Early alterations in neutrophil activation are associated with outcome in acute lung injury

STAT3-Mediated Ferroptosis is Involved in Sepsis-Associated Acute Respiratory Distress Syndrome

Sepsis-induced acute respiratory distress syndrome (ARDS) poses a grave danger to life, resulting from sepsis-induced multi-organ failure. Although ferroptosis, a form of iron-dependent lipid peroxidative cell death, has been associated with sepsis-induced ARDS, the specific mechanisms are not fully understood. In this study, we utilized WGCNA, PPI, friends analysis, and six machine learning techniques (Lasso, SVM, RFB, XGBoost, AdaBoost, and LightGBM) to pinpoint STAT3 as a potential diagnostic marker. A significant increase in monocyte and neutrophil levels was observed in patients with sepsis-induced ARDS, as revealed by immune infiltration analyses, when compared to controls. Moreover, there was a positive correlation between STAT3 expression and the level of infiltration. Single-cell analysis uncovered a notable disparity in B-cell expression between sepsis and sepsis-induced ARDS. Furthermore, in vitro experiments using LPS-treated human bronchial epithelial cells (BEAS-2B) and THP1 cells demonstrated a significant increase in STAT3 phosphorylation expression. Additionally, the inhibition of STAT3 phosphorylation by Stattic effectively prevented LPS-induced ferroptosis in both BEAS-2B and THP1 cells. This indicates that the activation of STAT3 phosphorylation promotes ferroptosis in human bronchial epithelial cells in response to LPS. In summary, this research has discovered and confirmed STAT3 as a potential biomarker for the diagnosis and treatment of sepsis-induced ARDS.

LncRNA HCG18 loaded by polymorphonuclear neutrophil-secreted exosomes aggravates sepsis acute lung injury by regulating macrophage polarization

Polymorphonuclear neutrophils (PMNs) exert significant roles in septic acute lung injury (ALI). Accumulating evidence suggests that PMN-derived exosomes (PMN-exo) are a novel subcellular entity that is the fundamental link between PMN-driven inflammation and tissue damage. However, the role of PMN-exo in septic ALI and the underlying mechanisms remain unclear. Tumor necrosis factor-α (TNF-α), a key regulator of innate immunity in septic ALI, was used to induce PMN activation in vitro. Using an in vitro co-culture system, the rat alveolar macrophage cell line NR8383 was co-cultured with TNF-α-stimulated PMN-released exosomes (TNF-α-exo) to further confirm the results of the in vitro studies and explore the underlying mechanisms involved. A septic lung injury model was established by cecal ligation and puncture surgery, and PMN-exo were injected into septic mice through the tail vein, and then lung injury, inflammatory release, macrophage polarization, and apoptosis were examined. The results reported that TNF-α-exo promoted the activation of M1 macrophages after i.p. injection in vivo or co-culture in vitro. Furthermore, TNF-α-exo affected alveolar macrophage polarization by delivering HCG18. Mechanistic studies indicated that HCG18 mediated the function of TNF-α-exo by targeting IL-32 in macrophages. In addition, tail vein injection of si-HCG18 in septic mice significantly reduced TNF-α-exo-induced M1 macrophage activation and lung macrophage death, as well as histological lesions. In conclusion, TNF-α-exo-loaded HCG18 contributes to septic ALI by regulating macrophage polarization. These findings may provide new insights into novel mechanisms of PMN-macrophage polarization interactions in septic ALI and may provide new therapeutic strategies for patients with sepsis.

Immunotherapy strategies and prospects for acute lung injury: Focus on immune cells and cytokines

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a disastrous condition, which can be caused by a wide range of diseases, such as pneumonia, sepsis, traumas, and the most recent, COVID-19. Even though we have gained an improved understanding of acute lung injury/acute respiratory distress syndrome pathogenesis and treatment mechanism, there is still no effective treatment for acute lung injury/acute respiratory distress syndrome, which is partly responsible for the unacceptable mortality rate. In the pathogenesis of acute lung injury, the inflammatory storm is the main pathological feature. More and more evidences show that immune cells and cytokines secreted by immune cells play an irreplaceable role in the pathogenesis of acute lung injury. Therefore, here we mainly reviewed the role of various immune cells in acute lung injury from the perspective of immunotherapy, and elaborated the crosstalk of immune cells and cytokines, aiming to provide novel ideas and targets for the treatment of acute lung injury.

The role of MAPK11/12/13/14 (p38 MAPK) protein in dopamine agonist-resistant prolactinomas

BACKGROUND

Prolactinoma is a functional pituitary adenoma that secretes excessive prolactin. Dopamine agonists (DAs) such as bromocriptine (BRC) are the first-line treatment for prolactinomas, but the resistance rate is increasing year by year, creating a clinical challenge. Therefore, it is urgent to explore the molecular mechanism of bromocriptine resistance in prolactinomas. Activation of the P38 MAPK pathway affects multidrug resistance in tumours. Our previous studies have demonstrated that inhibiting MAPK14 can suppress the occurrence of prolactinoma, but the role of MAPK11/12/13/14 (p38 MAPK) signalling in dopamine agonist-resistant prolactinomas is still unclear.

METHODS

A prolactinoma rat model was established to determine the effect of bromocriptine on MAPK11/12/13/14 signalling. DA-resistant GH3 cells and DA-sensitive MMQ cells were used, and the role of MAPK11/12/13/14 in bromocriptine-resistant prolactinomas was preliminarily verified by western blot, RT-qPCR, ELISA, flow cytometry and CCK-8 experiments. The effects of MAPK11 or MAPK14 on bromocriptine-resistant prolactinomas were further verified by siRNA transfection experiments.

RESULTS

Bromocriptine was used to treat rat prolactinoma by upregulating DRD2 expression and downregulating the expression level of MAPK11/12/13/14 in vivo experiments. The in vitro experiments showed that GH3 cells are resistant to bromocriptine and that MMQ cells are sensitive to bromocriptine. Bromocriptine could significantly reduce the expression of MAPK12 and MAPK13 in GH3 cells and MMQ cells. Bromocriptine could significantly reduce the expression of MAPK11, MAPK14, NF-κB p65 and Bcl2 in MMQ but had no effect on MAPK11, MAPK14, NF-κB p65 and Bcl2 in GH3 cells. In addition, knockdown of MAPK11 and MAPK14 in GH3 cells by siRNA transfection reversed the resistance of GH3 cells to bromocriptine, and haloperidol (HAL) blocked the inhibitory effect of bromocriptine on MAPK14, MAPK11, and PRL in MMQ cells. Our findings show that MAPK11 and MAPK14 proteins are involved in bromocriptine resistance in prolactinomas.

CONCLUSION

Bromocriptine reduces the expression of MAPK11/12/13/14 in prolactinomas, and MAPK11 and MAPK14 are involved in bromocriptine resistance in prolactinomas by regulating apoptosis. Reducing the expression of MAPK11 or MAPK14 can reverse bromocriptine resistance in prolactinomas.

CXCR7 Antagonism Reduces Acute Lung Injury Pathogenesis

Loss of control in the trafficking of immune cells to the inflamed lung tissue contributes to the pathogenesis of life-threatening acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS). Targeting CXCR7 has been proposed as a potential therapeutic approach to reduce pulmonary inflammation; however, its role and its crosstalk with the two chemokine receptors CXCR3 and CXCR4 via their shared ligands CXCL11 and CXCL12 is not yet completely understood. The present paper aimed to characterize the pathological role of the CXCR3/CXCR4/CXCR7 axis in a murine model of ALI. Lipopolysaccharide (LPS) inhalation in mice resulted in the development of key pathologic features of ALI/ARDS, including breathing dysfunctions, alteration in the alveolar capillary barrier, and lung inflammation. LPS inhalation induced immune cell infiltration into the bronchoalveolar space, including CXCR3⁺ and CXCR4⁺ cells, and enhanced the expression of the ligands of these two chemokine receptors. The first-in-class CXCR7 antagonist, ACT-1004-1239, increased levels of CXCL11 and CXCL12 in the plasma without affecting their levels in inflamed lung tissue, and consequently reduced CXCR3⁺ and CXCR4⁺ immune cell infiltrates into the bronchoalveolar space. In the early phase of lung inflammation, characterized by a massive influx of neutrophils, treatment with ACT-1004-1239 significantly reduced the LPS-induced breathing pattern alteration. Both preventive and therapeutic treatment with ACT-1004-1239 reduced lung vascular permeability and decreased inflammatory cell infiltrates. In conclusion, these results demonstrate a key pathological role of CXCR7 in ALI/ARDS and highlight the clinical potential of ACT-1004-1239 in ALI/ARDS pathogenesis.

Overexpressing long non-coding RNA OIP5-AS1 ameliorates sepsis-induced lung injury in a rat model via regulating the miR-128-3p/Sirtuin-1 pathway

Sepsis, resulting from infections, is a systemic inflammatory response syndrome with a high fatality rate. The present study revolves around probing into the function and molecular mechanism of long non-coding RNA OIP5 antisense RNA 1 (lncRNA OIP5-AS1) in modulating acute lung injury (ALI) mediated by sepsis. Here, a sepsis model was constructed using cecal ligation and puncture (CLP) surgery in vivo. The alveolar macrophage cell line NR8383 and the alveolar type II cell line RLE-6TN were dealt with lipopolysaccharide (LPS) for in-vitro experiments. We discovered that OIP5-AS1 and Sirtuin1 (SIRT1) were markedly down-regulated in sepsis models elicited by CLP or LPS, while miR-128-3p experienced a dramatic up-regulation. OIP5-AS1 overexpression attenuated NR8383 and RLE-6TN cell apoptosis triggered by LPS and suppressed the expressions of nuclear factor kappa B (NF-κB), inducible nitric oxide synthase (iNOS), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in NR8383 and RLE-6TN cells, whereas miR-128-3p overexpression resulted in the opposite phenomenon. Moreover, OIP5-AS1 overexpression relieved lung edema, lung epithelial cell apoptosis, infiltration of myeloperoxidase (MPO)-labeled polymorphonuclear neutrophils (PMN), inflammatory responses triggered by CLP in vivo. Mechanistically, miR-128-3p, which targeted SIRT1, was hobbled by OIP5-AS1. All in all, OIP5-AS1 overexpression enhanced sepsis-induced ALI by modulating the miR-128-3p/SIRT1 pathway, which helps create new insights into sepsis treatment.

Ruscogenin attenuates sepsis-induced acute lung injury and pulmonary endothelial barrier dysfunction via TLR4/Src/p120-catenin/VE-cadherin signalling pathway

OBJECTIVES

Sepsis-associated acute lung injury (ALI) occurs with the highest morbidity and carries the highest mortality rates among the pathogenies of ALI. Ruscogenin (RUS) has been found to exhibit anti-inflammation property and rescue lipopolysaccharide-induced ALI, but little is known about its role in sepsis-triggered ALI. The aim of this study was to investigate the potential role of RUS in sepsis-induced ALI and the probable mechanism.

METHODS

Mice model of cecal ligation and puncture (CLP) was replicated, and three doses of RUS (0.01, 0.03 and 0.1 mg/kg) were administrated 1 h before CLP surgeries.

KEY FINDINGS

RUS significantly extended the survival time and attenuated the lung pathological injury, oedema and vascular leakage in sepsis-induced ALI mice. RUS efficiently decreased the level of MPO in lung tissue and the WBC, NEU counts in BALF. In addition, RUS rescued the expression of VE-cadherin and p120-catenin and suppressed the TLR4/Src signalling in lung tissue.

CONCLUSIONS

RUS attenuated sepsis-induced ALI via protecting pulmonary endothelial barrier and regulating TLR4/Src/p120-catenin/VE-cadherin signalling pathway.

MicroRNA‑129 plays a protective role in sepsis‑induced acute lung injury through the suppression of pulmonary inflammation via the modulation of the TAK1/NF‑κB pathway

Excessive inflammatory response and apoptosis play key roles in the pathogenic mechanisms of sepsis-induced acute lung injury (ALI); however, the molecular pathways linked to ALI pathogenesis remain unclear. Recently, microRNAs (miRNAs/miRs) have emerged as important regulators of inflammation and apoptosis in sepsis-induced ALI; however, the exact regulatory mechanisms of miRNAs remain poorly understood. In the present study, the gene microarray dataset GSE133733 obtained from the Gene Expression Omnibus database was analyzed and a total of 38 differentially regulated miRNAs were identified, including 17 upregulated miRNAs and 21 downregulated miRNAs, in mice with lipopolysaccharide (LPS)-induced ALI, in comparison to the normal control mice. miR-129 was found to be the most significant miRNA, among the identified miRNAs. The upregulation of miR-129 markedly alleviated LPS-induced lung injury, as indicated by the decrease in lung permeability in and the wet-to-dry lung weight ratio, as well as the improved survival rate of mice with ALI administered miR-129 mimic. Moreover, the upregulation of miR-129 reduced pulmonary inflammation and apoptosis in mice with ALI. Of note, transforming growth factor activated kinase-1 (TAK1), a well-known regulator of the nuclear factor-κB (NF-κB) pathway, was directly targeted by miR-129 in RAW 264.7 cells. More importantly, miR-129 upregulation impeded the LPS-induced activation of the TAK1/NF-κB signaling pathway, as illustrated by the suppression of the nuclear phosphorylated-p65, p-IκB-α and p-IKKβ expression levels. Collectively, the findings of the present study indicate that miR-129 protects mice against sepsis-induced ALI by suppressing pulmonary inflammation and apoptosis through the regulation of the TAK1/NF-κB signaling pathway. This introduces the basis for future research concerning the application of miR-129 and its targets for the treatment of ALI.

Protective Effect of Dexmedetomidine on Acute Lung Injury via the Upregulation of Tumour Necrosis Factor-α-Induced Protein-8-like 2 in Septic Mice

The aim of the present study was to investigate whether TIPE2 participates in the protective actions of dexmedetomidine (DEX) in a mouse model of sepsis-induced acute lung injury (ALI). We administered TIPE2 adeno-associated virus (AAV-TIPE2) intratracheally into the lungs of mice. Control mice were infected with an adeno-associated virus expressing no transgene. Three weeks later, an animal model of caecal ligation-perforation (CLP)-induced sepsis was established. DEX was administered intravenously 30 min after CLP. Twenty-four hours after sepsis, lung injury was assayed by lung histology, the ratio of polymorphonuclear leukocytes (PMNs) to total cells in the bronchoalveolar lavage fluid (BALF), myeloperoxidase (MPO) activity, BALF protein content and the lung wet-to-dry (W/D) weight ratio. Proinflammatory factor levels in the BALF of mice were measured. The protein expression levels in lung tissues were analysed by Western blotting. The results showed that DEX treatment markedly mitigated sepsis-induced lung injury, which was characterized by the deterioration of histopathology, histologic scores, the W/D weight ratio and total protein levels in the BALF. Moreover, DEX markedly attenuated sepsis-induced lung inflammation, as evidenced by the decrease in the number of PMNs in the BALF, lung MPO activity and proinflammatory cytokines in the BALF. In addition, DEX dramatically prevented sepsis-induced pulmonary cell apoptosis in mice, as reflected by decreases in the number of TUNEL-positive cells, the protein expression of cleaved caspase-9 and cleaved caspase 3 and the Bax/Bcl-2 ratio. In addition, evaluation of protein expression showed that DEX blocked sepsis-activated JNK phosphorylation and NF-κB p65 nuclear translocation. Similar results were also observed in the TIPE2 overexpression group. Our study demonstrated that DEX inhibits acute inflammation and apoptosis in a murine model of sepsis-stimulated ALI via the upregulation of TIPE2 and the suppression of the activation of the NF-κB and JNK signalling pathways.

Attenuation of LPS-induced acute lung injury by continentalic acid in rodents through inhibition of inflammatory mediators correlates with increased Nrf2 protein expression

Background

Acute lung injury (ALI) together with acute respiratory distress syndrome (ARDS) are associated with high rate of mortality and morbidity in patients. In the current study, the anti-inflammatory effects of continentalic acid (CNT) in LPS-induced acute lung injury model was explored.

Methods

The acute lung injury model was established by administering LPS (5 mg/kg) intraperitonealy. Following LPS administration, the survival rate, temperature changes and lung Wet/Dry ratio were assessed. The antioxidants (GSH, GST, Catalase and SOD) and oxidative stress markers (MDA, NO, MPO) were evaluated in all the treated groups. Similarly, the cytokines such as IL-1β, IL-6 and TNF-α were analyzed using ELISA assay. The histological changes were determined using H and E staining, while Nrf2 and iNOS level were determined using immunohistochemistry analysis. The molecular docking analysis was performed to assess the pharmacokinetics parameters and interaction of the CNT with various protein targets.

Results

The results showed that CNT dose dependently (10, 50 and 100 mg/kg) reduced mortality rate, body temperature and lungs Wet/Dry ratio. CNT post-treatment significantly inhibited LPS-induced production of pro-inflammatory cytokines such as IL-1β, IL-6 and TNF-α. The CNT post-treatment markedly improved the hematological parameters, while significantly reduced the MPO (indicator of the neutrophilic infiltration) activity compared to the LPS treated group. Furthermore, the CNT (100 mg/kg) post-administration remarkably inhibited the lung Wet/Dry ratio. The CNT (100 mg/kg) treated group showed marked reduction in the oxidative stress markers such as malonaldehyde (MDA) and Nitric oxide (NO) concentration, while induced the level of the anti-oxidant enzymes such as GST, GSH, Catalase and SOD. Similarly, the CNT markedly reduced the iNOS expression level, while induced the Nrf2 protein expression. Additionally, the molecular docking study showed significant binding interaction with the Nrf2, p65, Keap1, HO-1, IL-1β, IL-6, TNF-α and COX-2, while exhibited excellent physicochemical properties.

Conclusion

The CNT showed marked protection against the LPS-induced lung injury and improved the behavioral, biochemical and histological parameters. Furthermore, the CNT showed significant interaction with several protein targets and exhibited better physicochemical properties.

Liquiritin, a novel inhibitor of TRPV1 and TRPA1, protects against LPS-induced acute lung injury

TRPV1 and TRPA1 are cation channels that play key roles in inflammatory signaling pathways. They are co-expressed on airway C-fibers, where they exert synergistic effects on causing inflammation and cough. Licorice, the root of Glycyrrhiza uralensis, has been widely used in China as an anti-inflammatory and anti-coughing herb. To learn if TRPV1 and TRPA1 might be key targets of the anti-inflammatory and antitussive effects of licorice, we examined liquiritin, the main flavonoid compound and active ingredient of licorice, on agonist-evoked TRPV1 and TRPA1 activation. Liquiritin inhibited capsaicin- and allyl isothiocyanate-evoked TRPV1 and TRPA1 whole-cell currents, respectively, with a similar potency and maximal inhibition. In a mouse acute lung injury (ALI) model induced by the bacterial endotoxin lipopolysaccharide, which involves both TRPV1 and TRPA1, an oral gavage of liquiritin prevented tissue damage and suppressed inflammation and the activation of NF-κB signaling pathway in the lung tissue. Liquiritin also suppressed LPS-induced increase in TRPV1 and TRPA1 protein expression in the lung tissue, as well as TRPV1 and TRPA1 mRNA levels in cells contained in mouse bronchoalveolar lavage fluid. In cultured THP-1 monocytes, liguiritin, or TRPV1 and TRPA1 antagonists capsazepine and HC030031, respectively, diminished not only cytokine-induced upregulation of NF-κB function but also TRPV1 and TRPA1 expression at both protein and mRNA levels. We conclude that the anti-inflammatory and antitussive effects of liquiritin are mediated by the dual inhibition of TRPV1 and TRPA1 channels, which are upregulated in nonneuronal cells through the NF-κB pathway during airway inflammation via a positive feedback mechanism.

DNA methyltransferase inhibitor alleviates bleomycin-induced pulmonary inflammation

Acute lung injury (ALI) is a severe disease characterized by several inflammatory responses in the lung with high mortality. We applied a mouse model of the pulmonary inflammation induced by the intratracheal instillation of bleomycin which is widely used to induce ALI and fibrosis in animal models. We hypothesized that DNA methyltransferase inhibitor, 5-azacytidine (5-Aza), with its anti-inflammatory benefits, might attenuate bleomycin-induced ALI through the alleviation of inflammation in the lung. We quantified white blood cells with cell blood count (CBC) test, lung inflammation by analyzing cells in the collected bronchoalveolar lavage fluid (BALF) and histological analysis of the lung tissues, and gene expression levels by real-time PCR. Intratracheal administration of bleomycin in mice induced pulmonary inflammation, characterized by increased neutrophil infiltration and inflammatory cytokine expression in the lungs. Mice treated with 5-Aza showed a significant reduction of lung neutrophilia, together with lower expressions of CXCL2 and MCP-1. Furthermore, 5-Aza treatment decreased the expression of proinflammatory cytokines in the lung tissue. Collectively, our data show that DNA methyltransferase inhibitor can alleviate the lung inflammation of bleomycin-induced ALI, indicating an alternative treatment option for the inflammation-triggered lung injury.

Neutrophil extracellular traps activate IL-8 and IL-1 expression in human bronchial epithelia

Neutrophil extracellular traps (NETs) provide host defense but can contribute to the pathobiology of diverse human diseases. We sought to determine the extent and mechanism by which NETs contribute to human airway cell inflammation. Primary normal human bronchial epithelial cells (HBEs) grown at air-liquid interface and wild-type (wt)CFBE41o- cells (expressing wtCFTR) were exposed to cell-free NETs from unrelated healthy volunteers for 18 h in vitro. Cytokines were measured in the apical supernatant by Luminex, and the effect on the HBE transcriptome was assessed by RNA sequencing. NETs consistently stimulated IL-8, TNF-α, and IL-1α secretion by HBEs from multiple donors, with variable effects on other cytokines (IL-6, G-CSF, and GM-CSF). Expression of HBE RNAs encoding IL-1 family cytokines, particularly IL-36 subfamily members, was increased in response to NETs. NET exposure in the presence of anakinra [recombinant human IL-1 receptor antagonist (rhIL-1RA)] dampened NET-induced changes in IL-8 and TNF-α proteins as well as IL-36α RNA. rhIL-36RA limited the increase in expression of proinflammatory cytokine RNAs in HBEs exposed to NETs. NETs selectively upregulate an IL-1 family cytokine response in HBEs, which enhances IL-8 production and is limited by rhIL-1RA. The present findings describe a unique mechanism by which NETs may contribute to inflammation in human lung disease in vivo. NET-driven IL-1 signaling may represent a novel target for modulating inflammation in diseases characterized by a substantial NET burden.

Red blood cell transfusion results in adhesion of neutrophils in human endotoxemia and in critically ill patients with sepsis

BACKGROUND

Red blood cell (RBC) transfusion is associated with adverse effects, which may involve activation of the host immune response. The effect of RBC transfusion on neutrophil Reactive Oxygen Species (ROS) production and adhesion ex vivo was investigated in endotoxemic volunteers and in critically ill patients that received a RBC transfusion. We hypothesized that RBC transfusion would cause neutrophil activation, the extent of which depends on the storage time and the inflammatory status of the recipient.

STUDY DESIGN AND METHODS

Volunteers were injected with lipopolysaccharide (LPS) and transfused with either saline, fresh, or stored autologous RBCs. In addition, 47 critically ill patients with and without sepsis receiving either fresh (<8 days) or standard stored RBC (2‐35 days) were included. Neutrophils from healthy volunteers were incubated with the plasma samples from the endotoxemic volunteers and from the critically ill patients, after which priming of neutrophil ROS production and adhesion were assessed.

RESULTS

In the endotoxemia model, ex vivo neutrophil adhesion, but not ROS production, was increased after transfusion, which was not affected by RBC storage duration. In the critically ill, ex vivo neutrophil ROS production was already increased prior to transfusion and was not increased following transfusion. Neutrophil adhesion was increased following transfusion, which was more notable in the septic patients than in non‐septic patients. Transfusion of fresh RBCs, but not standard issued RBCs, resulted in enhanced ROS production in neutrophils.

CONCLUSION

RBC transfusion was associated with increased neutrophil adhesion in a model of human endotoxemia as well as in critically ill patients with sepsis.

Regulatory mechanism of NOV/CCN3 in the inflammation and apoptosis of lung epithelial alveolar cells upon lipopolysaccharide stimulation

Lipopolysaccharide (LPS) induces inflammatory stress and apoptosis. Pulmonary epithelial cell apoptosis has been shown to accelerate the progression of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), and is the leading cause of mortality in patients with ALI/ARDS. Nephroblastoma overexpressed (NOV; also known as CCN3), an inflammatory modulator, is reported to be a biomarker in ALI. Using an LPS-induced ALI model, we investigated the expression of CCN3 and its possible molecular mechanism involved in lung alveolar epithelial cell inflammation and apoptosis. Our data revealed that LPS treatment greatly increased the level of CCN3 in human lung alveolar type II epithelial cells (A549 cell line). The A549 cells were also transfected with a specific CCN3 small interfering RNA (siRNA). CCN3 knockdown not only largely attenuated the expression of inflammatory cytokines, interleukin (IL)-1β and transforming growth factor (TGF)-β1, but also reduced the apoptotic rate of the A549 cells and altered the expression of apoptosis-associated proteins (Bcl-2 and caspase-3). Furthermore, CCN3 knockdown greatly inhibited the activation of nuclear factor (NF)-κB p65 in the A549 cells, and TGF-β/p-Smad and NF-κB inhibitors significantly decreased the expression level of CCN3 in A549 cells. In conclusion, our data indicate that CCN3 knockdown affects the expression of downstream genes through the TGF-β/p-Smad or NF-κB pathways, leading to the inhibition of cell inflammation and apoptosis in human alveolar epithelial cells.

Alveolar Macrophage Chemokine Secretion Mediates Neutrophilic Lung Injury in Nox2-Deficient Mice

Acute lung injury (ALI), developing as a component of the systemic inflammatory response syndrome (SIRS), leads to significant morbidity and mortality. Reactive oxygen species (ROS), produced in part by the neutrophil NADPH oxidase 2 (Nox2), have been implicated in the pathogenesis of ALI. Previous studies in our laboratory demonstrated the development of pulmonary inflammation in Nox2-deficient (gp91^phox-/y) mice that was absent in WT mice in a murine model of SIRS. Given this finding, we hypothesized that Nox2 in a resident cell in the lung, specifically the alveolar macrophage, has an essential anti-inflammatory role. Using a murine model of SIRS, we examined whole-lung digests and bronchoalveolar lavage fluid (BALf) from WT and gp91^phox-/y mice. Both genotypes demonstrated neutrophil sequestration in the lung during SIRS, but neutrophil migration into the alveolar space was only present in the gp91^phox-/y mice. Macrophage inflammatory protein (MIP)-1α gene expression and protein secretion were higher in whole-lung digest from uninjected gp91^phox-/y mice compared to the WT mice. Gene expression of MIP-1α, MCP-1, and MIP-2 was upregulated in alveolar macrophages obtained from gp91^phox-/y mice at baseline compared with WT mice. Further, ex vivo analysis of alveolar macrophages, but not bone marrow-derived macrophages or peritoneal macrophages, demonstrated higher gene expression of MIP-1α and MIP-2. Moreover, isolated lung polymorphonuclear neutrophils migrate to BALf obtained from gp91^phox-/y mice, further providing evidence of a cell-specific anti-inflammatory role for Nox2 in alveolar macrophages. We speculate that Nox2 represses the development of inflammatory lung injury by modulating chemokine expression by the alveolar macrophage.

Mesenchymal Stem Cell-Conditioned Medium Induces Neutrophil Apoptosis Associated with Inhibition of the NF-κB Pathway in Endotoxin-Induced Acute Lung Injury

The immunomodulatory effects of mesenchymal stem cells (MSCs) are established. However, the effects of MSCs on neutrophil survival in acute lung injury (ALI) remain unclear. The goal of this study was to investigate the effect of an MSC-conditioned medium (MSC-CM) on neutrophil apoptosis in endotoxin-induced ALI. In this study, an MSC-CM was delivered via tail vein injection to wild-type male C57BL/6 mice 4 h after an intratracheal injection of lipopolysaccharide (LPS). Twenty-four hours later, bronchoalveolar lavage fluid (BALF) and lung tissue were collected to perform histology, immunohistochemistry, apoptosis assay of neutrophil, enzyme-linked immunosorbent assays, and an electrophoretic mobility shift assay. Human neutrophils were also collected from patients with sepsis-induced acute respiratory distress syndrome (ARDS). Human neutrophils were treated in vitro with LPS, with or without subsequent MSC-CM co-treatment, and were then analyzed. Administration of the MSC-CM resulted in a significant attenuation of histopathological changes, the levels of interleukin-6 and macrophage inflammatory protein 2, and neutrophil accumulation in mouse lung tissues of LPS-induced ALI. Additionally, MSC-CM therapy enhanced the apoptosis of BALF neutrophils and reduced the expression of the anti-apoptotic molecules, Bcl-xL and Mcl-1, both in vivo and in vitro experiments. Furthermore, phosphorylated and total levels of nuclear factor (NF)-κB p65 were reduced in lung tissues from LPS + MSC-CM mice. Human MSC-CM also reduced the activity levels of NF-κB and matrix metalloproteinase-9 in the human neutrophils from ARDS patients. Thus, the results of this study suggest that the MSC-CM attenuated LPS-induced ALI by inducing neutrophil apoptosis, associated with inhibition of the NF-κB pathway.

Neutrophil transendothelial migration: updates and new perspectives

Neutrophils represent the first line of cellular defense against invading microorganism by rapidly moving across the blood-endothelial cell (EC) barrier and exerting effector cell functions. The neutrophil recruitment cascade to inflamed tissues involves elements of neutrophil rolling, firm adhesion, and crawling onto the EC surface before extravasating by breaching the EC barrier. The interaction between neutrophils and ECs occurs via various adhesive modules and is a critical event determining the mode of neutrophil transmigration, either at the EC junction (paracellular) or directly through the EC body (transcellular). Once thought to be a homogenous entity, new evidence clearly points to the plasticity of neutrophil functions. This review will focus on recent advances in our understanding of the mechanism of the neutrophil transmigration process. It will discuss how neutrophil-EC interactions and the subsequent mode of diapedesis, junctional or nonjunctional, can be context dependent and how this plasticity may be exploited clinically.

Kaempferol reduces K63-linked polyubiquitination to inhibit nuclear factor-κB and inflammatory responses in acute lung injury in mice

Acute lung injury (ALI) and its severe form, acute respiratory distress syndrome (ARDS), pose a major clinical challenge. The major driving force in this syndrome is pulmonary inflammation. Recent studies have shown that the naturally occurring flavonoid kaempferol (KPF) reduces endotoxin-induced inflammatory responses in mice. However, the mechanisms of these anti-inflammatory activities are not currently known. Here, we show that enhanced inflammatory cytokine production in response to lipopolysaccharide (LPS) is due to increased TGF-β-activated kinase-1 (TAK1) phosphorylation with subsequent activation of nuclear factor-κB (NF-κB). KPF attenuates LPS-mediated production of cytokines as well as activation of NF-κB. Furthermore, we identified that KPF prevents increased K63-linked polyubiquitination on TNF receptor associated factor-6 (TRAF6) and interleukin-1 receptor-associated kinase 1 (IRAK1). K63-linked polyubiquitination is a signal leading to enhanced activation of downstream pathways including TAK1. Our study shows that KPF is effective in reducing lung damage induced by LPS by modulating TRAF6 polyubiquitination. Furthermore, our findings may provide novel molecular targets to alleviate acute lung injury.

Remote ischemic preconditioning ameliorates indirect acute lung injury by modulating phosphorylation of IκBα in mice

OBJECTIVE

Acute lung injury is responsible for mortality in seriously ill patients. Previous studies have shown that systemic inflammation is attenuated by remote ischemic preconditioning (RIPC) via reducing nuclear factor-kappa B (NF-κB). Therefore, we investigated whether lipopolysaccharide (LPS)-induced indirect acute lung injury (ALI) can be protected by RIPC.

METHODS

RIPC was accomplished by 10 minutes of occlusion using a tourniquet on the right hind limb of mice, followed by 10 minutes of reperfusion. This process was repeated three times. Intraperitoneal LPS (20 mg/kg) was administered to induce indirect ALI. Inflammatory cytokines in bronchoalveolar lavage fluid were analyzed using an enzyme-linked immunosorbent assay. Pulmonary tissue was excised for histological examination, and for examining NF-κB activity and phosphorylation of inhibitor of κBα (IκBα).

RESULTS

NF-κB activation and LPS-induced histopathological changes in the lungs were significantly alleviated in the RIPC group. RIPC reduced phosphorylation of IκBα in lung tissue of ALI mice.

CONCLUSIONS

RIPC attenuates endotoxin-induced indirect ALI. This attenuation might occur through modification of NF-κB mediation of cytokines by modulating phosphorylation of IκBα.

Isoalantolactone protects LPS-induced acute lung injury through Nrf2 activation

Isoalantolactone (ISO), a sesquiterpene lactone isolated from Inula helenium, is known to have anti-inflammatory activity. Here, using a mouse model of acute lung injury, we investigated the effects of ISO on lung inflammation in vivo. ISO (2.5, 5, 10 mg/kg) was administered 1 h before LPS treatment. Histopathological changes suggested that ISO attenuated the injury of lung tissues induced by LPS. ISO also inhibited LPS-induced MPO activity, MDA content, lung W/D ratio, and the production of inflammatory cytokines TNF-α and IL-1β. LPS decreased the activities of the antioxidant enzymes SOD, GPX, and CAT and the decreases were inhibited by ISO. Further studies were performed to detect the Nrf2 and NF-κB signaling pathway. The results showed that ISO significantly suppressed LPS-induced NF-κB activation, as well as PI3K and AKT phosphorylation. Additionally, the expression of Nrf2 and HO-1 were dose-dependently up-regulated by the treatment of ISO. Taken together, the results indicate the protective action of ISO against LPS-induced ALI were through activation of the Nrf2 signaling pathway.

Atorvastatin and diacerein reduce insulin resistance and increase disease tolerance in rats with sepsis

Background

Sepsis is one of the leading causes of death among hospitalized patients. At the onset of this condition, there is an over-production of pro-inflammatory mediators that contribute to organ failure and death. The excess production of pro-inflammatory mediators also impairs insulin signaling, which may be a pathophysiological tissue marker of proinflammatory cytokine action before organ failure. Statins and diacerein have pleiotropic effects, such as the blockage of inflammatory signaling pathways, suggesting that these drugs may be an attractive therapeutic or prophylactic strategy against sepsis. The aim of the present study was to investigate whether a statin or diacerein can improve insulin signaling, disease tolerance and survival in sepsis by inhibiting inflammatory pathways.

Methods

We investigated the effect of these drugs on survival, tissue insulin signaling and inflammatory pathways in the liver and muscle of rats with sepsis induced by cecal ligation and puncture (CLP).

Results

The results showed that administration of medications, with anti-inflammatory ability, to septic animals increased survival and improved disease tolerance and insulin resistance in the liver and muscle. The treatment also attenuated ER stress, NF-κB, JNK activation and restored glucose-6-phosphatase (G6Pase) levels in the liver.

Conclusions

Our results indicate that atorvastatin and diacerein treatment can modulate inflammatory pathways and, in parallel, attenuate insulin resistance in sepsis. Since these two drugs have safety profiles and minimal side effects, we suggest that these drugs may be alternative therapies for the prevention or therapies for the treatment of insulin resistance in sepsis, which could potentially reduce mortality in patients with sepsis.

Electronic supplementary material

The online version of this article (10.1186/s12950-018-0184-9) contains supplementary material, which is available to authorized users.

Puerarin prevents LPS-induced acute lung injury via inhibiting inflammatory response

Acute lung injury (ALI) is a critical illness syndrome with high morbidity and mortality in patients. Inflammation has been known to be involved in the development of ALI. The purpose of this study was to investigate the effect of puerarin on lipopolysaccharide (LPS)-induced ALI in mice. The pro-inflammatory cytokines TNF-α, IL-6 and IL-1β were determined by ELISA. Western blot analysis was used for detecting the expression of NF-κB, IκBα, and LXRα. And myeloperoxidase (MPO) activity, lung wet/dry (W/D) ratio, and histopathological examination were also detected in lung tissues. The results showed that puerarin significantly inhibited LPS-stimulated MPO activity in lung tissues. Meanwhile, puerarin attenuated lung histopathological changes and lung wet/dry (W/D) ratio. We also found that the expression of pro-inflammatory cytokines, TNF-α, IL-6 and IL-1β were inhibited by puerarin. Puerarin also inhibited LPS-induced TNF-α in RAW264.7 cells and IL-8 in A549 cells. From the results of western blotting, puerarin significantly suppressed LPS-stimulated NF-κB activation. And the expression of LXRα was dose-dependently increased by treatment of puerarin. The inhibition of puerarin on TNF-α production in RAW264.7 cells and IL-8 production in A549 cells were blocked by LXRα inhibitor geranylgeranyl pyrophosphate (GGPP). These results suggested that puerarin attenuated ALI by activating LXRα, which subsequently inhibited LPS-induced inflammatory response.

3-Methyladenine and dexmedetomidine reverse lipopolysaccharide-induced acute lung injury through the inhibition of inflammation and autophagy

The aim of the present study was to investigate the effects of 3-methyladenine (3-MA) and dexmedetomidine (DEX) pretreatment on lipopolysaccharide (LPS)-induced acute lung injury (ALI) and the potential mechanism underlying the effects. LPS was instilled into the trachea of BALB/c mice to induce the ALI model. Solutions of 3-MA or DEX were intravenously injected into the mice 1 h later to establish the 3-MA and DEX groups. On days 1, 3 and 5 after the injections, arterial blood gas analysis was conducted, and the lung wet-dry weight ratio (W/D) was determined. In addition, albumin, cytokine and myeloperoxidase (MPO) contents were evaluated using ELISAs, and hematoxylin and eosin (H&E) staining was conducted. Furthermore, western blot analysis was used to evaluate the protein expression levels of microtubule-associated protein 1A/1B-light chain 3 (LC3)-I, LC3-II, autophagy protein 5 (ATG5), Rab7 and lysosome-associated membrane protein 1 (LAMP1), and reverse transcription quantitative polymerase chain reaction (RT-qPCR) was used to detect the mRNA expression levels of nuclear factor-κB (NF-κB) and Toll-like receptor 4 (TLR4). Treatment with 3-MA or DEX increased the blood partial pressure of oxygen level compared with that in the model group, and restored the W/D and blood partial pressure of carbon dioxide to normal levels. The content of tumor necrosis factor-α, interleukin-6 and albumin in bronchoalveolar fluid and MPO in lung tissue was significantly decreased in the 3-MA and DEX groups compared with the model group (P<0.05). H&E staining demonstrated that 3-MA and DEX each reversed the ALI. In addition, 3-MA and DEX reduced the protein expression levels of LC3-I, LC3-II, ATG5, Rab7 and LAMP1. Also, RT-qPCR results revealed that NF-κB and TLR4 mRNA expression levels were clearly decreased in the 3-MA and DEX groups compared with the model group. In conclusion, LPS-induced ALI was effectively reversed by treatment with 3-MA and DEX through the reduction of inflammation and autophagy and inhibition of the TLR4-NF-κB pathway.

Macrophage-targeting and reactive oxygen species (ROS)-responsive nanopolyplexes mediate anti-inflammatory siRNA delivery against acute liver failure (ALF)

Macrophage-targeting and ROS-degradable nanopolyplexes were developed to realize efficient TNF-α siRNA delivery toward the treatment of acute liver failure.

The response of muscle progenitor cells to cutaneous thermal injury

BACKGROUND

Severe burn results in a systemic response that leads to significant muscle wasting. It is believed that this rapid loss in muscle mass occurs due to increased protein degradation combined with reduced protein synthesis. Alterations in the microenvironment of muscle progenitor cells may partially account for this pathology. The aim of this study was to ascertain the response of muscle progenitor cells following thermal injury in mice and to enlighten the cellular cascades that contribute to the muscle wasting.

METHODS

C57BL/6 mice received a 20% total body surface area (TBSA) thermal injury. Gastrocnemius muscle was harvested at days 2, 7, and 14 following injury for protein and histological analysis.

RESULTS

We observed a decrease in myofiber cross-sectional area at 2 days post-burn. This muscle atrophy was compensated for by an increase in myofiber cross-sectional area at 7 and 14 days post-burn. Myeloperoxidase (MPO)-positive cells (neutrophils) increased significantly at 2 days. Moreover, through Western blot analysis of two key mediators of the proteolytic pathway, we show there is an increase in Murf1 and NF-κB 2 days post-burn. MPO-positive cells were also positive for NF-κB, suggesting that neutrophils attain NF-κB activity in the muscle. Unlike inflammatory and proteolytic pathways, the number of Pax7-positive muscle progenitor cells decreased significantly 2 days post-burn. This was followed by a recovery in the number of Pax7-positive cells at 7 and 14 days, suggesting proliferation of muscle progenitors that accompanied regrowth.

CONCLUSION

Our data show a biphasic response in the muscles of mice exposed to burn injury, with phenotypic characteristics of muscle atrophy at 2 days while compensation was observed later with a change in Pax7-positive muscle progenitor cells. Targeting muscle progenitors may be of therapeutic benefit in muscle wasting observed after burn injury.

Induced pluripotent stem cells reduce neutrophil chemotaxis via activating GRK2 in endotoxin-induced acute lung injury

BACKGROUND AND OBJECTIVE

We investigated the effect of induced pluripotent stem cells (iPSCs) in moderating neutrophil chemotaxis in endotoxin-induced acute lung injury (ALI).

METHODS

Male C57BL/6 mice at 8-12 weeks of age were studied. Murine iPSCs were delivered through the tail veins of mice 4 h after intratracheal instillation of endotoxin. Lung histopathological findings, neutrophil counts in peripheral blood and bronchoalveolar lavage fluid (BALF), bone marrow (BM) cell distribution, expression of chemokine receptors and regulatory signalling pathways were analysed after 24 h. Human neutrophils isolated from acute respiratory distress syndrome patients were used in a cell migration assay.

RESULTS

iPSCs significantly decreased the histopathological changes of ALI in mice compared to treatment with control cells. Numbers and activity levels of neutrophils in BALF were reduced in iPSC-treated ALI mice. The iPSC therapy restored neutrophil counts in the peripheral blood of ALI mice, but the percentages of mature neutrophils in BM were similar between iPSC-treated and -untreated groups. The iPSCs mediated a downregulation of the chemotactic response to endotoxin by reducing chemokine (C-X-C motif) receptor 2 (CXCR2) expression on mouse peripheral blood neutrophils. This result was confirmed by an in vitro human neutrophil migration assay. In addition, iPSCs or conditioned medium from iPSCs enhanced expression of G protein-coupled receptor kinase 2 (GRK2) on the surface of blood neutrophils in ALI mice.

CONCLUSION

iPSCs reduce neutrophil chemotaxis in endotoxin-induced ALI. These effects are associated with an enhancement of GRK2 activity and reduction of CXCR2 expression.

Human mesenchymal stem cells attenuate early damage in a ventilated pig model of acute lung injury

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a major cause of global morbidity and mortality. Mesenchymal stem cells (MSC) have shown promise in treating inflammatory lung conditions. We hypothesised that human MSC (hMSC) can improve ALI/ARDS through their anti-inflammatory actions. We subjected pigs (n=6) to intravenous oleic acid (OA) injury, ventilation and hMSC infusion, while the controls (n=5) had intravenous OA, ventilation and an infusion vehicle control. hMSC were infused 1h after the administration of OA. The animals were monitored for additional 4h. Nuclear translocation of nuclear factor-light chain enhancer of activated B cells (NF-κB), a transcription factor that mediates several inflammatory pathways was reduced in hMSC treated pigs compared to controls (p=0.04). There was no significant difference in lung injury, assessed by histological scoring in hMSC treated pigs versus controls (p=0.063). There was no difference in neutrophil counts between hMSC-treated pigs and controls. Within 4h, there was no difference in the levels of IL-10 and IL-8 pre- and post-treatment with hMSC. In addition, there was no difference in hemodynamics, lung mechanics or arterial blood gases between hMSC treated animals and controls. Subsequent studies are required to determine if the observed decrease in inflammatory transcription factors will translate into improvement in inflammation and in physiological parameters over the long term.

C1P Attenuates Lipopolysaccharide-Induced Acute Lung Injury by Preventing NF-κB Activation in Neutrophils

Recently, ceramide-1-phosphate (C1P) has been shown to modulate acute inflammatory events. Acute lung injury (Arnalich et al. 2000. Infect. Immun. 68: 1942-1945) is characterized by rapid alveolar injury, lung inflammation, induced cytokine production, neutrophil accumulation, and vascular leakage leading to lung edema. The aim of this study was to investigate the role of C1P during LPS-induced acute lung injury in mice. To evaluate the effect of C1P, we used a prophylactic and therapeutic LPS-induced ALI model in C57BL/6 male mice. Our studies revealed that intrapulmonary application of C1P before (prophylactic) or 24 h after (therapeutic) LPS instillation decreased neutrophil trafficking to the lung, proinflammatory cytokine levels in bronchoalveolar lavage, and alveolar capillary leakage. Mechanistically, C1P inhibited the LPS-triggered NF-κB levels in lung tissue in vivo. In addition, ex vivo experiments revealed that C1P also attenuates LPS-induced NF-κB phosphorylation and IL-8 production in human neutrophils. These results indicate C1P playing a role in dampening LPS-induced acute lung inflammation and suggest that C1P could be a valuable candidate for treatment of ALI.

Abandon the mouse research ship? Not just yet!

Many preclinical studies in critical care medicine and related disciplines rely on hypothesis-driven research in mice. The underlying premise posits that mice sufficiently emulate numerous pathophysiologic alterations produced by trauma/sepsis and can serve as an experimental platform for answering clinically relevant questions. Recently, the lay press severely criticized the translational relevance of mouse models in critical care medicine. A series of provocative editorials were elicited by a highly publicized research report in the Proceedings of the National Academy of Sciences (PNAS; February 2013), which identified an unrecognized gene expression profile mismatch between human and murine leukocytes following burn/trauma/endotoxemia. Based on their data, the authors concluded that mouse models of trauma/inflammation are unsuitable for studying corresponding human conditions. We believe this conclusion was not justified. In conjunction with resulting negative commentary in the popular press, it can seriously jeopardize future basic research in critical care medicine. We will address some limitations of that PNAS report to provide a framework for discussing its conclusions and attempt to present a balanced summary of strengths/weaknesses of use of mouse models. While many investigators agree that animal research is a central component for improved patient outcomes, it is important to acknowledge known limitations in clinical translation from mouse to man. The scientific community is responsible to discuss valid limitations without overinterpretation. Hopefully, a balanced view of the strengths/weaknesses of using animals for trauma/endotoxemia/critical care research will not result in hasty discount of the clear need for using animals to advance treatment of critically ill patients.

Silencing Bruton's tyrosine kinase in alveolar neutrophils protects mice from LPS/immune complex-induced acute lung injury

Previous observations made by our laboratory indicate that Bruton's tyrosine kinase (Btk) may play an important role in the pathophysiology of local inflammation in acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). We have shown that there is cross talk between FcγRIIa and TLR4 in alveolar neutrophils from patients with ALI/ARDS and that Btk mediates the molecular cooperation between these two receptors. To study the function of Btk in vivo we have developed a unique two-hit model of ALI: LPS/immune complex (IC)-induced ALI. Furthermore, we conjugated F(ab)2 fragments of anti-neutrophil antibodies (Ly6G1A8) with specific siRNA for Btk to silence Btk specifically in alveolar neutrophils. It should be stressed that we are the first group to perform noninvasive transfections of neutrophils, both in vitro and in vivo. Importantly, our present findings indicate that silencing Btk in alveolar neutrophils has a dramatic protective effect in mice with LPS/IC-induced ALI, and that Btk regulates neutrophil survival and clearance of apoptotic neutrophils in this model. In conclusion, we put forward a hypothesis that Btk-targeted neutrophil specific therapy is a valid goal of research geared toward restoring homeostasis in lungs of patients with ALI/ARDS.

mTOR and autophagy in regulation of acute lung injury: a review and perspective

The mammalian target of rapamycin (mTOR) is a central regulator of many major cellular processes including protein and lipid synthesis and autophagy, and is also implicated in an increasing number of pathological conditions. Emerging evidence suggests that both mTOR and autophagy are critically involved in the pathogenesis of pulmonary diseases including acute lung injury (ALI). However, the detailed mechanisms of these pathways in disease pathogenesis require further investigations. In certain cases within the same disease, the functions of mTOR and autophagy may vary from different cell types and pathogens. Here we review recent advances about the basic machinery of mTOR and autophagy, and their roles in ALI. We further discuss and propose the likelihood of cell type- and pathogen-dependent functions of these pathways in ALI pathogenesis.

Pulmonary overexpression of inhibitor κBα decreases the severity of ventilator-induced lung injury in a rat model

BACKGROUND

Activation of the nuclear factor-κB (NF-κB) pathway is central to the pathogenesis of lung injury and inflammation. We determined whether targeted overexpression of inhibitor-κBα (IκBα) in the lung could decrease the severity of ventilator-induced lung injury (VILI).

METHODS

Anaesthetized adult male Sprague-Dawley rats were randomly allocated to undergo intratracheal instillation of: (i) vehicle alone (surfactant, n=10); (ii) 1×10(10) adeno-associated virus encoding IκBα (AAV-IκBα, n=10); (iii) 5×10(10) AAV-IκBα (n=10); and (iv) 1×10(10) AAV-Null (n=5). This was followed by 4 h of injurious mechanical ventilation. Subsequent experiments examined the effect of IκBα overexpression in animals undergoing 'protective' mechanical ventilation.

RESULTS

IκBα overexpression increased survival duration at both the lower [3.8 h (0.4)] and higher [3.6 h (0.7)] doses compared with vehicle [2.7 h (1.0)] or the null transgene [2.2 h (0.8)]. IκBα overexpression reduced the alveolar-arterial oxygen gradient (kPa) at both the lower [53 (21)] and higher [52 (19)] doses compared with vehicle [75 (8.5)] or the null transgene [70 (15)], decreased alveolar neutrophil infiltration, and reduced alveolar concentrations of interleukin (IL)-1β and IL-10. The lower IκBα dose was as effective as the higher dose. IκBα overexpression had no effect in the setting of protective lung ventilation.

CONCLUSIONS

Inhibition of pulmonary NF-κB activity by IκBα overexpression reduced the severity of VILI in a rat model.

Neutrophil elastase inhibitor reduces ventilation-induced lung injury via nuclear factor-κB and NF-κB repressing factor in mice

Mechanical ventilation used in patients with acute lung injury can damage pulmonary epithelial cells through production of inflammatory cytokines, oxygen radicals, and neutrophil infiltration, termed ventilator-induced lung injury. Neutrophil elastase, nuclear factor-κB (NF-κB), and NF-κB repressing factor (NRF) have previously been shown to participate in the regulation of macrophage inflammatory protein-2 (MIP-2) during airway inflammation. However, the mechanisms regulating interactions among mechanical ventilation, neutrophil influx, and NF-κB/NRF remain unclear. Thus, we hypothesized that neutrophil elastase inhibitor attenuated ventilation-induced neutrophil recruitment and MIP-2 production through inhibition of the NF-κB/NRF pathway. Male C57BL/6 mice were exposed to low-tidal-volume (6 mL/kg) or high-tidal-volume (30 mL/kg) mechanical ventilation using room air with or without 2 µg/g NF-κB inhibitor SN50 or 6 µg/g NRF short interfering RNA or 100 µg/g neutrophil elastase inhibitor administration. Nonventilated mice served as a control group. Evan blue dye, lung wet-to-dry weight ratio, free radicals, myeloperoxidase, histopathologic grading of lung tissue, inflammatory cytokines, Western blot of NF-κB and NRF, and gene expression of NRF were measured to establish the extent of lung injury. Neutrophil elastase inhibitor ameliorated high-tidal-volume ventilation-induced lung injury, neutrophil influx, production of MIP-2 and malondialdehyde, activation of NF-κB and NRF, apoptotic epithelial cell death, and disruption of bronchial microstructure in mice. Mechanical stretch-augmented acute lung injury was also attenuated through pharmacological inhibition of NF-κB activity by SN50 and NRF expression by NRF short interfering RNA. Our data suggest that neutrophil elastase inhibitor attenuates high-tidal-volume mechanical ventilation-induced neutrophil influx, oxidative stress, and production of MIP-2, at least partly, through inhibition of NF-κB/NRF pathway. Understanding the protective effects of neutrophil elastase inhibitor associated with the reduction of MIP-2 allow clarification of the pathophysiological mechanisms regulating severe lung inflammation and development of possible therapeutic strategies involved in acute lung injury.

Hypercapnic acidosis confers antioxidant and anti-apoptosis effects against ventilator-induced lung injury

Hypercapnic acidosis may attenuate ventilator-induced lung oxidative stress injury and alveolar cell apoptosis, but the underlying mechanisms are poorly understood. We examined the effects of hypercapnic acidosis on the role of apoptosis signal-regulating kinase 1 (ASK1), which activates the c-Jun N-terminal kinase (JNK) and p38 cascade in both apoptosis and oxidative reactions, in high-pressure ventilation stimulated rat lungs. Rats were ventilated with a peak inspiratory pressure (PIP) of 30 cmH2O for 4 h and randomly given FiCO2 to achieve normocapnia (PaCO2 at 35-45 mm Hg) or hypercapnia (PaCO2 at 80-100 mm Hg); normally ventilated rats with PIP of 15 cmH2O were used as controls. Lung injury was quantified by gas exchange, microvascular leaks, histology, levels of inflammatory cytokines, and pulmonary oxidative reactions. Apoptosis through the ASK1-JNK/p38 mitogen-activated protein kinase (MAPK) cascade in type II alveolar epithelial cells (AECIIs) were evaluated by examination of caspase-3 activation. The results showed that injurious ventilation caused significant lung injury, including deteriorative oxygenation, changes of histology, and the release of inflammatory cytokines. In addition, the high-pressure mechanical stretch also induced apoptosis and caspase-3 activation in the AECIIs. Hypercapnia attenuated these responses, suppressing the ASK1 signal pathways with its downstream kinase phosphorylation of p38 MAPK and JNK, and caspase-3 activation. Thus, hypercapnia can attenuate cell apoptosis and oxidative stress damage in rat lungs during injurious ventilation, at least in part, due to the suppression of the ASK1-JNK/p38 MAPK pathways.

Vitamin C: a novel regulator of neutrophil extracellular trap formation

INTRODUCTION

Neutrophil extracellular trap (NET) formation was recently identified as a novel mechanism to kill pathogens. However, excessive NET formation in sepsis can injure host tissues. We have recently shown that parenteral vitamin C (VitC) is protective in sepsis. Whether VitC alters NETosis is unknown.

METHODS

We used Gulo-/- mice as they lack the ability to synthesize VitC. Sepsis was induced by intraperitoneal infusion of a fecal stem solution (abdominal peritonitis, FIP). Some VitC deficient Gulo-/- mice received an infusion of ascorbic acid (AscA, 200 mg/kg) 30 min after induction of FIP. NETosis was assessed histologically and by quantification for circulating free DNA (cf-DNA) in serum. Autophagy, histone citrullination, endoplasmic reticulum (ER) stress, NFκB activation and apoptosis were investigated in peritoneal PMNs.

RESULTS

Sepsis produced significant NETs in the lungs of VitC deficient Gulo-/- mice and increased circulating cf-DNA. This was attenuated in the VitC sufficient Gulo-/- mice and in VitC deficient Gulo-/- mice infused with AscA. Polymorphonuclear neutrophils (PMNs) from VitC deficient Gulo-/- mice demonstrated increased activation of ER stress, autophagy, histone citrullination, and NFκB activation, while apoptosis was inhibited. VitC also significantly attenuated PMA induced NETosis in PMNs from healthy human volunteers.

CONCLUSIONS

Our in vitro and in vivo findings identify VitC as a novel regulator of NET formation in sepsis. This study complements the notion that VitC is protective in sepsis settings.

Kinase AKT1 negatively controls neutrophil recruitment and function in mice

Neutrophils are critically involved in host defense and inflammatory injury. However, intrinsic signaling mechanisms controlling neutrophil recruitment and activities are poorly defined. In this article, we showed that protein kinase AKT1 (also known as PKBα) is the dominant isoform expressed in neutrophils and is downregulated upon bacterial infection and neutrophil activation. AKT1 deficiency resulted in severe disease progression accompanied by recruitment of neutrophils and enhanced bactericidal activity in the acute inflammatory lung injury (ALI) and the Staphylococcus aureus infection mouse models. Moreover, the depletion of neutrophils efficiently reversed the aggravated inflammatory response, but adoptive transfer of AKT1(-/-) neutrophils could potentiate the inflammatory immunity, indicating an intrinsic effect of the neutrophil in modulating inflammation in AKT1(-/-) mice. In the ALI model, the infiltration of neutrophils into the inflammatory site was associated with enhanced migration capacity, whereas inflammatory stimuli could promote neutrophil apoptosis. In accordance with these findings, neutralization of CXCR2 attenuated neutrophil infiltration and delayed the occurrence of inflammation. Finally, the enhanced bactericidal activity and inflammatory immunity of AKT-deficient neutrophils were mediated by a STAT1-dependent, but not a mammalian target of rapamycin-dependent, pathway. Thus, our findings indicated that the AKT1-STAT1 signaling axis negatively regulates neutrophil recruitment and activation in ALI and S. aureus infection in mice.

Apoptotic and inflammatory signaling via Fas and tumor necrosis factor receptor I contribute to the development of chest trauma-induced septic acute lung injury

BACKGROUND

Direct acute lung injury (ALI) is still associated with a high mortality, whereas the underlying pathomechanisms are not yet fully understood. In this regard, epithelial cell death in the lungs has been attributed an important role in the pathogenesis of this clinical entity. Based on this background here, we hypothesized that signaling through Fas and tumor necrosis factor receptor 1 (TNFR-1) is involved in mediating apoptosis and inflammation in chest trauma induced septic ALI.

METHODS

Male C57BL/6 mice (wild-type [WT]), male mutant mice expressing nonfunctional Fas receptor (B6.MRL-Faslpr/J [lpr]) (lpr) and male TNFR-1-deficient mice (TNFR-1(-/-)) were subjected to a model of direct ALI consisting of blunt chest trauma followed by cecal ligation and puncture.Cytokine/chemokine concentrations of plasma, bronchoalveolar lavage (BAL) fluids, and lung tissue were investigated as well as BAL protein and lung myeloperoxidase. Lung histology was assessed; lung caspase 3, TUNEL-positive cells, and apoptotic polymorphonuclear neutrophil were measured, followed by a survival study.

RESULTS

Cytokine/chemokine levels in plasma, BAL, and lung tissue were markedly increased in WT animals following ALI, whereas lpr and TNFR-1((-/-) showed significantly decreased levels. BAL protein levels were substantially elevated following ALI, but lpr animals presented markedly diminished protein levels compared with WT and TNFR-1(-/-) animals. Lung myeloperoxidase level was only increased 12 hours after ALI in WT animals, whereas lung myeloperoxidase levels in lpr and TNFR-1(-/-) animals were not increased compared with sham. Lung histology revealed beneficial effects in lpr and TNFR-1(-/-). Lung active caspase 3 after ALI was substantially decreased in lpr and TNFR-1(-/-) mice compared with WT. Interestingly, an early but not persisting survival benefit was observed in lpr and TNFR-1 animals(-/-).

CONCLUSION

Pathomechanistically, Fas and TNFR-1 signaling contributed to the apoptotic and inflammatory response in a clinically relevant double-hit model of trauma-induced septic ALI. Moreover, this was associated with a temporary survival benefit.

The dichotomy of inhibiting nuclear factor kappa-B in pneumonia

Activation of nuclear factor kappa-B (NF-κB) results in its translocation from the cytoplasm to the nucleus and binding to the promoters of a large number of genes, including those encoding proinflammatory cytokines and other mediators that can contribute to organ system dysfunction in severe infection. While inhibition of NF-κB activation has been proposed as a therapeutic approach in critical illness, several studies have indicated that such an approach may have deleterious effects in persistent infectious states, such as pneumonia. A new report from Devaney and colleagues shows that while inhibition of NF-κB may be useful in severe pneumonia associated with rapid progression to mortality, it leads to worsened pulmonary injury with increased bacterial numbers in the lungs in a model of prolonged pneumonia. Such data raise concerns about therapeutic approaches targeting NF-κB in critically ill patients with persistent infection.

Inhibition of IκB kinase reduces the multiple organ dysfunction caused by sepsis in the mouse

Nuclear factor κB (NF-κB) plays a pivotal role in sepsis. Activation of NF-κB is initiated by the signal-induced ubiquitylation and subsequent degradation of inhibitors of kappa B (IκBs) primarily via activation of the IκB kinase (IKK). This study was designed to investigate the effects of IKK inhibition on sepsis-associated multiple organ dysfunction and/or injury (MOD) and to elucidate underlying signaling mechanisms in two different in vivo models: male C57BL/6 mice were subjected to either bacterial cell wall components [lipopolysaccharide and peptidoglycan (LPS/PepG)] or underwent cecal ligation and puncture (CLP) to induce sepsis-associated MOD. At 1 hour after LPS/PepG or CLP, mice were treated with the IKK inhibitor IKK 16 (1 mg/kg body weight). At 24 hours, parameters of organ dysfunction and/or injury were assessed in both models. Mice developed a significant impairment in systolic contractility (echocardiography), and significant increases in serum creatinine, serum alanine aminotransferase and lung myeloperoxidase activity, thus indicating cardiac dysfunction, renal dysfunction, hepatocellular injury and lung inflammation, respectively. Treatment with IKK 16 attenuated the impairment in systolic contractility, renal dysfunction, hepatocellular injury and lung inflammation in LPS/PepG-induced MOD and in polymicrobial sepsis. Compared with mice that were injected with LPS/PepG or underwent CLP, immunoblot analyses of heart and liver tissues from mice that were injected with LPS/PepG or underwent CLP and were also treated with IKK 16 revealed: (1) significant attenuation of the increased phosphorylation of IκBα; (2) significant attenuation of the increased nuclear translocation of the NF-κB subunit p65; (3) significant attenuation of the increase in inducible nitric oxide synthase (iNOS) expression; and (4) a significant increase in the phosphorylation of Akt and endothelial nitric oxide synthase (eNOS). Here, we report for the first time that delayed IKK inhibition reduces MOD in experimental sepsis. We suggest that this protective effect is (at least in part) attributable to inhibition of inflammation through NF-κB, the subsequent decrease in iNOS expression and the activation of the Akt-eNOS survival pathway.

Curcumin modulates the inflammatory response and inhibits subsequent fibrosis in a mouse model of viral-induced acute respiratory distress syndrome

Acute Respiratory Distress Syndrome (ARDS) is a clinical syndrome characterized by diffuse alveolar damage usually secondary to an intense host inflammatory response of the lung to a pulmonary or extrapulmonary infectious or non-infectious insult often leading to the development of intra-alveolar and interstitial fibrosis. Curcumin, the principal curcumoid of the popular Indian spice turmeric, has been demonstrated as an anti-oxidant and anti-inflammatory agent in a broad spectrum of diseases. Using our well-established model of reovirus 1/L-induced acute viral pneumonia, which displays many of the characteristics of the human ALI/ARDS, we evaluated the anti-inflammatory and anti-fibrotic effects of curcumin. Female CBA/J mice were treated with curcumin (50 mg/kg) 5 days prior to intranasal inoculation with 10(7)pfu reovirus 1/L and daily, thereafter. Mice were evaluated for key features associated with ALI/ARDS. Administration of curcumin significantly modulated inflammation and fibrosis, as revealed by histological and biochemical analysis. The expression of IL-6, IL-10, IFNγ, and MCP-1, key chemokines/cytokines implicated in the development of ALI/ARDS, from both the inflammatory infiltrate and whole lung tissue were modulated by curcumin potentially through a reduction in the phosphorylated form of NFκB p65. While the expression of TGFß1 was not modulated by curcumin, TGFß Receptor II, which is required for TGFß signaling, was significantly reduced. In addition, curcumin also significantly inhibited the expression of α-smooth muscle actin and Tenascin-C, key markers of myofibroblast activation. This data strongly supports a role for curcumin in modulating the pathogenesis of viral-induced ALI/ARDS in a pre-clinical model potentially manifested through the alteration of inflammation and myofibroblast differentiation.

Protective effects of polydatin on septic lung injury in mice via upregulation of HO-1

The present study was carried out to investigate the effects and mechanisms of polydatin (PD) in septic mice. The model of cecal ligation and puncture (CLP-)induced sepsis was employed. Pretreatment of mice with PD (15, 45, and 100 mg/kg) dose-dependently reduced sepsis-induced mortality and lung injury, as indicated by alleviated lung pathological changes and infiltration of proteins and leukocytes. In addition, PD inhibited CLP-induced serum tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) production, lung cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase isoform (iNOS) protein expressions and NF-κB activation. Notably, PD upregulated the expression and activity of heme oxygenase (HO-)1 in lung tissue of septic mice. Further, the protective effects of PD on sepsis were abrogated by ZnPP IX, a specific HO-1 inhibitor. These findings indicated that PD might be an effective antisepsis drug.