Intratracheal Instillation Of Lipopolysaccharide Research Articles

S-allylmercaptocysteine ameliorates lipopolysaccharide-induced acute lung injury in mice by inhibiting inflammation and oxidative stress via nuclear factor kappa B and Keap1/Nrf2 pathways

The garlic-derived organosulfur compound S-allylmercaptocysteine (SAMC) has been reported to exhibit anti-inflammatory and anti-oxidative activities, whereas its potential therapeutic effect on lipopolysaccharide (LPS)-induced acute lung injury (ALI) is unknown. In this study, we focused on exploring the therapeutic effects of SAMC on LPS-induced ALI mice and the involvement of underlying molecular mechanisms. BalB/c mice were treated with SAMC (10, 30 and 60 mg/kg) or positive control N-acetylcysteine (NAC, 500 mg/kg) by gavage after intratracheal instillation of LPS for 30 min and were sacrificed 24 h after LPS administration. Our results indicate that the treatment with SAMC not only ameliorated the histological changes but also decreased LPS-triggered lung edema. Moreover, SAMC displayed an anti-inflammatory effect through reducing inflammatory cells infiltration, myeloperoxidase (MPO) formation and inhibiting pro-inflammatory cytokines/mediator production including tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX2) via suppressing the activation of nuclear factor-kappaB (NF-κB) signaling pathway. Furthermore, SAMC attenuated oxidative stress evoked by LPS via diminishing malondialdehyde (MDA) formation and reversing glutathione (GSH) and superoxide dismutase (SOD) depletion. Meanwhile, SAMC up-regulated expressions of endogenous antioxidant/detoxifying proteins including heme oxygenase-1 (HO-1) and NAD(P)H: quinone oxidoreductase 1(NQO1) through reversing the suppression of Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor erythroid-2 related factor 2 (Nrf2) signaling pathway. Our results demonstrate that SAMC effectively attenuated LPS-induced ALI which was largely dependent upon inhibition of inflammation and oxidative stress via NF-κB and Keap1/Nrf2 signaling pathways.

Comparative study on serum transitional components of Huatan Jiangqi Capsules in rats under pathological and physiological status

The differences of transitional components and metabolic processes of Huatan Jiangqi Capsules(HTJQ) in rats under normal physiological and pathological conditions of COPD were analyzed by UPLC-Q-TOF-MS. The rat COPD model was established by passive smoking and intratracheal instillation of lipopolysaccharide. After the normal and COPD model rats were douched with HTJQ, the blood was collected from hepatic portal vein and the drug-containing serum samples were prepared by methanol precipitation of protein. Then, 10 batches of drug-containing serum samples of HTJQ were prepared and analyzed by UPLC serum fingerprint to evaluate the quality and stability of drug-containing serum samples. UPLC-Q-TOF-MS was used to collect the mass spectrometric information of the transitional components. Twenty-eight transitional components of HTJQ in normal rats and 25 transitional components of HTJQ in COPD model rats were identified by UPLC-Q-TOF-MS. Under pathological and physiological conditions, there were not only the same transitional components in rat serum, but also corresponding differences. Further studies showed that there were also differences in the metabolic process of transitional components between the two conditions. In normal rats, most of the metabolic types of transitional components were phase I reactions. In COPD model rats, phase Ⅰ reactions decreased and phase Ⅱ reactions increased correspondingly. With UPLC-Q-TOF-MS technology, the differences of transitional components and the metabolism process of HTJQ in rats under normal physiological and pathological conditions were analyzed. The results showed that types of transitional components and the activity of some metabolic enzymes would be changed in COPD pathological state, which would affect the metabolic process of bioactive components in vivo. It laid a foundation for further elucidating the metabolic process and pharmacodynamic substance basis of HTJQ.

Protective effect of MOTS-c on acute lung injury induced by lipopolysaccharide in mice

MOTS-c (mitochondrial open-reading-frame of the twelve S rRNA-c), a mitochondrial-derived 16-amino acid peptide, targets the methionine-folate cycle, increases 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) levels, and eventually activates AMP-activated protein kinase (AMPK). AMPK activation can attenuate neutrophil pro-inflammatory activity and attenuates lipoteichoic acid (LTA) and lipopolysaccharide (LPS) induced acute lung injury (ALI) in mice. However, to our knowledge, the role of MOTS-c in LPS-induced ALI remains unclear. Hence, we investigated the potential effectiveness and underlying mechanism of MOTS-c against LPS-induced ALI in mice. The intraperitoneal administration of MOTS-c (5 mg/kg, i.p., bid, 6 days) before intratracheal LPS instillation attenuated body weight loss and pulmonary edema, inhibited neutrophilic tissue infiltration in lung tissue, downregulated the expression of cytokine-induced neutrophil chemoattractant-1 (CINC-1) and intercellular cell adhesion molecule-1 (ICAM-1) in lung tissues, decreased the levels of TNF-α, IL-1β, and IL-6, and increased the expression of IL-10 and SOD in serum, lung tissue, and bronchoalvelolar lavage fluid (BALF). Moreover, MOTS-c treatment significantly promoted p-AMPKα and SIRT1 expression and suppressed LPS-induced ERK, JNK, p38, p65, and STAT3 activation in the mouse lung tissues. Collectively, these findings suggest that MOTS-c plays important roles in protecting the lungs from the inflammatory effects of LPS-induced ALI. The effects of MOTS-c are probably orchestrated by activating AMPK and SIRT1, inhibiting ERK, JNK, p65, and STAT3 signaling pathways. Thus, MOTS-c appears to be a novel and promising candidate for the treatment of ALI.

Fengbaisan suppresses endoplasmic reticulum stress by up-regulating SIRT1 expression to protect rats with chronic obstructive pulmonary diseases

Context Our previous study found that Fengbaisan improved chronic obstructive pulmonary diseases (COPD). Objective To elucidate the mechanism of Fengbaisan in COPD. Materials and methods Rats in Model, FBS, FBS + DMSO and FBS + EX527 groups received cigarette smoke extract (CSE) inhalation and intratracheal instillation of lipopolysaccharide to establish COPD model. Normal group received room air and normal saline. The COPD rats were given Fengbaisan (1 mL/d) or combined with EX527 (5 mg/kg/2 d) by intraperitoneal injection. Human lung carcinoma (A549) cells were treated with 10% CSE, 10% serum-containing Fengbaisan or EX527. We observed lung percentage of forced expiratory volume in first 0.3 sec to forced vital capacity (FEV0.3/FVC), inspiratory resistance (RI) and lung dynamic compliance (Cdyn) of rats. The lung pathological changes, the number of inflammatory cells and neutrophils, inflammatory factor, apoptosis, gene and protein expression were examined. Results SIRT1 was downregulated in lung tissues of COPD rats and CSE-induced A549 cells. Fengbaisan enhanced FEV0.3/FVC (74.28%) and Cdyn (0.28 cm H2O/mL/s), and reduced RI (0.48 mL/cm H2O) of COPD rats. Moreover, Fengbaisan promoted SIRT1 expression, and repressed TIMP-1/MMP-9 expression. Fengbaisan enhanced apoptosis and the expression of GRP78, caspase-12 and caspase-3. The inflammatory factor levels, the number of inflammatory cells and neutrophils, and lung lesions were inhibited by Fengbaisan in COPD rats. The influence conferred by Fengbaisan was abolished by EX527. Discussion and conclusions Fengbaisan inhibits endoplasmic reticulum stress and inflammation reaction by up-regulating SIRT1 expression to improve COPD. Therefore, Fengbaisan may be an effective Chinese medicine for treating COPD.

Effects of dexmedetomidine on oxidative stress and inflammatory response in lungs during mechanical ventilation in COPD rats.

Effects of dexmedetomidine (Dex) on oxidative stress and inflammatory response in lungs during mechanical ventilation in chronic obstructive pulmonary disease (COPD) rats were investigated. Eleven out of 38 SD rats were randomly selected as the blank control group, and the other 27 rats were subjected to modeling. After the modeling, 11 rats in the blank control group and 11 rats randomly selected from the model group received non-invasive test for lung function. Three rats from the blank control group and 3 rats from the model group were selected for hematoxylin and eosin (HE) staining to confirm successful modeling, and the other 24 rats were randomly divided into 3 groups, 8 rats in each group, including model control, Dex low-dose and Dex high-dose group. A COPD rat model was established by passive cigarette smoking and intratracheal instillation of lipopolysaccharide. Each group underwent mechanical ventilation for 2 h. The Dex low-dose group and Dex high-dose group were intravenously administered at 1.0 µg/kg/h and 5.0 µg/kg/h of Dex, and the other two groups received intravenous drip of the same amount of normal saline. Blood gas analysis was performed to calculate carbon dioxide partial pressure (PaCO2), oxygen partial pressure (PaO2) and blood pH. HE staining was performed to analyze pulmonary pathological features of COPD rat model. Serum inflammatory factors interleukin-8 (IL-8), tumor necrosis factor-alpha (TNF-α) and malondialdehyde (MDA) were detected by ELISA, and the levels of antioxidant enzymes superoxide dismutase 2 (SOD2) and catalase were analyzed by western blot analysis. After 28 days of modeling, TV, PEF, FEV0.3 and FEV0.3/FVC decreased significantly in the COPD model group. HE staining showed that in the model group, the alveolar cells became larger, the alveolar wall became thinner, and some alveolar walls were even broken. The lung lobule showed obvious cell degeneration, necrosis and shedding, and the interstitial inflammatory cell infiltration, suggesting that the COPD rat model was successfully established. After 2 h of mechanical ventilation and Dex intravenous infusion, PaCO2 decreased, PaO2 increased, and blood pH value increased (p<0.05). Inflammatory factors IL-8 and TNF-α decreased (p<0.05). Oxidative stress index MDA also decreased (p<0.05), antioxidant enzymes SOD2 and catalase increased (p<0.05). Dexmedetomidine can improve the oxidative stress response during mechanical ventilation in rats with COPD, and can reduce the inflammation of lung tissue, thus protecting the lung tissue of COPD rats.

Mechanistic target of rapamycin-mediated autophagy is involved in the alleviation of lipopolysaccharide-induced acute lung injury in rats

Acute lung injury (ALI) is a complex clinical syndrome with high morbidity and mortality rates. Autophagy is an adaptive process that plays a complex role in ALI. The aim of this study was to investigate the effects of autophagy on lipopolysaccharide (LPS)-induced lung injury by establishing a rat ALI model and to further explore the possible mechanisms involved. Rats were pretreated with the autophagy inhibitor 3-methyladenine (3-MA) or the autophagy activator rapamycin before they were challenged with the intratracheal instillation of LPS (5 mg/kg). The level of autophagy in the lung tissue was detected. Lung injury and vascular permeability were assessed. The role of the mechanistic target of rapamycin (mTOR)-mediated Unc-51-like kinase 1 (ULK1) and the class III PI3 kinase VPS34 in autophagy regulation was examined. LPS challenge induced autophagy and rapamycin pretreatment enhanced autophagy activity in LPS-induced ALI rats. LPS caused severe lung injury and high pulmonary vascular permeability, which could be alleviated by enhancing autophagy. In addition, the inhibition of mTOR upregulated the expression of ULK1 and VPS34 and thus increased LPS-induced autophagy. Autophagy plays a protective role in LPS-induced ALI, and enhancing autophagy via the inhibition of mTOR alleviates lung injury and pulmonary barrier function. Moreover, mTOR negatively mediates ULK1 and VPS34 to regulate LPS-induced autophagy in rats.

The regulatory effect of microRNA-21a-3p on the promotion of telocyte angiogenesis mediated by PI3K (p110\u03b1)/AKT/mTOR in LPS induced mice ARDS

BackgroundTelocytes (TCs) are newly identified interstitial cells that participate in tissue protection and repair. The present study investigated the mechanisms underlying the protective effect of TCs in a mouse model of respiratory distress.MethodsThe mouse model of acute respiratory distress syndrome (ARDS) was established by intratracheal instillation of lipopolysaccharide (LPS). After instillation of TCs culture medium, lung injury was assessed, and angiogenesis markers, including CD31 and endothelial nitric oxide synthase (eNOS), were detected by immunofluorescence. Bioinformatics analysis was used to screen significantly differentially expressed microRNAs (miRNAs) in cultured TCs stimulated with LPS, and the regulation of downstream angiogenesis genes by these miRNAs was analysed and verified. PI3K subunits and pathways were evaluated by using a PI3K p110α inhibitor to study the involved mechanisms.ResultsIn ARDS mice, instillation of TCs culture medium ameliorated LPS-induced inflammation and lung injury and increased the protein levels of CD31 and eNOS in the injured lungs. A total of 7 miRNAs and 1899 mRNAs were differentially regulated in TCs stimulated with LPS. Functional prediction analysis showed that the differentially expressed mRNAs were enriched in angiogenesis-related processes, which were highly correlated with miR-21a-3p. Culture medium from TCs with miR-21a-3p inhibition failed to promote angiogenesis in mouse models of LPS-induced ARDS. In cultured TCs, LPS stimulation upregulated the expression of miR-21a-3p, which further targeted the transcription factor E2F8 and decreased Notch2 protein expression. TCs culture medium enhanced hemangioendothelioma endothelial cells (EOMA cells) proliferation, which was blocked by the miR-21a-3p inhibitor. The PI3K p110α inhibitor decreased vascular endothelial growth factor levels in LPS-stimulated TCs and reversed the enhancing effect of TCs culture medium on EOMA cells proliferation.ConclusionsTCs exerted protective effects under inflammatory conditions by promoting angiogenesis via miR-21a-3p. The PI3K p110α subunit and transcriptional factor E2F8 could be involved in this process.

Protective effect of sodium 4-phenylbutyrate on rats with acute respiratory distress syndrome related right ventricular dysfunction by alleviating endoplasmic reticulum stress

To investigate the role of endoplasmic reticulum stress (ERS) in rats with acute respiratory distress syndrome (ARDS) related right ventricular dysfunction and the protective effect of sodium 4-phenylbutyrate (4-PBA) on right ventricle. Sixty male Spragne-Dawley (SD) rats were randomly divided into control group (CON group), lipopolysaccharide (LPS) model group, 4-PBA prevention group and 4-PBA treatment group, with 15 rats in each group. ARDS rat model was established by intratracheal instillation of LPS 10 mg/kg after tracheotomy; CON group was given the same amount of saline. 4-PBA prevention group and 4-PBA treatment group were given 4-PBA 500 mg/kg intragastric administration 2 hours before and after LPS respectively. Echocardiography was performed 12 hours after treatment to evaluate the right ventricular function. Then, the rats were sacrificed by bloodletting, and the serum and right ventricular tissue were harvested. The histopathological changes of myocardial were observed by hematoxylin-eosin (HE) staining, the levels of tumor necrosis factor-α (TNF-α), interleukins (IL-1β and IL-6) in serum and myocardial were detected by enzyme linked immunosorbent assay (ELISA), and Western Blot was used to detect the expression of the marker proteins of ERS in myocardial, including glucose regulatory protein 78 (GRP78), C/EBP cyclic adenosine phosphate reaction primitive binding transcription factor homologous protein (CHOP), caspase-12 and caspase-3. Compared with the CON group, the echocardiography showed pulmonary artery maximum pressure gradient (PAmaxPG), pulmonary artery acceleration time (PAAT), tricuspid annular plane systolic excursion (TAPSE) in LPS model group were significantly decreased, and right ventricular end-diastolic excursion (RVDd) was significantly increased, and the levels of TNF-α, IL-1β and IL-6 in serum and myocardial, as well as the expressions of GRP78, CHOP, caspase-12 and caspase-3 in myocardial were significantly increased. Compared with LPS model group, TAPSE of 4-PBA preventive and treatment groups were significantly increased (mm: 3.08±0.65, 2.96±0.61 vs. 2.48±0.45), RVDd were significantly decreased (mm: 3.67±0.58, 3.60±0.61 vs. 4.18±0.71), the levels of TNF-α, IL-1β and IL-6 in serum and myocardial were significantly decreased [TNF-α (ng/L): 187.98±18.98, 176.08±17.98 vs. 332.00±19.90 in serum, 135.06±19.00, 132.78±17.00 vs. 155.00±20.00 in myocardial; IL-1β(ng/L): 12.07±2.98, 11.05±2.41 vs. 24.06±4.01 in serum, 19.89±2.80, 21.06±2.80 vs. 26.00±2.60 in myocardial; IL-6 (ng/L): 42.98±7.90, 34.05±6.09 vs. 89.80±10.07 in serum, 129.45±25.00, 127.08±26.06 vs. 145.77±23.00 in myocardial]; the expressions of GRP78, CHOP, caspase-12 and caspase-3 in myocardial were significantly decreased (GRP78/GAPDH: 0.090±0.070, 0.103±0.060 vs. 0.167±0.090, CHOP/GAPDH: 0.109±0.090, 0.090±0.080 vs. 0.186±0.090, caspase-12/GAPDH: 0.769±0.230, 0.799±0.210 vs. 1.040±0.350, caspase-3/GAPDH: 0.391±0.060, 0.401±0.054 vs. 0.603±0.340), with statistically significant differences (all P < 0.05). There were no significant differences in each indexes between 4-PBA prevention group and 4-PBA treatment group (all P > 0.05). ERS is involved in ARDS-related right ventricular dysfunction. 4-PBA can protect the right ventricular function of ARDS rats by inhibiting ERS and alleviating inflammation, and the preventive and therapeutic effects of 4-PBA are similar.

A novel chalcone derivative exerts anti-inflammatory and anti-oxidant effects after acute lung injury.

We explored the effects of compound 33, a synthetic chalcone derivative with antioxidant activity, on lipopolysaccharide (LPS)-induced acute lung injury (ALI). Compound 33, dexamethasone or vehicle was administered intragastrically to mice 6 h before intratracheal instillation of LPS. After 24 h, the effects of compound 33 on alveolar structural damage were evaluated by assessing lung morphology and the wet/dry weight ratio. Protein and proinflammatory cytokine levels and superoxide dismutase activity were also examined in the cell free supernatant of bronchoalveolar lavage fluid. Additionally, we investigated the anti-inflammatory and antioxidant activity of compound 33 in vitro and its effects on the MAPK/NF-κB and Nrf2/HO-1 pathways. Pretreatment with compound 33 prevented LPS-induced structural damage, tissue edema, protein exudation, and overproduction of proinflammatory mediators. The effects of compound 33 were similar to or greater in magnitude than those of the positive control, dexamethasone. Moreover, compound 33 exerted anti-inflammatory and antioxidant effects in vitro by inhibiting the MAPK/NF-κB pathway and activating the Nrf2/HO-1 pathway. Compound 33 may therefore be a promising candidate treatment for ALI.

Galloyl-Hexahydroxydiphenoyl (HHDP)-Glucose Isolated From Punica granatum L. Leaves Protects Against Lipopolysaccharide (LPS)-Induced Acute Lung Injury in BALB/c Mice.

The hydroalcoholic extract and ethyl acetate fraction of Punica granatum leaves have been known to exhibit anti-inflammatory activities. In this study, we investigated the therapeutic effects of galloyl-hexahydroxydiphenoyl (HHDP)-glucose isolated from pomegranate leaves on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice. Male BALB/c mice were treated with different doses of galloyl-HHDP-glucose (5, 50, and 100 mg/Kg) or dexamethasone at 5 mg/Kg (per os) 6 h after intra-tracheal instillation of LPS. Vehicle-treated mice were used as controls. Twenty-four hours after LPS challenge, bronchoalveolar lavage fluid (BALF), and lung samples were collected for analyses. They were evaluated by monitoring the expression of NF-κB, JNK, and cytokine genes and proteins, as well as cell migration and lung function. All doses of galloyl-HHDP-glucose inhibited LPS-induced JNK and NF-κB activation. Likewise, the galloyl-HHDP-glucose-treated animals presented reduced expression of the TNF-α, IL-6, and IL-1β genes in the lungs and reduced TNF-α, IL-6, IL-1β, and IL-8 protein levels when compared with the vehicle-treated LPS-challenged mice. In addition, the ALI mice treated with galloyl-HHDP-glucose also presented reduced lung inflammatory cell accumulation, especially that of neutrophils, in their BALF and lungs. In addition, galloyl-HHDP-glucose treatment markedly ameliorated the LPS-induced pulmonary mechanism complications and attenuated weight loss. Overall, we showed for the first time that galloyl-HHDP-glucose protects against ALI, and may be useful for treating ALI and other inflammatory disorders.

A potential role of microvesicle-containing miR-223/142 in lung inflammation

BackgroundUncontrolled lung inflammation is one of the prominent features in the pathogenesis of lung infection- associated acute lung injury (ALI). Microvesicles (MVs) are extracellular nanovesicles that are generated via direct...

Activation of death-associated protein kinase 1 promotes neutrophil apoptosis to accelerate inflammatory resolution in acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a uniform progression of overwhelming inflammation in lung tissue with extensive infiltration of inflammatory cells. Neutrophil apoptosis is thought to be a significant process in the control of the resolution phase of inflammation. It has been proved that 5-Aza-2′-deoxycytidine (Aza) can inhibit cancer by activating death-associated protein kinase 1 (DAPK1) to promote apoptosis. However, the effect of DAPK1 on neutrophil apoptosis is unclear, and research on the role of Aza in inflammation is lacking. Here, we investigated whether Aza can regulate DAPK1 expression to influence the fate of neutrophils in ARDS. In vitro, we stimulated neutrophil-like HL-60 (dHL-60) cells with different concentrations of Aza for different durations and used RNA interference to up- or downregulate DAPK1 expression. We observed that culturing dHL-60 cells with Aza increased apoptosis by inhibiting NF-κB activation to modulate the expression of Bcl-2 family proteins, which was closely related to the levels of DAPK1. In vivo, ARDS was evoked by intratracheal instillation of lipopolysaccharide (LPS; 3 mg/kg). One hour after LPS administration, mice were treated with Aza (1 mg/kg, i.p.). To inhibit DAPK1 expression, mice were intraperitoneally injected with a DAPK1 inhibitor. Aza treatment accelerated inflammatory resolution in LPS-induced ARDS by suppressing pulmonary edema, alleviating lung injury and decreasing the infiltration of inflammatory cells in bronchoalveolar lavage fluid (BALF). Moreover, Aza reduced the production of proinflammatory cytokines. However, administration of the DAPK1 inhibitor attenuated the protective effects of Aza. Similarly, the proapoptotic function of Aza was prevented when DAPK1 was inhibited either in vivo or in vitro. In summary, Aza promotes neutrophil apoptosis by activating DAPK1 to accelerate inflammatory resolution in LPS-induced ARDS. This study provides the first evidence that Aza prevents LPS-induced neutrophil survival by modulating DAPK1 expression.

Pseudoginsenoside-F11 Attenuates Lipopolysaccharide-Induced Acute Lung Injury by Suppressing Neutrophil Infiltration and Accelerating Neutrophil Clearance.

Pseudoginsenoside-F11 (PF11), an ocotillol-type saponin, has been reported to have anti-inflammatory properties, but the effects of PF11 on acute lung inflammation were unknown. The present study aimed to investigate the protective effects and potential mechanisms of PF11 on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in male BALB/c mice. After being treated with PF11 (3, 10, and 30mg/kg, intravenous) once a day for 3 consecutive days, the mice were challenged by intratracheal instillation of LPS, and then their lung tissues and bronchoalveolar lavage fluid (BALF) were collected for further analysis. The results showed that PF11 attenuated LPS-induced ALI, with alleviated histopathological damage, decreased lung wet/dry weight ratio, and reduced protein concentration and inflammatory cells number in BALF. Moreover, PF11 reversed the LPS-induced increases of mRNA expression and protein levels of interleukin-6, tumor necrosis factor-α, and interleukin-1β. Meanwhile, PF11 decreased LPS-induced myeloperoxidase activity and neutrophil infiltration in lung tissue by reducing the expression of macrophage inflammatory protein-2 and intercellular adhesion molecule-1, as well as enhanced neutrophil clearance by accelerating neutrophils apoptosis and their phagocytosis by alveolar macrophages. In conclusion, these results indicated that PF11 significantly attenuated LPS-induced ALI through suppressing neutrophil infiltration and accelerating neutrophil clearance, suggesting its potential in the treatment of ALI.

AMPK as a potential pharmacological target for alleviating LPS-induced acute lung injury partly via NLRC4 inflammasome pathway inhibition.

Old people are spectacularly susceptible to acute lung injury (ALI) and the accompanying complications. An acute aggravated inflammatory response is a characteristic feature of ALI, and inflammasomes play a critical role in the inflammatory response. Metformin has been shown to be an effective anti-inflammatory agent in ALI. However, the mechanism of this regulation still remains poorly understood. In this study, 18- to 19-month-old male mice were treated by intratracheal instillation of lipopolysaccharide (LPS) or PBS with or without metformin pretreatment. We found that the metformin pretreatment alleviated the lung injury and decreased the levels of TNF-a, IL-1β and IL-6 in the bronchoalveolar lavage fluid (BALF) and in lung tissues, as well as the levels of NLRP3, NLRC4 and cleaved caspase-1 associated with LPS-induced ALI in old mice. Furthermore, the in vitro study showed metformin dose-dependently suppressed NLRC4 inflammasome expression. Metformin activated AMPK by phosphorylation; thus, we investigated the role of AMPK in NLRC4 activation. The results demonstrated that the efficacy of metformin was reduced when using the AMPK pharmacological inhibitor compound C or AMPKα1 expression was knocked down in RAW 264.7 cells. In conclusion, our data indicated that metformin may inhibit NLRC4 inflammasome activation in LPS-induced ALI in old mice through AMPK signaling, and further understanding of the AMPK/NLRC4 axis may provide a novel therapeutic strategy for LPS-induced ALI in the future.

Inducing Acute Lung Injury in Mice by Direct Intratracheal Lipopolysaccharide Instillation.

Airway administration of lipopolysaccharide (LPS) is a common way to study pulmonary inflammation and acute lung injury (ALI) in small animal models. Various approaches have been described, such as the inhalation of aerosolized LPS as well as nasal or intratracheal instillation. The presented protocol describes a detailed step-by-step procedure to induce ALI in mice by direct intratracheal LPS instillation and perform FACS analysis of blood samples, bronchoalveolar lavage (BAL) fluid, and lung tissue. After intraperitoneal sedation, the trachea is exposed and LPS is administered via a 22 G venous catheter. A robust and reproducible inflammatory reaction with leukocyte invasion, upregulation of proinflammatory cytokines, and disruption of the alveolo-capillary barrier is induced within hours to days, depending on the LPS dosage used. Collection of blood samples, BAL fluid, and lung harvesting, as well as the processing for FACS analysis, are described in detail in the protocol. Although the use of the sterile LPS is not suitable to study pharmacologic interventions in infectious diseases, the described approach offers minimal invasiveness, simple handling, and good reproducibility to answer mechanistic immunological questions. Furthermore, dose titration as well as the use of alternative LPS preparations or mouse strains allow modulation of the clinical effects, which can exhibit different degrees of ALI severity or early vs. late onset of disease symptoms.

Inducing Acute Lung Injury in Mice by Direct Intratracheal Lipopolysaccharide Instillation

Inducing Acute Lung Injury in Mice by Direct Intratracheal Lipopolysaccharide Instillation

Aquaporin 4 Blockade Attenuates Acute Lung Injury Through Inhibition of Th17 Cell Proliferation in Mice

Acute lung injury (ALI) is a syndrome characterized by damage to the alveolar-capillary wall, pulmonary edema and recruitment of inflammatory cells. Previous studies have indicated that aquaporin 4 (AQP4) plays a key role in brain edema formation and resolution. However, the role of AQP4 in the development and progression of ALI is not clear and needs to be resolved. In our current study, mouse ALI was induced by intratracheal instillation of lipopolysaccharide (LPS) at a concentration of 30mg/kg. For the inhibition of AQP4, 200mg/kg of TGN-020 (Sigma, USA) was administered intraperitoneally every 6h starting at 30min before intratracheal instillation of LPS. The results of the present work indicate, for the first time, that mice treated with the AQP4 inhibitor TGN-020 had attenuated LPS-induced lung injury, reduced proinflammatory cytokine release (including IL-1α, IL-1β, IL-6, TNF-α, IL-23, and IL-17A), and an improved survival rate. Additionally, we found that the attenuated lung injury scores, increased survival rate, and decreased BALF total protein concentration in TGN-020-treated mice were all abrogated by rIL-17A administration. Furthermore, TGN-020 treatment downregulated the phosphorylation of PI3K and Akt, increased the expression of SOCS3, and decreased the expression of p-STAT3 and RORγt. In conclusion, inhibition of AQP4 by TGN-020 has a detectable protective effect against lung tissue injury induced by LPS, and this effect is associated with inhibition of IL-17A through the downregulation of the PI3K/Akt signaling pathway and upregulation of SOCS3 protein.

A CRTH2 antagonist, CT-133, suppresses NF-κB signalling to relieve lipopolysaccharide-induced acute lung injury

Acute lung injury (ALI) and acute respiratory distress syndrome are life-threatening conditions that still have no definite pharmacotherapy. Hence, we investigate the potential effectiveness and underlying mechanism of CT-133, a newly developed selective antagonist of prostaglandin D2 receptor 2 (DP2) or of chemoattractant receptor homologous molecule expressed on Th2 cells (CRTH2), against lipopolysaccharide (LPS)-induced ALI. CT-133 (10 or 30 mg/kg) or dexamethasone (1 mg/kg, positive control) were intragastrically administered 1 h before and 12 h after intratracheal LPS instillation, and primary neutrophils and macrophages and RAW264.7 macrophages were used to investigate the role of CT-133 in regulation of their functions. LPS induced a significant secretion of PGD2 from primary macrophages, however, CT-133 dose-dependently and markedly decreased the infiltration of neutrophils and macrophages into lungs, reduced the IL-1β, TNF-α, IL-6, and KC levels in broncho-alveolar lavage (BAL) fluids, decreased the wet weight and myeloperoxidase activity of lungs, reduced Evans blue and albumin exudation into lungs, and improved the lung histopathological changes and hypoxemia. Moreover, CT-133 significantly suppressed the primary neutrophil migration toward the PGD2 and robustly inhibited the mRNA and protein expression of IL-1β, TNF-α, IL-6, and KC in primary and RAW264.7 macrophages in response to either LPS- or PGD2 stimulation. Finally, CT-133 significantly blocked the LPS-induced P65 activation in both RAW264.7 macrophages and mouse lungs. Thus, This is the first report that a CRTH2 antagonist, CT-133, is capable of significantly alleviating LPS-induced lung injury by probably down-regulating the NF-κB signalling.

Protein S is Protective in Acute Lung Injury by Inhibiting Cell Apoptosis.

Acute lung injury is a fatal disease characterized by inflammatory cell infiltration, alveolar-capillary barrier disruption, protein-rich edema, and impairment of gas exchange. Protein S is a vitamin K-dependent glycoprotein that exerts anticoagulant, immunomodulatory, anti-inflammatory, anti-apoptotic, and neuroprotective effects. The aim of this study was to evaluate whether human protein S inhibits cell apoptosis in acute lung injury. Acute lung injury in human protein S transgenic and wild-type mice was induced by intratracheal instillation of lipopolysaccharide. The effect of human protein S on apoptosis of lung tissue cells was evaluated by Western blotting. Inflammatory cell infiltration, alveolar wall thickening, myeloperoxidase activity, and the expression of inflammatory cytokines were reduced in human protein S transgenic mice compared to the wild-type mice after lipopolysaccharide instillation. Apoptotic cells and caspase-3 activity were reduced while phosphorylation of extracellular signal-regulated kinase was enhanced in the lung tissue from human protein S transgenic mice compared to wild-type mice after lipopolysaccharide instillation. The results of this study suggest that human protein S is protective in lipopolysaccharide-induced acute lung injury by inhibiting apoptosis of lung cells.

Cathelicidin LL-37 restoring glucocorticoid function in smoking and lipopolysaccharide-induced airway inflammation in rats.

BackgroundGlucocorticoids have been widely used to treat patients with chronic obstructive pulmonary disease (COPD). Nevertheless, corticosteroid insensitivity is a major barrier to the effective treatment of COPD and its mechanism remains unclear. This study aimed to evaluate the effect of cathelicidin LL-37 on corticosteroid insensitivity in COPD rat model, and to explore the involved mechanisms.MethodsCOPD model was established by exposing male Wistar rats to cigarette smoke combined with intratracheal instillation of lipopolysaccharide (LPS). Inhaled budesonide and LL-37 were consequently applied to COPD models separately or collectively to confirm the effects on inflammatory cytokines (tumor necrosis factor [TNF]-α and transforming growth factor [TGF]-β) by enzyme-linked immunosorbent assay (ELISA) and lung tissue histopathological morphology. Expression of histone deacetylase-2 (HDAC2) and phosphorylation of Akt (p-AKT) in lung were also measured.ResultsBriefly, COPD model rats showed an increased basal release of inflammatory cytokines (lung TNF-α: 45.7 ± 6.1 vs. 20.1 ± 3.8 pg/mL, P < 0.01; serum TNF-α: 8.9 ± 1.2 vs. 6.7 ± 0.5 pg/mL, P = 0.01; lung TGF-β: 122.4 ± 20.8 vs. 81.9 ± 10.8 pg/mL, P < 0.01; serum TGF-β: 38.9 ± 8.5 vs. 20.6 ± 2.3 pg/mL, P < 0.01) and COPD related lung tissue histopathological changes, as well as corticosteroid resistance molecular profile characterized by an increase in phosphoinositide 3-kinase (PI3K)/Akt (0.5 ± 0.1 fold of control vs. 0.2 ± 0.1 fold of control, P = 0.04) and a decrease in HDAC2 expression and activity (expression: 13.1 ± 0.4 μmol/μg vs. 17.4 ± 1.1 μmol/μg, P < 0.01; activity: 1.1 ± 0.1 unit vs. 1.4 ± 0.1 unit, P < 0.01), compared with control group. In addition, LL-37 enhanced the anti-inflammatory effect of budesonide in an additive manner. Treatment with combination of inhaled corticosteroids (ICS) and LL-37 led to a significant increase of HDAC2 expression and activity (expression: 15.7 ± 0.4 μmol/μg vs. 14.1 ± 0.9 μmol/μg, P < 0.01; activity: 1.3 ± 0.1 unit vs. 1.0 ± 0.1 unit, P < 0.01), along with decrease of p-AKT compared to budesonide monotherapy (0.1 ± 0.0 fold of control vs. 0.3 ± 0.1 fold of control, P < 0.01).ConclusionsThis study suggested that LL-37 could improve the anti-inflammatory activity of budesonide in cigarette smoke and LPS-induced COPD rat model by enhancing the expression and activity of HDAC2. The mechanism of this function of LL-37 might involve the inhibition of PI3K/Akt pathway.