Chemokines in lung injury: Thomas A. Neff Lecture

23-O-acetylshengmanol-3-O-α-L-arabinoside alleviates lipopolysaccharide-induced acute lung injury through inhibiting IκB/NF-κB and MAPK/AP-1 signaling pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Cimicifuga foetida L. is a well-established traditional Chinese medicine with heat-clearing and detoxifying effects and has good therapeutic effect on oral mucosal ulcer and pharyngitis. The rhizome of this herb is rich in triterpenoid glycosides, including 23-O-acetylshengmanol-3-o-α-L-arabinoside (DA).

AIM OF THE STUDY

Whether and how DA attenuates acute lung injury (ALI) are unclear. Accordingly, we focused on its anti-inflammatory effects and underlying molecular mechanisms in lipopolysaccharide (LPS)-stimulated ALI mice and RAW264.7 cells.

MATERIALS AND METHODS

The model of ALI mice was established by exposed intratracheal instillation of LPS. Lung pathological changes were evaluated by hematoxylin and eosin staining. Pulmonary function was assessed by whole-body plethysmography. Total protein content in bronchoalveolar lavage fluid (BALF) was detected by bicinchoninic acid method. Wet/dry lung ratio was used to evaluate the degree of pulmonary edema in mice. The levels of pro-inflammatory mediators were measured using enzyme-linked immunosorbent assay. The relative expression of pro-inflammatory gene mRNA was examined by RT-qPCR. The expression of inflammatory-related proteins was detected by Western blot. RAW264.7 cells were used to test the anti-inflammatory effects of DA in vitro. Cytotoxicity was assessed using a MTT assay. Nitric oxide production was measured by Griess assay. The production and expression of inflammatory mediators and the protein levels of inflammatory signaling molecules in the NF-κB and MAPK pathways were measured. Furthermore, immunofluorescence staining was used to analyze the expression of p-IκBα, p-ERK, and p-p38 in lung macrophages and the nuclear translocation of NF-κB p65 and AP-1 in cells.

RESULTS

DA evidently alleviated histopathological changes and ameliorated pulmonary edema. Moreover, DA could reduce excessive inflammatory reaction in lung tissue as manifested by the reduction of proinflammatory mediators (IL-1β, IL-6, TNF-α, MCP-1, iNOS, and COX-2) in BALF, serum, and lung tissues. Further, DA inhibited the activation of the NLRP3/caspase-1 pathway in the lung. DA reduced the production and expression of the proinflammatory mediators above in RAW264.7 cells. Mechanistically, DA remarkably blocked the nuclear translocation of NF-κB p65, suppressed IκBα phosphorylation, and markedly reduced the nuclear translocation of AP-1 and the phosphorylation of ERK and p38.

CONCLUSIONS

The findings demonstrated that DA exerts anti-inflammatory effects in LPS-stimulated ALI mice and macrophages by downregulating the NLRP3/caspase-1 signaling pathway in lung tissue and the IκB/NF-κB and MAPKs/AP-1 pathways in macrophages, suggesting that DA may be promising in ALI treatment.

The holy basil administration diminishes the NF-kB expression and protects alveolar epithelial cells from pneumonia infection through interferon gamma

Bacterial pneumonia is one of the most important causes of mortality in the United States. The bacteria Klebsiella pneumoniae (KP) accounts for a significant proportion of community and hospital-acquired infections. Here, we determine that the holy basil (Ocimum sanctum) extract improves cell viability and dampens the proinflammatory cytokine response in an in vitro model of pneumonia. For this, A549, a human alveolar basal epithelial cell line, was subjected to a lethal KP model following a 24-hr pretreatment with basil extract. Bacteremia, cell viability, apoptosis, MTT assay, phagocytic capacity, cytokines, and Khe gene expression were assessed in these cells following pneumonia. Cell morphology analysis showed that holy basil protected A549 cells from KP infection-mediated effects by inhibiting cell death due to apoptosis. Additionally, in the presence of basil, A549 cells demonstrated significantly higher bactericidal capacity and phagocytosis. Administration of holy basil led to reduced expression of hypoxia-inducible factor-1/2a, nuclear factor kappa B, and Khe in the KP-infected cells while increasing interferon (IFN)-γ expression. Our results suggest that basil significantly reduced cell death in the setting of KP infection, likely via attenuation of cytokine and IFN-γ mediated signaling pathways. Holy basil is a promising therapeutic agent for managing and treating bacterial pneumonia based on its potency.

Redox and Inflammatory Signaling, the Unfolded Protein Response, and the Pathogenesis of Pulmonary Hypertension

Protein folding overload and oxidative stress disrupt endoplasmic reticulum (ER) homeostasis, generating reactive oxygen species (ROS) and activating the unfolded protein response (UPR). The altered ER redox state induces further ROS production through UPR signaling that balances the cell fates of survival and apoptosis, contributing to pulmonary microvascular inflammation and dysfunction and driving the development of pulmonary hypertension (PH). UPR-induced ROS production through ER calcium release along with NADPH oxidase activity results in endothelial injury and smooth muscle cell (SMC) proliferation. ROS and calcium signaling also promote endothelial nitric oxide (NO) synthase (eNOS) uncoupling, decreasing NO production and increasing vascular resistance through persistent vasoconstriction and SMC proliferation. C/EBP-homologous protein further inhibits eNOS, interfering with endothelial function. UPR-induced NF-κB activity regulates inflammatory processes in lung tissue and contributes to pulmonary vascular remodeling. Conversely, UPR-activated nuclear factor erythroid 2-related factor 2-mediated antioxidant signaling through heme oxygenase 1 attenuates inflammatory cytokine levels and protects against vascular SMC proliferation. A mutation in the bone morphogenic protein type 2 receptor (BMPR2) gene causes misfolded BMPR2 protein accumulation in the ER, implicating the UPR in familial pulmonary arterial hypertension pathogenesis. Altogether, there is substantial evidence that redox and inflammatory signaling associated with UPR activation is critical in PH pathogenesis.

Interleukin-6, CXCL10 and Infiltrating Macrophages in COVID-19-Related Cytokine Storm: Not One for All But All for One!

SARS-COV-2 virus is responsible for the ongoing devastating pandemic. Since the early phase of the pandemic, the "cytokine-storm" appeared a peculiar aspect of SARS-COV-2 infection which, at least in the severe cases, is responsible for respiratory treat damage and subsequent multi-organ failure. The efforts made in the last few months elucidated that the cytokine-storm results from a complex network involving cytokines/chemokines/infiltrating-immune-cells which orchestrate the aberrant immune response in COVID-19. Clinical and experimental studies aimed at depicting a potential "immune signature" of SARS-COV-2, identified three main "actors," namely the cytokine IL-6, the chemokine CXCL10 and the infiltrating immune cell type macrophages. Although other cytokines, chemokines and infiltrating immune cells are deeply involved and their role should not be neglected, based on currently available data, IL-6, CXCL10, and infiltrating macrophages could be considered prototype factors representing each component of the immune system. It rapidly became clear that a strong and continuous interplay among the three components of the immune response is mandatory in order to produce a severe clinical course of the disease. Indeed, while IL-6, CXCL10 and macrophages alone would not be able to fully drive the onset and maintenance of the cytokine-storm, the establishment of a IL-6/CXCL10/macrophages axis is crucial in driving the sequence of events characterizing this condition. The present review is specifically aimed at overviewing current evidences provided by both in vitro and in vivo studies addressing the issue of the interplay among IL-6, CXCL10 and macrophages in the onset and progression of cytokine storm. SARS-COV-2 infection and the "cytokine storm."

Long-term lung inflammation is reduced by estradiol treatment in brain dead female rats

OBJECTIVES

Lung transplantation is limited by the systemic repercussions of brain death (BD). Studies have shown the potential protective role of 17β-estradiol on the lungs. Here, we aimed to investigate the effect of estradiol on the long-lasting lung inflammatory state to understand a possible therapeutic application in lung donors with BD.

METHODS

Female Wistar rats were separated into 3 groups: BD, subjected to brain death (6h); E2-T0, treated with 17β-estradiol (50 μg/mL, 2 mL/h) immediately after brain death; and E2-T3, treated with 17β-estradiol (50 μg/ml, 2 ml/h) after 3h of BD. Complement system activity and macrophage presence were analyzed. TNF-α, IL-1β, IL-10, and IL-6 gene expression (RT-PCR) and levels in 24h lung culture medium were quantified. Finally, analysis of caspase-3 gene and protein expression in the lung was performed.

RESULTS

Estradiol reduced complement C3 protein and gene expression. The presence of lung macrophages was not modified by estradiol, but the release of inflammatory mediators was reduced and TNF-α and IL-1β gene expression were reduced in the E2-T3 group. In addition, caspase-3 protein expression was reduced by estradiol in the same group.

CONCLUSIONS

Brain death-induced lung inflammation in females is modulated by estradiol treatment. Study data suggest that estradiol can control the inflammatory response by modulating the release of mediators after brain death in the long term. These results strengthen the idea of estradiol as a therapy for donor lungs and improving transplant outcomes.

The protective effect of CXC chemokine receptor 2 antagonist on experimental bronchopulmonary dysplasia induced by postnatal systemic inflammation

BACKGROUND

Animal studies have shown that a leukocyte influx precedes the development of bronchopulmonary dysplasia (BPD) in premature sheep. The CXC chemokine receptor 2 (CXCR2) pathway has been implicated in the pathogenesis of BPD because of the predominance of CXCR2 ligands in tracheal aspirates of preterm infants who later developed BPD.

PURPOSE

To test the effect of CXCR2 antagonist on postnatal systemic and pulmonary inflammation and alveolarization in a newborn Sprague-Dawley rat model of BPD.

METHODS

Lipopolysaccharide (LPS) was injected intraperitoneally (i.p.) into the newborn rats on postnatal day 1 (P1), P3, and P5 to induce systemic inflammation and inhibit alveolarization. In the same time with LPS administration, CXCR2 antagonist (SB-265610) or vehicle was injected i.p. to investigate whether CXCR2 antagonist can alleviate the detrimental effect of LPS on alveolarization by attenuating inflammation. On P7 and P14, bronchoalveolar lavage fluid (BALF) and peripheral blood (PB) were collected from the pups. To assess alveolarization, mean cord length and alveolar surface area were measured on 4 random nonoverlapping fields per animal in 2 distal lung sections at ×100 magnification.

RESULTS

Early postnatal LPS administration significantly increased neutrophil counts in BALF and PB and inhibited alveolarization, which was indicated by a greater mean cord length and lesser alveolar surface area. CXCR2 antagonist significantly attenuated the increase of neutrophil counts in BALF and PB and restored alveolarization as indicated by a decreased mean cord length and increased alveolar surface area in rat pups exposed to early postnatal systemic LPS.

CONCLUSION

CXCR2 antagonist preserved alveolarization by alleviating pulmonary and systemic inflammation induced by early postnatal systemic LPS administration. These results suggest that CXCR2 antagonist can be considered a potential therapeutic agent for BPD that results from disrupted alveolarization induced by inflammation.

Blocking of gastric acid induced histopathological alterations, enhancing of DNA content and proliferation of goblet cells in the acute lung injury mice models by nano-fenugreek oral administration

This current study aimed at detecting the potential protective role of nano-fenugreek seed on acute lung injury (ALI) induced by instillation gastric acid in male Swiss albino mice using histological and histochemical studies. Forty animals were grouped as follows: control group, HCl-treated group, low nano-fenugreek + HCl treated group, and high nano-fenugreek + HCl treated group. Pretreatment with nano-fenugreek in animal model of ALI resulted in marked ameliorations of the lung histological lesions and injury induced by HCL instillation in a dose dependent manner. It also caused inhibition in the increase of the DNA content and prevented proliferation of goblet cells induced by HCl instillation alone. In conclusion, pretreatment with Nano-fenugreek prior induction ALI could be suppress the aggregations of inflammatory cells, enhancing of DNA content, and proliferation of goblet cells induced by gastric acid in a dose dependent manner. We suggest that Nano-fenugreek may be useful in combating lung injury.

RNA-seq transcriptome profiling of porcine lung from two pig breeds in response to Mycoplasma hyopneumoniae infection

Background

Mycoplasma hyopneumoniae (Mhp) is the main pathogen causing respiratory disease in the swine industry. Mhp infection rates differ across pig breeds, with Chinese native pig breeds that exhibit high fecundity (e.g., Jiangquhai, Meishan, Erhualian) more sensitive than Duroc, Landrace, and other imported pig breeds. However, the genetic basis of the immune response to Mhp infection in different pig breeds is largely unknown.

Aims

The aims of this study were to determine the relative Mhp susceptibility of the Chinese native Jiangquhai breed compared to the Duroc breed, and identify molecular mechanisms of differentially expressed genes (DEGs) using an RNA-sequencing (RNA-seq) approach.

Methods

Jiangquhai and Duroc pigs were artificially infected with the same Mhp dose. The entire experiment lasted 28 days. Daily weight gain, Mhp-specific antibody levels, and lung lesion scores were measured to evaluate the Mhp infection susceptibility of different breeds. Experimental pigs were slaughtered on the 28th day. Lung tissues were collected for total RNA extraction. RNA-seq was performed to identify DEGs, which were enriched by gene ontology (GO) and the Kyoto Encyclopedia annotation of Genes and Genomes (KEGG) databases. DEGs were validated with real-time quantitative polymerase chain reaction (RT-qPCR).

Results

Infection with the same Mhp dose produced a more serious condition in Jiangquhai pigs than in Duroc pigs. Jiangquhai pigs showed poorer growth, higher Mhp antibody levels, and more serious lung lesions compared with Duroc pigs. RNA-seq identified 2,250 and 3,526 DEGs in lung tissue from Jiangquhai and Duroc pigs, respectively. The two breeds shared 1,669 DEGs, which were involved in immune-relevant pathways including cytokine-cytokine receptor interaction, PI3K-Akt signaling pathway, and chemokine signaling pathway. Compared to Jiangquhai pigs, more chemokines, interferon response factors, and interleukins were specifically activated in Duroc pigs; CXCL10, CCL4, IL6 and IFNG genes were significantly up-regulated, which may help Duroc pigs enhance immune response and reduce Mhp susceptibility.

Conclusion

This study demonstrated differential immune-related DEGs in lung tissue from the two breeds, and revealed an important role of genetics in the immune response to Mhp infection. The biological functions of these important DEGs should be further confirmed and maybe applied as molecular markers that improve pig health.

Resveratrol downregulates TNF-α-induced monocyte chemoattractant protein-1 in primary rat pulmonary artery endothelial cells by P38 mitogen-activated protein kinase signaling

Background: To evaluate the effects of resveratrol to monocyte chemoattractant protein-1 (MCP-1) and the role of p38 mitogen-activated protein kinase (MAPK) in this process in vitro.

Materials and methods: Animal acute pulmonary thromboembolism (PTE) model: rat model was established by infusion of an autologous blood clot into the pulmonary artery through a polyethylene catheter. One hundred and thirty-two rats were randomly and equally divided into ten groups: rats-control (untreated), rats-1% DMSO, rats-TNF-α, rats-TNF-α + resveratrol, rats-TNF-α +C1142, rats-TNF-α+SB203580, rats-TNF-α+resveratrol + SB203580, rats-resveratrol only, rats-C1142 only, and rats-SB203580 only. Rat pulmonary artery endothelial cells (RPAs) tests: RPAs were isolated from above animal and designated as: RPAs-control, RPAs-1% DMSO control, RPAs-TNF-α, RPAs-TNF-α + resveratrol, RPAs-TNF-α + C1142, RPAs-TNF-α + SB203580, RPAs-TNF-α + resveratrol + SB203580, RPAs-resveratrol only, RPAs-C1142 only, and RPAs-SB203580 only. Each group was further divided into 1, 4, and 8 hrs time point for evaluation (n=6 rats per time point) except RPAs-TNF-α + SB203580, RPAs-TNF-α + resveratrol + SB203580, RPAs-C1142 and RPAs-SB203580 only, which were evaluated at 8 hrs time point. At each time point, mRNA and protein expressions of RPAs of MCP-1 were measured. The phosphorylation of p38 MAPK (p-pMAPK) of RPAs was also detected.

Results: We found that the RPAs-TNF-α elicited significant increases in MCP-1 expression and phosphorylation of p38 mitogen-activated protein kinase (p-p38 MAPK). Furthermore, the MCP-1 expressions of RPAs-Resveratrol, RPAs-C1142, and RPAs-SB203580 were significantly down-regulated, which was associated with robustly suppressed TNF-α-induced p-p38MAPK expression.

Conclusion: Our findings suggested that MCP-1 was involved in the formation of TNF-α-induced inflammatory response, and resveratrol could down-regulate the expression of MCP-1 via TNF-α- inhibition, which might contribute to the decline of acute PTE-induced PH in vivo.

Vitex agnus-castus safeguards the lung against lipopolysaccharide-induced toxicity in mice

Vitex agnus-castus (VAC, Verbenaceae) is widely used in Chinese traditional medicine as an antiinflammatory agent. This study aimed to explore the efficacy of the VAC extract to protect against lipopolysaccharide (LPS)-induced acute lung injury. The results have shown that VAC had a potent protective activity against LPS-induced acute lung damage. It significantly decreased pulmonary edema as there was a significant decrease in lung wet/dry ratio and in protein content. VAC also decreased the lactate dehydrogenase's activity in the bronchoalveolar fluid. VAC ameliorated LPS-induced inflammatory cells infiltration into the lung tissue and reversed the histopathological lesions of the lung. Furthermore, VAC counteracted LPS-induced oxidative stress as it attenuated the lipid peroxidation marker, malondialdehyde, in the lung. VAC increased the antioxidant activity as evident by elevated superoxide dismutase activity and increased reduced glutathione content in the lung tissue. Collectively, VAC has a protective activity against LPS-induced acute lung damage through its antioxidant potential. PRACTICAL APPLICATIONS: Vitex agnus-castus has been used in various traditional medicines for treating various ailments as digestive complains, acne, rheumatic pains, menstrual irregularities, premenstrual syndrome, infertility, and hyperprolactinemia. Its leaves are used as a spice and the fruits are used as a substitute for pepper. VAC food supplements are used by women against psychic and somatic premenstrual symptoms. The findings of this study can demonstrate the potent protective activity of the VAC extract against LPS-induced acute lung damage due to its antioxidative effects. Therefore, VAC could be developed as a health functional food to improve acute lung damage and many diseases caused by oxidative damage.

Role of glutamine in the mediation of E-cadherin, p120-catenin and inflammation in ventilator-induced lung injury

Background:

Ventilator-induced lung injury (VILI) is commonly associated with barrier dysfunction and inflammation reaction. Glutamine could ameliorate VILI, but its role has not been fully elucidated. This study examined the relationship between inflammatory cytokines (interleukin [IL]-6, tumor necrosis factor [TNF]-α, and IL-10) and adherens junctions (E-cadherin, p120-catenin), which were ameliorated by glutamine in VILI, both in vitro and in vivo.

Methods:

For the in vivo study, 30 healthy C57BL/6 mice weighing 25–30 g were randomly divided into five groups with random number table (n = 6 in each group): control (Group C); low tidal volume (Group L); low tidal volume + glutamine (Group L + G); high tidal volume (Group H); and high tidal volume + glutamine (Group H + G). Mice in all groups, except Group C, underwent mechanical ventilation for 4 h. For the in vitro study, mouse lung epithelial 12 (MLE-12) cells pretreated with glutamine underwent cyclic stretching at 20% for 4 h. Cell lysate and lung tissue were obtained to detect the junction proteins, inflammatory cytokines, and lung pathological changes by the Western blotting, cytokine assay, hematoxylin and eosin staining, and immunofluorescence.

Results:

In vivo, compared with Group C, total cell counts (t = −28.182, P < 0.01), the percentage of neutrophils (t = −28.095, P < 0.01), IL-6 (t = −28.296, P < 0.01), and TNF-α (t = −19.812, P < 0.01) in bronchoalveolar lavage (BAL) fluid, lung injury scores (t = −6.708, P < 0.01), and the wet-to-dry ratio (t = −15.595, P < 0.01) were increased in Group H; IL-10 in BAL fluid (t = 9.093, P < 0.01) and the expression of E-cadherin (t = 10.044, P < 0.01) and p120-catenin (t = 13.218, P < 0.01) were decreased in Group H. Compared with Group H, total cell counts (t = 14.844, P < 0.01), the percentage of neutrophils (t = 18.077, P < 0.01), IL-6 (t = 18.007, P < 0.01), and TNF-α (t = 10.171, P < 0.01) in BAL fluid were decreased in Group H + G; IL-10 in BAL fluid (t = −7.531, P < 0.01) and the expression of E-cadherin (t = −14.814, P < 0.01) and p120-catenin (t = −9.114, P < 0.01) were increased in Group H + G. In vitro, compared with the nonstretching group, the levels of IL-6 (t = −21.111, P < 0.01) and TNF-α (t = −15.270, P < 0.01) were increased in the 20% cyclic stretching group; the levels of IL-10 (t = 5.450, P < 0.01) and the expression of E-cadherin (t = 17.736, P < 0.01) and p120-catenin (t = 16.136, P < 0.01) were decreased in the 20% cyclic stretching group. Compared with the stretching group, the levels of IL-6 (t = 11.818, P < 0.01) and TNF-α (t = 8.631, P < 0.01) decreased in the glutamine group; the levels of IL-10 (t = −3.203, P < 0.05) and the expression of E-cadherin (t = −13.567, P < 0.01) and p120-catenin (t = −10.013, P < 0.01) were increased in the glutamine group.

Conclusions:

High tidal volume mechanical ventilation and 20% cyclic stretching could cause VILI. Glutamine regulates VILI by improving cytokines and increasing the adherens junctions, protein E-cadherin and p120-catenin, to enhance the epithelial barrier function.

Investigating Cyclooxygenase Inhibition in a Rat Pulmonary Contusion Model: A Laboratory Study Finding No Improvement with Ibuprofen

Minimal advances have been made in the management of pulmonary contusions (PCs). The purpose of this study was to evaluate the impact of cyclooxygenase inhibition on outcomes following PC in a rat model. PC was induced in anesthetized adult rats. Ibuprofen was given to the treatment group (TG) and water was given to the control group (CG). Lung injury was assessed with pulse oximetry, arterial blood gases, CT, and histopathologic examination. Inflammation was measured with both serum and bronchoalveolar lavage (BAL) levels of tumor necrosis factor a and interleukin-6. Rats in the TG did not differ from rats in the CG with respect to oxygenation. Pathologic examination demonstrated a trend toward more inflammatory infiltrate in the CG, yet the sizes of the contusions were larger in the TG. The CG trended toward decreased levels of interleukin-6 in the serum and BAL at both three and seven days. While BAL levels of tumor necrosis factor a were increased in the TG at three days compared to the CG, they trended toward a reduced amount at seven days. Our data do not support cyclooxygenase inhibition for treatment to decrease the respiratory compromise associated with PC in this model of rat PCs.

Biochemical and Ultrastructural Lung Damage Induced by Rhabdomyolysis in the Rat

Rhabdomyolysis-induced oxidative stress is associated with morphological and functional damage to the kidney and other organs, but applications of this model in the lung are still lacking. The aim of the present study was to determine the relationship between oxidative stress and the morphological changes occurring in the lungs of rats subjected to rhabdomyolysis. Rhabdomyolysis was induced by intramuscular glycerol injection (50% v/v, 10 ml/kg), and the control group was injected with saline vehicle. Arterial blood samples were drawn at 0, 2, 4, and 6 hrs for measurement of arterial gases, creatine kinase activity, and plasma free F2-isoprostane levels. Six hours later, the lungs were removed to determine the wet-to-dry weight ratio, reduced glutathione (GSH) and GSH disulfide (GSSG) levels, and activity of antioxidant enzymes (cataiase [CAT], superoxide dismutase [SOD], and GSH peroxidase [GSH-Px]). Protein carbonylation and lipid peroxidation were assessed in the lungs by measurement of carbonyl and malondialdehyde (MDA) production, respectively. Bronchoalveolar lavage, cell counts, and lung ultrastructural studies were also performed. Six hours after glycerol injection, arterial PO2 and PCO2 were 23% and 38% lower, respectively, and plasma free F2-isoprostane levels were 72% higher, compared with control values. In lungs, protein carbonyl and MDA production were 58% and 12% higher, respectively; the GSH:GSSG ratio and GSH-Px activity were 43% and 60% lower, respectively; and activities of CAT and SOD showed no significant differences compared with controls. Rhabdomyolysis-induced ultrastructural impairment of the lung showed Type II cell damage, extracytoplasmic lamellar bodies and lack of tubular myelin reorganization, endothelial cellular edema, and no disruption of the alveolar-capillary barrier. These results provide evidence that rhabdomyolysis could induce tissue injury associated with increased oxidative stress, suggesting the contribution of oxidative stress to the pathogenic mechanism of acute lung injury.

Genome-wide association studies identify susceptibility loci affecting respiratory disease in Chinese Erhualian pigs under natural conditions

Prevalence of swine respiratory disease causes poor growth performance in and serious economic losses to the swine industry. In this study, a categorical trait of enzootic pneumonia-like (EPL) score representing the infection gradient of a respiratory disease, more likely enzootic pneumonia, was recorded in a herd of 332 Chinese Erhualian pigs. According to their EPL scores and the disease effect on weight gains, these pigs were grouped into controls (EPL score ≤ 1) and cases (EPL score > 1). The weight gain of the case group reduced significantly at days 180, 210, 240 and 300 as compared to the control group. The heritability of EPL score was estimated to be 0.24 based on the pedigree information using a linear mixed model. All 332 Erhualian pigs and their nine sire parents were genotyped with Illumina Porcine 60K SNP chips. Two genome-wide association studies were performed under a generalized linear mixed model and a case-control model respectively. In total, five loci surpassed the suggestive significance level (P = 2.98 × 10^-5 ) on chromosomes 2, 8, 12 and 14. CXCL6, CXCL8, KIT and CTBP2 were highlighted as candidate genes that might play important roles in determining resistance/susceptibility to swine EP-like respiratory disease. The findings advance understanding of the genetic basis of resistance/susceptibility to respiratory disease in pigs.

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.

Glutamine Administration After Sublethal Lower Limb Ischemia Reduces Inflammatory Reaction and Offers Organ Protection in Ischemia/Reperfusion Injury

BACKGROUND

This study investigated the effects of intravenous glutamine (GLN) administration on the expression of adhesion molecules and inflammatory mediators in a mice model of hind limb ischemia/reperfusion (IR) injury.

METHODS

There were 3 IR groups and 1 normal control (NC) group. The NC group did not undergo the IR procedure. Mice in the IR groups underwent 90 minutes of limb ischemia followed by a variable period of reperfusion. Ischemia was performed by applying a 4.5-oz orthodontic rubber band to the left thigh. Mice in one IR group were sacrificed immediately after reperfusion. The other 2 IR groups were injected once with either 0.75 g GLN/kg body weight (G group) or an equal volume of saline (S group) via tail vein before reperfusion. Mice in the S and G groups were subdivided and sacrificed at 4 or 24 hours after reperfusion.

RESULTS

IR enhanced the inflammatory cytokine gene expressions in muscle. Also, plasma interleukin (IL)-6 levels, blood neutrophil percentage, and the adhesion molecule and chemokine receptors expressed by leukocytes were upregulated after reperfusion. The IR-induced muscle inflammatory mediator gene expressions, blood macrophage percentage, and plasma IL-6 concentration had declined at an early or a late phase of reperfusion when GLN was administered. Histologic findings also found that remote lung injury was attenuated during IR insult.

CONCLUSIONS

A single dose of GLN administration immediately after sublethal lower limb ischemia reduces the inflammatory reaction locally and systemically; this may offer local and distant organ protection in hind limb IR injury.

Increase in fitness of Streptococcus pneumoniae is associated with the severity of necrotizing pneumonia

BACKGROUND

The incidence of necrotizing pneumococcal pneumonia has increased during the past 2 decades. We hypothesized that increased pneumococcal load or augmented inflammatory cytokine production might lead to destructive pneumococcal lung disease.

METHODS

This study enrolled prospectively 0- to 18-year-old children with a diagnosis of community-acquired pneumonia with pleural effusion admitted to 6 medical centers from March 2010 to April 2012. Children were diagnosed with pneumococcal empyema if the pleural fluid tested positive for quantitative pneumococcal (lytA) detection by real-time polymerase chain reaction. Pneumococcal empyema cases were further divided into 4 groups according to necrosis severity: (0) nonnecrosis, (1) mild necrosis, (2) cavitation and (3) bronchopleural fistula. Nasopharyngeal and pleural pneumococcal load, as well as levels of proinflammatory cytokines (TNF-α, IL-1β, IL-6, IL-8), Th1-(IL-2, IFN-γ), Th2-(IL-4, IL-10) and Th17-cytokines (IL-17), in the pleural fluid was measured.

RESULTS

Serotypes 19A and 3 accounted for 69.4% and 12.5%, respectively, of 72 cases of pneumococcal empyema. Pleural pneumococcal load was significantly higher in serotypes 19A and 3 infection than in the other strains causing infection (P = 0.006). There was a correlation between nasopharyngeal and pleural pneumococcal load (ρ = 0.35; P = 0.05). In multivariate ordinal logistic regression analysis, pleural pneumococcal load (adjusted odds ratio: 1.79; 95% confidence interval: 1.03-3.06) and IL-8 (adjusted odds ratio: 2.64; 95% confidence interval: 1.21-5.75) were independent factors associated with the severity of lung necrosis.

CONCLUSIONS

Evolution of Streptococcus pneumoniae toward increased fitness in their interaction with host and exaggerated IL-8 expression may be responsible for the increase of necrotizing pneumococcal pneumonia.

Glutamine attenuates acute lung injury caused by acid aspiration

Inadequate ventilator settings may cause overwhelming inflammatory responses associated with ventilator-induced lung injury (VILI) in patients with acute respiratory distress syndrome (ARDS). Here, we examined potential benefits of glutamine (GLN) on a two-hit model for VILI after acid aspiration-induced lung injury in rats. Rats were intratracheally challenged with hydrochloric acid as a first hit to induce lung inflammation, then randomly received intravenous GLN or lactated Ringer's solution (vehicle control) thirty min before different ventilator strategies. Rats were then randomized to receive mechanical ventilation as a second hit with a high tidal volume (TV) of 15 mL/kg and zero positive end-expiratory pressure (PEEP) or a low TV of 6 mL/kg with PEEP of 5 cm H2O. We evaluated lung oxygenation, inflammation, mechanics, and histology. After ventilator use for 4 h, high TV resulted in greater lung injury physiologic and biologic indices. Compared with vehicle treated rats, GLN administration attenuated lung injury, with improved oxygenation and static compliance, and decreased respiratory elastance, lung edema, extended lung destruction (lung injury scores and lung histology), neutrophil recruitment in the lung, and cytokine production. Thus, GLN administration improved the physiologic and biologic profiles of this experimental model of VILI based on the two-hit theory.

Keratinocyte growth factor-2 is protective in lipopolysaccharide-induced acute lung injury in rats

Keratinocyte growth factor-2 (KGF-2) plays a key role in lung development, but its role in acute lung injury has not been well characterized. Lipopolysaccharide instillation caused acute lung injury, which significantly elevated lung wet-to-dry weight ratio, protein and neutrophils in bronchoalveolar lavage fluid (BALF), inhibited surfactant protein A and C expression in lung tissue, and increased pathological injury. Pretreatment with KGF-2 improved the above lung injury parameters, partially restored surfactant protein A and C expression, and KGF-2 given 2-3 days before LPS challenge showed maximum lung injury improvement. Pretreatment with KGF-2 also markedly reduced the levels of TNF-α, MIP-2, IL-1β and IL-6 in BALF and the levels of IL-1β and IL-6 in lung tissue. Histological analysis showed there was increased proliferation of alveolar type II epithelial cells in lung parenchyma, which reached maximal 2 days after KGF-2 instillation. Intratracheal administration of KGF-2 attenuates lung injury induced by LPS, suggesting KGF-2 may be potent in the intervention of acute lung injury.

Control of ventilation in COPD and lung injury

Breathing occurs in single breaths and in patterns which are altered by the onset, progression and resolution of respiratory diseases. Through modulations of rate, depth, and patterning of breathing, the ventilatory control system maintains numerous critical variables within their homeostatic ranges. A dynamic respiratory control system is critical to successful adaptation in the face of progressive pulmonary pathology. The objective of this review, is to illustrate functional changes and compensatory mechanisms which occur with the onset and progression of acute and chronic lung disease. Chronic obstructive pulmonary disease (COPD) will be considered as a model of a slowly progressive pulmonary process, where destruction of lung parenchyma and airway obstruction leads to hypoxemia and hypercapnia. Over time, adaptations of the respiratory control system to this disease include changes in the intrinsic properties of respiratory muscles, chemoreceptor signaling, and central respiratory drive which increase motor output to the respiratory muscles. In contrast, acute respiratory distress syndrome (ARDS) is an exemplar of an acute pulmonary process. The result of severe lung injury, ARDS is characterized by lung infiltrates, rapidly progressive hypoxemic respiratory failure, and possible progression to pulmonary fibrosis. Changes in breathing patterns result from these functional changes, as well as altered processing of afferent feedback by the central controller, possibly influenced by brainstem inflammation. Taken together, these disease models highlight the plasticity of the respiratory control system in response to the development and progression of lung disease.

Alanyl-glutamine administration suppresses Th17 and reduces inflammatory reaction in dextran sulfate sodium-induced acute colitis

T helper (Th) cells play a major role in the pathogenesis of inflammatory bowel disease (IBD). Glutamine (Gln) is known to have immunomodulatory effects in metabolic stressed conditions. This study investigated the effects of post-treatment of alanyl-glutamine (Ala-Gln) on Th cell-associated cytokine expressions and inflammatory reaction in dextran sulfate sodium (DSS)-induced colitis. C57BL/6 mice received distilled water containing 3% DSS for 5 days to induce colitis, whereas the normal control (NC) group received distilled water. After induction of colitis, one of the colitis groups (DG) was intraperitoneally injected with an Ala-Gln solution (0.5 g Gln/kg/d), and the saline DSS group (DS) received an identical volume of saline. After treatment for 3 days, mice were sacrificed, and the blood and tissue samples were collected for further analysis. DSS colitis resulted in higher percentages of blood interleukin (IL)-17-secreting Th cells and greater expression of Th cell-associated cytokine messenger RNA (mRNA) in the mesenteric lymph nodes (MLN). Also, luminal immunoglobin (Ig) G, keratinocyte-derived chemokine, and macrophage chemoattractant protein-1 levels were higher in the DS group than the NC group, whereas these parameters did not differ between the DG and NC groups. The DG group had lower blood IL-17A, 17F, MLN IL-17 mRNA and macrophage percentage in the peritoneal lavage fluid than those of the DS group. These results suggest that post-treatment with Ala-Gln suppressed Th17-associated cytokine expressions, reduced macrophage infiltration into the peritoneal cavity and decreased pro-inflammatory cytokine production in the colon, thus may have attenuated inflammatory response in DSS-induced colitis.

Tumor necrosis factor-α plays an initiating role in extracorporeal circulation-induced acute lung injury

BACKGROUND

Despite advances in critical care, the mortality rate for patients with acute lung injury (ALI) remains high. The aim of this study was to test the hypothesis that tumor necrosis factor-α (TNF-α) plays an initiating role in the onset of extracorporeal circulation (ECC)-induced ALI.

METHODS

Eight New Zealand rabbits subjected to 1 h of ECC and 40 min of observation after termination of ECC were used for monitoring pulmonary nociceptor activity. Fifty Sprague-Dawley (SD) rats that received 2 h of ECC and 4 h of rest were used to measure the pulmonary function and inflammatory cytokines release, including total cells, neutrophils, and TNF-α in bronchoalveolar lavage (BAL) and white blood cell (WBC) and neutrophils in blood. An additional 40 SD rats were randomized to pretreatment with inhalation of phosphate buffer solution (control group), IgG (IgG inh group), or TNF-α antibody (anti-TNF-α inh group) and venous injection of TNF-α antibody (anti-TNF-α iv group). After 2 h of ECC and 4 h of rest, the arterial blood and BAL fluid were collected for measurement of arterial oxygen pressure (PaO2) and inflammatory cytokines release. The left-lower-lung tissues of animals were stained with hematoxylin & eosin (H&E).

RESULTS

The results demonstrated that the activities of airway nociceptor and TNF-α release were similarly upregulated at the early stage and in a time-related manner in ECC-induced ALI. Pretreatment with TNF-α antibody inhalation, but not venous injection, improved pulmonary function, inhibited pulmonary inflammation, and attenuated pulmonary histopathological changes after ECC.

CONCLUSION

We concluded that TNF-α played an important role in the pathogenesis of ALI and acted as an initiating cytokine at the early stage of ECC-induced ALI.

Current knowledge of acute lung injury and acute respiratory distress syndrome

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) continues to be a major cause of mortality in adult and pediatric critical care medicine. This article discusses the pulmonary sequelae associated with ALI and ARDS, the support of ARDS with mechanical ventilation, available adjunctive therapies, and experimental therapies currently being tested. It is hoped that further understanding of the fundamental biology, improved identification of the patient's inflammatory state, and application of therapies directed at multiple sites of action may ultimately prove beneficial for patients suffering from ALI/ARDS.

Resuscitation with polymerized human placenta hemoglobin attenuated hemorrhagic shock-induced lung injury

This study was designed to investigate whether polymerized human placenta hemoglobin (PolyPHb) attenuated hemorrhagic shock-induced lung injury. A mean arterial pressure (MAP) of 30mmHg was maintained for 60 min. Then, all the rats were randomly resuscitated with hetastarch, whole blood, or PolyPHb. The result indicated that PolyPHb greatly improved the MAP and pulmonary function, and significantly reduced the release of inflammatory cytokines, histopathological changes, and pulmonary edema. Therefore, our findings suggest that PolyPHb could reduce pulmonary injury after hemorrhagic shock, and this effect was probably associated with the depressed inflammatory response.

Effects of alanyl-glutamine dipeptide on the expression of colon-inflammatory mediators during the recovery phase of colitis induced by dextran sulfate sodium

PURPOSE

Glutamine (Gln) is a nutrient with immunomodulatory effects in metabolic stressed conditions. This study investigated the effects of Gln on colonic-inflammatory-mediator expression and mucosal repair in mice with dextran sulfate sodium (DSS)-induced colitis.

METHODS

C57BL/6 mice received distilled water containing 3 % DSS for 5 d to induce colitis. One of the DSS-treated groups was intraperitoneally injected with an alanyl (Ala)-Gln solution 3 days before (G-DSS) while the other group was administered Ala-Gln 3 days after colitis (DSS-G) was induced. The Ala-Gln solution provided 0.5 g Gln/kg/d. The saline-DSS group (S-DSS) received an identical amount of saline before and after colitis was induced to serve as a positive control.

RESULTS

The S-DSS group had a shorter colon length, higher plasma haptoglobin level, and more-severe colon inflammation. Also, the toll-like receptor (TLR)4 level, nuclear factor (NF)-κB activation, and inflammatory cytokine gene expression in the colon were higher than those of the normal control group. Gln administration either before or after colitis suppressed TLR4 protein levels, decreased plasma haptoglobin, and reduced colon inflammation. Histological inflammatory scores were also lowered. Compared to the post-colitis Gln group, preventive use of Gln had higher colon length, expressions of mucin 2, trefoil factor 3, and heat shock protein 72 genes were also upregulated in the colon.

CONCLUSIONS

These results suggest that Gln administered either before or after the colitis mitigated inflammation of colitis that was not observed in group without Gln injection. Prophylactic treatment with Gln had more-beneficial effects on reducing inflammatory markers and enhancing the recovery of mucosa in DSS-induced colitis.

Resveratrol downregulates acute pulmonary thromboembolism-induced pulmonary artery hypertension via p38 mitogen-activated protein kinase and monocyte chemoattractant protein-1 signaling in rats

AIMS

In the present study, we explored the hypothesis that initiation of PH involves the upregulation of monocyte chemoattractant protein-1 (MCP-1) in acute PTE. We evaluated the effects of resveratrol and the role of p38 mitogen-activated protein kinase (MAPK) in this process.

MAIN METHODS

A rat model of acute PTE was established by infusion of an autologous blood clot into the pulmonary artery through a polyethylene catheter. Rats were randomly divided into 1, 4, and 8 hour time groups. Resveratrol, C1142 (a rodent chimeric mAb that neutralizes rat MCP-1) or SB203580 (a p38MAPK specific inhibitor) was administered to the animals beginning 1 h prior to the start of the acute PTE protocol. At each time point, the mean pulmonary artery pressure (mPAP), mRNA and protein expressions of MCP-1 were measured. The phosphorylation of p38 MAPK (p-pMAPK) was also detected.

KEY FINDINGS

Acute PTE elicited significant increases in mean pulmonary artery pressure (mPAP), and up-regulated the expression of monocyte chemoattractant protein-1 (MCP-1) and phosphorylation of p38 mitogen-activated protein kinase (p-p38 MAPK). Administration of C1142 markedly reduced mPAP. Furthermore, pre-treatment of rats with resveratrol significantly reduced mPAP and down-regulated the expression of MCP-1, which was associated with robustly suppressed acute PTE-induced p-p38MAPK expression.

SIGNIFICANCE

These findings suggested that MCP-1 was involved in the formation of acute PTE-induced PH, and resveratrol down-regulated the expression of MCP-1 by inhibiting acute PTE-induced p-p38MAPK activation, which contributed to the decrease in PH.

Nicotine exerts an anti-inflammatory effect in a murine model of acute lung injury

Activation of the cholinergic anti-inflammatory pathway through direct activation of nicotinic acetylcholine receptors on immune cells can inhibit pro-inflammatory chemokine and cytokine release and thereby protect in a variety of inflammatory diseases. The aim of this study was to investigate whether nicotine treatment protected against acute lung inflammation. Mice challenged with intratracheal lipopolysaccharide (LPS, 50 μg) were treated with nicotine (0.2 or 0.4 mg/kg, sc). After 24 h, bronchoalveolar lavage fluid (BALF) was obtained to measure leukocyte infiltration, lung edema, and pro-inflammatory chemokine (MIP-1α, MIP-2, and eotaxin) and cytokine (IL-1, IL-6, and TNF-α) levels. Nicotine treatment reduced the LPS-mediated infiltration of leukocytes and edema as evidenced by decreased BALF inflammatory cells, myeloperoxidase, and protein. Nicotine also downregulated lung production of pro-inflammatory chemokines and cytokines. These data support the proposal that activation of the cholinergic anti-inflammatory pathway may represent a useful addition to the therapy of acute respiratory distress syndrome.

Interleukin-1β regulates CXCL8 release and influences disease outcome in response to Streptococcus pneumoniae, defining intercellular cooperation between pulmonary epithelial cells and macrophages

The success of Streptococcus pneumoniae (the pneumococcus) as a pulmonary pathogen is related to its restriction of innate immune responses by respiratory epithelial cells. The mechanisms used to overcome this restriction are incompletely elucidated. Pulmonary chemokine expression involves complex cellular and molecular networks, involving the pulmonary epithelium, but the specific cellular interactions and the cytokines that control them are incompletely defined. We show that serotype 2 or 4 pneumococci induce only modest levels of CXCL8 expression from epithelial cell lines, even in the absence of a polysaccharide capsule. In contrast, coculture of A549 cells with the macrophage-like THP-1 cell line, differentiated with vitamin D, or monocyte-derived macrophages enhanced CXCL8 release. Supernatants from the THP-1 cell line prime A549 cells to release CXCL8 at levels similar to cocultures. Interleukin-1Ra (IL-1Ra) inhibits CXCL8 release from cocultures and reduces the activity of macrophage-conditioned media, but inhibition of tumor necrosis factor alpha (TNF-α) had only a minimal effect on CXCL8 release. Release of IL-1β but not TNF-α was upregulated in cocultures. IL-1 type 1 receptor knockout C57BL/6 and BALB/c mice confirmed the importance of IL-1 signaling in CXC chemokine expression and neutrophil recruitment in vivo. In fulminant disease, increased IL-1 signaling resulted in increased neutrophils in the airway and more invasive disease. These results demonstrate that IL-1 is an important component of the cellular network involving macrophages and epithelial cells, which facilitates CXC chemokine expression and aids neutrophil recruitment during pneumococcal pneumonia. They also highlight a potential clinical role for anti-IL-1 treatment to limit excessive neutrophilic inflammation in the lung.

Lung and brainstem cytokine levels are associated with breathing pattern changes in a rodent model of acute lung injury

Acute lung injury evokes a pulmonary inflammatory response and changes in the breathing pattern. The inflammatory response has a centrally mediated component which depends on the vagi. We hypothesize that the central inflammatory response, complimentary to the pulmonary inflammatory response, is expressed in the nuclei tractus solitarii (nTS) and that the expression of cytokines in the nTS is associated with breathing pattern changes. Adult, male Sprague-Dawley rats (n=12) received intratracheal instillation of either bleomycin (3units in 120μl of saline) or saline (120μl). Respiratory pattern changed by 24h. At 48h, bronchoalveolar lavage fluid and lung tissue had increased IL-1β and TNF-α levels, but not IL-6. No changes in these cytokines were noted in serum. Immunocytochemical analysis of the brainstem indicated increased expression of IL-1β in the nTS commissural subnucleus that was localized to neurons. We conclude that breathing pattern changes in acute lung injury were associated with increased levels of IL-1β in brainstem areas which integrate cardio-respiratory sensory input.

Preventive effects of valnemulin on lipopolysaccharide-induced acute lung injury in mice

Valnemulin reportedly regulates inflammatory responses in addition to its in vitro antibacterial activity. In this study, we established a mouse model of lipopolysaccharide (LPS)-induced inflammatory lung injury and investigated the effect of valnemulin (100 mg/kg) on acute lung injury (ALI) 8 h after LPS challenge. We prepared bronchoalveolar lavage fluid (BALF) for measuring protein concentrations, cytokine levels, and superoxidase dismutase (SOD) activity, and collected lungs for assaying wet-to-dry weight (W/D) ratios, myeloperoxidase (MPO) activity, cytokine mRNA expression, and histological change. We found that the pre-administration of valnemulin significantly decreases the W/D ratio of lungs, protein concentrations, and the number of total cells, neutrophils, macrophages, and leukomonocytes, and histologic analysis indicates that valnemulin significantly attenuates tissue injury. Furthermore, valnemulin significantly increases LPS-induced SOD activity in BALF and decreases lung MPO activity as well. In addition, valnemulin also inhibits the production of tumor necrosis factor-alpha, interleukin-6, and interleukin-1beta, which is consistent with mRNA expression in lung. The results showed that valnemulin had a protective effect on LPS-induced ALI in mice.

Ron receptor deficient alveolar myeloid cells exacerbate LPS-induced acute lung injury in the murine lung

Previous studies have shown that the Ron receptor tyrosine kinase is an important regulator of the acute lung inflammatory response induced by intranasal administration of bacterial LPS. Compared to wild-type mice, complete loss of the Ron receptor in all cell types in vivo was associated with increased lung damage as determined by histological analyses and several markers of lung injury including increases in pro-inflammatory cytokines such as TNF-α. Tumor-necrosis factor-α is a multifunctional cytokine secreted by macrophages, which plays a major role in inflammation and is a central mediator of several disease states including rheumatoid arthritis and sepsis. Based on increased TNF-α production observed in the Ron-deficient mice, we hypothesized that Ron receptor function in the inflammatory cell compartment is essential for the regulating lung injury in vivo. To test this hypothesis, we generated myeloid lineage-specific Ron-deficient mice. In this study, we report that loss of Ron signaling selectively in myeloid cells results in increased lung injury following intranasal administration of LPS as measured by increases in TNF-α production, ensuing neutrophil accumulation and increased lung histopathology. These findings corroborate the role of Ron receptor tyrosine kinase as a negative regulator of inflammation and further demonstrate the in vivo significance of Ron signaling selectively in myeloid cells as a major regulator of this response in vivo. These data authenticate Ron as a potential target in innate immunity and TNF-α-mediated pathologies.

Protective effects of luteolin against lipopolysaccharide-induced acute lung injury involves inhibition of MEK/ERK and PI3K/Akt pathways in neutrophils

AIM

To investigate whether luteolin, the major polyphenolic components of Lonicera japonica, has beneficial effects against lipopolysaccharide (LPS)-induced acute lung injury (ALI) and to determine whether the protective mechanism involves anti-inflammatory effects on neutrophils.

METHODS

ALI was induced with intratracheal instillation of LPS in mice. The level of ALI was determined by measuring the cell count and protein content in bronchoalveolar lavage (BAL) fluid. Neutrophils were stimulated with formyl-Met-Leu-Phe (fMLP) or LPS in vitro. Chemotaxis and superoxide anion generation were measured to evaluate neutrophil activation. The potential involvement of intracellular signaling molecules in regulating neutrophil activation was analyzed by using Western blot.

RESULTS

LPS induced ALI in mice, as evidenced with leukocyte infiltration and protein leakage into the lungs. Luteolin attenuated LPS-induced leukocyte infiltration and protein extravasation. In cell studies, luteolin attenuated the fMLP-induced neutrophil chemotaxis and respiratory burst (IC(50) 0.2+/-0.1 micromol/L and 2.2+/-0.8 micromol/L, respectively), but had a negligible effect on superoxide anion generation during phorbol myristate acetate stimulation. Furthermore luteolin effectively blocked MAPK/ERK kinase 1/2 (MEK), extracellular signal-regulated kinase (ERK), and Akt phosphorylation in fMLP- and LPS-stimulated neutrophils.

CONCLUSION

These results indicate that luteolin has beneficial effects against LPS-induced ALI in mice, and the attenuation of neutrophil chemotaxis and respiratory burst by luteolin involves the blockade of MEK-, ERK-, and Akt-related signaling cascades.

Endothelial microparticles induce inflammation in acute lung injury

BACKGROUND

Previously, we have shown that endothelial microparticles (EMPs) injected into mice induce acute lung injury (ALI) [1]. In this study, we hypothesize that EMPs induce ALI by initiating cytokine release in the lung, leading to recruitment and activation of neutrophils.

MATERIALS AND METHODS

C57BL/6J male mice (8-10 wk old) were intravenously injected with EMPs (200,000/mL), LPS (2 mg/kg), or both. Bronchoalveolar lavage (BAL) and serum levels of IL-1β and TNF-α were analyzed by enzyme-linked immunoassay (ELISA). Morphometric analysis was performed on H and E stained lung sections. Myeloperoxidase (MPO) levels were determined via an enzymatic assay and immunofluorescence of stained sections.

RESULTS

EMPs led to significantly increased pulmonary and systemic IL-1β and TNF-α levels, which correlated with increased neutrophil recruitment to the lung. MPO levels in the lungs were increased significantly following injection of EMPs or LPS, compared to PBS. In mice treated with EMPs and LPS either simultaneously or successively, the cytokine and MPO levels were significantly increased over that of either treatment alone.

CONCLUSION

EMPs contribute to lung injury through the initiation of a cytokine cascade that increases recruitment of neutrophils and subsequent release of MPO. Furthermore, treatment of mice with both EMPs and LPS induced greater lung injury than either treatment alone, suggesting that EMPs prime the lung for increased injury by other pathogens. Therapies aimed at reducing or blocking EMPs may be a useful strategy for attenuating lung injury.

Ron receptor tyrosine kinase negatively regulates TNFalpha production in alveolar macrophages by inhibiting NF-kappaB activity and Adam17 production

The Ron receptor tyrosine kinase (TK) plays a regulatory role in the inflammatory response to acute lung injury induced by intranasal administration of bacterial LPS. Previously, we have shown that mice with a targeted deletion of the TK signaling domain of the Ron receptor exhibited more severe lung injury in response to intranasal LPS administration as evidenced by an increased leakage of albumin in the lungs and a greater thickening of the alveolar septa compared with wild-type mice. In addition, lung injury in the Ron TK-deficient (TK(-/-)) mice was associated with increased activation of the transcription factor, nuclear factor-kappaB (NF-kappaB), and significantly increased intrapulmonary expression of TNFalpha. TNFalpha, a multifunctional proinflammatory cytokine, is a central mediator in several disease states, including rheumatoid arthritis and sepsis. On the basis of the observation that TNFalpha production is increased in the Ron TK-/- mice and that macrophages are a major source of this cytokine, we hypothesized that the alterations observed in the Ron TK(-/-) mice may be due, in part, to Ron signaling, specifically in alveolar macrophages. To test this hypothesis, we used the wild-type and Ron TK(-/-) primary alveolar macrophages and the murine alveolar macrophage cell line, MH-S, to examine the effects of Ron activation on LPS-induced TNFalpha production and NF-kappaB activity. Here, we reported that Ron is expressed on alveolar macrophages and MH-S cells. Activation of Ron by its ligand, hepatocyte growth factor-like protein, decreases TNFalpha production in alveolar macrophages after LPS challenge. Decreased TNFalpha is associated with hepatocyte growth factor-like protein-induced decreases in NF-kappaB activation and increases in the NF-kappaB inhibitory protein, IkappaB. We also provided the first evidence for Ron as a negative regulator of Adam17, the metalloprotease involved in TNFalpha processing. These results indicate that Ron plays a critical role in regulation of alveolar macrophage signaling and validates this receptor as a target in TNFalpha-mediated pulmonary pathologies.

The novel inosine analogue INO-2002 exerts an anti-inflammatory effect in a murine model of acute lung injury

Endogenous purines, including inosine, have been shown to exert immunomodulatory and anti-inflammatory effects in a variety of disease models. The dosage of inosine required for these effects has been shown to be between 200 and 600 mg kg(-1) because of the rapid metabolism of inosine in vivo. The aim of this study was to determine whether a metabolic resistant purine analog, INO-2002, exerts anti-inflammatory effects in an animal model of acute respiratory distress syndrome. Mice challenged with intratracheal LPS (50 microg) were treated with INO-2002 (30 or 100 mg kg(-1), i.p.) in divided doses at either 1 and 12 h or at 5 and 16 h. After 24 h, bronchoalveolar lavage fluid was obtained to measure leukocyte infiltration by myeloperoxidase levels, lung edema by protein levels, and proinflammatory chemokine (macrophage inflammatory protein 1alpha) and cytokine (TNF-alpha, IL-1, and IL-6) levels. INO-2002 (30 and 100 mg kg(-1)) reduced the LPS-mediated infiltration of leukocytes and edema as evidenced by bronchoalveolar lavage fluid reduction in levels of myeloperoxidase and protein. INO-2002 also downregulated expression of the proinflammatory mediators macrophage inflammatory protein 1alpha, TNF-alpha, IL-1, and IL-6. Delaying the start of treatment by 5 h after LPS administration affected the potency of INO-2002 protective effects, with 100 but not 30 mg kg(-1) having anti-inflammatory effects. The inosine analog INO-2002 largely suppressed LPS-induced inflammation in vivo at doses lower than those needed for the naturally occurring purine inosine. These data support the proposal that purine analogs, resistant to metabolic breakdown, may represent a useful addition to the therapy of acute respiratory distress syndrome.

Humanized monoclonal antibody against the chemokine CXCL-8 (IL-8) effectively prevents acute lung injury

As one of the most important endogenous chemotactic factors for neutrophils, the chemokine CXCL8 (IL-8) is involved in the pathogenesis of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), characterized by massive neutrophil infiltration in the lung. Since neutralization of CXCL8 with polyclonal antibody has been shown to reduce the severity of ALI/ARDS in animal models, we explored the potential of humanized anti-CXCL8 antibody as a preventive or therapeutic agent for ALI. We used a 'two-hit' protocol to induce ALI in rabbits that showed extensive edema in the alveolar lumina, marked infiltration of neutrophils in the lung tissue, fibrin deposition in alveolar space, and destruction of pulmonary architecture, culminating in severe hypoxemia. Concomitant challenge with endotoxin after priming with oleic acid (OA) induced a marked elevation of CXCL8 level in bronchoalveolar lavage fluid. Treatment of the rabbits with a humanized anti-CXCL8 antibody prevented neutrophil infiltration in the lung in association with alleviated ALI syndrome. Our results indicate a promising future for utilization of humanized anti-CXCL8 antibody in the prevention and treatment of ALI and ARDS in human.

Lung contusion: inflammatory mechanisms and interaction with other injuries

This article reviews current animal models and laboratory studies investigating the pathophysiology of lung contusion (LC), a common and severe condition in patients with blunt thoracic trauma. Emphasis is on studies elucidating cells, mediators, receptors, and processes important in the innate pulmonary inflammatory response that contribute to LC injury. Surfactant dysfunction in the pathogenesis of LC is also discussed, as is the potential role of epithelial cell or neutrophil apoptosis. Studies examining combination injuries where LC is exacerbated by secondary insults such as gastric aspiration in trauma patients are also noted. The need for continuing mechanism-based research to further clarify the pathophysiology of LC injury, and to define and test potential therapeutic interventions targeting specific aspects of inflammation or surfactant dysfunction to improve clinical outcomes in patients with LC, is also emphasized.

Role of the pulmonary epithelium and inflammatory signals in acute lung injury

Acute lung injury (ALI) is a clinical disease marked by respiratory failure due to disruption of the epithelial and endothelial barrier, flooding of the alveolar compartment with protein-rich fluid and recruitment of neutrophils into the alveolar space. ALI affects approximately 200,000 patients annually in the USA and results in approximately 75,000 deaths. It is associated with prolonged mechanical ventilation, intensive medical care, high morbidity and mortality, and rising healthcare costs. Owing to its impact on public health, great strides have been made towards understanding the pathobiology of ALI to affect outcome. This review will focus on the role of the epithelial cell in the pathogenesis and resolution of ALI and the role of various inflammatory mediators in ALI.

Myeloid cells control termination of lung inflammation through the NF-kappaB pathway

Although acute lung inflammation in response to local or systemic infection involves myeloid and nonmyeloid cells, the interplay between different cell types remains poorly defined. Since NF-kappaB is a key transcription factor for innate immunity, we investigated whether dysregulated NF-kappaB activation in myeloid cells impacts inflammatory signaling in nonmyeloid cells and generation of neutrophilic lung inflammation in response to systemic endotoxemia. We generated bone marrow chimeras by fetal liver transplantation of cells deficient in IkappaBalpha or p50 into lethally irradiated NF-kappaB reporter transgenic mice. No differences were apparent between bone marrow chimeras in the absence of an inflammatory stimulus; however, following intraperitoneal injection of Escherichia coli lipopolysaccharide (LPS), IkappaBalpha- or p50-deficient bone marrow chimeras showed increased NF-kappaB activation in nonhematopoietic cells, exaggerated neutrophilic inflammation, and higher mortality compared with untransplanted reporter mice and wild-type bone marrow chimeras. Primary bone marrow-derived macrophages (BMDM) from IkappaBalpha(-/-) or p50(-/-) exhibited increased NF-kappaB activation and macrophage inflammatory protein-2 production after LPS treatment compared with wild-type cells, and coculture of BMDM with lung epithelial (A549) cells resulted in increased NF-kappaB activation in A549 cells and excess IL-8 production by these epithelial cells. These studies indicate an important role for inhibitory members of the NF-kappaB family acting specifically within myeloid cells to limit inflammatory responses in the lungs.

Effects of dietary glutamine supplementation on lung injury induced by lipopolysaccharide administration

Acute lung injury (ALI) is a critical syndrome associated with respiratory dysfunction, and neutrophils are considered to be central to the pathogenesis of ALI. This study investigated the effects of glutamine (Gln) on neutrophil recruitment in a model of lipopolysaccharide (LPS)-induced ALI. C57BL/6 mice were fed a standard diet either with casein as the nitrogen source or with 25% of total nitrogen replaced by Gln. After 10 days, intratracheal instillation of LPS was used to induce ALI. Mice were killed at 0, 6, 12, and 24 h after LPS administration (n = 10/group). Bronchoalveolar lavage fluid and lung tissues were collected for further analysis. The results showed that, compared with the control group, lipid peroxide levels in the lungs were higher at 12 and 24 h after LPS administration in the Gln group. CXC chemokines as well as tumor necrosis factor-alpha were significantly elevated and reached peaks at 6 h in the Gln group, which was earlier than in the control group. Histopathological findings showed that the thickening of alveolar septal space was extensive in the Gln group 24 h and 2 wk after LPS. Also, greater amounts of collagen had accumulated in lung tissue in the Gln group. This study indicates that dietary Gln administration resulted in higher inflammatory cytokine production, with more neutrophils recruited at the early stage of ALI. These results were consistent with the histopathological findings that Gln supplementation causes more severe interstitial inflammation and fibrosis in a model of ALI induced by LPS.

IL-1 receptor antagonist as an aerosol in inflammation

The feasibility of efficient aerosol delivery of the human IL-1 receptor antagonist (IL-1Ra) for reduction of acute lung inflammation was demonstrated in a mouse model study. The therapeutic efficacy of dry powder formulations PM(2), PM(10) of IL-1Ra was studied at nonforced inhalation in an aerosol chamber using the DPI "Spinhaler". Micronized powder formulations for insufflation were produced by air-jet milling. The anti-inflammatory effect of IL-Ra preparation was assessed by differential cell counts and biochemical composition of bronchoalveolar lavage (BAL). Reactive oxygen species (ROS), metabolic parameters of BAL (pH, redox potential, total protein, and lactate), and morphological lung changes were investigated by methods of luminol-dependent chemoluminescence, electrochemistry, microscopy, optical, and NMR spectroscopy. Inhalation of IL-1Ra aerosol ensured the systemic absorption of IL-1Ra in the circulatory system and reduced the acute inflammatory response to intranasal lipopolysaccharide challenge. The inhaled anti-inflammatory dosage in aerosol administration appeared to be comparable with i.p. injection. The mechanism of positive action of pulmonary aerosol delivery of Il-Ra includes normalization of the oxidative activity of bronchoalveolar cells, prevention of neutrophil recruitment to the bronchoalveolar tract, and improving of cell respiration. The results were used to develop mathematical models of the anti-inflammatory effects of IL-Ra as functions of the doses and dispersion grades of IL-Ra preparations. Aerosol application of IL-Ra may be an apparent way for prophylactic treating of respiratory inflammation caused by bacterial antigens.

A genome-wide expression analysis in blood identifies pre-elafin as a biomarker in ARDS

Previous microarray-based studies of acute respiratory distress syndrome (ARDS) were performed using various models to mimic disease pathogenesis. The complexity of the pathophysiologic response to direct or indirect lung injury in ARDS is difficult to reconstruct in experimental conditions. Thus, direct analysis of ARDS patient blood may provide valuable information. We investigated genome-wide gene expression profiles in paired whole blood samples from patients with ARDS (n = 8) during the acute stage (within 3 d of diagnosis) and recovery stage of ARDS (around ICU discharge). Among 126 differentially expressed genes, peptidase inhibitor 3 (PI3, encoding elafin, a potent neutrophil elastase inhibitor) had the largest fold-change (-3-fold changes, acute stage/recovery stage) in expression, indicating down-regulation during the acute stage of ARDS. We further examined plasma PI3 levels in 40 patients with ARDS and 23 at-risk control subjects from the same cohort. There was a coincidence of the microarray findings of lower PI3 gene expression with the lower plasma PI3 during the acute-stage. The plasma PI3 levels were statistically significant different among pre-diagnosis, day of diagnosis, and post-diagnosis groups (ANOVA, P = 0.001), with a trend of decreasing from pre- to post-diagnosis group. The time course of plasma PI3 decrease is well correlated with the course of early ARDS development (Pearson correlation coefficient: -0.52, P = 0.0006). Considering that PI3 can covalently binding to extracellular matrix in lung, circulating PI3 may provide a useful clinical marker for monitoring the early development of ARDS and may have implications for ARDS treatment.

NFkappaB is persistently activated in continuously stimulated human neutrophils

Increased activation of the transcription factor NFkappaB in the neutrophils has been associated with the pathogenesis of sepsis, acute lung injury (ALI), bronchopulmonary dysplasia (BPD), and other neutrophil-mediated inflammatory disorders. Despite recent progress in analyzing early NFkappaB activation in human neutrophils, activation of NFkappaB in persistently stimulated neutrophils has not been previously studied. Because it is the persistent NFkappaB activation that is thought to be involved in the host response to sepsis and the pathogenesis of ALI and BPD, we hypothesized that continuously stimulated human neutrophils may exhibit a late phase of NFkappaB activity. The goal of this study was to analyze the NFkappaB activation and expression of IkappaB and NFkappaB proteins during neutrophil stimulation with inflammatory signals for prolonged times. We demonstrate that neutrophil stimulation with lipopolysaccharide (LPS) and tumor necrosis factor-alpha (TNFalpha) induces, in addition to the early activation at 30-60 min, a previously unrecognized late phase of NFkappaB activation. In LPS-stimulated neutrophils, this NFkappaB activity typically had a biphasic character, whereas TNFalpha-stimulated neutrophils exhibited a continuous NFkappaB activity peaking around 9 h after stimulation. In contrast to the early NFkappaB activation that inversely correlates to the nuclear levels of IkappaBalpha, however, in continuously stimulated neutrophils, NFkappaB is persistently activated despite considerable levels of IkappaBalpha present in the nucleus. Our data suggest that NFkappaB is persistently activated in human neutrophils during neutrophil-mediated inflammatory disorders, and this persistent NFkappaB activity may represent one of the underlying mechanisms for the continuous production of proinflammatory mediators.

The Ron receptor tyrosine kinase regulates acute lung injury and suppresses nuclear factor kappaB activation

Emerging information implies that the Ron receptor tyrosine kinase may play a role in the inflammatory response. However, the manner in which this receptor contributes to the response is not well understood. In the present studies, we investigated the role of the Ron receptor in the acute lung inflammatory response. Wild-type and mutant mice lacking the tyrosine kinase domain of Ron (Ron TK-/-) were subjected to acute lung injury induced by intranasal administration of bacterial lipopolysaccharide (LPS). Wild-type mice showed increased lung injury after LPS administration, as determined by the leakage of albumin into the lung and by histopathological changes. Ron TK-/- mice had more than twice the amount of albumin leak and much greater thickening of the alveolar septae. Lipopolysaccharide administration caused neutrophil recruitment into the lungs, as measured by myeloperoxidase. However, Ron TK-/- mice had much higher baseline levels of myeloperoxidase, which did not increase further after LPS. Lung injury in wild-type mice occurred with activation of the transcription factor, nuclear factor kappaB (NF-kappaB), and subsequent increases in intrapulmonary generation of tumor necrosis factor alpha. In TK-/- mice, there was far less IkappaB-alpha and IkappaB-beta protein and greater activation of NF-kappaB. This was associated with substantially increased production of tumor necrosis factor alpha and the nitric oxide (NO) by-product, nitrite. The data suggest that the Ron receptor tyrosine kinase plays an important regulatory role in acute inflammatory lung injury by suppressing signals leading to activation of NF-kappaB.