Imatinib mesylate inhibits the profibrogenic activity of TGF-beta and prevents bleomycin-mediated lung fibrosis

Cromolyn sodium and masitinib combination inhibits fibroblast-myofibroblast transition and exerts additive cell-protective and antioxidant effects on a bleomycin-induced in vitro fibrosis model

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal fibrotic lung disease. While recent studies have suggested the potential efficacy of tyrosine kinase inhibitors in managing IPF, masitinib, a clinically used tyrosine kinase inhibitor, has not yet been investigated for its efficacy in fibrotic lung diseases. In a previous study on an in vitro neurodegenerative model, we demonstrated the synergistic antitoxic and antioxidant effects of masitinib combined with cromolyn sodium, an FDA-approved mast cell stabilizer. This study aims to investigate the anti-fibrotic and antioxidant effects of the masitinib-cromolyn sodium combination in an in vitro model of pulmonary fibrosis. Fibroblast cell cultures treated with bleomycin and/or hydrogen peroxide (H2O2) were subjected to masitinib and/or cromolyn sodium, followed by assessments of cell viability, morphological and apoptotic nuclear changes, triple-immunofluorescence labeling, and total oxidant/antioxidant capacities, besides ratio of Bax and Bcl-2 mRNA expressions as an indication of apoptosis. The combined treatment of masitinib and cromolyn sodium effectively prevented the fibroblast myofibroblast transition, a hallmark of fibrosis, and significantly reduced bleomycin / H2O2-induced apoptosis and oxidative stress. This study is the first to demonstrate the additive anti-fibrotic, cell-protective, and antioxidant effects of the masitinib-cromolyn sodium combination in an in vitro fibrosis model, suggesting its potential as an innovative therapeutic approach for pulmonary fibrosis. Combination therapy may be more advantageous in that both drugs could be administered in lower doses, exerting less side effects, and at the same time providing diverse mechanisms of action simultaneously.

Use of a pH-responsive imatinib mesylate sustained-release hydrogel for the treatment of tendon adhesion by inhibiting PDGFRβ/CLDN1 pathway

Adhesion after tendon injury, which can result in limb movement disorders, is a common clinical complication; however, effective treatment methods are lacking. Hyaluronic acid hydrogels are a new biomedical material used to prevent tendon adhesion owing to their good biocompatibility. In addition, potential drugs that inhibit adhesion formation have gradually been discovered. The anti-adhesion effects of a combination of loaded drugs into hydrogels have become an emerging trend. However, current drug delivery systems usually lack specific regulation of drug release, and the effectiveness of drugs for treating tendon adhesions is mostly flawed. In this study, we identified a new drug, imatinib mesylate (IM), that prevents tendon adhesion and explored its related molecular pathways. In addition, we designed a pH-responsive sustained-release hydrogel for delivery. Using the metal-organic framework ZIF-8 as a drug carrier, we achieved controlled drug release to increase the effective drug dose at the peak of adhesion formation to achieve better therapeutic effects. The results showed that IM blocked the formation of peritendon adhesions by inhibiting the PDGFRβ/ERK/STAT3/CLDN1 pathway. Furthermore, the hydrogel with ZIF-8 exhibited better physical properties and drug release curves than the hydrogel loaded only with drugs, showing better prevention and treatment effects on tendon adhesion.

Perspective to precision medicine in scleroderma

Systemic sclerosis (SSc) is a rare and heterogeneous disease with no relevant environmental trigger or significant responsible gene. It has been and will continue to be difficult to identify large enough patients to conduct classic population-based epidemiologic exposure/non-exposure studies with adequate power to ascertain environmental and genetic risk factors for these entities. The complexity of pathogenesis and heterogeneity are likely to require personalized/precision medicine for SSc. Since several potential drugs are currently available for specific patients if not whole SSc, classification of SSc seems to form the foundation for a better therapeutic strategy. To date, SSc has been classified based on the extent/severity of the affected area as well as some disease markers, including the autoantibody profile. However, such an analysis should also lead to improvements in the design of appropriately stratified clinical trials to determine the effects and prediction of targeted therapies. An approach based on drug response preclinically conducted using patients' own fibroblasts in vitro, can provide a precise disease marker/therapeutic selection for clinical practice. Because scleroderma dermal fibroblasts have a persistent hyper-productive phenotype occurring not only in person, but also in cell culture conditions. Thus, an accumulating approach based on disease markers ensures progression and de-escalation to re-establish a better life with a personally optimized drug environment after the onset of SSc.

Inflammatory Markers Involved in the Pathogenesis of Dupuytren's Contracture

Dupuytren's disease is a common fibroproliferative disease that can result in debilitating hand deformities. Partial correction and return of deformity are common with surgical or clinical treatments at present. While current treatments are limited to local procedures for relatively late effects of the disease, the pathophysiology of this connective tissue disorder is associated with both local and systemic processes (e.g., fibrosis, inflammation). Hence, a better understanding of the systemic circulation of Dupuytren related cytokines and growth factors may provide important insights into disease progression. In addition, systemic biomarker analysis could yield new concepts for treatments of Dupuytren that attenuate circulatory factors (e.g., anti-inflammatory agents, neutralizing antibodies). Progress in the development of any disease modifying biologic treatment for Dupuytren has been hampered by the lack of clinically useful biomarkers. The characterization of nonsurgical Dupuytren biomarkers will permit disease staging from diagnostic and prognostic perspectives, as well as allows evaluation of biologic responses to treatment. Identification of such markers may transcend their use in Dupuytren treatment, because fibrotic biological processes fundamental to Dupuytren are relevant to fibrosis in many other connective tissues and organs with collagen-based tissue compartments. There is a wide range of potential Dupuytren biomarker categories that could be informative, including disease determinants linked to genetics, collagen metabolism, as well as immunity and inflammation (e.g., cytokines, chemokines). This narrative review provides a broad overview of previous studies and emphasizes the importance of inflammatory mediators as candidate circulating biomarkers for monitoring Dupuytren's disease.

An important call: Suggestion of using IL-10 as therapeutic agent for COVID-19 with ARDS and other complications

The global coronavirus disease 2019 (COVID-19) pandemic has a detrimental impact on public health. COVID-19 usually manifests as pneumonia, which can progress into acute respiratory distress syndrome (ARDS) related to uncontrolled TH17 immune reaction. Currently, there is no effective therapeutic agent to manage COVID-19 with complications. The currently available anti-viral drug remdesivir has an effectiveness of 30% in SARS-CoV-2-induced severe complications. Thus, there is a need to identify effective agents to treat COVID-19 and the associated acute lung injury and other complications. The host immunological pathway against this virus typically involves the THαβ immune response. THαβ immunity is triggered by type 1 interferon and interleukin-27 (IL-27), and the main effector cells of the THαβ immune response are IL10-CD4 T cells, CD8 T cells, NK cells, and IgG1-producing B cells. In particular, IL-10 exerts a potent immunomodulatory or anti-inflammatory effect and is an anti-fibrotic agent for pulmonary fibrosis. Concurrently, IL-10 can ameliorate acute lung injury or ARDS, especially those caused by viruses. Owing to its anti-viral activity and anti-pro-inflammatory effects, in this review, IL-10 is suggested as a possible treatment agent for COVID-19.

Myelofibrosis at diagnosis is associated with the failure of treatment-free remission in CML patients

The management of patients with chronic myeloid leukemia (CML) has been revolutionized by the introduction of tyrosine kinase inhibitors (TKIs), which induce deep molecular responses so that treatment can eventually be discontinued, leading to treatment-free remission (TFR) in a subset of patients. Unfortunately, leukemic stem cells (LSCs) often persist and a fraction of these can again expand in about half of patients that attempt TKI discontinuation. In this study, we show that presence of myelofibrosis (MF) at the time of diagnosis is a factor associating with TFR failure. Fibrotic transformation is governed by the action of several cytokines, and interestingly, some of them have also been described to support LSC persistence. At the cellular level, these could be produced by both malignant cells and by components of the bone marrow (BM) niche, including megakaryocytes (MKs) and mesenchymal stromal cells (MSCs). In our cohort of 57 patients, around 40% presented with MF at diagnosis and the number of blasts in the peripheral blood and BM was significantly elevated in patients with higher grade of MF. Employing a CML transgenic mouse model, we could observe higher levels of alpha-smooth muscle actin (α-SMA) in the BM when compared to control mice. Short-term treatment with the TKI nilotinib, efficiently reduced spleen weight and BCR::ABL1 mRNA levels, while α-SMA expression was only partially reduced. Interestingly, the number of MKs was increased in the spleen of CML mice and elevated in both BM and spleen upon nilotinib treatment. Analysis of human CML-vs healthy donor (HD)-derived MSCs showed an altered expression of gene signatures reflecting fibrosis as well as hematopoietic support, thus suggesting MSCs as a potential player in these two processes. Finally, in our cohort, 12 patients qualified for TKI discontinuation, and here we observed that all patients who failed TFR had BM fibrosis at diagnosis, whereas this was only the case in 25% of patients with achieved TFR, further supporting the link between fibrosis and LSC persistence.

AV-101, a novel inhaled dry-powder formulation of imatinib, in healthy adult participants: a phase 1 single and multiple ascending dose study

Background

Oral imatinib has been shown to be effective, but poorly tolerated, in patients with advanced pulmonary arterial hypertension (PAH). To maintain efficacy while improving tolerability, AV-101, a dry powder inhaled formulation of imatinib, was developed to deliver imatinib directly to the lungs.

Methods

This phase 1, placebo-controlled, randomised single ascending dose (SAD) and multiple ascending dose (MAD) study evaluated the safety/tolerability and pharmacokinetics of AV-101 in healthy adults. The SAD study included five AV-101 cohorts (1 mg, 3 mg, 10 mg, 30 mg, 90 mg) and placebo, and a single-dose oral imatinib 400-mg cohort. The MAD study included three AV-101 cohorts (10 mg, 30 mg, 90 mg) and placebo; dosing occurred twice daily for 7 days.

Results

82 participants (SAD n=48, MAD n=34) were enrolled. For the SAD study, peak plasma concentrations of imatinib occurred within 3 h of dosing with lower systemic exposure compared to oral imatinib (p<0.001). For the MAD study, systemic exposure of imatinib was higher after multiple doses of AV-101 compared to a single dose, but steady-state plasma concentrations were lower for the highest AV-101 cohort (90 mg) compared to simulated steady-state oral imatinib at day 7 (p=0.0002). Across AV-101 MAD dose cohorts, the most common treatment-emergent adverse events were cough (n=7, 27%) and headache (n=4, 15%).

Conclusions

AV-101 was well tolerated in healthy adults, and targeted doses of AV-101 significantly reduced the systemic exposure of imatinib compared with oral imatinib. An ongoing phase 2b/phase 3 study (IMPAHCT; clinicaltrials.gov identifier NCT05036135) will evaluate the safety/tolerability and clinical benefit of AV-101 for PAH.

The lymphocyte-specific protein tyrosine kinase-specific inhibitor A-770041 attenuates lung fibrosis via the suppression of TGF-β production in regulatory T-cells

Background

Lymphocyte-specific protein tyrosine kinase (Lck) is a member of the Src family of tyrosine kinases. The significance of Lck inhibition in lung fibrosis has not yet been fully elucidated, even though lung fibrosis is commonly preceded by inflammation caused by infiltration of T-cells expressing Lck. In this study, we examined the effect of Lck inhibition in an experimental mouse model of lung fibrosis. We also evaluated the effect of Lck inhibition on the expression of TGF-β1, an inhibitory cytokine regulating the immune function, in regulatory T-cells (Tregs).

Methods

Lung fibrosis was induced in mice by intratracheal administration of bleomycin. A-770041, a Lck-specific inhibitor, was administrated daily by gavage. Tregs were isolated from the lung using a CD4⁺CD25⁺ Regulatory T-cell Isolation Kit. The expression of Tgfb on Tregs was examined by flow cytometry and quantitative polymerase chain reaction. The concentration of TGF-β in bronchoalveolar lavage fluid (BALF) and cell culture supernatant from Tregs was quantified by an enzyme-linked immunosorbent assay.

Results

A-770041 inhibited the phosphorylation of Lck in murine lymphocytes to the same degree as nintedanib. A-770041 attenuated lung fibrosis in bleomycin-treated mice and reduced the concentration of TGF-β in BALF. A flow-cytometry analysis showed that A-770041 reduced the number of Tregs producing TGF-β1 in the lung. In isolated Tregs, Lck inhibition by A-770041 decreased the Tgfb mRNA level as well as the concentration of TGF-β in the supernatant.

Conclusions

These results suggest that Lck inhibition attenuated lung fibrosis by suppressing TGF-β production in Tregs and support the role of Tregs in the pathogenesis of lung fibrosis.

The compound LG283 inhibits bleomycin-induced skin fibrosis via antagonizing TGF-β signaling

Background

Systemic sclerosis (SSc) is a collagen disease that exhibits intractable fibrosis and vascular injury of the skin and internal organs. Transforming growth factor-β (TGF-β)/Smad signaling plays a central role in extracellular matrix (ECM) production by α-SMA-positive myofibroblasts. Myofibroblasts may be partially derived from various precursor cells in addition to resident fibroblasts. Recently, our high-throughput in vitro screening discovered a small compound, LG283, that may disrupt the differentiation of epithelial cells into myofibroblasts. This compound was originally generated as a curcumin derivative.

Methods

In this study, we investigated the effect of LG283 on inhibiting fibrosis and its mechanism. The action of LG283 on TGF-β-dependent fibrogenic activity and epithelial-mesenchymal transition (EMT) was analyzed in vitro. The effects of LG283 were also examined in a bleomycin-induced skin fibrosis mouse model.

Results

LG283 suppressed TGF-β-induced expression of ECM, α-SMA, and transcription factors Snail 1 and 2, and Smad3 phosphorylation in cultured human dermal fibroblasts. LG283 was also found to block EMT induction in cultured human epithelial cells. During these processes, Smad3 phosphorylation and/or expression of Snail 1 and 2 were inhibited by LG283 treatment. In the bleomycin-induced skin fibrosis model, oral administration of LG283 efficiently protected against the development of fibrosis and decrease of capillary vessels without significantly affecting cell infiltration or cytokine concentrations in the skin. No apparent adverse effects of LG283 were found. LG283 treatment remarkably inhibited the enhanced expression of α-SMA and phosphorylated Smad3, as well as those of Snail 1 and 2, in the bleomycin-injected skin.

Conclusions

The LG283 compound exhibits antagonistic activity on fibrosis and vascular injury through inhibition of TGF-β/Smad/Snail mesenchymal transition pathways and thus, may be a candidate therapeutic for the treatment of SSc. Although the involvement of EMT in the pathogenesis of SSc remains unclear, the screening of EMT regulatory compounds may be an attractive approach for SSc therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02773-2.

PDGF/PDGFR: A Possible Molecular Target in Scleroderma Fibrosis

Systemic sclerosis (SSc) is a clinically heterogeneous disorder of the connective tissue characterized by vascular alterations, immune/inflammatory manifestations, and organ fibrosis. SSc pathogenesis is complex and still poorly understood. Therefore, effective therapies are lacking and remain nonspecific and limited to disease symptoms. In the last few years, many molecular and cellular mediators of SSc fibrosis have been described, providing new potential options for targeted therapies. In this review: (i) we focused on the PDGF/PDGFR pathway as key signaling molecules in the development of tissue fibrosis; (ii) we highlighted the possible role of stimulatory anti-PDGFRα autoantibodies in the pathogenesis of SSc; (iii) we reported the most promising PDGF/PDGFR targeting therapies.

Shifting Paradigms for Suppressing Fibrosis in Kidney Transplants: Supplementing Perfusion Solutions With Anti-fibrotic Drugs

Great efforts have been made toward addressing the demand for donor kidneys. One of the most promising approaches is to use kidneys from donation after circulatory death donors. These kidneys, however, suffer from more severe ischemia and reperfusion injury than those obtained via donation after brain death and are thus more prone to develop interstitial fibrosis and tubular atrophy. Even though machine perfusion is increasingly used to reduce ischemia and reperfusion injury, there are no effective treatments available to ameliorate interstitial fibrosis and tubular atrophy, forcing patients to resume dialysis, undergo re-transplantation, or suffer from premature death. Safe and effective anti-fibrotic therapies are therefore greatly desired. We propose a new therapeutic approach in which machine perfusion solutions are supplemented with anti-fibrotic compounds. This allows the use of higher concentrations than those used in humans whilst eliminating side effects in other organs. To the authors' knowledge, no one has reviewed whether such an approach could reduce interstitial fibrosis and tubular atrophy; we therefore set out to explore its merit. In this review, we first provide background information on ischemia and reperfusion injury as well as interstitial fibrosis and tubular atrophy, after which we describe currently available approaches for preserving donor kidneys. We then present an evaluation of selected compounds. To identify promising compounds, we analyzed publications describing the effects of anti-fibrotic molecules in precision-cut kidneys slices, which are viable explants that can be cultured ex vivo for up to a few days whilst retaining functional and structural features. LY2109761, galunisertib, imatinib, nintedanib, and butaprost were shown to exert anti-fibrotic effects in slices within a relatively short timeframe (<48 h) and are therefore considered to be excellent candidates for follow-up ex vivo machine perfusion studies.

Results of Multicenter Phase II Study With Imatinib Mesylate in Allogeneic Recipients With Steroid-Refractory Chronic GVHD

In this multicenter phase II study, we evaluated the safety and efficacy of imatinib in patients with steroid-resistant chronic graft-versus-host disease (cGVHD) and evaluated the quality of life (QOL) of the enrolled patients using the Short Form 36 (SF-36) health survey questionnaire. Thirty-six patients who were diagnosed with steroid-refractory cGVHD and treated with imatinib between March 2013 and February 2019 received 100 mg/day of imatinib for 2 weeks. Depending on the patient’s condition and investigator’s decision, the imatinib dose was allowed to be increased by 100 mg every 2 weeks up to 400 mg/day. Patients who achieved stable disease (SD), partial remission (PR), and complete remission (CR) at 3-month response evaluations continued imatinib for up to 6 months. The majority of the patients had multi-organ cGVHD, with skin (63.9%), lungs (44.4%), mouth (38.9%), and eyes (38.9%) as the most common sites. The overall response rate was 58.3%, including 3 and 18 patients with CR and PR, respectively, and an overall decline in National Institutes of Health (NIH) severity scores was observed at study completion in the absence of significant adverse effects. The overall response rates were 70.5%, 66.7%, 34.8%, and 25% in patients with gastrointestinal, liver, skin, and lung cGVHD, respectively. Factors representing emotional well-being were significantly improved based on the patient-reported QOL evaluation using SF-36. The effect of imatinib on steroid tapering, which was notable in responders, was also present in 50% of those who achieved SD without worsening cGVHD. Imatinib exhibited therapeutic efficacy in steroid-refractory and steroid-dependent cGVHD with tolerable toxicity.

Clinical Trial Registration: KCT0006785.

Vardenafil Activity in Lung Fibrosis and In Vitro Synergy with Nintedanib

Idiopathic pulmonary fibrosis (IPF) remains an intractably fatal disorder, despite the recent advent of anti-fibrotic medication. Successful treatment of IPF, like many chronic diseases, may benefit from the concurrent use of multiple agents that exhibit synergistic benefit. In this light, phosphodiesterase type 5 inhibitors (PDE5-Is), have been studied in IPF primarily for their established pulmonary vascular effects. However, recent data suggest certain PDE5-Is, particularly vardenafil, may also reduce transforming growth factor beta 1 (TGF-β1) activation and extracellular matrix (ECM) accumulation, making them a potential target for therapy for IPF. We evaluated fibroblast TGF-β1-driven extracellular matrix (ECM) generation and signaling as well as epithelial mesenchymal transformation (EMT) with pretreatment using the PDE5-I vardenafil. In addition, combinations of vardenafil and nintedanib were evaluated for synergistic suppression of EMC using a fibronectin enzyme-linked immunosorbent assay (ELISA). Finally, the effects of vardenafil on fibrosis were investigated in a bleomycin mouse model. Our findings demonstrate that vardenafil suppresses ECM generation alone and also exhibits significant synergistic suppression of ECM in combination with nintedanib in vitro. Interestingly, vardenafil was shown to improve fibrosis markers and increase survival in bleomycin-treated mice. Vardenafil may represent a potential treatment for IPF alone or in combination with nintedanib. However, additional studies will be required.

Kinase Inhibition as Treatment for Acute and Chronic Graft-Versus-Host Disease

Allogeneic hematopoietic stem cell transplantation (allo-HCT) is a potentially curative therapy for patients suffering from hematological malignancies via the donor immune system driven graft-versus-leukemia effect. However, the therapy is mainly limited by severe acute and chronic graft-versus-host disease (GvHD), both being life-threatening complications after allo-HCT. GvHD develops when donor T cells do not only recognize remaining tumor cells as foreign, but also the recipient’s tissue, leading to a severe inflammatory disease. Typical GvHD target organs include the skin, liver and intestinal tract. Currently all approved strategies for GvHD treatment are immunosuppressive therapies, with the first-line therapy being glucocorticoids. However, therapeutic options for glucocorticoid-refractory patients are still limited. Novel therapeutic approaches, which reduce GvHD severity while preserving GvL activity, are urgently needed. Targeting kinase activity with small molecule inhibitors has shown promising results in preclinical animal models and clinical trials. Well-studied kinase targets in GvHD include Rho-associated coiled-coil-containing kinase 2 (ROCK2), spleen tyrosine kinase (SYK), Bruton’s tyrosine kinase (BTK) and interleukin-2-inducible T-cell kinase (ITK) to control B- and T-cell activation in acute and chronic GvHD. Janus Kinase 1 (JAK1) and 2 (JAK2) are among the most intensively studied kinases in GvHD due to their importance in cytokine production and inflammatory cell activation and migration. Here, we discuss the role of kinase inhibition as novel treatment strategies for acute and chronic GvHD after allo-HCT.

SMADS-Mediate Molecular Mechanisms in Sjögren's Syndrome

There is considerable interest in delineating the molecular mechanisms of action of transforming growth factor-β (TGF-β), considered as central player in a plethora of human conditions, including cancer, fibrosis and autoimmune disease. TGF-β elicits its biological effects through membrane bound serine/threonine kinase receptors which transmit their signals via downstream signalling molecules, SMADs, which regulate the transcription of target genes in collaboration with various co-activators and co-repressors. Until now, therapeutic strategy for primary Sjögren’s syndrome (pSS) has been focused on inflammation, but, recently, the involvement of TGF-β/SMADs signalling has been demonstrated in pSS salivary glands (SGs) as mediator of the epithelial-mesenchymal transition (EMT) activation. Although EMT seems to cause pSS SG fibrosis, TGF-β family members have ambiguous effects on the function of pSS SGs. Based on these premises, this review highlights recent advances in unravelling the molecular basis for the multi-faceted functions of TGF-β in pSS that are dictated by orchestrations of SMADs, and describe TGF-β/SMADs value as both disease markers and/or therapeutic target for pSS.

Organ Fibrosis and Autoimmunity: The Role of Inflammation in TGFβ-Dependent EMT

Recent advances in our understanding of the molecular pathways that control the link of inflammation with organ fibrosis and autoimmune diseases point to the epithelial to mesenchymal transition (EMT) as the common association in the progression of these diseases characterized by an intense inflammatory response. EMT, a process in which epithelial cells are gradually transformed to mesenchymal cells, is a major contributor to the pathogenesis of fibrosis. Importantly, the chronic inflammatory microenvironment has emerged as a decisive factor in the induction of pathological EMT. Transforming growth factor-β (TGF-β), a multifunctional cytokine, plays a crucial role in the induction of fibrosis, often associated with chronic phases of inflammatory diseases, contributing to marked fibrotic changes that severely impair normal tissue architecture and function. The understanding of molecular mechanisms underlying EMT-dependent fibrosis has both a basic and a translational relevance, since it may be useful to design therapies aimed at counteracting organ deterioration and failure. To this end, we reviewed the recent literature to better elucidate the molecular response to inflammatory/fibrogenic signals in autoimmune diseases in order to further the specific regulation of EMT-dependent fibrosis in more targeted therapies.

Mechanisms of progressive fibrosis in connective tissue disease (CTD)-associated interstitial lung diseases (ILDs)

Interstitial lung diseases (ILDs), which can arise from a broad spectrum of distinct aetiologies, can manifest as a pulmonary complication of an underlying autoimmune and connective tissue disease (CTD-ILD), such as rheumatoid arthritis-ILD and systemic sclerosis (SSc-ILD). Patients with clinically distinct ILDs, whether CTD-related or not, can exhibit a pattern of common clinical disease behaviour (declining lung function, worsening respiratory symptoms and higher mortality), attributable to progressive fibrosis in the lungs. In recent years, the tyrosine kinase inhibitor nintedanib has demonstrated efficacy and safety in idiopathic pulmonary fibrosis (IPF), SSc-ILD and a broad range of other fibrosing ILDs with a progressive phenotype, including those associated with CTDs. Data from phase II studies also suggest that pirfenidone, which has a different-yet largely unknown-mechanism of action, may also have activity in other fibrosing ILDs with a progressive phenotype, in addition to its known efficacy in IPF. Collectively, these studies add weight to the hypothesis that, irrespective of the original clinical diagnosis of ILD, a progressive fibrosing phenotype may arise from common, underlying pathophysiological mechanisms of fibrosis involving pathways associated with the targets of nintedanib and, potentially, pirfenidone. However, despite the early proof of concept provided by these clinical studies, very little is known about the mechanistic commonalities and differences between ILDs with a progressive phenotype. In this review, we explore the biological and genetic mechanisms that drive fibrosis, and identify the missing evidence needed to provide the rationale for further studies that use the progressive phenotype as a target population.

Molecular Pathogenesis and Treatment Perspectives for Hypereosinophilia and Hypereosinophilic Syndromes

Hypereosinophilia (HE) is a heterogeneous condition with a persistent elevated eosinophil count of >350/mm³, which is reported in various (inflammatory, allergic, infectious, or neoplastic) diseases with distinct pathophysiological pathways. HE may be associated with tissue or organ damage and, in this case, the disorder is classified as hypereosinophilic syndrome (HES). Different studies have allowed for the discovery of two major pathogenetic variants known as myeloid or lymphocytic HES. With the advent of molecular genetic analyses, such as T-cell receptor gene rearrangement assays and Next Generation Sequencing, it is possible to better characterize these syndromes and establish which patients will benefit from pharmacological targeted therapy. In this review, we highlight the molecular alterations that are involved in the pathogenesis of eosinophil disorders and revise possible therapeutic approaches, either implemented in clinical practice or currently under investigation in clinical trials.

OXALIPLATIN INDUCED PULMONARY FIBROSIS: A CASE REPORT

Oxaliplatin is part of the standard chemotherapy regimens for treating colorectal carcinoma. Pulmonary fibrosis is a serious but rare side effect of oxaliplatin treatment, which resulted in patient death in more than half of the reported cases. The precise pathophysiological mechanism of this phenomenon has not been clarified yet. Analysis of the reported cases strongly suggests that early diagnosis and immediate corticosteroid treatment are crucial for better prognosis. Here we report a case of pulmonary fibrosis related to the FOLFOX regimen in a patient with early colorectal carcinoma.

Loading Imatinib inside targeted nanoparticles to prevent Bronchiolitis Obliterans Syndrome

Bronchiolitis Obliterans Syndrome seriously reduces long-term survival of lung transplanted patients. Up to now there is no effective therapy once BOS is established. Nanomedicine introduces the possibility to administer drugs locally into lungs increasing drug accumulation in alveola reducing side effects. Imatinib was loaded in gold nanoparticles (GNP) functionalized with antibody against CD44 (GNP-HCIm). Lung fibroblasts (LFs) were derived from bronchoalveolar lavage of BOS patients. GNP-HCIm cytotoxicity was evaluated by MTT assay, apoptosis/necrosis and phosphorylated-cAbl (cAbl-p). Heterotopic tracheal transplantation (HTT) mouse model was used to evaluate the effect of local GNP-HCIm administration by Alzet pump. GNP-HCIm decreased LFs viability compared to Imatinib (44.4 ± 1.8% vs. 91.8 ± 3.2%, p < 0.001), inducing higher apoptosis (22.68 ± 4.3% vs. 6.43 ± 0.29; p < 0.001) and necrosis (18.65 ± 5.19%; p < 0.01). GNP-HCIm reduced cAbl-p (0.41 GNP-HCIm, 0.24 Imatinib vs. to control; p < 0.001). GNP-HCIm in HTT mouse model by Alzet pump significantly reduced tracheal lumen obliteration (p < 0.05), decreasing apoptosis (p < 0.05) and TGF-β-positive signal (p < 0.05) in surrounding tissue. GNP-HCIm treatment significantly reduced lymphocytic and neutrophil infiltration and mast cells degranulation (p < 0.05). Encapsulation of Imatinib into targeted nanoparticles could be considered a new option to inhibit the onset of allograft rejection acting on BOS specific features.

Endoglin Promotes Myofibroblast Differentiation and Extracellular Matrix Production in Diabetic Nephropathy

Diabetic nephropathy (DN) is a complication of diabetes mellitus that can lead to proteinuria and a progressive decline in renal function. Endoglin, a co-receptor of TGF-β, is known primarily for regulating endothelial cell function; however, endoglin is also associated with hepatic, cardiac, and intestinal fibrosis. This study investigates whether endoglin contributes to the development of interstitial fibrosis in DN. Kidney autopsy material from 80 diabetic patients was stained for endoglin and Sirius Red and scored semi-quantitatively. Interstitial endoglin expression was increased in samples with DN and was correlated with Sirius Red staining (p < 0.001). Endoglin expression was also correlated with reduced eGFR (p = 0.001), increased creatinine (p < 0.01), increased systolic blood pressure (p < 0.05), hypertension (p < 0.05), and higher IFTA scores (p < 0.001). Biopsy samples from DN patients were also co-immunostained for endoglin together with CD31, CD68, vimentin, or α-SMA Endoglin co-localized with both the endothelial marker CD31 and the myofibroblast marker α-SMA. Finally, we used shRNA to knockdown endoglin expression in a human kidney fibroblast cell line. We found that TGF-β1 stimulation upregulated SERPINE1, CTGF, and ACTA2 mRNA and α-SMA protein, and that these effects were significantly reduced in fibroblasts after endoglin knockdown. Taken together, these data suggest that endoglin plays a role in the pathogenesis of interstitial fibrosis in DN.

Repurposing of Kinase Inhibitors for Treatment of COVID-19

The outbreak of COVID-19, the pandemic disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spurred an intense search for treatments by the scientific community. In the absence of a vaccine, the goal is to target the viral life cycle and alleviate the lung-damaging symptoms of infection, which can be life-threatening. There are numerous protein kinases associated with these processes that can be inhibited by FDA-approved drugs, the repurposing of which presents an alluring option as they have been thoroughly vetted for safety and are more readily available for treatment of patients and testing in clinical trials. Here, we characterize more than 30 approved kinase inhibitors in terms of their antiviral potential, due to their measured potency against key kinases required for viral entry, metabolism, or reproduction. We also highlight inhibitors with potential to reverse pulmonary insufficiency because of their anti-inflammatory activity, cytokine suppression, or antifibrotic activity. Certain agents are projected to be dual-purpose drugs in terms of antiviral activity and alleviation of disease symptoms, however drug combination is also an option for inhibitors with optimal pharmacokinetic properties that allow safe and efficacious co-administration with other drugs, such as antiviral agents, IL-6 blocking agents, or other kinase inhibitors.

Lipid Mediators Regulate Pulmonary Fibrosis: Potential Mechanisms and Signaling Pathways

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease of unknown etiology characterized by distorted distal lung architecture, inflammation, and fibrosis. The molecular mechanisms involved in the pathophysiology of IPF are incompletely defined. Several lung cell types including alveolar epithelial cells, fibroblasts, monocyte-derived macrophages, and endothelial cells have been implicated in the development and progression of fibrosis. Regardless of the cell types involved, changes in gene expression, disrupted glycolysis, and mitochondrial oxidation, dysregulated protein folding, and altered phospholipid and sphingolipid metabolism result in activation of myofibroblast, deposition of extracellular matrix proteins, remodeling of lung architecture and fibrosis. Lipid mediators derived from phospholipids, sphingolipids, and polyunsaturated fatty acids play an important role in the pathogenesis of pulmonary fibrosis and have been described to exhibit pro- and anti-fibrotic effects in IPF and in preclinical animal models of lung fibrosis. This review describes the current understanding of the role and signaling pathways of prostanoids, lysophospholipids, and sphingolipids and their metabolizing enzymes in the development of lung fibrosis. Further, several of the lipid mediators and enzymes involved in their metabolism are therapeutic targets for drug development to treat IPF.

LncRNA GAS5 attenuates fibroblast activation through inhibiting Smad3 signaling

Transforming growth factor-β (TGF-β)-induced fibroblast activation is a key pathological event during tissue fibrosis. Long noncoding RNA (lncRNA) is a class of versatile gene regulators participating in various cellular and molecular processes. However, the function of lncRNA in fibroblast activation is still poorly understood. In this study, we identified growth arrest-specific transcript 5 (GAS5) as a novel regulator for TGF-β-induced fibroblast activation. GAS5 expression was downregulated in cultured fibroblasts by TGF-β and in resident fibroblasts from bleomycin-treated skin tissues. Overexpression of GAS5 suppressed TGF-β-induced fibroblast to myofibroblast differentiation. Mechanistically, GAS5 directly bound mothers against decapentaplegic homolog 3 (Smad3) and promoted Smad3 binding to Protein phosphatase 1A (PPM1A), a Smad3 dephosphatase, and thus accelerated Smad3 dephosphorylation in TGF-β-treated fibroblasts. In addition, GAS5 inhibited fibroblast proliferation. Importantly, local delivery of GAS5 via adenoviral vector suppressed bleomycin-induced skin fibrosis in mice. Collectively, our data revealed that GAS5 suppresses fibroblast activation and fibrogenesis through inhibiting TGF-β/Smad3 signaling, which provides a rationale for an lncRNA-based therapy to treat fibrotic diseases.

Arg mediates LPS-induced disruption of the pulmonary endothelial barrier

Acute Respiratory Distress Syndrome (ARDS) is a devastating disease process that involves dysregulated inflammation and decreased alveolar-capillary barrier function. Despite increased understanding of the pathophysiology, no effective targeted therapies exist to treat ARDS. Recent preclinical studies suggest that the multi-tyrosine kinase inhibitor, imatinib, which targets the Abl kinases c-Abl and Arg, has the potential to restore endothelial dysfunction caused by inflammatory agonists. Prior work demonstrates that imatinib attenuates LPS (lipopolysaccharide)-induced vascular leak and inflammation; however, the mechanisms underlying these effects remain incompletely understood. In the current study, we demonstrate that imatinib inhibits LPS-induced increase in the phosphorylation of CrkL, a specific substrate of Abl kinases, in human pulmonary endothelial cells. Specific silencing of Arg, and not c-Abl, attenuated LPS-induced pulmonary vascular permeability as measured by electrical cellular impedance sensing (ECIS) and gap formation assays. In addition, direct activation of Abl family kinases with the small molecule activator DPH resulted in endothelial barrier disruption that was attenuated by Arg siRNA. In complementary studies to characterize the mechanisms by which Arg mediates endothelial barrier function, Arg silencing was found to inhibit LPS-induced disruption of adherens junctions and phosphorylation of myosin light chains (MLC). Overall, these results characterize the mechanisms by which imatinib protects against LPS-induced endothelial barrier disruption and suggest that Arg inhibition may represent a novel strategy to enhance endothelial barrier function.

TGF-β Signaling

Transforming growth factor-β (TGF-β) represents an evolutionarily conserved family of secreted polypeptide factors that regulate many aspects of physiological embryogenesis and adult tissue homeostasis. The TGF-β family members are also involved in pathophysiological mechanisms that underlie many diseases. Although the family comprises many factors, which exhibit cell type-specific and developmental stage-dependent biological actions, they all signal via conserved signaling pathways. The signaling mechanisms of the TGF-β family are controlled at the extracellular level, where ligand secretion, deposition to the extracellular matrix and activation prior to signaling play important roles. At the plasma membrane level, TGF-βs associate with receptor kinases that mediate phosphorylation-dependent signaling to downstream mediators, mainly the SMAD proteins, and mediate oligomerization-dependent signaling to ubiquitin ligases and intracellular protein kinases. The interplay between SMADs and other signaling proteins mediate regulatory signals that control expression of target genes, RNA processing at multiple levels, mRNA translation and nuclear or cytoplasmic protein regulation. This article emphasizes signaling mechanisms and the importance of biochemical control in executing biological functions by the prototype member of the family, TGF-β.

Therapeutic Targets for the Treatment of Cardiac Fibrosis and Cancer: Focusing on TGF-β Signaling

Transforming growth factor-β (TGF-β) is a common mediator of cancer progression and fibrosis. Fibrosis can be a significant pathology in multiple organs, including the heart. In this review, we explain how inhibitors of TGF-β signaling can work as antifibrotic therapy. After cardiac injury, profibrotic mediators such as TGF-β, angiotensin II, and endothelin-1 simultaneously activate cardiac fibroblasts, resulting in fibroblast proliferation and migration, deposition of extracellular matrix proteins, and myofibroblast differentiation, which ultimately lead to the development of cardiac fibrosis. The consequences of fibrosis include a wide range of cardiac disorders, including contractile dysfunction, distortion of the cardiac structure, cardiac remodeling, and heart failure. Among various molecular contributors, TGF-β and its signaling pathways which play a major role in carcinogenesis are considered master fibrotic mediators. In fact, recently the inhibition of TGF-β signaling pathways using small molecule inhibitors, antibodies, and gene deletion has shown that the progression of several cancer types was suppressed. Therefore, inhibitors of TGF-β signaling are promising targets for the treatment of tissue fibrosis and cancers. In this review, we discuss the molecular mechanisms of TGF-β in the pathogenesis of cardiac fibrosis and cancer. We will review recent in vitro and in vivo evidence regarding antifibrotic and anticancer actions of TGF-β inhibitors. In addition, we also present available clinical data on therapy based on inhibiting TGF-β signaling for the treatment of cancers and cardiac fibrosis.

Transforming growth factor-β in tissue fibrosis

TGF-β is extensively implicated in the pathogenesis of fibrosis. In fibrotic lesions, spatially restricted generation of bioactive TGF-β from latent stores requires the cooperation of proteases, integrins, and specialized extracellular matrix molecules. Although fibroblasts are major targets of TGF-β, some fibrogenic actions may reflect activation of other cell types, including macrophages, epithelial cells, and vascular cells. TGF-β–driven fibrosis is mediated through Smad-dependent or non-Smad pathways and is modulated by coreceptors and by interacting networks. This review discusses the role of TGF-β in fibrosis, highlighting mechanisms of TGF-β activation and signaling, the cellular targets of TGF-β actions, and the challenges of therapeutic translation.

Targeting metabolic dysregulation for fibrosis therapy

Fibrosis is the abnormal deposition of extracellular matrix, which can lead to organ dysfunction, morbidity, and death. The disease burden caused by fibrosis is substantial, and there are currently no therapies that can prevent or reverse fibrosis. Metabolic alterations are increasingly recognized as an important pathogenic process that underlies fibrosis across many organ types. As a result, metabolically targeted therapies could become important strategies for fibrosis reduction. Indeed, some of the pathways targeted by antifibrotic drugs in development - such as the activation of transforming growth factor-β and the deposition of extracellular matrix - have metabolic implications. This Review summarizes the evidence to date and describes novel opportunities for the discovery and development of drugs for metabolic reprogramming, their associated challenges, and their utility in reducing fibrosis. Fibrotic therapies are potentially relevant to numerous common diseases such as cirrhosis, non-alcoholic steatohepatitis, chronic renal disease, heart failure, diabetes, idiopathic pulmonary fibrosis, and scleroderma.

Platelet-derived growth factor receptor-α is essential for cardiac fibroblast survival

Platelet-derived growth factor receptor α (PDGFRα), a receptor tyrosine kinase required for cardiac fibroblast development, is uniquely expressed by fibroblasts in the adult heart. Despite the consensus that PDGFRα is expressed in adult cardiac fibroblasts, we know little about its function when these cells are at rest. Here, we demonstrate that loss of PDGFRα in cardiac fibroblasts resulted in a rapid reduction of resident fibroblasts. Furthermore, we observe that phosphatidylinositol 3-kinase signaling was required for PDGFRα-dependent fibroblast maintenance. Interestingly, this reduced number of fibroblasts was maintained long-term, suggesting that there is no homeostatic mechanism to monitor fibroblast numbers and restore hearts to wild-type levels. Although we did not observe any systolic functional changes in hearts with depleted fibroblasts, the basement membrane and microvasculature of these hearts were perturbed. Through in vitro analyses, we showed that PDGFRα signaling inhibition resulted in an increase in fibroblast cell death, and PDGFRα stimulation led to increased levels of the cell survival factor activating transcription factor 3. Our data reveal a unique role for PDGFRα signaling in fibroblast maintenance and illustrate that a 50% loss in cardiac fibroblasts does not result in lethality.NEW & NOTEWORTHY Platelet-derived growth factor receptor α (PDGFRα) is required in developing cardiac fibroblasts, but a functional role in adult, quiescent fibroblasts has not been identified. Here, we demonstrate that PDGFRα signaling is essential for cardiac fibroblast maintenance and that there are no homeostatic mechanisms to regulate fibroblast numbers in the heart. PDGFR signaling is generally considered mitogenic in fibroblasts, but these data suggest that this receptor may direct different cellular processes depending on the cell's maturation and activation status.

IL-25 contributes to lung fibrosis by directly acting on alveolar epithelial cells and fibroblasts

IMPACT STATEMENT

Our work focused on alveolar epithelial cells (AECs)-derived type-2 cytokine (interleukin [IL]-25) in the pathogenesis of idiopathic pulmonary fibrosis (IPF). We showed that IL-25 and IL-17BR (IL-25's receptor) is upregulated in lung tissues (especially in AECs and lung fibroblasts) of IPF patients and contributes to lung fibrosis by directly activating lung fibroblasts and modulating epithelial-mesenchymal transition (EMT) of AECs. We suggest that IL-25 may be one of the master switches hidden in the milieu of abnormal epithelial-mesenchymal crosstalk. Treatment targeting IL-25 may be the potential and novel method for IPF patients.

Discoidin Domain Receptor 2 Signaling Regulates Fibroblast Apoptosis through PDK1/Akt

Progressive fibrosis is a complication of many chronic diseases, and collectively, organ fibrosis is the leading cause of death in the United States. Fibrosis is characterized by accumulation of activated fibroblasts and excessive deposition of extracellular matrix proteins, especially type I collagen. Extensive research has supported a role for matrix signaling in propagating fibrosis, but type I collagen itself is often considered an end product of fibrosis rather than an important regulator of continued collagen deposition. Type I collagen can activate several cell surface receptors, including α₂β₁ integrin and discoidin domain receptor 2 (DDR2). We have previously shown that mice deficient in type I collagen have reduced activation of DDR2 and reduced accumulation of activated myofibroblasts. In the present study, we found that DDR2-null mice are protected from fibrosis. Surprisingly, DDR2-null fibroblasts have a normal and possibly exaggerated activation response to transforming growth factor-β and do not have diminished proliferation compared with wild-type fibroblasts. DDR2-null fibroblasts are significantly more prone to apoptosis, in vitro and in vivo, than wild-type fibroblasts, supporting a paradigm in which fibroblast resistance to apoptosis is critical for progression of fibrosis. We have identified a novel molecular mechanism by which DDR2 can promote the activation of a PDK1 (3-phosphoinositide dependent protein kinase-1)/Akt survival pathway, and we have found that inhibition of PDK1 can augment fibroblast apoptosis. Furthermore, our studies demonstrate that DDR2 expression is heavily skewed to mesenchymal cells compared with epithelial cells and that idiopathic pulmonary fibrosis cells and tissue demonstrate increased activation of DDR2 and PDK1. Collectively, these findings identify a promising target for fibrosis therapy.

Wedelolactone Attenuates Pulmonary Fibrosis Partly Through Activating AMPK and Regulating Raf-MAPKs Signaling Pathway

Pulmonary fibrosis is common in a variety of inflammatory lung diseases, there is currently no effective clinical drug treatment. It has been reported that the ethanol extract of Eclipta prostrata L. can improve the lung collagen deposition and fibrosis pathology induced by bleomycin (BLM) in mice. In the present study, we studied whether wedelolactone (WEL), a major coumarin ingredient of E. prostrata, provided protection against BLM-induced pulmonary fibrosis. ICR or C57/BL6 strain mice were treated with BLM to establish lung fibrosis model. WEL (2 or 10 mg/kg) was given daily via intragastric administration for 2 weeks starting at 7-day after intratracheal instillation. WEL at 10 mg/kg significantly reduced BLM-induced inflammatory cells infiltration, pro-inflammatory factors expression, and collagen deposition in lung tissues. Additionally, treatment with WEL also impaired BLM-induced increases in fibrotic marker expression (collagen I and α-SMA) and decrease in an anti-fibrotic marker (E-cadherin). Treatment with WEL significantly prevented BLM-induced increase in TGF-β1 and Smad2/3 phosphorylation in the lungs. WEL administration (10 mg/kg) also significantly promoted AMPK activation compared to model group in BLM-treated mice. Further investigation indicated that activation of AMPK by WEL can suppressed the transdifferentiation of primary lung fibroblasts and the epithelial mesenchymal transition (EMT) of alveolar epithelial cells, the inhibitive effects of WEL was significantly blocked by an AMPK inhibitor (compound C) in vitro. Together, these results suggest that activation of AMPK by WEL followed by reduction in TGFβ1/Raf-MAPK signaling pathways may have a therapeutic potential in pulmonary fibrosis.

Specificity, versatility, and control of TGF-β family signaling

Encoded in mammalian cells by 33 genes, the transforming growth factor-β (TGF-β) family of secreted, homodimeric and heterodimeric proteins controls the differentiation of most, if not all, cell lineages and many aspects of cell and tissue physiology in multicellular eukaryotes. Deregulation of TGF-β family signaling leads to developmental anomalies and disease, whereas enhanced TGF-β signaling contributes to cancer and fibrosis. Here, we review the fundamentals of the signaling mechanisms that are initiated upon TGF-β ligand binding to its cell surface receptors and the dependence of the signaling responses on input from and cooperation with other signaling pathways. We discuss how cells exquisitely control the functional presentation and activation of heteromeric receptor complexes of transmembrane, dual-specificity kinases and, thus, define their context-dependent responsiveness to ligands. We also introduce the mechanisms through which proteins called Smads act as intracellular effectors of ligand-induced gene expression responses and show that the specificity and impressive versatility of Smad signaling depend on cross-talk from other pathways. Last, we discuss how non-Smad signaling mechanisms, initiated by distinct ligand-activated receptor complexes, complement Smad signaling and thus contribute to cellular responses.

Blockade of platelet-derived growth factor receptor-β, not receptor-α ameliorates bleomycin-induced pulmonary fibrosis in mice

Platelet-derived growth factor (PDGF) has been implicated in the pathogenesis of pulmonary fibrosis. Nintedanib, a multi-kinase inhibitor that targets several tyrosine kinases, including PDGF receptor (PDGFR), was recently approved as an anti-fibrotic agent to reduce the deterioration of FVC in patients with idiopathic pulmonary fibrosis (IPF). However, the effects of PDGFR-α or -β on pulmonary fibrosis remain unclear. In an attempt to clarify their effects, we herein used blocking antibodies specific for PDGFR-α (APA5) and -β (APB5) in a bleomycin (BLM)-induced pulmonary fibrosis mouse model. The effects of these treatments on the growth of lung fibroblasts were examined using the ³H-thymidine incorporation assay in vitro. The anti-fibrotic effects of these antibodies were investigated with the Ashcroft score and collagen content of lungs treated with BLM. Their effects on inflammatory cells in the lungs were also analyzed using bronchoalveolar lavage fluid. We investigated damage to epithelial cells and the proliferation of fibroblasts in the lungs. APA5 and APB5 inhibited the phosphorylation of PDGFR-α and -β as well as the proliferation of lung fibroblasts induced by PDGF-AA and BB. The administration of APB5, but not APA5 effectively inhibited BLM-induced pulmonary fibrosis in mice. Apoptosis and the proliferation of epithelial cells and fibroblasts were significantly decreased by the treatment with APB5, but not by APA5. The late treatment with APB5 also ameliorated fibrosis in lungs treated with BLM. These results suggest that PDGFR-α and -β exert different effects on BLM-induced pulmonary fibrosis in mice. A specific approach using the blocking antibody for PDGFR-β may be useful for the treatment of pulmonary fibrosis.

Unraveling SSc Pathophysiology; The Myofibroblast

Systemic sclerosis (SSc) is a severe auto-immune disease, characterized by vasculopathy and fibrosis of connective tissues. SSc has a high morbidity and mortality and unfortunately no disease modifying therapy is currently available. A key cell in the pathophysiology of SSc is the myofibroblast. Myofibroblasts are fibroblasts with contractile properties that produce a large amount of pro-fibrotic extracellular matrix molecules such as collagen type I. In this narrative review we will discuss the presence, formation, and role of myofibroblasts in SSc, and how these processes are stimulated and mediated by cells of the (innate) immune system such as mast cells and T helper 2 lymphocytes. Furthermore, current novel therapeutic approaches to target myofibroblasts will be highlighted for future perspective.

The Importance of Tyrosine Phosphorylation Control of Cellular Signaling Pathways in Respiratory Disease: pY and pY Not

Reversible phosphorylation of proteins on tyrosine residues is an essential signaling mechanism by which diverse cellular processes are closely regulated. The tight temporal and spatial control of the tyrosine phosphorylation status of proteins by protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs) is critical to cellular homeostasis as well as to adaptations to the external environment. Via regulation of cellular signaling cascades involving other protein kinases and phosphatases, receptors, adaptor proteins, and transcription factors, PTKs and PTPs closely control diverse cellular processes such as proliferation, differentiation, migration, inflammation, and maintenance of cellular barrier function. Given these key regulatory roles, it is not surprising that dysfunction of PTKs and PTPs is important in the pathogenesis of human disease, including many pulmonary diseases. The roles of various PTKs and PTPs in acute lung injury and repair, pulmonary fibrosis, pulmonary vascular disease, and inflammatory airway disease are discussed in this review. It is important to note that although there is overlap among many of these proteins in various disease states, the mechanisms by which they influence the pathogenesis of these conditions differ, suggesting wide-ranging roles for these enzymes and their potential as therapeutic targets.

Fatty acid synthase is required for profibrotic TGF-β signaling

Evidence is provided that the fibroproliferative actions of TGF-β are dependent on a metabolic adaptation that sustains pathologic growth. Specifically, profibrotic TGF-β signaling is shown to require fatty acid synthase (FASN), an essential anabolic enzyme responsible for the de novo synthesis of fatty acids. With the use of pharmacologic and genetic approaches, we show that TGF-β-stimulated FASN expression is independent of Smad2/3 and is mediated via mammalian target of rapamycin complex 1. In the absence of FASN activity or protein, TGF-β-driven fibrogenic processes are reduced with no apparent toxicity. Furthermore, as increased FASN expression was also observed to correlate with the degree of lung fibrosis in bleomycin-treated mice, inhibition of FASN was examined in a murine-treatment model of pulmonary fibrosis. Remarkably, inhibition of FASN not only decreased expression of profibrotic targets, but lung function was also stabilized/improved, as assessed by peripheral blood oxygenation.-Jung, M.-Y., Kang, J.-H., Hernandez, D. M., Yin, X., Andrianifahanana, M., Wang, Y., Gonzalez-Guerrico, A., Limper, A. H., Lupu, R., Leof, E. B. Fatty acid synthase is required for profibrotic TGF-β signaling.

NEDD9 targets COL3A1 to promote endothelial fibrosis and pulmonary arterial hypertension

Germline mutations involving small mothers against decapentaplegic-transforming growth factor-β (SMAD-TGF-β) signaling are an important but rare cause of pulmonary arterial hypertension (PAH), which is a disease characterized, in part, by vascular fibrosis and hyperaldosteronism (ALDO). We developed and analyzed a fibrosis protein-protein network (fibrosome) in silico, which predicted that the SMAD3 target neural precursor cell expressed developmentally down-regulated 9 (NEDD9) is a critical ALDO-regulated node underpinning pathogenic vascular fibrosis. Bioinformatics and microscale thermophoresis demonstrated that oxidation of Cys18 in the SMAD3 docking region of NEDD9 impairs SMAD3-NEDD9 protein-protein interactions in vitro. This effect was reproduced by ALDO-induced oxidant stress in cultured human pulmonary artery endothelial cells (HPAECs), resulting in impaired NEDD9 proteolytic degradation, increased NEDD9 complex formation with Nk2 homeobox 5 (NKX2-5), and increased NKX2-5 binding to COL3A1 Up-regulation of NEDD9-dependent collagen III expression corresponded to changes in cell stiffness measured by atomic force microscopy. HPAEC-derived exosomal signaling targeted NEDD9 to increase collagen I/III expression in human pulmonary artery smooth muscle cells, identifying a second endothelial mechanism regulating vascular fibrosis. ALDO-NEDD9 signaling was not affected by treatment with a TGF-β ligand trap and, thus, was not contingent on TGF-β signaling. Colocalization of NEDD9 with collagen III in HPAECs was observed in fibrotic pulmonary arterioles from PAH patients. Furthermore, NEDD9 ablation or inhibition prevented fibrotic vascular remodeling and pulmonary hypertension in animal models of PAH in vivo. These data identify a critical TGF-β-independent posttranslational modification that impairs SMAD3-NEDD9 binding in HPAECs to modulate vascular fibrosis and promote PAH.

pDCs in lung and skin fibrosis in a bleomycin-induced model and patients with systemic sclerosis

Fibrosis is the end result of most inflammatory conditions, but its pathogenesis remains unclear. We demonstrate that, in animals and humans with systemic fibrosis, plasmacytoid DCs (pDCs) are unaffected or are reduced systemically (spleen/peripheral blood), but they increase in the affected organs (lungs/skin/bronchoalveolar lavage). A pivotal role of pDCs was shown by depleting them in vivo, which ameliorated skin and/or lung fibrosis, reduced immune cell infiltration in the affected organs but not in spleen, and reduced the expression of genes and proteins implicated in chemotaxis, inflammation, and fibrosis in the affected organs of animals with bleomycin-induced fibrosis. As with animal findings, the frequency of pDCs in the lungs of patients with systemic sclerosis correlated with the severity of lung disease and with the frequency of CD4+ and IL-4+ T cells in the lung. Finally, treatment with imatinib that has been reported to reduce and/or prevent deterioration of skin and lung fibrosis profoundly reduced pDCs in lungs but not in peripheral blood of patients with systemic sclerosis. These observations suggest a role for pDCs in the pathogenesis of systemic fibrosis and identify the increased trafficking of pDCs to the affected organs as a potential therapeutic target in fibrotic diseases.

Abrogation of transforming growth factor-β-induced tissue fibrosis in TBRIcaCol1a2Cre transgenic mice by the second generation tyrosine kinase inhibitor SKI-606 (Bosutinib)

Transforming growth factor-β (TGF-β) plays a crucial role in the pathogenesis of Systemic Sclerosis (SSc) and other fibrotic disorders. TGF-β-mediated c-Abl and Src kinase activation induces strong profibrotic cascade signaling. The purpose of this study was to test in vivo the antifibrotic activity of Bosutinib (SKI-606), a second generation c-Abl and Src kinase inhibitor, on TGF-β induced cutaneous and pulmonary fibrosis. For this purpose, we employed the TBRIcaCol1a2Cre transgenic mice expressing an inducible constitutively active TGF-β receptor 1 constitutively activated by Col1a promoter-mediated Cre recombinase. The mice were treated parenterally with 2.5, 5.0 or 10.0 mg/kg/day of Bosutinib for 42 days. Skin and lungs from control and Bosutinib-treated mice (n = 6 per group) were assessed by histopathology, measurement of tissue hydroxyproline content, PCR analysis of tissue fibrosis associated gene expression, and evidence of myofibroblast activation. Mice with constitutive TGF-β-1 signaling displayed severe cutaneous and pulmonary fibrosis. Bosutinib administration decreased collagen deposition and hydroxyproline content in the dermis and lungs in a dose-dependent manner. Bosutinib also reversed the marked increase in profibrotic and myofibroblast activation-associated gene expression. These results demonstrate that constitutive TGF-β-1-signaling-induced cutaneous and pulmonary fibrosis were abrogated in a dose-related manner following parenteral administration of the c-Abl and Src tyrosine kinase inhibitor, Bosutinib. These results indicate that Bosutinib may be a potential therapeutic agent for tissue fibrosis in SSc and other fibroproliferative disorders.

Regulation of fibrosis in muscular dystrophy

The production of force and power are inherent properties of skeletal muscle, and regulated by contractile proteins within muscle fibers. However, skeletal muscle integrity and function also require strong connections between muscle fibers and their extracellular matrix (ECM). A well-organized and pliant ECM is integral to muscle function and the ability for many different cell populations to efficiently migrate through ECM is critical during growth and regeneration. For many neuromuscular diseases, genetic mutations cause disruption of these cytoskeletal-ECM connections, resulting in muscle fragility and chronic injury. Ultimately, these changes shift the balance from myogenic pathways toward fibrogenic pathways, culminating in the loss of muscle fibers and their replacement with fatty-fibrotic matrix. Hence a common pathological hallmark of muscular dystrophy is prominent fibrosis. This review will cover the salient features of muscular dystrophy pathogenesis, highlight the signals and cells that are important for myogenic and fibrogenic actions, and discuss how fibrosis alters the ECM of skeletal muscle, and the consequences of fibrosis in developing therapies.

Treatment of Systemic Sclerosis-related Interstitial Lung Disease: A Review of Existing and Emerging Therapies

Although interstitial lung disease accounts for the majority of deaths of patients with systemic sclerosis, treatment options for this manifestation of the disease are limited. Few high-quality, randomized, controlled trials exist for systemic sclerosis-related interstitial lung disease, and historically, studies have favored the use of cyclophosphamide. However, the benefit of cyclophosphamide for this disease is tempered by its complex adverse event profile. More recent studies have demonstrated the effectiveness of mycophenolate for systemic sclerosis-related interstitial lung disease, including Scleroderma Lung Study II. This review highlights the findings of this study, which was the first randomized controlled trial to compare cyclophosphamide with mycophenolate for the treatment of systemic sclerosis-related interstitial lung disease. The results reported in this trial suggest that there is no difference in treatment efficacy between mycophenolate and cyclophosphamide; however, mycophenolate appears to be safer and more tolerable than cyclophosphamide. In light of the ongoing advances in our understanding of the pathogenic mechanisms underlying interstitial lung disease in systemic sclerosis, this review also summarizes novel treatment approaches, presenting clinical and preclinical evidence for rituximab, tocilizumab, pirfenidone, and nintedanib, as well as hematopoietic stem cell transplantation and lung transplantation. This review further explores how reaching a consensus on appropriate study end points, as well as trial enrichment criteria, is central to improving our ability to judiciously evaluate the safety and efficacy of emerging experimental therapies for systemic sclerosis-related interstitial lung disease.

Novel lung imaging biomarkers and skin gene expression subsetting in dasatinib treatment of systemic sclerosis-associated interstitial lung disease

Background

There are no effective treatments or validated clinical response markers in systemic sclerosis (SSc). We assessed imaging biomarkers and performed gene expression profiling in a single-arm open-label clinical trial of tyrosine kinase inhibitor dasatinib in patients with SSc-associated interstitial lung disease (SSc-ILD).

Methods

Primary objectives were safety and pharmacokinetics. Secondary outcomes included clinical assessments, quantitative high-resolution computed tomography (HRCT) of the chest, serum biomarker assays and skin biopsy-based gene expression subset assignments. Clinical response was defined as decrease of >5 or >20% from baseline in the modified Rodnan Skin Score (MRSS). Pulmonary function was assessed at baseline and day 169.

Results

Dasatinib was well-tolerated in 31 patients receiving drug for a median of nine months. No significant changes in clinical assessments or serum biomarkers were seen at six months. By quantitative HRCT, 65% of patients showed no progression of lung fibrosis, and 39% showed no progression of total ILD. Among 12 subjects with available baseline and post-treatment skin biopsies, three were improvers and nine were non-improvers. Improvers mapped to the fibroproliferative or normal-like subsets, while seven out of nine non-improvers were in the inflammatory subset (p = 0.0455). Improvers showed stability in forced vital capacity (FVC) and diffusing capacity for carbon monoxide (D_LCO), while both measures showed a decline in non-improvers (p = 0.1289 and p = 0.0195, respectively). Inflammatory gene expression subset was associated with higher baseline HRCT score (p = 0.0556). Non-improvers showed significant increase in lung fibrosis (p = 0.0313).

Conclusions

In patients with SSc-ILD dasatinib treatment was associated with acceptable safety profile but no significant clinical efficacy. Patients in the inflammatory gene expression subset showed increase in skin fibrosis, decreasing pulmonary function and worsening lung fibrosis during the study. These findings suggest that target tissue-specific gene expression analyses can help match patients and therapeutic interventions in heterogeneous diseases such as SSc, and quantitative HRCT is useful for assessing clinical outcomes.

Trial registration

Clinicaltrials.gov NCT00764309

Advances in targeting the transforming growth factor β1 signaling pathway in lung cancer radiotherapy

Lung cancer was demonstrated to be the most lethal type of malignant tumor amongst humans in the global cancer statistics of 2012. As one of the primary treatments, radiotherapy has been reported to induce remission in, and even cure, patients with lung cancer. However, the side effects of radiotherapy may prove lethal in certain patients. In past decades, the transforming growth factor β1 (TGFB1) signaling pathway has been revealed to serve multiple functions in the control of lung cancer progression and the radiotherapy response. In mammals, this signaling pathway is initiated through activation of the TGFB1 receptor complex, which signals via cytoplasmic SMAD proteins or other downstream signaling pathways. Multiple studies have demonstrated that TGFB1 serves important functions in lung cancer radiotherapy. The present study summarized and reviewed recent progress in elucidating the function of the TGFB1 signaling pathway in predicting radiation pneumonitis, as well as current strategies for targeting the TGFB1 signaling pathway in lung cancer radiotherapy, which may provide potential targets for lung cancer therapy.

Imatinib Alters Agonists-mediated Cytoskeletal Biomechanics in Lung Endothelium

The endothelium serves as a size-selective barrier and tightly controls the fluid exchange from the circulation to the surrounding tissues. In this study, a multiplexed microscopy characterization is developed to study the spatio-temporal effects of Abl kinases on endothelial cytoskeletal structure using AFM, SEM, and immunofluorescence. Sphingosine 1-phosphate (S1P) produces significant endothelial barrier enhancement by means of peripheral actin rearrangement. However, Abl kinase inhibition by imatinib reduces rapid redistribution of the important cytoskeletal proteins to the periphery and their association with the cortical actin ring. Herein, it moderates the thickness of the cortical actin ring, and diminishes the increase in elastic modulus at the periphery and cytoplasm. These findings demonstrate that imatinib attenuates multiple cytoskeletal changes associated with S1P-mediated endothelial barrier enhancement and suggest a novel role for Abl kinases in mediating these S1P effects. These observations bridge the gap between molecule dynamics, structure complexity and function connectivity across varied length-scales to improve our understanding on human pulmonary endothelial barrier regulation. Moreover, our study suggests a framework for understanding form-function relationships in other biomechanical subsystems, wherein complex hierarchical organization programmed from the molecular scale to the cellular and tissue levels has an intimate relationship to the overall physiological function.

Activation of STAT3 integrates common profibrotic pathways to promote fibroblast activation and tissue fibrosis

Signal transducer and activator of transcription 3 (STAT3) is phosphorylated by various kinases, several of which have been implicated in aberrant fibroblast activation in fibrotic diseases including systemic sclerosis (SSc). Here we show that profibrotic signals converge on STAT3 and that STAT3 may be an important molecular checkpoint for tissue fibrosis. STAT3 signaling is hyperactivated in SSc in a TGFβ-dependent manner. Expression profiling and functional studies in vitro and in vivo demonstrate that STAT3 activation is mediated by the combined action of JAK, SRC, c-ABL, and JNK kinases. STAT3-deficient fibroblasts are less sensitive to the pro-fibrotic effects of TGFβ. Fibroblast-specific knockout of STAT3, or its pharmacological inhibition, ameliorate skin fibrosis in experimental mouse models. STAT3 thus integrates several profibrotic signals and might be a core mediator of fibrosis. Considering that several STAT3 inhibitors are currently tested in clinical trials, STAT3 might be a candidate for molecular targeted therapies of SSc.

STAT3 is a transcription factor that is activated in fibrotic diseases such as systemic sclerosis. Here the authors show that STAT3 is the converging point for multiple pro-fibrotic signalling pathways, and that its genetic ablation or inhibition ameliorate skin fibrosis in mouse models.

Invasive Intraneural Interfaces: Foreign Body Reaction Issues

Intraneural interfaces are stimulation/registration devices designed to couple the peripheral nervous system (PNS) with the environment. Over the last years, their use has increased in a wide range of applications, such as the control of a new generation of neural-interfaced prostheses. At present, the success of this technology is limited by an electrical impedance increase, due to an inflammatory response called foreign body reaction (FBR), which leads to the formation of a fibrotic tissue around the interface, eventually causing an inefficient transduction of the electrical signal. Based on recent developments in biomaterials and inflammatory/fibrotic pathologies, we explore and select the biological solutions that might be adopted in the neural interfaces FBR context: modifications of the interface surface, such as organic and synthetic coatings; the use of specific drugs or molecular biology tools to target the microenvironment around the interface; the development of bio-engineered-scaffold to reduce immune response and promote interface-tissue integration. By linking what we believe are the major crucial steps of the FBR process with related solutions, we point out the main issues that future research has to focus on: biocompatibility without losing signal conduction properties, good reproducible in vitro/in vivo models, drugs exhaustion and undesired side effects. The underlined pros and cons of proposed solutions show clearly the importance of a better understanding of all the molecular and cellular pathways involved and the need of a multi-target action based on a bio-engineered combination approach.

SH2 Domain-Containing Phosphatase-2 Is a Novel Antifibrotic Regulator in Pulmonary Fibrosis

RATIONALE

Idiopathic pulmonary fibrosis (IPF) is a chronic fatal lung disease with dismal prognosis and no cure. The potential role of the ubiquitously expressed SH2 domain-containing tyrosine phosphatase-2 (SHP2) as a therapeutic target has not been studied in IPF.

OBJECTIVES

To determine the expression, mechanistic role, and potential therapeutic usefulness of SHP2 in pulmonary fibrosis.

METHODS

The effects of SHP2 overexpression and inhibition on fibroblast response to profibrotic stimuli were analyzed in vitro in primary human and mouse lung fibroblasts. In vivo therapeutic effects were assessed in the bleomycin model of lung fibrosis by SHP2-lentiviral administration and transgenic mice carrying a constitutively active SHP2 mutation.

MEASUREMENTS AND MAIN RESULTS

SHP2 was down-regulated in lungs and lung fibroblasts obtained from patients with IPF. Immunolocalization studies revealed that SHP2 was absent within fibroblastic foci. Loss of SHP2 expression or activity was sufficient to induce fibroblast-to-myofibroblast differentiation in primary human lung fibroblasts. Overexpression of constitutively active SHP2 reduced the responsiveness of fibroblasts to profibrotic stimuli, including significant reductions in cell survival and myofibroblast differentiation. SHP2 effects were mediated through deactivation of fibrosis-relevant tyrosine kinase and serine/threonine kinase signaling pathways. Mice carrying the Noonan syndrome-associated gain-of-function SHP2 mutation (SHP2^D61G/+) were resistant to bleomycin-induced pulmonary fibrosis. Restoration of SHP2 levels in vivo through lentiviral delivery blunted bleomycin-induced pulmonary fibrosis.

CONCLUSIONS

Our data suggest that SHP2 is an important regulator of fibroblast differentiation, and its loss as observed in IPF facilitates profibrotic phenotypic changes. Augmentation of SHP2 activity or expression should be investigated as a novel therapeutic strategy for IPF.