Lipoteichoic acid induces surfactant protein-A biosynthesis in human alveolar type II epithelial cells through activating the MEK1/2-ERK1/2-NF-κB pathway.

BACKGROUND: Lipoteichoic acid (LTA), a gram-positive bacterial outer membrane component, can cause septic shock. Our previous studies showed that the gram-negative endotoxin, lipopolysaccharide (LPS), could induce surfactant protein-A (SP-A) production in human alveolar epithelial (A549) cells. OBJECTIVES: In this study, we further evaluated the effect of LTA on SP-A biosynthesis and its possible signal-transducing mechanisms. METHODS: A549 cells were exposed to LTA. Levels of SP-A, nuclear factor (NF)-κB, extracellular signal-regulated kinase 1/2 (ERK1/2), and mitogen-activated/extracellular signal-regulated kinase kinase (MEK)1 were determined. RESULTS: Exposure of A549 cells to 10, 30, and 50 µg/ml LTA for 24 h did not affect cell viability. Meanwhile, when exposed to 30 µg/ml LTA for 1, 6, and 24 h, the biosynthesis of SP-A mRNA and protein in A549 cells significantly increased. As to the mechanism, LTA enhanced cytosolic and nuclear NF-κB levels in time-dependent manners. Pretreatment with BAY 11-7082, an inhibitor of NF-κB activation, significantly inhibited LTA-induced SP-A mRNA expression. Sequentially, LTA time-dependently augmented phosphorylation of ERK1/2. In addition, levels of phosphorylated MEK1 were augmented following treatment with LTA. CONCLUSIONS: Therefore, this study showed that LTA can increase SP-A synthesis in human alveolar type II epithelial cells through sequentially activating the MEK1-ERK1/2-NF-κB-dependent pathway.

Lipopolysaccharide induces apoptotic insults to human alveolar epithelial A549 cells through reactive oxygen species-mediated activation of an intrinsic mitochondrion-dependent pathway.

Alveolar type II epithelial cells can regulate immune responses to sepsis-induced acute lung injury. Lipopolysaccharide (LPS), an outer membrane component of Gram-negative bacteria, can cause septic shock. This study was designed to evaluate the cytotoxic effects of LPS on human alveolar epithelial A549 cells and its possible molecular mechanisms. Exposure of A549 cells to LPS decreased cell viability in concentration- and time-dependent manners. In parallel, LPS concentration- and time-dependently induced apoptosis of A549 cells. Meanwhile, LPS only at a high concentration of 10 µg/ml caused mildly necrotic insults to A549 cells. In terms of the mechanism, exposure of A549 cells to LPS increased the levels of cellular nitric oxide and reactive oxygen species (ROS). Pretreatment with N-acetylcysteine (NAC), an antioxidant, significantly lowered LPS-caused enhancement of intracellular ROS in A549 cells and simultaneously attenuated the apoptotic insults. Sequentially, treatment of A549 cells with LPS caused significant decreases in the mitochondrial membrane potential and biosynthesis of adenosine triphosphate. In succession, LPS triggered the release of cytochrome c from the mitochondria to the cytoplasm. Activities of caspase-9 and caspase-6 were subsequently augmented following LPS administration. Consequently, exposure of A549 cells induced DNA fragmentation in a time-dependent manner. Pretreatment of A549 cells with NAC significantly ameliorated LPS-caused alterations in caspase-9 activation and DNA damage. Therefore, this study shows that LPS specifically induces apoptotic insults to human alveolar epithelial cells through ROS-mediated activation of the intrinsic mitochondrion-cytochrome c-caspase protease mechanism.

Liver nitrosation and inflammation in septic rats were suppressed by propofol via downregulating TLR4/NF-κB-mediated iNOS and IL-6 gene expressions.

AIMS: Propofol can be applied as an anesthetic or sedative agent for septic patients. Our previous studies showed that propofol ameliorated inflammation- and nitrosative stress-induced cellular insults. This study further evaluated effects of propofol on cecal ligation and puncture (CLP)-induced septic insults to rats and its possible mechanisms. MAIN METHODS: Wistar rats were administered with CLP and effects of propofol on CLP-induced liver dysfunction and rat death were evaluated. Levels of hepatic or systemic nitrogen oxides (NOx) and interleukin (IL)-6 were quantified. Sequentially, inducible nitric oxide synthase (iNOS) and IL-6 gene expressions, toll-like receptor 4 (TLR4) protein levels, and nuclear factor (NF)-κB translocation were determined. KEY FINDINGS: Subjecting rats to CLP led to body weight loss, liver weight gain, and death. Administration of propofol lessened CLP-induced augmentations of serum and hepatic nitrosative stress and IL-6 levels. Additionally, propofol suppressed CLP-induced enhancements in levels of hepatic iNOS protein. Furthermore, the CLP-induced iNOS and IL-6 mRNA expressions in the liver were inhibited following propofol administration. Sequentially, subjecting rats to CLP enhanced hepatic TLR4 protein levels and NF-κB translocation to nuclei, but propofol inhibited these augmentations. SIGNIFICANCE: Consequently, exposure to propofol protected against CLP-induced liver dysfunction and increased the survival rates of the animals. This study shows that propofol can protect rats against septic insults through suppression of systemic and hepatic nitrosative and inflammatory stress due to inhibition of TLR4/NF-κB-mediated iNOS and IL-6 mRNA and protein expressions.

Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitor Treatment Response in Advanced Lung Adenocarcinomas with G719X/L861Q/S768I Mutations.

BACKGROUND: Epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) is the standard therapy for advanced lung adenocarcinomas with common EGFR mutations. Preclinical studies have suggested that uncommon G719X, L861Q, and S768I mutations are also sensitive to EGFR-TKIs. However, the efficacy of EGFR-TKIs in patients with these uncommon mutations remains unclear. METHODS: A nationwide survey was performed to collect data from gefitinib and erlotinib treatment outcomes of patients with stage IIIB/IV lung adenocarcinoma bearing EGFR G719X/L861Q/S768I mutations. The results were compared with those regarding patients with exon 19 deletions or L858R mutations. RESULTS: One hundred and sixty-one patients with uncommon EGFR mutations were enrolled from 18 institutes throughout Taiwan. Mutations of G719X, L861Q, S768I, G719X + L861Q, and G719X + S768I were observed in 78, 57, 7, 9, and 10 patients, respectively. After receiving EGFR-TKI treatment, patients with uncommon mutations exhibited a significantly inferior tumor response rate (41.6% vs. 66.5%; p < 0.001) and progression-free survival (median, 7.7 vs. 11.4 months; p < 0.001) than patients with common mutations. Among the patients who used EGFR-TKIs as first-line treatment, there was a significant difference in overall survival between these two groups of patients (median, 24.0 vs. 29.7 months; p = 0.005). CONCLUSION: Gefitinib and erlotinib are active in patients with G719X/L861Q/S768I mutations; however, less effective than in those with common mutations.

Toll-like receptor 2-mediated sequential activation of MyD88 and MAPKs contributes to lipopolysaccharide-induced sp-a gene expression in human alveolar epithelial cells.

Surfactant proteins (SPs) produced by pulmonary epithelial cells participate in the regulation of sepsis-induced acute lung injury. Our previous study has shown that lipopolysaccharide (LPS), a Gram-negative bacterial outer membrane component, can regulate sp-a gene expression in human lung carcinoma type II epithelial A549 cells. This study was further designed to evaluate the signal-transducing mechanisms of LPS-induced sp-a gene expression. Exposure of A549 cells to LPS induced SP-A mRNA and protein production in time-dependent manners. Application of toll-like receptor 2 (TLR2) siRNA into A549 cells decreased the levels of this receptor and simultaneously inhibited LPS-induced SP-A mRNA expression. Sequentially, LPS enhanced phosphorylation of mitogen-activated protein kinase (MEK) 4 and c-Jun NH(2) terminal kinase 1 (JNK1) in time-dependent manners. Application of TLR2 siRNA decreased LPS-enhanced phosphorylation of MEK4 and JNK1. After knocking-down the translation of MyD88 by RNA interference, the LPS-triggered MEK4 phosphorylation was attenuated. Consequently, LPS augmented the translocation of c-Jun from the cytoplasm to nuclei without affecting c-Fos. Pretreatment of A549 cells with SP600125, an inhibitor of JNK1, significantly lowered LPS-induced SP-A mRNA production. Analyses of an electrophoretic mobility shift assay and a reporter gene further showed that LPS increased the transactivation activity of AP-1 in A549 cells. Therefore, the present study demonstrates that LPS can induce sp-a gene expression in human type II epithelial A549 cells through TLR2-mediated sequential activation of MyD88-MEK4-JNK1-AP-1.

Molecular mechanisms of lipopolysaccharide-caused induction of surfactant protein-A gene expression in human alveolar epithelial A549 cells.

Surfactant proteins (SPs) participate in the physiological and pathophysiological regulation of sepsis-induced acute lung injury. Lipopolysaccharide (LPS), a gram-negative bacterial outer membrane component, is one of the major causes of septic shock. This study was designed to evaluate the effects of LPS on the regulation of SP-A and SP-D gene expressions in human alveolar epithelial A549 cells. Exposure of A549 cells to LPS increased SP-A mRNA synthesis in concentration and time-dependent manners without affecting SP-D mRNA production. LPS selectively enhanced translocation of transcription factor c-Jun from the cytoplasm to nuclei, but not nuclear factor kappa-B. In parallel, the DNA-binding activity of AP-1 was increased by LPS. Pretreatment of A549 cells with SP600125, an inhibitor of c-Jun N-terminal kinase, decreased c-Jun translocation, and significantly ameliorated LPS-induced SP-A mRNA production. Levels of toll-like receptor (TLR2) mRNA in A549 cells were time-dependently induced following LPS treatment. Application of TLR2 small interference (si)RNA into A549 cells significantly knocked-down the translation of this receptor, and simultaneously alleviated LPS-induced SP-A synthesis. Taken together, this study has shown that LPS selectively induces SP-A gene expression possibly through TLR2-mediated activation of c-Jun in human alveolar epithelial A549 cells.