Pneumococcus activation of the 5-lipoxygenase pathway and production of glycoproteins in the middle ear of rats

Pneumococcal otitis media is associated with the production of potent inflammatory mediators (leukotrienes), but the mechanism by which pneumococcus induces production of leukotrienes in the middle ear is poorly understood. In this study, up-regulation of 2 genes that govern the lipoxygenase pathway, cPLA(2) and 5-LOX, was observed in rats following inoculation of pneumococcus into the middle ear cavity. Expression of cPLA(2) was low, and 5-LOX gene expression was not detected in control animals. Up-regulation of cPLA(2) and 5-LOX in middle ear epithelial cells was accompanied by an increase of high-molecular-weight glycoproteins in middle ear fluid and cells. These findings suggest that pneumococcus activates the lipoxygenase pathway by up-regulating expression of the cPLA(2) and 5-LOX genes. This, in turn, may stimulate synthesis and secretion of high-molecular-weight glycoproteins that facilitate production of fluid in the middle ear cleft.