Didox (3,4-dihydroxybenzohydroxamic acid) suppresses IL-33-induced cytokine production in primary mouse mast cells

IL33 and Mast Cells-The Key Regulators of Immune Responses in Gastrointestinal Cancers?

The Interleukin (IL-)1 family IL33 is best known for eliciting type 2 immune responses by stimulating mast cells (MCs), regulatory T-cells (Tregs), innate lymphoid cells (ILCs) and other immune cells. MCs and IL33 provide critical control of immunological and epithelial homeostasis in the gastrointestinal (GI) tract. Meanwhile, the role of MCs in solid malignancies appears tissue-specific with both pro and anti-tumorigenic activities. Likewise, IL33 signaling significantly shapes immune responses in the tumor microenvironment, but these effects remain often dichotomous when assessed in experimental models of cancer. Thus, the balance between tumor suppressing and tumor promoting activities of IL33 are highly context dependent, and most likely dictated by the mixture of cell types responding to IL33. Adding to this complexity is the promiscuous nature by which MCs respond to cytokines other than IL33 and release chemotactic factors that recruit immune cells into the tumor microenvironment. In this review, we integrate the outcomes of recent studies on the role of MCs and IL33 in cancer with our own observations in the GI tract. We propose a working model where the most abundant IL33 responsive immune cell type is likely to dictate an overall tumor-supporting or tumor suppressing outcome in vivo. We discuss how these opposing responses affect the therapeutic potential of targeting MC and IL33, and highlight the caveats and challenges facing our ability to effectively harness MCs and IL33 biology for anti-cancer immunotherapy.

Resveratrol attenuates IL‑33‑induced mast cell inflammation associated with inhibition of NF‑κB activation and the P38 signaling pathway

Resveratrol (RSV), a natural polyphenol found in grapes and other herbal plants, has been reported to possess anti‑inflammatory, anti‑oxidative and anti‑proliferative activities. The aim of the present study was to investigate the effect of RSV on interleukin (IL)‑33‑induced inflammatory responses in mast cells and identify the underlying molecular mechanisms. Rat basophilic leukemia (RBL‑2H3) cells were stimulated with IL‑33 in the presence or absence of RSV. MTT, ELISA, reverse transcription‑quantitative PCR and western blot analyses were then performed in order to assess cytotoxicity, inflammatory cytokine production, suppression of tumorigenicity 2 receptor expression, protein expression involved in mitogen‑activated protein kinase (MAPK) and nuclear factor (NF)‑κB signaling, respectively. Finally, rats were used to determine the biological effect of RSV in vivo. The results revealed that RSV inhibited cell viability and increased cytotoxicity in a dose‑dependent manner. Medium concentration of RSV (10 µM) treatment attenuated inflammatory cytokine production, such as IL‑6, IL‑13, tumor necrosis factor‑α and monocyte chemotactic protein‑1, and curbed IL‑33‑induced enhancement of immunoglobulin E‑mediated responses in RBL‑2H3 cells, which were associated with the suppression of NF‑κB‑mediated transcription and inhibition of P38 phosphorylation in response to IL‑33 stimulation, but not extracellular signal regulated kinase or JNK. Notably, RSV application also decreased the levels of inflammatory cytokines in rats induced by IL‑33 injection, which was similar to the anti‑inflammatory effect in vitro. The data from the present study demonstrated that RSV played a regulatory role in antagonizing the effects of IL‑33 on mast cells both in vitro and in vivo, suggesting that it has therapeutic potential in IL‑33‑mediated inflammatory diseases that are associated with mast cells.

Inhibiting Glycolysis and ATP Production Attenuates IL-33-Mediated Mast Cell Function and Peritonitis

Cellular metabolism and energy sensing pathways are closely linked to inflammation, but there is little understanding of how these pathways affect mast cell function. Mast cells are major effectors of allergy and asthma, and can be activated by the alarmin IL-33, which is linked to allergic disease. Therefore, we investigated the metabolic requirements for IL-33-induced mast cell function, to identify targets for controlling inflammation. We found that IL-33 increases glycolysis, glycolytic protein expression, and oxidative phosphorylation (OX PHOS). Inhibiting OX PHOS had little effect on cytokine production, but antagonizing glycolysis with 2-deoxyglucose or oxamate suppressed inflammatory cytokine production in vitro and in vivo. ATP reversed this suppression. Glycolytic blockade suppressed IL-33 signaling, including ERK phosphorylation, NFκB transcription, and ROS production in vitro, and suppressed IL-33-induced neutrophil recruitment in vivo. To test a clinically relevant way to modulate these pathways, we examined the effects of the FDA-approved drug metformin on IL-33 activation. Metformin activates AMPK, which suppresses glycolysis in immune cells. We found that metformin suppressed cytokine production in vitro and in vivo, effects that were reversed by ATP, mimicking the actions of the glycolytic inhibitors we tested. These data suggest that glycolytic ATP production is important for IL-33-induced mast cell activation, and that targeting this pathway may be useful in allergic disease.

Involvement of the Negative Feedback of IL-33 Signaling in the Anti-Inflammatory Effect of Electro-acupuncture on Allergic Contact Dermatitis via Targeting MicroRNA-155 in Mast Cells

In this study, we aimed to investigate the effect of electro-acupuncture (EA) at the Zusanli acupoint (ST36) on interleukin (IL)-33-mediated mast cell activation. Firstly, 2,4-dinitrofluorobenzene (DNFB)-induced allergic contact dermatitis (ACD) in rats was developed with or without EA treatment. Then, rat peritoneal mast cells (RPMCs) were obtained and cultured in the presence of IL-33. EA treatment relieved ear swelling and reduced mast cell infiltration in the local inflammation area with DNFB challenge, accompanying the decrement of IL-33 production. RPMCs isolated from ACD rats with EA treatment showed significant downregulation of IL-6, TNF-α, IL-13, and MCP-1 production following IL-33 stimulation. However, there was no obvious difference in surface ST2 receptor expression among different groups. In addition, EA selectively altered IL-33 signaling, suppressing p38 phosphorylation as well as NF-κB- and AP-1-mediated transcription but not Akt phosphorylation. Importantly, EA lowered microRNA (miR)-155 expression in the RPMCs, which presented a positive correlation with IL-33-induced IL-6 production. Furthermore, overexpression of miR-155 in the RPMCs was established following miR-155 mimic transfection. RPMCs with the overexpressed miR-155 displayed an obvious increment of inflammatory cytokine and abrogated the inhibitive effect of EA on NF-κB- and AP-1-regulated transcription in response to IL-33 compared with those without transfected-miR-155. These findings demonstrate EA treatment inhibits NF-κB and AP-1 activation as well as promotes the negative feedback regulation of IL-33 signaling via targeting miR-155 in mast cells, which contribute to the anti-inflammatory effect of EA on DNFB-induced ACD in rats.

Didox (3,4-dihydroxybenzohydroxamic acid) suppresses IgE-mediated mast cell activation through attenuation of NFκB and AP-1 transcription

Mast cell activation via the high-affinity IgE receptor (FcεRI) elicits production of inflammatory mediators central to allergic disease. As a synthetic antioxidant and a potent ribonucleotide reductase (RNR) inhibitor, Didox (3,4-dihyroxybenzohydroxamic acid) has been tested in clinical trials for cancer and is an attractive therapeutic for inflammatory disease. We found that Didox treatment of mouse bone marrow-derived mast cells (BMMC) reduced IgE-stimulated degranulation and cytokine production, including IL-6, IL-13, TNF and MIP-1a (CCL3). These effects were consistent using BMMC of different genetic backgrounds and peritoneal mast cells. While the RNR inhibitor hydroxyurea had little or no effect on IgE-mediated function, high concentrations of the antioxidant N-acetylcysteine mimicked Didox-mediated suppression. Furthermore, Didox increased expression of the antioxidant genes superoxide dismutase and catalase, and suppressed DCFH-DA fluorescence, indicating reduced reactive oxygen species production. Didox effects were not due to changes in FcεRI expression or cell viability, suggesting it inhibits signaling required for inflammatory cytokine production. In support of this, we found that Didox reduced FcεRI-mediated AP-1 and NFκB transcriptional activity. Finally, Didox suppressed mast cell-dependent, IgE-mediated passive systemic anaphylaxis in vivo. These data demonstrate the potential use for Didox asa means of antagonizing mast cell responses in allergic disease.