Reactive oxygen species (ROS) are products of normal cellular metabolism and are known to act as second messengers. Under physiological conditions, ROS participate in maintenance of cellular 'redox homeostasis' in order to protect cells against oxidative stress through various redox-regulatory mechanisms. Overproduction of ROS, most frequently due to excessive stimulation of either reduced nicotinamide adenine dinucleotide phosphate by cytokines or the mitochondrial electron transport chain and xanthine oxidase, results in oxidative stress. Oxidative stress is a deleterious process that leads to lung damage and consequently to various disease states. Knowledge of the mechanisms of ROS regulation could lead to the pharmacological manipulation of antioxidants in lung inflammation and injury.

Heme oxygenases (HOs) are the rate-limiting enzymes in the catabolism of heme into biliverdin, free iron, and carbon monoxide. Two genetically distinct isoforms of HO have been characterized: an inducible form, HO-1, and a constitutively expressed form, HO-2. HO-1 is a kind of stress protein, and thus regarded as a sensitive and reliable indicator of cellular oxidative stress. The HO system acts as potent antioxidants, protects endothelial cells from apoptosis, is involved in regulating vascular tone, attenuates inflammatory response in the vessel wall, and participates in angiogenesis and vasculogenesis. Endothelial integrity and activity are thought to occupy the central position in the pathogenesis of cardiovascular diseases. Cardiovascular disease risk conditions converge in the contribution to oxidative stress. The oxidative stress leads to endothelial and vascular smooth muscle cell dysfunction with increases in vessel tone, cell growth, and gene expression that create a pro-thrombotic= pro-inflammatory environment. Subsequent formation, progression, and obstruction of atherosclerotic plaque may result in myocardial infarction, stroke, and cardiovascular death. This background provides the rationale for exploring the potential therapeutic role for HO system in the amelioration of vascular inflammation and prevention of adverse cardiovascular outcomes. Antioxid. Redox Signal. 14, 137-167.

Lipopolysaccharide (LPS) is involved in a variety of inflammatory disorders. Under stress conditions, endoplasmic reticulum (ER) loses the homeostasis in its functions, which is defined as ER stress. Little is known how ER stress is implicated in LPS-induced lung inflammation. In this study, effects of inhibition of ER stress on LPS-induced lung inflammation and transcriptional regulation were examined. An ER stress regulator, 4-phenylbutyrate (PBA) reduced LPS-induced increases of various ER stress markers in the lung. Furthermore, inhibition of ER stress reduced the LPS-induced lung inflammation. Moreover, LPS-induced increases of NF-κB and HIF-1α activity were lowered by inhibition of ER stress. These results suggest that inhibition of ER stress ameliorates LPS-induced lung inflammation through modulation of NF-κB/IκB and HIF-1α signaling pathway.

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BackgroundPulmonary actinomycosis is a chronic pulmonary infection caused by Actinomyces. Both improving oral hygiene and early application of antibiotics to the case of suspicious pulmonary infections result in changes in incidences and presentations of pulmonary actinomycosis. However, there are little reports dealt with the recent clinical characteristics of pulmonary actinomycosis. This study aimed to review the characteristics of pulmonary actinomycosis occurred during the first decade of 21st century.MethodsThis retrospective study was performed on 94 subjects with pulmonary actinomycosis diagnosed pathologically from January 2000 to December 2010 in 13 hospitals in Korea.ResultsThe data of the study showed that pulmonary actinomycosis occurs frequently in middle to old-aged males (mean age; 57.7 years old) and that the most common symptoms are cough, hemoptysis, and sputum production. Various radiologic features such as the consolidation with central low attenuation (74.5%) and no regional predominance were also observed. Most of patients recovered completely with medical and/or surgical treatment, reaching approximately 98% cure rate.ConclusionsThe results demonstrate that pulmonary actinomycosis is one of the cautious pulmonary diseases. More importantly, in cases of persistent hemoptysis or for differential diagnosis from lung malignancy, our data have revealed that surgical resection appears to be a useful intervention and that radiologic diagnosis may not provide decisive information. These findings indicate that it is important for the clinicians to include pulmonary actinomycosis as one of differential diagnoses for refractory pulmonary abnormal lesions to the current usual management.

BackgroundSensitisation with Aspergillus fumigatus (Af) is known to be associated with severe allergic lung inflammation, but the mechanism remains to be clarified. Phosphoinositide 3-kinase (PI3K)-δ and endoplasmic reticulum (ER) stress are suggested to be involved in steroid-resistant lung inflammation. We aimed to elucidate the role of PI3K-δ and its relationship with ER stress in fungus-induced allergic lung inflammation.MethodsUsing Af-exposed in vivo and in vitro experimental systems, we examined whether PI3K-δ regulates ER stress, thereby contributing to steroid resistance in fungus-induced allergic lung inflammation. Moreover, we checked expression of an ER stress marker in lung tissues isolated from patients with allergic bronchopulmonary aspergillosis.ResultsAf-exposed mice showed that ER stress markers, unfolded protein response (UPR)-related proteins, phosphorylated Akt, generation of mitochondrial reactive oxygen species (mtROS), eosinophilic allergic inflammation, and airway hyperresponsiveness (AHR) were increased in the lung. Similarly, glucose-regulated protein 78 was increased in lung tissues of patients with ABPA. A PI3K-δ inhibitor reduced Af-induced increases in ER stress markers, UPR-related proteins, allergic inflammation and AHR in mice. However, dexamethasone failed to reduce Af-induced allergic inflammation, AHR and elevation of ER stress. Administration of an ER stress inhibitor or a mtROS scavenger improved Af-induced allergic inflammation. The PI3K-δ inhibitor reduced Af-induced mtROS generation and the mtROS scavenger ameliorated ER stress. In primary cultured tracheal epithelial cells, Af-induced ER stress was inhibited by blockade of PI3K-δ.ConclusionsThese findings suggest that PI3K-δ regulates Af-induced steroid-resistant eosinophilic allergic lung inflammation through ER stress.

IntroductionSynovial fibroblasts from rheumatoid arthritis show resistance to apoptotic stimuli, indicating they may be difficult to treat. To clearly understand these mechanisms of resistance, rheumatoid and osteoarthritis synovial fibroblasts (RASF and OASF) were exposed to endoplasmic reticulum (ER) stress such as thapsigargin, Ca2+-ATPase inhibitor.MethodsFibroblasts were assessed microscopically for cell viability by trypan blue exclusion and for autophagic cells by LC-3II formation. Caspase-3 activity was measured as aminomethyl-coumarin (AMC) liberated from AC-DEVD-AMC. Immunoblotting was performed to compare protein expression in OASF and RASF.ResultsER stress caused cell death in OASF but not in RASF. Thapsigargin, a Ca2+-ATPase inhibitor, did not change the expression of GRP78, an ER chaperone in OASF and RASF, but induced another ER stress protein, CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP) differently, showing high levels in OASF and low levels in RASF. Thapsigargin increased the autophagy response in RASF, with autophagosome formation, beclin expression, and LC3-II conversion. Transfection with beclin siRNA inhibited autophagy and increased the susceptibility to ER stress-induced cell death. On the other hand, CHOP siRNA increased autophagy and improved cell survival, especially in RASF, indicating that CHOP is involved in regulation of autophagy and cell death, but that low expression of CHOP protects RASF from apoptosis.ConclusionsAutophagy induction and CHOP under-expression increases cell resistance against ER stress-induced cell death in fibroblasts from rheumatoid arthritis patients.

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