Pathophysiological Involvement of Mast Cells and the Lipid Mediators in Pulmonary Vascular Remodeling

Abstract

Mast cells are responsible for IgE-dependent allergic responses, but they also produce various bioactive mediators and contribute to the pathogenesis of various cardiovascular diseases, including pulmonary hypertension (PH). The importance of lipid mediators in the pathogenesis of PH has become evident in recent years, as exemplified by prostaglandin I2, the most central therapeutic target in pulmonary arterial hypertension. New bioactive lipids other than eicosanoids have also been identified that are associated with the pathogenesis of PH. However, it remains largely unknown how mast cell-derived lipid mediators are involved in pulmonary vascular remodeling. Recently, it has been demonstrated that mast cells produce epoxidized n-3 fatty acid (n-3 epoxides) in a degranulation-independent manner, and that n-3 epoxides produced by mast cells regulate the abnormal activation of pulmonary fibroblasts and suppress the progression of pulmonary vascular remodeling. This review summarizes the role of mast cells and bioactive lipids in the pathogenesis of PH. In addition, we introduce the pathophysiological role and therapeutic potential of n-3 epoxides, a mast cell-derived novel lipid mediator, in the pulmonary vascular remodeling in PH. Further knowledge of mast cells and lipid mediators is expected to lead to the development of innovative therapies targeting pulmonary vascular remodeling.

Keywords: lipid mediator; mast cell; n-3 epoxides; omega-3; pulmonary hypertension; remodeling.

Figure 1

Mechanisms of vascular remodeling by mast cells and various lipid mediators. Abbreviations: TRPA1, transient receptor potential ankyrin 1; VEGF, vascular endothelial growth factor; PDGF, platelet-derived growth factor; LT, leukotriene; PGD2, prostaglandin D2; PGE2, prostaglandin E2; PAF, platelet activating factor; S1P, sphingosine-1 phosphate; LPA, lysophosphatidic acid; PGI2, prostaglandin I2; LTB4, leukotrien B4; HETE, hydroxyeicosatetraenoic acid; EET, epoxyeicosatrienoic acid; EPA, eicosapentaenoic acid; DHA, docosahexaenoic acid; SPMs, specialized pro-resolving mediators; RvD1, resolvin D1; RvE1, resolvin E1.

Figure 2

A novel mechanism of pulmonary vascular remodeling by n-3 epoxides. Mast cells-derived n-3 epoxides produced by PAF-AH2 regulate pulmonary vascular remodeling through inhibiting abnormal activation of adventitial fibroblasts. PAF-AH2, type II platelet activating factor acetylhydrolase.