Histamine: functions and associated disorders

Histamine is one of the most important building blocks in the world of medicine, and it is widely used in the treatment of health problems, especially allergic reactions.

Throughout this article we will see what exactly histamines are, And its effects on the human body.

    What is histamine

    Histamine is a molecule that works in our body both as a hormone and as a neurotransmitter, to regulate different biological functions.

    It is present in significant amounts in plants and animals, and it is used by cells as a messenger. In addition, it plays a very important role both in allergies and in cases of food intolerance and in the processes of the immune system in general. Let’s see what are its most important secrets and features.

    History of the discovery of this imidazole amine

    Histamine was first discovered in 1907 by Windaus and Vogt, in an experiment where it was synthesized from imidazole propionic acid, although it was not known to exist naturally until 1910, when it was it was discovered that the rye claviceps fungus had made it.

    From there, they began to study its biological effects. But It wasn’t until 1927 that histamine was finally discovered in animals and the human body.. This happened when physiologists Best, Dale, Dudley, and Thorpe successfully isolated the molecule from a fresh liver and lung. And it is here that it got its name, because it is an amine that is significantly found in tissues (histo).

    Histamine synthesis

    Histamine is a B-amino-ethyl-imidazole, a molecule made from the essential amino acid histidine, i.e. this amino acid cannot be generated in the human body and must be obtained through diet. The reaction used for its synthesis is decarboxylation, which is catalyzed by the enzyme L-histidine decarboxylase.

    The main cells that make histamine are mast cells and basophils, Two components of the immune system that store it in granules, along with other substances. But they are not the only ones to synthesize it, just like enterochromafin cells in the pyloric region and neurons in the hypothalamic region.

    Action mechanism

    Histamine is a messenger that acts as both a hormone and a neurotransmitter, depending on the tissue in which it is released. As such, the functions it activates will also be ensured through the action of histamine receptors. Of these, there are up to four different types, although there may be more.

    1. Receiver H1

    This type of receptor spreads throughout the body. It is located in the smooth muscle of the bronchi and intestines, Where reception of histamine causes bronchoconstriction and increased stool respectively. It also increases the production of mucus by the bronchi.

    Another location of this receptor is in the cells that make up the blood vessels, where it causes vasodilation and increased permeability. Leukocytes (i.e. cells of the immune system) also have H1 receptors on its surface, which serve to target the area where histamine has been released.

    In the central nervous system (CNS), histamine is also captured in different areas by H1, which stimulates the release of other neurotransmitters and acts in different processes, such as the regulation of sleep.

    2. H2 receiver

    This type of histamine receptor is located in a specific group of cells in the digestive tract, particularly the parietal cells of the stomach. Its main function is the production and secretion of stomach acid (HCl). Hormonal reception stimulates the release of acid for digestion.

    Tit is also localized in cells of the immune system, such as lymphocytes, By encouraging their response and proliferation; or in mast cells and basophils themselves, stimulating the release of more substances.

    3. Receiver H3

    It is a receptor with negative effects, that is, it inhibits the processes in the histamine receptor. In the CNS, the release of different neurotransmitters, such as acetylcholine, serotonin or histamine itself, decreases. In the stomach, it inhibits the release of stomach acid and in the lungs, it prevents bronchoconstriction. Thus, like many other parts of the organism of the same type, it does not perform a fixed function, but has several and these depend largely on its location and the context in which it works.

    4. H4 receiver

    It is the last histamine receptor discovered, and we do not yet know which processes it activates. There are indications that it likely acts on the recruitment of blood cells, as found in the spleen and the rip. Another hypothesis is that it participates in allergies and asthma, because it is located in the membrane of eosinophils and neutrophils, cells of the immune system, as well as in the bronchi, so it is exposed to many particles which come from outside and can generate a chain reaction in the body.

    Main functions of histamine

    Among its performance functions, we find it essential for promote the immune system response and it works at the level of the digestive system regulating gastric secretions and bowel motility. too much acts on the central nervous system by regulating the biological rhythm of sleep, Among many other tasks in which she participates as a mediator.

    However, histamine is well known for another less healthy reason because is the main one involved in allergic reactions. They are reactions that appear before the invasion of the own organism on the part of certain particles of others to this one, and can be born with this characteristic or can get to be developed at a concrete moment of the life, from which it is infrequent. disappearance. Much of the western population suffers from allergies and one of its main treatments is taking antihistamines.

    We will now go into more detail on some of these features.

    1. Inflammatory response

    One of the main known functions of histamine is in the immune system with the generation of inflammation, a defensive action that isolates and fights the problem. In order to initiate it, mast cells and basophils, which store histamine inside, must recognize an antibody, especially immunoglobulin E (IgE). Antibodies are molecules produced by other cells of the immune system (B lymphocytes) and are able to bind to unknown elements in the body, the so-called antigens.

    When a mast cell or basophil finds IgE bound to an antigen, it initiates a response, releasing its contents, including histamine. The amine acts on nearby blood vessels, increasing blood volume by vasodilation and allowing fluid to escape into the detected area. In addition, it acts as a chemotaxis on other leukocytes, that is, it attracts them to the site. All this results in inflammation, With their redness, warmth, swelling and itching, which is nothing more than an unwanted consequence of a process necessary to maintain good health, or at least to try.

    2. Sleep regulation

    Histaminergic neurons, that is, neurons that release histamine, are located in the posterior hypothalamus and tuberomamilar nucleus. From these areas, they extend into the prefrontal cortex of the brain.

    As a neurotransmitter, histamine prolongs wakefulness and reduces sleepIn other words, it works in the opposite way to melatonin. It is shown that upon awakening, these neurons activate quickly. In times of relaxation or fatigue, they work to a lesser extent and are handicapped during sleep.

    To stimulate wakefulness, histamine uses the H1 receptors, while to inhibit it, it does so through the H3 receptors. like that, H1 agonist and H3 antagonist drugs are a good way to treat insomnia. And conversely, H1 antagonists and H1 agonists H3 can be used to treat hypersomnia. This is why antihistamines, H1 receptor antagonists, have drowsiness effects.

    3. Sexual response

    We saw that during orgasm there is a release of histamine in mast cells located in the genital area. Some sexual dysfunctions are associated with the absence of this release, such as the absence of orgasm in the relationship. Therefore, too much histamine can lead to premature ejaculation.

    The truth is that the receiver used to perform this function is currently unknown and is under investigation; it is probably a new one and more needs to be learned as research progresses in this direction.

    major troubles

    Histamine is a messenger used to activate many tasks, however it is also involved in abnormalities that affect our health.

    Allergy and histamines

    One of the major disorders and most commonly associated with the release of histamine is type 1 hypersensitivity, a phenomenon known as allergy.

    allergy it’s an exaggerated response to a strange agent, called an allergen, Which in a normal situation should not cause this reaction. This is called overkill because it takes very little to generate the inflammatory response.

    Typical symptoms of this abnormality, such as breathing problems or low blood pressure, are due to the effects of histamine on the H1 receptors. For that, antihistamines work at this receptor, not allowing histamine to bind to them.

    Food intolerance

    Another of the abnormalities associated with histamine is food intolerance. In that case, the problem arises because the digestive system is unable to break down the messenger it finds in food due to the lack of the enzyme that performs this task, diamine oxidase (DAO). It may have been turned off by genetic or acquired dysfunction, in the same way that dairy intolerance occurs.

    here symptoms are similar to those of an allergy, And it is believed that this happens due to an excess of histamine in the body. The only difference is that there is no presence of IgE, as neither mast cells nor basophils are involved. Histamine intolerance may occur more frequently if you suffer from diseases related to the digestive system.

    conclusions

    Histamine is a substance that has effects far beyond its role in allergic inflammatory processes. However, in practice, one of its most interesting and useful applications is its ability to mitigate allergic events; for example, a relatively small histamine pill can cause skin redness and itching caused by an allergy.

    However, it should be noted that, as with all drugstore products, these histamine pills should not be abused, And that in certain severe allergic processes, it is necessary to resort to other types of treatment to bring them a solution, such as injections; always, of course, from health personnel duly accredited to practice.

    Bibliographical references:

    • Blandina, Patrizio; Munari, Leonardo; Provensi, Gustavo; Passani, Maria B. (2012). “Histamine neurons in the mammary-tuber nucleus: an entirely different center or subpopulation?”. Frontiers in systems neuroscience. 6.
    • Marieb, E. (2001). Human anatomy and physiology. San Francisco: Benjamin Cummings. p. 414.
    • Nieto-Alamillo, G; Marquez-Gómez, R; Garcia-Galvez, AM; Morales-Figueroa, GE; Arias-Montaño, JA (November 2016). “The histamine H3 receptor: structure, pharmacology and function”. Molecular pharmacology. 90 (5): 649-673.
    • Noszal, B .; Kraszni, M .; Racz, A. (2004). “Histamine: Fundamentals of Biological Chemistry”. A Falus, A .; Grosman, N .; Darvas, Z. Histamine: Biology and medical aspects. Budapest: SpringMed. pages 15-28.
    • Paiva, TB; Tominaga, M .; Paiva, ACM (1970). “Ionization of histamine, N-acetylhistamine and its iodine derivatives”. Journal of Medicinal Chemistry. 13 (4): 689-692.

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