Increased serum interleukin-37 (IL-37) levels correlate with oxidative stress parameters in Hashimoto's thyroiditis

Purpose Interleukin-37 (IL-37), member of the IL-1 family, is a natural suppressor of immune and inflammatory responses. Increased serum IL-37 levels were observed in several autoimmune diseases, including Graves' disease. To our knowledge, no data on Hashimoto's thyroiditis (HT) are available in the literature.Methods Aim of our study was to measure serum IL-37 levels and evaluate their relationship, if any, with oxidative stress markers in HT patients. We enrolled 45 euthyroid HT patients (5 M e 40 F, median age 40years) and 50 age- and sex-matched healthy controls. None was under l-thyroxine therapy. Serum IL-37 levels were measured by ELISA. Specific serum tests, such as derived reactive oxygen metabolites (d-ROMs), and biological anti-oxidant potential (BAP) test were performed in all subjects to investigate the changes in oxidative balance, and advanced glycation end products (AGEs) were determined as a specific marker of oxidative stress.ResultsIL-37 levels were significantly higher in HT than in controls (median 475 vs. 268pg/ml, P=0.018). In the same patients, serum oxidants (d-ROMs) were increased and anti-oxidants (BAP) decreased compared with controls (P=0.011 and<0.0001, respectively), clearly indicating an enhanced oxidative stress. In addition, AGEs levels were higher in HT patients than in controls (210 vs. 140AU/g prot, P<0.0001) and directly correlated with IL-37 levels (P=0.048). At multivariate analysis, the main independent predictors that influenced IL-37 levels were both anti-thyroid antibodies (P=0.026) and AGEs levels (P=0.001).ConclusionsIL-37 is up-regulated in HT and may exert a protective role by counteracting oxidative stress and inflammation.