Hypoxia and transforming growth factor β1 regulation of long non‐coding RNA transcriptomes in human pulmonary fibroblasts

Abstract

One of the key characteristics of idiopathic pulmonary fibrosis (IPF) is accumulation of excess fibrous tissue in the lung, which leads to hypoxic conditions. Transforming growth factor (TGF) β is a major mediator that promotes the differentiation of fibroblasts to myofibroblasts. However, how hypoxia and TGFβ together contribute the pathogenesis of IPF is poorly understood. Long non‐coding RNAs (lncRNAs) have regulatory effects on certain genes and are involved in many diseases. In this study, we determined the effects of hypoxia and/or TGFβ on mRNA and lncRNA transcriptomes in pulmonary fibroblasts. Hypoxia and TGFβ1 synergistically increased myofibroblast marker expression. RNA sequencing revealed that hypoxia and TGFβ1 treatment resulted in significant changes in 669 lncRNAs and 2,676 mRNAs compared to 150 lncRNAs and 858 mRNAs in TGFβ1 alone group and 222 lncRNAs and 785 mRNAs in hypoxia alone group. TGFβ1 induced the protein expression of HIF‐1α, but not HIF‐2α. On the other hand, hypoxia enhanced the TGFβ1‐induced phosphorylation of Smad3, suggesting a cross‐talk between these two signaling pathways. In all, 10 selected lncRNAs (five‐up and five‐down) in RNA sequencing data were validated using real‐time PCR. Two lncRNAs were primarily located in cytoplasm, three in nuclei and five in both nuclei and cytoplasm. The silencing of HIF‐1α and Smad3, but not Smad2 and HIF‐2α rescued the downregulation of FENDRR by hypoxia and TGFβ1. In conclusion, hypoxia and TGFβ1 synergistically regulate mRNAs and lncRNAs involved in several cellular processes, which may contribute to the pathogenesis of IPF.

Emerging cellular and molecular determinants of idiopathic pulmonary fibrosis

“…The interaction between hypoxia and other factors involved in IPF development has also been reported. For instance, hypoxia and TGF-β act synergistically in regulating a number of mRNAs and lncRNAs in lung fibroblasts, potentially contributing to IPF pathogenesis [ 288 ]. Compared to wild-type mice, bleomycin-treated mice deficient of the ER stress-regulated transcription factor C/EBP homologous protein (CHOP) are protected from the exacerbated lung fibrosis elicited by hypoxia [ 289 ].…”

Dihydroartemisinin attenuates inflammation and fibrosis in rats by suppressing JAK2/STAT3 signaling

“…TNFα directly induces the expression of TGF-β [25]; therefore, in the early stage of the bleomycin-induced rat model, the expression of TGF-β1 was also high in the lung tissue. TGF-β1 is a key direct fibrosis factor that can promote the transformation of pulmonary fibroblasts into myofibroblasts, produce more matrix protein components, and release them into extracellular matrix, thus leading to the occurrence and development of PF [26,27]. Furthermore, TGF-β1 signaling can induce phosphorylation and activation of JAK2, thereby activating the JAK2/STAT3 signaling pathway, and this vicious circle amplifies the inflammatory response and pulmonary fibrosis [28].…”

Long non‐coding RNAs: Promising new targets in pulmonary fibrosis

“…Mechanistically, lncFENDRR represses fibroblast activation by binding iron‐responsive element‐binding protein 1 to control iron levels and by competing with the pro‐fibrotic miR‐214 92 . From the microenvironment, Senavirathna et al 93 . have revealed that hypoxia and TGFβ1 treatment causes significant changes in 669 lncRNAs compared to 150 lncRNAs in a TGFβ1 alone group and 222 lncRNAs in a hypoxia alone group using an RNA sequencing method.…”

“…have revealed that hypoxia and TGFβ1 treatment causes significant changes in 669 lncRNAs compared to 150 lncRNAs in a TGFβ1 alone group and 222 lncRNAs in a hypoxia alone group using an RNA sequencing method. Among these lncRNAs, lncFENDRR is downregulated by hypoxia and TGFβ1 in human pulmonary fibroblasts 93 . lncMalat1can also sponge miR‐503 to control EMT through the PI3K signal pathway in silica‐induced pulmonary fibrosis 84 .…”