Lipid dysregulation associated with progression of silica-induced pulmonary fibrosis

Novel pilot study on plasma metabolites and biomarkers in a rat model of silica-induced lung inflammation and fibrosis

Silica-induced lung damage may be associated with changes in distinct metabolites potentially serving as biomarkers. Due to the lack of metabolomic data from animal models, this pilot study aimed to evaluate changes in markers of inflammation and fibrosis, as well as plasma metabolites in rats at 14 and 28 days after silica instillation. Adult male Wistar rats were administered a single oropharyngeal intratracheal dose of silica suspension or sterile saline in controls. Selected markers of inflammation, oxidative stress, fibrosis, and cell counts in blood and bronchoalveolar lavage fluid have been evaluated. Finally, plasma metabolites were detected using a targeted metabolomics approach with an MxP® Quant 500 kit. Silica instillation induced noticeable inflammatory, oxidative, and fibrotic changes in lung tissue within the first 14 days. During the next two weeks, the shifts in some markers were further accentuated. After exposure to silica, the metabolomic analysis identified significant changes in metabolites associated with lipid metabolism, biogenic amines, amino acid derivatives, carboxylic acids, bile acids, putrescine, glycosylceramides, and acylcarnitines. This pilot study provides initial evidence that significant alterations in plasma metabolite profiles accompany silica-induced lung injury in rats. These findings suggest a possible systemic impact, particularly on lipid metabolism, and indicate the urgent need for a deeper understanding of the metabolic reprogramming associated with silica-induced lung injury to pave the way for the discovery of novel biomarkers.

Blockade of TREM2 ameliorates pulmonary inflammation and fibrosis by modulating sphingolipid metabolism

Pulmonary fibrosis is a chronic interstitial lung disease involving systemic inflammation and abnormal collagen deposition. Dysregulations in lipid metabolism, such as macrophage-dependent lipid catabolism, have been recognized as critical factors for the development of pulmonary fibrosis. However, little is known about the signaling pathways involved and the key regulators. Here we found that triggering receptor expressed on myeloid cells 2 (TREM2) plays a pivotal role in regulating the lipid handling capacities of pulmonary macrophages and triggering fibrosis. By integrating analysis of single-cell and bulk RNA sequencing data from patients and mice with pulmonary fibrosis, we revealed that pulmonary macrophages consist of heterogeneous populations with distinct pro-fibrotic properties, and found that both sphingolipid metabolism and the expression of chemotaxis-related genes are elevated in fibrotic lungs. TREM2, a sensor recognizing multiple lipid species, is specifically upregulated in a subset of monocyte-derived macrophages. Blockade of TREM2 by conventional/conditional knock-out or soluble TREM2 administration can attenuate bleomycin-induced pulmonary fibrosis. By utilizing scRNA Seq and lipidomics, we found that Trem2 deficiency downregulates the synthesis of various sphingomyelins, and inhibits the expression of chemokines such as Ccl2. Together, our findings not only reveal the alterations in lipidomic profiles and the atlas of pulmonary macrophages during pulmonary fibrosis, but also suggest that targeting TREM2, the crucial regulator affecting both pulmonary sphingolipid metabolism and the chemokines secretion, can benefit pulmonary fibrosis patients in the future.

Arginine-Proline Metabolism as a Mediator in the Association Between Coal Dust Exposure and Lung Function: A Retrospective Analysis

OBJECTIVES

To investigate the mediating role of the activation degree of arginine-proline metabolism in the association of coal dust and decreased lung function.

METHODS

Cumulative dust exposure (CDE) represented coal dust exposure, whereas the hydroxyproline-to-arginine concentration ratio (Hyp/Arg) in bronchoalveolar lavage fluid gauged arginine-proline metabolism activation. Pulmonary function indicators, including predicted value of forced vital capacity (FVC%pred), forced expiratory volume in 1 second/forced vital capacity (FEV1/FVC%), and the ratio of actual to predicted value of FEV1 (FEV1%pred), diffusing capacity of the lungs for carbon monoxide (DLCO%pred), difference value between alveolar air and arterial partial oxygen pressure (P (A-a) O 2 ), and 6-minute walking distance test (6MWT), were assessed.

RESULTS

Findings revealed a significant association between elevated CDE and increased Hyp/Arg, increased P (A-a) O 2 , decreased 6MWT, DLCO%pred, and decreased FVC%pred. However, no statistically significant association was found between CDE and FEV1%pred or FEV1/FVC%. The mediating effect of Hyp/Arg was significant for CDE's impact on P (A-a) O 2 and DLCO%pred but not on 6MWT and FVC%pred.

CONCLUSIONS

These results highlight the role of Hyp/Arg in mediating the association between CDE and lung function parameters, shedding light on potential therapeutic avenues for mitigating coal dust-induced lung function impairment.

Tetrandrine Alleviates Silica-induced Pulmonary Fibrosis Through PI3K/AKT Pathway: Network Pharmacology Investigation and Experimental Validation

Tetrandrine (TET) is a bisbenzylisoquinoline alkaloid derived from Stephania tetrandra S. Moor, known for its potential use in attenuating the progression of silicosis. However, the precise effects and underlying mechanisms of TET remain controversial. In this study, we aimed to elucidate the pharmacological mechanism of TET using a network pharmacology approach, while also evaluating its effect on silica-induced lung fibrosis in mice and TGF-β1-stimulated pulmonary fibroblasts in vitro. We employed network pharmacology to unravel the biological mechanisms through which TET may exert its therapeutic effects on pulmonary fibrosis and silicosis. In a silica-induced mouse model of lung fibrosis, TET was administered orally either during the early or late stage of fibrotic progression. Additionally, we examined the effects of TET on fibroblasts stimulated by TGF-β1 in vitro. Through the analysis, we identified a total of 101 targets of TET, 7,851 genes associated with pulmonary fibrosis, and 80 overlapping genes. These genes were primarily associated with key pathways such as epidermal growth factor receptor tyrosine kinase inhibitor resistance, the vascular endothelial growth factor signaling pathway, and the phosphatidylinositol 3 kinase (PI3K)-protein kinase B (PKB or AKT) signaling pathway. Furthermore, molecular docking analysis revealed the binding of TET to AKT1, the catalytic subunit of phosphatidylinositol-3 kinase, and KDR. In vivo experiments demonstrated that TET significantly alleviated silica-induced pulmonary fibrosis and reduced the expression of fibrotic markers. Moreover, TET exhibited inhibitory effects on the migration, proliferation, and differentiation of TGF-β1-induced lung fibroblasts in vitro. Notably, TET mitigated silica-induced pulmonary fibrosis by suppressing the PI3K/AKT pathway. In conclusion, our findings suggest that TET possesses the ability to suppress silica-induced pulmonary fibrosis by targeting the PI3K/AKT signaling pathway. These results provide valuable insights into the therapeutic potential of TET in the treatment of pulmonary fibrosis and silicosis.

Cuproptosis-associated hub gene identification and immune cell infiltration patterns in silicosis

Recent research has hinted at a potential connection between silicosis, a fibrotic lung disease caused by exposure to crystalline silica particles, and cuproptosis. The aim of the study was to explore how cuproptosis-related genes (CRGs) may influence the development of silicosis and elucidate the underlying mechanisms. An analysis of genes associated with both silicosis and cuproptosis was conducted. Key gene identification was achieved through the application of two machine learning techniques. Additionally, the correlation between these key genes and immune cell populations was explored and the critical pathways were discerned. To corroborate our findings, the expression of key genes was verified in both a publicly available silica-induced mouse model and our own silicosis mouse model. A total of 12 differentially expressed CRGs associated with silicosis were identified. Further analysis resulted in the identification of 6 CRGs, namely LOX, SPARC, MOXD1, ALB, MT-CO2, and AOC2. Elevated immune cell infiltration of CD8 T cells, regulatory T cells, M0 macrophages, and neutrophils in silicosis patients compared to healthy controls was indicated. Validation in a silica-induced pulmonary fibrosis mouse model supported SPARC and MT-CO2 as potential signature genes for the prediction of silicosis. These findings highlight a strong association between silicosis and cuproptosis. Among CRGs, LOX, SPARC, MOXD1, ALB, MT-CO2, and AOC2 emerged as pivotal players in the context of silicosis by modulating CD8 T cells, regulatory T cells, M0 macrophages, and neutrophils.

An Analysis of Targeted Serum Lipidomics in Patients with Pneumoconiosis - China, 2022

Introduction

Pneumoconiosis emerges as the most critical and prevalent occupational disease in China at present, according to research. Studies indicate that pneumoconiosis may indeed impact the body's phospholipid metabolism.

Methods

In this study, serum samples were taken from 46 paired participants, which included patients with pneumoconiosis and dust-exposed workers. We employed ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) technology in targeted lipidomics to investigate serum target phospholipids. Initially, a pilot study was conducted with a selection of 24 pneumoconiosis patients and 24 dust-exposed workers, using both univariate and multivariate statistical analyses to preliminarily identify significant differences in phospholipids. Subsequent to this, the remaining subjects were engaged in a validation study, wherein receiver operating characteristic (ROC) analysis was performed to further substantiate the screening potency of potential lipid biomarkers for pneumoconiosis.

Results

The pilot study revealed significantly reduced serum levels of 16∶0 lysophosphatidylcholines (Lyso PC), 18∶0-18∶1 phosphatidylglycerol (PG), 18∶0-18∶1 phosphatidylethanolamine (PE), 18∶0 PE, and 18∶1 lysophosphatidylethanolamine（Lyso PE) in the case group in comparison to the control group. Additionally, 18∶0 PE, 18∶0-18∶1 PE, and 18∶1 Lyso PE emerged as significant phospholipids with superior diagnostic values [area under the curve (AUC)>0.7]. A diagnostic model was established, built on 16∶0 PC and 18∶0 PE (AUC>0.8). In the ROC analyses of validation studies, the 18∶0-18∶1 PE and this diagnostic model demonstrated excellent screening efficiency (AUC>0.7).

Discussion

A significant divergence in phospholipid metabolism has been observed between pneumoconiosis patients and dust-exposed workers. The 18∶0-18∶1 PE present in serum could potentially function as a lipid biomarker for pneumoconiosis. Additionally, diagnostic models were developed relying on 16∶0 PC and 18∶0 PE, proving to have superior screening efficiency.