Dong Im Kim

Endoplasmic reticulum stress influences bronchial asthma pathogenesis by modulating nuclear factor κB activation

BACKGROUND Despite many studies on endoplasmic reticulum (ER) stress in patients with various inflammatory diseases, there is scarce information on ER stress in patients with bronchial asthma. OBJECTIVE In this study we aimed to elucidate the role of ER stress in the pathogenesis of bronchial asthma. METHODS Using mice sensitized with ovalbumin (OVA) and LPS and challenged with OVA (OVA(LPS)-OVA mice), as well as mice sensitized and challenged with OVA (OVA-OVA mice), we investigated whether ER stress is involved in the pathogenesis of bronchial asthma. Moreover, we also determined the levels of ER stress markers in blood and bronchoalveolar lavage fluid from asthmatic patients. RESULTS The OVA(LPS)-OVA mice showed that the expression of ER stress markers and the protein levels of unfolded protein response-related markers in lung tissue were significantly increased after OVA challenge. Moreover, we found that ER stress markers in PBMCs and bronchoalveolar lavage fluid from human asthmatic patients were dramatically increased compared with those from healthy control subjects. In OVA(LPS)-OVA mice 4-phenylbutyric acid (4-PBA), a chemical chaperone, significantly reduced the increases in ER stress, nuclear translocation of nuclear factor κB, inflammatory cytokine levels, dendritic cell infiltration, Toll-like receptor 4 expression, airway inflammation, and bronchial hyperresponsiveness, whereas it further enhanced the increase in IL-10 levels. Additionally, the established asthmatic features of OVA-OVA mice were substantially attenuated by 4-PBA administered after completion of OVA challenge. CONCLUSION These results indicate that ER stress might be implicated in the pathogenesis of bronchial asthma at least in part through modulation of nuclear factor κB activation.

PI3K-γ Inhibition Ameliorates Acute Lung Injury Through Regulation of IκBα/NF-κB Pathway and Innate Immune Responses

BackgroundAcute lung injury (ALI) is a devastating disorder of the lung by various causes and its cardinal features are tissue inflammation, pulmonary edema, low lung compliance, and widespread capillary leakage. Among phosphoinositide 3-kinases (PI3Ks), PI3K-γ isoform has been shown to play an important role in a number of immune/inflammatory responses.MethodsWe investigated the role of PI3K-γ and its molecular basis in lipopolysaccharide (LPS)-induced ALI using a selective inhibitor for PI3K-γ, AS 605240, and LPS-treated C57BL/6 mice.ResultsTreatment of mice with LPS showed an increase of lung inflammation and vascular leakage. Production of reactive oxygen species (ROS), interleukin (IL)-1β, tumor necrosis factor-α, and IL-4, adhesion molecule, and vascular endothelial growth factor (VEGF) was also increased. Administration of AS 605240 to LPS-treated mice markedly reduced the pathophysiological features of ALI and the increased production of ROS, cytokines, adhesion molecule, and VEGF in the lung. Our results also showed that treatment of mice with LPS activates nuclear factor-κB (NF-κB) and degradation of inhibitory κBα (IκBα) through PI3K-γ. Additionally, infiltration of dendritic cells (DCs) and expression of toll-like receptor 4 (TLR4) were significantly increased in the lung of LPS-treated mice, and inhibition of PI3K-γ reduced the infiltration of DCs and TLR4 expression in the lung.ConclusionsThese results indicate that PI3K-γ is critically involved in LPS-induced ALI by regulating IκBα/NF-κB pathway and innate immune responses. Based on our data, we suggest that PI3K-γ isoform is a promising target for the treatment of ALI.

Blockade of Interplay between IL-17A and Endoplasmic Reticulum Stress Attenuates LPS-Induced Lung Injury.

IL-17 is a cytokine mainly from IL-17-producing T cells, which are one of subsets of CD4+ T cells and play a role in adaptive immune system. Recent studies have demonstrated that IL-17A can act rapidly as an innate immune responder during infection before the onset of its classic adaptive immune response. This role of IL-17A in innate immune response is implicated in lipopolysaccharide (LPS)-induced lung inflammation. Very recently, we have reported that endoplasmic reticulum (ER) stress is involved in LPS-induced lung inflammation in vivo and in vitro. This study aimed to elucidate the role of IL-17A in LPS-induced lung injury, focusing on the link with ER stress. We treated a murine model of LPS-induced lung injury with IL-17A neutralizing antibody and 4-phenylbutyrate (4-PBA), a representative ER stress inhibitor. In addition, we evaluated the effects of IL-17A on ER stress in LPS-stimulated bronchial epithelial cells. Our results showed that inhibition of IL-17A decreased LPS-induced pulmonary neutrophilia, vascular leakage, nuclear translocation of nuclear factor-κB (NF-κB), infiltration of dendritic cells, increased expression of Toll-like receptor 4 (TLR4), activation of NLRP3 inflammasome, and increased ER stress in the lung. 4-PBA or TAK-242, a TLR4 inhibitor attenuated expression of IL-17A thereby improving LPS-induced lung inflammation. Intriguingly, we observed that stimulation with LPS increased expression of IL-17A in airway epithelial cells and co-stimulation with IL-17A further increased ER stress and NF-κB activation. This study indicates that the interrelationship between IL-17A and ER stress plays an important role in LPS-induced injury showing a positive feedback in airway epithelial cells and suggests that targeting their interaction can be a potential therapeutic approach to overcome one of severe refractory pulmonary disorders.

AMPK activation reduces vascular permeability and airway inflammation by regulating HIF/VEGFA pathway in a murine model of toluene diisocyanate-induced asthma

BackgroundOccupational asthma is characterized by airway inflammation and hyperresponsiveness associated with increased vascular permeability. AMP-activated protein kinase (AMPK) has been suggested to be a novel signaling molecule modulating inflammatory responses.ObjectiveWe sought to evaluate the involvement of AMPK in pathogenesis of occupational asthma and more specifically investigate the effect and molecular mechanisms of AMPK activation in regulating vascular permeability.MethodsThe mechanisms of action and therapeutic potential of an AMPK activator, 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR) were tested in a murine model of toluene diisocyanate (TDI)-induced asthma.ResultsAICAR attenuated airway inflammation and hyperresponsiveness increased by TDI inhalation. Moreover, TDI-induced increases in levels of hypoxia-inducible factor (HIF)-1α, HIF-2α, vascular endothelial growth factor A (VEGFA), and plasma exudation were substantially decreased by treatment with AICAR. Our results also showed that VEGFA expression was remarkably reduced by inhibition of HIF-1α and HIF-2α with 2-methoxyestradiol (2ME2) and that an inhibitor of VEGFA activity, CBO-P11 as well as 2ME2 significantly suppressed vascular permeability, airway infiltration of inflammatory cells, and airway hyperresponsiveness induced by TDI. In addition, AICAR reduced reactive oxygen species (ROS) generation and levels of malondialdehyde and T-helper type 2 cytokines (IL-4, IL-5, and IL-13), while this agent enhanced expression of an anti-inflammatory cytokine, IL-10.ConclusionsThese results suggest that AMPK activation ameliorates airway inflammatory responses by reducing vascular permeability via HIF/VEGFA pathway as well as by inhibiting ROS production and thus may be a possible therapeutic strategy for TDI-induced asthma and other airway inflammatory diseases.

PI3Kγ activation is required for LPS-induced reactive oxygen species generation in respiratory epithelial cells

ObjectiveIn this study, we investigated the molecular basis of reactive oxygen species (ROS) generation induced by lipopolysaccharide (LPS) in A549 cells—an alveolar epithelial cell line.Experimental designA549 cells or normal human bronchial epithelial (NHBE) cells were stimulated with LPS. ROS generation was measured in A549 cells or NHBE cells pre-treated with a selective inhibitor of phosphatidylinositol 3-kinase γ (PI3Kγ), AS 605240, PI3Kγ siRNA, or a ROS scavenger, pyridoxamine (PM).ResultsTreatment of A549 cells or NHBE cells with LPS caused a significant increase in intracellular ROS generation. Pretreatment with the PI3Kγ inhibitor, AS 605240 decreased the LPS-induced increase of ROS generation, phosphorylation of Akt, and production of phosphatidyl 3,4,5-trisphosphate in A549 cells. In addition, interference with siRNA for PI3Kγ significantly reduced LPS-induced ROS generation in A549 cells. Treatment of A549 cells with LPS or hydrogen peroxide increased the nuclear factor-κB (NF-κB) in the nucleus, accompanying an increase in phosphorylation of inhibitory κB-α, degradation of the protein, and reduction of cytosolic NF-κB. Pretreatment with AS 605240 reduced these LPS-induced changes. In addition, pretreatment with PM or N-acetyl cysteine resulted in inhibition of nuclear NF-κB activation.ConclusionThese results suggest that PI3Kγ plays a key role in LPS-induced ROS generation in alveolar epithelial cells, thereby activating NF-κB.

Airway epithelial phosphoinositide 3-kinase-δ contributes to the modulation of fungi-induced innate immune response

Background Respiratory fungal exposure is known to be associated with severe allergic lung inflammation. Airway epithelium is an essential controller of allergic inflammation. An innate immune recognition receptor, nucleotide-binding domain, leucine-rich-containing family, pyrin-domain-containing-3 (NLRP3) inflammasome, and phosphoinositide 3 kinase (PI3K)-δ in airway epithelium are involved in various inflammatory processes. Objectives We investigated the role of NLRP3 inflammasome in fungi-induced allergic lung inflammation and examined the regulatory mechanism of NLRP3 inflammasome, focusing on PI3K-δ in airway epithelium. Methods We used two in vivo models induced by exposure to Aspergillus fumigatus (Af) and Alternaria alternata (Aa), as well as an Af-exposed in vitro system. We also checked NLRP3 expression in lung tissues from patients with allergic bronchopulmonary aspergillosis (ABPA). Results Assembly/activation of NLRP3 inflammasome was increased in the lung of Af-exposed mice. Elevation of NLRP3 inflammasome assembly/activation was observed in Af-stimulated murine and human epithelial cells. Similarly, pulmonary expression of NLRP3 in patients with ABPA was increased. Importantly, neutralisation of NLRP3 inflammasome derived IL-1β alleviated pathophysiological features of Af-induced allergic inflammation. Furthermore, PI3K-δ blockade improved Af-induced allergic inflammation through modulation of NLRP3 inflammasome, especially in epithelial cells. This modulatory role of PI3K-δ was mediated through the regulation of mitochondrial reactive oxygen species (mtROS) generation. NLRP3 inflammasome was also implicated in Aa-induced eosinophilic allergic inflammation, which was improved by PI3K-δ blockade. Conclusion These findings demonstrate that fungi-induced assembly/activation of NLRP3 inflammasome in airway epithelium may be modulated by PI3K-δ, which is mediated partly through the regulation of mtROS generation. Inhibition of PI3K-δ may have potential for treating fungi-induced severe allergic lung inflammation.