Phosphorylation of Signal Transducer and Activator of Transcription 6 (STAT6) and STAT1, but Not STAT3, Induced by Antigen Inhalation in Bronchial Smooth Muscles of Sensitized Mice

Abstract

The dramatic increase in the number of asthma cases over the last decades is of great concern for public health in the world.1) The CD4 ϩ T helper 2 lymphocytes (Th2 cells) are closely associated with disease severity, suggesting an integral role of Th2 cells in the pathophysiology of allergic bronchial asthma.2-5) Th2 cells secrete various cytokines, termed Th2 cytokines, which cause several key features of allergic bronchial asthma, including airway hyperresponsiveness (AHR).2-5) Increasing evidence indicates that interleukin-13 (IL-13), one of the members of Th2 cytokine family, is a crucial mediator in the development of AHR. [6][7][8] In addition, another Th2 cytokine IL-4 is also believed to play a role in asthma.9-11) Interestingly, IL-4 shares many functional properties with IL-13, presumably because they share a common receptor composed of IL4Ra chain as one of the two hetero chains. 12)Most of the activities of IL-13 and IL-4 can be ascribed to the activation of signal transducer and activator of transcription 6 (STAT6). [13][14][15] Indeed, a critical role of the STAT6 signal transduction in the development of AHR has been suggested in STAT6-deficient mice. 16,17) Similarly, a cell-penetrating dominant-negative STAT6 peptide could inhibit AHR in a mouse model of allergic bronchial asthma.18) On the other hand, recent studies also indicated an implication of the STAT family of molecules other than STAT6, such as STAT1 19) and STAT3,20) in the development of AHR. However, there is little information whether or not antigen challenge really causes the in vivo activation of these STAT molecules in bronchial smooth muscles (BSMs). In the present study, activations of these STAT molecules were examined in BSMs of a murine model of allergic asthma, which has marked BSM hyperresponsiveness. 21,22) MATERIALS AND METHODS AnimalsMale BALB/c mice were purchased from the Charles River Japan, Inc. (Kanagawa, Japan) and housed in a pathogen-free facility. All animal experiments were approved by the Animal Care Committee of the Hoshi University (Tokyo, Japan).Antigen Sensitization and Challenge Preparation of a murine model of allergic bronchial asthma was performed as described previously. [21][22][23][24][25] In brief, BALB/c mice (8 weeks of age) were actively sensitized by intraperitoneal (i.p.) injections of 8 mg ovalbumin (OA; Seikagaku Co., Tokyo, Japan) with 2 mg Imject Alum (Pierce Biotechnology, Inc., Rockfold, IL, U.S.A.) on day 0 and day 5. The sensitized mice were challenged with aerosolized OA-saline solution (5 mg/ml) for 30 min on days 12, 16 and 20. A control group of mice received the same immunization procedure except for inhaling saline aerosol instead of OA challenge. The aerosol was generated with an ultrasonic nebulizer (Nihon Kohden, Tokyo, Japan) and introduced to a Plexiglas chamber box (130ϫ200 mm, 100 mm height) in which the mice were placed. Three hours after the last OA challenge, mice were sacrificed by exsanguination from the abdominal aorta under urethane (1.6 g/kg, i.p.; Sigma-Aldric...

Activation of STAT6 by intranasal allergens correlated with the development of eosinophilic chronic rhinosinusitis in a mouse model

“…Although the levels of p-STAT1 and p-STAT3 were not significantly increased in our ECRS model, STAT1 and STAT3 were also previously considered potential targets for regulating airway inflammation. 18 – 20 STAT1 is critical for Th1 polarization, and its hallmark cytokine is IFN-γ, one of the Th1 cytokines. 40 However, no evidence of elevated IFN-γ levels was reported in AR or ECRS, although a previous study suggested that epithelial STAT1 was activated in asthmatic subjects.…”

“… 43 Cui et al 44 reported that elevated expression of STAT3 led to the overexpression of IgE and other inflammatory factors in an OVA-induced AR model. However, Chiba et al 19 suggested that STAT3 phosphorylation could not be induced by antigens in the lungs of a mouse asthma model. Further studies are needed to define the functional roles of STAT1 and STAT3 in ECRS.…”

“…16,17 Although these studies only emphasized the role of STAT6 in Th2 responses, some other studies indicated that STAT1 and/or STAT3 play important roles in antigen-induced airway inflammation and hyperresponsiveness. [18][19][20] In addition, induction by topical antigen failed to result in inflammation and hyperresponsiveness of nasal airways in STAT1-deficient mice. 21 Wang et al 22 reported that in addition to STAT6, STAT3 plays an important role in the development of AR.…”

Acute nitrogen dioxide (NO2) exposure enhances airway inflammation via modulating Th1/Th2 differentiation and activating JAK-STAT pathway

“…STAT6 has been demonstrated to regulate many pathologic features of lung inflammatory responses in animal models including airway eosinophilia, epithelial mucus production, smooth muscle changes, Th2 cell differentiation, and IgE production from B cells (Walford and Doherty, 2013). Also, a significant increase of STAT6 phosphorylation was observed in mice with allergic bronchial asthma (Chiba et al, 2010). Especially, Th2-dependent JAK/STAT activation pathway plays a critical role in the exacerbation of asthma.…”