The novel TAK1 inhibitor handelin inhibits NF-κB and AP-1 activity to alleviate elastase-induced emphysema in mice

Emphysema, one of the two major components of chronic obstructive pulmonary disease (COPD), is driven by aberrant inflammatory responses and associated with irreversible lung parenchymal destruction. As effective therapy for preventing or treating COPD/emphysema is yet unavailable, development of molecular targets and therapeutic agents for COPD/emphysema is required.We identified handelin-a guaianolide dimer of sesquiterpene lactones- from a chemical library of 431 natural products as it exhibited potent inhibitory effects on lipopolysaccharide (LPS)-induced nitric oxide (NO) and reactive oxygen species (ROS) production, LPS-induced activation of nuclear factor κB (NF-κB), mitogen-activated protein kinase (MAPK)/AP-1, and expression of proinflammatory mediators in macrophage cells. In silico docking and biochemical studies enabled the identification of the ATP-binding pocket of transforming growth factor beta-activated kinase 1 (TAK1), a kinase upstream of NF-κB and MAPK/AP-1 pathways, as a molecular target for handelin. Moreover, oral administration of handelin (10 mg/kg) suppressed elastase-induced development of emphysematous phenotypes, including lung function disturbance, airspace enlargement, and increases in the level of neutrophils and CD8+ T cells in lung tissues, without overt toxicity. Consistent with in vitro results, analyses of lung tissues revealed that treatment with handelin suppressed elastase-induced NF-κB and AP-1 activation in the lungs, followed by downregulation of their targets including interleukin-6 (IL-6), inducible nitric oxide synthase (iNOS), and matrix metalloproteinase 9 (MMP9).These findings suggest that handelin, as a TAK1 inhibitor, effectively prevents development of emphysema in an elastase-induced mouse model by inhibiting a proinflammatory mediators mediated by NF-κB and AP-1.