Salmonella enterica serovar Typhimurium-induced internalization and IL-8 expression in HeLa cells does not have a direct relationship with intracellular Ca(2+) levels

Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843-4467, USA.
Microbes and Infection (Impact Factor: 2.86). 06/2009; 11(10-11):850-8. DOI: 10.1016/j.micinf.2009.05.003
Source: PubMed


The invasion-associated type III secretion system (T3SS-1) of S. Typhimurium is required to initiate and sustain an acute inflammatory response in the intestine. We investigated the relationship of S. Typhimurium T3SS-1-induced IL-8 expression and invasion with intracellular Ca(2+) mobilization in HeLa cells. Compared to the sipAsopABDE2 mutant, strains carrying a mutation in sipA, or mutations in sopABDE2 induced higher levels of IL-8 and greater bacterial internalization despite the fact that these mutants elicited similarly low intracellular concentrations of Ca(2+). Likewise, complemented sipAsopABDE2 mutant with sopE2 did not affect intracellular Ca(2+) concentrations or IL-8 expression, but significantly increased bacterial internalization. Treating HeLa cells with the calcium chelator BAPTA-AM or with D-BAPTA-AM, a derivative with greatly reduced Ca(2+) chelating activity, yielded strong evidence that BAPTA-AM does not affect invasion and inhibits IL-8 secretion by a calcium-dependent mechanism. These findings suggest that, although wild-type S. Typhimurium-induced IL-8 expression and bacterial internalization in HeLa cells coincides with increased cytosolic Ca(2+), the differing levels of IL-8 and invasion induced by strains carrying different effector proteins are unrelated to levels of intracellular Ca(2+).

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    • "Cells (from ATCC) were grown in Dulbecco's Modified Eagle Medium (DMEM) (Hyclone) supplemented with 10% (20% for Caco-2 cells) Fetal Bovine Serum (FBS) (Sigma). HeLa cells are a commonly used cell line for invasion and pedestal research [12], [13], [38], [39], [40]. We opted to use them due to their flat morphology and ease of imaging. "
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    • "Listeria monocytogenes and Campylobacter jejuni induce intracellular Ca 2þ changes in host cells [1] [21], but while chelation of intracellular Ca 2þ interferes with C. jejuni internalization [1], it has no effect on L. monocytogenes invasion [21]. Contradictory results regarding the dependence on cytosolic Ca 2þ changes for intracellular invasion by Salmonella typhimurium and stimulation of IL-8 production have been also reported [2] [22]. "
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