Inhibition of Raf1 ameliorates bleomycin-induced pulmonary fibrosis through attenuation of TGF-β1 signaling

Regulation of Ras p21 and RalA GTPases activity by quinine in mammary epithelial cells

Quinine, a bitter compound, can act as an agonist to activate the family of bitter taste G protein-coupled receptor family of proteins. Previous work from our laboratory has demonstrated that quinine causes activation of RalA, a Ras p21-related small G protein. Ral proteins can be activated directly or indirectly through an alternative pathway that requires Ras p21 activation resulting in the recruitment of RalGDS, a guanine nucleotide exchange factor for Ral. Using normal mammary epithelial (MCF-10A) and non-invasive mammary epithelial (MCF-7) cell lines, we investigated the effect of quinine in regulating Ras p21 and RalA activity. Results showed that in the presence of quinine, Ras p21 is activated in both MCF-10A and MCF-7 cells; however, RalA was inhibited in MCF-10A cells, and no effect was observed in the case of MCF-7 cells. MAP kinase, a downstream effector for Ras p21, was activated in both MCF-10A and MCF-7 cells. Western blot analysis confirmed the expression of RalGDS in MCF-10A cells and MCF-7 cells. The expression of RalGDS was higher in MCF-10A cells in comparison to the MCF-7 cells. Although RalGDS was detected in MCF-10A and MCF-7 cells, it did not result in RalA activation upon Ras p21 activation with quinine suggesting that the Ras p21-RalGDS-RalA pathway is not active in the MCF-10A cells. The inhibition of RalA activity in MCF-10A cells due to quinine could be as a result of a direct effect of this bitter compound on RalA. Protein modeling and ligand docking analysis demonstrated that quinine can interact with RalA through the R79 amino acid, which is located in the switch II region loop of the RalA protein. It is possible that quinine causes a conformational change that results in the inhibition of RalA activation even though RalGDS is present in the cell. More studies are needed to elucidate the mechanism(s) that regulate Ral activity in mammary epithelial cells.

Targeting CRAF kinase in anti-cancer therapy: progress and opportunities

The RAS/mitogen-activated protein kinase (MAPK) signaling cascade is commonly dysregulated in human malignancies by processes driven by RAS or RAF oncogenes. Among the members of the RAF kinase family, CRAF plays an important role in the RAS-MAPK signaling pathway, as well as in the progression of cancer. Recent research has provided evidence implicating the role of CRAF in the physiological regulation and the resistance to BRAF inhibitors through MAPK-dependent and MAPK-independent mechanisms. Nevertheless, the effectiveness of solely targeting CRAF kinase activity remains controversial. Moreover, the kinase-independent function of CRAF may be essential for lung cancers with KRAS mutations. It is imperative to develop strategies to enhance efficacy and minimize toxicity in tumors driven by RAS or RAF oncogenes. The review investigates CRAF alterations observed in cancers and unravels the distinct roles of CRAF in cancers propelled by diverse oncogenes. This review also seeks to summarize CRAF-interacting proteins and delineate CRAF's regulation across various cancer hallmarks. Additionally, we discuss recent advances in pan-RAF inhibitors and their combination with other therapeutic approaches to improve treatment outcomes and minimize adverse effects in patients with RAF/RAS-mutant tumors. By providing a comprehensive understanding of the multifaceted role of CRAF in cancers and highlighting the latest developments in RAF inhibitor therapies, we endeavor to identify synergistic targets and elucidate resistance pathways, setting the stage for more robust and safer combination strategies for cancer treatment.

Protective effect of ebselen on bleomycin-induced lung fibrosis: analysis of the molecular mechanism of lung fibrosis mediated by oxidized diacylglycerol

The molecular mechanisms underlying the development of pulmonary fibrosis remain unknown, and effective treatments have not yet been developed. It has been shown that oxidative stress is involved in lung fibrosis. Oxidized diacylglycerol (DAG) produced by oxidative stress is thought to play an important role in lung fibrosis. This study assessed the effect of oxidized DAG in an animal model of pulmonary fibrosis induced by aspiration of bleomycin (BLM) into the lungs. The inhibitory effect of ebselen on pulmonary fibrosis was also investigated. In lung fibrotic tissue induced by BLM, an increase in lipid peroxides and collagen accumulation was observed. Moreover, the levels of oxidized DAG, which has strong protein kinase C (PKC) activation activity, were significantly increased over time following the administration of BLM. Western blotting showed that phosphorylation of PKCα and δ isoforms was increased by BLM. Oral administration of ebselen significantly suppressed the increase in oxidized DAG induced by BLM and improved lung fibrosis. PKCα and δ phosphorylation were also significantly inhibited. The mRNA expression of α-smooth muscle actin and collagen I (marker molecules for fibrosis), as well as the production of transforming growth factor-β and tumor necrosis factor-α(a potentially important factor in the fibrotic process), were increased by BLM and significantly decreased by ebselen. The administration of BLM may induce lipid peroxidation in lung tissue, while the oxidized DAG produced by BLM may induce overactivation of PKCα and δ, resulting in the induction of lung fibrosis.

NecroX-5 ameliorates bleomycin-induced pulmonary fibrosis via inhibiting NLRP3-mediated epithelial-mesenchymal transition

Background

Pulmonary fibrosis is a progressive and usually lethal pulmonary disease. Despite considerable research efforts, no effective therapeutic strategy for pulmonary fibrosis has been developed. NecroX-5 has been reported to possess anti-inflammatory, anti-oxidative and anti-tumor activities. In the present study, we aimed to determine whether NecroX-5 exhibits antifibrotic property in bleomycin (BLM)-induced pulmonary fibrosis.

Results

We found that pre-treatment with NecroX-5 alleviated inflammatory response, reduced oxidative stress, inhibited epithelial–mesenchymal transition (EMT), and ameliorated pulmonary fibrosis in vivo and in vitro. Our data further indicated that NecroX-5 substantially reduced activation of NLRP3 inflammasome and TGF-β1/Smad2/3 signaling in vivo and in vitro. Additionally, NLRP3 overexpression significantly reversed the protective effects of NecroX-5 in lung epithelial cells exposed to BLM.

Conclusions

Overall, our results demonstrate the potent antifibrotic properties of NecroX-5 and its therapeutic potential for pulmonary fibrosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02044-3.

Carbon nanotubes promote alveolar macrophages toward M2 polarization mediated epithelial-mesenchymal transition and fibroblast-to-myofibroblast transdifferentiation

With substantial progress of nanotechnology, carbon nanotubes (CNTs) are widely used in a variety of industrial and commercial applications. There is rising concern about potential adverse health effects, such as pulmonary fibrosis, related to inhalation of CNTs. The detailed cellular and molecular mechanisms of pulmonary fibrosis induced by CNTs are still not clear. Epithelial-mesenchymal transition (EMT) and fibroblast-to-myofibroblast transdifferentiation (FMT) are considered as critical events in pathogenesis of pulmonary fibrosis. Alveolar macrophages (AMs) polarization plays a key role of regulating EMT and FMT in pulmonary fibrosis. In this study, we applied CNTs to stimulate primary mouse AMs under M1 or M2 polarization conditions, then analyzed the proportion of F4/80⁺CD11c⁺ or F4/80⁺CD206⁺ AMs, mRNA expression and activities of iNOS or Arg-1, as well as mRNA expression and content of TNF-α and IL-6 or TGF-β and IL-10 to evaluate dynamic phenotypic and functional changes of AMs. Single-walled CNT (SWCNT), short-type multi-walled CNT (MWCNT), and long-type MWCNT exposure at dose of 50 µg/ml promote AMs polarization toward M1 phenotype at early stage, while promote AMs polarization toward M2 phenotype at late stage. The roles of AMs polarization during development of EMT and FMT were further investigated by conditioned medium (CM) experiments. CNTs-activated M2 AMs promote progression of EMT and FMT via secreting TGF-β. Furthermore, up-regulating IRF4 may be involved in CNTs-induced M2 AMs polarization. In conclusion, this study demonstrates a new insight that CNTs exposure promotes AMs polarization toward M2 phenotype which facilitate EMT and FMT through secreting TGF-β.

Yin/Yang expression of CCN family members: Transforming growth factor beta 1, via ALK5/FAK/MEK, induces CCN1 and CCN2, yet suppresses CCN3, expression in human dermal fibroblasts

The role of the microenvironment in driving connective tissue disease is being increasingly appreciated. Matricellular proteins of the CCN family are signaling modifiers that are secreted by cells into the extracellular matrix microenvironment where they have profound, context-dependent effects on organ development, homeostasis and disease. Indeed, CCN proteins are emergent targets for therapeutic intervention. Recent evidence suggests that, in vivo, CCN3 has effects opposing CCN2. Moreover, when CCN3 expression is high, CCN2 expression is low. That is, they appear to be regulated in a yin/yang fashion, leading to the hypothesis that the CCN2:CCN3 ratio is important to control tissue homeostasis. To begin to test the hypothesis that alterations in CCN2:CCN3 expression might be important in skin biology in vivo, we evaluated the relative ex vivo effects of the profibrotic protein TGFbeta1 on dermal fibroblasts on protein and RNA expression of CCN3 and CCN2, as well as the related protein CCN1. We also used signal transduction inhibitors to begin to identify the signal transduction pathways controlling the ability of fibroblasts to respond to TGFbeta1. As anticipated, CCN1 and CCN2 protein and mRNA were induced by TGFbeta1 in human dermal fibroblasts. This induction was blocked by TAK1, FAK, YAP1 and MEK inhibition. Conversely, TGFbeta1 suppressed CCN3 mRNA expression in a fashion insensitive to FAK, MEK, TAK1 or YAP1 inhibition. Unexpectedly, CCN3 protein was not detected in human dermal fibroblasts basally. These data suggest that, in dermal fibroblasts, the profibrotic protein TGFbeta1 has a divergent effect on CCN3 relative to CCN2 and CCN1, both at the mRNA and protein level. Given that the major source in skin in vivo of CCN proteins are fibroblasts, our data are consistent that alterations in CCN2/CCN1: CCN3 ratios in response to profibrotic agents such as TGFbeta1 may play a role in connective tissue pathologies including fibrosis.

Resolvin D1 attenuates mechanical stretch-induced pulmonary fibrosis via epithelial-mesenchymal transition

Mechanical ventilation-induced pulmonary fibrosis plays an important role in the high mortality rate of acute respiratory distress syndrome (ARDS). Resolvin D1 (RvD1) displays potent proresolving activities. Epithelial-mesenchymal transition (EMT) has been proved to be an important pathological feature of lung fibrosis. This study aimed to investigate whether RvD1 can attenuate mechanical ventilation-induced lung fibrosis. Human lung epithelial (BEAS-2B) cells were pretreated with RvD1 for 30 min and exposed to acid for 10 min before being subjected to mechanical stretch for 48 h. C57BL/6 mice were subjected to intratracheal acid aspiration followed by mechanical ventilation 24 h later (peak inspiratory pressure 22 cmH₂O, positive end-expiratory pressure 2 cmH₂O, and respiratory rate 120 breaths/min for 2 h). RvD1 was injected into mice for 5 consecutive days after mechanical ventilation. Treatment with RvD1 significantly inhibited mechanical stretch-induced mesenchymal markers (vimentin and α-smooth muscle actin) and stimulated epithelial markers (E-cadherin). Tert-butyloxycarbonyl 2 (BOC-2), a lipoxin A4 receptor/formyl peptide receptor 2 (ALX/FPR2) antagonist, is known to inhibit ALX/FPR2 function. BOC-2 could reverse the beneficial effects of RvD1. The antifibrotic effect of RvD1 was associated with the suppression of Smad2/3 phosphorylation. This study demonstrated that mechanical stretch could induce EMT and pulmonary fibrosis and that treatment with RvD1 could attenuate mechanical ventilation-induced lung fibrosis, thus highlighting RvD1 as an effective therapeutic agent against pulmonary fibrosis associated with mechanical ventilation.

Signaling Mechanisms of Myofibroblastic Activation: Outside-in and Inside-Out

Myofibroblasts are central mediators of fibrosis. Typically derived from resident fibroblasts, myofibroblasts represent a heterogeneous population of cells that are principally defined by acquired contractile function and high synthetic ability to produce extracellular matrix (ECM). Current literature sheds new light on the critical role of ECM signaling coupled with mechanotransduction in driving myofibroblastic activation. In particular, transforming growth factor β1 (TGF-β1) and extra domain A containing fibronectin (EDA-FN) are thought to be the primary ECM signaling mediators that form and also induce positive feedback loops. The outside-in and inside-out signaling circuits are transmitted and integrated by TGF-β receptors and integrins at the cell membrane, ultimately perpetuating the abundance and activities of TGF-β1 and EDA-FN in the ECM. In this review, we highlight these conceptual advances in understanding myofibroblastic activation, in hope of revealing its therapeutic anti-fibrotic implications.