Concomitant inhibition of hedgehog signalling and activation of retinoid receptors abolishes bleomycin-induced lung fibrosis

Total flavonoid extract from Dracocephalum moldavica L. improves pulmonary fibrosis by reducing inflammation and inhibiting the hedgehog signaling pathway

Dracocephalum Moldavica L. is a traditional herb for improving pharynx and relieving cough. However, the effect on pulmonary fibrosis is not clear. In this study, we explored the impact and molecular mechanism of total flavonoid extract from Dracocephalum moldavica L. (TFDM) on bleomycin-induced pulmonary fibrosis mouse model. Lung function testing, lung inflammation and fibrosis, and the related factors were detected by the lung function analysis system, HE and Masson staining, ELISA, respectively. The expression of proteins was studied through Western Blot, immunohistochemistry, and immunofluorescence while the expression of genes was analyzed by RT-PCR. The results showed that TFDM significantly improved lung function in mice, reduced the content of inflammatory factors, thereby reducing the inflammation. It was found that expression of collagen type I, fibronectin, and α-smooth muscle actin was significantly decreased by TFDM. The results further showed that TFDM interferes with hedgehog signaling pathway by decreasing the expression of Shh, Ptch1, and SMO proteins and thereby inhibiting the generation of downstream target gene Gli1 and thus improving pulmonary fibrosis. Conclusively, these findings suggest that TFDM improve pulmonary fibrosis by reducing inflammation and inhibition of the hedgehog signaling pathway.

Hedgehog pathway and its inhibitors in chronic obstructive pulmonary disease (COPD)

COPD affects millions of people and is now ranked as the third leading cause of death worldwide. This largely untreatable chronic airway disease results in irreversible destruction of lung architecture. The small lung hypothesis is now supported by epidemiological, physiological and clinical studies. Accordingly, the early and severe COPD phenotype carries the most dreadful prognosis and finds its roots during lung growth. Pathophysiological mechanisms remain poorly understood and implicate individual susceptibility (genetics), a large part of environmental factors (viral infections, tobacco consumption, air pollution) and the combined effects of those triggers on gene expression. Genetic susceptibility is most likely involved as the disease is severe and starts early in life. The latter observation led to the identification of Mendelian inheritance via disease-causing variants of SERPINA1 - known as the basis for alpha-1 anti-trypsin deficiency, and TERT. In the last two decades multiple genome wide association studies (GWAS) identified many single nucleotide polymorphisms (SNPs) associated with COPD. High significance SNPs are located in 4q31 near HHIP which encodes an evolutionarily highly conserved physiological inhibitor of the Hedgehog signaling pathway (HH). HHIP is critical to several in utero developmental lung processes. It is also implicated in homeostasis, injury response, epithelial-mesenchymal transition and tumor resistance to apoptosis. A few studies have reported decreased HHIP RNA and protein levels in human adult COPD lungs. HHIP^+/- murine models led to emphysema. HH pathway inhibitors, such as vismodegib and sonidegib, are already validated in oncology, whereas other drugs have evidenced in vitro effects. Targeting the Hedgehog pathway could lead to a new therapeutic avenue in COPD. In this review, we focused on the early and severe COPD phenotype and the small lung hypothesis by exploring genetic susceptibility traits that are potentially treatable, thus summarizing promising therapeutics for the future.

LncRNA MEG3 restrained pulmonary fibrosis induced by NiO NPs via regulating hedgehog signaling pathway-mediated autophagy

Long noncoding RNA maternally expressed gene 3 (lncRNA MEG3) was down-regulated in pulmonary fibrosis of rats induced by Nickel oxide nanoparticles (NiO NPs), while the downstream regulatory mechanisms of MEG3 remain unclear. This study aimed to investigate the relationship among MEG3, Hedgehog (Hh) signaling pathway and autophagy in pulmonary fibrosis caused by NiO NPs. The pulmonary fibrosis model in rats was constructed by intratracheal instillation of 0.015, 0.06, and 0.24 mg/kg NiO NPs twice a week for 9 weeks. Collagen deposition model was established by treating A549 cells with 25, 50, and 100 μg/mL NiO NPs for 24 h. Our results indicated that NiO NPs activated Hh pathway, down-regulated the expression of MEG3, and reduced autophagy activity in vivo and in vitro. Meanwhile, the autophagy process was promoted by Hh pathway inhibitor (CDG-0449), while the collagen formation in A549 cells was reduced by autophagy activator (Rapamycin). Furthermore, the overexpressed MEG3 inhibited the activation of Hh pathway, resulting in autophagy activity enhancement along with collagen formation reduction. In summary, lncRNA MEG3 can restrain pulmonary fibrosis induced by NiO NPs via regulating hedgehog signaling pathway-mediated autophagy, which may serve as a potential therapeutic strategy for pulmonary fibrosis.