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Immunostimulatory Flagellin from Burkholderia pseudomallei Effects on an Increase in the Intracellular Calcium Concentration and Up‐Regulation of TNF‐α by Mononuclear Cells
Author(s) -
Chen YaLei,
Chen YaoShen,
Lin HsiHsun,
Chan ChunWen,
Chen SsuChing,
Chen ChingHsein
Publication year - 2007
Publication title -
microbiology and immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.664
H-Index - 70
eISSN - 1348-0421
pISSN - 0385-5600
DOI - 10.1111/j.1348-0421.2007.tb03893.x
Subject(s) - flagellin , biology , peripheral blood mononuclear cell , calcium channel , calcium , microbiology and biotechnology , calcium in biology , biochemistry , intracellular , chemistry , in vitro , receptor , organic chemistry
Using flow cytometry analysis, the flagellin of Burkholderia pseudomallei acts as a signalling inducer, and evokes an increase in the intracellular calcium ion concentration ([Ca 2+ ]i) in human peripheral blood mononuclear cells (PBMC). The cells with increased [Ca 2+ ]i segregate into the live monocyte gate and not into the live lymphocyte gates. The stimulated [Ca 2+ ]i increase can be neutralized with anti‐flagellin antibodies. In the absence of [Ca 2+ ], [Ca 2+ ]i was increased rapidly in flagellin‐treated cells compared to non‐flagellin‐treated cells only after the addition of 1 mM CaCl 2 . Selective calcium antagonists were used to effectively block the [Ca 2+ ]i signal, revealing that this signal was decreased by the addition of L‐type calcium channel blockers (diltiazem, nifedipine and verapamil) and La 2+ but was not changed by the addition of a T‐type calcium channel blocker (flunarizine). It seemed that flagellin facilitates [Ca 2+ ]i influx via a La 2+ sensitive L‐type cellular membrane channel. Furthermore, flagellin also acts as a TNF‐α inducer in a time‐ and concentration‐dependent manner when adhered mononuclear cells are treated with flagellin. This ability to induce TNF‐α production was affected by the presence of [Ca 2+ ] in the culture medium. It suggested that B. pseudomallei flagellin is an immuno‐stimulatory molecule, causing an increase in [Ca 2+ ]i and an up‐regulation of TNF‐α, which may play an important role in the inflammation process.