Histamine and its “allergic” receptors

Published on April 30, 2023   24 min

Other Talks in the Series: Allergy - From Basics to Clinic

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Hello everybody. I'm Joao Paulo Fernandes, Associate Professor at the Federal University of Sao Paulo, Brazil. My talk will discuss, about the role of histamine in allergies and the effects that ligands of histamine receptors may cause on these situations.
Undoubtedly, histamine is one of the most pleiotropic substances in the human body and widely distributed in different tissues. Chemically it is part of a biogenic amine group, and this is comprised by an imidazoline ring linked to an ethylene amine group very similar to other biogenic amines, such as dopamine, serotonin, and others. Histamine was first reported by Dale and Laidlaw as an amine present in the tissues as similar to its biological precursor, the amino acid histidine. Biochemically, these amino acids suffers the decarboxylation reaction catalyzed by the enzyme histidine decarboxylase, which has vitamin B as co-factor, and is also a cellular marker of the histamine activity in experimental studies. In physiological pH, histamine is mainly ionized in the primary amino group. This characteristic is important to activate its receptors and also to keep it compartmentalized in cellular vesicles. When released the main metabolic route to eliminate histamine activity is the oxidation by diamino oxidase enzyme generating the imidazolacetic acid and afterwards it's ribosyation. This is the main metabolite of histamine after a massive release in an allergic reaction. However, during the years, histamine was identified as an important neurotransmitter in the central nervous system. Locally, the main bio-transformation route of histamine is its methylation in the imidazole nitrogen, followed by oxidation of the monoamine oxidase enzyme, giving the major neural metabolite N-methyl-imidazolacetic acid.