Adrenaline and adrenochrome

Metanephrine and normetanephrine associated with subclinical myocardial injuries in pheochromocytoma and paraganglioma

Objective

To analyze the correlation between metanephrine and normetanephrines (MNs) and subclinical myocardial injuries (SMI) diagnosed by low left ventricular global longitudinal strain (LV GLS) in patients with pheochromocytoma and paraganglioma (PPGL).

Methods

Seventy-six patients who underwent surgery for pheochromocytoma or paraganglioma from September 2017 to April 2022 were examined. All the patients enrolled had normal left ventricular ejection fraction (LVEF) and myocardial injury biomarkers including cardiac troponin I and B-natriuretic peptide. Univariate analysis and multivariate analysis were performed to evaluate the association of MNs and subclinical myocardial injury (SMI)(defined as LV GLS<18).

Results

LV GLS of 13(17.11%) PPGL patients was less than 18. The percentage of patients with elevation of single hormone (metanephrine, normetanephrine, 3-methoxytyramine) or any one of MNs was not significantly correlated with SMI (P=0.987, 0.666, 0.128 and 0.918, respectively). All MNs elevation was associated with SMI (OR: 11.27; 95% CI, 0.94—135.24; P= 0.056). After adjusting for age, All MNs elevation was significantly correlated with SMI (OR: 16.54; 95% CI, 1.22—223.62; P= 0.035).

Conclusion

MNs might be an important factor influencing myocardial function. All MNs elevation might indicate SMI. If all MNs elevated, LV GLS measurement was recommended for PPGL patients to detect SMI in the absence of decrease LVEF or other heart disease in clinical practice.

Catecholamine-Induced Cardiomyopathy in Pheochromocytoma: How to Manage a Rare Complication in a Rare Disease?

Pheochromocytomas and paragangliomas (PHEOs) are rare neuroendocrine tumors. Clinical manifestations include different cardiovascular signs and symptoms, which are related to excessive secretion of catecholamines. Catecholamine-induced cardiomyopathy in PHEO (CICMPP) is a rare but dreaded complication of PHEO. Once patient is diagnosed with this condition, the prognosis is worse and a surgical risk is much higher than expected. This article focuses on how catecholamines affect the heart and the pathophysiologic mechanism of CICMPP. The cardiovascular responses to catecholamine depend mostly on which catecholamine is released as well as the amount of catecholamine that is released. The acute release of norepinephrine and epinephrine from PHEO increases heart rate, systemic vascular resistance, myocardial contractility, and reduces venous compliance. The excessive adrenergic stimulation by catecholamine results in severe vasoconstriction and coronary vasospasm, myocardial ischemia, and subsequently damage, and necrosis. Chronically elevated catecholamine levels lead to significant desensitization of cardiac β-adrenoceptors. The increased levels of the enzyme β-adrenoceptors kinase (βARK) in the heart seems to mediate these biochemical and physiological changes that are consistently correlated with attenuated responsiveness to catecholamine stimulation. Through these mechanisms different types of cardiomyopathy (CMP) can be formed. This review discusses extensively the 3 types of cardiomyopathies that can be present in a PHEO patient. It also provides the clinical presentation and diagnostic and therapeutic algorithm in managing patients with CICMPP.

Vasopressors for cardiopulmonary resuscitation. Does pharmacological evidence support clinical practice?

Adrenaline (epinephrine) has been used for cardiopulmonary resuscitation (CPR) since 1896. The rationale behind its use is thought to be its alpha-adrenoceptor-mediated peripheral vasoconstriction, causing residual blood flow to be diverted to coronary and cerebral circulations. This protects these tissues from ischaemic damage and increases the likelihood of restoration of spontaneous circulation. Clinical trials have not demonstrated any benefit of adrenaline over placebo as an agent for resuscitation. Adrenaline has deleterious effects in the setting of resuscitation, predictable from its promiscuous pharmacological profile. This article discusses the relevant pharmacology of adrenaline in the context of CPR. Experimental and clinical evidences for the use of adrenaline and alternative vasopressor agents in resuscitation are given, and the properties of an ideal vasopressor are discussed.

The separation and quantification of aminochromes using high-pressure liquid chromatography with electrochemical detection

There is increasing evidence that oxidative stress plays an important role in the pathogenesis of many neurodegenerative diseases including Parkinson's disease (PD). In particular there is support for the participation of oxidized catecholamines in PD. Catecholamines are highly reactive and are readily oxidized to aminochromes. While aminochromes have been shown to be toxic, their formation in oxidative stress and subsequent participation in disease has yet to be confirmed. We propose that the characterization of aminochromes, specifically dopaminochrome, is important in clarifying the role that oxidized catecholamines play in PD. We have developed a novel method for the separation and quantification of aminochromes using high-pressure liquid chromatography with electrochemical detection (HPLC-ED). Our method utilizes the separation principles employed in measuring catecholamines by HPLC except that the electrochemical detection of aminochromes is achieved by reversing the detector's electrode. We have used this method to separate and quantify aminochrome standards, prepared by oxidizing catecholamines with sodium periodate (NaIO(4)) and we have also shown that aminochromes can be measured in plasma and cell lysates. Furthermore, we have characterized aminochromes to facilitate forthcoming studies on aminochromes and the role oxidized catecholamines may play in neurodegenerative disease.

Toxicology update: the cardiotoxicity of the oxidative stress metabolites of catecholamines (aminochromes)

This toxicology update reviews the oxidative stress metabolites of catecholamines, postulated to be the biochemical initiators of cardiotoxicity. A brief overview of catecholamine metabolism is provided with several noteworthy historical observations relating to the autoxidation and rearrangement of epinephrine. The basic chemical and physical properties of adrenochrome and adrenolutin are discussed. The autoxidative, enzymatic and cellular basis for the transformation of catecholamines to oxidative metabolites is reviewed. Mechanisms seeking to account for the observed cardiotoxic changes in isolated heart perfusion studies and in vivo models are described.

The role of adrenochrome in stimulating the oxidation of catecholamines

Adrenochrome, a stable oxidation product formed after oxidation of adrenaline, strongly stimulates oxygen uptake occurring during the autoxidation of adrenaline, other catecholamines and ascorbate. Oxygen consumed is converted to hydrogen peroxide suggesting the occurrence of a redox cycling process. The reduction of adrenochrome operated by adrenaline is accelerated by the exclusion of oxygen indicating that the oxidation of adrenaline occurs directly and superoxide anion does not necessarily mediate it. Oxygen consumption, observed in the catecholamine/adrenochrome and ascorbate/adrenochrome systems, is due to the autoxidation of leucoadrenochrome that, at variance with adrenaline, easily autoxidizes also at physiological pH. Therefore, in these systems, leucoadrenochrome appears to be the major determinant of the production of superoxide anion.

The oxidative metabolism of catecholamines in the brain: a review

This paper summarizes the strong evidence that we now have that the oxidative pathway of metabolism of the catecholamines, dopamine and norepinephrine via their respective quinones occurs in vivo in the brain. This fact is not yet widely appreciated. The evidence is based on the chemical structure of neuromelanin, advanced mass spectrometry techniques and the identification of intermediates of this system, such as 5-cysteinyl dopamine, in the brain. Supportive evidence is presented from a number of sources including enzymology. A suggestion as to the possible normal function of this system is made.

The nitric oxide/ascorbate cycle: how neurones may control their own oxygen supply

The brain requires an extremely precise means of controlling oxygen delivery to neurones. Too much, and the cells risk free-radical-mediated damage: too little, and the neurones die from hypoxic-excitotoxic mechanisms. Although nitric oxide (NO) is a powerful vasodilator in cerebral blood vessels, synthesis of NO from arginine requires oxygen and so is unsuitable as the mediator of hypoxia-induced cerebral vasodilation. This paper describes a model in which ascorbate, released from neurones during activity, generates NO from the reduction of nitrite ions in the extracellular space. This mechanism could subtly and accurately match the oxygen transport to the local metabolic demands of the nerve cells. The model predicts that the consequences of low ascorbate in the brain would be progressive damage from inaccurate oxygen delivery.

Biochemical and toxicological properties of the oxidation products of catecholamines

The normal catabolism of catecholamines proceeds through enzymatic pathways (monoaminooxidase, catechol-o-methyltranserase, and phenolsulphotransferase). In addition, nonenzymatic oxidative pathways might take place since catechols are readily oxidized. In this review article, the pathways of formation of the oxidation products of catecholamines and their reactions are described. The interactions of these products with different biological systems and their toxicity are examined. Among the reactions known to occur is that with sulfhydryls, which results in either a covalently linked adduct or disulfide production. Another interesting pathway to toxicity involves the oxidation of these catecholamine products by oxygen, with the formation of damaging oxygen-derived species. The action of the oxidation products of catecholamines is outlined, with special attention to the nervous and cardiac systems.

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.

Measurement of adrenolutin as an oxidation product of catecholamines in plasma

Using the reverse phase high-performance liquid chromatography (HPLC) with mobile phases composed of simple acids, we have developed an assay technique for the measurement of adrenolutin, one of the oxidation products of catecholamines, in rat plasma. Ion-pairing chromatography permits the separation and quantitation of plasma adrenolutin (microM) in a linear manner. Sample preparation involved the precipitation of plasma proteins with perchloric acid and it is easier to handle a large number of samples at a time. However, we were unable to demonstrate the presence of adrenochrome, another oxidation product of catecholamines, in plasma since adrenochrome was rapidly destroyed in acid as well as in blood and was quickly changed into adrenolutin. Adrenolutin peak in HPLC was confirmed by 1) the retention time; 2) co-injection of adrenolutin and; 3) the appearance of 3H-adrenolutin after injection of 3H-norepinephrine. Administration of different catecholamines as well as adrenochrome and adrenolutin in rats also increased the level of adrenolutin in plasma. Adrenolutin was found to be present in plasma in other species including dog, rabbit and pig. High level of adrenolutin, which may represent total concentration of aminolutin in plasma, suggests the presence of an efficient mechanism for the oxidation of catecholamines under in vivo conditions.

A new look at the rearrangement of adrenochrome under biomimetic conditions

At physiological pH values, the rearrangement of adrenochrome leads, besides adrenolutin, to a major dimeric compound consisting of an adrenolutin moiety covalently linked to the angular 9-position of adrenochrome. When the reaction is carried out in air, the initially generated adrenolutin undergoes autoxidation to give 5,6-dihydroxy-1-methyl-isatin (DHMIs), which is smoothly oxidized to the 4,4'-dimer. Under an oxygen-depleted atmosphere, formation of these latter compounds is prevented, and the rearrangement of adrenochrome leads mainly to the adrenochrome dimer (about 50% yield) along with adrenolutin and 5,6-dihydroxy-1-methylindole (DHMI) in about 10% yield each. The product distribution is markedly dependent on the concentration of the aminochrome undergoing rearrangement, the nature of the buffer system used, and the pH of the medium. Heavy metal ions of common occurrence in biological systems, such as Cu2+, Zn2+, Co2+, significantly direct the reaction course towards the formation of adrenolutin, while Fe2+ and other cations with low redox potentials induce the almost exclusive formation of DHMI.

Ventricular dysfunction and necrosis produced by adrenochrome metabolite of epinephrine: relation to pathogenesis of catecholamine cardiomyopathy

We have examined the effects of adrenochrome and other metabolites of epinephrine on the ultrastructure and contractile activity of isolated rat hearts perfused under conditions in which the heart rate and coronary flow were controlled. Perfusion of hearts with epinephrine or metanephrine significantly increased contractile force; vanillylmandelic acid and dihydroxymandelic acid did not alter contractile force development, whereas adrenochrome (50 mg/L) declined contractile force with epinephrine (50 mg/L) was associated with increased resting tension and maximum rates of force development and relaxation, and decreased time for peak tension development and 1/2 relaxation. On the other hand, hearts perfused with adrenochrome showed early decline followed by steady increase in resting tension; maximum rates of force development and relaxation were reduced and times for peak tension development and 1/2 relaxation were increased. Hearts perfused or 10 minutes or more with adrenochrome (50 mg/L), but not epinephrine, metanephrine, dihydroxymandelic acid or vanillylmandelic aicd, showed ultrastructural damage. Adrenochrome concentrations of 10 or 25 mg/L altered the appearance of mitochondria after 30 minutes of perfusion. Infusion of epinephrine (1 mg/L) during perfusion with adrenochrome partially maintained contractile force during the first 15 minutes of perfusion but did not alter the severity of ultrastructural changes due to adrenochrome. These results are consistent with the concept that oxidation products of catecholamines such as adrenochrome are partly responsible for inducing myocardial necrosis and failure following massive catecholamine injections in intact animals.

Covalent interaction of [3H]-dopamine with rat brain proteins in vivo and with the dopamine-reuptake site of nerve endings in vitro

Isolated nerve endings have been demonstrated to undergo saturable, covalent interactions with [3H]-dopamine under physiological conditions; and the reaction is greatly accelerated by flash photolysis with ultraviolet light. With intact nerve endings, under conditions where dopamine reuptake occurs, benztropine and cocaine (inhibitors of dopamine reuptake), but not atropine or haloperidol (a postsynaptic antagonist), prevent the reaction. The reaction also occurs in vivo following the intraventricular administration of [3H]-dopamine, the reaction being greatest with mitochondria, followed by the nerve ending and myelin. With the use of sodium dodecylsulfate-gel electrophoresis, a number of proteins of varying molecular weight were labeled, and the pattern of labeling was similar in vitro and in vivo. One protein, with a MW of about 60,000 was labeled to an exceptionally high degree. A number of protein bands showed decreased radiolabeling in the presence of benztropine, a finding which suggests that they may be associated with the reuptake site. Both the addition of ascorbic acid and unlabeled dopamine inhibited the reactivity of [3H]-dopamine, and the effects were concentration dependent. In the absence of photolysis, the reaction (3H]-dopamine to synaptic membranes attained saturation within 10 min, but with photolysis and reaction continued at a constant rate even after 20 min. The results are discussed in relation to the use of [3H]-dopamine as a photoaffinity label of the dopamine reuptake site and in relation to the nature of the reactions with and without photolysis.

The effect of ascorbic acid on the interaction of adrenaline and neostigmine on neuromuscular transmission

Ascorbic acid is used in the laboratory as a stabilizing agent to delay the oxidation of adrenaline solutions. The rat isolated phrenic nerve-diaphragm preparation was used to study the interaction of ascorbic acid, adrenaline and neostigmine on neuromuscular transmission. While ascorbic acid itself did not affect the response of the preparation to phrenic nerve stimulation, it significantly reduced the response of the preparation to neostigmine and the augmentation of this response by adrenaline. The results emphasize the need to consider the consequences of including preservatives or stabilizing agents in drug solutions when quantitative comparisons are made.