Histamine: functions and associated disorders

A substance widely used by the immune system as well as by the brain and gastrointestinal tract.

Histamine is one of the most important elements in the world of medicine, and its use is common when treating health problems, especially allergic reactions.

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

What is histamine?

The histamine is a molecule that acts in our body both as a hormone and as a neurotransmitter, to regulate different biological functions.

It is present in significant amounts in both plants and animals, and is used by cells as a messenger for is used by cells as a messenger. In addition, it has 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 its secrets and most important characteristics are.

History of the discovery of this imidazole amine

Histamine was discovered for the first time in 1907 by Windaus and Vogt, in an experiment where they synthesized it from imidazole propionic acid, although they did not know that it existed naturally until 1910, when they saw that the ergot fungus produced it.

From then on, they began to study its biological effects. But it was not until 1927 that it was finally discovered that histamine is found in animals and in the human body.. This occurred when physiologists Best, Dale, Dudley and Thorpe succeeded in isolating the molecule from fresh liver and lung. And this is when it received its name, since it is an amine that is found significantly in tissues (histo).

Histamine synthesis

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

The main cells that carry out histamine manufacture are mast cells and basophils, two components of the immune system that are responsible for the production of histamine.two components of the immune system that store it inside granules, together with other substances. But they are not the only ones that synthesize it, it is also synthesized by enterochromaffin cells in the pylorus region, and by neurons in the hypothalamus area.

Mechanism of action

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

H1 receptor

This type of receptor is distributed throughout the body. It is located in the smooth muscle of the bronchial tubes and intestine, where histamine reception is triggered by histamine.where receipt of histamine causes bronchoconstriction and increased bowel movements, respectively. It also increases mucus production by the bronchi.

Another localization of this receptor is in the cells forming the blood vessels, where it causes vasodilatation 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, and this stimulates the release of other neurotransmitters and acts in different processes, for example in the regulation of sleep.

2. H2 receptor

This type of histamine receptor is localized in a specific group of cells in the digestive tract, namely the parietal cells of the stomach.. Its main function is the production and secretion of gastric acid (HCl). Receipt of the hormone stimulates the release of acid for digestion.

Tt is also localized in cells of the immune system, such as lymphocytes, promoting their response and proliferation.It is also localized in cells of the immune system, such as lymphocytes, favoring their response and proliferation; or in the mast cells and basophils themselves, stimulating the release of more substances.

3. H3 Receptor

This is a receptor with negative effects, i.e., it inhibits processes upon receipt of histamine.. In the CNS, it decreases the release of different neurotransmitters, such as acetylcholine, serotonin or histamine itself. In the stomach it inhibits the release of gastric acid, and in the lung it prevents bronchoconstriction. Thus, as with many other elements of the organism of the same type, it does not have a fixed function, but has several and these depend largely on its location and the context in which it works.

4. H4 Receptor

This is the last histamine receptor to be discovered, and it is still is not yet known which processes it activates.. There are indications that it presumably acts in the recruitment of blood cells, since it is found in the spleen and thymus. Another hypothesis is that it is involved in allergies and asthma, since it is located in the membrane of eosinophils and neutrophils, cells of the immune system, as well as in the bronchus, so that it is exposed to many particles that arrive from outside and can generate a chain reaction in the body.

Main functions of histamine

Among its functions of action we find that it is essential to immune system response and that it works at the level of the digestive system by regulating gastric secretions. regulating gastric secretions and intestinal motility. Also It also acts in the central nervous system by regulating the biological rhythm of sleep, among many other tasks in which it is involved.among many other tasks in which it participates as a mediator.

Despite this, histamine is well known for another, less salutary reason, since it is the main one involved in allergic reactions.. These are reactions that appear before the invasion of the own organism by certain particles foreign to it, and it is possible to be born with this characteristic or it can be developed in some concrete moment of the life, from which it is infrequent that it disappears. A large part of the western population suffers from allergies, and one of their main treatments is medication with antihistamines.

We will now go into more detail about some of these functions.

1. Inflammatory response

One of the main known functions of histamine occurs at the level of the immune system with the generation of inflammation, a defensive action. inflammation, a defensive action that helps to isolate the problem and fight it off.. In order to initiate inflammation, mast cells and basophils, which store histamine inside them, need to recognize an antibody, namely Immunoglobulin E (IgE). Antibodies are molecules produced by other cells of the immune system (B lymphocytes), and are capable of binding to elements unknown to the body, called antigens. to elements unknown to the body, the so-called antigens..

When a mast cell or basophil finds an IgE bound to an antigen, it initiates a response to it, releasing its contents, including histamine. The amine acts on nearby blood vessels, increasing the blood volume by vasodilatation and allowing the outflow of fluid to the detected area. In addition, it acts as chemotaxis on the other leukocytes, i.e. it attracts them to the site. All this results in inflammationwith its redness, heat, edema and itching, which are nothing more than an undesired consequence of a process necessary to maintain a good state of health, or at least to try to do so.

2. Sleep regulation

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

As a neurotransmitter, histamine prolongs wakefulness and reduces sleep.It acts in the opposite way to melatonin. It has been shown that when awake, these neurons are rapidly activated. In moments of relaxation or tiredness, they work to a lesser extent and are deactivated during sleep.

To stimulate wakefulness, histamine makes use of H1 receptors, while to inhibit wakefulness it makes use of H3 receptors. Thus, H1 agonist and H3 antagonist drugs are a good way to treat insomnia.. Conversely, H1 antagonists and H3 agonists can be used to treat hypersomnia. This is why antihistamines, which are H1 receptor antagonists, have drowsiness effects.

3. Sexual response

It has been shown that during orgasm there is a release of histamine in the mast cells located in the genital area.. Some sexual dysfunctions are associated with the lack of this release, such as the absence of orgasm during intercourse. Therefore, excess histamine can cause premature ejaculation.

The fact is that the receptor used to carry out this function is currently unknown and is the subject of study; it is probably a new one and we will have to learn more about it as research in this area progresses.

Significant disorders

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

Allergy and histamines

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

Allergy is an exaggerated response to a foreign agent, called an allergen, which in a normal situation should not cause this reaction.which in a normal situation should not cause this reaction. It is said to be exaggerated because very little quantity is needed to generate the inflammatory response.

The typical symptoms of this anomaly, such as breathing problems or a drop in blood pressure, are due to the effects of histamine on the H1 receptors. Therefore, antihistamines act on the H1 receptors, antihistamines act at the level of this receptor, not allowing histamine to bind to them..

Food intolerance

Another histamine-associated abnormality is food intolerance. In this case, the problem occurs because the digestive system is unable to degrade the messenger found in food due to the absence of the enzyme that performs this task, DiAmin Oxidase (DAO). because of the absence of the enzyme that performs this task, DiAmin Oxidase (DAO). This may have been deactivated by a genetic or acquired dysfunction, in the same way that dairy intolerance occurs.

Here symptoms are similar to those of an allergy, and are thought to occurThe only difference is that there is no presence of histamine in the body. The only difference is that there is no IgE present, as neither mast cells nor basophils are involved. Histamine intolerance may occur more frequently if one suffers from diseases related to the digestive system.

Conclusions

Histamine is a substance that has effects far beyond its role in inflammatory processes linked to allergies. However, in practice, one of its most interesting and useful applications is its ability to attenuate the occurrence of allergies; for example, a relatively small-sized histamine tablet can make the reddening of the skin and itching caused by an Allergy fade away.

However, it should be borne in mind that, as with all pharmacy products, these pills should not be abused, it is advisable not to overuse these histamine tablets.In certain severe allergy processes, it is necessary to resort to other types of treatments to solve them, such as injections; always, of course, by health personnel duly accredited to practice.

Bibliographic references:

• Blandina, Patrizio; Munari, Leonardo; Provensi, Gustavo; Passani, Maria B. (2012). "Histamine neurons in the tuberomammillary nucleus: a whole center or distinct subpopulations?". Frontiers in Systems Neuroscience. 6.
• Marieb, E. (2001). Human anatomy & physiology. San Francisco: Benjamin Cummings. p. 414.
• Nieto-Alamilla, G; Márquez-Gómez, R; García-Gálvez, 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". In Falus, A.; Grosman, N.; Darvas, Z. Histamine: Biology and Medical Aspects. Budapest: SpringMed. pp. 15–28.
• Paiva, T. B.; Tominaga, M.; Paiva, A. C. M. (1970). "Ionization of histamine, N-acetylhistamine, and their iodinated derivatives". Journal of Medicinal Chemistry. 13 (4): 689–692.