Streptococcus pneumoniae is the major pathogen of community-acquired pneumonia and a common cause of otitis, meningitis and sepsis. During pneumococci infection accompanied with bacterial invasion and hematogenous spreading, the endothelium is directly targeted by pneumococci and their virulence factors. Therefore, we tested the hypothesis that pneumococci induced endothelial apoptosis. Unencapsulated R6x pneumococci strongly induced apoptosis of human endothelial cells both from lung microvasculature and umbilical vein, whereas an encapsulated strain D39 mainly led to necrotic cell death. Deletion of the gene coding for pneumolysin reduced pneumococci-induced apoptosis in HUVEC. Furthermore, N-acetyl-L-cysteine, an antioxidant thiol, significantly reduced apoptosis caused by R6x, and LDH release induced by D39, pointing to a role for reactive oxygen species in the pathogenesis. Apoptotic cells showed increased cleavage and activity of caspases 6 and 9 but only late activation of caspase 3. Programmed cell death could be strongly reduced by pan-caspase inhibitor zVAD. Reduced levels of Bcl2 and cytosolic increase of apoptosis-inducing factor in pneumococci-infected cells implicated involvement of mitochondrial death pathways. Caspase activation and apoptosis were abolished by cAMP elevation. Moreover, p38 mitogen-activated protein kinase and c-Jun NH(2)-terminal kinase were activated in pneumococci-infected cells and inhibitors of both kinases strongly reduced pneumococci-induced caspase activation and apoptosis. Hence, kinase- and caspase-dependence of pneumococci-induced endothelial apoptosis may bear relevance to novel therapeutic approaches to pneumococci-related disease.
Streptococcus pneumoniae R6x induced p38 MAPK JNK-mediated Caspase-dependent apoptosis in human endothelial cells
스트렙토코쿠스 뉴모니에 R6x는 인간 내피 세포에서 p38 MAPK JNK 매개 카스파제 의존적 세포자멸사를 유도했다.
[Category] 폐렴구균 감염증,
[Article Type] journal-article
[Source] pubmed
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