Immunomodulatory Effect of Linezolid on Methicillin-Resistant Staphylococcus aureus Supernatant-Induced MUC5AC Overexpression in Human Airway Epithelial Cells

Linezolid is the first member of the oxazolidinones and is active against drug-resistant Gram-positive pathogens, such as methi-cillin- resistant Staphylococcus aureus (MRSA). Additionally, linezolid shows an immunomodulatory effect, such as inhibition of inflammatory cytokine production. In this study, we examined the effect of linezolid on MRSA-induced MUC5AC overexpression in airway epithelial cells. In this study, an MRSA supernatant was used to avoid the direct effect of linezolid on MRSA. MUC5AC protein production was significantly increased with a 40-fold dilution of MRSA supernatant. At the mRNA level, MUC5AC gene expression was significantly increased 6 and 9 h after stimulation. In an inhibition study, linezolid significantly reduced MRSA-induced MUC5AC protein and mRNA overexpression at concentrations of 5 and 20 μg/ml, which were the same as the trough and peak concentrations in human epithelial lining fluid. In an analysis of cell signaling, among the mitogen-activated protein kinase inhibitors, only the extracellular signal-regulated protein kinase 1/2 (ERK1/2) inhibitor reduced the MUC5AC protein production to the same level as that of the control; on Western blot analysis, only ERK1/2 was phosphorylated by the MRSA supernatant. In addition, the ERK1/2 phosphorylation was inhibited by linezolid. MUC5AC and MUC5B are the major barrier that traps inhaled microbial organisms, particulates, and foreign irritants. However, in patients with chronic respiratory diseases, pathogen-induced MUC5AC overexpression causes many problems, and control of the overexpression is important. Thus, this study revealed that linezolid showed a direct immunomodulatory effect in airway epithelial cells

Efficacy of AiiM, an N-Acylhomoserine Lactonase, against Pseudomonas aeruginosa in a Mouse Model of Acute Pneumonia

Quorum sensing (QS) in Pseudomonas aeruginosa regulates the production of many virulence factors and plays an important role in the pathogenesis of P. aeruginosa infection. N-acyl homoserine lactones (AHL) are major QS signal molecules. Recently, a novel AHL-lactonase enzyme, AiiM, has been identified. The aim of this study was to evaluate the effect of AiiM on the virulence of P. aeruginosa in a mouse model of acute pneumonia. We developed a P. aeruginosa PAO1 strain harboring an AiiM-expressing plasmid. The production of several virulence factors by the AiiM-expressing strain was examined. Mice were intratracheally infected with an AiiM-expressing PAO1 strain. Lung histopathology, bacterial burden, and bronchoalveolar lavage (BAL) fluid were assessed at 24 h postinfection. AiiM expression in PAO1 reduced production of AHL-mediated virulence factors and attenuated cytotoxicity against human lung epithelial cells. In a mouse model of acute pneumonia, AiiM expression reduced lung injury and greatly improved the survival rates. The levels of proinflammatory cytokines and myeloperoxidase activity in BAL fluid were significantly lower in mice infected with AiiM-expressing PAO1. Thus, AiiM can strongly attenuate P. aeruginosa virulence in a mammalian model and is a potential candidate for use as a therapeutic agent against P. aeruginosa infection

Influence of antimicrobial regimen on decreased in-hospital mortality of patients with MRSA bacteremia

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most important causes of bacteremia. Recently, several epidemiological and microbiological changes have become evident in MRSA infections. The purposes of this study were to assess clinical characteristics of patients with MRSA bacteremia and microbiological changes in MRSA. We conducted a retrospective observational study on patients with MRSA bacteremia who were hospitalized between 2008 and 2011. We used univariate and multivariate analysis to evaluate the predictors associated with 30-day mortality. The 7-day and 30-day mortality rates were 12.0% and 25.3%, respectively. According to multivariate analysis, the independent predictors that associated with 30-day mortality were leukopenia, low serum albumin, high sequential organ failure assessment (SOFA) score, and quinolone use within 30 days. Compared to previous data (2003-2007), the SOFA score of the new data set remained unchanged, but in-hospital mortality decreased significantly. In particular, the mortality associated with use of vancomycin (VCM) was significantly lower. Although the minimuminhibitory concentration of VCM required to inhibit the growth of 90% of organisms (MIC90) had not changed, the trough value of VCM changed significantly; a VCM trough value of 10 or greater was significantly higher compared to previous data. Of the staphylococcal cassette chromosome mec (SCCmec) types, SCCmec II values decreased significantly, and SCCmec I and IV values increased significantly. Our results indicate that changes in VCM usage might contribute to decreased in-hospital mortality

Quorum sensing ソガイ ブッシツ ニ ヨル リョクノウキン ノ ビョウゲンセイ セイギョ

熊本大

Quorum sensing ソガイ ブッシツ ニ ヨル リョクノウキン ノ ビョウゲンセイ セイギョ

博士（医学）熊本大

ハイキシュ マウス モデル ニ オケル ガレクチン-9 ノ ヨボウ コウカ : コウチュウキュウ ユウソウ ト MMP-9 エ ノ エイキョウ

熊本大

Data from: Protective effect of Galectin-9 in murine model of lung emphysema: involvement of neutrophil migration and MMP-9 production

Purpose: Chronic obstructive pulmonary disease (COPD) is characterized by irreversible airflow obstruction and pulmonary emphysema. Persistent inflammation and remodeling of the lungs and airways result in reduced lung function and a lower quality of life. Galectin (Gal)-9 plays a crucial role as an immune modulator in various diseases. However, its role in the pathogenesis of pulmonary emphysema is unknown. This study investigates whether Gal-9 is involved in pulmonary inflammation and changes in emphysema in a porcine pancreatic elastase (PPE)-induced emphysema model. Materials and Methods: Gal-9 was administered to mice subcutaneously once daily from 1 day before PPE instillation to day 5. During the development of emphysema, lung tissue and bronchoalveolar lavage fluid (BALF) were collected. Histological and cytological findings, concentrations of chemokines and matrix metalloproteinases (MMPs) in the BALF, and the influence of Gal-9 treatment on neutrophils were analyzed. Results: Gal-9 suppressed the pathological changes of PPE-induced emphysema. The mean linear intercept (Lm) of Gal-9-treated emphysema mice was significantly lower than that of PBS-treated emphysema mice (66.1 ± 3.3 µm vs. 118.8 ± 14.8 µm, respectively; p < 0.01). Gal-9 decreased the number of neutrophils and levels of MMP-9, MMP-2 and tissue inhibitor of metalloproteinases (TIMP)-1 in the BALF. The number of neutrophils in the BALF correlated significantly with MMPs levels. Interestingly, Gal-9 pretreatment in vitro inhibited the chemotactic activity of neutrophils and MMP-9 production from neutrophils. Furthermore, in Gal-9-deficient mice, PPE-induced emphysema progressed significantly compared with that in wild–type (WT) mice (108.7 ± 6.58 µm vs. 77.19 ± 6.97 µm, respectively; p < 0.01). Conclusions: These results suggest that Gal-9 protects PPE-induced inflammation and emphysema by inhibiting the infiltration of neutrophils and decreasing MMPs levels. Exogenous Gal-9 could be a potential therapeutic agent for COPD

Macrolides Inhibit Fusobacterium nucleatum-Induced MUC5AC Production in Human Airway Epithelial Cells

Fusobacterium nucleatum is one of the most common anaerobic bacteria in periodontitis and is responsible for several extraoral infections, including respiratory tract diseases. In this study, we examined whether F. nucleatum induces mucin secretion in airway epithelial cells. We also examined the effects of macrolides on F. nucleatum-induced mucus production compared with the effects of other antibiotics that exert anti-anaerobic activities. The production of MUC5AC, the major core protein of mucin secreted from the airway surface epithelium, in bronchial epithelial cells after stimulation with culture supernatants (Sup) of F. nucleatum was analyzed by performing enzyme-linked immunosorbent assay and quantitative RT-PCR. The cell-signaling pathway of F. nucleatum Sup stimulation was also analyzed by Western blotting. For inhibition studies, cells were treated with azithromycin, clarithromycin, clindamycin (CLDM), and metronidazole (MTZ). The F. nucleatum Sup induced NCI-H292 cells to express MUC5AC at both the protein level and the mRNA level in both a time- and dose-dependent manner. Macrolides inhibited F. nucleatum Sup-induced MUC5AC production, while CLDM and MTZ were less effective. F. nucleatum Sup induced the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), and this induction was suppressed by macrolides. F. nucleatum Sup-induced MUC5AC production was blocked by the ERK pathway inhibitor U0126. F. nucleatum is likely to contribute to excessive mucin production, which suggests that periodontitis may correlate with the pathogenesis of chronic respiratory tract infection. Macrolides seem to reduce this mucin production and might represent an additional means of therapeutic intervention for F. nucleatum respiratory tract infections other than CLDM and MTZ