Short CommunicationInflammation profile of four early onset Crohn patients
Highlights
► Early onset Crohn disease (EOCD) is a multifactorial disorder. ► Genetic investigation may identify earlier children who risk EOCD. ► The K47E IL10R variant may be associated a disregulation of cytokine secretion.
Introduction
Crohn's disease (CD) is a chronic relapsing and remitting diseases of the gastrointestinal tract, characterized by discontinuous, transmural granulomatous inflammation. CD lesions can occur anywhere in the gastrointestinal tract from mouth to anus. (Cummings et al., 2010, Kim and Ferry, 2004).
Although CD is normally manifested in adulthood, it could be present in childhood before the age of 2 years (Heyman et al., 2005). The early onset Crohn Disease (EOCD) is typically more extensive (beyond the colon and/or oral or perianal disease) and characterized by a rapid progression, leading to severe repercussion in disease development (Cannioto et al., 2009).
Despite the precise etiology of CD remains elusive, epidemiological data conclusively point to a dysregulation of the immune response against the luminal flora in a genetically susceptible host. Crohn disease, as ulcerative colitis, is considered a complex genetic trait as inheritance does not follow any simple mendelian model. Both genetic and environmental factors seem to be important in its etiology.
About 40% of patients with CD carry at least one of the three independent CD-associated NOD2 (nucleotide-binding oligomerization domain containing 2) genetic variants(Barrett et al., 2008, Hugot et al., 2001, Lacher et al., 2010, Levine et al., 2007, Seidelin et al., 2009). These mutations are associated with early age at onset, ileal affection and fibrostenosis (Ferrero-Miliani et al., 2007). NOD2 is a member of a family of intracellular NLR (NOD like receptors) that maps on chromosome 16, able to recognize microbial components, in particular muramyl dipeptide (MDP), and stimulates an inflammatory response trough the activation of NF-kB. Altered NOD2 molecules lead to a dysregulated response against intestinal microflora (Cummings et al., n.d.) NOD2 is highly expressed in Paneth cells of gut and is involved in the production of defensins in response to gut microbiota. Another gene whose polymorphisms are associated to increased risk of developing CD is the ATG16L1 gene, involved together with NOD2 in the mechanism of autophagy.
On the other hand, a deregulation of some anti-inflammatory pathways has been proposed for EOCD pathogenesis, such as an impaired response to IL-10 (Amre et al., 2009, Szkaradkiewicz et al., 2009) or to IL23. The role of IL-10 signaling in inflammatory modulation has been recently reported in Turkish and Lebanese families with early onset Crohn Disease (EOCD) (Glocker et al., 2009) carrying mutations in IL10RA gene (c.G421A, p.Gly141Arg rs137853580 and c.C325T, p.Thr84Ile rs137853579) and in IL10RB gene (c.G477A, p.Trp159X rs121909601) respectively on chromosome 11 and 21.
We analyzed the entire coding region of IL10 receptor and of the exons 4 and 11 of NOD2 in four unrelated cases of EOCD presenting variable clinical severity. The secretion of the cytokine TNFα, that is the main marker of the functionality of the IL-10R, was tested to support genetic evidence.
Section snippets
Patients
We included in the study four patients (Caucasian, Italian) with EOCD enrolled at the Pediatric Gastroenterological Service of the Institute for Maternal and Child Health IRCCS “Burlo Garofolo” (Trieste, Italy). Familiar history, clinical signs and symptoms, laboratory data and previous treatments were recorded, after written informed consent of patients' parents, according to the protocol of the ethical board of Institute for Maternal and Child Health IRCCS “Burlo Garofolo” (Trieste, Italy)
Genetic investigation of IL-10R
We sequenced IL10RA and IL10RB and we did not evidence the mutations previously reported (Glocker et al., 2009). We identified the SNP rs2834167 (c.A139G, K47E) of IL10RB in P1 in homozygosis and in P2 in heterozygosis (Table 1). The P3 showed heterozygosis for both SNPs rs2834167 and rs2229113 (c.G1051A, G351R) while in P4 two SNPs, rs2228055 (c.G670A, I224V) of IL10RA and the rs2834167, were found both in heterozygosis (Table 1).
Genetic investigation of NOD2
SNP genotyping showed no significant difference in the allele
Discussion
EOCD is a multifactorial trait, both genetic and environmental factors seem to affect its etiology. As many genetic and environmental factors are likely to be involved, its inheritance pattern remains unclear. The importance of IL-10 in CD inflammatory modulation has been recently proven in different families with EOC (Gasche et al., 2003, Glocker et al., 2009).
The diagnosis of CD in infancy and early childhood has a high criticality. Several studies have standardized the parameter used for CD
Conclusion
Investigation of EOCD has a high criticality and several studies have standardized parameters used for CD diagnosis. Moreover the contribution of the genetic analysis should be highlighted because it may explain the presence of anomalous levels of inflammatory cytokine, such as TNFα. In conclusion despite very preliminary findings presented in our study due to the limited number of EOCD patients analyzed the results provide relevant about the already known correlation between TNFα and IL-10R.
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2013, GenomicsCitation Excerpt :If pedigrees are available, rare variants discovery can be further targeted by fine mapping, as shown by the identification of interleukin-10 receptor subunit alpha (IL10RA) polymorphisms associated with the development of early-onset IBD [58]. By the analysis of the entire coding region of the IL10 receptor and two exons of NOD2 in four unrelated cases, in one early-onset Crohn patient, with variable clinical severity, we recently identified one potentially important interleukin-10 receptor subunit beta (IL10RB) gene variation in homozygosis, probably able to affect the signaling of interleukin (IL)-10, [59]. The fact that the number of identified loci do not account for the total heritability of Crohn disease (30% approximately) is a difficult issue.
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2012, Medical HypothesesCitation Excerpt :The role of IL-10 signaling in inflammatory modulation has been recently reported in Turkish and Lebanese families with early-onset Crohn disease (EOCD) carrying mutations in IL10RA gene (rs137853580 and rs137853579) and in IL10RB gene (rs121909601) localized, respectively on chromosomes 11 and 21 [19]. We recently screened IL10R and IL10RB genes in four unrelated EOCD patients with variable clinical severity, finding one potentially important variation in homozygosis in the IL10RB gene probably able to affect the signaling of IL-10 [20]. The lack of interleukin-10 signaling is the principal malfunction and is likely cause of inflammatory bowel disease in patients with IL10RB deficiency [19].
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