Combined Polymorphisms in Genes Encoding the Inflammasome Components NALP3 and CARD8 Confer Susceptibility to Crohn's Disease in Swedish Men

OBJECTIVES : Crohn's disease (CD) is characterized by overproduction of proinflammatory cytokines like interleukin (IL)-1 beta. Production of mature IL-1 beta is dependent on a caspase-1-activating protein complex called the NALP3 inflammasome, composed of NALP3, ASC, and CARD8. NALP3 shares structural similarities with Nod2, and both of these proteins are required for bacteria-induced IL-1 beta secretion. The combination of the polymorphisms CARD8 (C10X) and NALP3 (Q705K) was recently shown to be associated with rheumatoid arthritis. Our aim was to investigate whether these combined polymorphisms play a role in the susceptibility to CD. METHODS: The study included 498 CD patients in two cohorts from different regions and 742 control individuals from a Swedish population. DNA was isolated from whole blood. Polymorphisms of (Q705K) NALP3 and (C10X) CARD8, as well as the Nod2 variants, R702W and G908R, were genotyped using the Taqman single nucleotide polymorphism assay. The Nod2 frameshift mutation, L1007fs, was detected by Megabace SNuPe genotyping. RESULTS: Our results show that men who have both the C10X and Q705K alleles in CARD8 and NALP3, and who express wild-type alleles of Nod2 are at an increased risk of developing CD (odds ratio, OR: 3.40 range: 1.32-8.76); P = 0.011). No association with these polymorphisms was found in women (OR: 0.89 (range: 0.44-1.77); P = 0.74). CONCLUSIONS: We suggest a role for combined polymorphisms in CARD8 and NALP3 in the development of CD in men, with obvious sex differences in the genetic susceptibility pattern. These findings give further support to the importance of innate immune responses in CD.