To determine whether polymorphism in the manganese superoxide dismutase (MnSOD) gene is associated with susceptibility or disease outcome in rheumatoid arthritis (RA).
We used a case-control approach with 153 RA patients and 218 control subjects to examine for any associations between MnSOD genotypes and susceptibility to RA. We also investigated the influence of genotypes on radiologic outcome, as measured using the Larsen score for radiographs of the hands and feet, and on functional outcome, as assessed by the Health Assessment Questionnaire. MnSOD typing was carried out using polymerase chain reaction-based methods. Results were analyzed using multiple regression analysis, with adjustment for age, sex, and disease duration. In separate analyses, we corrected for rheumatoid factor (RF) status and/or the presence of the HLA-DRB1 "shared epitope" (SE). We also examined whether radiologic outcome was influenced by interactions between MnSOD and glutathione S-transferase (GST) genes.
No association between MnSOD genotype and development of RA was found. The MnSOD VV genotype was associated with a significantly higher (P = 0.04) Larsen score (104.4) than MnSOD AA (83.0), while MnSOD AV was associated with an intermediate score (91.8). Correction for RF status had no significant effect on the results of the analysis, but significance was lost (P = 0.09) after correction for the presence of the SE. There was evidence of interaction between the GSTT1 and MnSOD genotypes, with the MnSOD VV/GSTT1-null combination being associated with the highest Larsen score (142.1; P = 0.007 after correction for the SE).
Polymorphism in the MnSOD gene is not associated with susceptibility to RA. Our data suggest that MnSOD VV is associated with more severe radiologic outcome, although this relationship may not be independent of the effect of the SE. However, interaction between MnSOD and GST genes appears to influence radiologic outcome independently of the SE.