HSP90 Inhibitor, AT13387 Mitigates Chronic Lung Injury in Pre-Pubertal Mice: A Therapeutic Axis in Bronchopulmonary...

Exposure to hydrochloric acid (HCl) can provoke severe chronic pulmonary injury. Children are particularly vulnerable due to their smaller airways, higher respiratory rate, and stronger inflammatory response; yet no countermeasures exist for HCl-induced chronic lung injury in the pediatric population. We have previously demonstrated the involvement of HSP90 during HCl-induced lung injury in pre-pubertal (p24) mice, who develop stronger persistent inflammation with higher NLRP3 inflammasome activation, but less pulmonary fibrosis compared to adults. Here, we tested the hypothesis that post-treatment with the second-generation HSP90 inhibitor AT13387 (Onalespib), administered subcutaneously beginning 24 h after HCl instillation, would prevent HCl-induced chronic lung injury and pulmonary fibrosis in young (p24) C57BL/6J mice. Pre-pubertal (p24) C57BL/6J mice received a single intratracheal instillation of 0.1 N HCl and were treated with AT13387 (10 mg/kg, s.c., 3×/week for 30 days) beginning 24 h post-exposure. Bronchoalveolar lavage fluid (BALF) analysis, lung function measurements, histological assessment (Ashcroft fibrosis score), and Western blot analysis of key signaling mediators were performed. Additionally, publicly available single-nucleus RNA sequencing (snRNA-Seq) data from a cohort of 13 infants with bronchopulmonary dysplasia (BPD) and 11 age-matched controls were analyzed to evaluate HSP90 isoform expression in human pediatric lung disease. AT13387 significantly reduced BALF white blood cell concentration without affecting total BALF protein levels. Importantly, AT13387 did not impair normal weight gain or development over the 30-day observation period. AT13387 abrogated HCl-induced expression of TGF-β1, phosphorylation of HSP90, ERK1/2, SMAD2, IκBα, and upregulation of the inflammasome NLRP3. Additionally, AT13387 prevented changes in lung function dynamics and reduced the Ashcroft fibrosis score. Analysis of the human snRNA-Seq BPD dataset revealed a widespread pan-overexpression of all three HSP90 isoforms, i.e., HSP90AA1, HSP90AB1, and HSP90B1. These findings suggest that the HSP90 inhibitor AT13387 exhibits strong antidotal properties against HCl-induced chronic lung injury and pulmonary fibrosis in a pre-clinical pediatric model and identify HSP90 as a conserved therapeutic target in pediatric chronic lung disease.