SOD1 and chronic obstructive pulmonary disease: Further previous studies [30] showed that serum CX3CL1 level in patients with chronic obstructive pulmonary disease (COPD) was positively correlated with nuclear factor-kB (NF-κB), ox-LDL, and pulmonary arterial pressure and negatively correlated with SOD, which indicated that CX3CL1 was closely correlated with oxidative stress.