Histamine is an organic nitrogen compound in the body involved in local immune responses, regulating physiological functions in the gut and acting as a neurotransmitter. In response to foreign pathogens and allergenic substances, histamine is produced by basophils and mast cells to interfere with inflammatory processes.
What is histamine?
Histamine is a basic amine stored in mast cells and basophils and bound by ionic forces. The interaction between a triggering substance and the antibody immunoglobulin (IgE) on the surface of mast cells leads to the degranulation of these cells and the release of messenger substances such as histamine. This acts on the receptors in the organism to cause necessary reactions such as stimulation of gastric secretion, muscle contractions or vasodilatation. About 1% of the European population suffers from histamine intolerance to histamine ingested from food.
Medical and health functions, roles, and meanings.
The nitrogen compound histamine is found in almost all body tissues, but is concentrated in the lungs, skin, and gastrointestinal tract. It is produced and stored by the decarboxylation of histidine by the so-called histidine decarboxylase in the Golgi apparatus of mast cells and basophils. Histamine can be released immediately during inflammatory or allergic reactions and acts by binding to receptors on target cells. Here, histamine causes intracellular events that lead to different effects in different cell types. Stimulation of H1 receptors in human bronchial muscle cells increases local muscle contraction. When H2 receptors located in the acid-producing cells of the stomach and heart are stimulated by histamine, the production of digestive enzymes and gastric acid, as well as the atrial rate of the heart, increase to support protein and fat digestion. When the H3 receptors in the nervous tissue are activated, the release of neurotransmitters is throttled, which has an influence on sleep or sexuality, for example. It also stimulates the production of melatonin in the pineal gland, which is necessary for fat metabolism. Histamine is involved as a messenger substance in the immediate hypersensitivity reaction and has an influence on leukocyte function. Via binding to H4 receptors, it further influences complex processes such as inhibition of lectin- or antigen-induced proliferation of T cells, release of lymphokines from T cells, or induction of cytotoxic T cells. If these processes are blocked by so-called antagonists, anti-inflammatory actions stimulated by histamine can dampen the antibodies in their hypersensitivity. However, the action of histamine on the blood vessels and skin inhibits immune responses when stimulated persistently, leading to opposite effects, which is why antihistamines are used.
Diseases, ailments, and disorders
Vascular permeability stimulated by histamine causes fluid to flow from capillaries into tissues to prevent an allergic reaction. Typically, the effect of histamine on a direct external irritation (e.g., resulting from an insect sting) is a threefold reaction:
Redness of the sting site, redness of the surrounding area (wheal formation) with itching, and a swelling of the affected area. When allergens encounter mast cell immunoglobulin in the nasal mucosa, histamine-associated reactions include watery eyes, sneezing due to sensory neuronal stimulation, hypersecretion of glandular tissue, and swelling of the nasal mucosa due to vascular congestion and increased capillary permeability. Immediate hypersensitivity to histamine, classified as type 1, is the result of misdirected histamine release due to the invasion of harmless substances such as grass pollen or certain foods. Histamine stimulated contraction of the muscles of the ileum, bronchi and bronchioles, and uterus may result in increased peristalsis with food allergy. In the study of asthmatics, histamine has been found to increase airway muscle tone and promote mucosal edema and glandular secretions, which can lead to airway constriction and airflow limitation. Histamine deficiency can cause the body to become dependent on carbohydrates, which are needed to synthesize cholesterol.At the same time, histamine deficiency leads to lower melatonin levels and lowers fat metabolism in the brain, which increases physical stress. Studies show that histamine deficiency lowers folic acid levels. Often, patients with multiple sclerosis suffer from histamine deficiency, so various histamine replacement therapies have been developed.
