Comprehensive lipid profiling of bleomycin-induced lung injury

PGC-1α regulates endoplasmic reticulum stress in IPF-derived fibroblasts

Idiopathic pulmonary fibrosis (IPF) is considered to be associated with aging. Both ER stress and the unfolded protein response (UPR) have been associated with pulmonary fibrosis via key mechanisms including AEC apoptosis, EMT, altered myofibroblast differentiation, and M2 macrophage polarization. A relationship between ER stress and aging has also been demonstrated in vitro, with increased p16 and p21 levels seen in lung epithelial cells of older IPF patients. The mechanism underlying ER stress regulation of IPF fibroblasts is still unclear. In this study, we aimed to delineate ER stress regulation in IPF-derived fibroblasts. Here, we found that ER stress markers (p-eIF2α, p-IREα, ATF6) and fibrosis markers (α-SMA and Collagen-I) were significantly increased in lung tissues of IPF patients and bleomycin-induced mouse models. Notably, the expression of PGC-1α was decreased in fibroblasts. In vivo experiments were designed using an AAV-6 vector mediated conditional PGC-1α knockout driven by a specific α-SMA promoter. Ablation of PGC-1α expression in fibroblasts promoted ER stress and supported the development of pulmonary fibrosis in a bleomycin-induced mouse model. In another experimental group, mice with conditional knockout of PGC-1α in fibroblasts and injected intraperitoneally with 4-PBA (an endoplasmic reticulum stress inhibitor) were protected from lung fibrosis. We further constructed an AAV-6 vector mediated PGC-1α overexpression model driven by a specific Collagen-I promoter. Overexpression of PGC-1α in fibroblasts suppressed ER stress and attenuated development of pulmonary fibrosis in bleomycin-induced mouse models. Taken together, this study identified PGC-1α as a promising target for developing novel therapeutic options for the treatment of lung fibrosis.

Lipids and lipid metabolism in cellular senescence: Emerging targets for age-related diseases

Cellular senescence is a kind of cellular state triggered by endogenous or exogenous stimuli, which is mainly characterized by stable cell cycle arrest and complex senescence-associated secretory phenotype (SASP). Once senescent cells accumulate in tissues, they may eventually accelerate the progression of age-related diseases, such as atherosclerosis, osteoarthritis, chronic lung diseases, cancers, etc. Recent studies have shown that the disorders of lipid metabolism are not only related to age-related diseases, but also regulate the cellular senescence process. Based on existing research evidences, the changes in lipid metabolism in senescent cells are mainly concentrated in the metabolic processes of phospholipids, fatty acids and cholesterol. Obviously, the changes in lipid-metabolizing enzymes and proteins involved in these pathways play a critical role in senescence. However, the link between cellular senescence, changes in lipid metabolism and age-related disease remains to be elucidated. Herein, we summarize the lipid metabolism changes in senescent cells, especially the senescent cells that promote age-related diseases, as well as focusing on the role of lipid-related enzymes or proteins in senescence. Finally, we explore the prospect of lipids in cellular senescence and their potential as drug targets for preventing and delaying age-related diseases.

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.

Advances in Ultra-High-Resolution Mass Spectrometry for Pharmaceutical Analysis

Pharmaceutical analysis refers to an area of analytical chemistry that deals with active compounds either by themselves (drug substance) or when formulated with excipients (drug product). In a less simplistic way, it can be defined as a complex science involving various disciplines, e.g., drug development, pharmacokinetics, drug metabolism, tissue distribution studies, and environmental contamination analyses. As such, the pharmaceutical analysis covers drug development to its impact on health and the environment. Moreover, due to the need for safe and effective medications, the pharmaceutical industry is one of the most heavily regulated sectors of the global economy. For this reason, powerful analytical instrumentation and efficient methods are required. In the last decades, mass spectrometry has been increasingly used in pharmaceutical analysis both for research aims and routine quality controls. Among different instrumental setups, ultra-high-resolution mass spectrometry with Fourier transform instruments, i.e., Fourier transform ion cyclotron resonance (FTICR) and Orbitrap, gives access to valuable molecular information for pharmaceutical analysis. In fact, thanks to their high resolving power, mass accuracy, and dynamic range, reliable molecular formula assignments or trace analysis in complex mixtures can be obtained. This review summarizes the principles of the two main types of Fourier transform mass spectrometers, and it highlights applications, developments, and future perspectives in pharmaceutical analysis.

Lysophosphatidylcholine acyltransferase 1 alleviates silica-induced pulmonary fibrosis by modulating lipid metabolism

Silicosis is an incurable lung disease that can progress even when exposure to silica dust has ended. Lipid metabolism plays an important role in the occurrence and development of silicosis. However, the mechanistic details have not been fully elucidated. This was investigated in the current study by high-performance liquid chromatography-mass spectrometry-based lipidomic analysis of lung tissue in a mouse model of silicosis. Lipid profiles and key metabolic enzymes were compared between silica and control groups. The lipidomic analysis revealed differentially-expressed lipids in the lungs of silicosis mice compared with controls. Among the identified lipid metabolism-related enzymes, the expression of lysophosphatidylcholine acyltransferase 1 (LPCAT1) was significantly down-regulated at the transcript and protein levels. LPCAT1 overexpression in vivo using adeno-associated virus altered the balance between phosphatidylcholine and lysophosphatidylcholine and inhibited the development of silicosis in mice. These results indicate that LPCAT1 dysregulation leads to abnormal lipid metabolism and silicosis, and is a potential therapeutic target for the treatment of silica-induced pulmonary fibrosis.

Lipidomics in Understanding Pathophysiology and Pharmacologic Effects in Inflammatory Diseases: Considerations for Drug Development

The lipidome has a broad range of biological and signaling functions, including serving as a structural scaffold for membranes and initiating and resolving inflammation. To investigate the biological activity of phospholipids and their bioactive metabolites, precise analytical techniques are necessary to identify specific lipids and quantify their levels. Simultaneous quantification of a set of lipids can be achieved using high sensitivity mass spectrometry (MS) techniques, whose technological advancements have significantly improved over the last decade. This has unlocked the power of metabolomics/lipidomics allowing the dynamic characterization of metabolic systems. Lipidomics is a subset of metabolomics for multianalyte identification and quantification of endogenous lipids and their metabolites. Lipidomics-based technology has the potential to drive novel biomarker discovery and therapeutic development programs; however, appropriate standards have not been established for the field. Standardization would improve lipidomic analyses and accelerate the development of innovative therapies. This review aims to summarize considerations for lipidomic study designs including instrumentation, sample stabilization, data validation, and data analysis. In addition, this review highlights how lipidomics can be applied to biomarker discovery and drug mechanism dissection in various inflammatory diseases including cardiovascular disease, neurodegeneration, lung disease, and autoimmune disease.

Extracellular Lipids in the Lung and Their Role in Pulmonary Fibrosis

Lipids are major actors and regulators of physiological processes within the lung. Initial research has described their critical role in tissue homeostasis and in orchestrating cellular communication to allow respiration. Over the past decades, a growing body of research has also emphasized how lipids and their metabolism may be altered, contributing to the development and progression of chronic lung diseases such as pulmonary fibrosis. In this review, we first describe the current working model of the mechanisms of lung fibrogenesis before introducing lipids and their cellular metabolism. We then summarize the evidence of altered lipid homeostasis during pulmonary fibrosis, focusing on their extracellular forms. Finally, we highlight how lipid targeting may open avenues to develop therapeutic options for patients with lung fibrosis.

Role of cardiolipins, mitochondria, and autophagy in the differentiation process activated by all-trans retinoic acid in acute promyelocytic leukemia

The role played by lipids in the process of granulocytic differentiation activated by all-trans retinoic acid (ATRA) in Acute-Promyelocytic-Leukemia (APL) blasts is unknown. The process of granulocytic differentiation activated by ATRA in APL blasts is recapitulated in the NB4 cell-line, which is characterized by expression of the pathogenic PML-RARα fusion protein. In the present study, we used the NB4 model to define the effects exerted by ATRA on lipid homeostasis. Using a high-throughput lipidomic approach, we demonstrate that exposure of the APL-derived NB4 cell-line to ATRA causes an early reduction in the amounts of cardiolipins, a major lipid component of the mitochondrial membranes. The decrease in the levels of cardiolipins results in a concomitant inhibition of mitochondrial activity. These ATRA-dependent effects are causally involved in the granulocytic maturation process. In fact, the ATRA-induced decrease of cardiolipins and the concomitant dysfunction of mitochondria precede the differentiation of retinoid-sensitive NB4 cells and the two phenomena are not observed in the retinoid-resistant NB4.306 counterparts. In addition, ethanolamine induced rescue of the mitochondrial dysfunction activated by cardiolipin deficiency inhibits ATRA-dependent granulocytic differentiation and induction of the associated autophagic process. The RNA-seq studies performed in parental NB4 cells and a NB4-derived cell population, characterized by silencing of the autophagy mediator, ATG5, provide insights into the mechanisms underlying the differentiating action of ATRA. The results indicate that ATRA causes a significant down-regulation of CRLS1 (Cardiolipin-synthase-1) and LPCAT1 (Lysophosphatidylcholine-Acyltransferase-1) mRNAs which code for two enzymes catalyzing the last steps of cardiolipin synthesis. ATRA-dependent down-regulation of CRLS1 and LPCAT1 mRNAs is functionally relevant, as it is accompanied by a significant decrease in the amounts of the corresponding proteins. Furthermore, the decrease in CRLS1 and LPCAT1 levels requires activation of the autophagic process, as down-regulation of the two proteins is blocked in ATG5-silenced NB4-shATG5 cells.

Revisiting the role of pulmonary surfactant in chronic inflammatory lung diseases and environmental exposure

Pulmonary surfactant is a crucial and dynamic lung structure whose primary functions are to reduce alveolar surface tension and facilitate breathing. Though disruptions in surfactant homeostasis are typically thought of in the context of respiratory distress and premature infants, many lung diseases have been noted to have significant surfactant abnormalities. Nevertheless, preclinical and clinical studies of pulmonary disease too often overlook the potential contribution of surfactant alterations - whether in quantity, quality or composition - to disease pathogenesis and symptoms. In inflammatory lung diseases, whether these changes are cause or consequence remains a subject of debate. This review will outline 1) the importance of pulmonary surfactant in the maintenance of respiratory health, 2) the diseases associated with primary surfactant dysregulation, 3) the surfactant abnormalities observed in inflammatory pulmonary diseases and, finally, 4) the available research on the interplay between surfactant homeostasis and smoking-associated lung disease. From these published studies, we posit that changes in surfactant integrity and composition contribute more considerably to chronic inflammatory pulmonary diseases and that more work is required to determine the mechanisms underlying these alterations and their potential treatability.

Combined transcriptomic and lipidomic analysis of D-4F ameliorating bleomycin-induced pulmonary fibrosis

Background

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease that leads to respiratory failure, and for which there is no effective treatment. Apolipoprotein A-1 (ApoA-1) has been reported to ameliorate the bleomycin (BLM)-induced IPF model.

Methods

To examine the function of D-4F, an ApoA-1 mimetic polypeptide, in IPF, we used an in-vivo BLM-induced model. We assigned mice into the following 3 groups: the Blank Group (BLK Group), the Bleomycin Treatment Group (Model Group), and the D-4F Interference Group (Inter Group). The BLM-induced fibrosis was examined by hematoxylin and eosin, Masson’s trichrome (M-T) staining and immunohistochemical staining. An untargeted lipidomic and transcriptomic analysis were used to examine the function of D-4F.

Results

There were 35 differentially altered lipids (DALs) in the BLK, Model and Inter Groups. A Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that glycerophospholipid metabolism was the most highly enriched of the 35 DALs. There were 99 differentially expressed genes (DEGs) in the BLK, Model and Inter Groups. The enriched KEGG pathway analysis showed that the mitogen-activated protein kinase (MAPK) pathway was 1 of the top 10 pathways. The results of the untargeted lipidomic and transcriptomic analysis showed that phospholipase A2 group 4c (Pla2g4c) was a crucial gene in both the MAPK pathway and glycerophospholipid metabolism. Pla2g4c was increased in the Model Group but decreased in the Inter Group.

Conclusions

It may be that D-4F prevented the BLM-induced pulmonary fibrosis model by inhibiting the expression of pla2g4c. Our findings suggest that D-4F may be a potential treatment of IPF.

Myeloid cell dynamics in bleomycin-induced pulmonary injury in mice; effects of anti-TNFα antibody

Bleomycin is a cancer therapeutic known to cause lung injury which progresses to fibrosis. Evidence suggests that macrophages contribute to this pathological response. Tumor necrosis factor (TNF)α is a macrophage-derived pro-inflammatory cytokine implicated in lung injury. Herein, we investigated the role of TNFα in macrophage responses to bleomycin. Treatment of mice with bleomycin (3 U/kg, i.t.) caused histopathological changes in the lung within 3 d which culminated in fibrosis at 21 d. This was accompanied by an early (3-7 d) influx of CD11b+ and iNOS+ macrophages into the lung, and Arg-1+ macrophages at 21 d. At this time, epithelial cell dysfunction, defined by increases in total phospholipids and SP-B was evident. Treatment of mice with anti-TNFα antibody (7.5 mg/kg, i.v.) beginning 15-30 min after bleomycin, and every 5 d thereafter reduced the number and size of fibrotic foci and restored epithelial cell function. Flow cytometric analysis of F4/80+ alveolar macrophages (AM) isolated by bronchoalveolar lavage and interstitial macrophages (IM) by tissue digestion identified resident (CD11b-CD11c+) and immature infiltrating (CD11b+CD11c-) AM, and mature (CD11b+CD11c+) and immature (CD11b+CD11c-) IM subsets in bleomycin treated mice. Greater numbers of mature (CD11c+) infiltrating (CD11b+) AM expressing the anti-inflammatory marker, mannose receptor (CD206) were observed at 21 d when compared to 7 d post bleomycin. Mature proinflammatory (Ly6C+) IM were greater at 7 d relative to 21 d. These cells transitioned into mature anti-inflammatory/pro-fibrotic (CD206+) IM between 7 and 21 d. Anti-TNFα antibody heightened the number of CD11b+ AM in the lung without altering their activation state. Conversely, it reduced the abundance of mature proinflammatory (Ly6C+) IM in the tissue at 7 d and immature pro-fibrotic IM at 21 d. Taken together, these data suggest that TNFα inhibition has beneficial effects in bleomycin induced injury, restoring epithelial function and reducing numbers of profibrotic IM and the extent of pulmonary fibrosis.

Application of comprehensive lipidomics to biomarker research on adverse drug reactions

Lipidomics is a relatively new field of omics that focuses on lipids, one of the major categories of metabolites. Owing to their various functions, lipids are considered suitable targets for biomarker development; in addition, lipidomics analysis of adverse drug reactions (ADRs) has been conducted recently. In this review, I have summarized information on comprehensive lipidomics, which involves the analysis of global lipids in a non-targeted manner. Mass spectrometry-based platforms are currently the dominant lipidomics platform owing to their versatile features. I have also summarized the application of lipidomics in biomarker research on ADRs caused by therapeutic drugs in humans and rodents. Additionally, general concerns in and emerging approaches of lipidomics research on ADR have been highlighted. Although biomarkers identified using the lipidomics analysis of ADRs have not been qualified, reported candidates will be evaluated for clinical application. In addition, novel biomarker candidates will be developed via classical and new approaches exemplified in this review.

Multi-omics study of silicosis reveals the potential therapeutic targets PGD2 and TXA2

Rationale: Silicosis is a severe occupational lung disease. Current treatments for silicosis have highly limited availability (i.e., lung transplantation) or, do not effectively prolong patient survival time (i.e., lung lavage). There is thus an urgent clinical need for effective drugs to retard the progression of silicosis.

Methods: To systematically characterize the molecular changes associated with silicosis and to discover potential therapeutic targets, we conducted a transcriptomics analysis of human lung tissues acquired during transplantation, which was integrated with transcriptomics and metabolomics analyses of silicosis mouse lungs. The results from the multi-omics analyses were then verified by qPCR, western blot, and immunohistochemistry. The effect of Ramatroban on the progression of silicosis was evaluated in a silica-induced mouse model.

Results: Wide metabolic alterations were found in lungs from both human patients and mice with silicosis. Targeted metabolite quantification and validation of expression of their synthases revealed that arachidonic acid (AA) pathway metabolites, prostaglandin D₂ (PGD₂) and thromboxane A₂ (TXA₂), were significantly up-regulated in silicosis lungs. We further examined the effect of Ramatroban, a clinical antagonist of both PGD₂ and TXA₂ receptors, on treating silicosis using a mouse model. The results showed that Ramatroban significantly alleviated silica-induced pulmonary inflammation, fibrosis, and cardiopulmonary dysfunction compared with the control group.

Conclusion: Our results revealed the importance of AA metabolic reprogramming, especially PGD₂ and TXA₂ in the progression of silicosis. By blocking the receptors of these two prostanoids, Ramatroban may be a novel potential therapeutic drug to inhibit the progression of silicosis.

Alveolar lipids in pulmonary disease. A review

Lung lipid metabolism participates both in infant and adult pulmonary disease. The lung is composed by multiple cell types with specialized functions and coordinately acting to meet specific physiologic requirements. The alveoli are the niche of the most active lipid metabolic cell in the lung, the type 2 cell (T2C). T2C synthesize surfactant lipids that are an absolute requirement for respiration, including dipalmitoylphosphatidylcholine. After its synthesis and secretion into the alveoli, surfactant is recycled by the T2C or degraded by the alveolar macrophages (AM). Surfactant biosynthesis and recycling is tightly regulated, and dysregulation of this pathway occurs in many pulmonary disease processes. Alveolar lipids can participate in the development of pulmonary disease from their extracellular location in the lumen of the alveoli, and from their intracellular location in T2C or AM. External insults like smoke and pollution can disturb surfactant homeostasis and result in either surfactant insufficiency or accumulation. But disruption of surfactant homeostasis is also observed in many chronic adult diseases, including chronic obstructive pulmonary disease (COPD), and others. Sustained damage to the T2C is one of the postulated causes of idiopathic pulmonary fibrosis (IPF), and surfactant homeostasis is disrupted during fibrotic conditions. Similarly, surfactant homeostasis is impacted during acute respiratory distress syndrome (ARDS) and infections. Bioactive lipids like eicosanoids and sphingolipids also participate in chronic lung disease and in respiratory infections. We review the most recent knowledge on alveolar lipids and their essential metabolic and signaling functions during homeostasis and during some of the most commonly observed pulmonary diseases.

Alveolar Dynamics and Beyond - The Importance of Surfactant Protein C and Cholesterol in Lung Homeostasis and Fibrosis

Surfactant protein C (SP-C) is an important player in enhancing the interfacial adsorption of lung surfactant lipid films to the alveolar air-liquid interface. Doing so, surface tension drops down enough to stabilize alveoli and the lung, reducing the work of breathing. In addition, it has been shown that SP-C counteracts the deleterious effect of high amounts of cholesterol in the surfactant lipid films. On its side, cholesterol is a well-known modulator of the biophysical properties of biological membranes and it has been proven that it activates the inflammasome pathways in the lung. Even though the molecular mechanism is not known, there are evidences suggesting that these two molecules may interplay with each other in order to keep the proper function of the lung. This review focuses in the role of SP-C and cholesterol in the development of lung fibrosis and the potential pathways in which impairment of both molecules leads to aberrant lung repair, and therefore impaired alveolar dynamics. From molecular to cellular mechanisms to evidences in animal models and human diseases. The evidences revised here highlight a potential SP-C/cholesterol axis as target for the treatment of lung fibrosis.