Immunostimulatory flagellin from Burkholderia pseudomallei effects on an increase in the intracellular calcium concentration and up-regulation of TNF-alpha by mononuclear cells.
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-alpha inducer in a time- and concentration-dependent manner when adhered mononuclear cells are treated with flagellin. This ability to induce TNF-alpha 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-alpha, which may play an important role in the inflammation process.
Chen
Ya-Lei
YL
Department of Biotechnology, National Kaohsiung Normal University.
Chen
Yao-Shen
YS
Lin
Hsi-Hsun
HH
Chan
Chun-Wen
CW
Chen
Ssu-Ching
SC
Chen
Ching-Hsein
CH
D016957:Burkholderia pseudomallei / Q000276:immunology*; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D003593:Cytoplasm / Q000737:chemistry; D004306:Dose-Response Relationship, Immunologic; D005408:Flagellin / Q000276:immunology*; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000378:metabolism*; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis*
D002121:Calcium Channel Blockers; D014409:Tumor Necrosis Factor-alpha; D005408:Flagellin; D002118:Calcium