Soluble gp130 inhibits Th17 polarization in neutrophilic asthma by blocking IL-6 trans-signaling in dendritic cells

Interleukin-6 (IL-6) trans-signaling modulates immune responses in asthma, yet the mechanisms linking this pathway to Th17 skewing in neutrophilic asthma remain incompletely defined. Here, we evaluated soluble gp130 (sgp130), a selective inhibitor of IL-6 trans-signaling, in vivo and in vitro. A murine neutrophilic asthma model was established by ovalbumin (OVA) sensitization followed by lipopolysaccharide (LPS) plus OVA challenge, and sgp130 was administered intratracheally. Airway neutrophilic inflammation, Th17/Treg responses, and IL-23 expression in lung dendritic cells (DCs) were assessed, and the contribution of Th17 cells was examined by adoptive transfer. In parallel, DCs were cocultured with naïve CD4⁺ T cells in the presence of Hyper-IL-6 (an IL-6/sIL-6R fusion protein that activates IL-6 trans-signaling) with or without sgp130 to quantify DC-derived IL-23 and Th17 differentiation; additionally, DCs conditioned with Hyper-IL-6 with or without sgp130 were delivered intratracheally to establish a DC-transfer asthma model. In neutrophilic asthma, bronchoalveolar lavage fluid (BALF) levels of IL-6/sIL-6R complex were elevated and positively associated with neutrophil counts and IL-17 production. Blockade of IL-6 trans-signaling with sgp130 attenuated airway neutrophilia, reduced Th17 polarization, increased Treg response, and decreased IL-23 expression in lung DCs, whereas adoptive transfer of Th17 cells partially abrogated these protective effects. Consistently, Hyper-IL-6 increased IL-23 expression in DCs and promoted Th17 differentiation in vitro, both of which were suppressed by sgp130. Moreover, airway transfer of Hyper-IL-6-conditioned DCs induced neutrophilic airway inflammation and Th17 polarization, while transfer of DCs conditioned with Hyper-IL-6 plus sgp130 markedly mitigated these responses. Collectively, IL-6 trans-signaling promotes Th17 polarization in neutrophilic asthma by enhancing DC IL-23 production, thereby driving neutrophilic airway inflammation, and selective inhibition with sgp130 may represent a mechanistically targeted therapeutic strategy.