GROUP-B STREPTOEOCCI (GBS) INJURE LUNG ENDOTHELIUM IN-VITRO - GBS INVASION AND GBS-INDUCED EICOSANOID PRODUCTION IS GREATER WITH MICROVASCULAR THAN WITH PULMONARY-ARTERY CELLS

Neonatal group B streptococcal (GBS) sepsis and pneumonia cause lung e ndothelial cell injury. GBS invasion of the lung endothelium may be a mechanism for injury and the release of vasoactive eicosanoids. Pulmon ary artery endothelial cells (PAEC) and lung microvascular endothelial cells (LMvEC) were isolated from neonatal piglets and were characteri zed as endothelial on the basis of morphology, uptake of acyl low-dens ity lipoprotein, factor WI staining, and formation of tube-like struct ures on Matrigel. PAEC and LMvEC monolayers were infected with COH-1 ( parent GBS strain), isogenic mutants of COH-1 devoid of capsuler siali c acid or all capsular polysaccharide, or a noninvasive Escherichia co li strain, DH5 alpha. Intracellular GBS were assayed by plate counting of colony-forming units resistant to incubation with extracellular an tibiotics, AH GBS strains invaded LMvEC significantly more than PAEC, showing that the site of lung endothelial cell origin influences invas ion. DH5 alpha was not invasive in either cell type. Both isogenic mut ants invaded PAEC and LMvEC more than COH-1 did, showing that GBS caps ular polysaccharide attenuates invasion. Live GBS caused both LMvEC an d PAEC injury as assessed by lactate dehydrogenase release; heat-kille d GBS and DH5 alpha caused no significant injury. Supernatants from PA EC and LMvEC were assayed by radioimmunoassay for prostaglandin E(2) ( PGE(2)), the stable metabolite of prostacyclin (6-keto PGF(1 alpha)), and the thromboxane metabolite thromoxane B-2. At 4 h, live COH-1 caus ed no significant increases in eicosanoids from both PAEC and LMvEC. A t 16 h, live COH-1, but not heat-killed COH-1, caused a significant in crease in 6-keto-PGF(1 alpha) greater than PGE(2) from LMvEC, but not PAEC. We conclude that live GBS injure and invade the lung microvascul ar endothelium and induce release of prostacyclin and PGE(2). We postu late that GBS invasion and injury of the lung microvasculature contrib ute to the pathogenesis of GBS disease,