PHYSIOLOGICAL ROLE OF HISTAMINE
The endogenous biogenic amine histamine is synthesized in the presence
of the amino acid L-histidine (Figure 3) . Initially, histamine
was recognized as a mediator of allergies. In early 1932, scientists
discovered its role in the modulation of allergic reactions.
Subsequently, researchers have established that histamine is a mediator
of autoimmune conditions, hematopoiesis and gastric acid secretion .
Histamine is circulated throughout the tissues and is mainly
concentrated the in lungs, skin, gastrointestinal tract, mast cells,
basophils, neurons and parietal cells. A large amount of histamine in
granules is delivered by basophils and mast cells and is linked with
chondroitin-4-sulfate and anionic proteoglycans heparin . The key reason
that triggers the histamine is an allergic reaction where B cells are
first activated and form plasma cells which release a large amount of
antibodies. The activation of IgE triggers the mast cell to release
granules rich in histamine (Figure 4) . Histamine-N-methyl
transferase which is responsible for the degradation of histamine in
epithelial cells of the airway and diamine oxidase present in the liver,
kidney, small intestine mucosa, eosinophils, placenta and skin are the
two major pathways that metabolized 97% of the synthesized histamine .
Histamine part in allergic disease and autoimmune has an important role
in numerous pathological and physiological progressions, specifically in
chronic urticaria due to histamine release from basophils and
circulating IgE antibodies against FcεRIα and IgE . Allergic rhinitis,
Atopic dermatitis, allergic rhinitis, anaphylaxis and
bronchoconstriction are other examples of allergic and autoimmune
diseases . Lately, histamine confirmed as a serious factor in
interaction with infiltrating immune cells and tumour tissues, where the
mechanism of the immune system containing histamine allows malignant
cells to escape. Various in vitro and in vivo studies of human cell
lines of cancers such as lymphoma, breast cancer, ovarian cancer, etc.
have shown clear participation of histamine in malignant cell
proliferation .