HSP90 Inhibition and Modulation of the Proteome: Therapeutical Implications for Idiopathic Pulmonary Fibrosis (IPF)

Current state of signaling pathways associated with the pathogenesis of idiopathic pulmonary fibrosis

Idiopathic Pulmonary Fibrosis (IPF) represents a chronic and progressive pulmonary disorder distinguished by a notable mortality rate. Despite the elusive nature of the pathogenic mechanisms, several signaling pathways have been elucidated for their pivotal roles in the progression of this ailment. This manuscript aims to comprehensively review the existing literature on the signaling pathways linked to the pathogenesis of IPF, both within national and international contexts. The objective is to enhance the comprehension of the pathogenic mechanisms underlying IPF and offer a scholarly foundation for the advancement of more efficacious therapeutic strategies, thereby fostering research and clinical practices within this domain.

Protective role of the HSP90 inhibitor, STA-9090, in lungs of SARS-CoV-2-infected Syrian golden hamsters

INTRODUCTION

The emergence of new SARS-CoV-2 variants, capable of escaping the humoral immunity acquired by the available vaccines, together with waning immunity and vaccine hesitancy, challenges the efficacy of the vaccination strategy in fighting COVID-19. Improved therapeutic strategies are urgently needed to better intervene particularly in severe cases of the disease. They should aim at controlling the hyperinflammatory state generated on infection, reducing lung tissue pathology and inhibiting viral replication. Previous research has pointed to a possible role for the chaperone HSP90 in SARS-CoV-2 replication and COVID-19 pathogenesis. Pharmacological intervention through HSP90 inhibitors was shown to be beneficial in the treatment of inflammatory diseases, infections and reducing replication of diverse viruses.

METHODS

In this study, we investigated the effects of the potent HSP90 inhibitor Ganetespib (STA-9090) in vitro on alveolar epithelial cells and alveolar macrophages to characterise its effects on cell activation and viral replication. Additionally, the Syrian hamster animal model was used to evaluate its efficacy in controlling systemic inflammation and viral burden after infection.

RESULTS

In vitro, STA-9090 reduced viral replication on alveolar epithelial cells in a dose-dependent manner and lowered significantly the expression of proinflammatory genes, in both alveolar epithelial cells and alveolar macrophages. In vivo, although no reduction in viral load was observed, administration of STA-9090 led to an overall improvement of the clinical condition of infected animals, with reduced oedema formation and lung tissue pathology.

CONCLUSION

Altogether, we show that HSP90 inhibition could serve as a potential treatment option for moderate and severe cases of COVID-19.

Regulation of Epithelial and Endothelial Barriers by Molecular Chaperones

The integrity and permeability of epithelial and endothelial barriers depend on the formation of tight junctions, adherens junctions, and a junction-associated cytoskeleton. The establishment of this junction-cytoskeletal module relies on the correct folding and oligomerization of its protein components. Molecular chaperones are known regulators of protein folding and complex formation in different cellular compartments. Mammalian cells possess an elaborate chaperone network consisting of several hundred chaperones and co-chaperones. Only a small part of this network has been linked, however, to the regulation of intercellular adhesions, and the systematic analysis of chaperone functions at epithelial and endothelial barriers is lacking. This review describes the functions and mechanisms of the chaperone-assisted regulation of intercellular junctions. The major focus of this review is on heat shock protein chaperones, their co-chaperones, and chaperonins since these molecules are the focus of the majority of the articles published on the chaperone-mediated control of tissue barriers. This review discusses the roles of chaperones in the regulation of the steady-state integrity of epithelial and vascular barriers as well as the disruption of these barriers by pathogenic factors and extracellular stressors. Since cytoskeletal coupling is essential for junctional integrity and remodeling, chaperone-assisted assembly of the actomyosin cytoskeleton is also discussed.

HSP70 Is a Critical Regulator of HSP90 Inhibitor's Effectiveness in Preventing HCl-Induced Chronic Lung Injury and Pulmonary Fibrosis

Exposure to hydrochloric acid (HCl) can provoke acute and chronic lung injury. Because of its extensive production for industrial use, frequent accidental exposures occur, making HCl one of the top five chemicals causing inhalation injuries. There are no Food and Drug Administration (FDA)-approved treatments for HCl exposure. Heat shock protein 90 (HSP90) inhibitors modulate transforming growth factor-β (TGF-β) signaling and the development of chemical-induced pulmonary fibrosis. However, little is known on the role of Heat Shock Protein 70 (HSP70) during injury and treatment with HSP90 inhibitors. We hypothesized that administration of geranylgeranyl-acetone (GGA), an HSP70 inducer, or gefitinib (GFT), an HSP70 suppressant, alone or in combination with the HSP90 inhibitor, TAS-116, would improve or worsen, respectively, HCl-induced chronic lung injury in vivo and endothelial barrier dysfunction in vitro. GGA, alone, improved HCl-induced human lung microvascular endothelial cells (HLMVEC) barrier dysfunction and, in combination with TAS-116, improved the protective effect of TAS-116. In mice, GGA reduced HCl toxicity and while TAS-116 alone blocked HCl-induced chronic lung injury, co-administration with GGA, resulted in further improvement. Conversely, GFT potentiated HCl-induced barrier dysfunction and impaired the antidotal effects of TAS-116. We conclude that combined treatments with HSP90 inhibitors and HSP70 inducers may represent a novel therapeutic approach to manage HCl-induced chronic lung injury and pulmonary fibrosis.

Ceapin-A7 potentiates lipopolysaccharide-induced endothelial injury

Barrier dysfunction is the hallmark of severe lung injury, including acute respiratory distress syndrome. Efficient medical countermeasures to counteract endothelial hyperpermeability do not exist, hence the mortality rates of disorders related to barrier abnormalities are unacceptable high. The unfolded protein response is a highly conserved mechanism, which aims to support the cells against endoplasmic reticulum stress, and ATF6 is a protein sensor that triggers its activation. In the current study, we investigate the effects of ATF6 suppression in LPS-induced endothelial inflammation. Our observations suggest that Ceapin-A7, which is an ATF6 suppressor, potentiates LPS-induced STAT3 and JAK2 activation. Hence ATF6 activation may serve as a new therapeutic possibility toward diseases related to barrier dysfunction.

An acute respiratory distress syndrome drug development collaboration stimulated by the Virginia Drug Discovery Consortium

The genesis of most older medicinal agents has generally been empirical. During the past one and a half centuries, at least in the Western countries, discovering and developing drugs has been primarily the domain of pharmaceutical companies largely built upon concepts emerging from organic chemistry. Public sector funding for the discovery of new therapeutics has more recently stimulated local, national, and international groups to band together and focus on new human disease targets and novel treatment approaches. This Perspective describes one contemporary example of a newly formed collaboration that was simulated by a regional drug discovery consortium. University of Virginia, Old Dominion University, and a university spinout company, KeViRx, Inc., partnered under a NIH Small Business Innovation Research grant, to produce potential therapeutics for acute respiratory distress syndrome resulting from the ongoing COVID-19 pandemic.

Molecular mechanisms of COVID-19-induced pulmonary fibrosis and epithelial-mesenchymal transition

As the outbreak of COVID-19 caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) first broke out in Hubei Province, China, at the end of 2019. It has brought great challenges and harms to global public health. SARS-CoV-2 mainly affects the lungs and is mainly manifested as pulmonary disease. However, one of the biggest crises arises from the emergence of COVID-19-induced fibrosis. At present, there are still many questions about how COVID-19 induced pulmonary fibrosis (PF) occurs and how to treat and regulate its long-term effects. In addition, as an important process of fibrosis, the effect of COVID-19 on epithelial-mesenchymal transition (EMT) may be an important factor driving PF. This review summarizes the main pathogenesis and treatment mechanisms of COVID-19 related to PF. Starting with the basic mechanisms of PF, such as EMT, transforming growth factor-β (TGF-β), fibroblasts and myofibroblasts, inflammation, macrophages, innate lymphoid cells, matrix metalloproteinases and tissue inhibitors of metalloproteinases, hedgehog pathway as well as Notch signaling. Further, we highlight the importance of COVID-19-induced EMT in the process of PF and provide an overview of the related molecular mechanisms, which will facilitate future research to propose new clinical therapeutic solutions for the treatment of COVID-19-induced PF.

STA9090 as a Potential Therapeutic Agent for Liver Fibrosis by Modulating the HSP90/TβRII/Proteasome Interplay: Novel Insights from In Vitro and In Vivo Investigations

Liver fibrosis is a progressive condition characterized by the build-up of fibrous tissue resulting from long-term liver injury. Although there have been advancements in research and treatment, there is still a need for effective antifibrotic medication. HSP90 plays a crucial role in the development of fibrosis. It acts as a molecular chaperone that assists in the proper folding and stability of TβRII, potentially regulating the signaling of TGF-β1. It has been established that TβRII can be degraded through the proteasome degradation system, either via ubiquitination-dependent or -independent pathways. In the present study, STA9090 demonstrated promising effects in both in vitro and in vivo models. It reduced LDH leakage, prolonged the survival rate of hepatocytes in rats with liver fibrosis, and improved liver function. Importantly, STA9090 exerted pleiotropic effects by targeting proteins involved in limiting collagen production, which resulted in improved microscopic features of the rat livers. Our findings suggest that STA9090-induced inhibition of HSP90 leads to the degradation of TβRII, a fibrogenic client protein of HSP90, through the activation of the 20S proteasomal degradation system. We also revealed that this degradation mechanism is not dependent on the autophagy-lysosomal pathway. Additionally, STA9090 was found to destabilize HIF-1α and facilitate its degradation, leading to the reduced transcription of VEGF. Moreover, STA9090's ability to deactivate the NFκB signaling pathway highlights its potential as an anti-inflammatory and antifibrotic agent. However, further research is necessary to fully elucidate the underlying mechanisms and fully capitalize on the therapeutic benefits of targeting HSP90 and associated pathways.

Potential of resveratrol in the treatment of interstitial lung disease

Interstitial lung disease (ILD) is a heterogeneous group of diseases characterized by lung injury caused by lung fibroblast proliferation, interstitial inflammation, and fibrosis. Different cell signal transduction pathways are activated in response to various proinflammatory or fibrotic cytokines, such as IL-6, and these cytokines are increased in different ILDs. The overexpressed cytokines and growth factors in ILD can activate TGF-β/Smad2/3/4, NF-κB, and JAK/STAT signal transduction pathways, promote the activation of immune cells, increase the release of pro-inflammatory and pro-fibrotic factors, differentiate fibroblasts into myofibroblasts, and promote the occurrence and development of ILD. This finding suggests the importance of signal transduction pathways in patients with ILD. Recent evidence suggests that resveratrol (RSV) attenuates excessive inflammation and pulmonary fibrosis by inhibiting the TGF-β/Smad2/3/4, NF-κB, and JAK/STAT signal transduction pathways and overactivation of immune cells. In this review, advances in lung protection and the underlying mechanisms of RSV are summarized, and the potential efficacy of RSV as a promising treatment option for ILD is highlighted.

Russian Registry of Idiopathic Pulmonary Fibrosis: Clinical Features, Treatment Management, and Outcomes

A registry of patients with idiopathic pulmonary fibrosis (IPF) was founded in Russia in 2016. The aim of this study was to analyze the demographic, clinical, functional, radiological, and morphological data of the patients included in this registry.

METHODS

This was a prospective multicenter, observational, non-interventional study. Patients' risk factors, demographics, clinical data, results of high-resolution computed tomography (HRCT) of the chest and pulmonary function testing, and lung tissue biopsy findings were analyzed. We also analyzed the exercise tolerance (6-min walking test) of patients, serological markers of systemic connective tissue diseases, treatment, clinical course, and outcomes of the disease. Multidisciplinary discussion (MDD) was used as needed.

RESULTS

One thousand three hundred and fifty-three patients were included in the registry from 2016 to 2020. The mean age was 64.4 ± 10.7 years, most patients were active smokers or ex-smokers. Antifibrotic therapy was administered to 90 of 948 patients (9.5%). Since starting the registry in 2016, the incidences of IPF have increased and the time period from manifestation of the disease to making the diagnosis has shortened, the number of patients on antifibrotic therapy has increased and the number of patients taking systemic steroids decreased.

CONCLUSION

The registry of patients with IPF was helpful to improve IPF diagnosis and to implement antifibrotic agents in clinical practice. Further analysis of the clinical course and prognostic markers of IPF in the Russian population is needed. An analysis of the long-term efficacy of antifibrotic therapy in this population is also important.

Wilms Tumor 1-Driven Fibroblast Activation and Subpleural Thickening in Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease that is often fatal due to the formation of irreversible scar tissue in the distal areas of the lung. Although the pathological and radiological features of IPF lungs are well defined, the lack of insight into the fibrogenic role of fibroblasts that accumulate in distinct anatomical regions of the lungs is a critical knowledge gap. Fibrotic lesions have been shown to originate in the subpleural areas and extend into the lung parenchyma through processes of dysregulated fibroproliferation, migration, fibroblast-to-myofibroblast transformation, and extracellular matrix production. Identifying the molecular targets underlying subpleural thickening at the early and late stages of fibrosis could facilitate the development of new therapies to attenuate fibroblast activation and improve the survival of patients with IPF. Here, we discuss the key cellular and molecular events that contribute to (myo)fibroblast activation and subpleural thickening in IPF. In particular, we highlight the transcriptional programs involved in mesothelial to mesenchymal transformation and fibroblast dysfunction that can be targeted to alter the course of the progressive expansion of fibrotic lesions in the distal areas of IPF lungs.

Nintedanib Inhibits Endothelial Mesenchymal Transition in Bleomycin-Induced Pulmonary Fibrosis via Focal Adhesion Kinase Activity Reduction

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease (ILD). Pulmonary fibroblasts play an important role in the development of IPF. Emerging evidence indicates that pulmonary endothelial cells could be the source of pulmonary fibroblasts through endothelial mesenchymal transition (EndoMT), which contributes to pulmonary fibrosis. EndoMT is a complex process in which endothelial cells lose their expression of endothelial markers and give rise to the characteristics of mesenchymal cells, including morphological fibroblast-like change and the expression of mesenchymal markers, which result in cardiac, renal, and dermal fibroses. Furthermore, EndoMT inhibition attenuates pulmonary fibrosis. Herein, we demonstrate that nintedanib, a tyrosine kinase receptor inhibitor, ameliorated murine bleomycin (BLM)-induced pulmonary fibrosis and suppressed the in vivo and in vitro models of EndoMT. We demonstrated that the activity of focal adhesion kinase (FAK), a key EndoMT regulator, increased in murine lung tissues and human pulmonary microvascular endothelial cells after BLM stimulation. Nintedanib treatment inhibited BLM-induced FAK activation and thus suppressed both in vivo and in vitro BLM-induced EndoMT. Importantly, we found that the VEGF/FAK signaling pathway was involved in nintedanib regulating EndoMT. These novel findings help us understand the mechanism and signaling pathway of EndoMT to further develop more efficacious drugs for IPF treatment.

Role of collagen regulators in cancer treatment: A comprehensive review

Abstract:

Collagen is the most important structural protein and also a main component of extra-cellular matrix (ECM). It plays a role in tumor progression. Collagen can be regulated by altering it’s biosynthesis pathway through various signaling pathways, receptors and genes. Activity of cancer cells can also be regulated by other ECM components like metalloproteinases, hyaluronic acid, fibronectin and so on. Hypoxia is also one of the condition which leads to cancer progression by stimulating the expression of procollagen lysine as a collagen crosslinker, which increases the size of collagen fibres promoting cancer spread. The collagen content in cancerous cells leads to resistance in chemotherapy. So, to reduce this resistance, some of the collagen regulating therapies are introduced, which include inhibiting its biosynthesis, disturbing cancer cell signaling pathway, mediating ECM components and directly utilizing collagenase. This study is an effort to compile the strategies reported to control the collagen level and different collagen inhibitors reported so far. More research is needed in this area, growing understandings of collagen’s structural features and its role in cancer progression will aid in the advancement of newer chemotherapies.

The Heat Shock Protein 90 Inhibitor, AT13387, Protects the Alveolo-Capillary Barrier and Prevents HCl-Induced Chronic Lung Injury and Pulmonary Fibrosis

Hydrochloric acid (HCl) exposure causes asthma-like conditions, reactive airways dysfunction syndrome, and pulmonary fibrosis. Heat Shock Protein 90 (HSP90) is a molecular chaperone that regulates multiple cellular processes. HSP90 inhibitors are undergoing clinical trials for cancer and are also being studied in various pre-clinical settings for their anti-inflammatory and anti-fibrotic effects. Here we investigated the ability of the heat shock protein 90 (HSP90) inhibitor AT13387 to prevent chronic lung injury induced by exposure to HCl in vivo and its protective role in the endothelial barrier in vitro. We instilled C57Bl/6J mice with 0.1N HCl (2 µL/g body weight, intratracheally) and after 24 h began treatment with vehicle or AT13387 (10 or 15 mg/kg, SC), administered 3×/week; we analyzed histological, functional, and molecular markers 30 days after HCl. In addition, we monitored transendothelial electrical resistance (TER) and protein expression in a monolayer of human lung microvascular endothelial cells (HLMVEC) exposed to HCl (0.02 N) and treated with vehicle or AT13387 (2 µM). HCl provoked persistent alveolar inflammation; activation of profibrotic pathways (MAPK/ERK, HSP90); increased deposition of collagen, fibronectin and elastin; histological evidence of fibrosis; and a decline in lung function reflected in a downward shift in pressure–volume curves, increased respiratory system resistance (Rrs), elastance (Ers), tissue damping (G), and hyperresponsiveness to methacholine. Treatment with 15 mg/kg AT13387reduced alveolar inflammation, fibrosis, and NLRP3 staining; blocked activation of ERK and HSP90; and attenuated the deposition of collagen and the development of chronic lung injury and airway hyperreactivity. In vitro, AT13387 prevented HCl-induced loss of barrier function and AKT, ERK, and ROCK1 activation, and restored HSP70 and cofilin expression. The HSP90 inhibitor, AT13387, represents a promising drug candidate for chronic lung injury that can be administered subcutaneously in the field, and at low, non-toxic doses.

Identification and Validation of Aging-Related Genes in Idiopathic Pulmonary Fibrosis

Aging plays a significant role in the occurrence and development of idiopathic pulmonary fibrosis (IPF). In this study, we aimed to identify and verify potential aging-associated genes involved in IPF using bioinformatic analysis. The mRNA expression profile dataset GSE150910 available in the Gene Expression Omnibus (GEO) database and R software were used to identify the differentially expressed aging-related genes involved in IPF. Hub gene expression was validated by other GEO datasets. Gene ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were performed on differentially expressed aging-related genes. Subsequently, aging-related genes were further screened using three techniques (least absolute shrinkage and selection operator (LASSO) regression, support vector machine, and random forest), and the receiver operating characteristic curves were plotted based on screening results. Finally, real-time quantitative polymerase chain reaction (qRT-PCR) was performed to verify the RNA expression of the six differentially expressed aging-related genes using the blood samples of patients with IPF and healthy individuals. Sixteen differentially expressed aging-related genes were detected, of which the expression of 12 were upregulated and four were downregulated. GO and KEGG enrichment analyses indicated the presence of several enriched terms related to senescence and apoptotic mitochondrial changes. Further screening by LASSO regression, support vector machine, and random forest identified six genes (IGF1, RET, IGFBP2, CDKN2A, JUN, and TFAP2A) that could serve as potential diagnostic biomarkers for IPF. Furthermore, qRT-PCR analysis indicated that among the above-mentioned six aging-related genes, only the expression levels of IGF1, RET, and IGFBP2 in patients with IPF and healthy individuals were consistent with the results of bioinformatic analysis. In conclusion, bioinformatics analysis identified 16 potential aging-related genes associated with IPF, and clinical sample validation suggested that among these, IGF1, RET, and IGFBP2 might play a role in the incidence and prognosis of IPF. Our findings may help understand the pathogenesis of IPF.

Natural Product-Based Potential Therapeutic Interventions of Pulmonary Fibrosis

Pulmonary fibrosis (PF) is a disease-refractive lung condition with an increased rate of mortality. The potential factors causing PF include viral infections, radiation exposure, and toxic airborne chemicals. Idiopathic PF (IPF) is related to pneumonia affecting the elderly and is characterized by recurring scar formation in the lungs. An impaired wound healing process, defined by the dysregulated aggregation of extracellular matrix components, triggers fibrotic scar formation in the lungs. The potential pathogenesis includes oxidative stress, altered cell signaling, inflammation, etc. Nintedanib and pirfenidone have been approved with a conditional endorsement for the management of IPF. In addition, natural product-based treatment strategies have shown promising results in treating PF. In this study, we reviewed the recently published literature and discussed the potential uses of natural products, classified into three types-isolated active compounds, crude extracts of plants, and traditional medicine, consisting of mixtures of different plant products-in treating PF. These natural products are promising in the treatment of PF via inhibiting inflammation, oxidative stress, and endothelial mesenchymal transition, as well as affecting TGF-β-mediated cell signaling, etc. Based on the current review, we have revealed the signaling mechanisms of PF pathogenesis and the potential opportunities offered by natural product-based medicine in treating PF.

HSP90 as a regulator of extracellular matrix dynamics

The extracellular matrix (ECM) is a dynamic and organised extracellular network assembled from proteins and carbohydrates exported from the cell. The ECM is critical for multicellular life, providing spatial and temporal cellular cues to maintain tissue homeostasis. Consequently, ECM production must be carefully balanced with turnover to ensure homeostasis; ECM dysfunction culminates in disease. Hsp90 is a molecular chaperone central to protein homeostasis, including in the ECM. Intracellular and extracellular Hsp90 isoforms collaborate to regulate the levels and status of proteins in the ECM via multiple mechanisms. In so doing, Hsp90 regulates ECM dynamics, and changes in Hsp90 levels or activity support the development of ECM-related diseases, like cancer and fibrosis. Consequently, Hsp90 levels may have prognostic value, while inhibition of Hsp90 may have therapeutic potential in conditions characterised by ECM dysfunction.

Dietary Phytoestrogens Ameliorate Hydrochloric Acid-Induced Chronic Lung Injury and Pulmonary Fibrosis in Mice

We previously reported that female mice exhibit protection against chemically induced pulmonary fibrosis and suggested a potential role of estrogen. Phytoestrogens act, at least in part, via stimulation of estrogen receptors; furthermore, compared to residents of Western countries, residents of East Asian countries consume higher amounts of phytoestrogens and exhibit lower rates of pulmonary fibrosis. Therefore, we tested the hypothesis that dietary phytoestrogens ameliorate the severity of experimentally induced pulmonary fibrosis. Male mice placed on either regular soybean diet or phytoestrogen-free diet were instilled with 0.1 N HCl to provoke pulmonary fibrosis. Thirty days later, lung mechanics were measured as indices of lung function and bronchoalveolar lavage fluid (BALF) and lung tissue were analyzed for biomarkers of fibrosis. Mice on phytoestrogen-free diet demonstrated increased mortality and stronger signs of chronic lung injury and pulmonary fibrosis, as reflected in the expression of collagen, extracellular matrix deposition, histology, and lung mechanics, compared to mice on regular diet. We conclude that dietary phytoestrogens play an important role in the pathogenesis of pulmonary fibrosis and suggest that phytoestrogens (e.g., genistein) may be useful as part of a therapeutic regimen against hydrochloric acid-induced lung fibrosis and chronic lung dysfunction.

TSSK4 upregulation in alveolar epithelial type-II cells facilitates pulmonary fibrosis through HSP90-AKT signaling restriction and AT-II apoptosis

Alveolar epithelial injury is one of the important pathological changes in idiopathic pulmonary interstitial fibrosis (IPF), but the regulatory mechanism remains unclear. Here, we reported that alveolar epithelial type-II cells (AT II) play important roles in pathological process of pulmonary fibrosis. Through iTRAQ (isobaric tagging for relative and absolute quantification) quantitative proteomics, TSSK4 was identified to be upregulated in bleomycin-induced fibrotic mice model, which was further confirmed in clinical IPF patients' tissue specimens. TSSK4 is a germ-related protein, but its expression in other tissues and the association with other diseases are not reported. Immunofluorescence staining showed that TSSK4 selectively expressed in AT-II cells, which are essential for inflammation-induced AT-II loss during fibrosis. Luciferase assay and other molecular biological experiments proved that TSSK4 expression is regulated by TNF-α-mediated NF-κB signaling. The TSSK4 kinase activity is found to be closely related to the function of HSP90-AKT pathway that TSSK4 can phosphorylate its substrate HSP90β on serine 255, to inhibit the ATPase activity of HSP90β and reduce its molecular chaperone function on AKT. Under this condition, kinase activity of AKT is diminished to interfere its survival function, subsequently facilitating AT-II cellular apoptosis through the mitochondrial death machinery. Our findings highlight the importance of TSSK4 in regulating pulmonary fibrosis by facilitating AT-II loss through HSP90-AKT signaling, all of which suggest TSSK4 and the regulating mechanism as attractive targets for the clinical intervention of pulmonary injury and fibrosis.

Extracellular HSP90α Interacts With ER Stress to Promote Fibroblasts Activation Through PI3K/AKT Pathway in Pulmonary Fibrosis

Pulmonary fibrosis is characterized by alveolar epithelial cell injury, lung fibroblast proliferation, differentiation, and extracellular matrix (ECM) deposition. Our previous study indicated that extracellular HSP90α (eHSP90α) promotes pulmonary fibrosis by activating the MAPK signaling pathway. Thus, treatment with 1G6-D7 (a selective HSP90α monoclonal antibody) to antagonize eHSP90α could effectively ameliorate fibrosis. This study aimed to elucidate the mechanism underlying the effects of eHSP90α in pulmonary fibrosis by focusing on its link with endoplasmic reticulum (ER) stress. Our results showed that eHSP90α promoted lung fibroblast differentiation by activating ER stress. Treatment with the ER stress inhibitor tauroursodeoxycholate (TUDCA) or glucose-regulated protein 78 kDa (GRP78) depletion significantly abrogated the effect of eHSP90α on ER stress and fibroblast activation. In addition, eHSP90α induced ER stress in fibroblasts via the phosphoinositide-4,5-bisphosphate 3-kinase (PI3K)-protein kinase B (AKT) signaling pathway, which could be blocked by the PI3K/AKT inhibitor LY294002, and blockade of eHSP90α by 1G6-D7 markedly inhibited ER stress in the model, indicating preventive and therapeutic applications. Intriguingly, we observed that TUDCA effectively reduced the secretion of eHSP90α in vitro and in vivo. In conclusion, this study shows that the interaction between eHSP90α and ER stress plays a crucial role in pulmonary fibrosis, indicating a positive feedback in lung fibroblasts. Targeting eHSP90α and alleviating fibroblast ER stress may be promising therapeutic approaches for pulmonary fibrosis.

Fibrotic Idiopathic Interstitial Lung Disease: The Molecular and Cellular Key Players

Interstitial lung diseases (ILDs) that are known as diffuse parenchymal lung diseases (DPLDs) lead to the damage of alveolar epithelium and lung parenchyma, culminating in inflammation and widespread fibrosis. ILDs that account for more than 200 different pathologies can be divided into two groups: ILDs that have a known cause and those where the cause is unknown, classified as idiopathic interstitial pneumonia (IIP). IIPs include idiopathic pulmonary fibrosis (IPF), non-specific interstitial pneumonia (NSIP), cryptogenic organizing pneumonia (COP) known also as bronchiolitis obliterans organizing pneumonia (BOOP), acute interstitial pneumonia (AIP), desquamative interstitial pneumonia (DIP), respiratory bronchiolitis-associated interstitial lung disease (RB-ILD), and lymphocytic interstitial pneumonia (LIP). In this review, our aim is to describe the pathogenic mechanisms that lead to the onset and progression of the different IIPs, starting from IPF as the most studied, in order to find both the common and standalone molecular and cellular key players among them. Finally, a deeper molecular and cellular characterization of different interstitial lung diseases without a known cause would contribute to giving a more accurate diagnosis to the patients, which would translate to a more effective treatment decision.

Age-Dependent Chronic Lung Injury and Pulmonary Fibrosis following Single Exposure to Hydrochloric Acid

Exposure to hydrochloric acid (HCl) represents a threat to public health. Children may inhale higher doses and develop greater injury because of their smaller airways and faster respiratory rate. We have developed a mouse model of pediatric exposure to HCl by intratracheally instilling p24 mice (mice 24 days old; 8-10 g) with 2 µL/g 0.1 N HCl, and compared the profile of lung injury to that in HCl-instilled adults (10 weeks old; 25-30 g) and their age-matched saline controls. After 30 days, alveolar inflammation was observed with increased proteinosis and mononuclear cells in the bronchoalveolar lavage fluid (BALF) in both HCl-instilled groups. Young p24 animals-but not adults-exhibited higher NLR family pyrin domain containing 3 (NLRP3) inflammasome levels. Increased amounts of Transforming Growth Factor-β (TGF-β) mRNA and its intracellular canonical and non-canonical pathways (p-Smad2 and p-ERK) were found in the lungs of both young and adult HCl-instilled mice. Constitutive age-related differences were observed in the levels of heat shock protein family (HSP70 and HSP90). HCl equally provoked the deposition of collagen and fibronectin; however, significant age-dependent differences were observed in the increase in elastin and tenascin C mRNA. HCl induced pulmonary fibrosis with an increased Ashcroft score, which was higher in adults, and a reduction in alveolar Mean Alveolar Linear Intercept (MALI). Young mice developed increased Newtonian resistance (Rn) and lower PV loops, while adults showed a higher respiratory system resistance and elastance. This data indicate that young p24 mice can suffer long-term complications from a single exposure to HCl, and can develop chronic lung injury characterized by a stronger persistent inflammation and lesser fibrotic pattern, mostly in the airways, differently from adults. Further data are required to characterize HCl time- and dose-dependent injury in young animals and to identify new key-molecular targets.

Kurarinone Attenuates BLM-Induced Pulmonary Fibrosis via Inhibiting TGF-β Signaling Pathways

Idiopathic pulmonary fibrosis (IPF) is a refractory interstitial lung disease for which there is no effective treatment. Although the pathogenesis of IPF is not fully understood, TGF-β and epithelial-mesenchymal transition (EMT) have been shown to be involved in the fibrotic changes of lung tissues. Kurarinone is a prenylated flavonoid isolated from Sophora Flavescens with antioxidant and anti-inflammatory properties. In this study, we investigated the effect of kurarinone on pulmonary fibrosis. Kurarinone suppressed the TGF-β-induced EMT of lung epithelial cells. To assess the therapeutic effects of kurarinone in bleomycin (BLM)-induced pulmonary fibrosis, mice were treated with kurarinone daily for 2 weeks starting 7 days after BLM instillation. Oral administration of kurarinone attenuated the fibrotic changes of lung tissues, including accumulation of collagen and improved mechanical pulmonary functions. Mechanistically, kurarinone suppressed phosphorylation of Smad2/3 and AKT induced by TGF-β1 in lung epithelial cells, as well as in lung tissues treated with BLM. Taken together, these results suggest that kurarinone has a therapeutic effect on pulmonary fibrosis via suppressing TGF-β signaling pathways and may be a novel drug candidate for pulmonary fibrosis.

The HSP90 Inhibitor, AUY-922, Protects and Repairs Human Lung Microvascular Endothelial Cells from Hydrochloric Acid-Induced Endothelial Barrier Dysfunction

Exposure to hydrochloric acid (HCl) leads acutely to asthma-like symptoms, acute respiratory distress syndrome (ARDS), including compromised alveolo-capillary barrier, and respiratory failure. To better understand the direct effects of HCl on pulmonary endothelial function, we studied the characteristics of HCl-induced endothelial barrier dysfunction in primary cultures of human lung microvascular endothelial cells (HLMVEC), defined the involved molecular pathways, and tested the potentially beneficial effects of Heat Shock Protein 90 (HSP90) inhibitors. HCl impaired barrier function in a time- and concentration-dependent manner and was associated with activation of Protein Kinase B (AKT), Ras homolog family member A (RhoA) and myosin light chain 2 (MLC2), as well as loss of plasmalemmal VE-cadherin, rearrangement of cortical actin, and appearance of inter-endothelial gaps. Pre-treatment or post-treatment of HLMVEC with AUY-922, a third-generation HSP90 inhibitor, prevented and restored HCl-induced endothelial barrier dysfunction. AUY-922 increased the expression of HSP70 and inhibited the activation (phosphorylation) of extracellular-signal regulated kinase (ERK) and AKT. AUY-922 also prevented the HCl-induced activation of RhoA and MLC2 and the internalization of plasmalemmal VE-cadherin. We conclude that, by increasing the expression of cytoprotective proteins, interfering with actomyosin contractility, and enhancing the expression of junction proteins, inhibition of HSP90 may represent a useful approach for the management of HCl-induced endothelial dysfunction and acute lung injury.

Molecular Pathogenesis of Pulmonary Fibrosis, with Focus on Pathways Related to TGF-β and the Ubiquitin-Proteasome Pathway

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal interstitial lung disease. During the past decade, novel pathogenic mechanisms of IPF have been elucidated that have shifted the concept of IPF from an inflammatory-driven to an epithelial-driven disease. Dysregulated repair responses induced by recurrent epithelial cell damage and excessive extracellular matrix accumulation result in pulmonary fibrosis. Although there is currently no curative therapy for IPF, two medications, pirfenidone and nintedanib, have been introduced based on understanding the pathogenesis of the disease. In this review, we discuss advances in understanding IPF pathogenesis, highlighting epithelial-mesenchymal transition (EMT), the ubiquitin-proteasome system, and endothelial cells. TGF-β is a central regulator involved in EMT and pulmonary fibrosis. HECT-, RING finger-, and U-box-type E3 ubiquitin ligases regulate TGF-β-Smad pathway-mediated EMT via the ubiquitin-proteasome pathway. p27 degradation mediated by the SCF-type E3 ligase, Skp2, contributes to the progression of pulmonary fibrosis by promotion of either mesenchymal fibroblast proliferation, EMT, or both. In addition to fibroblasts as key effector cells in myofibroblast differentiation and extracellular matrix deposition, endothelial cells also play a role in the processes of IPF. Endothelial cells can transform into myofibroblasts; therefore, endothelial-mesenchymal transition can be another source of myofibroblasts.

Sex-Related Differences in Murine Models of Chemically Induced Pulmonary Fibrosis

We developed two models of chemically induced chronic lung injury and pulmonary fibrosis in mice (intratracheally administered hydrochloric acid (HCl) and intratracheally administered nitrogen mustard (NM)) and investigated male–female differences. Female mice exhibited higher 30-day survival and less weight loss than male mice. Thirty days after the instillation of either HCl or NM, bronchoalveolar lavage fluid displayed a persistent, mild inflammatory response, but with higher white blood cell numbers and total protein content in males vs. females. Furthermore, females exhibited less collagen deposition, milder pulmonary fibrosis, and lower Ashcroft scores. After instillation of either HCl or NM, all animals displayed increased values of phosphorylated (activated) Heat Shock Protein 90, which plays a crucial role in the alveolar wound-healing processes; however, females presented lower activation of both transforming growth factor-β (TGF-β) signaling pathways: ERK and SMAD. We propose that female mice are protected from chronic complications of a single exposure to either HCl or NM through a lesser activation of TGF-β and downstream signaling. The understanding of the molecular mechanisms that confer a protective effect in females could help develop new, gender-specific therapeutics for IPF.

Small Hsps as Therapeutic Targets of Cystic Fibrosis Transmembrane Conductance Regulator Protein

Human small heat shock proteins are molecular chaperones that regulate fundamental cellular processes in normal and pathological cells. Here, we have reviewed the role played by HspB1, HspB4 and HspB5 in the context of Cystic Fibrosis (CF), a severe monogenic autosomal recessive disease linked to mutations in Cystic Fibrosis Transmembrane conductance Regulator protein (CFTR) some of which trigger its misfolding and rapid degradation, particularly the most frequent one, F508del-CFTR. While HspB1 and HspB4 favor the degradation of CFTR mutants, HspB5 and particularly one of its phosphorylated forms positively enhance the transport at the plasma membrane, stability and function of the CFTR mutant. Moreover, HspB5 molecules stimulate the cellular efficiency of currently used CF therapeutic molecules. Different strategies are suggested to modulate the level of expression or the activity of these small heat shock proteins in view of potential in vivo therapeutic approaches. We then conclude with other small heat shock proteins that should be tested or further studied to improve our knowledge of CFTR processing.

Heat shock protein 90 inhibitor ameliorates pancreatic fibrosis by degradation of transforming growth factor-β receptor

BACKGROUND AND AIM

Pancreatic fibrosis increases pancreatic cancer risk in chronic pancreatitis (CP). Pancreatic stellate cells (PSCs) play a critical role in pancreatic fibrosis by transforming growth factor-β (TGFβ) has been shown to inhibit transforming growth factor-β receptor (TGFβR)-mediated Smad and no-Smad signaling pathways. Thus, the effects of Hsp90 inhibitor on pancreatic fibrosis are evaluated in CP mice, and the association between Hsp90 and biological functions of PSCs is further investigated in vitro.

METHODS

The effects of Hsp90 inhibitor 17AAG on pancreatic fibrosis were assessed in caerulein-induced CP mice, and primary PSCs were used to determine the role of Hsp90 inhibitor 17AAG in vitro.

RESULTS

We observed increased expression of Hsp90 in pancreatic tissues of caerulein-induced CP mice. Hsp90 inhibitor 17AAG ameliorated pancreatic inflammation and fibrosis in caerulein-induced CP mice. In vitro, Hsp90 inhibitor 17AAG inhibited TGFβ1-induced activation and extracellular matrix accumulation of PSCs by blocking TGFβR-mediated Smad2/3 and PI3K /Akt/GSK-3β signaling pathways.Hsp90 inhibitor 17AAG degraded TGFβRII by a ubiquitin-proteasome pathway, co-immunoprecipitation showed an interaction between Hsp90 and TGFβRII in PSCs.

CONCLUSIONS

The study suggests that an Hsp90 inhibitor 17AAG remarkable prevents the development of pancreatic fibrosis in caerulein-induced CP mice, and suppresses activation and extracellular matrix accumulation of PSCs in vitro. The current results provide a potential treatment strategy based on Hsp90 inhibition for pancreatic fibrosis in CP.