Understanding the role of neutrophils in acute respiratory distress syndrome

Ribociclib leverages phosphodiesterase 4 inhibition in the treatment of neutrophilic inflammation and acute respiratory distress syndrome

INTRODUCTION

Overwhelming neutrophil activation and oxidative stress significantly contribute to acute respiratory distress syndrome (ARDS) pathogenesis. However, the potential of repurposing ribociclib, a cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitor used clinically in cancer treatment, for treating neutrophilic ARDS remains uncertain. This study illustrated the ability and underlying mechanism of ribociclib for treating ARDS and neutrophilic inflammation.

METHODS

Primary human neutrophils were used to determine the therapeutic effects of ribociclib on respiratory bursts, chemotactic responses, and inflammatory signaling. In vitro and silico analyses were performed to determine the underlying molecular mechanisms. The potential of ribociclib repurposing was evaluated using an in vivo ARDS model in lipopolysaccharide (LPS)-primed mice.

RESULTS

We found that treatment using ribociclib markedly limited overabundant oxidative stress (reactive oxygen species [ROS]) production and chemotactic responses (integrin levels and adhesion) in activated human neutrophils. Ribociclib was also shown to act as a selective inhibitor of phosphodiesterase 4 (PDE4), thereby promoting the cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) pathway, leading to the inhibition of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK) phosphorylation, and calcium influx. Notably, prophylactic administration and post-treatment with ribociclib ameliorated neutrophil infiltration, lung inflammation, accumulation of oxidative stress, pulmonary destruction, and mortality in mice with LPS-induced ARDS.

CONCLUSION

We demonstrated for the first time that ribociclib serves as a novel PDE4 inhibitor for treating neutrophilic inflammation and ARDS. The repurposing ribociclib and targeting neutrophilic PDE4 offer a potential off-label alternative for treating lung lesions and other inflammatory conditions.

S1PR3 inhibition protects against LPS-induced ARDS by inhibiting NF-κB and improving mitochondrial oxidative phosphorylation

BACKGROUND

Inflammation and endothelial barrier dysfunction are the major pathophysiological changes in acute respiratory distress syndrome (ARDS). Sphingosine-1-phosphate receptor 3 (S1PR3), a G protein-coupled receptor, has been found to mediate inflammation and endothelial cell (EC) integrity. However, the function of S1PR3 in ARDS has not been fully elucidated.

METHODS

We used a murine lipopolysaccharide (LPS)-induced ARDS model and an LPS- stimulated ECs model to investigate the role of S1PR3 in anti-inflammatory effects and endothelial barrier protection during ARDS.

RESULTS

We found that S1PR3 expression was increased in the lung tissues of mice with LPS-induced ARDS. TY-52156, a selective S1PR3 inhibitor, effectively attenuated LPS-induced inflammation by suppressing the expression of proinflammatory cytokines and restored the endothelial barrier by repairing adherens junctions and reducing vascular leakage. S1PR3 inhibition was achieved by an adeno-associated virus in vivo and a small interfering RNA in vitro. Both the in vivo and in vitro studies demonstrated that pharmacological or genetic inhibition of S1PR3 protected against ARDS by inhibiting the NF-κB pathway and improving mitochondrial oxidative phosphorylation.

CONCLUSIONS

S1PR3 inhibition protects against LPS-induced ARDS via suppression of pulmonary inflammation and promotion of the endothelial barrier by inhibiting NF-κB and improving mitochondrial oxidative phosphorylation, indicating that S1PR3 is a potential therapeutic target for ARDS.

Cell-derived biomimetic nanoparticles for the targeted therapy of ALI/ARDS

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are common clinical critical diseases with high morbidity and mortality. Especially since the COVID-19 outbreak, the mortality rates of critically ill patients with ARDS can be as high as 60%. Therefore, this problem has become a matter of concern to respiratory critical care. To date, the main clinical measures for ALI/ARDS are mechanical ventilation and drug therapy. Although ventilation treatment reduces mortality, it increases the risk of hyperxemia, and drug treatment lacks safe and effective delivery methods. Therefore, novel therapeutic strategies for ALI/ARDS are urgently needed. Developments in nanotechnology have allowed the construction of a safe, efficient, precise, and controllable drug delivery system. However, problems still encounter in the treatment of ALI/ARDS, such as the toxicity, poor targeting ability, and immunogenicity of nanomaterials. Cell-derived biomimetic nanodelivery drug systems have the advantages of low toxicity, long circulation, high targeting, and high bioavailability and show great therapeutic promises for ALI/ARDS owing to their acquired cellular biological features and some functions. This paper reviews ALI/ARDS treatments based on cell membrane biomimetic technology and extracellular vesicle biomimetic technology, aiming to achieve a significant breakthrough in ALI/ARDS treatments.

A Rapid In Vivo Toxicity Assessment Method for Antimicrobial Peptides

Antimicrobial peptides (AMPs) represent a promising antibiotic alternative to overcome drug-resistant bacteria by inserting into the membrane of bacteria, resulting in cell lysis. However, therapeutic applications of AMPs have been hindered by their ability to lyse eukaryotic cells. GF-17 is a truncated peptide of LL-37, which has perfect amphipathicity and a higher hydrophobicity, resulting in higher haemolytic activity. However, there is no significant difference in the cytotoxicity against human lung epithelial cells between the GF-17 and LL-37 groups, indicating that there are significant differences in the sensitivity of different human cells to GF-17. In this study, LL-37 and GF-17 were administered to mouse lungs via intranasal inoculation. Blood routine examination results showed that LL-37 did not affect the red blood cells, platelet, white blood cells and neutrophil counts, but GF-17 decreased the white blood cells and neutrophil counts with the increasing concentration of peptides. GF-17-treated mice suffer a body weight loss of about 2.3 g on average in 24 h, indicating that GF-17 is highly toxic to mice. The total cell counts in the bronchoalveolar lavage fluid from GF-17-treated mice were 4.66-fold that in the untreated group, suggesting that GF-17 treatment leads to inflammation in the lungs of mice. Similarly, the histological results showed the infiltration of neutrophils in the lungs of GF-17-treated mice. The results suggest that the administration of GF-17 in the lungs of mice does not affect the red blood cells and platelet counts in the blood but promotes neutrophil infiltration in the lungs, leading to an inflammatory response. Therefore, we established a mouse acute lung injury model to preliminarily evaluate the in vivo toxicity of AMPs. For AMPs with a clinical application value, systematic research is still needed to evaluate their acute and long-term toxicity.

Neutrophil-Derived Proteases in Lung Inflammation: Old Players and New Prospects

Neutrophil-derived proteases are critical to the pathology of many inflammatory lung diseases, both chronic and acute. These abundant enzymes play roles in key neutrophil functions, such as neutrophil extracellular trap formation and reactive oxygen species release. They may also be released, inducing tissue damage and loss of tissue function. Historically, the neutrophil serine proteases (NSPs) have been the main subject of neutrophil protease research. Despite highly promising cell-based and animal model work, clinical trials involving the inhibition of NSPs have shown mixed results in lung disease patients. As such, the cutting edge of neutrophil-derived protease research has shifted to proteases that have had little-to-no research in neutrophils to date. These include the cysteine and serine cathepsins, the metzincins and the calpains, among others. This review aims to outline the previous work carried out on NSPs, including the shortcomings of some of the inhibitor-orientated clinical trials. Our growing understanding of other proteases involved in neutrophil function and neutrophilic lung inflammation will then be discussed. Additionally, the potential of targeting these more obscure neutrophil proteases will be highlighted, as they may represent new targets for inhibitor-based treatments of neutrophil-mediated lung inflammation.

Antimicrobial resistance in intensive care patients hospitalized with SEPSIS: a comparison between the COVID-19 pandemic and pre-pandemic era

Introduction

Coronavirus disease 2019 (COVID-19) is a highly contagious viral illness caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It has had a dramatic effect on the world, resulting in millions of deaths worldwide and causing drastic changes in daily life. A study reported that septic complications were associated with high mortality in COVID-19 patients. This study aimed to evaluate how the COVID-19 pandemic changed the pre-pandemic and post-pandemic prevalence of sepsis in ICUs and to evaluate the different risk factors associated with mortality and the different diffusion of microorganisms and their resistance.

Materials and methods

We conducted a single-center retrospective observational clinical study, observing all patients in the ICU of the SS Annunziata Hospital in Chieti (Italy) who were diagnosed with sepsis and had a bacterial isolate from their blood culture. Sepsis was diagnosed by SEPSIIS III criteria. We enrolled all in-patients in the ICU from January 2018 to December 2021. We divided the patients into three groups: (1) non-pandemic period (Np) hospitalized in 2018-2019, (2) pandemic period (Pp)-COVID hospitalized in 2020-2021 with a diagnosis of COVID-19, and (3) Pp-non-COVID patients hospitalized in 2020-2021 without a diagnosis of COVID-19.

Results

From January 2018 to December 2021, 1,559 patients were admitted to the ICU, of which 211 patients [36 (17.1%) in 2018, 52 (24.6%) in 2019, 73 (34.6%) in 2020, and 50 (23.7%) in 2021, respectively] met the selection criteria: 88 patients in period Np, 67 patients in Pp without COVID-19, and 56 patients Pp with COVID-19. The overall mortality of these patients was high (65.9% at 30 days in Np), but decreased during the Pp (60.9%): Pp-non-COVID was 56.7% vs. Pp-COVID 66.1%, with a statistically significant association with APACHE III score (OR 1.08, 95%CI 1.04-1.12, p < 0.001), SOFA score (OR 1.12, 95%CI 1.03-1.22, p = 0.004), and age (OR 1.04, 95%CI 1.02-1.07, p < 0.0001). Between the Np vs. Pp periods, we observed an increase in a few Gram-positive bacteria such as S. capitis (1 pt. -0.9% vs. 14 pt. -7.65%- p = 0.008), S. epidermidis, Streptococcus spp., and E. faecalis, as well as a decrease in a case of blood culture positive for S. aureus, S. hominis, and E. faecium. In Gram-negative bacteria, we observed an increase in cases of Acinetobacter spp. (Np 6 pt. -5.1%- vs. Pp 20 pt. -10.9%, p = 0.082), and Serratia spp., while cases of sepsis decreased from E. faecium (Np 11 pt. -9.4%- vs. Pp 7 pt. -3.8%, p = 0.047), and Enterobacter spp., S. haemolyticus, S. maltophilia, Proteus spp., and P. aeruginosa have not changed. Finally, we found that resistance to OXA-48 (p = 0.040), ESBL (p = 0.002), carbapenems (p = 0.050), and colistin (p = 0.003) decreased with time from Np to Pp, particularly in Pp-COVID.

Conclusion

This study demonstrated how the COVID-19 pandemic changed the prevalence of sepsis in the ICU. It emerged that the risk factors associated with mortality were APACHE and SOFA scores, age, and, above all, the presence of ESBL-producing bacteria. Despite this, during the pandemic phase, we have observed a significant reduction in the emergence of resistant germs compared to the pre-pandemic phase.

Histone H3 posttranslational modified enzymes defined neutrophil plasticity and their vulnerability to IL-10 in the course of the inflammation

BACKGROUND

Neutrophils are a heterogeneous population capable of antimicrobial functions associated with pre-activation/activation and tissue regeneration. The specific polarisation of immune cells is mediated by the modification of 'chromatin landscapes', which enables differentiated access and activity of regulatory elements that guarantee their plasticity during inflammation No specific pattern within histone posttranslational modifications (PTMs) controlling this plasticity has been identified.

METHODS

Using the in vitro model of inflammation, reflecting different states of neutrophils from resting, pre-activated cells to activated and reducing tissue regeneration, we have analysed 11 different histone posttranslational modifications (PTMs), PTM enzymes associated with remodelling neutrophil chromatin, and H3K4me3 ChIP-Seq Gene Ontology analysis focusing on the processes related to histone PTMs. These findings were verified by extrapolation to adequate clinical status, using neutrophils derived from the patients with sepsis (systemic septic inflammation with LPS-stimulated neutrophils), neuromyelitis optical spectrum disorders (aseptic inflammation with pre-activated neutrophils) and periodontitis (local self-limiting septic inflammation with IL-10-positive neutrophils).

RESULTS

Physiological activation of neutrophils comprises a pre-activation characterised by histone H3K27ac and H3K4me1, which position enhancers; direct LPS exposure is induced explicitly by H3K4me3 which marked Transcription Start Site (TSS) regions and low-level of H3K9me3, H3K79me2 and H3K27me3 which, in turn, marked repressed genes. Contrary to antimicrobial action, IL-10 positively induced levels of H3S10p and negatively H3K9me3, which characterised processes related to the activation of genes within heterochromatin mediated by CHD1 and H3K9me3 specific demethylase JMJD2A. IL-10 protects changes within histone PTMs induced by TNF or LPS that affected H3K4me3-specific methyltransferase SETD1A and MLL1. Neutrophils previously exposed to inflammatory factors become unvulnerable to IL-10 because previous LPS stimulation interrupts TSS regions marked by H3K4me3 of CHD1 and JMJD2A genes. Therefore, LPS-activated neutrophils are disabled to induce CHD1/JMJD2A enzymes by IL-10, making this process irreversible. Because transcription of JMJD2A and CHD1 also depends on TSS positioning by H3K4me3, neutrophils before LPS stimulation become insensitive to IL-10.

CONCLUSION

Neutrophils, once pre-activated by TNF or directly stimulated by LPS, become insensitive to the anti-inflammatory effects of IL-10, and vice versa; IL-10 protects neutrophils against these proinflammatory stimuli. This phenomenon is responsible for disturbing the natural process of resolving inflammation and tissue regeneration.

Establishment of a Predictive Model for Acute Respiratory Distress Syndrome in Patients with Bacterial Pneumonia

Background

Community-acquired pneumonia (CAP) is a global health concern due to its high rates of morbidity and mortality. Bacterial pathogens are common causes of CAP. It is one of the most common causes of acute respiratory distress syndrome (ARDS), a common severe respiratory system manifestation threatening human health. This study aimed to establish a predictive model for ARDS in patients with bacterial pneumonia, which was conducive to early identification of the occurrence and effective prevention of ARDS.

Methods

We collected the clinical data of hospitalized patients with bacterial pneumonia in Affiliated Huzhou Hospital of Zhejiang University School of Medicine from January 2022 to November 2022. The independent risk factors for ARDS in patients with bacterial pneumonia were determined by univariate and multivariate binary logistic regression analyses. The nomogram was constructed to display the predictive model, and the receiver-operating characteristic curve was plotted to evaluate the predictive value of ARDS.

Results

This study included 254 patients with bacterial pneumonia, of which 114 developed ARDS. The multivariate logistic regression analysis revealed age [odds ratio (OR) = 1.041, P = 0.003], heart rate (OR = 1.020, P = 0.028), lymphocyte count (OR = 0.555, P = 0.033), white blood cell count (OR = 1.062, P = 0.033), bilateral lung lesions (OR = 7.352, P = 0.011) and pleural effusion (OR = 2.512, P = 0.002) as the independent risk factors for ARDS. The predictive model was constructed based on the six independent factors, which was valuable in predicting ARDS with area under the curve of 0.794.

Conclusion

The predictive model was beneficial to evaluate the disease progression in patients with bacterial pneumonia and identify ARDS. Further, our nomogram might help doctors predict the incidence of ARDS and conduct treatment as early as possible.

Systematic investigation of the material basis, effectiveness and safety of Thesium chinense Turcz. and its preparation Bairui Granules against lung inflammation

BACKGROUND

Thesium chinense Turcz. (Named as Bai Rui Cao in Chinese) and its preparations (e.g., Bairui Granules) have been used to treat inflammatory diseases, such as acute mastitis, lobar pneumonia, tonsillitis, coronavirus disease 2019 (COVID-19), and upper respiratory tract infection. However, the material basis, pharmacological efficiency, and safety have not been illustrated.

METHODS

Anti-inflammatory activity-guided isolation of constituents has been performed using multiple column chromatography, and their structures were elucidated by NMR spectroscopy and ECD calculations. The inhibitory effects on lung inflammation and safety of the crude ethanol extract (CE), Bairui Granules (BG), and the purified active constituents were evaluated using lipopolysaccharide (LPS)-stimulated acute lung inflammation (ALI) mice model or normal mice.

RESULTS

Seven new compounds (1-7) and fifty-six known compounds (8-63) were isolated from T. chinense, and fifty-four were reported from this plant for the first time. The new flavonoid glycosides 1-2, new fatty acids 4-5, new alkaloid 7 as well as the known constituents including flavonoid aglycones 8-11, lignans 46-54, alkaloids 34 and 45, coumarins 57, phenylpropionic acids 27, and simple aromatic compounds 39, 44 and 58 exhibited anti-inflammatory activity. Network pharmacology analysis indicated that anti-inflammation of T. chinense was attributed to flavonoids and alkaloids by regulating inflammation-related proteins (e.g., TNF, NF-κB, TGF-β). Furthermore, constituents of T. chinense including kaempferol-3-O-glucorhamnoside (KN, also named as Bairuisu I, 19), astragalin (AG, Bairuisu II, 12), and kaempferol (KF, Bairuisu III, 8), as well as CE and BG could alleviate lung inflammation caused by LPS in mice by preventing neutrophils infiltration and the expression of the genes for pro-inflammatory cytokines NLRP3, caspase-1, IL-1β, and COX-2. After a 28-day subacute toxicity test, BG at doses of 4.875 g/kg and 9.750 g/kg (equivalent to onefold and twofold the clinically recommended dose) and CE at a dose of 11.138 g/kg (equivalent to fourfold the clinical dose of BG) were found to be safe and non-toxic.

CONCLUSIONS

The discovery of sixty-three constituents comprehensively illustrated the material basis of T. chinense. T. chinense and Bairui Granules could alleviate lung inflammation by regulating inflammation-related proteins and no toxicity was observed under the twofold of clinically used doses.

The Effect of Roflumilast on Lipopolysaccharide-induced Acute Lung Injury During Neutropenia Recovery in Mice

BACKGROUND/AIM

Patients with pneumonia after prolonged neutropenia are at increased risk for acute respiratory distress syndrome (ARDS). The key molecule of endothelial barrier breakdown in sepsis is lipopolysaccharide (LPS), which is a component of the outer membrane of gram-negative bacterial cell walls. Maintaining increased cyclic adenosine monophosphate (cAMP) levels in endothelial cells is effective in preventing endothelial dysfunction and microvascular permeability. The aim of this study was to elucidate whether roflumilast, a phosphodiesterase-4 (PDE-4) inhibitor, is effective in LPS-induced acute lung injury (ALI) during neutropenia recovery in a murine model.

MATERIALS AND METHODS

To induce neutropenia, all mice were administered intraperitoneal cyclophosphamide. On day 2 after neutropenia, mice were administered LPS by intra-tracheal instillation. In the prevention group, roflumilast was given orally on day 0, when neutropenia was induced. In the treatment group, roflumilast was administered orally 1 hour after LPS injection.

RESULTS

Roflumilast attenuated histopathological changes associated with LPS-induced lung injury. The accumulation of neutrophils and the concentrations of inflammatory cytokines IL-1β, TNF-α, and IL-6 in bronchoalveolar lavage fluids were inhibited effectively by roflumilast. Also, MMP-9 and TGF-β expression was attenuated in the roflumilast group.

CONCLUSION

Roflumilast significantly attenuated LPS-induced ALI during neutropenia recovery.

Caffeic acid ethanolamide induces antifibrosis, anti-inflammatory, and antioxidant effects protects against bleomycin-induced pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive interstitial lung disease; its cause is unknown, and it leads to notable health problems. Currently, only two drugs are recommended for IPF treatment. Although these drugs can mitigate lung function decline, neither can improve nor stabilize IPF or the symptoms perceived by patients. Therefore, the development of novel treatment options for pulmonary fibrosis is required. The present study investigated the effects of a novel compound, caffeic acid ethanolamide (CAEA), on human pulmonary fibroblasts and evaluated its potential to mitigate bleomycin-induced pulmonary fibrosis in mice. CAEA inhibited TGF-β-induced α-SMA and collagen expression in human pulmonary fibroblasts, indicating that CAEA prevents fibroblasts from differentiating into myofibroblasts following TGF-β exposure. In animal studies, CAEA treatment efficiently suppressed immune cell infiltration and the elevation of TNF-α and IL-6 in bronchoalveolar lavage fluid in mice with bleomycin-induced pulmonary fibrosis. Additionally, CAEA exerted antioxidant effects by recovering the enzymatic activities of oxidant scavengers. CAEA directly inhibited activation of TGF-β receptors and protected against bleomycin-induced pulmonary fibrosis through inhibition of the TGF-β/SMAD/CTGF signaling pathway. The protective effect of CAEA was comparable to that of pirfenidone, a clinically available drug. Our findings support the potential of CAEA as a viable method for preventing the progression of pulmonary fibrosis.

Neutrophil hitchhiking: Riding the drug delivery wave to treat diseases

Neutrophils are a crucial component of the innate immune system and play a pivotal role in various physiological processes. From a physical perspective, hitchhiking is considered a phenomenon of efficient transportation. The combination of neutrophils and hitchhikers has given rise to effective delivery systems both in vivo and in vitro, thus neutrophils hitchhiking become a novel approach to disease treatment. This article provides an overview of the innovative and feasible application of neutrophils as drug carriers. It explores the mechanisms underlying neutrophil function, elucidates the mechanism of drug delivery mediated by neutrophil-hitchhiking, and discusses the potential applications of this strategy in the treatment of cancer, immune diseases, inflammatory diseases, and other medical conditions.

Sea Cucumber and Blueberry Extracts Suppress Inflammation and Reduce Acute Lung Injury through the Regulation of NF-κB/MAPK/JNK Signaling Pathway in Lipopolysaccharide-Treated C57BL/6 Mice

Acute lung injury (ALI) represents a life-threatening condition with high morbidity and mortality despite modern mechanical ventilators and multiple pharmacological strategies. Therefore, there is a need to develop efficacious interventions with minimal side effects. The anti-inflammatory activities of sea cucumber (Cucumaria frondosa) and wild blueberry (Vaccinium angustifolium) extracts have been reported recently. However, their anti-inflammatory activities and the mechanism of action against ALI are not fully elucidated. Thus, the present study aims to understand the mechanism of the anti-inflammatory activity of sea cucumber and wild blueberry extracts in the context of ALI. Experimental ALI was induced via intranasal lipopolysaccharide (LPS) instillation in C57BL/6 mice and the anti-inflammatory properties were determined by cytokine analysis, histological examination, western blot, and qRT-PCR. The results showed that oral supplementation of sea cucumber extracts repressed nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways, thereby downregulating the expression of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF) in the lung tissue and in the plasma. Wild blueberry extracts also suppressed the expression of IL-4. Furthermore, the combination of sea cucumber and wild blueberry extracts restrained MAPK signaling pathways by prominent attenuation of phosphorylation of NF-κB, c-Jun N-terminal kinase (JNK), and extracellular signal-regulated kinase (ERK) while the levels of pro-inflammatory cytokines were significantly suppressed. Moreover, there was a significant and synergistic reduction in varying degrees of ALI lesions such as distorted parenchyma, increased alveoli thickness, lymphocyte and neutrophil infiltrations, fibrin deposition, pulmonary emphysema, pneumonia, intra-alveolar hemorrhage, and edema. The anti-inflammatory effect of the combination of sea cucumber and wild blueberry extracts is associated with suppressing MAPK and NF-κB signaling pathways, thereby significantly reducing cytokine storm in LPS-induced experimental ALI.

Indole-3-carbinol attenuates lipopolysaccharide-induced acute respiratory distress syndrome through activation of AhR: role of CCR2+ monocyte activation and recruitment in the regulation of CXCR2+ neutrophils in the lungs

Introduction

Indole-3-carbinol (I3C) is found in cruciferous vegetables and used as a dietary supplement. It is known to act as a ligand for aryl hydrocarbon receptor (AhR). In the current study, we investigated the role of AhR and the ability of I3C to attenuate LPS-induced Acute Respiratory Distress Syndrome (ARDS).

Methods

To that end, we induced ARDS in wild-type C57BL/6 mice, Ccr2gfp/gfp KI/KO mice (mice deficient in the CCR2 receptor), and LyZcreAhRfl/fl mice (mice deficient in the AhR on myeloid linage cells). Additionally, mice were treated with I3C (65 mg/kg) or vehicle to investigate its efficacy to treat ARDS.

Results

I3C decreased the neutrophils expressing CXCR2, a receptor associated with neutrophil recruitment in the lungs. In addition, LPS-exposed mice treated with I3C revealed downregulation of CCR2+ monocytes in the lungs and lowered CCL2 (MCP-1) protein levels in serum and bronchoalveolar lavage fluid. Loss of CCR2 on monocytes blocked the recruitment of CXCR2+ neutrophils and decreased the total number of immune cells in the lungs during ARDS. In addition, loss of the AhR on myeloid linage cells ablated I3C-mediated attenuation of CXCR2+ neutrophils and CCR2+ monocytes in the lungs from ARDS animals. Interestingly, scRNASeq showed that in macrophage/monocyte cell clusters of LPS-exposed mice, I3C reduced the expression of CXCL2 and CXCL3, which bind to CXCR2 and are involved in neutrophil recruitment to the disease site.

Discussion

These findings suggest that CCR2+ monocytes are involved in the migration and recruitment of CXCR2+ neutrophils during ARDS, and the AhR ligand, I3C, can suppress ARDS through the regulation of immune cell trafficking.

RIPK1 inhibitor ameliorates pulmonary injury by modulating the function of neutrophils and vascular endothelial cells

Acute lung injury (ALI) is an acute and progressive hypoxic respiratory failure that could progress to acute respiratory distress syndrome (ARDS) with a high mortality rate, thus immediate medical attention and supportive care are necessary. The pathophysiology of ALI is characterized by the disruption of the alveolar-capillary barrier and activation of neutrophils, leading to lung tissue damage. The receptor-interacting protein kinase 1 (RIPK1) has emerged as a promising target for the treatment of multiple inflammatory diseases, but the role of RIPK1 in the ALI remains poorly understood. In this study, we aimed to figure out the pathological role of RIPK1 in ALI, especially in the pulmonary immune microenvironment involving neutrophils and endothelial cells. In vivo experiments showed that RIPK1 inhibitor protected against lipopolysaccharide (LPS)-induced lung injury in mouse models, with reduced neutrophils and monocytes infiltration in the lungs. Further studies demonstrated that, besides the inhibitory action on necroptosis, RIPK1 inhibitor directly suppressed reactive oxygen species (ROS) generation and inflammatory cytokines secretion from neutrophils. Furthermore, RIPK1 inhibition maintains the barrier function in TNF-α-primed vascular endothelial cells and prevents their activation induced by the supernatant from LPS-stimulated neutrophils. Mechanistically, the aforementioned effects of RIPK1 inhibitor are associated with the NF-κB signaling pathway, which is partially independent of necroptosis inhibition. These results provide new evidence that RIPK1 inhibitor directly regulates the function of neutrophils and endothelial cells, as well as interferes with the interactions between these two cell types, therefore contributing to a better understanding of RIPK1 in ALI and providing a potential avenue for future therapeutic interventions.

DPP-4 exacerbates LPS-induced endothelial cells inflammation via integrin-α5β1/FAK/AKT signaling

Endothelial dysfunction plays a pivotal role in the pathogenesis of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). Dipeptidyl peptidase IV (DPP-4), a cell surface glycoprotein, has been implicated in endothelial inflammation and barrier dysfunction. In this study, the role of DPP-4 on lipopolysaccharide (LPS)-induced pulmonary microvascular endothelial cells (HPMECs) dysfunction and the underlying mechanism were investigated by siRNA-mediated knockdown of DPP-4. Our results indicated that LPS (1 μg/ml) challenge resulted in either the production and releasing of DPP-4, as well as the secretion of IL-6 and IL-8 in HPMECs. DPP-4 knockdown inhibited chemokine releasing and monolayer hyper-permeability in LPS challenged HPMECs. When cocultured with human polymorphonuclear neutrophils (PMNs), DPP4 knockdown suppressed LPS-induced neutrophil-endothelial adhesion, PMN chemotaxis and trans-endothelial migration. Western blotting showed that DPP-4 knockdown attenuated LPS-induced activation of TLR4/NF-κB pathway. Immunoprecipitation and liquid chromatography-tandem mass spectrometry revealed that DPP-4 mediated LPS-induced endothelial inflammation by interacting with integrin-α5β1. Moreover, exogenous soluble DPP-4 treatment sufficiently activated integrin-α5β1 downstream FAK/AKT/NF-κB signaling, thereafter inducing ICAM-1 upregulation in HPMECs. Collectively, our results suggest that endothelia synthesis and release DPP-4 under the stress of endotoxin, which interact with integrin-α5β1 complex in an autocrine or paracrine manner to exacerbate endothelial inflammation and enhance endothelial cell permeability. Therefore, blocking DDP-4 could be a potential therapeutic strategy to prevent endothelial dysfunction in ALI/ARDS.

A Narrative Review: The Role of NETs in Acute Respiratory Distress Syndrome/Acute Lung Injury

Nowadays, acute respiratory distress syndrome (ARDS) still has a high mortality rate, and the alleviation and treatment of ARDS remains a major research focus. There are various causes of ARDS, among which pneumonia and non-pulmonary sepsis are the most common. Trauma and blood transfusion can also cause ARDS. In ARDS, the aggregation and infiltration of neutrophils in the lungs have a great influence on the development of the disease. Neutrophils regulate inflammatory responses through various pathways, and the release of neutrophils through neutrophil extracellular traps (NETs) is considered to be one of the most important mechanisms. NETs are mainly composed of DNA, histones, and granuloproteins, all of which can mediate downstream signaling pathways that can activate inflammatory responses, generate immune clots, and cause damage to surrounding tissues. At the same time, the components of NETs can also promote the formation and release of NETs, thus forming a vicious cycle that continuously aggravates the progression of the disease. NETs are also associated with cytokine storms and immune balance. Since DNA is the main component of NETs, DNase I is considered a viable drug for removing NETs. Other therapeutic methods to inhibit the formation of NETs are also worthy of further exploration. This review discusses the formation and mechanism of NETs in ARDS. Understanding the association between NETs and ARDS may help to develop new perspectives on the treatment of ARDS.

Jingfang granule alleviates Pseudomonas aeruginosa-induced acute lung inflammation through suppression of STAT3/IL-17/NF-κB pathway based on network pharmacology analysis and experimental validation

ETHNOPHARMACOLOGICAL RELEVANCE

Pseudomonas aeruginosa is an opportunistic bacterial pathogen which is the second leading cause of hospital-acquired pneumonia. Jingfang granule (JFG) is an herbal formula of Traditional Chinese medicine (TCM) widely used in treatment of acute respiratory tract infections in China. However, the molecular mechanisms of JFG in treatment of P. aeruginosa-induced acute pneumonia are not clear.

AIM OF STUDY

This study aimed to investigate the mechanisms underlying the effects of JFG on P. aeruginosa-induced acute inflammation using a mouse model of bacterial acute pneumonia.

MATERIALS AND METHODS

The chemical components and targets of JFG were retrieved from Traditional Chinese Medicine Systems Pharmacology (TCMSP) database, and the P. aeruginosa pneumonia-related targets were obtained from the disease databases, including Online Mendelian Inheritance in Man (OMIM), GeneCards and DisGeNet. The protein-protein interaction (PPI) network was constructed using STRING database. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were performed using the Database for Annotation, Visualization and Integrated Discovery (DAVID). Molecular docking was performed using AutoDockTools 1.5.6. Further in vivo experiments employed a mouse model of P. aeruginosa acute pneumonia to verify the target proteins and signaling pathways affected by JFG, which were predicted by the network pharmacology analysis.

RESULTS

A total of 218 active components and 257 targets of JFG were retrieved from TCMSP database. Moreover, 99 intersectant targets were obtained between the 257 JFG targets and 694 disease targets. Among the intersectant targets, STAT3, IL-6, AKT1, TNF, MAPK1, MAPK3 and EGFR were identified to be the key therapeutic targets through PPI network analysis, and STAT3 was in the center of the network, which is a key regulator of IL-17 expression. KEGG pathway enrichment analysis suggested that IL-17 signaling pathway was one of the crucial inflammatory pathways affected by JFG in treatment of P. aeruginosa pneumonia. Furthermore, the in vivo experiments demonstrated that the JFG-treated mice displayed reduced proinflammatory cytokine production (IL-17, IL-1β, IL-6 and TNF), diminished neutrophil infiltration and decreased mortality, compared with the non-drug-treated mice during P. aeruginosa lung infection. Moreover, the expression or phosphorylation levels of the key regulators in STAT3/IL-17/NF-κB axis including STAT3, ERK1/2 (MAPK3/1), AKT, NF-κB p65 and RORγt were significantly reduced in the lung tissues of the JFG-treated mice.

CONCLUSION

JFG was effective in treatment of P. aeruginosa acute lung infection, which reduced inflammatory responses through suppressing STAT3/IL-17/NF-κB pathway.

Neutrophil responsiveness to IL-10 impairs clearance of Streptococcus pneumoniae from the lungs

The early immune response to bacterial pneumonia requires a careful balance between pathogen clearance and tissue damage. The anti-inflammatory cytokine interleukin (IL)-10 is critical for restraining otherwise lethal pulmonary inflammation. However, pathogen-induced IL-10 is associated with bacterial persistence in the lungs. In this study, we used mice with myeloid cell specific deletion of IL-10R to investigate the cellular targets of IL-10 immune suppression during infection with Streptococcus pneumoniae, the most common bacterial cause of pneumonia. Our findings suggest that IL-10 restricts the neutrophil response to S. pneumoniae, as neutrophil recruitment to the lungs was elevated in myeloid IL-10 receptor (IL-10R)-deficient mice and neutrophils in the lungs of these mice were more effective at killing S. pneumoniae. Improved killing of S. pneumoniae was associated with increased production of reactive oxygen species and serine protease activity in IL-10R-deficient neutrophils. Similarly, IL-10 suppressed the ability of human neutrophils to kill S. pneumoniae. Burdens of S. pneumoniae were lower in myeloid IL-10R-deficient mice compared with wild-type mice, and adoptive transfer of IL-10R-deficient neutrophils into wild-type mice significantly improved pathogen clearance. Despite the potential for neutrophils to contribute to tissue damage, lung pathology scores were similar between genotypes. This contrasts with total IL-10 deficiency, which is associated with increased immunopathology during S. pneumoniae infection. Together, these findings identify neutrophils as a critical target of S. pneumoniae-induced immune suppression and highlight myeloid IL-10R abrogation as a mechanism to selectively reduce pathogen burdens without exacerbating pulmonary damage.

A 'one stone, two birds' approach with mesenchymal stem cells for acute respiratory distress syndrome and Type II diabetes mellitus

This review explores the intricate relationship between acute respiratory distress syndrome (ARDS) and Type II diabetes mellitus (T2DM). It covers ARDS epidemiology, etiology and pathophysiology, along with current treatment trends and challenges. The lipopolysaccharides (LPS) role in ARDS and its association between non-communicable diseases and COVID-19 are discussed. The review highlights the therapeutic potential of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) for ARDS and T2DM, emphasizing their immunomodulatory effects. This review also underlines how T2DM exacerbates ARDS pathophysiology and discusses the potential of hUC-MSCs in modulating immune responses. In conclusion, the review highlights the multidisciplinary approach to managing ARDS and T2DM, focusing on inflammation, oxidative stress and potential therapy of hUC-MSCs in the future.

Reactive Oxygen Species and Strategies for Antioxidant Intervention in Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a life-threatening pulmonary condition characterized by the sudden onset of respiratory failure, pulmonary edema, dysfunction of endothelial and epithelial barriers, and the activation of inflammatory cascades. Despite the increasing number of deaths attributed to ARDS, a comprehensive therapeutic approach for managing patients with ARDS remains elusive. To elucidate the pathological mechanisms underlying ARDS, numerous studies have employed various preclinical models, often utilizing lipopolysaccharide as the ARDS inducer. Accumulating evidence emphasizes the pivotal role of reactive oxygen species (ROS) in the pathophysiology of ARDS. Both preclinical and clinical investigations have asserted the potential of antioxidants in ameliorating ARDS. This review focuses on various sources of ROS, including NADPH oxidase, uncoupled endothelial nitric oxide synthase, cytochrome P450, and xanthine oxidase, and provides a comprehensive overview of their roles in ARDS. Additionally, we discuss the potential of using antioxidants as a strategy for treating ARDS.

Acute respiratory distress syndrome heterogeneity and the septic ARDS subgroup

Acute respiratory distress syndrome (ARDS) is an acute diffuse inflammatory lung injury characterized by the damage of alveolar epithelial cells and pulmonary capillary endothelial cells. It is mainly manifested by non-cardiogenic pulmonary edema, resulting from intrapulmonary and extrapulmonary risk factors. ARDS is often accompanied by immune system disturbance, both locally in the lungs and systemically. As a common heterogeneous disease in critical care medicine, researchers are often faced with the failure of clinical trials. Latent class analysis had been used to compensate for poor outcomes and found that targeted treatment after subgrouping contribute to ARDS therapy. The subphenotype of ARDS caused by sepsis has garnered attention due to its refractory nature and detrimental consequences. Sepsis stands as the most predominant extrapulmonary cause of ARDS, accounting for approximately 32% of ARDS cases. Studies indicate that sepsis-induced ARDS tends to be more severe than ARDS caused by other factors, leading to poorer prognosis and higher mortality rate. This comprehensive review delves into the immunological mechanisms of sepsis-ARDS, the heterogeneity of ARDS and existing research on targeted treatments, aiming to providing mechanism understanding and exploring ideas for accurate treatment of ARDS or sepsis-ARDS.

Role of Neutrophil Extracellular Traps in Health and Disease Pathophysiology: Recent Insights and Advances

Neutrophils are the principal trouper of the innate immune system. Activated neutrophils undergo a noble cell death termed NETosis and release a mesh-like structure called neutrophil extracellular traps (NETs) as a part of their defensive strategy against microbial pathogen attack. This web-like architecture includes a DNA backbone embedded with antimicrobial proteins like myeloperoxidase (MPO), neutrophil elastase (NE), histones and deploys in the entrapment and clearance of encountered pathogens. Thus NETs play an inevitable beneficial role in the host's protection. However, recent accumulated evidence shows that dysregulated and enhanced NET formation has various pathological aspects including the promotion of sepsis, pulmonary, cardiovascular, hepatic, nephrological, thrombotic, autoimmune, pregnancy, and cancer diseases, and the list is increasing gradually. In this review, we summarize the NET-mediated pathophysiology of different diseases and focus on some updated potential therapeutic approaches against NETs.

Early Depletion of Neutrophils Reduces Retinal Inflammation and Neovascularization in Mice with Oxygen-Induced Retinopathy

Retinal inflammation is a central feature of ocular neovascular diseases such as diabetic retinopathy and retinopathy of prematurity, but the contribution of neutrophils to this process is not fully understood. We studied oxygen-induced retinopathy (OIR) which develops in two phases, featuring hyperoxia-induced retinal vaso-obliteration in phase I, followed by retinal neovascularization in phase II. As neutrophils are acute responders to tissue damage, we evaluated whether neutrophil depletion with an anti-Ly6G mAb administered in phase I OIR influenced retinal inflammation and vascular injury. Neutrophils were measured in blood and spleen via flow cytometry, and myeloperoxidase, an indicator of neutrophil activity, was evaluated in the retina using Western blotting. Retinal vasculopathy was assessed by quantitating vaso-obliteration, neovascularization, vascular leakage, and VEGF levels. The inflammatory factors, TNF, MCP-1, and ICAM-1 were measured in retina. In the OIR controls, neutrophils were increased in the blood and spleen in phase I but not phase II OIR. In OIR, the anti-Ly6G mAb reduced neutrophils in the blood and spleen, and myeloperoxidase, inflammation, and vasculopathy in the retina. Our findings revealed that the early rise in neutrophils in OIR primes the retina for an inflammatory and angiogenic response that promotes severe damage to the retinal vasculature.

Neutrophil-specific ORAI1 Calcium Channel Inhibition Reduces Pancreatitis-associated Acute Lung Injury

Acute pancreatitis is initiated within pancreatic exocrine cells and sustained by dysregulated systemic inflammatory responses mediated by neutrophils. Store-operated Ca2+ entry (SOCE) through ORAI1 channels in pancreatic acinar cells triggers acute pancreatitis, and ORAI1 inhibitors ameliorate experimental acute pancreatitis, but the role of ORAI1 in pancreatitis-associated acute lung injury has not been determined. Here, we showed mice with pancreas-specific deletion of Orai1 (Orai1ΔPdx1, ∼70% reduction in the expression of Orai1) are protected against pancreatic tissue damage and immune cell infiltration, but not pancreatitis-associated acute lung injury, suggesting the involvement of unknown cells that may cause such injury through SOCE via ORAI1. Genetic (Orai1ΔMRP8) or pharmacological inhibition of ORAI1 in murine and human neutrophils decreased Ca2+ influx and impaired chemotaxis, reactive oxygen species production, and neutrophil extracellular trap formation. Unlike pancreas-specific Orai1 deletion, mice with neutrophil-specific deletion of Orai1 (Orai1ΔMRP8) were protected against pancreatitis- and sepsis-associated lung cytokine release and injury, but not pancreatic injury in experimental acute pancreatitis. These results define critical differences between contributions from different cell types to either pancreatic or systemic organ injury in acute pancreatitis. Our findings suggest that any therapy for acute pancreatitis that targets multiple rather than single cell types is more likely to be effective.

Variant-dependent oxidative and cytokine responses of human neutrophils to SARS-CoV-2 spike protein and anti-spike IgG1 antibodies

Introduction

Severe forms of COVID-19, the disease caused by SARS-CoV-2, are characterized by acute respiratory distress syndrome, robust lung inflammation and death in some patients. Strong evidence has been accumulating that polymorphonuclear neutrophilic granulocytes (PMN) play an important role in the pathophysiology of severe COVID-19. SARS-CoV-2 directly induces in vitro PMN activation, mainly the release of neutrophil extracellular traps (NETs). However, the viral components inducing this PMN response remain unclear.

Methods

In this work human PMN responses were assessed in vitro in response to the spike (S) protein of two different SARS-CoV-2 variants, anti-S IgG1 antibodies or immune complexes formed by them. Production of reactive oxygen species (ROS) was measured by Diogenes-based chemiluminescence. Release of myeloperoxidase (MPO) was assessed by ELISA while secretion of a list of cytokines and growth factors was determined by high-performance multiplex cytokine assay.

Results and discussion

We show that the SARS-CoV-2 Omicron variant S protein and anti-spike IgG1, either alone or together, stimulate ROS production in human PMNs. We also observed that the SARS-CoV-2 Wuhan S protein and anti-S IgG1 antibody together trigger MPO release from PMNs. Based on the relevance of SARS-CoV-2 and influenza co-infections, we have also investigated the impact of influenza virus infection on the previous PMN responses to S proteins or anti-S antibodies. We did not detect any significant effect of influenza co-infection on ROS generation in PMNs. Our data also show that PMN stimulation by S proteins induced the release of different chemokines, growth factors, regulatory and proinflammatory cytokines. Overall, our findings show that the SARS-CoV-2 S protein, an anti-spike IgG1 antibody or their immune complex, promote oxidative responses of PMNs in a variant-dependent manner, contributing to a better understanding of the role of PMN responses during SARS-CoV-2 infection.

PFKFB3 promotes sepsis-induced acute lung injury by enhancing NET formation by CXCR4hi neutrophils

CXCR4hi neutrophils, which are a subset of neutrophils with high CXCR4 expression, are important contributors to sepsis-induced acute lung injury (ALI). PFKFB3, a key glycolysis gene, plays an essential role in neutrophil inflammatory activation. However, the specific involvement of PFKFB3 in sepsis-induced ALI remains unclear. Here, we observed that PFKFB3 was upregulated in CXCR4hi neutrophils and facilitated sepsis-induced ALI. Mechanistically, we observed that PFKFB3 promoted sepsis-induced ALI by enhancing neutrophil extracellular trap (NET) formation by CXCR4hi neutrophils. Further study indicated that PFKFB3 promoted NET formation by upregulating glycolytic metabolism in CXCR4hi neutrophils. In summary, our study uncovered a new mechanism by which CXCR4hi neutrophils trigger sepsis-induced ALI by promoting NET formation, which is supported by PFKFB3-mediated glycolytic metabolism.

Synergistic Pulmonoprotective Effect of Natural Prolyl Oligopeptidase Inhibitors in In Vitro and In Vivo Models of Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a highly morbid inflammatory lung disease with limited pharmacological interventions. The present study aims to evaluate and compare the potential pulmonoprotective effects of natural prolyl oligopeptidase (POP) inhibitors namely rosmarinic acid (RA), chicoric acid (CA), epigallocatechin-3-gallate (EGCG) and gallic acid (GA), against lipopolysaccharide (LPS)-induced ARDS. Cell viability and expression of pro-inflammatory mediators were measured in RAW264.7 cells and in primary murine lung epithelial and bone marrow cells. Nitric oxide (NO) production was also assessed in unstimulated and LPS-stimulated RAW264.7 cells. For subsequent in vivo experiments, the two natural products (NPs) with the most favorable effects, RA and GA, were selected. Protein, cell content and lipid peroxidation levels in bronchoalveolar lavage fluid (BALF), as well as histopathological changes and respiratory parameters were evaluated in LPS-challenged mice. Expression of key mediators involved in ARDS pathophysiology was detected by Western blotting. RA and GA favorably reduced gene expression of pro-inflammatory mediators in vitro, while GA decreased NO production in macrophages. In LPS-challenged mice, RA and GA co-administration improved respiratory parameters, reduced cell and protein content and malondialdehyde (MDA) levels in BALF, decreased vascular cell adhesion molecule-1 (VCAM-1) and the inducible nitric oxide synthase (iNOS) protein expression, activated anti-apoptotic mechanisms and down-regulated POP in the lung. Conclusively, these synergistic pulmonoprotective effects of RA and GA co-administration could render them a promising prophylactic/therapeutic pharmacological intervention against ARDS.

The vascular perspective on acute and chronic lung disease

The pulmonary vasculature has been frequently overlooked in acute and chronic lung diseases, such as acute respiratory distress syndrome (ARDS), pulmonary fibrosis (PF), and chronic obstructive pulmonary disease (COPD). The primary emphasis in the management of these parenchymal disorders has largely revolved around the injury and aberrant repair of epithelial cells. However, there is increasing evidence that the vascular endothelium plays an active role in the development of acute and chronic lung diseases. The endothelial cell network in the capillary bed and the arterial and venous vessels provides a metabolically highly active barrier that controls the migration of immune cells, regulates vascular tone and permeability, and participates in the remodeling processes. Phenotypically and functionally altered endothelial cells, and remodeled vessels, can be found in acute and chronic lung diseases, although to different degrees, likely because of disease-specific mechanisms. Since vascular remodeling is associated with pulmonary hypertension, which worsens patient outcomes and survival, it is crucial to understand the underlying vascular alterations. In this Review, we describe the current knowledge regarding the role of the pulmonary vasculature in the development and progression of ARDS, PF, and COPD; we also outline future research directions with the hope of facilitating the development of mechanism-based therapies.

Genome-wide analysis of RNA-binding protein co-expression with alternative splicing events in acute respiratory distress syndrome following hematopoietic stem cell transplantation

Patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT) are at an increased risk of developing severe acute respiratory distress syndrome (ARDS), which is characterized by peripheral bilateral patchy lung involvement. The regulatory network of RNA-binding protein (RBP)-alternative splicing (AS) in ARDS following HSCT has not been investigated. We hypothesize that RBP-AS plays a regulatory role during HSCT-ARDS. The published ARDS transcriptome data after HSCT (GSE84439) were downloaded, and the transcriptome data of 13 mRNAs were obtained by sequencing the peripheral blood of 5 HSCT-ARDS patients and 8 ARDS patients through high-throughput sequencing technology. Systematic analysis of downloaded data was performed to obtain differentially expressed RBPs, and the differentially alternative spliced pre-mRNAs in HSCT-ARDS and control groups were used to explore the global gene RBP-AS regulatory network. A total of 1769 differentially expressed genes and 4714 regulated alternative splicing events were identified in peripheral blood from HSCT-ARDS, of which 254 genes had both differential expression and differential AS. In addition, 128 RBPs were identified, of which HDGF, PCBP2, RIOK3, CISD2, and TRIM21, DDX58, MOV10 showed significantly increased or decreased expression in the HSCT-ARDS. RBPs with decreased expression had antiviral activity, while those with increased expression were involved in ROS, fibrosis, and negative viral resistance. The RBP-RASE-RASG regulatory network is constructed. It is related to the dysregulation of antiviral immunomodulation, imbalance in ROS homeostasis and pro-pulmonary fibrosis, which are involved in the development of HSCT-ARDS.

The Role of Cytokines in Neutrophil Development, Tissue Homing, Function and Plasticity in Health and Disease

Neutrophils are crucial innate immune cells and comprise 50-70% of the white blood cell population under homeostatic conditions. Upon infection and in cancer, blood neutrophil numbers significantly increase because of the secretion of various chemo- and cytokines by, e.g., leukocytes, pericytes, fibroblasts and endothelial cells present in the inflamed tissue or in the tumor microenvironment (TME). The function of neutrophils in cancer has recently gained considerable attention, as they can exert both pro- and anti-tumorigenic functions, dependent on the cytokine milieu present in the TME. Here, we review the effect of cytokines on neutrophil development, tissue homing, function and plasticity in cancer and autoimmune diseases as well as under physiological conditions in the bone marrow, bloodstream and various organs like the spleen, kidney, liver, lung and lymph nodes. In addition, we address several promising therapeutic options, such as cytokine therapy, immunocytokines and immunotherapy, which aim to exploit the anti-tumorigenic potential of neutrophils in cancer treatment or block excessive neutrophil-mediated inflammation in autoimmune diseases.

Aged-Signal-Eliciting Nanoparticles Stimulated Macrophage-Mediated Programmed Removal of Inflammatory Neutrophils

Excessive infiltration of activated neutrophils is regarded as a predominant cause of tissue injury in neutrophilic inflammation. Although programmed cell death like apoptosis maintains the homeostasis of activated neutrophils, this process is disrupted by an abnormal inflammatory response. Unlike endogenous calreticulin exposed during apoptosis, exogenous calreticulin acts as an "aged" signal and initiates premature macrophage-mediated programmed cell removal (PrCR), which is independent of apoptosis. Here, we report a nano-mediated strategy to stimulate the precise clearance of activated neutrophils initiated with artificial aged signal and alleviated inflammation. Polymeric nanoparticles PC@PLGA were fabricated by cloaking poly(lactic-co-glycolic acid) (PLGA) with a hybrid membrane derived from platelet-derived extracellular vesicles (PEVs, denoted by P) and the calreticulin-expressed membrane obtained from doxorubicin-treated cells (denoted by C). P-selectin in PEVs favors PC@PLGA to anchor activated neutrophils, while calreticulin mimics exogenous "aged" signal secreted by macrophages to trigger PrCR. We showed that PC@PLGA specifically targeted activated neutrophils and misled macrophages to recognize them as "aged" neutrophils and then initiated premature PrCR and prevented proinflammatory response and tissue damage in a mouse model of acute lung injury and severe acute pancreatitis. The collective findings indicate the efficiency of specific elimination of activated neutrophils with exogenous aged signal in improving inflammation therapy.

Hematocytological Clues of Peripheral Blood in Different Clinical Presentations of COVID-19

Background

To gain insight into the pathogenesis and clinical course of COVID-19 from a historical perspective, we reviewed paraclinical diagnostic tools of this disease and prioritized the patients with a more severe form of disease admitted to intensive care units (ICUs). The objective was to better predict the course and severity of the disease by collecting more paraclinical data, specifically by examining the relationship between hematological findings and cytological variation of blood neutrophils and monocytes.

Methods

This retrospective study was conducted on 112 patients with confirmed COVID-19 admitted to Imam Hossein Hospital (Tehran, Iran) from August to September 2020. Peripheral blood smears of these patients were differentiated according to several cytological variations of neutrophils and monocytes, and the correlation to the severity of the disease was specified.

Results

The mean percentages of degenerated monocytes, degenerated granulocytes, and spiky biky neutrophils were significantly different among critical and non-critical patients (P<0.05). Degenerated monocytes and granulocytes were higher in critical patients as opposed to spiky biky neutrophils, which were higher among non-critical ones. Comparing the peripheral blood smears of COVID-19 patients (regarding pulmonary involvement in chest computed tomography [CT] scans [subtle, mild, moderate, and severe groups]), the twisted form of neutrophils was significantly higher in the subtle group than in the mild and moderate groups (P=0.003).

Conclusion

Different cytological morphologies of neutrophils and monocytes, including degenerated monocytes, degenerated granulocytes, and spiky biky and twisted neutrophils, could help to predict the course and severity of the disease.

Neutrophil extracellular traps predict postoperative pulmonary complications in paediatric patients undergoing parental liver transplantation

BACKGROUND

Parental liver transplantation (PLT) improves long-term survival rates in paediatric hepatic failure patients; however, the mechanism of PLT-induced postoperative pulmonary complications (PPCs) is unclear.

METHODS

A total of 133 paediatric patients undergoing PLT were included. Serum levels of NET components, including circulating free DNA (cfDNA), DNA-histone complex, and myeloperoxidase (MPO)-DNA complex, were detected. The occurrence of PPCs post-PLT, prolonged intensive care unit (ICU) stay and death within one year were recorded as the primary and secondary outcomes.

RESULTS

The overall rate of PPCs in the hospital was 47.4%. High levels of serum cfDNA, DNA-histone complexes and MPO-DNA complexes were associated with an increased risk of PPCs (for cfDNA, OR 2.24; for DNA-histone complex, OR 1.64; and for MPO-DNA, OR 1.94), prolonged ICU stay (OR 1.98, 4.26 and 3.69, respectively), and death within one year (OR 1.53, 2.65 and 1.85, respectively). The area under the curve of NET components for the prediction of PPCs was 0.843 for cfDNA, 0.813 for DNA-histone complexes, and 0.906 for MPO-DNA complexes. During the one-year follow-up, the death rate was higher in patients with PPCs than in patients without PPCs (14.3% vs. 2.9%, P = 0.001).

CONCLUSIONS

High serum levels of NET components are associated with an increased incidence of PPCs and death within one year in paediatric patients undergoing PLT. Serum levels of NET components serve as a biomarker for post-PLT PPCs and a prognostic indicator.

RNF128 regulates neutrophil infiltration and myeloperoxidase functions to prevent acute lung injury

Acute lung injury (ALI) is characterised by severe pulmonary inflammation, alveolar-capillary barrier disruption, and pulmonary oedema. Therefore, establishing effective therapeutic targets for ALI prevention is crucial. The present study reports a novel function of RNF128 in regulating LPS-induced ALI. Severe lung damage and increased immune cell infiltration were detected in RNF128-deficient mice. In vitro experiments revealed that RNF128 inhibits neutrophil activation by binding to myeloperoxidase (MPO) and reducing its levels and activity. Moreover, RNF128 regulates alveolar macrophage activation and neutrophil infiltration by interacting with TLR4, targeting it for degradation, and inhibiting NF-κB activation, hence decreasing pro-inflammatory cytokines. Our results demonstrate for the first time that RNF128 is a negative regulator of MPO and TLR4 in neutrophils and alveolar macrophages, respectively. However, AAV9-mediated RNF128 overexpression alleviated lung tissue damage and reduced inflammatory cell infiltration. Thus, RNF128 is a promising therapeutic candidate for pharmacological interventions in ALI.

Identification of macrophage-related genes in sepsis-induced ARDS using bioinformatics and machine learning

Sepsis-induced acute respiratory distress syndrome (ARDS) is one of the leading causes of death in critically ill patients, and macrophages play very important roles in the pathogenesis and treatment of sepsis-induced ARDS. The aim of this study was to screen macrophage-related biomarkers for the diagnosis and treatment of sepsis-induced ARDS by bioinformatics and machine learning algorithms. A dataset including gene expression profiles of sepsis-induced ARDS patients and healthy controls was downloaded from the gene expression omnibus database. The limma package was used to screen 325 differentially expressed genes, and enrichment analysis suggested enrichment mainly in immune-related pathways and reactive oxygen metabolism pathways. The level of immune cell infiltration was analysed using the ssGSEA method, and then 506 macrophage-related genes were screened using WGCNA; 48 showed differential expression. PPI analysis was also performed. SVM-RFE and random forest map analysis were used to screen 10 genes. Three key genes, SGK1, DYSF and MSRB1, were obtained after validation with external datasets. ROC curves suggested that all three genes had good diagnostic efficacy. The nomogram model consisting of the three genes also had good diagnostic efficacy. This study provides new targets for the early diagnosis of sepsis-induced ARDS.

The Neonatal Immune System and Respiratory Pathogens

Neonates are more susceptible to some pathogens, particularly those that cause infection in the respiratory tract. This is often attributed to an incompletely developed immune system, but recent work demonstrates effective neonatal immune responses to some infection. The emerging view is that neonates have a distinctly different immune response that is well-adapted to deal with unique immunological challenges of the transition from a relatively sterile uterus to a microbe-rich world, tending to suppress potentially dangerous inflammatory responses. Problematically, few animal models allow a mechanistic examination of the roles and effects of various immune functions in this critical transition period. This limits our understanding of neonatal immunity, and therefore our ability to rationally design and develop vaccines and therapeutics to best protect newborns. This review summarizes what is known of the neonatal immune system, focusing on protection against respiratory pathogens and describes challenges of various animal models. Highlighting recent advances in the mouse model, we identify knowledge gaps to be addressed.

Attenuation of LPS-Induced Lung Injury by Benziodarone via Reactive Oxygen Species Reduction

As overproduction of reactive oxygen species (ROS) causes various diseases, antioxidants that scavenge ROS, or inhibitors that suppress excessive ROS generation, can be used as therapeutic agents. From a library of approved drugs, we screened compounds that reduced superoxide anions produced by pyocyanin-stimulated leukemia cells and identified benzbromarone. Further investigation of several of its analogues showed that benziodarone possessed the highest activity in reducing superoxide anions without causing cytotoxicity. In contrast, in a cell-free assay, benziodarone induced only a minimal decrease in superoxide anion levels generated by xanthine oxidase. These results suggest that benziodarone is an inhibitor of NADPH oxidases in the plasma membrane but is not a superoxide anion scavenger. We investigated the preventive effect of benziodarone on lipopolysaccharide (LPS)-induced murine lung injury as a model of acute respiratory distress syndrome (ARDS). Intratracheal administration of benziodarone attenuated tissue damage and inflammation via its ROS-reducing activity. These results indicate the potential application of benziodarone as a therapeutic agent against diseases caused by ROS overproduction.

Targeting Neutrophil β2-Integrins: A Review of Relevant Resources, Tools, and Methods

Neutrophils are important innate immune cells that respond during inflammation and infection. These migratory cells utilize β₂-integrin cell surface receptors to move out of the vasculature into inflamed tissues and to perform various anti-inflammatory responses. Although critical for fighting off infection, neutrophil responses can also become dysregulated and contribute to disease pathophysiology. In order to limit neutrophil-mediated damage, investigators have focused on β₂-integrins as potential therapeutic targets, but so far these strategies have failed in clinical trials. As the field continues to move forward, a better understanding of β₂-integrin function and signaling will aid the design of future therapeutics. Here, we provide a detailed review of resources, tools, experimental methods, and in vivo models that have been and will continue to be utilized to investigate the vitally important cell surface receptors, neutrophil β₂-integrins.

Corticosteroids in ARDS

Acute respiratory distress syndrome (ARDS) is frequently associated with sepsis. ARDS and sepsis exhibit a common pathobiology, namely excessive inflammation. Corticosteroids are powerful anti-inflammatory agents that are routinely used in septic shock and in oxygen-dependent SARS-CoV-2 related acute respiratory failure. Recently, corticosteroids were found to reduce mortality in severe community-acquired pneumonia. Corticosteroids may therefore also have a role to play in the treatment of ARDS. This narrative review was undertaken following a PubMed search for English language reports published before January 2023 using the terms acute respiratory distress syndrome, sepsis and steroids. Additional reports were identified by examining the reference lists of selected articles and based on personnel knowledge of the authors of the field. High-quality research is needed to fully understand the role of corticosteroids in the treatment of ARDS and to determine the optimal timing, dosing and duration of treatment.

Prospects of Novel and Repurposed Immunomodulatory Drugs against Acute Respiratory Distress Syndrome (ARDS) Associated with COVID-19 Disease

Acute respiratory distress syndrome (ARDS) is intricately linked with SARS-CoV-2-associated disease severity and mortality, especially in patients with co-morbidities. Lung tissue injury caused as a consequence of ARDS leads to fluid build-up in the alveolar sacs, which in turn affects oxygen supply from the capillaries. ARDS is a result of a hyperinflammatory, non-specific local immune response (cytokine storm), which is aggravated as the virus evades and meddles with protective anti-viral innate immune responses. Treatment and management of ARDS remain a major challenge, first, because the condition develops as the virus keeps replicating and, therefore, immunomodulatory drugs are required to be used with caution. Second, the hyperinflammatory responses observed during ARDS are quite heterogeneous and dependent on the stage of the disease and the clinical history of the patients. In this review, we present different anti-rheumatic drugs, natural compounds, monoclonal antibodies, and RNA therapeutics and discuss their application in the management of ARDS. We also discuss on the suitability of each of these drug classes at different stages of the disease. In the last section, we discuss the potential applications of advanced computational approaches in identifying reliable drug targets and in screening out credible lead compounds against ARDS.

Synthesis and screening of cyclic diketone indanedione derivatives as future scaffolds for neutrophil elastase inhibition

Human neutrophil elastase (HNE) and proteinase 3 (Pr3) released from neutrophils at inflammatory sites are the major causes of pathogens in chronic obstructive pulmonary disease (COPD) and various lung tissue derangements, among which cystic fibrosis and blockade of airway passages are chronic. These proteolytic mediatory agents combined with induced oxidative reactions sustain pathogenicity. Cyclic diketone indane-1,3-dione derivatives were designed, and toxicity evaluation predictions were performed in silico. Benzimidazole and hydrazide derivatives of indanedione were synthesized and characterized. Synthesized compounds were run using neutrophil elastase inhibition assay protocols. The compounds exhibit considerable inhibition of neutrophil elastase enzymes.

Licochalcone A protects against LPS-induced inflammation and acute lung injury by directly binding with myeloid differentiation factor 2 (MD2)

BACKGROUND AND PURPOSE

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a challenging clinical syndrome that leads to various respiratory sequelae and even high mortality in patients with severe disease. The novel pharmacological strategies and therapeutic drugs are urgently needed. Natural products have played a fundamental role and provided an abundant pool in drug discovery.

EXPERIMENTAL APPROACH

A compound library containing 160 natural products was used to screen potential anti-inflammatory compounds. Mice with LPS-induced ALI was then used to verify the preventive and therapeutic effects of the selected compounds.

KEY RESULTS

Licochalcone A was discovered from the anti-inflammatory screening of natural products in macrophages. A qPCR array validated the inflammation-regulatory effects of licochalcone A and indicated that the potential targets of licochalcone A may be the upstream proteins in LPS pro-inflammatory signalling. Further studies showed that licochalcone A directly binds to myeloid differentiation factor 2 (MD2), an assistant protein of toll-like receptor 4 (TLR4), to block both LPS-induced TRIF- and MYD88-dependent pathways. LEU61 and PHE151 in MD2 protein are the two key residues that contribute to the binding of MD2 to licochalcone A. In vivo, licochalcone A treatment alleviated ALI in LPS-challenged mice through significantly reducing immunocyte infiltration, suppressing activation of TLR4 pathway and inflammatory cytokine induction.

CONCLUSION AND IMPLICATIONS

In summary, our study identified MD2 as a direct target of licochalcone A for its anti-inflammatory activity and suggested that licochalcone A might serve as a novel MD2 inhibitor and a potential drug for developing ALI/ARDS therapy.

YAP-regulated type II alveolar epithelial cell differentiation mediated by human umbilical cord-derived mesenchymal stem cells in acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) contributes to higher mortality worldwide. Human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) have immunomodulatory and regenerative potential. However, the effects of hUC-MSCs as an ARDS treatment remain unclear. We investigated the role of hUC-MSCs in the differentiation of type II alveolar epithelial cells (AECII) by regulating Yes-associated protein (YAP) in ARDS. Male C57BL/6JNarl mice were intratracheally (i.t.) administered lipopolysaccharide (LPS) to induce an ARDS model, followed by a single intravenous (i.v.) dose of hUC-MSCs. hUC-MSCs improved pulmonary function, decreased inflammation on day 3, and mitigated lung injury by reducing the lung injury score and increasing lung aeration (%) in mice on day 7 (p < 0.05). hUC-MSCs inactivated YAP on AECII and facilitated cell differentiation by decreasing Pro-surfactant protein C (Pro-SPC) and galectin 3 (LGALS3) while increasing podoplanin (T1α) in lungs of mice (p < 0.05). In AECII MLE-12 cells, both coculture with hUC-MSCs after LPS exposure and the YAP inhibitor, verteporfin, reduced Pro-SPC and LGALS3, whereas the YAP inhibitor increased T1α expression (p < 0.05). In conclusion, hUC-MSCs ameliorated lung injury of ARDS and regulated YAP to facilitate AECII differentiation.

THE ROLE OF NEUTROPHIL EXTRACELLULAR TRAPS (NETS) IN THE IMMUNOPATHOGENESIS OF SEVERE COVID-19: POTENTIAL IMMUNOTHERAPEUTIC STRATEGIES REGULATING NET FORMATION AND ACTIVITY

The role of neutrophil granulocytes (NG) in the pathogenesis of COVID-19 is associated with the recruitment of NG into inflammatory foci, activation of their functions and enhanced formation of neutrophil extracellular networks (NETs). In this review, we analyzed a fairly large volume of scientific literature devoted to the peculiarities of the formation of NETs, their role in the pathogenesis of COVID-19, participation in the occurrence of immunothrombosis, vasculitis, acute respiratory distress syndrome, cytokine storm syndrome, multi-organ lesions. Convincing data are presented that clearly indicate the significant involvement of NETs in the immunopathogenesis of COVID-19 and the associated severe complications resulting from the intensification of the inflammation process, which is key for the course of infection caused by the SARS-CoV-2 virus. The presented role of NG and NETs, along with the role of other immune system cells and pro-inflammatory cytokines, is extremely important in understanding the development of an overactive immune response in severe COVID-19. The obtained scientific results, available today, allow identifying the possibilities of regulatory effects on hyperactivated NG, on the formation of NETs at various stages and on limiting the negative impact of already formed NETs on various tissues and organs. All of the above should help in the creation of new, specialized immunotherapy strategies designed to increase the chances of survival, reduce the severity of clinical manifestations in patients with COVID-19, as well as significantly reduce mortality rates. Currently, it is possible to use existing drugs and a number of new drugs are being developed, the action of which can regulate the amount of NG, positively affect the functions of NG and limit the intensity of NETs formation. Continuing research on the role of hyperactive NG and netosis, as well as understanding the mechanisms of regulation of the phenomenon of formation and restriction of NETs activity in severe COVID-19, apparently, are a priority, since in the future the new data obtained could become the basis for the development of targeted approaches not only to immunotherapy aimed at limiting education and blocking negative effects already formed NETs in severe COVID-19, but also to immunotherapy, which could be used in the complex treatment of other netopathies, first of all, autoimmune diseases, auto-inflammatory syndromes, severe purulent-inflammatory processes, including bacterial sepsis and hematogenous osteomyelitis.

Bis(4-glycosyloxybenzyl) 2-isobutyltartrate and dihydrophenanthrene derivatives from the pseudobulbs of Pholidota chinensis and their anti-inflammatory activity

Six previously undescribed components, bis(4-glycosyloxybenzyl) 2-isobutyltartrate derivatives (pholidotoside A-E) and phenolic glycoside (pholidotosin A), together with twenty known compounds were isolated from the pseudobulbs of Pholidota chinensis. Their structures and absolute configuration were elucidated and established through various spectroscopic and chemical methods. The anti-inflammatory potential of selected compounds was examined using a human neutrophil cell model activated by N-formyl-methionyl-leucyl-phenylalanine/cytochalasin B (fMLP/CB). Among these, dihydrophenanthrenes exhibited potent inhibitory effect on both superoxide anion generation and elastase release assays with IC₅₀ values ranging from 0.41 ± 0.05 to 7.14 ± 0.30 μM.

DUOX2 regulates secreted factors in virus-infected respiratory epithelial cells that contribute to neutrophil attraction and activation

The first line of defense against respiratory viruses relies on the antiviral and proinflammatory cytokine response initiated in infected respiratory epithelial cells. The cytokine response not only restricts virus replication and spreading, but also orchestrates the subsequent immune response. The epithelial Dual Oxidase 2 (DUOX2) has recently emerged as a regulator of the interferon antiviral response. Here, we investigated the role of DUOX2 in the inflammatory cytokine response using a model of A549 cells deficient in DUOX2 generated using Crispr-Cas9 and infected by Sendai virus. We found that the absence of DUOX2 selectively reduced the induction of a restricted panel of 14 cytokines and chemokines secreted in response to Sendai virus by 20 to 89%. The secreted factors produced by epithelial cells upon virus infection promoted the migration, adhesion, and degranulation of primary human neutrophils, in part through the DUOX2-dependent secretion of TNF and chemokines. In contrast, DUOX2 expression did not impact neutrophil viability or NETosis, thereby highlighting a selective impact of DUOX2 in neutrophil functions. Overall, this study unveils previously unrecognized roles of epithelial DUOX2 in the epithelial-immune cells crosstalk during respiratory virus infection.

Anti-inflammatory and antioxidant activities of Gymnema Sylvestre extract rescue acute respiratory distress syndrome in rats via modulating the NF-κB/MAPK pathway

Acute respiratory distress syndrome (ARDS) is one of the major causes of mortality in COVID-19 patients, due to limited therapeutic options. This prompted us to explore natural sources to mitigate this condition. Gymnema Sylvestre (GS) is an ancient medicinal plant known to have various therapeutic effects. This investigation examined the therapeutic effect of hydroalcoholic extract of Gymnema Sylvestre (HAEGS) against lipopolysaccharide (LPS)-induced lung injury and ARDS in in vitro and in vivo models. UHPLC-HRMS/GC-MS was employed for characterizing the HAEGS and identified several active derivatives including gymnemic acid, gymnemasaponins, gymnemoside, gymnemasin, quercetin, and long fatty acids. Gene expression by RT-qPCR and DCFDA analysis by flow cytometry revealed that several inflammatory cytokine/chemokine, cell injury markers, and reactive oxygen species (ROS) levels were highly upregulated in LPS control and were significantly reduced upon HAEGS treatment. Consistent with the in vitro studies, we found that in LPS-induced ARDS model, pre-treatment with HAEGS significantly suppressed the LPS-induced elevation of inflammatory cell infiltrations, cytokine/chemokine marker expression, ROS levels, and lung injury in a dose-dependent manner. Further mechanistic studies demonstrated that HAEGS suppressed oxidative stress by modulating the NRF2 pathway and ameliorated the ARDS through the NF-κB/MAPK signalling pathway. Additional fractionation results revealed that fraction 6 which has the exclusive composition of gymnemic acid derivatives showed better anti-inflammatory effects (inhibition of IL-6 and IL-1β) at lower concentrations compared to HAEGS. Overall, HAEGS significantly mitigated LPS-induced lung injury and ARDS by targeting the NF-κB/MAPK signalling pathway. Thus, our work unravels the protective role of HAEGS for the first time in managing ARDS.

BAP31 regulates the expression of ICAM-1/VCAM-1 via MyD88/NF-κB pathway in acute lung injury mice model

AIMS

The cell adhesion molecules (CAMs) that mediate neutrophil-endothelium cell adhesion are deeply involved in the pathogenesis of acute lung injury (ALI). B-cell receptor associated protein 31 (BAP31) has been reported to engage in the expression of some CAMs. This study was undertaken to explore whether BAP31 in endotheliocyte affects the pathological process of ALI by regulating CAMs, and its possible mechanism.

MAIN METHODS

Our study used the shBAP31 endothelium cell lines and endothelial-specific BAP31 conditional knockdown mice constructed via Cre/loxP system. Hematoxylin and eosin staining was used to observe the histopathological manifestations. The adhesion of neutrophils to vascular wall was examined by intravital microscopy. The nuclear translocation of NF-κB was observed by immunofluorescence staining assay. Flow cytometric, real-time polymerase chain reaction and Western blot assay were performed to determine the expression of CAMs and key proteins in MyD88/NF-κB-related signaling pathway. Luciferase reporter and chromatin immunoprecipitation assay were analyzed for transcriptional activity of ICAM-1 and VCAM-1.

KEY FINDINGS

Mechanistic investigations indicated that endothelium-specific BAP31 depletion dramatically reduced the capacity of neutrophils adherence to endothelial cells (ECs), which was mainly attributed to the significant downregulation of ICAM-1 (p < 0.05) and VCAM-1 (p < 0.05) expression. Interestingly, BAP31 knockdown apparently deactivated MyD88/TRAF6-mediated TAK1/NF-κB and PI3K/Akt signaling cascades, resulting in the inhibition of NF-κB activation and nuclear translocation.

SIGNIFICANCE

Our data furnished convincing evidence that BAP31 deficiency performs a mitigative effect on ALI by decreasing neutrophils-ECs adhesion. These findings identified BAP31 as a promising protein for regulating the pathogenesis process of ALI.

In Vivo Visualization and Quantification of Neutrophil Elastase in Lungs of COVID-19 Patients: A First-in-Humans PET Study with 11C-NES

Coronavirus disease 2019 (COVID-19) can cause life-threatening lung inflammation that is thought to be mediated by neutrophils. The aim of the present work was to evaluate a novel PET tracer for neutrophil elastase (NE). Methods: In this first-in-humans study, 4 patients with hypoxia due to COVID-19 and 2 healthy controls were investigated with PET using ¹¹C-NES and ¹⁵O-water for visualization and quantification of NE and perfusion in the lungs, respectively. Results: ¹¹C-NES accumulated selectively in lung areas with COVID-19 opacities on CT scans, suggesting high levels of NE there. In the same areas, perfusion was severely reduced in comparison to healthy lung tissue as measured with ¹⁵O-water. Conclusion: The data suggest that NE is associated with severe lung inflammation in COVID-19 patients and that inhibition of NE could potentially reduce the acute inflammatory process and improve the condition.