Fluoxetine attenuates asthma symptoms in a murine model through modulation of innate and adaptive immune components, and regulation of ROR γ t signalling axis in a pathogenic Th17 cell population

BACKGROUND AND PURPOSE: Asthma is a heterogeneous chronic inflammatory airway disease, characterised by dysregulated interactions between innate and adaptive immune cells. Although Th2-mediated inflammation predominates, persistent Th17-associated immune responses contribute to chronic airway inflammation implicated in the corticosteroid-insensitive disease state. Fluoxetine, a SSRI with immunomodulatory properties, was investigated to determine its effects on inflammation and Th17 response in experimental allergic airway disease. EXPERIMENTAL APPROACH: Immunomodulatory effects of fluoxetine evaluated in exploratory in vitro assays. In vivo studies were performed in an ovalbumin (OVA)-induced murine model of allergic asthma using oral fluoxetine at clinically relevant doses. Airway pathology, immunophenotypes, cytokine production, gene and protein expression were evaluated by histology, flow cytometry, quantitative reverse transcription polymerase chain reaction (qRT-PCR), confocal microscopy and ex vivo functional assays. Public transcriptomic datasets were integrated with target enrichment analyses, molecular docking and molecular dynamics simulations used to explore potential molecular interactions. KEY RESULTS: Fluoxetine reduced the inflammatory response in activated macrophages without noticeable cytotoxicity. In an allergic asthma model, fluoxetine attenuated inflammatory cell infiltration, eosinophilia, IgE production and pulmonary macrophage activation, whilst reducing the accumulation of the phenotypically granulocytic myeloid-derived suppressor like cell population along with diminished T-cell activation and reduced Th17 responses, reduced IL-17 production together with decreased expression and nuclear localisation of RORγt. Ex vivo studies confirmed inhibition of RORγt expression and IL-17 production in Th17 cells. Transcriptomic integration identified significant enrichment of Th17-associated inflammatory pathways, whereas molecular docking and molecular dynamics analyses supported RORγt as a plausible molecular target. CONCLUSION AND IMPLICATIONS: Fluoxetine attenuates experimental allergic airway inflammation through coordinated modulation of innate and adaptive immune responses, with suppression of the RORγt-IL-17 signalling axis emerging as a key mechanistic feature. These findings expand the immunopharmacological profile of fluoxetine and provide an experimental rationale for further investigating its therapeutic potential in Th17-associated airway inflammatory diseases and in experimental models that more closely recapitulate corticosteroid-resistant asthma.