nanoclusters as a fluorescence enhancing sensor for the label-free detection of glucose

A novel label-free fluorescent probe based on blue-emitting gold nanoclusters capped by hemoglobin for the direct detection of glucose is presented.

On the source of the non-transferrin-bound iron which accumulates in packed red blood cell units during storage

BACKGROUND

Recent studies have shown large increases in non-transferrin-bound iron (NTBI) and biomarkers of oxidative stress in the extracellular medium of packed red blood cell units during storage. It has been further suggested that transfusion-mediated iron and oxidative load may contribute to transfusion-related morbidity in premature babies. The origin and nature of the NTBI is currently unclear, but the release of iron from oxidatively modified haemoglobin and haem has been suggested. The purpose of this study was to investigate whether this may be the case.

MATERIALS AND METHODS

The concentration of haem in the extracellular fluid of paediatric packed cell units stored from 3 to 35 days was measured using a commercial haem assay. In vitro studies were conducted using haem (haemin; ferriprotoporphyrin IX chloride) to determine whether the NTBI assay was able to react with and measure iron associated with haem in the presence and absence of oxidising agents.

RESULTS

The level of haem in the extracellular fluid of paediatric packed cell units rose gradually from day 3 to day 21, then more rapidly to day 35. Very little NTBI was released from haem in the absence of oxidising agents, but the amount rose in a dose- and time-dependent manner in proportion to the oxidation of haem by incubation with H2O2.

DISCUSSION

The results of the study imply that the NTBI measured in previous studies may derive from the oxidatively modified haem that builds up in the extracellular fluid of packed red blood cell units during storage. The potential influence of this on transfusion mediated morbidity is discussed.

Red blood cell oxidative stress impairs oxygen delivery and induces red blood cell aging

Red Blood Cells (RBCs) need to deform and squeeze through narrow capillaries. Decreased deformability of RBCs is, therefore, one of the factors that can contribute to the elimination of aged or damaged RBCs from the circulation. This process can also cause impaired oxygen delivery, which contributes to the pathology of a number of diseases. Studies from our laboratory have shown that oxidative stress plays a significant role in damaging the RBC membrane and impairing its deformability. RBCs are continuously exposed to both endogenous and exogenous sources of reactive oxygen species (ROS) like superoxide and hydrogen peroxide (H2O2). The bulk of the ROS are neutralized by the RBC antioxidant system consisting of both non-enzymatic and enzymatic antioxidants including catalase, glutathione peroxidase and peroxiredoxin-2. However, the autoxidation of hemoglobin (Hb) bound to the membrane is relatively inaccessible to the predominantly cytosolic RBC antioxidant system. This inaccessibility becomes more pronounced under hypoxic conditions when Hb is partially oxygenated, resulting in an increased rate of autoxidation and increased affinity for the RBC membrane. We have shown that a fraction of peroxyredoxin-2 present on the RBC membrane may play a major role in neutralizing these ROS. H2O2 that is not neutralized by the RBC antioxidant system can react with the heme producing fluorescent heme degradation products (HDPs). We have used the level of these HDP as a measure of RBC oxidative Stress. Increased levels of HDP are detected during cellular aging and various diseases. The negative correlation (p < 0.0001) between the level of HDP and RBC deformability establishes a contribution of RBC oxidative stress to impaired deformability and cellular stiffness. While decreased deformability contributes to the removal of RBCs from the circulation, oxidative stress also contributes to the uptake of RBCs by macrophages, which plays a major role in the removal of RBCs from circulation. The contribution of oxidative stress to the removal of RBCs by macrophages involves caspase-3 activation, which requires oxidative stress. RBC oxidative stress, therefore, plays a significant role in inducing RBC aging.

New insights provided by a comparison of impaired deformability with erythrocyte oxidative stress for sickle cell disease

Sickle cell disease (SCD) is associated with increase in oxidative stress and irreversible membrane changes that originates from the instability and polymerization of deoxygenated hemoglobin S (HbS). The relationship between erythrocyte membrane changes as assessed by a decrease in deformability and oxidative stress as assessed by an increase in heme degradation was investigated. The erythrocyte deformability and heme degradation for 27 subjects with SCD and 7 with sickle trait were compared with normal healthy adults. Changes in both deformability and heme degradation increased in the order of control to trait to non-crisis SCD to crisis SCD resulting in a very significantly negative correlation between deformability and heme degradation. However, a quantitative analysis of the changes in deformability and heme degradation for these different groups of subjects indicated that sickle trait had a much smaller effect on deformability than on heme degradation, while crisis affects deformability to a greater extent than heme degradation. These findings provide insights into the relative contributions of erythrocyte oxidative stress and membrane damage during the progression of SCD providing a better understanding of the pathophysiology of SCD.

Hemoglobin redox reactions and red blood cell aging

SIGNIFICANCE

The physiological mechanism(s) for recognition and removal of red blood cells (RBCs) from circulation after 120 days of its lifespan is not fully understood. Many of the processes thought to be associated with the removal of RBCs involve oxidative stress. We have focused on hemoglobin (Hb) redox reactions, which is the major source of RBC oxidative stress.

RECENT ADVANCES

The importance of Hb redox reactions have been shown to originate in large parts from the continuous slow autoxidation of Hb producing superoxide and its dramatic increase under hypoxic conditions. In addition, oxidative stress has been shown to be associated with redox reactions that originate from Hb reactions with nitrite and nitric oxide (NO) and the resultant formation of highly toxic peroxynitrite when NO reacts with superoxide released during Hb autoxidation.

CRITICAL ISSUES

The interaction of Hb, particularly under hypoxic conditions with band 3 of the RBC membrane is critical for the generating the RBC membrane changes that trigger the removal of cells from circulation. These changes include exposure of antigenic sites, increased calcium leakage into the RBC, and the resultant leakage of potassium out of the RBC causing cell shrinkage and impaired deformability.

FUTURE DIRECTIONS

The need to understand the oxidative damage to specific membrane proteins that result from redox reactions occurring when Hb is bound to the membrane. Proteomic studies that can pinpoint the specific proteins damaged under different conditions will help elucidate the cellular aging processes that result in cells being removed from circulation.

Markers of oxidant stress that are clinically relevant in aging and age-related disease

Despite the long held hypothesis that oxidant stress results in accumulated oxidative damage to cellular macromolecules and subsequently to aging and age-related chronic disease, it has been difficult to consistently define and specifically identify markers of oxidant stress that are consistently and directly linked to age and disease status. Inflammation because it is also linked to oxidant stress, aging, and chronic disease also plays an important role in understanding the clinical implications of oxidant stress and relevant markers. Much attention has focused on identifying specific markers of oxidative stress and inflammation that could be measured in easily accessible tissues and fluids (lymphocytes, plasma, serum). The purpose of this review is to discuss markers of oxidant stress used in the field as biomarkers of aging and age-related diseases, highlighting differences observed by race when data is available. We highlight DNA, RNA, protein, and lipid oxidation as measures of oxidative stress, as well as other well-characterized markers of oxidative damage and inflammation and discuss their strengths and limitations. We present the current state of the literature reporting use of these markers in studies of human cohorts in relation to age and age-related disease and also with a special emphasis on differences observed by race when relevant.

SOD2 deficiency in hematopoietic cells in mice results in reduced red blood cell deformability and increased heme degradation

Among the three types of super oxide dismutases (SODs) known, SOD2 deficiency is lethal in neonatal mice owing to cardiomyopathy caused by severe oxidative damage. SOD2 is found in red blood cell (RBC) precursors, but not in mature RBCs. To investigate the potential damage to mature RBCs resulting from SOD2 deficiency in precursor cells, we studied RBCs from mice in which fetal liver stem cells deficient in SOD2 were capable of efficiently rescuing lethally irradiated host animals. These transplanted animals lack SOD2 only in hematopoietically generated cells and live longer than SOD2 knockouts. In these mice, approximately 2.8% of their total RBCs in circulation are iron-laden reticulocytes, with numerous siderocytic granules and increased protein oxidation similar to that seen in sideroblastic anemia. We have studied the RBC deformability and oxidative stress in these animals and the control group by measuring them with a microfluidic ektacytometer and assaying fluorescent heme degradation products with a fluorimeter, respectively. In addition, the rate of hemoglobin oxidation in RBCs from these mice and the control group were measured spectrophotometrically. The results show that RBCs from these SOD2-deficient mice have reduced deformability, increased heme degradation products, and an increased rate of hemoglobin oxidation compared with control animals, indicative of increased RBC oxidative stress.

Role of peroxiredoxin-2 in protecting RBCs from hydrogen peroxide-induced oxidative stress

The role of peroxiredoxin-2 (PRDX2) in preventing hydrogen peroxide-induced oxidative stress in the red blood cell was investigated by comparing blood from PRDX2 knockout mice with superoxide dismutase-1 (SOD1) knockout and control mice. Loss of PRDX2 increased basal levels of methemoglobin and heme degradation (a marker for oxidative stress), and reduced red blood cell deformability. In vitro incubation under normoxic conditions, both with and without inhibition of catalase, resulted in a lag phase during which negligible heme degradation occurred followed by a more rapid rate of heme degradation in the absence of PRDX2. The appreciable basal increase in heme degradation for PRDX2 knockout mice, together with the lag during in vitro incubation, implies that PRDX2 neutralizes hydrogen peroxide generated in vivo under the transient hypoxic conditions experienced as the cells pass through the microcirculation.

Considering the vascular hypothesis of Alzheimer's disease: effect of copper associated amyloid on red blood cells

The vascular hypothesis of Alzheimer's disease (AD) considers cerebral hypoperfusion as a primary trigger for neuronal dysfunction. We have previously reported that red blood cells (RBCs) bind amyloid, which are the characteristic deposits found in AD brains, and interact with amyloid on the vasculature [1-3]. Oxidative stress triggered by these RBC/amyloid interactions could impair oxygen delivery. Recent literature has implicated copper bound amyloid-β peptide (CuAβ) and the associated production of reactive oxygen species (ROS) as one of the primary factors contributing to AD pathology. In this work, we have investigated CuAβ generated RBC oxidative stress. Aβ(1-40) peptide with a stoichiometric amount of copper bound was produced and compared to the metal-free form of the peptide. Different aggregation states of the peptides were isolated and incubated with RBCs for 15 h. Interestingly, CuAβ stimulated a pronounced increase in red cell oxidative stress as indicated by increased hemoglobin (Hb) oxidation, increased formation of fluorescent heme degradation products, and a decrease in RBC deformability. These findings demonstrate a potential role for CuAβ in promoting vascular oxidative stress leading to impaired cerebral oxygen delivery, which may contribute to neurodegeneration associated with AD.

Racial discrimination is associated with a measure of red blood cell oxidative stress: a potential pathway for racial health disparities

BACKGROUND

There are racial health disparities in many conditions for which oxidative stress is hypothesized to be a precursor. These include cardiovascular disease, diabetes, and premature aging. Small clinical studies suggest that psychological stress may increase oxidative stress. However, confirmation of this association in epidemiological studies has been limited by homogenous populations and unmeasured potential confounders.

PURPOSE

We tested the cross-sectional association between self-reported racial discrimination and red blood cell (RBC) oxidative stress in a biracial, socioeconomically heterogeneous population with well-measured confounders.

METHODS

We performed a cross-sectional analysis of a consecutive series of 629 participants enrolled in the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study. Conducted by the National Institute on Aging Intramural Research Program, HANDLS is a prospective epidemiological study of a socioeconomically diverse cohort of 3,721 Whites and African Americans aged 30-64 years. Racial discrimination was based on self-report. RBC oxidative stress was measured by fluorescent heme degradation products. Potential confounders were age, smoking status, obesity, and C-reactive protein.

RESULTS

Participants had a mean age of 49 years (SD = 9.27). In multivariable linear regression models, racial discrimination was significantly associated with RBC oxidative stress (Beta = 0.55, P < 0.05) after adjustment for age, smoking, C-reactive protein level, and obesity. When stratified by race, discrimination was not associated with RBC oxidative stress in Whites but was associated significantly for African Americans (Beta = 0.36, P < 0.05).

CONCLUSIONS

These findings suggest that there may be identifiable cellular pathways by which racial discrimination amplifies cardiovascular and other age-related disease risks.

Erythrocytes induce proinflammatory endothelial activation in hypoxia

Although exposure to ambient hypoxia is known to cause proinflammatory vascular responses, the mechanisms initiating these responses are not understood. We tested the hypothesis that in systemic hypoxia, erythrocyte-derived H(2)O(2) induces proinflammatory gene transcription in vascular endothelium. We exposed mice or isolated, perfused murine lungs to 4 hours of hypoxia (8% O(2)). Leukocyte counts increased in the bronchoalveolar lavage. The expression of leukocyte adhesion receptors, reactive oxygen species, and protein tyrosine phosphorylation increased in freshly recovered lung endothelial cells (FLECs). These effects were inhibited by extracellular catalase and by the removal of erythrocytes, indicating that the responses were attributable to erythrocyte-derived H(2)O(2). Concomitant nuclear translocation of the p65 subunit of NF-κB and hypoxia-inducible factor-1α stabilization in FLECs occurred only in the presence of erythrocytes. Hemoglobin binding to the erythrocyte membrane protein, band 3, induced the release of H(2)O(2) from erythrocytes and the p65 translocation in FLECs. These data indicate for the first time, to our knowledge, that erythrocytes are responsible for endothelial transcriptional responses in hypoxia.

Stabilization of erythrocytes against oxidative and hypotonic stress by tannins isolated from sumac leaves (Rhus typhina L.) and grape seeds (Vitis vinifera L.)

Erythrocytes are constantly exposed to ROS due to their function in the organism. High tension of oxygen, presence of hemoglobin iron and high concentration of polyunsaturated fatty acids in membrane make erythrocytes especially susceptible to oxidative stress. A comparison of the antioxidant activities of polyphenol-rich plant extracts containing hydrolysable tannins from sumac leaves (Rhus typhina L.) and condensed tannins from grape seeds (Vitis vinifera L.) showed that at the 5-50 μg/ml concentration range they reduced to the same extent hemolysis and glutathione, lipid and hemoglobin oxidation induced by erythrocyte treatment with 400 μM ONOO(-) or 1 mM HClO. However, extract (condensed tannins) from grape seeds in comparison with extract (hydrolysable tannins) from sumac leaves stabilized erythrocytes in hypotonic NaCl solutions weakly. Our data indicate that both hydrolysable and condensed tannins significantly decrease the fluidity of the surface of erythrocyte membranes but the effect of hydrolysable ones was more profound. In conclusion, our results indicate that extracts from sumac leaves (hydrolysable tannins) and grape seeds (condensed tannins) are very effective protectors against oxidative damage in erythrocytes.

Effects of pre-storage leukoreduction on stored red blood cells signaling: a time-course evaluation from shape to proteome

The introduction of pre-storage leukoreduction in the preparation of standard RBCs intended for transfusion provided significant improvement in the quality of labile products and their post transfusion viability and effects, although the literature data are controversial. To elucidate the issue of the probable leukoreduction effects on RBCs storage lesion, we evaluated various storage quality measures in RBCs stored in either leukoreduced (L) or non-leukoreduced (N) units, with emphasis to senescence and oxidative stress associated modifications. Our data suggest that the residual leukocytes/platelets of the labile products represent a stressful storage factor, countering the structural and functional integrity of stored RBCs. Hemolysis, irreversible echinocytosis, microvesiculation, removal signaling, ROS/calcium accumulation, band 3-related senescence modifications, membrane proteome stress biomarkers as well as emergence of a senescence phenotype in young RBCs that is disproportionate to their age, are all encountered more or mostly in N-RBCs compared to the L-RBCs, either for a part or for the whole of the storage period. The partial, yet significant, alleviation of so many storage-related manifestations in the L-RBCs compared to the N-RBCs, is presented for the first time and provides a rational mechanistic interpretation of the improved storage quality and transfusions observed by the introduction of pre-storage leukoreduction. This article is part of a Special Issue entitled: Integrated omics.

Alcohol drinking, mean corpuscular volume of erythrocytes, and alcohol metabolic genotypes in drunk drivers

Regular and irregular abuse of alcohol are global health priorities associated with diseases at multiple sites, including cancer. Mechanisms of diseases induced by alcohol are closely related to its metabolism. Among conventional markers of alcohol abuse, the mean corpuscular volume (MCV) of erythrocytes is prognostic of alcohol-related cancer and its predictivity increases when combined with functional polymorphisms of alcohol dehydrogenase (ADH1B [rs1229984] and ADH1C [rs698]) and the mitochondrial aldehyde dehydrogenase (ALDH2 [rs671]). Whether these genetic variants can influence abuse in alcohol drinking and MCV has never been examined in drunk-driving traffic offenders. We examined 149 drunk drivers, diagnosed as alcohol abusers according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth edition Text Revision (DSM-IV-TR) and enrolled in a probation program, and 257 social drinkers (controls), all Caucasian males. Alcohol intake was assessed according to self-reported drink-units/d and MCV unadjusted and adjusted for age, smoking, and body mass index. Multivariable models were used to compute MCV adjusted means. Genotype analyses were performed by PCR on DNA from blood. The adjusted MCV mean was higher in drunk-driving abusers than in controls (92 vs. 91fL; P<.0001) and increased with the number of drink-units/d in both abusers and controls (P-trend=.0316 and .0089) already at intermediate quantities (0-1 vs. 2-4 drink-units/d: P=.054 and .024). Carriers of the common ADH1B*1/*1 (rs1229984) genotype were more likely to be drunk-driving abusers (P=.008), reported higher drink-units/d (P=.0126), and had larger MCV (P=.035). The rs698 ADH1C and rs671 ALDH2 polymorphisms were not associated with MCV. ADH1B*1/*1 polymorphism is significantly associated with being a drunk-driving abuser, higher alcohol drinking, and MCV enlargement. This suggests that drunk drivers with augmented MCV modulated by the alcohol metabolic ADH1B*1/*1 genotype may be at higher risk of driving incapability and of alcohol-related cancer.

Carbonyl formation in erythrocyte membrane proteins during aging in humans

BACKGROUND

Studies have shown that oxidative stress increases with increasing human age. Protein carbonyl accumulation is an indicator of oxidative damage to proteins during aging in cells and tissues. The present study is focused on the relationship between human age and protein oxidation in erythrocyte membranes in a healthy Indian population.

MATERIALS AND METHODS

The sample included healthy human subjects (n = 49) between the ages of 17 to 80 years. Their blood was collected and assayed spectrophotometrically for oxidative protein damage in terms of protein carbonyls and plasma antioxidant capacity in terms of FRAP.

RESULTS

Protein carbonyl content was found to increase in an age-related pattern indicating an increase in oxidative protein damage in older subjects (p <0.0001, r = 0.8269). There was also a significant negative correlation between protein oxidation and plasma antioxidant capacity measured in terms of ferric reducing antioxidant potential (FRAP) values (p<0.0001; r = -0.8695).

CONCLUSION

Our results substantiate the occurrence of oxidative stress during human aging. Elevated erythrocyte membrane carbonyl levels found with increasing age in this study may be viewed as a biomarker for aging.

Reaction of hemoglobin with HOCl: mechanism of heme destruction and free iron release

Hypochlorous acid (HOCl) is generated by myeloperoxidase using chloride and hydrogen peroxide as substrates. HOCl and its conjugate base (OCl(-)) bind to the heme moiety of hemoglobin (Hb) and generate a transient ferric species whose formation and decay kinetics indicate it can participate in protein aggregation and heme destruction along with subsequent free iron release. The oxidation of the Hb heme moiety by OCl(-) was accompanied by marked heme destruction as judged by the decrease in and subsequent flattening of the Soret absorbance peak at 405 nm. HOCl-mediated Hb heme depletion was confirmed by HPLC analysis and in-gel heme staining. Exposure of Hb to increasing concentrations of HOCl produced a number of porphyrin degradation products resulting from oxidative cleavage of one or more of the carbon-methene bridges of the tetrapyrrole ring, as identified by their characteristic HPLC fluorescence and LC-MS. A nonreducing denaturing SDS-PAGE showed several degrees of protein aggregation. Similarly, porphyrin degradation products were identified after exposure of red blood cells to increasing concentrations of HOCl, indicating biological relevance of this finding. This work provides a direct link between Hb heme destruction and subsequent free iron accumulation, as occurs under inflammatory conditions where HOCl is formed in substantial amounts.

Blood aging, safety, and transfusion: capturing the "radical" menace

Throughout their life span, circulating red blood cells (RBCs) transport oxygen (O(2)) primarily from the lungs to tissues and return with carbon dioxide (CO(2)) from respiring tissues for final elimination by lungs. This simplistic view of RBCs as O(2) transporter has changed in recent years as other gases, for example, nitric oxide (NO), and small molecules, such as adenosine triphosphate (ATP), have been shown to either be produced and/or carried by RBCs to perform other signaling and O(2) sensing functions. In spite of the numerous biochemical and metabolic changes occurring within RBCs during storage, prior to, and after transfusion, perturbations of RBC membrane are likely to affect blood flow in the microcirculation. Subsequent hemolysis due to storage conditions and/or hemolytic disorders may have some pathophysiological consequences as a result of the release of Hb. In this review, we show that evolution has provided a multitude of protection and intervention strategies against free Hb from "cradle" to "death"; from early biosynthesis to its final degradation and a lot more in between. Furthermore, some of the same naturally occurring protective mechanisms can potentially be employed to oxidatively inactivate this redox active protein and control its damaging side reactions when released outside of the RBC.

Haptoglobin: old protein with new functions

When released from red blood cells (RBCs), hemoglobin (Hb) is extremely toxic due in large part to the redox activity of its heme center. Nature however, has provided a multitude of protective mechanisms that can detoxify free Hb effectively under physiological conditions. Chief amongst them is haptoglobin (Hp) which chaperones Hb subunits to the macrophages for safe degradation. Recent research on the interactions between Hb and Hp under oxidative conditions revealed that Hp specifically shields key amino acids on the Hb molecule, allowing the heme to consume oxidants and short-circuits the emerging and damaging radicals. Moreover, animal studies showed that the infusion of Hb complexed with Hp prevents Hb-induced systemic hypertension and tissue injury. It may prove necessary to explore these protective clearing mechanisms to counter the toxicity associated with free Hb when used as oxygen therapeutics in hemolytic anemias and in RBC storage lesions.

Cytotoxicity of chromium ions may be connected with induction of oxidative stress

Chromium ions are frequently found in aquatic ecosystems and are known to be inducers of oxidative stress in fish solid tissues. The present study was designed to determine whether fish blood samples can be used to allow nonlethal diagnostic testing for chromium intoxication. First, we confirmed that 96 h exposures to water containing 10.0 mg L(-1) chromium ions, either Cr3+ or Cr6+, induced oxidative stress in brain of goldfish (Carassius auratus). Multiple blood parameters were then evaluated. Cr6+ exposure triggered a 579% increase in the number of erythrocytes containing micronuclei, a frequently used marker of cellular toxicity. Leucocyte numbers were also perturbed by exposure to either Cr3+ or Cr6+ indicating that chromium ions could impair the immune system as well. The content of protein carbonyl groups, a marker of oxidative damage to proteins, was enhanced in fish plasma by exposure to either chromium ion and activities of catalase and lactate dehydrogenase also were affected. The data demonstrate that chromium ions induced oxidative stress in goldfish blood and were cytotoxic for erythrocytes. This indicates that analysis of plasma can be used as a good early nonlethal diagnostic marker of fish intoxication by transition metal ions.