The Role of Pulmonary and Systemic Immunosenescence in Acute Lung Injury

Methylprednisolone alleviates lung injury in sepsis by regulating miR-151-5p/USP38 pathway

BACKGROUND

Acute lung injury (ALI) is manifested by increased blood vessel permeability within the lungs and subsequent impairment of alveolar gas exchange. Methylprednisolone (MP) is commonly used as a treatment for ALI to reduce inflammation, yet its molecular mechanism remains unclear. This study aims to explore the underlying mechanisms of MP on ALI in a model induced by lipopolysaccharide (LPS).

MATERIAL AND METHODS

The proliferation, viability, apoptosis, and miR-151-5p expression of alveolar type II epithelial cells (AECII) were detected using the cell EdU assay, Annexin V/PI Apoptosis Kit, counting kit-8 (CCK-8) assay, and RT-qPCR. Western blot analysis was used to detect the Usp38 protein level. IL-6 and TNF-α were measured by ELISA. The combination of miR-151-5p and USP38 was determined by chromatin immunoprecipitation (ChIP)-PCR and dual-luciferase reporter assay.

RESULTS

MP greatly improved pulmonary function in vivo, reduced inflammation, and promoted the proliferation of the alveolar type II epithelial cells (AECII) in vitro. By comparing the alterations of microRNAs in lung tissues between MP treatment and control groups, we found that miR-151-5p exhibited a significant increase after LPS-treated AECII, but decreased after MP treatment. Confirmed by a luciferase reporter assay, USP38, identified as a downstream target of miR-151-5p, was found to increase after MP administration. Inhibition of miR-151-5p or overexpression of USP38 in AECII significantly improved the anti-inflammatory, anti-apoptotic, and proliferation-promotive effects of MP.

CONCLUSION

In summary, our data demonstrated that MP alleviates the inflammation and apoptosis of AECII induced by LPS, and promotes the proliferation of AECII partially via miR-151-5p suppression and subsequent USP38 activation.

ARDS and aging: TYMS emerges as a promising biomarker and therapeutic target

Background

Acute Respiratory Distress Syndrome (ARDS) is a common condition in the intensive care unit (ICU) with a high mortality rate, yet the diagnosis rate remains low. Recent studies have increasingly highlighted the role of aging in the occurrence and progression of ARDS. This study is committed to investigating the pathogenic mechanisms of cellular and genetic changes in elderly ARDS patients, providing theoretical support for the precise treatment of ARDS.

Methods

Gene expression profiles for control and ARDS samples were obtained from the Gene Expression Omnibus (GEO) database, while aging-related genes (ARGs) were sourced from the Human Aging Genomic Resources (HAGR) database. Differentially expressed genes (DEGs) were subjected to functional enrichment analysis to understand their roles in ARDS and aging. The Weighted Gene Co-expression Network Analysis (WGCNA) and machine learning pinpointed key modules and marker genes, with ROC curves illustrating their significance. The expression of four ARDS-ARDEGs was validated in lung samples from aged mice with ARDS using qRT-PCR. Gene set enrichment analysis (GSEA) investigated the signaling pathways and immune cell infiltration associated with TYMS expression. Single-nucleus RNA sequencing (snRNA-Seq) explored gene-level differences among cells to investigate intercellular communication during ARDS onset and progression.

Results

ARDEGs are involved in cellular responses to DNA damage stimuli, inflammatory reactions, and cellular senescence pathways. The MEmagenta module exhibited a significant correlation with elderly ARDS patients. The LASSO, RRF, and XGBoost algorithms were employed to screen for signature genes, including CKAP2, P2RY14, RBP2, and TYMS. Further validation emphasized the potential role of TYMS in the onset and progression of ARDS. Immune cell infiltration indicated differential proportion and correlations with TYMS expression. SnRNA-Seq and cell-cell communication analysis revealed that TYMS is highly expressed in endothelial cells, and the SEMA3 signaling pathway primarily mediates cell communication between endothelial cells and other cells.

Conclusion

Endothelial cell damage associated with aging could contribute to ARDS progression by triggering inflammation. TYMS emerges as a promising diagnostic biomarker and potential therapeutic target for ARDS.

Age-dependent inflammatory response is altered in an ex vivo model of bacterial pneumonia

BACKGROUND

Aging is associated with an increased incidence and mortality of Pseudomonas aeruginosa-induced pneumonias. This might be partly due to age-dependent increases in inflammatory mediators, referred to as inflamm-aging and a decline in immune functions, known as immunosenescence. Still, the impact of dysregulated immune responses on lung infection during aging is poorly understood. Here, we aimed to mimic inflamm-aging using ex vivo precision-cut lung slices (PCLS) and neutrophils - as important effector cells of innate immunity - from young and old mice and investigated the influence of aging on inflammation upon infection with P. aeruginosa bacteria.

METHODS

Murine PCLS were infected with the P. aeruginosa standard lab strain PAO1 and a clinical P. aeruginosa isolate D61. After infection, whole-transcriptome analysis of the tissue as well as cytokine expression in supernatants and tissue lysates were performed. Responses of isolated neutrophils towards the bacteria were investigated by quantifying neutrophil extracellular trap (NET) formation, cytokine secretion, and analyzing expression of surface activation markers using flow cytometry.

RESULTS

Inflamm-aging was observed by transcriptome analysis, showing an enrichment of biological processes related to inflammation, innate immune response, and chemotaxis in uninfected PCLS of old compared with young mice. Upon P. aeruginosa infection, the age-dependent pro-inflammatory response was even further promoted as shown by increased production of cytokines and chemokines such as IL-1β, IL-6, CXCL1, TNF-α, and IL-17A. In neutrophil cultures, aging did not influence NET formation or cytokine secretion during P. aeruginosa infection. However, expression of receptors associated with inflammatory responses such as complement, adhesion, phagocytosis, and degranulation was lower in neutrophils stimulated with bacteria from old mice as compared to young animals.

CONCLUSIONS

By using PCLS and neutrophils from young and old mice as immunocompetent ex vivo test systems, we could mimic dysregulated immune responses upon aging on levels of gene expression, cytokine production, and receptor expression. The results furthermore reflect the exacerbation of inflammation upon P. aeruginosa lung infection as a result of inflamm-aging in old age.

Impact of lipopolysaccharide-induced acute lung injury in aged mice

Study Aim: As the geriatric population rapidly expands, there has been a concurrent increase in elderly admissions to intensive care units (ICUs). Acute lung injury (ALI) is a prevalent reason for these admissions and carries poorer survival rates for the aged population compared to younger counterparts. The aging lung is subject to physiological, cellular, and immunological changes. However, our understanding of how aging impacts the clinical progression of ALI is limited. This study explored the effect of aging using a murine model of ALI. Methods: Female C57BL/6J mice, aged 7-8 wk (young) and 18 months (aged), were divided into four groups: young controls, aged controls, young with ALI (YL), and aged with ALI (AL). ALI was induced via intratracheal administration of lipopolysaccharide (LPS, 0.5 mg/kg). The animals were euthanized 72 h after LPS exposure. Results: The AL group exhibited a significantly increased wet/dry ratio compared to the other three groups, including the YL group. The bronchoalveolar lavage (BAL) fluid in the AL group had more cells overall, including more neutrophils, than the other groups. Inflammatory cytokines in BAL fluid showed similar trends. Histological analyses demonstrated more severe lung injury and fibrosis in the AL group than in the other groups. Increased transcription of senescence-associated secretory phenotype markers, including PAI-1 and MUC5B, was more prominent in the AL group than in the other groups. This trend was also observed in BAL samples from humans with pneumonia. Conclusions: Aging may amplify lung damage and inflammatory responses in ALI. This suggests that physicians should exercise increased caution in the clinical management of aged patients with ALI.

Alveolar macrophage modulation via the gut-lung axis in lung diseases

Several studies have demonstrated great potential implications for the gut-lung axis in lung disease etiology and treatment. The gut environment can be influenced by diet, metabolites, microbiotal composition, primary diseases, and medical interventions. These changes modulate the functions of alveolar macrophages (AMs) to shape the pulmonary immune response, which greatly impacts lung health. The immune modulation of AMs is implicated in the pathogenesis of various lung diseases. However, the mechanism of the gut-lung axis in lung diseases has not yet been determined. This mini-review aimed to shed light on the critical nature of communication between the gut and AMs during the development of pulmonary infection, injury, allergy, and malignancy. A better understanding of their crosstalk may provide new insights into future therapeutic strategies targeting the gut-AM interaction.

Network pharmacology and molecular docking to explore Polygoni Cuspidati Rhizoma et Radix treatment for acute lung injury

BACKGROUND

Polygoni Cuspidati Rhizoma et Radix (PCRR), a well-known traditional Chinese medicine (TCM), inhibits inflammation associated with various human diseases. However, the anti-inflammatory effects of PCRR in acute lung injury (ALI) and the underlying mechanisms of action remain unclear.

AIM

To determine the ingredients related to PCRR for treatment of ALI using multiple databases to obtain potential targets for fishing.

METHODS

Recognized and candidate active compounds for PCRR were obtained from Traditional Chinese Medicine Systems Pharmacology, STITCH, and PubMed databases. Target ALI databases were built using the Therapeutic Target, DrugBank, DisGeNET, Online Mendelian Inheritance in Man, and Genetic Association databases. Network pharmacology includes network construction, target prediction, topological feature analysis, and enrichment analysis. Bioinformatics resources from the Database for Annotation, Visualization and Integrated Discovery were utilized for gene ontology biological process and Kyoto Encyclopedia of Genes and Genomes network pathway enrichment analysis, and molecular docking techniques were adopted to verify the combination of major active ingredients and core targets.

RESULTS

Thirteen bioactive compounds corresponding to the 433 PCRR targets were identified. In addition, 128 genes were closely associated with ALI, 60 of which overlapped with PCRR targets and were considered therapeutically relevant. Functional enrichment analysis suggested that PCRR exerted its pharmacological effects in ALI by modulating multiple pathways, including the cell cycle, cell apoptosis, drug metabolism, inflammation, and immune modulation. Molecular docking results revealed a strong associative relationship between the active ingredient and core target.

CONCLUSION

PCRR alleviates ALI symptoms via molecular mechanisms predicted by network pharmacology. This study proposes a strategy to elucidate the mechanisms of TCM at the network pharmacology level.

Inhibition of gp130 alleviates LPS-induced lung injury by attenuating apoptosis and inflammation through JAK1/STAT3 signaling pathway

BACKGROUND AND OBJECTIVE

Acute lung injury or acute respiratory distress syndrome (ALI/ARDS) is a life-threatening respiratory disease. Gp130 is a signal transduction receptor that participates in a variety of essential biological processes. The biological function of gp130 in ALI/ARDS is unclear. This study aims to investigate the roles and potential mechanisms of gp130 in lung injury induced by lipopolysaccharide (LPS).

METHODS

The ALI/ARDS mouse model was established using intratracheal LPS administration. Hematoxylin and eosin staining and bronchoalveolar lavage fluid analysis were used to evaluate the degree of lung injury. Cell apoptosis was assessed by TUNEL staining, flow cytometry, and western blot. Then the expression of gp130, IL-6, IL-10, TNF-α, and the JAK1/STAT3 signaling pathway-related proteins was assessed by RT-PCR, western blot, and immunohistochemistry.

RESULTS

The expression of gp130 increased after 24 h of LPS treatment. Inhibiting gp130 improved inflammatory infiltration and alveolar collapsed, decreased IL-6 and TNF-α levels, raised IL-10 levels, and decreased cell apoptosis in LPS-induced mice. Meanwhile, suppressing gp130 reduced the inflammatory response and cell apoptosis in LPS-induced Beas-2B cells. Furthermore, p-JAK1 and p-STAT3 expressions were elevated after LPS stimulation and decreased following gp130 inhibition, suggesting that gp130 may regulate the JAK1/STAT3 signaling pathway in LPS-induced mice and Beas-2B cells.

CONCLUSION

The findings suggest that gp130 regulates the inflammatory response and cell apoptosis through the JAK1/STAT3 signaling pathway, thereby mitigating LPS-induced lung injury. Gp130 may be a potential therapeutic target for ALI/ARDS.

Activation of the NLRP3 inflammasome by HMGB1 through inhibition of the Nrf2/HO-1 pathway promotes bleomycin-induced pulmonary fibrosis after acute lung injury in rats

OBJECTIVE

Acute lung injury (ALI) is a common complication of critical diseases with high morbidity and mortality. This study explored the regulatory role and mechanism of high mobility histone box 1 protein (HMGB1) on pulmonary fibrosis (PF) after ALI in rats through nucleotide oligomerization domain-like receptor protein-3 (NLRP3) inflammasome.

METHODS

PF rat models after ALI were established by induction of bleomycin. Degree of fibrosis was assessed by Masson staining and Ashcroft scoring. Hydroxyproline (Hyp) contents in lung tissues and rat lung tissue morphology were detected by enzyme-linked-immunosorbent serologic assay (ELISA) and hematoxylin and eosin staining. The levels of NLRP3, major proteins of NLRP3 inflammasome (NLRP3/ASC/caspase-1), and downstream inflammatory cytokines interleukin (IL)-1 and IL-18 were determined using immunohistochemistry, Western blotting analysis, and ELISA. The nuclear/cytoplasmic nuclear factor erythroid 2-related factor 2 (Nrf2) levels and HO-1 levels were measured by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blotting analysis. Rats was injected with lentivirus carrying short hairpin (sh)-HMGB1 and zinc protoporphyria (ZNPP) (HO-1 inhibitor) to assess the effects of HMGB1 and HO-1 on PF and NLRP3 inflammasome activation.

RESULTS

Bleomycin induced PF after ALI in rats, manifested as patchy fibrosis, atelectasis, and excessive expansion, and increased Aschcroft score and Hyp content. Bleomycin treatment enhanced levels of NLRP3, ASC, caspase-1, IL-1, and IL-18 in rat lung tissues, which promoted activation of NLRP3 inflammasome. HMGB1 was up-regulated in bleomycin-induced rats. HMGB1 knockdown partially reversed NLRP3 inflammasome activation and PF progression. HMGB1 knockdown promoted Nrf2 nuclear translocation and up-regulated HO-1. Suppression of HO-1 partially reversed inhibition of HMGB1 knockdown on NLRP3 inflammasome activation and PF.

CONCLUSION

HMGB1 can activate NLRP3 inflammasomes and promote PF by inhibiting the Nrf2/HO-1 pathway.

Neutrophilic Pleuritis Is a Severe Complication of Klebsiella pneumoniae Pneumonia in Old Mice

The pathomechanisms underlying the frequently observed fatal outcome of Klebsiella pneumoniae pneumonia in elderly patients are understudied. In this study, we examined the early antibacterial immune response in young mice (age 2-3 mo) as compared with old mice (age 18-19 mo) postinfection with K. pneumoniae. Old mice exhibited significantly higher bacterial loads in lungs and bacteremia as early as 24 h postinfection compared with young mice, with neutrophilic pleuritis nearly exclusively developing in old but not young mice. Moreover, we observed heavily increased cytokine responses in lungs and pleural spaces along with increased mortality in old mice. Mechanistically, Nlrp3 inflammasome activation and caspase-1-dependent IL-1β secretion contributed to the observed hyperinflammation, which decreased upon caspase-1 inhibitor treatment of K. pneumoniae-infected old mice. Irradiated old mice transplanted with the bone marrow of young mice did not show hyperinflammation or early bacteremia in response to K. pneumoniae. Collectively, the accentuated lung pathology observed in K. pneumoniae-infected old mice appears to be due to regulatory defects of the bone marrow but not the lung, while involving dysregulated activation of the Nlrp3/caspase-1/IL-1β axis.

lncRNA SNHG12 Inhibition Based on Microsystem Cell Imaging Technology Protects the Endothelium from LPS-Induced Inflammation by Inhibiting the Expression of miR-140-3p Target Gene fndc5

Acute lung injury (ALI) is a serious disease with a high incidence rate, characterized by uncontrolled inflammation and apoptosis. At present, long-chain noncoding RNA (lncRNA) is a noncoding RNA with a length of more than 200 nucleotides. It plays an important role in ALI, cell cycle regulation, cell differentiation regulation, and many other life activities. Therefore, the current focus is to identify and evaluate the possible functions and potential molecular mechanisms of lncRNA small nuclear host gene 12 (SNHG12). Lipopolysaccharide (LPS)-induced mice model and in vitro cell model were established. Gene knockout is to use the principle of DNA homologous recombination to replace the target gene fragment with the designed homologous fragment, so as to achieve the purpose of gene knockout. The relationship between lncRNA SNHG12 expression and ALI was studied through knockdown and overexpression experiments. The qRT-PCR, ROS, immunohistochemistry, histopathology, TUNEL, and cell permeability tests were performed to further verify the possible targets and mechanisms of action. The expression of lncRNA SNHG12 in lung tissue was lower than that in normal tissue. The results showed that lncRNA SNHG12 could reduce lung cell injury and inflammatory cytokines induced by ALI. Bioinformatics analysis showed that lncRNA SNHG12 interacted with miR-140-3p. Subsequent experiments confirmed the link between lncRNA SNHG12, miR-140-3p, and fndc5. Furthermore, this study indicates that lncRNA SNHG12 has a key function in ALI. The results of this study demonstrated the role of lncRNA SNHG12 in the pathological process of ALI and provided a reference for developing novel anti-ALI treatments so that patients can get timely treatment, avoid causing multiple organ failure, and will not endanger their life safety.

The AI-Assisted Identification and Clinical Efficacy of Baricitinib in the Treatment of COVID-19

During the current pandemic, the vast majority of COVID-19 patients experienced mild symptoms, but some had a potentially fatal aberrant hyperinflammatory immune reaction characterized by high levels of IL-6 and other cytokines. Modulation of this immune reaction has proven to be the only method of reducing mortality in severe and critical COVID-19. The anti-inflammatory drug baricitinib (Olumiant) has recently been strongly recommended by the WHO for use in COVID-19 patients because it reduces the risk of progressive disease and death. It is a Janus Kinase (JAK) 1/2 inhibitor approved for rheumatoid arthritis which was suggested in early 2020 as a treatment for COVID-19. In this review the AI-assisted identification of baricitinib, its antiviral and anti-inflammatory properties, and efficacy in clinical trials are discussed and compared with those of other immune modulators including glucocorticoids, IL-6 and IL-1 receptor blockers and other JAK inhibitors. Baricitinib inhibits both virus infection and cytokine signalling and is not only important for COVID-19 management but is “non-immunological”, and so should remain effective if new SARS-CoV-2 variants escape immune control. The repurposing of baricitinib is an example of how advanced artificial intelligence (AI) can quickly identify new drug candidates that have clinical benefit in previously unsuspected therapeutic areas.

Herb Formula (GCis) Prevents Pulmonary Infection Secondary to Intracerebral Hemorrhage by Enhancing Peripheral Immunity and Intestinal Mucosal Immune Barrier

Lung infection is a common complication induced by stroke and seriously affects the prognosis and life quality of patients. However, effective therapeutic strategies are still lacking. In the present study, the herb formula GCis was confirmed to prevent pulmonary infection induced by intracerebral hemorrhage (ICH). The animal model of lung infection induced by ICH, GCis (Ginseng Radix et Rhizoma, Aconiti Lateralis Radix Praeparata, and Cistanches Herba) was orally administrated every day for 7 days. Lung microbial biomass and pathological results showed that the GCis formula pretreatment significantly reduced lung bacterial biomass and alleviated pathological abnormalities. These results indicated that the GCis formula has a clear pharmacological effect on preventing lung infection induced by ICH. Immunosuppression induced by ICH seemed to be the main mechanism of lung infection. Our results showed that the spleen and thymus indexes, WBC, and LY% contents were significantly increased in the GCis formula group. Moreover, bone marrow cells were further analyzed by transcriptome sequencing, and GO and KEGG enrichment analysis results showed that immune function was the main pathway enriched by differential genes after GCis formula intervention. More importantly, our results showed that GCis pretreatment had no significant effect on the mRNA expression of IL-1β, IL-6, and TNF-α in the brain. These results indicated that the GCis formula could enhance immunity after ICH. The intestinal barrier function was further investigated in the present study, considering the origin of the source of infection. Our results showed that the mRNA expressions of intestinal ZO-1, SIgA, and MUC2 were significantly increased, villi structure was intact, inflammatory cell infiltration was reduced, and goblet cell number was increased after GCis formula treatment. These results suggest that the GCis formula can enhance the intestinal mucosal immune barrier. This study provides a herb formula (GCis) that could enhance peripheral immunity and intestinal mucosal immune barrier to prevent pulmonary infection induced by ICH. It would be beneficial in the prevention of severe clinical infections.

Targeting HMGB1 for the treatment of sepsis and sepsis-induced organ injury

High mobility group box 1 (HMGB1) is a ubiquitous nuclear protein that is present in almost all cells and regulates the activity of innate immune responses in both intracellular and extracellular settings. Current evidence suggests that HMGB1 plays a pivotal role in human pathological and pathophysiological processes such as the inflammatory response, immune reactions, cell migration, aging, and cell death. Sepsis is a systemic inflammatory response syndrome (SIRS) that occurs in hosts in response to microbial infections with a proven or suspected infectious etiology and is the leading cause of death in intensive care units worldwide, particularly in the aging population. Dysregulated systemic inflammation is a classic characteristic of sepsis, and suppression of HMGB1 may ameliorate inflammation and improve patient outcomes. Here, we focus on the latest breakthroughs regarding the roles of HMGB1 in sepsis and sepsis-related organ injury, the ways by which HMGB1 are released, and the signaling pathways and therapeutics associated with HMGB1. This review highlights recent advances related to HMGB1: the regulation of HMBG1 might be helpful for both basic research and drug development for the treatment of sepsis and sepsis-related organ injury.

Prognostic value of pulmonary ultrasound score combined with plasma miR-21-3p expression in patients with acute lung injury

Purpose

The aim of this study was to explore the value of the combination between lung ultrasound score (LUS) and the expression of plasma miR‐21‐3p in predicting the prognosis of patients with acute lung injury (ALI).

Patients and methods

A total of 136 ALI patients were divided into survival (n = 86) and death groups (n = 50), or into low/middle‐risk (n = 77) and high‐risk groups (n = 59) according to APACHE II scores. Bioinformatics was used to explore the mechanism of action of miR‐21‐3p in humans. Real‐time fluorescent quantitative PCR was used to detect the expression of miR‐21‐3p in plasma, and LUS was recorded. Receiver operator characteristic (ROC) curve and Pearson correlation were also used.

Results

The LUS and expression level of plasma miR‐21‐3p in the death and high‐risk groups were significantly higher than those in the survival and low/middle‐risk groups (p < 0.01 and p < 0.05). miR‐21‐3p expression leads to pulmonary fibrosis and promotes the deterioration of ALI patients by regulating fibroblast growth factor and other target genes. ROC curve analysis showed that the best cutoff values for LUS and plasma miR‐21‐3p expression were 18.60 points and 1.75, respectively. LUS score and miR‐21‐3p combined predicted the death of ALI patients with the largest area under the curve (0.907, 95% CI: 0.850–0.964), with sensitivity and specificity of 91.6% and 85.2%, respectively. The expression level of plasma miR‐21‐3p was positively correlated with LUS in the death group (r = 0.827, p < 0.01).

Conclusion

LUS and expression level of miR‐21‐3p in plasma are correlated with the severity and prognosis of ALI patients, and their combination has a high value for the prognostic assessment of ALI patients.

Dynamic Process of Secondary Pulmonary Infection in Mice With Intracerebral Hemorrhage

Stroke is a common central nervous system disease in clinical practice. Stroke patients often have infectious complications, such as pneumonia and infections of the urinary tract and gastrointestinal tract. Although it has been shown that translocation of the host gut microbiota to the lungs and immune dysfunction plays a vital role in the development of infection after ischemic stroke, the occurrence and mechanism of pulmonary infection at different time points after hemorrhagic cerebral remain unclear. In this study, the changes in the immune system and intestinal barrier function in mice during disease development were investigated at 1 day (M 1 d), 3 days (M 3 d) and 7 days (M 7 d) following hemorrhagic stroke to clarify the mechanism of secondary pulmonary infection. The experimental results revealed that after hemorrhagic stroke, model mice showed increased brain damage from day 1 to 3, followed by a trend of brain recovery from day 3 to 7 . After hemorrhagic stroke, the immune system was disturbed in model mice. Significant immunosuppression of the peripheral immune system was observed in the M 3 d group but improved in the M 7 d group. Staining of lung tissues with hematoxylin and eosin (H&E) and for inflammatory factors revealed considerable disease and immune disorders in the M 7 d group. Stroke seriously impaired intestinal barrier function in mice and significantly changed the small intestine structure. From 1 to 7 d after stroke, intestinal permeability was increased, whereas the levels of markers for intestinal tight junctions, mucus and immunoglobulin A were decreased. Analysis based on 16S rRNA suggested that the microflora in the lung and ileum was significantly altered after stroke. The composition of microflora in lung and ileum tissue was similar in the M 7d group, suggesting that intestinal bacteria had migrated to lung tissue and caused lung infection at this time point after hemorrhagic stroke. In stroke mice, the aggravation of intestinal barrier dysfunction and immune disorders after intracerebral hemorrhage, promoted the migration of enteric bacteria, and increased the risk of pneumonia poststroke. Our findings reveal the dynamic process of infection after hemorrhagic stroke and provide clues for the optimal timing of intervention for secondary pulmonary infection in stroke patients.

Inflammatory alveolar macrophage-derived microvesicles damage lung epithelial cells and induce lung injury

Emerging evidence has demonstrated that several microvesicles (MVs) are secreted in bronchoalveolar lavage fluid (BALF) during the pathogenesis of acute lung injury/acute respiratory distress syndrome (ALI/ARDS). However, the impact of alveolar macrophage (AM)-derived MVs on epithelial cells and their in vivo effects on ALI/ARDS require further exploration. In this study, MVs were isolated from BALF of mice or mouse alveolar macrophage (MHS) cells by sequential centrifugation and then delivered to epithelial cells or mice. Enzyme-linked immunosorbent assay revealed that BALF-derived MVs (BALF-MVs) and MHS-derived MVs (AM-MVs) were rich in tumor necrosis factor-α (TNF-α) at the early stage of lung injury. In vitro, both inflammatory BALF-MVs and AM-MVs decreased the expression of α subunit of epithelial sodium channel (α-ENaC), γ-ENaC, and Na⁺,K⁺-ATPase α1 and β1 in lung epithelial cells. However, antibodies against TNF-α inhibited the effects of inflammatory AM-MVs in epithelial cells. In vivo, the inflammatory AM-MVs, delivered intratracheally to mice, impaired lung tissues and increased the injury score. They also resulted in decreased alveolar fluid clearance and increased lung wet weight/dry weight ratio. Furthermore, inflammatory AM-MVs downregulated the α-ENaC, γ-ENaC, and Na⁺,K⁺-ATPase α1 and β1 levels in lung tissues. According to our results, inflammatory AM-derived MVs may potentially contribute to lung injury and pulmonary edema, thereby indicating a potential novel therapeutic approach against ALI/ARDS based on AM-MVs.

A potential association between immunosenescence and high COVID-19 related mortality among elderly patients with cardiovascular diseases

Elderly patients with cardiovascular diseases account for a large proportion of Corona virus Disease 2019(COVID-19)related deaths. COVID-19, as a new coronavirus, mainly targets the patient's lung triggering a cascade of innate and adaptive immune responses in the host. The principal causes of death among COVID-19 patients, especially elderly subjects with cardiovascular diseases, are acute respiratory distress syndrome(ARDS), multiple organ dysfunction syndrome (MODS), and microvascular thrombosis. All prompted by an excessive uncontrolled systemic inflammatory response. Immunosenescence, characterized by systemic and chronic inflammation as well as innate/adaptive immune imbalance, presents both in the elderly and cardiovascular patients. COVID-19 infection further aggravates the existing inflammatory process and lymphocyte depletion leading to uncontrollable systemic inflammatory responses, which is the primary cause of death. Based on the higher mortality, this study attempts to elucidate the pathophysiological mechanisms of COVID-19 in elderly subjects with cardiovascular diseases as well as the cause of the high mortality result from COVID-19.

Cellular senescence: friend or foe to respiratory viral infections?

Cellular senescence permanently arrests the replication of various cell types and contributes to age-associated diseases. In particular, cellular senescence may enhance chronic lung diseases including COPD and idiopathic pulmonary fibrosis. However, the role cellular senescence plays in the pathophysiology of acute inflammatory diseases, especially viral infections, is less well understood. There is evidence that cellular senescence prevents viral replication by increasing antiviral cytokines, but other evidence shows that senescence may enhance viral replication by downregulating antiviral signalling. Furthermore, cellular senescence leads to the secretion of inflammatory mediators, which may either promote host defence or exacerbate immune pathology during viral infections. In this Perspective article, we summarise how senescence contributes to physiology and disease, the role of senescence in chronic lung diseases, and how senescence impacts acute respiratory viral infections. Finally, we develop a potential framework for how senescence may contribute, both positively and negatively, to the pathophysiology of viral respiratory infections, including severe acute respiratory syndrome due to the coronavirus SARS-CoV-2.

Cellular and molecular features of senescence in acute lung injury

A wide range of insults can trigger acute injury in the lungs, which eventually may lead to respiratory failure and death of patients. Current treatment relies mainly on supportive measures and mechanical ventilation. Even so, survivors frequently develop important sequels that compromise quality of life. In the search for new approaches to prevent and treat acute lung injury, many investigations have focused on molecular and cellular pathways which could exert a pathogenic role in this disease. Herein, we review recent findings in the literature suggesting that cellular senescence could be involved in lung injury and discuss the potential use of senotherapies to prevent disease progression.

Body Mass Index and Risk for Intubation or Death in SARS-CoV-2 Infection : A Retrospective Cohort Study

BACKGROUND

Obesity is a risk factor for pneumonia and acute respiratory distress syndrome.

OBJECTIVE

To determine whether obesity is associated with intubation or death, inflammation, cardiac injury, or fibrinolysis in coronavirus disease 2019 (COVID-19).

DESIGN

Retrospective cohort study.

SETTING

A quaternary academic medical center and community hospital in New York City.

PARTICIPANTS

2466 adults hospitalized with laboratory-confirmed severe acute respiratory syndrome coronavirus 2 infection over a 45-day period with at least 47 days of in-hospital observation.

MEASUREMENTS

Body mass index (BMI), admission biomarkers of inflammation (C-reactive protein [CRP] level and erythrocyte sedimentation rate [ESR]), cardiac injury (troponin level), and fibrinolysis (D-dimer level). The primary end point was a composite of intubation or death in time-to-event analysis.

RESULTS

Over a median hospital length of stay of 7 days (interquartile range, 3 to 14 days), 533 patients (22%) were intubated, 627 (25%) died, and 59 (2%) remained hospitalized. Compared with overweight patients, patients with obesity had higher risk for intubation or death, with the highest risk among those with class 3 obesity (hazard ratio, 1.6 [95% CI, 1.1 to 2.1]). This association was primarily observed among patients younger than 65 years and not in older patients (P for interaction by age = 0.042). Body mass index was not associated with admission levels of biomarkers of inflammation, cardiac injury, or fibrinolysis.

LIMITATIONS

Body mass index was missing for 28% of patients. The primary analyses were conducted with multiple imputation for missing BMI. Upper bounding factor analysis suggested that the results are robust to possible selection bias.

CONCLUSION

Obesity is associated with increased risk for intubation or death from COVID-19 in adults younger than 65 years, but not in adults aged 65 years or older.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Aging impairs alveolar epithelial type II cell function in acute lung injury

Morbidity and mortality rates in acute lung injury (ALI) increase with age. As alveolar epithelial type II cells (AE2) are crucial for lung function and repair, we hypothesized that aging promotes senescence in AE2 and contributes to the severity and impaired regeneration in ALI. ALI was induced with 2.5 μg lipopolysaccharide/g body weight in young (3 mo) and old (18 mo) mice that were euthanized 24 h, 72 h, and 10 days later. Lung function, pulmonary surfactant activity, stereology, cell senescence, and single-cell RNA sequencing analyses were performed to investigate AE2 function in aging and ALI. In old mice, surfactant activity was severely impaired. A 60% mortality rate and lung function decline were observed in old, but not in young, mice with ALI. AE2 of young mice adapted to injury by increasing intracellular surfactant volume and proliferation rate. In old mice, however, this adaptive response was compromised, and AE2 of old mice showed signs of cell senescence, increased inflammatory signaling, and impaired surfactant metabolism in ALI. These findings provide evidence that ALI promotes a limited proliferation rate, increased inflammatory response, and surfactant dysfunction in old, but not in young, mice, supporting an impaired regenerative capacity and reduced survival rate in ALI with advancing age.

The Impact of Aging in Acute Respiratory Distress Syndrome: A Clinical and Mechanistic Overview

Acute respiratory distress syndrome (ARDS) is associated with increased morbidity and mortality in the elderly population (≥65 years of age). Additionally, age is widely reported as a risk factor for the development of ARDS. However, the underlying pathophysiological mechanisms behind the increased risk of developing, and increased severity of, ARDS in the elderly population are not fully understood. This is compounded by the significant heterogeneity observed in patients with ARDS. With an aging population worldwide, a better understanding of these mechanisms could facilitate the development of therapies to improve outcomes in this population. In this review, the current clinical evidence of age as a risk factor and prognostic indicator in ARDS and the potential underlying mechanisms that may contribute to these factors are outlined. In addition, research on age-dependent treatment options and biomarkers, as well as future prospects for targeting these underlying mechanisms, are discussed.

[Pulmonary insufficiency in acute stroke: risk factors and mechanisms of development]

Various degrees of pulmonary insufficiency (PI) (PaO₂ ≤60 mm Hg, SaO₂ ≤90%) are diagnosed in most of patients with severe acute stroke (AS). Frequency and severity of PI positively correlates with the severity of AS. PI worsens patient's condition, prolongs the hospitalization period, and increases the probability of fatal outcome. Early clinical signs of PI may be undiagnosed due to the severity of stroke and thus not treated. The initiating pathogenic mechanism of PI is stress-related activation of sympathetic nervous system (SNS) and systemic immunosuppression. In severe stroke with mass effect, the rapid and significant increase in intracranial pressure may additionally activate the SNS. Risk factors of PI include older age, previous pulmonary disease, prolonged supine position, respiratory muscle dysfunction, apnea, and concomitant somatic diseases. Decompensation of somatic diseases leads to multiple stage reactions with facilitation of functional and morphologic changes in the pulmonary system, hypoxemia and hypoxia, promotes infectious complications and multiple organ failure and worsens neurological outcome. Diagnosis and treatment of PI in AS decreases mortality and improves rehabilitation prognosis.

Remodeling of the Immune Response With Aging: Immunosenescence and Its Potential Impact on COVID-19 Immune Response

Elderly individuals are the most susceptible to an aggressive form of coronavirus disease (COVID-19), caused by SARS-CoV-2. The remodeling of immune response that is observed among the elderly could explain, at least in part, the age gradient in lethality of COVID-19. In this review, we will discuss the phenomenon of immunosenescence, which entails changes that occur in both innate and adaptive immunity with aging. Furthermore, we will discuss inflamm-aging, a low-grade inflammatory state triggered by continuous antigenic stimulation, which may ultimately increase all-cause mortality. In general, the elderly are less capable of responding to neo-antigens, because of lower naïve T cell frequency. Furthermore, they have an expansion of memory T cells with a shrinkage of the T cell diversity repertoire. When infected by SARS-CoV-2, young people present with a milder disease as they frequently clear the virus through an efficient adaptive immune response. Indeed, antibody-secreting cells and follicular helper T cells are thought to be effectively activated in young patients that present a favorable prognosis. In contrast, the elderly are more prone to an uncontrolled activation of innate immune response that leads to cytokine release syndrome and tissue damage. The failure to trigger an effective adaptive immune response in combination with a higher pro-inflammatory tonus may explain why the elderly do not appropriately control viral replication and the potential clinical consequences triggered by a cytokine storm, endothelial injury, and disseminated organ injury. Enhancing the efficacy of the adaptive immune response may be an important issue both for infection resolution as well as for the appropriate generation of immunity upon vaccination, while inhibiting inflamm-aging will likely emerge as a potential complementary therapeutic approach in the management of patients with severe COVID-19.

SIRT7 deficiency suppresses inflammation, induces EndoMT, and increases vascular permeability in primary pulmonary endothelial cells

Acute lung injury (ALI), a common condition in critically ill patients, has limited treatments and high mortality. Aging is a risk factor for ALI. Sirtuins (SIRTs), central regulators of the aging process, decrease during normal aging and in aging-related diseases. We recently showed decreased SIRT7 expression in lung tissues and fibroblasts from patients with pulmonary fibrosis compared to controls. To gain insight into aging-related mechanisms in ALI, we investigated the effects of SIRT7 depletion on lipopolysaccharide (LPS)-induced inflammatory responses and endothelial barrier permeability in human primary pulmonary endothelial cells. Silencing SIRT7 in pulmonary artery or microvascular endothelial cells attenuated LPS-induced increases in ICAM1, VCAM1, IL8, and IL6 and induced endomesenchymal transition (EndoMT) with decreases in VE-Cadherin and PECAM1 and increases in collagen, alpha-smooth muscle actin, TGFβ receptor 1, and the transcription factor Snail. Loss of endothelial adhesion molecules was accompanied by increased F-actin stress fibers and increased endothelial barrier permeability. Together, these results show that an aging phenotype induced by SIRT7 deficiency promotes EndoMT with impaired inflammatory responses and dysfunction of the lung vascular barrier.

miR-21-KO Alleviates Alveolar Structural Remodeling and Inflammatory Signaling in Acute Lung Injury

Acute lung injury (ALI) is characterized by enhanced permeability of the air–blood barrier, pulmonary edema, and hypoxemia. MicroRNA-21 (miR-21) was shown to be involved in pulmonary remodeling and the pathology of ALI, and we hypothesized that miR-21 knock-out (KO) reduces injury and remodeling in ALI. ALI was induced in miR-21 KO and C57BL/6N (wildtype, WT) mice by an intranasal administration of 75 µg lipopolysaccharide (LPS) in saline (n = 10 per group). The control mice received saline alone (n = 7 per group). After 24 h, lung function was measured. The lungs were then excised for proteomics, cytokine, and stereological analysis to address inflammatory signaling and structural damage. LPS exposure induced ALI in both strains, however, only WT mice showed increased tissue resistance and septal thickening upon LPS treatment. Septal alterations due to LPS exposure in WT mice consisted of an increase in extracellular matrix (ECM), including collagen fibrils, elastic fibers, and amorphous ECM. Proteomics analysis revealed that the inflammatory response was dampened in miR-21 KO mice with reduced platelet and neutrophil activation compared with WT mice. The WT mice showed more functional and structural changes and inflammatory signaling in ALI than miR-21 KO mice, confirming the hypothesis that miR-21 KO reduces the development of pathological changes in ALI.

Age-Related Structural and Functional Changes in the Mouse Lung

Lung function declines with advancing age. To improve our understanding of the structure-function relationships leading to this decline, we investigated structural alterations in the lung and their impact on micromechanics and lung function in the aging mouse. Lung function analysis was performed in 3, 6, 12, 18, and 24 months old C57BL/6 mice (n = 7-8/age), followed by lung fixation and stereological sample preparation. Lung parenchymal volume, total, ductal and alveolar airspace volume, alveolar volume and number, septal volume, septal surface area and thickness were quantified by stereology as well as surfactant producing alveolar epithelial type II (ATII) cell volume and number. Parenchymal volume, total and ductal airspace volume increased in old (18 and 24 months) compared with middle-aged (6 and 12 months) and young (3 months) mice. While the alveolar number decreased from young (7.5 × 10⁶) to middle-aged (6 × 10⁶) and increased again in old (9 × 10⁶) mice, the mean alveolar volume and mean septal surface area per alveolus conversely first increased in middle-aged and then declined in old mice. The ATII cell number increased from middle-aged (8.8 × 10⁶) to old (11.8 × 10⁶) mice, along with the alveolar number, resulting in a constant ratio of ATII cells per alveolus in all age groups (1.4 ATII cells per alveolus). Lung compliance and inspiratory capacity increased, whereas tissue elastance and tissue resistance decreased with age, showing greatest changes between young and middle-aged mice. In conclusion, alveolar size declined significantly in old mice concomitant with a widening of alveolar ducts and late alveolarization. These changes may partly explain the functional alterations during aging. Interestingly, despite age-related lung remodeling, the number of ATII cells per alveolus showed a tightly controlled relation in all age groups.

The effects of aging and exercise on lung mechanics, surfactant and alveolar macrophages

Purpose: Advancing age leads to changes to the respiratory system associated with increased susceptibility to lung diseases, and exercise may counteract this effect. To explore the underlying processes, we investigated the effects of aging and exercise on lung mechanics, alveolar macrophage function, and surfactant pools and activity, in mice. It was hypothesized that aging would impact lung mechanics, macrophage polarization, and the status of the surfactant system, and that these changes would be mitigated by exercise. Methods: Male C57BL/6 mice were housed from 2-3 to 22 months, for the aged group, or until 4 months of age for young mice. Mice in both groups were randomized to voluntarily running exercise or to non-exercise, for a 2-month period. Mice were euthanized and lung mechanics were analyzed using a flexiVent ventilator. Subsequently, the lungs were lavaged to obtain pulmonary surfactant and alveolar macrophages. Pulmonary surfactant was analyzed for pool sizes and activity whereas alveolar macrophages were examined for response to pro and anti-inflammatory stimuli. Results: Changes in lung mechanics, such as increased compliance and decreased airway resistance, were associated with aging but were not affected by exercise. The quantity as well as the biophysical activity of the pulmonary surfactant system was unaffected by either aging or exercise. More alveolar macrophages were recovered from exercising aged mice compared to both the young and non-exercising groups. Macrophages in this aged exercise group were more responsive to an anti-inflammatory stimulus. Conclusions: Our data supports previous literature that suggest the development of emphysema-like alterations to lung mechanics with aging. This effect was independent of exercise. Our data also indicates that surfactant is unaffected by aging and exercise. Alveolar macrophage properties and numbers were affected by exercise in the aging lung and may represent the main, potentially beneficial, effect of exercise on the pulmonary system.

Genipin protects rats against lipopolysaccharide-induced acute lung injury by reinforcing autophagy

Although the protective effects of genipin against acute lung injury (ALI) have been described previously, the associated mechanism remains unclear. We have previously reported that genipin exerts its pharmacological effects by regulating autophagy. Here, we hypothesized that the up-regulation of autophagy may contribute to the protective effects exhibited by genipin against ALI. In the present study, ALI was induced by intratracheal LPS administration in rats. Genipin treatment significantly reduced LPS-induced lung injury as evidenced by improved histopathology, decreased lung edema, total cells, and protein concentration in the bronchoalveolar lavage fluid (BALF). This protection was inhibited by 3-methyladenine (3-MA), an inhibitor of autophagy. Genipin treatment reduced the expression of P62 and increased the expression of Beclin-1 and LC3II, indicating increased autophagy. Genipin treatment also alleviated LPS-induced cell apoptosis (down-regulation of Bax, up-regulation of Bcl-2, and decreased number of terminal deoxynucleotidyl transferase dUTP nick end label-positive cells) and oxidative stress (increased SOD and decreased MDA content) in the lung. Furthermore, genipin attenuated LPS-induced production of TNF-α, IL-1β, and IL-6 in the lung and BALF. These protective effects induced by genipin were reversed by 3-MA treatment, indicating that autophagy was involved in the protective effects exerted by genipin against inflammation and apoptosis in ALI. In A549 cells incubated with LPS for 6 h, genipin treatment increased the number of GFP-LC3 punctae. 3-MA prevented the protective effects of genipin against mitochondrial dysfunction and cell death. These findings suggest that genipin protects against apoptosis and inflammation in LPS-induced ALI by promoting autophagy.

Interleukin-18 binding protein attenuates lipopolysaccharide-induced acute lung injury in mice via suppression NF-κB and activation Nrf2 pathway

Interleukin (IL)-18 belongs to a rather large IL-1 gene family and is a proinflammatory cytokine. IL-18 plays important roles in lung injury. IL-18 binding protein (IL-18BP), a natural antagonist of IL-18, binds IL-18 with high affinity. IL-18BP is able to neutralize IL-18 biological activity and has a protective effect against renal fibrosis. The aim of this study was to evaluate the potential protective effect of IL-18BP on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice and to illuminate the underlying mechanisms. Results indicated that pretreatment with IL-18BP significantly attenuated LPS-induced pulmonary pathological injury. Meanwhile, IL-18BP pretreatment markedly inhibited infiltration of inflammatory cell and release of inflammatory factor in ALI mice in vivo and in primary macrophages after LPS insult in vitro. IL-18BP treatment dramatically reduced oxidative stress through increasing superoxide dismutase (SOD) and glutathione (GSH) contents, and decreasing the levels of malondialdehyde (MDA) and reactive oxygen species (ROS) in LPS-induced ALI mice and primary macrophages. Additionally, IL-18BP was also observed to markedly decreased the activation of nuclear factor-kappa B (NF-κB) and upregulated the nuclear factor erythroid 2-related factor 2 (Nrf2). Taken together, IL-18BP possessed protective effect against LPS-induced ALI, which might be associated with its regulation of NF-κB and Nrf2 activities. The results rendered IL-18BP worthy of further development into a pharmaceutical drug for the treatment of ALI.

MicroRNA-27a alleviates LPS-induced acute lung injury in mice via inhibiting inflammation and apoptosis through modulating TLR4/MyD88/NF-κB pathway

Acute lung injury (ALI) is a critical clinical condition with a high mortality rate, characterized with excessive uncontrolled inflammation and apoptosis. Recently, microRNAs (miRNAs) have been found to play crucial roles in the amelioration of various inflammation-induced diseases, including ALI. However, it remains unknown the biological function and regulatory mechanisms of miRNAs in the regulation of inflammation and apoptosis in ALI. The aim of this study is to identify and evaluate the potential role of miRNAs in ALI and reveal the underlying molecular mechanisms of their effects. Here, we analyzed microRNA expression profiles in lung tissues from LPS-challenged mice using miRNA microarray. Because microRNA-27a (miR-27a) was one of the miRNAs being most significantly downregulated, which has an important role in regulation of inflammation, we investigated its function. Overexpression of miR-27a by agomir-27a improved lung injury, as evidenced by the reduced histopathological changes, lung wet/dry (W/D) ratio, lung microvascular permeability and apoptosis in the lung tissues, as well as ameliorative survival of ALI mice. This was accompanied by the alleviating of inflammation, such as the reduced total BALF cell and neutrophil counts, decreased levels of tumor necrosis factor alpha (TNF-α), interleukin-1 (IL-6) interleukin-1β (IL-1β) and myeloperoxidase (MPO) activity in BAL fluid. Toll-like receptor 4 (TLR4), an important regulator of the nuclear factor kappa-B (NF-κB) signaling pathway, was identified as a novel target of miR-27a in RAW264.7 cells. Furthermore, our results showed that LPS stimulation increased the expression of MyD88 and NF-κB p65 (p-p65), but inhibited the expression of inhibitor of nuclear factor-κB-α (IκB-α), suggesting the activation of NF-κB signaling pathway. Further investigations revealed that agomir-miR-27a reversed the promoting effect of LPS on NF-κB signaling pathway. The results here suggested that miR-27a alleviates LPS-induced ALI in mice via reducing inflammation and apoptosis through blocking TLR4/MyD88/NF-κB activation.