Endotoxin, septic shock and acute lung injury: neutrophils, macrophages and inflammatory mediators

Identification of a distinct cluster of GDF15high macrophages induced by in vitro differentiation exhibiting anti-inflammatory activities

Introduction

Macrophage-mediated inflammatory response may have crucial roles in the pathogenesis of a variety of human diseases. Growth differentiation factor 15 (GDF15) is a cytokine of the transforming growth factor-β superfamily, with potential anti-inflammatory activities. Previous studies observed in human lungs some macrophages which expressed a high level of GDF15.

Methods

In the present study, we employed multiple techniques, including immunofluorescence, flow cytometry, and single-cell RNA sequencing, in order to further clarify the identity of such GDF15high macrophages.

Results

We demonstrated that macrophages derived from human peripheral blood mononuclear cells and rat bone marrow mononuclear cells by in vitro differentiation with granulocyte-macrophage colony stimulating factor contained a minor population (~1%) of GDF15high cells. GDF15high macrophages did not exhibit a typical M1 or M2 phenotype, but had a unique molecular signature as revealed by single-cell RNA sequencing. Functionally, the in vitro derived GDF15high macrophages were associated with reduced responsiveness to pro-inflammatory activation; furthermore, these GDF15high macrophages could inhibit the pro-inflammatory functions of other macrophages via a paracrine mechanism. We further confirmed that GDF15 per se was a key mediator of the anti-inflammatory effects of GDF15high macrophage. Also, we provided evidence showing that GDF15high macrophages were present in other macrophage-residing human tissues in addition to the lungs. Further scRNA-seq analysis in rat lung macrophages confirmed the presence of a GDF15high sub-population. However, these data indicated that GDF15high macrophages in the body were not a uniform population based on their molecular signatures. More importantly, as compared to the in vitro derived GDF15high macrophage, whether the tissue resident GDF15high counterpart is also associated with anti-inflammatory functions remains to be determined. We cannot exclude the possibility that the in vitro priming/induction protocol used in our study has a determinant role in inducing the anti-inflammatory phenotype in the resulting GDF15high macrophage cells.

Conclusion

In summary, our results suggest that the GDF15high macrophage cells obtained by in vitro induction may represent a distinct cluster with intrinsic anti-inflammatory functions. The (patho)physiological importance of these cells in vivo warrants further investigation.

Exploration of the role of oxidative stress-related genes in LPS-induced acute lung injury via bioinformatics and experimental studies

During the progression of acute lung injury (ALI), oxidative stress and inflammatory responses always promote each other. The datasets analyzed in this research were acquired from the Gene Expression Omnibus (GEO) database. The Weighted Gene Co-expression Network Analysis (WGCNA) and limma package were used to obtain the ALI-related genes (ALIRGs) and differentially expressed genes (DEGs), respectively. In total, two biological markers (Gch1 and Tnfaip3) related to oxidative stress were identified by machine learning algorithms, Receiver Operator Characteristic (ROC), and differential expression analyses. The area under the curve (AUC) value of biological markers was greater than 0.9, indicating an excellent power to distinguish between ALI and control groups. Moreover, 15 differential immune cells were selected between the ALI and control samples, and they were correlated to biological markers. The transcription factor (TF)-microRNA (miRNA)-Target network was constructed to explore the potential regulatory mechanisms. Finally, based on the quantitative reverse transcription polymerase chain reaction (qRT-PCR), the expression of Gch1 and Tnfaip3 was significantly higher in ALI lung tissue than in healthy controls. In conclusion, the differences in expression profiles between ALI and normal controls were found, and two biological markers were identified, providing a research basis for further understanding the pathogenesis of ALI.

Ferret acute lung injury model induced by repeated nebulized lipopolysaccharide administration

Inflammatory lung diseases affect millions of people worldwide. These diseases are caused by a number of factors such as pneumonia, sepsis, trauma, and inhalation of toxins. Pulmonary function testing (PFT) is a valuable functional methodology for better understanding mechanisms of lung disease, measuring disease progression, clinical diagnosis, and evaluating therapeutic interventions. Animal models of inflammatory lung diseases are needed that accurately recapitulate disease manifestations observed in human patients and provide an accurate prediction of clinical outcomes using clinically relevant pulmonary disease parameters. In this study, we evaluated a ferret lung inflammation model that closely represents multiple clinical manifestations of acute lung inflammation and injury observed in human patients. Lipopolysaccharide (LPS) from Pseudomonas aeruginosa was nebulized into ferrets for 7 repeated daily doses. Repeated exposure to nebulized LPS resulted in a restrictive pulmonary injury characterized using Buxco forced maneuver PFT system custom developed for ferrets. This is the first study to report repeated forced maneuver PFT in ferrets, establishing lung function measurements pre- and post-injury in live animals. Bronchoalveolar lavage and histological analysis confirmed that LPS exposure elicited pulmonary neutrophilic inflammation and structural damage to the alveoli. We believe this ferret model of lung inflammation, with clinically relevant disease manifestations and parameters for functional evaluation, is a useful pre-clinical model for understanding human inflammatory lung disease and for the evaluation of potential therapies.

The Alleviation of LPS-Induced Murine Acute Lung Injury by GSH-Mediated PEGylated Artesunate Prodrugs

Acute lung injury (ALI) or its aggravated stage acute respiratory distress syndrome (ARDS) is a common severe clinical syndrome in intensive care unit, may lead to a life-threatening form of respiratory failure, resulting in high mortality up to 30–40% in most studies. Nanotechnology-mediated anti-inflammatory therapy is an emerging novel strategy for the treatment of ALI, has been demonstrated with unique advantages in solving the dilemma of ALI drug therapy. Artesunate (ART), a derivative of artemisinin, has been reported to have anti-inflammatory effects. Therefore, in the present study, we designed and synthesized PEGylated ART prodrugs and assessed whether ART prodrugs could attenuate lipopolysaccharide (LPS) induced ALI in vitro and in vivo. All treatment groups were conditioned with ART prodrugs 1 h before challenge with LPS. Significant increased inflammatory cytokines production and decreased GSH levels were observed in the LPS stimulated mouse macrophage cell line RAW264.7. Lung histopathological changes, lung W/D ratio, MPO activity and total neutrophil counts were increased in the LPS-induced murine model of ALI via nasal administration. However, these results can be reversed to some extent by treatment of ART prodrugs. The effectiveness of mPEG_2k-SS-ART in inhibition of ALI induced by LPS was confirmed. In conclusion, our results demonstrated that the ART prodrugs could attenuate LPS-induced ALI effectively, and mPEG_2k-SS-ART may serve as a novel strategy for treatment of inflammation induced lung injury.

Nintedanib Regulates GRK2 and CXCR2 to Reduce Neutrophil Recruitment in Endotoxin-Induced Lung Injury

The role of nintedanib, a multiple tyrosine kinase inhibitor, in the treatment of sepsis-induced acute lung injury (ALI) remains unclear. Lipopolysaccharide (LPS), also known as endotoxin, has been used to induce ALI. The goal of this study was to assess the effect of nintedanib in attenuating the histopathological changes of LPS-induced ALI. Nintedanib was administered via oral gavage to male C57BL/6 mice 24 h and 10 min before intratracheal endotoxin instillation. Lung histopathological characteristics, adhesion molecule expression, and the regulatory signaling pathways of neutrophil chemotaxis were analyzed after 24 h. We found that nintedanib significantly reduced histopathological changes and neutrophil recruitment in LPS-induced ALI. The number of neutrophils in bronchoalveolar lavage fluid (BALF) was reduced in nintedanib-treated relative to untreated mice with ALI. Nintedanib mediated the downregulation of the chemotactic response to LPS by reducing the expression of adhesion molecules and the phosphorylated p38:total p38 mitogen-activated protein kinase (MAPK) ratio in the lungs of mice with ALI. Nintedanib also reduced the expression of lymphocyte antigen 6 complex locus G6D (Ly6G) and very late antigen 4 (VLA-4) in BALF neutrophils and mediated the downregulation of chemokine (C-X-C motif) receptor 2 (CXCR2) and upregulation of G protein-coupled receptor kinase 2 (GRK2) activity in peripheral blood neutrophils in mice with LPS-induced ALI. Nintedanib improved the histopathological changes of LPS-induced ALI by reducing neutrophil chemotaxis. These effects were mediated by the inhibition of adhesion molecules via the activation of GRK2 and the inhibition of p38 MAPK and CXCR2.

Inflammatory Activity in Atelectatic and Normally Aerated Regions During Early Acute Lung Injury

RATIONALE AND OBJECTIVES

Pulmonary atelectasis presumably promotes and facilitates lung injury. However, data are limited on its direct and remote relation to inflammation. We aimed to assess regional 2-deoxy-2-[¹⁸F]-fluoro-D-glucose (¹⁸F-FDG) kinetics representative of inflammation in atelectatic and normally aerated regions in models of early lung injury.

MATERIALS AND METHODS

We studied supine sheep in four groups: Permissive Atelectasis (n = 6)-16 hours protective tidal volume (V_T) and zero positive end-expiratory pressure; Mild (n = 5) and Moderate Endotoxemia (n = 6)- 20-24 hours protective ventilation and intravenous lipopolysaccharide (Mild = 2.5 and Moderate = 10.0 ng/kg/min), and Surfactant Depletion (n = 6)-saline lung lavage and 4 hours high V_T. Measurements performed immediately after anesthesia induction served as controls (n = 8). Atelectasis was defined as regions of gas fraction <0.1 in transmission or computed tomography scans. ¹⁸F-FDG kinetics measured with positron emission tomography were analyzed with a three-compartment model.

RESULTS

¹⁸F-FDG net uptake rate in atelectatic tissue was larger during Moderate Endotoxemia (0.0092 ± 0.0019/min) than controls (0.0051 ± 0.0014/min, p = 0.01). ¹⁸F-FDG phosphorylation rate in atelectatic tissue was larger in both endotoxemia groups (0.0287 ± 0.0075/min) than controls (0.0198 ± 0.0039/min, p = 0.05) while the ¹⁸F-FDG volume of distribution was not significantly different among groups. Additionally, normally aerated regions showed larger ¹⁸F-FDG uptake during Permissive Atelectasis (0.0031 ± 0.0005/min, p < 0.01), Mild (0.0028 ± 0.0006/min, p = 0.04), and Moderate Endotoxemia (0.0039 ± 0.0005/min, p < 0.01) than controls (0.0020 ± 0.0003/min).

CONCLUSION

Atelectatic regions present increased metabolic activation during moderate endotoxemia mostly due to increased ¹⁸F-FDG phosphorylation, indicative of increased cellular metabolic activation. Increased ¹⁸F-FDG uptake in normally aerated regions during permissive atelectasis suggests an injurious remote effect of atelectasis even with protective tidal volumes.

VISTA Re-programs Macrophage Biology Through the Combined Regulation of Tolerance and Anti-inflammatory Pathways

We present the novel finding that V-domain Ig suppressor of T cell activation (VISTA) negatively regulates innate inflammation through the transcriptional and epigenetic re-programming of macrophages. Representative of VISTA re-programming is the ability of VISTA agonistic antibodies to augment LPS tolerance and reduce septic shock lethality in mice. This anti-inflammatory effect of anti-VISTA was mimicked in vitro demonstrating that anti-VISTA treatment caused a significant reduction in LPS-induced IL-12p40, IL-6, CXCL2, and TNF; all hallmark pro-inflammatory mediators of endotoxin shock. Even under conditions that typically "break" LPS tolerance, VISTA agonists sustained a macrophage anti-inflammatory profile. Analysis of the proteomic and transcriptional changes imposed by anti-VISTA show that macrophage re-programming was mediated by a composite profile of mediators involved in both macrophage tolerance induction (IRG1, miR221, A20, IL-10) as well as transcription factors central to driving an anti-inflammatory profile (e.g., IRF5, IRF8, NFKB1). These findings underscore a novel and new activity of VISTA as a negative checkpoint regulator that induces both tolerance and anti-inflammatory programs in macrophages and controls the magnitude of innate inflammation in vivo.

Dihydroquercetin attenuates lipopolysaccharide-induced acute lung injury through modulating FOXO3-mediated NF-κB signaling via miR-132-3p

BACKGROUND

Dihydroquercetin (DHQ) is a potent flavonoid which has been demonstrated to have multiple biological activities including anti-inflammation activity, antioxidant activity as well as anti-cancer activity etc. Recently, many studies have focused on the antioxidant activity of DHQ. However, the use of the anti-inflammation activity of DHQ in acute lung injury (ALI) has not been reported.

METHODS

Cell viability was examined by CCK-8 assay. The relative expression of miR-132-3p, FOXO3 were detected by qPCR. The levels of TNF-α, IL-6 and IL-1β were detected using enzyme-linked immunosorbent assay. The amount of apoptosis cells was detected by flow cytometry. The protein levels of Bcl-2, Bax, p-p65 and p-IκBα were measured by western blot.

RESULTS

We found that DHQ-induced the expression of miR-132-3p in LPS-induced ALI. Overexpression of miR-132-3p resulted in the inhibition of FOXO3 expression and then suppressed FOXO3-activated NF-κB pathway, attenuating LPS-induced inflammatory response and apoptosis.

CONCLUSION

We demonstrated FOXO3 to be a target of miR-132-3p, and DHQ could induce the expression of miR-132-3p, relieving LPS-induced ALI via miR-132-3p/FOXO3/NF-κB axis, providing a promising therapeutic target for ALI.

Acetylated Polysaccharides From Pleurotus geesteranus Alleviate Lung Injury Via Regulating NF-κB Signal Pathway

The present work investigated the anti-inflammatory, antioxidant, and lung protection effects of acetylated Pleurotus geesteranus polysaccharides (AcPPS) on acute lung injury (ALI) mice. The acetylation of AcPPS was successfully shown by the peaks of 1737 cm⁻¹ and 1249 cm⁻¹ by FTIR. The animal experiments demonstrated that lung damage can be induced by zymosan. However, the supplementation of AcPPS had potential effects on reducing lung index, remitting inflammatory symptoms (TNF-α, IL-1β, and IL-6), inhibiting NF-κB signal pathway based on up-regulating the level of IκBα and down-regulating p-IκBα level by Western blotting and immunofluorescence assay, preventing oxidative stress (ROS, SOD, GSH-Px, CAT, T-AOC, and MDA), reducing lipid accumulation (TC, TG, LDL-C, HDL-C, and VLDL-C), and alleviating lung functions by histopathologic observation. These results demonstrated that AcPPS might be suitable for natural food for prevention or remission in ALI.

Anti-inflammatory effect of octyl gallate in alveolar macrophages cells and mice with acute lung injury

Acute lung injury (ALI) is an inflammatory process, and has high incidence and mortality. ALI and the acute respiratory distress syndrome are two common complications worldwide that result in acute lung failure, sepsis, and death. Pro-inflammatory substances, such as cytokines and chemokines, are responsible for activating the body's defense mechanisms and usually mediate inflammatory processes. Therefore, the research of substances that decrease the uncontrolled response of organism is seen as potential for patients with ALI. Octyl gallate (OG) is a phenolic compound with therapeutic actions namely antimicrobial, antiviral, and antifungal. In this study, we evaluated its action on lipopolysaccharide (LPS)-activated alveolar macrophages RAW 264.7 cells and ALI in male mice. Our results demonstrated protective effects of OG in alveolar macrophages activated with LPS and mice with ALI. The OG treatment significantly decreased the inflammatory markers in both studies in vitro and in vivo. The data suggested that OG can act as an anti-inflammatory agent for ALI.

Ma Xing Shi Gan Decoction Attenuates PM2.5 Induced Lung Injury via Inhibiting HMGB1/TLR4/NFκB Signal Pathway in Rat

Ma Xing Shi Gan Decoction (MXD), a classical traditional Chinese medicine prescription, is widely used for the treatment of upper respiratory tract infection. However, the effect of MXD against particulate matters with diameter of less than 2.5 μm (PM2.5) induced lung injury remains to be elucidated. In this study, rats were stimulated with PM2.5 to induce lung injury. MXD was given orally once daily for five days. Lung tissues were harvested to assess pathological changes and edema. Myeloperoxidase (MPO) activity and malonaldehyde (MDA) content in lung were determined to evaluate the degree of injury. To assess the barrier disruption, the bronchoalveolar lavage fluid (BALF) was collected to determine the total protein content and count the number of neutrophils and macrophages. For evaluating the activation of macrophage in lung tissue, CD68 was detected using immunohistochemistry (IHC). The levels of inflammatory factors including tumor necrosis factor-alpha (TNF-α), interleukin-1beta (IL-1β), and interleukin-6 (IL-6) in BALF and serum were measured. In vitro, a PM2.5-activated RAW 264.7 macrophages inflammatory model was introduced. To evaluate the protective effect of MXD-medicated serum, the cell viability and the release of inflammatory factors were measured. The effects of MXD on the High mobility group box-1/Toll-like receptor 4/Nuclear factor-kappa B (HMGB1/TLR4/NFκB) pathway in lung tissue and RAW 264.7 cells were assessed by Western blot. For further confirming the protective effect of MXD was mediated by inhibiting the HMGB1/TLR4/NFκB pathway, RAW 264.7 cells were incubated with MXD-medicated serum alone or MXD-medicated serum plus recombinant HMGB1 (rHMGB1). MXD significantly ameliorated the lung injury in rats, as evidenced by decreases in the pathological score, lung edema, MPO activity, MDA content, CD68 positive macrophages number, disruption of alveolar capillary barrier and the levels of inflammatory factors. In vitro, MXD-medicated serum increased cell viability and inhibited the release of inflammatory cytokines. Furthermore, MXD treatment was found to inhibit HMGB1/TLR4/NFκB signal pathway both in vivo and in vitro. Moreover, the protection of MXD could be reversed by rHMGB1 in RAW 264.7. Taken together, these results suggest MXD protects rats from PM2.5 induced acute lung injury, possibly through the modulation of HMGB1/TLR4/NFκB pathway and inflammatory responses.

L6H9 attenuates LPS-induced acute lung injury in rats through targeting MD2

Acute lung injury (ALI) is a clinical syndrome characterized by respiratory failure and acute inflammatory response. Myeloid differentiation protein 2 (MD2) has been reported to play a pivotal role in the recognition of LPS and LPS-mediates inflammatory response. There have been no clinically effective therapeutic drugs for ALI. L6H9, an inhibitor of MD2, showed anti-inflammatory effects and cardiac protective activity. However, its effect on ALI has not been elucidated. In this study, intratracheal instillation of LPS was employed to induce ALI in rats. L6H9 pretreatment attenuates LPS-induced pathological variations in lung tissue and pulmonary edema. LPS instillation enhanced lung microvascular permeability, thereby causing inflammatory cells flow into bronchoalveolar lavage fluid (BALF). However, L6H9 inhibited the LPS-induced upregulation of total protein concentration and the number of inflammatory cells in BALF. In the meantime, macrophages infiltration in lung tissue induced by LPS was also mitigated by L6H9 treatment. Furthermore, L6H9 suppressed LPS-induced inflammatory cytokines expression in BALF, serum, and lung tissue. It is noteworthy that LPS-induced MD2/TLR4 complex formation was inhibited by L6H9 in lung tissue. On the whole, these results show that L6H9 can attenuate LPS-induced ALI in vivo by targeting MD2. Our study provide new candidate for the treatment of ALI.

The relation of oxidative stress and apoptosis to histopathologic alterations in the lungs as a result of global cerebral ischemia

Heart attack and oxygen deficiency may cause necrosis in the brain and other tissues. We investigated the histopathological effects of nitric oxide (NO) on ischemia/reperfusion in lung and hippocampus using a rat brain bilateral occlusion ischemia model. Male rats were assigned to sham (SH), ischemic preconditioning (PC), global ischemia (GI) and ischemic reperfusion (IR) groups. Before ischemia was induced, blood was drawn to induce hypovolemic hypotension and for blood gas testing. After sacrifice, samples of hippocampus were harvested. Sections were examined using hematoxylin and eosin (H & E) staining and immunostaining using primary antibodies for GFAP, S100β, iNOS, eNOS and the TUNEL method. Following ischemia, we found evidence of gliosis induced oxidative stress and apoptosis in the hippocampus. No significant differences were detected between the SH and PC groups. In the GI and IR groups, apoptosis and necrosis were observed in the hippocampus. Lung sections were stained with H & E and Masson's trichrome (MT) and immunostained for iNOS and eNOS. The TUNEL method was used to detect apoptosis. Interstitial edema, vascular congestion, intra-alveolar hemorrhage, perivascular edema, neutrophil infiltration and disruption of alveoli were observed after global ischemia and ischemic reperfusion. Inflammatory cells were detected in the connective tissue. The IR and GI groups exhibited significantly more apoptotic cells than the SH or PC groups. Free radicals, such as nitric oxide (NO), that appear following ischemia and reperfusion in the brain may also injure the lungs. Increased NO in both lung and brain tissue suggests that apoptosis in these organs can be induced by reactive nitrogen species.

IRF-1 Intervention in the Classical ROS-Dependent Release of NETs during LPS-Induced Acute Lung Injury in Mice

Previously, we demonstrated that neutrophil extracellular traps (NETs) play an essential role in lipopolysaccharide (LPS)-induced acute lung injury. However, the underlying mechanism is unclear. In this study, we showed that knockout of interferon regulatory factor 1 (IRF-1) in mice strongly attenuated the generation of NETs and reactive oxygen species (ROS) production in neutrophils from bronchoalveolar lavage fluid and alleviated LPS-induced lung injury and systemic inflammation. Our in vitro experiments demonstrated that LPS-stimulated platelets induce NET release through two distinct processes: an ROS-independent early/rapid NETosis and a later ROS-dependent classical NETosis. Notably, the classical ROS-dependent pathway plays a dominant role in the generation of NETs. Furthermore, we showed that IRF-1 knockout does not affect the formation of NETs in early/rapid NETosis, but significantly attenuates ROS production and the generation of NETs in classical NETosis, which determines the total levels of NETs released by LPS-stimulated platelets. In conclusion, IRF-1 deficiency plays a key role in moderating the excessive NETs formed via ROS in the classical pathway and retaining the protective role of the low-NET levels generated in early/rapid NETosis, which may serve as a novel target in acute lung injury/acute respiratory distress syndrome.

GADD45β plays a protective role in acute lung injury by regulating apoptosis in experimental sepsis in vivo

Sepsis is a systemic inflammatory response syndrome due to microbial infection. Growth arrest and DNA-damage-inducible 45 beta (GADD45β) are induced by genotoxic stress and inflammatory cytokines. However, the role of GADD45β during bacterial infection remains unclear. This study was aimed at investigating the role of GADD45β in sepsis. We used GADD45β-knockout (KO) mice and C57BL/6J wild-type (WT) mice. Experimental sepsis was induced by lipopolysaccharide (LPS) administration or cecal ligation and puncture (CLP). Sepsis-induced mortality was higher in GADD45β-KO mice than in WT mice. Histopathological data demonstrated LPS treatment markedly increased lung injury in GADD45β-KO mice as compared to that in WT mice; however, no significant difference was observed in the liver and kidney. Further, mRNA levels of inflammatory cytokines, such as Il-1β, Il-6, Il-10, and Tnf-α, were higher in the lungs of LPS-treated GADD45β-KO mice than in WT mice. Interestingly, plasma levels of these inflammatory cytokines were decreased in LPS-administered GADD45β-KO mice. A significant increase in lung cell apoptosis was observed at early time points in GADD45β-KO mice after administration of LPS as compared to that in WT mice. In line with LPS-induced apoptosis, JNK, and p38 activity was higher in the lung of GADD45β-KO mice at 3 hr after LPS treatment than that in WT mice. In summary, this study is the first to demonstrate the protective role of GADD45β in sepsis and the results suggest that GADD45β could be used as a novel therapeutic target to cure sepsis.

MicroRNA-326 aggravates acute lung injury in septic shock by mediating the NF-κB signaling pathway

Our previous studies have demonstrated that the activation of the nuclear factor-kappa B (NF-κB) signaling pathway contributes to the development of lipopolysaccharide (LPS)-induced acute lung injury (ALI) as well as an inflammatory reaction, and its inhibition may provide future therapeutic values. Thereby, this study aims to explore the effects of miR-326 on inflammatory response and ALI in mice with septic shock via the NF-κB signaling pathway. The study included normal mice and LPS-induced mouse models of septic shock with ALI. Modeled mice were transfected with the blank plasmid, miR-326 mimic, miR-326 inhibitor, si-BCL2A1 and miR-326 inhibitor + si-BCL2A1. Mean arterial pressure (MAP), airway pressure (AP), heart rate (HR) and lung wet dry (W/D) ratio were determined. Serum levels of interleukin (IL)-6, IL-10, IL-1β, and tumor necrosis factor-α (TNF-α) were detected using ELISA. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis were performed to detect the miR-326 expression and expression levels of BCL2A1, related genes of inflammatory response and the NF-κB signaling pathway in lung tissues. Cell viability and apoptosis were measured using the CCK-8 assay and flow cytometry, respectively. Compared to the ALI models and those transfected with blank plasmid, the up-regulated miR-326 expression and silenced BCL2A1 lead to decreased levels of MAP, increased AP, HR and lung W/D, increased serum levels of IL-6, IL-10, IL-1β and TNF-α, increased expressions of IL-6, IL-1β, TNF-α, NF-κB p65 (p-NF-κB p65), and iNOS with decreased expressions of BCL2A1s as well as inhibition of cell viability and enhanced cell apoptosis; the down-regulated miR-326 expression reversed the aforementioned situation. MiR-326 targeting the BCL2A1 gene activated the NF-κB signaling pathway, resulting in aggravated inflammatory response and lung injury of septic shock with ALI in mice.

Gastrodin protects against LPS-induced acute lung injury by activating Nrf2 signaling pathway

Gastrodin (GAS), a phenolic glucoside derived from Gastrodiaelata Blume, has been reported to have anti-inflammatory effect. The aim of this study was to investigate the effects of GAS on LPS-induced acute lung injury in mice. ALI was induced by the intranasal administration of LPS and GAS was given 1 h or 12 h after LPS treatment. The results indicated that GAS treatment markedly attenuated the damage of lung injury induced by LPS. GAS attenuated the activity of myeloperoxidase (MPO) and down-regulated the levels of pro-inflammatory cytokines TNF-α, IL-6 and IL-1β in BALF. LPS-induced lung edema and lung function were also reversed by GAS. Furthermore, GAS was found to inhibit LPS-induced inflammatory cells infiltration. In addition, treatment of GAS inhibited LPS-induced NF-κB activation and up-regulated the expression of Nrf2 and HO-1. In conclusion, our results indicated that GAS had anti-inflammatory effects on LPS-induced acute lung injury. The anti-inflammatory mechanism of GAS was through the inhibition of NF-κB and activation of Nrf2 signaling pathways.

Shikonin inhibits myeloid differentiation protein 2 to prevent LPS-induced acute lung injury

BACKGROUND AND PURPOSE

Acute lung injury (ALI) is a challenging clinical syndrome, which manifests as an acute inflammatory response. Myeloid differentiation protein 2 (MD2) has an important role in mediating LPS-induced inflammation. Currently, there are no effective molecular-based therapies for ALI or viable biomarkers for predicting the severity of disease. Recent preclinical studies have shown that shikonin, a natural naphthoquinone, prevents LPS-induced inflammation. However, little is known about the underlying mechanisms.

EXPERIMENTAL APPROACH

The binding affinity of shikonin to MD2 was analysed using computer docking, surface plasmon resonance analysis and elisa. In vitro, the anti-inflammatory effect and mechanism of shikonin were investigated through elisa, real-time quantitative reverse transcription PCR, Western blotting and immunoprecipitation assay. In vivo, lung injury was induced by intratracheal administration of LPS and assessed by changes in the histopathological and inflammatory markers. The underlying mechanisms were investigated by immunoprecipitation in lung tissue.

KEY RESULTS

Shikonin directly bound to MD2 and interfered with the activation of toll-like receptor 4 (TLR4) induced by LPS. In cultured macrophages, shikonin inhibited TLR4 signalling and pro-inflammatory cytokine production. These effects were produced through suppression of key signalling proteins including the NF-κB and the MAPK pathway. We also showed that shikonin inhibits MD2-TLR4 complex formation and reduces LPS-induced inflammatory responses in a mouse model of ALI.

CONCLUSIONS AND IMPLICATIONS

Our studies have uncovered the mechanism underlying the biological activity of shikonin in ALI and suggest that the targeting of MD2 may prove to be beneficial as a treatment option for this condition.

Activation of the sweet taste receptor, T1R3, by the artificial sweetener sucralose regulates the pulmonary endothelium

A hallmark of acute respiratory distress syndrome (ARDS) is pulmonary vascular permeability. In these settings, loss of barrier integrity is mediated by cell-contact disassembly and actin remodeling. Studies into molecular mechanisms responsible for improving microvascular barrier function are therefore vital in the development of therapeutic targets for reducing vascular permeability in ARDS. The sweet taste receptor T1R3 is a G protein-coupled receptor, activated following exposure to sweet molecules, to trigger a gustducin-dependent signal cascade. In recent years, extraoral locations for T1R3 have been identified; however, no studies have focused on T1R3 within the vasculature. We hypothesize that activation of T1R3, in the pulmonary vasculature, plays a role in regulating endothelial barrier function in settings of ARDS. Our study demonstrated expression of T1R3 within the pulmonary vasculature, with a drop in expression levels following exposure to barrier-disruptive agents. Exposure of lung microvascular endothelial cells to the intensely sweet molecule sucralose attenuated LPS- and thrombin-induced endothelial barrier dysfunction. Likewise, sucralose exposure attenuated bacteria-induced lung edema formation in vivo. Inhibition of sweet taste signaling, through zinc sulfate, T1R3, or G-protein siRNA, blunted the protective effects of sucralose on the endothelium. Sucralose significantly reduced LPS-induced increased expression or phosphorylation of the key signaling molecules Src, p21-activated kinase (PAK), myosin light chain-2 (MLC2), heat shock protein 27 (HSP27), and p110α phosphatidylinositol 3-kinase (p110αPI3K). Activation of T1R3 by sucralose protects the pulmonary endothelium from edemagenic agent-induced barrier disruption, potentially through abrogation of Src/PAK/p110αPI3K-mediated cell-contact disassembly and Src/MLC2/HSP27-mediated actin remodeling. Identification of sweet taste sensing in the pulmonary vasculature may represent a novel therapeutic target to protect the endothelium in settings of ARDS.

Effects of alliin on LPS-induced acute lung injury by activating PPARγ

Alliin is a garlic organosulfur compound that possesses various pharmacological properties. In the present study, the protective effects and molecular mechanism of alliin on Lipopolysaccharides (LPS)-induced acute lung injury (ALI) were analyzed. LPS-induced ALI was induced in BALB/c mice by intranasal instillation of LPS. Alliin was administered intraperitoneally to mice 1 h after LPS treatment. The results showed that alliin markedly inhibited lung myeloperoxidase (MPO) activity and wet/dry (W/D) ratio induced by LPS. Alliin also inhibited TNF-α and IL-1β in the bronchoalveolar lavage fluid (BALF) induced by LPS. Furthermore, LPS-induced lung pathological injury was attenuated by treatment of alliin. LPS-induced NF-κB activation was significantly inhibited by alliin. In addition, the expression of peroxisome proliferator-activated receptor γ (PPARγ) was up-regulated by treatment of alliin. Taken together, these results suggested that alliin protected against LPS-induced ALI by activating PPARγ, which subsequently inhibited LPS-induced NF-κB activation and inflammatory response. Alliin might be used as an anti-inflammatory agent in the treatment of ALI.

Nedd8 modification of Cullin-5 regulates lipopolysaccharide-induced acute lung injury

Lung infections are major causes of acute lung injury (ALI), with limited effective treatment available. Tumor necrosis factor receptor-associated factor 6 (TRAF6) is an essential adaptor regulating Toll-like receptors (TLRs). We recently identified Cullin-5 (Cul-5) as a prominent component in the regulation of TRAF6 polyubiquitination, but its physiological significance in ALI has not been explored. In this study, we investigated the potential role of Cul-5 in regulating ALI using mice receiving intratracheal instillation of LPS. We observed that Cul-5-deficient mice displayed reduced lung injury compared with wild-type mice as evidenced by histological analysis, alveolar neutrophil infiltration, and lung liquid accumulation. In addition, inflammatory cytokine expression in bronchoalveolar lavage fluid and lung tissue was also markedly reduced in LPS-treated Cul-5-deficient mice. Interestingly, intratracheal adoptive transfer of Cul-5^+/- but not Cul-5^+/+ macrophages attenuated neutrophil recruitment, alveolar inflammation, and loss of barrier function in LPS-challenged wild-type mice. Finally, we demonstrated that Cul-5 neddylation following LPS exposure induced Cul-5 and TRAF6 interaction and, thereby, TFAR6 polyubiquitination, leading to NF-κB activation and generation of proinflammatory cytokines. Our data show that neural precursor cell expressed developmentally downregulated protein 8 (Nedd8) modification of Cul-5 is required for its interaction with TRAF6 and activation of the TLR4-TRAF6 signaling pathway in LPS-induced ALI, a feature that may be explored for therapeutic intervention.

Corynoline attenuates LPS-induced acute lung injury in mice by activating Nrf2

Corynoline, isolated from Corydalis bungeana Turcz, has been reported to possess anti-inflammatory and antibacterial activities. In this study, we aimed to explore the treatment effect of corynoline on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice. In the present study, the signaling pathways were measured by Western blot analysis. The levels of inflammatory cytokines were measured by enzyme-linked immunosorbent assays (ELISA). Additionally, the effects of corynoline on LPS-induced myeloperoxidase (MPO) activity was examined. The results showed that corynoline markedly inhibited LPS-induced neutrophils influx, MPO activity, and inflammatory cytokines IL-1β, TNF-α and IL-6 release. Corynoline also attenuated lung histopathological changes induced by LPS. Furthermore, corynoline inhibited LPS-induced NF-κB activation. In addition, corynoline up-regulated the expression of Nrf2 and HO-1 in a dose-dependent manner. The data suggest that corynoline has a treatment effect on LPS-induced ALI in mice by inhibiting inflammatory response.

Isoalantolactone inhibits LPS-induced inflammation via NF-κB inactivation in peritoneal macrophages and improves survival in sepsis

Sepsis, a clinical syndrome occurring in patients following infection or injury, is a leading cause of mortality worldwide. It involves uncontrolled inflammatory response resulting in multi-organ failure and even death. Isoalantolactone (IAL), a sesquiterpene lactone, is known for its anti-cancer effects. Nevertheless, little is known about the anti-inflammatory effects of IAL, and the role of IAL in sepsis is unclear. In this study, we demonstrated that IAL decreased lipopolysaccharide (LPS)-mediated production of nitric oxide, PEG₂ and cytokines (IL-6, TNF-α) in peritoneal macrophages and RAW 264.7 macrophages. Moreover, molecular mechanism studies indicated that IAL plays an anti-inflammatory role by inhibiting LPS-induced activation of NF-κB pathway in peritoneal macrophages. In vivo, IAL reduced the secretion of IL-6 and TNF-α in serum, and increased the survival rate of mice with LPS-induced sepsis. In addition, IAL attenuated the activation of NF-κB pathway in liver. Taken together, our data suggest that IAL may represent a potentially new drug candidate for the treatment of sepsis.

Geraniin attenuates LPS-induced acute lung injury via inhibiting NF-κB and activating Nrf2 signaling pathways

Geraniin, a typical ellagitannin isolated from Phyllanthusurinaria Linn, has been reported to have anti-inflammatory effect. The aim of the study is to investigate the therapeutic effects of geraniin on LPS-induced acute lung injury (ALI) in mice. The mice were intranasal adminisration of LPS for 12 h. Geraniin was intra-peritoneal injection 1 h after LPS treatment. The results showed that geraniin significantly attenuated LPS-induced pathological changes in the lung. Geraniin also inhibited LPS-induced macrophages and neutrophils infiltration in the lung. Geraniin significantly attenuated LPS-induced elevation of MPO level. LPS-induced TNF-α, IL-6 and IL-1β production were markedly suppressed by treatment of geraniin. Furthermore, geraniin inhibited NF-κB activation in LPS-induced ALI. In addition, geraniin was found to up-regulate the expression of Nrf2 and HO-1. In conclusion, these data suggested that geraniin had therapeutic effects in LPS-induced ALI by inhibiting NF-κB and activating Nrf2 signaling pathways.

In vitro and in vivo inhibitory effects of 6-hydroxyrubiadin on lipopolysaccharide-induced inflammation

Inflammation is a defensive response against a multitude of harmful stimuli and stress conditions such as tissue injury, and is one of the most common pathological processes of human diseases. 6-Hydroxyrubiadin, an anthraquinone isolated from Rubia cordifolia L., exhibits several bioactive properties. The aim of this study was to evaluate whether 6-hydroxyrubiadin can reduce the production of pro-inflammatory cytokines and ameliorate acute lung injury (ALI) in a mouse model. In this study, we demonstrated that 6-hydroxyrubiadin suppressed lipopolysaccharide (LPS)-induced nuclear factor-kappa B activation as well as the phosphorylation of c-Jun N-terminal kinase in RAW 264.7 macrophages. In addition, we also showed that 6-hydroxyrubiadin inhibited the expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6 in phorbol myristate acetate (PMA)-primed U937 and RAW 264.7 cells. Furthermore, 6-hydroxyrubiadin treatment reduced the production of these cytokines in vivo and attenuated the severity of LPS-induced ALI. Thus, these results suggested that 6-hydroxyrubiadin may be a potential therapeutic candidate for the treatment of inflammation and inflammatory diseases.

Association of LPS chemotype of Mannheimia (Pasteurella) haemolytica A1 with disease virulence in a model of ovine pneumonic pasteurellosis

Host responses during pneumonic pasteurellosis were compared in sheep infected with strains of Mannheimia (Pasteurella) haemolytica A1 differing in their O-antigen type. Nine-week-old, specific pathogen-free lambs were infected intratracheally with parainfluenza type 3 virus (108 TCID50) followed 7 days later by 5—6 . 107 CFU of M. haemolytica A1 possessing rough (group R, 6 lambs) or smooth (group S, 6 lambs) lipopolysaccharide, or saline (group C, 4 lambs). Group C lambs remained afebrile with no evidence of endotoxaemia or bacteraemia and biochemical parameters were normal. Group R and group S lambs became febrile within 2—3 h postinfection and the response was higher and more prolonged in group R lambs. Four group R and 2 group S lambs developed clinical pneumonic pasteurellosis within 24—48 h and the severity of disease correlated with episodes of endotoxaemia, bacteraemia and elevated eicosanoid concentrations. At postmortem, M. haemolytica (107—109 CFU/g) was isolated from the lungs of all 6 group R lambs but from only 1 group S lamb. The results indicate an association between the incidence and severity of ovine pneumonic pasteurellosis and LPS chemotype and suggest an important role for LPS chemotype in determining host-species susceptibility to lung infection.

Preclinical and clinical evaluation of carbohydrate immunopharmaceuticals in the prevention of sepsis and septic sequelae

Sepsis and sepsis syndrome are significant causes of morbidity and mortality in critically ill patients. Despite technological and therapeutic advances in critical care, sepsis continues to be a pivotal factor in 20-50 % of deaths in surgical intensive care units. It is clear that alternative approaches to the prevention and/or treatment of sepsis must be found. Preclinical data indicate that macrophage activation with (1→3)-β-D-glucans will ameliorate sequelae associated with Gram-negative septicemia. Recent clinical data indicate that macrophage activation with (1→3)-β-D-glucans will significantly reduce septic morbidity and mortality in trauma and/or high-risk surgical patients. This work reviews the preclinical and clinical evaluation of (1→3)-β-D-glucans in the prevention of sepsis and septic sequelae.

Neutrophil-Related Inflammatory Mediators in Septic Acute Respiratory Distress Syndrome

To disclose the participation of neutrophils in septic acute respiratory distress syndrome (ARDS), characteristics of various inflammatory mediators were examined in septic patients. Forty-seven gram-negative septic patients were divided into ARDS (n = 23) and non-ARDS (n = 24) groups at the transferred point to the intensive care unit. The mediators were measured simultaneously at the transferred point, and then subsequently on days 1, 3, and 5. At the transferred point, the ARDS group showed significantly higher levels of interleukin-8 (IL-8), macrophage inflammatory peptide-1-alpha (MIP-1-α), soluble intercellular adhesion molecule-1 (sICAM-1), and neutrophil elas-tase despite lower neutrophil counts compared to the non-ARDS group. The ARDS group sustained significantly higher levels of sICAM-1 until day 5 and neutrophil elas-tase until day 1 compare to the non-ARDS group. Furthermore, nonsurviving ARDS patients (n = 8) showed significantly higher levels of tumor necrosis factor-alpha, IL-6, IL-8, and IL-10 compared to surviving ARDS patients (n = 15) at the transferred point. In conclusion, neutrophil-related inflammatory mediators, IL-8, MIP-1-α, sICAM-1, and neutrophil elastase, appear to possibly participate in septic ARDS. Cytokines might also play an important role in the mortality of such cases.

Bigelovii A Protects against Lipopolysaccharide-Induced Acute Lung Injury by Blocking NF-κB and CCAAT/Enhancer-Binding Protein δ Pathways

Optimal methods are applied to acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS), but the mortality rate is still high. Accordingly, further studies dedicated to identify novel therapeutic approaches to ALI are urgently needed. Bigelovii A is a new natural product and may exhibit anti-inflammatory activity. Therefore, we sought to investigate its effect on lipopolysaccharide- (LPS-) induced ALI and the underlying mechanisms. We found that LPS-induced ALI was significantly alleviated by Bigelovii A treatment, characterized by reduction of proinflammatory mediator production, neutrophil infiltration, and lung permeability. Furthermore, Bigelovii A also downregulated LPS-stimulated inflammatory mediator expressions in vitro. Moreover, both NF-κB and CCAAT/enhancer-binding protein δ (C/EBPδ) activation were obviously attenuated by Bigelovii A treatment. Additionally, phosphorylation of both p38 MAPK and ERK1/2 (upstream signals of C/EBPδ activation) in response to LPS challenge was also inhibited by Bigelovii A. Therefore, Bigelovii A could attenuate LPS-induced inflammation by suppression of NF-κB, inflammatory mediators, and p38 MAPK/ERK1/2-C/EBPδ, inflammatory mediators signaling pathways, which provide a novel theoretical basis for the possible application of Bigelovii A in clinic.

Hesperetin attenuates ventilator-induced acute lung injury through inhibition of NF-κB-mediated inflammation

Hesperetin, a major bioflavonoid in sweet oranges and lemons, has been reported to have anti-inflammatory properties. However, the effect of hesperetin on ventilator-induced acute lung injury has not been studied. In present study, we investigated the protective effect of hesperetin on ventilator-induced acute lung injury in rats. Rats were orally administered hesperetin (10, 20, or 40mg/kg) two hour before acute lung injury was induced by mechanical ventilation. Rats were then randomly divided into six groups: the lung protective ventilation group (n=20, LV group), injurious ventilation group (n=20, HV group), vehicle-treated injurious ventilation group (n=20, LV+vehicle group), hesperetin (10mg/kg)-treated acute lung injury group (n=20, HV+Hsp (10mg)), hesperetin (20mg/kg)-treated acute lung injury group (n=20, HV+Hsp (20mg)), and hesperetin (40mg/kg)-treated acute lung injury group (n=20, HV+Hsp (40mg)). The lung tissues and bronchoalveolar lavage fluid were isolated for subsequent measurements. Treatment with hesperetin dramatically improved the histology of lung tissue, and reduced the wet/dry ratio, myeloperoxidase activity, protein concentration, and production of tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-1β, and MIP-2 in the bronchoalveolar lavage fluid of rats with ventilator-induced acute lung injury. Additionally, our study indicated that this protective effect of hesperetin results from its ability to increase the expression of peroxisome proliferator-activated receptor (PPAR)-γ and inhibit the activation of the nuclear factor (NF)-κB pathway. These results suggest that hesperetin may be a potential novel therapeutic candidate for protection against ventilator-induced acute lung injury.

Pretreatment with andrographolide pills(®) attenuates lipopolysaccharide-induced pulmonary microcirculatory disturbance and acute lung injury in rats

OBJECTIVE

The purpose of this study was to explore the protective effect of AP on LPS-induced PMD and ALI.

METHODS

Male SD rats were continuously infused with LPS (5 mg/kg/h) for one hour to induce PMD and ALI. AP was administrated orally one hour before LPS exposure. Arterial blood pressure and HR were monitored. Blood gas analysis, histological observation, cytokines in plasma, leukocyte recruitment, pulmonary oxidative stress, microvessel permeability, edema, and related proteins were evaluated six hours after LPS challenge.

RESULTS

Rats receiving LPS exhibited significant alterations, including hypotension, tachycardia, increase in cytokines, neutrophil adhesion and infiltration, oxidative stress, and microvessel hyperpermeability, resulting in pulmonary injury and dysfunction. AP (0.18 g/kg or 1.8 g/kg) improved rat survival rate, and significantly attenuated all aforementioned insults, and inhibited LPS-induced increase in adhesion molecules, up-regulation of Cav-1 and Src kinase and NADPH oxidase subunits (p47(phox) and p67(phox) ) membrane translocation in lung tissue, and preserved JAM-1 and claudin-5.

CONCLUSIONS

The results demonstrated the protective effect of AP on LPS-induced PMD and ALI, suggesting the potential of AP as a prophylactic strategy for LPS-induced ALI.

Patchouli alcohol protects against lipopolysaccharide-induced acute lung injury in mice

BACKGROUND

Patchouli alcohol (PA), a natural compound isolated from Pogostemon cablin, has been reported to possess anti-inflammatory activity. However, the effects of PA on lipopolysaccharide (LPS)-induced acute lung injury (ALI) have not yet been studied. In the present study, we investigated in vivo the effect of PA on ALI induced by LPS.

METHODS

Mice were administrated intranasally with LPS to induce lung injury. PA was administrated intraperitoneally 1 h before or after the LPS challenge.

RESULTS

The results showed that PA significantly decreased the wet-to-dry weight ratio of lungs and the number of total cells, neutrophils, and macrophages in bronchoalveolar lavage fluid at 7 h after the LPS challenge. In addition, PA also suppressed the production of inflammatory cytokines, such as tumor necrosis factor-α, interleukin-1β, and interleukin-6 in bronchoalveolar lavage fluid. Furthermore, Western blot analysis showed that PA inhibited the phosphorylation of IκB-α and p65 nuclear factor κB (NF-κB) induced by LPS.

CONCLUSIONS

Our results suggest that the anti-inflammatory effects of PA against LPS-induced ALI may be due to its ability to inhibit NF-κB signaling pathways.

Montelukast reduces sepsis-induced lung and renal injury in rats

This study was undertaken to examine the effects of montelukast (MNT) on lung and kidney injury in lipopolysaccharide (LPS) induced systemic inflammatory response. Rats were randomized into 5 groups (n = 8 rats/group): (i) Control; (ii) LPS treated (10 mg/kg body mass, by intraperitoneal (i.p.) injection); (iii) LPS + MNT (10 mg/kg, per oral (p.o.)); (iv) LPS + MNT (20 mg/kg, p.o); (v) LPS + dexamethasone (DEX; 1 mg/kg, i.p.). Twenty-four hours after sepsis was induced, the lung or kidney:body mass ratio and percent survival of rats were determined. Creatinine, blood urea nitrogen (BUN), albumin, total protein, and LDH activity were measured. Lung and kidney samples were taken for histological assessment and for determination of their malondialdehyde (MDA) and glutathione (GSH) contents. The expression of tumour necrosis factor α (TNF-α) in tissue was evaluated immunohistochemically. LPS significantly increased the organ:body mass ratio, serum creatinine, BUN, and LDH, and decreased serum albumin and total protein levels. MDA levels increased in lung and kidney tissues after treatment with LPS, and there was a concomitant reduction in GSH levels. Immunohistochemical staining of lung and kidney specimens from LPS-treated rats revealed high expression levels of TNF-α. MNT suppresses the release of inflammatory and oxidative stress markers. Additionally, MNT effectively preserved tissue morphology as evidenced by histological evaluation. These results demonstrate that MNT could have lung and renoprotective effects against the inflammatory process during endotoxemia. This effect can be attributed to its antioxidant and (or) anti-inflammatory properties.

A feedback loop in PPARγ-adenosine A2A receptor signaling inhibits inflammation and attenuates lung damages in a mouse model of LPS-induced acute lung injury

Although peroxisome proliferator-activated receptor-γ (PPARγ) and adenosine A2A receptor (A2AR) are reported to be anti-inflammatory factors in acute lung injury (ALI), their internal link and synergic or antagonistic effect after activation are poorly understood. Here, we found that PPARγ and A2AR could upregulate the mRNA and protein expressions of each other in lung tissues of LPS-induced mouse ALI model and murine macrophages. Further investigation demonstrated that PPARγ upregulated A2AR expression by directly binding to a DR10 response element (-218 to -197) within A2AR gene promoter region. Instead of directly interacting with PPARγ, A2AR stimulated PPARγ expression via protein kinase A (PKA)-cAMP response element binding protein (CREB) signaling by provoking the binding of CREB to a cAMP responsive element (CRE)-like site in PPARγ gene promoter region. In addition, combination of PPARγ and A2AR agonists was found to exert obviously better effect on suppressing neutrophil infiltration and inflammatory cytokine expressions, attenuating lung edema, pathological changes and improving lung function of blood gas exchange than their single application. These findings reveal a novel functional positive feedback loop between PPARγ and A2AR signaling to potentialize their effect on inhibiting inflammation and attenuating lung damages in ALI. It suggests that targeting this PPARγ-A2AR signaling rather than PPARγ or A2AR alone may be a more attractive and efficient potential therapeutic strategy for ALI.

Thrombosis in paroxysmal nocturnal hemoglobinuria

The most frequent and feared complication of paroxysmal nocturnal hemoglobinuria (PNH) is thrombosis. Recent research has demonstrated that the complement and coagulation systems are closely integrated with each influencing the activity of the other to the extent that thrombin itself has recently been shown to activate the alternative pathway of complement. This may explain some of the complexity of the thrombosis in PNH. In this review, the recent changes in our understanding of the pathophysiology of thrombosis in PNH, as well as the treatment of thrombosis, will be discussed. Mechanisms explored include platelet activation, toxicity of free hemoglobin, nitric oxide depletion, absence of other glycosylphosphatidylinositol-linked proteins such as urokinase-type plasminogen activator receptor and endothelial dysfunction. Complement inhibition with eculizumab has a dramatic effect in PNH and has a major impact in the prevention of thrombosis as well as its management in this disease.

Neonatal stress modulates sickness behavior: role for proinflammatory cytokines

Neonatal stress increased the duration and augmented symptoms of sickness behavior induced by influenza virus infection or endotoxin challenge in mice. Since proinflammatory cytokines were implicated in sickness behavior, the present study sought to determine the effect of neonatal stress on cytokines-induced sickness behavior and on proinflammatory cytokine secretion. Data indicate that separation of mouse pups from the dams at an early age (maternal separation, MSP) increased the duration and augmented some of the symptoms of sickness behavior induced by proinflammatory cytokines. In addition, MSP partially suppressed cytokine and corticosterone secretion in response to endotoxin administration. These data may suggest that MSP increased sensitivity to the effects of proinflammatory cytokines on sickness behavior following an immune challenge.

Lack of hepatic c-Met and gp130 expression is associated with an impaired antibacterial response and higher lethality after bile duct ligation

The prognosis of liver failure is often determined by infectious and cholestatic complications. As HGF/c-Met and interleukin (IL)-6/gp130 control hepatic cytoprotective pathways, we here investigated their cooperative role during the onset of cholestatic liver injury. Conditional hepatocyte-specific ((Δhepa)) c-Met, gp130 and c-Met/gp130 knockout mice (Cre-loxP system) were subjected to bile duct ligation (BDL) and lipopolysaccharide (LPS) stimulation. gp130(Δhepa) and c-Met/gp130(Δhepa) mice displayed increased lethality associated with severe bacteraemia early after BDL, whereas c-Met(Δhepa) and wild-type mice showed normal survival. Analysis of the innate immune response and the regulation of hepatic antibacterial pathways showed that the LPS-triggered hepatocellular response via the Toll-like receptor-4 pathway was regulated differentially by HGF/c-Met and IL-6/gp130. Activation of p38MAPK, c-Jun N-terminal kinase and signalling transducer and activator of transcription-3 was impaired in gp130(Δ) and c-Met(Δhepa) livers. In addition, the acute-phase response (APR) was reduced in c-Met(Δhepa) livers, whereas gp130(Δhepa) displayed a completely abolished APR. In contrast, TNF-α-dependent NF-κB activation was enhanced in gp130(Δhepa) and c-Met(Δhepa) mice and it was associated with a higher rate of apoptosis and inflammation. Moreover, expression of the neutrophil produced and secreted cathelin-related antimicrobial peptide and of genes related to the inflammasome complex correlated with the strength of the bacterial infection and with TNF-α expression. In conclusion, Gp130 and c-Met are involved in the hepatic antibacterial and innate immune response, control the APR and thus prevent sepsis and liver injury during cholestatic conditions.

Depletion of neutrophil extracellular traps in vivo results in hypersusceptibility to polymicrobial sepsis in mice

Introduction

Although the formation of neutrophil (PMN) extracellular traps (NETs) has been detected during infection and sepsis, their role in vivo is still unclear. This study was performed in order to evaluate the influence of NETs depletion by administration of recombinant human (rh)DNase on bacterial spreading, PMN tissue infiltration and inflammatory response in a mouse model of polymicrobial sepsis.

Methods

In a prospective controlled double-armed animal trial, polymicrobial sepsis was induced by cecal ligation and puncture (CLP). After CLP, mice were treated with rhDNase or phosphate buffered saline, respectively. Survival, colony forming unit (CFU) counts in the peritoneal cavity, lung, liver and blood were determined. PMN and platelet counts, IL-6 and circulating free (cf)-DNA/NETs levels were monitored. PMN infiltration, as well as organ damage, was analyzed histologically in the lungs and liver. Capability and capacity of PMN to form NETs were determined over time.

Results

cf-DNA/NETs were found to be significantly increased 6, 24, and 48 hours after CLP when compared to the levels determined in sham and naïve mice. Peak levels after 24 hours were correlated to enhanced capacity of bone marrow-derived PMN to form NETs after ex vivo stimulation with phorbol-12-myristate-13-acetate at the same time. rhDNase treatment of mice resulted in a significant reduction of cf-DNA/NETs levels 24 hours after CLP (P < 0.001). Although overall survival was not affected by rhDNase treatment, median survival after 24 hours was significantly lower when compared with the CLP group (P < 0.01). In mice receiving rhDNase treatment, CFU counts in the lung (P < 0.001) and peritoneal cavity (P < 0.05), as well as serum IL-6 levels (P < 0.001), were found to be already increased six hours after CLP. Additionally, enhanced PMN infiltration and tissue damage in the lungs and liver were found after 24 hours. In contrast, CFU counts in mice without rhDNase treatment increased later but more strongly 24 hours after CLP (P < 0.001). Similarly, serum IL-6 levels peaked after 24 hours (P < 0.01).

Conclusions

This study shows, for the first time, that depletion of NETs by rhDNase administration impedes the early immune response and aggravates the pathology that follows polymicrobial sepsis in vivo.

Mechanisms mediating propofol protection of pulmonary epithelial cells against lipopolysaccharide-induced cell death

Propofol (2,6-diisopropylphenol) is an anaesthetic agent with anti-oxidant properties. The aim of the present study was to determine whether propofol can protect pulmonary epithelial (A549) cells against lipopolysaccharide (LPS)-induced cell death and, if so, the mechanisms involved. The effects of LPS alone and in combination with propofol on A549 cell death were investigated. Cell viability was determined using the colourimetric 3-(4,5-dimethyl-2 thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Apoptotic A549 cells were detected by flow cytometry, as propidium iodide-negative and annexin-V-positive cells, and terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labelling (TUNEL). Mitochondrial membrane potential (MMP), caspase 9 activity, Ca(2+) concentrations and reactive oxygen species (ROS) were analysed by immunofluorescent methods. Aconitase 2 (ACO2), microtubule-associated light chain 3 (LC3) and beclin-1 levels were evaluated using reverse transcription-polymerase chain reaction and/or western blot analysis. Exposure of A549 cells to 1-50 μg/mL LPS for 3-24 h resulted in the concentration- and time-dependent induction of cell death. Cell apoptosis accounted for approximately 77% of cell death induced by LPS. Propofol (5-150 μmol/L) concentration-dependently inhibited LPS-induced A549 cell death. This protective effect of propofol was accompanied by prevention of LPS-induced mitochondrial dysfunction (reductions in MMP, ACO2 expression and ATP) and was associated with the inhibition of LPS-induced activation of apoptotic signals (caspase 9 activity, ROS overproduction and Ca(2+) accumulation). In addition, propofol blocked LPS-induced overexpression of the autophagy-associated proteins LC3 and beclin-1. The data indicate that propofol protects A549 cells against LPS-induced apoptosis, and probably autophagy, by blocking LPS-induced activation of ROS/caspase 9 pathways and upregulation of LC3 and beclin-1, respectively.

A biomimetic membrane device that modulates the excessive inflammatory response to sepsis

OBJECTIVE

Septic shock has a clinical mortality rate approaching fifty percent. The major clinical manifestations of sepsis are due to the dysregulation of the host's response to infection rather than the direct consequences of the invading pathogen. Central to this initial immunologic response is the activation of leukocytes and microvascular endothelium resulting in cardiovascular instability, lung injury and renal dysfunction. Due to the primary role of leukocyte activation in the sepsis syndrome, a synthetic biomimetic membrane, called a selective cytopheretic device (SCD), was developed to bind activated leukocytes. The incorporation of the SCD along an extracorporeal blood circuit coupled with regional anticoagulation with citrate to lower blood ionized calcium was devised to modulate leukocyte activation in sepsis.

DESIGN

Laboratory investigation.

SETTING

University of Michigan Medical School.

SUBJECTS

Pigs weighing 30-35 kg.

INTERVENTIONS

To assess the effect of the SCD in septic shock, pigs were administered 30×10(10) bacteria/kg body weight of Escherichia coli into the peritoneal cavity and within 1 hr were immediately placed in an extracorporeal circuit containing SCD.

MEASUREMENTS AND MAIN RESULTS

In this animal model, the SCD with citrate compared to control groups without the SCD or with heparin anticoagulation ameliorated the cardiovascular instability and lung sequestration of activated leukocytes, reduced renal dysfunction and improved survival time compared to various control groups. This effect was associated with minimal elevations of systemic circulating neutrophil activation.

CONCLUSIONS

These preclinical studies along with two favorable exploratory clinical trials form the basis of an FDA-approved investigational device exemption for a pivotal multicenter, randomized control trial currently underway.