Inhibition of c-Jun NH2-terminal kinase or extracellular signal-regulated kinase improves lung injury

Targeting the AMPK/Nrf2 Pathway: A Novel Therapeutic Approach for Acute Lung Injury

ALI(acute lung injury) is a severe respiratory dysfunction caused by various intrapulmonary and extrapulmonary factors. It is primarily characterized by oxidative stress and affects the integrity of the pulmonary barrier. In severe cases, ALI can progress to ARDS(acute respiratory distress syndrome), a condition that poses a serious threat to the lives of affected patients. To date, the etiological mechanisms underlying ALI remain elusive, and available therapeutic options are quite limited. AMPK(AMP-activated protein kinase), an essential serine/threonine protein kinase, performs a pivotal function in the regulation of cellular energy levels and cellular regulatory mechanisms, including the detection of redox signals and mitigating oxidative stress. Meanwhile, Nrf2(nuclear factor erythroid 2-related factor 2), a critical transcription factor, alleviates inflammation and oxidative responses by interacting with multiple signaling pathways and contributing to the modulation of oxidative enzymes associated with inflammation and programmed cell death. Indeed, AMPK induces the dissociation of Nrf2 from Keap1(kelch-like ECH-associated protein-1) and facilitates its translocation into the nucleus to trigger the transcription of downstream antioxidant genes, ultimately suppressing the expression of inflammatory cells in the lungs. Given their roles, AMPK and Nrf2 hold promise as novel treatment targets for ALI. This study aimed to summarise the current status of research on the AMPK/Nrf2 signaling pathway in ALI, encompassing recently reported natural compounds and drugs that can activate the AMPK/Nrf2 signaling pathway to alleviate lung injury, and provide a theoretical reference for early intervention in lung injury and future research on lung protection.

Regulation of CD18 stability by SIGIRR-modulated ubiquitination: new insights into the relationship between innate immune response and acute lung injury

Inappropriate accumulation of alveolar macrophages (AMs) and subsequent excessive production of immune responses play critical roles in the pathogenesis of acute lung injury (ALI), but the core negative regulators governing innate signalling in AMs are ill defined. We have previously shown that single immunoglobin IL-1 receptor-related protein (SIGIRR), a negative regulator of IL-1 receptor and Toll-like receptor signalling, inhibits lipopolysaccharide (LPS)-induced inflammatory responses in AMs. To address the biological relevance of SIGIRR in vivo, we generated a murine ALI model via intratracheal instillation of LPS. Intriguingly, SIGIRR expression was observed to be decreased in resident and recruited macrophages during ALI. This decrease was associated with parallel induction in CD18 protein levels in LPS-challenged lung tissues. Through intranasal injection of SIGIRR lentiviral particles studies, we showed that the overexpression of SIGIRR attenuated recruitment of macrophages and neutrophils, decreased production of inflammatory cytokines and ameliorated pathological changes in lungs. Whilst exploring the basis for this phenotype, SIGIRR was found to be coexpressed with CD18 in AMs, and SIGIRR potentiated the instability of CD18 protein via enhancement of its ubiquitination and proteasome degradation. Conversely, by using CD18^-/- mice, we further observed that CD18 deletion completely abolished the therapeutic effects of overexpression of SIGIRR on LPS-induced ALI. Mover, overexpression of CD18 in AMs promoted adhesion to ECM components, enhanced TLR4-mediated inflammasome activation and thereby potentiated IL-1β production. These data collectively identify SIGIRR/CD18 as a key negative regulatory circuit maintaining innate immune homeostasis in AMs along the pathogenesis of ALI.

Cigarette Smoke and Nicotine-Containing Electronic-Cigarette Vapor Downregulate Lung WWOX Expression, Which Is Associated with Increased Severity of Murine Acute Respiratory Distress Syndrome

A history of chronic cigarette smoking is known to increase risk for acute respiratory distress syndrome (ARDS), but the corresponding risks associated with chronic e-cigarette use are largely unknown. The chromosomal fragile site gene, WWOX, is highly susceptible to genotoxic stress from environmental exposures and thus an interesting candidate gene for the study of exposure-related lung disease. Lungs harvested from current versus former/never-smokers exhibited a 47% decrease in WWOX mRNA levels. Exposure to nicotine-containing e-cigarette vapor resulted in an average 57% decrease in WWOX mRNA levels relative to vehicle-treated controls. In separate studies, endothelial (EC)-specific WWOX knockout (KO) versus WWOX flox control mice were examined under ARDS-producing conditions. EC WWOX KO mice exhibited significantly greater levels of vascular leak and histologic lung injury. ECs were isolated from digested lungs of untreated EC WWOX KO mice using sorting by flow cytometry for CD31+ CD45-cells. These were grown in culture, confirmed to be WWOX deficient by RT-PCR and Western blotting, and analyzed by electric cell impedance sensing as well as an FITC dextran transwell assay for their barrier properties during methicillin-resistant Staphylococcus aureus or LPS exposure. WWOX KO ECs demonstrated significantly greater declines in barrier function relative to cells from WWOX flox controls during either methicillin-resistant S. aureus or LPS treatment as measured by both electric cell impedance sensing and the transwell assay. The increased risk for ARDS observed in chronic smokers may be mechanistically linked, at least in part, to lung WWOX downregulation, and this phenomenon may also manifest in the near future in chronic users of e-cigarettes.

The Promising Effects of Astaxanthin on Lung Diseases

Astaxanthin (ASX) is a naturally occurring xanthophyll carotenoid. Both in vitro and in vivo studies have shown that it is a potent antioxidant with anti-inflammatory properties. Lung cancer is the leading cause of cancer death worldwide, whereas other lung diseases such as chronic obstructive pulmonary disease, emphysema, and asthma are of high prevalence. In the past decade, mounting evidence has suggested a protective role for ASX against lung diseases. This article reviews the potential role of ASX in protecting against lung diseases, including lung cancer. It also summarizes the underlying molecular mechanisms by which ASX protects against pulmonary diseases, including regulating the nuclear factor erythroid 2-related factor/heme oxygenase-1 pathway, NF-κB signaling, mitogen-activated protein kinase signaling, Janus kinase-signal transducers and activators of transcription-3 signaling, the phosphoinositide 3-kinase/Akt pathway, and modulating immune response. Several future directions are proposed in this review. However, most in vitro and in vivo studies have used ASX at concentrations that are not achievable by humans. Also, no clinical trials have been conducted and/or reported. Thus, preclinical studies with ASX treatment within physiological concentrations as well as human studies are required to examine the health benefits of ASX with respect to lung diseases.

Vanillin protects lipopolysaccharide-induced acute lung injury by inhibiting ERK1/2, p38 and NF-κB pathway

Aim: Thus far, the anti-inflammatory effect of vanillin in acute lung injury (ALI) has not been studied. This study aimed to investigate the effect of vanillin in lipopolysaccharide (LPS)-induced ALI. Results & methodology: Our study detected the anti-inflammatory effects of vanillin by ELISA and western blot, respectively. Pretreatment of mice with vanillin significantly attenuated LPS-stimulated lung histopathological changes, myeloperoxidase activity and expression levels of proinflammatory cytokines by inhibiting the phosphorylation activities of ERK1/2, p38, AKT and NF-κB p65. In addition, vanillin inhibited LPS-induced TNF-α and IL-6 expression in RAW264.7 cells via ERK1/2, p38 and NF-κB signaling. Conclusion: Vanillin can inhibit macrophage activation and lung inflammation, which suggests new insights for clinical treatment of ALI.

TLR2 favors OVA-induced allergic airway inflammation in mice through JNK signaling pathway with activation of autophagy

AIMS

Numerous studies indicate that toll-like receptor 2 (TLR2) led to divergent effects in asthma. The occurrence of autophagy in asthma pathogenesis is still incompletely understood. Here, we aimed to investigate the role of TLR2 and the underlying mechanisms in allergic airway inflammation and autophagy activation.

MAIN METHODS

C57BL/6 and TLR2 knockout (TLR2^-/-) mice were subjected to an ovalbumin (OVA)-immunized allergic airway model, and were treated with SP600125. Differential cell counts in bronchoalveolar lavage fluid were determined by Wright's staining. Histological analysis of airway inflammation was determined by haematoxylin and eosin (H&E) and periodic acid-Schiff (PAS) staining. The levels of OVA-specific immunoglobulin E (IgE), tumor necrosis factor α (TNF-α) and interleukin 10 (IL-10) were detected by enzyme-linked immunosorbent assay (ELISA). Proteins expression in lung tissues was detected by western blot, expression of TLR2 was further observed by immunofluorescence. Autophagy activation was determined by western blot and transmission electron microscopy (TEM).

KEY FINDINGS

TLR2 expression was increased upon OVA challenge, and TLR2 deficiency was associated with decreased allergic airway inflammation. Meanwhile, TLR2 deficiency weakened autophagy activation. Moreover, inhibition of c-Jun N-terminal kinase (JNK) by SP600125 also suppressed OVA-induced allergic airway inflammation and autophagy activation. Interestingly, treating TLR2^-/- mice with SP600125 showed similar OVA-induced allergic airway inflammation and autophagy activation compared to that in vehicle-treated TLR2^-/- mice.

SIGNIFICANCE

TLR2 might contribute to the maintenance of allergic airway inflammation through JNK signaling pathway accompanying with autophagy activation. These findings may provide a novel signal target for prevention of allergic airway inflammation.

Inhibition Of JNK Phosphorylation By Curcumin Analog C66 Protects LPS-Induced Acute Lung Injury

Background

Acute lung injury (ALI) is characterized by high prevalence and high mortality. Thus far, no effective pharmacological treatment has been made for ALI in clinics. Inflammation is critical to the development of ALI. Curcumin analog C66, having reported as an inhibitor of c-Jun N-terminal kinase (JNK), exhibits anti-inflammatory property both in vitro and in vivo. However, whether C66 is capable of reducing lipopolysaccharide (LPS)-induced ALI through the inhibition of inflammation by targeting JNK remains unknown.

Methods

Intratracheal injection of LPS was employed to build a mouse ALI model. H&E staining, wet/dry ratio, immunofluorescence staining, inflammatory cell detection, and inflammatory gene expression were used to evaluate lung injury and lung inflammation. In vitro, LPS was used to induce the expression of inflammatory cytokines both in protein and gene levels.

Results

The results of our studies showed that the pretreatment with C66 and JNK inhibitor SP600125 was capable of attenuating the LPS-induced ALI by detecting pulmonary edema, pathological changes, total protein concentration, and inflammatory cell number in bronchoalveolar lavage fluid (BALF). Besides, C66 and SP600125 also suppressed LPS-induced inflammatory cytokine expression in BALF, serum, and lung tissue. In vitro, LPS-induced production of TNF-α and IL-6 and gene expression of TNF-α, IL-6, IL-1β, and COX-2 could be inhibited by the pretreatment with C66 and SP600125. It was found that C66 and SP600125 could inhibit LPS-induced phosphorylation of JNK both in vitro and in vivo.

Conclusion

In brief, our results suggested that C66 protects LPS-induced ALI through the inhibition of inflammation by targeting the JNK pathway. These findings further confirmed the pivotal role of JNK in ALI and implied that C66 is likely to serve as a potential therapeutic agent for ALI.

MCP-induced protein 1 attenuates sepsis-induced acute lung injury by modulating macrophage polarization via the JNK/c-Myc pathway

Sepsis is a potentially fatal systemic inflammatory response syndrome caused by infection. In this study, we evaluated the effects of MCP-induced protein 1 (MCPIP1), a recently discovered inflammation-related ribonuclease, on sepsis-induced acute lung injury (ALI) and investigated the underlying mechanisms. Cecal ligation puncture and lipopolysaccharide induction were performed on Sprague-Dawley rats and RAW264.7 cells, respectively, to establish sepsis-induced ALI models. The proteasome inhibitor MG132 used as an activator of MCPIP1 overexpression, and we showed that MG132 can indeed increase the expression of MCPIP1. MCPIP1 overexpression induced by MG132 alleviated sepsis-induced pathologic changes, water content and protein leakage in the lungs, and induction of systemic inflammatory mediators, and improved the 7-day mortality rate in the model rats. We also showed that MCPIP1 p showed romoted macrophage polarization from the M1 to the M2 type in sepsis-induced ALI. Furthermore, MCPIP1-enhanced M2 polarization was inhibited by an MCPIP1-targeting small interfering RNA (siMCPIP1) in RAW264.7 cells. Further mechanistic studies showed that the promotive effect of MCPIP1 on M2 polarization was related to the inhibition of c-Jun N-terminal kinase (JNK) and its downstream transcription factor c-Myc in the in vitro model. Conversely, siMCPIP1 transfection resulted in the recovery of JNK and c-Myc expression in LPS-treated cells. Taken together, these findings indicate that MCPIP1 plays a protective role in sepsis-induced ALI by modulating macrophage polarization through inhibition of the JNK/c-Myc signaling pathway. Our study presents a potentially novel therapeutic strategy for the treatment of lung injury involving the inflammatory cascade.

JNK Inhibitor SP600125 Attenuates Paraquat-Induced Acute Lung Injury: an In Vivo and In Vitro Study

Acute lung injury (ALI) is a major complication soon after paraquat poisoning and rapidly progresses with high mortality. However, the specific mechanism underlying paraquat-induced ALI is still unclear. In this study, the mechanism underlying the protective effects of SP600125 on paraquat-induced ALI was investigated according to oxidative stress, inflammation, and apoptosis. The rats were randomly assigned into the control group (CON), the paraquat poisoning group (PQ), and the PQ + SP600125 group (SP). A549 cells were divided into the Con group, Pq group, and Sp group. H&E staining and detection of lung wet/dry ratio were employed to evaluate lung injury. Annexin V-PI staining was done to evaluate A549 cell apoptosis. Dihydroethidium fluorescence was used to measure reactive oxygen species (ROS) in the lungs and A549 cells. ELISA was performed to detect TNF-α and IL-6 in the supernatant of bronchoalveolar lavage fluid (BALF) and A549 cells. RT-qPCR was done to measure the messenger RNA (mRNA) expression of TNF-α and IL-6 in the lungs and A549 cells. Western blotting assay was performed to detect the protein expression of phospho-JNK, total JNK, and cleaved caspase-3. Electrophoretic mobility shift assay was employed to detect the DNA binding activities of AP-1 and P-p65. JNK inhibitor SP600125 reduced JNK phosphorylation, downregulated cleaved caspase-3 protein level, decreased AP-1 transcriptional activity and ROS level, and reduced the transcription and expression of TNF-α and IL-6, which improved ALI and cell apoptosis after paraquat poisoning. Our results indicate that JNK/AP-1 mediates ALI as well as oxidative stress and inflammation deterioration secondary to paraquat poisoning.

The role of Src & ERK1/2 kinases in inspiratory resistive breathing induced acute lung injury and inflammation

Background

Inspiratory resistive breathing (IRB), a hallmark of obstructive airway diseases, is associated with large negative intrathoracic pressures, due to strenuous contractions of the inspiratory muscles. IRB is shown to induce lung injury in previously healthy animals. Src is a multifunctional kinase that is activated in the lung by mechanical stress. ERK1/2 kinase is a downstream target of Src. We hypothesized that Src is activated in the lung during IRB, mediates ERK1/2 activation and IRB-induced lung injury.

Methods

Anaesthetized, tracheostomized adult rats breathed spontaneously through a 2-way non-rebreathing valve. Resistance was added to the inspiratory port to provide a peak tidal inspiratory pressure of 50% of maximum (inspiratory resistive breathing). Activation of Src and ERK1/2 in the lung was estimated during IRB. Following 6 h of IRB, respiratory system mechanics were measured by the forced oscillation technique and bronchoalveolar lavage (BAL) was performed to measure total and differential cell count and total protein levels. IL-1b and MIP-2a protein levels were measured in lung tissue samples. Wet lung weight to total body weight was measured and Evans blue dye extravasation was estimated to measure lung permeability. Lung injury was evaluated by histology. The Src inhibitor, PP-2 or the inhibitor of ERK1/2 activation, PD98059 was administrated 30 min prior to IRB.

Results

Src kinase was activated 30 min after the initiation of IRB. Src inhibition ameliorated the increase in BAL cellularity after 6 h IRB, but not the increase of IL-1β and MIP-2a in the lung. The increase in BAL total protein and lung injury score were not affected. The increase in tissue elasticity was partly inhibited. Src inhibition blocked ERK1/2 activation at 3 but not at 6 h of IRB. ERK1/2 inhibition ameliorated the increase in BAL cellularity after 6 h of IRB, blocked the increase of IL-1β and returned Evans blue extravasation and wet lung weight to control values. BAL total protein and the increase in elasticity were partially affected. ERK1/2 inhibition did not significantly change total lung injury score compared to 6 h IRB.

Conclusions

Src and ERK1/2 are activated in the lung following IRB and participate in IRB-induced lung injury.

Treatments for Pulmonary Ricin Intoxication: Current Aspects and Future Prospects

Ricin, a plant-derived toxin originating from the seeds of Ricinus communis (castor beans), is one of the most lethal toxins known, particularly if inhaled. Ricin is considered a potential biological threat agent due to its high availability and ease of production. The clinical manifestation of pulmonary ricin intoxication in animal models is closely related to acute respiratory distress syndrome (ARDS), which involves pulmonary proinflammatory cytokine upregulation, massive neutrophil infiltration and severe edema. Currently, the only post-exposure measure that is effective against pulmonary ricinosis at clinically relevant time-points following intoxication in pre-clinical studies is passive immunization with anti-ricin neutralizing antibodies. The efficacy of this antitoxin treatment depends on antibody affinity and the time of treatment initiation within a limited therapeutic time window. Small-molecule compounds that interfere directly with the toxin or inhibit its intracellular trafficking may also be beneficial against ricinosis. Another approach relies on the co-administration of antitoxin antibodies with immunomodulatory drugs, thereby neutralizing the toxin while attenuating lung injury. Immunomodulators and other pharmacological-based treatment options should be tailored according to the particular pathogenesis pathways of pulmonary ricinosis. This review focuses on the current treatment options for pulmonary ricin intoxication using anti-ricin antibodies, disease-modifying countermeasures, anti-ricin small molecules and their various combinations.

Inhibition of c-Jun N-terminal Kinase Signaling Pathway Alleviates Lipopolysaccharide-induced Acute Respiratory Distress Syndrome in Rats

Background:

An acute respiratory distress syndrome (ARDS) is still one of the major challenges in critically ill patients. This study aimed to investigate the effect of inhibiting c-Jun N-terminal kinase (JNK) on ARDS in a lipopolysaccharide (LPS)-induced ARDS rat model.

Methods:

Thirty-six rats were randomized into three groups: control, LPS, and LPS + JNK inhibitor. Rats were sacrificed 8 h after LPS treatment. The lung edema was observed by measuring the wet-to-dry weight (W/D) ratio of the lung. The severity of pulmonary inflammation was observed by measuring myeloperoxidase (MPO) activity of lung tissue. Moreover, the neutrophils in bronchoalveolar lavage fluid (BALF) were counted to observe the airway inflammation. In addition, lung collagen accumulation was quantified by Sircol Collagen Assay. At the same time, the pulmonary histologic examination was performed, and lung injury score was achieved in all three groups.

Results:

MPO activity in lung tissue was found increased in rats treated with LPS comparing with that in control (1.26 ± 0.15 U in LPS vs. 0.77 ± 0.27 U in control, P < 0.05). Inhibiting JNK attenuated LPS-induced MPO activity upregulation (0.52 ± 0.12 U in LPS + JNK inhibitor vs. 1.26 ± 0.15 U in LPS, P < 0.05). Neutrophils in BALF were also found to be increased with LPS treatment, and inhibiting JNK attenuated LPS-induced neutrophils increase in BALF (255.0 ± 164.4 in LPS vs. 53 (44.5-103) in control vs. 127.0 ± 44.3 in LPS + JNK inhibitor, P < 0.05). At the same time, the lung injury score showed a reduction in LPS + JNK inhibitor group comparing with that in LPS group (13.42 ± 4.82 vs. 7.00 ± 1.83, P = 0.001). However, the lung W/D ratio and the collagen in BALF did not show any differences between LPS and LPS + JNK inhibitor group.

Conclusions:

Inhibiting JNK alleviated LPS-induced acute lung inflammation and had no effects on pulmonary edema and fibrosis. JNK inhibitor might be a potential therapeutic medication in ARDS, in the context of reducing lung inflammatory.

Loss of lung WWOX expression causes neutrophilic inflammation

The tumor suppressor WW domain-containing oxidoreductase (WWOX) exhibits regulatory interactions with an array of transcription factors and signaling molecules that are positioned at the well-known crossroads between inflammation and cancer. WWOX is also subject to downregulation by genotoxic environmental exposures, making it of potential interest to the study of lung pathobiology. Knockdown of lung WWOX expression in mice was observed to cause neutrophil influx and was accompanied by a corresponding vascular leak and inflammatory cytokine production. In cultured human alveolar epithelial cells, loss of WWOX expression resulted in increased c-Jun- and IL-8-dependent neutrophil chemotaxis toward cell monolayers. WWOX was observed to directly interact with c-Jun in these cells, and its absence resulted in increased nuclear translocation of c-Jun. Finally, inhibition of the c-Jun-activating kinase JNK abrogated the lung neutrophil influx observed during WWOX knockdown in mice. Altogether, these observations represent a novel mechanism of pulmonary neutrophil influx that is highly relevant to the pathobiology and potential treatment of a number of different lung inflammatory conditions.

Spred-2 deficiency exacerbates lipopolysaccharide-induced acute lung inflammation in mice

Background

Acute respiratory distress syndrome (ARDS) is a severe and life-threatening acute lung injury (ALI) that is caused by noxious stimuli and pathogens. ALI is characterized by marked acute inflammation with elevated alveolar cytokine levels. Mitogen-activated protein kinase (MAPK) pathways are involved in cytokine production, but the mechanisms that regulate these pathways remain poorly characterized. Here, we focused on the role of Sprouty-related EVH1-domain-containing protein (Spred)-2, a negative regulator of the Ras-Raf-extracellular signal-regulated kinase (ERK)-MAPK pathway, in lipopolysaccharide (LPS)-induced acute lung inflammation.

Methods

Wild-type (WT) mice and Spred-2^−/− mice were exposed to intratracheal LPS (50 µg in 50 µL PBS) to induce pulmonary inflammation. After LPS-injection, the lungs were harvested to assess leukocyte infiltration, cytokine and chemokine production, ERK-MAPK activation and immunopathology. For exvivo experiments, alveolar macrophages were harvested from untreated WT and Spred-2^−/− mice and stimulated with LPS. In invitro experiments, specific knock down of Spred-2 by siRNA or overexpression of Spred-2 by transfection with a plasmid encoding the Spred-2 sense sequence was introduced into murine RAW264.7 macrophage cells or MLE-12 lung epithelial cells.

Results

LPS-induced acute lung inflammation was significantly exacerbated in Spred-2^−/− mice compared with WT mice, as indicated by the numbers of infiltrating leukocytes, levels of alveolar TNF-α, CXCL2 and CCL2 in a later phase, and lung pathology. U0126, a selective MEK/ERK inhibitor, reduced the augmented LPS-induced inflammation in Spred-2^−/− mice. Specific knock down of Spred-2 augmented LPS-induced cytokine and chemokine responses in RAW264.7 cells and MLE-12 cells, whereas Spred-2 overexpression decreased this response in RAW264.7 cells.

Conclusions

The ERK-MAPK pathway is involved in LPS-induced acute lung inflammation. Spred-2 controls the development of LPS-induced lung inflammation by negatively regulating the ERK-MAPK pathway. Thus, Spred-2 may represent a therapeutic target for the treatment of ALI.

Protective effect of Ginkgo biloba leaves extract, EGb761, on endotoxin-induced acute lung injury via a JNK- and Akt-dependent NFκB pathway

Acute lung injury (ALI) is a clinical syndrome mainly caused by Gram-negative bacteria which is still in need of an effective therapeutic medicine. EGb761, an extract of Ginkgo biloba leaves, has several bioeffects including anti-inflammation, cardioprotection, neuroprotection, and free radical scavenging. Preadministration of EGb761 inhibited lipopolysaccharide (LPS)-induced histopathological changes and exchange of arterial blood gas. In addition, LPS-induced expression of proinflammatory mediators, such as tumor necrosis factor (TNF)-α, interleukin (IL)-6, macrophage inflammatory protein (MIP)-2, inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2), were suppressed by EGb761. The activation of nuclear factor (NF)κB, a transcription factor of proinflammatory mediators, and phosphorylation of IκB, an inhibitor of NFκB, were also reduced by EGb761. Furthermore, we found the inhibitory concentration of EGb761 on phosphorylation of JNK and Akt was less than those of ERK and p38 MAPK. In conclusion, EGb761 is a potential protective agent for ALI, possibly via downregulating the JNK- and Akt-dependent NFκB activation pathway.

JNK inhibitor SP600125 protects against lipopolysaccharide-induced acute lung injury via upregulation of claudin-4

Although in vitro studies have previously demonstrated that mitogen-activated protein kinases are important for the activation of transcription factors and the regulation of proinflammatory mediators, the function of c-Jun NH₂-terminal kinase (JNK) in acute lung injury (ALI) remains to be fully elucidated. The present study aimed to investigate the effect of the JNK selective inhibitor SP600125 on lipopolysaccharide (LPS)-induced ALI. Pulmonary edema, the expression of inflammatory cytokines and pathological alterations were found to be significantly attenuated in LPS-induced ALI following treatment with SP600125 in vivo. In vitro, it was demonstrated that SP600125 administration significantly improved A549 cell viability in a dose-dependent manner using the Cell Counting kit-8 and the 5-ethynyl-2'-deoxyuridine incorporation assay. Furthermore, flow cytometric analysis demonstrated that the apoptotic rate was significantly reduced in a concentration-dependent manner following SP600125 injection. At the molecular level, SP600125 treatment dose-dependently inhibited JNK activation and upregulated claudin-4 expression in vivo and in vitro. In combination, the results from the present study indicated that the JNK inhibitor SP600125 protected against LPS-induced ALI in vivo and in vitro, possibly by upregulating the expression of claudin-4.

Heparin rescues sepsis-associated acute lung injury and lethality through the suppression of inflammatory responses

Heparin, a potent blood anticoagulant, is known to possess anti-inflammatory activity. In this work, we investigated whether heparin can ameliorate acute lung injury and lethal response in lipopolysaccharide (LPS)-induced mouse model of sepsis. We found that heparin effectively rescued lethality, improved lung pathological changes, inhibited myeloperoxidase (MPO) activity, and reduced malondialdehyde (MDA) level, lung wet/dry weight ratio and Evans blue values in LPS-induced septic mice. In addition, heparin also inhibited the release of tumor necrosis factor (TNF)-α, interleukin-6 (IL-6) and IL-1β in serum and decreased the expression of p-p38, nuclear factor κB (NF-κB) and p-c-SRC kinase in lungs of septic mice. Our findings suggest that heparin is capable of suppressing the lethal response and acute lung injury associated with sepsis, and support the notion that heparin may be a potential therapeutic agent for the conditions associated with septic shock.

Antioxidant and anti-inflammatory effects in RAW264.7 macrophages of malvidin, a major red wine polyphenol

Background

Red wine polyphenols can prevent cardiovascular and inflammatory diseases. Resveratrol, the most extensively studied constituent, is unlikely to solely account for these beneficial effects because of its rather low abundance and bioavailability. Malvidin is far the most abundant polyphenol in red wine; however, very limited data are available about its effect on inflammatory processes and kinase signaling pathways.

Methods & Findings

The present study was carried out by using RAW 264.7 macrophages stimulated by bacterial lipopolysaccharide in the presence and absence of malvidin. From the cells, activation of nuclear factor-kappaB, mitogen-activated protein kinase, protein kinase B/Akt and poly ADP-ribose polymerase, reactive oxygen species production, mitogen-activated protein kinase phosphatase-1 expression and mitochondrial depolarization were determined. We found that malvidin attenuated lipopolysaccharide-induced nuclear factor-kappaB, poly ADP-ribose polymerase and mitogen-activated protein kinase activation, reactive oxygen species production and mitochondrial depolarization, while upregulated the compensatory processes; mitogen-activated protein kinase phosphatase-1 expression and Akt activation.

Conclusions

These effects of malvidin may explain the previous findings and at least partially account for the positive effects of moderate red wine consumption on inflammation-mediated chronic maladies such as obesity, diabetes, hypertension and cardiovascular disease.

In vivo transfection of nuclear factor κB decoy protects pulmonary function against acute lung contusion in rabbits

BACKGROUND

The transcription factor nuclear factor κB (NF-κB) regulates the expression of numerous proinflammatory factors that may exacerbate the response to acute injury. We investigated the effect of an inhibitory NF-κB decoy oligodeoxynucleotide on proinflammatory factor expression and pulmonary function after acute lung contusion in rabbits.

METHODS

Thirty-minutes after acute lung contusion, the NF-κB decoy or a scrambled control oligodeoxynucleotide was injected via the jugular vein. Blood samples were collected for blood gas analysis and plasma tumor necrosis factor α, interleukin 1β (IL-1β), IL-13, and IL-10 were measured by enzyme-linked immunosorbent assay at 1, 2, 3, and 4 hours after contusion. In addition, NF-κB protein expression in lung tissue was detected by Western blot analysis.

RESULTS

The blood PO2 decreased immediately after lung contusion, whereas PAO2 increased significantly, indicative of disrupted respiratory function. Respiratory function improved after sense NF-κB decoy injection but not after injection of the inactive scrambled form. Injection of NF-κB decoy resulted in significant inhibition of NF-κB protein expression in lung tissue and a reduction in the serum concentrations of proinflammatory cytokines tumor necrosis factor α and IL-1β compared with those of control rabbits injected with the scrambled decoy. In contrast, serum levels of the anti-inflammatory cytokines IL-10 and IL-13 increased after decoy injection compared with those of control animals and rabbits injected with the scrambled decoy.

CONCLUSION

The sense NF-κB decoy protected respiratory function and reduced serum proinflammatory factor secretion after acute lung contusion. Inhibition of NF-κB may allow for preservation of pulmonary function for patients with acute lung injury.

Intrapleural delivery of MSCs attenuates acute lung injury by paracrine/endocrine mechanism

Two different repair mechanisms of mesenchymal stem cells (MSCs) are suggested to participate in the repair of acute lung injury (ALI): (i) Cell engraftment mechanism, (ii) Paracrine/endocrine mechanism. However, the exact roles they play in the repair remain unclear. The aim of the study was to evaluate the role of paracrine/endocrine mechanism using a novel intrapleural delivery method of MSCs. Either 1 × 10(6) MSCs in 300 μl of PBS or 300 μl PBS alone were intrapleurally injected into rats with endotoxin-induced ALI. On days 1, 3 or 7 after injections, samples of lung tissues and bronchoalveolar lavage fluid (BALF) were collected from each rat for assessment of lung injury, biochemical analysis and histology. The distribution of MSCs was also traced by labelling the cells with 4',6-diamidino-2-phenylindole dihydrochloride (DAPI). MSCs intrapleural injection significantly improved LPS-induced lung histopathology compared with PBS-treated group at day 3. There was also a significant decrease in total cell counts and protein concentration in BALF at day 7 in the MSCs -treated rats compared to PBS control group. Tracking the DAPI-marked MSCs showed that there were no exotic MSCs in the lung parenchyma. MSCs administration resulted in a down-regulation of pro-inflammatory response to endotoxin by reducing TNF-α both in the BALF and in the lung, while up-regulating the anti-inflammatory cytokine IL-10 in the lung. In conclusion, treatment with intrapleural MSCs administration markedly attenuates the severity of endotoxin-induced ALI. This role is mediated by paracrine/endocrine repair mechanism of MSCs rather than by the cell engraftment mechanism.

p-Cymene protects mice against lipopolysaccharide-induced acute lung injury by inhibiting inflammatory cell activation

The objective of this study was to test the hypothesis that p-cymene can attenuate acute lung injury induced by lipopolysaccharide (LPS) in vivo. In the mouse model of LPS-induced acute lung injury, intraperitoneal preconditioning with p-cymene resulted in a significant reduction of pro-inflammatory cytokines (TNF-α, IL-1β and IL-6), lung water gain, inflammatory cell infiltration, lung tissue myeloperoxidase activity. In addition, p-cymene blocked the phosphorylation of IκBα protein and mitogen-activated protein kinases (MAPK) signaling pathway activation. Histopathologic examination of lung tissue indicated that p-cymene treatment markedly decreased focal thickening, congestion, pulmonary edema, and inflammatory cells infiltration. The results showed that p-cymene had a protective effect on LPS-induced ALI in mice.

Effects of c-Jun N-terminal kinase signaling pathway on severe acute pancreatitis-associated lung injury

OBJECTIVE

The objective of this study was to investigate the effects of the c-Jun N-terminal kinase (JNK) signaling pathway on rats' acute pancreatitis-associated lung injury (APALI).

METHODS

Seventy-two Sprague-Dawley rats were randomly divided into 3 groups, namely, the sham operation (SO) group, the severe acute pancreatitis (SAP) group, and the SP600125 group. The SAP model was established by injection of 5% sodium taurocholate into the pancreatic duct. The samples were taken at 3, 6, 12, and 24 hours. Serum amylase, pathologic lesions of the pancreas and lung tissues, wet-to-dry weight ratio of the lung, myeloperoxidase (MPO) activity of the lung, tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), intercellular adhesion molecule 1 (ICAM-1), and p-JNK of lung tissues were detected.

RESULTS

The wet-to-dry weight ratio, MPO activity, and IL-1β, TNF-α, ICAM-1, and p-JNK levels in the SAP group significantly increased compared with those in the SO group. The scores of lung pathologic injury significantly increased, consistent with the APALI. The wet-to-dry weight ratio, MPO activity, IL-1β, TNF-α, ICAM-1, p-JNK expressions, and lung pathologic injury scores in the SP600125 group decreased compared with those in the SAP group. p-JNK was closely correlated with MPO activity, IL-1β, ICAM-1, and total scores of lung injury.

CONCLUSIONS

The JNK signaling pathway plays a critical role in APALI. On the other hand, application of a specific JNK inhibitor can contribute to alleviation of APALI.

Anti-inflammatory effects of LASSBio-998, a new drug candidate designed to be a p38 MAPK inhibitor, in an experimental model of acute lung inflammation

We investigated the effects of LASSBio-998 (L-998), a compound designed to be a p38 MAPK (mitogen-activated protein kinase) inhibitor, on lipopolysaccharide (LPS)-induced acute lung inflammation in vivo. BALB/c mice were challenged with aerosolized LPS inhalation (0.5 mg/ml) 4 h after oral administration of L-998. Three hours after LPS inhalation, bronchoalveolar lavage fluid was obtained to measure the levels of the proinflammatory cytokines TNF-α (tumor necrosis factor-α) and IL-1 (interleukin-1) and the chemokines MCP-1 (monocyte chemoattractant protein-1) and KC (keratinocyte chemoattractant). In addition, neutrophil infiltration and p38 MAPK phosphorylation was measured. L-998 inhibited LPS-induced production of TNF-α and IL-1β and did not alter KC and MCP-1 levels. Furthermore, L-998 also significantly decreased neutrophil accumulation in lung tissues. As expected, L-998 diminished p38 MAPK phosphorylation and reduced acute lung inflammation. Inhibition of p38 MAPK phosphorylation by L-998 was also demonstrated in LPS-challenged murine C57BL/6 peritoneal macrophages in vitro, with concentration-dependent effects. L-998 suppressed LPS-induced lung inflammation, most likely by inhibition of the cytokine-p38 MAPK pathway, and we postulate that L-998 could be a clinically relevant anti-inflammatory drug candidate.

Models and mechanisms of acute lung injury caused by direct insults

Acute lung injury (ALI) and its more severe form acute respiratory distress syndrome (ARDS) are life-threatening diseases that are characterized by acute onset, pulmonary inflammation, oedema due to increased vascular permeability and severe hypoxemia. Clinically, ARDS can be divided into ARDS due to direct causes such as pneumonia, aspiration or injurious ventilation, and due to extrapulmonary indirect causes such as sepsis, severe burns or pancreatitis. In order to identify potential therapeutic targets, we asked here whether common molecular mechanisms can be identified that are relevant in different models of the direct form of ALI/ARDS. To this end, we reviewed three widely used models: (a) one based on a biological insult, i.e. instillation of bacterial endotoxins; (b) one based on a chemical insult, i.e. instillation of acid; and (c) one based on a mechanical insult, i.e. injurious ventilation. Studies were included only if the mediator or mechanism of interest was studied in at least two of the three animal models listed above. As endpoints, we selected neutrophil sequestration, permeability, hypoxemia (physiological dysfunction) and survival. Our analysis showed that most studies have focused on mechanisms of pulmonary neutrophil sequestration and models with moderate forms of oedema. The underlying mechanisms that involve canonical inflammatory pathways such as MAP kinases, CXCR2 chemokines, PAF, leukotrienes, adhesions molecules (CD18, ICAM-1) and elastase have been defined relatively well. Further mechanisms including TNF, DARC, HMGB1, PARP, GADD45 and collagenase are under investigation. Such mechanisms that are shared between the three ALI models may represent viable therapeutic targets. However, only few studies have linked these pathways to hypoxemia, the most important clinical aspect of ALI/ARDS. Since moderate oedema does not necessarily lead to hypoxemia, we suggest that the clinical relevance of experimental studies can be further improved by putting greater emphasis on gas exchange.

A potential role of the JNK pathway in hyperoxia-induced cell death, myofibroblast transdifferentiation and TGF-β1-mediated injury in the developing murine lung

Background

Transforming growth factor-beta 1 (TGF-β1) has been implicated in hyperoxia-induced cell death and impaired alveolarization in the developing lung. In addition, the c-JunNH2-terminal kinase (JNK) pathway has been shown to have a role for TGF-β1-mediated effects. We hypothesized that the JNK pathway is an important regulator of hyperoxia-induced pulmonary responses in the developing murine lung.

Results

We used cultured human lung epithelial cells, fetal rat lung fibroblasts and a neonatal TGF-β1 transgenic mouse model. We demonstrate that hyperoxia inhibits cell proliferation, activates cell death mediators and causes cell death, and promotes myofibroblast transdifferentiation, in a dose-dependent manner. Except for fibroblast proliferation, the effects were mediated via the JNK pathway. In addition, since we observed increased expression of TGF-β1 by epithelial cells on exposure to hyperoxia, we used a TGF-β1 transgenic mouse model to determine the role of JNK activation in TGF-β1 induced effects on lung development and on exposure to hyperoxia. We noted that, in this model, inhibition of JNK signaling significantly improved the spontaneously impaired alveolarization in room air and decreased mortality on exposure to hyperoxia.

Conclusions

When viewed in combination, these studies demonstrate that hyperoxia-induced cell death, myofibroblast transdifferentiation, TGF-β1- and hyperoxia-mediated pulmonary responses are mediated, at least in part, via signaling through the JNK pathway.

Lung injury caused by high tidal volume mechanical ventilation and hyperoxia is dependent on oxidant-mediated c-Jun NH2-terminal kinase activation

Both prolonged exposure to hyperoxia and large tidal volume mechanical ventilation can each independently cause lung injury. However, the combined impact of these insults is poorly understood. We recently reported that preexposure to hyperoxia for 12 h, followed by ventilation with large tidal volumes, induced significant lung injury and epithelial cell apoptosis compared with either stimulus alone (Makena et al. Am J Physiol Lung Cell Mol Physiol 299: L711-L719, 2010). The upstream mechanisms of this lung injury and apoptosis have not been clearly elucidated. We hypothesized that lung injury in this model was dependent on oxidative signaling via the c-Jun NH(2)-terminal kinases (JNK). We, therefore, evaluated lung injury and apoptosis in the presence of N-acetyl-cysteine (NAC) in both mouse and cell culture models, and we provide evidence that NAC significantly inhibited lung injury and apoptosis by reducing the production of ROS, activation of JNK, and apoptosis. To confirm JNK involvement in apoptosis, cells treated with a specific JNK inhibitor, SP600125, and subjected to preexposure to hyperoxia, followed by mechanical stretch, exhibited significantly reduced evidence of apoptosis. In conclusion, lung injury and apoptosis caused by preexposure to hyperoxia, followed by high tidal volume mechanical ventilation, induces ROS-mediated activation of JNK and mitochondrial-mediated apoptosis. NAC protects lung injury and apoptosis by inhibiting ROS-mediated activation of JNK and downstream proapoptotic signaling.

Effects of downregulation of aquaporin1 by peptidoglycan and lipopolysaccharide via MAPK pathways in MeT-5A cells

This study was designed to investigate the signaling pathway involved in aquaporin1 (AQP1) expression caused by peptidoglycan (PGN) from Staphylococcus aureus and lipopolysaccharide (LPS) in human pleural mesothelial cell lines (MeT-5A) in vitro. RT-PCR, immunoblot analysis, and immunofluorescence assay were used to determine the relative mRNA and protein levels of AQP1 caused by PGN and LPS in MeT-5A cells. Activation of MAPKs by PGN and LPS was reflected by detecting the phosphorylation constituents of extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK), and p38 using immunoblot. MAPKs inhibitors were used to determine the effects of PGN- and LPS-induced AQP1 expression by immunoblot. AQP1 transcription and protein expression were decreased by PGN and LPS in dose- and time-dependent manners in MeT-5A cells. Both PGN and LPS activated p38/ERK/JNK pathways in MeT-5A cells. Furthermore, downregulation of AQP1 expression by LPS was blocked by SB203580, SP600125, and PD98059, which are inhibitors of p38, JNK, and ERK1/2, respectively. In contrast, downregulation of AQP1 expression by PGN was blocked only by SB203580, not by SP600125 or PD98059, underlying the importance of p38 MAPK in the downregulation of AQP1 expression by PGN in MeT-5A cells. AQP1 expression was decreased by both PGN and LPS in dose- and time-dependent manners in MeT-5A cells. AQP1 expression was down-regulated by PGN via p38 MAPK pathway, while AQP1 expression was down-regulated by LPS via p38/JNK/ERK pathways.

Cancer dissemination--lessons from leukocytes

Cancer cells can move through tissues in a variety of different ways. In some cases, an epithelial-to-mesenchymal transition enables cancer cells to acquire fibroblast-like migratory properties. However, it is also becoming apparent that some cancer cells move in an amoeboid way similar to leukocytes. This theme will be the focus of the review, where we will discuss the similarities and differences between the mechanisms used by cancer cells and leukocytes to cross parenchymal basement membranes, move through interstitial tissue, and enter and exit the vasculature. Further, we propose that the ability to switch between different migratory mechanisms is critical for cells to relocate from one tissue to another.

Potential down-regulation of salivary gland AQP5 by LPS via cross-coupling of NF-kappaB and p-c-Jun/c-Fos

The mRNA and protein levels of aquaporin (AQP)5 in the parotid gland were found to be potentially decreased by lipopolysaccharide (LPS) in vivo in C3H/HeN mice, but only weakly in C3H/HeJ, a TLR4 mutant mouse strain. In the LPS-injected mice, pilocarpine-stimulated saliva production was reduced by more than 50%. In a tissue culture system, the LPS-induced decrease in the AQP5 mRNA level was blocked completely by pyrrolidine dithiocarbamate, MG132, tyrphostin AG126, SP600125, and partially by SB203580, which are inhibitors for IkappaB kinase, 26S proteasome, ERK1/2, JNK, and p38 MAPK, respectively. In contrast, the expression of AQP1 mRNA was down-regulated by LPS and such down-regulation was blocked only by SP600125. The transcription factors NF-kappaB (p65 subunit), p-c-Jun, and c-Fos were increased by LPS given in vivo, whereas the protein-binding activities of the parotid gland extract toward the sequences for NF-kappaB but not AP-1-responsive elements present at the promoter region of the AQP5 gene were increased by LPS injection. Co-immunoprecipitation by using antibody columns suggested the physical association of the three transcription factors. These results suggest that LPS-induced potential down-regulation of expression of AQP5 mRNA in the parotid gland is mediated via a complex(es) of these two classes of transcription factors, NF-kappaB and p-c-Jun/c-Fos.

Inhaled activated protein C protects mice from ventilator-induced lung injury

INTRODUCTION

Activated Protein C (APC), an endogenous anticoagulant, improves tissue microperfusion and endothelial cell survival in systemic inflammatory states such as sepsis, but intravenous administration may cause severe bleeding. We have thus addressed the role of APC delivered locally by inhalation in preventing acute lung injury from alveolar overdistention and the subsequent ventilator-induced lung injury (VILI). We also assessed the effects of APC on the activation status of Extracellular- Regulated Kinase 1/2 (ERK) pathway, which has been shown to be involved in regulating pulmonary responses to mechanical stretch.

METHODS

Inhaled APC (12.5 microg drotrecogin-alpha x 4 doses) or saline was given to tracheotomized C57/Bl6 mice starting 20 min prior to initiation of injurious mechanical ventilation with tidal volume 25 mL/Kg for 4 hours and then hourly thereafter; control groups receiving inhaled saline were ventilated with 8 mL/Kg for 30 min or 4 hr. We measured lung function (respiratory system elastance H), arterial blood gases, surrogates of vascular leak (broncho-alveolar lavage (BAL) total protein and angiotensin-converting enzyme (ACE)-activity), and parameters of inflammation (BAL neutrophils and lung tissue myeloperoxidase (MPO) activity). Morphological alterations induced by mechanical ventilation were examined in hematoxylin-eosin lung tissue sections. The activation status of ERK was probed in lung tissue homogenates by immunoblotting and in paraffin sections by immunohistochemistry. The effect of APC on ERK signaling downstream of the thrombin receptor was tested on A549 human lung epithelial cells by immunoblotting. Statistical analyses were performed using ANOVA with appropriate post-hoc testing.

RESULTS

In mice subjected to VILI without APC, we observed hypoxemia, increased respiratory system elastance and inflammation, assessed by BAL neutrophil counts and tissue MPO activity. BAL total protein levels and ACE activity were also elevated by VILI, indicating compromise of the alveolo-capillary barrier. In addition to preserving lung function, inhaled APC prevented endothelial barrier disruption and attenuated hypoxemia and the inflammatory response. Mechanistically, we found a strong activation of ERK in lung tissues by VILI, which was prevented by APC, suggestive of pathogenetic involvement of the Mitogen-Activated Kinase pathway. In cultured human lung epithelial cells challenged by thrombin, APC abrogated the activation of ERK and its downstream effector, cytosolic Phospholipase A2.

CONCLUSIONS

Topical application of APC by inhalation may effectively reduce lung injury induced by mechanical ventilation in mice.

Low-intensity swimming training partially inhibits lipopolysaccharide-induced acute lung injury

BACKGROUND

Aerobic exercise decreases pulmonary inflammation and remodeling in experimental models of allergic asthma. However, the effects of aerobic exercise on pulmonary inflammation of nonallergic origin, such as in experimental models of acute lung injury induced by lipopolysaccharide (LPS), have not been evaluated.

OBJECTIVE

The present study evaluated the effects of aerobic exercise in a model of LPS-induced acute lung injury.

METHODS

BALB/c mice were divided into four groups: Control, Aerobic Exercise, LPS, and Aerobic Exercise + LPS. Swimming tests were conducted at baseline and at 3 and 6 wk. Low-intensity swimming training was performed for 6 wk, four times per week, 60 min per session. Intranasal LPS (1 mg x kg(-1) (60 microg per mouse)) was instilled 24 h after the last swimming physical test in the LPS and Aerobic Exercise + LPS mice, and the animals were studied 24 h after LPS instillation. Exhaled nitric oxide, respiratory mechanics, total and differential cell counts in bronchoalveolar lavage, and lung parenchymal inflammation and remodeling were evaluated.

RESULTS

LPS instillation resulted in increased levels of exhaled nitric oxide (P < 0.001), higher numbers of neutrophils in the bronchoalveolar lavage (P < 0.001) and in the lung parenchyma (P < 0.001), and decreased lung tissue resistance (P < 0.05) and volume proportion of elastic fibers (P < 0.01) compared with the Control group. Swim training in LPS-instilled animals resulted in significantly lower exhaled nitric oxide levels (P < 0.001) and fewer neutrophils in the bronchoalveolar lavage (P < 0.001) and the lung parenchyma (P < 0.01) compared with the LPS group.

CONCLUSIONS

These results suggest that low-intensity swimming training inhibits lung neutrophilic inflammation, but not remodeling and impaired lung mechanics, in a model of LPS-induced acute lung injury.

Synthetic RGDS peptide attenuates lipopolysaccharide-induced pulmonary inflammation by inhibiting integrin signaled MAP kinase pathways

BACKGROUND

Synthetic peptides containing the RGD sequence inhibit integrin-related functions in different cell systems. Here, we investigated the effects of synthetic Arg-Gly-Asp-Ser (RGDS) peptide on key inflammatory responses to intratracheal (i.t.) lipopolysaccharide (LPS) treatment and on the integrin signaled mitogen-activated protein (MAP) kinase pathway during the development of acute lung injury.

METHODS

Saline or LPS (1.5 mg/kg) was administered i.t. with or without a single dose of RGDS (1, 2.5, or 5 mg/kg, i.p.), anti-alphav or anti-beta3 mAb (5 mg/kg, i.p.). Mice were sacrificed 4 or 24 h post-LPS.

RESULTS

A pretreatment with RGDS inhibited LPS-induced increases in neutrophil and macrophage numbers, total protein levels and TNF-alpha and MIP-2 levels, and matrix metalloproteinase-9 activity in bronchoalveolar lavage (BAL) fluid at 4 or 24 h post-LPS treatment. RGDS inhibited LPS-induced phosphorylation of focal adhesion kinase and MAP kinases, including ERK, JNK, and p38 MAP kinase, in lung tissue. Importantly, the inhibition of the inflammatory responses and the kinase pathways were still evident when this peptide was administered 2 h after LPS treatment. Similarly, a blocking antibody against integrin alphav significantly inhibited LPS-induced inflammatory cell migration into the lung, protein accumulation and proinflammatory mediator production in BAL fluid, at 4 or 24 h post-LPS. Anti-beta3 also inhibited all LPS-induced inflammatory responses, except the accumulation of BAL protein at 24 h post-LPS.

CONCLUSION

These results suggest that RGDS with high specificity for alphavintegrins attenuates inflammatory cascade during LPS-induced development of acute lung injury.

Role of p38 mitogen-activated protein kinase in ozone-induced airway hyperresponsiveness and inflammation

Ozone is a potent oxidant and causes airway hyperresponsiveness and neutrophilia. To determine the role of p38 mitogen-activated protein kinase (MAPK) activation, we studied the effect of a p38alpha inhibitor SD-282 (Scios Inc, Fremont, CA USA) on ozone-induced airway hyperresponsiveness and neutrophilia. Balb/c mice received SD-282 (30 or 90 mg/kg i.p) or vehicle 1 h before exposure to either ozone (3 ppm, 3 h) or air. Three hours after exposure, lungs were analysed for cytokine levels and bronchoalveolar lavage was performed. Another set of mice were dosed 6 h after exposure and 1 h before assessing airway hyperresponsiveness. SD-282 (90 mg/kg) significantly inhibited ozone-induced airway hyperresponsiveness (-LogPC(150): SD-282: -1.73+/-0.14 vs. vehicle: -0.99+/-0.15, P<0.05). Bronchoalveolar lavage neutrophil numbers were time-dependently increased in vehicle-dosed, ozone-exposed mice, greatest at 20-24 h after exposure. SD-282 (30 and 90 mg/kg) significantly inhibited ozone induced neutrophil numbers at 3 h and 20-24 h after ozone SD-282 significantly inhibited ozone-induced increases in phosphorylated p38 MAPK expression, and in cyclooxygenase-2 (COX-2), interleukin-6 (IL-6) and IL-1beta but not MIP-1alpha gene expression. We conclude that p38 MAPK is involved in ozone-induced airway hyperresponsiveness and lung neutrophilia. Inhibition of p38 MAPK with small molecule kinase inhibitors may be a means of reducing ozone-induced inflammation and airway hyperresponsiveness.

Emerging role of MAP kinase pathways as therapeutic targets in COPD

Studies examining the cellular mechanisms of inflammation and protease production in the lung tissue and airways of COPD patients have shed light on the important role of kinase-based signaling cascades. These pathways can be activated by environmental stimuli such as tobacco smoke, and by endogenous signals such as cytokines, growth factors, and inflammation-derived oxidants. The three most widely characterized cascades are those directed by the classical mitogen activated protein (MAP) kinase (ERK1/2), stress activated protein kinase/c-Jun N-terminal protein kinase, and p38 enzymes. These phosphorylation cascades transmit and amplify extracellular, receptor-mediated signals through the cytoplasm of the cell to activate nuclear transcription factors which bind and induce expression of target genes. The result is tight control of diverse cellular events, and rapid responses to external stimuli. However, recent research suggests that constitutive or aberrant activation of MAP kinases contributes to several COPD-associated phenotypes, including mucus overproduction and secretion, inflammation, cytokine expression, apoptosis, T cell activation, matrix metalloproteinase production, and fibrosis. This review explores the biological functions of the MAP kinase pathways in the pathogenesis of COPD, their activation by cigarette smoke, and discusses the potential role of MAP kinase inhibitors in COPD therapy.

Src tyrosine kinases mediate activations of NF-kappaB and integrin signal during lipopolysaccharide-induced acute lung injury

Src tyrosine kinases (TKs) are signaling proteins involved in cell signaling pathways toward cytoskeletal, membrane and nuclear targets. In the present study, using a selective Src TK inhibitor, PP1, we investigated the roles of Src TKs in the key pulmonary responses, NF-kappaB activation, and integrin signaling during acute lung injury in BALB/C mice intratracheally treated with LPS. LPS resulted in c-Src phosphorylation in lung tissue and the phospho-c-Src was predominantly localized in recruited neutrophils and alveolar macrophages. PP1 inhibited LPS-induced increases in total protein content in bronchoalveolar lavage fluid, neutrophil recruitment, and increases in the production or activity of TNF-alpha and matrix metalloproteinase-9. PP1 also blocked LPS-induced NF-kappaB activation, and phosphorylation and degradation of IkappaB-alpha. The inhibition of NF-kappaB activation by PP1 correlated with a depression of LPS-induced integrin signaling, which included increases in the phosphorylations of integrin beta(3), and of the focal adhesion kinase (FAK) family members, FAK and Pyk2, in lung tissue, and reductions in the fibrinogen-binding activity of alveolar macrophages. Moreover, treatment with anti-alpha(v), anti-beta(3), or Arg-Gly-Asp-Ser (RGDS), inhibited LPS-induced NF-kappaB activation. Taken together, our findings suggest that Src TKs play a critical role in LPS-induced activations of NF-kappaB and integrin (alpha(v)beta(3)) signaling during acute lung injury. Therefore, Src TK inhibition may provide a potential means of ameliorating inflammatory cascade-associated lung injury.

Lipid A fraction of LPS induces a discrete MAPK activation in acute lung injury

Lipopolysaccharide (LPS) induces acute lung injury (ALI) via Toll-like receptor 4 (TLR4)-mediated MAPK activation. The lipid A fraction of LPS is considered to be the active moiety, but whether the lipid A-TLR4 interaction accounts completely for ALI-associated MAPK activation in vivo has not been determined. The lipid A fraction of LPS induces a discrete MAPK activation pattern in murine ALI. Mice (C57BL/6J, C3H/HeJ) were treated with intratracheal instillations of purified lipid A or LPS (10, 30, and 100 μg per mouse) or vehicle. ALI was assessed by histology. Chromogenic myeloperoxidase (MPO) activity was measured in lung homogenates. MAPK expression was quantified by immunoblotting. In vitro ERK inhibitor studies using thioglycollate-elicited macrophages were also performed. MPO increased in a dose- and time-responsive fashion. Notably, MPO was 2.4-fold greater after lipid A compared with LPS and vehicle at 6 h after instillation (lipid A, 0.88 ± 0.25 vs. LPS, 0.37 ± 0.21 optical density units·min−1·mg−1; P < 0.05). However, ALI scores were comparable at 6 and 24 h between LPS and lipid A. MPO was also comparable in vehicle-treated or C3H/HeJ mice treated with LPS or lipid A at 6 and 24 h. Phospho-ERK activation was pronounced at 6 and 24 h after lipid A but not LPS treatment. In vitro studies confirmed the relationship between phospho-ERK activation and cytokine expression in macrophage stimulated with either LPS or lipid A. Compared with whole LPS, the lipid A fraction is associated with amplified whole lung MPO and ERK activation 6 h after intratracheal instillation in mice.

Dual effect of AMD3100, a CXCR4 antagonist, on bleomycin-induced lung inflammation

The chemokine receptor CXCR4, which binds the chemokine stromal cell-derived factor 1, has been reported to be involved in the chemotaxis of inflammatory cells. In addition, AMD3100, an antagonist of CXCR4, has been reported to be an attractive drug candidate for therapeutic intervention in several disorders in which CXCR4 is critically involved. However, little is known about the therapeutic value of AMD3100 in the treatment of pulmonary fibrosis. In this study, we examined the effects of AMD3100 on a murine bleomycin-induced pulmonary fibrosis model. Concurrent administration of AMD3100 and bleomycin apparently attenuated bleomycin-induced pulmonary inflammation. In this process, an inhibition of neutrophil recruitment at early stage followed by the decrease of other inflammatory cell recruitment in the lung were observed. In addition, it also inhibited the expression of cytokines, including MCP-1, MIP-2, MIP-1alpha, and TGF-beta. In contrast, when AMD3100 was administered following bleomycin treatment, the bleomycin-induced lung inflammation progressed and resulted in severe pulmonary fibrosis. In this process, an increase of inflammatory cell recruitment, an up-regulation of lung MCP-1 and TGF-beta, and a remarkable activation of p44/42 MAPK in neutrophils were observed. U0126, an inhibitor of p44/42 MAPK, significantly abolished these effects. Thus, AMD3100 has dual effect on bleomycin-induced pulmonary fibrosis. Difference of inflammatory cell recruitment and activation might be associated with the dual effect of AMD3100 on bleomycin-induced pulmonary fibrosis.

Hyperoxia increases ventilator-induced lung injury via mitogen-activated protein kinases: a prospective, controlled animal experiment

Introduction

Large-tidal volume (V_T) mechanical ventilation and hyperoxia used in patients with acute respiratory distress syndrome can damage pulmonary epithelial cells through lung inflammation and apoptotic cell death. Hyperoxia has been shown to increase ventilator-induced lung injury, but the mechanisms regulating interaction between large V_T and hyperoxia are unclear. We hypothesized that the addition of hyperoxia to large-V_T ventilation would increase neutrophil infiltration by upregulation of the cytokine macrophage inflammatory protein-2 (MIP-2) and would increase apoptosis via the mitogen-activated protein kinase pathways.

Methods

C57BL/6 mice were exposed to high-V_T (30 ml/kg) mechanical ventilation with room air or hyperoxia for one to five hours.

Results

The addition of hyperoxia to high-V_T ventilation augmented lung injury, as demonstrated by increased apoptotic cell death, neutrophil migration into the lung, MIP-2 production, MIP-2 mRNA expression, increased DNA binding activity of activator protein-1, increased microvascular permeability, and c-Jun NH₂-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) 1/2 activation. Hyperoxia-induced augmentation of high-V_T-induced lung injury was attenuated in JNK-deficient mice and in mice with pharmacologic inhibition of ERK activity by PD98059. However, only JNK-deficient mice, and not mice with ERK activity inhibition by PD98059, were protected from high-V_T-induced lung injury without hyperoxia.

Conclusion

We conclude that hyperoxia increased high-V_T-induced cytokine production, neutrophil influx, and apoptotic cell death through activation of the JNK and ERK1/2 pathways.

Isoflurane protects renal function against ischemia and reperfusion through inhibition of protein kinases, JNK and ERK

Isoflurane has a pharmacological preconditioning effect against ischemia in the heart and brain, but whether this also occurs in the kidney is unclear. In this study, we investigated pharmacological preconditioning by isoflurane in the rat kidney. In the isoflurane preconditioning group (1.5% isoflurane for 20 min before renal ischemia) serum creatinine (1.2 +/- 0.7 and 1.1 +/- 0.2 mg/dL) and blood urea nitrogen (99 +/- 29 and 187 +/- 31 mg/dL) were significantly smaller at 24 and 48 h after reperfusion than in the nonpreconditioning group (creatinine; 2.4 +/- 1.2 and 2.9 +/- 0.9 mg/dL, urea; 62 +/- 19 and 79 +/- 20 mg/dL). We also investigated the intracellular signal transduction involved in isoflurane preconditioning in the kidney. The activities of the stress protein kinases, JNK and ERK but not p38, were significantly less in the kidneys of the preconditioning group than in those of the nonpreconditioning group (P < 0.05). We conclude that isoflurane has a preconditioning effect against renal ischemia/reperfusion injury when administered before ischemia. Inhibition of the protein kinases, JNK and ERK, might be involved in the mechanisms of isoflurane preconditioning.

The paradox of matrix metalloproteinases in infectious disease

Matrix metalloproteinases (MMPs) are a family of proteolytic enzymes that perform multiple roles in the normal immune response to infection. MMPs facilitate leucocyte recruitment, cytokine and chemokine processing, defensin activation and matrix remodelling. However, excess MMP activity following infection may lead to immunopathology that causes host morbidity or mortality and favours pathogen dissemination or persistence. Here, we review the normal functions of MMPs in immunity and then discuss viral and bacterial infections where excess MMP activity has been implicated in pathology, specifically examining HIV, HTLV-1, hepatitis B, endotoxin shock, Helicobacter pylori and Mycobacterium tuberculosis. Tissue destruction may be exacerbated further by bacterial-derived enzymes which activate the host pro-MMPs. Finally, the potential for therapeutic targeting of excess MMP activity in infection is considered.

Induction of CXCL5 during inflammation in the rodent lung involves activation of alveolar epithelium

The lung is continuously exposed to bacteria and their products, and has developed a complex defense mechanism, including neutrophil recruitment. In mice, keratinocyte cell-derived chemokine and macrophage inflammatory protein-2 are the major chemokines for neutrophil recruitment into the lung. We have previously described a role for C-X-C chemokine (CXCL5) in neutrophil trafficking during lipopolysaccharide (LPS)-induced lung inflammation in mice. The aims of the present study were to identify the cellular origin of CXCL5 and to determine the signaling cascades that regulate its expression in the lung during LPS-induced inflammation and in isolated LPS-stimulated CXCL5-expressing cells. Our immunohistochemical analysis indicates that alveolar epithelial type II (AEII) cells are the primary source of CXCL5 in the rodent lung. These in vivo observations were confirmed with primary AEII cells. In addition, our data indicate that the Toll-like receptor 4 (TLR4) signaling cascade involving TLR4, myeloid differentiation factor 88, and Toll-IL-1R domain-containing adapter protein is required to induce CXCL5 expression in the lung. Furthermore, p38 and c-Jun N-terminal kinases are involved in lung CXCL5 expression. Similarly, TLR4, and p38 and c-Jun N-terminal kinases, are associated with LPS-induced CXCL5 expression in AEII cells. These novel observations demonstrate that activation of AEII cells via TLR4-dependent signaling is important for the production of CXCL5 in the lung exposed to LPS.