Air pollution particles diminish bacterial clearance in the primed lungs of mice.

Epidemiological studies reveal increased incidence of lung infection when air pollution particle levels are increased. We postulate that one risk factor for bacterial pneumonia, prior viral infection, can prime the lung for greater deleterious effects of particles via the interferon-gamma (IFN-gamma) characteristic of successful host anti-viral responses. To test this postulate, we developed a mouse model in which mice were treated with gamma-interferon aerosol, followed by exposure to concentrated ambient particles (CAPs) collected from urban air.

H2O2-induced proliferation of primary alveolar epithelial cells is mediated by MAP kinases.

Exposure to supraphysiological oxygen concentrations during ventilatory oxygen therapy often causes tissue damage. Alveolar type II (AT II) cells are a major target for oxidant injury, and their ability to proliferate plays a critical role during the repair phase following injury. We hypothesized that reactive oxygen species (ROS), which are produced during hyperoxia, not only cause cellular damage, but may also play a role in the repair process by promoting AT II cell proliferation.

Mitogen-activated protein kinases modulate H(2)O(2)-induced apoptosis in primary rat alveolar epithelial cells.

Increasing evidence suggests a role for apoptosis in the maintenance of the alveolar epithelium under normal and pathological conditions. However, the signaling pathways modulating alveolar type II (ATII) cell apoptosis remain poorly defined. Here we investigated the role of MAPKs as modulators of oxidant-mediated ATII cell apoptosis using in vitro models of H(2)O(2)-stress.

Expression of the bacterial catalase genes during Sinorhizobium meliloti-Medicago sativa symbiosis and their crucial role during the infection process.

Sinorhizobium meliloti possesses three distinct catalases to cope with oxidative stress: two monofunctional catalases (KatA and KatC) and one bifunctional catalase-peroxydase (KatB). The katB gene is constitutively expressed during growth in batch culture and is not induced under oxidative stress conditions. In contrast, the expression of katA and katC genes is mainly regulated at the transcription level in these conditions.