Primary sclerosing cholangitis (PSC) is a chronic cholestatic disorder commonly associated with inflammatory bowel disease (IBD). The pathogenesis of PSC remains unknown, but bacterial translocation from the gut to the portal circulation, resulting in activation of an immune cascade and subsequent bile duct injury, is believed to be one of the triggering factors. In a previous study,1 we found a significantly lower frequency of the Δ32 deletion in the CC‐type chemokine receptor 5 (CCR5) gene in patients with PSC compared with patients with IBD and healthy controls (HC), suggesting a protective effect of this mutation on the development of PSC. Given this association in our population, we further investigated the role of RANTES (Regulated on Activation Normal T Expressed and Secreted, also known as CC‐motif chemokine ligand 5 (CCL5)), one of the ligands for the CCR5 receptor.
RANTES, localised to the cytokine cluster on chromosome 17q11.2–q12, is a plausible candidate gene for PSC, given its proinflammatory properties both independent of and as a ligand for the CCR5 receptor. A higher expression of RANTES has been reported in the gut epithelium and lymphocytes of patients with IBD.2 Moreover, in an animal model of colitis, treatment with RANTES antagonists resulted in decreased bacterial translocation, as measured by portal blood endotoxin levels.3
Two promotor polymorphisms in RANTES (−28G and −403A) result in increased transcription of the gene, whereas a single‐nucleotide polymorphism (SNP) in the first intron (In1.1C) results in reduced transcription of RANTES.4 We studied these three SNPs together with a fourth known SNP of as yet unknown function in the 3′UTR (3′222), for their role in susceptibility to PSC, and behaviour and progression of PSC (fig 1).
Figure 1 The RANTES (Regulated on Activation Normal T Expressed and Secreted) gene and the position of the different studied polymorphisms.
We genotyped 124 patients with PSC (63 without IBD, 25 with Crohn's disease (CD), 31 with ulcerative colitis (UC) and 5 with indeterminate colitis (IC)) for the −403G/A, −28C/G, In1.1T.C and 3′222T/C variants in the RANTES gene. Patients with PSC and IBD were recruited from the hepatology and gastroenterology departments of the same tertiary care referral centre. Table 1 summarises and compares the disease characteristics of IBD in patients with and without PSC. Genotype and allele frequencies were compared with 595 patients with IBD without PSC (418 CD, 160 UC, 17 IC), and with 362 HC. SPSS V.14.0 software was used for statistical analysis, Haploview for calculation of linkage disequilibrium (LD)5 and fastPHASE 1.1.4 for haplotype estimation.6
Table 1 Characteristics of patients with IBD and of patients with PSC with concomitant IBD.
| Crohn's disease | Ulcerative colitis | |||
|---|---|---|---|---|
| CD with PSC | CD without PSC | UC with PSC | UC without PSC | |
| n = 25 (%) | n = 418 (%) | n = 31 (%) | n = 160 (%) | |
| Localisation of CD | ||||
| Ileal | 1/25 (4) | 107/396 (27) | — | — |
| Colonic | 8/25 (32) | 65/396 (16) | ||
| Ileocolonic | 15/25 (60) | 177/396 (45) | ||
| Upper | 1/25 (4) | 47/396 (12) | ||
| Anal involvement | 8/25 (35) | 132/392 (34) | ||
| Behaviour of CD | ||||
| Inflammatory | 16/25 (64) | 144/386 (37) | — | — |
| Stricturing | 3/25 (12) | 86/386 (22) | ||
| Penetrating | 6/25 (24) | 156/386 (40) | ||
| Localisation of UC | ||||
| Proctitis | — | — | 3/31 (10) | 33/146 (23) |
| Left‐sided colitis | 10/31 (32) | 66/146 (45) | ||
| Extensive colitis | 18/31 (58) | 47/146 (32) | ||
CD, Crohn's disease; PSC, primary sclerosing cholangitis; UC, ulcerative colitis.
Allele frequencies for the studied polymorphisms are summarised in table 2. All studied polymorphisms were in Hardy–Weinberg equilibrium. The −28G allele was significantly more frequent in patients with PSC (5.9%) compared with those with IBD (3.4%, p = 0.05) and HC (2.2%, p = 0.005). Furthermore, in patients with CD, the −28G allele was significantly more frequent in those patients who developed PSC (10.4%) compared with those who did not develop PSC (3%, p = 0.005), with an odds ratio (OR) of 4.16 (95% CI 1.4 to 12). The allele frequency for the RANTES 3′222 allele was <1% in our cohort. The –403, –28 and in1.1 SNPs were all in strong LD (D′ 0.838 for –403/–28, 0.946 for –403/in1.1 and 0.78 for –28/in1.1). Haplotype analysis could not identify differences between the studied groups. There was no association between any of the studied RANTES SNPs and location and behaviour of IBD or PSC in the different subgroups, nor with the CCR5Δ32 mutation.
Table 2 Allele frequencies for the –403, –28, in1.1 and 3′222 RANTES polymorphism in primary sclerosing cholangitis, inflammatory bowel disease and healthy controls.
| PSC total n = 124 (%) | PSC without IBD n = 63 (%) | PSC CD n = 25 (%) | PSC UC n = 31 (%) | IBD total n = 595 (%) | CD without PSC n = 418 (%) | UC without PSC n = 160 v(%) | HC n = 362 (%) | |
|---|---|---|---|---|---|---|---|---|
| RANTES‐403A | 18.1 | 14.9 | 25.0 | 20.0 | 18.6 | 19.1 | 17.9 | 19.7 |
| RANTES‐28G | 5.9 | 3.4 | 10.4 | 6.5 | 3.3 | 3.0 | 4.2 | 2.2 |
| RANTES in1.1C | 15.3 | 12.9 | 22.9 | 14.5 | 13.8 | 15.0 | 10.6 | 14.6 |
| RANTES 3′222C | 0.0 | 0.0 | 0.0 | 0.0 | 0.7 | 0.9 | 0.3 | 0.0 |
CD, Crohn's disease; IBD, inflammatory bowel disease; PSC, primary sclerosing cholangitis; RANTES, Regulated on Activation Normal T Expressed and Secreted; UC, ulcerative colitis.
In conclusion, this is the first report of an association between a functional promotor polymorphism in the RANTES gene, with an OR of 4.16 for the development of PSC in patients with CD. This –28G promotor polymorphism is known to result in increased RANTES transcription and expression. Given its known proinflammatory properties, and taking the data on the action of RANTES antagonists in experimental colitis into account,3 a possible mechanism to explain the association between the RANTES −28G allele and PSC could be that an increased inflammatory response in the gut predisposes to bacterial translocation through the bowel wall.
Footnotes
Competing interests: None.
References
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