Is methemoglobin an inert bystander, biomarker or a mediator of oxidative stress--The example of anemia?

Bilateral nephrectomy impairs cardiovascular function and cerebral perfusion in a rat model of acute hemodilutional anemia

Anemia and renal failure are independent risk factors for perioperative stroke, prompting us to assess the combined impact of acute hemodilutional anemia and bilateral nephrectomy (2Nx) on microvascular brain Po2 (PBro2) in a rat model. Changes in PBro2 (phosphorescence quenching) and cardiac output (CO, echocardiography) were measured in different groups of anesthetized Sprague-Dawley rats (1.5% isoflurane, n = 5-8/group) randomized to Sham 2Nx or 2Nx and subsequently exposed to acute hemodilutional anemia (50% estimated blood volume exchange with 6% hydroxyethyl starch) or time-based controls (no hemodilution). Outcomes were assessed by ANOVA with significance assigned at P < 0.05. At baseline, 2Nx rats demonstrated reduced CO (49.9 ± 9.4 vs. 66.3 ± 19.3 mL/min; P = 0.014) and PBro2 (21.1 ± 2.9 vs. 32.4 ± 3.1 mmHg; P < 0.001) relative to Sham 2Nx rats. Following hemodilution, 2Nx rats demonstrated a further decrease in PBro2 (15.0 ± 6.3 mmHg, P = 0.022). Hemodiluted 2Nx rats did not demonstrate a comparable increase in CO after hemodilution compared with Sham 2Nx (74.8 ± 22.4 vs. 108.9 ± 18.8 mL/min, P = 0.003) that likely contributed to the observed reduction in PBro2. This impaired CO response was associated with reduced fractional shortening (33 ± 9 vs. 51 ± 5%) and increased left ventricular end-systolic volume (156 ± 51 vs. 72 ± 15 µL, P < 0.001) suggestive of systolic dysfunction. By contrast, hemodiluted Sham 2Nx animals demonstrated a robust increase in CO and preserved PBro2. These data support the hypothesis that the kidney plays a central role in maintaining cerebral perfusion and initiating the adaptive increase in CO required to optimize PBro2 during acute anemia.NEW & NOTEWORTHY This study has demonstrated that bilateral nephrectomy acutely impaired cardiac output (CO) and microvascular brain Po2 (PBro2), at baseline. Following acute hemodilution, nephrectomy prevented the adaptive increase in CO associated with acute hemodilution leading to a further reduction in PBro2, accentuating the degree of cerebral tissue hypoxia. These data support a role for the kidney in maintaining PBro2 and initiating the increase in CO that optimized brain perfusion during acute anemia.

Methemoglobin as a marker of acute anemic stress in cardiac surgery

Biological evidence supports plasma methemoglobin as a biomarker for anemia-induced tissue hypoxia. In this translational planned substudy of the multinational randomized controlled transfusion thresholds in cardiac surgery (TRICS-III) trial, which included adults undergoing cardiac surgery requiring cardiopulmonary bypass with a moderate-to-high risk of death, we investigated the relationship between perioperative hemoglobin concentration (Hb) and methemoglobin; and evaluated its association with postoperative outcomes. The primary endpoint was a composite of death, myocardial infarction, stroke, and severe acute kidney injury at 28 days. We observe weak non-linear associations between decreasing Hb and increasing methemoglobin, which were strongest in magnitude at the post-surgical time point. Increased levels of post-surgical methemoglobin were associated with a trend toward an elevated risk for stroke and exploratory neurological outcomes. Our generalizable study demonstrates post-surgical methemoglobin may be a marker of anemia-induced organ injury/dysfunction, and may have utility for guiding personalized approaches to anemia management. Clinicaltrials.gov registration NCT02042898.

Assessment of Methemoglobin, Hemoglobin, Ferritin and Lactate dehydrogenase in COVID-19 Patients

Today world is trying to cope with the biggest pandemic caused by Coronavirus disease 2019 (COVID-19). The disease is graded as mild, moderate, serious and critical illness. Very few studies are done with methemoglobin along with other parameters for the assessment of the severity of COVID-19 disease. The objectives of the study were to estimate methemoglobin (Met-Hb), hemoglobin (Hb), ferritin and lactate dehydrogenase (LDH) levels in patients with COVID-19 disease and to investigate the interaction between these parameters and the severity of the disease. This observational study was conducted in three groups of COVID-19 patients- moderate, severe and critical, each group containing 30 patients, between June 2021 and September 2021 in the biochemistry department of a tertiary care hospital. For all patients, Met-Hb, Hb, ferritin, and LDH levels were estimated on the 2nd-3rd day of hospital admission. Patients in the critical group were older and had significantly high values of Met-Hb, ferritin and LDH and significantly low values of Hb (P<0.05). In multivariate ordinal regression analysis, older age (OR-3.08; 95%CI:1.19-7.19;P-0.019), higher values of LDH (OR-8.66; 95%CI:2.53-29.5; P-0.001) and ferritin (OR-3.08; 95%CI:1.09-8.7;P-0.033) were independently associated with severity of the disease. A cut-off value of 410.50 U/L for LDH predicted the severity of the disease with 90% sensitivity and 88.3% specificity. In conclusion, higher levels of LDH and ferritin were related to the severity of the disease in COVID-19 cases. Although Met-Hb showed a minimal increase without any association with severity, it may be an underlying cause of hypoxia that may go unnoticed. So, monitoring of all these parameters should be done at intervals.

Assessing the quality of stored red blood cells using handheld Spatially Offset Raman spectroscopy with multisource correlation analysis

In this work we employ Spatially Offset Raman Spectroscopy (SORS) to non-invasively identify storage-related changes in red blood cell concentrate (RCC) in-situ within standard plastic transfusion bags. To validate the measurements, we set up a parallel study comparing both bioanalytical data (obtained by blood-gas analysis, hematology analysis and spectrophotometric assays), and Raman spectrometry data from the same blood samples. We then employ Multisource Correlation Analysis (MuSCA) to correlate the different types of data in RCC. Our analysis confirmed a strong correlation of glucose, methemoglobin and oxyhemoglobin with their respective bioassay values in RCC units. Finally, by combining MuSCA with k-means clustering, we assessed changes in all Raman wavenumbers during cold storage in both RCC Raman data from the current study and parallel RCC supernatant Raman data previously acquired from the same units. Direct RCC quality monitoring during storage, would help to establish a basis for improved inventory management of blood products in blood banks and hospitals based on analytical data.

Evaluation of an extracorporeal ozone-based bactericide system for the treatment of Escherichia coli sepsis

BACKGROUND

Sepsis is associated with substantial mortality rates. Antibiotic treatment is crucial, but global antibiotic resistance is now classified as one of the top ten global public health risks facing humanity. Ozone (O₃) is an inorganic molecule with no evident function in the body. We investigated the bactericide properties of ozone, using a novel system of extracorporeal ozone blood treatment. We hypothesized that ozone would decrease the concentration of viable Escherichia coli (E. coli) in human whole blood and that the system would be technically feasible and physiologically tolerable in a clinically relevant model of E. coli sepsis in swine.

METHODS

The E. coli strain B09-11822, a clinical isolate from a patient with septic shock was used. The in vitro study treated E. coli infected human whole blood (n = 6) with ozone. The in vivo 3.5-h sepsis model randomized swine to E. coli infusion and ozone treatment (n = 5) or E. coli infusion and no ozone treatment (n = 5). Live E. coli, 5 × 10⁷ colony-forming units (CFU/mL) was infused in a peripheral vein. Ozone treatment was initiated with a duration of 30 min after 1.5 h.

RESULTS

The single pass in vitro treatment decreased E. coli by 27%, mean 1941 to 1422 CFU/mL, mean of differences - 519.0 (95% CI - 955.0 to - 82.98, P = 0.0281). pO₂ increased (95% CI 31.35 to 48.80, P = 0.0007), pCO₂ decreased (95% CI - 3.203 to - 1.134, P = 0.0069), oxyhemoglobin increased (95% CI 1.010 to 3.669, P = 0.0113). Methemoglobin was not affected. In the sepsis model, 9/10 swine survived. One swine randomized to ozone treatment died from septic shock before initiation of the treatment. Circulatory, respiratory, and metabolic parameters were not affected by the ozone treatment. E. coli in arterial blood, in organs and in aerobic and anaerobic blood cultures did not differ. Hemoglobin, leucocytes, and methemoglobin were not affected by the treatment.

CONCLUSIONS

Ozone decreased the concentration of viable E. coli in human whole blood. The system was technically feasible and physiologically tolerable in porcine sepsis/septic shock and should be considered for further studies towards clinical applications.

Implication of COVID-19 on Erythrocytes Functionality: Red Blood Cell Biochemical Implications and Morpho-Functional Aspects

Several diseases (such as diabetes, cancer, and neurodegenerative disorders) affect the morpho-functional aspects of red blood cells, sometimes altering their normal metabolism. In this review, the hematological changes are evaluated, with particular focus on the morphology and metabolic aspects of erythrocytes. Changes in the functionality of such cells may, in fact, help provide important information about disease severity and progression. The viral infection causes significant damage to the blood cells that are altered in size, rigidity, and distribution width. Lower levels of hemoglobin and anemia have been reported in several studies, and an alteration in the concentration of antioxidant enzymes has been shown to promote a dangerous state of oxidative stress in red blood cells. Patients with severe COVID-19 showed an increase in hematological changes, indicating a progressive worsening as COVID-19 severity progressed. Therefore, monitored hematological alterations in patients with COVID-19 may play an important role in the management of the disease and prevent the risk of a severe course of the disease. Finally, monitored changes in erythrocytes and blood, in general, may be one of the causes of the condition known as Long COVID.

Mid-Regional Pro-Adrenomedullin, Methemoglobin and Carboxyhemoglobin as Prognosis Biomarkers in Critically Ill Patients with COVID-19: An Observational Prospective Study

Mid-regional pro-adrenomedullin (MR-proADM), methemoglobin (MetHb), and carboxyhemoglobin (COHb) levels have been associated with sepsis. In this study, we assessed the role of this potential biomarkers in critically ill COVID-19 patients. Outcomes were mortality and a combined event (mortality, venous or arterial thrombosis, and orotracheal intubation (OTI)) during a 30-day follow-up. A total of 95 consecutive patients were included, 51.6% required OTI, 12.6% patients died, 8.4% developed VTE, and 3.1% developed arterial thrombosis. MetHb and COHb levels were not associated with mortality nor combined event. Higher MR-proADM levels were found in patients with mortality (median of 1.21 [interquartile range-IQR-0.84;2.33] nmol/L vs. 0.76 [IQR 0.60;1.03] nmol/L, p = 0.011) and combined event (median of 0.91 [IQR 0.66;1.39] nmol/L vs. 0.70 [IQR 0.51;0.82] nmol/L, p < 0.001); the positive likelihood ratio (LR+) and negative likelihood ratio (LR−) for mortality were 2.40 and 0.46, respectively. The LR+ and LR− for combined event were 3.16 and 0.63, respectively. MR-proADM ≥1 nmol/L was the optimal cut-off for mortality and combined event prediction. The predictive capacity of MR-proADM showed an area under the ROC curve of 0.73 (95% CI, 0.62–0.81) and 0.72 (95% CI, 0.62–0.81) for mortality and combined event, respectively. In conclusion, elevated on-admission MR-proADM levels were associated with higher risk of 30-day mortality and 30-day poor outcomes in a cohort of critically ill patients with COVID-19.

Efficacy of resuscitative infusion with hemoglobin vesicles in rabbits with massive obstetric hemorrhage

BACKGROUND

Hemoglobin vesicles have been developed as artificial oxygen carriers, and they have the potential to serve as a substitute for red blood cell transfusion.

OBJECTIVE

This study aimed to evaluate the efficacy of hemoglobin vesicle infusion for the initial treatment instead of red blood cell transfusion in rabbits with massive obstetric hemorrhage.

STUDY DESIGN

Pregnant New Zealand white rabbits (28th day of pregnancy; normal gestation period, 29-35 days) underwent uncontrolled hemorrhage to induce shock by transecting the right midartery and concomitant vein in the myometrium. Subsequently, rabbits received isovolemic fluid resuscitation through the femoral vein with an equivalent volume of hemorrhage every 5 minutes. Resuscitative infusion regimens included 5% human serum albumin (n=6), stored washed red blood cells with plasma (vol/vol=1:1; n=5), and hemoglobin vesicle with 5% human serum albumin (vol/vol=4:1; n=5). A total of 60 minutes after the start of bleeding, rabbits underwent surgical hemostasis by ligation of the bleeding vessels and then were monitored for survival within 24 hours.

RESULTS

During fluid resuscitation, hemoglobin vesicle infusion and red blood cell transfusion maintained a mean arterial pressure of >50 mm Hg and a hemoglobin concentration of >9 g/dL and prevented the elevation of plasma lactate. In contrast, resuscitation with 5% human serum albumin alone could not prevent hemorrhagic shock as evidenced by a low mean arterial pressure (40 mm Hg), a low hemoglobin concentration (2 g/dL), and a marked elevation of plasma lactate. All animals in the red blood cell group and the hemoglobin vesicle group survived more than 8 hours, whereas all animals in the 5% human serum albumin group died within 8 hours.

CONCLUSION

Hemoglobin vesicle infusion may be effective in the initial management of massive obstetric hemorrhage.

The Role of Methemoglobin and Carboxyhemoglobin in COVID-19: A Review

Following the outbreak of a novel coronavirus (SARS-CoV-2) associated with pneumonia in China (Corona Virus Disease 2019, COVID-19) at the end of 2019, the world is currently facing a global pandemic of infections with SARS-CoV-2 and cases of COVID-19. Since severely ill patients often show elevated methemoglobin (MetHb) and carboxyhemoglobin (COHb) concentrations in their blood as a marker of disease severity, we aimed to summarize the currently available published study results (case reports and cross-sectional studies) on MetHb and COHb concentrations in the blood of COVID-19 patients. To this end, a systematic literature research was performed. For the case of MetHb, seven publications were identified (five case reports and two cross-sectional studies), and for the case of COHb, three studies were found (two cross-sectional studies and one case report). The findings reported in the publications show that an increase in MetHb and COHb can happen in COVID-19 patients, especially in critically ill ones, and that MetHb and COHb can increase to dangerously high levels during the course of the disease in some patients. The medications given to the patient and the patient’s glucose-6-phospate dehydrogenase (G6PD) status seem to be important factors determining the severity of the methemoglobinemia and carboxyhemoglobinemia. Therefore, G6PD status should be determined before medications such as hydroxychloroquine are administered. In conclusion, MetHb and COHb can be elevated in COVID-19 patients and should be checked routinely in order to provide adequate medical treatment as well as to avoid misinterpretation of fingertip pulse oximetry readings, which can be inaccurate and unreliable in case of elevated MetHb and COHb levels in the blood.

Mitigation of Cu(II)-induced damage in human blood cells by carnosine: An in vitro study

Copper (Cu) is an essential micronutrient but human exposure to high level of this metal results in adverse health effects. Oxidative stress is assumed to play a major role in the mechanism of Cu-induced toxicity. The protective role of carnosine, an antioxidant and antiglycating agent, was examined against Cu-induced toxicity in isolated human blood cells. Red blood cells (RBC) were treated with 0.5 mM copper chloride (CuCl₂), a Cu(II) compound, either alone or after treatment with carnosine. Incubation of RBC with CuCl₂ increased protein oxidation, lipid peroxidation, methemoglobin formation and lowered glutathione content. The antioxidant defense system was impaired and production of reactive oxygen (ROS) and reactive nitrogen species (RNS) was enhanced. Pre-incubation of RBC with carnosine protected the cells against CuCl₂-induced oxidative damage. It restored the activities of several antioxidant, membrane-bound and metabolic enzymes, decreased the generation of ROS and RNS, enhanced the antioxidant power of cells and prevented inactivation of plasma membrane redox system. Carnosine also protected human lymphocytes from CuCl₂-induced DNA damage. The protective effects of carnosine were concentration-dependent while carnosine itself did not exhibit any adverse effect. Carnosine can, therefore, be used as a possible chemoprotectant against the harmful effects of this extremely redox active metal.

Taurine attenuates Cr(VI)-induced cellular and DNA damage: an in vitro study using human erythrocytes and lymphocytes

Hexavalent chromium [(Cr(VI)] is widely used in several industries, but human exposure results in multiple organ toxicity. Enhanced generation of free radicals and reactive species is thought to play a key role in Cr(VI)-induced toxicity. We have examined the effect of taurine, a simple sulphur-containing amino acid and an antioxidant, on potassium dichromate [K₂Cr₂O₇, a Cr(VI) compound]-induced cytotoxicity and genotoxicity in human blood cells. Erythrocytes were treated with K₂Cr₂O₇, either alone or after incubation with different concentrations of taurine. Treatment of erythrocytes with K₂Cr₂O₇ alone led to marked increase in generation of reactive oxygen and nitrogen species, lipid and protein oxidation. This was accompanied by decrease in total sulfhydryl and glutathione content and lowered antioxidant power of the cells. This suggests that Cr(VI) induces oxidative stress in the cells. Incubation of erythrocytes with taurine prior to addition of K₂Cr₂O₇, resulted in a concentration-dependent decrease in the generation of reactive oxygen and nitrogen species, mitigation of oxidative stress and amelioration of antioxidant power of these cells. It also restored the activities of several metabolic, antioxidant and membrane-bound enzymes. Cr(VI)-induced damage to erythrocyte membrane and lymphocyte DNA was also significantly attenuated by prior administration of taurine. These results suggest that taurine can function as a chemoprotectant against Cr(VI)-induced oxidative injury and can be potentially used to mitigate the toxic effects of this transition metal ion.

Efficacy of Resuscitative Transfusion With Hemoglobin Vesicles in the Treatment of Massive Hemorrhage in Rabbits With Thrombocytopenic Coagulopathy and Its Effect on Hemostasis by Platelet Transfusion

INTRODUCTION

We have developed hemoglobin vesicles (HbVs) as a substitute for red blood cells (RBCs). We investigated the efficacy of HbV transfusion in the treatment of massive hemorrhage in rabbits in the setting of thrombocytopenic coagulopathy, focusing on the efficacy of hemostasis by subsequent platelet transfusion.

METHODS

Thrombocytopenic coagulopathy was induced in rabbits by repeated blood withdrawal and isovolemic retransfusion of autologous RBC (platelet counts <45,000/μL). A penetrating liver injury was then made. For 30 min, bleeding volume was measured every 10 min, after which subjects were transfused with an equivalent volume of stored RBC, HbV, or platelet poor plasma (PPP) to compensate for blood loss, simulating initial prehospital resuscitation. Thereafter, we transfused platelet rich plasma (PRP) to stop bleeding, which simulated inhospital resuscitation.

RESULTS

During the initial resuscitation, the HbV group was similar to the RBC group (but not the PPP group) in their hemodynamics and tissue circulation/oxygenation as assessed by plasma lactate levels. All rabbits showed similar bleeding volumes (20-30 mL) in this period. HbV-transfused rabbits sustained hemoglobin levels, but showed lower hematocrit levels compared with RBC-transfused rabbits. Subsequent PRP transfusion effectively stopped bleeding in all RBC-transfused rabbits (6/6) and most HbV-transfused rabbits (7/8) but not PPP-transfused rabbits (2/8). In addition, 83% of RBC-transfused rabbits and 75% of HbV-transfused rabbits survived for 24 h, although no PPP-transfused rabbits survived. HbV transfusion did not scavenge nitric oxide in rabbits.

CONCLUSIONS

HbV transfusion effectively rescued rabbits from severe hemorrhage with coagulopathy, without disturbing hemostasis after the platelet transfusion. HbV transfusion may be practical and useful in prehospital resuscitation.

Combination therapy using fibrinogen γ-chain peptide-coated, ADP-encapsulated liposomes and hemoglobin vesicles for trauma-induced massive hemorrhage in thrombocytopenic rabbits

BACKGROUND

We previously developed substitutes for red blood cells (RBCs) and platelets (PLTs) for transfusion. These substitutes included hemoglobin vesicles (HbVs) and fibrinogen γ-chain (dodecapeptide HHLGGAKQAGDV, H12)-coated, adenosine diphosphate (ADP)-encapsulated liposomes [H12-(ADP)-liposomes]. Here, we examined the efficacy of combination therapy using these substitutes instead of RBC and PLT transfusion in a rabbit model with trauma-induced massive hemorrhage with coagulopathy.

STUDY DESIGN AND METHODS

Thrombocytopenia (PLT count approximately 40,000/μL) was induced in rabbits by repeated blood withdrawal and isovolemic transfusion with autologous RBCs. Thereafter, lethal hemorrhage was induced in rabbits by noncompressible penetrating liver injury. Subsequently, H12-(ADP)-liposomes with platelet-poor plasma (PPP), platelet-rich plasma (PRP), or PPP alone were administered to stop bleeding. Once achieving hemostasis, HbVs, allogenic RBCs, or 5% albumin were transfused into rabbits to rescue them from fatal anemia following massive hemorrhage.

RESULTS

Administration of H12-(ADP)-liposomes/PPP as well as PRP (but not PPP) effectively stopped liver bleeding (100% hemostasis). The subsequent administration with HbVs as well as RBCs after hemostasis markedly rescued rabbits from fatal anemia (75% and 70% survivals for 24 hr, respectively). In contrast, 5% albumin administration rescued none of the rabbits.

CONCLUSION

Combination therapy with H12-(ADP)-liposomes and HbVs may be effective for damage control resuscitation of trauma-induced massive hemorrhage.

Met-Hemoglobin Is a Biomarker for Poor Oxygen Delivery in Infants Following Surgical Palliation

BACKGROUND

Infants with cyanotic congenital heart disease demonstrate wide fluctuations in hemoglobin (Hb), oxygen saturation, and cardiac output following palliation. Methemoglobin (Met-Hb), the product of Hb oxidation, may represent a compensatory mechanism during hypoxia and may be utilized as a biomarker.

METHODS

Arterial and venous Met-Hb levels were obtained from infants requiring palliation. The primary outcome was to describe the relationship between Met-Hb and other indices of tissue oxygenation (venous saturation, estimated arteriovenous oxygen difference [Est AV-Diff], and lactate). Secondary outcomes were to determine the impact of elevated Met-Hb levels ≥1.0% and the effect of red blood cell (RBC) transfusion on Met-Hb levels.

RESULTS

Fifty infants and 465 Met-Hb values were studied. Venous Met-Hb levels were significantly higher than arterial levels (venous: 0.84% ± 0.36% vs arterial: 0.45% ± 0.18%; P < .001). Venous Met-Hb demonstrated a significant inverse relationship with venous oxygen saturation (R = -0.6; P < .001) and Hb (R = -0.3, P < .001) and a direct relationship with the Est AV-Diff (R = 0.3, P < .001). A total of 129 (29.6%) venous Met-Hb values were elevated (≥1.0%) and were associated with significantly lower Hb and venous saturation levels and higher Est AV-Diff and lactate levels. Methemoglobin levels decreased significantly following 65 RBC transfusions (0.94 ± 0.40 vs 0.77 ± 0.34; P < .001). Linear mixed models demonstrated that higher venous Met-Hb levels were associated with lower measures of tissue oxygenation and not related to any preoperative clinical differences.

CONCLUSION

Methemoglobin may be a clinically useful marker of tissue oxygenation in infants following surgical palliation.

Putting xanthine oxidoreductase and aldehyde oxidase on the NO metabolism map: Nitrite reduction by molybdoenzymes

Nitric oxide radical (NO) is a signaling molecule involved in several physiological and pathological processes and a new nitrate-nitrite-NO pathway has emerged as a physiological alternative to the "classic" pathway of NO formation from L-arginine. Since the late 1990s, it has become clear that nitrite can be reduced back to NO under hypoxic/anoxic conditions and exert a significant cytoprotective action in vivo under challenging conditions. To reduce nitrite to NO, mammalian cells can use different metalloproteins that are present in cells to perform other functions, including several heme proteins and molybdoenzymes, comprising what we denominated as the "non-dedicated nitrite reductases". Herein, we will review the current knowledge on two of those "non-dedicated nitrite reductases", the molybdoenzymes xanthine oxidoreductase and aldehyde oxidase, discussing the in vitro and in vivo studies to provide the current picture of the role of these enzymes on the NO metabolism in humans.

Gaseous Signaling Molecules in Cardiovascular Function: From Mechanisms to Clinical Translation

Carbon monoxide (CO), hydrogen sulfide (H₂S), and nitric oxide (NO) constitute endogenous gaseous molecules produced by specific enzymes. These gases are chemically simple, but exert multiple effects and act through shared molecular targets to control both physiology and pathophysiology in the cardiovascular system (CVS). The gases act via direct and/or indirect interactions with each other in proteins such as heme-containing enzymes, the mitochondrial respiratory complex, and ion channels, among others. Studies of the major impacts of CO, H₂S, and NO on the CVS have revealed their involvement in controlling blood pressure and in reducing cardiac reperfusion injuries, although their functional roles are not limited to these conditions. In this review, the basic aspects of CO, H₂S, and NO, including their production and effects on enzymes, mitochondrial respiration and biogenesis, and ion channels are briefly addressed to provide insight into their biology with respect to the CVS. Finally, potential therapeutic applications of CO, H₂S, and NO with the CVS are addressed, based on the use of exogenous donors and different types of delivery systems.

Transfusion Decision Making in Pediatric Critical Illness

Transfusion decision making (TDM) in the critically ill requires consideration of: (1) anemia tolerance, which is linked to active pathology and to physiologic reserve, (2) differences in donor RBC physiology from that of native RBCs, and (3) relative risk from anemia-attributable oxygen delivery failure vs hazards of transfusion, itself. Current approaches to TDM (e.g. hemoglobin thresholds) do not: (1) differentiate between patients with similar anemia, but dissimilar pathology/physiology, and (2) guide transfusion timing and amount to efficacy-based goals (other than resolution of hemoglobin thresholds). Here, we explore approaches to TDM that address the above gaps.

Oxidative stress and hemoglobin-cholesterol adduct in renal patients with different LDL phenotypes

PURPOSE

Unfavorable lipid profile is a major risk factor for cardiovascular disease in renal pathology. In this study, we compared chronic renal patients and healthy controls with different LDL phenotypes (A or B) in respect of various biochemical parameters related to cardiovascular disease.

METHODS

Oxidative stress and anti-oxidative defense parameters [thiobarbituric acid-reacting substances (TBARS), total oxidative status (TOS), total anti-oxidative status (TAS), total protein sulfhydryl (-SH) groups], as well as red blood cell cholesterol distribution were assessed in 40 renal patients and 40 control subjects by standardized assays. LDL particle diameters were determined by polyacrylamide gradient gel electrophoresis. LDL particles are subdivided according to their size into large LDL A phenotype (diameter >25.5 nm) and small LDL B phenotype (diameter ≤25.5 nm).

RESULTS

Renal patients with LDL A phenotype had increased oxidative stress (TOS: p < 0.01, and TBARS: p < 0.001) and decreased total SH- groups (p < 0.001) compared to controls with the same LDL phenotype. A notable decrease in hemoglobin-cholesterol adduct was detected in patients with LDL A phenotype (p < 0.001) and LDL B phenotype (p < 0.05) compared with appropriate controls. LDL B phenotype was characterized with increased TBARS (p < 0.05) compared with LDL A phenotype in control group.

CONCLUSION

Increased oxidative stress, decreased anti-oxidative defense followed with unfavorable changes in hemoglobin-cholesterol binding capacity, could have important influence on cardiovascular disease risk in renal patients regardless of LDL phenotype.

[The effect of antioxidants on in vivo and in vitro methemoglobin formation in erytrocytes of patients with Parkinson`s disease]

Methemoglobin formation was examined in erytrocytes of 16 patients with Parkinson`s disease (PD) (stage 3-4 by the Hoehn and Yahr scale). The patients receiving levodopa-containing drugs (madopar, nakom) were also treated with intramuscular injections of mexidol (daily dose 100 mg/day) for 14 days. Control group included 12 clinically healthy persons. The erythrocyte methemoglobin content was determined by electronic paramagnetic resonance (EPR) using the EPR signal intensity with g-factor 6.0. The methemoglobin content was significantly higher in erythrocytes of PD patients than in healthy donors. The complex therapy with mexidol normalized the methemoglobin content in erythrocytes of PD patients. Incubation in vitro of erythrocytes of donors and PD patients with acrolein increased the methemoglobin content, while incubation with carnosine normalized the methemoglobin content in erythrocytes of PD patients. Prophylactic (i.e. before acrolein addition) and therapeutic administration of carnosine to the incubation system with acrolein decreased the methemoglobin content to its initial level. Results of this study suggest that inclusion of the antioxidants mexidol and carnosine in the scheme of basic therapy of PD may reduce side effects associated with methemoglobinemia.

Oxygen tension, H2S, and NO bioavailability: is there an interaction?

Molecular oxygen (O2) is an essential component for survival and development. Variation in O2 levels leads to changes in molecular signaling and ultimately affects the physiological functions of many organisms. Nitric oxide (NO) and hydrogen sulfide (H2S) are two gaseous cellular signaling molecules that play key roles in several physiological functions involved in maintaining vascular homeostasis including vasodilation, anti-inflammation, and vascular growth. Apart from the aforementioned functions, NO and H2S are believed to mediate hypoxic responses and serve as O2 chemosensors in biological systems. In this literature review, we briefly discuss NO and H2S and their roles during hypoxia.

In Vitro Protective Effect and Antioxidant Mechanism of Resveratrol Induced by Dapsone Hydroxylamine in Human Cells

Dapsone (DDS) hydroxylamine metabolites cause oxidative stress- linked adverse effects in patients, such as methemoglobin formation and DNA damage. This study evaluated the ameliorating effect of the antioxidant resveratrol (RSV) on DDS hydroxylamine (DDS-NHOH) mediated toxicity in vitro using human erythrocytes and lymphocytes. The antioxidant mechanism was also studied using in-silico methods. In addition, RSV provided intracellular protection by inhibiting DNA damage in human lymphocytes induced by DDS-NHOH. However, whilst pretreatment with RSV (10-1000 μM significantly attenuated DDS-NHOH-induced methemoglobinemia, but it was not only significantly less effective than methylene blue (MET), but also post-treatment with RSV did not reverse methemoglobin formation, contrarily to that observed with MET. DDS-NHOH inhibited catalase (CAT) activity and reactive oxygen species (ROS) generation, but did not alter superoxide dismutase (SOD) activity in erythrocytes. Pretreatment with RSV did not alter these antioxidant enzymes activities in erythrocytes treated with DDS-NHOH. Theoretical calculations using density functional theory methods showed that DDS-NHOH has a pro-oxidant effect, whereas RSV and MET have antioxidant effect on ROS. The effect on methemoglobinemia reversion for MET was significantly higher than that of RSV. These data suggest that the pretreatment with resveratrol may decrease heme-iron oxidation and DNA damage through reduction of ROS generated in cells during DDS therapy.

Accelerated RBC senescence as a novel pathologic mechanism of blood stasis syndrome in traditional East Asian medicine

Blood stasis syndrome (BSS) is an important pathologic condition in traditional East Asian medicine, characterized by multiple signs and symptoms, including sublingual varicosis, angiotelectasis, slow and choppy pulse, local fixed pain, nyctalgia, menstrual cramps, dark-purple tongue and infra-orbital darkness. However, recent studies have been restricted to the circulatory disorder and could not suggest the pathologic core to explain all of the characteristics of BSS. Here, we review the current research on the senescence of red blood cells (RBCs), focusing on the correlation between the pathologic properties of senescent RBCs and BSS-specific manifestations. The accumulation of senescent RBCs and their products induce pathological conditions that affect blood flow resistance and cause thrombosis, vasoconstriction and methemoglobinemia. These pathological alterations are identical to the characteristics of BSS, therefore supporting the hypothesis that accelerated RBC aging could be considered as a novel pathologic mechanism of BSS.

Bio-content of Telferia occidentalis and their effect on methemoglobin formation in sickled erythrocytes

OBJECTIVE

To perform phytochemical and mineral analyses on leaves, stem and seeds of Telferia occidentalis (T. occidentalis), and examine the inhibition of methemoglobin build-up in sickled erythrocytes.

METHODS

The phytochemical evaluation was carried out by qualitative and quantitative analyses, whereas mineral elements were quantitatively analyzed. The effect of T. occidentalis on methemoglobin formation in sickled erythrocytes was examined using the ratio of ferric ion (Fe(2+)) to ferrous ion (Fe(3+)) concentration, as index.

RESULTS

The phytochemical evaluation showed the presence of total phenolics, cyanogenic glycosides, flavonoids and alkaloids. Mineral analysis revealed potassium, magnesium, sodium, iron and zinc. Extract concentrations (0.2%-0.8% w/v) of leaves, seeds and stem of T. occidentalis have shown the ability to inhibit the formation of methemoglobin in sickled erythrocytes. The methanolic leaves extract showed the highest effect at 0.8% w/v.

CONCLUSIONS

These results suggest that T. occidentalis has the capacity to mop-up methemoglobin in sickled erythrocytes, and may therefore enhance oxygen-hemoglobin binding and transport in sickle cell disease patients.

Endothelial nitric oxide synthase in red blood cells: key to a new erythrocrine function?

Red blood cells (RBC) have been considered almost exclusively as a transporter of metabolic gases and nutrients for the tissues. It is an accepted dogma that RBCs take up and inactivate endothelium-derived NO via rapid reaction with oxyhemoglobin to form methemoglobin and nitrate, thereby limiting NO available for vasodilatation. Yet it has also been shown that RBCs not only act as "NO sinks", but exert an erythrocrine function - i.e an endocrine function of RBC - by synthesizing, transporting and releasing NO metabolic products and ATP, thereby potentially controlling systemic NO bioavailability and vascular tone. Recent work from our and others laboratory demonstrated that human RBCs carry an active type 3, endothelial NO synthase (eNOS), constitutively producing NO under normoxic conditions, the activity of which is compromised in patients with coronary artery disease. In this review we aim to discuss the potential role of red cell eNOS in RBC signaling and function, and to critically revise evidence to this date showing a role of non-endothelial circulating eNOS in cardiovascular pathophysiology.