Characterization of Salmonella-induced cell death in human macrophage-like THP-1 cells.
Salmonella strains are facultative intracellular pathogens that produce marked cytopathology during infection of host cells. Different forms of cytopathic effects have been associated with the virulence systems encoded by the two Salmonella pathogenicity islands (SPI-1 and SPI-2) and the spv locus. We used Salmonella enterica serovar Dublin to investigate the induction of cytopathology during infection of the human macrophage-like cell line THP-1. Analysis of host cells by flow cytometry using a fluorescent terminal deoxynucleotidyltransferase dUTP-biotin nick end labeling (TUNEL) assay revealed that 70% of THP-1 cells showed DNA fragmentation after 4 h of infection, increasing to greater than 90% by 5.5 h. Moreover, the results showed that gentamicin-killed or chloramphenicol-treated bacteria did not induce DNA fragmentation. Serovar Dublin strains with mutations in SPI-1, SPI-2, or spvB induced these cytopathic effects similar to wild-type bacteria. In contrast, a mutation in the phoP regulatory gene abolished DNA fragmentation in the TUNEL assay. Caspase-3 activation was detected during Salmonella infection of THP-1 cells, but caspase-8 and caspase-9 activities were not found. However, inhibition of caspase-3 did not block Salmonella-induced DNA fragmentation. These results identify a previously undetected apoptotic effect in Salmonella-infected cells that is dependent on phoP gene function.
Valle
Eulalia
E
Division of Infectious Diseases, Department of Medicine, UCSD School of Medicine, 9500 Gilman Dr., La Jolla, CA 92093-0640, USA.
Guiney
Donald G
DG
D036002:ADP Ribose Transferases / Q000235:genetics / Q000378:metabolism; D017209:Apoptosis; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D005434:Flow Cytometry; D006801:Humans; D020287:In Situ Nick-End Labeling; D036341:Intercellular Signaling Peptides and Proteins; D008264:Macrophages / Q000382:microbiology / Q000473:pathology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D019779:Salmonella enterica / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity*; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D010455:Peptides; C440638:SPI-2 protein, Salmonella; D037521:Virulence Factors; C061064:PhoP protein, Bacteria; C086597:lambda Spi-1; D036002:ADP Ribose Transferases; C415223:spvB protein, Salmonella enterica virulence plasmid