Kasugamycin Is a Novel Chitinase 1 Inhibitor with Strong Antifibrotic Effects on Pulmonary Fibrosis

RationalePulmonary fibrosis is a devastating lung disease with few therapeutic options. Chitinase 1 (CHIT1), an 18 glycosyl hydrolase family member, contributes to the pathogenesis of pulmonary fibrosis through regulation of Transforming Growth Factor (TGF)-β signaling and effector function. Therefore, CHIT1 is a potential therapeutic target of pulmonary fibrosis.ObjectivesThis study aimed to identify and characterize a druggable CHIT1 inhibitor with strong antifibrotic activity and minimal toxicity for therapeutic application to pulmonary fibrosis.MethodsExtensive screening of small molecule libraries identified the aminoglycoside antibiotic Kasugamycin as a potent CHIT1 inhibitor.Measurements and Main ResultsElevated levels of CHIT1 were detected in the lungs of patients with pulmonary fibrosis. In vivo bleomycin- and TGF-β-stimulated murine models of pulmonary fibrosis, Kasugamycin showed impressive anti-fibrotic effects in both preventive and therapeutic conditions. In vitro studies also demonstrated that Kasugamycin inhibits fibrotic macrophage activation, fibroblast proliferation and myofibroblast transformation. Null mutation of transforming growth factor beta associated protein 1 (TGFBRAP1), a recently identified CHIT1 interacting signaling molecule, phenocopied antifibrotic effects of Kasugamycin in in vivo lungs and in vitro fibroblasts responses. Kasugamycin inhibits physical association between CHIT1 and TGFBRAP1, suggesting that antifibrotic effect of Kasugamycin is mediated through regulation of TGFBRAP1, at least in part.ConclusionsThese studies demonstrate that Kasugamycin is a novel CHIT1 inhibitor with strong antifibrotic effect that can be further developed as an effective and safe therapeutic drug for pulmonary fibrosis.