Polystyrene microplastics induce pulmonary fibrosis by promoting alveolar epithelial cell ferroptosis through cGAS/STING signaling.

Polystyrene microplastics (PS-MPs) are new types of environmental pollutant that have garnered significant attention in recent years since they were found to cause damage to the human respiratory system when they are inhaled. The pulmonary fibrosis is one of the serious consequences of PS-MPs inhalation. However, the impact and underlying mechanisms of PS-MPs on pulmonary fibrosis are not clear. In this study, we studied the potential lung toxicity and PS-MPs-developed pulmonary fibrosis by long-term intranasal inhalation of PS-MPs. The results showed that after exposing to the PS-MPs, the lungs of model mouse had different levels of damage and fibrosis. Meanwhile, exposing to the PS-MPs resulted in a markedly decrease in glutathione (GSH), an increase in malondialdehyde (MDA), and iron overload in the lung tissue of mice and alveolar epithelial cells (AECs). These findings suggested the occurrence of PS-MP-induced ferroptosis. Inhibitor of ferroptosis (Fer-1) had alleviated the PS-MPs-induced ferroptosis. Mechanically, PS-MPs triggered cell ferroptosis and promoted the development of pulmonary fibrosis via activating the cGAS/STING signaling pathway. Inhibition of cGAS/STING with G150/H151 attenuated pulmonary fibrosis after PS-MPs exposure. Together, these data provided novel mechanistic insights of PS-MPs-induced pulmonary fibrosis and a potential therapeutic paradigm.

Tetrandrine alleviates pulmonary fibrosis by inhibiting alveolar epithelial cell senescence through PINK1/Parkin-mediated mitophagy.

Idiopathic pulmonary fibrosis (IPF) is a fatal and insidious interstitial lung disease. So far, there are no effective drugs for preventing the disease process. Cellular senescence plays a critical role in the development of IPF, with the senescence and insufficient mitophagy of alveolar epithelial cells being implicated in its pathogenesis. Tetrandrine is a natural alkaloid which is now produced synthetically. It was known that the tetrandrine has anti-fibrotic effects, but the efficacy and mechanisms are still not well evaluated. Here, we reveal the roles of tetrandrine on AECs senescence and the antifibrotic effects by using a bleomycin challenged mouse model of pulmonary fibrosis and a bleomycin-stimulated mouse alveolar epithelial cell line (MLE-12). We performed the ß-galactosidase staining, immunohistochemistry and fluorescence to assess senescence in MLE-12 cells. The mitophagy levels were detected by co-localization of LC3 and COVIX. Our findings indicate that tetrandrine suppressed bleomycin-induced fibroblast activation and ultimately blocked the increase of collagen deposition in mouse model lung tissue. It has significantly inhibited the bleomycin-induced senescence and senescence-associated secretory phenotype (SASP) in alveolar epithelial cells (AECs). Mechanistically, tetrandrine suppressed the decrease of mitochondrial autophagy-related protein expression to rescue the bleomycin-stimulated impaired mitophagy in MLE-12 cells. We revealed that knockdown the putative kinase 1 (PINK1) gene by a short interfering RNA (siRNA) could abolish the ability of tetrandrine and reverse the MLE-12 cells senescence, which indicated the mitophagy of MLE-12 cells is PINK1 dependent. Our data suggest the tetrandrine could be a novel and effective drug candidate for lung fibrosis and senescence-related fibrotic diseases.

Indole-3-acetic acid attenuates pulmonary fibrosis by modulating lung microbiota, inhibiting fibroblast activation, and alleviating alveolar epithelial cell senescence.

AIM: Pulmonary fibrosis (PF) is a relentlessly progressive disorder characterized by high mortality and limited effective therapeutic options. Indole-3-acetic acid (IAA), originally recognized as a plant hormone, is also identified as a tryptophan-derived metabolite catabolized from microbiota in mammals. IAA has exhibited antioxidative, anti-inflammatory, and anti-tumor effects in various disorders, yet its role in PF remains elusive. MAIN METHODS: Bleomycin (BLM) was employed to induce PF in a mouse model. TGF-ß1 was utilized in primary mouse lung fibroblasts (pMLFs) to establish a pro-fibrotic in vitro cellular model, and in A549 cells to create an in vitro cellular senescence model. The therapeutic effects of IAA on PF were evaluated using hematoxylin-eosin staining, immunofluorescence staining, western blotting, SA-ß-gal assay, and network pharmacology analysis. Additionally, the effect of IAA on lung microbiota of PF was investigated using 16S rRNA gene sequencing analysis. KEY FINDINGS: we observed a significant reduction in IAA levels in both PF patients and mouse models. Moreover, we demonstrated the therapeutic potential of IAA in alleviating PF in BLM-induced mouse models, showing a dose-dependent response. Mechanistically, we delineated three perspectives. Firstly, IAA promoted autophagic flux by inhibiting the PI3K/AKT/mTOR pathway, thereby suppressing lung fibroblast differentiation and extracellular matrix (ECM) deposition. Secondly, IAA attenuated alveolar epithelial cell senescence by modulating the PI3K/AKT and HIF-1 pathways. Lastly, IAA displayed the ability to mitigate PF by modulating the structure and composition of lung microbiota. SIGNIFICANCE: Our study demonstrates that IAA alleviates PF through multiple pathways, highlighting its potential as a therapeutic agent.

Variations in pleural microbiota and metabolic phenotype associated with malignant pleural effusion in human lung adenocarcinoma.

BACKGROUND: Lung cancer is the most common cancer-related death worldwide. In 2022, the number of daily deaths of lung cancer was estimated to reach around 350 in the United States. Lung adenocarcinoma is the main subtype of lung cancer and patients with malignant pleural effusion (MPE) suffer from poor prognosis. Microbiota and its metabolites are associated with cancer progression. However, the effect of pleural microbiota on pleural metabolic profile of MPE in lung adenocarcinoma patients remains largely unknown. METHODS: Pleural effusion samples collected from lung adenocarcinoma patients with MPE (n = 14) and tuberculosis pleurisy patients with benign pleural effusion (BPE group, n = 10) were subjected to microbiome (16S rRNA gene sequencing) and metabolome (liquid chromatography tandem mass spectrometry [LC-MS/MS]) analyses. The datasets were analyzed individually and integrated for combined analysis using various bioinformatic approaches. RESULTS: The metabolic profile of MPE in lung adenocarcinoma patients were clearly distinguished from BPE with 121 differential metabolites across six significantly enriched pathways identified. Glycerophospholipids, fatty and carboxylic acids, and derivatives were the most common differential metabolites. Sequencing of microbial data revealed nine significantly enriched genera (i.e., Staphylococcus, Streptococcus, Lactobacillus) and 26 enriched ASVs (i.e., species Lactobacillus_delbrueckii) in MPE. Integrated analysis correlated MPE-associated microbes with metabolites, such as phosphatidylcholine and metabolites involved in the citrate cycle pathway. CONCLUSION: Our results provide substantial evidence of a novel interplay between the pleural microbiota and metabolome, which was drastically perturbed in MPE in lung adenocarcinoma patients. Microbe-associated metabolites can be used for further therapeutic explorations.