Idiopathic pulmonary fibrosis (IPF) is a devastating disease, and its pathogenic mechanisms remain incompletely understood. Peroxisomes are known to be important in ROS and proinflammatory lipid degradation, and their deficiency induces liver fibrosis. However, altered peroxisome functions in IPF pathogenesis have never been investigated. By comparing peroxisome-related protein and gene expression in lung tissue and isolated lung fibroblasts between human control and IPF patients, we found that IPF lungs exhibited a significant down-regulation of peroxisomal biogenesis and metabolism (e.g., PEX13p and acyl-CoA oxidase 1). Moreover, in vivo the bleomycin-induced down-regulation of peroxisomes was abrogated in transforming growth factor beta (TGF-β) receptor II knockout mice indicating a role for TGF-β signaling in the regulation of peroxisomes. Furthermore, in vitro treatment of IPF fibroblasts with the profibrotic factors TGF-β1 or tumor necrosis factor alpha (TNF-α) was found to down-regulate peroxisomes via the AP-1 signaling pathway. Therefore, the molecular mechanisms by which reduced peroxisomal functions contribute to enhanced fibrosis were further studied. Direct down-regulation of PEX13 by RNAi induced the activation of Smad-dependent TGF-β signaling accompanied by increased ROS production and resulted in the release of cytokines (e.g., IL-6, TGF-β) and excessive production of collagen I and III. In contrast, treatment of fibroblasts with ciprofibrate or WY14643, PPAR-α activators, led to peroxisome proliferation and reduced the TGF-β–induced myofibroblast differentiation and collagen protein in IPF cells. Taken together, our findings suggest that compromised peroxisome activity might play an important role in the molecular pathogenesis of IPF and fibrosis progression, possibly by exacerbating pulmonary inflammation and intensifying the fibrotic response in the patients.

Organ growth and tissue homeostasis rely on the proliferation and differentiation of progenitor cell populations. In the developing lung, localized Fgf10 expression maintains distal Sox9-expressing epithelial progenitors and promotes basal cell differentiation in the cartilaginous airways. Mesenchymal Fgf10 expression is induced by Wnt signaling but inhibited by Shh signaling, and epithelial Fgf10 signaling activates β-catenin signaling. The Hippo pathway is a wellconserved signaling cascade that regulates organ size and stem/ progenitor cell behavior. Here, we show that Hippo signaling promotes lineage commitment of lung epithelial progenitors by curbing Fgf10 and β-catenin signaling. Our findings show that both inactivation of the Hippo pathway (nuclear Yap) or ablation of Yap result in increased β-catenin and Fgf10 signaling, suggesting a cytoplasmic role for Yap in epithelial lineage commitment. We further demonstrate redundant and non-redundant functions for the two nuclear effectors of the Hippo pathway, Yap and Taz, during lung development.

The development of the lung involves a diverse group of molecules that regulate cellular processes, organ formation, and maturation. The various stages of lung development are marked by accumulation of small RNAs that promote or repress underlying mechanisms, depending on the physiological environment in utero and postnatally. To some extent, the pathogenesis of various lung diseases is regulated by small RNAs. In this review, we discussed miRNAs regulation of lung development and diseases, that is, COPD, asthma, pulmonary fibrosis, and pulmonary arterial hypertension, and also highlighted possible connotations for human lung health.After fertilization in the mouse, total miRNA in the two-cell-stage embryo was demonstrated to be significantly lower than the levels in one-cell zygote [15]. Notably, total miRNA in the four-cell-stage embryo was higher than the levels in the two-cell-stage embryo [15]. In the early mouse embryo, miR-127 was upregulated at E6.5 and E7.5 [16]. Overexpression of miR-127 in mouse embryonic stem cells, which differentiated into embryoid bodies, increased the mRNA levels of Gsc, Foxa2, and Brachyury (mesendoderm markers), but elicited no change in Pax6 and Otx2 (ectoderm markers) three days after transfection. Inhibition of miR-127 showed opposite regulation of Gsc, Foxa2, and Brachyury. miR-127, moreover, was suggested to control mesendoderm differentiation [16]. miR-326 regulated sonic hedgehog signaling by targeting Smo and Gli2 [17]. The inhibition of smoothened in cultured explanted E12 mouse lung resulted in the expansion of distal epithelium, and disruption of normal branching pattern and mesenchymal integrity [17]. Another study described the functional role of miR-142-3p in the mouse embryonic lung mesenchyme. The miRNA was shown to regulate adenomatous polyposis coli to further modulate Wnt signaling [18]. Taken together, miR-142-3p regulated the proliferation and differentiation of mesenchymal progenitors in the mouse embryonic lung [18].In the developing mouse lung, the level of miR-17 was stable (E11.5-E16.5), predominantly at the pseudoglandular stage, with higher epithelial levels at E12.5 [19]. Simultaneous knockdown of miR-17 and its paralogs, miR-20a and miR-106b, for 72 h in epithelial lung explants altered branching, even in FGF10-treated condition [19]. In the human fetal lung, miR-449a was upregulated at 18-20 weeks (canalicular stage), and in the mouse embryonic lung, miR-449a level was increased from E15.5 to E18.5 [20]. The inhibition of miR-449a in E16.5 mouse lung culture (end of pseudoglandular stage) increased the mRNA levels of Mycn and Sox9, and the protein levels of Ki-67 and SOX9 particularly in the distal epithelial region [20].Knockout of miR-26a-1/miR-26a-2 in the mouse promoted the formation of dilated lumens and aerated regions at the beginning of the canalicular stage (E16.5) of lung development [21]. Results at the saccular stage (E18.5) also indicated large lamellar bodies, and increased SP-A, SP-B, and SP-C protein levels in miR-26a knockout mice....

Background Active smoking has been reported among 7% of teenagers worldwide, with ages ranging from 13 to 15 years. An epidemiological study suggested that preconceptional paternal smoking is associated with adolescent obesity in boys. We developed a murine adolescent smoking model before conception to investigate the paternal molecular causes of changes in offspring’s phenotype. Method Male and female C57BL/6J mice were exposed to increasing doses of mainstream cigarette smoke (CS) from onset of puberty for 6 weeks and mated with room air (RA) controls. Results Thirteen miRNAs were upregulated and 32 downregulated in the spermatozoa of CS-exposed fathers, while there were no significant differences in the count and morphological integrity of spermatozoa, as well as the proliferation of spermatogonia between CS- and RA-exposed fathers. Offspring from preconceptional CS-exposed mothers had lower body weights (p = 0.007). Moreover, data from offspring from CS-exposed fathers suggested a potential increase in body weight (p = 0.062). Conclusion We showed that preconceptional paternal CS exposure regulates spermatozoal miRNAs, and possibly influences the body weight of F1 progeny in early life. The regulated miRNAs may modulate transmittable epigenetic changes to offspring, thus influence the development of respiratory- and metabolic-related diseases such as obesity, a mechanism that warrants further studies for elaborate explanations.