HLA-B27 modulates nuclear factor kappaB activation in human monocytic cells exposed to lipopolysaccharide.
OBJECTIVE
To study whether HLA-B27 modifies some key factors controlling inflammatory responses on lipopolysaccharide (LPS) stimulation in human monocytic cells.


METHODS
U937 human monocytic cells were stably transfected with either HLA-B27 genomic DNA, HLA-B27 complementary DNA, HLA-A2 genomic DNA, or with the resistant vector pSV2neo (mock) alone. The cells were stimulated with LPS. Electrophoretic mobility shift assay was performed to determine nuclear factor kappaB (NF-kappaB) and heat-shock factor 1 activities, Western blotting was performed to detect the expressions of inhibitory kappaBalpha (IkappaBalpha) and heat-shock proteins (HSPs), and enzyme-linked immunosorbent assay was performed to measure tumor necrosis factor alpha (TNFalpha) secretion.


RESULTS
The expression of HLA-B27 modulated the response to LPS in U937 human monocytic cells. Stimulation with LPS led to faster degradation of IkappaBalpha regulatory proteins, accompanied by faster and prolonged activation of NF-kappaB in HLA-B27-expressing cells compared with HLA-A2 and mock transfectants. The secretion of TNFalpha upon LPS stimulation correlated well with the activation of NF-kappaB. No activation of the heat-shock response was observed.


CONCLUSIONS
Our data indicate that HLA-B27 has effects on host responses to LPS that are unrelated to antigen presentation. Two crucial events in the development of arthritis, the activation of NF-kappaB and the secretion of TNFalpha, were found to be enhanced in HLA-B27-expressing cells upon LPS stimulation. Because LPS is known to be present in the inflamed joints of patients with reactive arthritis (ReA), the enhanced inflammatory response of HLA-B27-positive cells upon LPS stimulation offers an attractive explanation for the role of HLA-B27 in the development of ReA.
Penttinen
Markus A
MA
National Public Health Institute, Turku, and Turku Centre for Biotechnology, University of Turku, Turku, Finland. markus.penttinen@utu.fi
Holmberg
Carina I
CI
Sistonen
Lea
L
Granfors
Kaisa
K
D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000378:metabolism; D015793:HLA-B7 Antigen / Q000235:genetics / Q000276:immunology*; D000076249:Heat Shock Transcription Factors; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D009000:Monocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D016328:NF-kappa B / Q000096:biosynthesis*; D000091402:Prohibitins; D012477:Salmonella enteritidis / Q000276:immunology; D014157:Transcription Factors; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D020298:U937 Cells
D004268:DNA-Binding Proteins; D015793:HLA-B7 Antigen; D000076249:Heat Shock Transcription Factors; D008070:Lipopolysaccharides; D016328:NF-kappa B; C000717331:PHB2 protein, human; D000091402:Prohibitins; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha