Carbon monoxide production associated with ineffective erythropoiesis

Carbon monoxide breath test assessment of mild hemolysis in Gilbert's syndrome

BACKGROUND

Mild hemolysis is difficult to determinate by traditional methods, and its role in Gilbert's syndrome (GS) is unclear. The main aims were to inspect the erythrocyte (RBC) survival in GS by using Levitt's carbon monoxide (CO) breath test and to assess its contribution to unconjugated hyperbilirubinemia.

METHODS

Fifty subjects with GS and 1 with type-II Crigler-Najjar syndrome (CN2) received RBC lifespan measurement with Levitt's CO breath test. Mean RBC lifespan was compared with normal referral value. Correlations of serum total bilirubin (TB) with RBC lifespan, blood panel data, demographic factors, and uridine diphosphate glucuronosyltransferase (UGT1A1) mutation load were calculated by Spearman analysis. Susceptibility factors for mild hemolysis were analyzed by multivariate regression analysis.

RESULTS

The mean RBC lifespan of the GS subjects was significantly shorter than the normal reference value (95.4 ± 28.9 days vs 126 days; t = -7.504, P < .01), with 30.0% below the lower limit of the normal reference range (75 days). The RBC lifespan of the participant with CN2 was 82 days. Serum TB correlated positively with UGT1A1 mutation load (γ = 0.281, P = .048), hemoglobin (γ = .359, P = .010) and hematocrit (γ = 0.365, P = .010), but negatively with RBC lifespan (γ = -0.336, P = .017). No significant susceptibility factors for mild hemolysis were found.

CONCLUSIONS

The results indicate that mild hemolysis indeed, exists in a portion of patients with GS and might serve as an important contributor to unconjugated hyperbilirubinemia in addition to UGT1A1 polymorphism. Further studies on the mechanism and the potential risks in various medical treatments might be wanted.

Human erythrocyte lifespan measured by Levitt's CO breath test with newly developed automatic instrument

Existing standard techniques for erythrocyte (RBC) lifespan measurement, such as quantitation of labeling with isotopes or biotin, are cumbersome and time-consuming. Given that endogenous CO originates mainly from degraded RBCs, a team lead by Levitt developed a CO breath test to enable more efficient RBC lifespan estimation. The purpose of this study was to evaluate the reliability of Levitt's CO breath test method with our newly developed automatic instrument. RBC lifespan measurements conducted by Levitt's CO breath test method were conducted in 109 healthy subjects and 91 patients with chronic hemolytic anemia. In healthy subjects, the RBC lifespan was 126 ± 26 days, similar to values obtained with classical standard labeling methods. RBC lifespan did not differ significantly between males and females or between juveniles and adults, and did not correlate with age. To our knowledge, this datum represents an RBC lifespan average for the largest sample to date. In subjects with hemolytic anemia, RBC lifespan was 29 ± 14 days, which is significantly shorter than that of the healthy subjects (p = 0.001). Using 75 days as a cut-off, diagnostic accuracy for hemolytic anemia in the present study sample was 100%. In conclusion, the present results indicate that Levitt's CO breath test is an ideal method for human RBC lifespan measurement, and the newly developed automatic instrument is reliable and convenient for clinical practice.

Measurement of red cell lifespan and aging

SUMMARY

The measurement of red blood cell (RBC) survival has a long history, and a wide variety of methods have been utilized for this purpose. Current methods are of 2 types. First, those that label a representative sample of RBCs of all ages from the blood and then measure their rate of disappearance upon reinfusion. This category includes the (51)Cr and biotin labels. Second, those that use a metabolic precursor or product to determine the turnover of hemoglobin. Examples of these are carbon monoxide production and incorporation of labeled glycine. Recent studies with the covalent, nonradioactive biotin label show its unique suitability for both the accurate measurement of red cell survival and the determination of changes in red cell properties as they age in vivo.

The measurement of endogenous carbon monoxide production

Recent findings that heme oxygenase-1 can be induced by oxidative stress and inflammation in many different cellular systems, and that carbon monoxide (CO) produced as a by-product of this enzyme is a signaling molecule, have generated a major research area with hundreds of studies published over the last few years. The measurement of expired CO concentration has been used in humans as a biomarker of induced heme oxygenase resulting from inflammation or oxidative stress, but a precise method of measuring endogenous CO production that can be easily used to study patients is needed. The present study describes such a method. The described method allows calculation of the rate of heme catabolism with a precision of ±2 μmol/h, ∼10% of the mean normal rate in subjects used in this investigation. This method, which is subject-patient friendly, precise, and inexpensive to perform, should be applicable to studies performed on humans with induced heme oxygenase and studies of effects of therapy for inflammatory and hemolytic diseases.

Abnormal endogenous carbon monoxide production in children with ineffective erythropoiesis

The aim of this study was to evaluate the extent of endogenous carbon monoxide production in subjects with ineffective erythropoiesis. Carboxyhaemoglobin concentrations were measured in eight transfused and eight nontransfused thalassemic patients. Measurements were made on venous blood collected under controlled conditions and were corrected by simultaneous measurement of HbF levels. Nontransfused thalassaemic patients with abnormal erythropoiesis were found to have elevated levels of carboxyhaemoglobin, significantly higher than those found in transfused subjects, as well as decreased cardiac performance. It is important to consider carboxyhaemoglobin levels in planning transfusion programmes.

Increased levels of carboxyhemoglobin and serum iron as an indicator of increased red cell turnover in preeclampsia

Patients with severe preeclampsia are reported to have microangiopathic hemolytic anemia. This study demonstrates that increased red cell turnover with heme catabolism is also common in mild preeclampsia. Heme catabolism results in equimolar production of carboxyhemoglobin, iron, and bilirubin. A concomitant rise in these constituents of venous blood would support this hypothesis. Patients with antepartum preeclampsia had mean carboxyhemoglobin concentrations (2.72% total hemoglobin) greater than those of control patients (0.65%) (p less than 0.001) and serum iron concentrations (98.5 micrograms/dl) greater than those of control patients (66.1 micrograms/dl) (p less than 0.01). Bilirubin concentrations were not different. Post partum, carboxyhemoglobin and iron concentrations returned toward normal (1.38% and 50.2 micrograms/dl, respectively). Disparity in the magnitude of increase of heme catabolites produced in equimolar proportion is explained by differences in the kinetics of clearance. The data are most consistent with increased destruction of maternal red cells, even in mild preeclampsia. Potential implications of elevated carboxyhemoglobin on maternal and fetal oxygenation are discussed.

Primary refractory anemia: clinical and laboratory study of erythropoiesis in 16 patients

Erythropoiesis was studied in vitro in 16 selected patients with primary refractory anemia without excess of blasts who have been followed for an average of 4.8 years. The number of erythroid colonies and bursts grown in vitro from the patients' marrows did not correlate with any parameter of their disease or their prognosis. The response of marrow erythroid precursor cells to erythropoietin was found to be normal. In no case was a serum or IgG inhibitor of erythropoiesis detected either by quantitation of heme synthesized by marrow cells or by the erythroblast cytotoxicity assay. A clinically significant response of the anemia to corticosteroids was noted in three out of 14 patients. Ten patients died during the followup period, eight of them as a consequence of their hematologic disorder. Bone marrow aplasia with pancytopenia developed in six cases, increased number of marrow blasts in two cases, myelofibrosis with myeloid metaplasia in one case and a spontaneous remission in another case. Refractory anemia without excess of blasts is a heterogeneous disorder with variable natural history including evolution into marrow aplasia.

Carboxyhaemoglobin and plasma thiocyanate: complementary indicators of smoking behaviour?

Carboxyhaemoglobin and plasma thiocyanate concentrations were measured in 79 non-smokers and 360 cigarette smokers. The mean levels were 0.73% and 7.09% carboxyhaemoglobin and 40 . 2 and 133 . 8 mumol thiocyanate/1 plasma respectively. With 1 . 6% carboxyhaemoglobin and 73 . 0 mumol thiocyanate/1 plasma as critical values the concentrations of carboxyhaemoglobin in 96.6% of subjects and of thiocyanate in 93.4% were compatible with reported smoking status. This difference between the two tests is significant (p less than 0 . 005). Statistical combination of the carboxyhaemoglobin and thiocyanate results, with the use of linear discrimination analysis, only marginally improved their diagnostic efficiency (96.8% of subjects were grouped correctly). This analysis did, however, successfully regroup 21 of 26 individuals with contradictory carboxyhaemoglobin and thiocyanate classifications. It is concluded that in this study determination of thiocyanate added little to the information obtained from carboxyhaemoglobin measurements alone.

The contributions of erythropoietic and nonerythropoietic haem turnover to the early labelle peak of endogenous CO formation in man

The endogenous production of 14CO during the first week after administration of glycine-2-14C (early labelled peak, ELP) was determined in 13 healthy subjects. The subjects were studied during normal, suppressed or stimulated erythropoiesis induced by hypertransfusion and phlebotomy, respectively. The production of 14CO was calculated from determinations of the specific activity of the body CO store and the endogenous production of CO. The incorporation of labelled glycine into circulating red cell haemo;globin haem was calculated from the maximal specific activity of haemoglobin haem and the total amount of Hb. The average ELP was 73.0 X 10(3) disintegrations per min (dpm) and the incorportion of glycine into circulating haemoglobin haem 491 X 10(3) dpm in controls. The ELP and the incorporation of glycine increased by 86% and 92%, respectively, in phlebotomized subjects and decreased by 37% and 62%, respectively, in hypertransfused subjects. A linear regression equation was calculated for the relationship between ELP and erythropoiesis, expressed as the incorportion of glycine into circulating haemoglobin haem. The residual ELP remaining in the absence of erythropoiesis was 24.9 X 10(3) dpm calculated from data of all the subjects, and 32.8 X 10(3) dpm calculated from data of controls and hypertransfused subjects only. In conclusion, erythropoietic haem turnover was found to contribute about 60% and nonerythropoietic (mainly hepatic) haem turnover about 40% of the ELP in man.

Quantification of ineffective erythropoiesis in megaloblastic anaemia by determination of endogenous production of 14CO after administration of glycine-2-14C

The determination of the early peak of 14CO production that results from haem turnover after administration of glycine-2-14C was studied in patients with pernicious anaemia. The accuracy of this technique in measuring ineffective erythropoiesis was assessed by comparison with other measurements of the severity of the disease. 6 patients were studied before specific treatment and 2 of these also after treatment. The endogenous production of 14 CO was calculated from determinations of the production of CO by a rebreathing technique and of the specific activity of CO washed out from the body CO store by oxygen breathing. The early labelled peak was increased 7-39 times compared to that in healthy control subjects and represented 35-86% of the total production of 14CO as compared to 13% in controls. The early labelled peak was significantly correlated to the Hb concentration, mean red cell volume and endogenous production of CO. 2 patients, twice examined, showed a moderately increased early labelled peak also after specific treatment. This was attributed to persistence of some ineffective erythropoiesis in 1 patient and possibly increased hepatic haem turnover in the other. The magnitude of the early labelled peak and the maximal activity of 14CO found in the samples of CO collected from the body CO store were significantly correlated. In conclusion, with the present method the early peak of 14CO reflected the ineffective erythropoiesis in patients with pernicious anaemia. The early labelled peak could be predicted from the maximal activity of 14CO found in the samples of CO washed out from the body CO store.

Estimation of ferrokinetic parameters by a mathematical model in patients with primary acquired sideroblastic anaemia

Ferrokinetic parameters were estimated in eight patients with primary acquired sideroblastic anaemia (PASA) by means of a mathematical model of iron kinetics. Both plasma 59Fe clearance and red cell utilization curves were used to identify the model parameters. The close agreement between experimental and theoretical data proved that the model can describe iron kinetics in sideroblastic anaemia. Ineffective erythropoiesis was found to be major factor in the production of the anaemia. Various degrees and patterns of peripheral haemolysis were observed. The storage iron was always markedly increased and a large non-erythroid iron turnover was calculated in the most severely affected patients. The results are compared with present knowledge of erythropoiesis in PASA.

Quantitation of ineffective erythropoiesis from the incorporation of [15N] delta-aminolaevulinic acid and [15N] glycin into early labelled bilirubin. II. Anaemic patients

The incorporation of [15N]delta-aminolaevulinic acid and [15N glycine into haemoglobin haem and early labelled bilirubin was measured in subjects with various haematological disorders. The clearance of [14C bilirubin was used to measure bilirubin production rate, and the magnitude of the various sources of bilirubin production and the percentage ineffective erythropoiesis were calculated. Ineffective erythropoiesis was found to be a major factor in the production of the anaemia in patients with the following disorders: megaloblastic anaemia associated with the Lesch-Nyhan syndrome, thalassaemia intermedia, sideroblastic anaemia, and the anaemia of chronic disorders. In three patients with iron-deficiency anaemia ineffective erythropoiesis was increased, but was of minor importance in the production of the anaemia, while in two patients with aplastic anaemia and one with macrocytosis of alcoholism there was no increase in ineffective erythropoiesis.

Quantitation of ineffective erythropoiesis from the incorporation of [15N] delta-aminolaevulinic acid and [15N] glycine into early labelled bilirubin. I. Normal subjects

The incorporation of [15N] glycine into early labelled bilirubin and haemoglobin haem was measured in four haematologically normal subjects, using the clearance of [14C] bilirubin to measure total bilirubin production rate. Hepatic haem turnover was calculated from the incorporation of [15N]=sigma-aminolaevulinic acid into early labelled bilirubin. From the exprimental data previously published data in normal subjects a method is derived for the quantitation of ineffective erythropoiesis which can be applied to similar studies in patients with haematological disorders.

Erythropoiesis and carbon monoxide production in Hodgkin's disease

Endogenous production of carbon monoxide (VCO), red cell survival and iron kinetics were studied in 15 subjects with Hodgkin's disease. The subjects were divided into two groups, namely: eight patients with anaemia (group A, haemoglobin (Hb) concentration less than 11.5 g/dl) and seven patients without anaemia (group B, Hb concentration greater than 11.5 g/dl). Red cell survival was not significantly different in the two groups being 91 +/- 40 days (mean +/- 1 SD) in group A and 111 +/- 54 days in group B. Relative VCO (mumol/mmol total body haem (TBH/d) was, however, significantly higher (0.01 greater than P greater than 0.001) in group A (20.7 +/- 4.7) compared to group B (12.0 +/- 3.8). When absolute VCO (mumol/d) was compared to the daily turnover of circulating red cell haemoglobin haem (Vhaem-c), the VCO/Vhaem-c quotient was 2.1 +/- 0.9 in group A and 1.2 +/- 0.3 in group B. Erythron turnover of iron (ET, mumol Fe/mmol TBH/d) was calculated through subtraction of the non-erythron turnover (NET) from the total plasma iron turnover (PIT). ET was significantly higher (0.05 greater than P greater than 0.01) in group A (39 +/- 21) than in group B (20 +/- 8). The conclusion drawn from the finding of significant increases in VCO and ET without and concomitant significant decrease in red cell survival in the anaemia group is that ineffective erythropoiesis, i.e. bone marrow haemolysis, seems to play an important role in the anaemia of Hodgkin's disease.

Heme catabolism, carbon monoxide production and red cell survival in anemia

Total heme catabolism has been studied through measurement of the endogenous production of carbon monoxide (VCO) in 8 patients with hemolysis, 7 with hypoproliferative anemia, 10 with refractory anemia and hypercellular bone marrow and 7 with splenomegaly, 6 of whom had myeloid metaplasia. Simultaneously, catabolism of circulating red cell hemoglobin heme (Vheme-c) was measured through labelling of the red cells with 51Cr, and the VCA/Vheme-c ratio was calculated for each patient. From a control group it was calculated that this ratio should vary around 1.5. Since no isotope studies were performed in the control group, no range could be defined. Among patients with hemolysis the VCO/Vheme-c ratio was found to vary between 1.3 and 1.8 except in 2 cases of paroxysmal nocturnal hemoglobinuria (PNH) and PNH?, respectively, in whom the ratios were found to be 0.6 and 0.7 suggesting some heme catabolism without corresponding CO formation. In the hypoproliferative group the ratio varied between 1.2 and 1.8 except in one patient treated with androgens, in whom the ratio was found to be 2.9, suggesting increased extraerythrocytic heme turnover. In patients with myeloid metaplasia the ratio varied between 1.3 and 1.8. On the other hand, the ratio varied getween 2.4 and 3.0 among patients with refractory anemia and hypercellular bone marrow, thus confirming earlier findings that in this type of anemia turnover of bone marrow heme is markedly increased. A significant correlation was found between VCO and initial morning COHb%(r equals 0.84). The conclusions drawn are (a) that Vheme-c sometimes represents less than 50% of total heme turnover and (b) that COHb and/or VCO reflect total heme turnover except in patients with blood loss or intravascular hemolysis with hemoglobinuria.

Carbon monoxide production from heme compounds by bacteria

Carbon monoxide formation from heme compounds by bacteria was investigated to study microbial hemoprotein catabolism with reference to heme degradation by mammalian tissues. Hemolytic and nonhemolytic bacteria were incubated aerobically and anaerobically with the following substrates: erythrocytes, hemoglobin, myoglobin, cytochrome c, hematin, iron hematoporphyrin, copper hematoporphyrin, protoporphyrin, and bilirubin. After 18 hr at 37 C the evolved CO was measured by gas chromatography. None of the bacteria formed CO anaerobically. Under aerobic conditions both alpha-hemolytic Streptococcus mitis and hemolytic Bacillus cereus formed CO from all of the heme compounds tested, whereas nonhemolytic Streptococcus mitis did not evolve CO from any of the substrates. The hemolytic bacteria did not produce CO when the iron of heme was either replaced by copper or removed, as in copper hematoporphyrin and in protoporphyrin, respectively.

Endogenous production of carbon monoxide in normal and erythroblastotic newborn infants

The endogenous production of carbon monoxide ( V(CO)) in newborn infants was measured by serial determinations of blood carboxyhemoglobin during rebreathing in a closed system. Mean V(CO) in nine full-term infants was 13.7 +/-3.6 mul CO/kg per hr (SD), and in four erythroblastotic infants V(CO) ranged from 37 to 154 mul CO/kg per hr preceding exchange transfusion. Mean red cell life-span (MLS) and total bilirubin production were calculated from V(CO). MLS in normal newborns was 88 +/-15 days (SD), and bilirubin production was 8.5 +/-2.3 mg/kg per 24 hr. This is more than twice the amount of bilirubin normally produced in the adult per kilogram of body weight. Normal infants achieved a net excretion of bilirubin of at least 5.6 +/-2.3 mg/kg per 24 hr (SD) as calculated from the bilirubin production and the measured rise in serum bilirubin concentration.The measurement of V(CO) should prove valuable in the study of red blood cell survival and bilirubin metabolism in the newborn infant.

Catabolism of heme in vivo: comparison of the simultaneous production of bilirubin and carbon monoxide

The quantitative relationship between the catabolism of heme and the formation of bilirubin and carbon monoxide (CO) was studied in untreated rats and in animals treated with phenobarbital or the porphyrogenic drug, allylisopropylacetamide (AIA). A novel metabolic chamber permitting continuous collection of the bile and breath was utilized for quantitation of bilirubin-(14)C and (14)CO after the administration of hematin-(14)C or glycine-(14)C. After intravenous infusion of hematin-(14)C, control and phenobarbital-treated rats produced equimolar amounts of labeled bilirubin and CO; a minor fraction of the infused radioactivity appeared in the bile in other metabolites. The equimolar relationship in the formation of bilirubin and CO was also observed after pulse-labeling with glycine-2-(14)C; in phenobarbital-treated rats both metabolites were formed at an increased rate as compared to controls. By contrast, AIA treatment reduced the fractional conversion of hematin-(14)C to bilirubin and CO; a major fraction of the infused radioactivity appeared in the bile in metabolites other than bilirubin. In addition, in AIA-treated animals the molar CO/bilirubin recovery ratio was consistently greater than 1.0. Comparable results were obtained in AIA-treated rats after pulse-labeling with glycine-2-(14)C. These findings suggest that (a) in control and phenobarbital-treated rats infused hematin and heme formed in the liver are converted predominantly to bilirubin and CO, appearing in equimolar amounts; only a minor fraction of the hematin is degraded to other metabolites; (b) treatment with phenobarbital results in a proportional increase in the formation of both bilirubin and CO, reflecting increased heme synthesis and degradation in the liver; and (c) treatment with the porphyrogenic drug AIA shifts the CO/bilirubin ratio in favor of the gas, and enhances the formation of nonbilirubin metabolites.

Mechanically induced intravascular hemolysis in dogs

The endogenous production of carbon monoxide and the flow of hemoglobin to and from plasma were measured in 11 anesthetized dogs after pumping blood through an extracorporeal circuit for short periods. Two different pumps were used. In all animals the increase in CO production was greater than could be explained by catabolism of hemoglobin lost from plasma, an average of 11.4 times greater with one pump and 2.49 times greater with the other pump. Evidence is presented that this discrepancy could not be explained by catabolism of heme other than that of hemoglobin, and we therefore concluded that rates of hemoglobin catabolism were much greater than indicated by plasma hemoglobin kinetics and that extravascular hemolysis is a major cause of erythrocyte destruction during mechanically induced hemolysis. Extravascular hemolysis apparently caused an average of 72.9% and 37.2% (with the two pumps) of the total quantity of erythrocytes destroyed during pumping and for 3 hours after pumping.