Stimulated human mast cells secrete mitochondrial components that have autocrine and paracrine inflammatory actions.

Bodi Zhang,Shahrzad Asadi,Nikolaos Sismanopoulos,Zuyi Weng,Theoharis C Theoharides,Valli De Re

doi:10.1371/journal.pone.0049767

Bodi Zhang, Shahrzad Asadi + Show 4 more

Open Access

https://doi.org/10.1371/journal.pone.0049767

Copy DOI

Journal: PloS one	Publication Date: Dec 17, 2012
Citations: 138	License type: CC BY 4.0

Affiliation: Tufts University, Tufts Medical Center

Abstract

Mast cells are hematopoietically-derived tissue immune cells that participate in acquired and innate immunity, as well as in inflammation through release of many chemokines and cytokines, especially in response to the pro-inflammatory peptide substance P (SP). Inflammation is critical in the pathogenesis of many diseases, but the trigger(s) is often unknown. We investigated if mast cell stimulation leads to secretion of mitochondrial components and whether these could elicit autocrine and/or paracrine inflammatory effects. Here we show that human LAD2 mast cells stimulated by IgE/anti-IgE or by the SP led to secretion of mitochondrial particles, mitochondrial (mt) mtDNA and ATP without cell death. Mitochondria purified fromLAD2 cells and, when mitochondria added to mast cells trigger degranulation and release of histamine, PGD2, IL-8, TNF, and IL-1β. This stimulatory effect is partially inhibited by an ATP receptor antagonist and by DNAse. These results suggest that the mitochondrial protein fraction may also contribute. Purified mitochondria also stimulate IL-8 and vascular endothelial growth factor (VEGF) release from cultured human keratinocytes, and VEGF release from primary human microvascular endothelial cells. In order to investigate if mitochondrial components could be secreted in vivo, we injected rats intraperiotoneally (ip) with compound 48/80, which mimicks the action of SP. Peritoneal mast cells degranulated and mitochondrial particles were documented by transimission electron microscopy outside the cells. We also wished to investigate if mitochondrial components secreted locally could reach the systemic circulation. Administration ip of mtDNA isolated from LAD2 cells in rats was detected in their serum within 4 hr, indicating that extravascular mtDNA could enter the systemic circulation. Secretion of mitochondrial components from stimulated live mast cells may act as “autopathogens” contributing to the pathogenesis of inflammatory diseases and may be used as targets for novel treatments.

Highlights

Mast cells are hematopoietic tissue immune cells that secrete pre-stored mediators, such as histamine and tryptase through degranulation, as well as numerous de novo synthesized chemokines and cytokines in response to allergic or non-immune triggers [1,2]
Mast cell degranulation leads to extracellular mitochondrial particles secretion Human cord blood mast cells stimulated by IgE/ anti-IgE (Fig. 1) for 30 min at 37uC undergo rapid degranulation with concomitant mitochondrial fission and translocation from a perinuclear region to a more generalized distribution throughout the cell (Fig. 1), especially close to the cell surface (Fig. 1 upper panels)
Serum human mt-7s DNAand mt-CytB DNA levels were significantly increased and could have only come from the human mitochondria injected due to PCR primer sequence specificity (Fig. 7D), indicating human mitochondria can enter the systemic circulation. This is the first time to our knowledge that mitochondrial components are shown to be secreted from activated live cells, and to stimulate mast cells, keratinocytes and endothelial cells to produce pro-inflammtory cytokines

Summary

Introduction

Mast cells are hematopoietic tissue immune cells that secrete pre-stored mediators, such as histamine and tryptase through degranulation, as well as numerous de novo synthesized chemokines and cytokines in response to allergic or non-immune triggers [1,2]. Mast cells are the only cell type that stores preformed tumor necrosis factor (TNF) in secretory granules [3]. We recently showed that human mast cell degranulation and preformed TNF secretion in response to both allergic and nonallergic triggers requires mitochondrial fission and translocation to the cell surface [7]. Mitochondria are the primary energy-generating organelles in eukaryotic cells [10], but they participate in multiple intracellular processes and diseases [11], many of which require mitochondrial fission and translocation [12]. Recent evidence indicates that damage-associated molecular patterns (DAMPs), released from damaged dead cells, can act as ‘‘alarmins’’ [13] and activate polymorphonuclear leukocytes (PMNs) through toll like receptors (TLR)-9, leading to inflammatory responses in the absence of an active infection [14]

Methods

Results

Conclusion