FSTL-1 Attenuation Causes Spontaneous Smoke-Resistant Pulmonary Emphysema

Nuclear receptor 4A1 is critical for neutrophil-dependent pulmonary immunity to Klebsiella pneumoniae infection

Introduction

Bacterial pneumonia is a burdensome, costly disease and increasingly challenging to treat due to antibiotic resistance. Complex host-pathogen interactions regulate protective immunity. Neutrophils play a central role in pulmonary bacterial immunity, and mechanistic understanding of neutrophil functions in bacterial pneumonia has potential clinical and fundamental application. Nuclear receptor 4a1 (Nr4a1), a member of the nuclear orphan receptor family, has been described to regulate inflammation and immune development in a cell type-specific manner, but its role in pulmonary host defense is not well understood.

Methods

Wild-type (WT) and Nr4a1-/- mice, as well as bone marrow chimeric and Gr-1+ antibody depleted mice, were infected with Klebsiella pneumoniae and assessed for bacterial burden in the lung and spleen, gene transcription, protein levels, histology and cellular abundance by flow cytometry in the lung. WT and Nr4a1-/- neutrophils were exposed to live Klebsiella pneumoniae to quantify bacterial killing, as well as bulk RNA sequencing to assess transcriptomic differences.

Results

Nr4a1-deficient mice are highly susceptible to Klebsiella pneumoniae pneumonia, which was mediated by Nr4a1 expression in immune cells. Gr-1+ antibody depletion ameliorated the Nr4a1-dependent phenotype. Ex vivo, Nr4a1-deficient neutrophils had impaired bactericidal capacity, and transcriptomic analysis identified an Nr4a1-dependent host defense program in neutrophils.

Discussion

Neutrophil Nr4a1 expression is critical for defense against K. pneumoniae infection by regulating the neutrophil transcriptome. These findings suggest targeting Nr4a1 signaling pathways in neutrophils may be useful for bacterial pneumonia treatment.

Case-Control Study: Evaluating the Role and Therapeutic Potential of FSTL1 in Type 2 Inflammation of Chronic Rhinosinusitis

Purpose

Follicle suppressor-like protein 1 (FSTL1) plays a contributory role in chronic inflammation, and it currently been demonstrated in studies of asthma and chronic obstructive pulmonary disease (COPD), but studies in chronic sinusitis with nasal polyps have not been addressed. The aim of this study was to explore the expression of follicle suppressor-like protein 1 (FSTL1) in chronic sinusitis and its possible association with type 2 inflammation.

Patients and Methods

This study included 34 CRS patients (24 ECRS, 10 non-ECRS) and 10 controls. Hematoxylin-eosin (HE) staining to observe the pathomorphological changes of these three groups of tissue specimens in detail, Immunohistochemistry (IHC), real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) technology and Western blotting (WB) were used to evaluate the expression levels of FSTL1 and type 2 inflammatory cytokines IL-4, IL-5, and IL-13 in the three groups.

Results

In the ECRS group, there was thickening of the tissue mucosa and hyperplasia of glands, along with a significant infiltration of inflammatory cells and eosinophils. The experimental results showed that the expression levels of FSTL1 and type 2 inflammatory cytokines IL - 4, IL - 5, and IL - 13 were higher in the ECRS and non - ECRS groups than in the control group (P<0.05). Additionally, FSTL1 and IL-4, IL-5, IL-13 were positively correlated in the ECRS group(P<0.05).

Conclusion

FSTL1, IL-4, IL-5 and IL-13 were highly expressed in chronic sinusitis, and FSTL1 was positively correlated with IL-4, IL-5 and IL-13 in the ECRS group, suggesting that FSTL1 contributes to the development of type 2 inflammation in ECRS, and FSTL1 may serve as a potential therapeutic target for ECRS.

Systemic Immune Inflammation Index, Systemic Inflammation Response Index, Aggregate Index of Systemic Inflammation, and Follistatin-Like Protein-1 Levels in Children Diagnosed with Pneumonia

Background: This study aims to evaluate systemic immune inflammation index, systemic inflammatory response index (SIRI), aggregate index of systemic inflammation (AISI), and follistatin-like protein-1 (FSTL-1) levels in children with pneumonia and healthy controls. Methods: The study was carried out at the Seydisehir State Hospital between February 1, 2024 and June 1, 2024. The patient group included 44 children diagnosed with pneumonia and the control group included 45 healthy children without any disease. Index values obtained from hemogram data. Enzyme-linked immunosorbent assay was used to measure FSTL-1 levels. Results: A total of 89 participants, 44 in the patient group and 45 in the healthy control group, were included in the study. White blood cells, monocyte, eosinophil, neutrophil, c-reactive protein, SIRI, and AISI levels were significantly higher in the patient group than in the control group. FSTL-1 levels were higher in the patient group, but did not differ statistically significant. The patient and control groups were compared in the receiver operating characteristics analysis, we found the highest area under curve (AUC) in the SIRI (AUC: 0.754) and AISI (AUC: 0.713) parameters. Conclusion: In conclusion, compared to healthy controls, SIRI and AISI levels were significantly higher in the patient group, and the highest AUC values belonged to these indices. Therefore, we believe that SIRI and AISI indices, which are inexpensive and simple tests, are useful for early diagnosis and treatment of pneumonia.

Screening COPD-Related Biomarkers and Traditional Chinese Medicine Prediction Based on Bioinformatics and Machine Learning

Purpose

To employ bioinformatics and machine learning to predict the characteristics of immune cells and genes associated with the inflammatory response and ferroptosis in chronic obstructive pulmonary disease (COPD) patients and to aid in the development of targeted traditional Chinese medicine (TCM). Mendelian randomization analysis elucidates the causal relationships among immune cells, genes, and COPD, offering novel insights for the early diagnosis, prevention, and treatment of COPD. This approach also provides a fresh perspective on the use of traditional Chinese medicine for treating COPD.

Methods

R software was used to extract COPD-related data from the Gene Expression Omnibus (GEO) database, differentially expressed genes were identified for enrichment analysis, and WGCNA was used to pinpoint genes within relevant modules associated with COPD. This analysis included determining genes linked to the inflammatory response in COPD patients and analyzing their correlation with ferroptosis. Further steps involved filtering core genes, constructing TF-miRNA‒mRNA network diagrams, and employing three types of machine learning to predict the core miRNAs, key immune cells, and characteristic genes of COPD patients. This process also delves into their correlations, single-gene GSEA, and diagnostic model predictions. Reverse inference complemented by molecular docking was used to predict compounds and traditional Chinese medicines for treating COPD; Mendelian randomization was applied to explore the causal relationships among immune cells, genes, and COPD.

Results

We identified 2443 differential genes associated with COPD through the GEO database, along with 8435 genes relevant to WGCNA and 1226 inflammation-related genes. A total of 141 genes related to the inflammatory response in COPD patients were identified, and 37 core genes related to ferroptosis were selected for further enrichment analysis and analysis. The core miRNAs predicted for COPD include hsa-miR-543, hsa-miR-181c, and hsa-miR-200a, among others. The key immune cells identified were plasma cells, activated memory CD4 T cells, gamma delta T cells, activated NK cells, M2 macrophages, and eosinophils. Characteristic genes included EGF, PLG, PTPN22, and NR4A1. A total of 78 compounds and 437 traditional Chinese medicines were predicted. Mendelian randomization analysis revealed a causal relationship between 36 types of immune cells and COPD, whereas no causal relationship was found between the core genes and COPD.

Conclusion

A definitive causal relationship exists between immune cells and COPD, while the prediction of core miRNAs, key immune cells, characteristic genes, and targeted traditional Chinese medicines offers novel insights for the early diagnosis, prevention, and treatment of COPD.

The fix is not yet in: recommendation for fixation of lungs within physiological/pathophysiological volume range in preclinical pulmonary structure-function studies

Quantitative characterization of lung structures by morphometrical or stereological analysis of histological sections is a powerful means of elucidating pulmonary structure-function relations. The overwhelming majority of studies, however, fix lungs for histology at pressures outside the physiological/pathophysiological respiratory volume range. Thus, valuable information is being lost. In this perspective article, we argue that investigators performing pulmonary histological studies should consider whether the aims of their studies would benefit from fixation at functional transpulmonary pressures, particularly those of end-inspiration and end-expiration. We survey the pressures at which lungs are typically fixed in preclinical structure-function studies, provide examples of conditions that would benefit from histological evaluation at functional lung volumes, summarize available fixation methods, discuss alternative imaging modalities, and discuss challenges to implementing the suggested approach and means of addressing those challenges. We aim to persuade investigators that modifying or complementing the traditional histological approach by fixing lungs at minimal and maximal functional volumes could enable new understanding of pulmonary structure-function relations.

FSTL1 promotes liver fibrosis by reprogramming macrophage function through modulating the intracellular function of PKM2

OBJECTIVE

Follistatin-like protein 1 (FSTL1) is widely recognised as a secreted glycoprotein, but its role in modulating macrophage-related inflammation during liver fibrosis has not been documented. Herein, we aimed to characterise the roles of macrophage FSTL1 in the development of liver fibrosis.

DESIGN

Expression analysis was conducted with human liver samples obtained from 33 patients with liver fibrosis and 18 individuals without fibrosis serving as controls. Myeloid-specific FSTL1-knockout (FSTL1^M-KO) mice were constructed to explore the function and mechanism of macrophage FSTL1 in 3 murine models of liver fibrosis induced by carbon tetrachloride injection, bile duct ligation or a methionine-deficient and choline-deficient diet.

RESULTS

FSTL1 expression was significantly elevated in macrophages from fibrotic livers of both humans and mice. Myeloid-specific FSTL1 deficiency effectively attenuated the progression of liver fibrosis. In FSTL1^M-KO mice, the microenvironment that developed during liver fibrosis showed relatively less inflammation, as demonstrated by attenuated infiltration of monocytes/macrophages and neutrophils and decreased expression of proinflammatory factors. FSTL1^M-KO macrophages exhibited suppressed proinflammatory M1 polarisation and nuclear factor kappa B pathway activation in vivo and in vitro. Furthermore, this study showed that, through its FK domain, FSTL1 bound directly to the pyruvate kinase M2 (PKM2). Interestingly, FSTL1 promoted PKM2 phosphorylation and nuclear translocation, reduced PKM2 ubiquitination to enhance PKM2-dependent glycolysis and increased M1 polarisation. Pharmacological activation of PKM2 (DASA-58) partially countered FSTL1-mediated glycolysis and inflammation.

CONCLUSION

Macrophage FSTL1 promotes the progression of liver fibrosis by inducing M1 polarisation and inflammation based on the intracellular PKM2 reprogramming function of macrophages.

Follistatin-like 1 ameliorates severe acute pancreatitis associated lung injury via inhibiting the activation of NLRP3 inflammasome and NF-κB pathway

OBJECTIVE

Severe acute pancreatitis (SAP) is one of the most common abdominal conditions of digestive system that usually causes acute lung injury through systemic inflammation. Follistatin-like 1 (FSTL-1) has been reported to have anti-inflammatory and anti-apoptotic effects in a variety of diseases. The aim of this study was to investigate the effects of FSTL-1 on SAP-associated lung injury (SAPALI) and the underlying mechanism.

METHODS

SAP model was induced by intraperitoneal injection of the L-arginine in C57BL/6 mice. The haematoxylin and eosin (H&E) staining was applied to determine the severity of lung and pancreatic injury. ELISA kits were used to determine serum amylase and inflammatory cytokines levels. TUNEL staining was carried out to measure cell apoptosis. Western blotting was applied to analyze the related proteins of NLRP3 inflammasome and NF-κB pathways.

RESULTS

FSTL-1 was significantly increased in the lung of SAP mice. Knockout of FSTL-1 ameliorated pancreatic injury, lung injury, inflammation and apoptosis in mice with SAP. Moreover, the protein levels of NLRP3, ASC, Caspase-1, p-p65 and p-IκBα were obviously reduced in the FSTL-1 KO+SAP group in comparison with SAP group, suggesting that inhibition of FSTL-1 repressed the activation of the NLRP3 inflammasome and NF-κB pathway.

CONCLUSION

This study helps us understand the mechanism of FSTL-1 in SAPALI and might provide a potential new strategy for the treatment of SAPALI.

Follistatin-Like Proteins: Structure, Functions and Biomedical Importance

Main forms of cellular signal transmission are known to be autocrine and paracrine signaling. Several cells secrete messengers called autocrine or paracrine agents that can bind the corresponding receptors on the surface of the cells themselves or their microenvironment. Follistatin and follistatin-like proteins can be called one of the most important bifunctional messengers capable of displaying both autocrine and paracrine activity. Whilst they are not as diverse as protein hormones or protein kinases, there are only five types of proteins. However, unlike protein kinases, there are no minor proteins among them; each follistatin-like protein performs an important physiological function. These proteins are involved in a variety of signaling pathways and biological processes, having the ability to bind to receptors such as DIP2A, TLR4, BMP and some others. The activation or experimentally induced knockout of the protein-coding genes often leads to fatal consequences for individual cells and the whole body as follistatin-like proteins indirectly regulate the cell cycle, tissue differentiation, metabolic pathways, and participate in the transmission chains of the pro-inflammatory intracellular signal. Abnormal course of these processes can cause the development of oncology or apoptosis, programmed cell death. There is still no comprehensive understanding of the spectrum of mechanisms of action of follistatin-like proteins, so the systematization and study of their cellular functions and regulation is an important direction of modern molecular and cell biology. Therefore, this review focuses on follistatin-related proteins that affect multiple targets and have direct or indirect effects on cellular signaling pathways, as well as to characterize the directions of their practical application in the field of biomedicine.

Innate Immune Responses and Pulmonary Diseases

Innate immunity is the first defense line of the host against various infectious pathogens, environmental insults, and other stimuli causing cell damages. Upon stimulation, pattern recognition receptors (PRRs) act as sensors to activate innate immune responses, containing NF-κB signaling, IFN response, and inflammasome activation. Toll-like receptors (TLRs), retinoic acid-inducible gene I-like receptors (RLRs), NOD-like receptors (NLRs), and other nucleic acid sensors are involved in innate immune responses. The activation of innate immune responses can facilitate the host to eliminate pathogens and maintain tissue homeostasis. However, the activity of innate immune responses needs to be tightly controlled to ensure the optimal intensity and duration of activation under various contexts. Uncontrolled innate immune responses can lead to various disorders associated with aberrant inflammatory response, including pulmonary diseases such as COPD, asthma, and COVID-19. In this chapter, we will have a broad overview of how innate immune responses function and the regulation and activation of innate immune response at molecular levels as well as their contribution to various pulmonary diseases. A better understanding of such association between innate immune responses and pulmonary diseases may provide potential therapeutic strategies.

FSTL1 aggravates cigarette smoke-induced airway inflammation and airway remodeling by regulating autophagy

BACKGROUND

Cigarette smoke (CS) is a major risk factor for Chronic Obstructive Pulmonary Disease (COPD). Follistatin-like protein 1 (FSTL1), a critical factor during embryogenesis particularly in respiratory lung development, is a novel mediator related to inflammation and tissue remodeling. We tried to investigate the role of FSTL1 in CS-induced autophagy dysregulation, airway inflammation and remodeling.

METHODS

Serum and lung specimens were obtained from COPD patients and controls. Adult female wild-type (WT) mice, FSTL1^± mice and FSTL1^flox/+ mice were exposed to room air or chronic CS. Additionally, 3-methyladenine (3-MA), an inhibitor of autophagy, was applied in CS-exposed WT mice. The lung tissues and serum from patients and murine models were tested for FSTL1 and autophagy-associated protein expression by ELISA, western blotting and immunohistochemical. Autophagosome were observed using electron microscope technology. LTB4, IL-8 and TNF-α in bronchoalveolar lavage fluid of mice were examined using ELISA. Airway remodeling and lung function were also assessed.

RESULTS

Both FSTL1 and autophagy biomarkers increased in COPD patients and CS-exposed WT mice. Autophagy activation was upregulated in CS-exposed mice accompanied by airway remodeling and airway inflammation. FSTL1^± mice showed a lower level of CS-induced autophagy compared with the control mice. FSTL1^± mice can also resist CS-induced inflammatory response, airway remodeling and impaired lung function. CS-exposed WT mice with 3-MA pretreatment have a similar manifestation with CS-exposed FSTL1^± mice.

CONCLUSIONS

FSTL1 promotes CS-induced COPD by modulating autophagy, therefore targeting FSTL1 and autophagy may shed light on treating cigarette smoke-induced COPD.

Regulation of Pulmonary Bacterial Immunity by Follistatin-Like Protein 1

Klebsiella pneumoniae is a common cause of antibiotic-resistant pneumonia. Follistatin-like protein 1 (FSTL-1) is highly expressed in the lung and is critical for lung homeostasis. The role of FSTL-1 in immunity to bacterial pneumonia is unknown. Wild-type (WT) and FSTL-1 hypomorphic (Hypo) mice were infected with Klebsiella pneumoniae to determine infectious burden, immune cell abundance, and cytokine production. FSTL-1 Hypo/TCRδ^-/- and FSTL-1 Hypo/IL17ra^-/- were also generated to assess the role of γδT17 cells in this model. FSTL-1 Hypo mice had reduced K. pneumoniae lung burden compared with that of WT controls. FSTL-1 Hypo mice had increased Il17a/interleukin-17A (IL-17A) and IL-17-dependent cytokine expression. FSTL-1 Hypo lungs also had increased IL-17A⁺ and TCRγδ⁺ cells. FSTL-1 Hypo/TCRδ^-/- displayed a lung burden similar to that of FSTL-1 Hypo and reduced lung burden compared with the TCRδ^-/- controls. However, FSTL-1 Hypo/TCRδ^-/- mice had greater bacterial dissemination than FSTL-1 Hypo mice, suggesting that gamma delta T (γδT) cells are dispensable for FSTL-1 Hypo control of pulmonary infection but are required for dissemination control. Confusing these observations, FSTL-1 Hypo/TCRδ^-/- lungs had an increased percentage of IL-17A-producing cells compared with that of TCRδ^-/- mice. Removal of IL-17A signaling in the FSTL-1 Hypo mouse resulted in an increased lung burden. These findings identify a novel role for FSTL-1 in innate lung immunity to bacterial infection, suggesting that FSTL-1 influences type-17 pulmonary bacterial immunity.

The Role of the ECM in Lung Cancer Dormancy and Outgrowth

The dissemination of tumor cells to local and distant sites presents a significant challenge in the clinical management of many solid tumors. These cells may remain dormant for months or years before overt metastases are re-awakened. The components of the extracellular matrix, their posttranslational modifications and their associated factors provide mechanical, physical and chemical cues to these disseminated tumor cells. These cues regulate the proliferative and survival capacity of these cells and lay the foundation for their engraftment and colonization. Crosstalk between tumor cells, stromal and immune cells within primary and secondary sites is fundamental to extracellular matrix remodeling that feeds back to regulate tumor cell dormancy and outgrowth. This review will examine the role of the extracellular matrix and its associated factors in establishing a fertile soil from which individual tumor cells and micrometastases establish primary and secondary tumors. We will focus on the role of the lung extracellular matrix in providing the architectural support for local metastases in lung cancer, and distant metastases in many solid tumors. This review will define how the matrix and matrix associated components are collectively regulated by lung epithelial cells, fibroblasts and resident immune cells to orchestrate tumor dormancy and outgrowth in the lung. Recent advances in targeting these lung-resident tumor cell subpopulations to prevent metastatic disease will be discussed. The development of novel matrix-targeted strategies have the potential to significantly reduce the burden of metastatic disease in lung and other solid tumors and significantly improve patient outcome in these diseases.

Long noncoding RNA MCM3AP antisense RNA 1 is downregulated in chronic obstructive pulmonary disease and regulates human bronchial smooth muscle cell proliferation

OBJECTIVES

This study aimed to investigate the involvement of MCM3AP antisense RNA 1 (MCM3AP-AS1) in chronic obstructive pulmonary disease (COPD).

METHODS

The expression levels of plasma MCM3AP-AS1 in COPD patients and healthy controls were measured by quantitative PCR before treatment and at 3 months after the initiation of treatment (post-treatment) from COPD patients. The role of MCM3AP-AS1 in regulating the proliferation of human bronchial smooth muscle cells (HBSMCs) was explored by a cell proliferation assay.

RESULTS

We found that MCM3AP-AS1 expression was downregulated in the plasma of COPD patients compared with controls. Among controls, MCM3AP-AS1 expression was lower in smokers than never-smokers. A 3-year follow-up study showed that, among smokers, patients with low MCM3AP-AS1 expression showed a higher incidence of COPD. After treatment for COPD, MCM3AP-AS1 expression significantly increased. The cell proliferation assay showed that MCM3AP-AS1 overexpression decreased the proliferation rate of HBSMCs. MCM3AP-AS1 silencing had the opposite effect.

CONCLUSIONS

MCM3AP-AS1 appears to be downregulated in COPD and to predict its occurrence. MCM3AP-AS1 regulates the proliferation of HBSMCs to participate in airway remodeling.