Pathogenesis exploration and timely intervention of lung injury is quite necessary as it has harmed human health worldwide for years. Ficolin B (Fcn B) is a recognition molecule that can recognize a variety of ligands and play an important role in mediating the cell cycle, immune response, and tissue homeostasis in the lung. However, the role of Fcn B in bleomycin (BLM)-induced lung injury is obscure. This study aims to investigate the sources of Fcn B and its mechanism in BLM-induced lung injury. WT, Fcna^-/-, and Fcnb^-/- mice were selected to construct the BLM-induced lung injury model. Lung epithelial cells were utilized to construct the BLM-induced cell model. Exosomes that were secreted from alveolar macrophages (AMs) were applied for intervention by transporting Fcn B. Clinical data suggested M-ficolin (homologous of Fcn B) was raised in plasma of interstitial lung disease (ILD) patients. In the mouse model, macrophage-derived Fcn B aggravated BLM-induced lung injury and fibrosis. Fcn B further promoted the development of autophagy and ferroptosis. Remarkably, cell experiment results revealed that Fcn B transported by BLM-induced AMs exosomes accelerated autophagy and ferroptosis in lung epithelial cells through the activation of the cGAS-STING pathway. In contrast, the application of 3-Methyladenine (3-MA) reversed the promotion effect of Fcn B from BLM-induced AMs exosomes on lung epithelial cell damage by inhibiting autophagy-dependent ferroptosis. Meanwhile, in the BLM-induced mice model, the intervention of Fcn B secreted from BLM-induced AMs exosomes facilitated lung injury and fibrosis via ferroptosis. In summary, this study demonstrated that Fcn B transported by exosomes from AMs exacerbated BLM-induced lung injury by promoting lung epithelial cells ferroptosis through the cGAS-STING signaling pathway.

In patients with sepsis, neutrophil apoptosis tends to be inversely proportional to the severity of sepsis, but its mechanism is not yet clear. This study aimed to explore the mechanism of fatty acid binding protein 4 (FABP4) regulating neutrophil apoptosis through combined analysis of gut microbiota and short-chain fatty acids (SCFAs) metabolism. First, neutrophils from bronchoalveolar lavage fluid (BALF) of patients with sepsis-induced acute respiratory distress syndrome (ARDS) were purified and isolated RNA was applied for sequencing. Then, the cecal ligation and puncture (CLP) method was applied to induce the mouse sepsis model. After intervention with differential SCFAs sodium acetate, neutrophil apoptosis and FABP4 expression were further analyzed. Then, FABP4 inhibitor BMS309403 was used to treat neutrophils. We found CLP group had increased lung injury score, lung tissue wet/dry ratio, lung vascular permeability, and inflammatory factors IL-1β, TNF-α, IL-6, IFN-γ, and CCL3 levels in both bronchoalveolar lavage fluid and lung tissue. Additionally, FABP4 was lower in neutrophils of ARDS patients and mice. Meanwhile, CLP-induced dysbiosis of gut microbiota and changes in SCFAs levels were observed. Further verification showed that acetic acids reduced neutrophil apoptosis and FABP4 expression via FFAR2. Besides, FABP4 affected neutrophil apoptosis through endoplasmic reticulum (ER) stress, and neutrophil depletion alleviated the promotion of ARDS development by BMS309403. Moreover, FABP4 in neutrophils regulated the injury of RLE-6TN through inflammatory factors. In conclusion, FABP4 affected by gut microbiota-derived SCFAs delayed neutrophil apoptosis through ER stress, leading to increased inflammatory factors mediating lung epithelial cell damage.

Secondary pneumonia, a common complication of sepsis‐induced immunosuppression (SII), is closely linked to alveolar macrophage (AM) dysfunction primarily due to impaired glycolytic activity. However, the underlying molecular mechanisms remain unclear. In this study, it is found that exosomal RNA component of the mitochondrial RNA processing endoribonuclease (Rmrp), derived from type II alveolar epithelial cells (AEC‐IIs), drives glycolytic defects and immune tolerance in AMs following cecal ligation and puncture (CLP) sepsis. Targeted depletion of Rmrp in either AEC‐IIs or AMs alleviated SII and secondary pneumonia induced by Pseudomonas aeruginosa infection 48 h post CLP. Mechanistically, Rmrp interacts with and inhibits the ubiquitination and degradation of the RNA‐binding protein zinc finger protein 36 (ZFP36). This results in ZFP36 upregulation, subsequently accelerating the decay of 6‐phosphofructo‐2‐kinase/fructose‐2,6‐bisphosphatase 3 (Pfkfb3 ) mRNA by binding to its AU‐rich elements in the 3′ untranslated region. The degradation of Pfkfb3 mRNA leads to impaired glycolysis and suppresses immune responses in AMs after sepsis. Additionally, it is found that exosomal Rmrp levels are correlated with AM immune tolerance and the prognosis of patients with sepsis. These findings highlight the critical role of AEC‐II‐derived exosomal Rmrp in the pathogenesis of SII and secondary pneumonia. Importantly, the study suggests that exosomal Rmrp may serve as a biomarker for predicting and managing SII in clinical settings.

Lung adenocarcinoma (LUAD) is a prevalent subtype of lung cancer (LC) whose progression is regulated by multiple genes. This study sought to find the impact and mechanism of HNRNPH1 on LUAD. The expression and role of HSP90AB1, HNRNPH1, and autophagy-related protein MAP1LC3B in LUAD were detected. Additionally, bioinformatics analysis, silencing and overexpression techniques, and in vivo modeling were used to explore the regulatory mechanisms of these proteins in the progression of LUAD. HSP90AB1 showed high expression in LUAD and was linked to a worse prognosis. Overexpression of HSP90AB1 significantly promoted the malignant phenotype of LUAD cells and inhibited MAP1LC3B-mediated autophagy. However, overexpression of HNRNPH1 could reverse the malignant phenotype resulting from HSP90AB1 overexpression and promote MAP1LC3B-mediated autophagy by binding to HSP90AB1 mRNA and inhibiting its protein expression. Animal experiments also revealed that overexpression of HNRNPH1 could inhibit tumor progression by promoting cellular autophagy. We verified the key role of HSP90AB1, HNRNPH1, and MAP1LC3B in LUAD, and revealed a possible regulatory mechanism, namely, HNRNPH1 could inhibit the development of LUAD by promoting autophagy through the HSP90AB1/MAP1LC3B axis. These findings may offer new insights for improving the treatment and prognosis of LUAD. Not applicable.