Rationale: The receptor for advanced glycation end products (RAGE) engages a number of ligands implicated in inflammatory processes. The RAGE coding gene maps to the 6p21.32 region, close to the genes DRB1 and BTNL2, which are associated with sarcoidosis.
Objectives: We investigated a possible implication of RAGE in sarcoid granulomas.
Methods: RAGE and major ligands (N-epsilon-carboxy-methyl-lysine [CML], S100A12, and S100B) expression was investigated by immunostaining of 99 paraffin-embedded biopsies of sarcoid tissues, and expression patterns were determined. Among the three RAGE gene single-nucleotide polymorphisms investigated, -374 T/A was selected, characterized in terms of transcriptional effect (immunocytochemistry and real-time polymerase chain reaction), and its frequency was determined in DNA extracted from biopsies.
Measurements and results: RAGE, CML, S100A12, and S100B immunoreactivity was observed in all sarcoid granulomas, although at different intensities. The degree of RAGE expression significantly correlated with the degree of S100A12 expression. The -374 TT/AT genotypes, associated with higher RAGE transcriptional activity, were more frequent in the sarcoidosis biopsy group than in control subjects, and the association was confirmed in a second, independent series of 101 patients with sarcoidosis.
Conclusions: We showed the association of RAGE and its ligands with sarcoidosis and suggest that an intrinsic genetic factor could be in part involved in its expression. In Italian patients, the -374 T/A polymorphism seems to be significantly associated with this disease.