STAT3 and IL-6 Contribute to Corticosteroid Resistance in an OVA and Ozone-induced Asthma Model with Neutrophil Infiltration

Abstract

Exposure to high levels of ozone contributes to insensitivity to glucocorticoids in asthma treatment, but the underlying mechanisms are not known. We built two asthma models: a “T2-high” asthma model was established by ovalbumin (OVA) sensitization/challenge and OVA sensitization/challenge combined with ozone exposure (OVA + ozone) was used to induce airway inflammation with increased numbers of neutrophils to simulate “T2-low” asthma. The expression of T-helper (Th)1/2/17-related cytokines was measured by cytokine antibody arrays. Bronchial provocation tests were carried out to evaluate the lung resistance of mice. Hematoxylin and eosin staining, periodic acid-Schiff staining, and immunohistochemical (IHC) analyses of alpha-smooth muscle actin were undertaken to observe morphology changes in lungs. The expression of glucocorticoid receptors (GRs) and phosphorylated-GR (p-GR) was measured by western blotting. Nr3c1 mRNA was quantified by RT-qPCR. Protein expression of proinflammatory cytokines, signal transducer and activator of transcription 3 (STAT3), suppressor of cytokine signaling 3 (SOCS3), and CXCL1 was measured through ELISAs, western blotting, or IHC analyses. Resected lung tissue from seven asthma patients and 10 healthy controls undergoing thoracotomy for pulmonary nodules was evaluated by IHC analyses and ELISAs. In both asthma models, mucus hypersecretion, as well as inflammation, hyperresponsiveness, and remodeling of the airways, was present compared with the control group, whereas the OVA + ozone group showed severe neutrophil infiltration. The expression of Th17-related cytokines (interleukin (IL)-6, IL-17A, IL-21), GR protein, and CXCL1 increased in the OVA + ozone group, whereas the expression of p-GR decreased. Dexamethasone (Dex) could not totally reverse the expression of p-GR and histone deacetylase-2 in the OVA + ozone group. STAT3 expression increased in the OVA + ozone group and could not be completely reversed by Dex, and nor could IL-6 expression. A positive correlation between IL-6 or IL-17A and STAT3 and negative correlation between SOCS3 and STAT3 were shown, suggesting that the IL-6/STAT3 pathway may be involved in OVA + ozone–induced corticosteroid-resistant airway inflammation. In clinical samples, IL-17A expression in lung tissue was positively correlated with percent STAT3-positive area and negatively correlated with SOCS3 expression. The IL-6/STAT3 pathway may contribute to corticosteroid insensitivity in OVA + ozone–induced neutrophilic airway inflammation through regulation of Th17 cells and could provide new targets for individual treatment of corticosteroid resistance in asthma.

Role of Glucocorticoid Signaling and HDAC4 Activation in Diaphragm and Gastrocnemius Proteolytic Activity in Septic Rats

“…In this sense, acute IL-6 administration induces protein synthesis in myotube cultures [ 38 ]. Another mechanism by which IL-6 can increase muscle mass can be by decreasing the inhibitory effect of glucocorticoid, since the role of IL-6 in experimental asthma-induced glucocorticoid insensitivity has been recently reported [ 39 ].…”

Therapeutic Potential of Combining IL-6 and TNF Blockade in a Mouse Model of Allergic Asthma

“…TNF participates in training macrophages to rapidly mediate Th2 response following repetitive allergen exposure [ 16 ]. On the other hand, IL-6 orchestrates Th17 cell differentiation and may enhance Th17-driven neutrophilic inflammation in the airways [ 27 , 54 , 73 , 74 , 75 ]. In the present study, we demonstrated that combined pharmacological inhibition of TNF and IL-6 prevents the accumulation of both Th2- and Th1/Th17-cells in the lungs ( Figure 2 A,C and Figure 3 B).…”

Immune Repertoire and Advancements in Nanotherapeutics for the Impediment of Severe Steroid Resistant Asthma (SSR)

“…Exposure to higher ozone levels could induce the development of glucocorticoid insensitivity during asthma treatment. 12 In this study, the signaling mechanism pertinent to corticosteroid resistance in asthmatic patients with the increased exposure to ozone was delineated. 12 For instance, T2-low asthmatic condition was induced by the infiltration of neutrophils in asthma models by exposure to ovalbumin and ozone.…”

“… 12 In this study, the signaling mechanism pertinent to corticosteroid resistance in asthmatic patients with the increased exposure to ozone was delineated. 12 For instance, T2-low asthmatic condition was induced by the infiltration of neutrophils in asthma models by exposure to ovalbumin and ozone. Inflammatory and pro-inflammatory cytokines expression, lung resistance, etiology of lungs, modulation in the levels of GR and p-GR receptors, Nr3c1 mRNA, (STAT3), (SOCS3), and CXCL1 were ascertained for inducing corticosteroid resistance.…”

“…STAT3/IL-6 signaling pathway can be considered as a crucial therapeutic target to mitigate corticosteroid resistance. 12 …”