Plasma levels of sphingosine 1-phosphate are strongly correlated with haematocrit, but variably restored by red blood cell transfusions.

Anaemia and RBC (red blood cell) transfusion may be associated with worse clinical outcomes, especially with longer blood storage duration prior to transfusion. The mechanisms underlying these harmful effects are unknown. RBCs have been proposed to buffer plasma S1P (sphingosine 1-phosphate), a lysophospholipid essential for the maintenance of endothelial integrity and important in the regulation of haematopoietic cell trafficking. The present study examined the effect of anaemia, RBC transfusion and RBC storage duration on plasma S1P levels. Plasma S1P from 30 individuals demonstrated a linear correlation with Hct (haematocrit; R2 = 0.51, P < 0.001) with no evidence for a plateau at Hct values as low as 19%. RBC transfusion in 23 anaemic patients with baseline mean Hct of 22.2 ± 0.34% (value is the mean ± S.D.) increased Hct to 28.3 ± 0.6% at 72 h. Despite an Hct increase, RBC transfusion failed to elevate plasma S1P consistently. A trend towards an inverse correlation was observed between RBC storage duration and the post-transfusion increase in plasma S1P. After 30 days of storage, RBC S1P decreased to 19% of that observed in fresh (3-7-day-old) RBC segments. RBC membranes contain low levels of both S1P phosphatase and S1P lyase activities that may account for the decline in S1P levels with storage. Our results support a role for RBCs in buffering plasma S1P and identify a disturbance in the capacity after transfusion. Changes in S1P content may contribute to an RBC storage lesion. Further studies should investigate the clinical significance of alterations in circulating S1P levels and the potential value of enriching stored RBCs with S1P.

Investigations of free anthraquinones from rhubarb against alpha-naphthylisothiocyanate-induced cholestatic liver injury in rats.

The protective effects of anthraquinones from Rhubarb, a Chinese herbal medicine, consisting of the root and rhizome of Rheum palmatum L., R. tanguticum Maxim. Ex Balf., or R. officinale Baill. (family Polygonaceae) were investigated and compared in rats with liver injury induced by alpha-naphthylisothiocyanate. alpha-Naphthylisothiocyanate was given intragastrically in rats, liver injury with cholestasis developed within 36 hrs, as indicated by characteristic serum levels of glutamate-pyruvate transaminase, glutamic oxaloacetic transaminase, total bilirubin, direct bilirubin, alkaline phosphatase, gamma-glutamyltransferase and total bile acid. The intragastrical administration of rhein, aloe-emodin and physione to alpha-naphthylisothiocyanate-treated rats reduced significantly the serum level of both glutamate-pyruvate transaminase, glutamic oxaloacetic transaminase and the serum total bilirubin, direct bilirubin, alkaline phosphatase, gamma-glutamyltransferase and total bile acid. For all hepatic biochemical markers and cholestasis index, rhein was most efficient. By comparison, the administration of emodin and chrysophanol did not reduce the serum levels of hepatic enzymes glutamate-pyruvate transaminase and glutamic oxaloacetic transaminase but decreased the levels of serum total bilirubin, direct bilirubin, alkaline phosphatase, gamma-glutamyltransferase, and total bile acid, showing their partial protective effects on cholestatic liver injury. The liver in alpha-naphthylisothiocyanate-treated rats showed cholangiolitic hepatitis characterized by intrahepatic cholestasis, necrosis of hepatocytes and biliary epithelial cells and bile obstruction. The concurrent intragastrical administration of rhein reduced the severity of all morphological alteration, especially the neutrophil infiltration and sinusoid congestion. Rhein, aloe-emodin, and physione all exhibited protective effects on hepatocytes and cholangiocytes against alpha-naphthylisothiocyanate-induced damage, whereas emodin and chrystophanol provided partial protection.

Ubiquitin aldehyde increases adenosine triphosphate-dependent proteolysis of hemoglobin alpha-subunits in beta-thalassemic hemolysates.

Two major causes of the anemia in beta-thalassemia are a deficiency in hemoglobin (Hb) beta-subunit (and consequently HbA) synthesis and, due to the resulting excess of Hb alpha-subunits, erythroid cell hemolysis. The hemolytic component might be ameliorated by increasing the intracellular proteolysis of the excess alpha-subunits. Isolated 3H-labeled alpha-chains are known to be degraded primarily by the adenosine triphosphate (ATP)- and ubiquitin (Ub)-dependent proteolysis pathway in unfractionated beta-thalassemic hemolysates. Our objective was to increase this degradation by targeted intervention. Ub aldehyde (Ubal), a synthetic inhibitor of isopeptidases (proteases that hydrolyze the bond between the Ub polypeptide and its protein adduct), was added to reaction mixtures containing a hemolysate from the blood cells of one of four beta-thalassemic donors and 3H-alpha-chains or 3H-alpha-globin as a substrate. Optimum enhancement of ATP-dependent degradation occurred at 0.4 to 1.5 micromol/L Ubal and ranged from 29% to 115% for 3H-alpha-chains and 47% to 96% for 3H-alpha-globin among the four hemolysates. We suggest that Ubal stimulates 3H-alpha-subunit proteolysis by inhibition of an isopeptidase(s) that deubiquitinates, or "edits," Ub-3H-alpha-subunit conjugates, intermediates in the degradative pathway. In control studies, similarly low Ubal concentrations did not enhance the degradation of 3H-alpha2beta2 (HbA) tetramers or inhibit the activities of methemoglobin reductase and four selected glycolysis pathway enzymes. These and other results may be the basis for a therapeutic approach to beta-thalassemia.

Plasma indicators of muscle damage in a model of nutritional myopathy in weaner sheep.

Subclinical nutritional myopathy was induced in 5-month-old sheep by feeding them a diet low in vitamin E and selenium. Subsequently clinical myopathy was induced by dosing with protected polyunsaturated fatty acids. Plasma activities of creatine kinase (CK), pyruvate kinase, aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase and aldolase, enzymes of muscle origin, all remained above their reference ranges in clinically affected sheep, but fluctuated widely. Similar fluctuations occurred in subclinically affected animals, resulting in some activities being within the reference ranges and some above, at different times. Plasma malondialdehyde, an indicator of lipid peroxidation, proved of no diagnostic value. Terminal plasma CK activities were significantly correlated with microscopic damage in the vastus lateralis (VL), but not the vastus intermedius (VI) or the tensor fascia lata (TFL) muscles. AST was the most highly correlated with damage in VI and VL. In two clinically affected sheep successfully treated with an oral dose of alpha-tocopherol acetate all enzymes decreased steadily to within their reference ranges, at rates probably related to their plasma half-lives. These results suggest that measurement of plasma CK activity would be useful in monitoring recovery of treated sheep.

Clearance of argininosuccinate synthetase from the circulation in acute liver disease.

Argininosuccinate synthetase is an enzyme which has been found to be a specific marker for liver damage. In patients with acute hepatitis, the concentration in serum increases at the onset of the disease, but later decreases more quickly, so that the time required for normalization is shorter than that of alanine aminotransferase. This is probably caused by rapid clearance of argininosuccinate synthetase from the serum. Rapid clearance was demonstrated in experimental animals given purified enzymes intravenously. Argininosuccinate synthetase disappeared from the serum with a half life of about 15 min, while the half lives of alanine aminotransferase and aspartate aminotransferase were 4 and 5 h, respectively, under the same conditions.

The effects of heat upon the glyoxalase I isoenzyme.

It was observed during the course of routine casework that different bloodstains from the same individual could produce anomalies in the glyoxalase I band patterns. Bloodstains were heated at different temperatures for periods of 4 and 6 h and then examined using electrophoretic techniques. It was demonstrated that upon heating, band alterations in the glyoxalase I Type 1 phenotype can occur, causing the analyst to render the results inconclusive.

Immunogenetics of early-onset insulin-dependent diabetes mellitus among the Japanese: HLA, Gm, BF, GLO, and organ-specific autoantibodies--the J.D.S. study.

The Japan Diabetes Society (JDS) conducted a multicenter study on the immunogenetics of early-onset insulin-dependent diabetes mellitus (IDDM) of the Japanese. Human leukocyte antigen (HLA), properdin factor B (BF), immunoglobulin heavy-chain complex (Gm), and glyoxalase of erythrocytes (GLO) were typed, and organ-specific autoantibodies, including islet cell antibody (ICA), were assayed in 159 Japanese IDDM patients and their family members and in 258 healthy Japanese controls. The HLA-DRw9 phenotype and HLA-Bw61/DRw9 haplotype were significantly increased among the patients with autoantibodies other than ICA but with no autoimmune diseases (RR = 5.84, cP less than 0.001; and RR = 7.45, P less than 0.001), whereas the HLA-DR4 phenotype and HLA-Bw54/DR4 haplotype were significantly increased in those without either the autoantibodies or autoimmune diseases (RR = 2.64, cP less than 0.001; and RR = 4.55, P less than 0.001). The HLA-DR4 phenotype was significantly increased in the patients with autoimmune thyroid diseases (RR = 6.21, cP less than 0.05). In all groups of patients, the HLA-DR2 phenotype was significantly decreased, and the relative risk of the HLA-DRw9/DR4 genotype was highest among all HLA-DR genotypes. No significant association was found between HLA type and the duration or incidence of ICA. Gm types of g and gft were significantly increased in the patients with the autoantibodies (RR = 2.11, P less than 0.05; and RR = 34.11, P less than 0.05), whereas the BF-F phenotype was significantly decreased in the patients either with or without autoantibodies (RR = 0.43, P less than 0.05; and RR = 0.46, P less than 0.05). There was no association between IDDM and GLO type. These data indicate that immunogenetic bases underlying IDDM of the Japanese are heterogeneous, as are those in Caucasians.

Erythropoietin, aluminium, and anaemia in patients on haemodialysis.

Effects of erythropoietin treatment on haem synthesis in peripheral blood were evaluated in 11 patients on haemodialysis. After 2 weeks of erythropoietin, mean (SEM) uroporphyrinogen-l synthase activity increased significantly from 88 (10) to 116 (9) pmol/h per mg protein. Haem synthase activity, thought to be the rate-limiting step in erythroid haem synthesis, also showed a significant increase from 4.5 (0.8) to 8.4 (1.8) pmol/h per 10(6) reticulocytes. 4 patients, who showed only a partial response to erythropoietin, had significantly higher serum aluminium concentrations than the 7 who responded fully (225 [44] vs 55 [23] micrograms/l); erythrocyte protoporphyrin concentrations in partial responders were also much higher than in responders (973 [120] vs 388 [29] nmol/l). Aluminium intoxication may cause resistance to erythropoietin by interference with haem synthesis, with accumulation of protoporphyrin.

The human red blood cell glyoxalase system in diabetes mellitus.

Methylglyoxal and other alpha-oxoaldehydes are formed from glycolytic intermediates and may be involved in the development of diabetic microangiopathy. Glyoxalase I and glyoxalase II metabolise methylglyoxal to D-lactic acid, via the intermediate S-D-lactoylglutathione. The activities of the glyoxalase enzymes and the concentrations of methylglyoxal and S-D-lactoylglutathione were measured in erythrocytes of 45 control and 85 diabetic subjects (41 with retinopathy and 44 uncomplicated). The concentration of S-D-lactoylglutathione was increased in diabetic patients vs. controls (21.4 +/- 9.3 vs. 12.4 +/- 4.8 mumol/l, P less than 0.001), as was methylglyoxal (3.6 +/- 2.3 vs. 1.4 +/- 0.2 mumol/l, P less than 0.001). There were no significant differences in the activities of glyoxalase I and glyoxalase II between diabetic patients and controls. For insulin-dependent patients only, those without retinopathy had a higher activity of glyoxalase II than those with retinopathy (P less than 0.05). A group of age- and duration-matched insulin-dependent diabetic patients with retinopathy also had a higher activity of glyoxalase I compared with a group of diabetic patients without retinopathy (P less than 0.025). This study provides evidence for elevated concentrations of oxoaldehydes in diabetes mellitus which might have pathogenic significance.

Decreased leukocyte ferrochelatase activity in erythropoietic protoporphyria.

We studied the porphyrin metabolism of a 7-year-old Japanese boy with erythropoietic protoporphyria (EPP) and his family members. Leukocyte ferrochelatase activity was markedly decreased in this patient, being approximately 12% of the mean value of normal controls (4 aged-matched healthy boys). In contrast, leukocyte delta-aminolevulinic acid (ALA) synthase activity was normal. The free protoporphyrin content of erythrocytes was greatly increased (4.3 mg/100 ml RBC), while erythrocyte ALA dehydratase and porphobilinogen (PBG) deaminase activities were 1.7- and 2.2-fold of respective control values. A survey of his family revealed that 12 of 19 members probably had manifest EPP or were EPP carriers. These results suggest that, in EPP, there might be an inherited impairement of ferrochelatase activity which gives rise to an elevation of erythroblast ALA dehydratase and PBG deaminase activities to compensate for a resultant decrease in heme production.

Glyoxalase activity in human red blood cells fractioned by age.

Human red blood cells were fractionated by density, which correlates with cell age, and the activities of glyoxalase I and glyoxalase II were determined for each fraction. The activity of glyoxalase I and glyoxalase II both significantly increased during maturation of the red blood cells (P less than 0.001), except in the most dense, old cell fraction where both glyoxalase activities decreased. The increase in glyoxalase activity from the reticulocyte-rich fraction to mature erythrocytes was substantial and markedly different from other glycolytic enzymes which typically decrease. This suggests that glyoxalase activity changes markedly during and probably after the maturation of reticulocytes to erythrocytes. The decrease in glyoxalase activity from the mature to old red blood cell fractions may be caused by oxidative inactivation of glyoxalases. The decreased capacity to metabolise methylglyoxal may be an important factor in red blood cell senesence. This is expected to be particularly important in diabetes mellitus where the rate of methylglyoxal formation is increased during hyperglycaemia.

Ferrochelatase activity in human lymphocytes, as quantified by a new high-performance liquid-chromatographic method.

We describe a new rapid, sensitive high-performance liquid-chromatographic (HPLC) method for determining ferrochelatase (EC 4.99.1.1) activity in lymphocytes. Zinc and mesoporphyrin are incubated aerobically with sonicated lymphocytes and the zinc mesoporphyrin formed is extracted with dimethyl sulfoxide-methanol-EDTA for quantification by HPLC. Incubation conditions, including the concentration of the palmitic acid activator, were optimized. The Michaelis constant (Km) was 2.1 mumol/L for mesoporphyrin, 22.2 mumol/L for zinc. The mean ferrochelatase activity (expressed as zinc mesoporphyrin formed per hour per milligram of lymphocyte protein) for a reference population was 3.25 (SD 0.43) nmol.h-1.mg-1. For three patients with erythrohepatic protoporphyria (EHP), activities were 1.11, 1.30, and 1.35. Neutrophils contain negligible ferrochelatase activity.

Zinc chelatase in human lymphocytes: detection of the enzymatic defect in erythropoietic protoporphyria.

We describe a fluorometric assay for heme synthetase, the enzyme that is genetically deficient in erythropoietic protoporphyria. The method, which can readily detect activity in 1 microliter of packed human lymphocytes, is based on the formation of zinc protoheme from protoporphyrin IX. That zinc chelatase and ferrochelatase activities reside in the same enzyme was shown by the competitive action of ferrous ions and the inhibitory effects of N-methyl protoporphyrin (a specific inhibitor of heme synthetase) on zinc chelatase. The Km for zinc was 11 micrograms and that for protoporphyrin IX was 6 microM. The Ki fro ferrous ions was 14 microM. Zinc chelatase was reduced to 15.3% of the mean control activity in lymphocytes obtained from patients with protoporphyria, thus confirming the defect of heme biosynthesis in this disorder. The assay should prove to be useful for determining heme synthetase in tissues with low specific activity and to investigate further the enzymatic defect in protoporphyria.

Optimization of efficiency in the glyoxalase pathway.

A quantitative kinetic model for the glutathione-dependent conversion of methylglyoxal to D-lactate in mammalian erythrocytes has been formulated, on the basis of the measured or calculated rate and equilibrium constants associated with (a) the hydration of methylglyoxal, (b) the specific base catalyzed formation of glutathione-(R,S)-methylglyoxal thiohemiacetals, (c) the glyoxalase I catalyzed conversion of the diastereotopic thiohemiacetals to (S)-D-lactoylglutathione, and (d) the glyoxalase II catalyzed hydrolysis of (S)-D-lactoylglutathione to form D-lactate and glutathione. The model exhibits the following properties under conditions where substrate concentrations are small in comparison to the Km values for the glyoxalase enzymes: The overall rate of conversion of methylglyoxal to D-lactate is primarily limited by the rate of formation of the diastereotopic thiohemiacetals. The hydration of methylglyoxal is kinetically unimportant, since the apparent rate constant for hydration is (approximately 500-10(3))-fold smaller than that for formation of the thiohemiacetals. The rate of conversion of methylglyoxal to (S)-D-lactoylglutathione is near optimal, on the basis that the apparent rate constant for the glyoxalase I reaction (kcatEt/Km congruent to 4-20 s-1 for pig, rat, and human erythrocytes) is roughly equal to the apparent rate constant for decomposition of the thiohemiacetals to form glutathione and methylglyoxal [k(obsd) = 11 s-1, pH 7]. The capacity of glyoxalase I to use both diastereotopic thiohemiacetals, versus only one of the diastereomers, as substrates represents a 3- to 6-fold advantage in the steady-state rate of conversion of the diastereomers to (S)-D-lactoylglutathione.(ABSTRACT TRUNCATED AT 250 WORDS)

Modification of the glyoxalase system in human red blood cells by glucose in vitro.

The human red-blood-cell glyoxalase system was modified by incubation with high concentrations of glucose in vitro. Red-blood-cell suspensions (50%, v/v) were incubated with 5 mM- and 25 mM-glucose to model normal and hyperglycaemic glucose metabolism. There was an increase in the flux of methylglyoxal metabolized to D-lactic acid via the glyoxalase pathway with high glucose concentration. The increase was approximately proportional to initial glucose concentration over the range studied (5-100 mM). The activities of glyoxalase I and glyoxalase II were not significantly changed, but the concentrations of the glyoxalase substrates, methylglyoxal and S-D-lactoylglutathione, and the percentage of glucotriose metabolized via the glyoxalase pathway, were significantly increased. The increase in the flux of intermediates metabolized via the glyoxalase pathway during periodic hyperglycaemia may be a biochemical factor involved in the development of chronic clinical complications associated with diabetes mellitus.

Disturbed iron metabolism among workers exposed to organic sulfides in a pulp plant.

The aim of this study was to investigate a possible relationship between exposure to sulfides and disturbances of the synthesis of heme and the erythrocytes. Eighteen workers exposed to sulfides at a pulp and paper plant were examined and compared with individually matched referents from a thermomechanical pulp plant without such exposure. The exposure levels of methylmercaptan, dimethylsulfide, and dimethyldisulfide were low. However, five subjects were exposed to high levels of short duration, and their data were analyzed separately. The activity of the enzymes delta-aminolevulinic acid synthase and heme synthase in reticulocytes, characteristics of the erythrocytes, and the iron status were analyzed. A minor decrease, not statistically significant, was observed for the enzymes among the five highly exposed subjects. However, the concentrations of iron and transferrin were elevated and the concentration of ferritin was low in comparison to the corresponding levels of the referents. This combination will not occur spontaneously. A previous study indicated that sulfides may inhibit heme synthesis, and the present study suggests that they may also disturb iron metabolism.

Modification of the glyoxalase system during the functional activation of human neutrophils.

The glyoxalase system catalyses the metabolism of methylglyoxal to D-lactic acid, via the intermediate S-D-lactoylglutathione. It is present in human neutrophils and undergoes a significant modification during functional activation--induction of chemotaxis, phagocytosis and degranulation. During the activation of neutrophils with serum-opsonised zymosan and the tumour-promoting phorbol diester 12-O-tetradecanoylphorbol 13-acetate, the activity of glyoxalase I increases and the activity of glyoxalase II decreases by 20-40% of their activities in resting cells, in the initial 10 min of the activation period. Determination of the Michaelis constant, Km, and the apparent maximum velocity, Vmax, for these enzymatic reactions indicates that the change in activity is due to a non-competitive activation and inhibition of glyoxalase I and glyoxalase II, respectively. This is consistent with a modification of the glyoxalase enzyme protein during the activation response. This modification occurs under aerobic and anaerobic incubation conditions. The concentration of S-D-lactoylglutathione increases approx. 100% of the resting cell concentration during the initial 10 min of the activation period. The presence of S-D-lactoylglutathione in neutrophils may be related to its ability to stimulate microtubule assembly.