Signals from the TAFA4-PTEN-PU.1 axis alleviate nasal allergy by modulating the expression of FcεRI in mast cells

Abstract

The high-affinity IgE receptor, FcεRI, plays a key role in the antigen-induced mast cell activation. Regulations for FcεRI are not yet well understood. TAFA4 is a molecule derived from neuron tissues, and has immune regulation functions. This study aims to clarify the role of TAFA4 in the regulation of FcεRI expression in mast cells. Nasal secretions were collected from patients with allergic rhinitis (AR) and healthy control (HC) subjects. TAFA4 levels of nasal secretions were evaluated by ELISA. A mouse model AR was developed using ovalbumin as the specific antigen. Negative correlation between TAFA4 and tryptase levels in nasal secretions was observed. TAFA4 could suppress the antigen-related mast cell activation. TAFA4 modulated the transcription of Fcer1g (FcεRI γ gene) in mast cells. Signals from the TAFA4-PTEN-PU.1 axis restricted FcεRI expression in mast cells. Administration of TAFA4 attenuated experimental AR. TAFA4 suppressed the expression of FcεRI in mast cells of airway tissues. TAFA4 can down regulate the expression of FcεRI in mast cells to suppress experimental AR. The data suggest that TAFA4 has translation potential to be developed as an anti-allergy therapy.

Keywords: IgE receptor; immunity; mast cell; nasal allergy; neuropeptide.

Graphical Abstract

Figure 1:

assessment of TAFA4 and tryptase in nasal secretions (NSN). NSN samples were collected from allergic rhinitis (AR) patients (n = 25) and healthy control (HC) subjects (n = 25), and analyzed by ELISA. A-B, median (IQR) of TAFA4 (A) or tryptase (B) levels in NSN. (C) Negative correlation between TAFA4 and tryptase levels in NSN.

Figure 2:

TAFA4 downregulates mast cell activation. BMMCs were sensitized to OVA-specific IgE, and treated with the procedures (denoted on the X-axis of boxplots) overnight. A, median (IQR) of hexo levels (compared against the hexo value induced by 0.1% Triton X-100) in supernatant from 3 experiments. B, median (IQR) of Fcer1g mRNA levels in BMMCs from 3 experiments. Hexo: β-hexosaminidase. OVA: Ovalbumin (0.5 µg/ml; the specific antigen). BSA: Bovine serum albumin (5 µg/ml; used as an irrelevant antigen).

Figure 3:

TAFA4 suppresses Fcer1g gene transcription. BMMCs were treated with the procedures denoted on the X axis of boxplots. ChIP results show the median (IQR) of PU.1 (A) and Pol II (B) in the Fcer1g promoter of BMMCs. (C), the median (IQR) of Fcer1g mRNA in BMMCs. BMMC: Bone marrow derived mast cells. ChIP: Chromatin immunoprecipitation. Pol II: RNA polymerase II.

Figure 4:

Assessment of the role of PTEN in regulating Fcer1g gene activity. BMMCs were treated with the procedures denoted on the X-axis of panel A. Boxplots show median (IQR) of Pten mRNA in BMMCs. B, immunoblots of IP show a complex of PTEN and PU.1 in sensitized BMMCs after treating with OVA.TAFA4. HEK293 cells were transfected with PTEN-plasmids or/and PU.1-plasmids, and a luciferase FCER1G promoter reporter. C, A complex of recombinant PTEN and PU.1 in HEK293 cells. D, Luciferase activity measurement.

Figure 5:

TAFA4 suppresses AR response. An AR mouse model was developed using OVA as a specific antigen. TAFA4 was employed in the period of immune boosting. A,B, AR clinical symptoms (Nasal itch and sneezing). C,D, allergic mediators (Mcpt1 and EPX) in NLF. E,G, Th2 cytokines (IL-4, IL-5, and IL-13) in NLF. H, serum sIgE levels. OVA: ovalbumin. NLF: nasal lavage fluid. PBS: using as a negative control agent. Each group consists of 6 mice.

Figure 6:

TAFA4 downregulates FcεRI in mast cells. An AR mouse model was developed using OVA as a specific antigen. TAFA4 was employed in the period of immune boosting. AMCs were prepared and analyzed by FCM. A, Gated FCM plots show mast cell counts. B, Median (IQR) of mast cell counts. C, Gated histograms show FcεRI⁺ mast cell counts. D, Median (IQR) of relative MFI of FcεRI in mast cells of panel C. AR: allergic rhinitis. OVA: ovalbumin. AMC: airway mononuclear cells. FCM: flow cytometry. MFI: median fluorescence intensity.