Increased serum levels of N^ε-(hexanoyl)lysine, a new marker of oxidative stress, in systemic sclerosis

Objective. To determine serum levels of N^ε-(hexanoyl)lysine (HEL), a new marker of oxidative stress, and its clinical association in patients with systemic sclerosis (SSc). Methods. Serum HEL levels from 26 patients with limited cutaneous SSc (lSSc), 34 with diffuse cutaneous SSc (dSSc), 20 with systemic lupus erythematosus (SLE), 20 with dermatomyositis (DM), and 40 healthy individuals were examined by enzyme linked immunosorbent assay. Results. Serum HEL levels were elevated in patients with SSc compared with healthy controls (n = 40) with similar levels between patients with lSSc and dSSc (p < 0.0001). SSc patients with elevated HEL levels had increased serum levels of anti-agalactosyl IgG antibody, rheumatoid factor (RF), and IgM than those with normal HEL levels (p < 0.05). HEL levels correlated positively with anti-agalactosyl IgG antibody (p = 0.013, r = 0.408) and RF titer (p = 0.0028, r = 0.426). Conclusion. Our results suggest that oxidative stress may play an important role in immunological abnormalities of SSc, especially in the production of autoantibodies including anti-agalactosyl IgG antibody and RF. The Journal of Rheumatology