RESUMO
Although Streptococcus pneumoniae is the leading cause of community-acquired pneumonia in humans, the mechanism whereby the organism penetrates lung tissue is poorly understood. In the present study we have examined the capacity of pneumococci to penetrate A549 cells, a human lung alveolar carcinoma (type II pneumocyte) cell line. Not all clinical S. pneumoniae isolates initially tested were capable of penetration of the cells, as judged by resistance to extracellular antibiotics. The presence of a polysaccharide capsule also significantly reduced the capacity to both adhere to and penetrate A549 cells. Electron micrographs showed the presence of pneumococci enclosed within vacuoles of intact A549 cells, but bacteria were also seen free in the cytoplasm of damaged cells. Ongoing bacterial DNA, RNA, or protein synthesis was not essential for uptake of pneumococci by A549 cells, and uptake was not diminished by pretreatment of the pneumococci with trypsin. However, inhibition of A549 microfilament assembly with cytochalasin D abolished the phenomenon.
Assuntos
Aderência Bacteriana , Alvéolos Pulmonares/microbiologia , Streptococcus pneumoniae/patogenicidade , Cápsulas Bacterianas , Proteínas de Bactérias/biossíntese , Células Cultivadas , Cloranfenicol/farmacologia , Ciprofloxacina/farmacologia , Citocalasina D/farmacologia , DNA Bacteriano/biossíntese , Inibidores Enzimáticos/farmacologia , Epitélio/microbiologia , Humanos , Microscopia Eletrônica , Infecções Pneumocócicas/microbiologia , Inibidores da Síntese de Proteínas/farmacologia , RNA Bacteriano/biossíntese , Rifampina/farmacologia , Tripsina/farmacologia , Fator de Necrose Tumoral alfa/farmacologiaRESUMO
This study has demonstrated the involvement of multiple forms of rat hepatic microsomal CoA ligases in the formation of 2-arylpropionyl-CoA thioesters. In the presence of (-)R-ibuprofen (0.1 microM-1 mM) two enzymic processes were observed, one of which exhibited enantiospecificity and apparent high affinity for the R enantiomer (Km 0.06 microM) whilst the second, a low-affinity component was non-enantiospecific. An equivalent high-affinity isoform catalysing R-flurbiprofen-CoA formation at concentrations less than 100 microM was not demonstrated. However, at higher substrate concentrations formation of both R- and S-flurbiprofenyl-CoA thioesters occurred. Marked inter-individual variation was observed in the formation of S-ibuprofen-CoA and S-flurbiprofen-CoA in the rats studied.
