Celastrol alleviates airway remodeling in severe steroid-resistant asthma via AMOTL1-dependent restoration of Hippo/YAP signaling

BACKGROUND: Severe steroid-resistant asthma (SSRA) is frequently associated with irreversible airway remodeling (AR), which contributes to persistent airflow limitation and poor therapeutic responsiveness. Celastrol (CEL) exhibits anti-inflammatory and tissue-protective properties; however, its role in steroid-resistant AR remains unclear. PURPOSE: This study aimed to evaluate the therapeutic effects of CEL on SSRA and to determine whether AMOTL1-dependent Hippo/Yes-associated protein (YAP)/transcriptional co-activator with PDZ-binding motif (TAZ) signaling contributes to its anti-remodeling activity. METHODS: SSRA mice were generated via OVA/CFA/LPS sensitization and challenge and treated with CEL or dexamethasone. Airway hyperresponsiveness (AHR), lung histopathology, inflammatory cell infiltration, mucus secretion, collagen deposition, and lung proteomic profiles were evaluated. Osteopontin (OPN)-stimulated human bronchial smooth muscle cells (HBSMCs) were used to model airway smooth muscle remodeling. AMOTL1 gain- and loss-of-function studies were conducted in HBSMCs, and airway-local Amotl1 knockdown was introduced into SSRA mice. RESULTS: CEL improved AHR and suppressed airway inflammation, mucus production, and collagen accumulation in SSRA mice. Proteomic analysis revealed that AMOTL1 was downregulated in SSRA and restored by CEL treatment. In HBSMCs, CEL suppressed OPN-induced proliferation, migration, and extracellular matrix production, accompanied by Hippo pathway reactivation and YAP/TAZ inhibition. AMOTL1 knockdown in HBSMCs attenuated these anti-remodeling effects, whereas AMOTL1 overexpression recapitulated the protective effects of CEL. In vivo, Amotl1 knockdown blunted CEL-mediated improvement in SSRA-associated AR. CONCLUSION: CEL alleviates steroid-resistant AR through AMOTL1-dependent restoration of Hippo/YAP signaling, highlighting the AMOTL1/Hippo/YAP axis as a potential therapeutic target in SSRA.