SOD1 and systemic sclerosis: Moreover, while in healthy ones, the combined treatment with sildenafil induced a major increase in SOD activity in both H2O2 doses tested (50 μM H2O2 vs. 50 μM H2O2 + S: 791.0 ± 46.7 vs. 1356.4 ± 112.9, p < 0.05 and 100 μM H2O2 vs. 100 μM H2O2 + S: 1127.8 ± 21.3 vs. 1213.8 ± 61.5, p < 0.05), in SSc, this increase was present only at the low dose (50 μM H2O2 vs. 50 μM H2O2 + S: 330.0 ± 22.5 vs. 745.7 ± 12.3, p < 0.05) (Figure 5C).