Impairment of the NKT-STAT1-CXCL9 Axis Contributes to Vessel Fibrosis in Pulmonary Hypertension Caused by Lung Fibrosis

The Immune Microenvironment: New Therapeutic Implications in Organ Fibrosis

Fibrosis, characterized by abnormal deposition of structural proteins, is a major cause of tissue dysfunction in chronic diseases. The disease burden associated with progressive fibrosis is substantial, and currently approved drugs are unable to effectively reverse it. Immune cells are increasingly recognized as crucial regulators in the pathological process of fibrosis by releasing effector molecules, such as cytokines, chemokines, extracellular vesicles, metabolites, proteases, or intercellular contact. Therefore, targeting the immune microenvironment can be a potential strategy for fibrosis reduction and reversion. This review summarizes the recent advances in the understanding of the immune microenvironment in fibrosis including phenotypic and functional transformations of immune cells and the interaction of immune cells with other cells. The novel opportunities for the discovery and development of drugs for immune microenvironment remodeling and their associated challenges are also discussed.

MHCIIhiLYVE1loCCR2hi Interstitial Macrophages Promote Medial Fibrosis in Pulmonary Arterioles and Contribute to Pulmonary Hypertension

BACKGROUND

Pulmonary hypertension (PH) is a lethal disease characterized in part by progressive pulmonary arteriole (PA) remodeling. Excessive PA fibrosis and macrophage infiltration are often present in PH, but the potential associations are obscure. We investigated the link between interstitial macrophage (iMΦ) infiltration and PA fibrosis in PH and idiopathic pulmonary arterial hypertension.

METHODS

Lung tissue samples from patients with idiopathic pulmonary arterial hypertension and experimental PH animals were obtained to analyze the extent of fibrosis and iMΦ infiltration in the different layers of PAs and their correlation with disease severity. Single-cell RNA sequencing, lineage tracing, histological analyses, iMΦ and PA smooth muscle cell coculture, and transgenic animal experiments were used to investigate the cell heterogeneity and origins and molecular mechanisms by which iMΦs promote PA fibrosis.

RESULTS

We found that increased collagen deposition and fibrosis in the PA media were most strongly related to the severity of PH, and medial iMΦ infiltration may be involved in these pathological processes. Single-cell transcriptomics revealed that MHCIIhiLYVE1loCCR2hi iMΦs were the major type of iMΦ that expanded upon Sugen-5416 and hypoxia plus normoxia stimulation and were responsible for PA medial fibrosis. Lineage tracing experiments suggested that these medial iMΦs were largely from recruited monocytes. Mechanistically, MHCIIhiLYVE1loCCR2hi iMΦs promoted the transition of PA smooth muscle cells to a fibroblast-like phenotype through the WNT11 (wingless member 11)/planar cell polarity (PCP) pathway. Wnt11 deletion in iMΦs from PH rats normalized the fibrotic PA smooth muscle cell phenotype and decreased PA medial fibrosis, thereby improving vascular compliance and protecting against PH. Moreover, myeloid-specific Ccr2 deficiency in PH-PAs inhibited the medial infiltration of MHCIIhiLYVE1loCCR2hi iMΦs, which also relieved PH.

CONCLUSIONS

This study demonstrates that the recruitment of MHCIIhiLYVE1loCCR2hi iMΦs leads to medial fibrosis in PH-PAs associated with PH severity and that inhibition of their pathogenicity or recruitment reverses PA medial fibrosis and PH.

ASH2L Deficiency in Smooth Muscle Drives Pulmonary Vascular Remodeling

BACKGROUND

Histone H3 lysine 4 methylation is one of the most abundant epigenetic modifications, which has been recently linked to vascular remodeling in pulmonary hypertension (PH). SET1/MLL methyltransferase complexes comprise the main enzymes responsible for methylating H3 lysine 4, yet their roles in vascular remodeling and PH are not fully understood. We aim to assess the contribution of ASH2L, a core SET1/MLL family member, to the pathogenesis of PH.

METHODS

Human pulmonary artery specimens and primary vascular cells, smooth muscle cell (SMC)-specific ASH2L-deficient mice, rats with SMC-specific ASH2L overexpression, mass spectrometry, immunoprecipitation, and chromatin immunoprecipitation were used to define the role of ASH2L in PH.

RESULTS

Analysis of bulk RNA-sequencing data sets from human lung vessels identified ASH2L as the only differentially expressed SET1/MLL family member in PH compared with healthy controls. Decreased ASH2L expression in human pulmonary arteries correlated with the clinical severity of PH, which contrasted with elevated H3 lysine 4 methylation and was primarily localized to SMCs. Depletion of ASH2L promoted whereas its restoration ameliorated SMC proliferation and vascular remodeling in PH. Mechanistically, we revealed that ASH2L functioned independently of the canonical H3 lysine 4 trimethylation-based transcriptional activation, while it formed a protein complex with KLF5 and FBXW7, thereby accelerating the ubiquitin-proteasomal degradation of KLF5. NOTCH3 was discovered as a new downstream target of KLF5, and the loss of ASH2L promoted the recruitment of KLF5 to the NOTCH3 promoter, thus enhancing NOTCH3 expression. Pharmacological blockage of KLF5 attenuated PH in chronic hypoxia-exposed SMC-specific ASH2L-deficient mice and sugen/hypoxia-challenged rats.

CONCLUSIONS

This study demonstrated that ASH2L deficiency causatively affects SMC proliferation and lung vascular remodeling that is partially mediated through KLF5-dependent NOTCH3 transcription. Activating ASH2L or targeting KLF5 might represent potential therapeutic strategies for PH.

Unveiling the key mechanisms of FOLR2+ macrophage-mediated antitumor immunity in breast cancer using integrated single-cell RNA sequencing and bulk RNA sequencing

Breast cancer (BRCA) is a common malignant tumor, and its immune microenvironment plays a crucial role in disease progression. In this research, we utilized single-cell RNA sequencing and bulk RNA sequencing technologies, combined with in vivo and in vitro experiments, to thoroughly investigate the immunological functions and mechanisms of FOLR2+ macrophages in BRCA. Our findings demonstrate a significant enhancement in the interaction between FOLR2+ macrophages and CD8+ T cells within the tumor tissues of BRCA patients. FOLR2 is closely associated with T cell infiltration in the tumor microenvironment of BRCA patients, particularly with CD8+ T cells. By secreting CXCL9 and engaging with CXCR3, FOLR2+ macrophages can activate the functionality of CD8+ T cells, thereby promoting cancer cell apoptosis. Further animal experiments confirm that FOLR2+ macrophages activate CD8+ T cells through the CXCL9-CXCR3 axis, exhibiting an antitumor immunity effect in BRCA. FOLR2+ macrophages play a crucial role in antitumor immunity in BRCA through the CXCL9-CXCR3 axis.

SPP1hi macrophages, NKG7 T cells, CCL5hi fibroblasts, and IgM plasma cells are dominant features of necrobiosis

Necrobiosis is a histologic term used to describe abnormal deposits of "degenerating" collagen within the skin. It can be found as an incidental finding in various granulomatous conditions, but is a hallmark of necrobiosis lipoidica (NL) and necrobiotic xanthogranuloma (NXG). There is limited prior research on necrobiosis. Here, we employed single-cell analysis of lesional and nonlesional skin to study the pathophysiology of necrobiosis. Our findings demonstrate that necrobiotic lesional skin is characterized by SPP1hi macrophages expressing MARCO; NKG7-expressing effector CD8+ T cells coexpressing CCL5, IFNG, GZMs, and PRF1; CCL5hi fibroblasts coexpressing CXCL9, diverse collagens (e.g., COL4A4, COL11A1, COL8A1), and TIMP1; and IGHM-expressing plasma cells. Integrative analysis of signaling ligands and receptor expression identified strong cell-cell communication between NKG7+ T cells, CCL5hi fibroblasts, and SPP1-expressing macrophages. In contrast, these cell populations were not dominant features of systemic sclerosis, another collagen deposition disease. Furthermore, although SPP1-expressing macrophages were detectable in sarcoidosis, IFNG-expressing T cells were a more defining feature of sarcoidosis compared with NL and NXG. From these findings, we speculate that necrobiosis results from the deposition of diverse collagens and ECM proteins through a process driven by CCL5-expressing fibroblasts and SPP1-expressing macrophages.

New insights into pulmonary arterial hypertension: interaction between PANoptosis and perivascular inflammatory responses

Pulmonary arterial hypertension (PAH) is a heterogeneous disease characterized by various etiologies, with pulmonary vascular remodeling recognized as a main pathological change. Currently, it is widely accepted that vascular remodeling is closely associated with abnormal pulmonary vascular cell death and perivascular inflammation. The simultaneous activation of various pulmonary vascular cell death leads to immune cell adhesion and inflammatory mediator releases; And in turn, the inflammatory response may also trigger cell death and jointly promote the progression of vascular remodeling. Recently, PANoptosis has been identified as a phenomenon that describes the simultaneous activation and interaction of multiple forms of programmed cell death (PCD). Therefore, the relationship between PANoptosis and inflammation in PAH warrants further investigation. This review examines the mechanisms underlying apoptosis, necroptosis, pyroptosis, and inflammatory responses in PAH, with a focus on PANoptosis and its interactions with inflammation. And it aims to elucidate the significance of this emerging form of cell death and inflammation in the pathophysiology of PAH and to explore its potential as a therapeutic target.

MMP8-mediated vascular remodeling in pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a vascular remodeling disease that impacts the cardiopulmonary system. Due to the currently limited understanding of vascular remodeling, a cure for PAH remains elusive. This study highlights the critical role of the STAT1 (signal transducer and activator of transcription 1)/MMP8 (matrix metallopeptidase 8)/DRP1 (dynamin-related protein 1) axis in vascular remodeling and the pathogenesis of pulmonary hypertension. Notably, MMP8 is significantly elevated in pulmonary arterial endothelial cells and its levels correlate with the severity of the disease. MMP8 binds to and activates DRP1, inducing mitochondrial fragmentation and promoting a malignant phenotype of endothelial cells under hypoxic conditions. Moreover, MMP8 is tightly regulated by STAT1. The knockout of MMP8 attenuates chronic pulmonary vascular remodeling, and drugs targeting MMP8 alleviate pulmonary hypertension and enhance cardiac function. This study offers fresh insights into hypoxia-induced vascular remodeling, laying a theoretical foundation for countering vascular remodeling by directly regulating the STAT1/MMP8/DRP1 axis.

Maternal Hypertension Aggravates Vascular Dysfunction After Injury in Male Adult Offspring Through Transgenerational Transmission of N6-Methyladenosine

BACKGROUND

Whether maternal hypertension contributes to the enhanced susceptibility to vascular remodeling in adult offspring through epigenetic mechanisms remains unclear. We aimed to address this gap in the literature using a transgenerational mouse model.

METHODS

Gestational hypertension was induced in pregnant mice using chronic angiotensin II infusion. Blood pressure was monitored using the tail-cuff method. Two months post-delivery, an N6-methyladenosine epitranscriptomic microarray analysis was performed on the carotid arteries of second-generation mice. A unilateral carotid artery injury model was used to study the postinjury vascular response in vivo. Furthermore, carotid ultrasonography, immunohistochemistry, and molecular biological parameters were assessed in adult offspring.

RESULTS

Exposure to maternal hypertension decreased the birth weight of live pups and increased the fetal death rate. Compared with normal offspring, adult offspring with hypertension had wire-induced injury that led to greater vascular remodeling, which was associated with aggravated inflammation imbalance, fibrosis, and oxidative stress. In addition, aberrant N6-methyladenosine methylation, increased N6-methyladenosine levels, and increased METTL3 (methyltransferase-like 3) expression were detected in the vessels of offspring with hypertension. Maternal METTL3 deficiency increased the birth weight of live pups with hypertension, improved vascular dysfunction, and alleviated vascular inflammation in adult offspring with hypertension after injury.

CONCLUSIONS

Maternal hypertension can induce transgenerational transmission of enhanced susceptibility to vascular remodeling, and the possible underlying mechanism is associated with altered METTL3-mediated N6-methyladenosine methylation. Therefore, this study reveals the role of epigenetic effects across generations and provides new insights into vascular remodeling causes.

Identification of an immune-related gene panel for the diagnosis of pulmonary arterial hypertension using bioinformatics and machine learning

OBJECTIVE

This study aimed to screen an immune-related gene (IRG) panel and develop a novel approach for diagnosing pulmonary arterial hypertension (PAH) utilizing bioinformatics and machine learning (ML).

METHODS

Gene expression profiles were retrieved from the Gene Expression Omnibus (GEO) database to identify differentially expressed immune-related genes (IRG-DEGs). We employed five machine learning algorithms-LASSO, random forest (RF), boosted regression trees (BRT), XGBoost, and support vector machine recursive feature elimination (SVM-RFE) to identify biomarkers derived from IRG-DEGs associated with the diagnosis of PAH, incorporating them into the IRG-DEGs panel. Validation of these biomarker levels in lung tissue was conducted in a hypoxia-induced mouse model of PAH, investigating the correlation between AIMP1, IL-15, GLRX, SOD1, Fulton's index (RVHI), and the ratio of pulmonary artery medial thickness to external diameter (MT%). Subsequently, we developed a nomogram model based on the IRG-DEGs panel in lung tissue for diagnosing PAH. The expression, distribution, and pseudotime analysis of these biomarkers across various immune cell types were assessed using single-cell sequencing datasets. Finally, we evaluated the diagnostic utility of the nomogram model based on the IRG-DEGs panel in peripheral blood mononuclear cells (PBMCs) for diagnosing PAH.

RESULTS

A total of 36 upregulated and 17 downregulated IRG-DEGs were identified in lung tissue from patients with PAH. AIMP1, IL-15, GLRX, and SOD1 were subsequently selected as novel immune-related biomarkers for PAH through the aforementioned machine learning algorithms and incorporated into the IRG-DEGs panel. Experimental results from mice with PAH validated that the expression levels of AIMP1, IL-15, and GLRX in lung tissue were elevated, while SOD1 expression was significantly reduced. Additionally, GLRX and AIMP1 exhibited positive correlations with Fulton's index (RVHI). The expression levels of GLRX, IL-15, and AIMP1 showed positive correlations with MT%, whereas SOD1 exhibited negative correlations with MT%. Analysis of single-cell sequencing data further revealed that the levels of IRG-DEG panel members gradually increased during the pseudotime trajectory from PBMCs to macrophages, correlating with macrophage activation. The area under the curve (AUC) for diagnosing PAH using a nomogram model based on the IRG-DEGs panel derived from lung tissue samples and PBMCs was ≥0.969 and 0.900, respectively.

CONCLUSIONS

We developed an IRG-DEGs panel containing AIMP1, IL-15, GLRX, and SOD1, which may facilitate the diagnosis of pulmonary arterial hypertension (PAH). These findings provide novel insights that may enhance diagnostic and therapeutic approaches for PAH.

The Chemokine System as a Key Regulator of Pulmonary Fibrosis: Converging Pathways in Human Idiopathic Pulmonary Fibrosis (IPF) and the Bleomycin-Induced Lung Fibrosis Model in Mice

Idiopathic pulmonary fibrosis (IPF) is a chronic and lethal interstitial lung disease (ILD) of unknown origin, characterized by limited treatment efficacy and a fibroproliferative nature. It is marked by excessive extracellular matrix deposition in the pulmonary parenchyma, leading to progressive lung volume decline and impaired gas exchange. The chemokine system, a network of proteins involved in cellular communication with diverse biological functions, plays a crucial role in various respiratory diseases. Chemokine receptors trigger the activation, proliferation, and migration of lung-resident cells, including pneumocytes, endothelial cells, alveolar macrophages, and fibroblasts. Around 50 chemokines can potentially interact with 20 receptors, expressed by both leukocytes and non-leukocytes such as tissue parenchyma cells, contributing to processes such as leukocyte mobilization from the bone marrow, recirculation through lymphoid organs, and tissue influx during inflammation or immune response. This narrative review explores the complexity of the chemokine system in the context of IPF and the bleomycin-induced lung fibrosis mouse model. The goal is to identify specific chemokines and receptors as potential therapeutic targets. Recent progress in understanding the role of the chemokine system during IPF, using experimental models and molecular diagnosis, underscores the complex nature of this system in the context of the disease. Despite advances in experimental models and molecular diagnostics, discovering an effective therapy for IPF remains a significant challenge in both medicine and pharmacology. This work delves into microarray results from lung samples of IPF patients and murine samples at different stages of bleomycin-induced pulmonary fibrosis. By discussing common pathways identified in both IPF and the experimental model, we aim to shed light on potential targets for therapeutic intervention. Dysregulation caused by abnormal chemokine levels observed in IPF lungs may activate multiple targets, suggesting that chemokine signaling plays a central role in maintaining or perpetuating lung fibrogenesis. The highlighted chemokine axes (CCL8-CCR2, CCL19/CCL21-CCR7, CXCL9-CXCR3, CCL3/CCL4/CCL5-CCR5, and CCL20-CCR6) present promising opportunities for advancing IPF treatment research and uncovering new pharmacological targets within the chemokine system.

PCSK9 inhibitor alleviates experimental pulmonary fibrosis-induced pulmonary hypertension via attenuating epithelial-mesenchymal transition by suppressing Wnt/β-catenin signaling in vivo and in vitro

Background

The co-occurrence of pulmonary hypertension (PH) in patients with pulmonary fibrosis (PF) is linked to a more unfavorable prognosis and increased mortality compared to PF cases without PH. Early intervention and comprehensive management are pivotal for improving survival outcomes. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a protein essential in cholesterol metabolism. However, the potential for PCSK9 inhibition to alleviate PF-induced PH has not been previously reported.

Methods

A mouse model of PF-induced PH was established using intratracheal injection of bleomycin (BLM), followed by administration of a PCSK9 inhibitor every other day. Data on right ventricle (RV) remodeling and changes in pulmonary arteries were collected and analyzed. Transforming growth factor-beta (TGF-β) was also administered to MLE-12 cells as an experimental lung fibrosis model. The mechanisms of PCSK9's impact on lung fibrosis were examined both in vivo and in vitro.

Results

Inhibition of PCSK9 significantly reduced pulmonary artery thickening and RV remodeling in the BLM-induced mouse model. Moreover, the blockage of PCSK9 effectively attenuated the migration and epithelial-mesenchymal transition (EMT) process of TGF-β-induced MLE-12 cells. We also observed that the PCSK9 inhibitor suppressed the expression of the Wnt/β-catenin pathway in both animal and cell experiments.

Conclusion

PCSK9 plays a crucial role in the progression of PF-induced PH by regulating cell EMT and Wnt/β-catenin signaling. Targeting PCSK9 expression or activity could effectively control lung fibrosis and its PH complication.

Understanding Comorbidities of Respiratory Models as Novel Platforms for Drug Discovery

Chronic respiratory diseases affect over 450 million people worldwide and result in 4 million deaths per year. The majority of lung diseases are treated with drugs delivered directly to the lungs. However, there is bidirectional crosstalk between the lung and other organs/tissues in health and disease. This crosstalk supports targeting of extrapulmonary sites in addition to the lung to improve the comorbidities associated with lung disease. However, new preclinical in vivo and in vitro assays that model the human pathophysiology are required. In this review, we showcase the latest knowledge of the bidirectional relationship between the respiratory system and organs affected by comorbidities such as obesity and atherosclerosis. We also discuss the impact of new cell culture systems, including complex 3D culture models that may be used as platforms to generate disease insights and for drug discovery. This review highlights work presented by Respiratory and Inflammation Special Interest Group researchers as part of the Australasian Society of Clinical and Experimental Pharmacologists and Toxicologists (ASCEPT) annual scientific meeting in 2023.

Over-activation of iNKT cells aggravate lung injury in bronchopulmonary dysplasia mice

Bronchopulmonary dysplasia (BPD) is a severe lung disease in preterm infants, the abnormal proliferate and differentiate ability of type II epithelial cells (AEC II) is the key to the pathological basis of BPD. Mechanisms regarding abnormal AEC II in BPD remain unclear. The present work investigated the role and mechanisms of invariant natural killer T (iNKT) cells in lung disorder in BPD using public datasets, clinical samples, a hyperoxia-induced BPD mouse model and AEC II-iNKT cells transwell co-culture system. Firstly, we found that the NKT cells development factor IL-15 increased over time in patients with BPD in public databases, and clinically collected peripheral blood NKT cells in patients with BPD were increased. Subsequently, the percentage of iNKT cells increased in hyperoxia group compared with normoxia group, with the highest at P7, accompanied by increased activation with abnormal lung development. The administration of anti-CD1d neutralizing antibody to inhibit iNKT cells could alleviate the abnormal lung development of hyperoxia group mice, while α-GalCer administration could aggravate lung injury in hyperoxia group mice, and adoptive transfer of iNKT cells could aggravate the abnormal lung development in hyperoxia group mice. In addition, to further verify the role of iNKT cells on AEC II, AEC II-iNKT cells co-culture system was established. The presence of iNKT cells could aggravate the abnormal expression of SP-C and T1α under hyperoxia. Meanwhile, RNA-seq analysis showed that ferroptosis-related genes were highly expressed in AEC II co-cultured with iNKT cells under hyperoxia. We further validated the effect of the presence of iNKT cells under hyperoxia environment on AEC II ferroptosis levels, suggested that iNKT cells promote AEC II ferroptosis under hyperoxia, accompanied by decreased expression of SP-C and T1α. Our study found that the recruitment of iNKT cells in the lung may be an important cause of alveolarization disorder in BPD.

What Is on the Horizon for Treatments in Idiopathic Pulmonary Fibrosis?

Idiopathic pulmonary fibrosis (IPF) is a progressive and often fatal lung disease most commonly encountered in older individuals. Several decades of research have contributed to a better understanding of its pathogenesis, though only two drugs thus far have shown treatment efficacy, i.e., by slowing the decline of lung function. The pathogenesis of IPF remains incompletely understood and involves multiple complex interactions and mechanisms working in tandem or separately to result in unchecked deposition of extracellular matrix components and collagen characteristic of the disease. These mechanisms include aberrant response to injury in the alveolar epithelium, inappropriate communication between epithelial cells and mesenchymal cells, imbalances between oxidative injury and tissue repair, recruitment of inflammatory pathways that induce fibrosis, and cell senescence leading to sustained activation and proliferation of fibroblasts and myofibroblasts. Targeted approaches to each of these mechanistic pathways have led to recent clinical studies evaluating the safety and efficacy of several agents. This review highlights selected concepts in the pathogenesis of IPF as a rationale for understanding current or future therapeutic approaches, followed by a review of several selected agents and their recent or active clinical studies. Current novel therapies include approaches to attenuating or modifying specific cellular or signaling processes in the fibrotic pathway, modifying inflammatory and metabolic derangements, and minimizing inappropriate cell senescence.

Pathology and pathobiology of pulmonary hypertension: current insights and future directions

In recent years, major advances have been made in the understanding of the cellular and molecular mechanisms driving pulmonary vascular remodelling in various forms of pulmonary hypertension, including pulmonary arterial hypertension, pulmonary hypertension associated with left heart disease, pulmonary hypertension associated with chronic lung disease and hypoxia, and chronic thromboembolic pulmonary hypertension. However, the survival rates for these different forms of pulmonary hypertension remain unsatisfactory, underscoring the crucial need to more effectively translate innovative scientific knowledge into healthcare interventions. In these proceedings of the 7th World Symposium on Pulmonary Hypertension, we delve into recent developments in the field of pathology and pathophysiology, prioritising them while questioning their relevance to different subsets of pulmonary hypertension. In addition, we explore how the latest omics and other technological advances can help us better and more rapidly understand the myriad basic mechanisms contributing to the initiation and progression of pulmonary vascular remodelling. Finally, we discuss strategies aimed at improving patient care, optimising drug development, and providing essential support to advance research in this field.

Causal association between circulating inflammatory proteins and peripheral artery disease: a bidirectional two-sample Mendelian randomization study

Introduction

A growing body of research has shown a strong connection between circulating inflammatory proteins and Peripheral artery disease (PAD). However, the causal relationship between circulating inflammatory proteins and PAD is still not fully understood. To investigate this association, we conducted a bidirectional Mendelian randomization study.

Materials and methods

Our study utilized genetic variation data obtained from genome-wide association studies (GWAS) datasets. Specifically, the GWAS dataset related to PAD (identifier: finn-b-I9_PAD) included 7,098 cases and 206,541 controls. Additionally, we extracted data on 91 inflammatory proteins from another GWAS dataset (identifiers: GCST90274758-GCST90274848), involving 14,824 participants. To assess the causal relationship between circulating inflammatory proteins and PAD development, we employed methodologies such as inverse variance weighting (IVW), MR Egger regression, and the weighted median approach. Furthermore, sensitivity analyses were conducted to ensure the reliability and robustness of our findings.

Results

Two inflammatory proteins were found to be significantly associated with PAD risk: Natural killer cell receptor 2B4 levels (OR, 1.219; 95% CI,1.019~1.457; P=0.03), Fractalkine levels (OR, 0.755; 95% CI=0.591~0.965; P=0.025). PAD had statistically significant effects on 12 inflammatory proteins: C-C motif chemokine 19 levels (OR, 0.714; 95% CI, 0.585 to 0.872; P=0.001), T-cell surface glycoprotein CD5 levels (OR, 0.818; 95% CI, 0.713 to 0.938; P=0.004), CUB domain-containing protein 1 levels (OR, 0.889; 95% CI, 0.809 to 0.977; P=0.015), Fibroblast growth factor 23 levels (OR, 1.129; 95% CI, 1.009 to 1.264; P=0.034), Interferon gamma levels (OR, 1.124; 95% CI, (1.011 to 1.250); P=0.031),Interleukin-15 receptor subunit alpha levels (OR, 1.183; 95% CI,(1.005 to 1.392); P=0.044), Interleukin-17C levels (OR,1.186; 95% CI, (1.048 to 1.342); P=0.007), Interleukin-1-alpha levels (OR, 1.349; 95% CI, (1.032 to 1.765); P=0.029), Interleukin-5 levels (OR, 1.119; 95% CI,(1.003 to 1.248); P=0.043), Latency-associated peptide transforming growth factor beta 1 levels (OR,1.123; 95% CI, (1.020 to 1.236); P=0.018), Matrix metalloproteinase-10 levels (OR, 1.119; 95% CI,(1.015 to 1.233); P=0.024), Signaling lymphocytic activation molecule levels (OR, 0.823; 95% CI, (0.693 to 0.978); P=0.027).

Conclusion

Our research expands on genetic studies exploring the strong association between circulating inflammatory proteins and PAD. This discovery has the potential to inform and shape future clinical and basic research endeavors in this area.

A comprehensive map of proteoglycan expression and deposition in the pulmonary arterial wall in health and pulmonary hypertension

Changes in the extracellular matrix of pulmonary arteries (PAs) are a key aspect of vascular remodeling in pulmonary hypertension (PH). Yet, our understanding of the alterations affecting the proteoglycan (PG) family remains limited. We sought to investigate the expression and spatial distribution of major vascular PGs in PAs from healthy individuals and various PH groups (chronic obstructive pulmonary disease: PH-COPD, pulmonary fibrosis: PH-PF, idiopathic: IPAH). PG regulation, deposition, and synthesis were notably heightened in IPAH, followed by PH-PF, with minor alterations in PH-COPD. Single-cell analysis unveiled cell-type and disease-specific PG regulation. Agrin expression, a basement membrane PG, was increased in IPAH, with PA endothelial cells (PAECs) identified as a major source. PA smooth muscle cells (PASMCs) mainly produced large-PGs, aggrecan and versican, and small-leucine-like proteoglycan (SLRP) biglycan, whereas the major PGs produced by adventitial fibroblasts were SLRP decorin and lumican. In IPAH and PF-PH, the neointima-forming PASMC population increased the expression of all investigated large-PGs and SLRPs, except fibroblast-predominant decorin (DCN). Expression of lumican, versican, and biglycan also positively correlated with collagen 1α1/1α2 expression in PASMCs in patients with IPAH and PH-PF. We demonstrated that transforming growth factor-beta (TGF-β) regulates versican and biglycan expression, indicating their contribution to vessel fibrosis in IPAH and PF-PH. We furthermore show that certain circulating PG levels display a disease-dependent pattern, with increased decorin and lumican across all patient groups, while versican was elevated in PH-COPD and IPAH and biglycan reduced in IPAH. These findings suggest unique compartment-specific PG regulation in different forms of PH, indicating distinct pathological processes.NEW & NOTEWORTHY Idiopathic pulmonary arterial hypertension (IPAH) pulmonary arteries (PAs) displayed the greatest proteoglycan (PG) changes, with PH associated with pulmonary fibrosis (PH-PF) and PH associated with chronic obstructive pulmonary disease (PH-COPD) following. Agrin, an endothelial cell-specific PG, was solely upregulated in IPAH. Among all cells, neo-intima-forming smooth muscle cells (SMCs) displayed the most significant PG increase. Increased levels of circulating decorin, lumican, and versican, mainly derived from SMCs, and adventitial fibroblasts, may serve as systemic indicators of pulmonary remodeling, reflecting perivascular fibrosis and neointima formation.

Simultaneous Positron Emission Tomography and Molecular Magnetic Resonance Imaging of Cardiopulmonary Fibrosis in a Mouse Model of Left Ventricular Dysfunction

BACKGROUND

Aging-associated left ventricular dysfunction promotes cardiopulmonary fibrogenic remodeling, Group 2 pulmonary hypertension (PH), and right ventricular failure. At the time of diagnosis, cardiac function has declined, and cardiopulmonary fibrosis has often developed. Here, we sought to develop a molecular positron emission tomography (PET)-magnetic resonance imaging (MRI) protocol to detect both cardiopulmonary fibrosis and fibrotic disease activity in a left ventricular dysfunction model.

METHODS AND RESULTS

Left ventricular dysfunction was induced by transverse aortic constriction (TAC) in 6-month-old senescence-accelerated prone mice, a subset of mice that received sham surgery. Three weeks after surgery, mice underwent simultaneous PET-MRI at 4.7 T. Collagen-targeted PET and fibrogenesis magnetic resonance (MR) probes were intravenously administered. PET signal was computed as myocardium- or lung-to-muscle ratio. Percent signal intensity increase and Δ lung-to-muscle ratio were computed from the pre-/postinjection magnetic resonance images. Elevated allysine in the heart (P=0.02) and lungs (P=0.17) of TAC mice corresponded to an increase in myocardial magnetic resonance imaging percent signal intensity increase (P<0.0001) and Δlung-to-muscle ratio (P<0.0001). Hydroxyproline in the heart (P<0.0001) and lungs (P<0.01) were elevated in TAC mice, which corresponded to an increase in heart (myocardium-to-muscle ratio, P=0.02) and lung (lung-to-muscle ratio, P<0.001) PET measurements. Pressure-volume loop and echocardiography demonstrated adverse left ventricular remodeling, function, and increased right ventricular systolic pressure in TAC mice.

CONCLUSIONS

Administration of collagen-targeted PET and allysine-targeted MR probes led to elevated PET-magnetic resonance imaging signals in the myocardium and lungs of TAC mice. The study demonstrates the potential to detect fibrosis and fibrogenesis in cardiopulmonary disease through a dual molecular PET-magnetic resonance imaging protocol.

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.

Bioinformatics analysis of hypoxia associated genes and inflammatory cytokine profiling in COPD-PH

Pulmonary hypertension (PH) in chronic obstructive pulmonary disease (COPD) is associated with worse clinical outcomes and decreased survival rates. In absence of disease specific diagnostic/therapeutic targets and unclear pathophysiology, there is an urgent need for the identification of potential genetic/molecular markers and disease associated pathways. The present study aims to use a bioinformatics approach to identify and validate hypoxia-associated gene signatures in COPD-PH patients. Additionally, hypoxia-related inflammatory profile is also explored in these patients. Microarray dataset obtained from the Gene Expression Omnibus repository was used to identify differentially expressed genes (DEGs) in a hypoxic PH mice model. The top three hub genes identified were further validated in COPD-PH patients, with chemokine (C-X-C motif) ligand 9 (CXCL9) and CXCL12 showing significant changes in comparison to healthy controls. Furthermore, multiplexed analysis of 10 inflammatory cytokines, tumor necrosis factor alpha (TNF-α), transforming growth factor β (TGF-β), interleukin 1-beta (IL-1β), IL-4, IL-5, IL-6, IL-13, IL-17, IL-18 and IL-21 was also performed. These markers showed significant changes in COPD-PH patients as compared to controls. They also exhibited the ability to differentially diagnose COPD-PH patients in comparison to COPD. Additionally, IL-6 and IL-17 showed significant positive correlation with systolic pulmonary artery pressure (sPAP). This study is the first report to assess the levels of CXCL9 and CXCL12 in COPD-PH patients and also explores their link with the inflammatory profile of these patients. Our findings could be extended to better understand the underlying disease mechanism and possibly used for tailoring therapies exclusive for the disease.

Study on Potential Differentially Expressed Genes in Idiopathic Pulmonary Fibrosis by Bioinformatics and Next-Generation Sequencing Data Analysis

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive lung disease with reduced quality of life and earlier mortality, but its pathogenesis and key genes are still unclear. In this investigation, bioinformatics was used to deeply analyze the pathogenesis of IPF and related key genes, so as to investigate the potential molecular pathogenesis of IPF and provide guidance for clinical treatment. Next-generation sequencing dataset GSE213001 was obtained from Gene Expression Omnibus (GEO), and the differentially expressed genes (DEGs) were identified between IPF and normal control group. The DEGs between IPF and normal control group were screened with the DESeq2 package of R language. The Gene Ontology (GO) and REACTOME pathway enrichment analyses of the DEGs were performed. Using the g:Profiler, the function and pathway enrichment analyses of DEGs were performed. Then, a protein-protein interaction (PPI) network was constructed via the Integrated Interactions Database (IID) database. Cytoscape with Network Analyzer was used to identify the hub genes. miRNet and NetworkAnalyst databaseswereused to construct the targeted microRNAs (miRNAs), transcription factors (TFs), and small drug molecules. Finally, receiver operating characteristic (ROC) curve analysis was used to validate the hub genes. A total of 958 DEGs were screened out in this study, including 479 up regulated genes and 479 down regulated genes. Most of the DEGs were significantly enriched in response to stimulus, GPCR ligand binding, microtubule-based process, and defective GALNT3 causes HFTC. In combination with the results of the PPI network, miRNA-hub gene regulatory network and TF-hub gene regulatory network, hub genes including LRRK2, BMI1, EBP, MNDA, KBTBD7, KRT15, OTX1, TEKT4, SPAG8, and EFHC2 were selected. Cyclothiazide and rotigotinethe are predicted small drug molecules for IPF treatment. Our findings will contribute to identification of potential biomarkers and novel strategies for the treatment of IPF, and provide a novel strategy for clinical therapy.

Pentastatin, a matrikine of the collagen IVα5, is a novel endogenous mediator of pulmonary endothelial dysfunction

Deposition of basement membrane components, such as collagen IVα5, is associated with altered endothelial cell function in pulmonary hypertension. Collagen IVα5 harbors a functionally active fragment within its C-terminal noncollageneous (NC1) domain, called pentastatin, whose role in pulmonary endothelial cell behavior remains unknown. Here, we demonstrate that pentastatin serves as a mediator of pulmonary endothelial cell dysfunction, contributing to pulmonary hypertension. In vitro, treatment with pentastatin induced transcription of immediate early genes and proinflammatory cytokines and led to a functional loss of endothelial barrier integrity in pulmonary arterial endothelial cells. Mechanistically, pentastatin leads to β1-integrin subunit clustering and Rho/ROCK activation. Blockage of the β1-integrin subunit or the Rho/ROCK pathway partially attenuated the pentastatin-induced endothelial barrier disruption. Although pentastatin reduced the viability of endothelial cells, smooth muscle cell proliferation was induced. These effects on the pulmonary vascular cells were recapitulated ex vivo in the isolated-perfused lung model, where treatment with pentastatin-induced swelling of the endothelium accompanied by occasional endothelial cell apoptosis. This was reflected by increased vascular permeability and elevated pulmonary arterial pressure induced by pentastatin. This study identifies pentastatin as a mediator of endothelial cell dysfunction, which thus might contribute to the pathogenesis of pulmonary vascular disorders such as pulmonary hypertension.NEW & NOTEWORTHY This study is the first to show that pentastatin, the matrikine of the basement membrane (BM) collagen IVα5 polypeptide, triggers rapid pulmonary arterial endothelial cell barrier disruption, activation, and apoptosis in vitro and ex vivo. Mechanistically, pentastatin partially acts through binding to the β1-integrin subunit and the Rho/ROCK pathway. These findings are the first to link pentastatin to pulmonary endothelial dysfunction and, thus, suggest a major role for BM-matrikines in pulmonary vascular diseases such as pulmonary hypertension.

Restoration of Foxp3+ Regulatory T Cells by HDAC-Dependent Epigenetic Modulation Plays a Pivotal Role in Resolving Pulmonary Arterial Hypertension Pathology

Rationale: Immune dysregulation is a common feature of pulmonary arterial hypertension (PAH). Histone deacetylase (HDAC)-dependent transcriptional reprogramming epigenetically modulates immune homeostasis and is a novel disease-oriented approach in modern times. Objectives: To identify a novel functional link between HDAC and regulatory T cells (Tregs) in PAH, aiming to establish disease-modified biomarkers and therapeutic targets. Methods: Peripheral blood mononuclear cells were isolated from patients with idiopathic PAH (IPAH) and rodent models of pulmonary hypertension (PH): monocrotaline rats, Sugen5416-hypoxia rats, and Treg-depleted mice. HDAC inhibitor vorinostat (suberoylanilide hydroxamic acid, SAHA) was used to examine the immune modulatory effects in vivo, ex vivo, and in vitro. Measurements and Main Results: Increased HDAC expression was associated with reduced Foxp3+ Tregs and increased PD-1 (programmed cell death-1) signaling in peripheral blood mononuclear cells from patients with IPAH. SAHA differentially modified a cluster of epigenetic-sensitive genes and induced Foxp3+ Treg conversion in IPAH T cells. Rodent models recapitulated these epigenetic aberrations and T-cell dysfunction. SAHA attenuated PH phenotypes and restored FOXP3 transcription and Tregs in PH rats; interestingly, the effects were more profound in female rats. Selective depletion of CD25+ Tregs in Sugen5416-hypoxia mice neutralized the effects of SAHA. Furthermore, SAHA inhibited endothelial cytokine/chemokine release upon stimulation and subsequent immune chemotaxis. Conclusions: Our results indicated HDAC aberration was associated with Foxp3+ Treg deficiency and demonstrated an epigenetic-mediated mechanism underlying immune dysfunction in PAH. Restoration of Foxp3+ Tregs by HDAC inhibitors is a promising approach to resolve pulmonary vascular pathology, highlighting the potential benefit of developing epigenetic therapies for PAH.

Bioinformatics analysis to identify potential biomarkers for the pulmonary artery hypertension associated with the basement membrane

Pulmonary arterial hypertension (PAH) is a rapidly progressing cardiopulmonary disease. It is characterized by increased pulmonary artery pressure and vascular resistance. The most notable histopathological characteristic is vascular remodeling. The changes in the basement membrane (BM) are believed to be related to vascular remodeling. It is crucial to identify potential biomarkers associated with the BM in PAH, to guide its treatment. The microarray datasets GSE117261 and GSE113439 were downloaded from the Gene Expression Omnibus. Two data sets were examined to identify genes associated with the BM by analyzing gene expression changes. Next, we analyzed the relevant genes in the Kyoto Encyclopedia of Genes and Genomes using Gene Ontology and Disease Ontology annotationand conducted pathway enrichment analysis. We conducted a protein-protein interaction network analysis on the genes related to BMs and used the cell cytoHubba plug-in to identify the hub genes. Furthermore, we conducted an immune infiltration analysis and implemented a histogram model. Finally, we predicted and analyzed potential therapeutic drugs for PAH and set up a miRNA network of genetic markers. Six candidate genes related to BMs, namely Integrin Subunit Alpha V, Integrin Subunit Alpha 4, ITGA2, ITGA9, Thrombospondin 1, and Collagen Type IV Alpha 3 Chain, were identified as potential modulators of the immune process in PAH. Furthermore, ginsenoside Rh1 was found to significantly impact drug targeting based on its interactions with the six BM-related genes identified earlier. A novel biomarker related to the BM, which plays a crucial role in the development of PAH, has been identified.

Type 1 invariant natural killer T cells in chronic inflammation and tissue fibrosis

Chronic tissue inflammation often results in fibrosis characterized by the accumulation of extracellular matrix components remodeling normal tissue architecture and function. Recent studies have suggested common immune mechanisms despite the complexity of the interactions between tissue-specific fibroblasts, macrophages, and distinct immune cell populations that mediate fibrosis in various tissues. Natural killer T (NKT) cells recognizing lipid antigens bound to CD1d molecules have been shown to play an important role in chronic inflammation and fibrosis. Here we review recent data in both experimental models and in humans that suggest a key role of type 1 invariant NKT (iNKT) cell activation in the progression of inflammatory cascades leading to recruitment of neutrophils and activation of the inflammasome, macrophages, fibroblasts, and, ultimately, fibrosis. Emerging evidence suggests that iNKT-associated mechanisms contribute to type 1, type 2 and type 3 immune pathways mediating tissue fibrosis, including idiopathic pulmonary fibrosis (IPF). Thus, targeting a pathway upstream of these immune mechanisms, such as the inhibition of iNKT activation, may be important in modulating various fibrotic conditions.

The vascular perspective on acute and chronic lung disease

The pulmonary vasculature has been frequently overlooked in acute and chronic lung diseases, such as acute respiratory distress syndrome (ARDS), pulmonary fibrosis (PF), and chronic obstructive pulmonary disease (COPD). The primary emphasis in the management of these parenchymal disorders has largely revolved around the injury and aberrant repair of epithelial cells. However, there is increasing evidence that the vascular endothelium plays an active role in the development of acute and chronic lung diseases. The endothelial cell network in the capillary bed and the arterial and venous vessels provides a metabolically highly active barrier that controls the migration of immune cells, regulates vascular tone and permeability, and participates in the remodeling processes. Phenotypically and functionally altered endothelial cells, and remodeled vessels, can be found in acute and chronic lung diseases, although to different degrees, likely because of disease-specific mechanisms. Since vascular remodeling is associated with pulmonary hypertension, which worsens patient outcomes and survival, it is crucial to understand the underlying vascular alterations. In this Review, we describe the current knowledge regarding the role of the pulmonary vasculature in the development and progression of ARDS, PF, and COPD; we also outline future research directions with the hope of facilitating the development of mechanism-based therapies.

Distribution and chemotactic mechanism of CD4+ T cells in traumatic tracheal stenosis

A systemic and local inflammatory immune imbalance is thought to be the cause of traumatic tracheal stenosis (TS). However, with CD4+ T lymphocytes being the predominant immune cells in TS, the mechanism of action and recruitment has not been described. In our research, using flow cytometry, ELISA, immunofluorescence, and Transwell chamber assays, the expression, distribution, and potential chemotactic function of CD4+ T cells in TS patients were examined before and after treatment. The results showed that the untreated group had significantly more CD4+ T cells and their secreted TGF-β1 than the treated group. Additionally, the untreated group's CD4+ T cells showed a significant rise in CCL22 and CCL1, as well as a larger proportion of CCR4 and CCR8. CD4+ T cells and CD68+ macrophages located in TS also expressed CCL1 and CCL22. In vitro, anti-CCL1 and anti-CCL22 can partially block the chemoattractant effect of TS bronchoalveolar lavage (BAL) on purified CD4+ T cells. The findings of this study indicated that TS contained unbalanced CD4 immune cells that were actively recruited locally by CCR4/CCL22 and CCR8/CCL1. As a result, it is anticipated that CD4 immune rebalancing can serve as a novel treatment for TS.

Inhibition of NK1.1 signaling attenuates pressure overload-induced heart failure, and consequent pulmonary inflammation and remodeling

Background

Inflammation contributes to heart failure (HF) development, the progression from left ventricular failure to pulmonary remodeling, and the consequent right ventricular hypertrophy and failure. NK1.1 plays a critical role in Natural killer (NK) and NK T (NKT) cells, but the role of NK1.1 in HF development and progression is unknown.

Methods

We studied the effects of NK1.1 inhibition on transverse aortic constriction (TAC)-induced cardiopulmonary inflammation, HF development, and HF progression in immunocompetent male mice of C57BL/6J background.

Results

We found that NK1.1+ cell-derived interferon gamma+ (IFN-γ+) was significantly increased in pulmonary tissues after HF. In addition, anti-NK1.1 antibodies simultaneously abolished both NK1.1+ cells, including the NK1.1+NK and NK1.1+NKT cells in peripheral blood, spleen, and lung tissues, but had no effect on cardiopulmonary structure and function under control conditions. However, systemic inhibition of NK1.1 signaling by anti-NK1.1 antibodies significantly rescued mice from TAC-induced left ventricular inflammation, fibrosis, and failure. Inhibition of NK1.1 signaling also significantly attenuated TAC-induced pulmonary leukocyte infiltration, fibrosis, vessel remodeling, and consequent right ventricular hypertrophy. Moreover, inhibition of NK1.1 signaling significantly reduced TAC-induced pulmonary macrophage and dendritic cell infiltration and activation.

Conclusions

Our data suggest that inhibition of NK1.1 signaling is effective in attenuating systolic overload-induced cardiac fibrosis, dysfunction, and consequent pulmonary remodeling in immunocompetent mice through modulating the cardiopulmonary inflammatory response.

Microenvironmental regulation of T-cells in pulmonary hypertension

Introduction

In pulmonary hypertension (PH), pulmonary arterial remodeling is often accompanied by perivascular inflammation. The inflammation is characterized by the accumulation of activated macrophages and lymphocytes within the adventitial stroma, which is comprised primarily of fibroblasts. The well-known ability of fibroblasts to secrete interleukins and chemokines has previously been implicated as contributing to this tissue-specific inflammation in PH vessels. We were interested if pulmonary fibroblasts from PH arteries contribute to microenvironmental changes that could activate and polarize T-cells in PH.

Methods

We used single-cell RNA sequencing of intact bovine distal pulmonary arteries (dPAs) from PH and control animals and flow cytometry, mRNA expression analysis, and respirometry analysis of blood-derived bovine/human T-cells exposed to conditioned media obtained from pulmonary fibroblasts of PH/control animals and IPAH/control patients (CM-(h)PH Fibs vs CM-(h)CO Fibs).

Results

Single-cell RNA sequencing of intact bovine dPAs from PH and control animals revealed a pro-inflammatory phenotype of CD4+ T-cells and simultaneous absence of regulatory T-cells (FoxP3+ Tregs). By exposing T-cells to CM-(h)PH Fibs we stimulated their proinflammatory differentiation documented by increased IFNγ and decreased IL4, IL10, and TGFβ mRNA and protein expression. Interestingly, we demonstrated a reduction in the number of suppressive T-cell subsets, i.e., human/bovine Tregs and bovine γδ T-cells treated with CM-(h)PH-Fibs. We also noted inhibition of anti-inflammatory cytokine expression (IL10, TGFβ, IL4). Pro-inflammatory polarization of bovine T-cells exposed to CM-PH Fibs correlated with metabolic shift to glycolysis and lactate production with increased prooxidant intracellular status as well as increased proliferation of T-cells. To determine whether metabolic reprogramming of PH-Fibs was directly contributing to the effects of PH-Fibs conditioned media on T-cell polarization, we treated PH-Fibs with the HDAC inhibitor SAHA, which was previously shown to normalize metabolic status and examined the effects of the conditioned media. We observed significant suppression of inflammatory polarization associated with decreased T-cell proliferation and recovery of mitochondrial energy metabolism.

Conclusion

This study demonstrates how the pulmonary fibroblast-derived microenvironment can activate and differentiate T-cells to trigger local inflammation, which is part of the vascular wall remodeling process in PH.

The endothelium in lung fibrosis: a core signaling hub in disease pathogenesis?

Pulmonary fibrosis (PF) is a progressive chronic lung disease characterized by excessive deposition of extracellular matrix (ECM) and structural destruction, associated with a severe 5-year mortality rate. The onset of the disease is thought to be triggered by chronic damage to the alveolar epithelium. Since the pulmonary endothelium is an important component of the alveolar-capillary niche, it is also affected by the initial injury. In addition to ensuring proper gas exchange, the endothelium has critical functional properties, including regulation of vascular tone, inflammatory responses, coagulation, and maintenance of vascular homeostasis and integrity. Recent single-cell analyses have shown that shifts in endothelial cell (EC) subtypes occur in PF. Furthermore, the increased vascular remodeling associated with PF leads to deteriorated outcomes for patients, underscoring the importance of the vascular bed in PF. To date, the causes and consequences of endothelial and vascular involvement in lung fibrosis are poorly understood. Therefore, it is of great importance to investigate the involvement of EC and the vascular system in the pathogenesis of the disease. In this review, we will outline the current knowledge on the role of the pulmonary vasculature in PF, in terms of abnormal cellular interactions, hyperinflammation, vascular barrier disorders, and an altered basement membrane composition. Finally, we will summarize recent advances in extensive therapeutic research and discuss the significant value of novel therapies targeting the endothelium.

Pulmonary vascular fibrosis in pulmonary hypertension - The role of the extracellular matrix as a therapeutic target

Pulmonary hypertension (PH) is a condition characterized by changes in the extracellular matrix (ECM) deposition and vascular remodeling of distal pulmonary arteries. These changes result in increased vessel wall thickness and lumen occlusion, leading to a loss of elasticity and vessel stiffening. Clinically, the mechanobiology of the pulmonary vasculature is becoming increasingly recognized for its prognostic and diagnostic value in PH. Specifically, the increased vascular fibrosis and stiffening resulting from ECM accumulation and crosslinking may be a promising target for the development of anti- or reverse-remodeling therapies. Indeed, there is a huge potential in therapeutic interference with mechano-associated pathways in vascular fibrosis and stiffening. The most direct approach is aiming to restore extracellular matrix homeostasis, by interference with its production, deposition, modification and turnover. Besides structural cells, immune cells contribute to the level of ECM maturation and degradation by direct cell-cell contact or the release of mediators and proteases, thereby opening a huge avenue to target vascular fibrosis via immunomodulation approaches. Indirectly, intracellular pathways associated with altered mechanobiology, ECM production, and fibrosis, offer a third option for therapeutic intervention. In PH, a vicious cycle of persistent activation of mechanosensing pathways such as YAP/TAZ initiates and perpetuates vascular stiffening, and is linked to key pathways disturbed in PH, such as TGF-beta/BMPR2/STAT. Together, this complexity of the regulation of vascular fibrosis and stiffening in PH allows the exploration of numerous potential therapeutic interventions. This review discusses connections and turning points of several of these interventions in detail.

Altered phenotypic and metabolic characteristics of FOXP3+CD3+CD56+ natural killer T (NKT)-like cells in human malignant pleural effusion

Malignant pleural effusion (MPE) is a functional 'cold' tumor microenvironment in which the antitumor activity of CD8⁺ T cells and natural killer T (NKT)-like cells is suppressed and the function of regulatory T (T_reg) cells is enhanced. Using flow cytometry and immunofluorescence staining, we detected a distinct subset of NKT-like cells expressing FOXP3 in MPE. Through single-cell RNA sequencing (scRNA-seq) analysis, we found that the glycolysis pathway and pyruvate metabolism were highly activated in FOXP3⁺ NKT-like cells. Similar to T_reg cells, FOXP3⁺ NKT-like cells highly expressed monocarboxylate transporter 1 (MCT1) and lactate dehydrogenase B to uptake and utilize lactate, thereby maintaining their immunosuppressive function and hyperlactylation in MPE. Furthermore, we found that MCT1 small molecule inhibitor 7ACC2 significantly reduced FOXP3 expression and histone lactylation levels in NKT-like cells in vitro. In conclusion, we reveal for the first time the altered phenotypic and metabolic features of FOXP3⁺ NKT-like cells in human MPE.

Role of CXCR3 in fibrotic tissue responses

Development of fibrosis leads to end stage diseases that defy treatments across all organs. This ensues as chronic inflammation is not dampened by physiologic processes that issue in the resolution phase of wound healing. Thus, these conditions can be considered diseases of "failure to heal". In the absence of broadly viable treatments, it is proposed to examine key switches in wound healing resolution to seek insights into novel approaches. Signaling through the GPCR CXCR3 has been shown to be one such critical player in this physiologic transition that limits and even reverses early fibrosis. As such, a number of investigators and early stage technology companies have posited that triggering this signaling network would limit fibrosis. While there are some conflicting results, a consensus is emerging that pharmacologic interventions that promote signaling through this pathway represent innovative ways to limit fibrotic diseases.