Exophilin-5 regulates allergic airway inflammation by controlling IL-33–mediated Th2 responses
Katsuhide Okunishi, … , Susumu Nakae, Tetsuro Izumi
Katsuhide Okunishi, … , Susumu Nakae, Tetsuro Izumi
Published April 2, 2020
Citation Information: J Clin Invest. 2020;130(7):3919-3935. https://doi.org/10.1172/JCI127839.
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Research Article Immunology

Exophilin-5 regulates allergic airway inflammation by controlling IL-33–mediated Th2 responses

Abstract

A common variant in the RAB27A gene in adults was recently found to be associated with the fractional exhaled nitric oxide level, a marker of eosinophilic airway inflammation. The small GTPase Rab27 is known to regulate intracellular vesicle traffic, although its role in allergic responses is unclear. We demonstrated that exophilin-5, a Rab27-binding protein, was predominantly expressed in both of the major IL-33 producers, lung epithelial cells, and the specialized IL-5 and IL-13 producers in the CD44hiCD62LloCXCR3lo pathogenic Th2 cell population in mice. Exophilin-5 deficiency increased stimulant-dependent damage and IL-33 secretion by lung epithelial cells. Moreover, it enhanced IL-5 and IL-13 production in response to TCR and IL-33 stimulation from a specific subset of pathogenic Th2 cells that expresses a high level of IL-33 receptor, which exacerbated allergic airway inflammation in a mouse model of asthma. Mechanistically, exophilin-5 regulates extracellular superoxide release, intracellular ROS production, and phosphoinositide 3-kinase activity by controlling intracellular trafficking of Nox2-containing vesicles, which seems to prevent the overactivation of pathogenic Th2 cells mediated by IL-33. This is the first report to our knowledge to establish the significance of the Rab27-related protein exophilin-5 in the development of allergic airway inflammation, and provides insights into the pathophysiology of asthma.

Authors

Katsuhide Okunishi, Hao Wang, Maho Suzukawa, Ray Ishizaki, Eri Kobayashi, Miho Kihara, Takaya Abe, Jun-ichi Miyazaki, Masafumi Horie, Akira Saito, Hirohisa Saito, Susumu Nakae, Tetsuro Izumi

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Figure 8

Enhanced IL-5 and IL-13 production in response to IL-33 stimulation by exophilin-5–deficient CD4+ T cells is mediated by the PI3K/Akt/mTOR pathway.

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Enhanced IL-5 and IL-13 production in response to IL-33 stimulation by e...
(A) Percentages of p-Akthi cells in CD44hiCD62LloCXCR3lo pathogenic Th2 cells (Tpath2) after 30 minutes of anti-CD3ε Ab (CD3) stimulation. Splenic CD4+ T cells obtained from OVA-sensitized WT mice or Exph5-KO mice were first stained for cell surface molecules, and were then cultured on anti-CD3ε Ab–coated plates. After a 30-minute culture, cells were fixed, permeabilized, and stained with anti–p-Akt–PE Ab. (B) Effect of the PI3K inhibitor wortmannin (PI3Ki, 100 nM), on cell surface IL-33R expression. (C and D) Effects of wortmannin (C) and the mTOR inhibitor rapamycin (Rapa, 10 nM) (D) on IL-5 and IL-13 production by CD4+ T cells. After a 10-minute preincubation with and without the indicated inhibitors, CD4+ T cells were cultured as described in Figure 5A for 2 days. Cytokine levels in the supernatants were then measured by ELISA. ΔIL-5 indicates the increase in IL-5 production induced by addition of IL-33. CD4+ T cells were obtained from OVA-sensitized WT and Exph5-KO mice. Data were obtained from n = 4 independent experiments in A and B. n = 3–5 mice in C and D gathered from 2 to 3 independent experiments. *P < 0.05 by unpaired t test. #P < 0.05; ##P < 0.01; ###P < 0.001 by 1-way ANOVA with Tukey’s post hoc test. †P < 0.05; ††P < 0.01 by repeated-measures ANOVA with Tukey’s post hoc test.