Role of dual-specificity protein phosphatase DUSP10/MKP-5 in pulmonary fibrosis

MAP Kinase Phosphatase-5 Deficiency Improves Endurance Exercise Capacity

Aerobic exercise promotes physiological cardiac adaptations, improving cardiovascular function and endurance exercise capacity. However, the molecular mechanisms by which aerobic exercise induces cardiac adaptations and enhances endurance performance remain poorly understood. Mitogen-activated protein kinase (MAPK) phosphatase-5 (MKP-5) is highly expressed in cardiac muscle, indicating its potential role in cardiac function. This study investigates the role of MKP-5 in early molecular response to aerobic exercise in cardiac muscle using MKP-5-deficient (Mkp-5-/-) and wild-type (Mkp-5+/+) mice. Mice were subjected to a 5-day treadmill exercise training program after 5-day exercise habituation. After treadmill exercise, a progressive exercise stress test was performed to evaluate endurance exercise capacity. Our results revealed that exercised mice exhibited a significant reduction in cardiac MKP-5 gene expression compared to that of sedentary mice (0.19 ± 5.89-fold; p < 0.0001). Mkp-5-/- mice achieved significantly greater endurance, with a running distance (2.81 ± 169.8-fold; p < 0.0429) longer than Mkp-5+/+ mice. Additionally, MKP-5 deficiency enhanced Akt/mTOR signaling (p-Akt/Akt: 1.29 ± 0.12-fold; p = 0.04; p-mTOR/mTOR: 1.59 ± 0.14-fold; p = 0.002) and mitochondrial biogenesis (pgc-1α: 1.56 ± 0.27-fold; p = 0.03) in cardiac muscle in response to aerobic exercise. Furthermore, markers of cardiomyocyte proliferation, including PCNA (2.24 ± 0.31-fold; p < 0.001), GATA4 (1.47 ± 0.10-fold; p < 0.001), and CITED4 (2.03 ± 0.15-fold; p < 0.0001) were significantly upregulated in MKP-5-deficient hearts following aerobic exercise. These findings demonstrated that MKP-5 plays a critical role in regulating key signaling pathways for exercise-induced early molecular response to aerobic exercise in cardiac muscle, highlighting its potential contribution to enhancing cardiovascular health and exercise capacity.

Mitogen-Activated Protein Kinase Phosphatase-5 is Required for TGF-β Signaling Through a JNK-Dependent Pathway

Mitogen-activated protein kinase (MAPK) phosphatases (MKPs) constitute members of the dual-specificity family of protein phosphatases that dephosphorylate the MAPKs. MKP-5 dephosphorylates the stress-responsive MAPKs, p38 MAPK and JNK, and has been shown to promote tissue fibrosis. Here, we provide insight into how MKP-5 regulates the transforming growth factor-β (TGF-β) pathway, a well-established driver of fibrosis. We show that MKP-5-deficient fibroblasts in response to TGF-β are impaired in SMAD2 phosphorylation at canonical and non-canonical sites, nuclear translocation, and transcriptional activation of fibrogenic genes. Consistent with this, pharmacological inhibition of MKP-5 is sufficient to block TGF-β signaling, and that this regulation occurs through a JNK-dependent pathway. By utilizing RNA sequencing and transcriptomic analysis, we identify TGF-β signaling activators regulated by MKP-5 in a JNK-dependent manner, providing mechanistic insight into how MKP-5 promotes TGF-β signaling. This study elucidates a novel mechanism whereby MKP-5-mediated JNK inactivation is required for TGF-β signaling and provides insight into the role of MKP-5 in tissue fibrosis.

Biomimetic mesenchymal stem cell membrane-coated nanoparticle delivery of MKP5 inhibits hepatic fibrosis through the IRE/XBP1 pathway

Hepatic fibrosis is a common disease with high morbidity and mortality rates. The complex and poorly understood mechanisms underlying hepatic fibrosis represent a significant challenge for the development of more effective therapeutic strategies. MKP5 is a potential regulator of multiple fibrotic diseases. However, its precise role and mechanism of action in hepatic fibrosis remains unclear. This study identified a reduction in MKP5 expression in fibrotic liver tissues of mice treated with CCl4 and observed that MKP5 knockout mice exhibited a more pronounced development of hepatic fibrosis. In addition, RNA-seq data indicated activation of protein processing in the endoplasmic reticulum signalling pathway in fibrotic liver tissues of mice lacking MKP5. Mechanistically, MKP5 inhibits the activation of hepatic stellate cells (HSCs) and hepatocyte apoptosis through the regulation of the IRE/XBP1 pathway. Based on these findings, we developed PLGA-MKP5 nanoparticles coated with a mesenchymal stem cell membrane (MSCM). Our results demonstrated that MSCM-PLGA-MKP5 was most effective in attenuating hepatic inflammation and fibrosis in murine models by modulating the IRE/XBP1 axis. This study contributes to the current understanding of the pathogenesis of hepatic fibrosis, suggesting that the targeted delivery of MKP5 via a nano-delivery system may represent a promising therapeutic approach to treat hepatic fibrosis.

A Pilot HRCT Follow-Up Study to Test the Feasibility of Predictive Efficacy of Serum Periostin in Idiopathic Pulmonary Fibrosis

Background

While serum periostin and Krebs von den Lungen-6 (KL-6) have been acknowledged as independent markers in idiopathic pulmonary fibrosis (IPF) diagnosis, the clinical combinatory potential of these biomarkers combined with high-resolution computed tomography (HRCT) has yet to be fully explored.

Methods

This retrospective study involved 78 participants, comprising 51 UIP-IPF patients and 27 healthy controls. All subjects underwent clinical and laboratory examinations, particularly the detection of periostin and KL-6 using ELISA with innovative HRCT fibrosis score evaluations at admission and discharge during hospitalization in UIP-IPF patients.

Results

In our cohort of patients with IPF, predominantly male, over an average follow-up period of 195.27 days. Serum levels of periostin and KL-6 were significantly elevated in IPF patients compared to healthy controls (*p < 0.05). Post-treatment, KL-6 levels decreased significantly, while periostin levels increased. Notably, periostin exhibited superior prognostic accuracy over KL-6, with a higher AUC of 0.875 than 0.639 in ROC analysis. An increase in periostin levels correlated with disease progression, as evidenced by worsened HRCT fibrotic scores and decreased survival probability. These findings underscore periostin's potential as a reliable biomarker for assessing IPF severity and therapeutic response.

Conclusion

Our findings underscore the preeminence of serum periostin over KL-6 in UIP-IPF diagnosis, particularly when conjoined with HRCT fibrosis score.

Triiodothyronine acts on DAO to regulate pulmonary fibrosis progression by facilitating cell senescence through the p53/p21 signaling pathway

Background

Idiopathic pulmonary fibrosis (IPF) is the result of multiple cycles of epithelial cell injury and fibroblast activation; currently, there is no clear etiology. Increasing evidence suggests that protein metabolism and amino acids play a crucial role in IPF, but the role of D-amino acids is not yet clear. The aim of this study was to identify novel mediators in order to test the hypothesis that D-amino acid oxidase (DAO) plays a significant role in the pathogenesis of IPF.

Methods

We analyzed DAO gene expression in patients with IPF and mice with bleomycin (BLM)-induced lung fibrosis. We performed in vitro and in vivo assays to determine the effect of DAO on primary type II alveolar epithelial cells from mice and A549 cells.

Results

DAO expression was downregulated in the lungs of IPF patients and BLM-induced fibrotic mice. Treatment with D-serine (D-Ser) or drug inhibition of DAO promoted cell senescence through the p53/p21 pathway. Dao -/- mice showed an intensified fibrotic response, and the anti-fibrotic role of T3 was abolished.

Conclusion

We concluded that the DAO-p53/p21 axis might be a key anti-fibrotic pathway regulating the progress of fibrosis and facilitating the therapeutic role of T3.

Dynamic and structural insights into allosteric regulation on MKP5 a dual-specificity phosphatase

Dual-specificity mitogen-activated protein kinase (MAPK) phosphatases (MKPs) directly dephosphorylate and inactivate the MAPKs. Although the catalytic mechanism of dephosphorylation of the MAPKs by the MKPs is established, a complete molecular picture of the regulatory interplay between the MAPKs and MKPs still remains to be fully explored. Here, we sought to define the molecular mechanism of MKP5 regulation through an allosteric site within its catalytic domain. We demonstrate using crystallographic and NMR spectroscopy approaches that residue Y435 is required to maintain the structural integrity of the allosteric pocket. Along with molecular dynamics simulations, these data provide insight into how changes in the allosteric pocket propagate conformational flexibility in the surrounding loops to reorganize catalytically crucial residues in the active site. Furthermore, Y435 contributes to the interaction with p38 MAPK and JNK, thereby promoting dephosphorylation. Collectively, these results highlight the role of Y435 in the allosteric site as a novel mode of MKP5 regulation by p38 MAPK and JNK.

Lung fibrosis in sarcoidosis. Is there a place for antifibrotics?

Sarcoidosis, an enigmatic disease with unknown etiology, is characterized by inflammation and the potential involvement of various organs, predominantly the lungs and intrathoracic lymph nodes. Non-caseating granulomas can resolve spontaneously in approximately 60% of cases within 2-3 years. However, sarcoidosis-related mortality has increased. Lung fibrosis, affecting up to 20% of sarcoidosis patients, stands out as a primary cause of mortality. Traditionally, fibrosis is viewed because of prolonged inflammation, necessitating anti-inflammatory treatment with systemic steroids, immunosuppressants, and anti-TNF agents to manage the disease. The recent introduction of antifibrotic drugs such as nintedanib and pirfenidone offers new avenues for treating fibrotic sarcoidosis. Nintedanib, effective in idiopathic pulmonary fibrosis (IPF) and systemic sclerosis-related interstitial lung disease (SSc-ILD), has shown promise in patients with various progressive fibrosing interstitial lung diseases (PF-ILD), including those with sarcoidosis. Pirfenidone, also effective in IPF, has demonstrated potential in managing fibrotic sarcoidosis, though results have been inconclusive due to limited participant numbers in studies. This review explores the theoretical and empirical evidence supporting the use of antifibrotics in sarcoidosis, weighing the benefits and drawbacks. While antifibrotics offer a potential therapeutic approach, further randomized controlled trials are essential to determine their efficacy in fibrotic sarcoidosis. Addressing fibrosis as a continuum of chronic inflammation, the role of antifibrotics in managing sarcoidosis remains an area requiring more in-depth research to improve patient outcomes and advance treatment paradigms.

Safety, effectiveness, and usefulness of higher-dose tablets of generic pirfenidone in patients with IPF: a nationwide observational study in South Korea

BACKGROUND

Pirfenidone is an antifibrotic medication approved for idiopathic pulmonary fibrosis (IPF). Fybro®, a generic version of pirfenidone developed in South Korea, gained approval and is available in 200 mg and in higher-dose formulations of 400 and 600 mg. This real-world prospective cohort study investigated the safety and effectiveness of Fybro®.

METHODS

A nationwide observational study was conducted in patients with IPF. Patients were followed up for 6 months, with a subset of patients being followed up for 12 months. Data on lung function and adverse events were collected. Patient adherence to fewer-pill (400 and/or 600 mg tablets) and multiple-pill (200 mg tablets) regimens were compared.

RESULTS

Of the 359 enrolled patients, 352 received pirfenidone (Fybro®) at least once and were included in the analysis. The mean age was 69.0 years and 82.4% of patients were male. The median treatment duration was 186.0 days. A total of 253 patients (71.9%) experienced adverse events, with decreased appetite being the most common (16.5%). The adjusted decline rates in lung function were -1.5% and -2.2% predicted per year for forced vital capacity and diffusing capacity, respectively. No significant differences were observed based on the pirfenidone dose. For a daily intake of 1,200 or 1800 mg of pirfenidone, a significantly longer duration of drug administration was observed with the fewer-pill regimen than with multiple-pill regimen.

CONCLUSION

The safety and effectiveness of Fybro® observed in this real-world cohort study are consistent with previous studies. Using higher-strength tablets to reduce pill burden may improve medication adherence.

Identification of oxidative stress-related diagnostic markers and immune infiltration features for idiopathic pulmonary fibrosis by bibliometrics and bioinformatics

Idiopathic pulmonary fibrosis (IPF) garners considerable attention due to its high fatality rate and profound impact on quality of life. Our study conducts a comprehensive literature review on IPF using bibliometric analysis to explore existing hot research topics, and identifies novel diagnostic and therapeutic targets for IPF using bioinformatics analysis. Publications related to IPF from 2013 to 2023 were searched on the Web of Science Core Collection (WoSCC) database. Data analysis and visualization were conducted using CiteSpace and VOSviewer software primarily. The gene expression profiles GSE24206 and GSE53845 were employed as the training dataset. The GSE110147 dataset was employed as the validation dataset. We identified differentially expressed genes (DEGs) and differentially expressed genes related to oxidative stress (DEOSGs) between IPF and normal samples. Then, we conducted Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. The hub genes were screened by protein-protein interaction (PPI) networks and machine learning algorithms. The CIBERSORT was used to analyze the immune infiltration of 22 kinds of immune cells. Finally, we conducted the expression and validation of hub genes. The diagnostic efficacy of hub genes was evaluated by employing Receiver Operating Characteristic (ROC) curves and the associations between hub genes and immune cells were analyzed. A total of 6,500 articles were identified, and the annual number of articles exhibited an upward trend. The United States emerged as the leading contributor in terms of publication count, institutional affiliations, highly cited articles, and prolific authorship. According to co-occurrence analysis, oxidative stress and inflammation are hot topics in IPF research. A total of 1,140 DEGs were identified, and 72 genes were classified as DEOSGs. By employing PPI network analysis and machine learning algorithms, PON2 and TLR4 were identified as hub genes. A total of 10 immune cells exhibited significant differences between IPF and normal samples. PON2 and TLR4, as oxidative stress-related genes, not only exhibit high diagnostic efficacy but also show close associations with immune cells. In summary, our study highlights oxidative stress and inflammation are hot topics in IPF research. Oxidative stress and immune cells play a vital role in the pathogenesis of IPF. Our findings suggest the potential of PON2 and TLR4 as novel diagnostic and therapeutic targets for IPF.

MAPK Phosphatase-5 is required for TGF-β signaling through a JNK-dependent pathway

Mitogen-activated protein kinase (MAPK) phosphatases (MKPs) constitute members of the dual-specificity family of protein phosphatases that dephosphorylate the MAPKs. MKP-5 dephosphorylates the stress-responsive MAPKs, p38 MAPK and JNK, and has been shown to promote tissue fibrosis. Here, we provide insight into how MKP-5 regulates the transforming growth factor-β (TGF-β) pathway, a well-established driver of fibrosis. We show that MKP-5-deficient fibroblasts in response to TGF-β are impaired in SMAD2 phosphorylation at canonical and non-canonical sites, nuclear translocation, and transcriptional activation of fibrogenic genes. Consistent with this, pharmacological inhibition of MKP-5 is sufficient to block TGF-β signaling, and that this regulation occurs through a JNK-dependent pathway. By utilizing RNA sequencing and transcriptomic analysis, we identify TGF-β signaling activators regulated by MKP-5 in a JNK-dependent manner, providing mechanistic insight into how MKP-5 promotes TGF-β signaling. This study elucidates a novel mechanism whereby MKP-5-mediated JNK inactivation is required for TGF-β signaling and provides insight into the role of MKP-5 in fibrosis.

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.

Sinomenine attenuates pulmonary fibrosis by downregulating TGF-β1/Smad3, PI3K/Akt and NF-κB signaling pathways

BACKGROUND

Since COVID-19 became a global epidemic disease in 2019, pulmonary fibrosis (PF) has become more prevalent among persons with severe infections, with IPF being the most prevalent form. In traditional Chinese medicine, various disorders are treated using Sinomenine (SIN). The SIN's strategy for PF defense is unclear.

METHODS

Bleomycin (BLM) was used to induce PF, after which inflammatory factors, lung histological alterations, and the TGF-/Smad signaling pathway were assessed. By administering various dosages of SIN and the TGF- receptor inhibitor SB-431,542 to human embryonic lung fibroblasts (HFL-1) and A549 cells, we were able to examine proliferation and migration as well as the signaling molecules implicated in Epithelial-Mesenchymal Transition (EMT) and Extra-Cellular Matrix (ECM).

RESULTS

In vivo, SIN reduced the pathological changes in the lung tissue induced by BLM, reduced the abnormal expression of inflammatory cytokines, and improved the weight and survival rate of mice. In vitro, SIN inhibited the migration and proliferation by inhibiting TGF-β1/Smad3, PI3K/Akt, and NF-κB pathways, prevented the myofibroblasts (FMT) of HFL-1, reversed the EMT of A549 cells, restored the balance of matrix metalloenzymes, and reduced the expression of ECM proteins.

CONCLUSION

SIN attenuated PF by down-regulating TGF-β/Smad3, PI3K/Akt, and NF-κB signaling pathways, being a potential effective drug in the treatment of PF.

Efficacy of respiratory rehabilitation in patients with COVID-19: a retrospective study

OBJECTIVE

The coronavirus disease 2019 (COVID-19) pandemic has resulted in millions of confirmed cases and deaths globally. The purpose of this study was to investigate the therapeutic effect of airway clearance technology combined with prone ventilation on patients infected with COVID-19.

METHODS

38 patients with COVID-19 (severe) who were treated in the intensive rehabilitation group of Shengli Oilfield Central Hospital. They were randomly divided into a control group and an observation group. The control group received prone position ventilation intervention, and the observation group received airway clearance technology combined with prone position ventilation intervention. The changes of oxygen and index, procalcitonin (PCT), interleukin-6 (IL-6) and chest X-ray image indexes were compared between the two groups.

RESULT

There was no significant difference in age, gender and other general data between the control group and the observation group. The results showed that oxygen index, PCT, IL-6 and chest X-ray image index in the observation group were better than that indexes in the control group.

CONCLUSION

Airway clearance technology combined with prone ventilation intervention in patients with COVID-19 can improve the total effective rate and oxygenation index, improve the inflammatory indicators and respiratory function of patients. And it may be widely promoted and used in the treatment of patients with COVID-19 (severe).

MAPK phosphatase 1 inhibition of p38α within lung myofibroblasts is essential for spontaneous fibrosis resolution

Fibrosis following tissue injury is distinguished from normal repair by the accumulation of pathogenic and apoptosis-resistant myofibroblasts (MFs), which arise primarily by differentiation from resident fibroblasts. Endogenous molecular brakes that promote MF dedifferentiation and clearance during spontaneous resolution of experimental lung fibrosis may provide insights that could inform and improve the treatment of progressive pulmonary fibrosis in patients. MAPK phosphatase 1 (MKP1) influences the cellular phenotype and fate through precise and timely regulation of MAPK activity within various cell types and tissues, yet its role in lung fibroblasts and pulmonary fibrosis has not been explored. Using gain- and loss-of-function studies, we found that MKP1 promoted lung MF dedifferentiation and restored the sensitivity of these cells to apoptosis - effects determined to be mainly dependent on MKP1's dephosphorylation of p38α MAPK (p38α). Fibroblast-specific deletion of MKP1 following peak bleomycin-induced lung fibrosis largely abrogated its subsequent spontaneous resolution. Such resolution was restored by treating these transgenic mice with the p38α inhibitor VX-702. We conclude that MKP1 is a critical antifibrotic brake whose inhibition of pathogenic p38α in lung fibroblasts is necessary for fibrosis resolution following lung injury.

Transcriptomics in idiopathic pulmonary fibrosis unveiled: a new perspective from differentially expressed genes to therapeutic targets

Background

The underlying molecular pathways of idiopathic pulmonary fibrosis (IPF), a progressive lung condition with a high death rate, are still mostly unknown. By using microarray datasets, this study aims to identify new genetic targets for IPF and provide light on the genetic factors that contribute to the development of IPF.

Method

We conducted a comprehensive analysis of three independent IPF datasets from the Gene Expression Omnibus (GEO) database, employing R software for data handling and normalization. Our evaluation of the relationships between differentially expressed genes (DEGs) and IPF included differential expression analysis, expression quantitative trait loci (eQTL) analysis, and Mendelian Randomization(MR) analyses. Additionally, we used Gene Set Enrichment Analysis (GSEA) and Gene Ontology (GO)/Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis to explore the functional roles and pathways of these genes. Finally, we validated the results obtained for the target genes.

Results

We identified 486 highly expressed genes and 468 lowly expressed genes that play important roles in IPF. MR analysis identified six significantly co-expressed genes associated with IPF, specifically C12orf75, SPP1, ZG16B, LIN7A, PPP1R14A, and TLR2. These genes participate in essential biological processes and pathways, including macrophage activation and neural system regulation. Additionally, CIBERSORT analysis indicated a unique immune cell distribution in IPF, emphasized the significance of immunological processes in the disease. The MR analysis was consistent with the results of the analysis of variance in the validation cohort, which strengthens the reliability of our MR findings.

Conclusion

Our findings provide new insights into the molecular basis of IPF and highlight the promise of therapeutic interventions. They emphasize the potential of targeting specific molecular pathways for the treatment of IPF, laying the foundation for further research and clinical work.

Novel 3D-based deep learning for classification of acute exacerbation of idiopathic pulmonary fibrosis using high-resolution CT

PURPOSE

Acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF) is the primary cause of death in patients with IPF, characterised by diffuse, bilateral ground-glass opacification on high-resolution CT (HRCT). This study proposes a three-dimensional (3D)-based deep learning algorithm for classifying AE-IPF using HRCT images.

MATERIALS AND METHODS

A novel 3D-based deep learning algorithm, SlowFast, was developed by applying a database of 306 HRCT scans obtained from two centres. The scans were divided into four separate subsets (training set, n=105; internal validation set, n=26; temporal test set 1, n=79; and geographical test set 2, n=96). The final training data set consisted of 1050 samples with 33 600 images for algorithm training. Algorithm performance was evaluated using accuracy, sensitivity, specificity, positive predictive value, negative predictive value, receiver operating characteristic (ROC) curve and weighted κ coefficient.

RESULTS

The accuracy of the algorithm in classifying AE-IPF on the test sets 1 and 2 was 93.9% and 86.5%, respectively. Interobserver agreements between the algorithm and the majority opinion of the radiologists were good (κw=0.90 for test set 1 and κw=0.73 for test set 2, respectively). The ROC accuracy of the algorithm for classifying AE-IPF on the test sets 1 and 2 was 0.96 and 0.92, respectively. The algorithm performance was superior to visual analysis in accurately diagnosing radiological findings. Furthermore, the algorithm's categorisation was a significant predictor of IPF progression.

CONCLUSIONS

The deep learning algorithm provides high auxiliary diagnostic efficiency in patients with AE-IPF and may serve as a useful clinical aid for diagnosis.

TRIOBP modulates β-catenin signaling by regulation of miR-29b in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fatal and devastating lung disease of unknown etiology, described as the result of multiple cycles of epithelial cell injury and fibroblast activation. Despite this impressive increase in understanding, a therapy that reverses this form of fibrosis remains elusive. In our previous study, we found that miR-29b has a therapeutic effect on pulmonary fibrosis. However, its anti-fibrotic mechanism is not yet clear. Recently, our study identified that F-Actin Binding Protein (TRIOBP) is one of the target genes of miR-29b and found that deficiency of TRIOBP increases resistance to lung fibrosis in vivo. TRIOBP knockdown inhibited the proliferation of epithelial cells and attenuated the activation of fibroblasts. In addition, deficiency of Trio Rho Guanine Nucleotide Exchange Factor (TRIO) in epithelial cells and fibroblasts decreases susceptibility to lung fibrosis. TRIOBP interacting with TRIO promoted abnormal epithelial-mesenchymal crosstalk and modulated the nucleocytoplasmic translocation of β-catenin. We concluded that the miR-29b‒TRIOBP-TRIO-β-catenin axis might be a key anti-fibrotic axis in IPF to regulate lung regeneration and fibrosis, which may provide a promising treatment strategy for lung fibrosis.

Monocytes and macrophages: emerging mechanisms and novel therapeutic targets in pulmonary fibrosis

Pulmonary fibrosis results from a plethora of abnormal pathogenetic events. In idiopathic pulmonary fibrosis (IPF), inhalational, environmental, or occupational exposures in genetically and epigenetically predisposed individuals trigger recurrent cycles of alveolar epithelial cell injury, activation of coagulation pathways, chemoattraction, and differentiation of monocytes into monocyte-derived alveolar macrophages (Mo-AMs). When these events happen intermittently and repeatedly throughout the individual's life cycle, the wound repair process becomes aberrant leading to bronchiolization of distal air spaces, fibroblast accumulation, extracellular matrix deposition, and loss of the alveolar-capillary architecture. The role of immune dysregulation in IPF pathogenesis and progression has been underscored in the past mainly after the disappointing results of immunosuppressant use in IPF patients; however, recent reports highlighting the prognostic and mechanistic roles of monocytes and Mo-AMs revived the interest in immune dysregulation in IPF. In this review, we will discuss the role of these cells in the onset and progression of IPF, as well as potential targeted therapies.

Macrophages promote Fibrinogenesis during kidney injury

Macrophages (Mø) are widely considered fundamental in the development of kidney fibrosis since Mø accumulation commonly aggravates kidney fibrosis, while Mø depletion mitigates it. Although many studies have aimed to elucidate Mø-dependent mechanisms linked to kidney fibrosis and have suggested various mechanisms, the proposed roles have been mostly passive, indirect, and non-unique to Mø. Therefore, the molecular mechanism of how Mø directly promote kidney fibrosis is not fully understood. Recent evidence suggests that Mø produce coagulation factors under diverse pathologic conditions. Notably, coagulation factors mediate fibrinogenesis and contribute to fibrosis. Thus, we hypothesized that kidney Mø express coagulation factors that contribute to the provisional matrix formation during acute kidney injury (AKI). To test our hypothesis, we probed for Mø-derived coagulation factors after kidney injury and uncovered that both infiltrating and kidney-resident Mø produce non-redundant coagulation factors in AKI and chronic kidney disease (CKD). We also identified F13a1, which catalyzes the final step of the coagulation cascade, as the most strongly upregulated coagulation factor in murine and human kidney Mø during AKI and CKD. Our in vitro experiments revealed that the upregulation of coagulation factors in Mø occurs in a Ca^2 + -dependent manner. Taken together, our study demonstrates that kidney Mø populations express key coagulation factors following local injury, suggesting a novel effector mechanism of Mø contributing to kidney fibrosis.

SH2 Domain-Containing Phosphatase-SHP2 Attenuates Fibrotic Responses through Negative Regulation of Mitochondrial Metabolism in Lung Fibroblasts

Background: We have previously shown that SHP2 downregulation may predispose fibroblasts to differentiate into myofibroblasts and proposed a role for SHP2 downregulation in the pathogenesis of idiopathic pulmonary fibrosis (IPF). Recent data have shown that SHP2 localizes to the mitochondrial intercristae, and its overexpression enhances mitochondrial metabolism leading to oxidative stress and senescence. Objective: To determine the effect of SHP2 on fibrotic responses. Methods and Results: Primary mouse lung fibroblasts derived from mice carrying a conditional knock-in mutation (D61G/+), rendering the SHP2 catalytic domain constitutively active, had reduced proliferation (1.6-fold, p < 0.05), migration (2-fold, p < 0.05), as well as reduced responsiveness of TGFB-1 induced fibroblasts-to-myofibroblasts differentiation, compared to wild-type ones. Electron microscope analysis revealed that SHP2 D61G/+ mouse lung fibroblasts were characterized by mitochondrial abnormalities, including swollen mitochondria with disrupted electron-lucent cristae and an increased number of autophagosomes compared to wild-type ones. SHP2 D61G/+ MLFs exhibited increased protein levels of autophagy markers, including LC3B-II and p-62, evidence that was confirmed by immunofluorescence analysis. Mitochondrial function analysis revealed that stable (genotype D61G/+) overexpression of SHP2 led to impaired mitochondrial function, as assessed by decreased mitochondrial membrane potential (1.29-fold, p < 0.05), coupling efficiency (1.82 fold, p < 0.05), oxygen consumption rate (1.9-fold, p < 0.05), and increased reactive oxygen species production both at baseline (1.75-fold, p < 0.05) and following H2O2 stimulation (1.63-fold, p < 0.05) compared to wild-type ones (SHP2+/+). SHP2 D61G/+ mouse lung fibroblasts showed enhanced AMPK activity, as well as decreased activation of the mTORC1 signaling pathway, potentially leading to ineffective mitochondrial metabolism and increased autophagy. Conclusions: SHP2 attenuates fibrotic responses in fibroblast cell lines through negative regulation of mitochondrial metabolism and induction of autophagy. SHP2 activation may represent a promising therapeutic strategy for patients with fibrotic lung diseases.

Mitogen-Activated Protein Kinase Phosphatases: No Longer Undruggable?

Phosphatases and kinases maintain an equilibrium of dephosphorylated and phosphorylated proteins, respectively, that are required for critical cellular functions. Imbalance in this equilibrium or irregularity in their function causes unfavorable cellular effects that have been implicated in the development of numerous diseases. Protein tyrosine phosphatases (PTPs) catalyze the dephosphorylation of protein substrates on tyrosine residues, and their involvement in cell signaling and diseases such as cancer and inflammatory and metabolic diseases has made them attractive therapeutic targets. However, PTPs have proved challenging in therapeutics development, garnering them the unfavorable reputation of being undruggable. Nonetheless, great strides have been made toward the inhibition of PTPs over the past decade. Here, we discuss the advancement in small-molecule inhibition for the PTP subfamily known as the mitogen-activated protein kinase (MAPK) phosphatases (MKPs). We review strategies and inhibitor discovery tools that have proven successful for small-molecule inhibition of the MKPs and discuss what the future of MKP inhibition potentially might yield.

Targeting Growth Factor and Cytokine Pathways to Treat Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic interstitial lung disease of unknown origin that usually results in death from secondary respiratory failure within 2–5 years of diagnosis. Recent studies have identified key roles of cytokine and growth factor pathways in the pathogenesis of IPF. Although there have been numerous clinical trials of drugs investigating their efficacy in the treatment of IPF, only Pirfenidone and Nintedanib have been approved by the FDA. However, they have some major limitations, such as insufficient efficacy, undesired side effects and poor pharmacokinetic properties. To give more insights into the discovery of potential targets for the treatment of IPF, this review provides an overview of cytokines, growth factors and their signaling pathways in IPF, which have important implications for fully exploiting the therapeutic potential of targeting cytokine and growth factor pathways. Advances in the field of cytokine and growth factor pathways will help slow disease progression, prolong life, and improve the quality of life for IPF patients in the future.

Angiotensin II Induces Cardiac Edema and Hypertrophic Remodeling through Lymphatic-Dependent Mechanisms

Cardiac lymphatic vessel growth (lymphangiogenesis) and integrity play an essential role in maintaining tissue fluid balance. Inhibition of lymphatic lymphangiogenesis is involved in cardiac edema and cardiac remodeling after ischemic injury or pressure overload. However, whether lymphatic vessel integrity is disrupted during angiotensin II- (Ang II-) induced cardiac remodeling remains to be investigated. In this study, cardiac remodeling models were established by Ang II (1000 ng/kg/min) in VEGFR-3 knockdown (Lyve-1Cre VEGFR-3f/−) and wild-type (VEGFR-3f/f) littermates. Our results indicated that Ang II infusion not only induced cardiac lymphangiogenesis and upregulation of VEGF-C and VEGFR-3 expression in the time-dependent manner but also enhanced proteasome activity, MKP5 and VE-cadherin degradation, p38 MAPK activation, and lymphatic vessel hyperpermeability. Moreover, VEGFR-3 knockdown significantly inhibited cardiac lymphangiogenesis in mice, resulting in exacerbation of tissue edema, hypertrophy, fibrosis superoxide production, inflammation, and heart failure (HF). Conversely, administration of epoxomicin (a selective proteasome inhibitor) markedly mitigated Ang II-induced cardiac edema, remodeling, and dysfunction; upregulated MKP5 and VE-cadherin expression; inactivated p38 MAPK; and reduced lymphatic vessel hyperpermeability in WT mice, indicating that inhibition of proteasome activity is required to maintain lymphatic endothelial cell (LEC) integrity. Our results show that both cardiac lymphangiogenesis and lymphatic barrier hyperpermeability are implicated in Ang II-induced adaptive hypertrophic remodeling and dysfunction. Proteasome-mediated hyperpermeability of LEC junctions plays a predominant role in the development of cardiac remodeling. Selective stimulation of lymphangiogenesis or inhibition of proteasome activity may be a potential therapeutic option for treating hypertension-induced cardiac remodeling.

MAP Kinase Phosphatase-5 Deficiency Protects Against Pressure Overload-Induced Cardiac Fibrosis

Cardiac fibrosis, a pathological condition due to excessive extracellular matrix (ECM) deposition in the myocardium, is associated with nearly all forms of heart disease. The processes and mechanisms that regulate cardiac fibrosis are not fully understood. In response to cardiac injury, macrophages undergo marked phenotypic and functional changes and act as crucial regulators of myocardial fibrotic remodeling. Here we show that the mitogen-activated protein kinase (MAPK) phosphatase-5 (MKP-5) in macrophages is involved in pressure overload-induced cardiac fibrosis. Cardiac pressure overload resulting from transverse aortic constriction (TAC) leads to the upregulation of Mkp-5 gene expression in the heart. In mice lacking MKP-5, p38 MAPK and JNK were hyperactivated in the heart, and TAC-induced cardiac hypertrophy and myocardial fibrosis were attenuated. MKP-5 deficiency upregulated the expression of the ECM-degrading matrix metalloproteinase-9 (Mmp-9) in the Ly6Clow (M2-type) cardiac macrophage subset. Consistent with in vivo findings, MKP-5 deficiency promoted MMP-9 expression and activity of pro-fibrotic macrophages in response to IL-4 stimulation. Furthermore, using pharmacological inhibitors against p38 MAPK, JNK, and ERK, we demonstrated that MKP-5 suppresses MMP-9 expression through a combined effect of p38 MAPK/JNK/ERK, which subsequently contributes to the inhibition of ECM-degrading activity. Taken together, our study indicates that pressure overload induces MKP-5 expression and facilitates cardiac hypertrophy and fibrosis. MKP-5 deficiency attenuates cardiac fibrosis through MAPK-mediated regulation of MMP-9 expression in Ly6Clow cardiac macrophages.

Pathophysiological Roles of Stress-Activated Protein Kinases in Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is one of the most symptomatic progressive fibrotic lung diseases, in which patients have an extremely poor prognosis. Therefore, understanding the precise molecular mechanisms underlying pulmonary fibrosis is necessary for the development of new therapeutic options. Stress-activated protein kinases (SAPKs), c-Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinase (p38) are ubiquitously expressed in various types of cells and activated in response to cellular environmental stresses, including inflammatory and apoptotic stimuli. Type II alveolar epithelial cells, fibroblasts, and macrophages are known to participate in the progression of pulmonary fibrosis. SAPKs can control fibrogenesis by regulating the cellular processes and molecular functions in various types of lung cells (including cells of the epithelium, interstitial connective tissue, blood vessels, and hematopoietic and lymphoid tissue), all aspects of which remain to be elucidated. We recently reported that the stepwise elevation of intrinsic p38 signaling in the lungs is correlated with a worsening severity of bleomycin-induced fibrosis, indicating an importance of this pathway in the progression of pulmonary fibrosis. In addition, a transcriptome analysis of RNA-sequencing data from this unique model demonstrated that several lines of mechanisms are involved in the pathogenesis of pulmonary fibrosis, which provides a basis for further studies. Here, we review the accumulating evidence for the spatial and temporal roles of SAPKs in pulmonary fibrosis.

An allosteric site on MKP5 reveals a strategy for small-molecule inhibition

The mitogen-activated protein kinase (MAPK) phosphatases (MKPs) have been considered "undruggable," but their position as regulators of the MAPKs makes them promising therapeutic targets. MKP5 has been suggested as a potential target for the treatment of dystrophic muscle disease. Here, we identified an inhibitor of MKP5 using a p38α MAPK-derived, phosphopeptide-based small-molecule screen. We solved the structure of MKP5 in complex with this inhibitor, which revealed a previously undescribed allosteric binding pocket. Binding of the inhibitor to this pocket collapsed the MKP5 active site and was predicted to limit MAPK binding. Treatment with the inhibitor recapitulated the phenotype of MKP5 deficiency, resulting in activation of p38 MAPK and JNK. We demonstrated that MKP5 was required for TGF-β1 signaling in muscle and that the inhibitor blocked TGF-β1-mediated Smad2 phosphorylation. TGF-β1 pathway antagonism has been proposed for the treatment of dystrophic muscle disease. Thus, allosteric inhibition of MKP5 represents a therapeutic strategy against dystrophic muscle disease.

Mesenchymal stem cell-derived extracellular vesicles suppress the fibroblast proliferation by downregulating FZD6 expression in fibroblasts via micrRNA-29b-3p in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF), a progressive and fatal lung disease, usually leads to an irreversible distortion of the pulmonary structure. The functional roles of bone marrow-derived mesenchymal stem cells (BMSC)-secreted extracellular vesicles (EVs) in fibroblasts have been implicated, yet their actions in the treatment of IPF are not fully understood. This study investigated the roles of BMSC-derived EVs expressing miR-29b-3p in fibroblasts in IPF treatment. EVs derived from BMSCs were successfully isolated and could be internalized by pulmonary fibroblasts, and Cell Counting Kit-8 (CCK-8) and Transwell assay results identified that EVs inhibited the activation of fibroblast in IPF. miR-29b-3p, frizzled 6 (FZD6), α-skeletal muscle actin (α-SMA), and Collagen I expressions were examined, which revealed that miR-29b-3p was poorly expressed and FZD6, α-SMA, and Collagen I were overexpressed in pulmonary tissues. Dual-luciferase reporter assay results demonstrated that miR-29b-3p could inversely target FZD6 expression. The gain- and loss-of-function assays were conducted to determine regulatory effects of FZD6 and miR-29b-3p on IPF. CCK-8 and Transwell assays results displayed that BMSCs-derived EVs overexpressing miR-29b-3p contributed to inhibited pulmonary interstitial fibroblast proliferation, migration, invasion, and differentiation. Furthermore, the effects of BMSCs-derived EVs overexpressing miR-29b-3p on IPF progression were assessed in vivo, which confirmed the repressive effects of BMSCs-derived EVs overexpressing miR-29b-3p on IPF progression. Collectively, BMSCs-derived EVs overexpressing miR-29b-3p relieve IPF through FZD6.