Safety and feasibility of the gene transfer of hemopexin for conditions with increased free heme.

Heme is a fundamental molecule for several biological processes, but when released in the extracellular space such as in hemolytic diseases, it can be toxic to cells and tissues. Hemopexin (HPX) is a circulating protein responsible for removing free heme from the circulation, whose levels can be severely depleted in conditions such as sickle cell diseases. Accordingly, increasing HPX levels represents an attractive strategy to mitigate the deleterious effects of heme in these conditions. Gene transfer of liver-produced proteins with adeno-associated virus (AAV) has been shown to be an effective and safety strategy in animal and human studies mainly in hemophilia. Here, we report the feasibility of increasing HPX levels using an AAV8 vector expressing human HPX (hHPX). C57Bl mice were injected with escalating doses of our vector, and expression was assessed by enzyme immunoassay (ELISA), Western blot, and quantitative polymerase chain reaction (qPCR). In addition, the biological activity of transgenic hHPX was confirmed using two different models of heme challenge consisting of serial heme injections or phenylhydrazine-induced hemolysis. Sustained expression of hHPX was confirmed for up to 26 weeks in plasma. Expression was dose-dependent and not associated with clinical signs of toxicity. hHPX levels were significantly reduced by heme infusions and phenylhydrazine-induced hemolysis. No clinical toxicity or laboratory signs of liver damage were observed in preliminary short-term heme challenge studies. Our results confirm that long-term expression of hHPX is feasible and safe in mice, even in the presence of heme overload. Additional studies are needed to explore the effect of transgenic HPX protein in animal models of chronic hemolysis.

Phenylhydrazine-induced anaemia reduces subcutaneous white and brown adipose tissues in hypothalamic obese rats.

NEW FINDINGS: What is the central question of this study? Can an anaemic state modify adiposity and metabolic parameters in hypothalamic obese rats? What is the main finding and its importance? Hypothalamic obese rats do not display iron deficiency. However, the pharmacological induction of anaemia in hypothalamic obese rats resulted in reduced adiposity, characterized by a decrease in subcutaneous white and brown adipose tissue depots. These findings suggest that iron imbalance in obesity may elevate lipolysis. ABSTRACT: Iron imbalance is frequent in obesity. Herein, we evaluated the impact of anaemia induced by phenylhydrazine on adiposity and metabolic state of hypothalamic obese rats. Hypothalamic obesity was induced by high doses of monosodium glutamate (MSG; 4 g/kg) administered to neonatal male rats (n = 20). Controls (CTL; non-obese rats) received equimolar saline (n = 20). Rats were weaned at 21 days of life. At 70 days, half of the rats received three intraperitoneal doses of phenylhydrazine (PHZ; 40 mg/kg/dose) or saline solution. Body weight and food intake were followed for 4 weeks after PHZ administration. At 92 days, rats were killed and blood was collected for microcapillary haematocrit (Hct) analysis and plasma quantification of glucose, triglycerides, total cholesterol and iron levels. The liver, the spleen, and the white (WAT) and brown (BAT) adipose tissues were excised, weighed and used for histology. MSG-treated rats developed obesity, hypertriglyceridaemia and insulin resistance, compared to CTL rats, without changes in iron levels and Hct. PHZ administration reduced plasma iron levels and promoted similar tissue injuries in the spleen and liver from MSG and CTL rats. However, in MSG-treated rats, PHZ decreased fasting glucose levels and Hct, as well as diminishing the subcutaneous WAT and BAT mass. Although MSG-obesity does not affect plasma iron levels and Hct by itself, PHZ-induced anaemia associated with obesity induces a marked drop in subcutaneous WAT and BAT mass, suggesting that iron imbalance may lead to increased lipolytic responses in obese rats, compared to lean rats.

Phenylhydrazides as inhibitors of Leishmania amazonensis arginase and antileishmanial activity.

Searching for new substances with antileishmanial activity, we synthesized and evaluated a series of α,α-difluorohydrazide and α,α-difluoramides against Leishmania amazonensis arginase (LaArg). Four α,α-difluorohydrazide derivatives showed activity against LaArg with Ki in the range of 1.3-26 µM. The study of the kinetics of LaArg inhibition showed that these substances might act via different inhibitory mechanisms or even by a combination of these. The compounds were tested against L. amazonensis promastigotes and the best result was obtained to the compound 4 (EC50 of 12.7 ±â€¯0.3 µM). In addition, in order to obtain further insight into the binding mode of such compounds, molecular docking studies were performed to obtain additional validation of experimental results. Considering these results, it is possible to conclude that α,α-difluorohydrazide derivatives are a promising scaffold in the development of new substances against the etiological agent of leishmaniasis by targeting LaArg.

Laboratory evidence for the hematopoietic potential of Beta vulgaris leaf and stalk extract in a phenylhydrazine model of anemia.

This study was designed to provide laboratory evidence supporting the hematopoietic effect of Beta vulgaris (beet) leaf aqueous extract in phenylhydrazine-induced anemia model in albino rats. Extraction of the leaves/stalks was done by maceration in 30% hydro-ethanol for 48 h. An intraperitoneal injection of 20 mg/kg phenylhydrazine was applied for two consecutive days to develop hemolytic anemia on the 4th day after the 1st injection in 24 of 30 male albino rats. The animals were divided into 5 groups and received the following treatments: standard (ferrous ascorbate + folic acid; 13.5 + 0.135 mg/kg), B. vulgaris extract (100 and 200 mg/kg), or left untreated (normal and diseased controls). Blood samples were taken at 0, 4, 8, and 12 days of the experiment for hematological and clinico-chemical analysis. Beet leaf extract significantly restored the levels of red blood cells, white blood cells, hemoglobin, and hematocrit in dose- and time-dependent manners. Blood indices have been significantly corrected. Erythropoietin level was maintained at higher levels. Erythrocytic membrane oxidation biomarker (malondialdehyde) level was significantly reduced compared to the anemic untreated group. The extract exhibited potent, concentration (4-512 µg/mL)-dependent antioxidant activity indicated by the 2,2-diphenyl-1-picryl-hydrazyl (DPPH) assay, with IC50 value of 37.91 µg/mL. Beet leaf extract resulted in detection of flavonoid and phenolic compounds that may underlie its hematinic properties. These findings may indicate B. vulgaris as a good natural source for pharmaceutical preparations with hematopoietic effects and treatment of anemia and/or associated conditions.

Laboratory evidence for the hematopoietic potential of Beta vulgaris leaf and stalk extract in a phenylhydrazine model of anemia

This study was designed to provide laboratory evidence supporting the hematopoietic effect of Beta vulgaris (beet) leaf aqueous extract in phenylhydrazine-induced anemia model in albino rats. Extraction of the leaves/stalks was done by maceration in 30% hydro-ethanol for 48 h. An intraperitoneal injection of 20 mg/kg phenylhydrazine was applied for two consecutive days to develop hemolytic anemia on the 4th day after the 1st injection in 24 of 30 male albino rats. The animals were divided into 5 groups and received the following treatments: standard (ferrous ascorbate + folic acid; 13.5 + 0.135 mg/kg), B. vulgaris extract (100 and 200 mg/kg), or left untreated (normal and diseased controls). Blood samples were taken at 0, 4, 8, and 12 days of the experiment for hematological and clinico-chemical analysis. Beet leaf extract significantly restored the levels of red blood cells, white blood cells, hemoglobin, and hematocrit in dose- and time-dependent manners. Blood indices have been significantly corrected. Erythropoietin level was maintained at higher levels. Erythrocytic membrane oxidation biomarker (malondialdehyde) level was significantly reduced compared to the anemic untreated group. The extract exhibited potent, concentration (4-512 μg/mL)-dependent antioxidant activity indicated by the 2,2-diphenyl-1-picryl-hydrazyl (DPPH) assay, with IC50 value of 37.91 μg/mL. Beet leaf extract resulted in detection of flavonoid and phenolic compounds that may underlie its hematinic properties. These findings may indicate B. vulgaris as a good natural source for pharmaceutical preparations with hematopoietic effects and treatment of anemia and/or associated conditions.

In Silico Study and Bioprospection of the Antibacterial and Antioxidant Effects of Flavone and Its Hydroxylated Derivatives.

Flavonoid compounds are widely used as natural protective species, which can act as anti-inflammatory, antioxidant, anticoagulant, antihypertensive and antitumor agents. This study set out to investigate the probable pharmacological activities, along with the antibacterial and antioxidant effects, of flavone and its hydroxy derivatives: 3-hydroxyflavone, 5-hydroxyflavone and 6-hydroxyflavone. To do so, we investigated their pharmacological characteristics, using in silico tests that indicate likelihood of activity or inactivity, with the PASS online software, and the antimicrobial potential against Gram positive and Gram negative bacteria was also analyzed, including bacteria of clinical importance. We also tested for oxidant and antioxidant potential in these molecules in the presence of reactive oxygen species (ROS) and phenylhydrazine (Ph). The results revealed the following characteristics: pharmacological activities for the flavonoids as agonists of cell membrane integrity and as permeability inhibitors, as antagonists of anaphylatoxin receptors, as inhibitors of both kinase and peroxidase, and as having both antimutagenic capacity and vaso-protective potential. All of the flavonoids exhibited moderate antibacterial activity against Gram positive and Gram negative strains, with the flavones being bactericidal at 200 µg/mL for the strains of P. aeruginosa ATCC 8027, S. aureus ATCC 25619 and E. coli 104; the other flavonoids revealed bacteriostatic action. The substances did not promote erythrocyte oxidation and behaved as sequestrators and antioxidants of hydrogen peroxide (H2O2) and phenylhydrazine (Ph). It was concluded that the analyzed compounds have various pharmacological activities in accordance with the predictions of PASS online, as their antibacterial and antioxidant activities were confirmed. The study also helps to consolidate the use of computational chemistry in silico tools to guide new drug search and discovery protocols.

Role of SDF-1 (CXCL12) in regulating hematopoietic stem and progenitor cells traffic into the liver during extramedullary hematopoiesis induced by G-CSF, AMD3100 and PHZ.

The stromal cell derived factor 1 (SDF-1/CXCL12) plays an essential role in the homing of hematopoietic stem and progenitor cells (HSPCs) to bone marrow (BM). It is not known whether SDF-1 may also regulate the homing of HSPCs to the liver during extramedullary hematopoiesis (EMH). Here, we investigated the possible role of SDF-1 in attracting HSPCs to the liver during experimental EMH induced by the hematopoietic mobilizers G-CSF, AMD3100 and phenylhydrazine (PHZ). Mice treated with G-CSF, AMD3100 and PHZ showed a significant increase in the expression of SDF-1 in the liver sinusoidal endothelial cells (LSECs) microenvironments. Liver from mice treated with the hematopoietic mobilizers showed HSPCs located adjacent to the LSEC microenvironments, expressing high levels of SDF-1. An inverse relationship was found between the hepatic SDF-1 levels and those in the BM. In vitro, LSEC monolayers induced the migration of HSPCs, and this effect was significantly reduced by AMD3100. In conclusion, our results provide the first evidence showing that SDF-1 expressed by LSEC can be a major player in the recruitment of HSPCs to the liver during EMH induced by hematopoietic mobilizers.

Therapeutic effect of Agaricus brasiliensis on phenylhydrazine-induced neonatal jaundice in rats.

The present study was designed to investigate the effect of Agaricus brasiliensis extract (ABE) on phenylhydrazine-induced neonatal jaundice in rats. Administration of ABE dose-dependently reduced the elevated bilirubin level induced by phenylhydrazine. It can be somewhat supported from the results of in vitro bilirubin degradation experiment. ABE treatment also reduced the total antioxidant status (TAOS), cascade O2(-)/SOD, level of NF-κB protein, and adrenomedullin (AM). Overall, the results of this study demonstrated that Agaricus brasiliensis extract may be beneficial to reducing bilirubin level without causing hepatotoxicity in neonatal jaundice.

(E)-1-[(5-chloro-3-methyl-1-phenyl-1H-pyrazol-4-yl)methylidene]-2-phenylhydrazine: sheets built from π-stacked hydrogen-bonded chains.

The reaction between 5-chloro-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde and phenylhydrazine proceeds via condensation to provide the title compound, C17H15ClN4, (I), rather than via the alternative routes of simple nucleophilic substitution or cyclocondensation. With the exception of the phenyl group bonded directly to the pyrazole ring, the non-H atoms of (I) are nearly coplanar, with an r.m.s. deviation of 0.058 Å. The molecules are linked into C(7) chains by a single N-H···N hydrogen bond, and the chains are linked by π-π stacking interactions to form sheets.

[13C2]-Acetaldehyde promotes unequivocal formation of 1,N2-propano-2'-deoxyguanosine in human cells.

Acetaldehyde is an environmentally widespread genotoxic aldehyde present in tobacco smoke, vehicle exhaust and several food products. Endogenously, acetaldehyde is produced by the metabolic oxidation of ethanol by hepatic NAD-dependent alcohol dehydrogenase and during threonine catabolism. The formation of DNA adducts has been regarded as a critical factor in the mechanisms of acetaldehyde mutagenicity and carcinogenesis. Acetaldehyde reacts with 2'-deoxyguanosine in DNA to form primarily N(2)-ethylidene-2'-deoxyguanosine. The subsequent reaction of N(2)-ethylidenedGuo with another molecule of acetaldehyde gives rise to 1,N(2)-propano-2'-deoxyguanosine (1,N(2)-propanodGuo), an adduct also found as a product of the crotonaldehyde reaction with dGuo. However, adducts resulting from the reaction of more than one molecule of acetaldehyde in vivo are still controversial. In this study, the unequivocal formation of 1,N(2)-propanodGuo by acetaldehyde was assessed in human cells via treatment with [(13)C(2)]-acetaldehyde. Detection of labeled 1,N(2)-propanodGuo was performed by HPLC/MS/MS. Upon acetaldehyde exposure (703 µM), increased levels of both 1,N(2)-etheno-2'-deoxyguanosine (1,N(2)-εdGuo), which is produced from α,ß-unsaturated aldehydes formed during the lipid peroxidation process, and 1,N(2)-propanodGuo were observed. The unequivocal formation of 1,N(2)-propanodGuo in cells exposed to this aldehyde can be used to elucidate the mechanisms associated with acetaldehyde exposure and cancer risk.

Human erythrocytes as a system for evaluating the antioxidant capacity of vegetable extracts.

Free radicals are fairly unstable and highly reactive substances, able of causing oxidation and sometimes-irreversible damage to cells, compromising their function. The Brassicaceae family has many important species for the regular human diet as they provide several antioxidant constituents. In this study, the antioxidant potential of the hydroethanolic extracts prepared from the edible parts of kale, broccoli, and radish was investigated in vitro using human erythrocytes under oxidative stress imposed by phenylhydrazine as an experimental model, in which the methemoglobin levels were measured. When the results were compared with the antioxidant capacity shown by the traditional 2,2-diphenyl-2-picrylhydrazyl hydrate free radical and phosphomolybdenum complex methods, the extracts tested showed significant and correspondent antioxidant activity. Broccoli extract presented the highest antioxidant activity, followed closely by the kale, whereas the radish extract occupied the lowest position. The results derived from the human erythrocyte system have shown it as an alternative method for evaluating the antioxidant properties of vegetable extracts.

Experimental hemolysis model to study bilirubin encephalopathy in rat brain.

None of experimental models used to study the toxic effect of unconjugated bilirubin brain accumulation, reproduce the conditions in which the hyperbilirubinemia is a consequence of a hemolytic process, i.e. when important amounts of bilirubin and iron are released. The aim was to develop an animal model to determine the role of bilirubin and iron, in the encephalopathy secondary to a hemolytic disease. Male Wistar rats 7 days old (n=30) were treated with phenylhydrazine as hemolytic at 75 mg/kg body weight intraperitoneally for 2 days and euthanized 24 h after the last dose. Hemoglobin, hematocrit, serum and brain bilirubin, serum iron and lipoperoxidation products, as well as neuronal damage and iron positive staining were evaluated and compared among treated and untreated (n=10) animals. The animals with induced hemolysis showed significant reduction in hemoglobin and hematocrit, increased concentration of total and conjugated bilirubin, as well as of serum iron and lipid peroxidation products. The neuronal damage in treated animals included the presence of altered neurons spread out among normal cells, as well as of iron-staining positive cells. With the use of appropriated pharmacological procedures, the characteristics of the model can be useful to dissect the participation of both bilirubin and iron, on the bilirubin encephalopathy secondary to hemolysis.

N-(4-nitrobenzoyl)-N'-phenylhydrazine: a three-dimensional hydrogen-bonded framework.

In the title compound (systematic name: N-anilino-4-nitrobenzamide), C(13)H(11)N(3)O(3), the molecules are linked into a complex three-dimensional framework structure by a combination of two-centre N-H...O and C-H...O hydrogen bonds and a three-centre N-H...(O,N) hydrogen bond.

Effect of vitamins C and E on oxidative processes in human erythrocytes.

The oxidative action of 1 mmol l(-1) phenylhydrazine hydrochloride (PH) was studied on human erythrocytes treated with the antioxidants vitamin C (vit. C) and vitamin E (vit. E). The erythrocytes were resuspended in PBS to obtain 35% cell packed volume, and then submitted to the oxidative action of PH for 20 min, with or without previous incubation for 60 min with vit. C or vit. E. Heinz bodies and methemoglobin formation by PH were inhibited in the presence of vit. C. At the concentration of 90 mmol l(-1), vit. C, not only seemed to lose its antioxidant effect, but it also promoted an increase in methemoglobin formation. Vit. C (0.5-80 mmol l(-1)) did not protect against GSH depletion by PH. Vit. C alone produced insignificant hemolysis, but, in the presence of PH, the hemolysis indices were more accentuated. Heinz body formation by PH was inhibited in the presence of vit. E. Formation of methemoglobin induced by PH was decreased by vit. E (0.1-2 mmol l(-1)), although vit. E (3-80 mmol l(-1)) did not lower the concentration of methemoglobin and did not lead to the recovery of the GSH depleted by PH. The results obtained suggest that vit. C and vit. E contribute to the decrease in oxidative stress caused by PH.

Enhanced erythropoietin production during hypobaric hypoxia in mice under treatments to keep the erythrocyte mass from rising: implications for the adaptive role of polycythemia.

Stress erythropoiesis is usually considered as a compensatory effort to counteract tissue hypoxia. Its homeostatic importance in anemic hypoxia has not been questioned, but researchers, clinicians, and mountain climbers have had second thoughts on polycythemia as to its appropriateness for hypoxic or altitude hypoxia (HA). Therefore, polycythemia, one of the responses to HA seen in nongenetically adapted mammals, could or could not be considered beneficial. The present study was thus performed to obtain further information on the importance of HA polycythemia on acclimation of mice to HA. To this end, the development of polycythemia was prevented by experimental manipulations (administration of 20 mg/kg/d of the hemolytic drug phenylhydrazine or removal of 0.225 mL/d of blood), and the degree of tissue hypoxia was evaluated from plasma erythropoietin (pEPO) concentration, as determined by immunoassay, in adult female mice exposed to air maintained at 506 mbar (380 mmHg) in a simulated HA (SHA) chamber during at least 23.5 h/d for 9 d. Plasma EPO concentration in those treated hypoxic mice whose hematocrit values remained almost unchanged was between 5.55 and 7.89 times higher (depending on the experimental designs) than in control hypoxic mice allowed to develop HA polycythemia. These results, plus the finding of an inverse relationship between the hematocrit value and pEPO concentration in both the polycythemic and normocythemic SHA-exposed mice indicate that HA polycythemia is highly effective in ameliorating tissue hypoxia under SHA conditions, thus giving support to the concept of the important role of the increased hemoglobin mass in nongenetically adapted animals, whereas a left-shifted oxyhemoglobin dissociation curve confers a good degree of adaptation to HA in genetically adapted animals.

Intravascular hemolysis increases atherogenicity of diet-induced hypercholesterolemia in rabbits in spite of heme oxygenase-1 gene and protein induction.

Free radical mediated oxidation of apoB lipoproteins in the arterial intima appears to contribute to atherogenicity of the entrapped particles. A plausible pathogenic mechanism for oxidation is the one induced by heme leaking from erythrocytes that is then carried into the arterial wall by its high affinity for lipoproteins. In the intima, in the presence of H(2)O(2) secreted by macrophages, heme can be a potent oxidant. To study the role of heme as a promoter of oxidative stress damage in vivo we used a model of intravascular hemolysis (IVH) caused by phenylhydrazine in rabbits with and without diet-induced moderate hypercholesterolemia (MHC). Evaluation of the antioxidant status of plasma indicated that at the end of the treatment period this was compromised by the MHC-IVH. After 10 weeks the animals with combined MHC-IVH showed more of the aorta surface covered by lesions (27%+/-8, mean (SD) than the animals with only MHC (11%+/-7), in spite of having similar plasma levels of VLDL+LDL lipoproteins. The animals with only IVH, as well as the controls, showed minimal lesions (<1%). Heme oxygenase (HO-1) expression in aorta and other tissues was markedly increased in the group with MHC-IVH and it was correlated with the extent of IVH. The data suggest that the oxidative stress associated with IVH potentiates the atherogenicity of moderate hypercholesterolemia and that in spite of a strong induction of HO-1 this is not sufficient to counteract the atherogenicity of the combined condition.

Bone healing under experimental anemia in rats.

The effects of anemia on different physiological parameters have been the object of permanent study. There are no studies in the literature on the effects of this disorder on the process on bone healing. The aim of the present study was to evaluate, histologically and histomorphometrically, the process of osteogenesis in the post-extraction alvcolus of the lower molar, and in the peri-implant environment of rats. Twenty male Wistar rats (body weight (b.w.): 60 +/- 7 g) were grouped into two experimental sets. The control group (n:10) was given 0.5 mL saline solution i.p. The anemic group (n:10) was injected with 6 mg/100 g of b.w. or 3 mg/100 g b.w. phenylhidrazine, a well known hemolytic agent. Under ketamine-xylazine anesthesia the rats were submitted to extraction of the first lower molars, and to implantation in the tibia in keeping with the "laminar test" procedure. Other parameters, i.e. body weight (b.w.), food intake (FI), hematocrit (Htc), and hemoglobinemia (Hb) were monitored every 48 hs. The results showed a reduction in b.w., FI, Htc and Hb in the experimental group. The histological and histomorphometrical data show that the condition of anemia affects osteogenesis quali-quantitatively in the post-extraction alveolus and peri-implant microenvironment. Both bone reparative situations showed that ostegenesis is "sensitive" to anemia and/or the associated conditions, causing a delay in bone healing.

Inadequate treatment of excessive erythrocytosis / Tratamiento inadecuado en la eritrocitosis excesiva

Los pacientes con el mal de montaña crónico o eritrocitosis excesiva (EE) son residentes de la altura (3600 m), con mayor o igual 6.5 x 10 a la sexta glóbulos rojos (GR) que presentan cianosis.Esto ocasiona problemas estéticos y psicológicos en su vida ya que las demás personas creen que son alcohólicos. Cuando hay aumento de los GR, ellos buscan una cura milagrosa. De acuerdo a los conceptos evolutivos de la EE, los tratamientos han incluído; sanguijuelas, radioterapia de la médula ósea mediante administración de substancias radiactivas como el fósforo, y más recientemente, flebotomías, infusiuones de té, tabletas de ajo y la más peligrosa la administración de la fenilhidrazina, agente citotóxico prohibido. Encontramos que la mayoría de los pacientes con EE tienen placas radiográficas de tórax anormales. El concepto de los tratamientos es el de disminuir los GR. Sin embargo, la fenilhidrazina es tóxica para la médula ósea, el hígado y otros tejidos, cambiando el color de la piel de cianótica a icterica. Las conjuntivas se tornan ictéricas y la harina de café oscura. Una vez iniciado el tratamiento, la sangre de los pacientes es analizada periódicamente y el recuento de GR disminuyue, con lo que quedan satisfechos. Sin embargo, este medicamento tóxico puede producir la muerte. Al reducir los GR, el contenido arterial de oxígeno (CaO2) en la sangre disminuye. Las pruebas ergométricas en estos pacientes durante el tratamiento producen gran débito de oxígeno. En el paciente descrito, en el 4to nivel del protocolo de Bruce,m el dolor intenso de ambasd pantorrillas se hizo intolerable y requirió oxígeno post ejercicio. Al interrumpirse la fenilhidrazina, el, CaO2 retorna a niveles normales en aproximadamente 60 días, con una elevación de los GR por encima de los valores iniciales, y mejoría de la capacidad de ejercicio. Este y muchos otros casos nos llevan a creer que la EE es un mecanismo de compensación de la enfermedad pulmonar en la altura y que la cantidad de GR no debe ser disminuída.

The dual oxygenase and peroxidase activities of porphobilinogen oxygenase and horseradish peroxidase: a study using the reaction with phenylhydrazine.

Porphobilinogen oxygenase and horseradish peroxidase show dual oxygenase and peroxidase activities. By treating porphobilinogen oxygenase with phenylhydrazine in the presence of H2O2 both activities were inhibited. When horseradish peroxidase was treated in the same manner only the peroxidase activity was lost while its oxygenase activity toward porphobilinogen remained unchanged. The phenylhydrazine treatment alkylated the prosthetic heme group of porphobilinogen oxygenase and N-phenylheme as well as N-phenylprotoporphyrin IX were isolated from the treated hemoprotein. In horseradish peroxidase the modified heme was mainly 8-hydroxymethylheme. The apoproteins of the alkylated enzymes were isolated and recombined with hemin IX. The oxygenase and peroxidase activities of porphobilinogen oxygenase were entirely recovered in the reconstituted enzyme, while the reconstituted horseradish peroxidase regained 75% of its peroxidase activity.

[An in vitro study of the mechanism by which captopril attenuates myocardial reperfusion damage]. / Estudio in vitro del mecanismo por el cual el captopril atenúa el daño miocárdico por reperfusión.

The purpose of this study was to establish the molecular mechanism whereby captopril prevents the formation of active oxygen species, since many studies have provided evidence that postischemic myocardial dysfunction is mediated, at least in part, by the generation of these agents. Results indicate that captopril is a potent inhibitor of certain reactions mediated by O2-. However, this interference of captopril was not understood as an scavenging activity against the free radicals generated. The data could be explained by considering a direct interaction of captopril with the metal ions present that catalyse the formation of O2-. This mechanism could be of biological relevance.