Role of Digoxin in Preventing Cigarette Smoke-Induced COPD via HIF-1α Inhibition in a Mouse Model

Hypoxia-inducible factor-1α (HIF-1α) plays an important regulatory role in inflammatory and hypoxic diseases. Higher HIF-1α level was found in the lungs of chronic obstructive pulmonary disease (COPD) patients, however, its role in cigarette smoke (CS)-induced COPD has not been fully studied. Digoxin has been showed to inhibit HIF-1α translation and block HIF-1α activity and thus is often used as the HIF-1α inhibitor. Therefore, in the present study, we chose digoxin as the inhibitor to investigate whether HIF-1α contributes to the progression in a mouse model of COPD and possible mechanism.

The COPD model was established by cigarette smoke (CS) exposed; animals were intragastrically treated with vehicle or different doses of digoxin (0.02 mg/kg and 0.1 mg/kg). COPD associated phenotypes such as pathological changes in lungs, inflammation, lung function and mucus secretion in airways were evaluated. Meanwhile, cigarette smoke extract (CSE) treated A549 cells were administrated with digoxin (50nM) or Smad3 inhibitor (S7959 100uM). Moreover, EMT associated markers together with HIF-1α/TGF-β1/Smad3 signaling pathway were detected both in vivo and in vitro.

The level of HIF-1α was significantly increased in lungs of COPD mice and CSE-exposed A549 cells, which was markedly suppressed by digoxin. Moreover, digoxin inhibited CS-induced inflammatory responses, lung function decline, and mucus hyper-secretion in COPD mouse model. In vitro studies, digoxin decreased CSE-induced pro-inflammatory cytokine release. Importantly, CS-induced or CSE-induced EMT and up-regulation of HIF-1α/TGF-β1/Smad pathway were inhibited by digoxin in vitro. Additionally, S7959 mitigated CSE-induced EMT in A549 cells.

Digoxin can protect CS-induced COPD and prevent CS-induced EMT possibly through HIF-1α/TGF-β1/Smad3 signaling pathway in mice. This study suggests HIF1-α could be a potential intervention target for COPD prevention and treatment, especially for EMT in CS-induced COPD.