Annexin A1 Mimetic Peptide Ac2-26 Modulates the Function of Murine Colonic and Human Mast Cells

Mast cells (MCs) are main effector cells in allergic inflammation and after activation, they release stored (histamine, heparin, proteases) and newly synthesized (lipid mediators and cytokines) substances. In the gastrointestinal tract the largest MC population is located in the lamina propria and submucosa whereas several signals such as the cytokine IL-4, seem to increase the granule content and to stimulate a remarkable expansion of intestinal MCs. The broad range of MC-derived bioactive molecules may explain their involvement in many different allergic disorders of the gastrointestinal tract. Annexin A1 (AnxA1) is a 37 KDa glucocorticoid induced monomeric protein selectively distributed in certain tissues. Its activity can be reproduced by mimetic peptides of the N-terminal portion, such as Ac2-26, that share the same receptor FPR-L1. Although previous reports demonstrated that AnxA1 inhibits MC degranulation in murine models, the effects of exogenous peptide Ac2-26 on intestinal MCs or the biological functions of the Ac2-26/FPR2 system in human MCs have been poorly studied. To determine the effects of Ac2-26 on the function of MCs toward the possibility of AnxA1-based therapeutics, we treated WT and IL-4 knockout mice with peptide Ac2-26, and we examined the spontaneous and compound 48/80 stimulated colonic MC degranulation and cytokine production. Moreover, in vitro, using human mast cell line HMC-1 we demonstrated that exogenous AnxA1 peptide is capable of interfering with the HMC-1 degranulation in a direct pathway through formyl peptide receptors (FPRs). We envisage that our results can provide therapeutic strategies to reduce the release of MC mediators in inflammatory allergic processes.

YKL-40 Enhanced the Permeability of HDMECs with Histamine Through Activating Akt and p38 Pathways

Background, YKL-40 is currently considered as an important marker of endothelial dysfunction. Chronic spontaneous urticaria (CSU) is a common vascular skin disease. The increased vascular permeability play an important role in the occurrence and pathogenesis of CSU.Objective, the aim of this study is to explore the role of YKL-40 on the permeability of HDMECs.Methods, in this study, the mRNA level of YKL-40 in human mast cell line (HMC-1) were detected by RT-PCR. The effects of YKL-40 on vascular permeability, VE-cadherin release, VE-cadherin disruption in human dermal microvascular endothelial cells (HDMECs) were investigated by transwell, ELISA or immunofluorescence. The phosphorylation of VE-cadherin, p38 and Akt, in histamine plus YKL-40 treated HDMECs were detected by Western Blot.Results, we found that YKL-40 significantly promoted the permeability changes and leaded to the released, disruption of VE-cadherin in HDMECs induced by histamine. Furthermore, YKL-40 also enhanced the Akt and p38 pathways. Conclusion, we suggest that YKL-40 may serve as pro-permeability cytokines, and play a role in the pathogenesis of CSU. This study will help to further elucidate the pathogenesis of CSU and provide a new target for the development of anti-histamine resistance drugs for CSU.

Interleukin-35 inhibited the production of histamine and pro-inflammatory cytokines through suppression MAPKs pathway in HMC-1 cells

Background IL-35 is a newly anti-inflammatory cytokine that belongs to the IL-12 family. Mast cells, as one of the major effector cells in the immune response system, plays an important role in the pathogenesis of chronic spontaneous urticarial (CSU). Our study aims to explore the inhibited role of IL-35 in HMC-1. Methods The effects of IL-35 on cell proliferation, cytokine expression, and histamine release in a human mast cell line (HMC­1) were investigated by CCK8, ELISA, or RT-PCR. The phosphorylation levels of ERK1/2, p38, and JNK1/2, in PMA plus A23187 induced HMC-1 cells was detected by Western Blot. Results We found that IL-35 significantly inhibited the proliferation of HMC-1 cells stimulated by PMA and A23187. IL-35 also down-regulates the release of histamine and the mRNA expression of IL-6 and IL-17 in activated HMC-1. Furthermore, IL-35 markedly inhibited the phosphorylation levels of ERK1/2, p38, and JNK1/2, in PMA plus A23187 induced HMC-1 cells. Conclusions This study provides the first observations on the inhibitory and anti-inflammatory effect of IL-35 in activated HMC-1 cells. We suggest that IL35 may play an inhibited role in the pathogenesis of CSU.

Human Mast Cell Line HMC1 Expresses Functional Mas-Related G-Protein Coupled Receptor 2

The Mas-related G-protein-coupled receptor X2 (MRGPRX2) is prominently expressed by mast cells and induces degranulation upon binding by different ligands. Its activation has been linked to various mast cell-related diseases, such as chronic spontaneous urticaria, atopic dermatitis and asthma. Therefore, inhibition of MRGPRX2 activity represents a therapeutic target for these conditions. However, the exact pathophysiology of this receptor is still unknown. In vitro research with mast cells is often hampered by the technical limitations of available cell lines. The human mast cell types LAD2 and HuMC (human mast cells cultured from CD34+ progenitor cells) most closely resemble mature human mast cells, yet have a very slow growth rate. A fast proliferating alternative is the human mast cell line HMC1, but they are considered unsuitable for degranulation assays due to their immature phenotype. Moreover, the expression and functionality of MRGPRX2 on HMC1 is controversial. Here, we describe the MRGPRX2 expression and functionality in HMC1 cells, and compare these with LAD2 and HuMC. We also propose a model to render HMC1 suitable for degranulation assays by pre-incubating them with latrunculin-B (Lat-B). Expression of MRGPRX2 by HMC1 was proven by RQ-PCR and flowcytometry, although at lower levels compared with LAD2 and HuMC. Pre-incubation of HMC1 cells with Lat-B significantly increased the overall degranulation capacity, without significantly changing their MRGPRX2 expression, phenotype or morphology. The MRGPRX2 specific compound 48/80 (C48/80) effectively induced degranulation of HMC1 as measured by CD63 membrane expression and β-hexosaminidase release, albeit in lower levels than for LAD2 or HuMC. HMC1, LAD2 and HuMC each had different degranulation kinetics upon stimulation with C48/80. Incubation with the MRGPRX2 specific inhibitor QWF inhibited C48/80-induced degranulation, confirming the functionality of MRGPRX2 on HMC1. In conclusion, HMC1 cells have lower levels of MRGPRX2 expression than LAD2 or HuMC, but are attractive for in vitro research because of their high growth rate and stable phenotype. HMC1 can be used to study MRGPRX2-mediated degranulation after pre-incubation with Lat-B, which provides the opportunity to explore MPRGRX2 biology in mast cells in a feasible way.

Interleukin-35 inhibited production of histamine and pro-inflammatory cytokines through suppression MAPKs pathway in HMC-1 cells

Background: IL-35 is a newly anti-inflammatory cytokine which belong to the IL-12 family. Mast cells, as one of the major effector cells in the immune response system, play important roles in the pathogenesis of chronic spontaneous urticarial (CSU). The aim of our study is to explore the inhibited role of IL-35 in HMC-1.Methods: The effects of IL-35 on cell proliferation, cytokine expression and histamine release in human mast cell line (HMC­1) were investigated by CCK8, ELISA or RT-PCR. The phosphorylation of ERK1/2, p38 and JNK1/2, in PMA and A23187 induced HMC-1 cells were detected by Western Blot.Results: We found that IL-35 significantly inhibited the proliferation of HMC-1 cells stimulated by PMA and A23187. IL-35 also down-regulates the released of histamine and the mRNA expression of IL-6 and IL-17 in activated HMC-1. Furthermore, IL-35 markedly inhibited the phosphorylation of ERK1/2, p38 and JNK1/2, in PMA and A23187 induced HMC-1 cells.Conclusions: This study provides first observations on the inhibitory and anti-inflammtory effect of IL-35 on activated HMC-1 cells. We suggest that IL35 may play an inhibited role in the pathogenesis of CSU.

Disrupted Lipid Raft Shuttling of FcεRI by n-3 Polyunsaturated Fatty Acid Is Associated With Ligation of G Protein-Coupled Receptor 120 (GPR120) in Human Mast Cell Line LAD2

n-3 polyunsaturated fatty acids (PUFA) influences a variety of disease conditions, such as hypertension, heart disease, diabetes, cancer and allergic diseases, by modulating membrane constitution, inhibiting production of proinflammatory eicosanoids and cytokines, and binding to cell surface and nuclear receptors. We have previously shown that n-3 PUFA inhibit mast cell functions by disrupting high affinity IgE receptor (FcεRI) lipid raft partitioning and subsequent suppression of FcεRI signaling in mouse bone marrow-derived mast cells. However, it is still largely unknown how n-3 PUFA modulate human mast cell function, which could be attributed to multiple mechanisms. Using a human mast cell line (LAD2), we have shown similar modulating effects of n-3 PUFA on FcεRI lipid raft shuttling, FcεRI signaling, and mediator release after cell activation through FcεRI. We have further shown that these effects are at least partially associated with ligation of G protein-coupled receptor 120 expressed on LAD2 cells. This observation has advanced our mechanistic knowledge of n-3 PUFA's effect on mast cells and demonstrated the interplay between n-3 PUFA, lipid rafts, FcεRI, and G protein-coupled receptor 120. Future research in this direction may present new targets for nutritional intervention and therapeutic agents.

Interleukin-35 inhibited production of histamine and pro-inflammatory cytokines through suppression MAPKs pathway in HMC-1 cells

Background: IL-35 is a newly anti-inflammatory cytokine which belong to the IL-12 family. Mast cells, as one of the major effector cells in the immune response system, play important roles in the pathogenesis of chronic spontaneous urticarial (CSU). The aim of our study is to explore the inhibited role of IL-35 in HMC-1. Methods: The effects of IL-35 on cell proliferation, cytokine expression and histamine release in human mast cell line (HMC­1) were investigated by CCK8, ELISA or RT-PCR. The phosphorylation of ERK1/2, p38 and JNK1/2, in PMA and A23187 induced HMC-1 cells were detected by Western Blot.Results: We found that IL-35 significantly inhibited the proliferation of HMC-1 cells stimulated by PMA and A23187. IL-35 also down-regulates the released of histamine and the mRNA expression of IL-6 and IL-17 in activated HMC-1. Furthermore, IL-35 markedly inhibited the phosphorylation of ERK1/2, p38 and JNK1/2, in PMA and A23187 induced HMC-1 cells. Conclusions: This study provides first observations on the inhibitory and anti-inflammtory effect of IL-35 on activated HMC-1 cells. We suggest that IL35 may play an inhibited role in the pathogenesis of CSU.