A plant histaminase modulates cardiac anaphylactic response in guinea pig Emanuela Masini, a Alfredo Vannacci, a Cosimo Marzocca, a Pier Francesco Mannaioni, a Olivia Befani, b Rodolfo Federico, c Alessandro Toma, c and Bruno Mondov  ı b, * a Department of Preclinical and Clinical Pharmacology, ‘‘A. Rossi Fanelli’’ and CNR Centre of Molecular Biology, Rome University ‘‘La Sapienza,’’ Piazzale A. Moro 5, 00185 Rome, Italy b Department of Biochemical Sciences, ‘‘A. Rossi Fanelli’’ and CNR Centre of Molecular Biology, Rome University ‘‘La Sapienza,’’ Piazzale A. Moro 5, 00185 Rome, Italy c Department of Biology, University of Rome, Rome, Italy Received 24 July 2002 Abstract The effect of a copper amine oxidase (histaminase) purified from the pea seedling as free or immobilized enzyme on the response to specific antigen was studied in isolated hearts from actively sensitized guinea pigs. In vitro challenge with the specific antigen of hearts from actively sensitized animals evokes a positive inotropic and chronotropic effect, a coronary constriction, followed by dilation and an increase in the amount of histamine and nitrites, the oxidation product of nitric oxide, in the perfusates. In the presence of both forms of histaminases, the positive inotropic and chronotropic responses as well as the coronary constriction and the release of histamine were fully blocked. The amount of nitrites, appearing in the perfusates when anaphylaxis is elicited in the presence of both forms of histaminases, is significantly increased, as well as nitric oxide synthase activity and cyclic GMP content in cardiac tissue, while cardiac calcium overload was significantly prevented. These observations demonstrate that the decrease in the anaphylactic release of histamine and the subsequent abatement of the cardiac response to antigen can be accounted for by the inactivation by histaminase of the released histamine and by a stimulation of endogenous nitric oxide production. Ó 2002 Elsevier Science (USA). All rights reserved. Keywords: Pea seedling histaminase; Cardiac anaphylaxis; Histamine; Mast cells; Nitric oxide; Cyclic GMP; Intracellular calcium The release of histamine from tissue mast cells elicited by the cross-linking of antigen with IgE bound to specific receptor of mast cells membrane is still considered an event of paramount relevance in type I allergic reaction. Cardiac anaphylaxis is widely recognized as an example of type I hypersensitivity in which the release of hista- mine participates in myocardial damage and arrhyth- mias [1]. The model described by Cesaris Demel [2], in which the challenge in vitro with a specific antigen of isolated heart preparations from actively sensitized gui- nea pigs results in an increase in the rate and strength of contraction, arrhythmias, and sudden changes in coro- nary outflow, provides a reproducible tool to study the cardiac anaphylactic reaction. Amine oxidases (AOs) are enzymes widely distributed among living organisms: animals, plants, and bacteria [3]. These enzymes are involved in the metabolism of biogenic amines and therefore play a pathophysiological role of primary importance. Histamine released during anaphylactic re- action undergoes oxidative deamination by amine ox- idases, enzymes divided into two main groups-based on the chemical nature of their attached cofactors. The first one (E.C.1.4.3.4.) contains flavin adenine dinucleotide (FAD) as cofactor and includes mitochondrial types A and B monoamine oxidases and cytosolic polyamine oxidases. The second one (E.C.1.4.3.6.) contains copper (CuAO) and in most cases 2, 4, 5 trihydroxyphenylala- nine quinone (TPQ), a cofactor derived from the post- translational oxidation of a tyrosine residue [4]. CuAOs catalyze the oxidative deamination of pri- mary amine groups of several biogenic amines in the presence of molecular oxygen by accepting two electrons Biochemical and Biophysical Research Communications 296 (2002) 840–846 www.academicpress.com BBRC * Corresponding author. Fax: +39-06-4440062. E-mail address: bruno.mondovi@uniroma1.it (B. Mondov  ı). 0006-291X/02/$ - see front matter Ó 2002 Elsevier Science (USA). All rights reserved. PII:S0006-291X(02)00938-5