Negative regulation of myofibroblast differentiation by PTEN (Phosphatase and Tensin Homolog Deleted on chromosome 10)

Aloperine Protects Mice against Bleomycin-induced Pulmonary Fibrosis by Attenuating Fibroblast Proliferation and Differentiation

Aloperine is a quinolizidine alkaloid extracted from Sophora alopecuroides. It has been proven to alleviate oxidative stress and effectively promote tumor cell apoptosis in mice. Herein, we investigated whether aloperine could also mediate its protective effects on bleomycin (BLM)-induced pulmonary fibrosis. Pathological staining, western blot, RT-PCR and flow cytometry were used to evaluate the impact of aloperine on the development of pulmonary fibrosis. The effect of aloperine on fibroblast proliferation, differentiation and related signaling pathways were next investigated to demonstrate the underlying mechanisms. In the present report, we showed that aloperine provided protection for mice against BLM-induced pulmonary fibrosis as manifested by the attenuated lung injury and reduced fibrosis along with alleviated fibroblast proliferation and differentiation. Additionally, we provided in vitro evidence revealing that aloperine inhibited cellular proliferation in PDGF-BB-stimulated mouse lung fibroblasts by repressed PI3K/AKT/mTOR signaling and fibroblast to myofibroblast differentiation by repressed TGF-β/Smad signaling. Overall, our data showed that aloperine could protect the mice against BLM-induced pulmonary fibrosis by attenuated fibroblast proliferation and differentiation, which indicated that aloperine may be therapeutically beneficial for IPF patients.

Novel Role for the Immunoproteasome Subunit PSMB10 in Angiotensin II-Induced Atrial Fibrillation in Mice

Angiotensin II (Ang II) and inflammation are associated with pathogenesis of atrial fibrillation (AF), but the underlying molecular mechanisms of these events remain unknown. The immunoproteasome has emerged as a critical regulator of inflammatory responses. Here, we investigated its role in Ang II-induced AF in immunosubunit PSMB10 (also known as β2i or LMP10) knockout (KO) mice. AF was induced by Ang II infusion (2000 ng/min per kg). PSMB10 expression and trypsin-like activity were increased in atrial tissues and serum from Ang II-treated mice or serum from patients with AF. Moreover, Ang II-infused wild-type (WT) mice had a higher AF and increased atrial fibrosis, reactive oxygen species production, and inflammation compared with saline-treated WT animals. These effects were attenuated in PSMB10 KO mice but were aggravated in recombinant adeno-associated virus serotype 9-PSMB10-treated mice. Administration of IKKβ-specific inhibitor IMD 0354 reduced Ang II-induced AF, reactive oxygen species production, inflammation, and NF-kB (nuclear factor-kB) activation. Mechanistically, Ang II infusion upregulated PSMB10 expression to promote PTEN (phosphatase and tensin homolog deleted on chromosome ten) degradation and AKT1 activation, which not only activated TGF-β-Smad2/3 signaling leading to cardiac fibrosis but also induced IKKβ activation and ubiquitin-mediated degradation of IkBα ultimately resulting in activation of NF-kB target genes (IL [interleukin]-1β, IL-6, NOX [NADPH oxidase] 2, NOX4, and CX43 [connexin 43]). Overall, our study identifies immunosubunit PSMB10 as a novel regulator that contributes to Ang II-induced AF and suggests that inhibition of PSMB10 may represent a potential therapeutic target for treating hypertensive AF.

MiR-185/AKT and miR-29a/collagen 1a pathways are activated in IPF BAL cells

MicroRNA signatures of BAL cells and alveolar macrophages are currently lacking in IPF. Here we sought to investigate the expression of fibrosis-related microRNAs in the cellular component of the BAL in IPF. We thus focused on microRNAs previously associated with fibrosis (miR-29a, miR-29b, miR-29c, let-7d, and miR-21) and rapid IPF progression (miR-185, miR-210, miR-302c-3p miR-376c and miR-423-5p). Among the tested microRNAs miR-29a and miR-185 were found significantly downregulated in IPF while miR-302c-3p and miR-376c were not expressed by BAL cells. Importantly, the downregulation of miR-29a inversely correlated with the significantly increased levels of COL1A1 mRNA in IPF BAL cells. Collagen 1 a was found mainly overexpressed in alveolar macrophages and not other cell types of the BAL by immunofluorescence. In view of the downregulation of miR-185, we tested the response of THP-1 macrophages to profibrotic cytokine TGFb and observed the downregulation of miR-185. Conversely, proinflammatory stimulation lead to miR-185 upregulation. Upon examination of the mRNA levels of known miR-185 targets AKT1, DNMT1 and HMGA2, no significant correlations were observed in the BAL cells. However, increased levels of total AKT and AKTser473 phosphorylation were observed in the IPF BAL cells. Furthermore, miR-185 inhibition in THP-1 macrophages resulted in significant increase of AKTser473 phosphorylation. Our study highlights the importance of BAL microRNA signatures in IPF and identifies significant differences in miR-185/AKT and miR-29a/collagen axes in the BAL cells of IPF patients.

Thermodynamic Aspects and Reprogramming Cellular Energy Metabolism during the Fibrosis Process

Fibrosis is characterized by fibroblast proliferation and fibroblast differentiation into myofibroblasts, which generate a relaxation-free contraction mechanism associated with excessive collagen synthesis in the extracellular matrix, which promotes irreversible tissue retraction evolving towards fibrosis. From a thermodynamic point of view, the mechanisms leading to fibrosis are irreversible processes that can occur through changing the entropy production rate. The thermodynamic behaviors of metabolic enzymes involved in fibrosis are modified by the dysregulation of both transforming growth factor β (TGF-β) signaling and the canonical WNT/β-catenin pathway, leading to aerobic glycolysis, called the Warburg effect. Molecular signaling pathways leading to fibrosis are considered dissipative structures that exchange energy or matter with their environment far from the thermodynamic equilibrium. The myofibroblastic cells arise from exergonic processes by switching the core metabolism from oxidative phosphorylation to glycolysis, which generates energy and reprograms cellular energy metabolism to induce the process of myofibroblast differentiation. Circadian rhythms are far-from-equilibrium thermodynamic processes. They directly participate in regulating the TGF-β and WNT/β-catenin pathways involved in energetic dysregulation and enabling fibrosis. The present review focusses on the thermodynamic implications of the reprogramming of cellular energy metabolism, leading to fibroblast differentiation into myofibroblasts through the positive interplay between TGF-β and WNT/β-catenin pathways underlying in fibrosis.

A miR-335/COX-2/PTEN axis regulates the secretory phenotype of senescent cancer-associated fibroblasts

Senescent cancer-associated fibroblasts (CAF) develop a senescence-associated secretory phenotype (SASP) that is believed to contribute to cancer progression. The mechanisms underlying SASP development are, however, poorly understood. Here we examined the functional role of microRNA in the development of the SASP in normal fibroblasts and CAF. We identified a microRNA, miR-335, up-regulated in the senescent normal fibroblasts and CAF and able to modulate the secretion of SASP factors and induce cancer cell motility in co-cultures, at least in part by suppressing the expression of phosphatase and tensin homologue (PTEN). Additionally, elevated levels of cyclo-oxygenase 2 (PTGS2; COX-2) and prostaglandin E2 (PGE2) secretion were observed in senescent fibroblasts, and inhibition of COX-2 by celecoxib reduced the expression of miR-335, restored PTEN expression and decreased the pro-tumourigenic effects of the SASP. Collectively these data demonstrate the existence of a novel miRNA/PTEN-regulated pathway modulating the inflammasome in senescent fibroblasts.

Tubastatin ameliorates pulmonary fibrosis by targeting the TGFβ-PI3K-Akt pathway

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive and fatal disease. Histone deacetylase 6 (HDAC6) alters function and fate of various proteins via deacetylation of lysine residues, and is implicated in TGF-β1-induced EMT (epithelial-mesenchymal transition). However, the role of HDAC6 in pulmonary fibrosis is unknown.

METHODS

HDAC6 expression in IPF and control lungs was assessed by quantitative real-time PCR (qRT-PCR) and immunoblots. Lung fibroblasts were treated with TGF-β1 ± HDAC6 inhibitors (Tubacin, Tubastatin, ACY1215, or MC1568), and fibrotic markers such as type I collagen were assessed using qRT-PCR and immunoblots. Mice were treated with bleomycin (oropharyngeal aspiration; single dose) ± Tubastatin (intraperitoneally injection; daily for 21 days), and lung collagen expression was gauged using immunoblots and trichrome staining. In a separate experiment, HDAC6 wild-type (WT) and knockout (KO) mice were administered bleomycin, and lungs were evaluated in the same manner.

RESULTS

HDAC6 expression was deregulated in IPF lungs. Among the HDAC6 inhibitors tested, only Tubastatin significantly repressed TGF-β1-induced expression of type-1 collagen in lung fibroblasts, and this finding was coupled with decreased Akt phosphorylation and increased Akt-PHLPP (PH domain and Leucine rich repeat Protein Phosphatase) association. Tubastatin repressed TGF-β1-induced S6K phosphorylation, HIF-1α expression, and VEGF expression. Tubastatin also repressed TGF-β1-induced inhibition of LC3B-II (a marker of autophagosome formation). In bleomycin-treated mouse lungs, HDAC6 expression was increased, and Tubastatin repressed type-1 collagen expression. However, in HDAC6 KO mice, bleomycin-induced type-1 collagen expression was not repressed compared to WT mice. Knockdown of HDAC6, as well as HDAC10, another potential Tubastatin target, did not inhibit TGF-β1-induced collagen expression in lung fibroblasts.

CONCLUSIONS

HDAC6 expression is altered during lung fibrogenesis. Tubastatin represses TGF-β1-induced collagen expression, by diminishing Akt phosphorylation and regulating downstream targets such as HIF-1α-VEGF axis and autophagy. Tubastatin-treated WT mice are protected against bleomycin-induced fibrosis, but HDAC6 KO mice are not. Our data suggest that Tubastatin ameliorates pulmonary fibrosis, by targeting the TGFβ-PI3K-Akt pathway, likely via an HDAC6-independent mechanism.

Interactions between TGF-β1, canonical WNT/β-catenin pathway and PPAR γ in radiation-induced fibrosis

Radiation therapy induces DNA damage and inflammation leading to fibrosis. Fibrosis can occur 4 to 12 months after radiation therapy. This process worsens with time and years. Radiation-induced fibrosis is characterized by fibroblasts proliferation, myofibroblast differentiation, and synthesis of collagen, proteoglycans and extracellular matrix. Myofibroblasts are non-muscle cells that can contract and relax. Myofibroblasts evolve towards irreversible retraction during fibrosis process. In this review, we discussed the interplays between transforming growth factor-β1 (TGF-β1), canonical WNT/β-catenin pathway and peroxisome proliferator-activated receptor gamma (PPAR γ) in regulating the molecular mechanisms underlying the radiation-induced fibrosis, and the potential role of PPAR γ agonists. Overexpression of TGF-β and canonical WNT/β-catenin pathway stimulate fibroblasts accumulation and myofibroblast differentiation whereas PPAR γ expression decreases due to the opposite interplay of canonical WNT/β-catenin pathway. Both TGF-β1 and canonical WNT/β-catenin pathway stimulate each other through the Smad pathway and non-Smad pathways such as phosphatidylinositol 3-kinase/serine/threonine kinase (PI3K/Akt) signaling. WNT/β-catenin pathway and PPAR γ interact in an opposite manner. PPAR γ agonists decrease β-catenin levels through activation of inhibitors of the WNT pathway such as Smad7, glycogen synthase kinase-3 (GSK-3 β) and dickkopf-related protein 1 (DKK1). PPAR γ agonists also stimulate phosphatase and tensin homolog (PTEN) expression, which decreases both TGF-β1 and PI3K/Akt pathways. PPAR γ agonists by activating Smad7 decrease Smads pathway and then TGF-β signaling leading to decrease radiation-induced fibrosis. TGF-β1 and canonical WNT/β-catenin pathway promote radiation-induced fibrosis whereas PPAR γ agonists can prevent radiation-induced fibrosis.

Effects and mechanism of adenovirus-mediated phosphatase and tension homologue deleted on chromosome ten gene on collagen deposition in rat liver fibrosis

AIM

To evaluate the effects of phosphatase and tension homologue deleted on chromosome ten (PTEN) gene on collagen metabolism in hepatic fibrosis and the underlying mechanisms.

METHODS

Rat primary hepatic stellate cells (HSCs) and human LX-2 cells were transfected with adenovirus containing cDNA constructs encoding wild-type PTEN (Ad-PTEN), PTEN mutant G129E gene (Ad-G129E), and RNA interference constructs targeting the PTEN sequence PTEN short hairpin RNA to up-regulate and down-regulate the expression of PTEN. HSCs were assayed using fluorescent microscopy, real-time polymerase chain reaction, and western blotting. Moreover, a CCl4-induced rat hepatic fibrosis model was established to investigate the in vivo effects. Hematoxylin and eosin, and Masson's trichrome were used to assess the histological changes. The expression of collagen I and III was assessed using immunohistochemistry and western blot analysis.

RESULTS

Elevated expression of PTEN gene reduced serum levels of alanine transaminase and aspartate transaminase, decreased collagen deposition in the liver, and reduced hepatocyte necrosis. In contrast, knockdown of PTEN expression had an opposite effect, such as increased collagen deposition in the liver, and was molecularly characterized by the increased expression of matrix metalloproteinase (MMP)-13 (P < 0.01) and MMP-2 (P < 0.01), as well as decreased expression of the tissue inhibitor of metalloproteinase (TIMP)-1 (P < 0.01) and TIMP-2 (P < 0.01).

CONCLUSION

These data indicated that gene therapy using recombinant adenovirus encoding PTEN might be a novel way of treating hepatic fibrosis.

TNF-α-induced NF-κB activation promotes myofibroblast differentiation of LR-MSCs and exacerbates bleomycin-induced pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and irreversible lung disease of unknown cause. It has been reported that both lung resident mesenchymal stem cells (LR-MSCs) and tumor necrosis factor-α (TNF-α) play important roles in the development of pulmonary fibrosis. However, the underlying connections between LR-MSCs and TNF-α in the pathogenesis of pulmonary fibrosis are still elusive. In this study, we found that the pro-inflammatory cytokine TNF-α and the transcription factor nuclear factor kappa B (NF-κB) p65 subunit were both upregulated in bleomycin-induced fibrotic lung tissue. In addition, we discovered that TNF-α promotes myofibroblast differentiation of LR-MSCs through activating NF-κB signaling. Interestingly, we also found that TNF-α promotes the expression of β-catenin. Moreover, we demonstrated that suppression of the NF-κB signaling could attenuate myofibroblast differentiation of LR-MSCs and bleomycin-induced pulmonary fibrosis which were accompanied with decreased expression of β-catenin. Our data implicates that inhibition of the NF-κB signaling pathway may provide a therapeutic strategy for pulmonary fibrosis, a disease that warrants more effective treatment approaches.

Is There a Potential Therapeutic Role for Caveolin-1 in Fibrosis?

Fibrosis is a process of dysfunctional wound repair, described by a failure of tissue regeneration and excessive deposition of extracellular matrix, resulting in tissue scarring and subsequent organ deterioration. There are a broad range of stimuli that may trigger, and exacerbate the process of fibrosis, which can contribute to the growing rates of morbidity and mortality. Whilst the process of fibrosis is widely described and understood, there are no current standard treatments that can reduce or reverse the process effectively, likely due to the continuing knowledge gaps surrounding the cellular mechanisms involved. Several cellular targets have been implicated in the regulation of the fibrotic process including membrane domains, ion channels and more recently mechanosensors, specifically caveolae, particularly since these latter contain various signaling components, such as members of the TGFβ and MAPK/ERK signaling pathways, all of which are key players in the process of fibrosis. This review explores the anti-fibrotic influences of the caveola, and in particular the key underpinning protein, caveolin-1, and its potential as a novel therapeutic target.

Decreased phosphatase PTEN amplifies PI3K signaling and enhances proinflammatory cytokine release in COPD

The phosphatidylinositol 3-kinase (PI3K) pathway is activated in chronic obstructive pulmonary disease (COPD), but the regulatory mechanisms for this pathway are yet to be elucidated. The aim of this study was to determine the expression and role of phosphatase and tensin homolog deleted from chromosome 10 (PTEN), a negative regulator of the PI3K pathway, in COPD. PTEN protein expression was measured in the peripheral lung of COPD patients compared with smoking and nonsmoking controls. The direct influence of cigarette smoke extract (CSE) on PTEN expression was assessed using primary lung epithelial cells and a cell line (BEAS-2B) in the presence or absence of l-buthionine-sulfoximine (BSO) to deplete intracellular glutathione. The impact of PTEN knockdown by RNA interference on cytokine production was also examined. In peripheral lung, PTEN protein was significantly decreased in patients with COPD compared with the subjects without COPD (P < 0.001) and positively correlated with the severity of airflow obstruction (forced expiratory volume in 1-s percent predicted; r = 0.50; P = 0.0012). Conversely, phosphorylated Akt, as a marker of PI3K activation, showed a negative correlation with PTEN protein levels (r = -0.41; P = 0.0042). In both primary bronchial epithelial cells and BEAS-2B cells, CSE decreased PTEN protein, which was reversed by N-acetyl cysteine treatment. PTEN knockdown potentiated Akt phosphorylation and enhanced production of proinflammatory cytokines, such as IL-6, CXCL8, CCL2, and CCL5. In conclusion, oxidative stress reduces PTEN protein levels, which may result in increased PI3K signaling and amplification of inflammation in COPD.

TGF-β induces phosphorylation of phosphatase and tensin homolog: implications for fibrosis of the trabecular meshwork tissue in glaucoma

Fundamental cell signaling mechanisms that regulate dynamic remodeling of the extracellular matrix (ECM) in mechanically loaded tissues are not yet clearly understood. Trabecular meshwork (TM) tissue in the eye is under constant mechanical stress and continuous remodeling of ECM is crucial to maintain normal aqueous humor drainage and intraocular pressure (IOP). However, excessive ECM remodeling can cause fibrosis of the TM as in primary open-angle glaucoma (POAG) patients, and is characterized by increased resistance to aqueous humor drainage, elevated IOP, optic nerve degeneration and blindness. Increased levels of active transforming growth factor-β2 (TGF-β2) in the aqueous humor is the main cause of fibrosis of TM in POAG patients. Herein, we report a novel finding that, in TM cells, TGF-β-induced increase in collagen expression is associated with phosphorylation of phosphatase and tensin homolog (PTEN) at residues Ser380/Thr382/383. Exogenous overexpression of a mutated form of PTEN with enhanced phosphatase activity prevented the TGF-β-induced collagen expression by TM cells. We propose that rapid alteration of PTEN activity through changes in its phosphorylation status could uniquely regulate the continuous remodeling of ECM in the normal TM. Modulating PTEN activity may have high therapeutic potential to alleviating the fibrosis of TM in POAG patients.

Lung cancer in patients with idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic fibrotic lung disease of unknown etiology. With a gradually increasing worldwide prevalence and a mortality rate exceeding that of many cancers, IPF diagnosis and management are critically important and require a comprehensive multidisciplinary approach. This approach also involves assessment of comorbid conditions, such as lung cancer, that exerts a dramatic impact on disease survival. Emerging evidence suggests that progressive lung scarring in the context of IPF represents a risk factor for lung carcinogenesis. Both disease entities present with major similarities in terms of pathogenetic pathways, as well as potential causative factors, such as smoking and viral infections. Besides disease pathogenesis, anti-cancer agents, including nintedanib, have been successfully applied in the treatment of patients with IPF while an oncologic approach with a cocktail of several pleiotropic anti-fibrotic agents is currently in the therapeutic pipeline of IPF. Nevertheless, epidemiologic association between IPF and lung cancer does not prove causality. Currently there is significant lack of knowledge supporting a direct association between lung fibrosis and cancer reflecting to disappointing therapeutic algorithms. An optimal therapeutic strategy for patients with both IPF and lung cancer represents an amenable need. This review article synthesizes the current state of knowledge regarding pathogenetic commonalities between IPF and lung cancer and focuses on clinical and therapeutic data that involve both disease entities.

The organic anion transporting polypeptide 1a5 is a pivotal transporter for the uptake of microcystin-LR by gonadotropin-releasing hormone neurons

Microcystins (MCs) are widely distributed hepatotoxic polypeptides produced by cyanobacteria. Microcystin-LR (MC-LR) has the broadest distribution and strongest toxicity among more than 80 isoforms of hepatotoxic MCs. MC-LR suppresses the expression of gonadotropin-releasing hormone (GnRH) that is critically required for the release of testosterone, resulting in the induction of male reproductive toxicity. However, the specific mechanisms of the uptake of MC-LR by GnRH-secreting neurons still remain unclear. In this study, GT1-7 cells were exposed to MC-LR in order to determine whether the GnRH-secreting neurons were the target of MC-LR that could induce male reproductive toxicity. Our data demonstrated that at least four organic anion transporting polypeptides (Oatp1a4, Oatp1a5, Oatp5a1, Oatp2b1) were expressed in GnRH neurons at the mRNA level, but only Oatp1a5 was expressed at the protein level. Furthermore, we demonstrated that MC-LR could not be transported into Oatp1a5-deficient GT1-7 cells which were protected from cell viability loss induced by MC-LR. These data suggest that Oatp1a5 may play an important role in the toxic effect of MC-LR on GnRH neurons.

miR-877-3p targets Smad7 and is associated with myofibroblast differentiation and bleomycin-induced lung fibrosis

Myofibroblast differentiation of lung resident mesenchymal stem cells (LR-MSC) plays an important role in idiopathic pulmonary fibrosis. By comparing the expression profiles of miRNAs before and after myofibroblast differentiation of LR-MSC, we identified miR-877-3p as a fibrosis-related miRNA. We found that miR-877-3p sequestration inhibited the myofibroblast differentiation of LR-MSC and attenuates bleomycin-induced lung fibrosis by targeting Smad7. Smad7, as an inhibitory smad in the TGF-β1 signaling pathway, was decreased in the myofibroblast differentiation of LR-MSC and up-regulation of Smad7 could inhibit the differentiation process. Our data implicates a potential application of miR-877-3p as a fibrosis suppressor for pulmonary fibrosis therapy and also as a fibrosis marker for predicting prognosis.

MicroRNA-21 drives severe, steroid-insensitive experimental asthma by amplifying phosphoinositide 3-kinase-mediated suppression of histone deacetylase 2

BACKGROUND

Severe steroid-insensitive asthma is a substantial clinical problem. Effective treatments are urgently required, however, their development is hampered by a lack of understanding of the mechanisms of disease pathogenesis. Steroid-insensitive asthma is associated with respiratory tract infections and noneosinophilic endotypes, including neutrophilic forms of disease. However, steroid-insensitive patients with eosinophil-enriched inflammation have also been described. The mechanisms that underpin infection-induced, severe steroid-insensitive asthma can be elucidated by using mouse models of disease.

OBJECTIVE

We sought to develop representative mouse models of severe, steroid-insensitive asthma and to use them to identify pathogenic mechanisms and investigate new treatment approaches.

METHODS

Novel mouse models of Chlamydia, Haemophilus influenzae, influenza, and respiratory syncytial virus respiratory tract infections and ovalbumin-induced, severe, steroid-insensitive allergic airway disease (SSIAAD) in BALB/c mice were developed and interrogated.

RESULTS

Infection induced increases in the levels of microRNA (miRNA)-21 (miR-21) expression in the lung during SSIAAD, whereas expression of the miR-21 target phosphatase and tensin homolog was reduced. This was associated with an increase in levels of phosphorylated Akt, an indicator of phosphoinositide 3-kinase (PI3K) activity, and decreased nuclear histone deacetylase (HDAC)2 levels. Treatment with an miR-21-specific antagomir (Ant-21) increased phosphatase and tensin homolog levels. Treatment with Ant-21, or the pan-PI3K inhibitor LY294002, reduced PI3K activity and restored HDAC2 levels. This led to suppression of airway hyperresponsiveness and restored steroid sensitivity to allergic airway disease. These observations were replicated with SSIAAD associated with 4 different pathogens.

CONCLUSION

We identify a previously unrecognized role for an miR-21/PI3K/HDAC2 axis in SSIAAD. Our data highlight miR-21 as a novel therapeutic target for the treatment of this form of asthma.

Newer developments in idiopathic pulmonary fibrosis in the era of anti-fibrotic medications

Idiopathic pulmonary fibrosis (IPF) is the most common interstitial lung disease with a fatal prognosis. Over the last decade, the concepts in pathobiology of pulmonary fibrosis have shifted from a model of chronic inflammation to dysregulated fibroproliferative repair in genetically predisposed patients. Although new breakthrough treatments are now available that slow the progression of the disease, several newer anti-inflammatory and anti-fibrotic drugs are under investigation. Patients with IPF often have coexistent conditions; prompt detection and interventions of which may improve the overall outcome of patients with IPF. Here, we summarize the present understanding of pathogenesis of IPF and treatment options for IPF in the current landscape of new anti-fibrotic treatment options.

Exploration of a potent PI3 kinase/mTOR inhibitor as a novel anti-fibrotic agent in IPF

Rationale

Idiopathic pulmonary fibrosis (IPF) is the most rapidly progressive and fatal of all fibrotic conditions with no curative therapies. Common pathomechanisms between IPF and cancer are increasingly recognised, including dysfunctional pan-PI3 kinase (PI3K) signalling as a driver of aberrant proliferative responses. GSK2126458 is a novel, potent, PI3K/mammalian target of rapamycin (mTOR) inhibitor which has recently completed phase I trials in the oncology setting. Our aim was to establish a scientific and dosing framework for PI3K inhibition with this agent in IPF at a clinically developable dose.

Methods

We explored evidence for pathway signalling in IPF lung tissue and examined the potency of GSK2126458 in fibroblast functional assays and precision-cut IPF lung tissue. We further explored the potential of IPF patient-derived bronchoalveolar lavage (BAL) cells to serve as pharmacodynamic biosensors to monitor GSK2126458 target engagement within the lung.

Results

We provide evidence for PI3K pathway activation in fibrotic foci, the cardinal lesions in IPF. GSK2126458 inhibited PI3K signalling and functional responses in IPF-derived lung fibroblasts, inhibiting Akt phosphorylation in IPF lung tissue and BAL derived cells with comparable potency. Integration of these data with GSK2126458 pharmacokinetic data from clinical trials in cancer enabled modelling of an optimal dosing regimen for patients with IPF.

Conclusions

Our data define PI3K as a promising therapeutic target in IPF and provide a scientific and dosing framework for progressing GSK2126458 to clinical testing in this disease setting. A proof-of-mechanism trial of this agent is currently underway.

Trial registration number

NCT01725139, pre-clinical.

Regulatory Effects and Mechanism of Adenovirus-Mediated PTEN Gene on Hepatic Stellate Cells

BACKGROUND

Tension homology deleted on chromosome ten (PTEN) is important in liver fibrosis.

AIMS

The purpose of this study was to evaluate the PTEN gene effects and mechanism of action on hepatic stellate cells (HSCs).

METHODS

The rat primary HSCs and human LX-2 cells were transfected by an adenovirus containing cDNA constructs encoding the wild-type PTEN (Ad-PTEN), the PTEN mutant G129E gene (Ad-G129E) and RNA interference targeting the PTEN sequence PTEN short hairpin RNA (PTEN shRNA), to up-regulate and down-regulate PTEN expression, respectively. The HSCs were assayed with a fluorescent microscope, real time PCR, Western blot, MTT, flow cytometry and Terminal-deoxynucleoitidyl transferase mediated nick end labeling. In addition, the CCl4 induced rat hepatic fibrosis model was also established to check the in vivo effects of the recombinant adenovirus with various levels of PTEN expression.

RESULTS

The data have shown that the over-expressed PTEN gene led to reduced HSCs activation and viability, caspase-3 activity and cell cycle arrest in the G0/G1 and G2/M phases, as well as negative regulation of the PI3K/Akt and FAK/ERK signaling pathways in vitro. The over-expressed PTEN gene improved liver function, inhibited proliferation and promoted apoptosis of HSCs both in vitro and in vivo.

CONCLUSIONS

These data have shown that gene therapy using the recombinant adenovirus encoding wild-type PTEN inhibits proliferation and induces apoptosis of HSCs, which is a potential treatment option for hepatic fibrosis.

Fibronectin induction abrogates the BRAF inhibitor response of BRAF V600E/PTEN-null melanoma cells

The mechanisms by which some melanoma cells adapt to Serine/threonine-protein kinase B-Raf (BRAF) inhibitor therapy are incompletely understood. In the present study, we used mass spectrometry-based phosphoproteomics to determine how BRAF inhibition remodeled the signaling network of melanoma cell lines that were BRAF mutant and PTEN null. Short-term BRAF inhibition was associated with marked changes in fibronectin-based adhesion signaling that were PTEN dependent. These effects were recapitulated through BRAF siRNA knockdown and following treatment with chemotherapeutic drugs. Increased fibronectin expression was also observed in mouse xenograft models as well as specimens from melanoma patients undergoing BRAF inhibitor treatment. Analysis of a melanoma tissue microarray showed loss of PTEN expression to predict for a lower overall survival, with a trend for even lower survival being seen when loss of fibronectin was included in the analysis. Mechanistically, the induction of fibronectin limited the responses of these PTEN-null melanoma cell lines to vemurafenib, with enhanced cytotoxicity observed following the knockdown of either fibronectin or its receptor α5β1 integrin. This in turn abrogated the cytotoxic response to BRAF inhibition via increased AKT signaling, which prevented the induction of cell death by maintaining the expression of the pro-survival protein Mcl-1. The protection conveyed by the induction of FN expression could be overcome through combined treatment with a BRAF and PI3K inhibitor.

Effects of the tumor suppressor PTEN on the pathogenesis of idiopathic pulmonary fibrosis in Chinese patients

Idiopathic pulmonary fibrosis (IPF) is characterized by progressive interstitial fibrosis, and is associated with a fatal outcome. The critical pathological mechanisms underlying IPF are largely unknown; however, accumulating evidence has indicated similarities between IPF and cancer. Therefore, the present study examined the expression levels of the tumor suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN) in Chinese patients with IPF, using an enzyme‑linked immunosorbent assay. To determine the effects of PTEN on the development of pulmonary fibrosis, PTEN was overexpressed in transforming growth factor (TGF)‑β1‑treated human embryonic lung fibroblasts (HFL‑I cells). The serum levels of PTEN were significantly lower in 42 patients with IPF, as compared with in the healthy controls. In addition, PTEN overexpression enhanced apoptosis, and suppressed basal levels of proliferation and migration in fibroblasts. Notably, PTEN was able to specifically inhibit TGF‑β1‑induced proliferation and migration of the cells. Overexpression of PTEN also suppressed phosphorylation of Akt and Smad3, and decreased the expression levels of numerous proteins with critical roles in TGF‑β1‑induced fibrosis, including α‑smooth muscle actin, matrix metalloproteinase (MMP)‑2 and MMP‑9. These results indicated that PTEN may inhibit TGF‑β1‑mediated myofibroblast differentiation of fibroblasts by attenuating signaling via the phosphatidylinositol 3‑kinase/Akt and TGF‑β/Smad3 pathways.

Regulatory roles of microRNA-21 in fibrosis through interaction with diverse pathways (Review)

MicroRNA-21 (miR-21) is a small, non-coding RNA which can regulate gene expression at the post‑transcriptional level. While the fibrogenic process is vital in tissue repair, proliferation and transition of fibrogenic cells combined with an imbalance of secretion and degradation of the extracellular matrix results in excessive tissue remodeling and fibrosis. Recent studies have indicated that miR‑21 is overexpressed during fibrosis and can regulate the fibrogenic process in a variety of organs and tissues via diverse pathways. The present review summarized the significant roles of miR-21 in fibrosis and discussed the underlying key pathways.

PTEN: a yin-yang master regulator protein in health and disease

The PTEN gene is a tumor suppressor gene frequently mutated in human tumors, which encodes a ubiquitous protein whose major activity is to act as a lipid phosphatase that counteracts the action of the oncogenic PI3K. In addition, PTEN displays protein phosphatase- and catalytically-independent activities. The physiologic control of PTEN function, and its inactivation in cancer and other human diseases, including some neurodevelopmental disorders, is upon the action of multiple regulatory mechanisms. This provides a wide spectrum of potential therapeutic approaches to reconstitute PTEN activity. By contrast, inhibition of PTEN function may be beneficial in a different group of human diseases, such as type 2 diabetes or neuroregeneration-related pathologies. This makes PTEN a functionally dual yin-yang protein with high potential in the clinics. Here, a brief overview on PTEN and its relation with human disease is presented.

Down-regulation of USP13 mediates phenotype transformation of fibroblasts in idiopathic pulmonary fibrosis

Background

Idiopathic pulmonary fibrosis (IPF) is a fatal disease characterized by fibroblastic foci and progressive scarring of the pulmonary parenchyma. IPF fibroblasts display increased proliferation and enhanced migration and invasion, analogous to cancer cells. This transformation-like phenotype of fibroblasts plays an important role in the development of pulmonary fibrosis, but the mechanism for this is not well understood.

Methods

In this study, we compared gene expression profiles in fibrotic lung tissues from IPF patients and normal lung tissues from patients with primary spontaneous pneumothorax using a cDNA microarray to examine the mechanisms involved in the pathogenesis of IPF. In a cDNA microarray, we found that USP13 was decreased in lung tissues from patients with IPF, which was further confirmed by results from immunohistochemistry and western blot assays. Then, we used RNA interference in MRC-5 cells to inhibit USP13 and evaluated its effects by western blot, real-time RT-PCR, bromodeoxyuridine incorporation, and transwell assays. We also used co-immunoprecipitation and immunofluorescence staining to identify the correlation between USP13 and PTEN in IPF.

Results

USP13 expression levels were markedly reduced in fibroblastic foci and primary IPF fibroblast lines. The depletion of USP13 resulted in the transformation of fibroblasts into an aggressive phenotype with enhanced proliferative, migratory, and invasive capacities. Additionally, USP13 interacted with PTEN and mediated PTEN ubiquitination and degradation in lung fibroblasts.

Conclusions

Down-regulation of USP13 mediates PTEN protein loss and fibroblast phenotypic change, and thereby plays a crucial role in IPF pathogenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0286-3) contains supplementary material, which is available to authorized users.

Breakdown of Epithelial Barrier Integrity and Overdrive Activation of Alveolar Epithelial Cells in the Pathogenesis of Acute Respiratory Distress Syndrome and Lung Fibrosis

Individual alveolar epithelial cells (AECs) collaboratively form a tight barrier between atmosphere and fluid-filled tissue to enable normal gas exchange. The tight junctions of AECs provide intercellular sealing and are integral to the maintenance of the AEC barrier integrity. Disruption and failure of reconstitution of AEC barrier result in catastrophic consequences, leading to alveolar flooding and subsequent devastating fibrotic scarring. Recent evidences reveal that many of the fibrotic lung diseases involve AECs both as a frequent target of injury and as a driver of ongoing pathological processes. Aberrantly activated AECs express most of the growth factors and chemokines responsible for the proliferation, migration, and activation of fibroblasts. Current evidences suggest that AECs may acquire overdrive activation in the initial step of fibrosis by several mechanisms, including abnormal recapitulation of the developmental pathway, defects of the molecules essential for epithelial integrity, and acceleration of aging-related properties. Among these initial triggering events, epithelial Pten, a multiple phosphatase that negatively regulates the PI3K/Akt pathway and is crucial for lung development, is essential for the prevention of alveolar flooding and lung fibrosis through the regulation of AEC barrier integrity after injury. Reestablishment of AEC barrier integrity also involves the deployment of specialized stem/progenitor cells.

TGF-β1 epigenetically modifies Thy-1 expression in primary lung fibroblasts

Idiopathic pulmonary fibrosis is a progressive lung disease that increases in incidence with age. We identified a profibrotic lung phenotype in aging mice characterized by an increase in the number of fibroblasts lacking the expression of thymocyte differentiation antigen 1 (Thy-1) and an increase in transforming growth factor (TGF)-β1 expression. It has been shown that Thy-1 expression can be epigenetically modified. Lung fibroblasts (PLFs) were treated with TGF-β1 ± DNA methyltransferase (DNMT) inhibitor 5-aza-2'-deoxycytidine (5-AZA) and analyzed for Thy-1 gene and protein expression, DNMT protein expression, and activity. α-Smooth muscle actin (α-SMA) and collagen type 1 (Col1A1) gene and protein expression was assessed. PLFs were transfected with DNMT1 silencing RNA ± TGF-β1. TGF-β1 inhibited Thy-1 gene and protein expression in PLFs, and cotreatment with 5-AZA ameliorated this effect and appeared to inhibit DNMT1 activation. TGF-β1 induced Thy-1 promoter methylation as assessed by quantitative methyl PCR. Treatment with 5-AZA attenuated TGF-β1-induced Col1A1 gene and protein expression and α-SMA gene expression (but not α-SMA protein expression). Inhibiting DNMT1 with silencing RNA attenuated TGF-β1-induced DNMT activity and its downstream suppression of Thy-1 mRNA and protein expression as well as inhibited α-SMA mRNA and Col1A1 mRNA and protein expression, and showed a decreased trend in Thy-1 promoter methylation. Immunofluorescence for α-SMA suggested that 5-AZA inhibited stress fiber formation. These findings suggest that TGF-β1 epigenetically regulates lung fibroblast phenotype through methylation of the Thy-1 promoter. Targeted inhibition of DNMT in the right clinical context might prevent fibroblast to myofibroblast transdifferentiation and collagen deposition, which in turn could prevent fibrogenesis in the lung and other organs.

Phosphatase and tensin homolog deleted on chromosome 10 contributes to phenotype transformation of fibroblasts in idiopathic pulmonary fibrosis via multiple pathways

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal disease and considered as a cancer-like disease. The phosphatase and tensin homologue deleted on chromosome 10 (PTEN) tumor suppressor has drawn attention in the pathogenesis of IPF. However, the role of PTEN in phenotypic transformation of lung fibroblasts, particularly in the migratory and invasive phenotype, is still elusive. Our data showed that PTEN expression was markedly reduced in both fibroblasts and myofibroblasts from IPF patients. Furthermore, loss of PTEN led to the transformation of normal fibroblasts to myofibroblasts and increased proliferation, apoptosis resistance, and migration/invasion activities. PTEN deficiency upregulated hyaluronan synthase 2 expression and thereby enhanced the invasion ability of fibroblasts. Cross-talk between PTEN and the transforming growth factor β1 (TGF-β1) pathway and PTEN reduction by hypoxia were observed. These findings suggest that PTEN is implicated in multiple pathways and plays a crucial role in the pathogenesis of IPF.

Validated prediction of pro-invasive growth factors using a transcriptome-wide invasion signature derived from a complex 3D invasion assay

The invasion of activated fibroblasts represents a key pathomechanism in fibrotic diseases, carcinogenesis and metastasis. Invading fibroblasts contribute to fibrotic extracellular matrix (ECM) formation and the initiation, progression, or resistance of cancer. To construct transcriptome-wide signatures of fibroblast invasion, we used a multiplex phenotypic 3D invasion assay using lung fibroblasts. Microarray-based gene expression profiles of invading and non-invading fibroblasts demonstrated that 1,049 genes were differentially regulated (>1.5-fold). Unbiased pathway analysis (Ingenuity) identified significant enrichment for the functional clusters 'invasion of cells', 'idiopathic pulmonary fibrosis', and 'metastasis'. Matrix metalloprotease 13 (MMP13), transforming growth factor (TGF)-β1, Caveolin (Cav) 1, Phosphatase and Tensin Homolog (Pten), and secreted frizzled-related protein (Sfrp) 1 were among the highest regulated genes, confirmed by qRT-PCR and Western Blotting. We next performed in silico analysis (Ingenuity Pathway Analysis) to predict mediators that induced fibroblast invasion. Of these, TGFβ1, epidermal growth factor (EGF), fibroblast growth factor (FGF) 2, and platelet-derived growth factor (PDGF)-BB were tested in our 3D invasion assay and found to significantly induce invasion, thus validating the transcriptome profile. Accordingly, our transcriptomic invasion signature describes the invading fibroblast phenotype in unprecedented detail and provides a tool for future functional studies of cell invasion and therapeutic modulation thereof using complex phenotypic assays.

The Role of PPAR Gamma in Systemic Sclerosis

Fibrosis is recognized as an important feature of many chronic diseases, such as systemic sclerosis (SSc), an autoimmune disease of unknown etiology, characterized by immune dysregulation and vascular injury, followed by progressive fibrosis affecting the skin and multiple internal organs. SSc has a poor prognosis because no therapy has been shown to reverse or arrest the progression of fibrosis, representing a major unmet medical need. Recently, antifibrotic effects of PPARγ ligands have been studied in vitro and in vivo and some theories have emerged leading to new insights. Aberrant PPARγ function seems to be implicated in pathological fibrosis in the skin and lungs. This antifibrotic effect is mainly related to the inhibition of TGF-β/Smad signal transduction but other pathways can be involved. This review focused on recent studies that identified PPARγ as an important novel pathway with critical roles in regulating connective tissue homeostasis, with emphasis on skin and lung fibrosis and its role on systemic sclerosis.

Loss of tumour suppressor PTEN expression in renal injury initiates SMAD3- and p53-dependent fibrotic responses

Deregulation of the tumour suppressor PTEN occurs in lung and skin fibrosis and diabetic and ischaemic renal injury. However, the potential role of PTEN and associated mechanisms in the progression of kidney fibrosis is unknown. Tubular and interstitial PTEN expression was dramatically decreased in several models of renal injury, including aristolochic acid nephropathy (AAN), streptozotocin (STZ)-mediated injury and ureteral unilateral obstruction (UUO), correlating with Akt, p53 and SMAD3 activation and fibrosis. Stable silencing of PTEN in HK-2 human tubular epithelial cells induced dedifferentiation and CTGF, PAI-1, vimentin, α-SMA and fibronectin expression, compared to HK-2 cells expressing control shRNA. Furthermore, PTEN knockdown stimulated Akt, SMAD3 and p53(Ser15) phosphorylation, with an accompanying decrease in population density and an increase in epithelial G1 cell cycle arrest. SMAD3 or p53 gene silencing or pharmacological blockade partially suppressed fibrotic gene expression and relieved growth inhibition orchestrated by deficiency or inhibition of PTEN. Similarly, shRNA suppression of PAI-1 rescued the PTEN loss-associated epithelial proliferative arrest. Moreover, TGFβ1-initiated fibrotic gene expression is further enhanced by PTEN depletion. Combined TGFβ1 treatment and PTEN silencing potentiated epithelial cell death via p53-dependent pathways. Thus, PTEN loss initiates tubular dysfunction via SMAD3- and p53-mediated fibrotic gene induction, with accompanying PAI-1-dependent proliferative arrest, and cooperates with TGFβ1 to induce the expression of profibrotic genes and tubular apoptosis.

Neutrophil elastase promotes myofibroblast differentiation in lung fibrosis

IPF is a progressive lung disorder characterized by fibroblast proliferation and myofibroblast differentiation. Although neutrophil accumulation within IPF lungs has been negatively correlated with outcomes, the role played by neutrophils in lung fibrosis remains poorly understood. We have demonstrated previously that NE promotes lung cancer cell proliferation and hypothesized that it may have a similar effect on fibroblasts. In the current study, we show that NE(-/-) mice are protected from asbestos-induced lung fibrosis. NE(-/-) mice displayed reduced fibroblast and myofibroblast content when compared with controls. NE directly both lung fibroblast proliferation and myofibroblast differentiation in vitro, as evidenced by proliferation assays, collagen gel contractility assays, and αSMA induction. Furthermore, αSMA induction occurs in a TGF-β-independent fashion. Treatment of asbestos-recipient mice with ONO-5046, a synthetic NE antagonist, reduced hydroxyproline content. Thus, the current study points to a key role for neutrophils and NE in the progression of lung fibrosis. Lastly, the study lends rationale to use of NE-inhibitory approaches as a novel therapeutic strategy for patients with lung fibrosis.

Mechanisms of alveolar epithelial injury, repair, and fibrosis

The challenge facing many fibrotic lung diseases is that these conditions usually present late, often after several decades of repetitive alveolar epithelial injury, during which functional alveolar units are gradually obliterated and replaced with nonfunctional connective tissue. The resulting fibrosis is often progressive and, in the case of idiopathic pulmonary fibrosis (IPF), invariably leads to respiratory insufficiency and, ultimately, the premature death of affected individuals. Recent years have seen a greater appreciation of the relative importance of chronic inflammation as a driver of fibrotic responses. Current evidence suggests that IPF arises as a result of repetitive epithelial injury and a highly aberrant wound healing response in genetically susceptible and aged individuals. Nonspecific anti-inflammatory agents offer no clinical benefit, but the potential contribution of maladaptive immune responses in determining outcome is gaining increasing recognition. The importance of key differences in the tissue-regenerative potential in young versus aged individuals is also beginning to be more fully appreciated. Moreover, there is considerable overlap in the mechanisms underlying tissue repair and cancer, and patients with IPF are at heightened risk of developing lung cancer. Progressive fibrosis and cancer may therefore represent the extremes of a highly dysregulated tissue injury response. This brief review focuses on some of this evidence and on our current understanding of abnormal tissue repair responses after chronic epithelial injury in the specific context of IPF.

Hallmarks of the ageing lung

Ageing is the main risk factor for major non-communicable chronic lung diseases, including chronic obstructive pulmonary disease, most forms of lung cancer and idiopathic pulmonary fibrosis. While the prevalence of these diseases continually increases with age, their respective incidence peaks at different times during the lifespan, suggesting specific effects of ageing on the onset and/or pathogenesis of chronic obstructive pulmonary disease, lung cancer and idiopathic pulmonary fibrosis. Recently, the nine hallmarks of ageing have been defined as cell-autonomous and non-autonomous pathways involved in ageing. Here, we review the available evidence for the involvement of each of these hallmarks in the pathogenesis of chronic obstructive pulmonary disease, lung cancer, or idiopathic pulmonary fibrosis. Importantly, we propose an additional hallmark, “dysregulation of the extracellular matrix”, which we argue acts as a crucial modifier of cell-autonomous changes and functions, and as a key feature of the above-mentioned lung diseases.

PTEN

The importance of PTEN in cellular function is underscored by the frequency of its deregulation in cancer. PTEN tumor-suppressor activity depends largely on its lipid phosphatase activity, which opposes PI3K/AKT activation. As such, PTEN regulates many cellular processes, including proliferation, survival, energy metabolism, cellular architecture, and motility. More than a decade of research has expanded our knowledge about how PTEN is controlled at the transcriptional level as well as by numerous posttranscriptional modifications that regulate its enzymatic activity, protein stability, and cellular location. Although the role of PTEN in cancers has long been appreciated, it is also emerging as an important factor in other diseases, such as diabetes and autism spectrum disorders. Our understanding of PTEN function and regulation will hopefully translate into improved prognosis and treatment for patients suffering from these ailments.

Dasatinib attenuated bleomycin-induced pulmonary fibrosis in mice

Anti-fibrotic effect of dasatinib, a platelet-derived growth factor receptor (PDGFR) and Src-kinase inhibitor, was tested on pulmonary fibrosis (PF). Adult mice were divided into four groups: mice dissected 21 d after the bleomycin (BLM) instillation (0.08 mg/kg in 200 µl) (I) and their controls (II), and mice treated with dasatinib (8 mg/kg in 100 µl, gavage) for one week 14 d after BLM instillation and dissected 21 d after instillation (III) and their controls (IV). The fibrosis score and the levels of fibrotic markers were analyzed in lungs. BLM treatment-induced cell proliferation and increased the levels of collagen-1, alpha smooth muscle actin, phospho (p)-PDGFR-alpha, p-Src, p-extracellular signal-regulated kinases1/2 and p-cytoplasmic-Abelson-kinase (c-Abl) in lungs, and down-regulated PTEN expression. Dasatinib reversed these alterations in the fibrotic lung. Dasatinib limited myofibroblast activation and collagen-1 accumulation by the inhibition of PDGFR-alpha, and Src and c-Abl activations. In conclusion, dasatinib may be a novel tyrosine and Src-kinase inhibitor for PF regression in mice.

Activation of oncogenic pathways in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is defined as a specific form of chronic, progressive fibrosing interstitial pneumonia of unknown cause. The most recent hypotheses on IPF pathogenesis suggest a central role of epithelial cell damage, followed by a dysregulated molecular cross talk between epithelial cells and fibroblasts. Thus, IPF progression has often been assimilated to that of cancer, and several signaling patterns appear to be disrupted in both diseases. Here, we analyze the expression in an IPF series of a panel of molecules, which are known to play a role in tumorigenic process. Our findings, although preliminary, reveal that IPF landscape is enriched in neoplastic potential expressed in a context of complex genomic polyclonality and cellular heterogeneity. These results provide a rationale for further investigations aimed to exploit—in a similar fashion to cancer—targeted therapies for a “precision medicine” approach to IPF.

Inhibition of Wnt/β-catenin signaling promotes epithelial differentiation of mesenchymal stem cells and repairs bleomycin-induced lung injury

Idiopathic pulmonary fibrosis is a progressive lung disorder of unknown etiology. Previous studies have shown that aberrant activation of the Wnt/β-catenin signaling cascade occurs in lungs of patients with idiopathic pulmonary fibrosis. Given the important roles of the Wnt/β-catenin signaling pathway in the development of pulmonary fibrosis, we targeted this pathway for the intervention of pulmonary fibrosis with XAV939, a small molecule that specifically inhibits Tankyrase 1/2, eventually leading to the degradation of β-catenin and suppression of the Wnt/β-catenin signaling pathway. Our results demonstrated that XAV939 significantly inhibited the activation of Wnt/β-catenin signaling and attenuated bleomycin-induced lung fibrosis in mice, and thus improved the survival of mice with lung injury. Interestingly, previous investigations have confirmed that endogenous and exogenous mesenchymal stem cells could be recruited to the injured lung, although the exact effects of these cells are debatable. To determine the effect of Wnt/β-catenin signaling in the epithelial differentiation of bone marrow-derived mesenchymal stem cells (BM-MSCs), we established a coculture system that contains BM-MSCs and alveolar type II epithelial cells. The in vitro experiments demonstrated that XAV939 could promote the differentiation of BM-MSCs into an epithelium-like phenotype in the coculture system. We also found that XAV939 could inhibit the proliferation and myofibroblast differentiation of NIH/3T3 fibroblasts. This work supports that inhibition of the Wnt/β-catenin signaling pathway may be exploited for the treatment of idiopathic pulmonary fibrosis for which effective treatment strategies are still lacking.

Activated Wnt signaling induces myofibroblast differentiation of mesenchymal stem cells, contributing to pulmonary fibrosis

Acute lung injury may lead to fibrogenesis. However, no treatment is currently available. This study was conducted to determine the effects of bone marrow-derived mesenchymal stem cells (MSCs) in a model of HCl-induced acute lung injury in Sprague-Dawley (SD) rats. Stromal cell-derived factor (SDF)-1 and its receptor CXC chemokine receptor (CXCR)4 have been shown to participate in mobilizing MSCs. Adenovirus carrying the CXCR4 gene was used to transfect MSCs in order to increase the engraftment numbers of MSCs at injured sites. Histological examination data demonstrated that the engraftment of MSCs did not attenuate lung injury and pulmonary fibrosis. The results showed that engraftment of MSCs almost differentiated into myofibroblasts, but rarely differentiated into lung epithelial cells. Additionally, it was demonstrated that activated canonical Wnt/β-catenin signaling in injured lung tissue regulated the myofibroblast differentiation of MSCs in vivo. The in vitro study results demonstrated that activation of the Wnt/β-catenin signaling stimulated MSCs to express myofibroblast markers; however, this process was attenuated by Wnt antagonist DKK1. Therefore, the results demonstrated that the aberrant activation of Wnt signaling induces the myofibroblast differentiation of engrafted MSCs, thus contributing to pulmonary fibrosis following lung injury.

Involvement of TGFβ-induced phosphorylation of the PTEN C-terminus on TGFβ-induced acquisition of malignant phenotypes in lung cancer cells

Transforming growth factor β (TGFβ) derived from the tumor microenvironment induces malignant phenotypes such as epithelial-mesenchymal transition (EMT) and aberrant cell motility in lung cancers. TGFβ-induced translocation of β-catenin from E-cadherin complexes into the cytoplasm is involved in the transcription of EMT target genes. PTEN (phosphatase and tensin homologue deleted from chromosome 10) is known to exert phosphatase activity by binding to E-cadherin complexes via β-catenin, and recent studies suggest that phosphorylation of the PTEN C-terminus tail might cause loss of this PTEN phosphatase activity. However, whether TGFβ can modulate both β-catenin translocation and PTEN phosphatase activity via phosphorylation of the PTEN C-terminus remains elusive. Furthermore, the role of phosphorylation of the PTEN C-terminus in TGFβ-induced malignant phenotypes has not been evaluated. To investigate whether modulation of phosphorylation of the PTEN C-terminus can regulate malignant phenotypes, here we established lung cancer cells expressing PTEN protein with mutation of phosphorylation sites in the PTEN C-terminus (PTEN4A). We found that TGFβ stimulation yielded a two-fold increase in the phosphorylated -PTEN/PTEN ratio. Expression of PTEN4A repressed TGFβ-induced EMT and cell motility even after snail expression. Our data showed that PTEN4A might repress EMT through complete blockade of β-catenin translocation into the cytoplasm, besides the inhibitory effect of PTEN4A on TGFβ-induced activation of smad-independent signaling pathways. In a xenograft model, the tumor growth ratio was repressed in cells expressing PTEN4A. Taken together, these data suggest that phosphorylation sites in the PTEN C-terminus might be a therapeutic target for TGFβ-induced malignant phenotypes in lung cancer cells.

Akt1 mediates α-smooth muscle actin expression and myofibroblast differentiation via myocardin and serum response factor

Myofibroblast (MF) differentiation, marked by the de novo expression of smooth muscle α-actin (αSMA) stress fibers, plays a central role in wound healing and its persistence is a hallmark of fibrotic diseases. We have previously shown that Akt1 is necessary for wound healing through matrix regulation. However, the role of Akt1 in regulating MF differentiation with implications in fibrosis remains poorly defined. Here, we show that sustained activation of Akt1 was associated with a 6-fold increase in αSMA expression and assembly; an effect that is blunted in cells expressing inactive Akt1 despite TGFβ stimulation. Mechanistically, Akt1 mediated TGFβ-induced αSMA synthesis through the contractile gene transcription factors myocardin and serum response factor (SRF), independent of mammalian target of rapamycin in mouse embryonic fibroblasts and fibroblasts overexpressing active Akt1. Akt1 deficiency was associated with decreased myocardin, SRF, and αSMA expressions in vivo. Furthermore, sustained Akt1-induced αSMA synthesis markedly decreased upon RNA silencing of SRF and myocardin. In addition to its integral role in αSMA synthesis, we also show that Akt1 mediates fibronectin splice variant expression, which is required for MF differentiation, as well as total fibronectin, which generates the contractile force that promotes MF differentiation. In summary, our results constitute evidence that sustained Akt1 activation is crucial for TGFβ-induced MF formation and persistent differentiation. These findings highlight Akt1 as a novel potential therapeutic target for fibrotic diseases.

The epigenetic feedback loop between DNA methylation and microRNAs in fibrotic disease with an emphasis on DNA methyltransferases

Epigenetic processes play a key regulatory role in many cancers. Recently, it also has been demonstrated to participate in fibrogenesis, especially in fibrotic disease. Fibrotic disease is a pathological response to tissue injury which can occur in any organ. Mechanisms that orchestrate fibrotic disorders in different organs are amazingly generic, involving generation of activated fibroblasts and myofibroblasts by differentiation processes that require extensive alterations in gene expression. Apart from genetic and environmental factors, epigenetic modifications including a combination of microRNAs and DNA methylation are supposed as regulatory mechanisms to control myofibroblast differentiation. It has become obvious that microRNAs, which act as regulators of gene expression at a post-transcriptional level, are differentially expressed in differentiating cells and play important roles in governing DNA methyltransferases (DNMTs) which are enzymes responsible for setting up and maintaining DNA methylation patterns at specific regions of the genome. Some microRNAs targeting DNMT transcripts lead to the demethylation and transcriptional activation of numerous protein coding gene sequences, thereby contributing to gene expression. Moreover, DNMTs also have a critical role in controlling some specific microRNA expression. This cooperative action among DNMTs, microRNAs and DNA methylation indicates that DNMTs may participate in the pathogenesis of myofibroblast differentiation through silencing of certain gene transcription. In this review, we summarize the current knowledge of a potential link between microRNA expression and DNA methylation on how DNMTs work in the process of fibrogenesis.

Phospho-tyrosine phosphatase inhibitor Bpv(Hopic) enhances C2C12 myoblast migration in vitro. Requirement of PI3K/AKT and MAPK/ERK pathways

Muscle progenitor cell migration is an important step in skeletal muscle myogenesis and regeneration. Migration is required for muscle precursors to reach the site of damage and for the alignment of myoblasts prior to their fusion, which ultimately contributes to muscle regeneration. Limited spreading and migration of donor myoblasts are reported problems of myoblast transfer therapy, a proposed therapeutic strategy for Duchenne Muscular Dystrophy, warranting further investigation into different approaches for improving the motility and homing of these cells. In this article, the effect of protein phospho-tyrosine phosphatase and PTEN inhibitor BpV(Hopic) on C2C12 myoblast migration and differentiation was investigated. Applying a wound healing migration model, it is reported that 1 μM BpV(Hopic) is capable of enhancing the migration of C2C12 myoblasts by approximately 40 % in the presence of myotube conditioned media, without significantly affecting their capacity to differentiate and fuse into multinucleated myotubes. Improved migration of myoblasts treated with 1 μM BpV(Hopic) was associated with activation of PI3K/AKT and MAPK/ERK pathways, while their inhibition with either LY294002 or UO126, respectively, resulted in a reduction of C2C12 migration back to control levels. These results propose that bisperoxovanadium compounds may be considered as potential tools for enhancing the migration of myoblasts, while not reducing their differentiation capacity and underpin the importance of PI3K/AKT and MAPK/ERK signalling for the process of myogenic progenitor migration.

Pulmonary hypertension secondary to left-heart failure involves peroxynitrite-induced downregulation of PTEN in the lung

Pulmonary hypertension (PH) that occurs after left-heart failure (LHF), classified as Group 2 PH, involves progressive pulmonary vascular remodeling induced by smooth muscle cell (SMC) proliferation. However, mechanisms involved in the activation of SMCs remain unknown. The objective of this study was to determine the involvement of peroxynitrite and phosphatase-and-tensin homolog on chromosome 10 (PTEN) in vascular SMC proliferation and remodeling in the LHF-induced PH (LHF-PH). LHF was induced by permanent ligation of left anterior descending coronary artery in rats for 4 weeks. MRI, ultrasound, and hemodynamic measurements were performed to confirm LHF and PH. Histopathology, Western blot, and real-time polymerase chain reaction analyses were used to identify key molecular signatures. Therapeutic intervention was demonstrated using an antiproliferative compound, HO-3867. LHF-PH was confirmed by significant elevation of pulmonary artery pressure (mean pulmonary artery pressure/mm Hg: 35.9±1.8 versus 14.8±2.0, control; P<0.001) and vascular remodeling. HO-3867 treatment decreased mean pulmonary artery pressure to 22.6±0.8 mm Hg (P<0.001). Substantially higher levels of peroxynitrite and significant loss of PTEN expression were observed in the lungs of LHF rats when compared with control. In vitro studies using human pulmonary artery SMCs implicated peroxynitrite-mediated downregulation of PTEN expression as a key mechanism of SMC proliferation. The results further established that HO-3867 attenuated LHF-PH by decreasing oxidative stress and increasing PTEN expression in the lung. In conclusion, peroxynitrite and peroxynitrite-mediated PTEN inactivation seem to be key mediators of lung microvascular remodeling associated with PH secondary to LHF.

Mesodermal Pten inactivation leads to alveolar capillary dysplasia- like phenotype

Alveolar capillary dysplasia (ACD) is a congenital, lethal disorder of the pulmonary vasculature. Phosphatase and tensin homologue deleted from chromosome 10 (Pten) encodes a lipid phosphatase controlling key cellular functions, including stem/progenitor cell proliferation and differentiation; however, the role of PTEN in mesodermal lung cell lineage formation remains unexamined. To determine the role of mesodermal PTEN in the ontogeny of various mesenchymal cell lineages during lung development, we specifically deleted Pten in early embryonic lung mesenchyme in mice. Pups lacking Pten died at birth, with evidence of failure in blood oxygenation. Analysis at the cellular level showed defects in angioblast differentiation to endothelial cells and an accompanying accumulation of the angioblast cell population that was associated with disorganized capillary beds. We also found decreased expression of Forkhead box protein F1 (Foxf1), a gene associated with the ACD human phenotype. Analysis of human samples for ACD revealed a significant decrease in PTEN and increased activated protein kinase B (AKT). These studies demonstrate that mesodermal PTEN has a key role in controlling the amplification of angioblasts as well as their differentiation into endothelial cells, thereby directing the establishment of a functional gas exchange interface. Additionally, these mice could serve as a murine model of ACD.

Effects of tacrolimus and nifedipine, alone or in combination, on gingival tissues

BACKGROUND

The aim of this study is to compare gingival changes induced by short- and long-term tacrolimus and nifedipine administration, alone or in combination, and evaluate the expression levels of tumor suppressor phosphatase and tensin homolog (PTEN) in drug-induced gingival overgrowth.

METHODS

Eighty rats were equally divided into eight groups: 1) tacrolimus for 8 weeks; 2) nifedipine for 8 weeks; 3) tacrolimus and nifedipine for 8 weeks; 4) 8-week control; 5) tacrolimus for 24 weeks; 6) nifedipine for 24 weeks; 7) tacrolimus and nifedipine for 24 weeks; and 8) 24-week control. Histomorphometric analyses included measurements of epithelial thickness, connective tissue thickness, and height. Stereologic analyses included measurements of volumetric densities of fibroblasts (Vf), collagen fibers (Vcf), and blood vessels (Vbv). In addition, PTEN expression was analyzed using immunohistochemistry.

RESULTS

Epithelial thickness and connective tissue thickness were significantly increased in groups 5, 6, and 7 compared to group 8 (P <0.05), whereas connective tissue height was significantly increased in groups 5 and 7 (P <0.001). Vf and Vcf were significantly increased in group 7 compared to group 8 (P <0.001). PTEN immunoreactivity was significantly decreased in all experimental groups compared to the control groups (P <0.05).

CONCLUSIONS

Results suggest that duration of drug administration is a more important risk factor than drug combination. The results include a potentially new insight about PTEN's role in the etiology of drug-induced gingival overgrowth.