Preventive Effect of the Total Polyphenols from Nymphaea candida on Sepsis-Induced Acute Lung Injury in Mice via Gut Microbiota and NLRP3, TLR-4/NF-κB Pathway

This study aimed to investigate the preventive effects of the total polyphenols from Nymphaea candida (NCTP) on LPS-induced septic acute lung injury (ALI) in mice and its mechanisms. NCTP could significantly ameliorate LPS-induced lung tissue pathological injury in mice as well as lung wet/dry ratio and MPO activities (p < 0.05). NCTP could significantly decrease the blood leukocyte, neutrophil, monocyte, basophil, and eosinophil amounts and LPS contents in ALI mice compared with the model group (p < 0.05), improving lymphocyte amounts (p < 0.05). Moreover, compared with the model group, NCTP could decrease lung tissue TNF-α, IL-6, and IL-1β levels (p < 0.05) and downregulate the protein expression of TLR4, MyD88, TRAF6, IKKβ, IκB-α, p-IκB-α, NF-κB p65, p-NF-κB p65, NLRP3, ASC, and Caspase1 in lung tissues (p < 0.05). Furthermore, NCTP could inhibit ileum histopathological injuries, restoring the ileum tight junctions by increasing the expression of ZO-1 and occludin. Simultaneously, NCTP could reverse the gut microbiota disorder, restore the diversity of gut microbiota, increase the relative abundance of Clostridiales and Lachnospiraceae, and enhance the content of SCFAs (acetic acid, propionic acid, and butyric acid) in feces. These results suggested that NCTP has preventive effects on septic ALI, and its mechanism is related to the regulation of gut microbiota, SCFA metabolism, and the TLR-4/NF-κB and NLRP3 pathways.

Self-Assembly of Antimicrobial Peptide-Based Micelles Breaks the Limitation of Trypsin

Targeting the limitation of antimicrobial peptides (AMPs) application in vivo, self-assembled AMPs library with specific nanostructures is expected to gradually overtake monomer AMPs libraries in the future. Peptide polymers are fascinating self-assembling nanoscale structures that have great advantage in biomedical applications because of their satisfactory biocompatibility and versatile properties. Herein, we describe a strategy for inducing the self-assembly of T9W into nanostructured antimicrobial micelles with evidently improved pharmacological properties, that is, PEGylation at the C-terminal of T9W (CT9W₁₀₀₀), an antibacterial biomaterial that self-assembles in aqueous media without exogenous excipients, has been developed. Compared with parental molecular, the CT9W₁₀₀₀ is more effective against Pseudomonas aeruginosa, and its antibacterial spectrum had also been broadened. Additionally, CT9W₁₀₀₀ micelles had higher stability under salt ion, serum, and acid-base environments. Importantly, the self-assembled structure is highly resistant to trypsin degradation, probably allowing T9W to be applied in clinical settings in the future. Mechanistically, by acting on membranes and through supplementary bactericidal mechanisms, CT9W₁₀₀₀ micelles contribute to the antibacterial process. Collectively, CT9W₁₀₀₀ micelles exhibited good biocompatibility in vitro and in vivo, resulting in highly effective treatment in a mouse acute lung injury model induced by P. aeruginosa PAO1 without drug resistance. These advances may profoundly accelerate the clinical transformation of T9W and promote the development of a combination of peptide-based antibiotics and PEGylated nanotechnology.

Storage conditions of high-fat diets affect pulmonary inflammation

Obesity alters the risks and outcomes of inflammatory lung diseases. It is important to accurately recapitulate the obese state in animal models to understand these effects on the pathogenesis of disease. Diet-induced obesity is a commonly used model of obesity, but when applied to other disease models like acute respiratory distress syndrome, pneumonia, and asthma, it yields widely divergent. We hypothesized high-fat chow storage conditions would affect lipid oxidation and inflammatory response in the lungs of lipopolysaccharide (LPS)-challenged mice. For 6 weeks, C57BL/6crl mice were fed either a 10% (low-fat diet, LFD) or 60% (high-fat diet, HFD) stored at room temperature (RT, 23°C) for up to 7, 14, 21, or 42 days. Mice were treated with nebulized LPS to induce lung inflammation, and neutrophil levels in bronchoalveolar lavage were determined 24 h later. Lipid oxidation (malondialdehyde, MDA) was assayed by thiobarbituric acid reactive substances in chow and mouse plasma. Concentrations of MDA in chow and plasma rose in proportion to the duration of RT chow storage. Mice fed a HFD stored <2 weeks at RT had an attenuated response 24 h after LPS compared with mice fed an LFD. This effect was reversed after 2 weeks of chow storage at RT. Chow stored above freezing underwent lipid oxidation associated with significant alterations in the LPS-induced pulmonary inflammatory response. Our data show that storage conditions affect lipid peroxidation, which in turn affects pulmonary inflammatory responses in a mouse model of disease. It also suggests changes in the microbiome, although not significantly different suggests decreased variety and richness of bacteria in the gut, a large aspect of the immune system. Dietary composition and storage of chow may also affect pulmonary inflammation and the gut microbiome in humans.

Mechanical Ventilation Exacerbates Poly (I:C) Induced Acute Lung Injury: Central Role for Caspase-11 and Gut-Lung Axis

Background

The mechanisms by which moderate tidal volume ventilation (MTV) exacerbates preexisting lung injury are unclear. We hypothesized that systemic endotoxemia via the gut-lung axis would lead to non-canonical and canonical inflammasome activation and pyroptosis in a two-hit model involving polyinosinic-polycytidylic acid (Poly(I:C)), a synthetic analog of dsRNA and MTV and that this would associate with acute lung injury (ALI).

Methods

Anesthetized mice were administered Poly(I:C) intratracheally and then 6 h later, they were mechanically ventilated for 4 h with otherwise non-injurious MTV (10ml/kg). Changes in intestinal and alveolar capillary permeability were measured. Further documentation of ALI was assessed by evans blue albumin permeability, protein and IL-1 family concentration in bronchoalveolar lavage fluid (BALF) or plasma, and histopathology in cohorts of wildtype (WT), whole body genetically ablated caspase-11 (caspase-11-/-), caspase-1/caspase-11 double knockout (caspase-1/11-/-), gasdermin D (GSDMD)-/-, nucleotide-binding domain leucine-rich repeat-containing protein 3 (NLRP3)-/- and advanced glycosylation end product-specific receptor (RAGE) -/- mice.

Results

Non-injurious MTV exacerbated the mild lung injury associated with Poly(I:C) administration. This included the disruption of alveolar-capillary barrier and increased levels of interleukin (IL)-6, high mobility group proteins 1 (HMGB-1), IL-1β in BALF and IL-18 in plasma. Combined (Poly(I:C)-MTV) injury was associated with increase in gastrointestinal permeability and endotoxin in plasma and BALF. Poly(I:C)-MTV injury was sensitive to caspase-11 deletion with no further contribution of caspase-1 except for maturation and release of IL-18 (that itself was sensitive to deletion of NLRP3). Combined injury led to large increases in caspase-1 and caspase-11. Genetic ablation of GSDMD attenuated alveolar-capillary disruption and release of cytokines in combined injury model.

Conclusions

The previously noted exacerbation of mild Poly(I:C)-induced ALI by otherwise non-injurious MTV is associated with an increase in gut permeability resulting in systemic endotoxemia. The gut-lung axis resulted in activation of pulmonary non-canonical (cytosolic mediated caspase-11 activation) and canonical (caspase-1) inflammasome (NLRP3) mediated ALI in this two-hit model resulting in GSDMD sensitive alveolar capillary barrier disruption, pyroptosis (alveolar macrophages) and cytokine maturation and release (IL-1β; IL-18). Pharmacologic strategies aimed at disrupting communication between gut and lung, inhibition of inflammasomes or GSDMD in pyroptosis may be useful in ALI.

Group V Phospholipase A2 Mediates Endothelial Dysfunction and Acute Lung Injury Caused by Methicillin-Resistant Staphylococcus Aureus

Lung endothelial dysfunction is a key feature of acute lung injury (ALI) and clinical acute respiratory distress syndrome (ARDS). Previous studies have identified the lipid-generating enzyme, group V phospholipase A2 (gVPLA2), as a mediator of lung endothelial barrier disruption and inflammation. The current study aimed to determine the role of gVPLA2 in mediating lung endothelial responses to methicillin-resistant Staphylococcus aureus (MRSA, USA300 strain), a major cause of ALI/ARDS. In vitro studies assessed the effects of gVPLA2 inhibition on lung endothelial cell (EC) permeability after exposure to heat-killed (HK) MRSA. In vivo studies assessed the effects of intratracheal live or HK-MRSA on multiple indices of ALI in wild-type (WT) and gVPLA2-deficient (KO) mice. In vitro, HK-MRSA increased gVPLA2 expression and permeability in human lung EC. Inhibition of gVPLA2 with either the PLA2 inhibitor, LY311727, or with a specific monoclonal antibody, attenuated the barrier disruption caused by HK-MRSA. LY311727 also reduced HK-MRSA-induced permeability in mouse lung EC isolated from WT but not gVPLA2-KO mice. In vivo, live MRSA caused significantly less ALI in gVPLA2 KO mice compared to WT, findings confirmed by intravital microscopy assessment in HK-MRSA-treated mice. After targeted delivery of gVPLA2 plasmid to lung endothelium using ACE antibody-conjugated liposomes, MRSA-induced ALI was significantly increased in gVPLA2-KO mice, indicating that lung endothelial expression of gVPLA2 is critical in vivo. In summary, these results demonstrate an important role for gVPLA2 in mediating MRSA-induced lung EC permeability and ALI. Thus, gVPLA2 may represent a novel therapeutic target in ALI/ARDS caused by bacterial infection.

Extrathoracic multiple trauma dysregulates neutrophil function and exacerbates pneumonia-induced lung injury

BACKGROUND

Forty percent of critically ill trauma patients will develop an infectious complication. Pneumonia is the most common cause of death of trauma patients surviving their initial insult. We previously demonstrated that polytrauma (PT), defined as two or more severe injuries in at least two areas of the body, induces emergency hematopoiesis characterized by accelerated myelopoiesis in the bone marrow and increased myeloid cell frequency in the peripheral tissues. We hypothesized that PT alone induces priming of neutrophils, resulting in hyperactivation upon secondary exposure to bacteria and causing acute lung injury and increased susceptibility to secondary exposure to Pseudomonas aeruginosa pneumonia.

METHODS

C57BL/6 mice were subjected to PT consisting of a lower extremity pseudofracture, liver crush injury, and 15% blood-volume hemorrhage. Pneumonia was induced by intratracheal injection of 5 × 106 CFU live P. aeruginosa or 1 × 107 of heat-killed P. aeruginosa (HKPA). For reactive oxygen species (ROS), studies polymorphonuclear neutrophils (PMNs) were isolated by immunomagnetic bead negative selection and stimulated ex-vivo with HKPA. Reactive oxygen species production was measured by immunofluorescence. For histology, lung sections were stained by hematoxylin-eosin and analyzed by a blinded grader.

RESULTS

Polytrauma induced persistent changes in immune function at baseline and to secondary infection. Pneumonia after injury resulted in increased mortality (60% vs. 5% p < 0.01). Blood neutrophils from PT mice had higher resting (unstimulated) ROS production than in naive animals (p < 0.02) demonstrating priming of the neutrophils following PT. After intratracheal HKPA injection, bronchoalveolar lavage PMNs from injured mice had higher ROS production compared with naive mice (p < 0.01), demonstrating an overexuberant immunopathologic response of neutrophils following PT.

CONCLUSION

Polytrauma primes neutrophils and causes immunopathologic PMN ROS production, increased lung injury and susceptibility to secondary bacterial pneumonia. These results suggest that trauma-induced immune dysfunction can cause immunopathologic response to secondary infection and suggests neutrophil-mediated pulmonary damage as a therapeutic target for posttrauma pneumonia.

Effect of gut microbiota on LPS-induced acute lung injury by regulating the TLR4/NF-kB signaling pathway

Acute lung injury (ALI) is a common acute respiratory disease treated in the clinic. Intestinal microflora disorder affect lung diseases through the gut-lung axis. In this study, we explored the regulatory mechanism of the gut flora in the host defense against lipopolysaccharide (LPS)-induced ALI through the TLR4/NF-kB pathway by constructing a gut microflora dysbiosis-model with antibiotic administration and reconstruction of the intestinal microecology. Then, high-throughput sequencing was performed, and the levels of secreted IgA (sIgA), β-defensins, and Muc2 were measured to assess the gut flora and mucosal barrier. The expression of TLR4, NF-kB, TNF-α, IL-1β, oxidative stress and the lung wet/dry (W/D) ratio were evaluated to assess lung damage. Hematoxylin and eosin (HE) staining was performed to evaluate the damage to the gut and lung tissues. Accordingly, gut microbiota imbalance may regulate the TLR4/NF-kB signaling pathway in the lung immune system, activating oxidative stress in the lung and mediating lung injury through the regulation of the gut barrier. However, fecal microbiota transplantation (FMT) impairs the activity of the TLR4/NF-kB signaling pathway in the lung and decreases oxidative stress in animals with ALI by restoring the gut microecology. CONCLUSIONS: Our results indicated the protective effect of gut flora in regulating immunity of LPS-induced ALI by modulating the TLR4/NF-kB signaling pathway which may induce inflammation and oxidative stress.

SOCS3-microtubule interaction via CLIP-170 and CLASP2 is critical for modulation of endothelial inflammation and lung injury

Proinflammatory cytokines such as IL-6 induce endothelial cell (EC) barrier disruption and trigger an inflammatory response in part by activating the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway. The protein suppressor of cytokine signaling-3 (SOCS3) is a negative regulator of JAK-STAT, but its role in modulation of lung EC barrier dysfunction caused by bacterial pathogens has not been investigated. Using human lung ECs and EC-specific SOCS3 knockout mice, we tested the hypothesis that SOCS3 confers microtubule (MT)-mediated protection against endothelial dysfunction. SOCS3 knockdown in cultured ECs or EC-specific SOCS3 knockout in mice resulted in exacerbated lung injury characterized by increased permeability and inflammation in response to IL-6 or heat-killed Staphylococcus aureus (HKSA). Ectopic expression of SOCS3 attenuated HKSA-induced EC dysfunction, and this effect required assembled MTs. SOCS3 was enriched in the MT fractions, and treatment with HKSA disrupted SOCS3-MT association. We discovered that-in addition to its known partners gp130 and JAK2-SOCS3 interacts with MT plus-end binding proteins CLIP-170 and CLASP2 via its N-terminal domain. The resulting SOCS3-CLIP-170/CLASP2 complex was essential for maximal SOCS3 anti-inflammatory effects. Both IL-6 and HKSA promoted MT disassembly and disrupted SOCS3 interaction with CLIP-170 and CLASP2. Moreover, knockdown of CLIP-170 or CLASP2 impaired SOCS3-JAK2 interaction and abolished the anti-inflammatory effects of SOCS3. Together, these findings demonstrate for the first time an interaction between SOCS3 and CLIP-170/CLASP2 and reveal that this interaction is essential to the protective effects of SOCS3 in lung endothelium.

Salvinorin A protects against methicillin resistant staphylococcus aureus-induced acute lung injury via Nrf2 pathway

Salvinorin A (SA), a neoclerodane diterpene, is isolated from the dried leaves ofSalvia divinorum. SA has traditionally been used treatments for chronic pain diseases. Recent research has demonstrated that SA possesses the anti-inflammatory property. The present study aim to explore the effects and potentialmechanisms ofSA in protection against Methicillin Resistant Staphylococcus aureus (MRSA)-induced acute lung injury (ALI). Here, we firstly found that verylowdosesof SA (50 μg/kg) could markedly decrease the infiltration of pulmonary neutrophils, mRNA expression of pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) and then attenuated ALI cause by MRSA infection in mice. In vitro findings revealed that SA attenuated lipoteichoicacid-induced apoptosis, inflammation and oxidative stress in RAW264.7 cells. Mechanism research revealed that SA increased both mRNA levels and protein levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and up-regulated mRNA expression of its downstream genes (HO-1, Gclm, Trx-1, SOD1 and SOD2). Additionally, Nrf2 knockout mice abolished the inhibitory effect of SA on neutrophil accumulation and oxidative stress in MRSA-induced ALI. In conclusion, SA attenuates MRSA-induced ALI via Nrf2 signaling pathways.

Levonadifloxacin, a Novel Benzoquinolizine Fluoroquinolone, Modulates Lipopolysaccharide-Induced Inflammatory Responses in Human Whole-Blood Assay and Murine Acute Lung Injury Model

Fluoroquinolones are reported to possess immunomodulatory activity; hence, a novel benzoquinolizine fluoroquinolone, levonadifloxacin, was evaluated in lipopolysaccharide-stimulated human whole-blood (HWB) and mouse acute lung injury (ALI) models. Levonadifloxacin significantly mitigated the inflammatory responses in an HWB assay through inhibition of proinflammatory cytokines and in the ALI model by lowering lung total white blood cell count, myeloperoxidase, and cytokine levels. The immunomodulatory effect of levonadifloxacin, along with promising antibacterial activity, is expected to provide clinical benefits in the treatment of infections.

Blockade of equilibrative nucleoside transporter 1/2 protects against Pseudomonas aeruginosa-induced acute lung injury and NLRP3 inflammasome activation

Pseudomonas aeruginosa infections are increasingly multidrug resistant and cause healthcare-associated pneumonia, a major risk factor for acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). Adenosine is a signaling nucleoside with potential opposing effects; adenosine can either protect against acute lung injury via adenosine receptors or cause lung injury via adenosine receptors or equilibrative nucleoside transporter (ENT)-dependent intracellular adenosine uptake. We hypothesized that blockade of intracellular adenosine uptake by inhibition of ENT1/2 would increase adenosine receptor signaling and protect against P. aeruginosa-induced acute lung injury. We observed that P. aeruginosa (strain: PA103) infection induced acute lung injury in C57BL/6 mice in a dose- and time-dependent manner. Using ENT1/2 pharmacological inhibitor, nitrobenzylthioinosine (NBTI), and ENT1-null mice, we demonstrated that ENT blockade elevated lung adenosine levels and significantly attenuated P. aeruginosa-induced acute lung injury, as assessed by lung wet-to-dry weight ratio, BAL protein levels, BAL inflammatory cell counts, pro-inflammatory cytokines, and pulmonary function (total lung volume, static lung compliance, tissue damping, and tissue elastance). Using both agonists and antagonists directed against adenosine receptors A2AR and A2BR, we further demonstrated that ENT1/2 blockade protected against P. aeruginosa -induced acute lung injury via activation of A2AR and A2BR. Additionally, ENT1/2 chemical inhibition and ENT1 knockout prevented P. aeruginosa-induced lung NLRP3 inflammasome activation. Finally, inhibition of inflammasome prevented P. aeruginosa-induced acute lung injury. Our results suggest that targeting ENT1/2 and NLRP3 inflammasome may be novel strategies for prevention and treatment of P. aeruginosa-induced pneumonia and subsequent ARDS.

Protective effect of Jie-Geng-Tang against Staphylococcus aureus induced acute lung injury in mice and discovery of its effective constituents

ETHNOPHARMACOLOGICAL RELEVANCE

Jie-Geng-Tang (JGT), a famous traditional Chinese medicine prescription, consists of Platycodonis Radix and Glycyrrhizae Radix et Rhizoma. According to traditional medicinal theory, JGT exerts various effects, including apocenosis, detoxifying, moisturizing the lung and relieving sore throat. It is often used to treat throat inflammation and lung diseases.

AIM OF THE STUDY

To determine the protective effect of JGT on Staphylococcus aureus (S. aureus)-induced acute lung injury (ALI) in mice and to identify the compounds in the prescription that may be responsible for antibacterial activity.

MATERIALS AND METHODS

The protective effect of JGT was assessed using S. aureus-induced ALI mice (i.g., 2.7 g/kg/day). Bacterial burden, pathological morphology, cytokine levels of TNF-α, IL-1β, KC, and MIP-2 were evaluated in the lung and bronchoalveolar lavage fluid at 24 h post-infection, respectively. Twenty three compounds in the prescription were evaluated for their minimum inhibitory concentration (MIC) in vitro by means of microbroth dilution method against S. aureus. The antibacterial effects in vitro of licochalcone A and isoliquiritigenin were also investigated by transmission electron microscopy. In vivo antibacterial activities of licochalcone A and isoliquiritigenin were evaluated by survival rates, bacterial burden, and pathological morphology of lung tissues on S. aureus-induced ALI in mice (i.p., 160 mg/kg/day).

RESULTS

Pretreatment with JGT significantly improved the pathological morphology of lung tissues on S. aureus-induced ALI in mice, accompanied with the reduced bacterial burden in the lungs and inhibited expression of inflammatory cytokine levels at 24 h post-infection. Five compounds, namely licochalcone A, licoisoflavone B, glyasperin A, isoliquiritigenin, and licochalcone B from Jie-Geng-Tang displayed good antibacterial activities against S. aureus (MIC < 128 μg/mL). Furthermore, applications of licochalcone A and isoliquiritigenin resulted in the increased survival rates, reduced bacterial burden in the lungs, and improved pathological morphology of lung tissues in S. aureus infected mice.

CONCLUSION

The study demonstrated that Jie-Geng-Tang presented protective role of acute lung injury, which supported its traditional use for the treatment of lung diseases. Licochalcone A, isoliquiritigenin, licoisoflavone B, glyasperin A, and licochalcone B might contribute to the antibacterial activity of JGT on S. aureus-induced acute lung injury. The anti-S. aureus activity of licoisoflavone B, glyasperin A, and licochalcone B in vitro, as well as the anti-S. aureus activity of licochalcone A in vivo, were first reported in this study.

Targeting Neutrophils to Prevent Malaria-Associated Acute Lung Injury/Acute Respiratory Distress Syndrome in Mice

Malaria remains one of the greatest burdens to global health, causing nearly 500,000 deaths in 2014. When manifesting in the lungs, severe malaria causes acute lung injury/acute respiratory distress syndrome (ALI/ARDS). We have previously shown that a proportion of DBA/2 mice infected with Plasmodium berghei ANKA (PbA) develop ALI/ARDS and that these mice recapitulate various aspects of the human syndrome, such as pulmonary edema, hemorrhaging, pleural effusion and hypoxemia. Herein, we investigated the role of neutrophils in the pathogenesis of malaria-associated ALI/ARDS. Mice developing ALI/ARDS showed greater neutrophil accumulation in the lungs compared with mice that did not develop pulmonary complications. In addition, mice with ALI/ARDS produced more neutrophil-attracting chemokines, myeloperoxidase and reactive oxygen species. We also observed that the parasites Plasmodium falciparum and PbA induced the formation of neutrophil extracellular traps (NETs) ex vivo, which were associated with inflammation and tissue injury. The depletion of neutrophils, treatment with AMD3100 (a CXCR4 antagonist), Pulmozyme (human recombinant DNase) or Sivelestat (inhibitor of neutrophil elastase) decreased the development of malaria-associated ALI/ARDS and significantly increased mouse survival. This study implicates neutrophils and NETs in the genesis of experimentally induced malaria-associated ALI/ARDS and proposes a new therapeutic approach to improve the prognosis of severe malaria.

Diguanylate cyclase DgcP is involved in plant and human Pseudomonas spp. infections

The second messenger cyclic di-GMP (c-di-GMP) controls the transition between different lifestyles in bacterial pathogens. Here, we report the identification of DgcP (diguanylate cyclase conserved in Pseudomonads), whose activity in the olive tree pathogen Pseudomonas savastanoi pv. savastanoi is dependent on the integrity of its GGDEF domain. Furthermore, deletion of the dgcP gene revealed that DgcP negatively regulates motility and positively controls biofilm formation in both the olive tree pathogen P. savastanoi pv. savastanoi and the human opportunistic pathogen Pseudomonas aeruginosa. Overexpression of the dgcP gene in P. aeruginosa PAK led to increased exopolysaccharide production and upregulation of the type VI secretion system; in turn, it repressed the type III secretion system, which is a hallmark of chronic infections and persistence for P. aeruginosa. Deletion of the dgcP gene in P. savastanoi pv. savastanoi NCPPB 3335 and P. aeruginosa PAK reduced their virulence in olive plants and in a mouse acute lung injury model respectively. Our results show that diguanylate cyclase DgcP is a conserved Pseudomonas protein with a role in virulence, and confirm the existence of common c-di-GMP signalling pathways that are capable of regulating plant and human Pseudomonas spp. infections.

Changes in the bacterial microbiota in gut, blood, and lungs following acute LPS instillation into mice lungs

Introduction

Previous reports have shown that the gastrointestinal (GI) bacterial microbiota can have profound effects on the lungs, which has been described as the “gut-lung axis”. However, whether a “lung-gut” axis exists wherein acute lung inflammation perturbs the gut and blood microbiota is unknown.

Methods

Adult C57/Bl6 mice were exposed to one dose of LPS or PBS instillation (n = 3 for each group) directly into lungs. Bacterial microbiota of the bronchoalveolar lavage fluid, blood, and cecum were determined using 454 pyrotag sequencing and quantitative polymerase chain reaction (qPCR) at 4 through 168 hours post-instillation. We then investigated the effects of oral neomycin and streptomycin (n = 8) on the microbiota at 4 and 24 hours post LPS instillation versus control treatment (n = 5 at baseline and 4 hours, n = 7 at 24 hours).

Results

At 24 hours post LPS instillation, the total bacterial count was significantly increased in the cecum (P<0.05); whereas the total bacterial count in blood was increased at 4, 48, and 72 hours (P<0.05). Antibiotic treatment reduced the total bacteria in blood but not in the cecum. The increase in total bacteria in the blood correlated with Phyllobacteriaceae OTU 40 and was significantly reduced in the blood for both antibiotic groups (P<0.05).

Conclusion

LPS instillation in lungs leads to acute changes in the bacterial microbiota in the blood and cecum, which can be modulated with antibiotics.

Changes in intestinal microflora in rats with acute respiratory distress syndrome

AIM: To implement high-throughput 16S rDNA sequencing to study microbial diversity in the fecal matter of rats with acute lung injury/acute respiratory distress syndrome (ALI/ARDS).

METHODS: Intratracheal instillation of lipopolysaccharide was used to induce ALI, and the pathological changes in the lungs and intestines were observed. D-lactate levels and diamine oxidase (DAO) activities were determined by enzymatic spectrophotometry. The fragments encompassing V4 16S rDNA hypervariable regions were PCR amplified from fecal samples, and the PCR products of V4 were sequenced by Illumina MiSeq.

RESULTS: Increased D-lactate levels and DAO activities were observed in the model group (P < 0.01). Sequencing results revealed the presence of 3780 and 4142 species in the control and model groups, respectively. The percentage of shared species was 18.8419%. Compared with the control group, the model group had a higher diversity index and a lower number of species of Fusobacteria (at the phylum level), Helicobacter and Roseburia (at the genus level) (P < 0.01). Differences in species diversity, structure, distribution and composition were found between the control group and early ARDS group.

CONCLUSION: The detection of specific bacteria allows early detection and diagnosis of ALI/ARDS.

Intravenous infusion of mesenteric lymph from severe intraperitoneal infection rats causes lung injury in healthy rats

AIM: To investigate whether mesenteric lymph from rats with severe intraperitoneal infection (SII) induces lung injury in healthy rats.

METHODS: Twenty adult male specific pathogen-free Wistar rats were divided into two groups. Animals in the SII group received intraperitoneal injection of Escherichia coli (E. coli) at a dose of 0.3 mL/100 g. Control rats underwent the same procedure, but were injected with normal saline rather than E. coli. We ligated and drained the mesenteric lymphatic vessels and collected the mesenteric lymph. Mesenteric lymph collected from SII or control rats was infused intravenously into male healthy rats at a rate of 1 mL/h for 4 h. At the end of the infusion, all rats were sacrificed. Lungs were removed and examined histologically, and wet-to-dry weight (W/D) ratio and myeloperoxidase (MPO) activity were determined. Enzyme-linked immunosorbent assay (ELISA) was performed to determine the levels of the proinflammatory cytokines tumor necrosis factor (TNF)-α and interleukin (IL)-6. We performed Western blot to investigate the activation of Toll-like receptor (TLR)-4, and nuclear factor (NF)-κB p65.

RESULTS: Compared with the control infusion group, there were obvious pathological changes in the SII group. The W/D ratio was significantly increased in the SII compared to control infusion group (5.86 ± 0.06 vs 5.37 ± 0.06, P < 0.01). MPO activity significantly increased in the SII infusion rats with a mean level of 0.86 ± 0.02 U/g compared to 0.18 ± 0.05 U/g in the control group (P < 0.01). The concentrations of TNF-α and IL-6 were significantly increased in the SII infusion group. The concentration of TNF-α was significantly increased in the SII infusion rats compared to control infusion rats (2104.46 ± 245.91 vs 1475.13 ± 137.82 pg/mL, P < 0.01). The concentration of IL-6 was significantly increased in the SII infusion rats with a mean level of 50.56 ± 2.85 pg/mL compared to 43.29 ± 2.02 pg/mL (P < 0.01). The expression levels of TLR-4 (7496.68 ± 376.43 vs 4589.02 ± 233.16, P < 0.01) and NF-κB (8722.19 ± 323.96 vs 6498.91 ± 338.76, P < 0.01) were significantly increased in the SII infusion group compared to the control infusion group. The infusion of SII lymph, but not control lymph, caused lung injury.

CONCLUSION: The results indicate that SII lymph is sufficient to induce acute lung injury.

The ubiquitin-CXCR4 axis plays an important role in acute lung infection-enhanced lung tumor metastasis

PURPOSE

Our goals were to test the effect of acute lung infection on tumor metastasis and to investigate the underlying mechanisms.

EXPERIMENTAL DESIGN

We combined bacteria-induced and lipopolysaccharide (LPS)-induced acute lung injury/inflammation (ALI) mouse models with mouse metastatic models to study the effect of acute inflammation on lung metastasis in mice. The mechanisms were investigated in ex vivo, in vitro, and in vivo studies.

RESULTS

Both bacteria- and LPS-induced ALI significantly enhanced lung metastasis of four tail vein-injected mouse tumor cell lines. Bacteria also enhanced lung metastasis when 4T1 cells were orthotopically injected. The bronchoalveolar lavage fluid (BALF) from LPS- or bacteria-injected mice stimulated migration of tumor cells. In vivo tracking of metastatic RM-9 cells showed that bacterial injection enhanced early dissemination of tumor cells to the lung. The majority of the BALF migratory activity could be blocked by AMD3100, a chemokine receptor 4 (CXCR4) inhibitor. All tested cell lines expressed CXCR4. The levels of extracellular ubiquitin, but not stromal cell-derived factor-1, in BALF were significantly increased by LPS. Ubiquitin was able to induce AMD3100-sensitive migration of tumor cells. Finally, the antibacterial agent amoxicillin and the CXCR4 inhibitor AMD3100 blocked the enhancement effect of bacterial infection on tumor metastasis.

CONCLUSIONS

Acute lung infection dramatically increased cancer cell homing to the lung and lung metastasis. This change may be due to an alteration of the lung microenvironment and preparation of a favorable metastatic "niche." This effect was seen in multiple cancer types and thus may have broad applications for cancer patients in prevention and/or treatment of metastasis.

Role of different nitric oxide synthase isoforms in a murine model of acute lung injury and sepsis

Excessive production of nitric oxide (NO) by NO synthase (NOS) with subsequent formation of peroxynitrite and poly(adenosine diphosphate ribose) is critically implemented in the pathophysiology of acute lung injury and sepsis. To elucidate the roles of different isoforms of NOS, we tested the effects of non-selective NOS inhibition and neuronal NOS (nNOS)- and inducible NOS (iNOS)-gene deficiency on the pulmonary oxidative and nitrosative stress reaction in a murine sepsis model. The injury was induced by four sets of cotton smoke using an inhalation chamber and subsequent intranasal administration of live Pseudomonas aeruginosa (3.2x10(7) colony-forming units). In wild type mice, the injury was associated with excessive releases of pro-inflammatory cytokines in the plasma, enhanced neutrophil accumulation, increased lipid peroxidation, and excessive formation of reactive nitrogen species and vascular endothelial growth factor in the lung. Both nNOS- and iNOS-gene deficiency led to significantly reduced oxidative and nitrosative stress markers in the lung, but failed to significantly improve survival. Treatment with a non-selective NOS inhibitor failed to reduce the oxidative and nitrosative stress reaction to the same extent and even tended to increase mortality. In conclusion, the current study demonstrates that both nNOS and iNOS are partially responsible for the pulmonary oxidative and nitrosative stress reaction in this model. Future studies should investigate the effects of specific pharmacological inhibition of nNOS and iNOS at different time points during the disease process.

[Effects of different doses of hydrocortisone on acute lung injury in rats with early septic shock induced by Escherichia coli]

OBJECTIVE

To observe the effects of different doses of hydrocortisone (HC) on acute lung injury (ALI) and inflammatory response in rats at early stage of septic shock induced by Escherichia coli and to investigate the possible mechanisms for such differences.

METHODS

ALI model of early septic shock was induced in rats by two injections of Escherichia coli at 5 hours interval, with the first intraperitoneal injection of 6.50 x 10(10) cfu/kg and followed by an external jugular vein injection of 2.00 x 10(11) cfu/kg. Forty Wistar rats were randomly divided into the following five groups: normal control, ALI without HC treatment, high-dose HC (150 mg/kg), medium-dose HC (20 mg/kg) and low-dose HC (6 mg/kg). Two hours after the treatment, the specimens were collected for histopathological examination and the biological indexes of lung injury were measured. The expressions of intercellular adhesion molecule-1 (ICAM-1) and glucocorticoid receptor (GR) in lung tissues were also investigated by immunohistochemical assays.

RESULTS

The biological indexes of lung injury [wet/dry weight ratio (g/g), total protein concentration in bronchoalveolar lavage fluid (mg/L) and lung permeability index (10(-3))] in ALI group (4.76 +/- 0.10, 278.96 +/- 60.45, 4.73 +/- 0.60) were significantly increased as compared to those in normal control group (4.10 +/- 0.07, 67.46 +/- 13.27, 1.12 +/- 0.15) (P < 0.05). The grades of ALI pathologic changes in ALI group (11.13 +/- 1.13) was significantly higher than that in the normal control group (0.50 +/- 0.53, P < 0.05). The ratio of expression area of ICAM-1 in ALI group (0.149 +/- 0.037) was significantly increased as compared to that in the normal control group (0.051 +/- 0.018) (P < 0.05). The ratio of expression area of GR all group (0.043 +/- 0.037) was significantly decreased as compared to that in the normal Control group (0.124 +/- 9.040) (P < 0.05) After administration of HC, all the lung injury indexes, pathological grades and the ratios of expression area of ICAM-1 and GR were significantly improved, with the most remarkable effects observed in the low-dose HC group. The expressions of ICAM-1 and GR showed a significantly negative linear correlation (r = 0.55, P < 0.0001).

CONCLUSION

These results indicated that the low-dose HC treatment had the most remarkable effects of improving the biological indexes of lung injury, inflammatory mediators and pathological changes. These HC dose dependent therapeutic effects might be associated with the level of GR expression.