Cu,Zn-Superoxide Dismutase-Mediated Redox Regulation of Jumonji Domain Containing 3 Modulates Macrophage Polarization and Pulmonary Fibrosis

Macrophage polarization and its impact on idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a lung disease that worsens over time, causing fibrosis in the lungs and ultimately resulting in respiratory failure and a high risk of death. Macrophages play a crucial role in the immune system, showing flexibility by transforming into either pro-inflammatory (M1) or anti-inflammatory (M2) macrophages when exposed to different stimuli, ultimately impacting the development of IPF. Recent research has indicated that the polarization of macrophages is crucial in the onset and progression of IPF. M1 macrophages secrete inflammatory cytokines and agents causing early lung damage and fibrosis, while M2 macrophages support tissue healing and fibrosis by releasing anti-inflammatory cytokines. Developing novel treatments for IPF relies on a thorough comprehension of the processes involved in macrophage polarization in IPF. The review outlines the regulation of macrophage polarization and its impact on the development of IPF, with the goal of investigating the possible therapeutic benefits of macrophage polarization in the advancement of IPF.

Copper homeostasis dysregulation in respiratory diseases: a review of current knowledge

Cu is an essential micronutrient for various physiological processes in almost all human cell types. Given the critical role of Cu in a wide range of cellular processes, the local concentrations of Cu and the cellular distribution of Cu transporter proteins in the lung are essential for maintaining a steady-state internal environment. Dysfunctional Cu metabolism or regulatory pathways can lead to an imbalance in Cu homeostasis in the lungs, affecting both acute and chronic pathological processes. Recent studies have identified a new form of Cu-dependent cell death called cuproptosis, which has generated renewed interest in the role of Cu homeostasis in diseases. Cuproptosis differs from other known cell death pathways. This occurs through the direct binding of Cu ions to lipoylated components of the tricarboxylic acid cycle during mitochondrial respiration, leading to the aggregation of lipoylated proteins and the subsequent downregulation of Fe-S cluster proteins, which causes toxic stress to the proteins and ultimately leads to cell death. Here, we discuss the impact of dysregulated Cu homeostasis on the pathogenesis of various respiratory diseases, including asthma, chronic obstructive pulmonary disease, idiopathic interstitial fibrosis, and lung cancer. We also discuss the therapeutic potential of targeting Cu. This study highlights the intricate interplay between copper, cellular processes, and respiratory health. Copper, while essential, must be carefully regulated to maintain the delicate balance between necessity and toxicity in living organisms. This review highlights the need to further investigate the precise mechanisms of copper interactions with infections and immune inflammation in the context of respiratory diseases and explore the potential of therapeutic strategies for copper, cuproptosis, and other related effects.

The JMJD family of histone demethylase and their intimate links to cardiovascular disease

The incidence rate and mortality rate of cardiovascular disease rank first in the world. It is associated with various high-risk factors, and there is no single cause. Epigenetic modifications, such as DNA methylation or histone modification, actively participate in the initiation and development of cardiovascular diseases. Histone lysine methylation is a type of histone post-translational modification. The human Jumonji C domain (JMJD) protein family consists of more than 30 members. JMJD proteins participate in many key nuclear processes and play a key role in the specific regulation of gene expression, DNA damage and repair, and DNA replication. Importantly, increasing evidence shows that JMJD proteins are abnormally expressed in cardiovascular diseases, which may be a potential mechanism for the occurrence and development of these diseases. Here, we discuss the key roles of JMJD proteins in various common cardiovascular diseases. This includes histone lysine demethylase, which has been studied in depth, and less-studied JMJD members. Furthermore, we focus on the epigenetic changes induced by each JMJD member, summarize recent research progress, and evaluate their relationship with cardiovascular diseases and therapeutic potential.

Signaling pathways in macrophages: molecular mechanisms and therapeutic targets

Macrophages play diverse roles in development, homeostasis, and immunity. Accordingly, the dysfunction of macrophages is involved in the occurrence and progression of various diseases, such as coronavirus disease 2019 and atherosclerosis. The protective or pathogenic effect that macrophages exert in different conditions largely depends on their functional plasticity, which is regulated via signal transduction such as Janus kinase-signal transducer and activator of transcription, Wnt and Notch pathways, stimulated by environmental cues. Over the past few decades, the molecular mechanisms of signaling pathways in macrophages have been gradually elucidated, providing more alternative therapeutic targets for diseases treatment. Here, we provide an overview of the basic physiology of macrophages and expound the regulatory pathways within them. We also address the crucial role macrophages play in the pathogenesis of diseases, including autoimmune, neurodegenerative, metabolic, infectious diseases, and cancer, with a focus on advances in macrophage-targeted strategies exploring modulation of components and regulators of signaling pathways. Last, we discuss the challenges and possible solutions of macrophage-targeted therapy in clinical applications. We hope that this comprehensive review will provide directions for further research on therapeutic strategies targeting macrophage signaling pathways, which are promising to improve the efficacy of disease treatment.

JMJD3 ablation in myeloid cells confers renoprotection in mice with DOCA/salt-induced hypertension

Hypertension-induced renal injury is characterized by robust inflammation and tubulointerstitial fibrosis. Jumonji domain containing-3 (JMJD3) is closely linked with inflammatory response and fibrogenesis. Here we examined the effect of myeloid JMJD3 ablation on kidney inflammation and fibrosis in deoxycorticosterone acetate (DOCA)/salt hypertension. Our results showed that JMJD3 is notably induced in the kidneys with hypertensive injury. DOCA/salt stress causes an elevation in blood pressure that was no difference between myeloid specific JMJD3-deficient mice and wild-type control mice. Compared with wild-type control mice, myeloid JMJD3 ablation ameliorated kidney function and injury of mice in response to DOCA/salt challenge. Myeloid JMJD3 ablation attenuated collagen deposition, extracellular matrix proteins expression, and fibroblasts activation in injured kidneys following DOCA/salt treatment. Furthermore, myeloid JMJD3 ablation blunts inflammatory response in injured kidneys after DOCA/salt stress. Finally, myeloid JMJD3 ablation precluded myeloid myofibroblasts activation and protected against macrophages to myofibroblasts transition in injured kidneys. These beneficial effects were accompanied by reduced expression of interferon regulator factor 4. In summary, JMJD3 ablation in myeloid cells reduces kidney inflammation and fibrosis in DOCA salt-induced hypertension. Inhibition of myeloid JMJD3 may be a novel potential therapeutic target for hypertensive nephropathy. Myeloid JMJD3 deficiency reduces inflammatory response, myeloid fibroblasts activation, macrophages to myofibroblasts transition, and delays kidney fibrosis progression.

Immunometabolism changes in fibrosis: from mechanisms to therapeutic strategies

Immune cells are essential for initiating and developing the fibrotic process by releasing cytokines and growth factors that activate fibroblasts and promote extracellular matrix deposition. Immunometabolism describes how metabolic alterations affect the function of immune cells and how inflammation and immune responses regulate systemic metabolism. The disturbed immune cell function and their interactions with other cells in the tissue microenvironment lead to the origin and advancement of fibrosis. Understanding the dysregulated metabolic alterations and interactions between fibroblasts and the immune cells is critical for providing new therapeutic targets for fibrosis. This review provides an overview of recent advances in the pathophysiology of fibrosis from the immunometabolism aspect, highlighting the altered metabolic pathways in critical immune cell populations and the impact of inflammation on fibroblast metabolism during the development of fibrosis. We also discuss how this knowledge could be leveraged to develop novel therapeutic strategies for treating fibrotic diseases.

The Role of Macrophages in Connective Tissue Disease-Associated Interstitial Lung Disease: Focusing on Molecular Mechanisms and Potential Treatment Strategies

Connective tissue disease-associated interstitial lung disease (CTD-ILD) is a severe manifestation of CTD that leads to significant morbidity and mortality. Clinically, ILD can occur in diverse CTDs. Pathologically, CTD-ILD is characterized by various histologic patterns, such as nonspecific interstitial pneumonia, organizing pneumonia, and usual interstitial pneumonia. Abnormal immune system responses have traditionally been instrumental in its pathophysiology, and various changes in immune cells have been described, especially in macrophages. This article first briefly overviews the epidemiology, clinical characteristics, impacts, and histopathologic changes associated with CTD-ILD. Next, it summarizes the roles of various signaling pathways in macrophages or products of macrophages in ILD, helped by insights gained from animal models. In the following sections, this review returns to studies of macrophages in CTD-ILD in humans for an overall picture of the current understanding. Finally, we direct attention to potential therapies targeting macrophages in CTD-ILD in investigation or in clinical trials, as well as the future directions regarding macrophages in the context of CTD-ILD. Although the field of macrophages in CTD-ILD is still in its infancy, several lines of evidence suggest the potential of this area.

Histone demethylases in the regulation of immunity and inflammation

Pathogens or danger signals trigger the immune response. Moderate immune response activation removes pathogens and avoids excessive inflammation and tissue damage. Histone demethylases (KDMs) regulate gene expression and play essential roles in numerous physiological processes by removing methyl groups from lysine residues on target proteins. Abnormal expression of KDMs is closely associated with the pathogenesis of various inflammatory diseases such as liver fibrosis, lung injury, and autoimmune diseases. Despite becoming exciting targets for diagnosing and treating these diseases, the role of these enzymes in the regulation of immune and inflammatory response is still unclear. Here, we review the underlying mechanisms through which KDMs regulate immune-related pathways and inflammatory responses. In addition, we also discuss the future applications of KDMs inhibitors in immune and inflammatory diseases.

The identification of metabolism-related subtypes and potential treatments for idiopathic pulmonary fibrosis

Background: Idiopathic pulmonary fibrosis (IPF) is caused by aberrant repair because of alveolar epithelial injury and can only be effectively treated with several compounds. Several metabolism-related biomolecular processes were found to be involved in IPF. We aimed to identify IPF subtypes based on metabolism-related pathways and explore potential drugs for each subtype. Methods: Gene profiles and clinical information were obtained from the Gene Expression Omnibus (GEO) database (GSE70867 and GSE93606). The enrichment scores for 41 metabolism-related pathways, immune cells, and immune pathways were calculated using the Gene Set Variation Analysis (GSVA) package. The ConsensusClusterPlus package was used to cluster samples. Novel modules and hub genes were identified using weighted correlation network analysis (WGCNA). Receiver operating characteristic (ROC) and calibration curves were plotted, and decision curve analysis (DCA) were performed to evaluate the model in the training and validation cohorts. A connectivity map was used as a drug probe. Results: Two subtypes with significant differences in prognosis were identified based on the metabolism-related pathways. Subtype C1 had a poor prognosis, low metabolic levels, and a unique immune signature. CDS2, LCLAT1, GPD1L, AGPAT1, ALDH3A1, LAP3, ADH5, AHCYL2, and MDH1 were used to distinguish between the two subtypes. Finally, subtype-specific drugs, which can potentially treat IPF, were identified. Conclusion: The aberrant activation of metabolism-related pathways contributes to differential prognoses in patients with IPF. Collectively, our findings provide novel mechanistic insights into subtyping IPF based on the metabolism-related pathway and potential treatments, which would help clinicians provide subtype-specific individualized therapeutic management to patients.

NOX4-TIM23 interaction regulates NOX4 mitochondrial import and metabolic reprogramming

Pulmonary fibrosis is a progressive lung disease characterized by macrophage activation. Asbestos-induced expression of nicotinamide adenine dinucleotide phosphate hydrogen oxidase 4 (NOX4) in lung macrophages mediates fibrotic progression by the generation of mitochondrial reactive oxygen species (ROS), modulating mitochondrial biogenesis, and promoting apoptosis resistance; however, the mechanism(s) by which NOX4 localizes to mitochondria during fibrosis is not known. Here, we show that NOX4 localized to the mitochondrial matrix following asbestos exposure in lung macrophages via direct interaction with TIM23. TIM23 and NOX4 interaction was found in lung macrophages from human subjects with asbestosis, while it was absent in mice harboring a conditional deletion of NOX4 in lung macrophages. This interaction was localized to the proximal transmembrane region of NOX4. Mechanistically, TIM23 augmented NOX4-induced mitochondrial ROS and metabolic reprogramming to oxidative phosphorylation. Silencing TIM23 decreased mitochondrial ROS and oxidative phosphorylation. These observations highlight the important role of the mitochondrial translocase TIM23 interaction with NOX4. Moreover, this interaction is required for mitochondrial redox signaling and metabolic reprogramming in lung macrophages.

Protective Effect of Tunisian Red Seaweed (Corallina officinalis) Against Bleomycin-Induced Pulmonary Fibrosis and Oxidative Stress in Rats

Idiopathic pulmonary fibrosis is a chronic and progressive respiratory disease whose diagnosis and physiopathogenesis are still poorly understood and for which, until recently, there were no effective treatments. Over the past few decades, many studies have demonstrated that marine macroalgae such as red seaweeds are potential alternative sources of useful bioactive compounds possessing various physiological and biological activities. The present study was aimed to investigate the effect of Corallina officinalis aqueous extract (COAE) against bleomycin (BLM)-induced lung fibrosis in rat. Thus, Wistar rats were divided into 4 groups of 10 each: control, BLM (2 mg/kg), BLM/COAE-150 mg/kg and BLM/COAE-300 mg/kg once a day for 21 days. Obtained results showed that COAE is rich in phenolic compounds and exhibited relatively high antioxidant activity. COAE might significantly reduce the damage caused by BLM by rewarding the decline in weight and pulmonary index in rats given only BLM. Moreover, lungs, liver and kidneys lipid peroxidation, and sulfhydryl group levels were reversed significantly in a dose-dependent manner in the COAE-treated groups. BLM decreased superoxide dismutase (SOD) and catalase (CAT) activities, while COAE administration increased the antioxidant enzyme activities. Histopathologically, COAE attenuates the severity of the inflammatory lungs state caused by instillation of BLM in rats. These findings suggest that COAE can be a potential therapeutic candidate against BLM-induced lung fibrosis.

3D printed Ti-5Cu alloy accelerates osteogenic differentiation of MC3T3-E1 cells by stimulating the M2 phenotype polarization of macrophages

Ti-5Cu alloy has been proved to have excellent mechanical properties and cell compatibility and has certain antibacterial properties due to the addition of Cu. However, there are few studies on the effects of Ti-5Cu alloy on macrophage polarization and immune-related bone formation. In this study, we prepared Ti-5Cu alloy by three-dimensional printing technology and found that Ti-5Cu alloy presented a much smoother surface compared with Ti. In addition, the CCK-8 results indicated the Ti-5Cu alloy had no cytotoxicity to RAW264.7 cells by co-culture. The results of inductively coupled plasma mass spectrometry showed that the concentration of Cu²⁺ was 0.133 mg/L after 7 days of co-culture, and the CCK-8 results proved that Cu²⁺ had no cytotoxicity to RAW264.7 at this concentration. Then, we studied the effects of Ti-5Cu alloy on macrophage polarization; it was shown that the Ti-5Cu alloy is more prone to modulate the RAW264.7 polarization towards the M2 phenotype and the conditioned medium derived from Ti-5Cu alloy significantly promoted the proliferation and osteogenic differentiation of MC3T3-E1 cells. However, when the expression of Oncostatin M (OSM) gene of RAW264.7 was knocked down, the osteogenic differentiation of MC3T3-E1 cells was decreased. This suggests that the OSM secreted by RAW264.7 co-cultured with Ti-5Cu alloy could accelerate the osteogenic differentiation of MC3T3-E1 cells by acting on OSMR/gp130 receptors.

Plasticity towards Rigidity: A Macrophage Conundrum in Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive, chronic, and ultimately fatal diffuse parenchymal lung disease. The molecular mechanisms of fibrosis in IPF patients are not fully understood and there is a lack of effective treatments. For decades, different types of drugs such as immunosuppressants and antioxidants have been tested, usually with unsuccessful results. Although two antifibrotic drugs (Nintedanib and Pirfenidone) are approved and used for the treatment of IPF, side effects are common, and they only slow down disease progression without improving patients’ survival. Macrophages are central to lung homeostasis, wound healing, and injury. Depending on the stimulus in the microenvironment, macrophages may contribute to fibrosis, but also, they may play a role in the amelioration of fibrosis. In this review, we explore the role of macrophages in IPF in relation to the fibrotic processes, epithelial–mesenchymal transition (EMT), and their crosstalk with resident and recruited cells and we emphasized the importance of macrophages in finding new treatments.

Jmjd3/IRF4 axis aggravates myeloid fibroblast activation and m2 macrophage to myofibroblast transition in renal fibrosis

Renal fibrosis commonly occurs in the process of chronic kidney diseases. Here, we explored the role of Jumonji domain containing 3 (Jmjd3)/interferon regulatory factor 4 (IRF4) axis in activation of myeloid fibroblasts and transition of M2 macrophages into myofibroblasts transition (M2MMT) in kidney fibrosis. In mice, Jmjd3 and IRF4 were highly induced in interstitial cells of kidneys with folic acid or obstructive injury. Jmjd3 deletion in myeloid cells or Jmjd3 inhibitor reduced the levels of IRF4 in injured kidneys. Myeloid Jmjd3 depletion impaired bone marrow-derived fibroblasts activation and M2MMT in folic acid or obstructive nephropathy, resulting in reduction of extracellular matrix (ECM) proteins expression, myofibroblasts formation and renal fibrosis progression. Pharmacological inhibition of Jmjd3 also prevented myeloid fibroblasts activation, M2MMT, and kidney fibrosis development in folic acid nephropathy. Furthermore, IRF4 disruption inhibited myeloid myofibroblasts accumulation, M2MMT, ECM proteins accumulation, and showed milder fibrotic response in obstructed kidneys. Bone marrow transplantation experiment showed that wild-type mice received IRF4^-/- bone marrow cells presented less myeloid fibroblasts activation in injured kidneys and exhibited much less kidney fibrosis after unilateral ureteral obstruction. Myeloid Jmjd3 deletion or Jmjd3 inhibitor attenuated expressions of IRF4, α-smooth muscle actin and fibronectin and impeded M2MMT in cultured monocytes exposed to IL-4. Conversely, overexpression IRF4 abrogated the effect of myeloid Jmjd3 deletion on M2MMT. Thus, Jmjd3/IRF4 signaling has a crucial role in myeloid fibroblasts activation, M2 macrophages to myofibroblasts transition, extracellular matrix protein deposition, and kidney fibrosis progression.

Protective Effect of Eucalyptus globulus Extracts Against Bleomycin-Induced Pulmonary Fibrosis in Rats

Pulmonary fibrosis (PF) is a fibrous interstitial pneumonia that causes damage to the lung tissue and thus alters all respiratory functions. In this study, we aim to investigate the therapeutic effects of fresh leaves of Eucalyptus globulus extracts on bleomycin (BLM)-induced (PF). Twenty-four rats were divided into four groups. The control group received no treatment, the BLM group received only intratracheally BLM (2 mg/kg), the essential water of Eucalyptus globulus (EWEG) group underwent administration of BLM followed by E. globulus hydrosol (2000 mg/kg), and the essential oil of Eucalyptus globulus (EOCG) group received BLM followed by E. globulus essential oil (10 mg/kg). Gas chromatography-mass spectrometry analysis showed that the main compounds of EOEG and EWEG are eucalyptol and spathulenol. Obtained results showed that BLM-induced PF caused a large accumulation of lymphocytes and monocytes in lung bronchoalveolar lavage fluid, a high fibrosis score, and an inflammatory index coupled to an oxidative stress state assessed by an increase in lipid peroxidation and depletion of the activities of antioxidant enzymes: superoxide dismutase and catalase. Otherwise, the treatment with EWEG and EOEG reversed the deleterious effects of reactive oxygen species and the inflammation raised by BLM. E. globulus extracts could improve BLM-induced PF, thus suggesting that the latter could serve as a potential therapeutic approach for PF.

ROS-responsive liposomes as an inhaled drug delivery nanoplatform for idiopathic pulmonary fibrosis treatment via Nrf2 signaling

Background

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic disease with pathophysiological characteristics of transforming growth factor-β (TGF-β), and reactive oxygen species (ROS)-induced excessive fibroblast-to-myofibroblast transition and extracellular matrix deposition. Macrophages are closely involved in the development of fibrosis. Nuclear factor erythroid 2 related factor 2 (Nrf2) is a key molecule regulating ROS and TGF-β expression. Therefore, Nrf2 signaling modulation might be a promising therapy for fibrosis. The inhalation-based drug delivery can reduce systemic side effects and improve therapeutic effects, and is currently receiving increasing attention, but direct inhaled drugs are easily cleared and difficult to exert their efficacy. Therefore, we aimed to design a ROS-responsive liposome for the Nrf2 agonist dimethyl fumarate (DMF) delivery in the fibrotic lung. Moreover, we explored its therapeutic effect on pulmonary fibrosis and macrophage activation.

Results

We synthesized DMF-loaded ROS-responsive DSPE-TK-PEG@DMF liposomes (DTP@DMF NPs). DTP@DMF NPs had suitable size and negative zeta potential and excellent capability to rapidly release DMF in a high-ROS environment. We found that macrophage accumulation and polarization were closely related to fibrosis development, while DTP@DMF NPs could attenuate macrophage activity and fibrosis in mice. RAW264.7 and NIH-3T3 cells coculture revealed that DTP@DMF NPs could promote Nrf2 and downstream heme oxygenase-1 (HO-1) expression and suppress TGF-β and ROS production in macrophages, thereby reducing fibroblast-to-myofibroblast transition and collagen production by NIH-3T3 cells. In vivo experiments confirmed the above findings. Compared with direct DMF instillation, DTP@DMF NPs treatment presented enhanced antifibrotic effect. DTP@DMF NPs also had a prolonged residence time in the lung as well as excellent biocompatibility.

Conclusions

DTP@DMF NPs can reduce macrophage-mediated fibroblast-to-myofibroblast transition and extracellular matrix deposition to attenuate lung fibrosis by upregulating Nrf2 signaling. This ROS-responsive liposome is clinically promising as an ideal delivery system for inhaled drug delivery.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01435-4.

Diverse Epigenetic Regulations of Macrophages in Atherosclerosis

Emerging research on epigenetics has resulted in many novel discoveries in atherosclerosis (AS), an inflammaging-associated disease characterized by chronic inflammation primarily driven by macrophages. The bulk of evidence has demonstrated the central role of epigenetic machinery in macrophage polarization to pro- (M1-like) or anti-inflammatory (M2-like) phenotype. An increasing number of epigenetic alterations and their modifiers involved in reprogramming macrophages by regulating DNA methylation or histone modifications (e.g., methylation, acetylation, and recently lactylation) have been identified. They may act to determine or skew the direction of macrophage polarization in AS lesions, thereby representing a promising target. Here we describe the current understanding of the epigenetic machinery involving macrophage polarization, to shed light on chronic inflammation-driving onset and progression of inflammaging-associated diseases, using AS as a prototypic example, and discuss the challenge for developing effective therapies targeting the epigenetic modifiers against these diseases, particularly highlighting a potential strategy based on epigenetically-governed repolarization from M1-like to M2-like phenotype.

Targeting monocytes/macrophages in fibrosis and cancer diseases: Therapeutic approaches

Over almost 140 years since their identification, the knowledge about macrophages has unbelievably evolved. The 'big eaters' from being thought of as simple phagocytic cells have been recognized as master regulators in immunity, homeostasis, healing/repair and organ development. Long considered to originate exclusively from bone marrow-derived circulating monocytes, macrophages have been also demonstrated to be the first immune cells colonizing tissues in the developing embryo and persisting in adult life by self-renewal, as long-lived tissue resident macrophages. Therefore, heterogeneous populations of macrophages with different ontogeny and functions co-exist in tissues. Macrophages act as sentinels of homeostasis and are intrinsically programmed to lead the wound healing and repair processes that occur after injury. However, in certain pathological circumstances macrophages get dysfunctional, and impaired or aberrant macrophage activities become key features of diseases. For instance, in both fibrosis and cancer, that have been defined 'wounds that do not heal', dysfunctional monocyte-derived macrophages overall play a key detrimental role. On the other hand, due to their plasticity these cells can be 're-educated' and exert anti-fibrotic and anti-cancer functions. Therefore macrophages represent an important therapeutic target in both fibrosis and cancer diseases. The current review will illustrate new insights into the role of monocytes/macrophages in these devastating diseases and summarize new therapeutic strategies and applications of macrophage-targeted drug development in their clinical setting.

Targeting epigenetic modifiers to reprogramme macrophages in non-resolving inflammation-driven atherosclerosis

Epigenomic and epigenetic research has been providing several new insights into a variety of diseases caused by non-resolving inflammation, including cardiovascular diseases. Atherosclerosis (AS) has long been recognized as a chronic inflammatory disease of the arterial walls, characterized by local persistent and stepwise accelerating inflammation without resolution, also known as uncontrolled inflammation. The pathogenesis of AS is driven primarily by highly plastic macrophages via their polarization to pro- or anti-inflammatory phenotypes as well as other novel subtypes recently identified by single-cell sequencing. Although emerging evidence has indicated the key role of the epigenetic machinery in the regulation of macrophage plasticity, the investigation of epigenetic alterations and modifiers in AS and related inflammation is still in its infancy. An increasing number of the epigenetic modifiers (e.g. TET2, DNMT3A, HDAC3, HDAC9, JMJD3, KDM4A) have been identified in epigenetic remodelling of macrophages through DNA methylation or histone modifications (e.g. methylation, acetylation, and recently lactylation) in inflammation. These or many unexplored modifiers function to determine or switch the direction of macrophage polarization via transcriptional reprogramming of gene expression and intracellular metabolic rewiring upon microenvironmental cues, thereby representing a promising target for anti-inflammatory therapy in AS. Here, we review up-to-date findings involving the epigenetic regulation of macrophages to shed light on the mechanism of uncontrolled inflammation during AS onset and progression. We also discuss current challenges for developing an effective and safe anti-AS therapy that targets the epigenetic modifiers and propose a potential anti-inflammatory strategy that repolarizes macrophages from pro- to anti-inflammatory phenotypes.

The emerging role of metabolism in fibrosis

The metabolic shift that cancer cells undergo towards aerobic glycolysis was identified as a defining feature in tumours almost 100 years ago; however, it has only recently become apparent that similar metabolic reprogramming is a key feature in other diseases - with fibrosis now entering the fray. In this perspective, an overview of the recent evidence implicating increased glycolysis and glutaminolysis as mediators of fibrosis is presented, with a particular emphasis on the novel therapeutic possibilities this introduces. Furthermore, the impact that metabolic reprogramming has on redox homeostasis is discussed, providing an insight into how this often-overlooked mechanism may drive the pathogenesis.

Nutritional immunity: the impact of metals on lung immune cells and the airway microbiome during chronic respiratory disease

Nutritional immunity is the sequestration of bioavailable trace metals such as iron, zinc and copper by the host to limit pathogenicity by invading microorganisms. As one of the most conserved activities of the innate immune system, limiting the availability of free trace metals by cells of the immune system serves not only to conceal these vital nutrients from invading bacteria but also operates to tightly regulate host immune cell responses and function. In the setting of chronic lung disease, the regulation of trace metals by the host is often disrupted, leading to the altered availability of these nutrients to commensal and invading opportunistic pathogenic microbes. Similarly, alterations in the uptake, secretion, turnover and redox activity of these vitally important metals has significant repercussions for immune cell function including the response to and resolution of infection. This review will discuss the intricate role of nutritional immunity in host immune cells of the lung and how changes in this fundamental process as a result of chronic lung disease may alter the airway microbiome, disease progression and the response to infection.

Rhodiola rosea L. Attenuates Cigarette Smoke and Lipopolysaccharide-Induced COPD in Rats via Inflammation Inhibition and Antioxidant and Antifibrosis Pathways

The root cause behind the development of chronic obstructive pulmonary disease (COPD) is cigarette smoke that induces the inflammation of the lung tissue and alveolar destruction. Long-term cigarette smoking can lead to deterioration in lung parenchymal function and cause structural changes in the lung, further resulting in pulmonary fibrosis. Rhodiola rosea L., a traditional medicinal perennial herb, is well known for its numerous pharmacological benefits, including anti-inflammation, antioxidant, antifatigue, antidepressive, and antifibrotic properties. Here, we evaluated the pharmacological effects and mechanisms of the Rhodiola rosea L. (RRL) macroporous resin extract on COPD caused by lipopolysaccharide (LPS) and cigarette smoke (CS) in rats. The RRL significantly improved the pathological structure of the lung tissue. Additionally, RRL decreased the infiltration of inflammatory cells and, subsequently, oxidative stress. Furthermore, the RNAseq assay indicated that RRL attenuated the CS and LPS-induced COPD via anti-inflammatory, antifibrotic, and antiapoptotic activities. Western blot analysis substantiated that the RRL resulted in upregulated levels of Nrf2 and HO-1 as well as downregulated levels of IκBα, NF-κB p65, α-SMA, and TGF-β1. Interestingly, the RRL could protect rats from CS and LPS-induced COPD by inhibiting the ERK1/2 and Smad3 signaling pathways and apoptosis. Thus, the RRL could attenuate CS and LPS-induced COPD through inflammation inhibition and antioxidant and antifibrosis pathways.

Phagosome-regulated mTOR signalling during sarcoidosis granuloma biogenesis

INTRODUCTION

Sarcoidosis and tuberculosis are granulomatous pulmonary diseases characterised by heightened immune reactivity to Mycobacterium tuberculosis antigens. We hypothesised that an unsupervised analysis comparing the molecular characteristics of granulomas formed in response to M. tuberculosis antigens in patients with sarcoidosis or latent tuberculosis infection (LTBI) would provide novel insights into the pathogenesis of sarcoidosis.

METHODS

A genomic analysis identified differentially expressed genes in granuloma-like cell aggregates formed by sarcoidosis (n=12) or LTBI patients (n=5) in an established in vitro human granuloma model wherein peripheral blood mononuclear cells were exposed to M. tuberculosis antigens (beads coated with purified protein derivative) and cultured for 7 days. Pathway analysis of differentially expressed genes identified canonical pathways, most notably antigen processing and presentation via phagolysosomes, as a prominent pathway in sarcoidosis granuloma formation. The phagolysosomal pathway promoted mechanistic target of rapamycin complex 1 (mTORc1)/STAT3 signal transduction. Thus, granuloma formation and related immune mediators were evaluated in the absence or presence of various pre-treatments known to prevent phagolysosome formation (chloroquine) or phagosome acidification (bafilomycin A1) or directly inhibit mTORc1 activation (rapamycin).

RESULTS

In keeping with genomic analyses indicating enhanced phagolysosomal activation and predicted mTORc1 signalling, it was determined that sarcoidosis granuloma formation and related inflammatory mediator release was dependent upon phagolysosome assembly and acidification and mTORc1/S6/STAT3 signal transduction.

CONCLUSIONS

Sarcoidosis granulomas exhibit enhanced and sustained intracellular antigen processing and presentation capacities, and related phagolysosome assembly and acidification are required to support mTORc1 signalling to promote sarcoidosis granuloma formation.

Catalpol Protects Against Pulmonary Fibrosis Through Inhibiting TGF-β1/Smad3 and Wnt/β-Catenin Signaling Pathways

Idiopathic pulmonary fibrosis (IPF) is a fatal lung disease characterized by fibroblast proliferation and extracellular matrix remodeling; however, the molecular mechanisms underlying its occurrence and development are not yet fully understood. Despite it having a variety of beneficial pharmacological activities, the effects of catalpol (CAT), which is extracted from Rehmannia glutinosa, in IPF are not known. In this study, the differentially expressed genes, proteins, and pathways of IPF in the Gene Expression Omnibus database were analyzed, and CAT was molecularly docked with the corresponding key proteins to screen its pharmacological targets, which were then verified using an animal model. The results show that collagen metabolism imbalance, inflammatory response, and epithelial-mesenchymal transition (EMT) are the core processes in IPF, and the TGF-β1/Smad3 and Wnt/β-catenin pathways are the key signaling pathways for the development of pulmonary fibrosis. Our results also suggest that CAT binds to TGF-βR1, Smad3, Wnt3a, and GSK-3β through hydrogen bonds, van der Waals bonds, and other interactions to downregulate the expression and phosphorylation of Smad3, Wnt3a, GSK-3β, and β-catenin, inhibit the expression of cytokines, and reduce the degree of oxidative stress in lung tissue. Furthermore, CAT can inhibit the EMT process and collagen remodeling by downregulating fibrotic biomarkers and promoting the expression of epithelial cadherin. This study elucidates several key processes and signaling pathways involved in the development of IPF, and suggests the potential value of CAT in the treatment of IPF.

Histone methylation and demethylation are implicated in the transient and sustained activation of the interleukin-1β gene in murine macrophages

Macrophages play a crucial role in the development of atherosclerosis. To explore the mechanism by which macrophages attain a proinflammatory phenotype for a sustained period, we stimulated macrophages with lipopolysaccharide (LPS) and interferon-γ (IFN-γ) and measured the interleukin-1β (IL-1β) expression. The IL-1β expression increased transiently, and its expression lasted for, at least, 1 week after the cessation of LPS and IFN-γ stimulation. At the promoter region of the IL-1β gene, the demethylation of histone H3 lysine 27 (H3K27) was significantly induced for 1 week after transient stimulation with LPS and IFN-γ. The expression of H3K27 demethylases ubiquitously transcribed tetratricopeptide repeat, X chromosome (UTX) and jumonji domain-containing 3 (JMJD3) increased significantly for 1 week after transient stimulation with LPS and IFN-γ. When the UTX expression was inhibited by using small interfering RNA (siRNA) for UTX, the IL-1β expression was significantly suppressed in both transient and sustained phases, whereas siRNA for JMJD3 significantly inhibited only the sustained phase of the IL-1β expression. These results suggested that H3K27 demethylation was implicated in the transient and sustained increase in the IL-1β expression after LPS and IFN-γ stimulation.

Increased flux through the mevalonate pathway mediates fibrotic repair without injury

Macrophages are important in mounting an innate immune response to injury as well as in repair of injury. Gene expression of Rho proteins is known to be increased in fibrotic models; however, the role of these proteins in idiopathic pulmonary fibrosis (IPF) is not known. Here, we show that BAL cells from patients with IPF have a profibrotic phenotype secondary to increased activation of the small GTPase Rac1. Rac1 activation requires a posttranslational modification, geranylgeranylation, of the C-terminal cysteine residue. We found that by supplying more substrate for geranylgeranylation, Rac1 activation was substantially increased, resulting in profibrotic polarization by increasing flux through the mevalonate pathway. The increased flux was secondary to greater levels of acetyl-CoA from metabolic reprogramming to β oxidation. The polarization mediated fibrotic repair in the absence of injury by enhancing macrophage/fibroblast signaling. These observations suggest that targeting the mevalonate pathway may abrogate the role of macrophages in dysregulated fibrotic repair.

Overexpression of TIM-3 in Macrophages Aggravates Pathogenesis of Pulmonary Fibrosis in Mice

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive lung disorder and lacks effective treatments because of unclear mechanisms. Aberrant function of alveolar macrophages is directly linked to pulmonary fibrosis. Here, we show TIM-3 (T-cell immunoglobulin domain and mucin domain-3), a key regulator of macrophage function, aggravates pulmonary fibrosis. TIM-3 mRNA of patients with IPF was analyzed based on the Gene Expression Omnibus and Array Express databases. Lung pathology and profibrotic molecules were assessed in a bleomycin (BLM)-induced pulmonary fibrosis model using wild-type (WT) and TIM-3 transgenic (TIM-3-TG) mice. Macrophage cells, RAW264.7, were then applied to investigate the effect of macrophage TIM-3 under BLM exposure in vitro. Macrophage depletion and adoptive-transfer experiments were finally performed to examine lung morphology and profibrotic molecules. TIM-3 expression was increased both in patients with IPF and in our BLM-induced mouse model. TIM-3-TG mice developed more serious pathological changes in lung tissue and higher expressions of TGF-β1 (transforming growth factor-β1) and IL-10 than WT mice. After BLM treatment, TGF-β1 and IL-10 expression was significantly decreased in RAW264.7 cells after TIM-3 knock-out, whereas it was increased in TIM-3-TG peritoneal macrophages. The scores of pulmonary fibrosis in WT and TIM-3-TG mice were significantly reduced, and there was no difference between them after macrophage depletion. Furthermore, WT mice receiving adoptive macrophages from TIM-3-TG mice also had more serious lung fibrosis and increased expression of TGF-β1 and IL-10 than those receiving macrophages from WT mice. Our findings revealed that overexpressed TIM-3 in alveolar macrophages aggravated pulmonary fibrosis.

Oxidative Stress in Pulmonary Fibrosis

Oxidative stress has been linked to various disease states as well as physiological aging. The lungs are uniquely exposed to a highly oxidizing environment and have evolved several mechanisms to attenuate oxidative stress. Idiopathic pulmonary fibrosis (IPF) is a progressive age-related disorder that leads to architectural remodeling, impaired gas exchange, respiratory failure, and death. In this article, we discuss cellular sources of oxidant production, and antioxidant defenses, both enzymatic and nonenzymatic. We outline the current understanding of the pathogenesis of IPF and how oxidative stress contributes to fibrosis. Further, we link oxidative stress to the biology of aging that involves DNA damage responses, loss of proteostasis, and mitochondrial dysfunction. We discuss the recent findings on the role of reactive oxygen species (ROS) in specific fibrotic processes such as macrophage polarization and immunosenescence, alveolar epithelial cell apoptosis and senescence, myofibroblast differentiation and senescence, and alterations in the acellular extracellular matrix. Finally, we provide an overview of the current preclinical studies and clinical trials targeting oxidative stress in fibrosis and potential new strategies for future therapeutic interventions. © 2020 American Physiological Society. Compr Physiol 10:509-547, 2020.

PAI-1 Regulation of TGF-β1-induced Alveolar Type II Cell Senescence, SASP Secretion, and SASP-mediated Activation of Alveolar Macrophages

Senescence of alveolar type II (ATII) cells, progenitors of the alveolar epithelium, is a pathological feature and contributes importantly to the pathogenesis of idiopathic pulmonary fibrosis. Despite recognition of the importance of ATII cell senescence in idiopathic pulmonary fibrosis pathogenesis, how ATII cell senescence is regulated and how senescent ATII cells contribute to lung fibrogenesis remain unclear. In this study, we show that TGF-β1 (transforming growth factor-β1), a most ubiquitous and potent profibrotic cytokine, induces plasminogen activator inhibitor-1 (PAI-1), a cell senescence and fibrosis mediator, and p16 as well as senescence, but not apoptosis, in primary mouse ATII cells. We also found that senescent ATII cells secrete various cytokines and chemokines, including IL-4 and IL-13, which stimulate the expression of genes associated with a profibrotic phenotype in alveolar macrophages. Similar responses were also observed in TGF-β1-treated rat ATII (L2) and rat macrophage NR8383 cells. Deletion of PAI-1 or inhibition of PAI-1 activity with a small molecule PAI-1 inhibitor, however, blocks TGF-β1-induced senescence as well as a senescence-associated secretory phenotype in ATII and L2 cells and, consequently, the stimulatory effects of the conditioned medium from senescent ATII/L2 cells on macrophages. Moreover, we show that silencing p16 ameliorates PAI-1 protein-induced ATII cell senescence and secretion of profibrotic mediators. Our data suggest that PAI-1 mediates TGF-β1-induced ATII cell senescence and secretion of profibrotic mediators through inducing p16, and they also suggest that senescent ATII cells contribute to lung fibrogenesis in part by activating alveolar macrophages through secreting profibrotic and proinflammatory mediators.

Mitochondrial quality control in pulmonary fibrosis

Mechanisms underlying the pathogenesis of pulmonary fibrosis remain incompletely understood. Emerging evidence suggests changes in mitochondrial quality control are a critical determinant in many lung diseases, including chronic obstructive pulmonary disease, asthma, pulmonary hypertension, acute lung injury, lung cancer, and in the susceptibility to pulmonary fibrosis. Once thought of as the kidney-bean shaped powerhouses of the cell, mitochondria are now known to form interconnected networks that rapidly and continuously change their size to meet cellular metabolic demands. Mitochondrial quality control modulates cell fate and homeostasis, and diminished mitochondrial quality control results in mitochondrial dysfunction, increased reactive oxygen species (ROS) production, reduced ATP production, and often induces intrinsic apoptosis. Here, we review the role of the mitochondria in alveolar epithelial cells, lung macrophages, and fibroblasts within the context of pulmonary fibrosis.

JMJD3 in the regulation of human diseases

In recent years, many studies have shown that histone methylation plays an important role in maintaining the active and silent state of gene expression in human diseases. The Jumonji domain-containing protein D3 (JMJD3), specifically demethylate di- and trimethyl-lysine 27 on histone H3 (H3K27me2/3), has been widely studied in immune diseases, infectious diseases, cancer, developmental diseases, and aging related diseases. We will focus on the recent advances of JMJD3 function in human diseases, and looks ahead to the future of JMJD3 gene research in this review.

The anti-cancer drug doxorubicin induces substantial epigenetic changes in cultured cardiomyocytes

The anthracycline doxorubicin (DOX) is widely used in cancer therapy with the limitation of cardiotoxicity leading to the development of congestive heart failure. DOX-induced oxidative stress and changes of the phosphoproteome as well as epigenome were described but the exact mechanisms of the adverse long-term effects are still elusive. Here, we tested the impact of DOX treatment on cell death, oxidative stress parameters and expression profiles of proteins involved in epigenetic pathways in a cardiomyocyte cell culture model. Markers of oxidative stress, apoptosis and expression of proteins involved in epigenetic processes were assessed by immunoblotting in cultured rat myoblasts (H9c2) upon treatment with DOX (1 or 5 μM for 24 or 48 h) in adherent viable and detached apoptotic cells. The apoptosis markers cleaved caspase-3 and fractin as well as oxidative stress markers 3-nitrotyrosine and malondialdehyde were dose-dependently increased by DOX treatment. Histone deacetylases (SIRT1 and HDAC2), histone lysine demethylases (KDM3A and LSD1) and histone lysine methyltransferases (SET7 and SMYD1) were significantly regulated by DOX treatment with generation of cleaved protein fragments and posttranslational modifications. Overall, we found significant decrease in histone 3 acetylation in DOX-treated cells. DOX treatment of cultured cardiomyocyte precursor cells causes severe cell death by apoptosis associated with cellular oxidative stress. In addition, significant regulation of proteins involved in epigenetic processes and changes in global histone 3 acetylation were observed. However, the significance and clinical impact of these changes remain elusive.

NOX4 modulates macrophage phenotype and mitochondrial biogenesis in asbestosis

Macrophage activation is implicated in the development of pulmonary fibrosis by generation of profibrotic molecules. Although NADPH oxidase 4 (NOX4) is known to contribute to pulmonary fibrosis, its effects on macrophage activation and mitochondrial redox signaling are unclear. Here, we show that NOX4 is crucial for lung macrophage profibrotic polarization and fibrotic repair after asbestos exposure. NOX4 was elevated in lung macrophages from subjects with asbestosis, and mice harboring a deletion of NOX4 in lung macrophages were protected from asbestos-induced fibrosis. NOX4 promoted lung macrophage profibrotic polarization and increased production of profibrotic molecules that induce collagen deposition. Mechanistically, NOX4 further augmented mitochondrial ROS production and induced mitochondrial biogenesis. Targeting redox signaling and mitochondrial biogenesis prevented the profibrotic polarization of lung macrophages by reducing the production of profibrotic molecules. These observations provide evidence that macrophage NOX4 is a potentially novel therapeutic target to halt the development of asbestos-induced pulmonary fibrosis.

Protective effects of Rosavin on bleomycin-induced pulmonary fibrosis via suppressing fibrotic and inflammatory signaling pathways in mice

Idiopathic Pulmonary fibrosis (IPF) is diagnosed as a life-threatening, progressive and incurable lung disease characterized by accumulation of extracellular matrix and myofibroblasts, resulting in the function degradation and structural alterations in normal lung parenchyma. Notably, Pulmonary Fibrosis has been considering as a difficult problem in clinical with high mortality and effective treatment strategies. Rosavin, a benzylPropylene glycoside, is isolated from Rhodiola rosea L., exhibiting nootropic, anti-depressant, anti-cancer, anti-inflammatory and anti-oxidative activities. In this study, we attended to elucidate the pharmacological activity of Rosavin for treatment of pulmonary fibrosis induced by bleomycin in mice. The results indicated that Rosavin could significantly ameliorate the lung index and Pathological structure of mice with Pulmonary fibrosis by bleomycin-induced. Additionally, Rosavin could evidently decreased inflammatory cells infiltration in bronchoalveolar lavage fluid and pro-inflammatory cytokines expression in lung tissue specimens induced by bleomycin. Rosavin could down-regulate the expression of hydroxyproline and malondialdehyde and increased the activities of superoxide dismutase, glutathione peroxidase in lung tissue. The expression of Nrf2 were increased, and the expression of NF-κB p65, TGF-β1 and α-SMA were inhibited. The findings revealed the protective effects and the primary mechanism of rosavin on bleomycin-induced pulmonary fibrosis, which provided a scientific foundation for Rosavin as a promising candidate for Pulmonary fibrosis treatment.

Vitamin C and immune cell function in inflammation and cancer

Vitamin C (ascorbate) is maintained at high levels in most immune cells and can affect many aspects of the immune response. Intracellular levels generally respond to variations in plasma ascorbate availability, and a combination of inadequate intake and increased turnover during severe stress can result in low plasma ascorbate status. Intracellular ascorbate supports essential functions and, in particular, acts as an enzyme cofactor for Fe- or Cu-containing oxygenases. Newly discovered enzymes in this family regulate cell metabolism and epigenetics, and dysregulation of their activity can affect cell phenotype, growth and survival pathways, and stem cell phenotype. This brief overview details some of the recent advances in our understanding of how ascorbate availability can affect the hydroxylases controlling the hypoxic response and the DNA and histone demethylases. These processes play important roles in the regulation of the immune system, altering cell survival pathways, metabolism and functions.

Macrophages: friend or foe in idiopathic pulmonary fibrosis?

Idiopathic pulmonary fibrosis (IPF) is a prototype of lethal, chronic, progressive interstitial lung disease of unknown etiology. Over the past decade, macrophage has been recognized to play a significant role in IPF pathogenesis. Depending on the local microenvironments, macrophages can be polarized to either classically activated (M1) or alternatively activated (M2) phenotypes. In general, M1 macrophages are responsible for wound healing after alveolar epithelial injury, while M2 macrophages are designated to resolve wound healing processes or terminate inflammatory responses in the lung. IPF is a pathological consequence resulted from altered wound healing in response to persistent lung injury. In this review, we intend to summarize the current state of knowledge regarding the process of macrophage polarization and its mediators in the pathogenesis of pulmonary fibrosis. Our goal is to update the understanding of the mechanisms underlying the initiation and progression of IPF, and by which, we expect to provide help for developing effective therapeutic strategies in clinical settings.

Leflunomide attenuates oxidative stress in fetal human lung endothelial cells via superoxide dismutase 2 and catalase

Hyperoxia-induced oxidative stress contributes to the pathogenesis of bronchopulmonary dysplasia (BPD), the most common respiratory morbidity of preterm infants. Importantly, the disease lack specific therapies and is associated with long-term cardio-pulmonary and neurodevelopmental morbidities, signifying the need to discover novel therapies and decrease the disease burden. We and others have demonstrated that leflunomide, a food and drug administration approved drug to treat humans with rheumatoid arthritis, increases the expression of the anti-oxidant enzymes, NAD(P)H quinone dehydrogenase 1 (NQO1), catalase, and superoxide dismutase (SOD). However, whether this drug can decrease oxidative stress in fetal human pulmonary arterial endothelial cells (HPAECs) is unknown. Therefore, we tested the hypothesis that leflunomide will decrease hyperoxia-induced oxidative stress by upregulating these anti-oxidant enzymes in HPAECs. Leflunomide decreased hydrogen peroxide (H₂O₂) levels and increased the mRNA and protein levels of catalase, NQO1, and SOD2 in HPAECs at basal conditions. Further, leflunomide-treated cells continued to have decreased H₂O₂ and increased SOD2 levels upon hyperoxia exposure. Leflunomide did not affect the expression of other anti-oxidant enzymes, including hemoxygenase-1 and SOD1. AhR-knockdown experiments suggested that leflunomide regulated NQO1 levels via AhR-dependent mechanisms and H₂O₂, catalase, and SOD2 levels via AhR-independent mechanisms. Collectively, the results support the hypothesis that leflunomide decreases oxidative stress in HPAECs via SOD2-and catalase-dependent, but AhR- and NQO1-independent mechanisms. Our findings indicate that leflunomide is a potential drug for the management of BPD in preterm infants.

The IL-4 receptor α has a critical role in bone marrow-derived fibroblast activation and renal fibrosis

Renal fibrosis is a common pathway leading to the progression of chronic kidney disease, and bone marrow-derived fibroblasts contribute significantly to the development of renal fibrosis. However, the signaling mechanisms underlying the activation of these fibroblasts are not completely understood. Here, we examined the role of IL-4 receptor α (IL-4Rα) in the activation of myeloid fibroblasts in two experimental models of renal fibrosis. Compared with wild-type mice, IL-4Rα knockout mice accumulated fewer bone marrow-derived fibroblasts and myofibroblasts in their kidneys. IL-4Rα deficiency suppressed the expression of α-smooth muscle actin, extracellular matrix proteins and the development of renal fibrosis. Furthermore, IL-4Rα deficiency inhibited the activation of signal transducer and activator of transcription 6 (STAT6) in the kidney. Moreover, wild-type mice engrafted with bone marrow cells from IL-4Rα knockout mice exhibited fewer myeloid fibroblasts in the kidney and displayed less severe renal fibrosis following ureteral obstructive injury compared with wild-type mice engrafted with wild-type bone marrow cells. In vitro, IL-4 activated STAT6 and stimulated expression of α-smooth muscle actin and fibronectin in mouse bone marrow monocytes. This was abolished in the absence of IL-4Rα. Thus, IL-4Rα plays an important role in bone marrow-derived fibroblast activation, resulting in extracellular matrix protein production and fibrosis development. Hence, the IL-4Rα/STAT6 signaling pathway may serve as a novel therapeutic target for chronic kidney disease.

The epigenetic landscape related to reactive oxygen species formation in the cardiovascular system

Cardiovascular diseases are among the leading causes of death worldwide. Reactive oxygen species (ROS) can act as damaging molecules but also represent central hubs in cellular signalling networks. Increasing evidence indicates that ROS play an important role in the pathogenesis of cardiovascular diseases, although the underlying mechanisms and consequences of pathophysiologically elevated ROS in the cardiovascular system are still not completely resolved. More recently, alterations of the epigenetic landscape, which can affect DNA methylation, post-translational histone modifications, ATP-dependent alterations to chromatin and non-coding RNA transcripts, have been considered to be of increasing importance in the pathogenesis of cardiovascular diseases. While it has long been accepted that epigenetic changes are imprinted during development or even inherited and are not changed after reaching the lineage-specific expression profile, it becomes more and more clear that epigenetic modifications are highly dynamic. Thus, they might provide an important link between the actions of ROS and cardiovascular diseases. This review will provide an overview of the role of ROS in modulating the epigenetic landscape in the context of the cardiovascular system.

LINKED ARTICLES

This article is part of a themed section on Redox Biology and Oxidative Stress in Health and Disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.12/issuetoc.

Macrophages utilize the mitochondrial calcium uniporter for profibrotic polarization

Fibrosis in multiple organs, including the liver, kidney, and lung, often occurs secondary to environmental exposure. Asbestos exposure is one important environmental cause of lung fibrosis. The mechanisms that mediate fibrosis is not fully understood, although mitochondrial oxidative stress in alveolar macrophages is critical for fibrosis development. Mitochondrial Ca²⁺ levels can be associated with production of reactive oxygen species. Here, we show that patients with asbestosis have higher levels of mitochondrial Ca²⁺ compared with normal patients. The mitochondrial calcium uniporter (MCU) is a highly selective ion channel that transports Ca²⁺ into the mitochondrial matrix to modulate metabolism. Asbestos exposure increased mitochondrial Ca²⁺ influx in alveolar macrophages from wild-type, but not MCU^+/-, mice. MCU expression polarized macrophages to a profibrotic phenotype after exposure to asbestos, and the profibrotic polarization was regulated by MCU-mediated ATP production. Profibrotic polarization was abrogated when MCU was absent or its activity was blocked. Of more importance, mice that were deficient in MCU were protected from pulmonary fibrosis. Regulation of mitochondrial Ca²⁺ suggests that MCU may play a pivotal role in the development of fibrosis and could potentially be a therapeutic target for pulmonary fibrosis.-Gu, L., Larson-Casey, J. L., Carter, A. B. Macrophages utilize the mitochondrial calcium uniporter for profibrotic polarization.

Redox mechanisms in age-related lung fibrosis

Redox signaling and oxidative stress are associated with tissue fibrosis and aging. Aging is recognized as a major risk factor for fibrotic diseases involving multiple organ systems, including that of the lung. A number of oxidant generating enzymes are upregulated while antioxidant defenses are deficient with aging and cellular senescence, leading to redox imbalance and oxidative stress. However, the precise mechanisms by which redox signaling and oxidative stress contribute to the pathogenesis of lung fibrosis are not well understood. Tissue repair is a highly regulated process that involves the interactions of several cell types, including epithelial cells, fibroblasts and inflammatory cells. Fibrosis may develop when these interactions are dysregulated with the acquisition of pro-fibrotic cellular phenotypes. In this review, we explore the roles of redox mechanisms that promote and perpetuate fibrosis in the context of cellular senescence and aging.