| Abstract: | Salmonella spp. have been shown to cause apoptosis of various host cell types as a part of their infection process. However, the induction of apoptosis remains to be looked into under the different host environments experienced by the pathogens. One of these is iron limitation, due to binding of iron in the host with proteins like lactoferrin, transferrin, haptoglobulin and hemoglobin etc. making non-availability of free iron to the pathogen for its growth and metabolism. In order to simulate the iron-limited in vivo situation, we studied the potential of Salmonella enterica serovar Typhimurium and its proteins under in vitro-created iron-stressed conditions, to cause apoptosis of macrophages (the first line of defence system). The apoptotic potential was evaluated qualitatively and quantitatively by various methods like assessment of nucleosomal DNA ladder (hallmark of apoptosis) and morphological evaluation by DNA intercalating dyes like acridine orange staining and Hoechst 33342-propidium iodide co-staining. It was observed that iron limitation could cause apoptotic cell death in a higher number of cells with the overexpression of proteins with subunit molecular weights of approximately 89, 54, 32 and 20 kDa. Salmonella may initiate apoptosis as a virulence strategy, but the death of host cells by the process of apoptosis rather than necrosis after getting a suicidal signal might be helpful for the host in order to save the surrounding cells, as well as to the parasite to enable it to spread systemically without inducing an inflammatory response. |
