The role of bradykinin

Bradykinin, a naturally occurring peptide in the body whose actions resemble those of histamine, plays a key role in non-histamine-mediated angioedema. Bradykinin is synthesised through activation of the so-called Kinin-Kallikrein System, or Kinin System for short. The Kinin System consists of a number of proteins in the blood that influence numerous processes and reactions in the body, including inflammation, blood coagulation, control of blood pressure and pain.

Bradykinin acts to dilate (widen) the blood vessels and increases the permeability of the vascular wall. This effect occurs when bradykinin binds to certain receptors in the cells of the blood vessel wall known as bradykinin B2 receptors. As a result of binding to these receptors, bradykinin sets in motion various processes that lead to increased permeability of the vascular wall, resulting in increased escape (extravasation) of fluid from the blood into the surrounding tissues. One consequence of this process can be the development of non-pruritic (non-itchy) swelling of the skin or mucous membranes.

Elevated bradykinin concentrations lead to angioedema: