Erythrocyte delta-aminolaevulic acid dehydrase activity in anaemia

Pb(II) Induces Scramblase Activation and Ceramide-Domain Generation in Red Blood Cells

The mechanisms of Pb(II) toxicity have been studied in human red blood cells using confocal microscopy, immunolabeling, fluorescence-activated cell sorting and atomic force microscopy. The process follows a sequence of events, starting with calcium entry, followed by potassium release, morphological change, generation of ceramide, lipid flip-flop and finally cell lysis. Clotrimazole blocks potassium channels and the whole process is inhibited. Immunolabeling reveals the generation of ceramide-enriched domains linked to a cell morphological change, while the use of a neutral sphingomyelinase inhibitor greatly delays the process after the morphological change, and lipid flip-flop is significantly reduced. These facts point to three major checkpoints in the process: first the upstream exchange of calcium and potassium, then ceramide domain formation, and finally the downstream scramblase activation necessary for cell lysis. In addition, partial non-cytotoxic cholesterol depletion of red blood cells accelerates the process as the morphological change occurs faster. Cholesterol could have a role in modulating the properties of the ceramide-enriched domains. This work is relevant in the context of cell death, heavy metal toxicity and sphingolipid signaling.

Effect of Lead(IV) Acetate on Procoagulant Activity in Human Red Blood Cells

Lead (Pb) is a ubiquitously occurring environmental heavy metal which is widely used in industry and human life. Possibly due to a global industrial expansion, recent studies have revealed the prevalent human exposure to Pb and increased risk of Pb toxicity. Once ingested by human, 95% of absorbed Pb is accumulated into erythrocytes and erythrocytes are known to be a prime target for Pb toxicity. Most of the studies were however, focused on Pb²⁺ whereas the effects of Pb⁴⁺, another major form of Pb on erythrocytes are poorly understood yet. In this study, we investigated and compared the effects of Pb⁴⁺, Pb²⁺ and other heavy metals on procoagulant activation of erythrocytes, an important factor for the participation of erythrocytes in thrombotic events in an effort to address the cardiovascular toxicity of Pb⁴⁺. Freshly isolated erythrocytes from human were incubated with Pb⁴⁺, Pb²⁺, Cd²⁺ and Ag⁺ and the exposure of phosphatidylserine (PS), key marker for procoagulant activation was measured using flow cytometry. As a result, while Cd²⁺ and Ag⁺ did not affect PS exposure, Pb⁴⁺ and Pb²⁺ induced significantly PS exposure in a dose-dependent manner. Of a particular note, Pb⁴⁺ induced PS exposure with a similar potency with Pb²⁺. PS bearing microvesicle (MV), another important contributor to procoagulant activation was also generated by Pb⁴⁺. These PS exposure and MV generation by Pb⁴⁺ were well in line with the shape change of erythrocyte from normal discocytes to MV shedding echinocytes following Pb⁴⁺ treatment. Meanwhile, nonspecific hemolysis was not observed suggesting the specificity of Pb⁴⁺-induced PS exposure and MV generation. These results indicated that Pb⁴⁺ could induce procoagulant activation of erythrocytes through PS exposure and MV generation, suggesting that Pb⁴⁺ exposure might ultimately lead to increased thrombotic events.

Lead distribution in blood and organs of mice exposed to lead by vein injection

To study lead (Pb) distribution in organs and blood in the case of Pb poisoning, mice were firstly exposed to Pb as 0.1 mL or 0.2 mL of lead nitrate solution (0.1 mg/mL) by vein injection every other day. Then, after metabolic absorption, the Pb level in the blood and organs of the mice was measured using flame atomic absorption spectrometry. The resulting data showed that 93% of Pb in blood was accumulated in red cells, but this percentage slightly decreased with increasing exposure time and injection volume. For other target organs, the highest Pb level was in the kidney, followed by the liver, spleen, heart and lung, and was lowest in the brain. Moreover, the Pb level in the heart and brain is in a growth trend at all times for 0.1 mL and 0.2 mL of Pb injection exposure in 15 days, while the growth trend of Pb in other target organs become slow for 0.2 mL of injection after exposure Pb 11 days.

Effect of lead (Pb) exposure on the activity of superoxide dismutase and catalase in battery manufacturing workers (BMW) of Western Maharashtra (India) with reference to heme biosynthesis

The aim of this study was to estimate the activity of superoxide dismutase (SOD) and catalase in erythrocytes and malondialdehyde (MDA) in plasma of battery manufacturing workers (BMW) of Western Maharashtra (India) who were occupationally exposed to lead (Pb) over a long period of time (about 15 years). This study was also aimed to determine the Pb intoxication resulted in a disturbance of heme biosynthesis in BMW group. The blood Pb level of BMW group (n = 28) was found to be in the range of 25.8 - 78.0 microg/dL (mean + SD, 53.63 + 16.98) whereas in Pb unexposed control group (n = 35) the range was 2.8 - 22.0 microg/dL (mean + SD, 12.52 + 4.08). The blood level (Pb-B) and urinary lead level (Pb-U) were significantly increased in BMW group as compared to unexposed control. Though activated d- aminolevulinic acid dehydratase (ALAD) activities in BMW group did not show any significant change when compared to control group but activated / non activated erythrocyte - ALAD activities in BMW group showed a significant increase. Erythrocyte- zinc protoporphyrin (ZPP), urinary daminolevulinic acid (ALA-U) and porphobilinogen (PBG-U) of BMW groups elevated significantly as compared to control. A positive correlation (r = 0.66, p < 0.001) between Pb-B and ALA-U were found in BMW group but no such significant correlation (r = 0.02, p> 1.0) were observed in control group. Hematological study revealed a significant decrease of hemoglobin concentration, packed cell volume (%) and other blood indices and a significant increase of total leucocytes count in BMW group in comparison to control group. The serum MDA content was significantly increased (p < 0.001) and the activities of antioxidant enzymes such as erythrocyte- SOD (p < 0.001) and erythrocytecatalase (p < 0.001) were significantly reduced in BMW group as compared to control group. A positive correlation (r = 0.45, p < 0.02) between Pb-B and serum MDA level was observed in BMW group (Pb-B range 25.8 - 78.0 microg / dL) but such significant correlation did not notice in control group (Pb-B range 2.8 - 22.0 microg / dL). The study clearly showed an adverse effect of heme biosynthesis and imbalance of pro-oxidant / antioxidant status in lead exposed battery manufacturing workers resulting in increase in lipid peroxidation associated with decrease in erythrocyte-SOD and erythrocyte-catalase activities.

Lead-Induced Procoagulant Activation of Erythrocytes through Phosphatidylserine Exposure May Lead To Thrombotic Diseases

Lead (Pb) is a ubiquitous heavy metal pollutant in various environmental media, especially in food and drinking water. In human blood, about 95% of lead is associated with erythrocytes, suggesting that erythrocytes could be an important target of lead toxicity in the cardiovascular system. Recent studies suggested that erythrocytes could contribute to blood coagulation via phosphatidylserine (PS) exposure and resultant procoagulant activation. We investigated the effects of lead on the procoagulant activity of erythrocytes using in vitro human erythrocyte and in vivo rat models. In a flow cytometric analysis, lead (Pb2+) enhanced PS exposure on human erythrocytes in a concentration- and time-dependent manner. The concentration of lead (1-5 microM) used in the current investigation is well within the ranges observed in blood from lead-exposed populations. PS exposure by lead appeared to be mediated by increased intracellular calcium levels as shown by 19F-NMR and intracellular ATP depletion. Consistent with these findings, the activity of scramblase, which is important in the induction of PS exposure, was enhanced, whereas the activity of flippase, which translocates exposed PS to inner membrane, was inhibited by lead treatment. Furthermore, lead-exposed erythrocytes increased thrombin generation as determined by a prothrombinase assay and accelerated the coagulation process initiated by tissue factor in plasma. These procoagulant activations by lead were also confirmed in vivo. Administration of lead significantly enhanced PS exposure on erythrocytes and, more importantly, elevated thrombus formation in a rat venous thrombosis model. These results suggest that lead exposure can provoke procoagulant activity in erythrocytes by PS exposure, contributing to enhanced clot formation. These data will provide new insights into the mechanism of lead-induced cardiovascular diseases.

In vivo effects of lead on erythrocytes following chronic exposure through drinking water

More than 95% of lead, a environmental heavy metal, entering into blood accumulates in erythrocytes suggesting erythrocytes as an important target of lead toxicity. Recent studies reported that erythrocytes could contribute to blood coagulation via phosphatidylserine (PS) exposure in erythrocytes. However, in vivo effects of chronic lead exposure especially by drinking water on procoagulant activity of erythrocytes have not been studied yet. In the present study, we investigated the effects of chronic exposure of lead by drinking water on erythrocytes in rats. Groups of 40 male rats were provided with drinking water containing various concentrations of lead for 4 weeks and complete blood cell count, procoagulant activities of erythrocytes and platelets were evaluated with basic inspections on body weight and food/ water consumption. The administration of lead containing drinking water increased the blood lead level (BLL) in a dose-dependent manner up to 22.39 +/- 2.26 microg/dL. Water consumption was significantly decreased while food consumption or body weight gain was not affected. In contrast to the "previous findings with acute lead exposure, chronic lead exposure failed to increase PS exposure in erythrocytes with statistical significance although some trends of enhancement were observed. It implies that a certain adaptation might have happened in body during repeated exposure to lead, resulting in attenuation of PS exposure. With this study, we believe that a valuable information was provided for the study on the toxicological significance and the risk assessment of lead contaminated drinking water.

Effect of lead concentration on the level of glutathione, glutathione S-transferase, reductase and peroxidase in human blood

Incubation of human whole blood for 24 h at 37 degrees C in the presence of 100-400 microg/dl lead chloride or lead acetate caused a concentration-dependent decrease in the level of reduced glutathione up to 40%. Similarly, the activities of glutathione reductase, glutathione peroxidase and glutathione S-transferase were decreased up to 25%, 50%, and 19%, respectively. Moreover, 100 microg/dl lead chloride or lead acetate slowed the process of glutathione regeneration, and delayed the time for complete regeneration from 20 to 40 min. When glutathione S-transferase was purified by affinity chromatography on Sepharose-linked glutathione, incubated with lead chloride or lead acetate, a concentration-dependent inhibition of the enzymatic activity was observed reaching 50% inhibition at a lead salt concentration of 6000 microg/dl.

delta-Aminolaevulinic acid dehydratase as an index of lead toxicity. Time for a reappraisal?

delta-Aminolaevulinic acid dehydratase activity is traditionally accepted as the most sensitive measurable biological index of lead toxicity. We have measured delta-aminolaevulinic acid dehydratase activity and blood lead concentration in 47 healthy controls (A), 42 iron deficient patients (B) and 38 occupationally exposed to lead subjects (C). Blood lead levels [mean (SD)] did not differ between groups A and B [0.51 (0.21) and 0.43 (0.19) mumol L-1, respectively] while those of group C [2.28 (0.56) mumol L-1 were significantly higher (P < 0.001) as compared to the controls. delta-Aminolaevulinic acid dehydratase activity [mean (SD)] was significantly increased [3599 (1909) mumol L-1 h-1] in group B and decreased in group C [1052 (532) mumol L-1 h-1] as compared to the controls [2034 (446) mumol L-1 h-1] (P < 0.001). There was a significantly negative correlation of logarithm of delta-aminolaevulinic acid dehydratase with lead in both groups B (P < 0.05) and C (P < 0.001) but not in group A (P = 0.1). delta-Aminolaevulinic acid dehydratase activity had a high specificity (100%) but a low sensitivity (37%) as an index of toxic lead exposure. According to our data the value of delta-aminolaevulinic acid dehydratase measurement in the diagnosis of lead intoxication is doubtful in cases with low blood lead levels, while in the presence of iron deficiency its reliability is further reduced, since low blood lead levels may be falsely predicted. delta-Aminolaevulinic acid dehydratase activity should be restricted only to monitoring cases with moderate or severe lead poisoning.

delta-Aminolevulinate dehydrase: a new genetic polymorphism in man

A method has been developed for the electrophoretic and quantitative analyses of human red cell delta-aminolevulinate dehydrase (ALADH). The enzyme is under the control of an autosomal gene, with two common codominant alleles. ALADH1 and ALADH2, with frequencies of 0.89 and 0.11, respectively, in the Italian population. Mean phenotypic enzyme activities are nearly identical: 52,. 49 and 55 mIU/g Hb for ALADH 1, 2-1 and 2 phenotypes respectively.

Erythrocyte delta-aminolaevulinic acid dehydratase activity and changes in delta-aminolaevulinic acid concentration in various forms of anaemia

Whole blood delta-aminolaevulinic acid (ALA) concentrations and erythrocyte ALA dehydratase activity have been measured in patients with iron deficiency anaemia, megaloblastic anaemia and secondary anaemia, and in normal subjects. ALA concentration was found to be significantly increased in all types of anaemia compared with normal. Erythrocyte ALA dehydratase activity was significantly increased in iron deficiency and megaloblastic anaemia but not in secondary anaemia.

Increased blood lead levels in mentally retarded children in Greece

In 60 children with mental retardation of unknown etiology, the whole blood lead, as well as the activity of the red cell delta-aminolevulinic acid dehydratase (delta-ALAD), was measured. Thirty normal children and 30 with mental retardation of known etiology were used as controls. The lead values were found significantly higher in the study patients compared with both control groups (P less than 0.001). The delta-ALAD activity in the 14 patients with blood lead levels greater than or equal to 40 microgram/dl, was significantly reduced compared with the normal controls (P less than 0.001) and the mentally retarded controls (P less than 0.01). In more than 20% of the patients with mental retardation of unknown etiology, indications of significant exposure to lead were found. There was no difference in blood lead values between children from cities and those from rural areas. The possible role of lead in the etiology of mental retardation is discussed.

Comparative study of effect of inorganic lead and cadmium on blood delta-aminolevulinate dehydratase in man

Lauwerys, R. R., Buchet, J.-P., and Roels, H. A. (1973).British Journal of Industrial Medicine,30, 359-364. Comparative study of effect of inorganic lead and cadmium on blood δ-aminolevulinate dehydratase in man. δ-Aminolevulinate dehydratase (ALA¹-D) of red blood cells, lead concentration in blood (Pb-B) and in urine (Pb-U), cadmium concentration in blood (Cd-B) and in urine (Cd-U), and ALA in urine (ALA-U) were measured in 77 workers occupationally exposed to cadmium, and in 73 control workers. An excellent negative correlation was found between log ALA-D and Pb-B (r = - 0·660) or Pb-U (r = - 0·501), but no significant correlation was found between Cd-B and log ALA-D activity. Unlike ALA-D, ALA-U is not correlated with Pb and Pb-U in the `normal' range of Pb concentration investigated. Mean ALA-D activity in smokers is lower than in nonsmokers, and this is probably related to the fact that a higher mean Pb-B concentration is found in smokers than in nonsmokers. It is clear from this investigation that in the general population, and even in Cd-exposed workers, Cd has no significant effect on ALA-D. Moreover, all the available evidence indicates that ALA-D activity of erythrocytes is a very sensitive and specific parameter of lead in blood.

Aberration of porphyrin metabolism in iron-deficient anaemic rats

Iron-deficient rats excreted greater amounts of 5-aminolaevulinate in urine but the output of porphobilinogen was decreased considerably. In addition, activity of the enzyme 5-aminolaevulinate dehydratase was diminished in bone marrow and liver. The results suggest that in iron deficiency a defect occurs in porphyrin synthesis at the level of porphobilinogen formation.