Dual targeting of MEK and PI3K pathways attenuates established and progressive pulmonary fibrosis

SEMA3B inhibits TGFβ-induced extracellular matrix protein production and its reduced levels are associated with a decline in lung function in IPF

Idiopathic pulmonary fibrosis (IPF) is marked by the activation of fibroblasts, leading to excessive production and deposition of extracellular matrix (ECM) within the lung parenchyma. Despite the pivotal role of ECM overexpression in IPF, potential negative regulators of ECM production in fibroblasts have yet to be identified. Semaphorin class 3B (SEMA3B), a secreted protein highly expressed in lung tissues, has established roles in axonal guidance and tumor suppression. However, the role of SEMA3B in ECM production by fibroblasts in the pathogenesis of IPF remains unexplored. Here, we show the downregulation of SEMA3B and its cognate binding receptor, neuropilin 1 (NRP1), in IPF lungs compared with healthy controls. Notably, the reduced expression of SEMA3B and NRP1 is associated with a decline in lung function in IPF. The downregulation of SEMA3B and NRP1 transcripts was validated in the lung tissues of patients with IPF, and two alternative mouse models of pulmonary fibrosis. In addition, we show that transforming growth factor-β (TGFβ) functions as a negative regulator of SEMA3B and NRP1 expression in lung fibroblasts. Furthermore, we demonstrate the antifibrotic effects of SEMA3B against TGFβ-induced ECM production in IPF lung fibroblasts. Overall, our findings uncovered a novel role of SEMA3B in the pathogenesis of pulmonary fibrosis and provided novel insights into modulating the SEMA3B-NRP1 axis to attenuate pulmonary fibrosis.NEW & NOTEWORTHY The excessive production and secretion of collagens and other extracellular matrix proteins by fibroblasts lead to the scarring of the lung in severe fibrotic lung diseases. This study unveils an antifibrotic role for semaphorin class 3B (SEMA3B) in the pathogenesis of idiopathic pulmonary fibrosis. SEMA3B functions as an inhibitor of transforming growth factor-β-driven fibroblast activation and reduced levels of SEMA3B and its receptor, neuropilin 1, are associated with decreased lung function in idiopathic pulmonary fibrosis.

Integrating inflammatory biomarker analysis and artificial-intelligence-enabled image-based profiling to identify drug targets for intestinal fibrosis

Intestinal fibrosis, often caused by inflammatory bowel disease, can lead to intestinal stenosis and obstruction, but there are no approved treatments. Drug discovery has been hindered by the lack of screenable cellular phenotypes. To address this, we used a scalable image-based morphology assay called Cell Painting, augmented with machine learning algorithms, to identify small molecules that could reverse the activated fibrotic phenotype of intestinal myofibroblasts. We then conducted a high-throughput small molecule chemogenomics screen of approximately 5,000 compounds with known targets or mechanisms, which have achieved clinical stage or approval by the FDA. By integrating morphological analyses and AI using pathologically relevant cells and disease-relevant stimuli, we identified several compounds and target classes that are potentially able to treat intestinal fibrosis. This phenotypic screening platform offers significant improvements over conventional methods for identifying a wide range of drug targets.

PI3K Signaling in Mechanisms and Treatments of Pulmonary Fibrosis Following Sepsis and Acute Lung Injury

Pulmonary fibrosis is a pathological fibrotic process affecting the lungs of five million people worldwide. The incidence rate will increase even more in the next years due to the long-COVID-19 syndrome, but a resolving treatment is not available yet and usually prognosis is poor. The emerging role of the phosphatidylinositol 3-kinase (PI3K)/AKT signaling in fibrotic processes has inspired the testing of drugs targeting the PI3K/Akt pathway that are currently under clinical evaluation. This review highlights the progress in understanding the role of PI3K/Akt in the development of lung fibrosis and its causative pathological context, including sepsis as well as acute lung injury (ALI) and its consequent acute respiratory distress syndrome (ARDS). We further summarize current knowledge about PI3K inhibitors for pulmonary fibrosis treatment, including drugs under development as well as in clinical trials. We finally discuss how the design of inhaled compounds targeting the PI3K pathways might potentiate efficacy and improve tolerability.

Dysregulated overexpression of Sox9 induces fibroblast activation in pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fatal fibrotic lung disease associated with unremitting fibroblast activation including fibroblast-to-myofibroblast transformation (FMT), migration, resistance to apoptotic clearance, and excessive deposition of extracellular matrix (ECM) proteins in the distal lung parenchyma. Aberrant activation of lung-developmental pathways is associated with severe fibrotic lung disease; however, the mechanisms through which these pathways activate fibroblasts in IPF remain unclear. Sry-box transcription factor 9 (Sox9) is a member of the high-mobility group box family of DNA-binding transcription factors that are selectively expressed by epithelial cell progenitors to modulate branching morphogenesis during lung development. We demonstrate that Sox9 is upregulated via MAPK/PI3K-dependent signaling and by the transcription factor Wilms' tumor 1 in distal lung-resident fibroblasts in IPF. Mechanistically, using fibroblast activation assays, we demonstrate that Sox9 functions as a positive regulator of FMT, migration, survival, and ECM production. Importantly, our in vivo studies demonstrate that fibroblast-specific deletion of Sox9 is sufficient to attenuate collagen deposition and improve lung function during TGF-α-induced pulmonary fibrosis. Using a mouse model of bleomycin-induced pulmonary fibrosis, we show that myofibroblast-specific Sox9 overexpression augments fibroblast activation and pulmonary fibrosis. Thus, Sox9 functions as a profibrotic transcription factor in activating fibroblasts, illustrating the potential utility of targeting Sox9 in IPF treatment.

The Protective Effects of IL-31RA Deficiency During Bleomycin-Induced Pulmonary Fibrosis

Idiopathic Pulmonary Fibrosis (IPF) is a severe fibrotic lung disease characterized by excessive collagen deposition and progressive decline in lung function. Th2 T cell-derived cytokines including IL-4 and IL-13 have been shown to contribute to inflammation and fibrotic remodeling in multiple tissues. Interleukin-31 (IL-31) is a newly identified cytokine that is predominantly produced by CD4 Th2 T cells, but its signaling receptor IL-31RA is primarily expressed by non-hematopoietic cells. However, the potential role of the IL-31-IL31RA axis in pulmonary inflammation and fibrosis has remained largely unknown. To determine the role of IL-31RA deficiency in pulmonary fibrosis, wildtype, and IL-31RA knockout mice were treated with bleomycin and measured changes in collagen deposition and lung function. Notably, the loss of IL-31 signaling attenuated collagen deposition and lung function decline during bleomycin-induced pulmonary fibrosis. The total lung transcriptome analysis showed a significant reduction in fibrosis-associated gene transcripts including extracellular matrix and epithelial cell-associated gene networks. Furthermore, the lungs of human IPF showed an elevated expression of IL-31 when compared to healthy subjects. In support, the percentage of IL-31 producing CD4⁺ T cells was greater in the lungs and PBMCs from IPF patients compared to healthy controls. Our findings suggest a pathogenic role for IL-31/IL-31RA signaling during bleomycin-induced pulmonary fibrosis. Thus, therapeutic targeting the IL-31-IL-31RA axis may prevent collagen deposition, improve lung function, and have therapeutic potential in pulmonary fibrosis.

Dysregulation of Mesenchymal Cell Survival Pathways in Severe Fibrotic Lung Disease: The Effect of Nintedanib Therapy

Impaired apoptotic clearance of myofibroblasts can result in the continuous expansion of scar tissue during the persistent injury in the lung. However, the molecular and cellular mechanisms underlying the apoptotic clearance of multiple mesenchymal cells including fibrocytes, fibroblasts and myofibroblasts in severe fibrotic lung diseases such as idiopathic pulmonary fibrosis (IPF) remain largely unknown. We analyzed the apoptotic pathways activated in mesenchymal cells of IPF and in a mouse model of TGFα-induced pulmonary fibrosis. We found that fibrocytes and myofibroblasts in fibrotic lung lesions have acquired resistance to Fas-induced apoptosis, and an FDA-approved anti-fibrotic agent, nintedanib, effectively induced apoptotic cell death in both. In support, comparative gene expression analyses suggest that apoptosis-linked gene networks similarly dysregulated in both IPF and a mouse model of TGFα-induced pulmonary fibrosis. TGFα mice treated with nintedanib show increased active caspase 3-positive cells in fibrotic lesions and reduced fibroproliferation and collagen production. Further, the long-term nintedanib therapy attenuated fibrocyte accumulation, collagen deposition, and lung function decline during TGFα-induced pulmonary fibrosis. These results highlight the importance of inhibiting survival pathways and other pro-fibrotic processes in the various types of mesenchymal cells and suggest that the TGFα mouse model is relevant for testing of anti-fibrotic drugs either alone or in combination with nintedanib.

Mechanisms for the Resolution of Organ Fibrosis

Fibrosis is a dynamic process with the potential for reversibility and restoration of near-normal tissue architecture and organ function. Herein, we review mechanisms for resolution of organ fibrosis, in particular that involving the lung, with an emphasis on the critical roles of myofibroblast apoptosis and clearance of deposited matrix.

New therapeutics based on emerging concepts in pulmonary fibrosis

INTRODUCTION

Fibrosis is an irreversible pathological endpoint in many chronic diseases, including pulmonary fibrosis. Idiopathic pulmonary fibrosis (IPF) is a progressive and often fatal condition characterized by (myo)fibroblast proliferation and transformation in the lung, expansion of the extracellular matrix, and extensive remodeling of the lung parenchyma. Recent evidence indicates that IPF prevalence and mortality rates are growing in the United States and elsewhere. Despite decades of research on the pathogenic mechanisms of pulmonary fibrosis, few therapeutics have succeeded in the clinic, and they have failed to improve IPF patient survival. Areas covered: Based on a literature search and our own results, we discuss the key cellular and molecular responses that contribute to (myo)fibroblast actions and pulmonary fibrosis pathogenesis; this includes signaling pathways in various cells that aberrantly and persistently activate (myo)fibroblasts in fibrotic lesions and promote scar tissue formation in the lung. Expert opinion: Lessons learned from recent failures and successes with new therapeutics point toward approaches that can target multiple pro-fibrotic processes in IPF. Advances in preclinical modeling and single-cell genomics will also accelerate novel discoveries for effective treatment of IPF.

Comparison of the antifibrotic effects of the pan-histone deacetylase-inhibitor panobinostat versus the IPF-drug pirfenidone in fibroblasts from patients with idiopathic pulmonary fibrosis

Background

Idiopathic pulmonary fibrosis (IPF) is a devastating lung disease with a poor prognosis. Pirfenidone is the first antifibrotic agent to be approved for IPF-treatment as it is able to slow down disease progression. However, there is no curative treatment other than lung transplantation. Because epigenetic alterations are associated with IPF, histone deacetylase (HDAC)-inhibitors have recently been proven to attenuate fibrotic remodeling in vitro and in vivo. This study compared the effects of pirfenidone with the pan-HDAC-inhibitor panobinostat/LBH589, a FDA-approved drug for the treatment of multiple myeloma, head-to-head on survival, fibrotic activity and proliferation of primary IPF-fibroblasts in vitro.

Methods

Primary fibroblasts from six IPF-patients were incubated for 24h with vehicle (0.25% DMSO), panobinostat (LBH589, 85 nM) or pirfenidone (2.7 mM), followed by assessment of proliferation and expression analyses for profibrotic and anti-apoptosis genes, as well as for ER stress and apoptosis-markers. In addition, the expression status of all HDAC enzymes was examined.

Results

Treatment of IPF-fibroblasts with panobinostat or pirfenidone resulted in a downregulated expression of various extracellular matrix (ECM)-associated genes, as compared to vehicle-treated cells. In agreement, both drugs decreased protein level of phosphorylated (p)-STAT3, a transcription factor mediating profibrotic responses, in treated IPF-fibroblasts. Further, an increase in histone acetylation was observed in response to both treatments, but was much more pronounced and excessive in panobinostat-treated IPF-fibroblasts. Panobinostat, but not pirfenidone, led to a significant suppression of proliferation in IPF-fibroblasts, as indicated by WST1- and BrdU assay and markedly diminished levels of cyclin-D1 and p-histone H3. Furthermore, panobinostat-treatment enhanced α-tubulin-acetylation, decreased the expression of survival-related genes Bcl-XL and BIRC5/survivin, and was associated with induction of ER stress and apoptosis in IPF-fibroblasts. In contrast, pirfenidone-treatment maintained Bcl-XL expression, and was neither associated with ER stress-induction nor any apoptotic signaling. Pirfenidone also led to increased expression of HDAC6 and sirtuin-2, and enhanced α-tubulin-deacetylation. But in line with its ability to increase histone acetylation, pirfenidone reduced the expression of HDAC enzymes HDAC1, -2 and -9.

Conclusions

We conclude that, beside other antifibrotic mechanisms, pirfenidone reduces profibrotic signaling also through STAT3 inactivation and weak epigenetic alterations in IPF-fibroblasts, and permits survival of (altered) fibroblasts. The pan-HDAC-inhibitor panobinostat reduces profibrotic phenotypes while inducing cell cycle arrest and apoptosis in IPF-fibroblasts, thus indicating more efficiency than pirfenidone in inactivating IPF-fibroblasts. We therefore believe that HDAC-inhibitors such as panobinostat can present a novel therapeutic strategy for IPF.

Wilms' tumor 1 drives fibroproliferation and myofibroblast transformation in severe fibrotic lung disease

Wilms' tumor 1 (WT1) is a critical transcriptional regulator of mesothelial cells during lung development but is downregulated in postnatal stages and adult lungs. We recently showed that WT1 is upregulated in both mesothelial cells and mesenchymal cells in the pathogenesis of idiopathic pulmonary fibrosis (IPF), a fatal fibrotic lung disease. Although WT1-positive cell accumulation leading to severe fibrotic lung disease has been studied, the role of WT1 in fibroblast activation and pulmonary fibrosis remains elusive. Here, we show that WT1 functions as a positive regulator of fibroblast activation, including fibroproliferation, myofibroblast transformation, and extracellular matrix (ECM) production. Chromatin immunoprecipitation experiments indicate that WT1 binds directly to the promoter DNA sequence of α-smooth muscle actin (αSMA) to induce myofibroblast transformation. In support, the genetic lineage tracing identifies WT1 as a key driver of mesothelial-to-myofibroblast and fibroblast-to-myofibroblast transformation. Importantly, the partial loss of WT1 was sufficient to attenuate myofibroblast accumulation and pulmonary fibrosis in vivo. Further, our coculture studies show that WT1 upregulation leads to non-cell autonomous effects on neighboring cells. Thus, our data uncovered a pathogenic role of WT1 in IPF by promoting fibroblast activation in the peripheral areas of the lung and as a target for therapeutic intervention.

S100A4+ Macrophages Are Necessary for Pulmonary Fibrosis by Activating Lung Fibroblasts

S100A4, a calcium-binding protein, can promote pulmonary fibrosis via fibroblast activation. Due partly to its various cellular origins, the exact role of S100A4 in the development of lung fibrosis remains elusive. Here, we show that in the bronchoalveolar lavage fluid, numbers of S100A4⁺ macrophages correlated well with S100A4 protein levels and occurrence of idiopathic pulmonary fibrosis (IPF) in patients. A mouse model of bleomycin-induced pulmonary fibrosis demonstrated S100A4⁺ macrophages as main source for extracellular S100A4 in the inflammatory phase. In vitro studies revealed that extracellular S100A4 could activate both mouse and human lung fibroblasts by upregulation of α-SMA and type I collagen, during which sphingosine-1-phosphate (S1P) increased. Inhibiting the S1P receptor subtypes S1P₁/S1P₃ abrogated fibroblast activation. Accordingly, absence or neutralization of S100A4 significantly attenuated bleomycin-induced lung fibrosis in vivo. Importantly, adoptive transfer of S100A4⁺ but not of S100A4⁻ macrophages installed experimental lung injury in S100A4^−/− mice that were otherwise not sensitive to fibrosis induction. Taken together, S100A4 released by macrophages promotes pulmonary fibrosis through activation of lung fibroblasts which is associated with S1P. This suggests that extracellular S100A4 or S100A4⁺ macrophages within the lung as promising targets for early clinical diagnosis or therapy of IPF.

Unique and Redundant Functions of p70 Ribosomal S6 Kinase Isoforms Regulate Mesenchymal Cell Proliferation and Migration in Pulmonary Fibrosis

The p70 ribosomal S6 kinase (p70S6K) is a downstream substrate that is phosphorylated and activated by the mammalian target of rapamycin complex and regulates multiple cellular processes associated with pulmonary fibrogenesis. Two isoforms of the p70S6K have been identified (S6K1 and S6K2), but their relative contributions in mediating pulmonary fibrosis are unknown. To interrogate the roles of the p70S6K isoforms, we overexpressed transforming growth factor (TGF)-α in mice deficient for the S6K1 or S6K2 genes and measured changes in lung histology, morphometry, total lung collagen, lung function, and proliferation between wild-type and isoform-deficient mice. Deficiency of S6K1, but not S6K2, had a significant effect on reducing proliferation in subpleural fibrotic lesions during TGF-α-induced fibrosis. Migration was significantly decreased in mesenchymal cells isolated from the lungs of S6K1 knockout mice compared with wild-type or S6K2 knockout mice. Conversely, increases in subpleural thickening were significantly decreased in S6K2-deficient mice compared with wild type. Deficiency of S6K2 significantly reduced phosphorylation of the downstream S6 ribosomal protein in lung homogenates and isolated mesenchymal cells after TGF-α expression. However, deficiency of neither isoform alone significantly altered TGF-α-induced collagen accumulation or lung function decline in vivo. Furthermore, deficiency in neither isoform prevented changes in collagen accumulation or lung compliance decline after administration of intradermal bleomycin. Together, these findings demonstrate that the p70S6K isoforms have unique and redundant functions in mediating fibrogenic processes, including proliferation, migration, and S6 phosphorylation, signifying that both isoforms must be targeted to modulate p70S6K-mediated pulmonary fibrosis.

Impact of obesity with impaired glucose tolerance on retinal degeneration in a rat model of metabolic syndrome

PURPOSE

Metabolic syndrome (MetS) is associated with several degenerative diseases, including retinal degeneration. Previously, we reported on progressive retinal degeneration in a spontaneous obese rat (WNIN/Ob) model. In this study, we investigated the additional effect of impaired glucose tolerance (IGT), an essential component of MetS, on retinal degeneration using the WNIN/GR-Ob rat model.

METHODS

The retinal morphology and ultrastructure of WNIN/GR-Ob and age-matched littermate lean rats were studied by microscopy and immunohistochemistry. The retinal transcriptome of WNIN/GR-Ob was compared with the respective lean controls and with the WNIN/Ob model using microarray analysis. Expression of selected retinal marker genes was studied via real-time PCR.

RESULTS

Progressive loss of photoreceptor cells was observed in WNIN/GR-Ob rats with an onset as early as 3 months. Similarly, thinning of the inner nuclear layer was observed from 6 months in these rats. Immunohistochemical analysis showed decreased levels of rhodopsin and postsynaptic density protein-95 (PSD-95) proteins and increased levels of glial fibrillary acidic protein (GFAP), vascular endothelial growth factor (VEGF), and calretinin in WNIN/GR-Ob rats compared with the age-matched lean controls, further supporting cellular stress/damage and retinal degeneration. The retinal transcriptome analysis indicated altered expression profiles in both the WNIN/GR-Ob and WNIN/Ob rat models compared to their respective lean controls; these pathways are associated with activation of pathways like cellular oxidative stress response, inflammation, apoptosis, and phototransduction, although the changes were more prominent in WNIN/GR-Ob than in WNIN/Ob animals.

CONCLUSIONS

WNIN/GR-Ob rats with added glucose intolerance developed retinal degeneration similar to the parent line WNIN/Ob. The severity of retinal degeneration was greater in WNIN/GR-Ob rats compared to WNIN/Ob, suggesting a possible role for IGT in this model. Hence, the WNIN/GR-Ob model could be a valuable tool for investigating the impact of MetS on retinal degeneration pathology.

Deficiency of α7 nicotinic acetylcholine receptor attenuates bleomycin-induced lung fibrosis in mice

α7 nicotinic acetylcholine receptor (α7 nAChR, coded by Chrna7) is indispensible in dampening proinflammatory responses. However, whether α7 nAChR would play a role in regulating bleomycin (BLM)-induced lung fibrosis is less investigated. Here, we intratracheally challenged wildtype and Chrna7^-/- mice with BLM to elicit lung fibrosis. Taken advantage of this model, we measured body weight loss, lung fibrogenic genes (Acta2, Col1a1, Fsp1, and Fstl1), histology, Masson's trichrome staining, hydroxyproline levels, and expression of α-SMA at protein levels in the BLM-challenged lung for evaluating severity of lung fibrosis. We also pretreated human fibroblasts (MRC5 cell line) and isolated mouse lung fibroblasts with GTS-21 (an α7 nAChR agonist) to study its effects on TGF-β-stimulated profibrotic profiles. We found that lung Chrna7 expression and CD4⁺CHAT⁺ (Choline acetyltransferase, an enzyme for local acetylcholine synthesis) cells were 12-fold and 4.5-fold respectively elevated in the early stage of lung fibrosis. Deletion of Chrna7 prevented body weight loss and reduced lung fibrogenic genes (Acta2, Col1a1, Fsp1, and Fstl1) and Arg 1 (coding arginase 1). Deletion of Chrna7 attenuated lung arginase 1⁺Ly6C⁺ cells, Masson's trichrome staining, hydroxyproline levels, and expression of α-SMA at protein levels in BLM-challenged mice. Mechanistically, activation of α7 nAChR in human fibroblasts increased TGF-β-induced phosphorylation of Smad2/3 and transcription of fibrogenic genes (Acta2, Col1a1). In isolated mouse lung fibroblasts, activation of α7 nAChR also enhanced TGF-β induced-transcription of fibrogenic genes; however, deletion of Chrna7 diminished these effects. Taken together, deficiency of α7 nAChR could suppress the development of BLM-induced lung fibrosis. Thus, α7 nAChR might be a novel therapeutic target for treating lung fibrosis.

Hsp90 regulation of fibroblast activation in pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a severe fibrotic lung disease associated with fibroblast activation that includes excessive proliferation, tissue invasiveness, myofibroblast transformation, and extracellular matrix (ECM) production. To identify inhibitors that can attenuate fibroblast activation, we queried IPF gene signatures against a library of small-molecule-induced gene-expression profiles and identified Hsp90 inhibitors as potential therapeutic agents that can suppress fibroblast activation in IPF. Although Hsp90 is a molecular chaperone that regulates multiple processes involved in fibroblast activation, it has not been previously proposed as a molecular target in IPF. Here, we found elevated Hsp90 staining in lung biopsies of patients with IPF. Notably, fibroblasts isolated from fibrotic lesions showed heightened Hsp90 ATPase activity compared with normal fibroblasts. 17-N-allylamino-17-demethoxygeldanamycin (17-AAG), a small-molecule inhibitor of Hsp90 ATPase activity, attenuated fibroblast activation and also TGF-β-driven effects on fibroblast to myofibroblast transformation. The loss of the Hsp90AB, but not the Hsp90AA isoform, resulted in reduced fibroblast proliferation, myofibroblast transformation, and ECM production. Finally, in vivo therapy with 17-AAG attenuated progression of established and ongoing fibrosis in a mouse model of pulmonary fibrosis, suggesting that targeting Hsp90 represents an effective strategy for the treatment of fibrotic lung disease.

MicroRNA‑185 regulates transforming growth factor‑β1 and collagen‑1 in hypertrophic scar fibroblasts

Transforming growth factor-β1 (TGF-β1) and collagen type I (Col-1) serve a critical role in the development and progression of hypertrophic scarring (HS). The present study hypothesized that a post‑translational mechanism of microRNAs (miR) regulated the expression of TGF‑β1 and Col‑1 in HS fibroblasts (HSFBs). A collection of 20 HS tissues was compared with corresponding normal tissues from clinical patients, and the expression of miR‑185 was measured. Using PicTar, TargetScan and miRBase databases, it was identified that miR‑185 may be a regulator of TGF‑β1 and Col‑1 in humans. Based on these hypotheses, the expression of miR‑185, TGF‑β1 and Col‑1 in HS tissues was investigated. The results demonstrated that the expression of miR‑185 was markedly suppressed, and TGF‑β1 and Col‑1 levels were increased, in HS tissues. The expression levels of endogenous miR‑185 negatively correlated with the TGF‑β1 and Col‑1 mRNA levels (Pearson's correlation coefficient r=‑0.674, P<0.01 and r=‑0.590, P<0.01, respectively). In vitro, miR‑185 can regulate TGF‑β1 and Col‑1 through the predicted binding sites in its 3'‑untranslated region. miR‑185 had an effect on cell proliferation and apoptosis, thereby regulating HSFBs growth. In addition, miR‑185 gain‑of‑function decreased TGF‑β1 and Col‑1 protein expression, and miR‑185 loss‑of‑function increased TGF‑β1 and Col‑1 protein expression in HSFBs. In conclusion, overexpressed miR‑185 could inhibit HSFBs growth, and the underlying mechanism was mediated, at least partly, through the suppression of TGF‑β1 and Col‑1 expression. However, above all, miR‑185 might serve as a potential therapeutic approach for the treatment of HS.

IL-31-Driven Skin Remodeling Involves Epidermal Cell Proliferation and Thickening That Lead to Impaired Skin-Barrier Function

Interleukin-31 (IL-31) is a type 2 helper T-cell-derived cytokine that has recently been shown to cause severe inflammation and tissue remodeling in multiple chronic diseases of the skin and lungs. IL-31 is upregulated in allergic and inflammatory diseases, including atopic dermatitis, asthma, cutaneous T-cell lymphomas, and allergic rhinitis, as well as autoimmune diseases such as systemic erythematosus. Overexpression of IL-31 in T cells causes severe inflammation, with histological features similar to skin lesions of patients with atopic dermatitis. However, the molecular mechanisms involved in IL31-driven pathological remodeling in skin diseases remain largely unknown. Here, we studied the role of IL-31 in skin damage as a result of intradermal administration of recombinant IL-31 into mice. Notably, IL-31 was sufficient to increase epidermal basal-cell proliferation and thickening of the epidermal skin layer. Our findings demonstrate a progressive increase in transepidermal water loss with chronic administration of IL-31 into the skin. Further, analysis of the skin transcriptome indicates a significant increase in the transcripts involved in epidermal-cell proliferation, epidermal thickening, and mechanical integrity. In summary, our findings demonstrate an important role for IL-31 signaling in epidermal cell proliferation and thickening that together may lead to impaired skin-barrier function in pathological remodeling of the skin.

p70 ribosomal S6 kinase regulates subpleural fibrosis following transforming growth factor-α expression in the lung

The p70 ribosomal S6 kinase (S6K) is a downstream substrate that is phosphorylated and activated by the mammalian target of rapamycin complex and regulates multiple cellular processes associated with fibrogenesis. Recent studies demonstrate that aberrant mTORC1-S6K signaling contributes to various pathological conditions, but a direct role in pulmonary fibroproliferation has not been established. Increased phosphorylation of the S6K pathway is detected immediately following transforming growth factor-α (TGF-α) expression in a transgenic model of progressive lung fibrosis. To test the hypothesis that the S6K directly regulates pulmonary fibroproliferative disease we determined the cellular sites of S6K phosphorylation during the induction of fibrosis in the TGF-α model and tested the efficacy of specific pharmacological inhibition of the S6K pathway to prevent and reverse fibrotic disease. Following TGF-α expression increased phosphorylation of the S6K was detected in the airway and alveolar epithelium and the mesenchyme of advanced subpleural fibrotic regions. Specific inhibition of the S6K with the small molecule inhibitor LY-2584702 decreased TGF-α and platelet-derived growth factor-β-induced proliferation of lung fibroblasts in vitro. Administration of S6K inhibitors to TGF-α mice prevented the development of extensive subpleural fibrosis and alterations in lung mechanics, and attenuated the increase in total lung hydroxyproline. S6K inhibition after fibrosis was established attenuated the progression of subpleural fibrosis. Together these studies demonstrate targeting the S6K pathway selectively modifies the progression of pulmonary fibrosis in the subpleural compartment of the lung.

Fibrocytes Regulate Wilms Tumor 1-Positive Cell Accumulation in Severe Fibrotic Lung Disease

Collagen-producing myofibroblast transdifferentiation is considered a crucial determinant in the formation of scar tissue in the lungs of patients with idiopathic pulmonary fibrosis. Multiple resident pulmonary cell types and bone marrow-derived fibrocytes have been implicated as contributors to fibrotic lesions because of the transdifferentiation potential of these cells into myofibroblasts. In this study, we assessed the expression of Wilms tumor 1 (WT1), a known marker of mesothelial cells, in various cell types in normal and fibrotic lungs. We demonstrate that WT1 is expressed by both mesothelial and mesenchymal cells in idiopathic pulmonary fibrosis lungs but has limited or no expression in normal human lungs. We also demonstrate that WT1(+) cells accumulate in fibrotic lung lesions, using two different mouse models of pulmonary fibrosis and WT1 promoter-driven fluorescent reporter mice. Reconstitution of bone marrow cells into a TGF-α transgenic mouse model demonstrated that fibrocytes do not transform into WT1(+) mesenchymal cells, but they do augment accumulation of WT1(+) cells in severe fibrotic lung disease. Importantly, the number of WT1(+) cells in fibrotic lesions was correlated with severity of lung disease as assessed by changes in lung function, histology, and hydroxyproline levels in mice. Finally, inhibition of WT1 expression was sufficient to attenuate collagen and other extracellular matrix gene production by mesenchymal cells from both murine and human fibrotic lungs. Thus, the results of this study demonstrate a novel association between fibrocyte-driven WT1(+) cell accumulation and severe fibrotic lung disease.

Targeting phosphatidylinositol-3-kinase pathway for the treatment of Philadelphia-negative myeloproliferative neoplasms

Myeloproliferative neoplasms (MPN) are a diverse group of chronic hematological disorders that involve unregulated clonal proliferation of white blood cells. Sevearl of them are associated with mutations in receptor tyrosine kinases or cytokine receptor associated tyrosine kinases rendering them independent of cytokine-mediated regulation. Classically they have been broadly divided into BCR-ABL1 fusion + ve (Ph + ve) or -ve (Ph-ve) MPNs. Identification of BCR-ABL1 tyrosine kinase as a driver of chronic myeloid leukemia (CML) and successful application of small molecule inhibitors of the tyrosine kinases in the clinic have triggered the search for kinase dependent pathways in other Ph-ve MPNs. In the past few years, identification of mutations in JAK2 associated with a majority of MPNs raised the hopes for similar success with specific targeting of JAK2. However, targeting JAK2 kinase activity has met with limited success. Subsequently, mutations in genes other than JAK2 have been identified. These mutations specifically associate with certain MPNs and can drive cytokine independent growth. Therefore, targeting alternate molecules and pathways may be more successful in management of MPNs. Among other pathways, phosphatidylinositol -3 kinase (PI3K) has emerged as a promising target as different cell surface receptor induced signaling pathways converge on the PI3K signaling axis to regulate cell metabolism, growth, proliferation, and survival. Herein, we will review the clinically relevant inhibitors of the PI3K pathway that have been evaluated or hold promise for the treatment of Ph-ve MPNs.

Novel insights into TRPM7 function in fibrotic diseases: a potential therapeutic target

"Transient receptor potential (TRP) channels are cellular sensors for a wide spectrum of physical and chemical stimuli. Activation of TRP channels changes the membrane potential, translocates important signaling ions crossing the cell membrane, alters enzymatic activity, and initiates endocytosis/exocytosis (Zheng, 2013)." Fibrosis is the leading cause of organ dysfunction in diseases, which is characterized by an imbalance in the turnover of extracellular matrix components. Accumulating evidence has demonstrated that TRPM7, a member of TRP channels superfamily, participates in the development and pathogenesis of fibrotic diseases, such as hepatic, pulmonary and cardiac fibrosis. In this review, we discuss the comprehensive role of TRPM7 in modulating profibrotic response and its potential as therapeutic target for fibrotic diseases.