Mitochondria Distinguish Granule-Stored from de novo Synthesized Tumor Necrosis Factor Secretion in Human Mast Cells

Abstract

Background: Mast cells are immune cells derived from hematopoietic precursors that mature in the tissue microenvironment. Mast cells are critical for allergic, immune and inflammatory processes, many of which involve tumor necrosis factor (TNF). These cells uniquely store TNF in their secretory granules. Upon stimulation, mast cells rapidly (30 min) secrete β-hexosaminidase and granule-stored TNF through degranulation, but also increase TNF mRNA and release de novo synthesized TNF 24 h later. The regulation of these two distinct pathways is poorly understood. Methods: Human LAD2 leukemic mast cells are stimulated by substance P. TNF secretion and gene expression were measured by ELISA and real-time PCR, and mitochondrial dynamics was observed in live cells under confocal microscopy. Cell energy consumption was measured in terms of oxygen consumption rate. Results: Here, we show that granule-stored TNF is preformed, and its secretion from LAD2 mast cells stimulated by substance P (1) exhibits higher energy consumption and is inhibited by the mitochondrial ATP pump blocker oligomycin, (2) shows rapid increase in intracellular calcium levels, and (3) exhibits reversible mitochondrial translocation, from a perinuclear distribution to the cell surface, as compared to de novo synthesized TNF release induced by lipopolysaccharide. This mitochondrial translocation is confirmed using primary human umbilical cord blood-derived mast cells stimulated by an allergic trigger (IgE/streptavidin). Conclusion: Our findings indicate that unique mitochondrial functions distinguish granule-stored from newly synthesized TNF release from human mast cells, thus permitting the versatile involvement of mast cells in different biological processes.

SP and IL-33 together markedly enhance TNF synthesis and secretion from human mast cells mediated by the interaction of their receptors

“…Moreover, IL-33 has been implicated in the pathogenesis of psoriasis via keratinocyte and mast cell activation (30), and has been reported to be elevated in the serum of patients with generalized psoriasis and correlated with high serum TNF levels (31). In addition to the newly synthesized TNF secretion reported here, mast cells are the only immune cells that also store and rapidly secrete preformed TNF (32)(33)(34)(35)(36). Given the foregoing findings, we decided to investigate whether the interactions between SP and IL-33 affect human mast cell secretion of TNF.…”

Cytokine effects and cellular signaling pathways of grass carp HSP70 in head kidney leukocytes

“…This phenomenon may be due to the distinct regulatory mechanisms for TNF-a synthesis and secretion [35]. Actually, there are multiple pathways responsible for the release of newly synthesized or stored cytokines [36]. For example, the granule-stored TNF is rapidly (30 min) secreted from human mast cells (a bone marrow-derived immune cell) upon stimulation, which differs from the delayed (12e24 h) release of newly synthesized TNF [36].…”

“…Actually, there are multiple pathways responsible for the release of newly synthesized or stored cytokines [36]. For example, the granule-stored TNF is rapidly (30 min) secreted from human mast cells (a bone marrow-derived immune cell) upon stimulation, which differs from the delayed (12e24 h) release of newly synthesized TNF [36]. Notably, regarding the stimulation intensity and duration, rgcHSP70 displayed more potential to regulate the secretion rather than the transcription of the cytokines, promoting us to speculate that gcHSP70 may induce release of proinflammatory cytokines in a rapid or efficient kinetics.…”

“…Notably, regarding the stimulation intensity and duration, rgcHSP70 displayed more potential to regulate the secretion rather than the transcription of the cytokines, promoting us to speculate that gcHSP70 may induce release of proinflammatory cytokines in a rapid or efficient kinetics. In line with this speculation, there should be the existence of secretary granules used for pre-storing cytokines in fish cells as in mammalian immune cells [35,36]. Although this hypothesis is needed to be proved in the future, we do not exclude the possibility that HSP70 is involved in a specific route of cytokine secretion in fish, thereby facilitating rapidly delivering cytokines to a particular target or in response to a specific signal as occurred in mammals [36e38].…”

Stimulated human melanocytes express and release interleukin-8, which is inhibited by luteolin: relevance to early vitiligo

“…1 Apoptotic cells could in turn release high amounts of pro-inflammatory IL-1 and TNF, further enhancing skin inflammation. We previously showed that both preformed and newly synthesized TNF can be released from mast cells, 7 the numbers of which seem to be increased in the centre of vitiligo lesions. 2 A recent paper reported that chemically induced vitiligo led to increased production of IL-6 and IL-8.…”