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 infla mmatory mediators (leukotrienes), but the mechanism by which pneumococcus i nduces production of leukotrienes in the middle ear is poorly understood. I n this study, up-regulation of 2 genes that govern the lipoxygenase pathway , cPLA(2) and 5-LOX, was observed in rats following inoculation of pneumoco ccus into the middle ear cavity. Expression of cPLA(2) was low, and 5-LOX g ene 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 o f 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 s timulate synthesis and secretion of high-molecular-weight glycoproteins tha t facilitate production of fluid in the middle ear cleft.