Mast Cell: A Multi-Functional Master Cell

Abstract

Mast cells are immune cells of the myeloid lineage and are present in connective tissues throughout the body. The activation and degranulation of mast cells significantly modulates many aspects of physiological and pathological conditions in various settings. With respect to normal physiological functions, mast cells are known to regulate vasodilation, vascular homeostasis, innate and adaptive immune responses, angiogenesis, and venom detoxification. On the other hand, mast cells have also been implicated in the pathophysiology of many diseases, including allergy, asthma, anaphylaxis, gastrointestinal disorders, many types of malignancies, and cardiovascular diseases. This review summarizes the current understanding of the role of mast cells in many pathophysiological conditions.

Keywords: atherogenesis; immune system; inflammatory mediators; mast cell; systemic hypoxia.

Figure 1

Major substances released by activated mast cells.

Figure 2

Scheme showing the synergistic activation of inflammatory response in endothelial cells by mast cell-derived histamine and bacterial products. (A) Histamine secreted by the mast cell stimulates H1R on endothelial cells. (B) H1R-mediated endothelial cell activation leads to increased expression of TLR2 and TLR4, and become hyperresponsive to the TLR ligands leading to enhanced inflammatory response. (C) Increased TLR2 and TLR4 signaling increases H1R expression. Finally, collective actions of newly expressed TLR2/TLR4 and H1R lead to increased COX2 expression and other proinflammatory changes in the endothelium resulting in persistent vascular inflammation.