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Respiratory syncytial virus (RSV), rhinovirus, and parainfluenza virus type 3 often are associated with exacerbations of asthma and airways hyperreactivity.[1,2] Their effects are thought to be mediated by direct airway [...]

The mitogen-activated protein kinase (MAPK) signalling pathway serves to translocate information from activated plasma-membrane receptors to initiate nuclear transcriptional events. This cascade has recently been subdivided into two analogous pathways: the extracellular signal-regulated kinase (ERK) cascade, which preferentially signals mitogenesis, and the stress-activated protein kinase (SAPK) cascade, which is linked to growth arrest and/or cellular inflammation. In concurrent experiments utilizing rat glomerular mesangial cells (MCs), we demonstrate that growth factors or sphingosine activate ERK but not SAPK. In contrast, inflammatory cytokines or cell-permeable ceramide analogues activate SAPK but not ERK. Ceramide, but not sphingosine, induces interleukin-6 secretion, a marker of an inflamed phenotype. Moreover, ceramide can suppress growth factor- or sphingosine-induced ERK activation as well as proliferation. These studies implicate sphingolipid metabolites as opposing regulators of cell proliferation and inflammation through activation of separate kinase cascades.

Thirteen previously healthy children with acute onset of severe lower respiratory tract signs and symptoms underwent bronchoscopy and bronchoalveolar lavage (BAL) for diagnostic purposes. HAL samples were assessed for viral, bacterial, mycobacterial, and fungal cultures. Cytospin preparations of HALcells were assessed for expression of respiratory syncytial virus (RSV), HLA-DR, interleukin-1β, and tumor necrosis factor proteins. Purified alveolar macrophages from 2 RSV-infected children were assessed for viral replication. Three children had bacterial pneumonia and 6 were infected with RSV. BAL cells from RSV-infected children demonstrated viral protein expression. Alveolar macrophages were the predominant cell type recovered by BAL and demonstrated coexpression of RSV, HLA-DR, interleukin-1β, and tumor necrosis factor proteins. Purified alveolar macrophages from 2 RSV-infected children replicated RSV by infectious center assays. Thus, alveolar macrophages are infected by RSV in vivo and coexpress potent immunomodulatory molecules that potentially regulate the local immune response or lung injury due to this virus.