Forsythiasides-Rich Extract From Forsythiae Fructus Inhibits Mast Cell Degranulation by Enhancing Mitochondrial Ca2+ Uptake.

Ruijuan Qi,Xiaoyu Zhang,Yuan Gao,Ximeng Li,Yun Qi,Runlan Cai,Yuan Kang,Yixin Han

doi:10.3389/fphar.2021.696729

Ruijuan Qi, Xiaoyu Zhang + Show 6 more

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https://doi.org/10.3389/fphar.2021.696729

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Abstract

Mast cells (MCs) activated via IgE/FcεRI or MAS-related G protein coupled receptor (Mrgpr)-mediated pathway can release granules that play prominent roles in hypersensitivity reactions. Forsythiae Fructus, a well-known traditional Chinese medicine, has been clinically used for allergic diseases. Although previous studies indicated that Forsythiae Fructus extract inhibited compound 48/80-induced histamine release from MCs, its effect on IgE-dependent MC degranulation and possible underlying mechanisms remain to be explored. Herein, we prepared the forsythiasides-rich extract (FRE) and investigated its action on MC degranulation and explored its underlying mechanism. Our data showed that FRE could dampen IgE/FcεRI- and Mrgpr-mediated MC degranulation in vitro and in vivo. Mechanism study indicated that FRE decreased cytosolic Ca2+ (Ca2+ [c]) level rapidly and reversibly. Moreover, FRE decreased Ca2+ [c] of MCs independent of plasma membrane Ca2+-ATPase (PMCA), sarco/endoplasmic Ca2+-ATPase (SERCA) and Na+/Ca2+ exchanger (NCX). While, along with Ca2+ [c] decrease, the increase of mitochondrial Ca2+ (Ca2+ [m]) occurred simultaneously in FRE-treated RBL-2H3 cells. In the isolated mitochondria, FRE also promoted the subcellular organelle to uptake more extramitochondrial Ca2+. In conclusion, by increasing Ca2+ [m] uptake, FRE decreases Ca2+ [c] level to suppress MC degranulation. Our findings may provide theoretical support for the clinical application of Forsythiae Fructus on allergy and other MC-involved diseases.

Highlights

Mast cells (MCs), distributing at the host-environment interfaces, are a class of tissue-resident innate immune cells that can respond to various immunogenic stimuli in the first place
The data showed that forsythiasides-rich extract (FRE) reduced IgE/FcεRImediated β-hexosaminidase release with an IC50 value of 540.4 μg/ml (Figure 3C). These results indicated that FRE could dampen both Mas-related G-protein coupled receptor (Mrgpr)- and IgE/FcεRI-mediated MC degranulation in vitro
MCs can be activated via IgE/ FcεRI or Mrgpr-mediated signaling and release lots of preformed granules which contain many biologically active mediators (e.g., β-hexosaminidase and tryptases) (Wernersson and Pejler, 2014)

Summary

Introduction

Mast cells (MCs), distributing at the host-environment interfaces, are a class of tissue-resident innate immune cells that can respond to various immunogenic stimuli in the first place. In IgE-dependent pathway, MC activation can be initiated by crosslinking the IgE-FcεRI complexes with multivalent antigens, Abbreviations: C48/80, compound 48/80; Ca2[c+], cytosolic Ca2+; Ca2[m+], mitochondrial Ca2+; FRE, forsythiasides-rich extracts; MCs, mast cell; Mrgpr, the mas-related G-protein receptor; MPMCs, mouse peritoneal mast cells; RFF, ripe forsythiae fructus; SP, shrimp protein; UFF, unripe forsythiae fructus. In IgE-independent pathway, MCs possess unique responsiveness to the basic secretagogues [e.g., compound 48/80 (C48/80) and substance P], which can directly induce MC degranulation via activating the Mas-related G-protein coupled receptor (Mrgpr) (MrgprX2 for human MCs and MrgprB2 for mouse) (McNeil et al, 2015). Crosslinking of IgE-FcεRI complexes with antigens and activation of Mrgpr by C48/80 can induce different intracellular signal cascades, they reach the same outcome—elevation of cytosolic Ca2+ (Ca2[c+]) and subsequent MC degranulation (Chen et al, 2017). Preventing MC degranulation is regarded as an attractive therapeutic strategy in treating allergic diseases

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