Fatty acid nitroalkene reversal of established lung fibrosis

Characterizing the Emergence of Myeloid-Derived Suppressor Cell Subsets in a Murine Model of Pulmonary Fibrosis

The immune system plays a major role in pulmonary fibrosis (PF), a devastating lung disease with limited treatment options. Myeloid-derived suppressor cells (MDSCs) are immune cells with remarkable immunosuppressive functions. We hypothesized that their anti-inflammatory activity may dampen PF by inhibiting inflammation and its transition to fibrosis. Here, we studied the emergence of both polymorphonuclear (PMN)- and monocytic (M)-MDSCs in a murine model of PF. We assessed immunological, histopathological, and clinical changes at days 3, 7, 14, and 21 following bleomycin challenge. A comprehensive overview of the role of MDSCs during the acute lung injury and chronic phase of pulmonary fibrosis is provided, along with the effects of MDSCs adoptive transfer and depletion. Inflammation and fibrosis increased over a period of 21 days after bleomycin administration. In the lung, the number of PMN-MDSCs increased, while M-MDSCs decreased over the time following bleomycin challenge. Especially, M-MDSCs showed enhanced suppressive activity on day 3 following bleomycin challenge. Adoptive transfer of PMN-MDSCs attenuated inflammation and fibrosis development. However, depletion of PMN-MDSCs did not lead to an exacerbation of PF. Our results suggest that adoptive transfer of PMN-MDSCs can ameliorate the inflammatory responses and thus the development of fibrosis in a bleomycin-induced pulmonary fibrosis model.

Lipoxin A4 yields an electrophilic 15-oxo metabolite that mediates FPR2 receptor-independent anti-inflammatory signaling

The enzymatic oxidation of arachidonic acid is proposed to yield trihydroxytetraene species (termed lipoxins) that resolve inflammation via ligand activation of the formyl peptide receptor, FPR2. While cell and murine models activate signaling responses to synthetic lipoxins, primarily lipoxin A4 (LXA4), there are expanding concerns about the reported biological formation, detection, and signaling mechanisms ascribed to LXA4 and related di- and tri-hydroxy ω-6 and ω-3 fatty acids. The generation and signaling actions of LXA4 and its primary 15-oxo metabolite were assessed in control, lipopolysaccharide-activated, and arachidonic acid-supplemented RAW264.7 and bone marrow-derived macrophages. Despite the expression of catalytically active enzymes required for LXA4 synthesis, both LXA4 and its 15-oxo-LXA4 metabolite were undetectable in all conditions. Moreover, synthetic LXA4 and the membrane-permeable 15-oxo-LXA4 methyl ester, which rapidly de-esterified to 15-oxo-LXA4, displayed no ligand activity for the putative LXA4 receptor FPR2. Alternatively, 15-oxo-LXA4, an electrophilic α,β-unsaturated ketone, alkylates nucleophilic amino acids and can modulate redox-sensitive transcriptional regulatory protein and enzyme function. 15-oxo-LXA4 activated nuclear factor (erythroid related factor 2)-like 2-regulated expression of anti-inflammatory and repair genes and inhibited NF-κB-regulated pro-inflammatory mediator expression. Synthetic LXA4 showed no impact on these macrophage anti-inflammatory and repair responses. In summary, these data show an absence of macrophage LXA4 formation and receptor-mediated signaling actions of synthetic LXA4. Rather, if present in sufficient concentrations, LXA4 and other mono- and poly-hydroxylated unsaturated fatty acids synthesized by macrophages would be readily oxidized to electrophilic α,β-unsaturated ketone products that modulate the redox-sensitive cysteine proteome via G-protein coupled receptor-independent mechanisms.

Precision Cut Lung Slices: Emerging Tools for Preclinical and Translational Lung Research. An Official American Thoracic Society Workshop Report

The urgent need for effective treatments for acute and chronic lung diseases underscores the significance of developing innovative preclinical human research tools. The 2023 ATS Workshop on Precision Cut Lung Slices (PCLS) brought together 35 experts to discuss and address the role of human tissue-derived PCLS as a unique tool for target and drug discovery and validation in pulmonary medicine. With increasing interest and usage, along with advancements in methods and technology, there is a growing need for consensus on PCLS methodology and readouts. The current document recommends standard reporting criteria and emphasizes the requirement for careful collection and integration of clinical metadata. We further discuss current clinically relevant readouts that can be applied to PCLS and highlight recent developments and future steps for implementing novel technologies for PCLS modeling and analysis. The collection and correlation of clinical metadata and multiomic analysis will further advent the integration of this preclinical platform into patient endotyping and the development of tailored therapies for lung disease patients.

YAP/TAZ Signaling in the Pathobiology of Pulmonary Fibrosis

Pulmonary fibrosis (PF) is a severe, irreversible lung disease characterized by progressive scarring, with idiopathic pulmonary fibrosis (IPF) being the most prevalent form. IPF's pathogenesis involves repetitive lung epithelial injury leading to fibroblast activation and excessive extracellular matrix (ECM) deposition. The prognosis for IPF is poor, with limited therapeutic options like nintedanib and pirfenidone offering only modest benefits. Emerging research highlights the dysregulation of the yes-associated protein (YAP)/transcriptional coactivator with PDZ-binding motif (TAZ) signaling pathway as a critical factor in PF. YAP and TAZ, components of the Hippo pathway, play significant roles in cell proliferation, differentiation, and fibrosis by modulating gene expression through interactions with TEA domain (TEAD) transcription factors. The aberrant activation of YAP/TAZ in lung tissue promotes fibroblast activation and ECM accumulation. Targeting the YAP/TAZ pathway offers a promising therapeutic avenue. Preclinical studies have identified potential treatments, such as trigonelline, dopamine receptor D1 (DRD1) agonists, and statins, which inhibit YAP/TAZ activity and demonstrate antifibrotic effects. These findings underscore the importance of YAP/TAZ in PF pathogenesis and the potential of novel therapies aimed at this pathway, suggesting a new direction for improving IPF treatment outcomes. Further research is needed to validate these approaches and translate them into clinical practice.

Selenium Species in Diabetes Mellitus Type 2

Selenium is an important trace element for humans and animals as it plays a key role in several major metabolic pathways. Several studies were conducted to better understand the role of selenium against diabetes mellitus (DM), particularly type 2 (T2DM), but the obtained conclusions are contradictory. A simple linear relationship does not exist between the risk of T2DM and selenium levels but is best represented in a dose-dependent manner, getting often the U-graph. This relation also depends on selenium chemical forms that are present in a diet or supplements. Both too low and too high selenium intakes could increase the risk of diabetes. Moreover, the baseline status of Se should be taken into consideration to avoid over-supplementation. The focus of this brief overview is to report the recent updates concerning selenium participation in diabetes mellitus.

WISP-1 Regulates Cardiac Fibrosis by Promoting Cardiac Fibroblasts' Activation and Collagen Processing

Hypertension induces cardiac fibrotic remodelling characterised by the phenotypic switching of cardiac fibroblasts (CFs) and collagen deposition. We tested the hypothesis that Wnt1-inducible signalling pathway protein-1 (WISP-1) promotes CFs' phenotypic switch, type I collagen synthesis, and in vivo fibrotic remodelling. The treatment of human CFs (HCFs, n = 16) with WISP-1 (500 ng/mL) induced a phenotypic switch (α-smooth muscle actin-positive) and type I procollagen cleavage to an intermediate form of collagen (pC-collagen) in conditioned media after 24h, facilitating collagen maturation. WISP-1-induced collagen processing was mediated by Akt phosphorylation via integrin β1, and disintegrin and metalloproteinase with thrombospondin motifs 2 (ADAMTS-2). WISP-1 wild-type (WISP-1+/+) mice and WISP-1 knockout (WISP-1-/-) mice (n = 5-7) were subcutaneously infused with angiotensin II (AngII, 1000 ng/kg/min) for 28 days. Immunohistochemistry revealed the deletion of WISP-1 attenuated type I collagen deposition in the coronary artery perivascular area compared to WISP-1+/+ mice after a 28-day AngII infusion, and therefore, the deletion of WISP-1 attenuated AngII-induced cardiac fibrosis in vivo. Collectively, our findings demonstrated WISP-1 is a critical mediator in cardiac fibrotic remodelling, by promoting CFs' activation via the integrin β1-Akt signalling pathway, and induced collagen processing and maturation via ADAMTS-2. Thereby, the modulation of WISP-1 levels could provide potential therapeutic targets in clinical treatment.

Precision cut lung slices: an integrated ex vivo model for studying lung physiology, pharmacology, disease pathogenesis and drug discovery

Precision Cut Lung Slices (PCLS) have emerged as a sophisticated and physiologically relevant ex vivo model for studying the intricacies of lung diseases, including fibrosis, injury, repair, and host defense mechanisms. This innovative methodology presents a unique opportunity to bridge the gap between traditional in vitro cell cultures and in vivo animal models, offering researchers a more accurate representation of the intricate microenvironment of the lung. PCLS require the precise sectioning of lung tissue to maintain its structural and functional integrity. These thin slices serve as invaluable tools for various research endeavors, particularly in the realm of airway diseases. By providing a controlled microenvironment, precision-cut lung slices empower researchers to dissect and comprehend the multifaceted interactions and responses within lung tissue, thereby advancing our understanding of pulmonary pathophysiology.

Phœnix dactylifera, L. seed oil alleviates Bleomycin-induced pulmonary fibrosis and oxidative stress in Wistar rats

OBJECTIVE

Idiopathic pulmonary fibrosis (IPF) is the most serious form of interstitial lung disease. We aimed to investigate the effect of Phœnix dactylifera, L. seed oil (DSO) on a murine model of IPF induced by bleomycin (BLM).

METHODS

Male Wistar rats were treated with a single intra-tracheal injection of BLM (4 mg/kg) and a daily intraperitoneal injection of DSO (75, 150 and 300 mg/kg) for 4 weeks.

RESULTS

Our phytochemical results showed that DSO has an important antioxidant activity with a high content of polyphenols and flavonoids. High-Performance Liquid Chromatography (HPLC) and Gas chromatography/mass spectrometry (GC-MS) analysis revealed a high amount of oleic and lauric acids and a large quantity of vitamins. Histological examination showed a significant reduction in fibrosis score and collagen bands in the group of rats treated with 75 mg/kg of DSO compared to the BLM group. DSO (75 mg/kg) reversed also the increase in catalase and malondialdehyde (MDA) levels while higher doses (150 and 300 mg/kg) are ineffective against the deleterious effects of BLM. We revealed also that DSO has no renal or hepatic cytotoxic effects.

CONCLUSION

DSO can play antioxidant and antifibrotic effects on rat models of pulmonary fibrosis at the lowest dose administered.

Lipoxin A4 yields an electrophilic 15-oxo metabolite that mediates FPR2 receptor-independent anti-inflammatory signaling

The enzymatic oxidation of arachidonic acid is proposed to yield trihydroxytetraene species (termed lipoxins) that resolve inflammation via ligand activation of the formyl peptide receptor, FPR2. While cell and murine models activate signaling responses to synthetic lipoxins, primarily 5S,6R,15S-trihydroxy-7E,9E,11Z,13E-eicosatetraenoic acid (lipoxin A4, LXA4), there are expanding concerns about the biological formation, detection and signaling mechanisms ascribed to LXA4 and related di- and tri-hydroxy ω-6 and ω-3 fatty acids. Herein, the generation and actions of LXA4 and its primary 15-oxo metabolite were assessed in control, LPS-activated and arachidonic acid supplemented RAW 264.7 macrophages. Despite protein expression of all enzymes required for LXA4 synthesis, both LXA4 and its 15-oxo-LXA4 metabolite were undetectable. Moreover, synthetic LXA4 and the membrane permeable 15-oxo-LXA4 methyl ester that is rapidly de-esterified to 15-oxo-LXA4, displayed no ligand activity for the putative LXA4 receptor FPR2, as opposed to the FPR2 ligand WKYMVm. Alternatively, 15-oxo-LXA4, an electrophilic α,β-unsaturated ketone, alkylates nucleophilic amino acids such as cysteine to modulate redox-sensitive transcriptional regulatory protein and enzyme function. 15-oxo-LXA4 activated nuclear factor (erythroid related factor 2)-like 2 (Nrf2)-regulated gene expression of anti-inflammatory and repair genes and inhibited nuclear factor (NF)-κB-regulated pro-inflammatory mediator expression. LXA4 did not impact these macrophage anti-inflammatory and repair responses. In summary, these data show an absence of macrophage LXA4 formation and receptor-mediated signaling actions. Rather, if LXA4 were present in sufficient concentrations, this, and other more abundant mono- and poly-hydroxylated unsaturated fatty acids can be readily oxidized to electrophilic α,β-unsaturated ketone products that modulate the redox-sensitive cysteine proteome via G-protein coupled receptor-independent mechanisms.

Glycolysis Reprogramming in Idiopathic Pulmonary Fibrosis: Unveiling the Mystery of Lactate in the Lung

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive lung disease characterized by excessive deposition of fibrotic connective tissue in the lungs. Emerging evidence suggests that metabolic alterations, particularly glycolysis reprogramming, play a crucial role in the pathogenesis of IPF. Lactate, once considered a metabolic waste product, is now recognized as a signaling molecule involved in various cellular processes. In the context of IPF, lactate has been shown to promote fibroblast activation, myofibroblast differentiation, and extracellular matrix remodeling. Furthermore, lactate can modulate immune responses and contribute to the pro-inflammatory microenvironment observed in IPF. In addition, lactate has been implicated in the crosstalk between different cell types involved in IPF; it can influence cell-cell communication, cytokine production, and the activation of profibrotic signaling pathways. This review aims to summarize the current research progress on the role of glycolytic reprogramming and lactate in IPF and its potential implications to clarify the role of lactate in IPF and to provide a reference and direction for future research. In conclusion, elucidating the intricate interplay between lactate metabolism and fibrotic processes may lead to the development of innovative therapeutic strategies for IPF.

A Methodological Approach to Identify Natural Compounds with Antifibrotic Activity and the Potential to Treat Pulmonary Fibrosis Using Single-Cell Sequencing and Primary Human Lung Macrophages

Idiopathic pulmonary fibrosis (IPF) is the most common and lethal form of the interstitial pneumonias. The cause of the disease is unknown, and new therapies that stop or reverse disease progression are desperately needed. Recent advances in next-generation sequencing have led to an abundance of freely available, clinically relevant, organ-and-disease-specific, single-cell transcriptomic data, including studies from patients with IPF. We mined data from published IPF data sets and identified gene signatures delineating pro-fibrotic or antifibrotic macrophages and then used the Enrichr platform to identify compounds with the potential to drive the macrophages toward the antifibrotic transcriptotype. We then began testing these compounds in a novel in vitro phenotypic drug screening assay utilising human lung macrophages recovered from whole-lung lavage of patients with silicosis. As predicted by the Enrichr tool, glitazones potently modulated macrophage gene expression towards the antifibrotic phenotype. Next, we assayed a subset of the NatureBank pure compound library and identified the cyclobutane lignan, endiandrin A, which was isolated from the roots of the endemic Australian rainforest plant, Endiandra anthropophagorum, with a similar antifibrotic potential to the glitazones. These methods open new avenues of exploration to find treatments for lung fibrosis.

Perspectives on precision cut lung slices-powerful tools for investigation of mechanisms and therapeutic targets in lung diseases

Precision cut lung slices (PCLS) have emerged as powerful experimental tools for respiratory research. Pioneering studies using mouse PCLS to visualize intrapulmonary airway contractility have been extended to pulmonary arteries and for assessment of novel bronchodilators and vasodilators as therapeutics. Additional disease-relevant outcomes, including inflammatory, fibrotic, and regenerative responses, are now routinely measured in PCLS from multiple species, including humans. This review provides an overview of established and innovative uses of PCLS as an intermediary between cellular and organ-based studies and focuses on opportunities to increase their application to investigate mechanisms and therapeutic targets to oppose excessive airway contraction and fibrosis in lung diseases.

Meta-omics profiling of the gut-lung axis illuminates metabolic networks and host-microbial interactions associated with elevated lung elastance in a murine model of obese allergic asthma

Obesity and associated changes to the gut microbiome worsen airway inflammation and hyperresponsiveness in asthma. Obesogenic host-microbial metabolomes have altered production of metabolites that may influence lung function and inflammatory responses in asthma. To understand the interplay of the gut microbiome, metabolism, and host inflammation in obesity-associated asthma, we used a multi-omics approach to profile the gut-lung axis in the setting of allergic airway disease and diet-induced obesity. We evaluated an immunomodulator, nitro-oleic acid (NO₂-OA), as a host- and microbial-targeted treatment intervention for obesity-associated allergic asthma. Allergic airway disease was induced using house dust mite and cholera toxin adjuvant in C57BL6/J mice with diet-induced obesity to model obesity-associated asthma. Lung function was measured by flexiVent following a week of NO₂-OA treatment and allergen challenge. 16S rRNA gene (from DNA, taxa presence) and 16S rRNA (from RNA, taxa activity) sequencing, metabolomics, and host gene expression were paired with a Treatment-Measured-Response model as a data integration framework for identifying latent/hidden relationships with linear regression among variables identified from high-dimensional meta-omics datasets. Targeting both the host and gut microbiota, NO₂-OA attenuated airway inflammation, improved lung elastance, and modified the gut microbiome. Meta-omics data integration and modeling determined that gut-associated inflammation, metabolites, and functionally active gut microbiota were linked to lung function outcomes. Using Treatment-Measured-Response modeling and meta-omics profiling of the gut-lung axis, we uncovered a previously hidden network of interactions between gut levels of amino acid metabolites involved in elastin and collagen synthesis, gut microbiota, NO₂-OA, and lung elastance. Further targeted metabolomics analyses revealed that obese mice with allergic airway disease had higher levels of proline and hydroxyproline in the lungs. NO₂-OA treatment reduced proline biosynthesis by downregulation of pyrroline-5-carboxylate reductase 1 (PYCR1) expression. These findings are relevant to human disease: adults with mild-moderate asthma and BMI ≥ 25 had higher plasma hydroxyproline levels. Our results suggest that changes to structural proteins in the lung airways and parenchyma may contribute to heightened lung elastance and serve as a potential therapeutic target for obese allergic asthma.

Nitro-oleic acid regulates T cell activation through post-translational modification of calcineurin

Nitro-fatty acids (NO₂-FAs) are unsaturated fatty acid nitration products that exhibit anti-inflammatory actions in experimental mouse models of autoimmune and allergic diseases. These electrophilic molecules interfere with intracellular signaling pathways by reversible post-translational modification of nucleophilic amino-acid residues. Several regulatory proteins have been identified as targets of NO₂-FAs, modifying their activity and promoting gene expression changes that result in anti-inflammatory effects. Herein, we report the effects of nitro-oleic acid (NO₂-OA) on pro-inflammatory T cell functions, showing that 9- and 10-NOA, but not their oleic acid precursor, decrease T cell proliferation, expression of activation markers CD25 and CD71 on the plasma membrane, and IL-2, IL-4, and IFN-γ cytokine gene expressions. Moreover, we have found that NO₂-OA inhibits the transcriptional activity of nuclear factor of activated T cells (NFAT) and that this inhibition takes place through the regulation of the phosphatase activity of calcineurin (CaN), hindering NFAT dephosphorylation, and nuclear translocation in activated T cells. Finally, using mass spectrometry-based approaches, we have found that NO₂-OA nitroalkylates CaNA on four Cys (Cys129, 228, 266, and 372), of which only nitroalkylation on Cys372 was of importance for the regulation of CaN phosphatase activity in cells, disturbing functional CaNA/CaNB heterodimer formation. These results provide evidence for an additional mechanism by which NO₂-FAs exert their anti-inflammatory actions, pointing to their potential as therapeutic bioactive lipids for the modulation of harmful T cell-mediated immune responses.

Nitrated fatty acid, 10-nitrooleate protects against hyperoxia-induced acute lung injury in mice

The antioxidant and anti-inflammatory effects of electrophilic nitrated fatty acid (NFA); 10-nitrooleate, have been reported. The present study investigated whether 10-nitrooleate has a protective role against hyperoxic-induced acute lung injury (HALI). Using a C57BL/6 mice model of HALI, we investigated the protective effect of 10-nitrooleate. C57BL/6 mice were administered with NFA intratracheally, exposed to hyperoxia for 48 h to induce HALI, and kept at room air for 24 h. Bronchoalveolar lavage (BAL) fluid and lung samples were collected after 24 h of post hyperoxia to analyze markers associated with HALI. Intratracheal (IT) and intraperitoneal (IP) administration of NFA notably attenuated hyperoxia-induced infiltration of inflammatory cells, alveolar-capillary leakage, upregulation of proinflammatory cytokine levels (IL-6 and TNFα) into the BAL fluid, and resolution of inflammation in the lung. Western blot analyses showed that 10-nitrooleate reduced the expression of the inflammatory transcription factor NFκB p65 subunit and increased antioxidant proteins HO-1 and NQO1 expression in the lung tissues compared to vehicle-treated animals. Moreover, 10-nitrooleate reversed the hyperoxia-induced expression of mitophagy-associated markers (PINK1 and p62/SQSTM1), thereby protecting the HALI/ acute respiratory distress syndrome (ARDS). IT and IP delivery of 10-nitrooleate reduces hyperoxia-induced ALI/ARDS by regulating the antioxidant pathways and restoring the mitochondrial homeostasis by regulating mitophagy. It is suggested that NFAs can be further evaluated as supplementary therapy for critically ill patients like COVID-19/ARDS.