Increased expression of the chemokine fractalkine in Crohn's disease and association of the fractalkine receptor T280M polymorphism with a fibrostenosing disease Phenotype.
BACKGROUND
The fractalkine receptor CX3CR1 has been shown to be involved in inflammation and immune response. Recently, two polymorphisms of CX3CR1 (V249I and T280M) were reported.


OBJECTIVE
Our aim was to analyze fractalkine expression and the role of CX3CR1 polymorphisms in Crohn's disease (CD).


METHODS
We determined fractalkine mRNA expression in the intestinal epithelial cell (IEC) line SW480 after stimulation with proinflammatory cytokines as well as in inflamed (n = 14) and noninflamed (n = 14) CD lesions by quantitative PCR. By restriction fragment length polymorphism analysis, genomic DNA from 206 patients with CD and 211 unrelated controls was analyzed for the two single nucleotide polymorphisms in the CX3CR1 gene, which result in the V249I and T280M substitutions.


RESULTS
All proinflammatory stimuli (TNF-alpha, IL-1beta, LPS) significantly increased fractalkine mRNA expression in IEC. There was also a significant increase in fractalkine mRNA expression in inflamed lesions of CD patients when compared to noninflamed colonic mucosa (p = 0.02). Intestinal fractalkine mRNA levels correlated highly with IL-8 mRNA expression levels (r = 0.931). However, there was no difference in the V249I and T280M genotype frequencies between CD patients and the control group. In the CD group, 33.0% were heterozygous and 8.3% homozygous for the V249I polymorphism, while 23.3% were heterozygous and 4.4% homozygous for the T280M polymorphism. All T280M homozygotes were diagnosed of intestinal stenosis (p = 0.03 vs wildtype and heterozygous carriers) and had significantly more often ileocolonic involvement more often than patients with wildtype and heterozygous genotypes (p = 0.01). These associations were independent of the CARD15 genotype status.


CONCLUSIONS
The expression of the chemokine fractalkine is upregulated by proinflammatory cytokines and enhanced in inflamed CD lesions. The CX3CR1 T280M polymorphism appears to influence CD phenotype and localization.
Brand
Stephan
S
Department of Medicine II, Grosshadern, University of Munich, Munich, Germany.
Hofbauer
Katrin
K
Dambacher
Julia
J
Schnitzler
Fabian
F
Staudinger
Tanja
T
Pfennig
Simone
S
Seiderer
Julia
J
Tillack
Cornelia
C
Konrad
Astrid
A
Göke
Burkhard
B
Ochsenkühn
Thomas
T
Lohse
Peter
P
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001483:Base Sequence; D000073883:CX3C Chemokine Receptor 1; D016022:Case-Control Studies; D002478:Cells, Cultured; D054428:Chemokine CX3CL1; D020523:Chemokines, CX3C / Q000235:genetics / Q000378:metabolism*; D016001:Confidence Intervals; D003424:Crohn Disease / Q000235:genetics* / Q000473:pathology; D005260:Female; D005819:Genetic Markers; D020022:Genetic Predisposition to Disease; D006801:Humans; D007415:Intestinal Obstruction / Q000235:genetics / Q000473:pathology; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008875:Middle Aged; D008969:Molecular Sequence Data; D016017:Odds Ratio; D010641:Phenotype; D011110:Polymorphism, Genetic; D011336:Probability; D011379:Prognosis; D012333:RNA, Messenger / Q000032:analysis; D019707:Receptors, Chemokine / Q000235:genetics / Q000378:metabolism*; D018121:Receptors, Cytokine / Q000235:genetics / Q000378:metabolism*; D015728:Receptors, HIV / Q000235:genetics / Q000378:metabolism*; D012016:Reference Values; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index
D000073883:CX3C Chemokine Receptor 1; C515538:CX3CL1 protein, human; C095235:CX3CR1 protein, human; D054428:Chemokine CX3CL1; D020523:Chemokines, CX3C; D005819:Genetic Markers; D008565:Membrane Proteins; D012333:RNA, Messenger; D019707:Receptors, Chemokine; D018121:Receptors, Cytokine; D015728:Receptors, HIV