Lower Oligomeric Form of Surfactant Protein D in Murine Acute Lung Injury Induces M1 Subtype Macrophages Through Calreticulin/p38 MAPK Signaling Pathway

Sputum SLC40A1 as a Novel Biomarker is Increased in Patients with Acute Exacerbation of Chronic Obstructive Pulmonary Disease

Background

Solute carrier family 40 member 1 (SLC40A1 or Ferroportin) is a cell surface glycoprotein that participates in the efflux of cellular iron and disease pathogenesis. Induced sputum is a non-invasive method for lung sample collection. However, it remains unknown whether SLC40A1 is a potential diagnostic biomarker in induced sputum cells of patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). We in this study aimed to investigate the expression and the anti-inflammatory role of SLC40A1 in the induced-sputum cells of AECOPD patients.

Methods

A total of 35 induced sputum samples were collected from patients with AECOPD. Flow cytometry analysis was used to determine inflammatory cell phenotypes and SLC40A1 expression. Murine RAW 264.7 cell lines were treated with cigarette smoke extract (CSE) and SLC40A1-shRNA for SLC40A1 expression in vitro. ELISA was used for measurement of pro-inflammatory cytokine expression in vitro.

Results

Flow cytometry analysis showed that sputum neutrophils were increased in AECOPD patients with 3-5 exacerbations per year compared to 1 exacerbation per year, accompanied by elevated expression of CD40 and SLC40A1 in macrophages. The lung function (FEV1%pred) was reduced with a higher COPD exacerbation rate. There was a negative correlation between the FEV1% predicted and sputum neutrophil count. Patients expressing high levels of SLC40A1 exhibited higher exacerbation rates. SLC40A1 expression levels positively correlated with sputum neutrophils and negatively correlated with predicted FEV1%. In addition, mechanical ventilation reduces sputum neutrophils and SLC40A1 expression, particularly in patients with a high exacerbation rate. Further analysis in RAW 264.7 macrophage cell lines showed that cigarette smoke extract (CSE) increased the expression of SLC40A1, TNF-α, IL-6 and IL-10 at a concentration-dependent manner. SLC40A1 knockdown increased the expression of TNF-α and IL-6 and reduced the expression of IL-10 in CSE-treated macrophages.

Conclusion

SLC40A1 in sputum macrophages is increased and closely related to AECOPD severity, it would be a potential anti-inflammatory biomarker of patients with AECOPD.

Advances in acute respiratory distress syndrome: focusing on heterogeneity, pathophysiology, and therapeutic strategies

In recent years, the incidence of acute respiratory distress syndrome (ARDS) has been gradually increasing. Despite advances in supportive care, ARDS remains a significant cause of morbidity and mortality in critically ill patients. ARDS is characterized by acute hypoxaemic respiratory failure with diffuse pulmonary inflammation and bilateral edema due to excessive alveolocapillary permeability in patients with non-cardiogenic pulmonary diseases. Over the past seven decades, our understanding of the pathology and clinical characteristics of ARDS has evolved significantly, yet it remains an area of active research and discovery. ARDS is highly heterogeneous, including diverse pathological causes, clinical presentations, and treatment responses, presenting a significant challenge for clinicians and researchers. In this review, we comprehensively discuss the latest advancements in ARDS research, focusing on its heterogeneity, pathophysiological mechanisms, and emerging therapeutic approaches, such as cellular therapy, immunotherapy, and targeted therapy. Moreover, we also examine the pathological characteristics of COVID-19-related ARDS and discuss the corresponding therapeutic approaches. In the face of challenges posed by ARDS heterogeneity, recent advancements offer hope for improved patient outcomes. Further research is essential to translate these findings into effective clinical interventions and personalized treatment approaches for ARDS, ultimately leading to better outcomes for patients suffering from ARDS.

aFGF gene-modified adipose-derived mesenchymal stem cells promote healing of full-thickness skin defects in diabetic rats

BACKGROUND

Chronic diabetic wounds pose a significant clinical challenge due to the limited efficacy of current treatments. This study aimed to investigate the role and potential mechanisms of adipose-derived mesenchymal stem cells (ADSCs) overexpressing acidic fibroblast growth factor (aFGF) in diabetic wound healing in a rat model.

METHODS

ADSCs were genetically modified to achieve stable overexpression of aFGF. Varying doses of aFGF-ADSCs (1 × 106, 2 × 106, 3 × 106, 4 × 106) were injected into the muscular tissue surrounding diabetic rat wounds. We assessed aFGF expression and its impact on various stages of wound healing, including angiogenesis, inflammatory response, epithelialization, and collagen deposition. Transcriptomic sequencing was performed to explore the underlying mechanisms driving enhanced wound healing.

RESULTS

Lentiviral transduction successfully induced stable aFGF overexpression in ADSCs. In vivo experiments revealed that varying doses of aFGF-ADSCs markedly enhanced wound healing in diabetic rats in a dose-dependent manner. The dose of 3 × 10⁶ aFGF-ADSCs demonstrated the most significant effect. In the 3 × 106 aFGF-ADSCs group, expression levels of aFGF, CD31, and CD163 were significantly higher than in other groups (p < 0.05), while CD86 expression was significantly lower (p < 0.05).

CONCLUSION

Single doses of aFGF-ADSCs comprehensively improved various aspects of wound repair in diabetic rats, offering a potential new approach for treating chronic diabetic wounds. The mechanism of action involves promoting angiogenesis, modulating inflammatory responses, accelerating epithelialization, and optimizing collagen deposition.

Identification and Functional Analysis of PANoptosis-Associated Genes in the Progression From Sepsis to ARDS

BACKGROUND

Sepsis and acute respiratory distress syndrome (ARDS) are common inflammatory conditions in intensive care, with ARDS significantly increasing mortality in septic patients. PANoptosis, a newly discovered form of programmed cell death involving multiple cell death pathways, plays a critical role in inflammatory diseases. This study aims to elucidate the PANoptosis-related genes (PRGs) and their involvement in the progression of sepsis to ARDS.

METHODS

This study analyzed differentially expressed genes (DEGs) associated with PRGs to explore their role in the progression of immune disorders from sepsis to septic ARDS. A diagnostic prediction model was constructed based on key PRGs identified through bioinformatics analysis. Functional enrichment analyses were conducted to determine pathway involvement, and correlations with immune cells were assessed. Mendelian randomization analysis was applied to investigate potential causal links between specific PRGs and ARDS. Immunohistochemical analysis was used to evaluate PRG expression in lung tissue.

RESULTS

The prediction model effectively distinguished septic ARDS patients from those with sepsis. NDRG1 expression was elevated in ARDS, while DDX3X, PTPRC, and TNFSF8 were downregulated. NDRG1 showed a positive correlation with activated dendritic cells, whereas DDX3X, PTPRC, and TNFSF8 were positively associated with neutrophils and negatively correlated with CD56bright NK cells. Functional enrichment analysis highlighted spliceosome function, MAPK signaling, endocytosis, and antigen processing pathways as significantly associated with these PRGs. Mendelian randomization suggested a causal link between NDRG1 and ARDS, and immunohistochemical analysis revealed its predominant expression near vascular walls. In a mouse model of sepsis, suppression of NDRG1 alleviated lung injury.

CONCLUSION

PANoptosis may contribute to immune dysregulation in sepsis-associated ARDS. NDRG1 is identified as a potential therapeutic target, offering new avenues for mitigating ARDS progression and improving patient outcomes.

Impact of acute stress disorder on surfactant protein D levels in acute lung injury

Many people sustain acute lung injuries in road traffic collisions, but few studies have dealt with such injuries in live models. This study aimed to explore the basic pathophysiological and inflammatory changes in adult rabbits following acute thoracic trauma. We randomly assigned 50 rabbits to control and injury groups. Rabbits in the injury group were subjected to right chest pressure (2600 g) using a Hopkinson bar. Measurements were taken in the control group and 0, 24, 48, and 72 h after injury in the injury group. Injury severity was evaluated in gross view; with haematoxylin and eosin (H&E) staining; and through the serum changes of tumor necrosis factor alpha (TNF-α), surfactant protein D (SP-D), and neutrophils. Secretion changes in SP-D in right lung injured tissues were estimated by western blotting and qPCR. Serum TNF-α levels increased rapidly immediately after injury, gradually recovering after 24, 48, and 72 h (p < 0.01). The percentage of neutrophils in the accompanying blood showed a consistent trend. Gross necropsy and H&E staining indicated different levels of bleeding, alveoli exudation, and inflammatory transformation after impact. ELISA depicted the same trend in circulation (F = 22.902, p < 0.01). Western blotting showed that SP-D protein levels in tissues decreased at 0 h and increased at 24, 48, and 72 h. We demonstrate the feasibility of a model of impact lung injury. Primary impact caused injury without external signs. Inflammation began immediately, and the lungs began recovering at 24, 48, and 72 h, as shown by increased SP-D levels in circulation and tissues.With complaints of ALI and inflammation, SP-D may be a potential biomarker after chest trauma.

Immunomodulatory Role of Surfactant Protein-D in a Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) Model

Surfactant protein D (SP-D), a pattern recognition molecule, is emerging as a potent anti-tumoural innate immune defense molecule in a range of cancers. Previously, SP-D expression was found to be significantly downregulated at the malignant sites of human prostate adenocarcinoma and associated with an increasing Gleason score and severity. We recently reported selective induction of intrinsic apoptosis by a recombinant fragment of human SP-D (rfhSP-D) in the human Prostate cancer (PCa) biopsy explants and cells with glucose regulated protein of 78 (GRP78) as one of the key interacting partners. The present study evaluated the expression of SP-D in early and advanced stages of PCa using transgenic adenocarcinoma of mouse prostate (TRAMP) model. Both early and late stages of PCa showed significantly decreased SP-D mRNA expression and increased proteolytic degradation of SP-D protein. Systemic and tumoural immunophenotyping of TRAMP model revealed increased serine proteases producing granulocytes and polymorphonuclear myeloid-derived suppressor cells (PMN MDSCs) in the late stage; the serine proteases secreted by these cells could be involved in the degradation of SP-D. Susceptibility of rfhSP-D to elastase-mediated proteolysis provided the rationale to use an elastase-inhibitor to sustain intact rfhSP-D in the tumour microenvironment. The study revealed an immunomodulatory potential of rfhSP-D and elastase inhibitor, sivelestat, to induce macrophage polarization towards M1 with downregulation of PMN MDSCs in ex-vivo cultured TRAMP tumours. Furthermore, rfhSP-D induced immunogenic cell death in murine PCa cells and in TRAMP explants. The findings highlight that SP-D plays an anti-tumourigenic role in PCa by inducing immunogenic cell death and immunomodulation while the prostate tumour milieu adversely impacts SP-D by inhibiting its transcription, and enhancing its proteolytic degradation. Transformation of an immunologically "cold tumour" into a "hot tumour" implicates therapeutic potential of rfhSP-D in PCa.

Classic Signaling Pathways in Alveolar Injury and Repair Involved in Sepsis-Induced ALI/ARDS: New Research Progress and Prospect

Sepsis is a common critical clinical disease with high mortality that can cause approximately 10 million deaths worldwide each year. Acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) is a common clinical complication of sepsis, which occurs primarily as diffuse alveolar injury, hypoxemia, and respiratory distress. The mortality rate of ALI/ARDS is as high as 30%-40%, which greatly endangers human health. Due to the unclear pathogenesis of ALI/ARDS, its treatment is still a worldwide problem. At present, clinical treatment mainly relies on lung-protective ventilation, prone position ventilation, and fluid management. However, there is a lack of effective and specific treatment measures. In recent years, domestic and foreign scholars have committed to basic research on ALI/ARDS, trying to further clarify its pathogenesis and find new targets and methods for the treatment of ALI/ARDS. In this review, we summarize the signaling pathways related to alveolar injury and repair in sepsis-induced ALI/ARDS and their latest research progress. They include the NF-κB, JAK2/STAT3, mitogen-activated protein kinase (MAPK), mTOR, and Notch signaling pathways. Understanding the molecular mechanisms of these signaling pathways in sepsis-induced ALI/ARDS may provide new targets and ideas for the clinical treatment of this disease.

Soluble SIRP-Alpha Promotes Murine Acute Lung Injury Through Suppressing Macrophage Phagocytosis

Soluble signal regulatory protein-alpha (SIRP-alpha) is elevated in bronchoalveolar lavage (BAL) of mice with lipopolysaccharides (LPS)-induced acute lung injury (ALI). To define the role of soluble SIRP-alpha in the pathogenesis of ALI, we established murine ALI in wild-type (WT) and SIRP-alpha knock-out (KO) mice by intratracheal administration of LPS. The results indicated that lack of SIRP-alpha significantly reduced the pathogenesis of ALI, in association with attenuated lung inflammation, infiltration of neutrophils and expression of pro-inflammatory cytokines in mice. In addition, lack of SIRP-alpha reduced the expression of pro-inflammatory cytokines in LPS-treated bone marrow-derived macrophages (BMDMs) from KO mice, accompanied with improved macrophage phagocytosis. Blockade of soluble SIRP-alpha activity in ALI BAL by anti-SIRP-alpha antibody (aSIRP) effectively reduced the expression of TNF-alpha and IL-6 mRNA transcripts and proteins, improved macrophage phagocytosis in vitro. In addition, lack of SIRP-alpha reduced activation of Src homology 2 domain-containing protein tyrosine phosphatase 1 (SHP-1) and improved activation of signal transducer and activator of transcription-3 (STAT3) and STAT6. Suppression of SHP-1 activity by tyrosine phosphatase inhibitor 1 (TPI-1) increased activation of STAT3 and STAT6, and improved macrophage phagocytosis, that was effectively reversed by STAT3 and STAT6 inhibitors. Thereby, SIRP-alpha suppressed macrophage phagocytosis through activation of SHP-1, subsequently inhibiting downstream STAT3 and STAT6 signaling. Lack of SIRP-alpha attenuated murine ALI possibly through increasing phagocytosis, and improving STAT3 and STAT6 signaling in macrophages. SIRP-alpha would be promising biomarker and molecular target in the treatment of murine ALI and patients with acute respiratory distress syndrome (ARDS).

Lack of STAT6 enhances murine acute lung injury through NLRP3/p38 MAPK signaling pathway in macrophages

Background

Signal transducer and activator of transcription 6 (STAT6) is an intracelluar transcriotion factor and NLRP3 (Nod-like receptor containing a pyrin domain 3) is a component of NLRP3 inflammasome in pyroptotic cells. There was increased activation of STAT6 and expression of NLRP3 in mice with murine acute lung injury (ALI). However, it is unknown their roles in the development of murine ALI. We in this study, investigated the effects of STAT6 signaling on murine ALI and pyroptosis in STAT6 knock-out (KO) mice and macrophages.

Results

STAT6 was activated in the lung tissues of mice 2 days after intratracheal treatmemt with 5 mg/kg LPS. Lack of STAT6 expression in KO mice induced more severe lung inflammation, associated with elevated neutrophil influx and expression of TNF-alpha, IL-6 and IL-1beta in the inflamed lung tissues. In addition, the expression of NLRP3, ASC (apoptosis-associated speck-like protein containing a CARD), p-p38 MAPK (p38 mitogen-activated protein kinase) and ratio of LC3-II/I (microtubule-associated protein-1 light chain-3) was increased, accompanied with the increased polarization of Siglec-F(−) subtype macrophages in KO mice with ALI. Further studies in bone marrow-derived macrophages (BMDMs) revealed that lack of STAT6 increased the expression of NLRP3 and p-p38 MAPK, in association with elevated expression of TNF-alpha, IL-1beta and Calreticulin in LPS-treated KO BMDMs.

Conclusions

Lack of STAT6 exacerbated murine ALI through improving the expression of NLRP3 and activation of p38 MAPK in macrophages. STAT6 has an immune suppressive role in the development of ALI and would be a promising therapeutic target in the treatment of ALI and possibly among patients with acute respiratory distress syndrome (ARDS).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12865-022-00500-9.