c-Jun N-terminal kinase (JNK)-mediated induction of mSin1 expression and mTORC2 activation in mesenchymal cells during fibrosis

Inhibition of the rapamycin-insensitive mTORC1 /4E-BP1 axis attenuates TGF-β1-induced fibrotic response in human Tenon's fibroblasts

Subconjunctival fibrosis is the major cause of failure in both conventional and modern minimally invasive glaucoma surgeries (MIGSs) with subconjunctival filtration. The search for safe and effective anti-fibrotic agents is critical for improving long-term surgical outcomes. In this study, we investigated the effect of inhibiting the rapamycin-insensitive mTORC1/4E-BP1 axis on the transforming growth factor-beta 1(TGF-β1)-induced fibrotic responses in human Tenon's fibroblasts (HTFs), as well as in a rat model of glaucoma filtration surgery (GFS). Primary cultured HTFs were treated with 3 ng/mL TGF-β1 for 24 h, followed by treatment with 10 μM CZ415 for additional 24 h. Rapamycin (10 μM) was utilized as a control for mTORC1/4E-BP1 signaling insensitivity. The expression levels of fibrosis-associated molecules were measured using quantitative real-time PCR, Western blotting, and immunofluorescence analysis. Cell migration was assessed through the scratch wound assay. Additionally, a rat model of GFS was employed to evaluate the anti-fibrotic effect of CZ415 in vivo. Our findings indicated that both rapamycin and CZ415 treatment significantly reduced the TGF-β1-induced cell proliferation, migration, and the expression of pro-fibrotic factors in HTFs. CZ415 also more effectively inhibited TGF-β1-mediated collagen synthesis in HTFs compared to rapamycin. Activation of mTORC1/4E-BP signaling following TGF-β1 exposure was highly suppressed by CZ415 but was only modestly inhibited by rapamycin. Furthermore, CZ415 was found to decrease subconjunctival collagen deposition in rats post GFS. Our results suggest that rapamycin-insensitive mTORC1/4E-BP1 signaling plays a critical role in TGF-β1-driven collagen synthesis in HTFs. This study demonstrated that inhibition of the mTORC1/4E-BP1 axis offers superior anti-fibrotic efficacy compared to rapamycin and represents a promising target for improving the success rate of both traditional and modern GFSs.

The mTORC2 signaling network: targets and cross-talks

The mechanistic target of rapamycin, mTOR, controls cell metabolism in response to growth signals and stress stimuli. The cellular functions of mTOR are mediated by two distinct protein complexes, mTOR complex 1 (mTORC1) and mTORC2. Rapamycin and its analogs are currently used in the clinic to treat a variety of diseases and have been instrumental in delineating the functions of its direct target, mTORC1. Despite the lack of a specific mTORC2 inhibitor, genetic studies that disrupt mTORC2 expression unravel the functions of this more elusive mTOR complex. Like mTORC1 which responds to growth signals, mTORC2 is also activated by anabolic signals but is additionally triggered by stress. mTORC2 mediates signals from growth factor receptors and G-protein coupled receptors. How stress conditions such as nutrient limitation modulate mTORC2 activation to allow metabolic reprogramming and ensure cell survival remains poorly understood. A variety of downstream effectors of mTORC2 have been identified but the most well-characterized mTORC2 substrates include Akt, PKC, and SGK, which are members of the AGC protein kinase family. Here, we review how mTORC2 is regulated by cellular stimuli including how compartmentalization and modulation of complex components affect mTORC2 signaling. We elaborate on how phosphorylation of its substrates, particularly the AGC kinases, mediates its diverse functions in growth, proliferation, survival, and differentiation. We discuss other signaling and metabolic components that cross-talk with mTORC2 and the cellular output of these signals. Lastly, we consider how to more effectively target the mTORC2 pathway to treat diseases that have deregulated mTOR signaling.

Genetic deficiency of the transcription factor NFAT1 confers protection against fibrogenic responses independent of immune influx

Idiopathic pulmonary fibrosis (IPF) is marked by unremitting matrix deposition and architectural distortion. Multiple profibrotic pathways contribute to the persistent activation of mesenchymal cells (MCs) in fibrosis, highlighting the need to identify and target common signaling pathways. The transcription factor nuclear factor of activated T cells 1 (NFAT1) lies downstream of second messenger calcium signaling and has been recently shown to regulate key profibrotic mediator autotaxin (ATX) in lung MCs. Herein, we investigate the role of NFAT1 in regulating fibroproliferative responses during the development of lung fibrosis. Nfat1-/--deficient mice subjected to bleomycin injury demonstrated improved survival and protection from lung fibrosis and collagen deposition as compared with bleomycin-injured wild-type (WT) mice. Chimera mice, generated by reconstituting bone marrow cells from WT or Nfat1-/- mice into irradiated WT mice (WT→WT and Nfat1-/-→WT), demonstrated no difference in bleomycin-induced fibrosis, suggesting immune influx-independent fibroprotection in Nfat1-/- mice. Examination of lung tissue and flow sorted lineageneg/platelet-derived growth factor receptor alpha (PDGFRα)pos MCs demonstrated decreased MC numbers, proliferation [↓ cyclin D1 and 5-ethynyl-2'-deoxyuridine (EdU) incorporation], myofibroblast differentiation [↓ α-smooth muscle actin (α-SMA)], and survival (↓ Birc5) in Nfat1-/- mice. Nfat1 deficiency abrogated ATX expression in response to bleomycin in vivo and MCs derived from Nfat1-/- mice demonstrated decreased ATX expression and migration in vitro. Human IPF MCs demonstrated constitutive NFAT1 activation, and regulation of ATX in these cells by NFAT1 was confirmed using pharmacological and genetic inhibition. Our findings identify NFAT1 as a critical mediator of profibrotic processes, contributing to dysregulated lung remodeling and suggest its targeting in MCs as a potential therapeutic strategy in IPF.NEW & NOTEWORTHY Idiopathic pulmonary fibrosis (IPF) is a fatal disease with hallmarks of fibroblastic foci and exuberant matrix deposition, unknown etiology, and ineffective therapies. Several profibrotic/proinflammatory pathways are implicated in accelerating tissue remodeling toward a honeycombed end-stage disease. NFAT1 is a transcriptional factor activated in IPF tissues. Nfat1-deficient mice subjected to chronic injury are protected against fibrosis independent of immune influxes, with suppression of profibrotic mesenchymal phenotypes including proliferation, differentiation, resistance to apoptosis, and autotaxin-related migration.

The mitigating effect of exogenous carbon monoxide on chronic allograft rejection and fibrosis post-lung transplantation

BACKGROUND

Small airway inflammation and fibrosis or bronchiolitis obliterans (BO) is the predominant presentation of chronic lung allograft dysfunction (CLAD) post-lung transplantation. Carbon monoxide (CO) is a critical endogenous signaling transducer with known anti-inflammatory and anti-fibrotic effects but its therapeutic potential in CLAD remains to be fully elucidated.

METHODS

Here we investigate the effect of inhaled CO in modulating chronic lung allograft rejection pathology in a murine orthotopic lung transplant model of BO (B6D2F1/J→DBA/2J). Additionally, the effects of CO on the activated phenotype of mesenchymal cells isolated from human lung transplant recipients with CLAD were studied.

RESULTS

Murine lung allografts treated with CO (250 ppm × 30 minutes twice daily from days 7 to 40 post-transplantation) demonstrated decreased immune cell infiltration, fibrosis, and airway obliteration by flow cytometry, trichrome staining, and morphometric analysis, respectively. Decreased total collagen, with levels comparable to isografts, was noted in CO-treated allografts by quantitative hydroxyproline assay. In vitro, CO (250 ppm × 16h) was effective in reversing the fibrotic phenotype of human CLAD mesenchymal cells with decreased collagen I and β-catenin expression as well as an inhibitory effect on ERK1/2 MAPK, and mTORC1/2 signaling. Sildenafil, a phosphodiesterase 5 inhibitor, partially mimicked the effects of CO on CLAD mesenchymal cells and was partially effective in decreasing collagen deposition in murine allografts, suggesting the contribution of cGMP-dependent and -independent mechanisms in mediating the effect of CO.

CONCLUSION

These results suggest a potential role for CO in alleviating allograft fibrosis and mitigating chronic rejection pathology post-lung transplant.

Analysis of ferroptosis-associated genes in Crohn's disease based on bioinformatics

Background

Ferroptosis, a novel mode of apoptosis has recently been shown to be associated with fibrosis, tumor, cardiovascular, and other diseases. In this study, using bioinformatic analysis, we identified ferroptosis genes associated with Crohn's disease (CD) and performed biological function analysis, identified potential drug targets, and provided new directions for the future treatment of CD.

Methods

Differential expression analysis was performed using the GSE186582 dataset from the Gene Expression Omnibus (GEO) database. Ferroptosis-associated genes were downloaded from the FerrDB database, and overlapping genes associated with CD and ferroptosis were extracted. Then, we performed functional enrichment analysis, constructed a protein-protein interaction network (PPI), identified the correlation between hub genes and immune infiltration, performed external validation using a second and third dataset (GSE102133, GSE95095), and identified potential therapeutic agents. Finally, we validated the protein expression levels of the identified hub genes by immunohistochemical staining in the colon tissues from CD and healthy participants.

Results

A total of 28 ferroptosis-associated genes associated with CD were identified in our analysis, which included 22 up-regulated and 6 down-regulated genes. Gene Ontology (GO) analysis showed that these genes are essential for the apical plasma membrane and amide transport, and Metascape analysis showed that these genes mainly act on IL-4 and IL-13 signaling pathways. Five hub genes, PTGS2, IL6, IL1B, NOS2, and IDO1, were identified by a protein interaction network, and external validation of these hub genes showed statistically significant differences in expression between the CD patients and normal participants (p < 0.05), and all AUC values were greater than 0.8. Further, we predicted the top 10 drugs used to treat CD. Immune infiltration results suggest that Hub gene is related to T cells, macrophages, dendritic cells, and other immune cells. Finally, the results of immunohistochemical experiments showed that the protein expression of the hub gene was higher in CD colon tissue than in normal subjects (p < 0.05).

Conclusion

Bioinformatics analysis showed that ferroptosis is closely related to the development of CD, and the prediction of potential drugs provides new targets for the treatment of CD. Moreover, five hub genes identified are potentially new and effective markers for the diagnosis of CD.

Lung Fibrosis after COVID-19: Treatment Prospects

At the end of 2019, a highly contagious infection began its ominous conquest of the world. It was soon discovered that the disease was caused by a novel coronavirus designated as SARS-CoV-2, and the disease was thus abbreviated to COVID-19 (COVID). The global medical community has directed its efforts not only to find effective therapies against the deadly pathogen but also to combat the concomitant complications. Two of the most common respiratory manifestations of COVID are a significant reduction in the diffusing capacity of the lungs (DLCO) and the associated pulmonary interstitial damage. One year after moderate COVID, the incidence rate of impaired DLCO and persistent lung damage still exceeds 30%, and one-third of the patients have severe DLCO impairment and fibrotic lung damage. The persistent respiratory complications may cause substantial population morbidity, long-term disability, and even death due to the lung fibrosis progression. The incidence of COVID-induced pulmonary fibrosis caused by COVID can be estimated based on a 15-year observational study of lung pathology after SARS. Most SARS patients with fibrotic lung damage recovered within the first year and then remained healthy; however, in 20% of the cases, significant fibrosis progression was found in 5-10 years. Based on these data, the incidence rate of post-COVID lung fibrosis can be estimated at 2-6% after moderate illness. What is worse, there are reasons to believe that fibrosis may become one of the major long-term complications of COVID, even in asymptomatic individuals. Currently, despite the best efforts of the global medical community, there are no treatments for COVID-induced pulmonary fibrosis. In this review, we analyze the latest data from ongoing clinical trials aimed at treating post-COVID lung fibrosis and analyze the rationale for the current drug candidates. We discuss the use of antifibrotic therapy for idiopathic pulmonary fibrosis, the IN01 vaccine, glucocorticosteroids as well as the stromal vascular fraction for the treatment and rehabilitation of patients with COVID-associated pulmonary damage.

Interleukin 6 trans-signaling is a critical driver of lung allograft fibrosis

Histopathologic examination of lungs afflicted by chronic lung allograft dysfunction (CLAD) consistently shows both mononuclear cell (MNC) inflammation and mesenchymal cell (MC) fibroproliferation. We hypothesize that interleukin 6 (IL-6) trans-signaling may be a critical mediator of MNC-MC crosstalk and necessary for the pathogenesis of CLAD. Bronchoalveolar lavage (BAL) fluid obtained after the diagnosis of CLAD has approximately twofold higher IL-6 and soluble IL-6 receptor (sIL-6R) levels compared to matched pre-CLAD samples. Human BAL-derived MCs do not respond to treatment with IL-6 alone but have rapid and prolonged JAK2-mediated STAT3 Tyr705 phosphorylation when exposed to the combination of IL-6 and sIL-6R. STAT3 phosphorylation within MCs upregulates numerous genes causing increased invasion and fibrotic differentiation. MNC, a key source of both IL-6 and sIL-6R, produce minimal amounts of these proteins at baseline but significantly upregulate production when cocultured with MCs. Finally, the use of an IL-6 deficient recipient in a murine orthotopic transplant model of CLAD reduces allograft fibrosis by over 50%. Taken together these results support a mechanism where infiltrating MNCs are stimulated by resident MCs to release large quantities of IL-6 and sIL-6R which then feedback onto the MCs to increase invasion and fibrotic differentiation.

The protective effect of Hederagenin on pulmonary fibrosis by regulating the Ras/JNK/NFAT4 axis in rats

As a respiratory disease with high morbidity and mortality, pulmonary fibrosis (PF) has been a serious threat to people's health. Hederagenin (HDG) is a pentacyclic triterpenoid saponin widely distributed in various plants. This study explored the role of HDG in Bleomycin (BLM)-induced PF and the molecular mechanism. The results showed that HDG reduced BLM-induced pulmonary dysfunction, pathological damage in a dose-dependent manner. Besides, HDG reduced BLM-induced collagen deposition by decreasing the levels of α-SMA, Collagen I and hydroxproline. Furthermore, HDG reduced the levels of inflammatory cytokines (TNF-α and IL-6), TGF-β1 and connective tissue growth factor (CTGF) in bronchoalveolar lavage fluid (BALF) or serum. Further mechanism analysis indicated that HDG inhibited the expression of Ras and phosphorylation of JNK and NFAT4 in a dose-dependent manner. However, the JNK pathway activator Anisomycin reversed this inhibitory effect. In conclusion, these findings suggest that HDG may be a potential target drug for PF therapy.