Involvement of carbonyl reductase in superoxide formation through redox cycling of adrenochrome and 9,10-phenanthrenequinone in pig heart

The effects of adrenochrome, a metabolite of epinephrine (adrenaline), and 9,10-phenanthrenequinone (PQ), a component of diesel exhaust particles, on the stereoselective reduction of 4-benzoylpyridine (4-BP) were examined in pig heart cytosol. PQ was a potent inhibitor for the 4-BP reduction, while adrenochrome was a poor inhibitor. A similar result was observed in the effects of adrenochrome and PQ on the reduction of all-trans retinal. Furthermore, although PQ mediated efficiently the formation of superoxide anion radical through its redox cycling in pig heart cytosol, adrenochrome had no ability to mediate the superoxide formation. These may be because the reactivity for adrenochrome, catalyzed by pig heart carbonyl reductase (PHCR), is much lower than that for PQ. The optimal pH for the reduction of PQ in pig heart cytosol was around 5.5. Dicumarol, a potent inhibitor of DT-diaphorase, had little effect on the time course of NADPH oxidation during the reduction of PQ. Therefore, it is concluded that PHCR plays a critical role in superoxide formation through redox cycling of PQ.

Studies on the role of superoxide anion radicals for the cardiotoxicity of adrenochrome

Adrenochrome is an oxidative product of adrenaline and possesses cardiotoxic properties. As oxygen free radicals play a role in the cytotoxic effects of catecholamines, the role of superoxide anion radicals, as mediators of adrenochrome toxicity, was investigated using electrically-driven Langendorff rabbit hearts with depleted catecholamine stores. Repetitive regional myocardial ischemia (MI) was induced by coronary artery branch ligature, and MI was quantitated from epicardial NADH-fluorescence photography. Adrenochrome (10(-6) mol/l) was added to the perfusion solution after a reperfusion period of 20 min, 30 min before the 2nd coronary occlusion, with or without the additional application of SOD (30 U/ml). Left ventricular pressure was significantly enhanced by adrenochrome (p < 0.05), but it fell rapidly down below its initial value (p < 0.05). Coronary flow was significantly decreased by adrenochrome (p < 0.05). Whereas epicardial NADH-fluorescence was similar after repetitive coronary occlusions in untreated controls, it was significantly enhanced by adrenochrome (p < 0.05). The deleterious effects of adrenochrome on MI were not inhibited by SOD. Thus, there is no evidence for superoxide anion radicals as mediators of the deleterious effects of adrenochrome on MI in isolated rabbit hearts. The deleterious effects of adrenochrome on MI in isolated rabbit hearts might be caused by functional effects, impairing the oxygen consumption/oxygen supply balance.

Functional effects of adrenochrome in isolated rabbit heart

The cardiotoxic effects of catecholamines have been explained in part by the generation of oxygen free radicals and aminochromes. The role of aminochromes remains however controversial. It has previously been demonstrated that adrenochrome, an oxidation product of adrenaline, shows cardiotoxic properties only at very high concentrations, and it has been suggested that the deleterious effects observed may be caused by a worsening in myocardial perfusion. The functional properties of adrenochrome were examined in isolated spontaneously-beating rabbit hearts with depleted catecholamine stores (reserpin 7.0 mg/kg 16-24 hr before preparation, Langendorff, constant pressure: 70 cm H2O, Tyrode solution, [Ca++]sol. 1.8 mmol/l, 37 degrees). Cumulative concentration-response curves show an adrenochrome-concentration-dependent increase of contractility (left ventricular pressure, EC50 = 3.6 x 10(-6) M; +dp/dtmax, EC50 = 1.6 x 10(-5) M), whereas myocardial relaxation was impaired (-dp/dtmax, EC50 = 2.6 x 10(-5) M; -dp/dtmax/+dp/dtmax = 0.68 at 10(-4) M). Heart-rate was only slightly enhanced (+10% at 10(-4) M), and the coronary flow was markedly influenced only by adrenochrome 10(-4) M (-17%). The relative coronary flow (= global coronary flow/pressure-rate product) was concentration-dependently reduced (EC50 = 10(-5) M; -49% at 10(-4) M). We conclude that in isolated rabbit hearts, adrenochrome has a positive inotropic action but impairs myocardial relaxation, and coronary constrictor activity prevents an increase of myocardial oxygen supply, thus worsening myocardial oxygen-demand/supply balance.

Effects of adrenochrome and epinephrine on human arterial endothelial cells in vitro

The effects of adrenochrome and epinephrine were investigated in cultured human umbilical arterial endothelial cells. The cells were exposed to either adrenochrome or epinephrine at levels of 50 and 200 microM, respectively, up to 24 hrs. At 3, 5, 7 and 24 hrs of the designed harvesting time, [3H]thymidine incorporation, protein content, [3H]cholesterol uptake, prostacyclin production and lipid peroxidation were measured. We found that adrenochrome at a level of 200 microM inhibited [3H]thymidine incorporation, decreased protein content, stimulated [3H]cholesterol uptake, and decreased prostacyclin production after 3, 5, 24 and 5 hrs of exposure, respectively, compared with control. It took 24 hrs however for epinephrine at a level of 200 microM to inhibit [3H]thymidine incorporation and prostacyclin production. When the concentration was reduced to 50 microM, only adrenochrome inhibited [3H]thymidine incorporation after 24 hrs of treatment. Both adrenochrome and epinephrine had no effect on lipid peroxidation. We suggest that atherogenic changes found in severe hypertension may be due to abnormal high concentration of epinephrine, especially oxidized epinephrine, on endothelial cell functions, such as DNA synthesis, cholesterol uptake and prostacyclin production.

Cardiotoxicity of adrenochrome in isolated rabbit hearts assessed by epicardial NADH fluorescence

Noradrenaline in a micromolar concentration has recently been shown to contribute to ischemic tissue injury by direct cardiotoxic effects independent of functional alterations. Oxygen free radicals, generated during the auto-oxidation of catecholamines, are important mediators of catecholamine cardiotoxicity. However, the role of the oxidative products (aminochromes) is still unclear. We examined the effects of adrenochrome on functional parameters and on regional myocardial ischemia (MI) in isolated electrically-driven rabbit hearts with depleted catecholamine stores (reserpine 7.0 mg/kg i.p. 16-24 h before preparation, Langendorff, constant pressure: 70 cm H2O, Tyrode solution, Ca++ 1.8 mmol/l, 37 degrees C). Repetitive MI, separated by a reperfusion period of 50 min, was induced by coronary artery branch ligature, and MI was quantitated from epicardial NADH fluorescence photography. Adrenochrome-treatment (10(-6) M or 10(-4) M) was started after a reperfusion period of 20 min. The left ventricular pressure (LVP) was significantly enhanced by adrenochrome (p < 0.05), but it fell thereafter to below its initial value in hearts treated with adrenochrome 10(-4) M. The global coronary flow (CF) was not affected by adrenochrome 10(-6) M (P > 0.05), but it was significantly decreased by adrenochrome 10(-4) M (P < 0.05). The relative CF (= CF/LVP x heart-rate) was numerically decreased by adrenochrome 10(-6) M (p > 0.05) and more markedly by adrenochrome 10(-4) M (p < 0.05). Whereas epicardial NADH fluorescence was similar after repetitive coronary artery occlusions in controls and in hearts treated with adrenochrome 10(-6) M (p > 0.05), it was significantly enhanced by adrenochrome 10(-4) M (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Toxicity of aminochromes

The first part of the present review deals with the chemical and enzymatic synthesis of adrenochrome and other aminochromes from the corresponding catecholamines. A description of the most significant pathways of formation and the reactivity of the aminochromes is presented. In the second part of the toxicity of aminochromes, mainly at the cardiac and CNS level, is described and some of the molecular mechanisms of the toxic action are outlined. The toxicity of the aminochromes appears to depend mainly on the production of reduced oxygen species through redox cycling. The interaction of aminochromes with sulfhydryl groups and the induced depletion of oxygen, ascorbate and glutathione are additional mechanisms resulting in noxious effects at a cellular level.

The effect of oxidized isoprenaline on the chick embryonic heart

Intra-amnial administration of isoprenaline (IPRO) to chick embryos induces a number of myocardial lesions. The purpose of the present study was to investigate whether similar changes may also be induced after injection of spontaneously oxidized isoprenaline and commercially obtained adrenochrome. Cardiotoxicity of these substances has been demonstrated in adult animals. IPRO, oxidized IPRO, or adrenochrome were administered intra-amnially to 10-day-old chick embryos at doses of 0.1, 1.0, 10.0, and 100.0 mg X kg-1. Parallel experimental groups received propranolol at a dose of 1 mg X kg-1, 15 s before injection of IPRO or oxidized IPRO. The cAMP level in the heart was determined by radioimmunoassay 2 and 30 min after administration of IPRO, oxidized IPRO, or adrenochrome at a single dose of 10.0 mg X kg-1. It has been found that in embryos the effect of IPRO and oxidized IPRO is dose dependent. The rise in mortality and development of cardiomegaly together with increased hydration and disturbances of the development of coronary vascularization were highly significant starting from the dose of 10 mg X kg-1. Furthermore, both drugs significantly increased cAMP levels in the embryonic heart. On the other hand, the administration of adrenochrome was without any effect. The changes induced by IPRO were prevented by the administration of the beta-blocking agent propranolol; the lesions induced by spontaneously oxidized IPRO were, however, prevented only partially.

[Pharmacological actions of iprazochrome on the vascular system]

The pharmacological actions of iprazochrome (IC) on the vascular system were studied, and the following results were obtained: No death nor abnormal behaviors were observed in acute toxicity tests conducted on male and female mice and rats despite the administration of large doses of IC (10,000 mg/kg, p.o. and 80 mg/kg, i.v., respectively). IC inhibited dose-dependently platelet aggregation in vitro induced by arachidonate and ADP, whereas no effect was observed on ADP-induced respiratory depression in mice, which is closely related to platelet aggregation in vivo. The antiserotonergic actions of IC on the isolated external carotid arteries and femoral arteries in dogs observed in a noncompetitive manner were found to be 1/24 to 1/65 that of methysergide. On the other hand, IC showed no inhibitory effect on the paw edema of rats in vivo induced by serotonin. The inhibitory effect of IC on peritoneal dye leakage in mice was less than half that of phenylbutazone. IC prevented apoplexy in stroke-prone SHR (SHRSP) without lowering the blood pressure. Histological changes in the cerebrum of SHRSP were ischemic changes such as swelling of the neurons and shrinkage of the nuclei, mainly in the cerebral cortex and corpus striatum area.

Myocardial cell damage and cardiovascular changes due to i.v. infusion of adrenochrome in rats

In vivo effects of adrenochrome (1-32 mg/kg), an oxidation product of catecholamines, on the heart ultrastructure, ECG and blood pressure were studied in rats over a period of 60 min following a single i.v. injection of the drug. One milligram of the drug had no influence on the myocardium or the cardiovascular system, whereas maximum changes in these parameters were recorded at 32 mg/kg of adrenochrome. The maximum structural damage, reached within 5-10 min, included marked swelling of mitochondria and sarcotubular system, intracellular and perinuclear oedema, hypercontraction of myofibrils and partial separation of the intercalated disc. Ultrastructural changes in the myocardium due to 4 and 8 mg of adrenochrome were not accompanied by any cardiovascular effects and the changes were fully reversed within 60 min of the injection of the drug. However, at 16 and 32 mg/kg of adrenochrome both heart rate and blood pressure were depressed within 5 min of drug administration. At these concentrations of adrenochrome arrhythmias, mainly due to premature ventricular contractions, were also noticed. Ultrastructural and cardiovascular changes seen at these higher concentrations of adrenochrome showed only a partial recovery. The data indicates that adrenochrome-induced ultrastructural changes in the heart are due to a direct myocardial effect of the drug which may not involve haemodynamic changes and the latter are most probably a consequence of this effect. However, the present study has not been able to rule out direct vascular effects at higher concentrations of adrenochrome.

Protection against adrenochrome-induced myocardial damage by various pharmacological interventions

Perfusion of the isolated rat heart with Krebs-Henseleit solution containing adrenochrome (25 or 50 mg/l), and oxidation product of catechalmines, resulted in contractile failure and myocardial necrosis. Various pharmacological agents known to protect the myocardium against catecholamine-induced necrosis were also found to be effective against adrenochrome-induced changes in the ultrastructure of the isolated perfused rat heart. The alpha-receptor-blocking drugs tolazoline and Dibenamine (dibenzylchlorethamine), and the adrenergic neurone-blocking agents guanethidine and bretylium did not alter the development of contractile failure and necrosis due to adrenochrome. The beta-receptor-blocking compounds propranolol and practolol effectively protected the heart from adrenochrome-induced necrotic damage, and partially prevented contractile failure. The hydrazine-type monoamine oxidase inhibitor iproniazid completely prevented ultrastructural damage and partially maintained contractile-force development in adrenochrome perfused hearts. The non-hydrazine-type monoamine oxidase inhibitor tranylcypromine partially protected the isolated rat heart against adrenochrome necrosis, but disruption of mitochondrial structure was still seen. Tranylcypromine did not significantly improve contractile force development during adrenochrome perfusion. The calcium antagonist D-600 reduced the severity of adrenochrome-induced ultrastructural damage. These results provide strong support for the view that catecholamine-induced cardiotoxicity is mediated through the formation of adrenochrome.