| Summary: | 碩士 === 大葉大學 === 分子生物科技學系碩士班 === 94 === Salmonella, a gram-negative rod, is one of the most common bacterial pathogens to humans. There are more than 2,500 serotypes among Salmonella. S. Typhi and S. Paratyphi cause typhoid and paratyphoid fevers in humans, respectively, while other non-typhoid Salmonella, such as S. Typhimurium, S. Enteritidis, and S. Choleraesuis, usually cause gastrointestinal infections and bacteremia. In this study, we used human macrophage cell line, THP-1, and different serotypes of Salmonella to investigate the Salmonella-host cell interactions. All serotypes of Salmonella appeared to survive within THP-1 cells following the ingestion. Nevertheless, S. Choleraesuis, compared to S. Typhimurium, S. Typhi, and S. Enteritidis, expressed higher ability to survive and replicate within macrophages. Flow cytometry with Annexin V-FITC/PI double staining was used to evaluate the cell death of macrophages caused by Salmonella. At 12- and 14- hr post-infection, S. Choleraesuis provoked 16% and 18% of THP-1 macrophages to cell death. Only the PMA-activated THP-1 cells exhibited significant level of apoptosis, compared to non-activated THP-1 cells following Salmonella infection. Transmission electron microscope demonstrated typical morphological changes of apoptosis in THP-1 cells, including nuclear condensation and cytoplasmic vacuolization. We also used Oligo GEArray (Superarray) to assess the gene expression profiles of macrophages that underwent apoptosis following ingestion of Salmonella. S. Choleraesuis SC-B67 apparently induced the expression of genes associated with apoptosis in THP-1, including caspase-3, caspase-8, caspase-9, Bax and Bad. Our data suggested that Salmonella induced the late-phase apoptosis of macrophages mainly through intrinsic pathway. The ability to modulate the activity of effector caspases may represent an unexploited avenue for therapeutic intervention in Salmonella infections.
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