Oxidative damage of canine erythrocytes after treatment with non-steroidal anti-inflammatory drugs

Objective To investigate oxidative erythrocyte damage in dogs treated with different non-steroidal anti-inflammatory drugs. Material and methods Case-controlled prospective observational study using blood obtained from dogs presenting for lameness examinations or standard surgical procedures to a private referral clinic. Sampling was performed from April 2018 to July 2019. Groups comprised dogs receiving either metamizole (dipyrone) (22 dogs), carprofen (20 dogs) or meloxicam (20 dogs) for a minimum of 10 days. Dogs with gastrointestinal hemorrhage were excluded from the study. A complete hematological, as well as a basic biochemical profile were performed in every dog. Pappenheim stained blood smears were evaluated for eccentrocytes and brilliant cresyl blue stained smears for Heinz bodies. EDTA blood was frozen at –80°C immediately after sampling for measurement of superoxide dismutase and gluthathione peroxidase activity at an external laboratory. Hemoglobin concentration, superoxide dismutase and gluthathione peroxidase activities, reticulocyte count, eccentrocyte and Heinz body numbers were determined prospectively as key parameters for further statistical assessment with Kruskal-Wallis test and Dunn’s multiple comparisons test. Results Dogs receiving metamizole showed a significant increase in eccentrocyte (median 14.5/500 cells vs. 0/500 cells in the other groups, p < 0.0001) and reticulocyte number (median 191.4 × 109/l vs. 31.6–37.9 × 109/l, p < 0.0001) and a significant decrease in hemoglobin concentration (median 8.4 mmol/l vs. 10.1–10.5 mmol/l, p < 0.0003). No significant difference in superoxide dismutase and gluthathione peroxidase activities was observed between dogs receiving metamizole and the other groups. Heinz bodies were not found in any of the dogs. Conclusion Treatment with metamizole for 10 or more days resulted in decreased hemoglobin concentration, eccentrocytosis and reticulocytosis in dogs in this study. This might be a sign of increased oxidative damage caused by this drug. Clinical significance Prolonged metamizole therapy should be evaluated critically in patients already affected by severe illness or underlying anaemia.

The interplay between molten globules and heme disassociation defines human hemoglobin disassembly

Hemoglobin functions as an oxygen transport protein, with each subunit containing a heme cofactor. We have developed a global disassembly model for human hemoglobin, linking hemin (ferric heme) disassociation and apo(heme-free)-protein unfolding pathways. The model was based on the evaluation of circular dichroism and visible absorbance measurements of guanidine hydrochloride-induced disassembly of holo (heme-bound)-hemoglobin and previous measurements of apohemoglobin unfolding. The populations of holo-intermediates and equilibrium disassembly parameters were determined quantitatively for adult and fetal hemoglobins. The key stages for disassembly into unfolded monomers are characterized by hemichrome intermediates with molten globule characteristics. Hemichromes, which occur when both hemin iron axial sites coordinate amino acids, are not energetically favored in native human hemoglobins. However, these hexacoordinate iron complexes are important for preventing hemin disassociation from partially unfolded species during early disassembly and late stage assembly events. Both our model evaluation and independent small angle X-ray scattering measurements demonstrate that heme disassociation during early disassembly leads to loss of tetrameric structural integrity. Dimeric and monomeric hemichrome intermediates occur along the disassembly pathway inside red cells where the hemoglobin concentration is very high. This prediction explains why in the red cells of patients with unstable hemoglobinopathies, misassembled hemoglobins often get trapped as hemichromes that accumulate into insoluble Heinz bodies. These Heinz bodies become deposited on the cell membranes and can lead to hemolysis. Alternatively, when acellular hemoglobin is diluted into blood plasma after red cell lysis, the disassembly pathway is dominated by early hemin disassociation events, which leads to the generation of higher fractions of apo-subunits and free hemin known to damage to the integrity of blood vessel walls. Thus, our model illuminates the pathophysiology of hemoglobinopathies and other disease states associated with unstable globins and red cell lysis, and provides insights into the factors governing hemoglobin assembly during erythropoiesis.SignificanceOur deconvolution and global analysis of spectral data led to both the characterization of “hidden” hemichrome intermediates and the development of a quantitative model for human hemoglobin disassembly/assembly. The importance of this mechanism is several-fold. First, the hemoglobin system serves as a general biological model for understanding the role of oligomerization and cofactor binding in facilitating protein folding and assembly. Second, the fitted parameters provide: (a) estimates of hemin affinity for apoprotein states; (b) quantitative interpretations of the pathophysiology of hemoglobinopathies and other diseases associated with unstable globins and red cell lysis; (c) insights into the factors governing hemoglobin assembly during erythropoiesis; and (d) a framework for designing targeted hemoglobinopathy therapeutics.

Phenylhydrazine and its salts – calculated on phenylhydrazine. Documentation of proposed values of occupational exposure limits (OELs)

Phenylhydrazine at room temperature is a colorless or yellow oily liquid, at lower temperatures it occurs in a form of a crystalline Phenylhydrazine is used in an organic synthesis as a powerful reducing agent or as an intermediate in synthesis of other chemical compounds, such as dyes and drugs. Phenylhydrazine is also used as a chemical reagent. At the beginning of the 20th century, phenylhydrazine was used as a drug in polycythemia vera and other blood disorders. Occupational exposure to phenylhydrazine and its salts may occur during the production, further processing and distribution of these compounds, and also during their use. In 2014, 711 people were exposed to phenylhydrazine in Poland (including 531 women), of which 2 people only were exposed to phenylhydrazine in the air at a concentration range> 0.1–0.5 of the MAC value (20 mg/m3) . Phenylhydrazine is classified as a toxic substance after oral administration, in contact with skin and after inhalation. The available literature describes several cases of human poisoning with phenylhydrazine with inhalation and through the skin. Adverse effects of phenylhydrazine exposure are progressive hemolytic anemia with hyperbilirubinaemia and urobilinemia, presence of Heinz bodies in red blood cells, impairment of renal and hepatic function as secondary symptom to the haemolytic activity of phenylhydrazine. Methemoglobinemia and leukocytosis sometimes occurred. General symptoms of poisoning included dizziness, diarrhea, general weakness and reduced blood pressure. Phenylhydrazine irritates the skin. Several cases of skin hypersensitivity reactions to phenylhydrazine and its hydrochloride have also been described. It has been shown that phenylhydrazine gives cross-reactions with hydrazine salts. In animals, the main symptoms of acute phenylhydrazine poisoning were the formation of significant amounts of methaemoglobin and its consequences: hemolysis, Heinz bodies formation, reticulocytosis, bone marrow hyperplasia, splenomegaly and liver damage. Motor excitation and tonic-clonic spasms were also observed. As a result of repeated exposure, it was found that phenylhydrazine also causes hemostatic disorders in addition to haemolytic anemia and leads to acute pulmonary thrombosis. The dose-effect relationship cannot be derived from existing data nor the NOAEL value be determined. Phenylhydrazine is an in vitro mutagen and some evidence points to its genotoxic activity in vivo (DNA methylation and fragmentation ). Phenylhydrazine and its salts have been classified as category 2 mutagenic substances. In the available literature and databases, no information was found on the carcinogenic activity of phenylhydrazine and its salts in humans. Carcinogenic activity of phenylhydrazine has been demonstrated in experimental animals. Exposure of mice via oral route resulted in the occurrence of lung tumors and tumors of blood vessels. The International Agency for Research on Cancer (IARC) does not classify phenylhydrazine and its salts as carcinogenic. In the European Union, phenylhydrazine and its salts have been classified as category 1B carcinogens. There is also insufficient data on the effect of phenylhydrazine on reproduction and developmental toxicity, so it is difficult to assess whether these effects may occur in humans exposed to phenylhydrazine and its salts. Based on the observed systemic effects in humans and animals exposed to phenylhydrazine and its salts, it can be assumed that these compounds are absorbed into the body by inhalation, oral route, through the skin and after parenteral administration. There are no quantitative data on the absorption efficiency of individual routes. The main metabolic pathways of phenylhydrazine are hydroxylation to p-hydroxyphenylhydrazine and formation of phenylhydrazones by reaction with natural keto-acids. Metabolites in the form of glucuronides are mainly excreted in the urine. The existing two studies of the carcinogenic activity of phenylhydrazine hydrochloride have shown that the compound administered via the oral route caused a significant increase in the formation of lung tumors or tumors of blood vessels. In the second study, despite the longer exposure time, no significant increase in lung cancer was observed. Although the results of both studies seem to be unreliable in the light of current criteria and are limited to one species (mice) only and one dose, on the basis of them, phenylhydrazine was classified in the EU as a carcinogen category 1B with the assigned phrase H350 - may cause cancer. A quantitative evaluation of phenylhydrazine carcinogenicity was performed using data on the incidence of lung cancer in mice of both genders exposed to phenylhydrazine hydrochloride, administered intragastrically at 1 mg/day. The model adopted for calculations shows that exposure to phenylhydrazine, at the level of the adopted MAC value in Poland (20 mg/m3) over 40 years of work, corresponds to the risk of lung cancer at the level of 5.7 · 10-2. Such risk is unacceptable. From the estimation of cancer risk, it appears that the current value of MAC for substance should be reduced. The existing database on the toxicity of phenylhydrazine and its salts is insufficient to derive a MAC value based on NOAEL/LOAEL values. Due to the mechanism of action and the main toxic effects (haematotoxicity), phenylhydrazine has an aniline-like toxicological profile. It was proposed that the MAC value for phenylhydrazine should be taken analogously to the MAC value for aniline, i.e. 1.9 mg/m3, which corresponds to the risk of lung cancer in occupational exposure conditions of 5.4 · 10-3. Due to the dermal absorption of phenylhydrazine, the "skin" notation has been proposed (absorption through the skin may be as important as in the case of inhalation). Additionally, due to irritating, sensitizing, carcinogenic and mutagenic effects of phenylhydrazine, the normative should be marked with the letters "I" (substance with an irritating effect), "A" (a substance with sensitizing effect), Carc. 1B (carcinogenic substance category 1B) and Muta. 2 (mutagen category 2). There are no evidence to establish the STEL and BEI values.