Down-Regulation of INSR Restores Th17/Treg Immune Balance and Alleviates Airway Hyperviscosity in Asthmatic Mice via Inactivation of STAT3 Pathway.

BACKGROUND: Allergic asthma (AA) is a prevalent chronic airway inflammation disease. In this study, this study aims to investigate the biological functions and potential regulatory mechanisms of the insulin receptor ( INSR ) in the progression of AA.

METHODS: BALB/c mice (n = 48) were randomly divided into the following groups: control group, AA group, AA+Lentivirus (Lv)-vector short hairpin RNA (shRNA) group, AA+Lv-vector group, AA+Lv- INSR shRNA group, and AA+Lv- INSR group. The pulmonary index was calculated. mRNA and protein expression levels of INSR , signal transducer and activator of transcription 3 (STAT3), Janus kinase 2 (JAK2), phosphorylated-STAT3 (p-STAT3), phosphorylated-JAK2 (p-JAK2), alpha-smooth muscle actin ( α-SMA ), febrile neutropenia ( FN ), mucin 5AC ( MUC5AC ), and mucin 5B ( MUC5B ) were examined using reverse-transcription quantitative PCR (RT-qPCR) and western blot assays. Positive expressions of INSR , retinoic acid-related orphan receptor gamma-t (RORγt), and forkhead box protein P3 (Foxp3) were quantified by immunohistochemistry. Fluorescence intensities of α-SMA and FN were detected by immunofluorescence. Pathological morphology was observed through hematoxylin-eosin (H&E) staining, Masson staining, and Periodic Acid-Schiff (PAS) staining. Contents of immunoglobulin E (IgE), interleukin-6 (IL-6), eotaxin, interleukin-4 (IL-4), interleukin-13 (IL-13), interferon-γ (IFN-γ), interleukin-17 (IL-17), and interleukin-10 (IL-10) were quantified using enzyme-linked immunosorbent assay (ELISA). The percentage of T helper 17 (Th17) and regulatory T (Treg) cells was determined through flow cytometry.

RESULTS: Compared to the control group, expression levels of INSR , p-STAT3, p-JAK2, α-SMA , FN , MUC5AC , MUC5B , RORγt, and Foxp3, as well as IgE, IL-6, eotaxin, IL-4, IL-13, and IL-17 contents, pulmonary index, glycogen-positive area (%), and Th17 cell percentage significantly increased ( p < 0.05). Additionally, pulmonary histopathological deterioration and collagen deposition were aggravated, while Treg cell percentage and IFN-γ and IL-10 contents remarkably decreased ( p < 0.05). The overexpression of INSR further exacerbated the progression of allergic asthma, but the down-regulation of INSR reversed the trends of the above indicators.

CONCLUSIONS: The down-regulation of INSR alleviates airway hyperviscosity, inflammatory infiltration, and airway remodeling, restoring Th17/Treg immune balance in AA mice by inactivating the STAT3 pathway.