Respiratory syncytial virus infection influences tight junction integrity.

Respiratory syncytial virus (RSV) is an important risk factor of asthma development and is responsible for severe respiratory tract infections. However, the influence of RSV infection on barrier function of bronchial epithelial cells in vitro and in vivo is still unclear. The aim of this study was to analyse the role of RSV in tight junction (TJ) regulation and to compare epithelial integrity between asthmatic and healthy individuals upon RSV infection. Healthy and asthmatic human bronchial epithelial cells (HBECs) were differentiated at air-liquid interface (ALI) and infected with RSV and ultraviolet (UV)-irradiated RSV. TJ expression and their integrity were analysed by quantitative polymerase chain reaction (qPCR), transepithelial resistance (TER) and paracellular flux. To determine the effect in vivo, BALB/c mice were infected intranasally with RSV or UV-irradiated RSV A2. Bronchoalveolar lavage and TJ integrity were analysed on days 1, 2, 4 and 6 post-infection by qPCR, bioplex and confocal microscopy. RSV increased barrier integrity in ALI cultures of HBEC from healthy subjects, but no effect was found in HBECs from asthmatics. This was not associated with an increase in TJ mRNA expression. In vivo, RSV induced lung inflammation in mice and down-regulated claudin-1 and occludin mRNA expression in whole lungs. Surprisingly, RSV infection was not observed in bronchial epithelial cells, but was found in the lung parenchyma. Decreased expression of occludin upon RSV infection was visible in mouse bronchial epithelial cells in confocal microscopy. However, there was no regulation of claudin-1 and claudin-7 at protein level.

Altered fatty acid metabolism and reduced stearoyl-coenzyme a desaturase activity in asthma.

BACKGROUND: Fatty acids and lipid mediator signaling play an important role in the pathogenesis of asthma, yet this area remains largely underexplored. The aims of this study were (i) to examine fatty acid levels and their metabolism in obese and nonobese asthma patients and (ii) to determine the functional effects of altered fatty acid metabolism in experimental models. METHODS: Medium- and long-chain fatty acid levels were quantified in serum from 161 human volunteers by LC/MS. Changes in stearoyl-coenzyme A desaturase (SCD) expression and activity were evaluated in the ovalbumin (OVA) and house dust mite (HDM) murine models. Primary human bronchial epithelial cells from asthma patients and controls were evaluated for SCD expression and activity. RESULTS: The serum desaturation index (an indirect measure of SCD) was significantly reduced in nonobese asthma patients and in the OVA murine model. SCD1 gene expression was significantly reduced within the lungs following OVA or HDM challenge. Inhibition of SCD in mice promoted airway hyper-responsiveness. SCD1 expression was suppressed in bronchial epithelial cells from asthma patients. IL-4 and IL-13 reduced epithelial cell SCD1 expression. Inhibition of SCD reduced surfactant protein C expression and suppressed rhinovirus-induced IP-10 secretion, which was associated with increased viral titers. CONCLUSIONS: This is the first study to demonstrate decreased fatty acid desaturase activity in humans with asthma. Experimental models in mice and human epithelial cells suggest that inhibition of desaturase activity leads to airway hyper-responsiveness and reduced antiviral defense. SCD may represent a new target for therapeutic intervention in asthma patients.

A novel, dual cytokine-secretion assay for the purification of human Th22 cells that do not co-produce IL-17A.

BACKGROUND: Interleukin-22 is produced by certain T helper cells subsets (Th17, Th22) and at lower levels by γ-δ T cells, NKT and innate lymphoid cells. Th22 cells are unique immune cells that regulate tissue responses by IL-22 production. The exact discrimination between Th17 cells that co-produce IL-22 and single IL-22-producing Th22 cells has not been possible until the present study. Isolation of pure Th22 cells without co-expression of cytokines of other T-cell subsets is essential to better understand their function in humans. The aim of this study is the isolation and characterization of viable, human IL-22-producing CD4+ T cells that do not produce IL-17A. METHODS: Isolation of viable Th22 cells was performed with the combination of two cytokine secretion assays detecting IL-17A- and IL-22-producing cells in a single purification step. RESULTS: The newly developed cytokine secretion assay consists of anti-IL-22 and anti-IL-17A catch antibodies, which via biotin-streptavidin interaction are bound to the biotinylated surface of the target cell, and anti-IL-22 and IL-17A detection antibody labelled with a fluorescent dye, which detects cytokines bound to these catch antibodies. A unique population of human Th22 cells, which do not produce IL-17A, was sorted, and cytokine expression pattern was confirmed by quantitative PCR analysis and ELISA. The presented technique allows the detection and isolation of pure human Th22 cells. CONCLUSIONS: This technique may allow the purification of any single cytokine-producing cell subset, and the combination of several different cytokine secretion assays can be used to purify and characterize novel and unique cell subsets.

Acetyl group orientation modulates the electronic ground-state asymmetry of the special pair in purple bacterial reaction centers.

Recent experimental data point to an asymmetric ground-state electronic distribution in the special pair (P) of purple bacterial reaction centers, which acts as the primary electron donor in photosynthesis. We have performed a density functional theory investigation on an extended model including the bacteriochlorophyll dimer and a few relevant surrounding residues to explore the origin of this asymmetry. We find strong evidence that the ground-state electron density in P is intrinsically asymmetric due to protein-induced distortions of the porphyrin rings, with excess electron charge on the P(M) bacteriochlorophyll cofactor. Moreover, the electron charge asymmetry is strongly modulated by the specific orientation of the C3(1) acetyl group, which is hydrogen bonded to His168. The electronic excitation has a significant charge transfer character inducing a displacement of electron charge from P(L) to P(M), in agreement with experimental data in the excited state. These results are relevant for the understanding of the unidirectional electron transfer path in photosynthesis.