Mitogen-activated protein kinase-activated protein kinase 2 mediates apoptosis during lung vascular permeability by regulating movement of cleaved caspase 3

Unlocking the protective potential of the angiotensin type 2 receptor (AT2R) in acute lung injury and age-related pulmonary dysfunction

Despite its known importance in the cardiovascular system, the specific role and impact of the angiotensin type 2 receptor (AT2R) in lung physiology and pathophysiology remain largely elusive. In this study, we highlight the distinct and specialized lung-specific roles of AT2R, primarily localized to an alveolar fibroblast subpopulation, in contrast to the angiotensin type 1 receptor (AT1R), which is almost exclusively expressed in lung pericytes. Evidence from our research demonstrates that the disruption of AT2R (AT2R-/y), is associated with a surge in oxidative stress and impaired lung permeability, which were further intensified by Hyperoxic Acute Lung Injury (HALI). With aging, AT2R-/y mice show an increase in oxidative stress, premature enlargement of airspaces, as well as increased mortality when exposed to hyperoxia as compared to age-matched WT mice. Our investigation into Losartan, an AT1R blocker, suggests that its primary HALI lung-protective effects are channeled through AT2R, as its protective benefits are absent in AT2R-/y mice. Importantly, a non-peptide AT2R agonist, Compound 21 (C21), successfully reverses lung oxidative stress and TGFβ activation in wild-type (WT) mice exposed to HALI. These findings suggest a possible paradigm shift in the therapeutic approach for lung injury and age-associated pulmonary dysfunction, from targeting AT1R with angiotensin receptor blockers (ARBs) towards boosting the protective function of AT2R.

THE CRITICAL ROLE OF THE HISTONE MODIFICATION ENZYME SETDB2 IN THE PATHOGENESIS OF ACUTE RESPIRATORY DISTRESS SYNDROME

ABSTRACT

Introduction: Acute respiratory distress syndrome (ARDS) is a severe hypoxemic respiratory failure with a high in-hospital mortality. However, the molecular mechanisms underlying ARDS remain unclear. Recent findings have indicated that the onset of severe inflammatory diseases, such as sepsis, is regulated by epigenetic changes. We investigated the role of epigenetic changes in ARDS pathogenesis using mouse models and human samples. Methods: Acute respiratory distress syndrome was induced in a mouse model (C57BL/6 mice, myeloid cell or vascular endothelial cell [VEC]-specific SET domain bifurcated 2 [Setdb2]-deficient mice [Setdb2 ff Lyz2 Cre+ or Setdb2 ff Tie2 Cre+ ], and Cre - littermates) by intratracheal administration of lipopolysaccharide (LPS). Analyses were performed at 6 and 72 h after LPS administration. Sera and lung autopsy specimens from ARDS patients were examined. Results: In the murine ARDS model, we observed high expression of the histone modification enzyme SET domain bifurcated 2 ( Setdb2 ) in the lungs. In situ hybridization examination of the lungs revealed Setdb2 expression in macrophages and VECs. The histological score and albumin level of bronchoalveolar lavage fluid were significantly increased in Setdb2 ff Tie2 Cre+ mice following LPS administration compared with Setdb2 ff Tie2 Cre- mice, whereas there was no significant difference between the control and Setdb2 ff Lyz2 Cre+ mice. Apoptosis of VECs was enhanced in Setdb2 ff Tie2 Cre+ mice. Among the 84 apoptosis-related genes, the expression of TNF receptor superfamily member 10b ( Tnfrsf10b ) was significantly higher in Setdb2 ff Tie2 Cre+ mice than in control mice. Acute respiratory distress syndrome patients' serum showed higher SETDB2 levels than those of healthy volunteers. SETDB2 levels were negatively correlated with the partial pressure of oxygen in arterial blood/fraction of inspiratory oxygen concentration ratio. Conclusion: Acute respiratory distress syndrome elevates Setdb2 , apoptosis of VECs, and vascular permeability. Elevation of histone methyltransferase Setdb2 suggests the possibility to histone change and epigenetic modification. Thus, Setdb2 may be a novel therapeutic target for controlling the pathogenesis of ARDS.

MK2 nonenzymatically promotes nuclear translocation of caspase-3 and resultant apoptosis

We have previously identified mitogen-activated protein kinase-activated protein kinase 2 (MK2) is required for caspase-3 nuclear translocation in the execution of apoptosis; however, little is known of the underlying mechanisms. Therefore, we sought to determine the role of kinase and nonkinase functions of MK2 in promoting nuclear translocation of caspase-3. We identified two non-small cell lung cancer cell lines for use in these experiments based on low MK2 expression. Wild-type, enzymatic and cellular localization mutant MK2 constructs were expressed using adenoviral infection. Cell death was evaluated by flow cytometry. In addition, cell lysates were harvested for protein analyses. Phosphorylation of caspase-3 was determined using two-dimensional gel electrophoresis followed by immunoblotting and in vitro kinase assay. Association between MK2 and caspase-3 was evaluated using proximity-based biotin ligation assays and co-immunoprecipitation. Overexpression of MK2 resulted in nuclear translocation of caspase-3 and caspase-3-mediated apoptosis. MK2 directly phosphorylates caspase-3; however, phosphorylation status of caspase-3 or MK2-dependent phosphorylation of caspase-3 did not alter caspase-3 activity. The enzymatic function of MK2 was dispensable in nuclear translocation of caspase-3. MK2 and caspase-3 associated together and a nonenzymatic function of MK2, chaperoned nuclear trafficking, is required for caspase-3-mediated apoptosis. Taken together, our results demonstrate a nonenzymatic role for MK2 in the nuclear translocation of caspase-3. Furthermore, MK2 may function as a molecular switch in regulating the transition between the cytosolic and nuclear functions of caspase-3.

Tumor MK2 transcript levels are associated with improved response to chemotherapy and patient survival in non-small cell lung cancer

Non-small cell lung cancers (NSCLCs) demonstrate intrinsic resistance to cell death, even after chemotherapy. Previous work suggested defective nuclear translocation of active caspase-3 in observed resistance to cell death. We have identified mitogen-activated protein kinase-activated protein kinase 2 (MK2; encoded by the gene MAPKAPK2) is required for caspase-3 nuclear translocation in the execution of apoptosis in endothelial cells. The objective was to determine MK2 expression in NSCLCs and the association between MK2 and clinical outcomes in patients with NSCLC. Clinical and MK2 mRNA data were extracted from two demographically distinct NSCLC clinical cohorts, North American (The Cancer Genome Atlas, TCGA) and East Asian (EA). Tumor responses following first round of chemotherapy were dichotomized as clinical response (complete response, partial response, and stable disease) or progression of disease. Multivariable survival analyses were performed using Cox proportional hazard ratios and Kaplan-Meier curves. NSCLC exhibited lower MK2 expression than SCLC cell lines. In patients, lower tumor MK2 transcript levels were observed in those presenting with late-stage NSCLC. Higher MK2 expression was associated with clinical response following initial chemotherapy and independently associated with improved 2-yr survival in two distinct cohorts, 0.52 (0.28-0.98) and 0.1 (0.01-0.81), TCGA and EA, respectively, even after adjusting for common oncogenic driver mutations. Survival benefit of higher MK2 expression was unique to lung adenocarcinoma when comparing across various cancers. This study implicates MK2 in apoptosis resistance in NSCLC and suggests prognostic value of MK2 transcript levels in patients with lung adenocarcinoma.

Terbutaline attenuates LPS-induced injury of pulmonary microvascular endothelial cells by cAMP/Epac signaling

Acute lung injury (ALI), characterized by an acute onset of severe hypoxemia, is a common and devastating syndrome usually triggered by lipopolysaccharide (LPS) infection from bacteria. This study is intended to explore whether terbutaline can alleviate LPS-induced human pulmonary microvascular endothelial cell (HPMVEC) injury through cAMP/Epac signaling. LPS was utilized to induce ALI in HPMVECs, and after exposure of LPS-induced HPMVECs to terbutaline, the cellular functions including cell viability and apoptosis were measured by cell counting kit-8 and terminal deoxynucleotidyl transferase dUTP nick-end labeling. The protein expression related to cAMP/Epac signaling, apoptosis, and that of tight junction and inflammatory factors were evaluated at the same time. The effects of terbutaline on cellular functions were confirmed again after the addition of antagonists of cAMP and Epac, respectively. The levels of both cAMP and Epac reduced by LPS was concentration-dependently increased by terbutaline. The apoptosis and endothelial cell permeability damage of LPS-induced HPMVECs were enhanced after the addition of KT-5720 and ESI-09. The beneficial effects of terbutaline on alleviating the inflammation and apoptosis in HPMVECs injured by LPS are mediated by cAMP/Epac signaling, and this evidence would demonstrate the potential of terbutaline in the treatment of ALI.

Comparison of polynomial fitting versus single time point analysis of ECIS data for barrier assessment

Electrical cell-substrate impedance sensing (ECIS) is an in vitro methodology for measuring the barrier integrity of a variety of cell types, including pulmonary endothelial cells. These experiments are frequently used for in vitro assessment of lung injury. The data derived from ECIS experiments consists of repeated measures of resistance across an endothelial monolayer. As such, these data reflect the dynamic changes in electrical resistance that occur over time. Currently methodologies for assessing ECIS data rely on single point assessments of barrier function, such as the maximal drop in trans-endothelial electrical resistance (TERMax ). However, this approach ignores the myriad of changes in resistance that occur before and after the TERMax data point. Herein, we utilize polynomial curve fitting on experimentally generated ECIS data, thus allowing for comparing ECIS experiments by examining the mean polynomial coefficients between groups. We show that polynomial curves accurately fit a variety of ECIS data, and that concordance between TERMax and coefficient analysis varies by type of stimulus, suggesting that TERMax differences may not always correlate with a significant difference in the overall shape of the ECIS profile. Lastly, we identify factors that impact coefficient values obtained in our analyses, including the length of time devoted to baseline measurements before addition of stimuli. Polynomial coefficient analysis is another tool that can be used for more comprehensive interrogation of ECIS data to better understand the biological underpinnings that lead to changes in barrier dysfunction in vitro.

Mitogen-activated protein kinase-activated protein kinase-2 (MK2) and its role in cell survival, inflammatory signaling, and migration in promoting cancer

Cancer and the immune system share an intimate relationship. Chronic inflammation increases the risk of cancer occurrence and can also drive inflammatory mediators into the tumor microenvironment enhancing tumor growth and survival. The p38 MAPK pathway is activated both acutely and chronically by stress, inflammatory chemokines, chronic inflammatory conditions, and cancer. These properties have led to extensive efforts to find effective drugs targeting p38, which have been unsuccessful. The immediate downstream serine/threonine kinase and substrate of p38 MAPK, mitogen-activated-protein-kinase-activated-protein-kinase-2 (MK2) protects cells against stressors by regulating the DNA damage response, transcription, protein and messenger RNA stability, and motility. The phosphorylation of downstream substrates by MK2 increases inflammatory cytokine production, drives an immune response, and contributes to wound healing. By binding directly to p38 MAPK, MK2 is responsible for the export of p38 MAPK from the nucleus which gives MK2 properties that make it unique among the large number of p38 MAPK substrates. Many of the substrates of both p38 MAPK and MK2 are separated between the cytosol and nucleus and interfering with MK2 and altering this intracellular translocation has implications for the actions of both p38 MAPK and MK2. The inhibition of MK2 has shown promise in combination with both chemotherapy and radiotherapy as a method for controlling cancer growth and metastasis in a variety of cancers. Whereas the current data are encouraging the field requires the development of selective and well tolerated drugs to target MK2 and a better understanding of its effects for effective clinical use.

Dexmedetomidine Protects Human Renal Tubular Epithelial HK-2 Cells against Hypoxia/Reoxygenation Injury by Inactivating Endoplasmic Reticulum Stress Pathway

Objective

The study was aimed to investigate the effects and potential mechanisms of Dexmedetomidine (Dex) on hypoxia/reoxygenation (H/R) injury in human renal tubular epithelial HK-2 cells.

Materials and Methods

In this experimental study, HK-2 cells were divided into four groups: control group, Dex group, H/R group, and Dex+H/R group. The cells in control group received no treatment, and cells in Dex group were only treated with 0.1 nmol/L Dex. The cells in H/R group and Dex+H/R group were all treated with H/R (hypoxia for 24 hours and normoxia for 4 hours), and only the cells in Dex+H/R group were pre-administrated with 0.1 nmol/L Dex. Following treatments at 37˚C for 28 hours, cell viability and apoptosis were measured by MTT assay and flow cytometry, respectively. Also, the expressions of hypoxia-inducible factor 1 (HIF-1α), glucose-regulated protein 78 (GRP78), C/EBP homologous protein (CHOP), caspase-12 and cleaved caspase-3 were determined by western blot.

Results

The cell viability was significant decreased in H/R group compared with control group (P<0.05), while was significantly increased in Dex+H/R group compared with that in H/R group (P<0.05). However, the change tendency of the cell apoptosis was opposite to that of cell viability. Compared with H/R group, the expression of HIF-1α was evidently up-regulated, while GRP78, CHOP, capase-12 and cleaved caspase-3 expressions were all obviously down- regulated in Dex+H/R group (P<0.05). In addition, the concentrations of malondialdehyde (MDA) in H/R group and Dex+H/R group were 1.68 ± 0.22 nmol/mgprot and 0.85 ± 0.16 nmol/mgprot, respectively. The superoxide dismutase (SOD) activity was higher in Dex+H/R group (121 ± 11 U/L), which which was more than twice larger than that in H/R group (57 ± 10 U/L).

Conclusion

Dex could promote cell viability and inhibit apoptosis through up-regulating HIF-1α, reducing endoplasmic reticulum (ER) stress and mediating oxidative stress, thus ameliorating the H/R injury.

Role of Oxidative Stress in Reperfusion following Myocardial Ischemia and Its Treatments

Myocardial ischemia is a disease with high morbidity and mortality, for which reperfusion is currently the standard intervention. However, the reperfusion may lead to further myocardial damage, known as myocardial ischemia/reperfusion injury (MI/RI). Oxidative stress is one of the most important pathological mechanisms in reperfusion injury, which causes apoptosis, autophagy, inflammation, and some other damage in cardiomyocytes through multiple pathways, thus causing irreversible cardiomyocyte damage and cardiac dysfunction. This article reviews the pathological mechanisms of oxidative stress involved in reperfusion injury and the interventions for different pathways and targets, so as to form systematic treatments for oxidative stress-induced myocardial reperfusion injury and make up for the lack of monotherapy.

Pivotal role of endothelial cell autophagy in sepsis

Sepsis is a fatal organ dysfunction resulting from a disordered host response to infection. Endothelial cells (ECs) are usually the primary targets of inflammatory mediators in sepsis; damage to ECs plays a pivotal part in vital organ failure. In recent studies, autophagy was suggested to play a critical role in the ECs injury although the mechanisms by which ECs are injured in sepsis are not well elucidated. Autophagy is a highly conserved catabolic process that includes sequestrating plasma contents and transporting cargo to lysosomes for recycling the vital substrates required for metabolism. This pathway also counteracts microbial invasion to balance and retain homeostasis, especially during sepsis. Increasing evidence indicates that autophagy is closely associated with endothelial function. The role of autophagy in sepsis may or may not be favorable depending upon conditions. In the present review, the current knowledge of autophagy in the process of sepsis and its influence on ECs was evaluated. In addition, the potential of targeting EC autophagy for clinical treatment of sepsis was discussed.

Novel Therapeutic Potential of Mitogen-Activated Protein Kinase Activated Protein Kinase 2 (MK2) in Chronic Airway Inflammatory Disorders

OBJECTIVE

The primary focus of this review is to highlight the current and emerging proinflammatory role of MK2 kinase signaling in p38MAPK pathway and to provide a detailed evaluation on the prospects of MK2 inhibition with special emphasis on the etiology of chronic inflammatory airway diseases, such as asthma, idiopathic pulmonary fibrosis, lung cancer, acute lung injury and acute respiratory distress syndrome.

BACKGROUND

MK2 belongs to serine-threonine kinase family and is activated directly by stress and inflammatory signal through p38MAPK phosphorylation in diverse inflammatory conditions through the Toll-like receptor signaling pathway. MK2 has been thought to be a critical factor involved in the regulation of synthesis and release of pro-inflammatory (TNF-α, IL-6 and IL-1β, etc.) proteins. Targeted inhibition of MK2 kinase has been shown to significantly reduce the production and release of these cytokine molecules. Therefore, MK2 has been identified as an effective strategy (alternative to p38MAPK) to block this pro-inflammatory signaling pathway.

RESULTS

The inhibition of MK2 may lead to similar or better efficacy as that of p38 inhibitors, and interestingly avoids the systemic toxicity shown by the p38 inhibitors. Thus, MK2 has been the focus of intense interdisciplinary research and its specific inhibition can be a novel and potential therapeutic strategy for the treatment of chronic airway inflammatory diseases.

CONCLUSION

Promising advancement in understanding and rigorous exploration of the role of MK2 kinase in inflammatory processes may contribute to the development of newer and safer therapy for the treatment of chronic airway inflammatory diseases in the future.

Dengue virus non-structural protein 1 activates the p38 MAPK pathway to decrease barrier integrity in primary human endothelial cells

Dengue virus (DENV) causes an estimated 390 million infections worldwide annually, with severe forms of disease marked by vascular leakage. Endothelial cells (EC) are directly responsible for vascular homeostasis and are highly responsive to circulating mediators but are not commonly infected. DENV encodes seven non-structural (NS) proteins; with only one of those, NS1, secreted from infected cells and accumulating in the blood of patients. NS1 has been implicated in the pathogenesis of vascular permeability, but the mechanism is not completely understood. Here we used primary endothelial cells and an array of in vitro approaches to study the effect of NS1 in disease-relevant human ECs. Confocal microscopy demonstrated rapid NS1 internalization by ECs into endosomes with accumulation over time. Transcriptomic and pathway analysis showed significant changes in functions associated with EC homeostasis and vascular permeability. Functional significance of this activation was assessed by trans-endothelial electrical resistance and showed that NS1 induced rapid and transient loss in EC barrier function within 3 h post-treatment. To understand the molecular mechanism by which NS1 induced EC activation, we evaluated the stress-sensing p38 MAPK pathway known to be directly involved in EC permeability and inflammation. WB analysis of NS1-stimulated ECs showed clear activation of p38 MAPK and downstream effectors MAPKAPK-2 and HSP27 with chemical inhibition of the p38 MAP kinase pathway restoring barrier function. Our results suggest that DENV NS1 may be involved in the pathogenesis of severe dengue by activating the p38 MAPK in ECs, promoting increased permeability that characterizes severe disease.

Genistein-3'-sodium sulphonate protects against lipopolysaccharide-induced lung vascular endothelial cell apoptosis and acute lung injury via BCL-2 signalling

Under septic conditions, Lipopolysaccharide (LPS)‐induced apoptosis of lung vascular endothelial cells (ECs) triggers and aggravates acute lung injury (ALI), which so far has no effective therapeutic options. Genistein‐3′‐sodium sulphonate (GSS) is a derivative of native soy isoflavone, which has neuro‐protective effects through its anti‐apoptotic property. However, whether GSS protects against sepsis‐induced lung vascular endothelial cell apoptosis and ALI has not been determined. In this study, we found that LPS‐induced Myd88/NF‐κB/BCL‐2 signalling pathway activation and subsequent EC apoptosis were effectively down‐regulated by GSS in vitro. Furthermore, GSS not only reversed the sepsis‐induced BCL‐2 changes in expression in mouse lungs but also blocked sepsis‐associated lung vascular barrier disruption and ALI in vivo. Taken together, our results demonstrated that GSS might be a promising candidate for sepsis‐induced ALI via its regulating effects on Myd88/NF‐κB/BCL‐2 signalling in lung ECs.

A nonapoptotic endothelial barrier-protective role for caspase-3

Noncanonical roles for caspase-3 are emerging in the fields of cancer and developmental biology. However, little is known of nonapoptotic functions of caspase-3 in most cell types. We have recently demonstrated a disassociation between caspase-3 activation and execution of apoptosis with accompanying cytoplasmic caspase-3 sequestration and preserved endothelial barrier function. Therefore, we tested the hypothesis that nonapoptotic caspase-3 activation promotes endothelial barrier integrity. Human lung microvascular endothelial cells were exposed to thrombin, a nonapoptotic stimulus, and endothelial barrier function was assessed using electric cell-substrate impedance sensing. Actin cytoskeletal rearrangement and paracellular gap formation were assessed using phalloidin staining. Cell stiffness was evaluated using magnetic twisting cytometry. In addition, cell lysates were harvested for protein analyses. Caspase-3 was inhibited pharmacologically with pan-caspase and a caspase-3-specific inhibitor. Molecular inhibition of caspase-3 was achieved using RNA interference. Cells exposed to thrombin exhibited a cytoplasmic activation of caspase-3 with transient and nonapoptotic decrease in endothelial barrier function as measured by a drop in electrical resistance followed by a rapid recovery. Inhibition of caspases led to a more pronounced and rapid drop in thrombin-induced endothelial barrier function, accompanied by increased endothelial cell stiffness and paracellular gaps. Caspase-3-specific inhibition and caspase-3 knockdown both resulted in more pronounced thrombin-induced endothelial barrier disruption. Taken together, our results suggest cytoplasmic caspase-3 has nonapoptotic functions in human endothelium and can promote endothelial barrier integrity.

Recombinant Human Superoxide Dismutase and N-Acetylcysteine Addition to Exogenous Surfactant in the Treatment of Meconium Aspiration Syndrome

This study aimed to evaluate the molecular background of N-acetylcysteine (NAC) and recombinant human superoxide dismutase (rhSOD) antioxidant action when combined with exogenous surfactant in the treatment of meconium aspiration syndrome (MAS), considering redox signalling a principal part of cell response to meconium. Young New Zealand rabbits were instilled with meconium suspension (Mec) and treated by surfactant alone (Surf) or surfactant in combination with i.v. NAC (Surf + NAC) or i.t. rhSOD (Surf + SOD), and oxygen-ventilated for 5 h. Dynamic lung-thorax compliance, mean airway pressure, PaO₂/FiO₂ and ventilation efficiency index were evaluated every hour; post mortem, inflammatory and oxidative markers (advanced oxidation protein products, total antioxidant capacity, hydroxynonenal (HNE), p38 mitogen activated protein kinase, caspase 3, thromboxane, endothelin-1 and secretory phospholipase A₂) were assessed in pulmonary tissue homogenates. rhSOD addition to surfactant improved significantly, but transiently, gas exchange and reduced levels of inflammatory and oxidative molecules with higher impact; Surf + NAC had stronger effect only on HNE formation, and duration of treatment efficacy in respiratory parameters. In both antioxidants, it seems that targeting reactive oxygen species may be strong supporting factor in surfactant treatment of MAS due to redox sensitivity of many intracellular pathways triggered by meconium.

Curcuminoids: Implication for inflammation and oxidative stress in cardiovascular diseases

It has been extensively verified that inflammation and oxidative stress play important roles in the pathogenesis of cardiovascular diseases (CVDs). Curcuminoids, from the plant Curcuma longa, have three major active ingredients, which include curcumin (curcumin I), demethoxycurcumin, and bisdemethoxycurcumin. Curcuminoids have been used in traditional medicine for CVDs' management and other comorbidities for centuries. Numerous studies had delineated their anti-inflammatory, antioxidative, and other medicinally relevant properties. Animal experiments and clinical trials have also demonstrated that turmeric and curcuminoids can effectively reduce atherosclerosis, cardiac hypertrophy, hypertension, ischemia/reperfusion injury, and diabetic cardiovascular complications. In this review, we introduce and summarize curcuminoids' molecular and biological significance, while focusing on their mechanistic anti-inflammatory/antioxidative involvements in CVDs and preventive effects against CVDs, and, finally, discuss relevant clinical applications.

Apoptosis regulation by subcellular relocation of caspases

The cleavage of nuclear proteins by caspases promotes nuclear breakdown and, therefore, plays a key role in apoptosis execution. However, the detailed molecular mechanisms of these events remain unclear. To get more insights into the mechanisms of nuclear events during apoptosis we set up a rapid fractionation protocol for the separation of the cytoplasmic and nuclear fractions of cells undergoing cisplatin-induced apoptosis. Importantly, nuclear accumulation of effector caspase-3 as well as initiator caspase-2, -8 and -9 was observed using the developed protocol and immunofluorescence microscopy. The detection of caspases and their cleavage products in the nucleus occurred within the same time interval after cisplatin treatment and took place shortly before nuclear fragmentation. The entry of initiator caspases to the nucleus was independent of caspase-3. Given that all three initiator caspases had catalytic activity in the nuclei, our findings indicate that initiator caspases might participate in the proteolysis of nuclear components during apoptosis, promoting its disintegration and apoptotic cell death.

Selective inhibition of NF-kappaB and surfactant therapy in experimental meconium-induced lung injury

Meconium aspiration syndrome (MAS) in newborns is characterized mainly by respiratory failure due to surfactant dysfunction and inflammation. Previous meta-analyses did not prove any effect of exogenous surfactant treatment nor glucocorticoid administration on final outcome of children with MAS despite oxygenation improvement. As we supposed there is the need to intervene in both these fields simultaneously, we evaluated therapeutic effect of combination of exogenous surfactant and selective inhibitor of NF-kappaB (IKK-NBD peptide). Young New Zealand rabbits were instilled by meconium suspension and treated by surfactant alone or surfactant in combination with IKK-NBD, and oxygen-ventilated for 5 h. PaO(2)/FiO(2), oxygenation index, oxygen saturation and ventilation efficiency index were evaluated every hour; post mortem, total and differential leukocyte counts were investigated in bronchoalveolar lavage fluid (BALF) and inflammatory, oxidative and apoptotic markers were assessed in lung tissue homogenates. Exogenous surfactant combined with IKK-NBD improved oxygenation, reduced neutrophil count in BALF and levels of IL-1beta, IL-6, p38 MAPK and caspase 3 in comparison with surfactant-only therapy. It seems that inhibition of inflammation may be strong supporting factor in surfactant treatment of MAS.

Altered expression of TIAM1 in endotoxin-challenged airway epithelial cells and rodent septic models

BACKGROUND

In sepsis, reorganization of the actin cytoskeleton in the epithelium during inflammation will lead to a breakdown of epithelial barrier integrity, and contribute to the pathogenesis of sepsis, but the exact changes of various components regulating the actin cytoskeleton pathway remain unclear.

METHODS

We used lipopolysaccharide (LPS) challenged primary epithelial cells cultured at the air-liquid interface (ALI) to mimic epithelial barrier dysfunction during sepsis. Then we detected differential expression of T-lymphoma invasion and metastasis 1 (TIAM1) gene in lung epithelial cells and septic models.

RESULTS

LPS induced barrier dysfunction in human tracheobronchial epithelial cells (HTBEs) as measured by statistically significant changes in ionic and macromolecular permeability. We observed differential expression of TIAM1 gene. The protein expression of TIAM1 was decreased after LPS challenge, in human bronchial epithelial cells. Furthermore, the expression levels of both TIAM1 mRNA and protein were decreased in lungs of septic rodent models.

CONCLUSIONS

Given that expression levels of TIAM1 have been associated with mortality among sepsis patients, our findings have the potential for the development of diagnostic and treatment strategies relevant for patient management.

XOR inhibition with febuxostat accelerates pulmonary endothelial barrier recovery and improves survival in lipopolysaccharide-induced murine sepsis

Sepsis is a leading cause of death among patients in the intensive care unit, resulting from multi‐organ failure. Activity of xanthine oxidoreductase (XOR), a reactive oxygen species (ROS) producing enzyme, is known to be elevated in nonsurvivors of sepsis compared to survivors. We have previously demonstrated that XOR is critical for ventilator‐induced lung injury. Using febuxostat, a novel nonpurine inhibitor of XOR, we sought to determine the role of XOR inhibition in a murine model of sepsis‐induced lung injury and mortality. C57BL/6J mice were subjected to intravenous (IV) lipopolysaccharide (LPS) for various time points, and lungs were harvested for analyses. Subsets of mice were treated with febuxostat, pre or post LPS exposure, or vehicle. Separate groups of mice were followed up for mortality after LPS exposure. After 24 hr of IV LPS_, mice exhibited an increase in XOR activity in lung tissue and a significant increase in pulmonary endothelial barrier disruption. Pretreatment of animals with febuxostat before exposure to LPS, or treatment 4 h after LPS, resulted in complete abrogation of XOR activity. Inhibition of XOR with febuxostat did not prevent LPS‐induced pulmonary vascular permeability at 24 h, however, it accelerated recovery of the pulmonary endothelial barrier integrity in response to LPS exposure. Furthermore, treatment with febuxostat resulted in significant reduction in mortality. Inhibition of XOR with febuxostat accelerates recovery of the pulmonary endothelial barrier and prevents LPS‐induced mortality, whether given before or after exposure to LPS.

Allicin attenuates lipopolysaccharide‑induced acute lung injury in neonatal rats via the PI3K/Akt pathway

Allicin is an oxygenated carotenoid derivative that exhibits strong antioxidant activity, which effectively removes reactive oxygen species from the body and has important roles in disease prevention and treatment. Therefore, the present study aimed to investigate whether allicin attenuates lipopolysaccharide (LPS)‑induced acute lung injury (ALI) in neonatal rats and the potential underlying mechanisms. An LPS‑induced ALI neonatal rat model was utilized to assess the therapeutic value and mechanisms of allicin. Following allicin treatment, increases in lung wet/dry ratio and the lung protein concentration were significantly suppressed in LPS‑induced ALI neonatal rats. Furthermore, ELISA results demonstrated that allicin significantly reduced the levels of malondialdehyde, tumor necrosis factor‑α and interleukin‑6, and increased superoxide dismutase activity, in the bronchoalveolar lavage fluid of LPS‑treated rats. Additionally, allicin administration increased the protein expression of Bcl‑2 and reduced the activity of caspase‑3/-9, as determined by western blotting or ELISA, respectively, and increased phosphatidylinositol 3‑kinase (PI3K) and phosphorylated‑Akt protein levels, in LPS‑treated ALI neonatal rats. The results of the present study indicate that allicin attenuate LPS‑induced ALI in neonatal rats by ameliorating oxidative stress, inflammation and apoptosis via the PI3K/Akt pathway. Allicin may be used for development of a novel drug for treatment of ALI.

The influence of isoflavone for denervation-induced muscle atrophy

PURPOSE

Decrease in activity stress induces skeletal muscle atrophy. A previous study showed that treatment with a high level (20%) of isoflavone inhibits muscle atrophy after short-term denervation (at 4 days) in mice. The present study was designed to elucidate whether the dietary isoflavone aglycone (AglyMax) at a 0.6% prevents denervation-mediated muscle atrophy, based on the modulation of atrogin-1- or apoptosis-dependent signaling.

METHODS

Mice were fed either a normal diet or 0.6% AglyMax diet. One week later, the right sciatic nerve was cut. The wet weight, mean fiber area, amount of atrogin-1 and cleaved caspase-3 proteins, and the percentages of apoptotic nuclei were examined in the gastrocnemius muscle at 14 days after denervation.

RESULTS

The 0.6% AglyMax diet significantly attenuated denervation-induced decreases in fiber atrophy but not the muscle wet weight. In addition, dietary isoflavone suppressed the denervation-induced apoptosis in spite of there being no significant changes in the amount of cleaved caspase-3 protein. In contrast, the 0.6% AglyMax diet did not significantly modulate the protein expression of atrogin-1 in the denervated muscle of mice.

CONCLUSIONS

The isoflavone aglycone (AglyMax) at a 0.6% significantly would modulate muscle atrophy after denervation in mice, probably due to the decrease in apoptosis-dependent signaling.

Shikonin suppresses pulmonary fibroblasts proliferation and activation by regulating Akt and p38 MAPK signaling pathways

Fibroblast is believed to be the primary effector in idiopathic pulmonary fibrosis (IPF), a progressive lung disorder characterized by aberrant tissue remodeling and the formation of fibroblastic foci. Due to the complicated etiology and mechanism, there are few effective drugs for this fatal disease. Shikonin (SHI), which is the major ingredient isolated from the plant Lithospermum Erythrorhizon, has long been used as traditional medicine for many diseases including inflammation and cancer. The roles of SHI in attenuating skin scar and renal fibrosis by reducing TGFβ1-stimulated fibroblast activation are also reported. But whether SHI works on IPF which exhibits both inflammatory and carcinoma-like features remains unknown. In this study, using isolated pulmonary fibroblasts, we demonstrated that SHI inhibited the proliferation, migration of fibroblasts, enhanced cell apoptosis and led to cell cycle arrest at G1 and G2/M phase. Moreover, SHI reduced the production of α-SMA, fibronectin, collagen I and III in response to TGF-β induction in pulmonary fibroblasts, and all of these gene production is the key component of extracellular matrix for tissue remodeling for IPF. The phosphorylation of Akt was down-regulated, p53 increased, the mRNA levels of p21 and p27 enhanced after SHI treatments. The phosphorylation of both p38 MAPK and Akt stimulated by TGF-β was reduced after SHI treatments. Collectively, these data indicate that SHI has a strong cytotoxicity in pulmonary fibroblast via inhibiting Akt activation signaling pathway, and attenuates TGF-β induced extracellular matrix genes production in pulmonary fibroblasts via modulating the activities of p38 MAPK and Akt. SHI might serve as a therapeutically candidate for IPF patients.

Necroptosis: A Novel Cell Death Modality and Its Potential Relevance for Critical Care Medicine

Cell death is intertwined with life in development, homeostasis, pathology, and aging. Until recently, apoptosis was the best known form of programmed cell death, whereas necrosis was for a long time considered accidental owing to physicochemical injury. However, identification of crucial signaling and execution molecules, which are highly regulated, revealed that necrosis encompasses several cell death modalities that can be therapeutically targeted. The best understood form of regulated necrosis is necroptosis, which is transduced by the kinase activities of receptor interacting protein kinase-1 and receptor interacting protein kinase-3, eventually leading to the activation of mixed lineage kinase domain-like and plasma membrane permeabilization. We are only beginning to appreciate the role of necroptosis in different pathological conditions, including critical illnesses. In this review, we discuss the molecular mechanisms of necroptosis and analyze the effect of inhibiting necroptosis in experimental models of critical illnesses. In view of the identification of an increasing number of cell death modalities, we also briefly discuss the simultaneous targeting of multiple cell death modalities because, depending on the cell type and cellular conditions, various types of cell death may contribute to the pathology.

Pivotal Role of Mitogen-Activated Protein Kinase-Activated Protein Kinase 2 in Inflammatory Pulmonary Diseases

Mitogen-activated protein kinase (MAPK)-activated protein kinase (MK2) is exclusively regulated by p38 MAPK in vivo. Upon activation of p38 MAPK, MK2 binds with p38 MAPK, leading to phosphorylation of TTP, Hsp27, Akt, and Cdc25 that are involved in regulation of various essential cellular functions. In this review, we discuss current knowledge about molecular mechanisms of MK2 in regulation of TNF-α production, NADPH oxidase activation, neutrophil migration, and DNA-damage-induced cell cycle arrest which are involved in the molecular pathogenesis of acute lung injury, pulmonary fibrosis, and non-small-cell lung cancer. Collectively current and emerging new information indicate that developing MK2 inhibitors and blocking MK2-mediated signal pathways are potential therapeutic strategies for treatment of inflammatory and fibrotic lung diseases and lung cancer.

Lipopolysaccharide Induces Human Pulmonary Micro-Vascular Endothelial Apoptosis via the YAP Signaling Pathway

Gram-negative bacterial lipopolysaccharide (LPS) induces a pathologic increase in lung vascular leakage under septic conditions. LPS-induced human pulmonary micro-vascular endothelial cell (HPMEC) apoptosis launches and aggravates micro-vascular hyper-permeability and acute lung injury (ALI). Previous studies show that the activation of intrinsic apoptotic pathway is vital for LPS-induced EC apoptosis. Yes-associated protein (YAP) has been reported to positively regulate intrinsic apoptotic pathway in tumor cells apoptosis. However, the potential role of YAP protein in LPS-induced HPMEC apoptosis has not been determined. In this study, we found that LPS-induced activation and nuclear accumulation of YAP accelerated HPMECs apoptosis. LPS-induced YAP translocation from cytoplasm to nucleus by the increased phosphorylation on Y357 resulted in the interaction between YAP and transcription factor P73. Furthermore, inhibition of YAP by small interfering RNA (siRNA) not only suppressed the LPS-induced HPMEC apoptosis but also regulated P73-mediated up-regulation of BAX and down-regulation of BCL-2. Taken together, our results demonstrated that activation of the YAP/P73/(BAX and BCL-2)/caspase-3 signaling pathway played a critical role in LPS-induced HPMEC apoptosis. Inhibition of the YAP might be a potential therapeutic strategy for lung injury under sepsis.

Flow-cytometric method for simultaneous analysis of mouse lung epithelial, endothelial, and hematopoietic lineage cells

Flow cytometry is a powerful tool capable of simultaneously analyzing multiple parameters on a cell-by-cell basis. Lung tissue preparation for flow cytometry requires creation of a single-cell suspension, which often employs enzymatic and mechanical dissociation techniques. These practices may damage cells and cause cell death that is unrelated to the experimental conditions under study. We tested methods of lung tissue dissociation and sought to minimize cell death in the epithelial, endothelial, and hematopoietic lineage cellular compartments. A protocol that involved flushing the pulmonary circulation and inflating the lung with Dispase, a bacillus-derived neutral metalloprotease, at the time of tissue harvest followed by mincing, digestion in a DNase and collagenase solution, and filtration before staining with fluorescent reagents concurrently maximized viable yields of epithelial, endothelial, and hematopoietic lineage cells compared with a standard method that did not use enzymes at the time of tissue harvest. Flow cytometry identified each population-epithelial (CD326(+)CD31(-)CD45(-)), endothelial (CD326(-)CD31(+)CD45(-)), and hematopoietic lineage (CD326(-)CD31(-)CD45(+))-and measured cellular viability by 7-aminoactinomycin D (7-AAD) staining. The Dispase method permitted discrimination of epithelial vs. endothelial cell death in a systemic lipopolysaccharide model of increased pulmonary vascular permeability. We conclude that application of a dissociative enzyme solution directly to the cellular compartments of interest at the time of tissue harvest maximized viable cellular yields of those compartments. Investigators could employ this dissociation method to simultaneously harvest epithelial, endothelial, and hematopoietic lineage and other lineage-negative cells for flow-cytometric analysis.

Angiotensin II induces apoptosis of human pulmonary microvascular endothelial cells in acute aortic dissection complicated with lung injury patients through modulating the expression of monocyte chemoattractant protein-1

Patients with acute aortic dissection (AAD) usually showed acute lung injury (ALI). However, its pathogenesis is still not well defined. Apoptosis of pulmonary microvascular endothelial cells (PMVECs) is closely related to the alveolus-capillary barrier injury and the increased vascular permeability. In this study, we aim to investigate the human PMVECs (hPMVECs) apoptosis induced by angiotensin II (AngII) and monocyte chemoattractant protein-1 (MCP-1) and their potential interaction in the pathogenesis of AAD complicated with ALI. Fifty-eight newly diagnosed AAD, 12 matched healthy individuals were included. Pulmonary tissues of AAD complicated with lung injury were obtained from 2 cadavers to determine the levels of AngII type 1 receptor (AT1-R) and MCP-1. Serum AngII was measured using commercial ELISA kit. H&E staining and immunohistostaining were performed to determine the expression of AT1-R and MCP-1. For the in vitro experiment, hPMVECs were divided into control, AngII group, AngII+Bindarit group and Bindarit group, respectively. Flow cytometry was performed to analyze the apoptosis in each group. Reverse transcription-polymerase chain reaction was performed to determine the mRNA expression of MCP-1. Western blot analysis was performed to evaluate the expression of MCP-1 and apoptosis related protein. Apoptosis of hPMVECs was observed in the lung tissues in the cadavers with AAD complicated with ALI. Besides, the expression of AT1-R and MCP-1 was remarkably elevated. Compared with normal individuals and the non-lung injury AAD patients, the expression of serum AngII was remarkably elevated in AAD patients complicated with ALI. In vitro experiments showed AngII contributed to the apoptosis and elevation of MCP1 in hPMVECs. Besides, it involved in the down-regulation of Bcl-2 protein, and up-regulation of Bax and Caspase-3. Such phenomenon was completely reversed after administration of MCP-1 inhibitor (Bindarit). The production of MCP-1 and cellular apoptosis induced by AngII in hPMVECs are closely related to the pathogenesis of AAD complicated with ALI. The association between MCP-1 and AngII is crucial in the apoptosis of hPMVECs.

Modulation of p38 kinase by DUSP4 is important in regulating cardiovascular function under oxidative stress

Over-activation of p38 is implicated in many cardiovascular diseases (CVDs), including myocardial infarction, hypertrophy, heart failure, and ischemic heart disease. Numerous therapeutic interventions for CVDs have been directed toward the inhibition of the p38 mitogen-activated protein kinase activation that contributes to the detrimental effect after ischemia/reperfusion (I/R) injuries. However, the efficacy of these treatments is far from ideal, as they lack specificity and are associated with high toxicity. Previously, we demonstrated that N-acetyl cysteine (NAC) pretreatment up-regulates DUSP4 expression in endothelial cells, regulating p38 and ERK1/2 activities, and thus providing a protective effect against oxidative stress. Here, endothelial cells under hypoxia/reoxygenation (H/R) insult and isolated heart I/R injury were used to investigate the role of DUSP4 in the modulation of the p38 pathway. In rat endothelial cells, DUSP4 is time-dependently degraded by H/R (0.25 ± 0.07-fold change of control after 2h H/R). Its degradation is closely associated with hyperphosphorylation of p38 (2.1 ± 0.36-fold change) and cell apoptosis, as indicated by the increase in cells immunopositive for cleaved caspase-3 (12.59 ± 3.38%) or TUNEL labeling (29.46 ± 3.75%). The inhibition of p38 kinase activity with 20 µM SB203580 during H/R prevents H/R-induced apoptosis, assessed via TUNEL (12.99 ± 1.89%). Conversely, DUSP4 gene silencing in endothelial cells augments their sensitivity to H/R-induced apoptosis (45.81 ± 5.23%). This sensitivity is diminished via the inhibition of p38 activity (total apoptotic cells drop to 17.47 ± 1.45%). Interestingly, DUSP4 gene silencing contributes to the increase in superoxide generation from cells. Isolated Langendorff-perfused mouse hearts were subjected to global I/R injury. DUSP4(-/-) hearts had significantly larger infarct size than WT. The increase in I/R-induced infarct in DUSP4(-/-) mice significantly correlates with reduced functional recovery (assessed by RPP%, LVDP%, HR%, and dP/dtmax) as well as lower CF% and a higher initial LVEDP. From immunoblotting analysis, it is evident that p38 is significantly overactivated in DUSP4(-/-) mice after I/R injury. The activation of cleaved caspase-3 is seen in both WT and DUSP4(-/-) I/R hearts. Infusion of a p38 inhibitor prior to ischemia and during the reperfusion improves both WT and DUSP4(-/-) cardiac function. Therefore, the identification of p38 kinase modulation by DUSP4 provides a novel therapeutic target for oxidant-induced diseases, especially myocardial infarction.

The tyrosine kinase inhibitor imatinib prevents lung injury and death after intravenous LPS in mice

Severe sepsis and septic shock are frequent causes of the acute respiratory distress syndrome, and important sources of human mortality. Lipopolysaccharide (LPS), a component of Gram-negative bacterial cell walls, plays a major role in the pathogenesis of severe sepsis and septic shock. LPS exposure induces the production of harmful reactive oxygen species, and the resultant oxidant injury has been implicated in the pathogenesis of both severe sepsis and ARDS. We previously showed that the tyrosine kinase inhibitor imatinib increases lung endothelial antioxidant enzymes and protects against pulmonary endothelial antioxidant injury. In the present study, we tested the hypothesis that imatinib would protect against lung injury and systemic inflammation caused by intravenous LPS in an intact mouse model of endotoxemia mimicking early sepsis. We found that intravenous LPS induced a significant increase in the activity of lung xanthine oxidoreductase (XOR), an enzyme which is a major source of reactive oxygen species and implicated in the pathogenesis of acute lung injury. Imatinib had no effect of LPS-induced XOR activity. However, pretreatment of mice with imatinib increased lung catalase activity and decreased intravenous LPS-induced lung oxidant injury as measured by γ-H2AX, a marker of oxidant-induced DNA damage, lung apoptosis, and pulmonary edema. Imatinib also attenuated systemic cytokine expression after intravenous LPS exposure. Finally, imatinib completely prevented mortality in an in vivo, intravenous LPS mouse model of endotoxemia and lung injury. These results support the testing of imatinib as a novel pharmacologic agent in the treatment of Gram-negative sepsis and sepsis-induced ARDS.

Molecular mechanisms in lipopolysaccharide-induced pulmonary endothelial barrier dysfunction

The confluent pulmonary endothelium plays an important role as a semi-permeable barrier between the vascular space of blood vessels and the underlying tissues, and it contributes to the maintenance of circulatory fluid homeostasis. Pulmonary endothelial barrier dysfunction is a pivotal early step in the development of a variety of high mortality diseases, such as acute lung injury (ALI). Endothelium barrier dysfunction in response to inflammatory or infectious mediators, including lipopolysaccharide (LPS), is accompanied by invertible cell deformation and interendothelial gap formation. However, specific pharmacological therapies aiming at ameliorating pulmonary endothelial barrier function in patients are still lacking. A full understanding of the fundamental mechanisms that are involved in the regulation of pulmonary endothelial permeability is essential for the development of barrier protective therapeutic strategies. Therefore, this review summarizes several important molecular mechanisms involved in LPS-induced changes in pulmonary endothelial barrier function. As for barrier-disruption, the activation of myosin light chain kinase (MLCK), RhoA and tyrosine kinases; increase of calcium influx; and apoptosis of the endothelium lead to an elevation of lung endothelial permeability. Additionally, the activation of Rac1, Cdc42, protease activated receptor 1 (PAR1) and adenosine receptors (ARs), as well as the increase of cyclic AMP and sphingosine-1-phosphate (S1P) content, protect against LPS-induced lung endothelial barrier dysfunction. Furthermore, current regulatory factors and strategies against the development of LPS-induced lung endothelial hyper-permeability are discussed.

Glycyrrhizic Acid Prevents Sepsis-Induced Acute Lung Injury and Mortality in Rats

Glycyrrhizic acid (GA), an active ingredient in licorice, has multiple pharmacological activities. However, the effects of GA on sepsis-induced acute lung injury (ALI) have not been determined. Tthe aim of this study was to investigate the molecular mechanism involved in the effects of GA against sepsis-induced ALI in rats. We found that GA alleviated sepsis-induced ALI through improvements in various pathological changes, as well as decreases in the lung wet/dry weight ratio and total protein content in bronchoalveolar lavage fluid, and a significant increase in the survival rate of treated rats. Additionally, GA markedly inhibited sepsis-induced pulmonary inflammatory responses. Moreover, we found that treatment with GA inhibited oxidative stress damage and apoptosis in lung tissue induced by ALI. Finally, GA treatment significantly inhibited NF-κ B, JNK and P38 MAPK activation. Our data indicate that GA has a protective effect against sepsis-induced ALI by inhibiting the inflammatory response, damage from oxidative stress, and apoptosis via inactivation of NF-κB and MAPK signaling pathways, providing a molecular basis for a new medical treatment for sepsis-induced ALI.